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Title:
DECODING OF A SIGNAL COMPRISING ENCODED DATA SYMBOLS
Document Type and Number:
WIPO Patent Application WO/2019/088884
Kind Code:
A1
Abstract:
A first radio node (108-1,108-2; 110) and a method therein for transmitting a signal comprising encoded data symbols to a second radio node (110; 108-1,108-2). The first and second radio nodes are operating in a wireless communications network (100). The 5 first radio node repeats n times a sequence of data symbols S0,S1,…,Sk-1 to be transmitted, wherein k is a multiple of n. The first radio node encodes the n sequences of data symbols S0,S1,…,Sk-1 using n orthogonal code sequences, wherein each code sequence comprises n code elements. Further, the first radio node transmits, to the second radio node, a signal comprising the respective encoded sequence of data 10 symbols S0,S1,…,Sk-1 and an optional respective affix for separating two encoded sequences of data symbols S0,S1,…,Sk-1.

Inventors:
LOPEZ, Miguel (Fridensborgvägen 24, SOLNA, SE-170 69, SE)
ERIKSSON LÖWENMARK, Stefan (Älghornsvägen 35, FÄRENTUNA, SE-179 98, SE)
Application Number:
SE2017/051060
Publication Date:
May 09, 2019
Filing Date:
October 30, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
TELEFONAKTIEBOLAGET LM ERICSSON (PUBL) (164 83 Stockholm, 164 83, SE)
International Classes:
H04L1/08; H04J13/00; H04J13/18
Domestic Patent References:
WO2016200358A12016-12-15
Foreign References:
US20170195096A12017-07-06
Other References:
ERICSSON LM: "EC -GSM, Overlaid CDMA for extended coverage", 3RD GENERATION PARTNERSHIP PROJECT (3GPP, 22 May 2015 (2015-05-22), 650, route des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France
PANASONIC: "Multiple subframe code spreading for MTC UEs", 3RD GENERATION PARTNERSHIP PROJECT (3GPP, 14 August 2015 (2015-08-14), 650, route des Lucioles ; F-06921 Sophia-Antipolis Cedex ; France
Attorney, Agent or Firm:
AYOUB, Nabil (Ericsson AB, Patent Unit Kista RAN 2, Stockholm, 164 80, SE)
Download PDF:
Claims:
CLAIMS

1. A method performed by a first radio node (108-1 , 108-2; 1 10) for transmitting a signal comprising encoded data symbols to a second radio node (1 10;

5 108-1 , 108-2), wherein the first radio node (108-1 , 108-2; 1 10) and the second radio node (110; 108-1 , 108-2) are operating in a wireless communications network (100), and wherein the method comprises:

- repeating (201) n times a sequence of data symbols So,Si ,... ,Sk-i to be transmitted, wherein k is a multiple of n;

0 - encoding (202) the n sequences of data symbols So,Si ,... ,Sk-i using n

orthogonal code sequences, wherein each code sequence comprises n code elements; and

- transmitting (204), to the second radio node (1 10; 108-1 , 108-2), a signal comprising the respective encoded sequence of data symbols So,Si ,... ,Sk-i and an5 optional respective affix for separating two encoded sequences of data symbols

So,Si ,... ,Sk-i .

2. The method of claim 1 , wherein the encoding (202) of the n sequences of data symbols So,Si ,... ,Sk-i comprises:

0 - element-wise multiplying one code sequence out of the n orthogonal code sequences to the n times repeated data symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , k-1].

3. The method of claim 1 or 2, wherein the encoding (202) of the n5 sequences of data symbols So,Si ,... ,Sk-i comprises:

- repeatedly using the n orthogonal code sequences for the encoding of the n sequences of data symbols So,Si ,... ,Sk-i , wherein the n orthogonal code sequences are used k/n times each for encoding each n times repeated symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , k-1],

0

4. The method of any one of claims 1-3, comprising:

- providing (203) the respective affix before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i

5. The method of claim 4, wherein the providing (203) of the respective affix comprises:

- inserting a respective cyclic prefix before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i , wherein the respective cyclic prefix comprises one or more of the last n-1 data symbols of the respective encoded sequence of data symbols So,Si ,... ,Sk-i . 6. The method of claim 4, wherein the providing (203) of the respective affix comprises:

- providing a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i . 7. The method of any one of claims 1-6, wherein the data symbols

So,Si ,... ,Sk-i are data symbols from a symbol constellation of a linear modulation or a non-linear modulation.

8. The method of claim 7, wherein the linear modulation is one out of:

- a Phase-Shift Keying, PSK and

- a Quadrature Amplitude Modulation, QAM.

9. The method of claim 7, wherein the non-linear modulation is one out of:

- a Gaussian Minimum Shift Keying, GMSK;

- a Gaussian Frequency-Shift Keying, GFSK; and

- a Minimum-Shift Keying, MSK.

10. The method of any one of claims 1-9, wherein one or more of the data symbols So,Si ,... ,Sk-i are training symbols.

1 1. The method of any one of claims 1-10, wherein the n orthogonal code sequences comprise real values.

12. The method of claim 1 1 , wherein the n orthogonal code sequences are comprised in an n by n Hadamard matrix.

13. The method of any one of claims 1-10, wherein the n orthogonal code sequences comprise complex values.

14. The method of any one of claims 1-13, wherein the transmitting (204) of the signal comprising the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i comprises one out of:

- transmitting the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in sequence using a single carrier; and

- transmitting the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in parallel using a respective subcarrier in a multicarrier signal. 15. The method of any one of claims 1-14, wherein the repeating (201) n times of the sequence of data symbols So,Si ,... ,Sk-i comprises:

- generating an n by k matrix, wherein each row is a copy of a sequence of data symbols So,Si ,... ,Sk-i , wherein n is the number of repetitions of the sequence of data symbols So,Si ,... ,Sk-i ; wherein the encoding (202) of the n sequences of data symbols So,Si ,... ,Sk-i using n orthogonal code words comprises:

- encoding the generated n by k matrix by performing element-wise matrix multiplication using a k/n times repeated n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein the encoding results in an encoded n by k matrix; wherein the providing (203) of the respective affix comprises:

- inserting a cyclic prefix before the encoded n by k matrix, which cyclic prefix comprises one or more of the last n-1 columns of the encoded n by k matrix, wherein the inserting results in an n by (x+k) matrix, wherein x is the number of columns of the inserted cyclic prefix, or

- providing a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i ; and wherein the transmitting (204) of the respective affix and the respective sequence of data symbols So,Si ,... ,Sk-i comprises: - transmitting row wise the respective affix and the data symbols So,Si , ... ,Sk-i comprised in the n by (x+k) matrix.

16. A method performed by a second radio node (1 10; 108-1 , 108-2) for decoding and extracting data symbols from a signal received from a first radio node (108-1 , 108-2; 1 10), wherein the second radio node (1 10; 108-1 , 108-2) and the first radio node (108-1 , 108-2; 1 10) are operating in a wireless communications network (100), and wherein the method comprises:

- receiving (401) a signal from the first radio node (108-1 , 108-2; 1 10);

- removing (402) an affix from the received signal resulting in n sequences of k received samples;

- stacking (403) the n sequences of k received samples;

- decoding (404) the stacked n sequences of k received samples using n orthogonal code sequences, wherein each code sequence comprises n code elements, wherein for each code sequence each of the n sequences of k received samples is multiplied to one out of the n code elements of the code sequence and wherein the multiplied sequences of received samples are subsequently added, and wherein the decoding results in n different decoded sequences of samples of length k each decoded sequence of samples corresponding to one of the n applied code sequences; and

- extracting (406) a sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples.

17. The method of claim 16, comprising:

- reordering (405) the n different decoded sequences of samples and possibly moving elements between the n different decoded sequences of samples to obtain n different decoded and reordered sequences of samples.

18. The method of claim 16 or 17, comprising:

- estimating (407) n channel coefficients ho,hi , ... ,hn-i , wherein each one of the n different decoded sequences of samples corresponds to the sequence of data symbols

So,Si ,... ,Sk-i multiplied by a respective channel coefficient.

19. The method of any one of claims 17-20, comprising:

- combining (508) the n different decoded sequences of samples by performing a Maximum Ratio Combination, MRC, whereby the signal to noise ratio is increased.

20. The method of any one of claims 16-19, wherein the stacking (403) of the n sequences of k received samples comprises:

5 - stacking the n sequences of k received samples into a first n by k matrix;

wherein the decoding (404) of the stacked sequences of k received samples using n orthogonal code sequences comprises:

- decoding the first n by k matrix using an n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein each code sequence comprises

10 n code elements and wherein the decoding results in a second n by k matrix; and

wherein the extracting (406) of the sequence of data symbols So,Si , ... ,Sk-i from the n different decoded sequences of samples comprises:

- extracting the sequence of data symbols So,Si , ... ,Sk-i from the second n by k matrix.

15

21. A first radio node (108-1 , 108-2; 1 10) for transmitting a signal comprising encoded data symbols to a second radio node (1 10; 108-1 , 108-2), wherein the first radio node (108-1 , 108-2; 1 10) and the second radio node (1 10; 108-1 , 108-2) are operating in a wireless communications, and wherein the first radio node (108-1 , 108-2;

20 1 10) is configured to:

- repeat n times a sequence of data symbols So,Si ,... ,Sk-i to be transmitted, wherein k is a multiple of n;

- encode the n sequences of data symbols So,Si , ... ,Sk-i using n orthogonal code sequences, wherein each code sequence comprises n code elements; and

25 - transmit, to the second radio node (1 10; 108-1 , 108-2), a signal comprising the respective encoded sequence of data symbols So,Si ,... ,Sk-i and an optional respective affix for separating two encoded sequences of data symbols So,Si ,... ,Sk-i .

22. The first radio node (108-1 , 108-2; 1 10) of claim 21 , being configured to 30 encode the n sequences of data symbols So,Si , ... ,Sk-i by further being configured to:

- element-wise multiply one code sequence out of the n orthogonal code sequences to the n times repeated data symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , ... , k-1].

23. The first radio node (108-1 , 108-2; 1 10) of claim 21 or 22, being configured to encode the n sequences of data symbols So,Si ,... ,Sk-i by further being configured to:

- repeatedly use the n orthogonal code sequences for the encoding of the n sequences of data symbols So,Si ,... ,Sk-i , wherein the n orthogonal code sequences are used k/n times each for encoding n times repeated symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , k-1],

24. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-23, being configured to:

- provide the respective affix before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

25. The first radio node (108-1 , 108-2; 1 10) of claim 24, being configured to provide the respective affix by further being configured to:

- insert a respective cyclic prefix before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i , wherein the respective cyclic prefix comprises one or more of the last n-1 data symbols of the respective encoded sequence of data symbols So,Si ,... ,Sk-L

26. The first radio node (108-1 , 108-2; 1 10) of claim 24, being configured to provide the respective affix by further being configured to:

- provide a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

27. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-25, wherein the data symbols So,Si ,... ,Sk-i are data symbols from a symbol constellation of a linear modulation or a non-linear modulation.

28. The first radio node (108-1 , 108-2; 1 10) of claim 27, wherein the linear modulation is one out of:

- a Phase-Shift Keying, PSK; and

- a Quadrature Amplitude Modulation, QAM.

29. The first radio node (108-1 , 108-2; 1 10) of claim 27, wherein the nonlinear modulation is one out of:

- a Gaussian Minimum Shift Keying, GMSK;

- a Gaussian Frequency-Shift Keying, GFSK; and

- a Minimum-Shift Keying, MSK.

30. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-29, wherein one or more of the data symbols So,Si , ... ,Sk-i are training symbols. 31. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-30, wherein the n orthogonal code sequences comprise real values.

32. The first radio node (108-1 , 108-2; 1 10) of claim 31 , wherein the n orthogonal code sequences are comprised in an n by n Hadamard matrix.

33. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-32, wherein the n orthogonal code sequences comprise complex values.

34. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-33, being configured to transmit the signal comprising the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i by further being configured to:

- transmit the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in sequence using a single carrier; or

- transmit the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in parallel using a respective subcarrier in a multicarrier signal.

35. The first radio node (108-1 , 108-2; 1 10) of any one of claims 21-34, wherein the first radio node (108-1 , 108-2; 1 10) is configured to repeat n times of the sequence of data symbols So,Si ,... ,Sk-i by being configured to: - generate an n by k matrix, wherein each row is a copy of a sequence of data symbols So,Si ,... ,Sk-i , wherein n is the number of repetitions of the sequence of data symbols So,Si ,... ,Sk-i ; wherein the first radio node (108-1 , 108-2; 1 10) is configured to encode the n sequences of data symbols So,Si , ... ,Sk-i using n orthogonal code words by being configured to:

- encode the generated n by k matrix by performing element-wise matrix multiplication using an k/n times repeated n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein the encoding results in an encoded n by k matrix; wherein the first radio node (108-1 , 108-2; 1 10) is configured to provide the respective affix by being configured to:

- insert a cyclic prefix before the encoded n by k matrix, which cyclic prefix comprises one or more of the last n-1 columns of the encoded n by k matrix, wherein the inserting results in an n by (x+k) matrix, wherein x is the number of columns of the inserted cyclic prefix, or

- provide a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i ; and wherein the first radio node (108- 1 , 108-2; 1 10) is configured to transmit the respective affix and the respective sequence of data symbols So,Si ,... ,Sk-i by being configured to:

- transmit row wise the respective affix and the data symbols So,Si , ... ,Sk-i comprised in the n by (x+k) matrix.

36. A second radio node (1 10; 108-1 , 108-2) for decoding and extracting data symbols from a received signal, wherein the second radio node (1 10; 108-1 , 108-2) and a first radio node (108-1 , 108-2; 1 10) are operating in a wireless communications network (100), and wherein the second radio node (1 10; 108-1 , 108-2) is configured to:

- receive a signal from the first radio node (108-1 , 108-2; 1 10);

- remove an affix from the received signal resulting in n sequences of k received samples;

- stack the n sequences of k received samples;

- decode the stacked n sequences of k received samples using n orthogonal code sequences, wherein each code sequence comprises n code elements, wherein for each code sequence each of the n sequences of k received samples is multiplied to one out of the n code elements of the code sequence and wherein the multiplied sequences of received samples are subsequently added, and wherein the decoding results in n different decoded sequences of samples of length k each decoded sample

corresponding to one of the n applied code sequences; and

- extract a sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples.

37. The second radio node (1 10; 108-1 , 108-2) of claim 36, being configured to:

- reorder the n different decoded sequences of samples and possibly moving elements between the n different decoded sequences of samples to obtain n different decoded and reordered sequences of samples.

38. The second radio node (1 10; 108-1 , 108-2) of claim 36 or 37, being configured to:

- estimate n channel coefficients ho,hi , ... ,hn-i , wherein each one of the n different decoded sequences of samples corresponds to the sequence of data symbols So,Si ,... ,Sk-i multiplied by a respective channel coefficient.

39. The second radio node (1 10; 108-1 , 108-2) of any one of claims 36-38, being configured to:

- combine the n different decoded sequences of samples by performing a Maximum Ratio Combination, MRC, whereby the signal to noise ratio is increased.

40. The second radio node (1 10; 108-1 , 108-2) of any one of claims 36-39, wherein second radio node (1 10; 108-1 , 108-2) is configured to stack the n sequences of k received samples by being configured to:

- stack the n sequences of k received samples into a first n by k matrix; wherein second radio node (1 10; 108-1 , 108-2) is configured to decode the stacked sequences of k received samples using n orthogonal code sequences by being configured to:

- decode the first n by k matrix using an n by n orthogonal code matrix

comprising the n orthogonal code sequences, wherein each code sequence comprises n code elements and wherein the decoding results in a second n by k matrix; and wherein second radio node (1 10; 108-1 , 108-2) is configured to extract the sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples by being configured to:

- extract the sequence of data symbols So,Si ,... ,Sk-i from the second n by k matrix. 41. A computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out the method according to any one of claims 1-20.

42. A carrier comprising the computer program of claim 41 , wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

Description:
DECODING OF A SIGNAL COMPRISING ENCODED DATA SYMBOLS

TECHNICAL FIELD

Embodiments herein relate generally to a first radio node, a second radio node and to methods therein. In particular, embodiments relate to respective transmission and decoding of a signal comprising encoded data symbols. BACKGROUND

Communication devices such as terminals or wireless devices are also known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and/or mobile stations. Such terminals are enabled to communicate wirelessly in a wireless communication system or a cellular communications network, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the wireless communications network.

The above terminals or wireless devices may further be referred to as mobile telephones, cellular telephones, laptops, or tablets with wireless capability, just to mention some further examples. The terminals or wireless devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle- mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.

The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. an "eNB", an "eNodeB", a "NodeB", a "B node", or a Base Transceiver Station (BTS), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated at the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals or wireless devices within range of the base stations. In the context of this disclosure, the expression

Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.

A Universal Mobile Telecommunications System (UMTS) is a third generation (3G) telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code-division multiple access (WCDMA) and/or High-Speed Packet Access (HSPA) for user equipment. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third and higher generation networks, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several radio network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a Base Station Controller (BSC), which supervises and coordinates various activities of the plural radio network nodes connected thereto. This type of connection is sometimes referred to as a backhaul connection. The RNCs and BSCs are typically connected to one or more core networks.

Specifications for the Evolved Packet System (EPS), also called a Fourth

Generation (4G) network, have been completed within the 3GPP and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long-Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E- UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio network nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of an RNC are distributed between the radio network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially "flat" architecture comprising radio network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E- UTRAN specification defines a direct interface between the radio network nodes, this interface being denoted the X2 interface.

In the 3GPP LTE, base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks. The 3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.

Multi-antenna techniques may significantly increase the data rates and reliability of 5 a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO systems.

10 A single carrier transmission means that one Radio Frequency (RF) carrier is used to carry the data to be transmitted. Hence data in the form of bits is carried by one single RF carrier. A single carrier modulation is a modulation wherein data is modulated on a single Radio frequency (RF) carrier frequency. Single carrier modulations typically exhibit low Peak to Average Power Ratio (PAPR) and this property allows cost and power

15 efficient transmitter implementations since there is no need to use power amplifiers with high linearity requirements, and there is no need to back-off the power amplifier. Single carrier modulations are often used in communications networks with low to moderate data rates, such as Bluetooth or Zigbee, but are also employed in high data rate

communications networks, such as LTE uplink. Single carrier modulations are also

20 appealing in new broadband wireless technologies like Visible Light Communications (VLC), again due to the low PAPR, as well as their ease of implementation.

Many broadband and Internet of Things (loT) wireless communications technologies incorporate coverage enhancements as essential features in order to widen their appeal and applicability. For example, the IEEE 802.1 1 ax standard, the IEEE

25 802.1 1ah standard, the Bluetooth Long Range (BLR), the Narrow Band loT (NB-loT), and the extended Coverage GSM (EC-GSM) provide extended coverage modes. Repetition codes are easy to implement as a means to enhance other channel codes, and sometimes they are essential components of a communications chain intended to provide extended coverage. By the expression "extended coverage" when used in this disclosure

30 is meant that measures have been taken to allow a device to communicate with the

network at lower received signal levels than in normal coverage (i.e., how the system was originally designed to operate). For example, when catering for devices in extended coverage, one common measure to take is to let the transmitter blindly repeat the transmitted information without waiting for an acknowledgement from the receiver. If the

35 procedure on how the repetitions have been performed is known to the receiver, it can make use of that knowledge to maximize processing gain, and improve probability of decoding the transmitted information. Furthermore, repetitions can be useful for low power transmitters such as those found in e.g. backscattering radios.

Time dispersion on the radio channel as well as in filters in both the transmitter and receiver causes Inter-Symbol Interference (ISI), meaning that each received sample is a weighted sum of several transmitted symbols. The ISI is conventionally handled by an equalizer that attempts to resolve, e.g. extract, the transmitted symbols. Alternatively, non-coherent modulation/demodulation can be used. Radio channels with time

dispersions is sometimes referred to as time dispersive radio channels or just time dispersive channels.

As mentioned above, an equalizer may be used to handle the ISI and to extract the transmitted symbols. However, equalization usually involves a high computational complexity. Suboptimal equalization algorithms exist with lower complexity at the cost of reduced performance. Further, prior to equalization, an estimation of the channel impulse response is needed, which requires that a number of consecutive training symbols are needed in the transmitted data. Since the number of training symbols does not scale with the number of useful data symbols, the overhead can be significant if a small number of useful data symbols is desired (allowing more repetitions in the same time period). Low complexity equalization is often a requirement in low end loT devices, where low cost and low energy consumption are of great importance.

Non-coherent modulation techniques are well suited for low complexity receivers, since the equalization process is greatly simplified, but the price is a non-negligible loss in link performance.

SUMMARY

According to developments of wireless communications networks improved modulation and demodulation methods are needed for improving the performance of the wireless communications network.

An object of embodiments herein is to address at least some drawbacks with the prior art and to improve the performance in the wireless communications network. For example, an object is to provide modulation and demodulation methods suitable for extended coverage in a single carrier wireless communications network, which modulation and demodulation methods provide good link performance with low computational complexity. According to one aspect of embodiments herein, the object is achieved by a method performed by a first radio node for transmitting a signal comprising encoded data symbols to a second radio node. The first radio node and the second radio node are operating in a wireless communications network.

The first radio node repeats n times a sequence of data symbols So,Si ,... ,Sk-i to be transmitted, wherein k is a multiple of n.

Further, the first radio node encodes the n sequences of data symbols

So,Si ,... ,Sk-i using n orthogonal code sequences, wherein each code sequence comprises n code elements.

Furthermore, the first radio node transmits, to the second radio node, a signal comprising the respective encoded sequence of data symbols So,Si ,... ,Sk-i and an optional respective affix for separating two encoded sequences of data symbols So,Si ,... ,Sk-i .

According to another aspect of embodiments herein, the object is achieved by a first radio node for transmitting a signal comprising encoded data symbols to a second radio node. The first radio node and the second radio node are configured to operate in a wireless communications network.

The first radio node is configured to repeat n times a sequence of data symbols

So,Si ,... ,Sk-i to be transmitted, wherein k is a multiple of n.

Further, the first radio node is configured to encode the n sequences of data symbols So,Si ,... ,Sk-i using n orthogonal code sequences, wherein each code sequence comprises n code elements.

Furthermore, the first radio node is configured to transmit, to the second radio node, a signal comprising the respective encoded sequence of data symbols

So,Si ,... ,Sk-i and an optional respective affix for separating two encoded sequences of data symbols So,Si ,... ,Sk-i . According to another aspect of embodiments herein, the object is achieved by a method performed by a second radio node for decoding and extracting data symbols from a signal received from a first radio node. The second radio node and the first radio node are operating in a wireless communications network. The second radio node receives a signal from the first radio node and removes an affix from the received signal resulting in n sequences of k received samples.

Further, the second radio node stacks the n sequences of k received samples.

Furthermore, the second radio node decodes the stacked n sequences of k received samples using n orthogonal code sequences, wherein each code sequence comprises n code elements. For each code sequence, the second radio node multiplies each of the n sequences of k received samples to one out of the n code elements of the code sequence. The second radio node subsequently adds the multiplied sequences of received samples. The decoding results in n different decoded sequences of samples of length k each decoded sequence of samples corresponding to one of the n applied code sequences.

Yet further, the second radio node extracts a sequence of data symbols

So,Si ,... ,Sk-i from the n different decoded sequences of samples. According to another aspect of embodiments herein, the object is achieved by a second radio node for decoding and extracting data symbols from a signal received from a first radio node. The second radio node and the first radio node are configured to operate in a wireless communications network.

The second radio node is configured to receive a signal from the first radio node and removes an affix from the received signal resulting in n sequences of k received samples.

Further, the second radio node is configured to stack the n sequences of k received samples.

Furthermore, the second radio node is configured to decode the stacked n sequences of k received samples using n orthogonal code sequences, wherein each code sequence comprises n code elements. For each code sequence, the second radio node is configured to multiply each of the n sequences of k received samples to one out of the n code elements of the code sequence. The second radio node is configured to subsequently add the multiplied sequences of received samples. The decoding results in n different decoded sequences of samples of length k each decoded sequence of samples corresponding to one of the n applied code sequences.

Yet further, the second radio node is configured to extract a sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples. According to another aspect of embodiments herein, the object is achieved by a computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out the method performed by the first radio node.

According to another aspect of embodiments herein, the object is achieved by a computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out the method performed by the second radio node.

According to another aspect of embodiments herein, the object is achieved by a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer readable storage medium. Since the first radio node transmits n times repeated sequences of data symbols

So,Si ,... ,Sk-i that have been encoded using n orthogonal code sequences, and since the second radio node uses the n orthogonal code sequences when extracting the transmitted data symbols, the inter-symbol interference is resolved without the need of equalization and channel estimation. Thereby providing a simplified procedure. This results in an improved performance in the communications network.

Thus, an advantage with embodiments herein is that the need for equalization is eliminated, enabling a low complexity receiver, but preserving the performance of receivers using computationally complex coherent equalization and demodulation.

Another advantage with embodiments herein is that the number of training symbols may be reduced, giving a lower overhead and increasing the spectrum efficiency.

BRIEF DESCRIPTION OF DRAWINGS

Examples of embodiments herein are described in more detail with reference to attached drawings in which:

Figure 1 schematically illustrates embodiments of a wireless communications network; Figure 2 is a flowchart schematically illustrating embodiments of a method performed by a first radio node;

Figure 3 is a block diagram schematically illustrating embodiments of a first radio node; Figure 4 is a flowchart schematically illustrating embodiments of a method performed by a second radio node;

Figure 5 is a block diagram schematically illustrating embodiments of a second radio node;

Figure 6 schematically illustrates a vector with data symbols to be transmitted and a code matrix;

Figure 7 is a matrix schematically illustrating repeated data symbols;

Figure 8 is a matrix schematically illustrating encoded data symbols;

Figure 9 is a matrix schematically illustrating a cyclic prefix added to the encoded data symbols;

Figure 10 is a vector schematically illustrating the transmitted symbol sequence;

Figure 11 schematically illustrates a received signal comprising delayed versions of the transmitted symbol sequence;

Figure 12 schematically illustrates the received samples after removal of a cyclic prefix; Figure 13 is a matrix schematically illustrating the stacked received samples;

Figure 14A shows a matrix and a vector schematically illustrating the result after decoding with a first code word;

Figure 14B shows a matrix and a vector schematically illustrating the result after decoding with a second code word;

Figure 14C shows a matrix and a vector schematically illustrating the result after decoding with a third code word;

Figure 14D shows a matrix and a vector schematically illustrating the result after decoding with a fourth code word;

Figure 15 shows matrices and vectors schematically illustrating the result after sorting of the decoded sequences; and

Figure 16 schematically illustrates Maximum Ratio Combining.

DETAILED DESCRIPTION

According to developments of wireless communications networks improved modulation and equalization methods are needed for improving the performance of the wireless communications network.

An object of embodiments herein is therefore how to provide an improved performance in a wireless communications network. In embodiments disclosed herein, an orthogonal code is applied, by a transmitter, to symbols of a repeated transmission. By the term "orthogonal code" when used in this disclosure is meant that each code word is orthogonal to all other code words, i.e., that the scalar product between any two code words is zero. Further, different code sequences are applied to different repetitions of the transmission. An affix, e.g. a cyclic prefix, may be added to each repetition and the repetitions are transmitted in sequence. At the receiver side, the code is used when combining the repeated blocks. Different code sequences are used to extract different transmitted symbols. The inter-symbol interference will be resolved in the decoding process and thereby the need for equalization and multi-tap channel estimation is eliminated. From the decoding process one diversity branch for each channel tap in the time-dispersive channel is obtained when assuming that the number of channel taps is not larger than the number of coded repetitions. To combine the diversity branches, a Maximum Ratio Combining (MRC) may be used.

In this disclosure the "channel tap" is sometimes referred to as a "channel coefficient", and it should be understood that the terms "channel tap" and "channel coefficient" may be used interchangeably.

Note that although terminology from 3GPP LTE is used in this disclosure to exemplify the embodiments herein, this should not be seen as limiting the scope of the embodiments herein to only the aforementioned system. Other wireless systems, such as for example 5G, Wideband Code-Division Multiple Access (WCDMA), Worldwide

Interoperability for Microwave Access (WMax), Ultra-Mobile Broadband (UMB) and GSM, may also benefit from exploiting the ideas covered within this disclosure.

In this section, the embodiments herein will be illustrated in more detail by a number of exemplary embodiments. It should be noted that these embodiments are not mutually exclusive. Components from one embodiment may be assumed to be present in another embodiment and it will be obvious to a person skilled in the art how those components may be used in the other exemplary embodiments.

Further, the description frequently refers to wireless transmissions in the downlink, but embodiments herein are equally applicable in the uplink.

Figure 1 depicts an example of the wireless communications network 100 in which embodiments herein may be implemented. The wireless communications network 100 is a wireless communication network such as a New radio (NR) network, a 5G network, a GSM EDGE Radio Access Network (GERAN) network, an LTE network, a WCDMA network, a GSM network such as an Extended Coverage (EC) GSM, any 3GPP cellular network, a WiMAX network, a Wireless Local Area Network (WLAN), a Bluetooth communications network such as a Bluetooth Long Range (BLR) communications network, a NB-loT communications network, or any wireless or cellular network/system.

The wireless communications network 100 may be a wireless communications network providing extended coverage.

Some embodiments disclose modulation and demodulation methods for single carrier modulation wireless communications network operating in extended coverage mode. Thus, the wireless communications network 100 may be a wireless

communications network operating in extended coverage mode and applying single carrier modulation.

Some embodiments disclosed herein may be applied to any wireless

communications network using single carrier linear or linearizable modulations, such as Gaussian Frequency-Shift Keying (GFSK), Gaussian Minimum Shift Keying (GMSK) or Offset Quadrature Phase-Shift Keying (OQPSK), employed in Bluetooth, DECT, GSM and Zigbee.

Further, it should be understood that some embodiments may be applied in new and emerging fields of wireless communications networks such as in light

communications network. Thus, the wireless communications network 100 may be a light communications network.

A core network 102 may be comprised in the wireless communications network 100. The core network 102 is a wireless core network such as a NR core network, a 5G core network, GERAN core network, an LTE core network, e.g. an Evolved Packet Core (EPC); a WCDMA core network; a GSM core network; any 3GPP core network; WMAX core network; or any wireless or cellular core network.

A core network node 104 may operate in the core network 102. The core network node 104 may be an Evolved Serving Mobile Location Centre (E-SMLC), a Mobile Switching Centre (MSC), a Mobility-Management Entity (MME), an Operation and Maintenance (O&M) node, a Serving GateWay (S-GW), a Serving General Packet-Radio Service (GPRS) Node (SGSN), etc.

A first radio node 108-1 , 108-2; 110 and a second radio node 110; 108-1 ,108-2 are operating in the wireless communications network 100. In this disclosure the first radio node 108-1 , 108-2; 110 is acting as a transmitter, e.g. as a transmitting node, and the second radio node 1 10; 108-1 , 108-2 is acting as a receiver, e.g. as a receiving node. However, it should be understood that the second radio node may be the transmitter and that the first radio node may be the receiver. Thus, both the first and second radio nodes may be configured with functionality to act as both a transmitter and a receiver. In case the first radio node 108-1 , 108-2; 110 is a base station, e.g. an eNB, 108-1 or a WLAN AP 108-2, the second radio node 1 10; 108-1 , 108-2 is a wireless device 1 10, and vice versa.

The first radio node 108-1 , 108-2 may serve the second radio node 1 10 when located within an area, e.g. a first serving area 108a-1 , 108a-2. The first radio node 108- 1 , 108-2 may be a transmission and reception point e.g. a radio access network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of

communicating with a wireless device within the service area served by the access point depending e.g. on the first radio access technology and terminology used. The first radio node 108 may be referred to as a serving radio network node and communicates with a wireless device with Downlink (DL) transmissions to the wireless device and Uplink (UL) transmissions from the wireless device. Other examples of the first radio node 108 are Multi-Standard Radio (MSR) nodes such as MSR BS, network controllers, Radio Network Controllers (RNCs), Base Station Controllers (BSCs), relays, donor nodes controlling relay, Base Transceiver Stations (BTSs), Access Points (APs), transmission points, transmission nodes, Remote Radio Units (RRUs), Remote Radio Heads (RRHs), nodes in Distributed Antenna System (DAS), etc. In case of Device-to-Device communication, the first radio node may be a wireless device.

The second radio node 1 10 may be a wireless device, such as a mobile station, a non-Access Point (non-AP) STA, a STA, a user equipment (UE) and/or a wireless terminals, communicate via one or more Access Networks (AN), e.g. RAN, to one or more Core Networks (CN).

It should be understood by the skilled in the art that "wireless device" is a non- limiting term which means any terminal, communications device, wireless communication terminal, user equipment, Machine-Type Communication (MTC) device, Device-to-Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets, an Internet-of-Things (loT) device, e.g. a Cellular loT (CloT) device or even a small base station communicating within a service area.

In this disclosure the terms communications device, terminal, wireless device and UE are used interchangeably. Please note the term user equipment used in this document also covers other wireless devices such as Machine-to-Machine (M2M) devices, even though they do not have any user.

Methods e.g. for transmitting a signal comprising encoded data symbols in the wireless communications network 100, is performed by the first radio node 108-1 , 108-2; 1 10. Further, methods e.g. for decoding and extracting data symbols from a signal received from the first radio node108-1 , 108-2; 1 10 is performed by the second radio node 1 10; 108-1 , 108-2. As an alternative, a Distributed Node (DN) and functionality, e.g. comprised in a cloud 106 as shown in Figure 1 may be used for performing or partly performing the methods.

Examples of methods performed by the first radio node 108-1 , 108-2; 1 10 for transmitting a signal comprising encoded data symbols to the second radio node 1 10; 108-1 , 108-2 will now be described with reference to flowchart depicted in Figure 2. As previously mentioned, the first radio node 108-1 , 108-2; 1 10 and the second radio node 1 10; 108-1 , 108-2 are operating in the wireless communications network 100. Thus, the first radio node 108-1 , 108-2; 1 10 is acting as a transmitter and the second radio node 1 10; 108-1 , 108-2 is acting as a receiver. However, it should be understood that the second radio node may be the transmitter and that the first radio node may be the receiver. In case the first radio node is a base station e.g. an eNB, 108-1 or a WLAN AP 108-2, the second radio node is a wireless device 1 10, and vice versa.

Action 201

The first radio node 108-1 , 108-2; 1 10 repeats n times a sequence of data symbols So,Si ,... ,Sk-i to be transmitted, wherein k is a multiple of n. The repetition is done in order to obtain extended coverage by transmitting the sequence of data symbols So,Si ,... ,Sk-i several times, i.e. n times, k should be a multiple of n in order to ensure that the inter-symbol interference from the cyclic prefix is orthogonal to the transmitted sequence of data. The data symbols So,Si ,... ,Sk-i may be data symbols from a symbol

constellation of a linear modulation or a non-linear modulation.

The linear modulation may be a Phase-Shift Keying (PSK), such as Binary PSK (BPSK), Quadrature PSK (QPSK) or 8PSK, or a Quadrature Amplitude Modulation (QAM) such as 16QAM, 32QAM, or 64QAM, just to give some examples.

The non-linear modulation may be one out of a Gaussian Minimum Shift Keying (GMSK), a Gaussian Frequency-Shift Keying (GFSK), and a Minimum-Shift Keying (MSK), just to give some examples.

In some embodiments, one or more of the data symbols So,Si ,... ,Sk-i are training symbols. For example, this may be the case when a phase/amplitude reference is needed, relative to which the information bearing data symbols are interpreted (demodulated), and thereby coherent demodulation is achieved.

Embodiments described herein may be realized using matrices. In such embodiments, the first radio node 108-1 , 108-2; 1 10, when repeating n times the sequence of data symbols So,Si ,... ,Sk-i , generates an n by k matrix, wherein each row is a copy of a sequence of data symbols So,Si ,... ,Sk-i , wherein n is the number of repetitions of the sequence of data symbols So,Si ,... ,Sk-i .

Figure 6 schematically illustrates a vector with data symbols So,Si ,... ,S7 to be transmitted and a code matrix. Figure 6 will be described in more detail below.

Figure 7 is a matrix schematically illustrating n=4 times repeated data symbols

So,Si ,... ,S7. Figure 7 will be described in more detail below. Action 202

The first radio node 108-1 , 108-2; 1 10 encodes the n sequences of data symbols So,Si ,... ,Sk-i using n orthogonal code sequences, wherein each code sequence comprises n code elements.

In some embodiments, the first radio node 108-1 , 108-2; 1 10 encodes the n sequences of data symbols So,Si ,... ,Sk-i by element-wise multiplying one code sequence out of the n orthogonal code sequences to the n times repeated data symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , ... , k-1].

In some embodiments, the first radio node 108-1 , 108-2; 1 10 encodes the n sequences of data symbols So,Si ,... ,Sk-i by repeatedly using the n orthogonal code sequences for the encoding of the n sequences of data symbols So,Si ,... ,Sk-i , wherein the n orthogonal code sequences are used k/n times each for encoding (each) n times repeated symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , ... , k-1],

The n orthogonal code sequences may comprise real values. In some

embodiments, the n orthogonal code sequences are comprised in an n by n Hadamard matrix. Alternatively, the n orthogonal code sequences comprise complex values.

In embodiments realized using the matrices, the the first radio node 108-1 , 108-2;

1 10 encodes the n sequences of data symbols So,Si ,... ,Sk-i using n orthogonal code words by encoding the generated n by k matrix by performing element-wise matrix multiplication using a k/n times repeated n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein the encoding results in an encoded n by k matrix.

Figure 8 is a matrix schematically illustrating encoded data symbols. In this example, the data symbols have been encoded using the code matrix of Figure 6. Figure 8 will be described in more detail below.

Action 203

The first radio node 108-1 , 108-2; 110 may provide the respective affix before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

In some embodiments, the first radio node 108-1 , 108-2; 1 10 provides the respective affix by inserting a respective cyclic prefix before the first data symbol So of each encoded sequence of data symbols So,Si , ... ,Sk-i , wherein the respective cyclic prefix comprises one or more of the last n-1 data symbols of the respective encoded sequence of data symbols So,Si ,... ,Sk-i .

In some alternative embodiments, the first radio node 108-1 , 108-2; 1 10 provides the respective affix by providing a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

In embodiments realized using the matrices, the the first radio node 108-1 , 108-2; 1 10 provides the respective affix by inserting a cyclic prefix before the encoded n by k matrix, which cyclic prefix comprises one or more of the last n-1 columns of the encoded n by k matrix, wherein the inserting results in an n by (x+k) matrix, wherein x is the number of columns of the inserted cyclic prefix. Alternatively, the the first radio node 108-1 , 108-2; 1 10 provides the respective affix by providing a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

Figure 9 is a matrix schematically illustrating a cyclic prefix added to the encoded data symbols. In this example, the cyclic prefix corresponds to the last n-1 (n=4) = 3 5 columns of the matrix shown in Figure 8. Figure 9 will be described in more detail below.

Action 204

The first radio node 108-1 , 108-2; 1 10 transmits, to the second radio node 1 10; 108-1 , 108-2, a signal comprising the respective encoded sequence of data symbols

10 So,Si ,... ,Sk-i and an optional respective affix for separating two encoded sequences of data symbols So,Si ,... ,Sk-i .

In some alternative embodiments, the first radio node 108-1 , 108-2; 1 10 transmits the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in sequence using a single carrier. Alternatively, the first radio node 108-1 , 108-2; 110 15 transmits the respective affix and the respective encoded sequence of data symbols

So,Si ,... ,Sk-i in parallel using a respective subcarrier in a multicarrier signal.

The first radio node 108-1 , 108-2; 1 10 transmits the respective sequence of data symbols So,Si ,... ,Sk-i by further performing one or more out of: pulse shaping; digital to analog conversion; up-conversion to radio frequency; and power amplification.

20 In embodiments realized using the matrices, the the first radio node 108-1 , 108-2;

110 transmits the respective affix and the respective sequence of data symbols

So,Si ,... ,Sk-i by transmitting row wise the respective affix and the data symbols

So,Si ,... ,Sk-i comprised in the n by (x+k) matrix.

Figure 10 is a vector schematically illustrating an example of a transmitted symbol 25 sequence. The underlined symbols correspond to symbols of the cyclic prefix. Figure 10 will be described in more detail below.

To perform the method for transmitting a signal comprising encoded data symbols to the second radio node 1 10; 108-1 , 108-2, the first radio node 108-1 , 108-2; 30 1 10 may comprise an arrangement depicted in Figure 3. As previously mentioned, the first radio node 108-1 , 108-2; 1 10 and the second radio node 1 10; 108-1 , 108-2 are configured to operate in the wireless communications network 100. Thus, the first radio node 108-1 , 108-2; 1 10 is acting as a transmitter and the second radio node 1 10; 108- 1 , 108-2 is acting as a receiver. However, it should be understood that the second radio node may be the transmitter and that the first radio node may be the receiver. In case the first radio node is a base station e.g. an eNB, 108-1 or a WLAN AP 108-2, the second radio node is a wireless device 1 10, and vice versa.

5

In some embodiments, the first radio node 108-1 , 108-2; 1 10 via an input and output interface 300 is configured to communicate with one or more second radio node 1 10; 108-1 , 108-2. The input and output interface 300 may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

10

The first radio node 108-1 , 108-2; 1 10 is configured to receive, e.g. by means of a receiving module 301 configured to receive, transmissions from one or more second radio nodes 1 10; 108-1 , 108-2. The receiving module 301 may be implemented by or arranged in communication with a processor 307 of the first radio node 108-1 , 108-2; 15 1 10. The processor 307 will be described in more detail below.

The first radio node 108-1 , 108-2; 1 10 is configured to transmit, e.g. by means of a transmitting module 302 configured to transmit, transmit, to the second radio node 1 10; 108-1 , 108-2, a signal comprising a respective encoded sequence of data symbols

20 So,Si ,... ,Sk-i and an optional respective affix for separating two encoded sequences of data symbols So,Si ,... ,Sk-i . The transmitting module 302 may be implemented by or arranged in communication with the processor 307 of the first radio node 108-1 , 108-2; 1 10.

As previously mentioned, the data symbols So,Si ,... ,Sk-i may be data symbols 25 from a symbol constellation of a linear modulation or a non-linear modulation.

The linear modulation may be a PSK, such as BPSK, PSK, a QPSK or an 8PSK, or a QAM such as 16QAM, 32QAM, or 64QAM, just to give some examples.

The non-linear modulation may be one out of a GMSK, a GFSK, and a MSK, just to give some examples.

30 In some embodiments, one or more of the data symbols So,Si ,... ,Sk-i are

training symbols.

In some embodiments, the first radio node 108-1 , 108-2; 1 10 is configured to transmit the signal comprising the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i by further being configured to transmit the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in sequence using a single carrier; or to transmit the respective affix and the respective encoded sequence of data symbols So,Si ,... ,Sk-i in parallel using a respective subcarrier in a multicarrier signal.

5 The first radio node 108-1 , 108-2; 1 10 may further be configured to transmit to the respective sequence of data symbols So,Si , ... ,Sk-i by further being configured to perform one or more out of: pulse shaping; digital to analog conversion; up-conversion to radio frequency; and power amplification.

In embodiments realized using the matrices, the first radio node 108-1 , 108-2; 10 1 10 is configured to transmit the respective affix and the respective sequence of data symbols So,Si ,... ,Sk-i by being configured to transmit row wise the respective affix and the data symbols So,Si , ... ,Sk-i comprised in the n by (x+k) matrix.

The first radio node 108-1 , 108-2; 1 10 is configured to repeat, e.g. by means of a 15 repeating module 303 configured to repeat, n times a sequence of data symbols

So,Si ,... ,Sk-i to be transmitted, wherein k is a multiple of n. The repeating module 303 may be implemented by or arranged in communication with the processor 307 of the first radio node 108-1 , 108-2; 1 10.

In embodiments realized using the matrices, the first radio node 108-1 , 108-2;

20 1 10 is configured to repeat n times of the sequence of data symbols So,Si ,... ,Sk-i by being configured to generate an n by k matrix, wherein each row is a copy of a sequence of data symbols So,Si ,... ,Sk-i , wherein n is the number of repetitions of the sequence of data symbols So,Si ,... ,Sk-i .

25 The first radio node 108-1 , 108-2; 1 10 is configured to encode, e.g. by means of an encoding module 304 configured to encode, the n sequences of data symbols

So,Si ,... ,Sk-i using n orthogonal code sequences, wherein each code sequence comprises n code elements. The encoding module 304 may be implemented by or arranged in communication with the processor 507 of the first radio node 108-1 , 108-2; 30 1 10.

In some embodiments, the first radio node 108-1 , 108-2; 1 10 is configured to encode the n sequences of data symbols So,Si , ... ,Sk-i by further being configured to element-wise multiply one code sequence out of the n orthogonal code sequences to the n times repeated data symbol Si comprised in the n sequences of data symbols

So,Si ,... ,Sk-i , wherein i e [0, 1 , k-1].

In some embodiments, the first radio node 108-1 , 108-2; 1 10 is configured to 5 encode the n sequences of data symbols So,Si , ... ,Sk-i by further being configured to repeatedly use the n orthogonal code sequences for the encoding of the n sequences of data symbols So,Si ,... ,Sk-i , wherein the n orthogonal code sequences are used k/n times each for encoding (each) n times repeated symbol Si comprised in the n sequences of data symbols So,Si ,... ,Sk-i , wherein i e [0, 1 , k-1],

10 As previously mentioned, the n orthogonal code sequences may comprise real values. In some embodiments, the n orthogonal code sequences are comprised in an n by n Hadamard matrix. Alternatively, the n orthogonal code sequences comprise complex values.

In embodiments realized using the matrices, the first radio node 108-1 , 108-2; 15 1 10 is configured to encode the n sequences of data symbols So,Si , ... ,Sk-i using n

orthogonal code words by encoding the generated n by k matrix by performing element- wise matrix multiplication using a k/n times repeated n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein the encoding results in an encoded n by k matrix.

20

The first radio node 108-1 , 108-2; 1 10 may be configured to provide, e.g. by means of a providing module 305 configured to provide, the respective affix before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i . The providing module 305 may be implemented by or arranged in communication with the 25 processor 507 of the first radio node 108-1 , 108-2; 1 10.

In some embodiments, the first radio node 108-1 , 108-2; 1 10 is configured to provide the respective affix by further being configured to insert a respective cyclic prefix before the first data symbol So of each encoded sequence of data symbols So,Si , ... ,Sk-

1 , wherein the respective cyclic prefix comprises one or more of the last n-1 data

30 symbols of the respective encoded sequence of data symbols So,Si ,... ,Sk-i .

In some alternative embodiments, the first radio node 108-1 , 108-2; 1 10 is configured to provide the respective affix by further being configured to provide a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

In embodiments realized using the matrices, the first radio node 108-1 , 108-2; 1 10 is configured to provide the respective affix by being configured to insert a cyclic prefix before the encoded n by k matrix, which cyclic prefix comprises one or more of the last n-1 columns of the encoded n by k matrix, wherein the inserting results in an n by (x+k) matrix, wherein x is the number of columns of the inserted cyclic prefix.

Alternatively, the first radio node 108-1 , 108-2; 1 10 may be configured to provide the respective affix by being configured to provide a respective guard time period before the first data symbol So of each encoded sequence of data symbols So,Si ,... ,Sk-i .

The first radio node 108-1 , 108-2; 1 10 may also comprise means for storing data. In some embodiments, the first radio node 108-1 , 108-2; 1 10 comprises a memory 306 configured to store the data. The data may be processed or non-processed data and/or information relating thereto. The memory 306 may comprise one or more memory units. Further, the memory 306 may be a computer data storage or a semiconductor memory such as a computer memory, a read-only memory, a volatile memory or a non-volatile memory. The memory is arranged to be used to store obtained information, data, configurations, scheduling decisions, and applications, etc. to perform the methods herein when being executed in the first radio node 108-1 , 108-2; 1 10.

Embodiments herein for transmitting a signal comprising encoded data symbols to the second radio node 1 10; 108-1 , 108-2 may be implemented through one or more processors, such as the processor 307 in the arrangement depicted in Figure 3, together with computer program code for performing the functions and/or method actions of embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the first radio node 108-1 , 108-2; 1 10. One such carrier may be in the form of an electronic signal, an optical signal, a radio signal or a computer-readable storage medium. The computer- readable storage medium may be a CD ROM disc or a memory stick.

The computer program code may furthermore be provided as program code stored on a server and downloaded to the first radio node 108-1 , 108-2; 1 10. Those skilled in the art will also appreciate that the input/output interface 300, the receiving module 301 , the transmitting module 302, the repeating module 303, and the encoding module 304, and the providing module 305 above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the memory 306, that when executed by the one or more processors such as the processors in the first radio node 108-1 , 108-2; 1 10 perform as described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a System-on-a-Chip (SoC).

Examples of methods performed by the second radio node 110; 108-1 ,108-2 for decoding and extracting data symbols from a signal received from the first radio node 108-1 , 108-2; 1 10 will now be described with reference to flowchart depicted in

Figure 4. As previously mentioned, the first radio node 108-1 , 108-2; 1 10 and the second radio node 1 10; 108-1 , 108-2 are operating in the wireless communications network 100. Thus, the first radio node 108-1 , 108-2; 1 10 is acting as a transmitter and the second radio node 1 10; 108-1 , 108-2 is acting as a receiver. However, it should be understood that the second radio node may be the transmitter and that the first radio node may be the receiver. In case the first radio node is a base station e.g. an eNB, 108-1 or a WLAN AP 108-2, the second radio node is a wireless device 1 10, and vice versa.

The methods comprise one or more of the following actions. Thus one or more of the actions may be optional. It should be understood that the actions may be taken in any suitable order and that some actions may be combined.

Action 401

The second radio node 1 10; 108-1 , 108-2 receives a signal from the first radio node 108-1 , 108-2; 1 10. The signal may be a weighted sum of delayed versions of a signal transmitted from the first radio node 108-1 , 108-2; 1 10.

On the received signal, the second radio node 1 10; 108-1 , 108-2 may perform signal processing such as one or more out of: analog filtering, down-conversion to baseband, analog to digital conversion, and digital filtering. Figure 11 schematically illustrates an example of a received signal comprising delayed versions of the transmitted symbol sequence. Figure 1 1 will be described in more detail below. Action 402

The second radio node 1 10; 108-1 , 108-2 removes a possible affix from the received signal resulting in n sequences of k received samples. As previously mentioned, the affix is optional and thus the received signal may not comprise an affix and consequently the second radio node 1 10; 108-1 , 108-2 does not have to remove an affix. If the received signal comprises an affix, the affix is used to separate the sequences of received samples and is not part of the sequences of received samples that should be decoded, and therefore the affix should be removed.

Each received sample is a weighted sum of several data symbols due to ISI plus possible noise and interference.

Figure 12 schematically illustrates an example of the received samples after removal of a cyclic prefix. Figure 12 will be described in more detail below.

Action 403

The second radio node 1 10; 108-1 , 108-2 stacks the n sequences of k received samples. The reason for stacking the n sequences of k received samples is to align received samples corresponding to the same transmitted symbols, thereby simplifying subsequent processing performed per symbol position (the subsequent adding which will be described in Action 404 below).

As previously mentioned, embodiments described herein may be realized using matrices. In such embodiments, the second radio node 1 10; 108-1 , 108-2 stacks the n sequences of k received samples by stacking the n sequences of k received samples into a first n by k matrix.

Figure 13 is a matrix schematically illustrating an example of the stacked received samples. Figure 13 will be described in more detail below.

Action 404

The second radio node 1 10; 108-1 , 108-2 decodes the stacked n sequences of k received samples using n orthogonal code sequences, wherein each code sequence comprises n code elements. Further, for each code sequence each of the n sequences of k received samples is multiplied to one out of the n code elements of the code sequence and the multiplied sequences of received samples are subsequently added. Thereby, the decoding results in n different decoded sequences of samples of length k, wherein each decoded sequence of samples corresponds to one of the n applied code sequences.

5 In embodiments realized using the matrices, the second radio node 1 10; 108-1 ,

108-2 decodes the stacked sequences of k received samples using n orthogonal code sequences by decoding the first n by k matrix using an n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein each code sequence comprises n code elements. The decoding results in a second n by k matrix.

10 Figures 14A-14D shows matrices and vectors schematically illustrating the result after decoding with a first code word, a second code word, a third code word and a fourth code word, respectively. Figures 14A-14D will be described in more detail below.

Action 405

15 In some embodiments, the second radio node 1 10; 108-1 , 108-2 reorders the n different decoded sequences of samples and possibly moving elements between the n different decoded sequences of samples to obtain n different decoded and reordered sequences of samples.

Figure 15 shows matrices and vectors schematically illustrating the result after

20 sorting of the decoded sequences. Figure 15 will be described in more detail below.

Action 406

The second radio node 1 10; 108-1 , 108-2 extracts a sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples. The extracted

25 sequence of data symbols So,Si ,... ,Sk-i are the same sequence of data symbols as the one that was to be transmitted by the first radio node 108-1 , 108-2; 1 10 in Action 201 above. Thus, the signal received by the second radio node 1 10; 108-1 , 108-2 has been successfully decoded and the correct sequence of data symbols extracted.

In embodiments realized using the matrices, the second radio node 1 10; 108-1 ,

30 108-2 extracts the sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples by extracting the sequence of data symbols So,Si ,... ,Sk-i from the second n by k matrix. Action 407

In some embodiments, the second radio node 1 10; 108-1 , 108-2 estimates n channel coefficients ho,hi , ... ,hn-i , wherein each one of the n different decoded sequences of samples corresponds to the sequence of data symbols So,Si ,... ,Sk-i multiplied by a respective channel coefficient.

Each channel coefficient is a complex number corresponding to an amplification and a phase shift for one of the delayed versions of the transmitted symbol sequence (as illustrated in Figure 11). The channel coefficients may be estimated if one or a few of the data symbols are training symbols. The use of training symbols and their positions would typically be a predetermined part of the used transmission scheme. The alternative to using training symbols would be to use a differential modulation.

Differential modulation means that the relative phase (and possibly amplitude) changes between consecutive transmitted symbols is determined by the information bits to be communicated, thereby making an absolute phase/amplitude reference unnecessary.

Action 408

In some embodiments, the second radio node 1 10; 108-1 , 108-2 combines the n different decoded sequences of samples by performing a Maximum Ratio Combination, MRC, whereby the signal to noise ratio is increased. By the term "signal" when used here is meant the n reordered sequences, i.e. the rows of the matrix in the middle part of Figure 15. Thus, by performing a MRC the ratio between the signal strength of the n reordered sequences and noise is increased.

Figure 16 schematically illustrates Maximum Ratio Combining. Figure 16 will be described in more detail below.

Actions 407 and 408 described above may in some embodiments be seen as one possible way of performing Action 406 previously described. Thus, the extracting of the sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples may be performed by MRC combining the rows of the matrix. However, it should be understood that other possible ways may exist, such as just selecting one row and extracting the symbols from that row (estimating only the channel coefficient

corresponding to that row). To perform the method for decoding and extracting data symbols from a received signal, the second radio node 1 10; 108-1 , 108-2 may comprise an arrangement depicted in Figure 5. As previously mentioned, the first radio node 108-1 , 108-2; 1 10 and the 5 second radio node 1 10; 108-1 , 108-2 are configured to operate in the wireless

communications network 100. Thus, the first radio node 108-1 , 108-2; 1 10 is acting as a transmitter and the second radio node 1 10; 108-1 , 108-2 is acting as a receiver.

However, it should be understood that the second radio node may be the transmitter and that the first radio node may be the receiver. In case the first radio node is a base 10 station e.g. an eNB, 108-1 or a WLAN AP 108-2, the second radio node is a wireless device 1 10, and vice versa.

In some embodiments, the second radio node 1 10; 108-1 , 108-2 via an input and output interface 500 is configured to communicate with one or more first radio nodes 15 108-1 , 108-2; 1 10. The input and output interface 500 may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

The second radio node 1 10; 108-1 , 108-2 is configured to receive, e.g. by means of a receiving module 501 configured to receive, transmissions from the first radio node 20 108-1 , 108-2; 1 10. The receiving module 501 may be implemented by or arranged in

communication with a processor 511 of the second radio node 1 10; 108-1 , 108-2. The processor 51 1 will be described in more detail below.

The second radio node 1 10; 108-1 , 108-2 is configured to receive a signal from the first radio node 108-1 , 108-2; 1 10. As previously mentioned, the signal may be a 25 weighted sum of delayed versions of a signal transmitted from the first radio node 108- 1 , 108-2;1 10.

The second radio node 1 10; 108-1 , 108-2 may be configured to receive the signal by further being configured to perform signal processing such as one or more out of analog filtering, down-conversion to baseband, analog to digital conversion, and digital 30 filtering.

The second radio node 1 10; 108-1 , 108-2 is configured to transmit, e.g. by means of a transmitting module 502 configured to transmit, a transmission to the first radio node 108-1 , 108-2; 1 10. The transmitting module 502 may be implemented by or arranged 35 in communication with the processor 51 1 of the second radio node 1 10; 108-1 , 108-2. The second radio node 1 10; 108-1 , 108-2 is configured to remove, e.g. by means of a removing module 503 configured to remove, a possible affix from the received signal resulting in n sequences of k received samples. The removing module 503 may be implemented by or arranged in communication with the processor 51 1 of the second radio node 1 10; 108-1 , 108-2.

As previously mentioned, each received sample is a weighted sum of several data symbols (due to I SI) plus possible noise and interference. The second radio node 1 10; 108-1 , 108-2 is configured to stack, e.g. by means of a stacking module 504 configured to stack, the n sequences of k received samples;.

The stacking module 504 may be implemented by or arranged in communication with the processor 511 of the second radio node 1 10; 108-1 , 108-2.

Embodiments described herein may be realized using matrices. In such embodiments, the second radio node 1 10; 108-1 , 108-2 is configured to to stack the n sequences of k received samples by being configured to stack the n sequences of k received samples into a first n by k matrix.

The second radio node 1 10; 108-1 , 108-2 is configured to decode, e.g. by means of a decoding module 505 configured to decode, sequences of received samples. The decoding module 505 may be implemented by or arranged in communication with the processor 51 1 of the second radio node 1 10; 108-1 , 108-2.

The second radio node 1 10; 108-1 , 108-2 is configured to decode the stacked n sequences of k received samples using n orthogonal code sequences, wherein each code sequence comprises n code elements. Further, for each code sequence each of the n sequences of k received samples is multiplied to one out of the n code elements of the code sequence . The multiplied sequences of received samples are subsequently added, and the decoding results in n different decoded sequences of samples of length k each decoded sample corresponding to one of the n applied code sequences.

In embodiments realized using the matrices, the second radio node 1 10; 108-1 ,

108-2 is configured to decode the stacked sequences of k received samples using n orthogonal code sequences by being configured to decode the first n by k matrix using an n by n orthogonal code matrix comprising the n orthogonal code sequences, wherein each code sequence comprises n code elements. The decoding results in a second n by k matrix. The second radio node 1 10; 108-1 , 108-2 may be configured to reorder, e.g. by means of a reordering module 506 configured to reorder, decoded sequences of samples. The reordering module 506 may be implemented by or arranged in

communication with the processor 511 of the second radio node 1 10; 108-1 , 108-2.

The second radio node 1 10; 108-1 , 108-2 may be configured to reorder the n different decoded sequences of samples and possibly moving elements between the n different decoded sequences of samples to obtain n different decoded and reordered sequences of samples.

The second radio node 1 10; 108-1 , 108-2 is configured to extract, e.g. by means of an extracting module 507 configured to extract, a sequence of data symbols. The extracting module 507 may be implemented by or arranged in communication with the processor 51 1 of the second radio node 1 10; 108-1 , 108-2.

The second radio node 1 10; 108-1 , 108-2 is configured to extract a sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples.

In embodiments realized using the matrices, the second radio node 1 10; 108-1 , 108-2 is configured to extract the sequence of data symbols So,Si ,... ,Sk-i from the n different decoded sequences of samples by being configured to extract the sequence of data symbols So,Si ,... ,Sk-i from the second n by k matrix.

The second radio node 1 10; 108-1 , 108-2 may be configured to estimate, e.g. by means of an estimating module 508 configured to estimate, one or more channel coefficients. The estimating module 508 may be implemented by or arranged in communication with the processor 511 of the second radio node 1 10; 108-1 , 108-2.

The second radio node 1 10; 108-1 , 108-2 may be configured to estimate n channel coefficients ho,hi , ... ,hn-i , wherein each one of the n different decoded sequences of samples corresponds to the sequence of data symbols So,Si ,... ,Sk-i multiplied by a respective channel coefficient.

As previously mentioned, each channel coefficient is a complex number corresponding to an amplification and a phase shift for one of the delayed versions of the transmitted symbol sequence (as illustrated in Figure 11). The channel coefficients may be estimated if one or a few of the data symbols are training symbols. The use of training symbols and their positions would typically be a predetermined part of the used transmission scheme. As mentioned above, an alternative to using training symbols would be to use a differential modulation.

The second radio node 1 10; 108-1 , 108-2 may be configured to combine, e.g. by means of a combining module 509 configured to combine, decoded sequences of samples. The combining module 509 may be implemented by or arranged in

communication with the processor 511 of the second radio node 1 10; 108-1 , 108-2.

The second radio node 1 10; 108-1 , 108-2 may be configured to combine the n different decoded sequences of samples by performing a Maximum Ratio Combination, MRC, whereby the signal to noise ratio is increased.

The second radio node 1 10; 108-1 , 108-2 may also comprise means for storing data. In some embodiments, the second radio node 1 10; 108-1 , 108-2 comprises a memory 510 configured to store the data. The data may be processed or non-processed data and/or information relating thereto. The memory 510 may comprise one or more memory units. Further, the memory 510 may be a computer data storage or a

semiconductor memory such as a computer memory, a read-only memory, a volatile memory or a non-volatile memory. The memory is arranged to be used to store obtained information, data, configurations, scheduling decisions, and applications, etc. to perform the methods herein when being executed in the second radio node 110; 108-1 , 108-2.

Embodiments herein for decoding and extracting data symbols from a received signal may be implemented through one or more processors, such as the processor 511 in the arrangement depicted in Figure 5, together with computer program code for performing the functions and/or method actions of embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the second radio node 1 10; 108-1 , 108-2. One such carrier may be in the form of an electronic signal, an optical signal, a radio signal or a computer-readable storage medium. The computer-readable storage medium may be a CD ROM disc or a memory stick.

The computer program code may furthermore be provided as program code stored on a server and downloaded to the second radio node 1 10; 108-1 , 108-2.

Those skilled in the art will also appreciate that the input/output interface 500, the receiving module 501 , the transmitting module 502, the removing module 503, the stacking module 504, the decoding module 505, the reordering module 506, the extracting module 507, the estimating module 508, and the combining module 509 above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the memory 510, that when executed by the one or more processors such as the processors in the second radio node 1 10; 108- 1 , 108-2 perform as described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a System-on-a-Chip (SoC).

EXAMPLIFYING EMBODIMENT

In this section a step-by-step description of one embodiment of the coded repetition scheme is described and illustrated.

Introduction

A sequence of data symbols to be transmitted is illustrated in Figure 6. Also, a code matrix is given in Figure 6. In Figure 6 the grey shades are used to illustrate the four code words, e.g. rows, of the code matrix. In the example, the code matrix is a 4x4 Hadamard matrix, but any n by n orthogonal real- or complex valued code may be used. The size n of the code matrix shall be equal to the number of coded repetitions to be transmitted. The code words (rows) of the code matrix have been given different grey shades for illustrative purposes The number of data symbols is arbitrarily chosen to be k=8 but may be any multiple of n. The data symbols may be taken from the symbol constellation of any linear modulation. Non-linear modulations such as GFSK and GMSK may also be used but the description below assumes a linear modulation for simplicity. Non-linear modulations will be discussed in more detail below. Some of the data symbols may be training symbols. One or more actions relating to repetition, encoding, cyclic prefix, and transmission mentioned below are performed by the first radio node 108-1 , 108-2; 110 acting as a transmitter. Repetition

The data symbols are repeated n=4 times. This is illustrated as four rows in the matrix of Figure 7.

This relates to Action 201 previously described.

Encoding

The Hadamard code matrix of Figure 6 is applied symbol-wise, repeatedly. Each column, i.e. repeated symbol, in the matrix is multiplied (element-wise) by a code word, e.g. a row, of the code matrix. The grey shades in Figure 8 schematically illustrate the code words used for each column.

This relates to Action 202 previously described.

Cyclic prefix

As previously mentioned an optional affix may be added to separate two encoded sequences of data symbols So,Si ,... ,Sk-i . In this example, a cyclic prefix is added. The last n-1 columns of the matrix in Figure 8 are added before the matrix, as schematically illustrated in Figure 9. Since n=4 in this example, the three last columns of the matrix in Figure 9 is added.

This relates to Action 203 previously described.

Transmission

The symbols are transmitted sequentially, row by row in the matrix, as

schematically illustrated in Figure 10. The transmission may involve pulse shaping and one or more other regular transmitter functions.

This relates to Action 204 previously described.

One or more actions relating to reception, encoding, cyclic prefix removal, stacking, decoding, sorting and MRC mentioned below are performed by the second radio node 110; 108-1 , 108-2 acting as a receiver.

Reception

As previously mentioned, due to inter-symbol interference in filters, e.g. in the transmitter filter and/or in the receiver filter, and due to inter-symbol interference in the channel, the received signal will be a weighted sum of delayed versions of the signal, as schematically illustrated in Figure 11. The weights are the complex valued channel taps hi. Here it is assumed that the total channel length is n. In addition, there will be noise added (not illustrated).

This relates to Action 501 previously described.

Cyclic prefix removal

The cyclic prefix is removed and n sequences of received samples are extracted. The blocks in the lower end of Figure 12 schematically illustrate n=4 sequences of k=8 samples each. As mentioned above, each sample is a sum of delayed versions of the signal due to ISI.

This relates to Action 502 previously described.

Stacking

The n sequences of k received samples are stacked into a matrix. This is schematically illustrated in Figure 13, which figure illustrates a 4x8 matrix.

This relates to Action 503 previously described.

Decoding

The code words are applied row-wise and the rows are added. Figure 14A

schematically illustrates the result when the first code word +1 ,+1 ,+1 ,+1 has been applied. The rows are multiplied by +1 , +1 , +1 , +1 , respectively, and added. The sum is shown in the lower part of Figure 14A. Only symbols originally coded with the first code word are present while others have been cancelled. Note that the ISI is removed or rather resolved, since each ISI tap of the channel is represented by a different sample.

Similarly, the second, third and fourth code words are applied to extract the remaining data symbols, as illustrated in Figures 14B-14D.

This relates to Action 504 previously described.

Sorting

The n=4 different decoded sequences illustrated on the upper part in Figure 15 are sorted into a matrix as shown in the middle part of Figure 14. The n=4 times repeated signal transmitted over a channel with ISI of four symbols has been transformed into n=4 ISI-free signals as schematically illustrated in the lower part of Figure 15, each with n=4 times processing gain.

This relates to Action 505 previously described. Extracting

The data symbols So,Si , ... ,S7 is extracted from the ISI-free signal schematically illustrated in the lower part of figure 15.

5 This relates to Action 506 previously described.

Maximum Ratio Combining (MRC)

In presence of Additive White Gaussian Noise (AWGN), the SNR of the combined signal is maximized if the n signals are combined using the MRC. This means that the 10 signals should be coherently combined after each have been scaled with the square root of the SNR of the individual signal. Since the noise energy is the same in all n signals, this is equivalent to multiplication by the conjugate of the channel coefficient hi of each signal. This is schematically illustrated in Figure 16. Channel coefficients may be estimated if one or a few of the data symbols are training symbols. Since the ISI has been removed, 15 the channel estimation is straightforward.

This relates to Actions 507 and 508 previously described.

Other aspects

The scheme is applicable for any linear modulation, such as BPSK, 8PSK, 20 16QAM, etc. Since differentially encoded GMSK, GFSK, or MSK, may be approximately or exactly described as a linear modulation, the scheme may be applied to these modulations as well. Multiplications with the code (+1 , -1) is then replaced by XORing of bits. It is straightforward to add Rx antenna diversity to the scheme. The Rx branches are processed separately in the receiver and combined using MRC. The MRC between Rx 25 branches is done in the same way as the MRC between diversity branches created by the coded repetition scheme. Coded repetition may be combined with conventional blind transmissions and l/Q combining.

Exemplifying formal description of some embodiments

30 Below, the following notation is used:

a T denotes the transpose of vector (or matrix) a.

a H denotes the conjugate transpose of vector (or matrix) a.

a * denotes the (element-wise) conjugate of vector (or matrix) a.

35 Actions of the first radio node 108-1 , 108-2; 1 10, e.g. the transmitter Given k data symbols s = [¾ ■■■ s k-i] , and an n x n code matrix C = with orthogonal columns, where k is an

integer multiple of n, the transmitter performs the following steps:

Generate an x fc matrix R in which each row is a copy of s.

This relates to Action 201 previously described.

Encoding

Generate an x fc matrix

eo,o " ■ e 0,k-l

E =

-n-1,0 -n-l,fc-l

where e t j = r i j C i j mod n , i.e., R is multiplied element-wise with a repeated version of the code matrix C. E can also be written as

E =

T T] Γ - T T]

5 n-l c n-l J L 5 n c 0 5 2n-l c n-l J [%-η c 0

This relates to Action 202 previously described.

Cyclic prefix: Generate an n x (k + n— 1) matrix

e0,fc-n+l e 0,k-l -0,0 e 0,fc-l

P =

I e n-l,k-n+l e n-l,fc-l e n-l,0 e n-l,fc-lJ

I.e., the n— 1 last columns of E are concatenated with £\

This relates to Action 203 previously described.

Transmission

Transmit the symbols of P row-wise, as a sequence u of n(k + n— 1) symbols, using regular transmitter functions (pulse shaping, digital to analog conversion, up- conversion to radio frequency, power amplification, etc.)

This relates to Action 204 previously described. Actions of the second radio node 110: 108-1 , 108-2, e.g. the receiver

Reception

After regular receiver functions (analog filtering, down-conversion to baseband, analog to digital conversion, digital filtering, etc.), the received signal is represented by n(k + n)— 1 symbol-spaced complex samples v = [ v o " ' v n(k+n)-2] . Here it is assumed that the combined effect of filtering in the transmitter, time dispersion on the channel and filtering in the receiver can be expressed as v = u * h + n, where h =

[h Q ■■■ /i n--1 ] are the channel taps and n is a vector with noise samples.

This relates to Action 501 previously described.

Stacking (including removal of possible cyclic prefix)

Stack subsequences of v into an x fe matrix

I.e., n sequences of k samples are put in the rows of F, skipping the n— 1 first samples, the n - 1 last samples and n - 1 samples between every stored subsequence of v. Note that due to the cyclic prefix, F = h * E + N, where h is the channel, E are the encoded symbols, N is a matrix of AWGN samples with variance σ 2 and * denotes row-wise cyclic convolution.

This relates to Actions 502 and 503 previously described.

Decoding

Multiply F with the transpose of the code matrix C from left, giving the n x k matrix D = C T F = C T (h * E + N)

= T (h

+ C T N

= h

* [C T [s 0 c 0 T · · · C T [s n c 0 T · ·· s 2n _ 1 c n -i T ] · ·· cT k-nC 0 T - - ΐ - ]] + C T N

+ N'

where N' is a matrix of AWGN samples with variance ησ

This relates to Action 504 previously described.

Reordering

Generate a n x k matrix X by reordering the elements in D

where N" is the reordered version of N'.

It can be noted that the signal received on the time dispersive channel has been separated into n ISI-free signals (represented by the rows in X).

Thereafter, the sequence of data symbols may be extracted. One possible way of doing the extraction is explained by the "MRC combining" action, which requires the channel coefficients from a "Channel estimation" action.

This relates to Actions 505 and 506 previously described.

Channel estimation

Estimate the channel vector h. Since each channel tap impacts only one of the n signals, the channel estimation is straightforward. Using the weights h * implies that the n signals will be coherently combined, i.e., they are added constructively. Further, the magnitude of the weights will maximize the SNR of the combined signal. The channel coefficients can be estimated if one or a few of the data symbols s are training symbols.

This relates to Action 507 previously described.

MRC combining

Calculate

y = hX = nh * h T s + h * N" = n\\h\\ s + w where w is a vector of AWGN samples with variance n\\h\\ σ 2 . Note that the derived signal is the vector of transmitted symbols s, plus noise. Assuming that s has unit

II J ii 2

energy, the signal-to-noise ratio is n|1 J 1 , i.e., n times the signal-to-noise ratio of the received signal. A processing gain of n times has been achieved.

This relates to Action 508 previously described.

ABBREVIATIONS

AWGN Additive White Gaussian Noise

ISI Inter-Symbol Interference

MRC Maximum Ratio Combining

SNR Signal to Noise Ratio

When using the word "comprise" or "comprising" it shall be interpreted as non- limiting, i.e. meaning "consist at least of".

Modifications and other variants of the described embodiment(s) will come to mind to one skilled in the art having the benefit of teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the embodiment(s) herein is/are not be limited to the specific examples disclosed and that modifications and other variants are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.