Technical Field

The present invention relates generally to the field of wireless communication. More particularly, it relates to efficient spectrum utilization in network environments comprising multiple radio access technologies.

Background

Several technologies that today predominantly support very high data rates are not always well suited for IoT (Internet of Things), Energy Management, and Sensor applications which typically have applications that may operate with lower data rates and longer ranges. For this reason several standardization development organizations like 3GPP and IEEE are developing variants of their main stream technology that are optimized to support communication at longer range, but at lower data rate and also preferably having less power consumption.

Long Range Low Power (LRLP) is a new topic interest group within the IEEE 802.11 working group that aims at targeting the above features.

LRLP is typically expected to be based on technologies and features found in IEEE 802.1 lax (currently being standardized). This is in turn typically expected to speed up development of future LRLP products in order to put them on a commercial market as fast as possible. Thus, it is likely that an access point (AP) supporting 1 lax typically also should be able to support LRLP. Good coexistence between LRLP and 1 lax devices will thus be important.

For high data rate transmissions, such as in 802.1 lax, coherent reception is typically required. In order to achieve coherent reception, known symbols are transmitted together with the actual data. The known symbols, commonly referred to as pilots, pilot tones, pilot symbols or pilot signals (the terms may be used interchangeably in this disclosure), can then be used for frequency tracking and for channel estimation.

The known symbols may be sent in various ways. They may e.g. be sent over the full bandwidth of a channel which typically allows a receiver to e.g. perform channel estimation as well as estimation of parameters such as signal quality and signal strength.

In case a system is utilizing orthogonal frequency division multiplexing (OFDM), it is common to let some of the sub-carriers be used as pilot signals. These pilots are then typically used by e.g. a wireless communication device for phase tracking, which may be needed to compensate for phase noise or for residual frequency errors.

Currently, an 802.11 communication device may be using the tracking pilots to perform phase tracking during reception of the data field. This is typically important since the channel estimation is only performed using the preamble and not for every OFDM symbol in the data field. Estimation and compensation of the phase is then performed continuously in the data field. The actual channel can be estimated using the tracking pilots for single input, single output (SISO) and typically not for more than one transmitting antenna. The tracking pilot sequence is known by the communication device and specified in the 802.11 standard.

However, although 802.1 lax supports a relatively small bandwidth, i.e., about 2 MHz, this small bandwidth is still based on OFDM. One way to actually obtain better coverage is to typically increase the power spectrum density of the transmitted signal, which effectively translates into increasing the energy per transmitted information bit.

Furthermore, if 802.11 ax is used to support LRLP transmission by allocating proportionally higher power to one resource unit (RU) within a channel used for LRLP, the other RUs would typically have to be transmitted at reduced power in order to keep the overall transmitted power the same. Thus, concurrent operation of standard

802.1 lax and LRLP may result in degraded performance for 802.1 lax.

Patent application US 2004/0202142 Al describes a way of reducing pilot overhead and improving data rate by utilizing low order modulated data as substitute for pilot symbols during transmission. A user that is trying to receive a higher order modulation may detect low order transmissions and use them as pilot signals, thus reducing the overall amount of pilots. However, this solution is dependant on that there is a system with low order modulation nearby in order for the high data rate to be improved. This may, however, not always be the case. Thus there exist a need for methods and arrangements that enables smooth and efficient concurrent operation between systems operating at different data rates, e.g. an 8021 lax system and a LRLP system without negatively affecting the performance of either system. Summary

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

It is an object of some embodiments to mitigate at least some of the above disadvantages and to provide methods and arrangements of a an access point and a terminal operating in a wireless network which enables reliable communication in systems where terminals utilizing e.g. low order modulation, low data rates and/or low transmission power rates (e.g. IoT devices and LRLP terminals) operate concurrently with terminals operating with high order modulations, high data rates, and/or high transmission power rates (e.g. IEEE 8021 lax terminals).

According to a first aspect, this is achieved by a method of a network access point - AP - configured to support transmissions to one or more terminals of a first type in a wireless network, and transmissions to one or more terminals of a second type in the same wireless network.

The AP is configured to perform transmissions using at least one

communication channel having a bandwidth, wherein the bandwidth comprises a number of subcarriers.

The method comprises initiating a downlink transmission to at least one of the one or more terminals of the second type in the wireless network and allocating at least one of the number of subcarriers for data transmission to the at least one terminal of the second type.

The allocated at least one subcarrier may be decoded for use as a pilot symbol by the at least one terminal of the first type, wherein the allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type. The method also comprises performing the data transmission on the at least one allocated subcarrier.

In some embodiments, the first type of terminals may be configured to operate using orthogonal frequency division multiplexing - OFDM, and the second type of terminals may be configured to operate using single carrier modulation.

In some embodiments, the single carrier modulation may comprise binary modulation.

In some embodiments, the second type of terminal may be configured to operate using Gaussian frequency shift keying.

The first type of terminal may e.g. be wireless communication device operating according to IEEE 8021 lax. The second type of terminal may e.g. be a wireless communication device supporting IoT applications and/or be a LRLP terminal. The second type of terminal may e.g. comprise a receiver that is only capable of single carrier reception. The first type of terminal may e.g. comprise a receiver that is capable of OFDM reception.

In some embodiments, the down link transmission may also be initiated to at least one of the one or more terminals of the first type, and the method may further comprise, prior to initiating a down link transmission to the at least one terminal of the first type and to the at least one terminal of the second type, determining a suitable resource unit of a plurality of resource units comprised in the bandwidth for the downlink transmission, and allocating the determined resource unit to the at least one terminal of the first type.

In some embodiments, the allocated at least one of the number of subcarriers for data transmission to the at least one terminal of the second type is located within said determined resource unit to the at least one terminal of the first type.

Thus, transmission is made to the terminals of the first type and to the terminals of the second type concurrently and may furthermore be transmitted to the two types of terminals in the same RU.

Thus joint scheduling of the terminal of the first type and the terminal of the second type is enabled which may lead to improved spectrum efficiency. In some embodiments, the method may further comprise determining the suitable resource unit of the plurality of resource units based on at least one of a link quality between the AP and the at least one terminal of the first type and between the AP and the at least one terminal of the second type, and a total transmission time of the down link transmission.

The link quality may e.g. be measured in terms of signal strength, signal quality, channel congestion, delay etc. In some embodiments, the RU may be determined such that a total transmission time for both the terminal of the first type and the terminal of the second type is minimized.

In some embodiments, the method may further comprise allocating the at least one of the number of subcarriers such that the at least one subcarrier is a subcarrier which is not used for transmissions to the at least one terminal of the first type.

The allocated subcarrier may e.g. be a non-populated subcarrier in an IEEE 8021 lax system.

A non-populated subcarrier may e.g. be a subcarrier which during normal operation is not used for transmitting either data or pilot signals to the terminal of the first type.

The non-populated subcarriers are typically subcarriers that are left over when a bandwidth of a communication channel has been divided into a number of resource units, wherein each resource unit comprises a predetermined number of subcarriers. The number of non-populated subcarriers may typically vary depending on the number of resource units of the communication channel.

In some embodiments, the method may further comprise allocating only one subcarrier of the number of subcarriers to each of the one or more terminals of the second type and modulating the subcarrier using binary antipodal modulation.

The modulated subcarrier may carry a positive or a negative sign and is intended for being decoded by the at least one terminal of the first type for use as a pilot symbol based on the positive or negative sign.

Thus, every terminal of the second type within the network may be allocated to only one subcarrier each. If binary antipodal modulation is used to modulate the subcarrier it will be transmitted either with a positive or a negative sign. The terminal of the first type may determine the sign and then use the determination in order to use the subcarrier as if the subcarrier were a known symbol for use as pilot signal.

In some embodiments, the terminal of the first type may use non-data aided estimation when using the sub-carrier as a pilot signal and first raise the signal to the power of two to remove the sign of the signal.

In some embodiments, the method may further comprise allocating two subcarriers of the number of subcarriers to each of the one or more terminals of the second type for transmitting information or data to the at least one terminal of the second type, by letting one of the sub-carriers represent a logical one and let the other subcarrier represent a logical zero. The data transmission can in this case effectively be seen as frequency shift keying (FSK), where the data is transmitted using one of the two frequencies and where a logical one is transmitted using one of the frequencies and a logical zero is transmitted using the other frequency.

Both frequencies are received within the bandwidth of the at least one terminal of the second type for demodulation.

In this case, the subcarrier currently used for transmitting the respective FSK symbol is suitable for being decoded by the least one terminal of the first type for use as a pilot symbol, whereas the sub-carrier not currently used for transmitting the FSK symbol cannot be used as a pilot for the terminal of the first type.

Thus the terminal of the first type need to determine which of the two subcarriers is currently used before trying to use that one as a pilot.

The terminal of the first type may e.g. determine which of the two subcarriers contained the FSK symbol by comparing which of the two subcarriers comprises the most energy.

When the terminal of the first type has determined which of the subcarriers contained a FSK symbol to the terminal of the second type, the terminal of the first type may use the determined subcarrier as a pilot symbol in order to e.g. perform phase estimation.

In some embodiments, the method may further comprise boosting a transmission power of the allocated at least one subcarrier used for transmitting the FSK symbol to the at least one terminal of the second type. The power offset of the boosted transmission power may in some embodiments be set such that it is large enough to ensure reliable detection by the terminal of the second type. However, the power offset should not be so high that it affects the transmission power used for the subcarriers which only carry data to the terminals of the first type too much and thus possibly leads to a severe degradation of network performance. Since the total transmission power should be kept constant, increasing it for one subcarrier will mean decreasing it for another. The offset for a single sub-carrier should preferably not exceed 100%. Thus, the total power for the first type of terminal is not reduced by more than about 10% as the number of subcarriers for the second type of terminal is much smaller.

In some embodiments, a subcarrier which is adjacent to the at least one subcarrier allocated for the data transmission to the at least one terminal of the second type is allocated as guard band and is not used for transmitting data.

Thus, the data transmission for the terminal of the second type is additionally protected from interference from data transmissions intended to the terminals of the first type. Introducing guard bands may result in reduced data transmissions for the terminals of the first type. However this cost may be worthwhile since the overall spectrum efficiency is still kept high.

A second aspect is a method of a terminal configured to receive transmission using orthogonal frequency division multiplexing - OFDM - from a network access point - AP. The AP is configured to perform transmissions using at least one communication channel having a bandwidth, wherein the bandwidth comprises a number of subcarriers.

The method comprises receiving a downlink transmission initiated by the AP on at least one of the number of subcarriers, wherein the at least one of the number of subcarriers is allocated for data transmission to at least one terminal of a second type and decoding the allocated at least one subcarrier for use as a pilot symbol. The allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type.

In some embodiments, the second type of terminal is configured to operate using single carrier modulation. In some embodiments, the single carrier modulation comprises binary modulation.

In some embodiments, only one subcarrier of the number of subcarriers is allocated to each of the one or more terminals of the second type, wherein the subcarrier may be modulated using binary antipodal modulation. The modulated subcarrier carries a positive or a negative sign. The method may further comprise decoding the modulated subcarrier for use as a pilot symbol based on the positive or negative sign.

In some embodiments, two subcarriers of the number of subcarriers are allocated to each of the one or more terminals of the second type for transmitting information or data to the at least one terminal of the second type, by letting one of the sub-carriers represent a logical one and let the other sub-carrier represent a logical zero.

The data transmission can in this case effectively be seen as frequency shift keying (FSK), where the data is transmitted using one of the two frequencies for the respective FSK symbol. A logical one is transmitted using one of the frequencies and a logical zero is transmitted using the other frequency.

Both frequencies are received within the bandwidth of the at least one terminal of the second type for demodulation.

In this case, the subcarrier currently used for transmitting the respective FSK symbol is suitable for being decoded by the least one terminal of the first type for use as a pilot symbol, whereas the subcarrier not currently used for transmitting the FSK symbol cannot be used as a pilot for the terminal of the first type.

In some embodiments, the method may comprise determining which of the two subcarriers comprises more information in order to decode the subcarrier for use as a pilot symbol.

The terminal of the first type may e.g. determine which of the two subcarriers was used for transmitting a FSK symbol by comparing which of the two subcarriers comprises the most energy.

A third aspect is a computer program product comprising a computer readable medium, having thereon a computer program comprising program instructions. The computer program may be loadable into a data-processing unit comprising a memory and a processor and configured to cause execution of the method according to any of first and second aspects when the computer program is run by the data-processing unit.

A fourth aspect is an arrangement of a network access point - AP - configured to support transmissions to one or more terminals of a first type in a wireless network, and transmissions to one or more terminals of a second type in the same wireless network. The AP is configured to perform transmissions using at least one

communication channel having a bandwidth, wherein the bandwidth comprises a number of subcarriers.

The arrangement further comprises a controller configured to cause initiation of a downlink transmission to at least one of the one or more terminals of the second type in the wireless network and allocation of at least one of the number of subcarriers for data transmission to the at least one terminal of the second type. The allocated at least one subcarrier may be decoded for use as a pilot symbol by the at least one terminal of the first type, wherein the allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type.

The controller is further configured to cause performing of the data

transmission on the allocated at least one subcarrier.

In some embodiments, the first type of terminals may be configured to operate using orthogonal frequency division multiplexing - OFDM, and the second type of terminals may be configured to operate using single carrier modulation.

In some embodiments, the single carrier modulation may comprise binary modulation.

In some embodiments, the second type of terminals may be configured to operate using Gaussian frequency shift keying.

In some embodiments, the down link transmission may also be initiated to at least one of the one or more terminals of the first type, and the controller may further be configured to cause, prior to initiating the down link transmission to the at least one terminal of the first type and to the at least one terminal of the second type,

determination of a suitable resource unit of a plurality of resource units comprised in the bandwidth for the downlink transmission and allocation of the determined resource unit to the at least one terminal of the first type. In some embodiments, the allocated at least one of the number of subcarriers for data transmission to the at least one terminal of the second type is located within said determined resource unit to the at least one terminal of the first type.

In some embodiments, the controller may further be configured to cause determination of the suitable resource unit of the plurality of resource units based on at least one of a link quality between the AP and the at least one terminal of the first type and between the AP and the at least one terminal of the second type, and a total transmission time of the down link transmission.

In some embodiments, the controller may further be configured to cause allocation of the at least one of the number of subcarriers such that the at least one subcarrier is a subcarrier which is not used for transmissions to the at least one terminal of the first type.

In some embodiments, the controller is further configured to cause allocation of only one subcarrier of the number of subcarriers to each of the one or more terminals of the second type and cause modulation of the subcarrier using binary antipodal modulation. The modulated subcarrier carries a positive or a negative sign, and the modulated subcarrier is intended for decoding by the at least one terminal of the first type for use as a pilot symbol based on the positive or negative sign.

In some embodiments, the controller may be further configured to cause allocation of two subcarriers of the number of subcarriers to each of the one or more terminals of the second type for transmitting information or data to the at least one terminal of the second type, by letting one of the sub-carriers represent a logical one and let the other sub-carrier represent a logical zero.

The data transmission can in this case effectively be seen as frequency shift keying (FSK), where the data is transmitted using one of the two frequencies and where a logical one is transmitted using one of the frequencies and a logical zero is transmitted using the other frequency.

Both frequencies are received within the bandwidth of the at least one terminal of the second type for demodulation.

In this case, the subcarrier currently used for transmitting the respective FSK symbol is suitable for being decoded by the least one terminal of the first type for use as a pilot symbol, whereas the sub-carrier not currently used for transmitting the FSK symbol cannot be used as a pilot for the terminal of the first type.

Thus the terminal of the first type need to determine which of the two subcarriers currently comprises the FSK symbol before trying to use that one as a pilot.

The terminal of the first type may e.g. determine which of the two subcarriers was used for transmitting the FSK symbol by comparing which of the two subcarriers comprises the most energy.

In some embodiments, the controller may be further configured to cause boosting of a transmission power of the allocated at least one subcarrier used for the data transmission to the at least one terminal of the second type.

In some embodiments, the controller may be further configured to cause allocation of a subcarrier which is adjacent to the at least one subcarrier allocated for the data transmission to the at least one terminal of the second type as guard band not being used for transmitting data.

A fifth aspect is a network node comprising the arrangement according to the fourth aspect.

A sixth aspect is an arrangement of a terminal configured to receive

transmission using orthogonal frequency division multiplexing - OFDM - from a network access point - AP. The AP is configured to perform transmissions using at least one communication channel having a bandwidth, wherein the bandwidth comprises a number of subcarriers.

The arrangement further comprises a controller configured to cause reception of a downlink transmission initiated by the AP on at least one of the number of subcarriers, wherein the at least one of the number of subcarriers is allocated for data transmission to at least one terminal of a second type, and decoding of the allocated at least one subcarrier for use as a pilot symbol. The allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type.

In some embodiments, the second type of terminal may be configured to operate using single carrier modulation.

In some embodiments, the single carrier modulation may comprise binary modulation. In some embodiments, only one subcamer of the number of subcarriers is allocated to each of the one or more terminals of the second type, wherein the subcarrier is modulated using binary antipodal modulation. The modulated subcarrier carries a positive or a negative sign, and the controller may be further configured to cause decoding of the modulated subcarrier for use as a pilot symbol based on the positive or negative sign.

In some embodiments, two subcarriers of the number of subcarriers are allocated to each of the one or more terminals of the second type for transmitting information or data to the at least one terminal of the second type, by letting one of the subcarriers represent a logical one and let the other subcarrier represent a logical zero.

The data transmission can in this case effectively be seen as frequency shift keying (FSK), where the data is transmitted using one of the two frequencies for the respective FSK symbol, where a logical one is transmitted using one of the frequencies and a logical zero is transmitted using the other frequency.

Both frequencies are received within the bandwidth of the at least one terminal of the second type for demodulation.

In this case, the subcarrier currently used for transmitting the respective FSK symbol is suitable for being decoded by the least one terminal of the first type for use as a pilot symbol, whereas the sub-carrier not currently used for transmitting the FSK symbol cannot be used as a pilot for the terminal of the first type.

Thus the terminal of the first type need to determine which of the two subcarriers currently comprises the FSK symbol before trying to use that one as a pilot.

The terminal of the first type may e.g. determine which of the two subcarriers was used for transmitting the FSK symbol by comparing which of the two subcarriers comprises the most energy.

A seventh aspect is a terminal comprising the arrangement according to the sixth aspect.

In some embodiments, the second, fourth, fifth, sixth and seventh aspects may additionally share or have identically or corresponding features described for any of the aspects, and may additionally have features identical with or corresponding to any of the various features as explained above for the first aspect. An advantage of some embodiments is that spectrum resources are utilized in an efficient manner.

Another advantage of some of the embodiments is that efficient and concurrent transmission for different systems using different modulation orders is enabled.

Another advantage of some embodiments is that no additional spectrum is needed to support both terminals operating at higher data rates and terminals operating at lower data rates in the same system.

Another advantage of some embodiments is that latency may be reduced for terminals using a low modulation order and/or operating with low power relative to time multiplexing. Specifically, if the data to the first type of terminal and the second type of terminal respectively would instead be time multiplexed, i.e., sent one at a time, the transmission time may be doubled. In particular, when the data to the second type of terminal is sent, the spectrum efficiency may be very low as a relatively large bandwidth may be occupied to transmit a stream with low data rate. Brief Description of the Drawings

Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings, in which:

Fig. 1 is a schematic drawing illustrating an example network environment according to some embodiments;

Fig. 2 is a schematic drawing illustrating an example of how a communication channel may be divided into resource units with pilot tones according to some embodiments;

Fig. 3 is a flow chart illustrating an example method according to some embodiments;

Fig. 4 is a block diagram illustrating an example arrangement according to some embodiments;

Fig. 5 is a flow chart illustrating an example method according to some embodiments; Fig. 6 is a block diagram illustrating an example arrangement according to some embodiments;

Figs. 7A and 7B are schematic drawings illustrating example pilot symbols and data symbols in a channel according to some embodiments; and

Fig. 8 is a block diagram illustrating a computer program product according to some embodiments.

Detailed Description

In the following, embodiments will be described where concurrent

transmission to two or more different types of terminals is enabled.

It is to be noted, that the term terminal may in this disclosure be interpreted e.g. as a wireless communication device (such as a mobile phone, smartphone, tablet computer, laptop, a network station or the like).

In the same manner, the term access point (AP) may e.g. be a network node, an eNB, a base station or the like.

Furthermore, in this disclosure, the term wireless terminal and terminal may be used interchangeably.

Fig. 1 illustrates an example network 100 according to some embodiments. The network 100 comprises an access point 102 and four wireless terminals 103, 104, 105, 106 served by the access point 102. The circle 101 illustrates the coverage area for a system supporting high data rate and/or high order modulation, e.g. an IEEE 8021 lax system.

The wireless terminals 103, 104 may be of a first type that supports high data rate and/or high order modulation. The wireless terminals of the first type may e.g. be IEEE 8021 lax compatible terminals.

The wireless terminals 105, 106 may be of a second type that supports low data rates and/or low order modulation. The wireless terminals of the second type may e.g. be long range, low power terminals, and/or terminals operating with a receiver only supporting single carrier modulation. Note that the wireless terminals 105, 106 need not achieve an absolute long range, e.g. at very low power, and may also be located within the coverage area 101 of the high data rate system. A problem may arise when terminals of the first type is to be served by the same access point as terminals of the second type since they typically have such different requirements in range and data rate which may affect network performance and coverage. One simple way to actually obtain better coverage is to increase the power spectrum density of the transmitted signal, which effectively translates into increasing the energy per transmitted information bit. This will be beneficial for the terminals of the second type, but may have a negative impact on the terminals of the first type since if the transmission power is increased in one part it may need to be decreased in another (as elaborated on above in the background section).

One idea is to design the transmission to the terminals of the second type such that the transmitted signal effectively can be used both for transmitting data to the second type of terminals and serve as pilots for the first type of terminals. For 802.1 lax this translates into using the so called tracking pilots (also commonly referred to as pilot tones, pilot signals, pilot symbols) found at specific subcarriers in every OFDM symbol to transmit data in the downlink from an access point to terminals of the second type. At the same time, data may be transmitted to terminals of the first type, if there is anything to send. If there is nothing to send to terminals of the first type, the tracking pilots can still be used to transmit data to terminals of the second type.

This presents a way to embed a low rate data stream to a low data rate system in the transmissions to another high data rate system. The fixed pilot sequence may be replaced by modulated data symbols having a robust modulation.

The wireless terminals 103, 104 may e.g. share the channel by means of orthogonal frequency division multiple access (OFDMA).

The wideband bandwidth of a network channel using OFDMA is typically divided into a plurality of resource units (RUs) comprising a number of subcarriers.

Fig. 2 illustrates how a bandwidth may be divided into RUs and how the subcarriers may be allocated to the RUs along with the pilot tones. In Fig. 2 an IEEE 802.11 system using orthogonal frequency division multiplexing (OFDM) is assumed. The nominal channel bandwidth is 20 MHz, and a signal is generated using a 256 point inverse fast Fourier transform (IFFT). The spacing between the sub-carriers then becomes 20/256 MHz = 78.125 kHz. The duration of one OFDM symbol is 256/20 = 12.8 (not including the cyclic prefix (CP)).

For IEEE 802.11 ax it is proposed to use orthogonal frequency division multiple access (OFDMA) to allow simultaneous transmission to and from several terminals.

Depending on the amount of information to be transmitted to a terminal, the terminal may be allocated more or less of the total available bandwidth.

As seen in Fig. 2, RUs can comprise different amount of sub-carriers depending on their intended use for various applications.

Bandwidths 210, 220, 230 and 240 each illustrate different sizes of RUs.

The smallest amount of subcarriers making up a RU is 26 subcarriers. This is illustrated in bandwidth 210 by the nine resource units 211, 211a which comprise 26 sub-carriers each. Resource unit 21 la is divided by a group of unused tones (not shown), e.g. seven sub-carriers around DC (direct current) where DC is around zero Hertz. A 26 sub-carrier RU corresponds to a bandwidth of about 2 MHz (26*78.125 kHz = 2.031 MHz). Also present in bandwidth 210 is four non-populated tones 212 that are not used for any transmissions and comprise no energy.

Bandwidth 220 comprises five resource units 221 and 221a. Resource units 221 comprise 52-subcarriers each. Resource unit 221a comprises 26 subcarriers and is divided by a group of unused tones (not shown), e.g. seven tones around DC, and the band 220 further comprises four non-populated tones 222.

Bandwidth 230 comprises two resource units 231 comprising 206 sub-carriers each. Resource unit 231a comprises 26 subcarriers and is divided by a group of unused tones (not shown), e.g. around DC.

Bandwidth 240 comprises one resource unit 241 comprising 242 subcarriers.

Bandwidths 210, 220, 230, 240 usually have adjacent guard subcarriers (not shown) separating them from other bandwidths or channels.

In general, a RU may comprise 26 subcarriers (top row 210 in Fig. 2), 52 sub- carriers (second row 220 in Fig. 2), 206 subcarriers (third row 230 in Fig. 2) or 242 subcarriers (bottom row 240 in Fig. 1) which correspond to the entire bandwidth of the channel. Each RU comprises a number of pilot tones (arrows marked PT) that are present on one or more subcarriers within the RU. For instance, in the bandwidth 210 each RU 211 comprises two pilot tones which are located on two different subcarriers. In bandwidth 220, each RU 221 comprises four pilot tones located on four different subcarriers. In bandwidth 230, each RU 231 comprises four pilot tones located on four different subcarriers. In bandwidth 240 the RU 241 comprises six pilot tones located on six different subcarriers.

As an example, the wireless terminals 103, 104 of Fig. 1 may receive e.g. IEEE 8021 lax signals according to the appearance of Fig. 2.

In a typical high order modulation system, such as an IEEE 8021 lax system, the terminals are typically aware of on what subcarriers the pilot tones are located.

However, according to some embodiments, the subcarriers intended as pilot tones to the first type of terminals may instead be used for data transmission to the second type of terminals, leading to that the value of the subcarriers is unknown to the first type of terminals.

Fig. 3 illustrates an example method 300 of a network access point - AP - configured to support transmissions to one or more terminals of a first type in a wireless network, and transmissions to one or more terminals of a second type in the same wireless network.

The terminals of the first type may e.g. be the terminals 103, 104 as described in conjunction with any of the Figs. 1 and 2, and the second type of terminals may e.g. be the terminals 105, 106 as described in conjunction with any of the Figs. 1 and 2.

The AP may e.g. be AP described in conjunction with Fig. 1.

The AP is configured to perform transmissions using at least one

communication channel having a bandwidth (e.g. any of the bandwidths described in Fig. 2), wherein the bandwidth comprises a number of subcarriers. In some

embodiments, the bandwidth may further be divided into a plurality of resource units each comprising a number of subcarriers.

The method 300 starts in 301 where the AP initiates a downlink transmission to at least one of the one or more terminals of the second type in the wireless network. In 302 the AP allocates at least one of the number of subcarriers for data transmission to the at least one terminal of the second type, wherein the allocated at least one subcarrier may be decoded for use as a pilot symbol by the at least one terminal of the first type, and wherein the allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type.

In 303 the AP performs the data transmission on the allocated at least one subcarrier.

The first type of terminals may typically be configured to operate using orthogonal frequency division multiplexing - OFDM, and the second type of terminals may typically be configured to operate using single carrier modulation.

The method may be particularly beneficial when terminals being of Long Range, Low Power (LRLP) type are to operate in, or together with, an IEEE 8021 lax system.

In this disclosure, the term LRLP terminal may be used interchangeably with the term a terminal of the second type, or second type of terminal. It is however to be understood that a terminal of the second type is not limited to a LRLP terminal, but should be seen as terminal using low data rate and/or a low order modulation, e.g. binary phase shift keying (BPSK) or binary frequency shift keying (BFSK).

In the same manner, the term 8021 lax terminal may be used interchangeably with the term terminal of the first type or first type of terminal. It is however to be understood that a terminal of the first type is not limited to a 8021 lax terminal, but should be seen as a terminal using high data rate and/or a high order modulation such as e.g. quadrature phase shift keying (QPSK) or quadrature amplitude modulation (QAM), like 16-QAM , 64-QAM, or 256-QAM.

It can be noted that the introduction of LRLP in the above described manner is done with no additional spectrum being required for LRLP transmissions and with only a small additional complexity in the software implementation of the terminals not being LRLP terminals, so that decision directed estimation may be performed on subcarriers comprising data transmission to the LRLP terminals.

However, a legacy 802.1 lax terminal cannot receive modulated pilot tones in the above described way since a legacy terminal expects the pilot tones to be perfectly known. Thus, the AP is configured not to use subcarriers intended as pilot tones in RUs for legacy terminals, but only subcarriers intended as pilot tones in RUs for updated (non-legacy) 802.11 ax terminals and/or "spare" sub-carriers that currently are not used, for example the non-populated subcarriers (e.g. the non-populated tones 212 and 222).

The capability as legacy or updated (non-legacy) 802.11 ax terminal is signaled when a terminal is initially associated with the AP. Then the AP uses this information when allocating data carrying subcarriers to LRLP terminals.

Embodiments of the present invention allow for LRLP to be introduced as described above by using the pilots tones of an 802.1 lax signal for sending LRLP data, provided that the 802.1 lax terminal is capable of first decoding the LRLP data and does not use the signal directly as being a known pilot symbol. It may furthermore be possible to allocate the LRLP terminal and the updated 802.1 lax terminal to the same RU.

Thus, in some embodiments, the downlink transmission may also be initiated to at least one of the one or more terminals of the first type and the AP may further determine, in accordance with the method 300, prior to initiating the downlink transmission to the at least one terminal of the first type and to the at least one terminal of the second type in step 301, a suitable resource unit of a plurality of resource units comprised in the bandwidth for the downlink transmission and allocate the determined resource unit to the at least one terminal of the first type.

The allocated at least one of the number of subcarriers for data transmission to the at least one terminal of the second type may be located within said determined resource unit to the at least one terminal of the first type.

Thus, the scheduling of LRLP terminals, legacy 802.1 lax terminals, and updated 802.1 lax terminals may be done in such a way that LRLP terminals are as far as possible allocated to the same RUs as the updated 802.1 lax terminals in order to allow for joint scheduling and thus also improve spectrum efficiency.

In some embodiments, the suitable resource unit of the plurality of resource units may be determined based on at least one of a link quality between the AP and the at least one terminal of the first type and between the AP and the at least one terminal of the second type, and a total transmission time of the down link transmission. It may be desirable to use a RU where the receiver has favorable conditions. However, as one RU may be intended for two receivers, e.g. one LRLP and one 802.1 lax compliant, such as an updated 802.1 lax terminal, the selection of RU may be based on both links. It may for instance be based on a max-min criteria, where it is first determined whether the LRLP terminal or the 802.11 ax terminal has the worst channel condition in relation to what data rate is required, and then effectively trying to select the one RU where the worst channel is as good as possible.

The RU is thus based on the receiver (either LRLP or 802.1 lax) with the worst conditions. Alternatively, the RU is selected such as the total transmission time for both LRLP and 802.11 ax is minimized.

The RU may thus be selected based on the receiver that has the best conditions since this may increase the probability that the transmission is received quickly by the terminals.

In some embodiments, an access point which transmits using several antennas may apply precoding to beamform a specific pilot subcarrier to a LRLP device. This will work even if the AP is transmitting with multiple input, multiple output (MIMO) to 8021 lax terminals since the MIMO receiver only can estimate one phase and not the channels for each stream. The cyclic shift will not be applied for those subcarriers and the precoders need to be constant over time not to cause problems in the phase tracking for 80211 ax devices.

To further increase efficient utilization of the available spectrum, the non- populated subcarriers (e.g. the non-populated tones as described in conjunction with Fig. 2) may be used for combined pilot and data transmission. The method 300 may thus in some embodiments further comprise allocating the at least one of the number of subcarriers such that the at least one subcarrier is a subcarrier which is not used for transmission to the at least one terminal of the first type.

The allocated subcarrier may e.g. be a non-populated subcarrier for the terminal of the first type. A non-populated subcarrier is typically a subcarrier which has been left over when the channel bandwidth has been divided into resource units, and is thus not used for transmitting neither data, nor pilot symbols to the terminal of the first type. Allocating the non-populated subcarriers would require no change in the channel estimation approach for terminals of the first type since these subcarriers are not part of the available RUs that can be allocated.

However, the non-populated subcarriers are limited and depend on the size of allocated RUs and can thus only support a limited number of terminals of the second type.

If the terminals of the first type are aware of the allocation on the usually non- populated subcarriers they can use e.g. a decision directed approach to obtain additional channel estimates and/or phase tracking estimates.

The AP may e.g. inform the terminals of the first type that the usually non- populated subcarriers are allocated, e.g. by dedicated signaling.

According to some of the embodiments of the present invention, the second type terminal system may be designed such that one or more of the pilot subcarriers for a subband (one or several RUs) in an OFDMA transmission are allocated to a second type terminal. That is, the network node, e.g. an access point (AP), may transmit concurrently to both second type terminals and to first type terminals, where the signals intended to both type of terminals are generated using an IFFT, so it can effectively be seen as an OFDMA signal. The second type terminal does not need to know whether there actually is any transmission for the first type terminals going on as the signal not intended for the second type terminal receiver can be neglected in the demodulation of the second type terminal signal. The first type terminal, on the other hand, may preferably use the second type terminal signal in order to enhance the receiver performance, e.g. by using the second type signal as pilot signals.

Fig. 4 illustrates an example arrangement 400 of a network access point - AP - 401 configured to support transmissions to one or more terminals of a first type in a wireless network, and transmissions to one or more terminals of a second type in the same wireless network.

The AP 401 may e.g. be the AP as described in conjunction with any of the Figs. 1 and 3, and the first and second type of terminals may e.g. be any of the terminals of the first and second type as described in conjunction with any of the Figs. 1-3. The AP 401 is configured to perform transmissions using at least one communication channel having a bandwidth (e.g. any of the bandwidths described in Fig. 2), wherein the bandwidth comprises a number of subcarriers.

The arrangement 400 comprises a transceiver (RX/TX) 402 and a controller 403. In some embodiments, the transceiver 402 is a separate receiver and a separate transmitter. The transceiver 402 may be configured to communicate with the controller 403 and/or may be integrated into the controller 403.

In some embodiments, the controller 403 may further comprise a subcarrier allocator (SUB) 404, a modulator (MOD) 405 and resource unit determiner (RU DET) 406.

The controller 403 may be configured to cause initiation of a downlink transmission to at least one of the one or more terminals of the second type in the wireless network.

The controller 403 may be configured to cause allocation of at least one of the number of subcarriers for data transmission to the at least one terminal of the second type, wherein the allocated at least one subcarrier may be decoded for use as a pilot symbol by the at least one terminal of the first type, and wherein the allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type.

The controller 403 may e.g. cause the subcarrier allocator 404 to determine which subcarrier or subcarriers should be allocated to the terminals for use as both pilot and data transmission. The subcarrier allocator 404 may e.g. perform allocation of the at least one of the number of subcarriers such that the at least one subcarrier is a subcarrier which is not used for transmission to the first type of terminal.

The allocated subcarrier may e.g. be a non-populated subcarrier of an 802.1 lax system.

In some embodiments, the subcarrier allocator 404 may be caused, e.g. by the controller 403, to allocate a subcarrier which is adjacent to the at least one subcarrier allocated for the data transmission to the at least one terminal of the second type as guard band so that it is not used for transmitting data The controller 403 may further cause performance of the data transmission on the allocated at least one subcarrier. The controller 403 may e.g. cause the transceiver 402 to transmit to the terminals in the network.

In some embodiments, the first type of terminals may be configured to operate using orthogonal frequency division multiplexing (OFDM) and the second type of terminals are configured to operate using single carrier modulation.

In some embodiments, the single carrier modulation may comprise binary modulation.

The controller 403 may further be configured to cause the modulator 405 to modulate the subcarrier using a suitable modulation which is easily decodable by the first type of terminal for use as a pilot symbol, and which may be received and demodulated by the second type of terminal so that it may extract the data.

In some embodiments, the downlink transmission may also be initiated to at least one of the one or more terminals of the first type and the controller 403 may be further configured to cause, prior to initiating the down link transmission to the at least one terminal of the first type and to the at least one terminal of the second type, determination of a suitable resource unit of the plurality of resource units for the downlink transmission and allocation of the determined resource unit to the at least one terminal of the first type.

The controller 403 may further be configured to allocate the determined resource unit such that the allocated at least one of the number of subcarriers for data transmission to the at least one terminal of the second type is located within said determined resource unit to the at least one terminal of the first type.

The controller 403 may e.g. cause the resource unit determiner 406 to determine a suitable resource unit based on at least one of a link quality between the AP and the at least one terminal of the first type and between the AP and the at least one terminal of the second type, and a total transmission time of the down link transmission.

In some embodiments, the controller 403 may be further configured to cause boosting of a transmission power of the allocated at least one subcarrier used for the data transmission to the at least one terminal of the second type. The controller 403 may e.g. cause the transceiver 402 to boost the transmission power. Fig. 5 illustrates an example method 500 of a terminal configured to receive transmission using OFDM from a network access point - AP.

In some embodiments, the terminal may be a terminal of the first type as described in conjunction with any of the Figs. 1-4. The AP may be the AP as described in conjunction with any of the Figs. 1, 3, 4.

The AP is configured to perform transmissions using at least one

communication channel having a bandwidth (e.g. any of the bandwidths described in Fig. 2), wherein the bandwidth comprises a number of subcarriers.

The method 500 may start in 501 where the terminal receives a downlink transmission initiated by the AP on at least one of the number of subcarriers, wherein the at least one of the number of subcarriers is allocated for data transmission to at least one terminal of a second type.

The terminals of the second type may e.g. be a terminal of the second type as described in conjunction with any of the Figs. 1-4.

In 502 of the method 500, the terminal decodes the allocated at least one subcarrier for use as a pilot symbol, wherein the allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type.

In some embodiments the second type of terminal is configured to operate using single carrier modulation.

The single carrier modulation may e.g. comprise binary modulation.

As elaborated on above, the subcarriers allocated for pilot signals to terminals using a high order modulation are typically known to the terminals.

However, according to some embodiments disclosed herein, the terminals of the first type is not made aware of which subcarriers they should use as pilot signals, as e.g. only one out of two subcarriers will carry a signal for any OFDM symbol. Since the transmission may be using all resource units in the communication channel, the terminals of the first type will still receive them and they should thus be easily decodable so that the terminals of the first type may decode and use them as if they were known from the beginning. This method of first making a decision on a symbol and then use the decision as if the symbol would have been known from the very beginning is commonly referred to as decision directed (DD) estimation.

In some embodiments, the AP may e.g. allocate only one subcarrier of the number of subcarriers to each of the one or more terminals of the second type. I.e. each terminal of the second type has only one allocated subcarrier each.

The allocated subcarrier may be modulated using binary antipodal modulation, wherein the modulated subcarrier carries a positive or a negative sign.

Essentially this may be seen as the binary information to the terminal of the second type is sent as either +1 or -1. In order for the terminal of the first type to use this information it makes use of the fact that the information on this subcarrier is either +1 or -1 and makes a decision which of the alternatives it was.

Once the decision is made the terminal of the first type can then use the subcarrier as if it would have been a known symbol. Due to that the data transmission is intended for a terminal that may be farther away from the AP than terminals of the first type generally are, it is robustly modulated and can therefore be easily decoded by a terminal that is much closer to the AP, such as a terminal of the first type. The method 500 may thus further comprise decoding the modulated subcarrier for use as a pilot symbol based on the positive or negative sign.

In some embodiments, non-data aided (NDA) estimation may be used instead of DD estimation.

For instance, in case the subcarrier is modulated as +1 or -1, the terminal of the first type may use the data on the subcarrier by raising the signal to the power of two. Thus a non-linear operation is performed which removes the data.

If only one subcarrier is allocated, the terminal of the second type may perform coherent reception in order to extract the data. This usually results in good performance, but may prevent some very low cost implementations of a terminal of the second type.

Thus in some embodiments, two subcarriers of the number of subcarriers may be allocated to each of the one or more terminals of the second type.

The allocated two subcarriers are for transmitting information or data to the at least one terminal of the second type. The data transmission can in this case effectively be seen as frequency shift keying (FSK), where the data is transmitted using one of two frequencies for the respective FSK symbol (i.e. logical one and logical zero), where a logical one is transmitted using one of the frequencies and a logical zero is transmitted using the other frequency. Both frequencies are received within the bandwidth of the at least one terminal of the second type for demodulation.

The method 500 may then further comprise decoding the subcarrier currently used for transmitting the respective FSK symbol (a logical one or zero to the terminal of the second type) for use as a pilot symbol.

If two subcarriers are allocated to each terminal of the second type, then the terminal of the first type may determine which of the subcarrier was used for transmitting the FSK symbol and should subsequently be decoded for use as a pilot symbol by simply comparing the energy content of the two allocated subcarriers since the subcarrier containing the FSK symbol comprises more energy than the subcarrier not containing the FSK symbol.

Regardless of whether one or two subcarriers are allocated to each terminal of the second type, it may be assumed that the terminal of the second type would be able to demodulate the data transmission, unaffected by transmission to the terminal of the first type and that the terminal of the first type could reliably decode the data transmission and then use it for e.g. phase estimation.

In order to achieve this, the subcarriers intended for data to the terminals of the second type may be boosted in power such that they are transmitted with a power offset.

The power offset is preferably large enough to ensure reliable detection for terminals of the second type, but not much more as this may in some cases require that the power of the subcarriers only intended for terminals of the first type to be reduced too much, assuming that the total transmitted power is to be kept constant.

In some embodiments, the pilot subcarrier allocated to the terminal of the second type may be changed for every OFDM symbol in a frequency hopping fashion. This will improve the diversity for the terminal of the second type. The terminal of the first type may still perform a decision directed approach or may simply ignore to estimate the phase for symbols and subcarriers allocated to the terminal of the second type. This embodiment is particularly beneficial if only a few terminals of the second type are allocated in this way.

According to some embodiments, every Kth symbol on the pilot subcarriers contains known pilot symbols. This fact may be used to estimate the initial phase in the transmissions. A large phase drift can cause problems in the decision directed approach for both terminals of the first type and terminals of the second type. This approach is applicable regardless of what modulation is used for second type terminals or how many second type terminals are supported concurrently with first type terminal transmission.

Fig. 6 illustrates an arrangement 600 of a terminal 601 configured to receive transmission using OFDM from a network access point - AP.

In some embodiments, the terminal 601 may be a terminal of the first type as described in conjunction with any of the Figs. 1-5. The AP may be the AP as described in conjunction with any of the Figs. 1 , 3, 4, 5.

The AP is configured to perform transmissions using at least one

communication channel having a bandwidth (e.g. any of the bandwidths described in Fig. 2), wherein the bandwidth comprises a number of subcarriers.

The arrangement 602 may further comprise a transceiver 602 and a controller 603. In some embodiments, the transceiver 602 may be integrated with the controller 603. The transceiver 602 may in some embodiments be a separate transmitter and a separate receiver.

The controller 603 may further comprise a decoder (DECODE) 604 and subcarrier determiner (DET) 605.

The controller 603 may further be configured to cause reception of a downlink transmission initiated by the AP on at least one of the number of subcarriers, wherein the at least one of the number of subcarriers is allocated for data transmission to at least one terminal of a second type. The controller 603 may e.g. cause the transceiver 602 to receive the transmission.

The terminal of the second type may e.g. be a terminal of the second type as described in conjunction with any of the Figs. 1-5.

The controller 603 may further be configured to cause decoding of the allocated at least one subcarrier for use as a pilot symbol, wherein the allocated at least one subcarrier is intended for carrying data for the at least one terminal of the second type. The controller 603 may e.g. cause the decoder 604 to decode the subcarrier.

In some embodiments, the second type of terminal is configured to operate using single carrier modulation.

The single carrier modulation may e.g. comprise binary modulation.

In some embodiments, the AP may have allocated only one subcarrier of the number of subcarriers to each of the one or more terminals of the second type and the subcarrier may be modulated using binary antipodal modulation. The modulated subcarrier may thus carry a positive or a negative sign. The controller 603 may then be further configured to cause decoding of the modulated subcarrier for use as a pilot symbol based on the positive or negative sign. The controller 603 may e.g. cause the subcarrier determiner 605 to determine the sign of the subcarrier and the decoder 605 to decode the subcarrier with the determined sign (compare with method 500).

In some embodiments, the AP may allocate two subcarriers of the number of subcarriers to each of the one or more terminals of the second type. The allocated two subcarriers may be used for transmitting information or data to the at least one terminal of the second type.

The data transmission can in this case effectively be seen as frequency shift keying (FSK), where the data is transmitted using one of the two frequencies for the respective FSK symbol (i.e. a logical one or a logical zero), where a logical one is transmitted using one of the frequencies and a logical zero is transmitted using the other frequency. Both frequencies are received within the bandwidth of the at least one terminal of the second type for demodulation.

The controller 603 may be further configured to cause decoding of the subcarrier currently used for transmitting the respective FSK symbol (a logical one or zero to the terminal of the second type) for use as a pilot symbol.

In order to know which of the two subcarriers was used for transmitting the FSK symbol, the controller 603 may cause the subcarrier determiner 605 to compare the energy content of the two subcarriers, and then cause the decoder 604 to decode the subcarrier which had the highest energy content of the two. Fig. 7A illustrates how a typical OFDM transmission looks where no low order modulation terminals are present, whereas Fig. 7B illustrates how the OFDM

transmission may look when some of the pilot signals are used for transmitting data to low order modulation terminals according to some embodiments.

In both Fig. 7A and 7B, the Y-axis represents frequency and the X-axis represents time. Both figures comprise subcarriers 701 and pilot subcarriers 702 comprising symbols 1 to N (Symbols 1, 2, N-l, N).

However, in Fig. 7B some of the symbols of the pilot subcarriers 702 comprise symbols 703 that constitute data used for data transmissions intended to terminals using a low order modulation or low data rate as described for any of the above embodiments.

Fig. 8 illustrates a computer program product 800 comprising a computer readable medium, having thereon a computer program comprising program instructions. The computer program 800 is loadable into a data-processing unit 801 comprising a memory (MEM) 802 and a processor (PROC) 803 and adapted to cause execution of any of the methods 300 and 500 of Figs. 3 and 5 when the computer program is run by the data-processing unit 801.

Disclosed herein are embodiments that enable concurrent operation of terminals using a high order modulation and/or high data rates and terminals using a low order modulation and/or low data rates in a network.

By utilizing that data transmission to the terminals using a low order modulation may concurrently be used as pilot signals for the terminals using a high order modulation, efficient spectrum utilization is achieved without having to negatively impact either of the systems. However, none of the systems are dependent on each other in order to function ideally, and will operate with good performance when not operating concurrently.

However, spectrum efficiency may be increased even more according to some embodiments since subcarriers which typically aren't used for any type of transmissions may be utilized in some situations.

Furthermore, in low order modulation systems, delay and overhead may be reduced compared to prior art systems utilizing time multiplexing. The described embodiments and their equivalents may be realized in software or hardware or a combination thereof. They may be performed by general-purpose circuits associated with or integral to a communication device, such as digital signal processors (DSP), central processing units (CPU), co-processor units, field- programmable gate arrays (FPGA) or other programmable hardware, or by specialized circuits such as for example application-specific integrated circuits (ASIC). All such forms are contemplated to be within the scope of this disclosure.

Embodiments may appear within an electronic apparatus (such as a wireless communication terminal or device) comprising circuitry/logic or performing methods according to any of the embodiments. The electronic apparatus may, for example, be a portable or handheld mobile radio communication equipment, a mobile radio terminal, a mobile telephone, a base station, a base station controller, a pager, a communicator, an electronic organizer, a smartphone, a computer, a notebook, a USB-stick, a plug-in card, an embedded drive, or a mobile gaming device.

Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims. For example, the method

embodiments described herein describes example methods through method steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims.

Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence.

In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means limiting.

Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. In the same manner, functional blocks that are described herein as being implemented as two or more units may be implemented as a single unit without departing from the scope of the claims.

Hence, it should be understood that the details of the described embodiments are merely for illustrative purpose and by no means limiting. Instead, all variations that fall within the range of the claims are intended to be embraced therein.