COMMUNICATION SYSTEM

Field of the Invention

The present invention relates to communication field, and more particularly to a method and an apparatus for data transmission in a wireless communication system.

Background of the Invention

M2M (Machine to Machine) communication refers to transmitting data from one M2M device to another M2M device, namely, communication between machines. Experts in this field call M2M as Internet of Things. Wireless communication technologies can be employed in the inter-machine communication. For example, the third generation of wireless communication technology or LTE (Long Term Evolution) wireless communication technology can be employed to enable a lot of M2M devices such as instruments, household electrical appliance, vehicles, lighting apparatus, and medical monitors to achieve connection and communication.

Summary of the Invention

According to one aspect of the present invention, there is provided a method for data transmission in a wireless communication system which comprises a first type of terminal, a second type of terminal and a base station. The method comprises:

in at least one of an uplink time slot and a downlink time slot between the first type of terminal and the base station,

wherein the uplink time slot and the downlink time slot respectively comprise a plurality of OFDM symbols for first data transmission between the first type of terminal and the base station, wherein each of the OFDM symbols has a protecting interval,

in a duration of a corresponding protecting interval, carrying out second data transmission between the second type of terminal and the base station.

According to another aspect of the present invention, there is provided an apparatus for data transmission in a wireless communication system which comprises a first type of terminal, a second type of terminal and a base station. The apparatus comprises:

a transmitting unit for, in at least one of an uplink time slot and a downlink time slot between the first type of terminal and the base station,

wherein the uplink time slot and the downlink time slot respectively comprise a plurality of OFDM symbols for first data transmission between the first type of terminal and the base station, wherein each of the OFDM symbols has a protecting interval,

in a duration of a corresponding protecting interval, carrying out second data transmission between the second type of terminal and the base station.

The first type of terminal may be a conventional terminal, such as a mobile phone, a portable computer, or a PDA, and it generally requires a high data transmission rate. The second type of terminal may be a M2M device, such as instrument, household electrical appliance, vehicle, lighting apparatus, or medical monitor, and it generally requires a low data transmission rate.

According to the present invention, service can be provided to an M2M-type terminal in a broad scope. Substantially no influence is exerted to the conventional first type of terminal and frequency spectrum is utilized at a high rate.

Brief Description of Drawings

As the present invention is better understood, other objects and effects of the present invention will become more apparent and easy to understand from the following description, taken in conjunction with the accompanying drawings wherein:

Fig.1 illustrates a wireless communication system in which the present invention can be implemented;

Figs.2A and 2B respectively illustrate a LTE TDD (Time Division Duplex) frame structure according to the prior art;

Fig.2C illustrates a LTE FDD (Frequency Division Duplex) frame structure according to the prior art; Fig.3A and Fig.3B respectively illustrate a time slot structure corresponding to a CP form, wherein Fig.3A corresponds to a conventional CP situation and Fig.3B corresponds to an extended CP situation;

Fig.4A and Fig.4B respectively illustrate a situation of second data transmission between a second type of terminal and a base station in a duration of a cyclic prefix of an OFDM symbol in an uplink time slot and/or a downlink time slot between a first type of terminal and the base station of the LTE communication system according to one embodiment of the present invention;

In all of the above figures, the same reference numbers denote the same, like or corresponding feature or function.

Detailed Description of Preferred Embodiments

The basic idea of the present invention is as follows: in at least one of an uplink time slot and a downlink time slot between a first type of terminal and a base station, wherein the uplink time slot and the downlink time slot respectively comprise a plurality OFDM (Orthogonal Frequency Division ultiplexing) symbols for carrying out first data transmission between the first type of terminal and the base station, and wherein each of the OFDM symbols has an protecting interval, second data transmission is carried out between the second type of terminal and the base station in a duration of a corresponding protecting interval.

Specific embodiments of the present invention are described in detail with reference to figures.

Fig.1 illustrates a wireless communication system in which the present invention can be implemented.

As shown in Fig. l, the wireless communication system 100 comprises a base station 110, a fist type of terminal 120, a fist type of terminal 130, a second type of terminal 140 and a second type of terminal 150, wherein the first type of terminals 120 and 130 communicate with the base station 110 via wireless links 160 and 170, and the second type of terminals 140 and 150 communicate with the base station 110 via wireless links 180 and 190. The first type of terminals 120 and 130 are conventional terminals, such as mobile phones, portable computers, or PDAs, and they generally require a high data transmission rate. The second type of terminals 140 and 150 are M2M devices such as instruments, household electrical appliance, vehicles, lighting apparatus, or medical monitors, and they generally require a low data transmission rate.

The wireless communication system 100 can be an LTE TDD system, an LTE FDD system or other types of system.

Certainly, those skilled in the art can appreciate that the wireless communication system 100 can also comprise more base stations, more or less first type of terminals, and more or less second type of terminals.

Figs.2A and 2B respectively illustrate a LTE TDD (Time Division Duplex) frame structure according to the prior art, namely, frame structures by which data transmission is carried out between the first type of terminals 120 and 130 and the base station 110. The frame structures shown in Fig.2A and Fig.2B both comprise ten sub-frames: a sub-frame 0, a sub-frame 1, a sub-frame 2, a sub-frame 3, a sub-frame 4, a sub-frame 5, a sub-frame 6, a sub-frame 7, a sub-frame 8 and a sub-frame 9. The difference is that the frame structure shown in Fig.2 A comprises two special sub-frames, namely, sub-frame 1 and sub-frame 6, whereas the frame structure shown in Fig.2B only comprises one special sub-frame, namely, sub-frame 1. The special sub-frame has three special time slots: a downlink pilot time slot (DwPTS), a protecting interval (GP) and an uplink pilot time slot (UpPTS).

The ten sub-frames employ a uniform 1ms (corresponding to minimum transmission time interval TTI) sub-frame length. A conventional sub-frame comprises two 0.5ms time slots.

According to occurrence frequency of the special sub-frame, the LTE TDD frame structure can be classified into two types: 5ms periodic frame structure and 10ms periodic frame structure. Hence, what is shown in Fig.2A is the 5ms periodic frame structure, whereas what is shown in Fig.2B is the 10ms periodic frame structure.

The 5ms periodic frame structure divides one 10ms wireless frame into two 5ms "semi-frames". The two semi-frames have completely the same structure and the same ratio of uplink sub-frames to downlink sub-frames.

In the five sub-frames included in one semi-frame of the 5ms periodic frame structure, one special sub-frame always includes one downlink DwPTS, one uplink UpPTS and one GP, and among the remaining four conventional sub-frames, the ratio of downlink sub-frames to uplink sub-frames can be 3: 1, 2:2 or 1:3.

In the 10 sub-frames included in one wireless frame of the 10ms periodic frame structure, in nine conventional sub-frames except for one special sub-frame, the ratio of downlink sub-frames to uplink sub-frames can be 8: 1, 7:2, 6:3 or 3:5. In the event of 3:5, one 10ms wireless frame includes two special sub-frames. The last configuration is divided into two semi-frames, but the two semi-frames have a different uplink-to-downlink sub-frame ratio, so the cycle is still 10ms.

Fig.2C illustrates a LTE FDD (Frequency Division Duplex) frame structure according to the prior art, namely, a frame structure by which data transmission is carried out between the first type of terminals 120 and 130 and the base station 110. In FDD, the uplink and downlink have the same frame structure, but employ different frequency ranges. Hence, the LTE FDD frame structure shown in Fig.2C can be understood as either an uplink frame structure or a downlink frame structure.

Similar to the LTE TDD frame structure, each LTE FDD frame comprises ten sub-frames: a sub-frame 0, a sub-frame 1, a sub-frame 2, a sub-frame 3, a sub-frame 4, a sub-frame 5, a sub-frame 6, a sub-frame 7, a sub-frame 8 and a sub-frame 9. The ten sub-frames employ a uniform 1ms (corresponding to minimum transmission time interval TTI) sub-frame length. Furthermore, each sub-frame comprises two 0.5ms time slots.

According to difference of the employed cyclic prefixes (CP), each time slot can comprise seven or six OFDM symbols in either TDD system or FDD system.

Fig.3A and Fig.3B respectively illustrate a time slot structure corresponding to a CP form, wherein Fig.3A corresponds to a conventional CP situation and Fig.3B corresponds to an extended CP situation.

As shown in Fig.3A, regarding the conventional CP situation, each time slot comprises seven OFDM symbols. The duration of each OFDM symbol is 2048 time units (Ts), wherein Ts=l/30720ms, the CP duration of the first OFDM symbol is 160Ts, and the CP duration of each of the remaining six OFDM symbols is 144Ts.

As shown in Fig.3B, regarding the extended CP situation, each time slot comprises six OFDM symbols, the duration of each OFDM symbol is 2048 time units (Ts), and , the CP duration of each OFDM symbol is the same, namely, 512Ts.

The cyclic prefix (CP) of the OFDM symbol is constituted by duplicating a portion of the tail of each OFDM symbol and putting in front of the OFDM symbol. The CP functions to eliminate inter-symbol interference (ISI) and inter-channel interference (ICI).

Certainly, those skilled in the art should appreciate that if in order to eliminate the ISI only, the CP may not be used, and the only thing to do is arrange a protecting interval between the OFDM symbols.

Fig.4A and Fig.4B respectively illustrate a situation of second data transmission between a second type of terminal and a base station in a duration of a cyclic prefix of an OFDM symbol in an uplink time slot and/or a downlink time slot between a first type of terminal and the base station of the LTE communication system according to one embodiment of the present invention.

In other words, in the embodiments shown in Fig.4A and Fig.4B, in a duration of a corresponding protecting interval, the cyclic prefix or a cyclic suffix of a corresponding OFDM symbol is transmitted between the first type of terminal and the base station.

In the situation shown in Fig.4A, the cyclic prefix of the corresponding OFDM symbol is an extended cyclic prefix, so there are 6 OFDM symbols in one time slot, and the length, namely, the duration, of each cyclic prefix is 512Ts.

In the situation shown in Fig.4A, the second data transmission is carried out between the second type of terminal and the base station in the length 401 shown in Fig.4A, namely, in 208Ts after 160Ts after the beginning of the protecting interval of the first OFDM symbol and before 144Ts before the ending of the protecting interval of the first OFDM symbol, and in lengths 403, 405, 407, 409, 411 shown in Fig.4A, namely, in 368Ts before 144Ts before the ending of the protecting interval of each of the remaining five OFDM symbols.

According to the embodiment, a total duration for performing the second data transmission between the second type of terminal and the base station is 208Ts+368Ts*5=2048Ts, exactly the duration of one OFDM symbol.

An advantage of this embodiment is as follows: the second data transmission is carried out between the second type of terminal and the base station not in the total CP duration, and 144Ts margin is left between it and next OFDM symbol and the margin in general is sufficient to resist inter-symbol interference, so the second data transmission between the second type of terminal and the base station in the CP duration does not exert much interference to the first data transmission between the first type of terminal and the base station on next OFDM symbol.

Certainly, those skilled in the art can further envisage an embodiment in which with regard to the protecting interval of each of the remaining five OFDM symbols, the second data transmission is carried out between the second type of terminal and the base station in 224Ts after 144Ts after the beginning of the protecting interval and before 144Ts before the ending of the protecting interval.

An advantage of this embodiment is as follows: the second data transmission is carried out between the second type of terminal and the base station not in the total CP duration, and a 144Ts margin is left between it and the preceding OFDM symbol and the next OFDM symbol and the margin in general is sufficient to resist inter-symbol interference, so the second data transmission between the second type of terminal and the base station in the CP duration does not exert much interference to the first data transmission between the first type of terminal and the base station on the next OFDM symbol, and the first data transmission between the first type of terminal and the base station on the preceding OFDM symbol does not exert much interference to the second data transmission between the second type of terminal and the base station in the CP duration.

In the case shown in Fig.4B, the cyclic prefix of the OFDM symbol is a conventional cyclic prefix, so there are seven OFDM symbols in one time slot, and the CP duration of the first OFDM symbol is 160Ts, and the CP duration of each of the remaining six OFDM symbols is 144Ts.

In the case shown in Fig.4B, the second data transmission is carried out between the second type of terminal and the base station in the second, fourth, fifth and seventh of the seven protecting intervals, namely, in the duration of the lengths 413, 415, 417 and 419 shown in Fig.4B.

According to this embodiment, a total duration for performing the second data transmission between the second type of terminal and the base station is 144Ts*4=576Ts.

Certainly, those skilled in the art can envisage that the second data transmission is carried out between the second type of terminal and the base station in more, or less protecting intervals of the seven protecting intervals or protecting intervals different from the protecting intervals shown in Fig.4B.

Those skilled in the art can further envisage that the second data transmission is carried out between the second type of terminal and the base station in a special subcarrier of a special CP.

In the case that the second data transmission is carried out between the second type of terminal and the base station in a protecting interval of a corresponding OFDM symbol in the uplink time slot between the first type of terminal and the base station, carrying out the second data transmission between the second type of terminal and the base station comprises:

sending second data at the second type of terminal, and receiving the second data at the base station.

In the case that the second data transmission is carried out between the second type of terminal and the base station in a protecting interval of a corresponding OFDM symbol in the downlink time slot between the first type of terminal and the base station, carrying out the second data transmission between the second type of terminal and the base station comprises:

sending second data at the base station, and receiving the second data at the second type of terminal.

In the case that in the duration of a protecting interval, the cyclic prefix or the cyclic suffix of the corresponding OFDM symbol is transmitted between the first type of terminal and the base station, namely, in the case described with reference to Fig.4A and Fig.4B, at the second type of terminal and/or at the base station, a mixed signal including second data and partial first data transmitted on the cyclic prefix or the cyclic suffix of the OFDM symbol is received, and the second data is separated from the mixed signal.

More generally, the mixed signal can further comprise a time domain delay extension of partial first data transmitted on a preceding OFDM symbol of the corresponding protecting interval.

Since partial first data transmitted on the cyclic prefix or the cyclic suffix of the OFDM symbol can be obtained correctly, second data can be separated from the mixed signal.

Besides, since the time domain delay extension property of a channel can be obtained by measure such as evaluation, the second data can be separated from the mixed signal even the mixed signal further comprises the time domain delay extension of partial first data transmitted on the preceding OFDM symbol of the corresponding protecting interval.

According to an embodiment of the present invention, an apparatus for data transmission in a wireless communication system (wherein the wireless communication system comprises a first type of terminal, a second type of terminal and a base station) comprises:

a transmitting unit for, in at least one of an uplink time slot and a downlink time slot between the first type of terminal and the base station,

wherein the uplink time slot and the downlink time slot respectively comprise a plurality of OFDM symbols for first data transmission between the first type of terminal and the base station, wherein each of the OFDM symbols has a protecting interval,

in a duration of a corresponding protecting interval, carrying out second data transmission between the second type of terminal and the base station.

In the case that in a protecting interval of a corresponding OFDM symbol in the uplink time slot between the first type of terminal and the base station, the second data transmission is carried out between the second type of terminal and the base station, the transmitting unit of the apparatus in the second type of terminal comprises a sending unit configured to send second data; the transmitting unit of the apparatus in the base station comprises a receiving unit configured to receive the second data.

In the case that in a protecting interval of a corresponding OFDM symbol in the downlink time slot between the first type of terminal and the base station, the second data transmission is carried out between the second type of terminal and the base station, the transmitting unit of the apparatus in the base station comprises a sending unit configured to send second data; the transmitting unit of the apparatus in the second type of terminal comprises a receiving unit configured to receive the second data.

In an embodiment of the present invention, in the case that in a duration of a protecting interval, the cyclic prefix or the cyclic suffix of the corresponding OFDM symbol is transmitted between the first type of terminal and the base station, the receiving unit is configured to receive a mixed signal including second data and the cyclic prefix or the cyclic suffix of the corresponding OFDM symbol, the apparatus further comprises: a separating unit configured to separate the second data from the mixed signal.

As stated above, the mixed signal can further comprise a time domain delay extension of a preceding OFDM symbol of the corresponding protecting interval.

As stated above, the second data transmission can be carried out between the second type of terminal and the base station only in a special portion of the duration of the corresponding protecting interval.

As stated above, the second data transmission can be carried out between the second type of terminal and the base station only in a duration of a special protecting interval.

As stated above, the uplink time slot and the downlink time slot respectively comprise 6 OFDM symbols, each of the OFDM symbols has a duration of 2048 time units (Ts) and the protecting interval of 512Ts, wherein one time unit is equal to l/30720ms. The second data transmission is carried out between the second type of terminal and the base station in 208Ts after 160Ts after the beginning of the protecting interval of the first OFDM symbol and before 144Ts before the ending of the protecting interval of the first OFDM symbol, and in 368Ts before 144Ts before the ending of the protecting interval of each of the remaining five OFDM symbols.

As stated above, the uplink time slot and the downlink time slot respectively comprise 7 OFDM symbols, each of the OFDM symbols has a duration of 2048 time units (Ts), the first OFDM symbol has a protecting interval of 160Ts and each of the remaining 6 OFDM symbols has a protecting interval of 144Ts, wherein one time unit Ts is equal to l/30720ms. The second data transmission can be carried out between the second type of terminal and the base station in the duration of any one or more of the 7 protecting intervals.

The above second data can comprise scheduling information, for informing in which subframes, which time slots, or the protecting intervals of which OFDM symbols, the second type of terminal can carry out the second data transmission, particularly in the case that in the protecting interval of a corresponding OFDM symbol in the downlink time slot between the first type of terminal and the base station, the second data transmission is carried out between the second type of terminal and the base station.

According to the present invention, since the third generation or LTE wireless communication system covering a broad scope is employed to carry out data transmission between M2M-type terminals, service can be provided to M2M-type terminals in the broad scope. Besides, since the protecting interval of the corresponding OFDM symbol of each time slot in the uplink frame and the downlink frame between the conventional terminal and the base station in the wireless communication system is used to carry out data transmission between the M2M-type terminal and the base station, a small influence is exerted to the conventional terminal and frequency spectrum is utilized at a high rate.

It should be noted that in order to make the present invention more apparent, the above description omits some more specific technical details which are known for those skilled in the art and might be requisite for implementation of the present invention.

Those skilled in the art should appreciate that the present invention is not limited to the steps described above, and the present invention also includes combinations of the above-described steps, changes of their order and the like. The final scope of the present invention is defined by the appended claims.

Therefore, selection and description of the embodiments aim to better explain principles and practical applications of the present invention and make those skilled in the are understand that without departing from the essence of the present invention, all modifications and alterations fall within the scope of the present invention defined by the appended claims.

Further, those skilled in the art may understand, the steps of various methods as above described may be implemented through a programmed computer. Here, some embodiments intend to cover program storage that is a machine or computer-readable and encoded with machine-executable or computer-executable instruction program, wherein the instruction performs some or all steps of the above methods. The program storage may be a magnetic storage medium, for example, a disc, a diskette, a hard disk driver, or an optical readable digital data storage medium. The embodiments also intend to cover a computer that is programmed to perform the steps of the methods.