WO2007081182A1

WO2007081182A1 - Method and apparatus for cyclic shifted sub-carrier mapping

Info

Publication number: WO2007081182A1
Application number: PCT/KR2007/000238
Authority: WO
Inventors: Bing Bu; Ju-Ho Lee; Xiaoqiang Li; Yujian Zhang
Original assignee: Samsung Electronics Co., Ltd.; Beijing Samsung Telecom R & D Center
Priority date: 2006-01-13
Filing date: 2007-01-15
Publication date: 2007-07-19
Also published as: CN101001136A

Abstract

The method for cyclic shifted sub-carrier mapping in a transmitting end comprising steps of: mapping several input data bits to a symbol from a modulation symbol set and output the resulting modulated symbol; when retransmitting data packets, obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; modulating and sending the modulated symbols on various sub-carriers. The present invention is uses the method on cyclic shifted sub-carrier mapping to make the same bits transmitted on different sub-carriers when transmitting in different transmissions of the same HARQ process, thus acquiring frequency diversity gain, reducing HARQ transmission failure rate due to some bits transmitted all the time in sub-carrier that experiences deep fading.

Description

METHOD AND APPARATUS FOR CYCLIC SHIFTED SUB-CARRIER

MAPPING

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to data transmission in a wireless communication system, especially to a method and an apparatus for cyclic shifted sub-carrier mapping.

2. Description of the Related Art

Compared with a 3 G system at present, an evolved next generation mobile communication system offers shorter transmission delay (including time for access, air-interface transmission, network process and network transmission), higher user uplink/downlink data transmission rate, higher spectrum utilization factor, and larger system coverage. In the meantime, it reduces construction cost and maintenance cost at a network operator as much as possible. To meet the demand mentioned above, technique schemes such as AMC, HARQ, OFDM (A) (including Localized OFDM and Distributed OFDM) and SC-FDMA are being evaluated at present and may be adopted in the next generation mobile communication system. The transmission mechanism of Hybrid Automatic Retransmission Request (HARQ) is adopted in the uplink/downlink data service. With the technique of data retransmission, time diversity and combining gain can be obtained so that throughput rate of the system may be effective improved. OFDM (Orthogonal Frequency Division Multiplexing) is a special technique of multi-carrier modulation/multiplexing. The block diagram of its transmitter/receiver is shown in Figure 1. Information stream for single user is de-serialized into multiple low-rate code streams which are simultaneously transmitted via a group of sub-carriers whose spectrums are superposed but orthogonal. The advantages of the OFDM technique are as follows:

1) Better performance in anti-frequency selective fading and anti-narrow band interference. In a single-carrier system, a single fading or interference may cause the entire link out of work. But in a multi-carrier system, only a few carriers will be affected. In an OFDM system, user information stream is de-serialized into multiple low-rate information streams which are simultaneously transmitted via a group of sub-carriers. Signaling time on each sub-carrier is times longer than that in the single-carrier system with the same rate. This improves performance of the OFDM in anti-narrow-band interference and the anti-fast fading in channel. In addition, with combining coding in sub-carrier, the frequency diversity effect is gained for sub-channels so that the performance in anti-narrow-band interference and anti-fast fading in channel is improved.

2) Higher frequency utilization factor. The OFDM adopts superposed but orthogonal sub-carriers as sub-channels instead of the traditional system that applies guard bands in dividing of the sub-channel, so that the frequency utilization factor improves.

3) Suitable for data transmission in high rate. With the adaptive modulation mechanism, an OFDM system may apply different modulation schemes in modulation on different sub-carrier according to the channel conditions and the noise backgrounds. When the channel is in good condition, modulation scheme with high efficiency is applied. When the channel is in poor condition, the modulation scheme with powerful performance in anti-interference is applied. In addition, with the application of loadable algorithm, more data can be transmitted collectively in high data rate via the channel with good conditions in the OFDM system. Therefore, the technique of OFDM is very suitable for data transmission in high rate.

4) Better performance in anti-InterSymbol Interference (ISI). Besides the noise interference, ISI is the main interference in a digital communication system. Since OFDM adopts the cyclic prefix, it has better performance in anti-ISI.

The capability in anti-frequency selective fading and anti-narrow-band interference is improved in OFDM. In a single-carrier system, one fading or interference may cause the entire link out of work, but in a multi-carrier system, only a few carriers would be affected.

5) In the technique of OFDM, the modulation/demodulation can be realized through the base-band IFFT/FFT, which bears available fast calculation method and can be conveniently implemented in a DSP chip and hardware structure.

However, OFDM has following disadvantages:

1) Sensitive to frequency deviation and phase noise so that attenuation is easily caused to the system; 2) Comparatively higher Peak-to-Average Power Ratio (PAPR), which results in that the power efficiency of the RF amplifier is poor.

Since the Peak Average Power Ratio (PAPR) is high in a multi-carrier system, and considering factors such as transmission power of a mobile means, its size, its stand-by time, and coverage of a cell and so on, the technique of Single-Carrier Frequency Division Multiple Access (SC-FDMA) may be possibly adopted in the uplink of the next generation mobile communication system. Still multiple sub-carriers are adopted to transmit signals in a SC-FDMA system. However there's some difference between the SC-FDMA system and the multi-carrier system: in the multi-carrier system, each sub-carrier transmits a single modulation symbol, and in the SC-FDMA system, each sub-carrier transmits the whole modulation symbols. The SC-FDMA signal can be generated in time domain or frequency domain approaches. The block diagram illustrating the SC-FDMA transmitter/receiver (in frequency domain) is shown in Figure 2, after QAM modulation, FFT transform is made on modulation symbol sequence, and the spectrum that is used to send signals is transmitted in the appointed sub-carriers.

HARQ (Hybrid Automatic Retransmission Request) is a link adaptive technique. It is combination of Forward Error Correction (FEC) Coding and Automatic Retransmission Request (ARQ). With the application of FEC, the transmission reliability is improved. However in the case of better channel conditions, throughput of the system is on the contrary reduced because of excessive error correction bits. In the case of not high error bit rate, ideal throughput may be gained with ARQ. But the ARQ will bring about extra retransmission delay, so that it is considered to combine FEC with ARQ to generate the Hybrid ARQ. Each transmitted data packet contains the check bits for error correction and error detection. If the number of error bits in the received data packet is within the range that can be corrected, any error will be corrected automatically. However if severe error go beyond the range that FEC can correct the error, retransmission is requested. HARQ is able to adaptively adjust with the change of the channel, i.e., it can elaborately regulate the data rate according to the channel conditions.

In order to make full use of the system resources and reduce the overhead in signaling and buffer, the N-channel Stop-and-Wait (N-SAW) HARQ transmission mechanism is applied in the system, as shown in Figure 3 in principle. Figure 3 indicates principle of N-SAW HARQ, including: - A -

301 HARQ process 1,

302 HARQ process 2,

303 HARQ process 3,

304 HARQ process 4, 305 HARQ process 1, for transmitting data response information in TTI m₅

306 HARQ process 2, for transmitting data response information in TTI m+1,

307 HARQ process 3, for transmitting data response information in TTI m+2,

308 HARQ process 4, for transmitting data response information in TTI m+3, and

309 HARQ process 1, for transmitting data response information in TTI m+4. With the N-SAW HARQ, data packets of N HARQ processes can be transmitted via a single channel. When the forward link is adopted to transmit the data packet of some HARQ process, the backward link is applied to transmit the response information of other HARQ processes. With the N-SAW HARQ, data transmission can be operated continuously via the forward link. The system resources are fully utilized. But in this case, it is necessary for the receiver to be able to buffer the information of N data packets.

N-Channel Stop & Wait HARQ falls into two kinds:

1) N-SAW synchronous HARQ: a HARQ process is initiated to retransmit only at the specific moment as defined by following Equation (1) below. t = m + kxN (k = l, 2, ---, n_mj (1)

Where: t denotes the TTI of retransmission; m denotes the TTI of the initial transmission; n_max denotes the maximum number of retransmission of

HARQ; N denotes the number of HARQ processes.

2) N-SAW asynchronous HARQ: the HARQ process can be initiated to retransmit at any moment as defined by following Equation (2) below, after the response information to the previous data packet is received. t ≥ m+N (2)

Where: t denotes the TTI of retransmission; m denotes the TTI for the transmission of the previous data packet; N denotes the number of HARQ processes. To meet the demand of delay, a shorter Transmission Time Interval

(referred to as TTI) will be adopted in the next generation mobile communication system. Three possible lengths of TTI can be 0.5 ms, 0.625 ms and 0.667 ms. The

TTI is used as the base time interval in N-SAW HARQ. For N-SAW synchronous HARQ, time interval of retransmission for the same data packet is N • TTI . For the N-SAW asynchronous HARQ, time interval of the same data packet's retransmission is k-N-TTI (l < k < n_max), of which n_max means the maximum retransmission times in a HARQ process. In the case that N • TTI is less than coherence time of the channel, the channel fading experienced by the retransmitted data packet in a HARQ process is similar to that experienced by the data packets transmitted N TTI before in the said HARQ process. Although N may be increased to make N • TTI greater than the coherence time of channel, it is not suitable for the next generation mobile communication system, for the next generation mobile communication system adopts shorter TTI. Because the increase of N results in the increase of the received buffer (N HARQ processes corresponds to N buffers for soft-combination). In the meantime, the increase of N results in the increase of average delay (average delay = HARQ average retransmission times xNxTTi). Concluded from the above, a problem existed in using HARQ transmission scheme in next generation mobile communication system lies in that: the channel fading that the retransmission data packet experiences in a HARQ process is similar to what the data packet has experienced N TTI time ago in the HARQ process. Namely if some carrier in a HARQ process experiences deep fading in a transmission, it will experience deep fading again in the retransmission. Some bits of data packet in HARQ transmission process transmitted in a sub-carrier that experiences deep fading all the time will result in transmission failure of the HARQ.

An existing solving method to the above mentioned problem comprises steps of: using variable bit (modulation symbol) interleaver in transmitting and receiving end respectively, making the same bits transmit in different sub-carriers in different transmissions of the same HARQ process, thus acquiring frequency diversity gain to make up for the deficiency of time diversity, reducing HARQ transmission failure rate due to some bits transmitted all the time in the sub-carrier that experiences deep fading.

Downlink signal transmission doesn't require strictly on PAPR of transmitted signal, and frequency diversity gain may be acquired by introducing variable bit (modulation symbol) interleaver to the transmitting and receiving end. But as for uplink information transmission, due to high PAPR of traditional OFDM modulation signal, considering factors such as transmitting power, cubage, standby duration and cell coverage etc., SC-FDMA may possibly be used. In a system that supports SC-FDMA, using variable bit (modulation symbol) interleaving in the transmitting end of UE will result in notable increase of PAPR in transmitted signal. Thus the PAPR of transmitted signal is close to that of the traditional OFDM signal, and SC-FDMA will fully be without its characteristics of low PAPR. Therefore, considering notable impact on PAPR, variable bit (modulation symbol) interleaving is inapplicable to uplink information transmission.

SUMMARY OF THE INVENTION

Therefore, an object of present invention is to provide a method for cyclic shifted sub-carrier mapping in data transmission process (including initial transmission and retransmission).

According to one aspect of present invention, a method for cyclic shifted sub-carrier mapping in a transmitting end, the method comprising steps of: mapping several input data bits to a symbol from a modulation symbol set and output the resulting modulation symbol; when transmitting retransmission data packets, obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; and modulating and sending the modulation symbols in various sub-carriers. According to another aspect of present invention, a method for cyclic shifted sub-carrier mapping in a receiving end, the method comprising steps of: when receiving retransmission data packets, obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; extracting modulation symbols orderly from a corresponding sub-carrier position; and demodulating the modulation symbols. According to another aspect of present invention, a transmitting apparatus for OFDMA cyclic shifted sub-carrier mapping, the transmitting apparatus comprising: a HARQ module for outputting data bits of each transmission according to response information from a receivers; a modulation module for modulating the data bits and outputting modulation symbols; a cyclic shifted sub-carrier mapping module for obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; and a transmitting means for transmitting radio signals via an air-interface.

According to another aspect of present invention, a receiving apparatus for OFDMA cyclic shifted sub-carrier mapping, the receiving apparatus comprising: a receiving means for receiving radio signals transmitted from a transmitting apparatus via an air-interface; a cyclic shifted sub-carrier mapping module for obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; a modulation symbol weighting combination module for performing weighting and combination according to channel estimation accuracy and fading event of sub-carriers used by the same modulation symbol before and after cyclic shift; a demodulation module for demodulating the modulation symbols to output data bits; and a FIARQ module for performing soft combination and decoding on data packets of each transmission, and generating response information according to the decoding result. According to another aspect of present invention, a transmitting apparatus for SC-FDMA cyclic shifted sub-carrier mapping, the transmitting apparatus comprising: a HARQ module for outputs data bits of each transmission according to response information from a receiving apparatus; a modulation module for modulating the data bits and outputting modulation symbols, a Pre-FFT module for performing FFT transform for input signals; a cyclic shifted sub-carrier mapping module for obtaining a mapping relationship between modulation symbols and sub-carriers used in a current transmission by cyclic shifting a mapping relationship between modulation symbols and sub-carriers in a last transmission; and a transmitting means for transmitting radio signals via an air-interface.

According to another aspect of present invention, a receiving apparatus for SC-FDMA that uses cyclic shifted sub-carrier mapping, the receiving apparatus comprising: a receiving means for receiving radio signals transmitted from a transmitting apparatus via an air-interface; a cyclic shifted sub-carrier mapping module for obtaining a mapping relationship between modulation symbols and sub-carriers used in a current transmission by cyclic shifting a mapping relationship between modulation symbols and sub-carriers in a last transmission; a Post-IFFT module for performing IFFT transform for input signals; a demodulation module for demodulating the modulation symbols to output data bits; and a HARQ module for performing soft combination and decoding to data packets of each transmission, and generating response information according to the decoding result.

The present invention uses the method of cyclic shifted sub-carrier mapping to make the same bits transmit in different sub-carriers when transmitting in different transmissions of the same ELARQ process, thus acquiring frequency diversity gain, reducing HARQ transmission failure rate due to some bits transmitted all the time in sub-carrier that experiences deep fading. In this way, the average HARQ retransmission times and the average transmission delay can be reduced and the system throughput can be improved. Meanwhile, cyclic shifted sub-carrier mapping method neither impacts the PAPR of the transmitted signals nor changes the low PAPR characteristics of SC-FDMA. The cyclic shifted sub-carrier mapping method is suitable for both uplink and downlink information transmission.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: Figure 1 is a block diagram illustrating an OFDM transmitter/receiver;

Figure 2 is a block diagram illustrating a SC-FDMA transmitter/receiver (in frequency domain);

Figure 3 indicates principle of N-SAW HARQ, including;

Figure 4 shows that a transmitting (receiving) end sets a mapping relationship between modulation symbols and sub-carriers;

Figure 5 shows a transmitting apparatus of OFDMA that uses cyclic shifted sub-carrier mapping;

Figure 6 shows a receiving apparatus of OFDMA that uses cyclic shifted sub-carrier mapping; Figure 7 shows a transmitting apparatus of SC-FDMA that uses cyclic shifted sub-carrier mapping;

Figure 8 shows a receiving apparatus of SC-FDMA that uses cyclic shifted sub-carrier mapping;

Figure 9 shows sub-carriers that are continuously distributed and used by the transmitting end and the fixed cyclic shift interval; and

Figure 10 shows sub-carriers that are discretely distributed and used by the transmitting end and variable cyclic shift interval.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention provide a cyclic shifted sub-carrier mapping method for multi-carrier communication system that uses HARQ. The present invention uses the method on cyclic shifted sub-carrier mapping to make the same bits transmit in different sub-carriers when transmitting in different transmissions of the same HARQ process, thus acquiring frequency diversity gain, reducing HARQ transmission failure rate due to some bits transmitted all the time in sub-carrier that experiences deep fading.

The present invention proposes the following solution: a transmitting end determines the mapping relationship between modulation symbols and sub-carriers used in every transmission of HARQ process by the cyclic shift method, and modulates the appointed number of modulation symbols onto every sub-carrier and transmits. The receiving end determines the mapping relationship between modulation symbols and sub-carriers used in every transmission of HARQ process by the cyclic shift method, and extracts modulation symbols orderly from the corresponding sub-carrier position.

The transmitting end performs the following steps:

I. Symbol modulating

The transmitting end matches several inputted data bits to a symbol from the modulation symbol set and outputs the corresponding modulation symbol. II. Mapping relationship setting of modulation symbols and sub-carriers

When transmitting data, the transmitting end uses a different mapping relationship between modulation symbols and sub-carriers in every transmission of a HARQ process.

When transmitting new data packets, the transmitting end uses initial mapping relationship between modulation symbols and sub-carriers, as is shown in Figure 4(a). The initial mapping relationship between modulation symbols and sub-carriers may be fixed or configurable by the system.

When the transmitting end retransmits data packets, it performs cyclic shift on mapping relationship between modulation symbols and sub-carriers in the last transmission to obtain a mapping relationship between modulation symbols and sub-carriers in the current transmission, as is shown in Figure 4(b), 4(c) (the cyclic shift interval of the first retransmission is k, and the cyclic shift interval of the second retransmission is m).

Figure 4 shows that a transmitting (receiving) end sets a mapping relationship between modulation symbols and sub-carriers, including:

401 Modulation symbol sequence,

402 Sub-carrier sequence number,

403 Cyclic shift interval of the first retransmission, and

404 Cyclic shift interval of the second retransmission. The cyclic shift interval used every time when the transmitting end transmits retransmission data packets may be the same or variable. It could be fixed or configured by the system through half-static or dynamic method in both cases.

III. Sub-carrier modulation The transmitting end modulates modulated symbols onto every sub-carrier and transmits according to the mapping relationship between modulation symbols and sub-carriers used in every transmission.

The receiving end takes the following steps:

I. Setting of mapping relationship between modulation symbols and sub-carriers

When receiving data packets, the receiving end uses a different mapping relationship between modulation symbols and sub-carriers in every reception of a HARQ process.

When receiving new data packets, the receiving end uses initial mapping relationship between modulation symbols and sub-carriers, as is shown in Figure 4(a). Initial mapping relationship between modulation symbols and sub-carriers can be fixed or configurable by the system.

When the receiving end receives retransmission data packets, it performs cyclic shift on mapping relationship between modulation symbols and sub-carriers used in receiving the last data packets to get mapping relationship between modulation symbols and sub-carriers of the present reception, as is shown in Figure 4(b), 4(c) (the cyclic shift interval of the first retransmission is k, and the cyclic shift interval of the second retransmission is m).

The cyclic shift interval used every time when the receiving end to receive retransmission data packets can be the same or variable. It could be fixed or configured by the system through half-static or dynamic method in both cases.

II. Sub-carrier demodulation

The receiving end extracts modulation symbols orderly from corresponding sub-carrier position according to mapping relationship between modulation symbols and sub-carriers used in every receiving.

III. Symbol demodulation

The receiving end performs demodulation for the inputted modulated symbols.

The present invention gives a transmitting and receiving apparatus for OFDMA and SC-FDMA that uses cyclic shifted sub-carrier mapping:

1) Transmitting apparatus for OFDMA that uses cyclic shifted sub-carrier mapping

As shown in Figure 5, the equipment consists of a HARQ module, a modulation module, a cyclic shifted sub-carrier mapping module and a transmitting means. Here, the HARQ module outputs the data bits of each transmission according to the response information from the receivers. The modulation module is used for modulating the data bits and outputting the modulation symbols. The cyclic shifted sub-carrier mapping module makes cyclic shift of mapping relationship between modulation symbols and sub-carriers used in the last transmission to get mapping relationship between modulation symbols and sub-carriers used in the present transmission. The transmitting means transmits radio signals via an air-interface.

2) Receiving apparatus for OFDMA that uses cyclic shifted sub-carrier mapping As shown in Figure 6, the receiving apparatus consists of a receiving means, a cyclic shifted sub-carrier mapping module, a modulation symbols weighting combination module, a demodulation module and a HARQ module. The receiving means receives radio signals transmitted from the transmitting device via the air-interface. The cyclic shifted sub-carrier mapping module makes cyclic shift of the mapping relationship between modulation symbols and sub-carriers used in the last transmission to get the mapping relationship between modulation symbols and sub-carriers that should be used in the present transmission. Modulation symbol weighting combination module makes weighting combination according to the channel estimation accuracy and fading event of sub-carriers used by the same modulation symbol before and after cyclic shift. The demodulation module is responsible for demodulating the modulation symbols to output data bits. The HARQ module performs soft combination and decoding to data packets of each transmission, and generates the response message according to the decoding result. 3) Transmitting apparatus of SC-FDMA that uses cyclic shifted sub-carrier mapping

As shown in Figure 7, the transmitting apparatus consists of: a HARQ module, a modulation module, a Pre-FFT module, a Cyclic shifted sub-carrier mapping module and a transmitting means. The HARQ module outputs the data bits of each transmission according to the response information from the receivers. The modulation module is responsible for modulating the data bits and outputting the modulation symbols. The Pre-FFT module makes FFT transform for the input signals. The cyclic shifted sub-carrier mapping module makes cyclic shift of mapping relationship between modulation symbols and sub-carriers used in the last transmission to get the mapping relationship between modulation symbols and sub-carriers that should be used in the present transmission The transmitting set transmits radio signals via the air-interface.

4) Receiving apparatus of SC-FDMA that uses cyclic shifted sub-carrier mapping As shown in Figure 8, the receiving apparatus consist of a receiving means, a cyclic sub-carrier mapping module, a modulation symbols weighting combination module, a Post-IFFT module, a demodulation module and a HARQ module. The receiving means receives radio signals transmitted from the transmitting device via the air-interface. The cyclic shifted sub-carrier mapping module makes cyclic shift of mapping relationship between modulation symbols and sub-carriers used in the last transmission to get the mapping relationship between modulation symbols and sub-carriers that should be used in the present transmission. The Post-IFFT module makes IFFT transform for the input signals. The demodulation module is responsible for demodulating the modulation symbols to output data bits.

The FIARQ module performs soft combination and decoding on data packets of each transmission, and generates the response message according to the decoding result.

Embodiment 1 : Sub-carriers used in the transmitting end are continuously distributed, fixed cyclic shift interval

As shown in Figure 9, sub-carriers (64 sub-carriers) used when the transmitting end transmits data are continuously distributed, the maximum retransmission times of HARQ is 3. Sub-carrier sequence number 1~64 is the ordinal sub-carrier number used by the transmitting end, and modulation symbol sequence 1-64 is the ordinal modulation symbol number in the transmitting end.

Mapping relationship between modulation symbols and sub-carriers used in the first retransmission is gained by making cyclic shift of 20 sub-carriers downward of the mapping relationship used in the initial transmission. Mapping relationship between modulation symbols and sub-carriers used in the second retransmission is gained by making cyclic shift of 20 sub-carriers downward of the mapping relationship in the first retransmission.

Figure 9 shows sub-carriers that are continuously distributed and used by the transmitting end and the fixed cyclic shift interval, including: 901 Sub-carriers that are not allocated to a transmitting end, 902 Sub-carriers (continuously distributed) used by a transmitting end,

903 Sub-carriers that are not allocated to a transmitting end,

904 Cyclic shift interval of a first retransmission, and

905 Cyclic shift interval of a second retransmission.

Embodiment 2: Sub-carriers used in the transmitting end are discretely distributed, variable cyclic shift interval

As shown in Figure 10, sub-carriers (128 sub-carriers) used when the transmission end transmits data are discretely distributed, the maximum retransmission times of HARQ is 3. Sub-carrier sequence number 1-128 is the ordinal sub-carrier sequence number used by the transmitting end, and modulation symbol sequence 1~128 is the ordinal modulation symbol sequence number. Mapping relationship between modulation symbols and sub-carriers used in the first retransmission is gained by making cyclic shift of 40 sub-carriers downward of the mapping relationship used in the initial transmission. Mapping relationship between modulation symbols and sub-carriers used in the second retransmission is gained by making cyclic shift of 30 sub-carriers downward of the mapping relationship in the first retransmission.

Figure 10 shows sub-carriers that are discretely distributed and used by the transmitting end and variable cyclic shift interval, including:

1001 Sub-carriers that are allocated to transmitting end,

1002 Sub-carriers that are not allocated to transmitting end,

1003 Cyclic shift interval of the first retransmission, and

1004 Cyclic shift interval of the second retransmission.

The advantage of the method according to present invention consists that:

1) Mapping relationship between modulation symbols and sub-carriers used in initial transmission and cyclic shift interval used in every transmission is default in the BS and the UE, without introducing additional signaling overhead, and the performance gain brought about by the present invention will not reduce from physical layer signaling transmission failure.

2) The same modulation symbol is transmitted in different sub-carriers in HARQ transmission process, thus acquiring frequency diversity gain. And the probability of failure of HARQ transmission caused by that some bits are always transmitted via the sub-carrier with the same deep fading is reduced. The average number of HARQ transmissions is reduced and the average delay is reduced also so that the system throughput is improved.

3) It will not affect peak-to-average power ratio of the sent signal power when using cyclic shifted sub-carrier mapping method to acquire frequency diversity gain.

4) The receiving end makes weighting combination of modulation symbols in every reception according to the channel estimation accuracy and fading event of sub-carriers used by the same modulation symbol before and after cyclic shift, reducing the impact of channel estimate error and sub-carrier deep fading.

The present invention has extensive application field, which can be used in sub-carrier continuous division, discrete division or jumping SC-FDMA, OFDMA.

Claims

WHAT IS CLAIMED IS:

1. A method for cyclic shifted sub-carrier mapping in the transmitting end, the method comprising steps of: mapping several input data bits to a symbol from a modulation symbol set and output the resulting modulation symbol; when retransmitting data packets, obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; and modulating and sending the modulated symbols on various sub-carriers.

2. The method according to Claim 1, further comprising step of: using a different mapping relationship between modulation symbols and sub-carriers in every transmission of a HARQ process.

3 . The method according to Claim 1, wherein the sub-carriers are continuously distributed, discretely distributed, partially continuously and partially discretely distributed in frequency domain.

4. The method according to Claim 1, wherein a fixed or variable cyclic shift interval is used in every transmission of a HARQ process.

5. A method for cyclic shifted sub-carrier mapping in the receiving end, the method comprising steps of: when receiving retransmitted data packets, obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; extracting modulated symbols orderly from a corresponding sub-carrier position; and demodulating the modulated symbols.

6. The method according to Claim 5, further comprising step of: using different mapping relationship between modulation symbols and sub-carriers in every transmission of a HARQ process.

7. The method according to Claim 5, wherein the sub-carriers are continuously distributed, discretely distributed, partially continuously and partially discretely distributed in frequency domain.

8. The method according to Claim 5, wherein a fixed or variable cyclic shift interval is used in every transmission of a HARQ process.

9. A transmitting apparatus for OFDMA cyclic shifted sub-carrier mapping, the transmitting apparatus comprising: a HARQ module for outputting data bits of each transmission according to response information from the receivers; a modulation module for modulating the data bits and outputting modulation symbols; a cyclic shifted sub-carrier mapping module for obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; and a transmitting means for transmitting radio signals via an air-interface.

10. A receiving apparatus for OFDMA cyclic shifted sub-carrier mapping, the receiving apparatus comprising: a receiving means for receiving radio signals transmitted from a transmitting apparatus via an air-interface; a cyclic shifted sub-carrier mapping module for obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; a modulation symbol weighting combination module for performing weighting and combination according to channel estimation accuracy and fading event of sub-carriers used by the same modulation symbol before and after cyclic shift; a demodulation module for demodulating the modulation symbols to output data bits; and a HARQ module for performing soft combination and decoding on data packets of each transmission, and generating response information according to the decoding result.

11. A transmitting apparatus for SC-FDMA cyclic shifted sub-carrier mapping, the transmitting apparatus comprising: a HARQ module for outputs data bits of each transmission according to response information from a receiving apparatus; a modulation module for modulating the data bits and outputting modulation symbols; a Pre-FFT module for performing FFT transform for input signals; a cyclic shifted sub-carrier mapping module for obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; and a transmitting means for transmitting radio signals via an air-interface.

12. A receiving apparatus for SC-FDMA that uses cyclic shifted sub-carrier mapping, the receiving apparatus comprising: a receiving means for receiving radio signals transmitted from a transmitting apparatus via an air-interface; a cyclic shifted sub-carrier mapping module for obtaining the mapping relationship between modulation symbols and sub-carriers used in the current transmission by cyclic shifting the mapping relationship between modulation symbols and sub-carriers in the last transmission; a Post-IFFT module for performing IFFT transform for input signals; a demodulation module for demodulating the modulation symbols to output data bits; and a HARQ module for performing soft combination and decoding to data packets of each transmission, and generating response information according to the decoding result.