WO2006125343A1

WO2006125343A1 - A orthogonal frequency-time division multiplex transmitter, a receiver and methods

Info

Publication number: WO2006125343A1
Application number: PCT/CN2005/000726
Authority: WO
Inventors: Xiaodong Zhang; Zhiyong Bu; Bin Zhou; Mingqi Li; Xiumei Yang; Ping Zhou
Original assignee: Shanghai Institute Of Microsystem And Information Technology; Shanghai Research Centre For Wireless Technologies
Priority date: 2005-05-25
Filing date: 2005-05-25
Publication date: 2006-11-30
Also published as: CN101204030A

Abstract

Techniques are provided to support orthogonal multiple carriers frequency-time division multiplex based on orthogonal frequency division multiplex and single carrier with frequency domain equalization in prior art. At a transmitter end, Serial to Parallel Transform and Inverse Fast Fourier Transform are performed for the input serial data stream, then data blocks after IFFT are multiplexed to be a OFTDM symbol data part in temporal sequence; and then a circulation prefix is added in its front-part to form a final OFTDM symbol. At a receiver end, the CP in the front-part of the OFTDM symbol down-converted to a baseband is removed, and after the operations of data de-multiplex, FFT and P/S corresponding to the transmitter end are performed, the original serial data stream is recovered. Except for including the advantage of said prior art, this disclosure can overcome their disadvantage, and a preferable tradeoff between the general performance and complexity of the system can be acquired.

Description

Orthogonal frequency division time division transmitter, receiver and method thereof

The present invention relates to wireless communication technologies, and more particularly to a technique for transmitting signals over a plurality of orthogonal carriers in a wireless communication system. Background technique

In wireless communication systems, especially in broadband mobile communication systems, airborne signal transmission technology is becoming the focus of research. In order to obtain higher, for example, up to lObps/Hz, spectral efficiency, support communication requirements of multiple scenarios, and support various adaptive control technologies, the signal transmission technology of broadband mobile communication systems must support more than any similar technology in the past. Good performance while maintaining controllable implementation complexity. Now, the signal transmission technology of broadband mobile communication is mainly based on OFDM (Orthogonal Frequency Division Multiplexing) technology, and various variant technologies such as OFDMA (Orthogonal Frequency Division Multiple Access) and MC-CDMAC Multi-Carrier-Code are derived. Multiple access), MT-CDMA (multi-tone-code division multiple access), VSF-OFCDM (orthogonal frequency division code division multiplexing), etc. In addition, filter bank based generalized multi-carrier modulation (GMC) and traditional The enhanced technology of CDMA, CP-CDMA (Cyclic Prefix-Code Division Multiple Access), has also received attention and attention.

However, combining the performance of existing transmission technologies, they show superior performance under certain conditions. However, the applicable scenarios are still not broad enough. For example, the symbol length, CP length and spectrum utilization of OFDM technology are directly related. It affects its adaptability to different terrain and mobile scenes, and other technologies derived from it also have this disadvantage; while single-carrier technology, such as CP-CDMA, has insufficient adaptability to the channel frequency domain, directly affecting it. Frequency domain diversity performance; the GMC technology placed between OFDM technology and single carrier technology does not have the inherent adaptability to the channel time-frequency plane like OFDM and CP-CDMA technology, in the implementation complexity It appears that the artificial trace is heavy and the design is not natural enough. At the same time, it also has the same shortcomings as the OFDM technology and the poor adaptability of the scene.

The technologies closely related to the present invention mainly include OFDM and SC/FDE (single carrier-frequency domain equalization), which respectively represent two different information transmission methods: multi-carrier communication and single-carrier communication. Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique that uses parallel transmission to decompose and modulate the transmitted high-speed data into multiple overlapping but orthogonal subchannels (frequency domain), such that each The period of the modulated signals is larger than the multipath delay spread. If a guard interval of a certain width is added between the modulation symbols, the intersymbol interference caused by the multipath transmission is basically eliminated, so the OFDM system has a high spectrum utilization rate. It is robust to inter-symbol interference caused by multipath transmission and can support high-speed data transmission.

The multi-carrier communication method of OFDM maps a sequence of symbols to be transmitted to a plurality of parallel sub-carriers for transmission; in the transmission process, symbols on each sub-carrier are only weighted by their corresponding sub-channel amplitude-frequency responses, and Gaussian additive noise Contamination; On the receiving side, as long as the amplitude-frequency response of the sub-channel is normalized, the symbols transmitted on the sub-carriers can be estimated, thereby estimating the transmission sequence. In order to facilitate the lossless equalization of the amplitude-frequency response characteristics of the subchannels on the receiving side, a cyclic prefix (CP) having a length of the channel maximum delay spread must be added at the front end of each OFDM transmission symbol, which is copied from the tail end of the OFDM symbol. Come.

1 is a block diagram of a prior art OFDM radio transmitter and receiver. The wireless transmitter 1 includes a serial to parallel conversion device 11 for converting and converting a serial symbol stream obtained by data modulation mapping into a plurality of parallel symbol streams; and an IFFT conversion device 12 for IDFT transforming to modulate the plurality of parallel symbol streams onto a plurality of orthogonal subcarriers and synthesizing into OFDM symbols; a CP adding device 13 for copying a portion of the OFDM symbol tail to a front end of the symbol to form The final OFDM symbol with CP, CP makes the transmitted symbol have periodicity. When the length of the CP is longer than the delay time of the signal transmitted in the channel, the inter-symbol interference (ISI) only affects the CP of the OFDM symbol front end. ISI can be eliminated at the receiver by simply removing the CP. Of course, the wireless transmitter should further include: channel coding and modulating means for channel coding and data modulation of the input data; and performing D/A conversion and analog signal processing (eg, channel shaping filtering) on the OFDM symbol, and Modulation to the radio frequency and then transmission through the antenna, since these parts are not directly related to the present invention, they are omitted here for the sake of brevity.

Correspondingly, in the receiver 2, including a de-CP device 21, for removing the CP of the OFDM symbol front end obtained by down-converting to the baseband; an FFT device 22, for removing the CP by DFT transform After the OFDM symbol is correlated and demodulated, after demodulation is obtained Parallel symbol stream; a parallel to serial conversion device 23 for parallel-converting the demodulated parallel symbol stream into a serial symbol stream. Of course, the wireless receiver machine should further include a receiving antenna for receiving the radio frequency signal; a downconverting device for downconverting the radio frequency signal to the baseband; and a matching filtering device for performing matched filtering on the downconverted baseband signal; and, based on the transmitting end Channel coding and modulation rules for channel decoding and demodulation of the serial symbol stream to obtain channel decoding and demodulation means for the initially transmitted signal stream, since these portions are not directly related to the present invention, Therefore, for the sake of brevity, it is omitted here.

Compared with the traditional single-carrier communication system based on the transverse filter architecture, the OFDM system has low implementation complexity (sub-channel signal shaping and receive matching filtering based on IFFT/FFT), high frequency efficiency, and easy to be used in broadband. Applications in wireless communication systems, however, the spectrum utilization and power efficiency of OFDM decreases as the CP length of the CP is included in OFDM, and in order to maintain a high level of spectrum utilization and power efficiency, no more than (for example, at least 4 times), thus directly causing the number of subcarriers of the OFDM symbol to generally exhibit a large value (for example, 256 subcarriers) in a broadband wireless communication scenario, so that the equivalent bandwidth of the subcarrier is far Less than the coherence bandwidth of the channel improves the receiver's sensitivity to frequency synchronization accuracy and reduces the frequency domain diversity performance of the OFDM system. At the same time, the time-domain superposition of a large number of subcarriers causes a large amplitude-to-average ratio of the transmitted signal. The upgrade also increases the transmitter's requirements for the linearity of the power amplification period. In short, although OFDM has strong adaptability to the channel time-frequency plane, its symbol design length is greatly affected by spectrum utilization, and frequency domain subcarrier division is redundant, which is not conducive to fast moving speed and carrier frequency. In high-Doppler communication scenarios with large frequency shifts; conversely, in low-speed mobile, low carrier frequency, and small Doppler frequency shift scenarios, the length of OFDM symbols cannot be lengthened appropriately to improve spectrum utilization. Therefore, the design of the entire OFDM system appears to be rather rigid, and its symbol length must be designed for the harsh scene of the communication scenario, resulting in potential capacity loss.

The SC/FDE (single-carrier frequency-domain equalization) communication system is very close to the traditional single-carrier communication system, but it divides the transmitted symbol sequence into blocks of equal length and copies a cyclic prefix for each data block. (CP), the design principle of this CP is similar to the present invention. The OFDM orthogonal frequency division multiplexing system differs in that the data to be copied is the tail of each data block. In this way, the receiver side can equalize the channel according to the frequency domain equalization method, thereby repairing the damage of the channel to the transmitted symbol, and then estimating the corresponding transmitted symbol sequence. SC/FDE system has low implementation complexity (the receiving end is based on FFT/IFFT transform and single-point zero-forcing equalizer to complete frequency domain equalization), and has complete equalizer design criteria, signal peak-to-average ratio is not high, CP and data block length The design is flexible and easy to use in broadband wireless communication systems. However, the design of this scheme does not consider the adaptability to the channel time-frequency characteristics, making it difficult for the receiver to provide a large frequency domain diversity gain for channel decoding. The comprehensive performance is not high; at the same time, the single-carrier receiving algorithm is likely to cause the noise enhancement and proliferation, which will seriously affect the receiving error performance of the system.

The present invention has been made to solve the above problems existing in the prior art. Summary of the invention

The invention is a novel orthogonal multi-carrier frequency division time division technique-OFTDM which is proposed based on combining the advantages and disadvantages of various conventional single-carrier and multi-carrier transmission technologies.

The wireless transmitter of the present invention first converts the serial-parallel converted plurality of parallel modulation symbol streams into a sequence of data blocks of a corresponding length based on an inverse fast Fourier transform (IFFT), and chronologically processes the plurality of IFFT-transformed data blocks. Performing block multiplexing, defining a plurality of multiplexed data blocks as one OFTDM (orthogonal frequency division-time division multiplexing) symbol data portion; secondly, copying a plurality of data at the tail of the OFTDM symbol data portion as a loop a prefix (CP) portion to the forefront of the OFTDM symbol data portion to generate the OFTDM symbol; again, channel shaping filtering of the OFTDM symbol components (data portion and CP portion); and finally, the baseband of the OFTDM system The signal is converted to a radio frequency (RF) signal and radiated by the antenna system onto the wireless channel.

The wireless receiver of the present invention first converts the received wireless signal into a baseband signal, and performs matched filtering on the received signal to complete symbol timing and frequency synchronization; subsequently, removes the cyclic prefix of the OFTDM symbol front end, and then the data portion of the OFTDM symbol. Demultiplexing is performed to restore a plurality of data block sequences of the same length as the transmitting end; finally, the transmitting end data block is mapped to the corresponding modulation symbol stream based on the FFT Fourier transform. Preferably, it can also be carried out Before demultiplexing the OFTDM symbol data portion, the OFTDM symbol level frequency domain equalization (FDE) is implemented based on channel estimation, FFT/IFFT forward and inverse Fourier transform equal to the length of the data portion of the OFTDM symbol, and channel equalizer. The frequency domain equalized OFTDM symbol data portion is provided to the demultiplexing step.

Preferably, in the wireless transmitter of the present invention, the following control method for adjusting the IFFT transform matrix size, the cyclic prefix length, and the number of data block demultiplexing is also proposed:

1) adjusting the size of the transform matrix of the IFFT transform device according to the channel bandwidth and the channel time extension;

2) adjusting the length of the cyclic prefix according to the length of the channel delay spread and the size of the IFFT transform matrix to be greater than or equal to the length of the channel delay spread, and less than or equal to the size of the IFFT transform matrix; that is, the loop The prefix (CP) must be greater than the channel spread length; the transmitter IFFT transform length is at least greater than the CP length (which remains unchanged during communication);

3) adjusting the number of time domain multiplexing of the transmitter IFFT transform data block according to the change of the Doppler frequency shift (or channel coherence time), so that the equivalent time length of the OFTDM symbol is smaller than the channel Coherence time length.

According to a first aspect of the present invention, there is provided a wireless transmitter for transmitting signals over a plurality of orthogonal carriers in a wireless communication system, comprising: a serial to parallel conversion device for inputting serial symbol data sequences Serializing and converting a plurality of parallel symbol data sequences; an IFFT transforming apparatus, configured to perform IFFT orthogonal transform on the plurality of parallel symbol data sequences to generate a plurality of time domain data blocks; and further comprising: a data block multiplexing device, configured to multiplex the plurality of time-domain data blocks that have undergone IFFT orthogonal transform into a baseband OFTDM symbol data sequence in a sequence of generation time; and a guard interval adding device, configured to The header or trailer of the baseband OFTDM symbol data sequence generates a guard interval of a specific length to generate a baseband OFTDM signal to be transmitted.

According to a second aspect of the present invention, there is provided a method for transmitting a signal over a plurality of orthogonal carriers in a wireless transmitter of a wireless communication system, comprising the steps of: converting and converting an input serial symbol data sequence a plurality of parallel symbol data sequences; performing IFFT orthogonal transform on the plurality of parallel symbol data sequences to generate a plurality of time domain data blocks; and generating the plurality of time domain data blocks subjected to the IFFT orthogonal transform according to a generation time Sequentially multiplexed into baseband OFTDM symbol data sequence; a guard interval of a specific length is added to the head or tail of the OFTDM symbol data sequence of the baseband.

According to a third aspect of the present invention, there is provided a wireless receiver for receiving an OFTDM signal transmitted over a plurality of orthogonal carriers in a wireless communication system, comprising: a guard interval removing means for removing a transform to a baseband a guard interval between guard sequences of OFTDM symbols; a data block demultiplexing apparatus for demultiplexing the guard interval-free OFTDM symbol sequence into a plurality of data block sequences; an FFT transform device, Performing FFT transformation on the plurality of data blocks in order of reception time, converting the plurality of data blocks into a plurality of parallel symbol data sequences; and a parallel to serial conversion device for converting the plurality of parallel symbol data sequences into strings Line symbol data sequence.

Preferably, the radio receiver further includes: a channel estimating apparatus, configured to estimate a channel response of the time domain according to the OFTDM symbol sequence converted to the baseband, to obtain an estimated value of the channel response; and a time/frequency a transforming apparatus, configured to transform the guard interval-removed OFTDM data block sequence into a frequency domain OFTDM data block sequence; a frequency domain equalizer, configured to convert the TOFTDM data block based on the estimated value of the channel response The frequency domain OFTDM data block sequence performs phase compensation and amplitude compensation of channel impairment to obtain a frequency domain equalized frequency domain OFTDM data block sequence; a frequency/time transform device for frequency domain OFTDM that has been frequency domain equalized The data block sequence is reconverted into a time domain OFTDM data block sequence for transmission to the data block demultiplexing device.

According to a fourth aspect of the present invention, a method for receiving an OFTDM signal transmitted over a plurality of orthogonal carriers in a wireless receiver of a wireless communication system, comprising the steps of: removing a guard interval of a baseband OFTDM symbol; Demultiplexing the OFTDM symbol sequence of the removal guard interval into a plurality of data block sequences; performing FFT transformation on the plurality of data blocks in order of receiving time, and converting the plurality of data blocks into a plurality of parallel symbol data sequences; The plurality of parallel data symbol sequences are parallel-converted into a serial symbol data sequence.

Preferably, the receiving method further comprises the steps of: estimating a channel response of the time domain according to the OFTDM symbol sequence or the pilot training sequence transformed to the baseband, to obtain an estimated value of the channel response; The sequence of spaced OFTDM data blocks is transformed into a sequence of OFTDM data blocks in the frequency domain; based on the estimated value of the channel response, The OFTDM data block sequence transformed into the frequency domain performs phase compensation and amplitude compensation of the channel impairment to obtain a frequency domain equalized frequency domain OFTDM data block sequence; re-converts the frequency domain OFTDM data block sequence that has undergone frequency domain equalization to A sequence of OFTDM data blocks in the time domain for performing the data block demultiplexing operation.

The wireless transmitter and receiver of the present invention are a novel combination and expansion scheme of a conventional cyclic prefix (CP) based orthogonal frequency division multiplexing (OFDM) system and a single carrier frequency domain equalization system (SC FDE), It has the advantages of low implementation complexity and high spectral efficiency of OFDM, and has the advantages of SC FDE frequency shift robustness and easy frequency synchronization; it has the same reception error performance characteristics as OFDM, and has much larger mobility than OFDM. Speed adapts to the range. Based on the OFTDM technology solution, the inherent advantages of multi-carrier communication and single-carrier communication can be simultaneously integrated on the same communication system. At the same time, their deficiencies can be avoided as much as possible, and the overall performance and complexity of the system can be better compromised.

More specifically, compared with the prior art, the present invention has the spectrum adaptability of multi-carrier transmission technology (such as OFDM), the flexibility of single-carrier communication, and the transmission performance is equivalent to that of OFDM technology, and the implementation complexity is achieved. Lower. More importantly, by controlling the number of time domain multiplexing of the transmitter IFFT transform data block, the system can obtain a larger throughput gain and a wider range of mobile speed adaptability; design the transmitter IFFT based on the channel coherence bandwidth The size of the transform can improve the frequency shift robustness of the system; by introducing the CP prefix, the OFTDM can maintain the system and OFDM with similar timing robustness. DRAWINGS

The invention is described in detail below with reference to the drawings, wherein the same or similar reference numerals represent the same parts.

1 is a block diagram of a prior art OFDM radio transmitter and receiver.

2 is a block diagram of a wireless transmitter for transmitting signals via orthogonal multi-carriers in a broadband mobile communication network, in accordance with an embodiment of the present invention;

3 is a flow chart of a method for wireless transmission of signals transmitted over orthogonal multi-carriers in a broadband mobile communication network, in accordance with an embodiment of the present invention;

4 is a schematic structural diagram of an OFTDM symbol sequence to which a cyclic prefix is added; 5 is a block diagram of a wireless receiver for transmitting signals via orthogonal multi-carriers in a broadband mobile communication network, in accordance with an embodiment of the present invention;

6 is a flowchart of a wireless receiving method for transmitting signals via orthogonal multi-carriers in a broadband mobile communication network according to an embodiment of the present invention;

FIG. 7 shows a simulated schematic diagram based on the MATLAB/SIMULink simulation platform; FIG. 8 shows three schemes of the OFTDM scheme of the present invention and the prior art OFDM and SC/FDE schemes on the simulation platform shown in FIG. The result of the simulation operation under the simulation parameters (bit error rate). detailed description

The present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the invention is not limited to the specific embodiments.

2 shows a block diagram of a wireless transmitter 1 for transmitting signals over a plurality of orthogonal carriers in a wireless communication network, particularly a broadband mobile communication network, in accordance with an embodiment of the present invention. The method includes a channel coding device 1 1 , a digital modulation device 12 , a serial to parallel conversion device 13 , an inverse Fourier transform (IDFT ) conversion device 14 , a data block multiplexing device 15 , a guard interval adding device 16 , and a shaping filter Apparatus 17, an RF inverter unit 18 and a transmitting antenna 19.

It should be noted that the channel coding apparatus, the digital modulation apparatus, the shaping and filtering apparatus, the RF frequency conversion apparatus, and the transmitting antenna shown in FIG. 2 are not directly related to the object of the present invention, and are only used as a preferred embodiment. And describe it.

Assuming that A = o, i, 2....} is the output digital sequence of the input wireless transmitter, the wireless transmitter of the present invention will be described in detail below with reference to FIG. 2 in conjunction with FIG.

The channel coding apparatus 11 is configured to perform channel coding on the input data sequence, t-0, 1, 2, . . . using a predetermined channel coding rule, and convert it into an output data sequence fe ^ = 0, l, 2. The channel coding rule may employ a concatenated code, such as an RS code and a convolutional code, a Turbo code, or an LDPC code, or an adaptive coding scheme composed of multiple technologies, such as adaptive coding. Modulation scheme (AMC);

The digital modulation device 12 is used, for example, according to the Gray coding specification, to be channel coded The data sequence is mapped to the dot pattern of the modulation symbol. The selected modulation mode is determined by the system design, and can be determined as one of BPSK and QPSK QAM modulation modes, and can also be based on the bit error rate and the carrier-to-interference ratio. Multiple dynamic modulation methods for adaptive selection. After the digital modulation device 12, the input data sequence fe = o, i, 2....} is transformed into an output symbol sequence fc, Α = 0, 1, 2, ....}; the serial/parallel conversion device 13 is used for The serial symbol sequence obtained by the digital modulation mapping is divided into a plurality of serial symbol data blocks according to the size of the subsequent IFFT transformation matrix, and the serial-to-parallel conversion operation is performed on the plurality of serial symbol data blocks to form a corresponding plurality of Parallel symbol data block. After serial/parallel conversion means 13, the input serial symbol sequence 3⁄4, = 0, 1, 2....} is transformed into a plurality of parallel symbol data blocks {e _t , A = 0, 1, 2... .} , where ^ denotes a column vector with the same number of elements as the IFFT transform size;

An inverse Fourier transform (IDFT) transforming device 14 is preferably implemented by an inverse fast Fourier transform (IFFT) module for performing IDFT transform on each input parallel symbol data block to generate a corresponding plurality of time domain symbol data blocks. Wherein the IDFT transform is equivalent to orthogonal multi-carrier modulation and synthesis of the input parallel data, and the input parallel data block sequence = 0, 1, 2, L } is transformed into a corresponding time domain data block by an IFFT transform module. The sequence {/„A: = 0,1,2,L } , the relationship between them obeys = JF r(e Here, Λ also represents a column vector with the same number of elements and the size of the IFFT transform;

The data block multiplexing means 15 is adapted to multiplex a certain number of IFFT-transformed data blocks into a data portion of a longer-length orthogonal frequency division time division multiplexing (OFTDM) symbol in accordance with the generated order. After data block multiplexing, the input data block sequence {A = 0, 1, ² , L } is transformed into a sequence of data portions of the OFTDM symbol, 0, l, 2, L } , where an element number and OFTDM symbol are represented. a column vector of the same size as the data portion;

The guard interval adding means 16 is configured to add a guard interval of a specific length to the head or the tail of the OFITM) symbol data portion after the data block multiplexing, for reducing inter-channel interference (the length of the guard interval should be greater than the channel maximum delay) Extended length). Preferably, the guard interval adding means may employ a cyclic prefix (CP) adding means, that is, copy a part of the tail portion of the OFTDM symbol data portion to the front end of the OFTDM symbol data portion to form a final OFTDM symbol with CP, and the CP transmits the The symbol has periodicity. When the length of the CP is longer than the maximum delay time of the signal transmitted in the channel, inter-symbol interference (ISI) only affects The CP at the front end of the OFTDM symbol is used, so that ISI can be eliminated at the receiver end simply by removing the CP. After the cyclic prefix adding means, the input sequence { , /t = 0, i, 2, L } is transformed into a complete 0? 10] ^ symbol sequence { , = 0, 1, 2 mountain }, where, represents the number of elements and The OFTDM symbol size is the same as the column vector, and its structure is shown in Figure 4.

The channel signal shaping means 17 is configured to perform shaping filtering on the OFTDM signal waveform to be transmitted in accordance with the frequency template. Through the signal shaping device 17, the input OFTDM symbol sequence {h _k , k = 0, 1, 2, L } is transformed into an output waveform sequence {i _k , k = 0, 1, 2, L };

The RF transform means 18 is operative to transform the baseband OFTDM symbol sequence into a radio frequency signal and transmit it to the radio channel via the transmit antenna.

Preferably, the wireless transmitter 1 further includes a control device 19 (not shown) for performing the following functions:

2) adjusting the length of the cyclic prefix according to the length of the channel delay spread and the size of the IFFT transform matrix to be greater than or equal to the length of the channel delay spread, and less than or equal to the size of the IFFT transform matrix; that is, the loop The prefix (CP) must be greater than the channel extension length; the transmitter IFFT transform length is at least greater than the CP length (which remains unchanged during communication);

3) expanding or reducing the number of transmitter IFFT time domain multiplexing in reverse with the Doppler frequency shift (or channel coherence time); and adjusting the data block according to the channel coherence time length The number is used such that the equivalent time length of its OFTDM symbol is less than the channel coherence time length.

3 is a flow diagram of a method of wireless transmission for transmitting signals over orthogonal multi-carriers in a broadband mobile communication network, in accordance with an embodiment of the present invention.

It should be noted that the channel coding step, the digital modulation step, the shaping filtering step, the RF frequency conversion step, and the step of transmitting the wireless signal shown in FIG. 2 are not directly related to the purpose of the present invention, and are only a preferred embodiment. This is described together.

Similarly, assume that k, A = o, i, 2..} are the output digital sequences of the input wireless transmitter; in step S101, the input data sequence fe, = o, i, 2 is applied using predetermined channel coding rules. ....} channel coding, which is transformed into an output data sequence fc, 0, 1, 2, ..., where The channel coding rule may use a concatenated code, a turbo code, or an LDPC code, for example, an RS code and a convolutional code, or an adaptive coding scheme composed of multiple technologies, such as an adaptive coding modulation scheme (AMC);

In step S102, the channel-coded data sequence is mapped to the bitmap of the modulation symbol according to the Gray coding specification, for example, and the selected modulation mode is determined by the system design, and can be determined as BPSK, QPSK, QAM modulation mode. One type can also be a plurality of dynamic modulation modes that are adaptively selected according to the bit error rate and the carrier frequency ratio. After the modulation operation, the input data sequence 3⁄4, = 0, 1, 2....} is transformed into the output symbol sequence 3⁄4^ = 0,1,2....};

In step S103, the serial symbol sequence after symbol modulation is divided into a plurality of serial symbol data blocks according to the size of the subsequent IFFT transformation matrix, and the serial-to-parallel conversion operation is performed on the plurality of serial symbol data blocks. To form a corresponding plurality of parallel symbol data blocks. After the serial/parallel conversion operation, the input serial symbol sequence fc, ^ 0, i, 2....} is transformed into a plurality of parallel symbol data blocks {e, , l = 0, 1, 2, .... } , here, represents a column vector with the same number of elements and the size of the IFFT transform;

In step S104, IDFT transform is performed on each input parallel symbol data block to generate a corresponding plurality of time domain symbol data blocks (where the IDFT transform is equivalent to performing orthogonal multi-carrier modulation and synthesis on the input parallel data). Preferably, the IDFT transform can be implemented by an inverse fast Fourier transform (IFFT) algorithm. After the IFFT transform operation, input parallel data block sequence 3⁄4, fc = 0, l, ² , L } is transformed into the corresponding time domain data block sequence {/ _3⁄4 , & = 0,1, ² }, the relationship between each other Obey Λ = IFFT(e _k ), where Λ also denotes a column vector with the same number of elements as the IFFT transform;

In step S105, a specific number of IFFT-transformed data blocks are multiplexed into the data portion of the longer orthogonal frequency division time division multiplexing (OFTDM) symbol in the order of generation. After the data block multiplexing operation, the input data block sequence {/ = 0, 1, 2 } is transformed into the sequence of the data portion of the OFTDM symbol { , ^: = 0, 1, 2 mountain }, where ^ represents the number of elements a column vector of the same size as the OFTDM symbol data portion;

In step S106, a guard interval of a specific length is added to the header or the tail of the OFITM) symbol data portion after the data block multiplexing, for reducing inter-channel interference (the length of the guard interval should be greater than the maximum delay spread length of the channel) ). Preferably, the guard interval is a loop a prefix (CP), that is, a portion of the tail portion of the OFTDM symbol data portion is copied to the front end of the OFTDM symbol data portion to form a final OFTDM. dance number with the CP, and the CP causes the transmitted symbol to have periodicity, when the CP The length of the signal is longer than the maximum delay of the signal transmitted in the channel. Inter-symbol interference (ISI) only affects the CP of the OFTDM symbol front end, so that the ISI can be eliminated at the receiver end simply by removing the CP. After the cyclic prefix addition step, the input sequence { , ;==0,1,2,L} is transformed into a complete OFTDM symbol sequence {3⁄4,l = 0,l,2,L}, where an element number and OFTDM are represented. A column vector of the same size as the symbol, and its structure is shown in Figure 4;

In step S107, the OFTDM signal waveform to be transmitted is shaped and filtered according to the frequency template. After the signal shaping operation, the input OFTDM symbol sequence { , / = 0, l, 2, L} is converted into an output waveform sequence, = 0, 1, 2 mountain };

In step S108, the OFTDM symbol sequence of the baseband is converted into a radio frequency signal; in step S109, it is transmitted to the radio channel via the transmitting antenna.

Preferably, the wireless transmitting method of the present invention further comprises the following control steps:

3) corresponding to the Doppler frequency shift (or channel coherence time) size change to expand or reduce the number of transmitter IFFT time domain multiplexing; and adjust the data block complex according to the channel coherence time length The number is used such that the equivalent time length of its OFTDM symbol is less than the channel coherence time length.

5 is a block diagram of a wireless receiver 2 for receiving signals transmitted via a plurality of orthogonal carriers in a wireless communication network, particularly a broadband mobile communication network, in accordance with an embodiment of the present invention. Wherein, the wireless receiver includes a matched filtering/synchronizing device 21, and Guard interval removing means 22, channel estimating means 23, frequency/time converting means 24, single-point frequency domain equalizing means 25, time/frequency converting means 26, block demultiplexing means 27, FFT converting means 28, parallel/serial conversion The device 29, the decoding device 30, and the channel decoding device 31.

It should be noted that the matched filter device, the decoding device, and the channel decoding device for baseband processing are not directly related to the object of the present invention, and are merely described as a preferred embodiment. In addition, the wireless receiver should also include a receiving antenna for receiving wireless signals and a radio frequency converting device for downconverting the wireless signals to the baseband, which are not directly related to the object of the present invention, for the sake of simplicity, in the figure Not shown.

It is assumed that the radio receiver 2 can obtain a baseband signal 3⁄4, O, l, 2, L } through the receiving antenna and the R radio frequency conversion module. Hereinafter, the wireless receiver of the present invention will be described in detail with reference to FIG. 5 in conjunction with FIG. 6:

The matched filtering and synchronizing device 21 is configured to perform matched filtering on the received baseband signal, and at the same time, complete the time-frequency synchronization function of the received signal. After the matched filtering and synchronizing device 21, the input data sequence, l _k , k = 0, 1, 2, L } is transformed into an output data sequence = 0, 1, 2, L };

The guard interval removal means 22 is used to remove the guard interval added to the OFTDM symbol sequence. When the guard interval is a cyclic prefix, it is used to remove the cyclic prefix (CP) of the OFTDM symbol front end, thereby eliminating interference between OFTDM symbols. After removing the cyclic prefix, the input data sequence 歹{m : ₌ 0,l,2,L } is transformed into the output data block sequence 歹 { ^ = 0,1,2,L }, where, represents the number of elements and 3-5 The FFT transforms the same column vector size;

Channel estimation means 23 is operative to estimate the channel response in the time domain based on the OFTDM symbol sequence or the pilot training sequence. Through the channel estimation means 23, an estimated value of the channel response { _Wi = o, l, 2, L 1} can be obtained, where L is the maximum delay of the time domain response;

The time/frequency conversion device 24 is configured to transform the received time-domain data block of a certain length into the frequency domain, so that the frequency domain equalizer can eliminate the influence of the channel on the data block. Specifically, the time/frequency conversion device can It is implemented by algorithms such as DFT and FFT transform. After the time/frequency conversion device, the input data block sequence, n _k , k = 0, 1, 2, L } is transformed into an output data block sequence, o _k , k = 0, 1, ² , L } The relationship obeys = FFT(n _k ), where a column vector representing the same number of elements as the FFT transform size;

The frequency domain equalization means 25 is operative based on the channel estimation value provided by the channel estimation means 23. The phase and amplitude compensation of the channel impairment is performed on the OFTDM symbol data of the removed cyclic prefix in the frequency domain. The frequency domain equalization device may adopt a single-point frequency domain minimum mean square error MMSE equalizer or a single-point frequency domain zero-forcing equalizer. Specifically, if the frequency domain equalization is completed by the single-point zero-forcing (ZF) method, the frequency domain equalization device 25 outputs the data block sequence {p _k , k = 0, l, 2, L } and the input data block. The relationship between the order 歹l {o _k , k = 0,l,2,L } is:

_Pk =

, ilw _x , L , i / w _L _ _{ ]} o _k , where diagO represents the diagonalization operation of a vector,

[W ₀ W _x LW _L _ _x f = FFT(w) , and the latter w = [w. w, L

, that is, the channel response column vector.

The frequency/time transforming means 26 is configured to recover the frequency domain subband signal synthesis that has undergone frequency domain equalization into the time domain for further processing. Specifically, the frequency/time transforming apparatus may use an algorithm such as IDFT, IFFT transform or the like. achieve. After the frequency/time conversion means 26, the input data block sequence {;3⁄4 = 0,1,2,L } is transformed into an output data block sequence, A: = 0,1,2,L } , where q _k =IFF _Pk And, and, _A and a column vector indicating the same number of elements and the size of the IFFT transform;

The data block demultiplexing means 27 is for demultiplexing the data block of the same size as the data portion of the OFTDM symbol of the radio transmitter side into a data block sequence of the same size as the radio transmitter side IFFT transform matrix. After the data block demultiplexing means 27, the input OFTDM symbol data ^ = 0, 1, 2 mountain} is transformed into a plurality of data block sequences, ^; = 0, 1, ² mountain}, where ^ represents an element number a column vector of the same size as the transmitter-side IFFT transform;

The FFT transforming means 28 of the same size as the transform matrix of the OFTDM transmitter-side IFFT transforming apparatus is configured to perform an inverse operation corresponding to the transmitter-side IFFT transform on the plurality of symbol data blocks for inputting the time-domain data block. Remap to the frequency domain. After the FFT transform means 28, the input OFTDM data block sequence {^-0, l, 2, L} is transformed into a parallel symbol data block block sequence { = (U2, L}, indicating that the number of elements is the same as the FFT transform size) Vector

The parallel/serial conversion means 29 is for converting the input parallel symbol data block sequence into a serial symbol data sequence. After the parallel/serial conversion means 29, the input symbol data block sequence { _3⁄4 ^ = 0, 1, 2, L } is transformed into a serial data sequence, 0, 1, 2, L };

The digital demodulating device 30 is configured to demodulate the input data sequence into a corresponding digital sequence according to the Gray encoding rule of the transmitter. If the channel decoding algorithm to be executed is based on hard decision The input information, then the sequence of hard information digital sequences is a random arrangement of {0} and {1}, otherwise the symbol demodulating means 30 will provide a corresponding sequence of soft information digits based on the quantization of the bits. After the digital demodulation device 30, the input data sequence, = 0, 1, 2, 1^ is transformed into the input digital information.

{u _k ,k = 0,l,2,L } ;

The channel decoding means 31 is operative to perform a channel decoding algorithm based on channel coding rules at the transmitter side. After channel decoding means 31, the input digital sequence = 0, 1, 2, L } is transformed into an output digital sequence, = 0, 1, 2 mountains}.

6 is a flow chart of a wireless receiving method for transmitting signals via orthogonal multi-carriers in a broadband mobile communication network, in accordance with an embodiment of the present invention.

It should be noted that the steps of receiving a wireless signal, down-converting a wireless signal to a baseband, matching filtering step, digital demodulating step, and channel decoding step are not directly related to the purpose of the present invention. Only as a preferred embodiment, the description will be made here.

In step S201, receiving a wireless signal through the receiving antenna;

In step S202, the wireless signal is down-converted to a baseband OFTDM signal, and it is assumed that the baseband OFTDM signal = 0, 1, ² , L } is obtained after the receiving step and the down-conversion step;

In step S203, the received baseband OFTDM signal is matched and filtered, and at the same time, the time-frequency synchronization function of the received signal is completed. After the matched filtering and synchronization steps, the input data sequence {l _k , k = 0, 1, 2, L } is transformed into the OFTDT symbol data sequence m _k , k = 0, 1, 2, L };

In step S204, the guard interval added to the OFTDM symbol sequence is removed. When the guard interval is a cyclic prefix, it is used to remove the cyclic prefix (CP) of the OFTDM symbol front end, thereby eliminating interference between OFTDM symbols. After the step of removing the cyclic prefix, the input data sequence { , = 0, 1, 2, ]:} is transformed into an output data block sequence { = 0, 1, 2, L } , where n _k represents the number of elements and 3 FFT transforms the same size column vector in -5;

In step S205, the channel response is estimated in the time domain based on the OFTDM symbol sequence or the pilot training sequence to obtain a channel estimation value {^^ = 0, 1, 2, mountain - 1}, where L is The maximum delay of the domain response;

In step S206, a certain length of the received data block is transformed into the frequency domain, so that the influence of the channel on the data block can be eliminated by frequency domain equalization. Specifically, the step can be adopted. DFT, FFT transform and other algorithms to achieve. After the time/frequency conversion step, the input data block sequence {"^ = 0, 1, 2 mountain} is transformed into an output data block sequence { = o, i, 2, L }, and the relationship between them obeys o _k = FFT { n _k ) , here, represents a column vector having the same number of elements as the FFT transform large d; in step S207, for removing the cyclic prefix in the frequency domain by single-point frequency domain equalization based on the above channel estimation value The OFTDM symbol data is used for phase and amplitude compensation of channel impairments. The frequency domain equalization device may use a single-point frequency-domain minimum mean square error MMSE equalizer or a single-point frequency-domain zero-forcing equalizer. Zero (ZF) method to complete the frequency domain equalization, after the frequency domain equalization operation, the output data block sequence ^ = 0,1,2 mountain} and the input data block sequence { _Ot = 0,l,2,L } The relationship is:

_Λ

Here, diag() represents the diagonalization operation on a vector, [W ₀ WLW _L _ _} ] ^T = FFT(w) , and the latter 1 ^T , the channel response column vector.

In step S208, the frequency domain subband signal synthesis that has undergone frequency domain equalization is restored to the time domain for further processing. Specifically, it can be implemented by an algorithm such as IDFT, IFFT transform or the like. After the frequency/time conversion means 26, the input data block sequence { _A = 0, U, L} is transformed into an output data block sequence ^^^^. , ^^!^ , where q _k = IFFn _Pk ) , and, A and the column vector indicating the number of elements and the size of the IFFT transform;

In step S209, the data block of the same size as the OFTDM symbol data portion of the radio transmitter side is demultiplexed into a data block sequence of the same size as the radio transmitter side IFFT transform matrix. After the data block demultiplexing step, the input OFTDM symbol data sequence { , t = 0, l, 2, L } is transformed into a plurality of symbol data block sequences {r^ = 0, l, 2, L }, where r _A denotes a column vector having the same number of elements as the transmitter-side IFFT transform;

In step S210, performing an inverse operation corresponding to the transmitter-side IFFT transformation on the plurality of symbol data blocks by using an FFT transformation matrix of the same size as the OFTDM transmitter-side IFFT transformation matrix, for inputting the time domain data. The block is remapped into the frequency domain. After the FFT transform step, the input OFTDM symbol data block sequence \x _k , k- o, i, 2, L } is transformed into a plurality of parallel symbol data block block sequences = 0, 1, 2, L } , representing a column vector with the same number of elements as the FFT transform size;

In step S211, the input parallel symbol data block sequence is parallel/serial converted into serial Symbolic data sequence. After the parallel/serial conversion operation, the input sequence of multiple symbol data blocks {s _k , k = 0, l, 2, L } is transformed into a serial data sequence {t _A = 0, l, 2, L };

In step S212, the input data sequence is demodulated into a corresponding digital sequence according to the Gray coding rule of the transmitter. If the channel decoding algorithm to be executed is based on hard decision input information, the output hard information digital sequence is a random arrangement of {0} and {1 }, otherwise, a corresponding soft information digital sequence based on digital quantization is output. After the symbol demodulation step, the input data sequence, = 0, 1, 2, L } is transformed into the output digital information {" _A ., it = 0, l, 2, L };

In step S213, the channel decoding algorithm is performed based on the channel coding rules of the transmitter. After the channel decoding step, the input digital sequence {^ = o, i, 2, L } is transformed into an output digital sequence 歹 ' j {v„/c = 0, l, 2, L }.

Figure 7 shows the simulation schematic based on the MATLAB/SIMULink simulation platform;

8 shows the result (bit error rate) obtained by performing simulation operations on the simulation scheme of the present invention on the simulation platform shown in FIG. 6 and the prior art OFDM and SC/FDE schemes under the following simulation parameters. It can be seen from FIG. 7 that the error rate of the OFTDM of the present invention is significantly better than the error rate of the SC/FDE scheme, which is comparable to the error rate of OFDM, but due to the implementation complexity of the present invention (256 subcarriers) due to OFDM (2048 subcarriers), so the present invention achieves a good compromise between performance and implementation complexity.

Set the simulation environment parameters as follows:

Channel bandwidth: 10M, channel model: SUI-4, channel coding: convolutional code (coding: code rate 1/2, constraint length 7, generator polynomial [171, 133], decoding: 8 levels of 3 bit quantization, Viterbi soft translation Code, decoding depth 34)

Set system simulation parameters:

Number of OFTDM subcarriers: 256, number of data block multiplexing: 8, frequency domain equalization points: 2048, frequency domain equalization method: single point zero forcing (ZF) equalizer

Set the system parameters to participate in the comparison:

OFDM:

Number of subcarriers: 2048, frequency domain equalization points: 2048, frequency domain equalization method: single point zero forcing (ZF) equalizer;

SC-FDE/LE:

Frequency domain equalization points: 2048, frequency domain equalization method: single point zero forcing (ZF) equalizer; Simulation schematic based on MATLAB/SIMULink simulation platform:

The specific embodiments of the present invention have been described above. It is to be understood that the invention is not limited to the specific embodiments described above, and various modifications and changes can be made by those skilled in the art within the scope of the appended claims.

Claims

Claim

A wireless transmitter for transmitting signals over a plurality of orthogonal carriers in a wireless communication system, comprising:

a serial to parallel conversion device for serially converting the input serial symbol data sequence into a plurality of parallel symbol data sequences;

An IFFT transforming apparatus, configured to perform IFFT orthogonal transform on the plurality of parallel symbol data sequences to generate a plurality of time domain data blocks;

It is characterized in that it further comprises:

a data block multiplexing device, configured to multiplex the plurality of time-domain data blocks that have undergone IFFT orthogonal transform into a baseband OFTDM symbol data sequence in a sequence of generation time; and a guard interval adding device, configured to A guard interval of a specific length is generated at the head or tail of the OFTDM symbol data sequence of the baseband to generate a baseband OFTDM signal to be transmitted.

2. The wireless transmitter according to claim 1, further comprising: the guard interval adding means is a cyclic prefix generating means for using a specific amount of data of a tail portion of the OFTDM symbol data sequence, As a cyclic prefix, it is copied to the head of the OFTDM data sequence to generate a sequence of orthogonal frequency division time division symbols having a cyclic prefix.

The wireless transmitter according to claim 1 or 2, further comprising: a control device, configured to adjust a transform of the IFFT transform device according to a channel bandwidth, a channel coherence bandwidth, and a channel time extension The size of the matrix.

4. The wireless transmitter of claim 3, wherein

The control device is further configured to adjust the length of the cyclic prefix to be greater than or equal to the length of the channel delay spread, and less than or equal to the size of the IFFT transform matrix, according to the length of the channel delay spread and the size of the IFFT transform matrix. .

5. The wireless transmitter of claim 4, wherein

The control device is further configured to adjust the number of multiplexing of the data block according to a change in the size of the Doppler shift or the channel coherence time, so that the equivalent time length of the OFTDM symbol is small. The length of the channel coherence time.

6. A method for transmitting a signal over a plurality of orthogonal carriers in a wireless transmitter of a wireless communication system, comprising the steps of:

And serially converting the input serial symbol data sequence into a plurality of parallel symbol data sequences; performing IFFT orthogonal transform on the plurality of parallel symbol data sequences to generate a plurality of time domain data blocks;

And multiplexing the plurality of time domain data blocks subjected to the IFFT orthogonal transform into a baseband OFTDM symbol data sequence in order of generation time;

A guard interval of a specific length is added to the head or tail of the OFTDM symbol data sequence of the baseband.

7. The method according to claim 6, wherein the step of generating a guard interval comprises:

A specific amount of data at the end of the OFTDM symbol data sequence is copied as a cyclic prefix to the header of the OFTDM symbol data sequence to generate an OFTDM symbol sequence having a cyclic prefix.

The method according to claim 6 or 7, further comprising the step of: adjusting a size of the transform matrix of the IFFT transform device according to a channel bandwidth and a channel time extension.

9. The method of claim 8 wherein:

Adjusting the length of the cyclic prefix to be greater than or equal to the length of the channel delay spread according to the length of the channel delay spread and the size of the IFFT transform matrix, and adaptively adjusting the IFFT less than or equal to the size of the IFFT transform matrix Transforming the length of the transformation matrix of the device to be greater than or equal to the length of the cyclic prefix.

10. The method according to claim 9, further comprising the step of: adjusting the number of the IFFT transform devices corresponding to a change in magnitude of a Doppler shift or a channel coherence time to make the OFTDM symbol The equivalent time length is less than the length of the channel phase

11. A wireless receiver for receiving an OFTDM signal transmitted over a plurality of orthogonal carriers in a wireless communication system, comprising a guard interval removing device for removing guarded intervals that are converted to baseband

The guard interval between OFTDM symbol sequences;

a data block demultiplexing apparatus, configured to demultiplex the guard interval-removed OFTDM symbol sequence into a plurality of data block sequences;

An FFT transforming apparatus, configured to perform FFT transform on the plurality of data blocks in order of receiving time, and transform the plurality of data blocks into a plurality of parallel symbol data sequences;

A parallel-to-serial conversion device for transforming the plurality of parallel symbol data sequences into serial symbol data sequences.

The radio receiver according to claim 11, further comprising a channel estimating means for estimating a channel response of the time domain according to the OFTDM symbol sequence converted to the baseband to obtain a channel response Estimated value;

a time/frequency transforming apparatus, configured to transform the OFTDM data block sequence of the guard interval to a frequency domain OFTDM data block sequence;

a frequency domain equalizer, configured to perform phase compensation and amplitude compensation of the channel impairment on the OFTDM data block sequence transformed into the frequency domain based on the estimated value of the channel response, to obtain a frequency domain that is subjected to frequency domain equalization. OFTDM data block sequence;

And a frequency/time transforming apparatus, configured to re-transform the frequency domain OFTDM data block sequence that has undergone frequency domain equalization into a time domain OFTDM data block sequence, and transmit the sequence to the data block demultiplexing device.

The wireless receiver according to claim 11 or 12, wherein the frequency domain equalizer comprises: a single point frequency domain minimum mean square error MMSE equalizer.

The wireless receiver according to claim 11 or 12, wherein the frequency domain equalizer is a single-point frequency domain zero-forcing equalizer.

15. A method for receiving an OFTDM signal transmitted over a plurality of orthogonal carriers in a wireless receiver of a wireless communication system, comprising the steps of:

Removing the guard interval of the baseband OFTDM symbol;

Demultiplexing the guard interval-removed OFTDM symbol sequence into a plurality of data block sequences;

Performing FFT transformation on the plurality of data blocks in order of reception time, and transforming the same a sequence of multiple parallel symbol data;

The plurality of parallel data symbol sequences are parallel-converted into a serial-characterized data sequence.

16. The method according to claim 15, further comprising the step of: estimating a channel response of the time domain according to the OFTDM symbol sequence or the pilot training sequence transformed to the baseband to obtain a channel response. estimated value;

Transforming the guard interval-removed OFTDM data block sequence into a frequency domain OFTDM data block sequence;

Performing phase compensation and amplitude compensation of the channel impairment on the OFTDM data block sequence transformed into the frequency domain based on the estimated value of the channel response to obtain a frequency domain equalized frequency domain OFTDM data block sequence;

The frequency domain OFTDM data block sequence that has undergone frequency domain equalization is reconverted into a time domain OFTDM data block sequence for performing the data block demultiplexing operation.

17. Method according to claim 15 or 16, characterized in that

The frequency domain equalization step is a single point frequency domain minimum mean square error MMSE equalization method.

18. Method according to claim 15 or 16, characterized in that

The frequency domain equalization step is a single point frequency domain zero forcing equalization method.