CN1812386A - Quadrature frequency division multiplexing communication system with low-complexity and multi-user switching-in method - Google Patents

Abstract

This invention is a kind of multi-user switch-in supportable low-complexity multi-input-multi-output orthogonal frequency division multiplex transmission system. Cycle postfix is used to replace cycle prefix of common OFDM system. Thus, seizing of memory resource is decreased; a pairs of orthogonal polar antennas are used to replace two single polar antennas. It decreases the complexity of system and acquires polar diversity gain. This invention also provides a kind of dynamic multi-user switch-in method. Through dynamically allocating carrier set to different user in frequency domain, a group of multi-address family is got. It increases the mobility of multi-user MIMO OFDM system. The said multiaddress family contains from FDMA each subcarrier allocated to one user, to CDMA all the subcarriers allocated to all the users. Multi-user multiplex gains are used to unified define the said multiaddress switch-in method.

Description

Low complexity orthogonal frequency division communication system and multiple-user access method

Technical field

The present invention relates to a kind of multi-I/O OFDM (MIMOOFMD) communication system and multiple-user access method thereof of low complex degree.Particularly, relate to the Cyclic Prefix (CP) that utilizes cyclic suffix (CS) to replace general ofdm system, reduced taking of memory resource, have the multiuser MIMO ofdm system of high flexibility.

Background technology

Along with the fusion gradually of wireless network, multimedia technology and internet, people are more and more higher to the requirement of the type of radio communication service and quality.For satisfying the requirement of radio multimedium and high speed data transfers, need the Development of New Generation wireless communication system.Recently, the MIMO OFDM Radio Transmission Technology that many antennas input and output (MIMO) and OFDM (OFDM) combine is subjected to extensive concern.

The technology of relevant many antennas input and output can be entitled as the paper of when empty " be used for the layering of wireless communication framework (Layeredspace-time architecture for wireless communication in a fading environmentwhen using multi-element antennas) " with reference to G J.Foschini in the fading environment of using many antennas in delivering in 1996, this article is published in Bell Labs Tech.J., vol.1,1996, the 41-59 pages or leaves.I.E.Telatar has delivered the article that is entitled as " capacity of many antennas Gaussian channel (Capacity of multi-antenna Gaussian channels) " in 1999, this article is published in Eur.Trans.Tel., vol.10, no.6, Nov./Dec.1999, the 585-595 page or leaf.The data that combines with OFDM (OFDM) about MIMO can be with reference to people such as A.J.Paularj in 2004 at Proceedings of IEEE, vol.92, no.2, Feb.2004, the article that is entitled as " key (An Overview ofMIMO Communications-A Key to Gigabit Wireless) that a gigabit radio communication is scanned in MIMO communication " that pp.198-218 delivers.

The MIMO OFDM technology that MIMO and OFDM combine has both advantages, it both resolved into one group of parallel flat fading channel to frequency selectivity MIMO fading channel by the OFDM modulation, utilize MIMO to improve power system capacity again, be applicable to the multimedia service such as sound, video of transmission of high-rate.

With respect to the single antenna ofdm system, many antennas ofdm system has feature performance benefits such as transmission rate and reliability height, but that its shortcoming is an implementation complexity is higher.In the general ofdm system, all adopted the last part sample of each OFDM symbol copied to obtain Cyclic Prefix (CP) before each OFDM symbolic blocks with anti-intersymbol interference.In this scheme, only after having obtained a complete OFDM symbol, just can carry out CP and insert operation, this need consume certain storage space, and has processing delay.And in mimo wireless communication system, in order to obtain diversity or spatial multiplexing gain, requiring the antenna spacing of in the base station (BS) usually is the dozens of wavelength, and the antenna spacing of user terminal (UE) is a wavelength magnitude.Along with the increase of antenna spacing, will inevitably increase the size and the cost of base station.In present working frequency range, user terminal adopts many antennas also comparatively difficult.Therefore, the MIMO ofdm system of low complex degree is the target of seeking always.For this reason, two basic fundamental OFDM and the MIMO of the present invention from the MIMO ofdm system proposed to reduce the method for Project Realization difficulty.

Summary of the invention

The multi-I/O OFDM communication system and the multiple-user access method thereof that the purpose of this invention is to provide a kind of low complex degree.Use this communication system and method can realize the reduction of the complexity of OFDM and the combination of MIMO technology.

In order to realize purpose of the present invention, according to an aspect of the present invention, the low complex degree multi-I/O OFDM dispensing device that provides a kind of multi-user of support to insert, comprise: pilot frequency sequence inserts device, is used for inserting the pilot frequency sequence that is used for timing, channel estimating in the transmission symbols streams of modulation; Contrary discrete fourier transform processing unit is used for stream of modulation symbols is done contrary discrete fourier transform; The cyclic suffix adding apparatus is used for a protection space character and inserts after each OFDM symbol that is subjected to the symbols streams after contrary discrete fourier transform is handled; With the dispensing device that comprises at least one width of cloth dual polarized antenna, be used for the orthogonal frequency-division multiplex base tape symbol that obtains is carried out carrier modulation and emission.

According to another aspect of the present invention, the low complex degree multi-I/O OFDM receiving system that provides a kind of multi-user of support to insert, comprise: the receiving system that comprises at least one width of cloth dual polarized antenna, be used to receive the multi-I/O OFDM carrier signal, and the signal of described reception is down-converted to baseband signalling; The Time and Frequency Synchronization device is used for the symbol through frequency conversion is carried out timing, Frequency Synchronization; The cyclic suffix moving-out device is used to delete the cyclic suffix that is inserted into after each OFDM symbol; With the discrete fourier transform device, be used for the OFDM symbol of deleting cyclic suffix is carried out N Dian Lisanfushi conversion.

According to a further aspect of the invention, provide a kind of multi-user to insert the method for low complex degree multi-input multi-output orthogonal frequency division multiplexing system, comprise step: stream of modulation symbols is done the contrary discrete fourier transform of N point, and wherein N is counting of IDFT computing; After each OFDM symbol in the symbols streams of protecting after the space character insertion is subjected to the IDFT processing; Distribute different OFDM sub-carrier set to different user, dynamically change user's number of collisions, obtain one group of multiple access scheme in frequency domain; Give a user each subcarrier allocation inserting under the situation that the user adopts the frequency division multiple access pattern; With whole subcarrier allocation are being inserted the user to all inserting under the situation that the user adopts the code division multiple access pattern.

According to a further aspect of the invention, provide a kind of multi-user to insert the method for low complex degree multi-input multi-output orthogonal frequency division multiplexing system, comprise step: transmitting terminal according to channel condition information adaptively to user's allocation of subcarriers; When OFDM was applied to access channel, all insert, and the user worked under low-power amplifier and be user's dynamic bandwidth allocation; With when OFDM is applied to broadcast channel, to the parallel emission of a plurality of users data, so that by adjusting subcarrier down transmitting power control link-quality.

According to a further aspect of the invention, the low complex degree multi-I/O OFDM dispensing device that provides a kind of multi-user of support to insert, comprise: pilot frequency sequence inserts device, is used for inserting the pilot frequency sequence that is used for timing, channel estimating in the transmission symbols streams of modulation; The spread spectrum device utilizes each user's frequency expansion sequence that symbols streams is carried out spread spectrum; Medium access control allocation of carriers device is used for distributing predetermined carrier number to the symbols streams of modulation; Contrary discrete fourier transform processing unit is done the contrary discrete fourier transform of the point corresponding with the carrier number that distributes to stream of modulation symbols according to the carrier number of distributing to the user; The cyclic suffix adding apparatus is used for a protection space character and inserts after each OFDM symbol that is subjected to the symbols streams after contrary discrete fourier transform is handled; With the dispensing device that comprises at least one width of cloth dual polarized antenna, be used for the orthogonal frequency-division multiplex base tape symbol that obtains is carried out carrier modulation and emission.

According to communication system of the present invention and method, utilize cyclic suffix to replace the Cyclic Prefix of general ofdm system, reduced taking of memory resource; Utilize at least one width of cloth cross-polarized antennas to replace two width of cloth single-polarized antennas, reduced the complexity of system, and obtain polarization diversity gain; Promote general ofdma scheme, improved the flexibility of multiuser MIMO ofdm system.

Description of drawings

By reading and understanding the detailed description of the preferred embodiment of the present invention being done below with reference to accompanying drawing, these and other objects of the present invention, feature and advantage will be become apparent.Wherein:

Figure 1A and 1B are the transmitter of multiaerial system of prior art and the block diagram of receiver structure;

Fig. 2 A and 2B are the block diagrams according to MIMO ofdm system transmitter of the present invention and receiver structure;

Fig. 3 is the schematic diagram of the data format of explanation Cyclic Prefix (CP) OFDM and cyclic suffix (CS) OFDM;

Fig. 4 is the schematic diagram of the bit error rate (BER) performance of expression MIMO CP-OFDM and MIMO CS-OFDM;

Fig. 5 is the schematic diagram of the bit error rate (BER) performance of the different linear receivers of expression;

Fig. 6 is the schematic diagram of the bit error rate (BER) performance under the expression different modulating mode;

Fig. 7 is the schematic diagram that the multi-user of expression MIMO ofdm system inserts;

Fig. 8 is the schematic diagram of the general OFDMA multiple access of expression;

Fig. 9 is the schematic diagram of expression OFDMA multiple access, and wherein every user distributes a subcarrier;

Figure 10 is the schematic diagram of expression OFDMA multiple access, and wherein all users share whole subcarriers;

Figure 11 is the multi-user access protocol family of expression according to the MIMO ofdm system of the embodiment of the invention.

Embodiment

With reference to the accompanying drawings embodiments of the invention are described in detail, having omitted in the description process is unnecessary details and function for the present invention, obscures to prevent that the understanding of the present invention from causing.

In order to understand the present invention better, structure and its operation of mimo system transmitter and receiver are described with reference to Figure 1A and 1B at first.Figure 1A and 1B represent the transmitting terminal and the receiving terminal of space division multiplexing mimo system respectively.Transmitting terminal and receiving terminal all adopt two width of cloth single-polarized antennas.

Shown in Figure 1A, the transmitter of mimo system comprises serial/parallel converter 11a, channel encoder 12a, interleaver 13a, modulator 14a, pilot frequency sequence inserts unit 15a, contrary discrete fourier transform (IDFT) modulating unit 16a, Cyclic Prefix (CP) adds unit 17a and two width of cloth single-polarized antenna 18a.Shown in Figure 1B, receiver comprises discrete fourier transform (DFT) demodulation unit 16b, and CP shifts out unit 17b, Time and Frequency Synchronization unit 15 and two width of cloth single-polarized antenna 18b.In addition, for simplicity, replace carrying out demodulation in the receiver with signal processing unit 19 among Figure 1B, deinterleaving, the relative assembly of decode operation, and omit the description of the operation relevant with the operation of these devices, because these parts and the present invention do not have direct relation.

Operation below in conjunction with Figure 1A and 1B explanation space division multiplexing mimo system.Shown in Figure 1A and 1B, transmitting terminal and receiving terminal all adopt two width of cloth single-polarized antennas.At transmitting terminal, serial/parallel converter 11a is multiplexed into every width of cloth antenna branch end to the bit stream of input, obtains two emission streams.For the Zhi Luduan of each antenna, adopt channel encoder 12a that bit stream input, the serial/parallel conversion of process is carried out chnnel coding with antinoise.After this, utilize interleaver 13a that the data of channel encoder 12a output are carried out interleaving treatment with reduction bit stream correlation, and the bit stream after will handling offer modulator 14a.Modulator 14a is modulated to symbols streams with the bit stream of interleaver 13a output.Pilot frequency sequence inserts unit 15a and insert the pilot frequency sequence that is used for timing, channel estimating in the transmission symbols streams of modulation.Then, adopt contrary discrete fourier transform (IDFT) processor 16a to stream of modulation symbols do the N point (N is counting of IDFT computing, as 64,1024 etc., down with) contrary discrete fourier transform.The symbols streams that CP adds after unit 17a handles IDFT adds Cyclic Prefix.After this, transmitting element 18a launches the OFDM baseband signalling that obtains after carrier modulation.

At receiving terminal, receiving element 18b down-converts to baseband signalling to the OFDM carrier signal that receives, and the 15 pairs of symbols through frequency conversion in Time and Frequency Synchronization unit carry out regularly, Frequency Synchronization.Cyclic Prefix (CP) shifts out the unit Cyclic Prefix of OFDM symbol is deleted.Discrete fourier transform (DFT) unit 16b carries out N Dian Lisanfushi conversion to deleting the Cyclic Prefix in OFDM System symbol.After this, the signal of 19 pairs of DFT unit of signal processing unit 16b output carries out recovering information bit stream after received signal processing, channel estimating, demodulation, deinterleaving, the decoding.

The following describes the structure and the operation of the transmitting terminal and the receiving terminal of MIMO ofdm system of the present invention.Fig. 2 A and 2B show respectively according to the transmitting terminal of the MIMO ofdm system of the embodiment of the invention and the block diagram of receiving terminal.

Transmitter according to MIMO ofdm system of the present invention comprises serial/parallel converter 21a, channel encoder 22a, interleaver 23a, modulator 24a, pilot frequency sequence inserts unit 25a, contrary discrete fourier transform (IDFT) modulating unit 26a, cyclic suffix (CS) adds a unit 27a and a width of cloth dual polarized antenna 28a.Be noted that to the invention is not restricted to a width of cloth dual polarized antenna as used herein, also can adopt several dual polarized antennas as required.Shown in Fig. 2 B, the receiver of present embodiment comprises discrete fourier transform (DFT) demodulation unit 26b, and cyclic suffix (CS) shifts out unit 27b, a Time and Frequency Synchronization unit 25 and a width of cloth dual polarized antenna 28b.Equally, receiving terminal also is not limited to adopt a width of cloth dual polarized antenna, but can adopt several dual polarized antennas as required.In addition, for simplicity, replace carrying out demodulation in the receiver with signal processing unit 29 among Fig. 2 B, deinterleaving, the relative assembly of decode operation, and omit the description of the operation relevant with the operation of these devices, because these parts and the present invention do not have direct relation.

Operation according to the MIMO ofdm system of the embodiment of the invention is described below.Shown in Fig. 2 A and 2B, at transmitting terminal, serial/parallel converter 21a is multiplexed into every Zhi Luduan of poliarizing antenna to the bit stream of input, obtains two emission and flows.For every Zhi Luduan of antenna, channel encoder 22a carries out chnnel coding with antinoise to bit stream input, the serial/parallel conversion of process.After this, utilize interleaver 23a that the data of channel encoder 22a output are carried out interleaving treatment with reduction bit stream correlation, and the bit stream after will handling offer modulator 24a.Modulator 24a is modulated to symbols streams with the bit stream of interleaver 23a output.Pilot frequency sequence inserts unit 25a and insert the pilot frequency sequence that is used for timing, channel estimating in the transmission symbols streams of modulation.Then, adopt contrary discrete fourier transform (IDFT) processor 26a that stream of modulation symbols is done the contrary discrete fourier transform of N point.The symbols streams that CS adds after unit 27a handles IDFT adds cyclic suffix.After this, transmitting element 18a launches the OFDM baseband signalling that obtains after carrier modulation.

At receiving terminal, receiving element 28b down-converts to baseband signalling to the MIMO OFDM carrier signal that receives, and the 25 pairs of symbols through frequency conversion in Time and Frequency Synchronization unit carry out regularly, Frequency Synchronization.CS shifts out the unit cyclic suffix of OFDM symbol is deleted.Discrete fourier transform (DFT) unit 26b carries out N Dian Lisanfushi conversion (N is counting of IDFT computing) to the OFDM symbol of deleting cyclic suffix.After this, the signal of 29 pairs of DFT unit of signal processing unit 26b output carries out recovering information bit stream after received signal processing, MIMO detection, channel estimating, demodulation, deinterleaving, the decoding.

MIMO ofdm system according to the present invention is compared with the MIMO ofdm system of prior art, its main difference part is that the CP that utilizes CS adding unit and CS to shift out unit replacement prior OFDM system adds the unit and CP shifts out the unit, and utilizes a secondary cross-polarized antennas to replace two width of cloth single-polarized antennas.By system having been done after these change, reduced implementation complexity and performance is suitable.

In addition, in prior OFDM system, CP is inserted into before each OFDM symbolic blocks, with the orthogonality of hold mark interblock.In the ofdm system that utilizes CS of the present invention, the preceding N of OFDM symbol _GSymbol (i.e. protection at interval) is inserted into after each OFDM symbol.Through after the Channel Transmission, identical at receiving terminal with the operation of existing C P ofdm system, shift out preceding N _GCarry out the DFT demodulation behind the symbol.

In existing C P ofdm system, owing to be inserted into the front end that the sample of CP position is positioned at the OFDM symbol, only when obtaining just can to launch the OFDM symbol behind an OFDM symbol, needing word length is the buffer of N.And in CS OFDM of the present invention, CS is positioned at OFDM symbol rear end, and needing word length is N _GBuffer, the symbol after IDFT handles can be directly inputted to next stage and need not to wait for time delay.By contrast, the buffer resource that takies of CS OFDM of the present invention still less.

In prior OFDM system, CP is inserted into before each OFDM symbolic blocks, with the orthogonality of hold mark interblock, as Fig. 3 (a).From n _tThe signal subspace stream of individual antenna end emission is represented by following formula (1):

$x_{\mathrm{CP}}^{n_t}\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{X}^{n_t}\left(k\right)\exp (\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;kn}/N)$ n＝-N _G…0…N-1 (1)

N is the OFDM sub-carrier number in the formula, N _GBe protection interval (GI) sample number.Through after the Channel Transmission, the preceding n of DFT demodulation _tThe received signal of root antenna end by following formula (2) expression (suppose to signal the time, the frequency synchronous error compensates):

$y_{\mathrm{CP}}^{n_r}\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{h}_{n_r{n}_t}\left(k\right)X^{n_t}\left(k\right)\exp (\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;kn}/N)+w\left(n\right)---\left(2\right)$

H in the formula _Nrnt(k) be the channel gain coefficient, w (n) is a noise.

In the ofdm system that utilizes CS according to the present invention, the preceding N of OFDM symbol _GSymbol is inserted into after each OFDM symbol, as Fig. 3 (b).From n _tThe signal subspace stream of antenna end emission is represented by following formula (3):

$x_{\mathrm{CS}}^{n_t}\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{X}^{n_t}\left(k\right)\exp (\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;kn}/N)$ n＝0?1…N+N _G-1 (3)

Through Channel Transmission, shift out preceding N _GBehind the symbol, n _rThe received signal of root antenna can be expressed as following formula (4)

$y_{\mathrm{CS}}^{n_r}(n+N_G)=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{h}_{n_r{n}_t}\left(k\right)X^{n_t}\left(k\right)\exp [\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;k}(n+N_G)/N]+w(n+N_G)---\left(4\right)$

After the DFT demodulation, obtain the signal flow of following formula (5) expression

$Y_{\mathrm{CS}}^{n_r}\left(k\right)=Y_{\mathrm{CP}}^{n_r}\left(k\right)\exp (\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{N}_{G}k/N)---\left(5\right)$

Y in the formula _CS ^Nr, Y _CP ^NrBe respectively y _CS ^Nr, y _CP ^Nr(k) DFT demodulation output.Can find out Y from formula (5) _CS ^NrBy Y _CP ^NrObtain through the phase place rotation, can see that also CS OFDM shifts out preceding N from Fig. 3 _GSymbol behind the sample is the circular shifting that shifts out the symbol sample behind the CP in the existing OFDM symbol.

Go out to send from hard-wired angle, CP OFDM is different with the computation complexity of CS OFDM.In the CP ofdm system, because of the CP scope is positioned at OFDM symbol front end, the sample that is inserted into the CP scope is positioned at the front end of OFDM symbol, only when obtaining just can to launch the OFDM symbol behind an OFDM symbol.On hardware, just need N buffer like this.And in CS OFDM, the CS scope is positioned at OFDM symbol rear end, and the symbol after IDFT handles can be directly inputted to next stage and need not to wait for time delay, and only needing word length is N _GBuffer.Therefore, CS OFDM is easier to adopt streamline (pipeline) structure to realize.

Except that utilizing CS to reduce the complexity of OFDM modulation, consider in the polarization diversity, adopt a secondary cross-polarized antennas to replace two width of cloth single-polarized antennas can effectively reduce the complexity and the cost of system, obtain diversity gain simultaneously.Therefore, the present invention is from reducing system complexity and realizability, in the multiaerial system of transmitting terminal and receiving terminal employing dual polarized antenna.In this system, after the serial/parallel conversion of symbol from, for example, one secondary tilts (+45 °/-45 °) or the poliarizing antenna of quadrature (0 °/90 °) sends.At receiving terminal, also adopt a width of cloth dual polarized antenna received signal.Be noted that to the invention is not restricted to a width of cloth dual polarized antenna, but can adopt several dual polarized antennas.Though only adopted a secondary emission, reception antenna, every kind of polarization mode can be regarded an independent channel as.Therefore, the equivalence of system channel model is a dual input dual output channel, so receiving symbol is for to represent with following formula (6):

y＝Hx+w (6)

Wherein x can be expressed as x=[x for the emission symbolic vector ₁x ₂] ^T, y is a received signal vector, $H={\left[\begin{array}{cc}{h}_{11}& h_{12}\\ h_{21}& h_{22}\end{array}\right]}_{N_r\&times;N_t}$ Be in Channel Transmission matrix (polarization matrix) that w is a noise vector.

The polarization matrix description energy mutual coupling when cross-correlation between polarisation unit and polarized state conversion.The polarization matrix H is decomposed into fixed component (direct wave) H _fAnd change component (scattered wave) H _v, transmission matrix H then can be represented by following formula (7):

$H=\sqrt{\frac{K}{1+K}}{H}_f+\sqrt{\frac{1}{1+K}}{H}_v---\left(7\right)$

In the formula $\sqrt{K/(1+K)},\sqrt{1/(1+K)}$ Be normalization factor, K is the Ricean K factor.H _fEach component satisfy ${\left|h_{11}^f\right|}^2={\left|h_{22}^f\right|}^2=1,{\left|h_{12}^f\right|}^2={\left|h_{21}^f\right|}^2={\mathrm{\&alpha;}}_f,$ So $H_f=\left[\begin{array}{cc}1& \sqrt{{\mathrm{\&alpha;}}_f}\\ \sqrt{{\mathrm{\&alpha;}}_f}& 1\end{array}\right],$ α _f(0≤α _f≤ 1) depends on the cross polarization discrimination (XPD) of channel fixed component. $H_v=\left[\begin{array}{cc}{h}_{11}^v& h_{12}^v\\ h_{21}^v& h_{22}^v\end{array}\right]$ Each component be the multiple Gaussian random variable of zero-mean, its variance is relevant with dissemination channel environment and The Research of Antenna Polarization with the correlation between each component.Generally have $E\left\{{\left|h_{11}^v\right|}^2\right\}=E\left\{{\left|h_{22}^v\right|}^2\right\}=1,E\left\{{\left|{\mathrm{<figure-callout\; id="12"\; label="h"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">h</figure-callout>}}_{12}\right|}^2\right\}=E\left\{{\left|h_{21}\right|}^2\right\}=\mathrm{\&alpha;}$ (0＜α≤1), α depends on the cross polarization discrimination (XPD) of channel variation component, and the XPD of antenna is good more, and α is more little; If α=1, expression sending and receiving end The Research of Antenna Polarization is identical.Experimental data shows that each component of H normally is correlated with, so definition emission coefficient correlation $t=\frac{E\left\{h_{11}^{\mathrm{<figure-callout\; id="12"\; label="v\; h"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">v</figure-callout>}}{h}_{}^{}{}_{12}^{*\left(v\right)}\right\}}{\sqrt{\mathrm{\&alpha;}}}=\frac{E\left\{h_{21}^v{h}_{22}^{*\left(v\right)}\right\}}{\sqrt{\mathrm{\&alpha;}}}$ With the reception coefficient correlation $r=\frac{E\left\{h_{11}^v{h}_{21}^{*\left(v\right)}\right\}}{\sqrt{\mathrm{\&alpha;}}}=\frac{E\left\{h_{12}^v{h}_{22}^{*\left(v\right)}\right\}}{\sqrt{\mathrm{\&alpha;}}}.$

The performance of system of the present invention is described below by l-G simulation test.Simulation parameter is: adopt the physical layer basic parameter of IEEE 802.11a, the data carrier number is 48,64 point (I) FFT conversion, optional BPSK, QPSK, 16QAM, 64QAM modulation; The Ricean K factor is 10, α _f=0.3, α=0.4, t=0.5, r=0.3 sends 500 OFDM frames.Fig. 4 adopts QPSK modulation, the MIMO CP-OFDM of coding, VBLAST detection and the performance of MIMO CS-OFDM to compare.As can be seen from Figure 4, the bit error rate of existing MIMO CP-OFDM and MIMOCS-OFDM of the present invention (BER) performance is more consistent, but adopts the solution of the present invention can reduce the complexity of system.

Fig. 5 represents to adopt respectively the system BER performance of different linear receivers such as VBLAST, MMSE, ZF, QPSK modulation.From Fig. 5 as seen, the BER performance of VBLAST reception is more excellent than MMSE, ZF.Fig. 6 is for adopting VBLAT receiver, the system BER performance under the different modulating modes such as BPSK, QPSK, 16QAM, 64QAM.Simulation result shows that the bit error rate (BER) performance of the MIMOCS-OFDM system that the present invention proposes is consistent with general MIMO ofdm system performance, and implementation complexity is lower.In addition,, the invention is not restricted to this, may be used on the sending and receiving end and adopt in the system of several dual polarized antennas though it may be noted that the system that the dual-mode antenna end all adopts a secondary dual polarized antenna only has been discussed in the present embodiment.

System of the present invention has reduced implementation complexity on physical structure, but when supporting that the multi-user inserts, also need consider the design of medium access control (MAC) layer.This respect need solve a plurality of users' access problem at the MAC layer.As everyone knows, the wireless system of practicability must be supported multi-user communication.Therefore, no matter be general ofdm system, still the ofdm system of many antennas all need have the ability of supporting that the multi-user inserts.

In order to improve the flexibility and the scalability of the MIMO ofdm system of supporting that the multi-user inserts, the present invention also proposes a kind of dynamic multi-user's access scheme.It distributes different OFDM sub-carrier set to different user, dynamically changes user's number of collisions in frequency domain (subcarrier), obtains a multiple access family.It comprises from the frequency division multiple access (FDMA) of each subcarrier allocation being given a user inserts users' code division multiple access (CDMA) to a whole subcarrier allocation to all.The solution of the present invention can be regarded OFDM (OFDMA) mechanism of popularization as.

In the existing OFDM (OFDMA), in each OFDM symbol, distribute a part of subcarrier in all carrier waves for each user.The OFDMA advantage is dynamically distributing carrier wave, bit rate.But it only distributes the subcarrier of some to the user, does not consider the situation of all subcarriers of multiple users share, as shown in Figure 8.The present invention had both utilized the advantage of OFDMA, again it had been done popularization, made it have better flexibility, and utilized multiuser multiplexing to gain to unify to evaluate multi-user's access scheme of proposition.

Fig. 7 is the schematic diagram that the multi-user of expression MIMO ofdm system inserts.As shown in Figure 7, a plurality of users are by MIMO OFDM wireless network access base station.Multi-user's access mechanism of this system of following surface analysis.

Access mechanism commonly used comprises: compete class at random, as Aloha series; The fixed allocation class is as frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA) etc.Different multiple access technologies respectively have characteristics, are applicable to different communication services respectively.As CDMA zero channel access delay, bandwidth availability ratio advantages of higher are arranged, but also have shortcomings such as transmission rate is limited.Insert at random and be applicable to sudden Packet Service, but when network traffic is heavier, the Business Stream collision easily takes place cause blocking.The MIMO OFDM transmission system that proposes as facing the future radio communication, it will support high, medium and low different rates, the multiclass business of different service quality (QoS) is as speech, data, video etc.Simultaneously, this system is as a kind of integrated communications system, with backward compatible other system, as supporting CDMA user's access.Consider the influence of these factors, need the access mode of flexible design, to support user's access from different system, carrying different business.

Existing multi-access mode, time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA) and space division multiple access (SDMA) all can be used for multi-user OFDM system.AnaGarcia-Armada, Gil Jimenez, people such as M.J.Fernandez-Getino have proposed the mixing OFDM multiple access access scheme based on OFDMA and TDMA being entitled as " H-OFDM (H-OFDM design for wireless personal areacommunications) that is used for the radio individual area communication " literary composition, but this scheme can not support CDMA user to insert.

The present invention proposes a kind of dynamic multi-user's access scheme.It distributes different OFDM sub-carrier set to different user, dynamically changes user's number of collisions in frequency domain (subcarrier), obtains one group of multiple access scheme.This multi-user's access protocol family comprise from the FDMA (as shown in Figure 9) that each subcarrier allocation given a user to whole subcarrier allocation to all access users' CDMA (as shown in figure 10).This scheme can be seen the OFDMA mechanism of popularization as.

In the existing OFDM (OFDMA), be in each OFDM symbol, for each user distributes a part of subcarrier in all carrier waves, as shown in Figure 8.When unknown each user's of transmitter channel condition information (CSI), can be that each user distributes one group of subcarrier arbitrarily.And when the channel response of transmitter known users, the CSI that obtains as the receiving terminal channel estimating sends back to transmitter by feedback path.Transmitting terminal is given the user according to CSI self adaptation allocation of subcarriers, obtains any allocation of subcarriers more performance of each user of comparison.When OFDMA was applied to access channel (up), all access users can work under low-power amplifier and be user's dynamic bandwidth allocation.When it is applied to broadcast channel (descending), to the parallel emission of a plurality of users data, can be by adjusting subcarrier down transmitting power control link-quality.Compare with TDMA, the OFDMA advantage is dynamically distributing carrier wave, bit rate, paired pulses noise and disturb very strong robustness is arranged.General OFDMA multiple access scheme is only considered the subcarrier that distributes some to the user, does not consider the situation of all subcarriers of multiple users share.The present invention had both utilized the advantage of OFDMA, again it had been done popularization, made it have better flexibility and wider range of application.

This multi-user's access protocol family that we utilize multiuser multiplexing gain (MuG) to come unified Definition to propose.If total user power is $\stackrel{\&OverBar;}{P}=\underset{u=1}{\overset{U}{\mathrm{\&Sigma;}}}{P}_u,$ P _uBe each user power, and $P_u=d_u\stackrel{\&OverBar;}{P},$ Satisfy $\underset{u=1}{\overset{U}{\mathrm{\&Sigma;}}}{d}_u=1,$ d _uThe fraction scale that the power of distributing to user u accounts for gross power has been described; U _kBe user's subcarrier allocation,, then can be expressed as U if all subcarrier allocation is given all users _k=1 ..., U-1}, k=1,2 ..., N if each allocation of carriers is given a user, then can be expressed as U _k=1, k=1,2 ..., N; Various allocation of carriers collection { U ₁, U ₂..., U _NCorresponding total information capacity is C ({ U ₁, U ₂..., U _N), and $C=E\left\{{\log }_2\det (I_{N_r}+\underset{u=1}{\overset{U}{\mathrm{\&Sigma;}}}\frac{P_i}{{\mathrm{NN}}_t}{H}_u{H}_u^H)\right\}.$ Multiuser multiplexing gain according to the allocation of carriers definition can be represented with following formula (8):

$\mathrm{MuG}\left(\right\{U_1,{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">U</figure-callout>}}_2,...,U_N\left\}\right)=\underset{\stackrel{\&OverBar;}{P}\&RightArrow;\&infin;}{\lim }\frac{C\left(\right\{U_1,{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="A20051000585900231.png,A20051000585900232.png"\; state="\{\{state\}\}">U</figure-callout>}}_2,...,U_N\left\}\right)}{{\log }_2\left(\stackrel{\&OverBar;}{P}\right)}---\left(8\right)$

Can see that the multiuser multiplexing gain that system obtains is subjected to the several factors influence, for example, the quantity of transmission, reception antenna, channel circumstance, number of users, carrier number etc.For certain P _i, can obtain following formula (9):

MuG({U ₁})≤MuG({U ₁?U ₂…U _n})≤MuG({U ₁?U ₂…U _N})，1＜n＜N

(9)

The multiuser multiplexing gain that each user obtains when sharing all carrier waves is maximum, MCCDMA system that Here it is.Though be noted that each user can obtain maximum multiuser multiplexing and gain when sharing all carrier waves, and to compare to different user distribution OFDMA single or the parton carrier wave, its system complexity is also higher.Therefore, need consider the reasonable overhead of systematic function and complexity during system design.

Figure 11 is MOMI ofdm system proposed by the invention and another embodiment of multi-user's access protocol family.As shown in figure 11, the transmitter of MIMO ofdm system comprises serial/parallel converter 111a, channel encoder 112a, interleaver 113a, modulator 114a, pilot frequency sequence inserts unit 115a, contrary discrete fourier transform (IDFT) modulating unit 116a, CS adds unit 117a, a width of cloth dual polarized antenna 118a, and MAC carrier assigning unit 119 and spectrum-spreading unit 120.Be noted that to the invention is not restricted to a width of cloth dual polarized antenna as used herein, also can adopt several poliarizing antennas as required.The receiver of present embodiment comprises discrete fourier transform (DFT) demodulation unit 116b, and CS shifts out unit 117b, a Time and Frequency Synchronization unit 115 and a width of cloth dual polarized antenna 118b.Equally, receiving terminal also is not limited to adopt a width of cloth dual polarized antenna, but can adopt several poliarizing antennas as required.In addition, for simplicity, replace carrying out demodulation in the receivers with signal processing unit 29 among the figure, deinterleaving, the relative assembly of decode operation, and omit the description of the operation relevant with the operation of these devices, because these parts and the present invention do not have direct relation.

As previously mentioned, if the MAC layer of this communication system adopts the multiple access protocol family that proposes, then it supports to give a user's FDMA access way and the CDMA access way that each user shares all subcarriers subcarrier allocation.There is U user to insert in the supposing the system simultaneously, can establish the 1st and adopt the OFDMA mode, and distribute to each user k carrier wave to (u-1) individual user; U adopts the CDMA mode to work to U user, and promptly these users share all carrier waves.

For the user that the OFDMA mode inserts, at transmitting terminal, the MAC layer forms OFDM symbol, each user's carrier wave non-overlapping copies according to the carrier number of distributing to each user.For every user, the operation of each functional module of physical layer is as follows.At transmitting terminal, serial/parallel converter 111a is multiplexed into every Zhi Luduan of poliarizing antenna to the bit stream of input, obtains two emission and flows.For every Zhi Luduan of antenna, channel encoder 112a carries out chnnel coding with antinoise to bit stream input, the serial/parallel conversion of process.After this, utilize interleaver 113a that the data of channel encoder 112a output are carried out interleaving treatment with reduction bit stream correlation, and the bit stream after will handling offer modulator 114a.Modulator 114a is modulated to symbols streams with the bit stream of interleaver 113a output.Pilot frequency sequence inserts unit 115a and insert the pilot frequency sequence that is used for timing, channel estimating in modulated spread spectrum transmission symbols streams.The MAC carrier assigning unit is distributed predetermined carrier number, for example k to the symbols streams of modulation.Then, adopt contrary discrete fourier transform (IDFT) processor 116a stream of modulation symbols to be done the contrary discrete fourier transform of k point according to the carrier number k that distributes to the user.The symbols streams that CS adds after unit 117a handles IDFT adds cyclic suffix.After this, transmitting element 118a launches the OFDM baseband signalling that obtains after carrier modulation.

At user's receiving terminal, receiving element 118b down-converts to baseband signalling to the OFDM carrier signal that receives, and the 115 pairs of symbols through frequency conversion in Time and Frequency Synchronization unit carry out regularly, Frequency Synchronization.CS shifts out unit 117b the cyclic suffix of OFDM symbol is deleted.Discrete fourier transform (DFT) unit 116b carries out k Dian Lisanfushi conversion to the OFDM symbol of deleting cyclic suffix.After this, the signal of 29 pairs of DFT unit of signal processing unit 26b output carries out recovering information bit stream after received signal processing, MIMO detection, channel estimating, demodulation, deinterleaving, the decoding.

For the user who inserts in the CDMA mode, at transmitting terminal, the symbol of modulation is sent into the IDFT module behind spectrum-spreading unit 120, and all users share carrier wave, can adopt same IDFT module modulation.Operation under the situation that the user inserts in the CDMA mode is described below.At transmitting terminal, serial/parallel converter 111a is multiplexed into every Zhi Luduan of poliarizing antenna to the bit stream of input, obtains two emission and flows.For every Zhi Luduan of antenna, channel encoder 112a carries out chnnel coding with antinoise to the sub-stream of bit input, the serial/parallel conversion of process.After this, utilize interleaver 113a that the data of channel encoder 112a output are carried out interleaving treatment with reduction bit stream correlation, and the bit stream after will handling offer modulator 114a.Modulator 114a is modulated to symbols streams with the bit stream of interleaver 113a output.Spectrum-spreading unit 120 utilizes each user's characteristic sequence (frequency expansion sequence) to the symbols streams spread spectrum.Pilot frequency sequence inserts unit 115a and insert the pilot frequency sequence that is used for timing, channel estimating in modulated spread spectrum transmission symbols streams.Then, adopt contrary discrete fourier transform (IDFT) processor 116a that stream of modulation symbols is done the contrary discrete fourier transform (N is counting of IDFT computing) of N point.The symbols streams that CS adds after unit 117a handles IDFT adds cyclic suffix.After this, transmitting element 118a launches the OFDM baseband signalling that obtains after carrier modulation.

At user's receiving terminal, receiving element 118b down-converts to baseband signalling to the OFDM carrier signal that receives, and the 115 pairs of symbols through frequency conversion in Time and Frequency Synchronization unit carry out regularly, Frequency Synchronization.CS shifts out unit 117b the cyclic suffix of OFDM symbol is deleted.Discrete fourier transform (DFT) unit 116b carries out N Dian Lisanfushi conversion to the OFDM symbol of deleting cyclic suffix.After this, the signal of 29 pairs of DFT unit of signal processing unit 116b output carries out recovering information bit stream after received signal processing, MIMO detection, channel estimating, demodulation, deinterleaving, the decoding.

By the foregoing description as can be known, by using multiple access protocol family at the MAC layer, it can insert OFDM and CDMA user simultaneously, makes it to become the integrated communications system of energy compatible CDMA (3G mobile communication technology) and OFDM (4G wireless communication technology).

According to the present invention, replace the Cyclic Prefix of prior OFDM system can reduce taking of memory resource with cyclic suffix.In addition, utilize a pair or several poliarizing antennas to replace two width of cloth single-polarized antennas, reduced the complexity of system, and can obtain polarization diversity gain, improved the flexibility of multiuser MIMO ofdm system.

So far invention has been described in conjunction with the preferred embodiments.It should be appreciated by those skilled in the art that under the situation that does not break away from the spirit and scope of the present invention, can carry out various other change, replacement and interpolations.Therefore, scope of the present invention should not be understood that to be limited to above-mentioned specific embodiment, and should be limited by claims.

Claims (15)

1. low complex degree multi-I/O OFDM dispensing device of supporting that the multi-user inserts comprises:

Pilot frequency sequence inserts device, is used for inserting the pilot frequency sequence that is used for timing, channel estimating in the transmission symbols streams of modulation;

Contrary discrete fourier transform processing unit is used for stream of modulation symbols is done contrary discrete fourier transform;

The cyclic suffix adding apparatus is used for a protection space character and inserts after each OFDM symbol that is subjected to the symbols streams after contrary discrete fourier transform is handled; With

The dispensing device that comprises at least one width of cloth dual polarized antenna is used for the orthogonal frequency-division multiplex base tape symbol that obtains is carried out carrier modulation and emission.

2. dispensing device according to claim 1, wherein said dual polarized antenna are the dual polarized antennas of+45 °/-45 ° of inclinations.

3. dispensing device according to claim 1, wherein said dual polarized antenna are the dual polarized antennas of 0 °/90 ° of quadratures.

4. according to any one the described dispensing device in the claim 1 to 3, wherein further comprise:

Serial/parallel conversion equipment is used for incoming bit stream is carried out serial/parallel conversion, and it is multiplexed with the symbol substream of each the antenna branch end in a plurality of antennas;

A plurality of channel coding devices carry out chnnel coding with antinoise to the bit stream of importing;

A plurality of interlaced devices carry out interleaving treatment to reduce the bit stream correlation to the bit stream through chnnel coding; With

A plurality of modulating devices are used for the bit stream after interweaving is modulated to symbols streams.

5. low complex degree multi-I/O OFDM receiving system of supporting that the multi-user inserts comprises:

The receiving system that comprises at least one width of cloth dual polarized antenna is used to receive the multi-I/O OFDM carrier signal, and the signal of described reception is down-converted to baseband signalling;

The Time and Frequency Synchronization device is used for the symbol through frequency conversion is carried out timing, Frequency Synchronization;

The cyclic suffix moving-out device is used to delete the cyclic suffix that is inserted into after each OFDM symbol; With

The discrete fourier transform device is used for the OFDM symbol of deleting cyclic suffix is carried out N Dian Lisanfushi conversion, and wherein N is counting of IDFT computing.

6. receiving system according to claim 5, wherein said dual polarized antenna are the dual polarized antennas of+45 °/-45 ° of inclinations.

7. receiving system according to claim 5, wherein said dual polarized antenna are the dual polarized antennas of 0 °/90 ° of quadratures.

8. according to any one the described receiving system in the claim 5 to 7, comprise further that wherein signal to the output of discrete fourier transform device carries out the signal processing apparatus of recovering information bit stream after received signal processing, channel estimating, demodulation, deinterleaving, the decoding.

9. low complex degree multi-input multi-output orthogonal frequency division multiplexing system of supporting that the multi-user inserts comprises any one described dispensing device in the claim 1 to 4 and any one the described receiving system in the claim 5 to 8.

10. a multi-user inserts the method for low complex degree multi-input multi-output orthogonal frequency division multiplexing system, comprises step:

Stream of modulation symbols is done contrary discrete fourier transform;

After each OFDM symbol in the symbols streams of protecting after the space character insertion is subjected to the IDFT processing;

Distribute different OFDM sub-carrier set to different user, dynamically change user's number of collisions, obtain one group of multiple access scheme in frequency domain;

Give a user each subcarrier allocation inserting under the situation that the user adopts the frequency division multiple access pattern; With

Whole subcarrier allocation are being inserted the user to all inserting under the situation that the user adopts the code division multiple access pattern.

11. a multi-user inserts the method for low complex degree multi-input multi-output orthogonal frequency division multiplexing system, comprises step:

Transmitting terminal according to channel condition information adaptively to user's allocation of subcarriers;

When OFDM was applied to access channel, all insert, and the user worked under low-power amplifier and be user's dynamic bandwidth allocation; With

When OFDM is applied to broadcast channel, to the parallel emission of a plurality of users data, so that by adjusting subcarrier down transmitting power control link-quality.

12. a low complex degree multi-I/O OFDM dispensing device of supporting that the multi-user inserts comprises:

Pilot frequency sequence inserts device, is used for inserting the pilot frequency sequence that is used for timing, channel estimating in the transmission symbols streams of modulation;

The spread spectrum device utilizes each user's frequency expansion sequence that symbols streams is carried out spread spectrum;

Medium access control allocation of carriers device is used for distributing predetermined carrier number to the symbols streams of modulation;

Contrary discrete fourier transform processing unit is done the contrary discrete fourier transform of the point corresponding with the carrier number that distributes to stream of modulation symbols according to the carrier number of distributing to the user;

The cyclic suffix adding apparatus is used for a protection space character and inserts after each OFDM symbol that is subjected to the symbols streams after contrary discrete fourier transform is handled; With

The dispensing device that comprises at least one width of cloth dual polarized antenna is used for the orthogonal frequency-division multiplex base tape symbol that obtains is carried out carrier modulation and emission.

13. dispensing device according to claim 12, wherein said dual polarized antenna are the dual polarized antennas of+45 °/-45 ° of inclinations.

14. dispensing device according to claim 12, wherein said dual polarized antenna are the dual polarized antennas of 0 °/90 ° of quadratures.

15. any one the described dispensing device according in the claim 12 to 14 wherein further comprises:

Serial/parallel conversion equipment is used for incoming bit stream is carried out serial/parallel conversion, and it is multiplexed with the symbol substream of each the antenna branch end in a plurality of antennas;

A plurality of channel coding devices carry out chnnel coding with antinoise to the bit stream of importing;

A plurality of interlaced devices carry out interleaving treatment to reduce the bit stream correlation to the bit stream through chnnel coding; With

A plurality of modulating devices are used for the bit stream after interweaving is modulated to symbols streams.

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