CN1694441A - Method for compatible OFDM technology by TD-SCDMA system - Google Patents

Abstract

This invention discloses a method for TD-SCDMA compatible with OFDM technology, which carries out serial parallel conversion to the due-out high speed serial code sheet sequence and generates multiple parallel sub-sequences to be modulated to multiple sub-carriers for parallel transmission to reduce the transmit rate of each channel so as to increase the symbol period and weaken the influence of multi-channel interference, at the same time, it uses the circular prefix as the protection interval, the interference among symbols are reduced greatly and the orthogonality among channels are ensured.

Description

A kind of method of TD-SCDMA system compatible OFDM technology

Technical field:

The present invention relates to communication system, particularly a kind of TD-SCDMA system compatible OFDM (Orthogonal Frequency Division Multiplexing, the OFDM) method of technology.

Background technology:

IMT-2000 is the 3-G (Generation Three mobile communication system) that International Telecommunication Union proposes, and TD-SCDMA is one of mainstream standard wherein, is to propose and obtain the 3G wireless communication standard that ITU passes through by China Wireless Telecommunication Standar tissue (CWTS).The TD-SCDMA system has its outstanding characteristics: unique employing time division duplex (TDD) mode in three kinds of mainstream standard of 3-G (Generation Three mobile communication system) has bigger flexibility on spectrum utilization.This system synthesis has adopted the advanced technology in the radio communications such as smart antenna, S-CDMA (CDMA), joint-detection, software radio, makes system have the higher performance and the availability of frequency spectrum.

The TD-SCDMA system will inevitably face the limitation that CDMA is introduced self because it adopts CDMA technology.In cdma system, adopt different spread spectrum code words to distinguish the user, this has strong autocorrelation and weak cross correlation with regard to the spreading code that requires each user.But the in fact impossible complete obiteration of the mutual interference between each user, thereby cause that multiple access disturbs.

On the other hand, the radio wave propagation has characteristics such as free space propagation loss, shadow fading and multipath fading, and wherein multipath fading has very the signal that transmits on the wireless channel and seriously influences.Complicated radio wave propagation mechanism has caused the multipath transmisstion and the fading characteristic of wireless channel, the destructiveness stack of the mainly many signals that come by different propagated of this multipath fading causes, it can seriously slacken the instantaneous power of received signal, significantly reduces the performance of wireless communication system.The multipath transmisstion result makes received signal produce time delay expansion, frequency (Doppler) expansion and angle spread, and this can cause the generation of three class selectivity decline respectively.

(1) time delay expansion

Supposing to transmit is a pulse signal that time width is extremely narrow, through after the multipath channel, because the difference of each channel delay, the signal that receives is a pulse train, so the waveform of received signal can cause intersymbol interference (ISI) than former pulse stretching.Consider that from the frequency domain angle time delay expansion of multipath signal can cause frequency selective fading, promptly different frequency content fading characteristic is different in the signal.

(2) frequency expansion

Because the relative motion of mobile subscriber and base station, every multipath all can have a tangible frequency shifts, produces Doppler's expansion on signal frequency domain, causes time selective fading, and is promptly different in different moment fading characteristics.

(3) angle spread

Angle spread is the broadening that multipath signal arrives the arrival angle of aerial array, has produced space selective fading, and promptly (space) fading characteristic is different in the different location.

Therefore, cdma system is an interference limiting system, and its capacity mainly is subject to multiple access and disturbs and the multipath interference.Under the mobile communication environment of complexity and limited frequency resource, reach the communication of high power capacity, high-quality, two-forty, must overcome the influence of these factors.

At present, TD-SCDMA adopts Quadrature Phase Shift Keying (QPSK) modulation, for the business of 2Mbit/s, uses 8PSK modulation mode.Such modulation efficiency is still lower, can not adopt the reason of higher system modulation to be: more high efficiency modulation such as quadrature amplitude modulation (QAM), can introduce serious disturbance, and this is totally unfavorable for interference-limited cdma system.The message transmission rate that the TD-SCDMA system can provide remains limited, still is restricted concerning the high efficiency of transmission multimedia messages.

Though many advanced technologies that the TD-SCDMA system adopts, as smart antenna, synchronization CDMA, joint-detection etc., can suppress effectively to disturb, but be difficult to provide more high-speed data transmission speed, particularly under high-speed mobile condition, the serious intersymbol interference that is caused is difficult to overcome.

As previously mentioned and since channel the time become the multipath feature, on the signal mulitpath with different intensity with postpone incoming terminal, can bring the time delay expansion, and make that channel is a frequency selectivity, this can cause serious ISI, is particularly difficult and reduce ISI when high data rate transfer.Generally be used to resist the technology of ISI, for example maximum-likelihood sequence estimation (MLSE) or linear and nonlinear equalizer, MLSE is a kind of detection algorithm of optimum existing under the situation of ISI, but because amount of calculation is bigger, does not have too big attraction in high data rate wireless communication.And on the other hand, multi-carrier modulation has bigger resistivity for ISI than single-carrier modulated.

Determined by the objective characteristic of channel, and the decision systems transmission performance is not absolute value between the diffusion region, but between the diffusion region in being transmitted information code element shared relative percentage.

The principle of multicarrier transmission systems as shown in Figure 1, multi-transceiver technology is with the serial/parallel conversion of flowing through of the information data of two-forty, be divided into the several low rate data streams, increase the information code element cycle, reduced multidiameter delay and be diffused in relative percentage value shared in the information code element that receives, disturbed the transmission system Effect on Performance to weaken multipath.Every then road low speed data adopts the independently carrier modulation and the formation transmission signal that is superimposed.After receiving terminal carries out coherent reception with the carrier wave of same quantity to sending signal, obtains the low rate information data, obtain original high speed signal through parallel/serial conversion again.As a kind of OFDM technology of special multi-transceiver technology, all be efficiently on frequency spectrum and computation complexity.Traditional parallel multicarrier system is sent in the subchannel after whole bandwidth division, and frequency band does not have overlapping, and its availability of frequency spectrum is very low.OFDM is divided into many orthogonal sub-channels to channel at frequency domain, the intercarrier of each subchannel have 1/2 overlapping, but keep quadrature because frequency spectrum is overlapped, so just improved the availability of frequency spectrum.And just can realize the modulation and demodulation of OFDM by inverse fast fourier transform and conversion (IFFT and FFT), and avoid using bank of filters at receiving terminal, can make spectrum efficiency improve nearly one times simultaneously.

OFDM expands to frequency selective fading on many symbols, effectively randomization by decline or the caused burst error of impulse disturbances, make it can is not that several adjacent symbol are suffered to destroy fully, but a lot of symbol only is subjected to slight influence.Because OFDM is divided into many narrow subchannels to whole channel width, the frequency response on each independent subchannel is a relatively flat, has reduced intersymbol interference greatly.And each subchannel only occupies the sub-fraction of original bandwidth, so equilibrium is simple more than tandem system.A kind of simple equalization algorithm just can minimize the mean square error on each subchannel, and adopts differential coding even can avoid adopting balanced fully.OFDM is applicable to the high speed data transfer in multi-path environment and the frequency selective fading channels.Because OFDM has the advantage that ability of anti-multipath is strong, the availability of frequency spectrum is high, therefore be subjected to extensive concern.People think that not only adopting OFDM in the broadband wireless access field is the trend of development, and it will become the key technology of future mobile communication system.

In order to eliminate ISI to greatest extent; to in each OFDM symbol, insert protection (guard interval) at interval; and this protection gap length generally is greater than the maximum delay expansion of wireless channel, and the multipath component of such symbol just can not cause interference to next symbol.In this segment protect interval, can not insert any symbol, promptly be the transmission period of one period free time.But, general OFDM symbol need be inserted Cyclic Prefix signal CP (cyclicprefix) in its protection at interval, can eliminate or is to have significantly reduced ISI at least.Certainly, the cost of doing like this is to have reduced the availability of frequency spectrum.The baseband OFDM system principle as shown in Figure 2.

Compare with single-carrier system, the major advantage of ofdm system has:

The resistivity that ofdm system paired pulses disturbs is more much bigger than single-carrier system, and this is because the demodulation of ofdm signal is in a lot of transmission information symbol cycle integrates, thereby the influence of impulse disturbances is dispersed.

The anti-multipath is propagated with the frequency selective fading ability strong; since ofdm system information dispersion to many carrier waves; greatly reduce each subcarrier signals speed; thereby can weaken the influence of multipath transmisstion; if protect method at interval by adopting again, even can eliminate intersymbol interference fully.OFDM is a kind of effective technology that overcomes the intersymbol interference in the two-forty digital communication.

helps adopting the dynamic bit distribution technique to make system reach Maximum Bit Rate.Make the gross bit rate maximum by the bit number of choosing each subchannel, each symbol and the power of distributing to each subchannel.Promptly require each sub-channel power to distribute " the water filling theorem " that should follow in the information theory, that is the high-quality channel transmits more, poor channel transmits less, the principle that channel inferior does not transmit.

has improved spectrum efficiency.

Just be based on ofdm system and having so many advantage, therefore, if in the TD-SCDMA system, propose a kind of technology (as OFDM technology) realization compatible method later, just can more effectively resist multipath and disturb, more easily solve deficiency of the prior art with 3G.

Summary of the invention:

Technical problem to be solved by this invention provides a kind of method of TD-SCDMA compatibility to OFDM tech; high speed serialization chip sequence to be sent is carried out serial to parallel conversion; after generating the subsequence of multidiameter delay; be modulated to respectively on a plurality of subcarriers of OFDM and carry out parallel transmission; though total message transmission rate is than higher; but reduced the transmission rate on each road; thereby increase code-element period; can more effectively weaken the influence that multipath disturbs; it uses Cyclic Prefix (CP) as protection at interval simultaneously; significantly reduce even eliminated intersymbol interference; and guaranteed the orthogonality of each interchannel; thereby significantly reduced interchannel interference; higher message transmission rate is provided; further improve spectrum efficiency; and the serious intersymbol interference that brings can effectively suppress high speed data transfer the time; simultaneously because the later system of 3G will mainly adopt OFDM as its core technology; the present invention can make that as the alternative of TD-SCDMA TD-SCDMA can be compatible better with system in the future, realizes transition smoothly easily.

For solving the problems of the technologies described above, the present invention is achieved in that

The invention provides a kind of method of TD-SCDMA compatibility to OFDM tech; described TD-SCDMA system comprises 4 kinds of time slot type: DwPTS, UpPTS, GP and TS0～TS6; wherein DwPTS and UpPTS are used separately as uplink synchronous and down-going synchronous; carrying user data not; GP protects as the propagation delay that uplink synchronous is set up in the process; conventional time slot TS0～TS6 is as carrying user data or control information; in order to combine with the OFDM technology; made corresponding processing for different time-gap, its implementation is:

(1) for the user data among conventional time slot TS0～TS6 or the processing of control information

(a) bit stream that derives from the physical channel mapping will pass through data-modulated earlier before carrying out spread processing, can adopt the modulator approach than higher exponent number among the TD-SCDMA, to improve spectrum efficiency and data rate

(b) after data symbol sequence is handled through conventional multiplication operator weighting, spread spectrum and scrambler, scrambler sequence is divided into groups, every group comprises N chip, it is carried out serial/parallel conversion, become a parallel data flow, carry out the inverse fast fourier transform IFFT that N is ordered then, just this N chip is modulated on the subcarrier of N parallel quadrature, realized the modulation of OFDM

(c) after the IFFT conversion, add one as protection at interval, to overcome the influence of intersymbol interference greater than the cyclic prefix CP of channel maximum delay spread

(d) conventional treatment of execution TD-SCDMA after the parallel/serial conversion

(2) for i.e. i.e. uplink synchronous code in the UpPTS time slot and the i.e. processing of thinking training sequence in conventional time slot of Midamble sign indicating number of descending synchronous code in the DwPTS time slot, SYNC-UL of SYNC-DL

(a) in the TD-SCDMA standard, these several sign indicating numbers of SYNC-DL, SYNC-UL and Midamble all are that direct form with spreading rate provides, not needing to carry out spread spectrum and scrambling handles, this code book of several yards can directly be found in the standard of 3GPP, carries out then directly carrying out the OFDM modulated process after the plural number processing

(b) for SYNC-DL, SYNC-UL and Midamble, its chip sequence is divided into groups respectively, every group comprises N chip, OFDM modulated process according to the front, carry out the IFFT conversion that N is ordered after the serial/parallel respectively conversion, add again and carry out parallel/serial conversion behind the CP, generate a plurality of continuous OFDM symbols

(c) further carry out the conventional process of TD-SCDMA, wherein the Midamble sign indicating number is further handled after will being combined into subframe with data after spread spectrum, scrambling and the OFDM modulation in the corresponding conventional time slot or control information again

(3) receiving terminal

(a) DO symbol timing synchronization procedure is promptly tried to achieve accurate moment of single OFDM sign-on and end.Symbol result regularly will determine the window of FFT.Can adopt methods such as data are auxiliary, non-data are auxiliary to realize that symbol regularly.Wherein the data householder method can periodically be inserted known training symbol as guide symbol in transmission signals.Non-data householder method adopts the CP structure of OFDM waveform to finish symbol regularly

(b) signal that receives is carried out serial/parallel conversion and removes CP

(c) carry out strict carrier frequency shift estimation error, carry out frequency correction.Frequency offset error is estimated and can be carried out based on the specific training information in the transmission signals, also can the received signal analysis in the frequency domain be obtained.A subject matter that faces in ofdm system is the sensitiveness to frequency offset error.Therefore, when introducing the OFDM technology in the TD-SCDMA system, then the FFT conversion that the carrier frequency accuracy requirement is ordered than more important (d) execution N in original T D-SCDMA system becomes signal again frequency domain from time domain, to realize the OFDM demodulation

(e) the certain channel estimation method of employing estimates the channel coefficients on each subcarrier of OFDM

(f) then for the signal after the OFDM demodulation fill order user or Multiuser Detection again, to rule out the data of transmission.

When TD-SCDMA combines with OFDM, adopt the simple balanced demodulation that just can realize OFDM, the thinking that receives with Rake (RAKE) is different, needn't adopt the RAKE reception technique again, original T D-SCDMA receiver adopts the RAKE diversity receiving technology to distinguish and bind the multiple signals energy, certain diversity gain can be provided, yet because the multiple signals energy is unequal, if number of path is more, the dispersion of sort signal energy will make accuracy of channel estimation reduce, and the receptivity of RAKE descends will be very fast.

When receiving terminal carries out channel estimating, can utilize in the DwPTS time slot a plurality of continuous OFDM symbol that sends SYNC-UL in a plurality of continuous OFDM symbol that sends SYNC-DL, the UpPTS time slot, and a plurality of continuous OFDM symbol that sends the Midamble sign indicating number in each conventional time slot is as frequency pilot sign, perhaps also can in the burst of transmitting terminal, insert specific frequency pilot sign, carry out channel estimating.

In receiving terminal list user detection scheme, according to the channel coefficients on each subcarrier of the OFDM that estimates, carry out simple balanced, can adopt high specific to merge (MRC), Po zero balanced (ZF) and least mean-square error equilibrium channel equalization algorithms such as (MMSE), descrambling and de-spreading operation are carried out in output for equalizer again, obtain final testing result, in addition, also can merge execution in receiving terminal equilibrium and descrambling and de-spreading, to estimate to send data.

In receiving terminal Multiuser Detection scheme, can adopt continuous Interference Cancellation (SIC), Parallel Interference Cancellation (PIC) and joint-detection (Joint Detection, method such as JD), they were applied to can be applicable to after algorithm in the single-carrier system is revised in this TD-SCDMA and the system that OFDM combines originally, can suppress the influence that multiple access disturbs effectively, further improve the performance of system.

Only need single FFT just can handle a plurality of users' signal at receiving terminal; TD-SCDMA is a synchro system; although can not guarantee synchronously accurate fully; yet in the OFDM modulation; the protection of inserting in order to resist intersymbol interference can allow that little time migration is arranged between the user at interval; can handle by symbol ground for signal in this case, and can not be subjected to the interference of adjacent-symbol.

In TD-SCDMA and system that OFDM combines, can realize technology for self-adaptively transmitting easily, in this system, can utilize the characteristics of multicarrier structure, use channel condition information (CSI), according to the channel status different user at the different information bit number of each subcarrier allocation, transmitted power, code rate or their combination are to obtain self adaptation, because Adaptive Transmission need obtain the channel estimating information of each user in the sub-district, this prerequisite makes Adaptive Transmission be more suitable in carrying out in down link, in the TD-SCDMA system, owing to adopt tdd mode, but up link is used same frequency band different time slots with down link, the similar decline of uplink downlink channel experience like this, Adaptive Transmission can be easy to realize and only need seldom extra signaling consumption, and for Frequency Division Duplexing (FDD) (FDD) pattern that other 3G standard adopted, because the uplink downlink channel uses different frequencies, then need the signaling consumption that adds exchanging current auto-adaptive parameter and channel status, thereby in TD-SCDMA and system that OFDM combines, be easier to adopt technology for self-adaptively transmitting.

Needn't too much consider to take the measure of very complicated reduction peak-to-average power ratio, the unfavorable aspect that ofdm system exists is to have higher peak-to-average power ratio, when introducing the OFDM technology in the TD-SCDMA system, also can there be this problem, but influence degree is much lower, in ofdm system, the worst situation usually occurs in all carrier waves and all uses same symbol to modulate, but in the system of TD-SCDMA and OFDM combination, this situation is easy to avoid, the pseudo random sequence that obtains behind each user's data process spread spectrum and the scrambler is modulated on each subcarrier of OFDM, the superimposed result of a plurality of users make the signal value on each subcarrier be random distribution bipolar signal and, then it tends to obey Gauss (Gaussian) distribution, and the superimposed effect of a plurality of like this users has reduced the peak-to-average power ratio effectively.

The advantage that the present invention has is:

The influence that can disturb anti-multipath effectively in conjunction with the OFDM technology in TD-SCDMA.

needs to support a plurality of users in mobile communication system, code division multiple access CDMA is an effective means of supporting multi-user communication, and adopts OFDM can reach the effect of comparatively ideal frequency diversity.

TD-SCDMA has adopted the synchronization CDMA technology, the signal that makes each portable terminal of up channel send keeps synchronously at the place, base station, and multi-user OFDM is very strict for regularly synchronous requirement, just is easy to like this combine with the OFDM technology in the TD-SCDMA system.

TD-SCDMA is a synchro system, although can not guarantee synchronously fully accurately, yet in the OFDM modulation, the protection of inserting in order to resist intersymbol interference can allow that little time migration is arranged between the user at interval.Can handle by symbol ground for signal in this case, and can not be subjected to the interference of adjacent-symbol.This also has an additional benefit is only to need single FFT just can handle a plurality of users' signal.

(the highest 2Mbit/s) that the message transmission rate that TD-SCDMA system can provide is still more limited, the exponent number of the modulation system that is adopted (QPSK or 8-PSK) is still lower.And OFDM is a kind of wideband transmit technology, can resist the influence of intersymbol interference effectively, can adopt higher order of modulation (as 16-QAM etc.) to improve modulation efficiency, can provide higher message transmission rate.

The multicarrier structure of OFDM makes and can realize technology for self-adaptively transmitting easily in the TD-SCDMA system.In the TD-SCDMA system, owing to adopt tdd mode, but up link and down link use same frequency band different time slots, and the uplink downlink channel experiences similar decline like this, and Adaptive Transmission can be easy to realize and only need seldom extra signaling consumption.

The unfavorable aspect that the ofdm system exists is to have higher peak-to-average power ratio.When introducing the OFDM technology in the TD-SCDMA system, also can have this problem, but influence degree is much lower.The pseudo random sequence that obtains behind each user's data process spread spectrum and the scrambler is modulated on each subcarrier of OFDM, the superimposed result of a plurality of users make the signal value on each subcarrier be random distribution bipolar signal and, then it tends to obey the Gaussian distribution, and the superimposed effect of a plurality of like this users has reduced the peak-to-average power ratio effectively.

TD-SCDMA and OFDM combine an alternative as TD-SCDMA, with making the later technology of TD-SCDMA system and 3G (will mainly adopt OFDM as its core technology) can realize better compatibility, realize seamlessly transitting.

Description of drawings:

Fig. 1 is a prior art multicarrier transmission systems theory diagram.

Fig. 2 is a prior art baseband OFDM system principle diagram.

Fig. 3 is the structural representation of TD-SCDMA subframe of the present invention.

Fig. 4 is the burst structure schematic diagram of the TD-SCDMA DwPTS of system of the present invention.

Fig. 5 is the burst structure schematic diagram of the TD-SCDMA UpPTS of system of the present invention.

Fig. 6 is the conventional structure of time slot schematic diagram of TD-SCDMA of the present invention system.

Fig. 7 is the 16-QAM planisphere of TD-SCDMA of the present invention system.

Fig. 8 is the schematic diagram of transmitting terminal baseband portion of the present invention.

Fig. 9 is the schematic diagram of spread spectrum, scrambling and the OFDM modulated process of data symbol of the present invention.

Figure 10 is the schematic diagram of receiving terminal baseband portion of the present invention.

Figure 11 is the schematic diagram of the single user's detection scheme of the present invention.

Embodiment:

The invention provides a kind of method of TD-SCDMA compatibility to OFDM tech, concrete scheme is as follows: in the TD-SCDMA system, in order to guarantee the reliable transmission of data on Radio Link, physical layer at first need to encode from MAC and high-rise data flow/multiplexing, through after the physical channel mapping, the data on the channel will carry out spread spectrum and scrambler is handled then.Spread spectrum multiplies each other with the Serial No. and the channel data that are higher than data bit rates, and multiplied result has been expanded the bandwidth of signal, has converted the data flow of bit rate to spreading rate data flow.Spread processing also is called channelisation operation usually, and employed Serial No. is called channel code, and this is that a group length can be different but still mutual code character.Scrambler and spread spectrum are similar, also are to multiply each other with the data after a Serial No. and the spread processing.Different with spread spectrum is, the burst behind the Serial No. that scrambler is used and the spread spectrum has identical spreading rate, and the multiplying of being done is a kind of computing of multiplying each other by chip.The purpose of scrambler is the cell attribute for identification data.

Spreading rate behind the TD-SCDMA spread spectrum is 1.28Mc/s, and the scope of spreading factor is 1～16, and the speed of modulation symbol is 80.0k symbol/s～1.28M symbol/s.

The frame structure and the burst structure of TD-SCDMA system

The TD-SCDMA frame length is 10ms, and is divided into two identical in structure 5ms subframes.Subframe structure as shown in Figure 3.Each subframe is formed (TS0～TS6) by 3 special time slots and 7 conventional time slots.

TD-SCDMA adopts tdd mode, is with the particular time-slot emission of a burst (Burst) in the radio frames of being distributed on physical channel.The structure that structure of time slot just happens suddenly.By Fig. 3, the TD-SCDMA system has defined 4 kinds of time slot type: DwPTS, UpPTS, GP and TS0～TS6 altogether.Wherein DwPTS and UpPTS are used separately as uplink synchronous and down-going synchronous, carrying user data not, and GP sets up propagation delay protection in the process as uplink synchronous, conventional time slot (TS0～TS6) as carrying user data or control information.

The DwPTS time slot is used for sending descending synchronous code (SYNC-DL), and its structure as shown in Figure 4.

The UpPTS time slot is used for sending uplink synchronous code (SYNC-UL) by UE, and its structure as shown in Figure 5.

Totally 7 conventional time slots are as the transmission of user data or control information for TS0～TS6, and they have identical structure of time slot, and its structure as shown in Figure 6.

Set forth the processing procedure of conventional time slot, DwPTS time slot and UpPTS time slot below respectively.

The processing of user data or control information in the conventional time slot of

A. data-modulated

As shown in Figure 6, each conventional time slot all is to be made of two data fields, and these two territories lay respectively at training sequence (Midamble) before and afterwards.The bit stream that derives from the physical channel mapping will pass through data-modulated earlier before carrying out spread processing.Data-modulated is mapped as continuous a plurality of bits the data symbol of a complex values.The general data modulation technique that adopts is QPSK in the TD-SCDMA system, and for the business of 2Mbit/s, uses 8PSK modulation mode.The efficient of these modulation systems is still lower, and in order further to improve spectrum efficiency, the present invention adopts the 16-QAM modulation.Owing to adopted the OFDM transmission technology that effectively to resist intersymbol interference, so can suitably improve the exponent number of modulation.16-QAM is mapped as the data symbol of a complex values to 4 continuous bits, and its planisphere as shown in Figure 7.In order to reduce the error rate between consecutive points in the receiver, bit mode adopts the Gray encoding scheme.

The input bit sequence is through after shining upon, and output sequence can be expressed as:

${\underset{\‾}{d}}^{(k,i)}={(\underset{\‾}{{\underset{\‾}{d}}_1^{(k,1)},{\underset{\‾}{d}}_2^{(k,i)}},\mathrm{\Λ}{,\underset{\‾}{d}}_{N_k}^{(k,i)})}^T,i=\mathrm{1,2};k=1,\mathrm{\Λ},K$

In the formula, k is a number of users in the time slot, is 16 to the maximum, N _kBe the symbolic number of k user in a data field, its value and the spreading factor Q that uses _kRelevant.Data block d ^{(k, 1)}Front at training sequence sends, and data block d ^{(k, 2)}Back at training sequence sends.

B. spread spectrum

After the complex value mapping, the complex-valued data symbol d _n ^{(k, i)}Will be by spread spectrum.In the TD-SCDMA system, the spread spectrum of up direction uses length to be Q _k∈ 1,2,4,8,16) real-valued channel code sequence, and at down direction, Q _k∈ 1,16}.Real-valued channel code sequence can be expressed as:

$c^{\left(k\right)}=(c_1^{\left(k\right)},c_2^{\left(k\right)},\mathrm{\Λ},c_{Q_k}^{\left(k\right)}),k=1,\mathrm{\Λ},K$

Element c in the sequence _q ^(k)∈ 1 ,-1}; K=1, Λ, K.c ^(k)Also be called Orthogonal Variable Spreading Factor OVSF (OVSF) sign indicating number.

In order to reduce the PAR peak to average ratio in many yards whens transmission, also has a channelizing feature multiplication operator with channel code accompanies $w_{Q_k}^{\left(k\right)}\∈\left\{e^{\mathrm{j\π}/2p_k}\right\},p_k\∈\{0,\mathrm{\Λ},Q_k-1\}$ , Q _kIt is spreading factor.Multiplication operator usually before spread spectrum with each data symbol through complex value mapping multiply each other (but also carrying out after the spread spectrum) thereby w _Qk ^(k)Usually also be called weighted factor.

C. scrambler

Data symbol also will carry out scrambler and handle through after the spread processing.Identified user's (Code Channel) if channelizing is handled, so data being carried out the scrambler processing then is for identifying cells.In the TD-SCDMA system, adopt short multiple scrambler to come that the data symbol is carried out scrambling and handle.The length of scrambler sequence is fixed as 16, can be expressed as: v=( v ₁, v ₂, Λ, v ₁₆).Element in the complex sequences v _i(i=1, Λ, 16) span be 1, j ,-1 ,-j}.Multiple scrambler is to be 16 binary system real number scrambler sequence v=(v by a length ₁, v ₂, Λ, v ₁₆) produce.The TD-SCDMA system has defined 128 such sequence of real numbers altogether, 4 of each cell configuration.Multiple scrambler sequence vWith the pass of each element among the real scrambler sequence v be:

v _i=(j) ⁱV _iv _i∈ 1 ,-1}; I=1, Λ, 16 complex sequences vIn each element v _iBe that actual situation replaces.

D. serial/parallel conversion and OFDM modulation

Data after user k process spread spectrum and the scrambling are with every Q _MaxIndividual chip is divided into one group.The scrambler of the spreading code of user k and sub-district combines and can be regarded as the specific spreading code of user k and sub-district in this group $s^{\left(k\right)}=\left(s_p^{\left(k\right)}\right),$ Wherein:

$s_p^{\left(k\right)}={\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="A20051002617100281.png,A20051002617100312.png"\; state="\{\{state\}\}">c</figure-callout>}}_{1+[(p-1)\mathrm{mod}{Q}_k]}^{\left(k\right)}{\underset{\&OverBar;}{v}}_p,p=\mathrm{1,2},...,Q_{\max }$ P chip u in this group of chip sequence then _p ^{(k, i)}Can be expressed as:

$u_p^{(k,i)}={\underset{\&OverBar;}{d}}_{1+\left[(p-1)\mathrm{mod}{Q}_k\right]}^{(k,i)}{w}_{Q_k}^{\left(k\right)}{s}_p^{\left(k\right)},p=\mathrm{1,2},...,Q_{\max }$

Q with this group sequence _MaxIndividual chip carries out serial/parallel conversion, becomes a parallel data flow, then by sending out after the OFDM modulation.The sub-carrier number N=Q of OFDM employing here _MaxAs shown in Figure 8.This group of chip sequence baseband signal that modulation is sent through OFDM is:

$x_n^{(k,i)}={\mathrm{\&Sigma;}}_{p=1}^{Q_{\max }}\exp (j2\mathrm{\&pi;pn}/Q_{\max })u_p^{(k,i)},n=1,...,Q_{\max }$ Be that the OFDM modulation can be by carrying out Q with the data after the serial/parallel conversion _MaxThe IFFT conversion of point realizes effectively.

In order to overcome the influence of intersymbol interference, after the IFFT conversion, to add one as protection at interval greater than the CP of channel maximum delay spread.By using this protection at interval, receiving terminal can take out the signal section that is not subjected to intersymbol interference, to realize the transmission of no intersymbol interference.

In sum, as shown in Figure 9 for the general process of the user data that sends in the conventional time slot or control information spread spectrum, scrambler and OFDM modulation.K represents user number, and { 1,2} represents the data block number in the conventional burst, Q to i ∈ _kBe the spreading factor of current use in the time slot, Q _Max=16 is the maximum spreading factor that uses in the time slot, also is the length of scrambler sequence simultaneously, n _k=Q _Max/ Q _k

3. for the processing of SYNC-DL, SYNC-UL and Midamble sign indicating number

In the standard of 3GPP, these several sign indicating numbers of SYNC-DL, SYNC-UL and Midamble all are that direct form with spreading rate provides, do not need to carry out spread spectrum, they send in DwPTS time slot (consulting Fig. 4), UpPTS time slot (consulting Fig. 5) and conventional time slot (consulting Fig. 6) respectively.In addition, these several sign indicating numbers have different configurations in different adjacent cells, thereby also do not need to carry out the scrambling processing.All these code books of several yards can directly be found in the standard of 3GPP, do not need any generative process (Midamble needs to distinguish the user by cyclic shift).Required processing be this several sign indicating number all be that form with real number value provides, need carry out the plural number processing.

If this real-valued sequence of several yards is:

$u=({\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="A20051002617100281.png,A20051002617100312.png"\; state="\{\{state\}\}">u</figure-callout>}}_1,u_2,{\mathrm{\&Lambda;},u}_i,\mathrm{\&Lambda;},u_k),K=\left\{\begin{array}{cc}64& \mathrm{SYNC}-\mathrm{DL}\\ 128& \mathrm{SYNC}-\mathrm{UL}\\ 144& \mathrm{Midamble}\end{array}\right.$

Relational expression below the plural numberization processing is used acts on each element among the real-valued sequence u.

u _i=(j) ⁱU _iu _i∈ 1, and-1} i=1,2, Λ, after the processing of K process plural numberization, complex-valued sequences u=( u ₁, u ₂, Λ, u _i, Λ, u _K) in element be that actual situation replaces, then it is carried out OFDM modulation again.For SYNC-DL, its 64 chips are divided into 4 groups, and every group of OFDM modulated process (consulting Fig. 8) according to the front carries out Q respectively _MaxThe IFFT conversion of point generates 4 continuous OFDM symbols and sends.For SYNC-UL, its 128 chips are divided into 8 groups, and every group is carried out Q respectively _MaxThe IFFT conversion of point generates 8 continuous OFDM symbols and sends.For Midamble, its 144 chips are divided into 9 groups, and every group is carried out Q respectively _MaxThe IFFT conversion of point generates 9 continuous OFDM symbols and sends.

4. receiver scheme

Want the DO symbol timing process at receiving terminal, promptly try to achieve the accurate moment of single OFDM sign-on and end.Symbol result regularly will determine the window of FFT.Can adopt the auxiliary and auxiliary two kinds of methods realization of the non-data symbol timing of data.The data householder method can periodically be inserted known training symbol as guide symbol in transmission signals.Non-data householder method adopts the circulating prefix structure of OFDM waveform to finish symbol regularly.And a subject matter that faces in ofdm system is the sensitiveness to frequency offset error.Therefore, more important in original T D-SCDMA system when in the TD-SCDMA system, introducing the OFDM technology for the accuracy ratio of estimating carrier frequencies, carry out strict carrier frequency shift estimation error, carry out frequency correction.Frequency offset error is estimated and can be carried out based on the specific training information in the transmission signals, also can the received signal analysis in the frequency domain be obtained.

Band receiver of base structure of the present invention as shown in figure 10.Carry out the process opposite at receiving terminal, after carrying out timing synchronization, serial/parallel conversion to the received signal and removing CP, carry out frequency correction, carry out Q again according to the frequency shift (FS) that estimates with transmitting terminal _MaxThe FFT conversion of point becomes signal again frequency domain from time domain, to realize the OFDM demodulation.Simultaneously, the certain channel estimation method of employing estimates the channel coefficients on each subcarrier of OFDM.Can utilize in the DwPTS time slot 8 continuous OFDM symbols that send SYNC-UL in 4 continuous OFDM symbols sending SYNC-DL, the UpPTS time slot, and 9 continuous OFDM symbols that send the Midamble sign indicating number in each conventional time slot are carried out channel estimating as frequency pilot sign.Then for the signal after the OFDM demodulation fill order user or Multiuser Detection again, to rule out the data of transmission.

K user's single user detector as shown in figure 11.Can think the arrowband flat fading on each subchannel of OFDM, the channel coefficients of estimated p the subchannel that goes out of channel estimation module is H (p).Carry out after the OFDM module received signal vector and be Y=(Y (1), Y (2) ..., Y (Q _Max)) ^T, its element Y (p) is the received signal on p subcarrier.G is single tap Q _Max* Q _MaxEqualizer, and

$G=\left[\begin{array}{cccc}G\left(1\right)& & & \\ & G\left(2\right)& & \\ & & O& \\ & & & G\left(Q_{\max }\right)\end{array}\right]$

Be a diagonal matrix, plural G (p) (p=1,2 ..., Q _Max) expression p subcarrier equalizing coefficient.The output result of equalizer is: R=GY.

In the present invention, can realize equilibrium at an easy rate by changing coefficient G (p) simply.Here be example with several simple equalization algorithms:

(a) high specific merges (MRC): equalizing coefficient G (p) is set to be complementary with channel, i.e. G (p)=H ^*(p), then it can be used to realize a frequency domain RAKE receiver.

(b) Po zero equilibrium (ZF): equalizing coefficient G (p)=H ^*(p)/| H (p) | ²For synchronization CDMA, it can rebuild the orthogonality between the different user, to eliminate the influence that multiple access disturbs MAI.The shortcoming of this receiver is to be restricted when some subchannel deep fading, and the noise on these subchannels can be amplified to the stage that reduces receiver performance at this moment.But this problem can be easy to by least mean-square error (MMSE) equalization methods below using solve.

(c) least mean-square error equilibrium (MMSE): equalizing coefficient G (p)=H ^*(p)/(| H (p) | ²+ λ).It and the Po zero balanced main distinction is to adjust factor lambda, and it is used for suffering, and any possible noise of restriction amplifies on deep fading's the subchannel.

In down link, for the user that will decode, the data of interference user send over from same base station, estimate that these channel coefficients are simple relatively.

Descrambling and de-spreading operation are carried out in output for equalizer again, obtain final testing result.In addition, also can merge execution, to estimate to send data in receiving terminal equilibrium and descrambling and de-spreading.

In the TD-SCDMA system, can resist the influence that multipath disturbs effectively, and on the other hand, it is the principal element that influences its performance that multiple access disturbs again in conjunction with the OFDM technology.Be directed to this, adopt Multiuser Detection can improve the performance of system effectively, wherein Interference Cancellation (IC) is a method relatively more commonly used, and can be applied in TD-SCDMA and the system that OFDM combines.

Fairly simple non-linear receiver is continuous Interference Cancellation (SIC).In this algorithm, at first detect user with peak power.Utilize this user's of testing result reconstruct signal then, and it is removed from the receiver input signal.Then remaining user being repeated this operation all detects up to all users.Can also adopt Parallel Interference Cancellation (PIC) in addition, processing speed is fast relatively.At first use channel matched filter output that all user's data are estimated, then,, obtain a new estimation after the interference that other users of removal cause from signal for each user.This process can repeat repeatedly.

Associated detection technique proposes on the multiuser detection basis.This technology is to weaken or eliminate the effective means of multiple access interference, multipath interference and near-far interference, can simplify power control, reduce the power control precision, remedy the undesirable negative influence that brings of orthogonal intersection cross correlation, thereby improve systematic function, raising power system capacity, increase cell coverage area.Associated detection technique equally also can be applicable in TD-SCDMA and the system that OFDM combines.

For the system that TD-SCDMA combines with OFDM, in the reception of down link, Interference Cancellation generally not will consider employing mainly due to its complexity.And such receiver needs the important information of all users in the system, for example their spreading code, power etc.Therefore adopt single user's detection scheme at down link.

In up link, during the design base station, Interference Cancellation and joint-detection can adopt.TD-SCDMA is a synchro system, although can not guarantee synchronously fully accurately, yet in the OFDM modulation, the protection of inserting in order to resist intersymbol interference can allow that little time migration is arranged between the user at interval.Can handle by symbol ground for signal in this case, and can not be subjected to the interference of adjacent-symbol.This also has an additional benefit is only to need single FFT just can handle a plurality of users' signal.And in other asynchronous system, each user is just needed an independent FFT operation.

Therefore, the advantage and the necessity that combine with OFDM of TD-SCDMA is as follows:

TD-SCDMA is an interference (or signal to noise ratio) constrained system, and its capacity mainly is subject to the main interference of mobile channel: multipath disturbs with multiple access and disturbs, and OFDM overcomes multipath to disturb the most effectively means.For anti-multipath is disturbed, the TD-SCDMA receiver adopts the RAKE diversity receiving technology to distinguish and bind the multiple signals energy, and certain diversity gain can be provided.Yet because the multiple signals energy is unequal, evidence, if number of path surpasses 7 or 8, the dispersion of sort signal energy will make accuracy of channel estimation reduce, the receptivity of RAKE descends will be very fast.And the OFDM technology is different with the thinking that RAKE receives, and it is that information code element to be sent is passed through serial to parallel conversion, changing down, thus increase code-element period, more effectively to weaken the influence that multipath disturbs.Simultaneously it uses CP as protection at interval, significantly reduces even has eliminated intersymbol interference, and guaranteed the orthogonality of each interchannel, thereby significantly reduced interchannel interference.

needs to support a plurality of users in mobile communication system, CDMA is an effective means of supporting multi-user communication, and adopts OFDM can reach the effect of comparatively ideal frequency diversity.

TD-SCDMA has adopted the synchronization CDMA technology, the signal that makes each portable terminal of up channel send keeps synchronously at the place, base station, and multi-user OFDM is very strict for regularly synchronous requirement, just is easy to like this combine with the OFDM technology in the TD-SCDMA system.

TD-SCDMA is a synchro system, although can not guarantee synchronously fully accurately, yet in the OFDM modulation, the protection of inserting in order to resist intersymbol interference can allow that little time migration is arranged between the user at interval.Can handle by symbol ground for signal in this case, and can not be subjected to the interference of adjacent-symbol.This also has an additional benefit is only to need single FFT just can handle a plurality of users' signal.

(the highest 2Mbit/s) that the message transmission rate that TD-SCDMA system can provide is still more limited, the exponent number of the modulation system that is adopted (QPSK or 8-PSK) is still lower.And OFDM is a kind of wideband transmit technology, can resist the influence of intersymbol interference effectively, can adopt higher order of modulation (as 16-QAM etc.) to improve modulation efficiency, can provide higher message transmission rate.

The multicarrier structure of OFDM makes and can realize technology for self-adaptively transmitting easily in the TD-SCDMA system.In general ofdm system, use CSI, according to the channel status different user at the different information bit number of each subcarrier allocation, constellation size, transmitted power, code rate or their combination are to obtain self adaptation.On the other hand, in TD-SCDMA and system that OFDM combines, can consider to utilize the characteristics of multicarrier structure to adopt technology for self-adaptively transmitting to obtain the raising of systematic function.Because Adaptive Transmission need obtain the channel estimating information of each user in the sub-district, this prerequisite makes Adaptive Transmission be more suitable in carrying out in down link.In the TD-SCDMA system, owing to adopt tdd mode, but up link and down link use same frequency band different time slots, and the uplink downlink channel experiences similar decline like this, and Adaptive Transmission can be easy to realize and only need seldom extra signaling consumption.And for the fdd mode that other 3G standard adopted, because the uplink downlink channel uses different frequencies, the signaling consumption that then needs to add is to exchange current auto-adaptive parameter and channel status.Therefore, in TD-SCDMA and system that OFDM combines, be easier to adopt technology for self-adaptively transmitting.

The unfavorable aspect that the ofdm system exists is to have higher peak-to-average power ratio.When introducing the OFDM technology in the TD-SCDMA system, also can have this problem, but influence degree is much lower.In ofdm system, the worst situation usually occurs in all carrier waves and all uses same symbol to modulate.But in the system of TD-SCDMA and OFDM combination, this situation is easy to avoid.The pseudo random sequence that obtains behind each user's data process spread spectrum and the scrambler is modulated on each subcarrier of OFDM, the superimposed result of a plurality of users make the signal value on each subcarrier be random distribution bipolar signal and, then it tends to obey the Gaussian distribution, and the superimposed effect of a plurality of like this users has reduced the peak-to-average power ratio effectively.

TD-SCDMA and OFDM combine an alternative as TD-SCDMA, with making the later technology of TD-SCDMA system and 3G (will mainly adopt OFDM as its core technology) can realize better compatibility, realize seamlessly transitting.

Thereby, in the TD-SCDMA system, synchronization CDMA and OFDM can be combined, as the alternative of TD-SCDMA, make full use of the advantage that the two combines, to overcome the multimedia service that multipath disturbed and provided higher quality of service and message transmission rate better.

In a word, the present invention makes full use of the advantage that synchronization CDMA and OFDM combine, and can remedy the deficiency of TD-SCDMA system, overcomes multipath better and disturbs, intersymbol interference when eliminating high speed data transfer effectively provides the more multimedia service of high data rate and quality of service.Also can make the later technology of TD-SCDMA system and 3G (will mainly adopt OFDM) can realize better compatibility, can be smoothly transitted into system in the future as its core technology.

Being preferred embodiment of the present invention only in sum, is not to be used for limiting practical range of the present invention.Be that all equivalences of doing according to the content of the present patent application claim change and modification, all should be technology category of the present invention.

Claims (18)

1, a kind of method of TD-SCDMA system compatible OFDM technology is characterized in that may further comprise the steps:

At transmitting terminal, the chip that the TD-SCDMA system is provided divides into groups, and every group of chip is carried out the modulation treatment of OFDM, carries out the conventional treatment of TD-SCDMA then;

At receiving terminal, comprising:

The DO symbol timing synchronization procedure;

Carrying out the carrier frequency shift estimation error line frequency of going forward side by side proofreaies and correct;

Carry out the OFDM demodulating process;

Carry out channel estimation process, thereby estimate the channel coefficients on each subcarrier of OFDM; And

To signal fill order user or the Multiuser Detection after the OFDM demodulation, with the data of judgement transmission.

2; the method of TD-SCDMA system compatible OFDM technology according to claim 1; it is characterized in that; described TD-SCDMA system comprises 4 kinds of time slot type: DwPTS; UpPTS; GP and TS0～TS6; wherein DwPTS and UpPTS are used separately as uplink synchronous and down-going synchronous; carrying user data not; GP protects as the propagation delay that uplink synchronous is set up in the process; conventional time slot TS0～TS6 is as carrying user data or control information; at described transmitting terminal, be that TD-SCDMA system different time-gap has been made corresponding processing so that better combine with the OFDM technology.

3, the method for TD-SCDMA system compatible OFDM technology according to claim 2, it is characterized in that: before described chip grouping, for the user data among described conventional time slot TS0～TS6 or the processing of control information, to deriving from the bit stream of physical channel mapping, after carrying out multiplication operator weighting, spread spectrum and the scrambler processing of data-modulated and routine, scrambler sequence is divided into groups.

4, the method for TD-SCDMA system compatible OFDM technology according to claim 3 is characterized in that the step of described execution data-modulated can adopt the modulator approach than higher exponent number among the TD-SCDMA, to improve spectrum efficiency and data rate.

5, the method for TD-SCDMA system compatible OFDM technology according to claim 2, it is characterized in that: for the i.e. i.e. i.e. training sequence in conventional time slot of uplink synchronous code in the UpPTS time slot and Midamble sign indicating number of descending synchronous code in the DwPTS time slot, SYNC-UL of SYNC-DL, these several sign indicating numbers are in the TD-SCDMA standard, all be that direct form with spreading rate provides, not needing to carry out spread spectrum and scrambling handles, can in the standard of 3GPP, directly find this code book of several yards, carry out then directly carrying out the OFDM modulated process after the plural number processing.

6, according to the method for claim 2 to 5 each described TD-SCDMA system compatible OFDM technology, it is characterized in that: the process of described execution OFDM modulation may further comprise the steps:

When the chip to different time-gap divides into groups, promptly the scrambler sequence among conventional time slot TS0～TS6 is divided into groups, for SYNC-DL, SYNC-UL and Midamble, its chip sequence is divided into groups respectively, make every group to comprise N chip;

Every group of chip is carried out serial/parallel conversion, become parallel data stream;

Carry out the inverse fast fourier transform IFFT that N is ordered, this N chip is modulated on the subcarrier of N parallel quadrature;

After the IFFT conversion, add one as protection at interval, to overcome the influence of intersymbol interference greater than the cyclic prefix CP of channel maximum delay spread;

Carry out parallel/serial conversion, generate a plurality of continuous OFDM symbols.

7, the method for TD-SCDMA system compatible OFDM technology according to claim 6, it is characterized in that: before carrying out the conventional treatment of TD-SCDMA, also comprise the step that data after spread spectrum, scrambling and the OFDM modulation that makes in Midamble sign indicating number and its corresponding conventional time slot or control information are combined into subframe.

8, the method for TD-SCDMA system compatible OFDM technology according to claim 2, it is characterized in that: when receiving terminal carries out channel estimating, can utilize in the DwPTS time slot a plurality of continuous OFDM symbol that sends SYNC-UL in a plurality of continuous OFDM symbol that sends SYNC-DL, the UpPTS time slot, and a plurality of continuous OFDM symbol that sends the Midamble sign indicating number in each conventional time slot is as frequency pilot sign, perhaps also can in the burst of transmitting terminal, insert specific frequency pilot sign, carry out channel estimating.

9, the method for TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: described DO symbol timing synchronization procedure can adopt the data householder method to realize symbol regularly, and described data householder method can periodically be inserted known training symbol as guide symbol in transmission signals.

10, the method for TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: described DO symbol timing synchronization procedure can adopt non-data householder method to realize symbol regularly, and described non-data householder method adopts the CP structure of OFDM waveform to finish symbol regularly.

11, the method for TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: described process in receiving terminal execution OFDM demodulation comprises, in baseband portion, carry out timing synchronization to the received signal, serial/parallel conversion, and after removing CP is carried out frequency correction according to the result of Carrier frequency offset estimation, carry out the FFT conversion that N is ordered again, signal is become again frequency domain from time domain.

12, the method of TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: when TD-SCDMA combines with OFDM, adopt the simple balanced demodulation that just can realize OFDM, the thinking that receives with RAKE is different, needn't adopt the RAKE reception technique again, original T D-SCDMA receiver adopts the RAKE diversity receiving technology to distinguish and bind the multiple signals energy, certain diversity gain can be provided, yet because the multiple signals energy is unequal, if number of path is more, the dispersion of sort signal energy will make accuracy of channel estimation reduce, and the receptivity of RAKE descends will be very fast.

13, the method for TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: in receiving terminal list user detection scheme, according to the channel coefficients on each subcarrier of the OFDM that estimates, carry out simple balanced, can adopt high specific to merge channel equalization algorithms such as MRC, Po zero balanced ZF and the balanced MMSE of least mean-square error, descrambling and de-spreading operation are carried out in output for equalizer again, obtain final testing result.

14, the method for TD-SCDMA system compatible OFDM technology according to claim 1 is characterized in that, in receiving terminal list user detection scheme, carries out the operation of equilibrium, descrambling and despreading, and these three kinds of operations can merge execution, to estimate to send data.

15,, it is characterized in that described equalization operation can adopt high specific to merge channel equalization algorithms such as MRC, Po zero balanced ZF and the balanced MMSE of least mean-square error according to the method for claim 13 or 14 described TD-SCDMA system compatible OFDM technology.

16, the method for TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: in receiving terminal Multiuser Detection scheme, can adopt methods such as continuous Interference Cancellation SIC, Parallel Interference Cancellation PIC and joint-detection JD, they were applied to can be applicable to after algorithm in the single-carrier system is revised in this TD-SCDMA and the system that OFDM combines originally, can suppress the influence that multiple access disturbs effectively, further improve the performance of system.

17, the method for TD-SCDMA system compatible OFDM technology according to claim 1; it is characterized in that: only need single FFT just can handle a plurality of users' signal at receiving terminal; TD-SCDMA is a synchro system; although can not guarantee synchronously accurate fully; yet in the OFDM modulation; the protection of inserting in order to resist intersymbol interference can allow that little time migration is arranged between the user at interval; can handle by symbol ground for signal in this case, and can not be subjected to the interference of adjacent-symbol.

18, the method of TD-SCDMA system compatible OFDM technology according to claim 1, it is characterized in that: in TD-SCDMA and system that OFDM combines, can realize technology for self-adaptively transmitting easily, in this system, can utilize the characteristics of multicarrier structure, use channel condition information CSI, according to the channel status different user at the different information bit number of each subcarrier allocation, transmitted power, code rate or their combination are to obtain self adaptation, because Adaptive Transmission need obtain the channel estimating information of each user in the sub-district, this prerequisite makes Adaptive Transmission be more suitable in carrying out in down link, in the TD-SCDMA system, owing to adopt tdd mode, but up link is used same frequency band different time slots with down link, the similar decline of uplink downlink channel experience like this, Adaptive Transmission can be easy to realize and only need seldom extra signaling consumption, and for fdd mode that other 3G standard adopted, because the uplink downlink channel uses different frequencies, then need the signaling consumption that adds exchanging current auto-adaptive parameter and channel status, thereby in TD-SCDMA and system that OFDM combines, be easier to adopt technology for self-adaptively transmitting.

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