CN101534279A - Direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing transmitting and receiving device, method and system - Google Patents

Abstract

The invention discloses a direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing transmitting and receiving device, a method and a system thereof, relating to the direct sequence spread spectrum technology and Multiple Carrier-Code Division Multiple Access technology in the field of wireless communication. The invention combines the time domain spread spectrum theory of Single Carrier-Code Division Multiple Access with the modulation manner of Multiple Carrier-Code Division Multiple Access to carry out spread spectrum treatment on the signals in the two dimensions of time and frequency, thus improving the disturbance resisting capacity of the signals in the transmission course, and to ensure that the data of each user full occupy the time and frequency resources, thus greatly improving the frequency spectrum utility ratio of the signal path.

Description

Direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing transmitting and receiving device, method and system

Technical field

The present invention relates to the direct sequence spread spectrum skill and CDMA multiple carrier (the Code Division Multiple Access of wireless communication field, code division multiple access) technology particularly relates to a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing transmitting and receiving device, method and system.

Background technology

The target of satellite of future generation and wireless communication system is that power system capacity also will be greatly improved for the user provides higher message transmission rate and better service quality.Therefore improve an important subject that becomes the next generation wireless communication technology of the availability of frequency spectrum of limited wireless frequency spectrum resource.

Traditional Single Carrier Frequency Division Multiple Access communication technology, the lower and antijamming capability of its availability of frequency spectrum a little less than, therefore substituted by the access scheme of multicarrier gradually.Typical multicarrier access scheme such as OFDMA (Orthogonal Frequency Division Multiplexing Access, OFDM inserts) technology, be based on a kind of multiple access access scheme of OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) technology.In the OFDM technology, one group of data is modulated onto on the subcarrier of one group of quadrature, does not have inter-carrier interference between each subcarrier, does not so just need the protection frequency band of broad, has improved the availability of frequency spectrum; And the modulation of multicarrier makes the speed of each mark signal of OFDM descend, and the shared time width of mark signal increases, and therefore can effectively resist the interference of multipath channel.And the OFDMA system has utilized the principle of OFDM, and it is divided into some groups with the subcarrier in the system, may comprise a more than subcarrier in each group, and one group of subcarrier of each CU inserts.Simultaneously, it can also select best channel by the mode of frequency hopping, can obtain higher received power, at WLAN (wireless local area network), WiMAX (Worldwide Interoperability forMicrowave Access, micro-wave access global inter communication) etc. in the field, the OFDMA technology is applied.In the OFDMA system, different user in the enterprising line data transmission of different subcarriers, therefore, for each user, can only utilize the band resource of part to carry out transfer of data at synchronization.

MC-CDMA (Multicarrier Code Division Multiplexing Access, MC-CDMA) technology is the problem that is widely studied in recent years, and it has proposed new thinking for user's access scheme of next generation wireless communication system.With the OFDMA system class seemingly, MC-CDMA also uses the modulation system of orthogonal sub-carriers.Different is, MC-CDMA carries out frequency domain spread spectrum to user data to be handled, and a data symbol is modulated on one group of subcarrier, like this by spreading code, the MC-CDMA system utilizes one group of subcarrier to transmit user's a mark signal, can resist the decline of frequency domain selectivity effectively.Aspect access, the signal after MC-CDMA system transmitting terminal will be modulated carries out spread processing according to its spreading code to data, supposes that spreading ratio is Nc, after string and conversion, data carrier behind the spread spectrum to Nc subcarrier, is carried out the OFDM modulation, enter channel through also going here and there to change again after the modulation.On Nc subcarrier,, can insert Nc user simultaneously at most according to the orthogonality of spreading code.

The MC-CDMA system receiving terminal carries out despreading to the signal on the respective sub and handles according to different users, can obtain each user's initial data.

This shows that in the utilization of subcarrier, the MC-CDMA system combines the advantage of cdma system and ofdm system, has obtained spreading gain on frequency.But on time domain, the MC-CDMA system does not obtain spreading gain, and the OFDM symbol has also kept the time span of data symbol.A little less than this makes antijamming capability that the MC-CDMA system disturbs for multipath.For each user, MC-CDMA system and OFDMA system class are seemingly, though in the transmission course of signal, all have certain opposing multipath interference capability, but transmission signals has all only used a part of subcarrier wherein, and do not use whole sub-carrier resources, so frequency spectrum resource is not utilized fully.

Summary of the invention

The purpose of this invention is to provide and a kind ofly can make full use of band resource, and have the uplink signal receiving/transmission method and a communication system of a kind of DS-FD-OCDM (Direct Sequence Spread Spectrum and Frequency Domain OrthogonalCode Division Multiplexing, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing) system of opposing multipath interference capability stronger with respect to prior art.

For achieving the above object, technical scheme of the present invention provides a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing transmitting and receiving device, method and system.

A kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing emitter comprises:

The time domain spread spectrum module is used to utilize l user's time domain spreading code w ^lWith this user's data x ^lCarry out the time domain spread processing, obtain time domain spread-spectrum code chip X ^l, described time domain spread-spectrum code chip X ^lLength be N; And

The frequency domain spread spectrum module is used for described time domain spread-spectrum code chip X ^lCarry out the time-domain and frequency-domain conversion, obtain signal X _p ^l, again with signal X _p ^lCarry out the frequency domain orthogonal spectrum expansion and handle, obtain signal S, signal S is carried out sending into channels transmit after the modulating in OFDM, wherein, p=0,1 ..., KN-1, K are positive integer.

Described time domain spread processing mode is that direct sequence spread spectrum is handled, and wherein the time domain spreading code of different user is mutually orthogonal.

Described frequency domain spread spectrum module comprises:

The time-domain and frequency-domain modular converter is used for the time domain spread-spectrum code chip is carried out serial to parallel conversion, obtains parallel symbol, and the single channel serial signal is transformed to KN road parallel signal ${X_p}^l=\{X_0^l,X_1^l\·\·\·X_{\mathrm{KN}-1}^l\};$

Frequency domain orthogonal spectrum expansion module is used for the parallel signal X with l user _p ^lFrequency domain orthogonal intersection with this user ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain the dateout that the KN group length is M, wherein M is the number of subcarrier, KN is organized dateout contraposition addition respectively again, obtains M road parallel signal $S=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{p=0}{\overset{\mathrm{KN}-1}{\mathrm{\Σ}}}{X}_p^l{C}_p^l,$ The frequency domain orthogonal intersection of different user is mutually orthogonal;

The OFDM modulation module is used for described signal S is carried out sending into channel after the OFDM modulation.

A kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing launching technique may further comprise the steps:

S1 utilizes the time domain spreading code w of time domain spread spectrum module according to l user ^lWith this user's data x ^lCarry out the time domain spread processing, obtain time domain spread-spectrum code chip X ^l, described time domain spread-spectrum code chip X ^lLength be N;

S2 utilizes the frequency domain spread spectrum module with described time domain spread-spectrum code chip X ^lCarry out the time-domain and frequency-domain conversion, obtain signal X _p ^l, again with signal X _p ^lCarry out the frequency domain orthogonal spectrum expansion and handle, obtain signal S, signal S is carried out sending into channels transmit after the modulating in OFDM, wherein, p=0,1 ..., KN-1, K are positive integer.

The time domain spread processing mode of described step S1 is that direct sequence spread spectrum is handled, and wherein the time domain spreading code of different user is mutually orthogonal.

Described step S2 comprises:

S21 utilizes the time-domain and frequency-domain modular converter of frequency domain spread spectrum module that the time domain spread-spectrum code chip is carried out serial to parallel conversion, obtains parallel symbol, and the single channel serial signal is transformed to KN road parallel signal ${X_p}^l=\{X_0^l,X_1^l\·\·\·X_{\mathrm{KN}-1}^l\};$

S21 utilizes the parallel signal X of the frequency domain orthogonal spectrum expansion module of frequency domain spread spectrum module with l user _p ^lFrequency domain orthogonal intersection with this user ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain the dateout that the KN group length is M, wherein M is the number of subcarrier, KN is organized dateout contraposition addition respectively again, obtains M road parallel signal $S=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{p=0}{\overset{\mathrm{KN}-1}{\mathrm{\Σ}}}{X}_p^l{C}_p^l,$ The frequency domain orthogonal intersection of different user is mutually orthogonal;

S23 utilizes the OFDM modulation module of frequency domain spread spectrum module that described signal S is carried out sending into channel after the OFDM modulation.

A kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving system comprises:

Frequency domain despreading module, the signal that is used for all users that will receive from channel carries out the orthogonal frequency division multiplex OFDM demodulation respectively, the signal after the OFDM demodulation is carried out specific signal handle, and obtains signal R ^l, with signal R ^lDuplicate L part, with L part signal R ^lCarry out the frequency domain despreading respectively and handle, obtain signal Y _p ^l, again with signal Y _p ^lCarry out the time domain frequency domain conversion, wherein L is user's a number, R ^lBe l user's the signal after the OFDM demodulation, Y _p ^lBe l user's the signal after frequency domain spread spectrum is handled, p=0,1 ..., KN-1, K are positive integer, N is the time domain spread-spectrum code chip X that the time domain spread spectrum module produces in the emitter of system ^lLength; And

Time domain despreading module is used for that the signal after all users' the time domain frequency domain conversion is carried out the time domain despreading and handles, and obtains each user's initial data x respectively ^l

Described time domain despreading processing mode is that the direct sequence despreading is handled.

Described frequency domain despreading module comprises:

The OFDM demodulation module, the signal that is used for all users that will receive from described channel carries out the orthogonal frequency division multiplex OFDM demodulation respectively;

Signal processing module is used for the signal of all users after the OFDM demodulation is carried out channel estimating and channel equalization;

Frequency domain orthogonal dispreading module is used for the signal R with each user after the described signal processing module processing ^lRespectively with this user's frequency domain orthogonal intersection ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain signal Y _p ^l

The time domain frequency domain modular converter is used for the signal after the frequency domain orthogonal dispreading resume module is rearranged, and the single channel serial signal is transformed to multi-path parallel signal.

A kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing method of reseptance may further comprise the steps:

Frequency domain despreading step utilizes all users' that frequency domain despreading module will receive from channel signal to carry out the orthogonal frequency division multiplex OFDM demodulation respectively, the signal after the OFDM demodulation is carried out specific signal handle, and obtains signal R ^l, with signal R ^lDuplicate L part, with L part signal R ^lCarry out the frequency domain despreading respectively and handle, obtain signal Y _p ^l, again with signal Y _p ^lCarry out the time domain frequency domain conversion, wherein L is user's a number, R ^lBe l user's the signal after the OFDM demodulation, Y _p ^lBe l user's the signal after frequency domain spread spectrum is handled, p=0,1 ..., KN-1, K are positive integer, N is the time domain spread-spectrum code chip X that the time domain spread spectrum module produces in the emitter of system ^lLength; And

Time domain despreading step utilizes the signal after time domain despreading module is changed all users' time domain frequency domain to carry out time domain despreading processing, obtains each user's initial data x respectively ^l

The time domain despreading processing mode of described time domain despreading step is that the direct sequence despreading is handled.

Described step frequency domain despreading step comprises:

The OFDM demodulation step, the OFDM demodulation module that utilizes frequency domain despreading module carries out the orthogonal frequency division multiplex OFDM demodulation respectively to all users' of receiving from described channel signal;

Signal processing step, the signal processing module that utilizes frequency domain despreading module all users' after to the OFDM demodulation signal carries out channel estimating and channel equalization;

The signal R of each user after frequency domain orthogonal dispreading step, the frequency domain orthogonal dispreading module of utilizing frequency domain despreading module are handled described signal processing module ^lRespectively with this user's frequency domain orthogonal intersection ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain signal Y _p ^l

Time domain frequency domain switch process, the time domain frequency domain modular converter that the utilizes frequency domain despreading module signal after to frequency domain orthogonal dispreading resume module rearranges, and the single channel serial signal is transformed to multi-path parallel signal.

A kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receive-transmit system, comprise L described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing emitter and described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving system, wherein L represents the number of user in the system, and described receiving system is from the signal of channel reception after described emitter is handled.

A kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving/transmission method may further comprise the steps:

The signal step of transmitting adopts described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing launching technique to transmit; And

The signal receiving step adopts described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing method of reseptance to receive above-mentioned signal.

Technique scheme has following advantage: by in time and two dimensions of frequency domain signal being carried out spread processing, improved the antijamming capability of signal in transmission course; Time that fully takies by the signal that makes each user and the resource on the frequency, thus the availability of frequency spectrum of channel improved greatly.

Description of drawings

Fig. 1 is the flow chart of DS-FD-OCDM receiving/transmission method of the present invention;

Fig. 2 is the structural representation of DS-FD-OCDM receive-transmit system of the present invention;

Fig. 3 is the receive-transmit system of DS-FD-OCDM under certain condition of the embodiment of the invention and the comparison schematic diagram of MC-CDMA error rate of system curve.

Wherein, BER is the error rate, and SNR is a signal to noise ratio.

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used to illustrate the present invention, but are not used for limiting the scope of the invention.

The flow chart of DS-FD-OCDM receiving/transmission method of the present invention, as shown in Figure 1:

Step 101 is utilized the time domain spreading code w of time domain spread spectrum module according to l user ^lInitial data x with this user ^lCarry out the time domain spread processing, obtain time domain spread-spectrum code chip X ^l, wherein the time domain spreading code of different user is mutually orthogonal.Described time domain spread processing mode is the time domain spectrum spreading method of traditional single carrier cdma system, specifically, is the direct sequence spread spectrum method in an embodiment of the present invention; For example, for user l, the time domain spreading code of hypothesis generation here is w ^l, its type can be orthogonal code or incomplete orthogonal code, as: Walsh sign indicating number, quadrature Golay sign indicating number, PN sequence, the selection to time domain spreading code type is not construed as limiting the invention.Here, each user's time domain spreading code is mutually orthogonal, is in order to distinguish different users by the time domain spreading code.The initial data x of user l ^lThrough time domain spreading code w ^lBehind the spread spectrum, output time domain spread-spectrum code chip X ^lIf time domain spreading code w ^lCode length be N, the time domain spread-spectrum code chip X that then obtains ^lLength is N.

Step 102 with the conversion of time domain spread-spectrum code chip time-domain and frequency-domain, is promptly carried out serial to parallel conversion, obtains signal ${X_p}^l=\{X_0^l,X_1^l\·\·\·X_{\mathrm{KN}-1}^l\},$ Wherein, p=0,1 ..., KN-1, K are positive integer.The supported number of users of supposing the system is L, and sub-carrier number is M, and M=K _MaxN, wherein K _Max=2,3 ...Be that sub-carrier number is time domain spreading code w ^lThe integral multiple of length, and greater than time domain spreading code w ^lLength.By M=K _MaxN as can be seen, K _MaxBe the ratio of system subcarrier number with time domain spread spectrum multiple.The method of above-mentioned string and conversion is for to be converted to KN road parallel signal with the single channel serial signal, wherein 1＜K≤K _Max, promptly require the time domain spread-spectrum code chip to carry out serial to parallel conversion after, the orthogonality the when quantity of the subcarrier of the no more than system of quantity of every group of chip, this point have guaranteed the frequency domain spread spectrum module operation.The information that comprises KN chip in the parallel signal that obtains after the conversion, the i.e. symbolic information of K initial data;

Step 103 will be carried out the frequency orthogonal spread processing through the KN road parallel signal behind the serial to parallel conversion.For example with l user's parallel signal X _p ^lFrequency domain orthogonal intersection with this user ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain the dateout that the KN group length is M, again KN is organized dateout contraposition addition respectively, obtain M road parallel signal $S=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{p=0}{\overset{\mathrm{KN}-1}{\mathrm{\Σ}}}{X}_p^l{C}_p^l,$ The frequency domain orthogonal intersection of different user is mutually orthogonal.Wherein, because therefore KN≤M can guarantee frequency domain orthogonal intersection C _p ^lIn KN the sign indicating number be quadrature.And because the data of different user are distinguished by the time domain spreading code, so the frequency domain orthogonal intersection of different user can be the same or different, the type of selected frequency domain orthogonal intersection can be identical with the type of above-mentioned time domain spreading code also can be different.Because each user's the mutually orthogonal property of frequency domain spread spectrum sign indicating number, a plurality of time domain spread-spectrum code chips of L user all pass through a sub-carrier transmission, and therefore, each user's data can take whole sub-carrier resources, has improved the availability of frequency spectrum.

Step 104 is carried out the OFDM modulation with described dateout, sends into channels transmit then.L user arranged in the system, therefore L emitter arranged, therefore, what transmit in channel is the stack of L user's total data.

Step 105 will be carried out the OFDM demodulation from the data that described channel receives.

Step 106 is carried out channel estimating and channel equalization with the data after the demodulation.So just provide channel parameter information for carrying out correct OFDM demodulation.

Step 107 is duplicated L part with the data after the signal processing module processing, to the despreading respectively of each user's data.For example, use the frequency domain orthogonal intersection when carrying out the frequency domain despreading to user l ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\},$ Signal R after handling with signal processing module respectively ^lMultiply each other and to obtain chip ${Y_p}^l=\{Y_0^l,Y_1^l\·\·\·Y_{\mathrm{KN}-1}^l\}.$ If channel is desirable, then the chip that obtains after the frequency domain despreading is the time domain spread-spectrum code chip that the initial data of user l obtains behind the time domain spread spectrum;

Step 108 rearranges the chip after the above-mentioned frequency domain despreading, KN road parallel signal is reconfigured be original N road time domain spread-spectrum code chip.

Step 109, above-mentioned N road time domain spread-spectrum code chip is carried out handling with the corresponding time domain despreading of above-mentioned time domain spread processing, be to handle in an embodiment of the present invention,, then obtain user's initial data if channel is desirable with the corresponding time domain despreading of direct sequence spread spectrum.

DS-FD-OCDM receive-transmit system of the present invention comprises emitter and receiving system.This system can comprise a plurality of emitters, the number of emitter depends on the number of user in the system, in an embodiment of the present invention, as shown in Figure 2, have three emitters, be respectively user 1 emitter 214, user 2 emitter 215 and user 3 emitter 201, the internal structure of each emitter is identical, is the example explanation at this emitter 214 with user 3.As shown in Figure 2, wherein, user 3 emitter 201 comprises time domain spread spectrum module 203 and frequency domain spread spectrum module 204, and frequency domain spread spectrum module 204 comprises time-domain and frequency-domain modular converter 207, frequency domain orthogonal spectrum expansion module 208 and OFDM modulation module 209 again; Receiving system 202 comprises frequency domain despreading module 205 and time domain despreading module 206.Wherein, frequency domain despreading module 205 comprises OFDM demodulation module 210, signal processing module 211, frequency domain orthogonal dispreading module 212 and time domain frequency domain modular converter 213.Solid arrow among Fig. 2 is represented the flow direction of the user data that transmitted, and these data are transferred to receiving system by wireless channel from emitter.In the emitter,

The time domain spread spectrum module is used for the time domain spreading code w according to l user ^lInitial data x with this user ^lCarry out the time domain spread processing, obtain time domain spread-spectrum code chip X ^l, wherein the time domain spreading code of different user is mutually orthogonal.Described time domain spread processing mode is the time domain spectrum spreading method of traditional single carrier cdma system, specifically, is the direct sequence spread spectrum method in an embodiment of the present invention; For example, for user l, the time domain spreading code of hypothesis generation here is w ^l, its type can be orthogonal code or incomplete orthogonal code, as: Walsh sign indicating number, quadrature Golay sign indicating number, PN sequence, the selection to time domain spreading code type is not construed as limiting the invention.Here, each user's time domain spreading code is mutually orthogonal, is in order to distinguish different users by the time domain spreading code.The initial data x of user l ^lThrough time domain spreading code w ^lBehind the spread spectrum, output time domain spread-spectrum code chip X ^lIf time domain spreading code w ^lCode length be N, the time domain spread-spectrum code chip X that then obtains ^lLength is N.

The frequency domain spread spectrum module is used for above-mentioned time domain spread-spectrum code chip is carried out the time-domain and frequency-domain conversion, carries out the frequency domain orthogonal spectrum expansion then and handles, and the data after the frequency domain orthogonal spectrum expansion is handled are carried out modulating in OFDM, send into channels transmit at last; Wherein,

The time-domain and frequency-domain modular converter is used for user's N road time domain spread-spectrum code chip is carried out serial to parallel conversion, obtains signal ${X_p}^l=\{X_0^l,X_1^l\·\·\·X_{\mathrm{KN}-1}^l\}$ Wherein, p=0,1 ..., KN-1, K are positive integer.The supported number of users of supposing the system is L, and sub-carrier number is M, and M=K _MaxN, wherein K _Max=2,3 ...Be that sub-carrier number is time domain spreading code w ^lThe integral multiple of length, and greater than time domain spreading code w ^lLength.By M=K _MaxN as can be seen, K _MaxBe the ratio of system subcarrier number with time domain spread spectrum multiple.The method of above-mentioned string and conversion is for to be converted to KN road parallel signal with the single channel serial signal, wherein 1＜K≤K _Max, promptly require the time domain spread-spectrum code chip to carry out serial to parallel conversion after, the orthogonality the when quantity of the subcarrier of the no more than system of quantity of every group of chip, this point have guaranteed the frequency domain spread spectrum module operation.The information that comprises KN chip in the parallel signal that obtains after the conversion, the i.e. symbolic information of K initial data;

The input signal of frequency domain orthogonal spectrum expansion module is the KN road parallel signal after changing through the time-domain and frequency-domain modular converter.For example with l user's parallel signal X _p ^lFrequency domain orthogonal intersection with this user ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain the dateout that the KN group length is M, again KN is organized dateout contraposition addition respectively, obtain M road parallel signal $S=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{p=0}{\overset{\mathrm{KN}-1}{\mathrm{\Σ}}}{X}_p^l{C}_p^l,$ The frequency domain orthogonal intersection of different user is mutually orthogonal.Wherein, because therefore KN≤M can guarantee frequency domain orthogonal intersection C _p ^lIn KN the sign indicating number be quadrature.And because the data of different user are distinguished by the time domain spreading code, so the frequency domain orthogonal intersection of different user can be the same or different, the type of selected frequency domain orthogonal intersection can be identical with the type of above-mentioned time domain spreading code also can be different.Because each user's the mutually orthogonal property of frequency domain spread spectrum sign indicating number, a plurality of time domain spread-spectrum code chips of L user all pass through a sub-carrier transmission, and therefore, each user's data can take whole sub-carrier resources, has improved the availability of frequency spectrum.

The OFDM modulation module is used for described dateout is carried out the OFDM modulation, sends into channels transmit then.L user arranged in the system, therefore L emitter arranged, therefore, what transmit in channel is the stack of L user's total data.In the receiving system,

Frequency domain despreading module will be carried out the OFDM demodulation from the data that channel receives, and carry out the frequency domain despreading then and handle, and the data after again the frequency domain despreading being handled are carried out the time domain frequency domain conversion.Wherein,

The OFDM demodulation module is used for the data that receive from described channel are carried out the OFDM demodulation; Signal processing module is used for the data after the demodulation are carried out channel estimating and channel equalization, and this module provides channel parameter information for carrying out correct OFDM demodulation; Frequency domain orthogonal dispreading module is with the signal replication L part after the signal processing module processing, to the despreading respectively of each user's data.For example, use the frequency domain orthogonal intersection when carrying out the frequency domain despreading to user l ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\},$ The signal R of the data after handling with signal processing module respectively ^lMultiply each other and to obtain chip ${Y_p}^l=\{Y_0^l,Y_1^l\·\·\·Y_{\mathrm{KN}-1}^l\}.$ If channel is desirable, then the chip that obtains after the frequency domain despreading is the time domain spread-spectrum code chip that the initial data of user l obtains behind the time domain spread spectrum; The time domain frequency domain modular converter is used for the chip after the above-mentioned frequency domain despreading is rearranged, and KN road parallel signal is reconfigured be N road time domain spread-spectrum code chip.

Time domain despreading module, be used for the N road time domain spread-spectrum code chip after the described time domain frequency domain modular converter conversion is carried out handling with the corresponding time domain despreading of the time domain spread processing of emitter, be to handle in an embodiment of the present invention with the corresponding time domain despreading of direct sequence spread spectrum, if channel is desirable, then obtain user's initial data.

Use the signal transmitting method of native system, the symbol holding time of the transmission data that obtain and the resource situation of frequency are as follows: the character rate of supposing l user's initial data is R, and symbol period is T _s, T wherein _s=1/R.After the time domain spread processing, by above as can be known, spreading rate is RN, and the chip time cycle is T _s/ N.The character rate that carries out each road after time-domain and frequency-domain is changed is RN/KN=R/K, and the chip time cycle is T _s/ N * KN=KT _sOwing to used the OFDM modulation technique, then total frequency bandwidth of taking of each subcarrier is about R/K * M/2=RM/2K.Because K≤M/N, therefore, total frequency bandwidth is at least RN/2.Than the symbol of original data, the frequency bandwidth that the symbol of the data of transmitting in the native system takies is at least original N/2 doubly, and the time resource that takies is original K times, therefore, has improved the availability of frequency spectrum greatly.

As shown in Figure 3, under the following implementation condition of choosing arbitrarily, respectively at AWGN (Additive White Gaussion Noise, additive white Gaussian noise) channel and frequency deviation value are in 0.1 the frequency deviation channel, the comparison schematic diagram of the ber curve of DS-FD-OCDM receive-transmit system of the present invention and MC-CDMA system: there are 4 users in the up link of native system, the highest number of users of system's support is 16, the N=16 in promptly above describing.The selection Walsh sign indicating number of time domain spreading code type, code length is 16.The sub-carrier number of selecting system is 1024, i.e. M=1024 in the foregoing description.The number of chips that the frequency domain orthogonal spectrum expansion module that dispensing device uses is carried out frequency domain spread spectrum is 64, and promptly K=4 in the foregoing description selects above-mentioned parameter to satisfy the orthogonality requirement of frequency domain spread spectrum.Select the frequency domain spread spectrum sign indicating number of one group of quadrature

And the time domain spreading code between each user is also mutually orthogonal.The type of frequency domain spread spectrum sign indicating number also may be selected to be the Walsh sign indicating number, and it is identical with the sub-carrier number of said system to choose its code length, is 1024.As can be seen from the figure, no matter in awgn channel or frequency deviation channel, the error rate of DS-FD-OCDM receive-transmit system of the present invention all is lower than the error rate of MC-CDMA system.

As can be seen from the above embodiments, the embodiment of the invention is utilized the spread processing on time domain and two dimensions of frequency domain, adopt the time domain spreading code to distinguish the user, the method for frequency domain spread spectrum sign indicating number superposition of data symbol makes the data symbol of transmission take whole sub-carrier resources and a plurality of time interval resource simultaneously.And because time domain spreading code and frequency domain spread spectrum sign indicating number all have orthogonality, therefore can the phase mutual interference when a plurality of initial data of a plurality of users are transmitted in same multicarrier data symbol, can distinguish each user's initial data in the sign indicating number branch mode of receiving terminal utilization two dimension.The availability of frequency spectrum and the antijamming capability of data in transmission course of channel have been improved.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the technology of the present invention principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (14)

1, a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing emitter is characterized in that, comprising:

The time domain spread spectrum module is used to utilize l user's time domain spreading code w ^lWith this user's data x ^lCarry out the time domain spread processing, obtain time domain spread-spectrum code chip X ^l, described time domain spread-spectrum code chip X ^lLength be N; And

The frequency domain spread spectrum module is used for described time domain spread-spectrum code chip X ^lCarry out the time-domain and frequency-domain conversion, obtain signal X _p ^l, again with signal X _p ^lCarry out the frequency domain orthogonal spectrum expansion and handle, obtain signal S, signal S is carried out sending into channels transmit after the modulating in OFDM, wherein, p=0,1 ..., KN-1, K are positive integer.

2, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing emitter as claimed in claim 1 is characterized in that, described time domain spread processing mode is that direct sequence spread spectrum is handled, and wherein the time domain spreading code of different user is mutually orthogonal.

3, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing emitter as claimed in claim 2 is characterized in that, described frequency domain spread spectrum module comprises:

The time-domain and frequency-domain modular converter is used for the time domain spread-spectrum code chip is carried out serial to parallel conversion, obtains parallel symbol, and the single channel serial signal is transformed to KN road parallel signal ${X_p}^l=\{X_0^l,X_1^l\·\·\·X_{\mathrm{KN}-1}^l\};$

Frequency domain orthogonal spectrum expansion module is used for the parallel signal X with l user _p ^lFrequency domain orthogonal intersection with this user ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain the dateout that the KN group length is M, wherein M is the number of subcarrier, KN is organized dateout contraposition addition respectively again, obtains M road parallel signal $S=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{p=0}{\overset{\mathrm{KN}-1}{\mathrm{\Σ}}}{X}_p^l{C}_p^l,$ The frequency domain orthogonal intersection of different user is mutually orthogonal;

The OFDM modulation module is used for described signal S is carried out sending into channel after the OFDM modulation.

4, a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing launching technique is characterized in that, may further comprise the steps:

S1 utilizes the time domain spreading code w of time domain spread spectrum module according to l user ^lWith this user's data x ^lCarry out the time domain spread processing, obtain time domain spread-spectrum code chip X ^l, described time domain spread-spectrum code chip X ^lLength be N;

S2 utilizes the frequency domain spread spectrum module with described time domain spread-spectrum code chip X ^lCarry out the time-domain and frequency-domain conversion, obtain signal X _p ^l, again with signal X _p ^lCarry out the frequency domain orthogonal spectrum expansion and handle, obtain signal S, signal S is carried out sending into channels transmit after the modulating in OFDM, wherein, p=0,1 ..., KN-1, K are positive integer.

5, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing launching technique as claimed in claim 4 is characterized in that, the time domain spread processing mode of described step S1 is that direct sequence spread spectrum is handled, and wherein the time domain spreading code of different user is mutually orthogonal.

6, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing launching technique as claimed in claim 5 is characterized in that described step S2 comprises:

S21 utilizes the time-domain and frequency-domain modular converter of frequency domain spread spectrum module that the time domain spread-spectrum code chip is carried out serial to parallel conversion, obtains parallel symbol, and the single channel serial signal is transformed to KN road parallel signal ${X_p}^l=\{X_0^l,X_1^l\·\·\·X_{\mathrm{KN}-1}^l\};$

S21 utilizes the parallel signal X of the frequency domain orthogonal spectrum expansion module of frequency domain spread spectrum module with l user _p ^lFrequency domain orthogonal intersection with this user ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain the dateout that the KN group length is M, wherein M is the number of subcarrier, KN is organized dateout contraposition addition respectively again, obtains M road parallel signal $S=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{p=0}{\overset{\mathrm{KN}-1}{\mathrm{\Σ}}}{X}_p^l{C}_p^l,$ The frequency domain orthogonal intersection of different user is mutually orthogonal;

S23 utilizes the OFDM modulation module of frequency domain spread spectrum module that described signal S is carried out sending into channel after the OFDM modulation.

7, a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving system is characterized in that, comprising:

Frequency domain despreading module, the signal that is used for all users that will receive from channel carries out the orthogonal frequency division multiplex OFDM demodulation respectively, the signal after the OFDM demodulation is carried out specific signal handle, and obtains signal R ^l, with signal R ^lDuplicate L part, with L part signal R ^lCarry out the frequency domain despreading respectively and handle, obtain signal Y _p ^l, again with signal Y _p ^lCarry out the time domain frequency domain conversion, wherein L is user's a number, R ^lBe l user's the signal after the OFDM demodulation, Y _p ^lBe l user's the signal after frequency domain spread spectrum is handled, p=0,1 ..., KN-1, K are positive integer, N is the time domain spread-spectrum code chip X that the time domain spread spectrum module produces in the emitter of system ^lLength; And

Time domain despreading module is used for that the signal after all users' the time domain frequency domain conversion is carried out the time domain despreading and handles, and obtains each user's initial data x respectively ^l

8, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving system as claimed in claim 7 is characterized in that, described time domain despreading processing mode is that the direct sequence despreading is handled.

9, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving system as claimed in claim 8 is characterized in that, described frequency domain despreading module comprises:

The OFDM demodulation module, the signal that is used for all users that will receive from described channel carries out the orthogonal frequency division multiplex OFDM demodulation respectively;

Signal processing module is used for the signal of all users after the OFDM demodulation is carried out channel estimating and channel equalization;

Frequency domain orthogonal dispreading module is used for the signal R with each user after the described signal processing module processing ^lRespectively with this user's frequency domain orthogonal intersection ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain signal Y _p ^l

The time domain frequency domain modular converter is used for the signal after the frequency domain orthogonal dispreading resume module is rearranged, and the single channel serial signal is transformed to multi-path parallel signal.

10, a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing method of reseptance is characterized in that, may further comprise the steps:

Frequency domain despreading step utilizes all users' that frequency domain despreading module will receive from channel signal to carry out the orthogonal frequency division multiplex OFDM demodulation respectively, the signal after the OFDM demodulation is carried out specific signal handle, and obtains signal R ^l, with signal R ^lDuplicate L part, with L part signal R ^lCarry out the frequency domain despreading respectively and handle, obtain signal Y _p ^l, again with signal Y _p ^lCarry out the time domain frequency domain conversion, wherein L is user's a number, R ^lBe l user's the signal after the OFDM demodulation, Y _p ^lBe l user's the signal after frequency domain spread spectrum is handled, p=0,1 ..., KN-1, K are positive integer, N is the length of the time domain spread-spectrum code chip Xl that the time domain spread spectrum module produces in the emitter of system; And

Time domain despreading step utilizes the signal after time domain despreading module is changed all users' time domain frequency domain to carry out time domain despreading processing, obtains each user's initial data x respectively ^l

11, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing method of reseptance as claimed in claim 10 is characterized in that, the time domain despreading processing mode of described time domain despreading step is that the direct sequence despreading is handled.

12, direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing method of reseptance as claimed in claim 11 is characterized in that, described step frequency domain despreading step comprises:

The OFDM demodulation step, the OFDM demodulation module that utilizes frequency domain despreading module carries out the orthogonal frequency division multiplex OFDM demodulation respectively to all users' of receiving from described channel signal;

Signal processing step, the signal processing module that utilizes frequency domain despreading module all users' after to the OFDM demodulation signal carries out channel estimating and channel equalization;

The signal R of each user after frequency domain orthogonal dispreading step, the frequency domain orthogonal dispreading module of utilizing frequency domain despreading module are handled described signal processing module ^lRespectively with this user's frequency domain orthogonal intersection ${C_p}^l=\{c_0^l,c_1^l\·\·\·c_{\mathrm{KN}-1}^l\}$ Multiply each other, obtain signal Y _p ^l

Time domain frequency domain switch process, the time domain frequency domain modular converter that the utilizes frequency domain despreading module signal after to frequency domain orthogonal dispreading resume module rearranges, and the single channel serial signal is transformed to multi-path parallel signal.

13, a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receive-transmit system, it is characterized in that, comprise L as the arbitrary described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing emitter of claim 1 to 3 with as the arbitrary described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving system of claim 7 to 9, wherein L represents the number of user in the system, and described receiving system is from the signal of channel reception after described emitter is handled.

14, a kind of direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing receiving/transmission method is characterized in that, may further comprise the steps:

The signal step of transmitting adopts the arbitrary described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing launching technique as claim 4 to 6 to transmit; And

The signal receiving step adopts the arbitrary described direct sequence spread spectrum cascade connection frequency domain Orthogonal Frequency Division Multiplexing method of reseptance as claim 10 to 12 to receive above-mentioned signal.

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