CN1695333A - A system of QS-CDMA with two-level spreading scheme and LS sequences - Google Patents

Abstract

The presented invention is to provide a system of QS-CDMA with two-level spreading scheme and LS sequences, the said system comprising: means for designating a user in the system to a user group according to the cell or the sector it belongs to; means for spreading the information signals both by the FL and SL spreaders; one-level despreading means coupled to the said means to simplify the receiver structure of the two-level spreading system; means for communicating information signals between users in the same user-group without MAI; means for communicating information signals between users in different user-group with suppressed MAI; means for employing the LS sequences as the spreading sequences so as to suppress the MAI. The presented invention can obtain satisfactory system error performance and system capacity.

Description

A kind of QS-CDMA system with secondary spread spectrum scheme and LS sequence

Technical field

The present invention relates to cdma system, particularly, the present invention relates to a kind of QS-CDMA system with secondary spread spectrum scheme and LS sequence.

Background technology

In the cdma system, many users share identical frequency band and time slot.By the frequency expansion sequence that distributes, promptly address sequence can be realized the multiple access transmission.According to used frequency expansion sequence, present cdma system can be divided into class: orthogonal CDMA (O-CDMA) system and pseudo noise CDMA (PN-CDMA) system.

Orthogonal sequence is generally used for the first kind with the sequence with zero correlation zone (ZCZ) characteristic, and supposition system synchronization or accurate (QS) synchronously.Traditional orthogonal spreading sequence can be used in the synchronous CDMA system to keep the orthogonality between the user as Walsh (Walsh) sequence and Orthogonal Variable Spreading Factor OVSF (OVSF) sequence.For the forward link in the mobile radio telecommunications, all users in same cells are synchronous naturally, can distribute orthogonal spreading sequence to it.In this case, if there is not the multipath transmisstion problem, just the multi-user that can not produce in the sub-district inserts interference (MAI).Yet, for reverse link, keep between the different user synchronously can be more difficulty.But in microcellulor and indoor environment, transmission delay is less relatively, therefore reverse link is modeled as a synchro system with the synchronous sequence error that is limited in the thresholding, and promptly so-called quasi-synchronous CDMA system (QS-CDMA) is feasible.In the QS-CDMA system, the orthogonality between the orthogonal sequence is destroyed by synchronous error.

For solving the problem that described QS-CDMA system exists, the PCT application number is PCT/CN00/00028, the patent about the LS sign indicating number of inventing artificial Li Daoben proposes a kind of arrangement set with noiseless window (IFW) characteristic, it is called as loose synchronizing sequence (LS sequence) set, is expressed as S (L hereinafter _s, M _s, IFW, L _Gap), L wherein _s, M _s, IFW and L _GapBe respectively length, the size of family, IFW width and one-sided gap length.In the QS-CDMA system,,, disturb and just can eliminate if the time delay between subscriber signal falls into the noiseless window (IFW) of LS arrangement set by utilizing the LS sequence as frequency expansion sequence.

Based on above-mentioned analysis, can see that for the cdma system of the first kind, because the multiple access transmission disturbs the excellent correlation properties by frequency expansion sequence effectively to be suppressed, the capacity of system mainly is subjected to the restriction of limited arrangement set size.In fact, in order to obtain excellent correlation properties, between the size of family and zero correlation block, a balance is arranged.For example, suppose spreading factor L=128, the time delay τ of the maximum between the user _m=3 chips, the interference that just can utilize LS S set (128,32,7,3) to suppress to exist.So the capacity of system is 32/134=0.239/T _c(bps), wherein the capacity of system is to obtain according to the gross bit rate of the maximum of all users in the system.

In second class of cdma system, the PN sequence is as frequency expansion sequence, and system is generally asynchronous mode.In such system, though can obtain a large amount of frequency expansion sequences, the nonopiate interference-limited that causes of PN sequence the capacity of system.Particularly in the QS-CDMA system, because time delay only is evenly distributed in one section limited interval, the enforcement of this class cdma system is also unsatisfactory usually.

From what has been discussed above as can be seen, how to obtain more available sequence and how to suppress multiple access in the cdma system simultaneously to disturb (MAI) be the key that improves power system capacity.

In synchronous CDMA system, different approach has been proposed, such as secondary spread spectrum-despreading scheme, improve the capacity of system.Application number is that 001109301.3 Chinese patent has proposed an invention that is used for the cdma system downlink transmission that comprises variable spreading rate spread spectrum of secondary and despreading method.Total spreading gain is the product of secondary spreading factor.Orthogonal sequence, ZCZ sequence and pseudo noise sequence can be used for as the first order (FL) and the second level (SL) sequence.The present invention is directed to and the error performance that improves in the cdma system down channel.

Summary of the invention

The purpose of this invention is to provide a kind of quasi-synchronous CDMA (QS-CDMA) system, to obtain satisfied system's error performance and power system capacity with secondary spread spectrum scheme and LS sequence.

QS-CDMA system with secondary spread spectrum scheme and LS sequence comprises:

Organize specified device according to a user in sub-district under the user or the sector appointing system to the user that the user organizes;

Information signal is carried out the device of spread spectrum by FL frequency multiplier and SL frequency multiplier;

Be coupled in order to the one-level spread spectrum device of the receiver architecture of simplifying the secondary spread spectrum system with said apparatus;

Between the user of same subscriber group, transmit the device of information signal when not having MAI;

Between the user of different user groups, transmit the device of information signal when having the MAI of inhibition;

Utilize the LS sequence to suppress the device that multiple access disturbs as frequency expansion sequence.

When having only user group to exist, described QS-CDMA system utilizes LS arrangement set S1 (L _s, L _s/ 2, IFW=3, L _Gap=1) as the FL frequency expansion sequence with a plurality of users in the containment.FL spreading factor L ₁=L _s+ 2L _GapCan hold L at most in the system _s/ 2 active users.

When having only user group to exist, described QS-CDMA system utilizes LS arrangement set S2 (L ₂, L ₂/ 2, IFW=1, L _Gap=0) think that as the SL frequency expansion sequence each user provides the multichannel transmission, each user's maximum can have L ₂Individual parallel channel; The SL spreading factor is L ₂

When having only user group to exist, the SL spreading factor of described secondary QS-CDMA system approaches in the middle of the user maximal phase to the number of chips of time delay.

When a plurality of user's groups existed, described user organized specified device and comprises a device, and it makes receiver adopt directional antenna, and made the user in the same sector belong to identical user's group; Make the user of different sectors belong to different groups.

When a plurality of user's groups existed, described user organized specified device and comprises a device, and it makes receiver utilize omnidirectional antenna, and made the user in same cells belong to identical user's group; The user who makes at different districts belongs to different groups.

Wherein, described user organizes specified device and comprises a device, and it makes the user in the common sector belong to identical user's group; Further comprise another device, make postpone to be limited in the threshold range correlation time between all users; SL spreading factor L ₂Select with all users between the number of chips of maximum time delay equate.

Wherein said user organizes specified device and comprises that user's component cuts device, and it makes the user in same cells or the sector belong to identical user's group, and described QS-CDMA system utilizes the m sequence to cut so that multicomponent to be provided as the SL frequency expansion sequence.

Wherein said user's component is cut device and further comprised: it is L that long m sequence is cut into length ₂Segment, each fragment all is used as the SL sequence in each bit duration, different fragments can be used for different bit durations.

Wherein said user's component is cut device and further comprised: in different user's groups, the long m sequence of out of phase is cut and is used as the device of SL sequence.

Wherein said user organizes specified device and comprises a device, and its user who makes in common sector belongs to the same subscriber group, and makes maximum time delay be limited in being not more than L ₂T _c, the segment of the m sequence that phase shift is long is used as the SL frequency expansion sequence, and described QS-CDMA system utilizes LS arrangement set S1 (L _s, L _s/ 2, IFW=3, L _Gap=1) cuts apart so that the user in the group to be provided as the FL frequency expansion sequence; FL spreading factor L ₁=L _s+ 2; Each group can be held L at most _s/ 2 active user; MAI in the group is eliminated by the IFW characteristic of FL sequence; Disturb between group and further suppressed by the IFW their cross correlation of FL sequence and the antenna of subregion.

Wherein said user organizes specified device and comprises a device, and it makes the user of same cells belong to identical user's group, and makes the maximum time between the phase user on the same group postpone to be limited in being not more than L ₂T _c, the long m sequence of phase shift segment as the SL frequency expansion sequence.Described QS-CDMA system utilizes LS arrangement set S1 (L _s, L _s/ 2, IFW=3, L _Gap) cut so that multicomponent to be provided as the FL frequency expansion sequence; FL spreading factor L ₁=L _s+ 2L _Gap, L _Gap〉=1; Each group can be held L at most _s/ 2 active users; MAI in the group is eliminated by the IFW characteristic of FL sequence.

LS S set 1 (L wherein _s, L _s/ 2, IFW=3, L _Gap) be used to FL frequency expansion sequence, L _GapSelection depend on the number of chips that relative time maximum among the user between the group postpones; Consider 2 or 3 layers sub-district on every side, desirable sub-district, L _GapCan equal 3 or 4; MAI between the group promptly adjoins area interference (ACI) and is suppressed by the IFW characteristic and the path loss of FL sequence.

Wherein, data message is by FL and two kinds of frequency multiplier spread spectrums of SL.Only by a despreader that utilizes local despreading sequence with the spread-spectrum signal despreading; Local despreading sequence forms by FL and the SL sequence structure that links FL and SL spreading rate respectively.

The invention provides a kind of standard (QS) code division multiple access (CDMA) system synchronously, performance and capacity that it utilizes secondary spread spectrum scheme and loose synchronous (LS) sequence to come the multiple access in the inhibition system to disturb (MAI) and increase system.

Figure of description

Fig. 1 is channel (r, the schematic diagram of spread-spectrum signal k) after the secondary spread spectrum under single user's group situation;

Fig. 2 is user (k, the schematic diagram of spread-spectrum signal c) after the secondary spread spectrum under multi-user's group situation;

Fig. 3 is the schematic diagram of transmitter and channel model under single user's group situation;

Fig. 4 is the schematic diagram of transmitter and channel model under multi-user's group situation;

Fig. 5 is the local despreading sequence of the used structure of despreader in j bit duration.

Embodiment

Reverse link is modeled as the QS-CDMA system and takes in, suppose to send through different paths, and be restricted through the signal of the access time between ideal signal and the interference signal from different users.Utilize the secondary spread spectrum scheme this moment, and FL and SL spreading factor are respectively L ₁And L ₂

The IFW width is cut apart so that the user to be provided as the FL frequency expansion sequence for 3 LS sequence.In addition, the IFW width for the long m sequence of 1 LS sequence and phase shift respectively under single group and many groups situation as the SL frequency expansion sequence so that to be provided cutting apart that channel or user organize.

The situation of single user's group:

At first consider LS S set 1 (L _S1, L _S1/ 2,3,1) and S2 (L _S2, L _S2, 1,0) and be used separately as the situation of FL and SL frequency expansion sequence.In such cases, only can hold one in the system and have L _S1User's group of/2 users, each user can have L at most _S2Individual parallel channel.And the spreading factor of FL and SL is respectively L ₁=L _S1+ 2 and L ₂=L _S2This part, k section FL and s section SL frequency expansion sequence are expressed as G respectively ^kAnd W ^k, k=0 wherein, 1 ..., L _S1/ 2, s=0,1 ..., L _S2

Based on being the method that proposes in 001109301.3 the Chinese patent at application number, each data bit is spread to L=L behind the secondary spread spectrum scheme ₁L ₂Individual chip, wherein L is the system spread-spectrum factor.Suppose (r, k) k user's of expression r channel, T _cThe expression chip duration.Usually, suppose that (q i) is ideal communication channel to channel, and we consider the 0th data bit at this.Based on the result who obtained in the past, if the time delay τ that can draw between ideal signal and the interference signal is not more than L ₂T _c, (r, the interference that k) causes is channel

$I_{r,k}\≈T_c{b}^{r,k}\left(0\right)[{\mathrm{\ρ}}_{r,q}^w\left(\mathrm{\τ}\right){\mathrm{\θ}}_{k,i}^g\left(1\right)+{\widehat{\mathrm{\ρ}}}_{r,q}^w\left(\mathrm{\τ}\right){\mathrm{\θ}}_{k,i}^g\left(0\right)]---\left(1\right)$

Wherein ${\mathrm{\&theta;}}_{k,i}^g\left(j\right)=\underset{n=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{g}_n^{\left(k\right)}{g}_{n+j}^{\left(i\right)}=\left\{\begin{array}{c}L,\mathrm{forj}=0,k=i\\ 0,\mathrm{forj}=0,,k\&NotEqual;i\\ 0,\mathrm{for}0<\left|j\right|\&le;Z\end{array}\right.$ Periodic correlation function for the FL sign indicating number; ρ _{R, q} ^w(τ) and For the continuous part correlation function of SL sequence, can be expressed as

${\mathrm{\&rho;}}_{r,q}^w\left(\mathrm{\&tau;}\right)=C_{r,q}^w(l+1-L_2)\mathrm{\&delta;}+C_{r,q}^w(1-L_2)(1-\mathrm{\&delta;})----\left(2\right)$

${\widehat{\mathrm{\&rho;}}}_{r,q}^w\left(\mathrm{\&tau;}\right)=C_{r,q}^w(l+1)\mathrm{\&delta;}+C_{r,q}^w\left(l\right)(1-\mathrm{\&delta;})$

L is for being equal to or less than τ/T _cMaximum integer, δ=(τ-lT _c)/T _cWith

$C_{r,q}^w\left(l\right)=\left\{\begin{array}{c}\underset{n=0}{\overset{L-m-1}{\mathrm{\&Sigma;}}}{w}_n^{\left(r\right)}{w}_{n+l}^{\left(q\right)},0\&le;l\&le;L\\ \underset{n=0}{\overset{L+m-1}{\mathrm{\&Sigma;}}}{w}_{n-l}^{\left(r\right)}{w}_n^{\left(q\right)},1-L\&le;l\&le;0\end{array}\right.---------\left(3\right)$

Part correlation function for the SL series of discrete.

Because the channel of same subscriber is synchronous, the interference that can obtain user inside is

$I_0=\underset{r=0,r\&NotEqual;q}{\overset{R-1}{\mathrm{\&Sigma;}}}{I}_{r,j}=T_c\underset{r=0,r\&NotEqual;q}{\overset{R-1}{\mathrm{\&Sigma;}}}{b}^{r,i}\left(0\right)\&CenterDot;{\mathrm{\&theta;}}_{r,q}^w\left(0\right){\&CenterDot;\mathrm{\&theta;}}_{i,i}^g\left(0\right)-----\left(4\right)$

Wherein R is each user's the number of channel.Because the orthogonality of SL frequency expansion sequence, the value of formula (4) is 0.

The interference that can obtain between the user is

${\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="A0282981500181.png,A0282981500182.png"\; state="\{\{state\}\}">I</figure-callout>}}_1=\underset{k=0,k\&NotEqual;i}{\overset{K-1}{\mathrm{\&Sigma;}}}\underset{r=0}{\overset{R-1}{\mathrm{\&Sigma;}}}{I}_{r,k}=T_c\underset{k=0,k\&NotEqual;i}{\overset{K-1}{\mathrm{\&Sigma;}}}\underset{r=0}{\overset{R-1}{\mathrm{\&Sigma;}}}{b}^{r,k}\left(0\right)[{\mathrm{\&rho;}}_{r,q}^w\left(\mathrm{\&tau;}\right){\mathrm{\&theta;}}_{k,i}^g\left(1\right)+{\widehat{\mathrm{\&rho;}}}_{r,q}^w\left(\mathrm{\&tau;}\right){\mathrm{\&theta;}}_{k,i}^g\left(0\right)]------\left(5\right)$

Wherein K is the number of user in the system.Because k ≠ during i for the S set 1 (L of LS sign indicating number _S1, L _S1/ 2,3,1), ${\mathrm{\&theta;}}_{k,i}^g\left(1\right)=0$ With ${\mathrm{\&theta;}}_{k,i}^g\left(0\right)=0,$ Therefore the value of equation (5) is 0.

Based on top discussion, illustrate if the time delay between interference signal and the ideal signal is not more than L ₂T _c, just do not have interference in the system.So each user can be up to L ₂Individual channel, and can hold L at most in the system ₁/ 2 users.

Table 1 has provided the example of current single user's secondary spread spectrum system, wherein τ _mThe maximum time that expression allows postpones, if the relative time between the user postpones to be not more than τ _m, then do not have interference.As can be seen, increase τ _m, then need bigger SL spreading factor L ₂, and system can hold user still less.But simultaneously, each user's the number of channel increases, and, from the capacity of system, the total bit rate that promptly provides, three instance systems all have identical capacity.Can reach a conclusion: for identical L ₁* L ₂Value, L ₂Value more little, the user who holds is many more, but the time delay that can bear is more little.When the sequential error big more, L ₂Can increase to guarantee not disturb generation, it should be noted that all parallel channels that have only as each user are utilized, just can obtain total bit rate, this means that in this case the user priority of high data rate is selected for use.

Table 2 is depicted as the example of the 1 grade of spread spectrum system that utilizes the LS sequence.Comparison by these two tables can clearly be seen that, the τ when two systems _mIn the time of much at one, the QS-CDMA system of Ti Chuing compares with 1 grade of orthogonal spectrum expansion system herein, has higher power system capacity.

That table 3 is represented is the spreading rate 1/T that works as current system and O-CDMA system _cEach user's bit rate r in (bandwidth) identical and two systems _bWhen being close, two systems comparison.Can reach a conclusion: when two systems provide much at one τ _m, when each user's bit rate and system bandwidth, current system can hold more user.

Utilize the secondary spread spectrum instance system of LS sign indicating number under the single user's situation of table 1. as the FL frequency expansion sequence

Parameter	System-I	System-II	System-III
				Spreading code	??FLS1(32，16，3，1)	??FL：S1(16，8，3，1)	??FL：S1(8，4，3，1)
??SL：S2(4，4，1，0)	??SL：S2(8，8，1，0)	??SL：S2(16，16，1，0)
			??FLSFL 1		??34	??18	??10
??SLSFL 2	??4	??8		??16
			System SFL		??136	??144	??160
Each user's the number of channel	??4	??8		??16
			Number of users		??16	??8	??4
Bit rate (the 1/T of each channel c)	??1/136	??1/144		??1/160
			Each user's bit rate (1/T c)		??1/34	??1/18	??1/10
Gross bit rate (1/T c)	??0.471	??0.444		??0.4
			The maximum time that allows postpones τ m		??4T c	??8T c	??16T c

Table 2. utilizes 1 grade of orthogonal spectrum expansion instance system of LS sign indicating number

Parameter	System-I	System-II	System-III
				Spreading code	??S(128，32，7，3)	??S(128，16，15，7)	??S(128，8，31，15)
System SFL	??128+3×2＝134	??128+7×2＝142	??128+15×2＝158
				Each user's the number of channel	??1	??1	??1
Number of users	??32	??16	??8
				Bit rate (the 1/T of each channel c)	??1/134	??1/142	??1/158
Gross bit rate (1/T c)	??32/134＝0.238	??16/142＝0.113	??8/158＝0.051
				The maximum time that allows postpones τ m	??3T c	??7T c	??15T c

The comparison of current system of table 3. and O-CDMA system

Current system	??τ m	??4T c	??8T c	??16T c
					The spreading code set	??S1(64，32，3，1)	??S1(64，32，3，1)	??S1(64，32，3，1)
	??S2(4，4，1，0)	??S2(8，8，1，0)	??S2(16，16，1，0)
				??L 1		??64	??64	??64
	??L 2	??4	??8		??16
				??S		??4	??8	??16
	??K	??32	??32		??32
				??r bT c		??1/66	??1/66	??1/66
	??RT c	??0.485	??0.485		??0.485
				The O-CDMA system		??τ m	??3T c	??7T c	??9T c
The spreading code set	??LS(64，16，7，3)	??LS(64，16，15， ??7)	??LS(64，16，31，1 ??5)
					??K	??16	??8	??4
??r bT c	??1/70	??1/77	??1/94
					??RT c	??0.229	??0.103	??0.043

The situation of multi-user's group:

In this case, system can hold a plurality of groups of user, and each user has only a channel.

According to sub-district under the user or sector the user in the system is assigned to different user's groups.When using directional antenna, the user in different sectors belongs to different user's groups, and when using omnidirectional antenna, the user in different districts belongs to identical user's group.

Under the component situation based on the sector, be identical because the relative time of all user's groups postpones restriction, then the same with single group situation, LS S set 1 (L _S1, L _S1/ 2,3,1) be used as the FL frequency expansion sequence.Yet, under component situation based on the sub-district, LS S set 1 (L _S1, L _S1/ 2,3, L _Gap〉=1) be used as the FL sequence, and L _GapSelection depend between the group maximal phase among the user to time delay.If consider ground floor, L is supposed in the sub-district of the second layer and the 3rd layer _Gap=3 or 4 is feasible.

For multi-unit message is provided, a long m sequence is cut into some segments, and each segment is 1 SL set conversely with replacement IFW width as the SL sequence in each bit duration.In addition, the m sequence T of phase shift ^c[P (L _p)] be cut into the SL sequence by c user's group, wherein be that length is L _pThe m sequence, T ^c[] expression is moved to the left the vector circulation operator in c space.The SL factor postponed to select according to the maximum time among the user between the group.T hereinafter ^c[P (L _p) simply be expressed as P ^cK FL sequence and c SL sequence are expressed as G respectively ^kAnd P ^c, wherein, k=0,1 ..., L _S1And c=0,1 ..., C-1, C is the number of group.

Based on application number is 001109301.3 the Chinese special method that proposes, and each data bit is spread to L behind the secondary spread spectrum scheme ₁L ₂Individual chip.Spread-spectrum signal is modulated through binary phase shift keying (BPSK) then by chip-pulse-shaping filter ψ (t) shaping.The signal that sends from different users passes through different time delays.Suppose to consider square wave chip waveform this moment, the input signal that base station receiver receives can be expressed as

$r\left(t\right)=\mathrm{Re}\left\{\underset{c=0}{\overset{C-1}{\mathrm{\&Sigma;}}}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}\sqrt{{2\mathrm{Pr}}_{k,c}}{s}_{k,c}(t-{\mathrm{\&tau;}}_{k,c})e^{j(2{\mathrm{\&pi;f}}_{c}t+{\mathrm{\&theta;}}_{k,c})}\right\}------\left(6\right)$

Wherein, For through data sequence The spread-spectrum signal of modulation; G ^(k)Be k FL sequence; P ^(c)For distributing to the SL sequence of c group; Pr _{K, c}(k, average power c) is when perfect power control techniques is incorporated in each group of user, for user in the group, Pr for the user that receives _{K, c}Value be identical, can be expressed as Pr _cf _cAnd θ _{K, c}Be respectively (k, c) frequency of individual carrier wave and phase place, τ _{K, c}Be (k, c) individual user's time delay.

The received signal that adds interchannel noise n (t) is modulated by BPSK, and through waveform matched filter, passes through despreader subsequently.Based on top discussion, (k, despreader output c) can be written as the user

$Z^{i,d}=\sqrt{\frac{\mathrm{Pr}}{2}}{\mathrm{LT}}_c{b}^{i,d}\left(0\right)+I_1+I_2+\mathrm{\&eta;}---\left(7\right)$

Wherein, L=L ₁L ₂Be the system spread-spectrum factor.First of equation (7) is ideal signal; Second is the interference in the group, and as long as the maximal phase between the user is limited in being not more than the SL spreading factor to time delay in the group, i.e. τ _{M, d}≤ L ₂, it just can be expressed as

$I_1\&ap;\sqrt{\frac{{\mathrm{Pr}}_d}{2}}{T}_c\underset{k=0,k\&NotEqual;i}{\overset{K-1}{\mathrm{\&Sigma;}}}{b}^{k,d}\left(0\right)\cos \left({\mathrm{\&phi;}}_{k,d}\right)[{\mathrm{\&rho;}}_{d,d}^p\left({\mathrm{\&tau;}}_{k,d}\right){\mathrm{\&theta;}}_{k,i}^g\left(1\right)+{\widehat{\mathrm{\&rho;}}}_{d,d}^p\left({\mathrm{\&tau;}}_{k,d}\right){\mathrm{\&theta;}}_{k,i}^g\left(0\right)]-----\left(8\right)$

φ wherein _{K, d}= _{K, d}- _{K, d}Be that (k is d) with respect to user (i, phase shift d), and suppose that it is evenly distributed on interval [O, 2 π] for the user.Because when k ≠ i, for the S set 1 (L of LS sign indicating number _S1, L _S1/ 2,3,1), ${\mathrm{\&theta;}}_{k,i}^g\left(1\right)=0$ With ${\mathrm{\&theta;}}_{k,i}^g\left(0\right)=0,$ Equation (8) equals 0.Do not produce so disturb in the group.

The 3rd of equation (7) for the interference between the group, can be write as

$I_2\&ap;T_c\underset{c=0,c\&NotEqual;d}{\overset{C-1}{\mathrm{\&Sigma;}}}\sqrt{\frac{{\mathrm{Pr}}_d}{2}}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{b}^{k,c}\left(0\right)\cos \left({\mathrm{\&phi;}}_{k,c}\right)[{\mathrm{\&rho;}}_{c,d}^p\left({\mathrm{\&tau;}}_{k,c}\right){\mathrm{\&theta;}}_{k,i}^g(m_c+1)+{\widehat{\mathrm{\&rho;}}}_{c,d}^p\left({\mathrm{\&tau;}}_{k,c}\right){\mathrm{\&theta;}}_{k,i}^g\left(m_c\right)]$

$=T_c\underset{c=0,c\&NotEqual;d}{\overset{C-1}{\mathrm{\&Sigma;}}}\sqrt{\frac{{\mathrm{Pr}}_d}{2}}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{b}^{k,c}\left(0\right)\cos \left({\mathrm{\&phi;}}_{k,c}\right)\left\{\right[C_{r,q}^w(l_{k,c}+1-L_2){\mathrm{\&delta;}}_{k,c}+C_{r,q}^w(l_{k,c}-L_2)(1-{\mathrm{\&delta;}}_{k,c})]{\&CenterDot;\mathrm{\&theta;}}_{k,i}^g(m_c+1)$

$+[C_{r,q}^w(l_{k,c}+1){\mathrm{\&delta;}}_{k,c}+C_{r,q}^w\left(l_{k,c}\right)(1-{\mathrm{\&delta;}}_{k,c})]{\&CenterDot;\mathrm{\&theta;}}_{k,i}^g\left(m_c\right)\}---\left(9\right)$

Wherein,

For user between the group (k, c) and the FL number of chips that postpones of the relative time between the ideal user, wherein c ≠ d.If τ _{K, c}≤ L ₂T _c, m then _{C, k}=0, and because k ≠ during i, ${\mathrm{\&theta;}}_{k,i}^g(-1)=0,$ So ideal user (i, d) interference is mainly by user (i, c) cause c=0 wherein, 1, ..., C-1 and c ≠ d, this is to have only a user to the contributive situation of the interference sections of ideal user, as a result of in each group in the group system of Quito, sector, compare with traditional PN-CDMA system, the interference that exists in the current system is effectively suppressed.Yet in the group system of Quito, sub-district, because the delay of the signal process longer time of sub-district propagation from afar, so m _{C, k}＞0.In this case, though, need only gap length L because the non-zero correlation in the IFW of LS sequence grid can cause disturbing _Gap〉=(m _{C, k}) _Max, the further interference between the effectively inhibition group of the IFW characteristic of LS sign indicating number.

So can reach a conclusion: current organize in the QS-CDMA system, do not have the interference in the group, and provide cutting apart by the phase shift m sequence as the SL frequency expansion sequence of group more.Simultaneously, the IFW characteristic that is used as the LS sequence of FL frequency expansion sequence of the MAI between the group further suppresses.

The one-level despreader:

In order to simplify receiver architecture, the despreader that uses in the current system is similar to traditional correlator, but the local despreading sequence demultiplexing that the signal that receives is configured, then in the interval [0, T _b] integrates.Local despreading sequence forms by link FL and SL sequence structure, but because the spreading rate of two frequency multipliers and inequality, link process is based on the different secondary spreading rate bases.

Below, embodiment of the invention will be described with reference to drawings.

Figure 1 shows that channel behind secondary spread spectrum under the situation of single user's group (r, spread-spectrum signal k), wherein (r, k) k user's of expression r channel, g _m ^kIndication code S set 1 (L _S1, L _S1/ 2,3,1) m chip of k sign indicating number in, w _n ^rExpression indication code S set 2 (L _S2, L _S2/ 2,1,0) n chip of r sign indicating number in, T _cBe chip duration, b represents the data bit that will launch, L ₁=L _S1+ 2 and L ₂=L _S2Be respectively FL and SL spreading factor, L=L ₁L ₂Be the system spread-spectrum factor.

Figure 2 shows that user behind secondary spread spectrum under the situation of multi-user group (k, spread-spectrum signal c), wherein (k, c) k user in the expression c group, c=0,1 ..., C-1, g _m ^kIndication code S set 1 (L _S1, L _S1/ 2,3,1) m chip of k sign indicating number in, P _n ^cExpression m sequence T ^cN the chip of P, T _cBe chip duration, T _fBe the duration of each frame, L=L ₁L ₂Be the system spread-spectrum factor.Each frame is by L as can be seen from Figure 2 _pIndividual data bit structure forms each the data bit b in each frame ^{K, c}(j) by identical FL sequence { g _m ^k, m=0,1 ..., L ₁But-1} PN sequence { P _n ^c, n=jL ₂, jL ₂+ 1 ..., (j+1) L ₂The different segment spread spectrums of-1}, j=0 wherein, 1..., L _p-1.

Figure 3 shows that reflector and channel model, wherein the data bit b that sends from k user under single user's group situation ^kBy the serial/parallel R channel that is transformed into, the data bit b of s channel ^SkAt first by FL sequence G ^kSpread to and have chip duration T ₁=T _b/ L ₁L ₁Individual chip, T _bWherein be bit duration, G ^kBe k FL sequence.Each FL chip b then ^{S, k}g ^k _m(m=0,1 ..., L ₁-1) again by SL sequence W ^sFurther spread spectrum, the chip duration T that obtains _c=T _b/ (L ₁* L ₂).

Figure 4 shows that reflector and channel model under multi-user's group situation, wherein c organizes the data bit b that k user sends ^{K, c}At first by FL sequence G ^kSpread to and have chip duration T ₁=T _b/ L ₁L ₁Individual chip, wherein T _bBe bit duration, G ^kBe k FL sequence.Each FL chip b then ^{K, c}g ^k _m(m=0,1 ..., L ₁-1) be L by length again ₂SL sequence T ^CcThe further spread spectrum of P, the chip duration T that obtains _c=T _b/ (L ₁* L ₂).

Figure 5 shows that user in j bit duration (k, the structure of the local frequency expansion sequence of the structure that despreader c) is used, k=0 wherein, 1 ..., K-1, c=0,1 ..., C-1.

The present invention will provide a QS-CDMA system with secondary spread spectrum scheme and LS sequence.System of the present invention can obtain satisfied system's error performance and power system capacity.

Though only the present invention is described in detail with reference to a preferred embodiment, anyly skilled in the art will recognize that embodiment can do multiple variation under the prerequisite that does not depart from the scope of the invention.Correspondingly, the present invention only is as the criterion with the definition of claim, and its intention comprises the present invention and all are equal to.

Claims (19)

1. the QS-CDMA system with secondary spread spectrum scheme and LS sequence is characterized in that, comprising:

User according to the user's group of a user in sub-district under the user or the sector appointing system organizes specified device;

Information signal is carried out the device of spread spectrum by FL and SL frequency multiplier;

Be coupled to simplify the one-level spread spectrum device of secondary spread spectrum system receiver architecture with described device;

The device of information carrying signal between the user under not having the situation of MAI in the same subscriber group;

The device of information carrying signal between the user of different user groups under the situation of the MAI that inhibition is arranged;

Utilize the LS sequence to suppress the device of MAI as frequency expansion sequence.

2. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 1 is characterized in that: only have user group, described QS-CDMA system utilizes length to be L _sLS arrangement set S1 as the FL frequency expansion sequence with a plurality of users in the containment; FL spreading factor L ₁=L _s+ 2; Can hold L at most in the system _s/ 2 active users.

3. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 1 is characterized in that: only have user group, described QS-CDMA system utilizes length to be L ₂LS arrangement set S2 provide multichannel transmission as the SL frequency expansion sequence for each user, each user has L at most ₂Individual parallel channel; The SL spreading factor is L ₂

4. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 1 is characterized in that: only have user group, described QS-CDMA system utilizes length to be L _sLS arrangement set S1 as the FL frequency expansion sequence with a plurality of users in the containment; FL spreading factor L ₁=L _s+ 2; Can hold L at most in the system _s/ 2 active users;

Described QS-CDMA system utilizes length to be L ₂LS arrangement set S2 provide multichannel transmission as the SL frequency expansion sequence for each user, each user has L at most ₂Individual parallel channel; The SL spreading factor is L ₂

5. according to any described QS-CDMA system in the claim 1 to 4 with secondary spread spectrum scheme and LS sequence, it is characterized in that: only have user group, the SL spreading factor of described secondary QS-CDMA system selects to be similar to the number of chips that maximum relative time postpones in the middle of the user.

6. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 1, it is characterized in that: exist the multi-user to organize, described user organizes specified device and comprises a device, its receiver adopts directional antenna, and make the user in the common sector belong to identical user's group, make the user in the different sectors belong to different groups.

7. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 1, it is characterized in that: exist the multi-user to organize, described user organizes specified device and comprises a device, its receiver adopts omnidirectional antenna, and make the user in the same cells belong to identical user's group, make the user in the different districts belong to different groups.

8. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 6 is characterized in that described user organizes specified device and comprises a device, and it makes the user of common sector belong to identical user's group; Further comprise another device, it makes the relative time between all users postpone to be limited in the thresholding; And select the SL spreading factor to equal the number of chips that maximum time postpones between all users.

9. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 7, it is characterized in that, described user organizes specified device and comprises a device, it makes the user of same cells belong to identical user's group, and the maximum time between the user in the group postpones to be limited in the thresholding; And selection SL spreading factor L ₂The number of chips that maximum time postpones between the user in equaling to organize.

10. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 8, it is characterized in that: described user organizes specified device and comprises the sector segmenting device, it makes user in the common sector belong to identical user's group, and described QS-CDMA system utilizes the m sequence to cut apart so that many sectors to be provided as the SL frequency expansion sequence.

11. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 9, it is characterized in that: described user organizes specified device and comprises the cell division device, it makes user in the same cells belong to identical user's group, described QS-CDMA system utilize the m sequence as the SL frequency expansion sequence so that many cell division to be provided.

12. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 10 is characterized in that: described sector segmenting device comprises that further it is L that long m sequence is cut into length ₂The device of segment, and each segment is used as the SL sequence in each bit duration, different segments belongs to different bit durations.

13. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 11 is characterized in that: described cell division device comprises that further it is L that long m sequence is cut into length ₂The device of segment, and each segment is used as the SL sequence in each bit duration, different segments belongs to different bit durations.

14. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 12 is characterized in that: described sector segmenting device further is included in different sectors, the long m sequence of out of phase is cut and is used as the device of SL sequence.

15. system according to claim 13 is characterized in that: described cell division device further is included in different districts, and the long m sequence of out of phase is cut and is used as the device of SL sequence.

16. according to Claim 8 or 10 or 12 or 14 described QS-CDMA systems with secondary spread spectrum scheme and LS sequence, it is characterized in that, described user organizes specified device and comprises: make the user of common sector belong to the device of same subscriber group, maximum time delay is limited in being not more than L ₂T _c, the segment of the long m sequence of phase shift is used as the SL frequency expansion sequence, described QS-CDMA system utilize SL arrangement set S1 as the FL frequency expansion sequence so that to be provided cutting apart of user in the group; FL spreading factor L ₁=L _s+ 2; Each group can be held L at most _s/ 2 active users; MAI in the group is eliminated by the IFW characteristic of FL sequence; Interference between the group is further suppressed by the IFW their cross correlation and the fan antenna of FL sequence.

17. according to claim 9 or 11 or 13 or 15 described QS-CDMA systems with secondary spread spectrum scheme and LS sequence, it is characterized in that, described user organizes specified device and comprises: the user of same cells belongs to the device of same subscriber group, and the maximum time between the middle on the same group user postpones to be limited in being not more than L ₂T _c, the segment of the long m sequence of phase shift is used as the SL frequency expansion sequence, described QS-CDMA system utilize SL arrangement set S1 as the FL frequency expansion sequence so that a plurality of groups cut apart to be provided; FL spreading factor L ₁=L _s+ 2L _Gap, L _Gap〉=1; Each group can be held L at most _s/ 2 active users; MAI in the group is eliminated by the IFW characteristic of FL sequence.

18. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 17, it is characterized in that: LS S set 1 is used as FL frequency expansion sequence, L _GapSelection depend on maximal phase between user between the group to time delay; Consider 2 or 3 layers of sub-district on every side, desirable sub-district, L _GapCan equal 3 or 4; ACI is suppressed by the IFW characteristic and the path loss of FL sequence.

19. the QS-CDMA system with secondary spread spectrum scheme and LS sequence according to claim 1 is characterized in that: data message is by FL and SL frequency multiplier spread spectrum, and spread-spectrum signal only is utilized a despreader despreading of local despreading sequence; The FL and the SL sequence of the spreading rate of local frequency expansion sequence by linking FL and SL are respectively constructed.

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