CN1211967C - Method for producing interference of adjacent channels in CDMA communication system - Google Patents

Abstract

The present invention discloses a method for decreasing or homogenizing the interference of adjacent channels in spread spectrum systems, code division multiple access (CDMA) systems and communication systems. A certain forward code channel relative to other code channels is delayed and controlled to a certain degree by the cross correlation characteristic of spread spectrum address codes. The occurrence probability distribution of a certain channel delay quantity or the reverse transmission delay of a mobile station is finished by a base station or the mobile station or the negotiation between the base station and the mobile station according to the interference size of adjacent channels and the orientation of the mobile station. The method of the present invention reduces the sensitivity of the region or the orientation of the mobile station on the interference of adjacent channels, and consequently reduces the total interference of the adjacent channels of the systems to minimum.

Description

Reduce the method for cdma communication system adjacent-channel interference

Technical field

The present invention relates to spread spectrum and cdma mobile communication technical field, the method for adjacent-channel interference (ACI) in particularly a kind of reduction CDMA mobile communication system.

Background technology

Along with the informationized society and the arrival in personal communication epoch, people become more and more urgent to the spectrum efficiency that improves in the wireless communication system.This is big more because of the high more power system capacity of spectrum efficiency.

At wireless communication field, the development of direct sequence spread spectrum (DS-SS) system is more and more rapider.A typical example is exactly code division multiple access (CDMA) communication system.

The cdma communication system capacity only is decided by wanted to interfering signal ratio, has the characteristics of big capacity and soft capacity.Increase the user and only can reduce wanted to interfering signal ratio, reduce communication quality, can not be rejected.Be power system capacity not picture frequency divide multiple access (FDMA) or time division multiple access (TDMA) that a deadline value is arranged like that.

The capacity of cdma communication system depends on intrasystem interference level.Therefore can will become cdma communication system success or failure or fine or not key by the interior interference level of control system.Interference can be divided into four major parts: the one, and this locality and internal system noise level except adopting low noise amplifier, do not have other method for it; The 2nd, intersymbol claims intersymbol interference (ISI) again; The 3rd, multiple access disturbs (MAI), promptly from the interference of other users in the sub-district; The 4th, neighbor cell or interchannel interference (ACI).For ISI, MAI, ACI can be by selecting well behaved address code or some control mode to reduce and even eliminating.

In cdma communication system, each user has own distinctive address code for identification.Moreover, also should be mutually orthogonal between each user's spectrum-spreading address code.The requirement of this orthogonality all is consistent concerning any multi-address system.

For the purpose of image, we claim that the auto-correlation function value at address code initial point place is the main peak of correlation function, and auto-correlation outside the initial point or cross-correlation function value are the submaximum of correlation function.The auto-correlation between desirable multiple access code and the submaximum of cross-correlation function should be zero entirely.

Application number is PCT/CN00/00028, invents artificial Li Daoben, denomination of invention in " a kind of spread spectrum multiple access coding method with zero correlation window " PCT patent application, a kind of spread spectrum multiple address code with zero correlation window is disclosed, be called the LS sign indicating number, because the LS sign indicating number is made up of C sign indicating number and S sign indicating number two parts, therefore be called the CS sign indicating number again.The generation method of LS sign indicating number has a detailed description in PCT/CN00/00028, is omitted at this, quotes this document at this as a reference.Designed have a noiseless window (IFW), and promptly the spread spectrum multiple address code of " zero correlation zone " has following two characteristics: first: the auto-correlation function of each spectrum-spreading address code is zero except that initial point everywhere, and promptly it has optimal characteristic.From the viewpoint of orthogonality, each spectrum-spreading address code and himself are except that the zero propagation place, to all complete quadrature of any non-zero propagation.Second: there be one " noiseless window " in the cross-correlation function between spectrum-spreading address code near initial point.From the orthogonality viewpoint, be completely orthogonal at relative time delay during less than this " noiseless window " width between each spectrum-spreading address code.

The spectrum-spreading address code method for designing of above-mentioned LS sign indicating number makes the correlation function of the spectrum-spreading address code of new formation form one " noiseless window (IFW) " near initial point.Thereby make pairing bi-directional synchronization code division multiple access system not have the fatal near-far interference of traditional C DMA communication system, promptly do not exist multiple access to disturb (MAI) and intersymbol interference (ISI).Lay the foundation for setting up jumbo radio digital communication system.But the same with other cdma communication systems, the system that the LS sign indicating number constitutes does not solve the problem of adjacent-channel interference (ACI) fully.

Adjacent-channel interference (ACI) is present in other cdma communication systems equally, for example, in the IS-95 system, the PN sign indicating number of unique PN biasing (PN Offset) is all used in each sub-district, to the signal spread-spectrum in the sub-district, the adjacent-channel interference (ACI) of neighbor cell is disappeared.

No matter also be based on the such cdma communication system of IS-95 based on the LS sign indicating number, the technology of any minimizing adjacent-channel interference all is favourable for increasing power system capacity raising systematic function.

The correlation properties of LS sign indicating number are good, and cross-correlation is zero in " noiseless window (IFW) "; And outside " noiseless window (IFW) ", it is bigger also only to be that certain some points are gone up in the adjacent cell in the channel and this sub-district the relevant submaximum peak value of channel, and other regional submaximums are all less.With " noiseless window (IFW) " length is that 7 chips are example, when phase phasic difference 4 chips of two adjacent channels, and 8 chips ..., the 4*i chip ... (i=1,2,3 ...) time, the cross-correlation peak value of two LS sign indicating numbers is bigger; And the peak value of other phase difference value cross-correlation is less, even equals zero.Therefore, in the system based on the LS sign indicating number, when phase difference between signals was the integral multiple in some cycles, adjacent-channel interference was bigger; And the interference of other situations is less.

These disturb bigger phase difference value point correspondence in the sub-district some zone between the base station, to be in the adjacent-channel interference that the travelling carriage in these zones is subjected to very big thereby make, and the interference that other regional travelling carriages are subjected to is less.And then increased the susceptibility of place, travelling carriage orientation of living in to adjacent-channel interference.

In existing or future direct sequence spread spectrum (DS-SS) system, the big and less situation of the peak value of other points of peak value on some point also may appear in the correlation between the employed spectrum-spreading address code, even the more a little bigger spacing of submaximum also has certain periodicity.

If the forward delay control with code channel makes the signal phase difference between most of receiving terminals place adjacent channel all avoid the bigger point of so relevant submaximum, must reduce the adjacent-channel interference of system, perhaps disturb the All Ranges be evenly distributed to the sub-district to the major general, the interference that is unlikely to certain areas is very big and interference some zone is very little.Certainly, this is conspicuous especially to the benefit that travelling carriage switches.

Summary of the invention

Therefore, the object of the present invention is to provide a kind of method that is used to reduce or eliminate adjacent-channel interference, solve the problems referred to above.

A kind of method that reduces the cdma communication system adjacent-channel interference, this cdma communication system comprise at least one base station and at least one travelling carriage, the method is characterized in that, comprise the steps:

Travelling carriage detects the adjacent-channel interference that its used code channel is subjected to;

A detected adjacent-channel interference value and a pre-set threshold value are compared; And

Determine the forward delay of the used code channel of travelling carriage;

The forward delay amount of used code channel is adjusted in the base station.

According to this method of the present invention, the code channel that travelling carriage uses avoids being subjected to the situation of other channel larger interferences, perhaps makes the interference homogenizing that the travelling carriage in all orientation is subjected in the sub-district, and the interference that some zone do not occur is far longer than other regional situations.Thereby make pairing cdma communication system minimizing adjacent-channel interference or make being evenly distributed of adjacent-channel interference.

Description of drawings

Fig. 1 shows a kind of block diagram of wireless communication system of routine;

Fig. 2 shows the process of adjusting the forward delay of the used code channel of travelling carriage according to base station of the present invention;

Fig. 3 shows the process of adjusting the forward delay of the code channel that uses according to travelling carriage of the present invention;

Fig. 4 shows a kind of auto-correlation result of LS sign indicating number;

Fig. 5 shows a kind of cross correlation results of LS sign indicating number;

Fig. 6 shows in the LAS-CDMA system distribution map of the adjacent-channel interference between two sub-districts; And

Fig. 7 shows the process of reduction adjacent-channel interference of the present invention.

Embodiment

Describe the present invention below in conjunction with accompanying drawing.

Fig. 1 shows a kind of block diagram of description wireless communication system of routine.Referring to Fig. 1, in this wireless communication system, relevant base station BTS1 among mobile station MS 1 and MS2 reception of neighboring cell C1, C2 and the C3, the signal of BTS2 and BTS3.With mobile station MS 1 is example, is base station BTS 1 when what provide service for mobile station MS 1, and then the signal that sends of base station BTS 2 and BTS3 if can be moved platform MS1 detects, for mobile station MS 1, is exactly adjacent-channel interference (ACI).Particularly, suppose that base station BTS 2 provides service for mobile station MS 2, then to send to the signal of mobile station MS 2 be exactly adjacent-channel interference for mobile station MS 1 to base station BTS 2.

Fig. 2 shows according to base station of the present invention and adjusts the process that the used code channel of travelling carriage postpones.Referring to Fig. 2, at first, at step S201, the signaling of base station BTS 1 receiving mobile MS1.Then, flow process enters step S202.At step S202, judge whether the operation that this mobile station MS 1 carries out is the request channel.

If at the new channel of step S202 mobile station MS 1 request, flow process enters step S203 so.At step S203, base station BTS 1 judges whether to obtain the locating information of mobile station MS 1, promptly whether obtains the orientation of mobile station MS 1.This dual mode of the measurement of the signal that locating information can be sent by tracking or 1 pair of base station BTS 1 of mobile station MS of 1 pair of mobile station MS 1 of base station BTS obtains.If "Yes", so, flow process enters step S204.

At step S204, base station BTS 1 is determined current forward delay of distributing code channel according to locating information, and its detailed process will hereinafter be described.Then, flow process enters step S206, and at step S206, base station BTS 1 is adjusted the forward delay amount of this code channel.Then, flow process enters step S207, and base station BTS 1 uses signaling mobile station MS 1 result.If judge the locating information that does not obtain mobile station MS 1 at step S203 base station BTS 1, so, flow process enters step S205.At step S205, base station BTS 1 occurs on average determining forward delay that subsequently, flow process enters step S206 according to each code channel retardation.

Turn back to step S202, if do not carry out channel request at step S202 mobile station MS 1, so, flow process enters step S208.At step S28, base station BTS 1 determines whether mobile station MS 1 carries out code channel and postpone to adjust request.If "Yes", flow process enters step S209 so.At step S209, base station BTS 1 judges whether the code channel retardation that postpones back mobile station MS 1 exceeds certain scope.If do not exceed adjusting range, then flow process enters step S206.If determine that at step S209 base station BTS 1 the code channel retardation that postpones back mobile station MS 1 exceeds certain scope, so, flow process enters step S210.

So-called retardation adjusting range can be determined by the width and the how delayed of wireless communications environment of " noiseless window ".For example, " noiseless window " width is 7 chips, the delay of two paths that arrive the earliest and arrive the latest is 2 chips, then the adjustment of retardation should be within the scope of 4～5 chips, with the size that guarantees all retardations all less than the width of " noiseless window " with how delayed poor.

At step S210, the forward delay amount of mobile station MS 1 code channel that uses is not adjusted in the base station, and enters step S207.At step S207, base station BTS 1 passes through signaling mobile station MS 1 result, and enters step S211, promptly finishes this control flow.At step S208, if base station BTS 1 judges that mobile station MS 1 does not carry out code channel and postpones to adjust request, then flow process enters step S211.

Fig. 3 shows the process of adjusting the forward delay amount of the code channel that uses according to travelling carriage of the present invention.Referring to Fig. 3, at step S301, mobile station MS 1 receives the signaling and the data of base station BTS 1.Then, flow process enters step S302.At step S302, mobile station MS 1 is judged the result whether base station BTS 1 notifies its code channel to postpone.If "Yes", then flow process enters S303.At step S303, travelling carriage is adjusted the receiver of MS1 according to the code channel delayed data that base station BTS 1 sends, and enters step S304.If at step S302, mobile station MS 1 is judged base station BTS 1 and fails to give notice the forward delay result of the code channel that uses that then flow process enters step S304.At step S304, mobile station MS 1 is measured all adjacent base stations, i.e. the signal energy and the receive delay of base station BTS 1, base station BTS 2 and base station BTS 3 signals, and enter step S305.At step S305, mobile station MS 1 is measured the energy of the adjacent-channel interference that receives.Then, flow process enters step S306.

At step S306, mobile station MS 1 judges whether the adjacent-channel interference energy that receives surpasses pre-set threshold value, and the concrete establishing method of this threshold values is described below.If "Yes", then flow process enters step S307.

At step S307, the orientation that whether energy of resulting all adjacent base station signals and receive delay can determine self among the mobile station MS 1 basis for estimation step S304.If "Yes", then flow process enters step S308.At step S308, mobile station MS 1 determines that according to locating information code channel postpones adjustment amount.Then, flow process enters step S309.In step S309, mobile station MS 1 sends adjustment amount and adjusts request to base station BTS 1.Flow process enters step S310 and finishes then.If at step S307, mobile station MS 1 judges and can not determine self orientation according to the base station signal that measures that then flow process enters step S311.At step S311, mobile station MS 1 produces code channel at random and postpones adjustment amount, and enters step S309.

The following describes among Fig. 3 the setting of pre-set threshold value among the step S306 and determine the process of code channel forward delay amount with step S308 among step S204 and Fig. 3 in the key diagram 2.

It is 7 chips that the present invention will mainly center on " noiseless window " width, and the LAS-CDMA system that the code length of C sign indicating number and S sign indicating number is 8 chips is described in detail. but and do not mean that the present invention only limits to this.Method of the present invention has in the Resistant DS Spread Spectrum System (DS-SS) of the spectrum-spreading address code of individual features applicable to other equally.

Fig. 4 is a kind of auto-correlation result of LS sign indicating number, and wherein the code length of C sign indicating number and S sign indicating number is 8, and the IFW width is 7.Among Fig. 4, its abscissa is a relative offset, and unit is a chip, and its ordinate is a correlation.The value of abscissa 0 place's ordinate is 16 for relevant main peak herein among Fig. 4, and other all ordinates are not that 0 place is relevant submaximum.Fig. 5 is the cross correlation results of two code words in this LS code character, and all ordinates are not that 0 place is relevant submaximum.As can be seen, when abscissa was interior in interval (3.5,3.5), no matter the submaximum of auto-correlation or cross-correlation was 0, promptly has only the main peak existence from Fig. 4 and Fig. 5.Therefore, interval (3.5,3.5) be exactly width be " the noiseless window " of 7 chips.The existence of " noiseless window " is the characteristic of LS sign indicating number.Along with the formation of the number of code word in code word size, the code character and code word is different, the width of " noiseless window " can be different.

Referring to Figure 4 and 5, the LAS-CDMA system that sets up according to the LS sign indicating number is when " noiseless window " when width is 7 chips, if phase phasic difference 4 chips of two adjacent channels, 8 chips ..., during the 4*i chip, i=1 wherein, 2,3 ..., the cross-correlation peak value of two LS sign indicating numbers is bigger; And the peak value of other phase difference value cross-correlation is less, even equals zero.Certainly, different or when using different LS sign indicating numbers when the gap length between C sign indicating number and the S sign indicating number, may be different with this routine situation, the phase difference that big submaximum occurs may be the 4+k chip, the 8+k chip ..., the 4i+k chip ... (i=1,2,3 ...; K is-fixed constant), but this does not influence the applicability of said method in this example.

Referring to Fig. 4 and Fig. 5, the main peak correlation is 16 o'clock, and submaximum only occurs when relative offset is 4 multiple, and the absolute value minimum of submaximum correlation is 4, and maximum can reach 12.

From Fig. 4 and Fig. 5 as can be seen, the submaximum absolute value is that 4 situation is in the majority, therefore, at this situation, the energy of supposing the relevant main peak that the mobile station MS 1 among Fig. 1 measures is 16, and unit is any, then among Fig. 3 among the step S306 pre-set threshold value then can be set at 25% of relevant main peak energy, promptly 4, unit is identical with the energy unit of main peak.So, when the ACI interfering energy that receives greater than the main peak energy 25% the time, mobile station MS 1 thinks and self is subjected to stronger adjacent-channel interference (ACI), and and then produces the forward direction code channel and postpone request.

The following describes among Fig. 2 among the step S204 and Fig. 3 step S308 according to locating information determine code channel forward delay amount the common method of using.

In communication system according to the present invention, when the moment that the frame of code channel that travelling carriage uses arrives, and the time (phase place) between the frame due in of other base station code channels is poor, just equal (i=1 in 4*i, 2,3 ...) during individual chip, this moment, adjacent channel was bigger to the channel disturbance that this travelling carriage uses, and adjacent-channel interference is less when other situations.In execution mode, the spreading rate of system is 1228800 chips/s.

Fig. 6 shows the distribution map of the adjacent-channel interference of LAS-CDMA system two sub-districts.

Referring to Fig. 6, two base station BTS 1 and BTS2 are arranged respectively in two neighbor cell C1 and C2.For any 1 G1, the distance of supposing base station BTS 1 and BTS2 and this G1 is respectively r ₁And r ₂, and | r ₂-r ₁|=d ₁₂If base station BTS 1 and BTS2 send signal simultaneously, the phase difference that arrives this G1 is

$\frac{|r_2-r_1|}{c}=\frac{d_{12}}{c}---\left(1\right)$

Wherein c is the light velocity, and unit is a meter per second, r ₁, r ₂With the unit of d be rice.When the spreading rate of system is 1228800 chips/s, can obtain its corresponding number of chips by formula (1):

$\frac{d_{12}}{244}=\frac{|r_2-r_1|}{244}---\left(2\right)$

According to the correlation properties of LS sign indicating number, when satisfying d ₁₂/ 244=4 * i (i=1,2,3 ...) during chip, adjacent-channel interference is bigger, at this moment

|r ₂-r ₁|＝d ₁₂＝244×4×i＝976×i(i＝1，2，3，...) (3)

In embodiments of the present invention, formula (3) is the condition that adjacent-channel interference is met when big.

Because the difference of two fixed point distances of arrival is that the track of the point of certain value is a hyperbola, then the value of corresponding each i all forms two hyperbolas between two base station BTS 1 and BTS2.As shown in Figure 6, near the zone these hyperbolas, the adjacent-channel interference that travelling carriage is subjected to is bigger.Because 1 chip is equivalent to 244 meters distance, and chip is the signal distinguishing unit of present cdma system, so on behalf of a width, every hyperbola be about 244 meters zone band among Fig. 6.In theory, when the spacing of two base stations just equaled 4*i chip, the zone band on the extended line of the line segment between two base station BTS 1 and the BTS2 also was the bigger zone of adjacent-channel interference.

Because other zones outside hyperbola, adjacent-channel interference is less, so, though the time difference of the signal point of arrival G1 of two base station BTS 1 and BTS2 emission can not change, but can be by changing the delay of down channel that this G1 place travelling carriage uses with respect to other code channels, yard sequence phase that changes between the code channel of this code channel and another base station is poor.

Fig. 7 shows the process of reduction adjacent-channel interference of the present invention.Referring to Fig. 7, what establish that mobile station MS 1 uses is descending code channel 2 in the base station BTS 1, and mobile station MS 2 uses is descending code channel 2 in the base station BTS 2; And code channel 1 and code channel 4 all are the standard delay code channels in base station BTS 1 and the BTS2 signal, and promptly to postpone be zero to code channel.Suppose that mobile station MS 1 and MS2 are in the zone of a certain curve representative described in Fig. 6, the adjacent-channel interference energy that promptly is subjected to will be above predetermined threshold value.4i chip (getting i=2 among Fig. 7) after the signal that base station BTS 1 sends arrives mobile station MS 1, the signal point of arrival mobile station MS 1 that base station BTS 2 sends; And the 4i chip (getting i=2 among Fig. 7) after the signal of base station BTS 2 arrives mobile station MS 2, the signal of base station BTS 1 arrives mobile station MS 2.If all code channels are zero with the phase difference of standard delay code channel all in the signal that base station BTS 1 and BTS2 send, then all signals of sending of base station BTS 2 have all produced big adjacent-channel interference to mobile station MS 1; Equally, base station BTS 1 ₁All signals that send have all produced larger interference to mobile station MS 2.

Now, mobile station MS 1 judges that the adjacent-channel interference (ACI) that is subjected to exceeds pre-set threshold value, and transmission request, perhaps base station BTS 1 has initiatively shifted to an earlier date chip (shown in Fig. 7 is situation after having shifted to an earlier date a chip) at code channel 2 that the base station end uses mobile station MS 1 according to the locating information of mobile station MS 1 than other code channels, the phase difference between the standard delay code channel in the signal that sends of this code channel 2 and base station BTS 2 then, increase to 9 chips by 8 original chips, thereby when the signal that base station BTS 2 is sent arrives mobile station MS 1, avoided the bigger situation of adjacent-channel interference energy, reduced interference mobile station MS 1.Equally, mobile station MS 2 also sends request or initiatively the code channel 2 that mobile station MS 2 uses has also been shifted to an earlier date a chip than other code channels by base station BTS 2, and this can make the standard delay code channel in the signal that base station BTS 1 sends that the interference of mobile station MS 2 is reduced.

But the code channel 2 in the base station BTS 2 and the phase difference of the code channel 2 among the BT1 of base station return to 8 chips again at this moment.Therefore, can obtain such conclusion: promptly be in when meeting bigger regional of adjacent-channel interference when travelling carriage, can be by the method for the employed code channel of this travelling carriage and other code channel phase differences of this sub-district in the change down channel, reduce the adjacent-channel interference that is subjected to, we are referred to as forward delay control this method.At this moment, the adjacent-channel interference that is subjected to of travelling carriage will mainly come from the neighbor cell interference with the identical code channel of adjustment situation of own code channel.

But through above-mentioned adjustment, can make the travelling carriage that is not subjected to bigger adjacent-channel interference originally, the phase difference between its channel and the adjacent channel satisfies the bigger condition of adjacent-channel interference.This is equivalent to the larger interference that some is regional and has almost on average arrived All Ranges, makes to disturb big zone to disturb minimizing, has increased and disturb little zone to disturb.

Describing in detail below by certain retardation selection mode makes overall adjacent-channel interference reduce to the minimum best approach.

If mobile station MS 1 and MS2 lay respectively among the sub-district C1 and C2 that base station BTS 1 and BTS2 covered, the delay of the descending code channel that mobile station MS 1 and MS2 use is respectively e ₁, e ₂, unit is a chip; The distance that base station BTS 1 and BTS2 arrive mobile station MS 1 is respectively r ₁And r ₂Then work as

$|\frac{|r_2-r_1|}{244}+(e_1-e_2)|=4\×i(i=\mathrm{1,2,3},...)---\left(4\right)$

The time, the signal that sends to mobile station MS 2 can cause larger interference to mobile station MS 1.

If e ₁And e ₂Each variable has+and 1,0 ,-1 three kind of value mode, represent channel to carry previous chip, the constant or chip that lags behind respectively, so (e ₁-e ₂) have-2 ,-1,0,1,2 five kind of possible result, as shown in table 1.

e 1	+1	+1	+1	0	0	0	-1	-1	-1
										e 2	+1	0	-1	+1	0	-1	+1	0	-1
e 1-e 2	0	+1	+2	-1	0	+1	-2	-1	0

Table 1:e ₁, e ₂Possible value combination and e ₁-e ₂Possible result considers again | r ₂-r ₁|=d ₁₂The possibility of value.d ₁₂Get remainder (also will round again) for/244 pairs 4 and have 0,1,2,3 four kind of possibility, and these four kinds of phase differences of 0,1,2,3 chips that the signal that corresponding respectively base station BTS 1 and BTS2 send forms respectively at different acceptance point places, and every kind of phase difference value all corresponding a width be approximately 244 meters hyperbolic tape.When the result is 0, meet the condition that is subjected to big adjacent-channel interference, if do not carry out forward delay control, the interference that mobile station MS 1 is subjected to base station BTS 2 is bigger; When the result is other three values, it is less that mobile station MS 1 is subjected to the interference of base station BTS 2, this moment, mobile station MS 1 was in a certain zone outside the zone that hyperbola is represented among Fig. 6, and when the result was 2, mobile station MS 1 just in time was positioned near two adjacent hyp middles.

Will | r ₂-r ₁|=d ₁₂(e ₁-e ₂) common consider, the result such as the table 2 that obtain, wherein (on behalf of x, x y) y is got result behind the remainder to function Mod.

Mod(d 12/244，4)	0	0	0	0	0	0	0	0	0
										e 1	+1	+1	+1	0	0	0	-1	-1	-1
e 2	+1	0	-1	+1	0	-1	+1	0	-1
										od(Mod(d 12/244，4)+(e 1-e 2)，4)	0	+1	+2	-1	0	+1	-2	-1	0

Table 2a Mod (d ₁₂/ 244,4) o'clock situation=0

Mod(d 12/244，4)	1	1	1	1	1	1	1	1	1
										e 1	+1	+1	+1	0	0	0	-1	-1	-1
e 2	+1	0	-1	+1	0	-1	+1	0	-1
										Mod(Mod(d 12/244，4)+(e 1-e 2)，4)	+1	+2	+3	0	+1	+2	-1	0	+1

Table 2b Mod (d ₁₂/ 244,4) o'clock situation=1

Mod(d 12/244，4)	2	2	2	2	2	2	2	2	2
										e 1	+1	+1	+1	0	0	0	-1	-1	-1
e 2	+1	0	-1	+1	0	-1	+1	0	-1
										Mod(Mod(d 12/244，4)+(e 1-e 2)，4)	+2	+3	0	+1	+2	+3	0	+1	+2

Table 2c Mod (d ₁₂/ 244,4) o'clock situation=2

Mod(d 12/244，4)	3	3	3	3	3	3	3	3	3
										e 1	+1	+1	+1	0	0	0	-1	-1	-1
e 2	+1	0	-1	+1	0	-1	+1	0	-1

Mod(Mod(d 12/244，4)+(e 1-e 2)，4)

+3

0

+1

+2

+3

0

+1

+2

+3

Table 2d Mod (d ₁₂/ 244,4) o'clock situation=3

Because Mod (Mod (d ₁₂/ 244,4)+(e ₁-e ₂), 4) the result be 0 o'clock, mean when signal that base station base station BTS 2 sends to mobile station MS 2 arrives mobile station MS 1, and the phase difference between the code channel of mobile station MS 1 just is a multiple chip of 4, will be to mobile station MS 1 formation larger interference; If Mod (Mod (d ₁₂/ 244,4)+(e ₁-e ₂), 4) the result be other values, when the signal that sends to mobile station MS 2 arrives mobile station MS 1, disturb less to mobile station MS 1.So, as can be seen from Table 2,

As Mod (d ₁₂/ 244,4) equal at 0 o'clock,, all will be subjected to postponing in the signal that base station BTS 2 sends the larger interference of identical with it code channel regardless of the phase delay of mobile station MS 1;

As Mod (d ₁₂/ 244,4) equal at 1 o'clock, as long as the phase delay of mobile station MS 1 is+1, then regardless of the delay of each code channel in the signal of base station BTS 2 transmissions, mobile station MS 1 all can be avoided the bigger situation of adjacent-channel interference;

As Mod (d ₁₂/ 244,4) equal at 2 o'clock, as long as the phase delay of mobile station MS 1 is 0, then regardless of the delay of each code channel in the signal of base station BTS 2 transmissions, mobile station MS 1 all can be avoided the bigger situation of adjacent-channel interference;

As Mod (d ₁₂/ 244,4) equal at 3 o'clock, as long as the phase delay of mobile station MS 1 is-1, then regardless of the delay of each code channel in the signal of base station BTS 2 transmissions, mobile station MS 1 all can be avoided the bigger situation of adjacent-channel interference.

According to the above, can obtain table 3.

Mod(d 12/244，4)	0	1	2	3
					e 1	-	+1	0	-1

Table 3 is as Mod (d ₁₂/ 244,4) value does not not simultaneously make system

The code channel of adjacent channel interference postpones value

From as can be seen last, the value rule makes Mod (d exactly ₁₂/ 244,4) and e ₁And be+2.

Therefore, if can determine the orientation of all travelling carriages, promptly can determine the distance of the big adjacent-channel interference zone band among the residing position of travelling carriage and Fig. 6 according to locating information exactly, situation when carrying out forward delay control, just can be according to table 3 value, at this moment, travelling carriage is subjected to the possibility minimizing of big adjacent-channel interference (ACI).

In above-mentioned example, only considered the situation of two base stations, and often simultaneously adjacent at the travelling carriage at cell boarder place with three base stations, therefore can be subjected to the interference of two adjacent base stations simultaneously.Infer that easily the front best value that forward channel postpones during only at an adjacent base station can not satisfy the optimal selection at the retardation of another adjacent base station simultaneously.Be that certain channel among the C1 of sub-district may be selected to carry previous chip at adjacent base station BTS2 and can avoid being subjected to larger interference, and require its chip that lags behind at adjacent base station BTS3.Be provided with three adjacent in twos base stations and be respectively BTS1, BTS2 and BTS3, a mobile station MS 1 is arranged in the C1 of sub-district, the distance of establishing BTS1, BTS2, BTS3 arrival mobile station MS 1 is respectively r ₁, r ₂And r ₃, and

d ₁₂＝|r ₂-r ₁|

d ₁₃＝|r ₃-r ₁|

e ₁Be the forward channel retardation that MS1 uses, e ₂, e ₃Represent the retardation of certain forward channel among sub-district BTS2 and the BTS3 respectively; Base station BTS 1, BTS2 and BTS3 send signal simultaneously.Then, can draw and work as according to the derivation of front

Mod (Mod (d ₁₂/ 244,4)+(e ₁-e ₂), 4)=0 o'clock, forward channel postpones to be e among the BTS2 of sub-district ₂Channel can form mobile station MS 1 and disturb; When

Mod (Mod (d ₁₃/ 244,4)+(e ₁-e ₃), 4)=0 o'clock, forward channel postpones to be e among the C3 of sub-district ₃Channel can form mobile station MS 1 and disturb.

Mod (d ₁₂/ 244,4) and Mod (d ₁₃/ 244,4) have 0,1,2 equally respectively, 3 four kind of value may, establish e ₁, e ₂, e ₃Have-1,0 equally respectively, 1 three kind of value may, independent separately.Then five variablees have 432 kinds of compound modes.Consider this wherein all values meet the combination that adjacent-channel interference (ACI) is disturbed bigger condition, can obtain table 4.

Table 4: when considering three adjacent in twos base stations, might form the variable d of big adjacent-channel interference ₁₂, d ₁₃, e ₁, e ₂, e ₃Compound mode

In table 4, Mod (d ₁₂/ 244,4) and Mod (d ₁₃/ 244,4) a certain region in each combination (having 16 kinds of combinations) respective cell.In each zone, work as e ₁Value is respectively-1,0,1 o'clock, can be subjected to the described base station b of respective cells in the table 4 ₂Signal in the signal of a certain delayedchannel and base station BTS 3 certain-larger interference of delayedchannel.For example, as Mod (d ₁₂/ 244,4)=0 and Mod (d ₁₃/ 244,4)=0 o'clock, corresponding to the first three columns of the first three rows in the data of table 4, if e ₁=0, then being subjected among the BTS2 postponing is the larger interference of 0 forward channel, is subjected to b simultaneously ₃In to postpone be the larger interference of 0 forward channel; As Mod (d ₁₂/ 244,4)=1 and Mod (d ₁₃/ 244,4)=1 o'clock, corresponding to first three of the row of three to six in the data of table 4 to six row, if e ₁=1, then neither be subjected to the larger interference of forward channel among the BTS2, be not subjected to the larger interference of the forward channel among the BTS3 yet.

As can be seen from Table 4, when being in Mod (d ₁₂/ 244,4) and Mod (d ₁₃The retardation that travelling carriage in the region of/244,4) various combination representative uses can make adjacent-channel interference (ACI) minimum of system during according to table 5 value.

	Mod(d 12/244，4)＝0	Mod(d 12/244，4)＝1	Mod(d 12/244，4)＝2	Mod(d 12/244，4)＝3
					Mod(d 13/244，4)＝0	-	1	0	-1
Mod(d 13/244，4)＝1	1	1	0 or 1	-1 or 1
					Mod(d 13/244，4)＝2	0	0 or 1	0	-1 or 0
Mod(d 13/244，4)＝3	-1	-1 or 1	-1 or 0	-1

Table 5 is under the situation of three adjacent base stations, at Mod (d ₁₂/ 244,4) and Mod (d ₁₃The optimal delay mode of the forward channel that travelling carriage uses during/244,4) various combination

At Mod (d ₁₂/ 244,4) and Mod (d ₁₃/ 244,4) each combination, if do not carry out forward delay control, the regional suffered disturbed condition of various compound mode representatives is as table 6a, numerical value in the bracket is the probability of interference of base station BTS 2 signals to travelling carriage in this zone to the numerical value of front, lining, and the numerical value of back is the probability of interference of BTS3 signal to this zone travelling carriage;

	Mod(d 12/244，4)＝0	Mod(d12/244，4)＝1	Mod(d 12/244，4)＝2	Mod(d 12//244，4)＝3
					Mod(d 13/244，4)＝0	(1，1)	(0，1)	(0，1)	(0，1)
Mod(d 13/244，4)＝1	(1，0)	(0，0)	(0，0)	(0，0)
					Mod(d 13/244，4)＝2	(1，0)	(0，0)	(0，0)	(0，0)
Mod(d 13/244，4)＝3	(1，0)	(0，0)	(0，0)	(0，0)

Table 6a does not carry out forward delay control, Mod (d ₁₂/ 244,4) and Mod (d ₁₃The probability that travelling carriage is interfered during/244,4) various combination

If use forward delay control, and, can obtain showing the disturbed condition of 6b according to the value mode of table 5.

	Mod(d 12/244，4)＝0	Mod(d 12/244，4)＝1	Mod(d 12/244，4)＝2	Mod(d 12/244，4)＝3
					Mod(d 13/244，4)＝0	(1/3，1/3)	(0，1/3)	(0，1/3)	(0，1/3)
Mod(d 13/244，4)＝1	(1/3，0)	(0，0)	(0,1/3) or (1/3,0)	(0,1/3) or (1/3,0)
					Mod(d 13/244，4)＝2	(1/3，0)	(0,1/3) or (1/3,0)	(0，0)	(0,1/3) or (1/3,0)
Mod(d 13/244，4)＝3	(1/3，0)	(0,1/3) or (1/3,0)	(0,1/3) or (1/3,0)	(0，0)

Table 6b carries out forward delay control, Mod (d ₁₂, 4) and Mod (d ₁₃, 4) various combination the time travelling carriage probability that is interfered all numerical value summations of his-and-hers watches 6a and table 6b respectively, can draw, the adjacent-channel interference of forward delay control back whole system can become original (14/3)/8=58.3%; Simultaneously, interference profile is more even, can not make some regional travelling carriage be subjected to very strong interference.

As can be seen from the above, when considering a plurality of adjacent base station, forward delay control still can reduce the adjacent-channel interference of system), and reduce the susceptibility of travelling carriage orientation to disturbing; And also exist best forward channel to postpone value mode, it is minimum that overall interference is reduced to.

The value of channel latency can have more possibilities, for example, can be-2 ,-1,0,1,2 chips, or-1 ,-0.5,0,0.5,1 chip, in a word, the value of delay is big more at interval, the possibility of value is many more, and it is good more to postpone control reduction effects of jamming.When retardation had 5 kinds of possible value mode, the entire system interference can be not use to postpone control (14/5)/8=35% under best situation.

Do not depart from the scope of the present invention and conceive and to make many other change and remodeling.Should be appreciated that the present invention is not limited to certain embodiments, scope of the present invention is defined by the following claims.

Claims (14)

1. method that reduces the cdma communication system adjacent-channel interference, this cdma communication system comprise at least one base station and at least one travelling carriage, the method is characterized in that, comprise the steps:

Travelling carriage detects the adjacent-channel interference that its used code channel is subjected to;

A detected adjacent-channel interference value and a pre-set threshold value are compared; And

Determine the forward delay of the used code channel of travelling carriage;

The forward delay amount of used code channel is adjusted in the base station.

2. the method for claim 1 is characterized in that:

The forward delay of determining the used code channel of travelling carriage has been utilized the their cross correlation of spectrum-spreading address code, wherein, this their cross correlation is meant that the relevant submaximum of spreading code on some phase places is bigger, and the relevant submaximum on other phase place is less, and the code channel that is in the relevant submaximum larger part of spectrum-spreading address code is carried out forward delay control.

3. method as claimed in claim 2 is characterized in that, described pre-set threshold value is 25% of the relevant main peak energy of spectrum-spreading address code.

4. method as claimed in claim 2 is characterized in that:

The their cross correlation of described spectrum-spreading address code has periodically.

5. method as claimed in claim 2 is characterized in that:

Described spectrum-spreading address code is the LS sign indicating number with " noiseless window ".

6. the method for claim 1 is characterized in that, also comprises step:

Travelling carriage is determined its azimuth information with respect to the base station.

7. method as claimed in claim 6 is characterized in that, this method further comprises step: travelling carriage sends detected information to the base station corresponding with it; And

The base station is according to coming from the carry out forward delay of mobile station information to the used code channel of travelling carriage.

8. the method for claim 1 is characterized in that, further comprises step:

The azimuth information of travelling carriage is detected to determine the forward delay amount in the base station.

9. the method for claim 1 is characterized in that, further comprises step:

The base station determines that according to the signal of travelling carriage emission azimuth information is to determine the forward delay amount.

10. the method for claim 1 is characterized in that, forward direction code channel retardation depends on the distance between travelling carriage and the base station, or the probability distribution of adjacent-channel interference appears in travelling carriage code channel of living in.

11. the method for claim 1 is characterized in that, further may further comprise the steps:

In with the system of LS sign indicating number,, detect the position of the travelling carriage that is in relevant submaximum value larger part according to the correlation properties of LS sign indicating number as spreading code; And

According to the width of LS sign indicating number " noiseless window ", determine the retardation of the used code channel of inspection positions travelling carriage.

12. method as claimed in claim 11 is characterized in that, further comprises step:

The forward delay amount of average each code channel of travelling carriage is to reduce adjacent-channel interference.

13. method as claimed in claim 11 is characterized in that:

The size of described retardation is less than the width of " noiseless window ".

14. the method for claim 1 is characterized in that, the size of forward delay is determined in the distribution of the number of sub-district, the size of adjacent-channel interference and adjacent-channel interference.

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