CN101917208A - Method for inhibiting neighboring cell interference - Google Patents

Abstract

The invention relates to a method for inhibiting neighboring cell interference, which belongs to the field of wireless communication. The method comprises the following steps of: 1) dividing cells in a communication system into a plurality of clusters, wherein each cluster comprises J neighboring cells, and cell channels maintains unchanged in the duration time of J information symbols; 2) selecting J orthogonal codes and distributing the J orthogonal codes to the J cells in one cluster respectively; 3) continuously transmitting the J information symbols at the same time by using the J cells in the cluster where a receiving terminal is positioned, and performing orthogonalization encoding on each piece of user data which is to be transmitted by the cell by using the orthogonal code in the cell, wherein the J information symbols transmitted by the same cell are J same information symbols; and 4) performing correlation processing on the received information symbols to demodulate the user data of the receiving terminal by using the receiving terminal. Compared with the prior art, the method has the advantages of greatly eliminating the neighboring cell interference and increasing a signal-to-noise ratio of receiving signals so as to improve spectrum efficiency.

Description

A kind of method that suppresses neighbor cell interference

Technical field

The present invention relates to a kind of method-quadrature cell code (OCC) that suppresses neighbor cell interference, purpose is to improve the dry ratio of letter of forward direction or this sub-district of reverse link, improves spectrum efficiency; Be applicable to wireless communication field.

Background technology

A basic task of wireless communication system is the communication link between foundation and maintenance wireless terminal and base station, realizes the transmitted in both directions of communication data, by the link of base station biography toward the wireless terminal direction, is called forward direction (or descending) link; Pass toward the link of base station direction by wireless terminal, be called oppositely (or up) link.According to the difference of duplex mode, communication system generally is divided into time division duplex (TDD) system and Frequency Division Duplexing (FDD) (FDD) system.

The TDD system adopts same frequency to carry out up, downlink transmission, and utilizes different time-gap to isolate interference between up, the down link, and promptly the base station receives only and do not launch in ascending time slot, and the base station is only launched and do not received in descending time slot.And the FDD system, receive and dispatch simultaneously the base station, distinguishes the uplink and downlink link with different frequencies, generally needs the frequency spectrum resource of symmetry.Existing mobile communication gsm system belongs to the FDD system and the TD-SCDMA system belongs to the TDD system.FDD system and TDD system all exist the interference problem of neighbor cell at cell edge, and the interference of adjacent sub-district can be effectively eliminated in the proposition of this programme, thereby improve signal interference ratio.

Summary of the invention

The object of the present invention is to provide a kind of method that suppresses neighbor cell interference, the present invention does orthogonal code modulation with the quadrature cell code to transmitting, make that the interference signal between the neighbor cell can quadrature, and then eliminated the interference of neighbor cell signal, reached the dry ratio of the letter that improves receiving terminal, band efficiency is 1/3 bandwidth, is 1/4 to compare with traditional C DMA technology band efficiency, has improved band efficiency.This technology both had been suitable for the TDD system, also was suitable for the FDD system.

For the OCC technology is used for present communication system, need require as follows at 3 of restriction:

At first, sub-clustering is carried out in the sub-district in the communication system; Consider actual cellular system, we stipulate that 3 sub-districts are cluster (cluster), and the concrete structure schematic diagram is seen Fig. 1;

The second, the base station of 3 sub-districts must guarantee synchronized transmissions in the receiving terminal place bunch, and this is to realize easily in technology at present;

The 3rd, channel remains unchanged in 3 symbol durations.

3 points above satisfying, receiving terminal is by doing orthogonalization process to received signal, the signal after the neighbor cell interference that just can be eliminated.Method flow of the present invention as shown in Figure 4, wherein concrete steps are as follows:

The first step defines 3 orthogonal codes, gives 3 sub-districts that are divided in cluster respectively.The orthogonal code sets symbol Expression comprises 3 sign indicating numbers, uses respectively

ξ=0,1,2 wherein ..J-1 represents cell id, and J represents the size of cluster sub-district, and the J value is that 3 (J can also get 4,7 ..a in the present invention ²+ ab+b ²(a=0,1,2 ..., b=0,1,2 ...) a, b does not get 0 simultaneously).The concrete dividing mode in sub-district as shown in Figure 1.If the J value is 4, then the sub-district dividing mode is a cluster for being numbered 1,2,3,4 sub-district among Fig. 2; If the J value is 7, then the sub-district dividing mode is for being numbered 1 among Fig. 2, and the sub-district of 2...7 is a cluster, and the rest may be inferred for remaining.Same group of cell orthogonal sign indicating number has following orthogonality:

$\underset{\mathrm{\ξ}=0}{\overset{N-1}{\mathrm{\Σ}}}{c}_j^{\left(\mathrm{occ}\right)}\left(\mathrm{\ξ}\right)c_{j^{\′}}^{{\left(\mathrm{occ}\right)}^{*}}\left(\mathrm{\ξ}\right)=\left\{\begin{array}{cc}1& j=j^{\′}\\ 0& j\≠j^{\′}\end{array}\right.$

The cell orthogonal sign indicating number is that 3 components of 3 orthogonal dimension matrixes get final product.

Second step, guaranteeing that base station synchronization transmits under the condition, further transmit information symbols is added the Cyclic Prefix protection, thereby the mutually orthogonal between 3 sign indicating numbers that the raising receiving terminal receives further improves the inhibition ability of receiving terminal to the neighbor cell interference signal; All base station transmit signals in the receiving terminal place bunch are as follows:

$s^{\left(j\right)}(i,\mathrm{\ξ})=\underset{k=0}{\overset{K-1}{\mathrm{\Σ}}}{c}_j^{\left(\mathrm{occ}\right)}\left(\mathrm{\ξ}\right)d_k^{\left(j\right)}\left(\mathrm{\ξ}\right)\mathrm{for\ξ}=\mathrm{0,1,2}---\left(1\right)$

The signal that receives can be expressed as form:

$r^{\left(j\right)}(i,\mathrm{\ξ})=\underset{j=0}{\overset{2}{\mathrm{\Σ}}}\underset{k=0}{\overset{K-1}{\mathrm{\Σ}}}{s}^{\left(j\right)}(i,\mathrm{\ξ})c_k^{\left(j\right)}\left(i\right)\mathrm{for\ξ}=\mathrm{0,1,2}---\left(2\right)$

Wherein ξ represents symbol sebolic addressing,

The orthogonal code of representing j sub-district, Represent that j base station issue k user's data,

Represent the channel of j base station at i chip.We do following regulation to the signal of base station:

$d_k^{\left(j\right)}\left(0\right)=d_k^{\left(j\right)}\left(1\right)=d_k^{\left(j\right)}\left(2\right)---\left(3\right)$

And the maximum multipath time delay of channel is no more than circulating prefix-length, to guarantee not destroy the circular convolution that transmits with channel.

In the 3rd step, receiving terminal is done cross correlation process to the received signal, the interference of cancellation neighbor cell.Concrete grammar: use

Multiply by and receive vector, promptly obtain transmitting of j base station, wherein in the existing communication system, the sub-district can automatically that this sub-district is used modulation code (be orthogonal code among the present invention when sending information symbol to receiving terminal

Issue receiving terminal, the breath symbol carries out demodulation so that the receiving terminal butt joint is collected mail.

In sum, technical scheme of the present invention is as follows:

A kind of method that suppresses neighbor cell interference the steps include:

1) microzonation in the communication system is divided into many bunches, each bunch comprises an adjacent J sub-district; Wherein cell channel remains unchanged in the duration at J information symbol, and J is a natural number;

2) choose J orthogonal code, distribute to a sub-district respectively with the J in the cluster;

3) J sub-district in the receiving terminal place bunch sends J information symbol simultaneously continuously; Wherein the J that same sub-district a sent information symbol is a J identical information symbol, and each user data that adopts the orthogonal code of this sub-district will send this sub-district carries out the orthogonalization coding;

4) receiving terminal carries out cross correlation process to the information symbol that receives, and demodulates the user data of this receiving terminal.

Further, described J J component that the cell orthogonal sign indicating number is a J orthogonal dimension matrix.

Further, adopt and obtain an orthogonal code sets based on the DFT method, this orthogonal code sets comprises described J cell orthogonal sign indicating number.

Further, the value of J is by formula a ²+ ab+b ²Determine a=0 wherein, 1,2 ..., b=0,1,2 ..., and a, b does not get 0 simultaneously.

Further, J=3.

Further, in the described step 3), each user data that the orthogonal code of this sub-district of employing will send this sub-district behind the interpolation Cyclic Prefix before each information symbol carries out the orthogonalization coding.

Further, with different districts in the cluster J identical information symbol sending continuously be one group of identical J identical information symbol.

Further, with different districts in the cluster one group of different each other J identical information symbol of J identical information symbol of sending continuously.

Further, the method for described cross correlation process is: receiving terminal utilizes the orthogonal code of sub-district, place multiply by and receives vector, demodulates the user data of this receiving terminal.

Further, the most most length that is no more than described Cyclic Prefix through time delay of cell channel.

Good effect of the present invention is:

Compared with prior art, the present invention can eliminate the interference of neighbor cell fully, has improved the dry ratio of letter of received signal, therefore improves spectrum efficiency.

The present invention can find out that to the lifting of believing dry ratio among Fig. 1, the interference of sub-district 1 is from the interference of the sub-district of 6 OCC1 of outer ring by the contrast of Fig. 1 and Fig. 2, and distance is 3R, and wherein R is a radius of society; Among Fig. 2, the interference of sub-district 2 is from the interference of the sub-district that is numbered 2-7 of inner ring, and distance is

By the dry computing formula of letter than amiable distance , the present invention can effectively increase the dry ratio of letter.

The present invention has been by having done orthogonal code modulation to transmitting, and makes that band efficiency is original 1/3, but still is better than traditional code division multiple access system, as shown in Figure 3.

Description of drawings

Fig. 1, OCC technology are to the division N=3 of cellular cell bunch;

Fig. 2, traditional cell cellular model neighbor cell interference model;

The letter drying of Fig. 3, cdma system that OCC technology VS is traditional is than performance comparison chart;

Fig. 4, method flow diagram of the present invention.

Embodiment

Below, by the derivation of formula, detailed does with explanation embodiments of the present invention.The present invention proposes a kind of scheme of eliminating neighbor cell interference, with the quadrature cell code transmitting of forward link done spread spectrum one time, make that the interference signal between the neighbor cell can quadrature, and then eliminated the interference of neighbor cell signal, reached the dry ratio of the letter that improves receiving terminal, band efficiency is 1/3 bandwidth, is 1/4 to compare with traditional C DMA technology band efficiency, has improved band efficiency.This technology both had been suitable for the TDD system, also was suitable for the FDD system.

3 of the restriction of OCC Technology Need require as follows:

At first, consider actual cellular system, we stipulate that 3 sub-districts are cluster (cluster), and the concrete structure schematic diagram is seen Fig. 1;

The second, the base station of 3 sub-districts in the receiving terminal place bunch must guarantee synchronized transmissions, and this is to realize easily in technology at present;

The 3rd, channel remains unchanged in 3 symbol durations.

3 points above satisfying, receiving terminal is by doing cross correlation process to received signal, the signal after the neighbor cell interference that just can be eliminated.Concrete steps are as follows:

The first step defines 3 orthogonal codes, gives 3 sub-districts that are divided in cluster respectively.The orthogonal code sets symbol Expression comprises 3 sign indicating numbers, uses respectively

ξ=0,1,2 wherein ..J-1 represents cell id, and J represents the size of cluster sub-district, and the J value is 3 in the present invention, what deserves to be mentioned is that J can also get 4,7,11 ...The concrete dividing mode in sub-district as shown in Figure 1.Same group of cell orthogonal sign indicating number has following orthogonality:

$\underset{\mathrm{\ξ}=0}{\overset{N-1}{\mathrm{\Σ}}}{c}_j^{\left(\mathrm{occ}\right)}\left(\mathrm{\ξ}\right)c_{j^{\′}}^{{\left(\mathrm{occ}\right)}^{*}}\left(\mathrm{\ξ}\right)=\left\{\begin{array}{cc}1& j=j^{\′}\\ 0& j\≠j^{\′}\end{array}\right.$

The cell orthogonal sign indicating number is that 3 components of 3 orthogonal dimension matrixes get final product, and the present invention adopts the orthogonal code sets that obtains based on the DFT method, and concrete form is as follows:

$\left[\begin{array}{c}{c}_0^{\left(\mathrm{occ}\right)}\left(\mathrm{\&xi;}\right)\\ c_1^{\left(\mathrm{occ}\right)}\left(\mathrm{\&xi;}\right)\\ c_2^{\left(\mathrm{occ}\right)}\left(\mathrm{\&xi;}\right)\end{array}\right]=\left[\begin{array}{ccc}1& 1& 1\\ 1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{4\mathrm{\&pi;}}{3}}\\ 1& e^{\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{4\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}\end{array}\right]$

Second step, guaranteeing that base station synchronization transmits under the condition, further transmit information symbols is added the Cyclic Prefix protection, thereby the mutually orthogonal between 3 sign indicating numbers that the raising receiving terminal receives further improves the inhibition ability of receiving terminal to the neighbor cell interference signal; Base station transmit signals in the receiving terminal place bunch is as follows:

$s^{\left(j\right)}(i,\mathrm{\&xi;})=\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{c}_j^{\left(\mathrm{occ}\right)}\left(\mathrm{\&xi;}\right)d_k^{\left(j\right)}\left(\mathrm{\&xi;}\right)\mathrm{for\&xi;}=\mathrm{0,1,2}---\left(4\right)$

The signal that receives can be expressed as form:

$r^{\left(j\right)}(i,\mathrm{\&xi;})=\underset{j=0}{\overset{2}{\mathrm{\&Sigma;}}}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{s}^{\left(j\right)}(i,\mathrm{\&xi;})c_k^{\left(j\right)}\left(i\right)\mathrm{for\&xi;}=\mathrm{0,1,2}---\left(5\right)$

Wherein ξ represents symbol sebolic addressing,

The orthogonal code of representing j sub-district,

Represent that j base station issue k user's data,

Represent the channel of j base station at i chip.We do following regulation to the signal of base station:

$d_k^{\left(j\right)}\left(0\right)=d_k^{\left(j\right)}\left(1\right)=d_k^{\left(j\right)}\left(2\right)---\left(6\right)$

And the maximum multipath time delay of channel is no more than circulating prefix-length, to guarantee not destroy the circular convolution that transmits with channel.

In the 3rd step, receiving terminal is done cross correlation process to the received signal, the interference of cancellation neighbor cell.Concrete grammar: the form of the signal that receives being write as matrix is as follows

$\left[\begin{array}{c}{s}^{\left(0\right)}(i,\mathrm{\&xi;})\\ s^{\left(1\right)}(i,\mathrm{\&xi;})\\ s^{\left(2\right)}(i,\mathrm{\&xi;})\end{array}\right]={\left[\begin{array}{ccc}1& 1& 1\\ 1& {\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j& {\mathrm{<figure-callout\; id="4"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j\\ 1& {\mathrm{<figure-callout\; id="4"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j& {\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j\end{array}\right]}^T\left[\begin{array}{c}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(0\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(0\right)}\left(i\right)\\ \underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(1\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(1\right)}\left(i\right)\\ \underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(2\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(2\right)}\left(i\right)\end{array}\right]$

With

Multiply by and receive vector, promptly obtain transmitting of j base station.With j=0 is the process that coherent detection is done in the example demonstration:

$c_0^{\left(\mathrm{OCC}\right)}\left[\begin{array}{c}{s}^{\left(0\right)}(i,\mathrm{\&xi;})\\ s^{\left(1\right)}(i,\mathrm{\&xi;})\\ s^{\left(2\right)}(i,\mathrm{\&xi;})\end{array}\right]=\left[\begin{array}{ccc}1& 1& 1\end{array}\right]{\left[\begin{array}{ccc}1& 1& 1\\ 1& {\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j& {\mathrm{<figure-callout\; id="4"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j\\ 1& {\mathrm{<figure-callout\; id="4"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j& {\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HSA00000228491300021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j\end{array}\right]}^H\left[\begin{array}{c}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(0\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(0\right)}\left(i\right)\\ \underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(1\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(1\right)}\left(i\right)\\ \underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(2\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(2\right)}\left(i\right)\end{array}\right]$

$=\left[\begin{array}{ccc}1& 0& 0\end{array}\right]\left[\begin{array}{c}\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(0\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(0\right)}\left(i\right)\\ \underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(1\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(1\right)}\left(i\right)\\ \underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(2\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(2\right)}\left(i\right)\end{array}\right]=\underset{k=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{d}_k^{\left(0\right)}\left(\mathrm{\&xi;}\right)c_k^{\left(0\right)}\left(i\right)$

The signal from base station 1,2 disturbs in the received signal thereby eliminated.

Claims (10)

1. a method that suppresses neighbor cell interference the steps include:

1) microzonation in the communication system is divided into many bunches, each bunch comprises an adjacent J sub-district; Wherein cell channel remains unchanged in the duration at J information symbol, and J is a natural number;

2) choose J orthogonal code, distribute to a sub-district respectively with the J in the cluster;

3) J sub-district in the receiving terminal place bunch sends J information symbol simultaneously continuously; Wherein the J that same sub-district a sent information symbol is a J identical information symbol, and each user data that adopts the orthogonal code of this sub-district will send this sub-district carries out the orthogonalization coding;

4) receiving terminal carries out cross correlation process to the information symbol that receives, and demodulates the user data of this receiving terminal.

2. the method for claim 1 is characterized in that described J cell orthogonal sign indicating number is J component of J orthogonal dimension matrix.

3. method as claimed in claim 2 is characterized in that adopting obtaining an orthogonal code sets based on the DFT method, and this orthogonal code sets comprises described J cell orthogonal sign indicating number.

4. method as claimed in claim 1 or 2, the value that it is characterized in that J is by formula a ²+ ab+b ²Determine, a=0 wherein, 1,2..., b=0,1,2..., and a, b do not get 0 simultaneously.

5. method as claimed in claim 4 is characterized in that J=3.

6. the method for claim 1 is characterized in that in the described step 3), and each user data that the orthogonal code of this sub-district of employing will send this sub-district behind the interpolation Cyclic Prefix before each information symbol carries out the orthogonalization coding.

7. as claim 1 or 6 described methods, it is characterized in that with different districts in the cluster J identical information symbol sending continuously be one group of identical J identical information symbol.

8. as claim 1 or 6 described methods, it is characterized in that with different districts in the cluster one group of different each other J identical information symbol of J identical information symbol of sending continuously.

9. the method for claim 1 is characterized in that the method for described cross correlation process is: receiving terminal utilizes the orthogonal code of sub-district, place multiply by and receives vector, demodulates the user data of this receiving terminal.

10. the method for claim 1 is characterized in that the most most length that is no more than described Cyclic Prefix through time delay of cell channel.

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