WO2008124983A1

WO2008124983A1 - Method for restraining same-frequency-interference by scheduling in network-organizing

Info

Publication number: WO2008124983A1
Application number: PCT/CN2007/003418
Authority: WO
Inventors: Sean Cai; Ying Liu
Original assignee: Zte Corporation
Priority date: 2007-04-11
Filing date: 2007-12-03
Publication date: 2008-10-23
Also published as: CN101286786A; CN101286786B

Abstract

A method for restraining same-frequency-interference by scheduling comprises the following steps: (1) acquiring the potential interference environment of the users in each cell for the users in the other cells; (2) classifying or sorting for the users in each cell based on the potential interference environment; (3) according to the classifying or sorting result, scheduling the users in each cell so that the allocated resources for one or more users who have the strongest potential interference for each cell in local cell and the other cells, stagger from each other in the same system time-frequency resources space. The method could restrainthe same-frequency-interference between cells, promote the receiving performance for edge user, increase the cell coverage, and promote the system throughput and spectrum efficiency.

Description

Method for performing interference suppression of co-frequency networking by scheduling

Technical field

The present invention relates to a co-channel interference suppression method for a wireless communication system, and more particularly to a co-channel interference suppression method in an OFDM system. Background technique

The interferences of wireless and mobile communication systems mainly include co-channel interference, adjacent-frequency interference, out-of-band interference, and intermodulation interference. The co-channel interference of the system means that some or all cells in the network use the same frequency point for data transmission, and there is mutual signal interference between the cells. Co-channel interference can be generally classified into small-area interference, small-area interference, interference between different communication systems, interference between different operators, and interference caused by system equipment.

The interference in the small area mainly includes multipath interference, near-far effect and multiple access interference. The generation of these disturbances is determined by the time-varying nature of the wireless channel and the delay and fading during electromagnetic wave propagation. It can be alleviated by modulation and demodulation technology, power control technology, and the like.

Inter-cell interference, or ICI for short, is an inherent problem in cellular mobile communication systems. The traditional solution is to use frequency reuse. Common multiplexing coefficients are 1, 3, and 7, etc. A multiplexing factor of 1 means that neighboring cells use the same frequency resource, and the interference at the cell edge is very serious. A higher multiplexing factor (3 or 7) can effectively suppress ICI, but the spectral efficiency will be reduced to 1/3 or 1/7.

Wireless mobile communication systems are increasingly demanding spectrum efficiency, and it is expected that intra-frequency networking can be performed to improve system efficiency. However, in the same frequency networking, if the co-channel interference problem between cells cannot be effectively solved, the spectrum efficiency of the system will be reduced, the system coverage will be reduced, and the system traffic will be lost.

Currently used interference suppression techniques include interference randomization, interference coordination, and interference cancellation. Interference randomization can not reduce the energy of interference, but can randomize the interference into "white noise", thus suppressing the harm of ICI, so it is also called "interference whitening". Methods for interference randomization include: scrambling, interleaving multiple access IDMA, and frequency hopping.

The interference cancellation technology is derived from multi-user detection technology, which can demodulate and solve the signal of the interfering cell. The code then copies and subtracts the ICI from the cell. IDMA cancellation technology based on IDMA means that different interleaving patterns are generated by a pseudo-random interleaver and allocated to different cells. The receiver can deinterleave the target signal and the interference signal by using different interleaving patterns, and then respectively, and then the target signal and the interference signal are respectively solved, and then Perform ICI elimination. This combination of technology and iterative receiver technology yields significant performance gains. The advantage of ICI cancellation compared with ICI coordination is that there is no limit to the frequency resources at the cell edge, and the cell edge spectral efficiency is 1 and the total spectral efficiency is 1. However, the computational complexity is high, which increases the requirements for the receiver's processing power.

Interference coordination is also referred to as "soft frequency reuse," or "partial frequency reuse," and IEEE 802.20 MBFDD / MBTDD uses this technology, and LTE is also considering this approach. This method divides the frequency resources into several multiplexed sets. Users in the cell center can use lower power transmission and reception. Even if they occupy the same frequency, they will not cause strong ICI, so they are allocated at the reuse coefficient. The multiplexing set of 1; the user at the cell edge needs to use higher power transmission and reception, which may cause strong ICI, and thus is allocated in a multiplexing set with a frequency reuse coefficient of N. The drawback of this technique is that the frequency resources at the cell edge are limited, and it is difficult to support a large number of users and a high data rate.

Other technologies, such as MIMO, smart antennas, partial power control, etc., can also be used for ICI suppression, but there are still various problems. Therefore, how to improve the spectrum efficiency of the wireless mobile communication system and solve the interference problem existing in the same frequency network has become an urgent problem to be solved.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for performing interference suppression in the same frequency group by scheduling, and to solve the problem of how to improve the spectrum efficiency of the wireless mobile communication system and solve the interference problem in the same frequency networking in the prior art. To solve the above technical problem, the present invention provides a method for performing interference suppression in the same frequency network by scheduling, which includes the following steps:

(1) obtaining potential interference of users in each cell to users in other cells;

(2) classifying or sorting users in each cell according to the potential interference situation of the user;

(3) scheduling, according to the result of the classification or sorting, users in each cell, so that the current cell and other cells are allocated to one or more users with the strongest interference in the respective cells. The resources are staggered in the same system time-frequency resource space. Further, in the method of the present invention, in the step (1), the interference indicator parameter of each cell user is obtained and summarized from each cell by using a main control module. In order to determine the potential interference situation of each user; or, the cell obtains the interference indicator parameter of the user in the cell, and determines the potential interference situation of each user; further, the method according to the present invention, wherein the interference The indicator parameter includes a combination of one or more of the following: an average transmit power of each user in the cell, an average link quality indicator, and an average link rate indication; further, the method according to the present invention, wherein, step (2) The user is divided into two types: an interfering user and a non-interfering user; in step (3), the resources allocated for other cell interfering users are staggered in the same system time-frequency resource space; further, the method according to the present invention In the step (2), when classifying users, according to users in each cell to users in other cells The potential interference conditions are randomly arranged, and then classified according to a set threshold value, and the user is divided into an interference user and a non-interfering user;

Or, according to the potential interference situation of the users in the other cell in the cell, the user is divided into the interfering user and the non-interfering user. Further, the method of the present invention, where the cell and other cells are not The interfering user occupies the same system time-frequency resource space, and the interfering user of the cell and other cells divides the remaining system time-frequency resource space; further, the method according to the present invention, where the cell and other cells are The interfering user occupies resources of different blocks in the system time-frequency resource space, and the non-interfering user of the cell and other cells occupy the remaining system time-frequency resource space; further, the method according to the present invention, wherein, step (3) The cells are sequentially scheduled according to the user ranking result, and the resources allocated by the local cell and other cells for the user occupy all the system time-frequency resource space, but when the different cells are mapped at the physical layer (that is, the physical layer resources are allocated to the user). Starting from different initial positions of time or frequency, in the same time or frequency order, when the mapping reaches the end of the resource space, and then back to the head end of the resource space for mapping; further, the method according to the present invention, wherein The order in which the users in each cell sort the potential interferences of users in other cells is from strong to weak; further, the method according to the present invention, wherein the initial time of the current cell and other cells Or the interval between the frequency positions is 1/N of the time domain or the frequency domain length of the system time-frequency resource space, where N is the number of the cell and the other cell; further, the method according to the present invention, wherein the other cell The neighboring cell of the cell, or the neighboring cell and the non-adjacent cell that cause interference to the cell; further, the method of the present invention, wherein the system time-frequency resource space is an OFDMA system radio interface physical frame , or a partial time-frequency region in the frame for resource allocation.

Compared with the prior art, the method of the present invention can effectively overcome inter-cell co-channel interference, improve edge user reception performance, increase cell coverage, and improve system traffic and spectrum efficiency. BRIEF abstract

1 is a network configuration in a typical wireless mobile communication system described in the prior art, and when inter-frequency networking is performed, relatively serious inter-cell interference occurs;

2 is a schematic diagram of frame scheduling of an OFDMA system at a certain time;

3 is a schematic diagram of frame scheduling of an OFDMA system at a certain time;

4 is a schematic diagram of an interference suppression scheduling mode 1 according to an embodiment of the present invention; FIG. 5 is a schematic diagram of interference suppression scheduling mode 2 according to an embodiment of the present invention; FIG. 6 is an interference according to an embodiment of the present invention. FIG. 7 is a schematic diagram of an interference suppression scheduling manner 4 according to an embodiment of the present invention; FIG. 8 is a schematic diagram of an interference suppression scheduling manner 5 according to an embodiment of the present invention; The embodiment is a schematic diagram of the interference suppression scheduling mode 6. Preferred embodiment of the invention

The present invention is mainly directed to a problem of system performance degradation caused by inter-cell interference in a wireless communication system in a wireless communication system, and a related solution for interference suppression is proposed, which aims to reduce inter-cell interference and increase by effective interference suppression technology. Coverage and flow, improve the spectral efficiency of the system.

The core idea of the method for performing interference suppression in the same frequency group by scheduling according to the present invention is as follows: (1) each cell classifies or ranks potential interferences of other cells according to users in the cell; (2) each cell performs scheduling based on user classification or ordering, and The users with high potential interference are interleaved in the same system time-frequency resource space of the cell and other cells, that is, users who have potential interference with each other are interleaved in the same system time-frequency resource space of the respective cells.

The other cell may be a neighboring cell of the local cell, or may be a neighboring cell and a non-adjacent cell that cause interference to the local cell, and may be determined according to the configuration or determined according to the detected interference information. The embodiments of the present invention are further described in the following, but are not intended to limit the present invention.

The interference suppression method of the present invention is applied to a wireless communication system, and the system specifically includes the following parts:

(1) At least two base stations, each of which transmits downlink and uplink control information (including scheduling information) to terminals within its cell range

The uplink and downlink control information refers to the information transmitted between the base station and the terminal; the control information related to the interference suppression is mainly: the downlink scheduling information sent by the base station, the uplink scheduling information sent by the base station, and the related terminal information sent by the base station. Request information.

(2) at least one terminal communicating with the base station of the cell in each cell

(3) The frequency deployment of two adjacent base stations is the same, and there is co-channel interference between adjacent cells.

A method for performing interference suppression of the same frequency network by scheduling according to the present invention will be further described below with reference to the accompanying drawings. The specific embodiments are described in detail below, but are not intended to limit the present invention.

As shown in FIG. 1, two cells controlled by the base stations BS1 and BS2 are adjacent. Terminal SS1 and SS2 Located within the coverage of BS1; terminals SS3 and SS4 are located within the coverage of BS2. SS1 and SS3 are located at the edge of the cell, and data transmission is generally performed with a relatively large uplink transmission power. In the same frequency networking, more serious inter-cell interference will occur.

As shown in Figure 2 and Figure 3, it is assumed that BS1 and BS2 in the figure are co-frequency networking. When SS1 and SS3 are respectively allocated on the uplink burst 1 of BS1 and BS2 for data transmission, since the time-frequency regions of the two bursts have overlapping portions, the two SSs received by the two BSs at the position are The uplink signals will interfere with each other, resulting in a decrease in the received signal-to-noise ratio, thereby increasing the bit error rate, reducing the transmission efficiency, and even causing dropped calls. Ultimately, the coverage and flow of the entire system is reduced.

The following takes the OFDMA system as an example, and further describes the implementation of the technical solution in conjunction with the drawings. The basic implementation steps are as follows:

(1) Each cell base station transmits downlink and uplink control information (including scheduling information);

(2) each base station receives uplink data of the corresponding terminal in the cell;

(3) Each cell classifies or ranks the strength of potential interference of users in neighboring cells according to users in each cell;

The following metrics can be used to measure the strength of potential interference for users in neighboring cells in each cell:

a) average transmit power of each user in each cell

b) average link quality indications for each user in each cell, such as SNR, RSSI, CINR, etc. c) Average link rate indications for each user in each cell, such as DIUC, UIUC, TFI, etc.

A main control module may be configured to perform information interaction with each cell base station to obtain user interference indicator parameters of each cell; and then, by using a main control module to summarize interference parameter parameters and scheduling information of users in each cell, the potential interference situation of each user is determined. Regarding the specific method herein, various methods described in the Chinese Patent Application No. 200710073801.0, the "Same Frequency Interference Suppression Method for a Wireless Communication System", which is filed by the present applicant, can be used. However, the present invention focuses on how to suppress interference caused by users with large interference to adjacent cells, and does not limit how to classify or sort users. For example, each cell can also be classified or sorted according to the configured threshold independently. The user's classification can be as follows:

Method 1: According to the strength of potential interference of users in neighboring cells in each cell, they are randomly arranged, and then divided into several categories by a certain threshold. For example, by setting a threshold, they are divided into two categories: interference For users and non-scrambled users, the following will be further scheduled according to the classification.

Method 2: According to the user's potential interference in the neighboring cell according to the strength of the user in each cell, and then divided into several categories by a certain threshold value, for example, by setting a threshold, it is divided into two categories: Disturb users and non-interfering users.

Method 3: Sort the strength of potential interference of users in the neighboring cell according to the user in each cell, and then classify according to the preset number of interference or non-interfering users, for example, the maximum number of interfering users in the current cell setting For example, the maximum number of non-interfering users is 15. In the order of potential interference from strong to weak, the first 10 users are selected as the interference users, and the last 15 users are selected as non-interfering users.

The interfering users mentioned in this document refer to users who may generate strong interference to neighboring cell users; non-interfering users refer to users who are less likely to generate strong interference to neighboring cell users. Of course, in other embodiments, it can be divided into three or more categories.

(4) Each cell then schedules the user based on user classification or ordering to achieve the purpose of suppressing or eliminating co-channel interference.

The following embodiments describe three neighboring cells. The principle of scheduling may be as follows: Method 1:

As shown in FIG. 4, the three sub-pictures in the figure respectively correspond to the resource space of three adjacent cells/sector i at the same time, and may be part of the time-frequency area of the physical frame or frame of the OFDMA system for resource allocation. The resource space of each cell/sector is divided into two zones, zonel and zone2, and the zone zonel is frequency-divided, that is, divided into multiple frequency bands, each cell uses only one of the frequency bands, and the cell/sector 1 is used. It is zonel 1, zone/sector 2 is zone21, and cell/sector 3 is zone31. Each cell/sector uses all resources of zone zone2.

In the scheduling process, the interfering users of the cell i are allocated in the area zoneil, and the area zoneil is interleaved by frequency division, so that each cell occupies a part of the resource space in the area zonel, leaving The other unoccupied resource space is used by the interfering users of the neighboring cells, so that each cell does not conflict with each other and avoids interference; at the same time, the non-interfering users are allocated in the same area zone 2, and both occupy the area zone 2 The entire resource space. In the case of the intra-frequency networking, the frequency of the zoneil of the neighboring cell/sector can ensure that interference cannot occur between users who may generate large interference in each cell, thereby achieving the purpose of interference suppression. The user assigned in Zonei2 is a user who is unlikely to generate large interference. Therefore, the area occupies the entire bandwidth, and the frequency reuse coefficient of the allocation time is 1, which can improve the bandwidth efficiency of the system.

The size division of the area can be adaptively adjusted according to the interference user load condition of each cell to improve the bandwidth efficiency when the interference of the user load is small.

Method Two:

As shown in Figure 5, the three sub-pictures in the figure correspond to the resource space of three adjacent cells/sector i at the same time. The resource space of each cell/sector is divided into two zones, zonel and zone2, and the zone zonel is divided into multiple time slots. Each cell uses only one of the time slots, and the cell/sector 1 uses Zonel 1 , cell/sector 2 uses zone 21 and cell/sector 3 uses zone 31. Each cell/sector uses all resources of zone zone2.

In the scheduling process, the interfering users of the cell i are allocated to the area zoneil, and the area zones are interleaved by time division. Thus, each cell occupies a part of the resource space in the area zonel, leaving other unoccupied resource space to the phase. The neighboring cell is used by the interfering user, so that each cell does not conflict with each other and avoids interference; at the same time, all non-interfering users are allocated in the same area zone2, and occupy the entire resource space on the zone zone2. In the case of the intra-frequency networking, due to the zoneil time division of the neighboring cell/sector, it is ensured that interference may not occur between users who may cause large interference in each cell, thereby achieving the purpose of interference suppression. The user assigned in Zonei2 is a user who is unlikely to generate large interference. Therefore, the area occupies the entire bandwidth, and the frequency reuse coefficient of the allocation time is 1, which can improve the bandwidth efficiency of the system.

The size division of the area can be adaptively adjusted according to the interference user load condition of each cell to improve bandwidth efficiency when the interference user load is small.

Method three:

As shown in Figure 6, the three sub-pictures in the figure correspond to the resources of three adjacent cells/sectors i at the same time. Source space. The resource space of each cell/sector is divided into two zones, zoneil and zonei2, by frequency division, in which the zone zoneil of each cell/sector is staggered throughout the time domain, and zonei2 is the remaining zone other than zoneil, each The resource space of the cell/sector does not contain free areas that cannot be used.

In the scheduling process, the interfering users of the cell i are allocated on the area zoneil, and the area zoneil is distributed over the entire resource space by time division, and the area zoneil of each cell does not conflict with each other; meanwhile, the non-interfering users are allocated in the area zonei2 . In the case of the intra-frequency networking, due to the zoneil time division of the neighboring cell/sector, it can be ensured that there is no interference between users that may cause large interference in each cell, and the interfering user of the cell i may only be different from the cell j. Interfering users are scheduled at the same time. In this way, the purpose of interference suppression is achieved, and the frequency reuse of all transmission time of the system is guaranteed to be 1, which further improves the bandwidth utilization.

Method 4: As shown in Figure 7, similar to the method of Method 3, the same effect can be achieved by changing the time division that interferes with the user into a frequency division relationship.

The three subgraphs in the figure correspond to the resource space of three adjacent cells/sector i at the same time. The resource space of each cell/sector is divided into two zones, zoneil and zonei2, by frequency division, where the zone zoneil of each cell/sector is staggered throughout the frequency domain, and zonei2 is the zone other than zoneil, each The resource space of the cell/sector does not contain free areas that cannot be used.

In the scheduling process, the interfering users of the cell i are allocated on the area zoneil, and the area zoneil is distributed in the entire resource space according to the frequency division, and the area zoneil of each cell does not conflict with each other; meanwhile, the non-interfering users are allocated in the area. Zonei2. In the case of the intra-frequency networking, due to the frequency division of the neighboring cells/sectors, it is ensured that there is no interference between users that may cause large interference in each cell, and the interfering users of the cell i may only be related to the cell j. Non-interfering users are scheduled at the same frequency division.

Method five two

As shown in Figure 8, the three sub-pictures in the figure correspond to the resource space on three adjacent cells/sector i at the same time. For unoccupied resource space, each cell/sector is no longer divided into fixed areas.

Before scheduling, according to the strength of potential interference of users in neighboring cells in each cell, the order is from strong to weak (or weak to strong). In the scheduling process, in this order Users, when mapping in the actual physical layer, different cells start from different initial time positions in the same system resource space and perform physical layer mapping in chronological order (small to large or large to small), and the mapping reaches the end of the resource space. At the end, it is transferred back to the head end of the resource space for mapping, so that the allocation can eventually fill the entire resource space.

It is assumed that the interval between the initial time positions of the neighboring cell physical layer mapping is the resource space length /n, so that the maximum interfering users occupying the resource space length /n between the cells will not affect each other. This method does not need to divide the area, reduces the control message overhead of the area description, and achieves the same bandwidth utilization and interference suppression effect as the third method in a more flexible manner.

Method 6: As shown in Figure 9, similar to the method of Method 5, only the time division that interferes with the user is changed into a frequency division relationship, and the time offset becomes a frequency offset, and the same effect can be achieved.

The three sub-pictures in the figure correspond to the resource space on three adjacent cells/sector i at the same time. For unoccupied resource space, each cell/sector is no longer divided into fixed areas.

Before the scheduling, the user's potential interference to the users in the neighboring cell is ranked according to the strength of the user in each cell, and the order is from strong to weak (or weak to strong). During the scheduling process, the users are tuned in this order. In actual physical layer mapping, different cells start with different initial frequency positions in the resource space and perform physical layer mapping according to the frequency order (large to small or small to large). When the mapping reaches the end of the resource space, it returns. Switch back to the head end of the resource space for mapping to ensure that the allocation eventually fills the entire resource space.

Assuming that the interval between the initial frequency positions of the physical layer mappings of the n neighboring cells is the resource space length /n, it can be ensured that the maximum interfering users occupying the resource space length /n between the cells do not affect each other.

Method 7: It is also possible to combine the potential interference of the users of each cell and the Qos requirements, and then schedule according to Method 5 or Method 6 above.

Each cell performs power reduction, rate reduction, and link adaptation processing for the primary interfering terminal with lower Qos requirements, and then processes it as a non-interfering user.

There are a variety of other modifications and variations that can be made by those skilled in the art without departing from the spirit and scope of the invention. However, such corresponding changes and modifications are intended to be included within the scope of the appended claims.

Industrial applicability

The invention provides a method for interference suppression in a wireless communication system, which can effectively overcome inter-cell co-channel interference, improve edge user reception performance, increase cell coverage, improve system traffic and spectrum efficiency, and therefore has industrial practicality. Sex.

Claims

Claim

A method for performing interference suppression in a same frequency network by scheduling, characterized in that the method comprises the following steps:

(3) scheduling, according to the result of the classification or sorting, users in each cell, so that the resources allocated by the current cell and other cells to the one or more users with the strongest interference in the respective cells are in the same system time-frequency The resource space is staggered from each other.

The method according to claim 1, wherein in the step (1), the interference parameter of each user of the cell is obtained from each cell through a main control module, and the potential interference situation of each user is determined. Or, the cells obtain the interference indicator parameters of the users in the cell, and determine the potential interference situation of each user.

The method according to claim 2, wherein the interference indicator parameter comprises a combination of one or more of the following: an average transmit power, an average link quality indicator, and an average link of each user in the cell. Rate indication.

The method according to claim 1, wherein the step (2) divides the user into two types: an interfering user and a non-interfering user; and (3) scheduling, the resources allocated to the other cell interfering users are in the same The system time-frequency resource space is staggered from each other.

The method according to claim 4, wherein when the user is classified in step (2), the potential interference of the users in other cells in each cell is randomly arranged, and then the set threshold is set. Classify the boundaries and classify users into interfering users and non-interfering users;

Or, according to the user's potential interference situation of users in other cells in each cell, and then sorted according to a set threshold value or according to each type of preset user number, the user is divided into interference users and non- Interfere with users.

The method according to claim 4, wherein the non-interfering user of the current cell and other cells occupy the same system time-frequency resource space, and the interference of the local cell and other cells is used. The user divides the remaining system time-frequency resource space.

The method according to claim 4, wherein the sub-interference of the cell and other cells interferes with the resources of different blocks in the time-frequency resource space of the system, and the non-interfering users of the cell and other cells occupy the remaining System time-frequency resource space.

The method according to claim 1, wherein in step (3), each cell sequentially schedules users based on user ranking results, and resources allocated by the cell and other cells for users occupy all system time-frequency resources. Space, but different cells start with different time or frequency initial positions when mapping in the physical layer, in the same time or frequency order, when the mapping reaches the end of the resource space, then return to the head end of the resource space for mapping.

9. The method according to claim 8, wherein the order of sorting potential interferences of users in other cells in each cell is from strong to weak.

The method according to claim 8, wherein the interval between the initial time or the frequency position of the local cell and the other cell is 1 N, N of the time domain or the frequency domain length of the system time-frequency resource space. The number of the current cell and other cells.

The method according to any one of claims 1 to 10, wherein the other cell is a neighboring cell of the current cell, or a neighboring cell and a non-adjacent cell causing interference to the local cell.

The method according to any one of claims 1 to 10, wherein the system time-frequency resource space is an OFDMA system radio interface physical frame, or a partial time-frequency region in a frame for resource allocation.