WO2007107097A1

WO2007107097A1 - Orthogonal frequency division multiplexing based cell users communicating method and system

Info

Publication number: WO2007107097A1
Application number: PCT/CN2007/000865
Authority: WO
Inventors: Bin Li
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-03-17
Filing date: 2007-03-16
Publication date: 2007-09-27
Also published as: CN101039500A; CN101039500B

Abstract

AN Orthogonal frequency division multiplexing based cell users communication method, which includes a step of grouping users within each cell of the orthogonal frequency division multiplexing mobile communication system; and a step of allowing users within a cell occupying different time domain symbol resources when transferring communication data. Also an orthogonal frequency division multiplexing based cell users communication system. The invention can reduce the interference between the users within a cell and between the cells of the mobile communication system.

Description

Cell user communication method based on orthogonal frequency division multiplexing and system thereof

The present invention relates to Orthogonal Frequency Division Multiplexing (OFDM) technology in the field of mobile communications, and in particular to a small OFDM based Orthogonal Frequency Division Multiplexing (OFDM)

5-zone user communication method and its system. Background technique

At present, multi-carrier technology has become a hotspot technology for broadband wireless communication. The basic idea is to divide a wideband carrier into multiple sub-carriers and simultaneously transmit data on multiple divided sub-carriers.

10 , Orthogonal Frequency Division Multiplex (OFDM) is a relatively representative technology of multi-carrier technology, which divides a given channel into several orthogonal sub-channels in the frequency domain, and allows sub-sub-channels. The carrier spectrum is partially overlapped because different data signals can be separated from the overlapping subcarriers as long as the different subcarriers are orthogonal to each other.

Since Orthogonal Frequency Division Multiplexing (OFDM) technology has better anti-multipath attenuation capability, it has been widely used in cellular mobile communication systems. However, it is well known that in cellular mobile communication systems, there are inevitable mutual interferences between users within the cell and mutual interference between users in each cell. User interference in these cells and user interference between cells may seriously affect the mobile communication system. User capacity, therefore, in order to improve the user capacity of the cellular mobile communication system, how to reduce the 20-cell interference in the cell and the inter-cell user interference inherent in the cellular mobile communication system is a problem that the industry has attached great importance to now.

In order to solve the negative impact of intra-cell user interference and inter-cell user interference on the system user capacity in the cellular mobile communication system, two simple solutions are proposed: The first one is adopted between adjacent cells. Different frequencies to carry data> This can avoid mutual interference between users in the cell, but this solution is due to the difference between adjacent cells.

25 using different frequencies to carry data, thus naturally reducing the frequency utilization;

The second is based on Code Division Multiple Access (CDMA) technology, where all neighboring cells adopt phase The same frequency is used to carry data to obtain higher frequency utilization. Different mobile users use different random spreading code sequences to distinguish between them, so that user interference in the cell and user interference between cells are spread by signal. It has been randomized, but this solution does not completely eliminate user interference and inter-cell user interference in the cell, so that intra-cell user interference and inter-cell user interference still exist in the CDMA system, resulting in the user capacity in the CDMA system still being affected. The limit. Summary of the invention

Embodiments of the present invention provide a cell user communication method based on orthogonal frequency division multiplexing and a system thereof, so as to improve user frequency interference and small-interval user interference in a mobile communication system while improving frequency utilization.

A cell user communication method based on orthogonal frequency division multiplexing according to an embodiment of the present invention includes the steps of: performing packet processing on users in each cell in an orthogonal frequency division multiplexing mobile communication system; and making different groups in the cell Users respectively occupy different time domain symbol resources for transmission of communication data.

A cell user communication system based on orthogonal frequency division multiplexing according to an embodiment of the present invention includes: a packet processing unit, configured to perform grouping processing on users in each cell in an orthogonal frequency division multiplexing mobile communication system; And a transmitting unit, configured to enable different group users in the cell processed by the packet processing unit to respectively use different time domain symbol resources to transmit the communication data.

The embodiment of the present invention transmits the communication data of the user in each cell in the OFDM cellular mobile communication system, so that different group users in the cell can avoid the user interference in the cell by using different subcarriers to carry the communication data. At the same time, the inter-cell user interference is reduced due to the intra-cell trust data. Therefore, the embodiments of the present invention can greatly reduce the inter-cell user interference and the intra-cell user interference in the OFDM cellular mobile communication system on the basis of saving frequency resources, thereby improving the user capacity of the OFDM cellular mobile communication system. DRAWINGS

1 is a schematic flowchart of an embodiment of a OFDM-based cell user communication method according to the present invention; FIG. 2 is a schematic diagram of an embodiment of a group user state in which users in the same cell are divided into two groups according to the method of the present invention;

3 is a schematic diagram of an embodiment of an OFDM time-frequency resource distribution state in which different packet users in a cell respectively occupy different subframe time-domain symbol resources to perform communication data transmission based on the principle of the method of the present invention;

4 is a schematic diagram of an embodiment of a first OFDM time-frequency resource distribution state in which different packet users in a cell respectively occupy the same subframe time-domain symbol resource to perform communication data transmission based on the principle of the method of the present invention;

FIG. 5 is a schematic diagram of a second OFDM time-frequency resource distribution state according to the principle of the method of the present invention, in which different packet users in a cell respectively occupy the same subframe time-domain symbol resource to perform communication data transmission;

6 is a structural block diagram of an embodiment of a OFDM-based cell user communication system according to the present invention; FIG. 7 is a block diagram showing the structure of an embodiment of a system after adding a spread spectrum processing unit in the system of the present invention; FIG. 8 is a flowchart of adding error correction coding in the system of the present invention; The embodiment after the unit constitutes a structural block diagram. detailed description

Since OFDM technology will be widely used in cellular mobile communication systems, in order to improve the user capacity of mobile communication systems, how to reduce intra-cell user interference and inter-cell user interference inherent in OFDM cellular mobile communication systems will be very important. The problem is that, in the embodiment of the present invention, the mobile subscriber located at the cell boundary is characterized by the inter-cell interference, and an OFDM scheme based on the interference situation is proposed, so that the inter-cell user interference and the cell are caused. Internal user interference is greatly reduced to fundamentally improve the user capacity of the mobile communication system.

In an OFDM mobile communication system, communication data is generally transmitted in parallel using a plurality of subcarriers. The method, that is, several OFDM symbols (such as 6 OFDM symbols) constitute one subframe, and the subcarriers in which each OFDM symbol is located may be allocated to one or more users for carrying communication data in different time periods, which is assumed in the embodiment of the present invention. The OFDM symbols used by the base stations of the respective cells remain synchronized or quasi-synchronized in time.

The implementation principle, the specific implementation manner and the corresponding beneficial effects that can be achieved by the solution of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, the figure is a schematic flowchart of an embodiment of a OFDM-based cell user communication method according to the present invention. The implementation process is as follows:

Step 10: Perform packet processing on users in each cell in the OFDM mobile communication system. The solution according to the present invention is based on different interference characteristics of different users in the same cell, and proposes according to the strength of the user's interference (or according to the received signal by the user). Signal-to-noise ratio (SNR) is used to group users in the same cell, that is, to group users with weaker interference (or higher signal-to-noise of received signals), and will be more interfered. Users of the user (or the signal-to-noise ratio of the received signal is low) are divided into another group, wherein the number of divided groups is two or more.

As can be seen, the embodiment of the present invention can perform grouping processing on users in the same cell based on one of the following three methods. Of course, in the specific implementation process, other packet processing methods are also available:

The first mode: The user in the cell can be grouped according to the order of the received signal strength of each user in the cell, and the specific implementation process is as follows:

Determining, in advance, a signal strength ratio threshold value for dividing adjacent packets;

The user in the cell receives and measures the signal strength transmitted from the transmitters of different base stations; and compares the ratio of the received strongest signal strength to the strength of the second strongest signal and the preset respective signal strength ratio threshold values;

The user can derive the packet to which the user should be divided according to the comparison result described above; after that, the user reports the result information of the packet that the user should be divided into to the system side. For example, it is assumed that users in the same cell are divided into two groups according to the signal-to-noise ratio of the received signals. As shown in FIG. 2, users in the central area of the cell are generally less interfered by users in the cell, Generally, the strength of the received signal is high, so the user in the central area of the cell is divided into the first group of users.

(Groupl); The user in the cell edge area is usually interfered by the inter-cell user, and the strength of the received signal is low. Therefore, the user in the cell edge area is divided into the second group of users (Group2 is based on the above-mentioned first mode. The user first measures the signal strengths transmitted by all nearby base station transmitters and compares the received signal strengths. If the ratio of the received strongest signal strength to the second strongest signal strength is greater than a fixed signal strength threshold (eg, 9 dB), then This user will inform the system side that it is a user located in the central area of the cell, that is, belongs to the first group of users; otherwise it will inform the system side that it is a user located in the cell edge area, that is, belongs to the second group of users.

The second mode: The user can be grouped according to the size of the signal to noise ratio of the received signals of each user in the cell. This method can be implemented in the following two ways:

Determining, in advance, respective signal to noise ratio ratio threshold values for dividing adjacent packets;

System tested at least two neighboring base station receivers receive and measure a signal to noise ratio of signals transmitted from the same user;

The system side compares a ratio of a maximum signal to noise ratio measured by the at least two adjacent base station receivers to a second largest signal to noise ratio and the preset respective signal to noise ratio ratio threshold values;

Based on the above comparison results, the packet to which the user should be divided is derived.

As shown in FIG. 2 above, the user in the central area of the cell is generally interfered by the inter-cell user, and the signal-to-noise of the received signal is relatively high. Therefore, the user in the central area of the cell is divided into the first group of users (Group!); The user in the edge area is usually interfered by the inter-cell user, and the signal-to-noise of the received signal is relatively low. Therefore, the user in the cell edge area is divided into the second group of users (Group2 is based on the second method described above, firstly, the system side The base station receiver simultaneously measures the signal-to-noise ratio of the transmission signal from the same mobile user to be measured. If it is found that the ratio of the measured maximum signal to noise ratio to the second largest signal to noise ratio is greater than a fixed signal to noise ratio threshold ( For example, 9dB), it is concluded that the user to be tested is a user located in the central area of the cell, belonging to the first group of users; otherwise, the user to be tested is a user located in the edge area of the cell and belongs to the second group of users.

The second is: pre-setting each signal-to-noise ratio threshold for dividing adjacent packets;

The system side receives the signal-to-noise ratio of the received signal from the user feedback received by the base station receiver and presets Comparing the individual SNR thresholds; and

According to the comparison result, the packet to which the user of the feedback received signal signal to noise ratio should be divided is obtained. As shown in FIG. 2 above, it is assumed that the user in the same cell is divided into two groups according to the signal-to-noise ratio of the received signal. The base station can determine that the mobile user should be determined according to the signal-to-noise ratio of the received signal fed back by the mobile user. The divided group, if the signal to noise ratio of the received signal fed back by the mobile user is greater than a certain fixed signal to noise ratio threshold (for example, 9 dB), it can be concluded that the mobile user is a user located in the central area of the cell and belongs to the first group of users; Otherwise, it can be concluded that the mobile user is a user located in the cell edge area and belongs to the second group of users.

The third mode: The user in the cell can be grouped according to the distance between the users in the cell and the central location of the base station. The specific implementation process is similar to the above two methods, and is not described here. For the transmission of communication data; the transmission of the communication data, that is, each user in each group separately occupies different frequency subcarriers in the same entire subframe to transmit communication data, and different group users occupy different subframe time domains. Symbol resource. FIG. 3 is a schematic diagram of an OFDM time-frequency resource distribution state according to the principle of the method of the present invention, in which different packet users in a cell respectively occupy different subframe time-domain symbol resources to transmit communication data, wherein FIG. 3 The internal user is divided into two groups of the cell center area user group and the cell edge area user group as an example of the OFDM time-frequency resource distribution state, assuming that there are 6 OFDM symbols in one OFDM subframe, where the first subframe is All OFDM symbols are provided to users in the central area of the cell, and all OFDM symbols in the second subframe are provided to users in the cell edge area, wherein for the two groups of users, the number of specifically adopted subframes may be It is fixed, and it can be adjusted dynamically according to specific needs.

In addition, different group users in the cell can also transmit different communication time data by occupying different time domain symbol resources in the same subframe, that is, different group users can respectively occupy different time domain symbol resources in the same OFDM subframe. Preferably, the signal to noise of the received signal in the small area is relatively large. The packet user preferentially occupies the time domain symbol resources in the same subframe to transmit the communication data. As shown in FIG. 4, a schematic diagram of a first OFDM time-frequency resource distribution state according to the principle of the method of the present invention, in which different packet users in a cell respectively occupy the same subframe time-domain symbol resource to perform communication data transmission, wherein FIG. 4 A schematic diagram of an OFDM time-frequency resource distribution state by dividing a user in a cell into a cell center area user group and a cell edge area user group as an example, assuming that there are 6 OFDM symbols in one OFDM subframe, where the same OFDM is used. The first few (such as the first 3) symbols in the subframe are provided to the users in the central area of the cell, and the remaining (such as the last 3) symbols in the same subframe are provided to the users in the cell edge area, where For the two groups of users, the number of symbols in the same OFDM subframe may be fixed, or may be dynamically changed according to specific needs.

FIG. 5 is a schematic diagram of a second OFDM time-frequency resource distribution state according to the principle of the method of the present invention, in which different packet users in a cell respectively occupy the same subframe time domain symbol resource to perform communication data transmission, wherein 5 is a schematic diagram of the OFDM time-frequency resource distribution state in which all users in the cell are divided into six groups according to the signal-to-noise ratio of the received signal as an example, assuming that there are 6 OFDM symbols in one OFDM subframe, here according to the movement The user's distance from the center of the cell (or the strength of the user's interference or the signal-to-noise ratio of the received signal, etc.) ranks all mobile users within the cell to assign the user closest to the cell center location. a packet, let all users in the first packet occupy the first OFDM symbol in the same OFDM subframe, and so on, and assign the user farthest from the center of the cell to the last group (ie, the sixth group) , let all users in the sixth packet occupy the last OFDM symbol in the same OFDM subframe (ie, the sixth symbol) ).

In addition, in order to obtain a better communication effect, the method of the present invention further needs to perform spreading and/or error correction coding processing on the communication data transmitted by the packet user that falls within the cell edge region, to further improve Inter-cell user interference generated between packet users falling within the cell edge region is reduced.

In summary, the principle of the method of the present invention and its specific implementation process can be seen. The present invention proposes a technical solution capable of improving the user capacity of an OFDM cellular mobile communication system. In the embodiment of the present invention, The base station in the OFDM system is synchronous or quasi-synchronous in time. The base station adopts the same OFDM frame structure, and each frame includes multiple OFDM symbols, and the users inside the cell are divided into two groups or more, and requirements are required. The first group of users and the second group of users are divided to send or receive data in different time periods. That is, the time at which different packet users in the cell send and receive data is staggered. As in the grouping case shown in Fig. 2 above, the first group user simultaneously transmits or receives data, and the second group user simultaneously transmits or receives data, but the two group users transmit or receive data in different time periods. Wherein, for the users in the first group, since they are located in the central area of the base station, the interference of users in the cell is eliminated due to different users using different subcarrier frequencies; and for the interference of users between cells, due to a certain base station center The first group user (Groupl) at the area is away from the first group user i Groupl H at the central area of the other base station. Therefore, the interference between the users of the inter-cell will be small for the first group user. For the user Group2 in the second group, the interference of users in the same cell is also eliminated because different users use different subcarrier frequencies, but the second group user Group2 is located in the cell edge area, so the receiving cell Inter-user interference will be more serious, that is, each user i Group2 in the second group will suffer interference from the second group user, Group2 from other neighboring cells, and thus for the users in the second group. In order to obtain satisfactory communication performance, the communication data transmitted by the user in the packet is preferably protected by an extension technique or a strong error correction coding technique with a low coding rate.

That is, for the first packet user located in the central area of the cell, there is a small inter-cell user interference, and thus has a higher communication signal to noise ratio, and thus it is not necessary for these users to adopt a high degree of protection measures (such as these The user's communication data uses strong error correction coding techniques such as spread spectrum and low-speed coding rate to avoid communication interference, and high-speed data communication can be realized. For the second group of users in the cell edge area, because they have more serious inter-cell user interference, and have lower communication signal to noise ratio, it is necessary to use spread spectrum or high protection strong error correction coding technology. The communication data transmitted by the user in the group is processed to avoid user interference between cells.

According to the above analysis, the embodiments of the present invention can greatly reduce inter-cell user interference and intra-cell user interference in the OFDM cellular mobile communication system, thereby improving OFDM cellular shift. User capacity of the communication system.

Correspondingly, according to the above-mentioned OFDM-based cell user communication method, the embodiment of the present invention further proposes an OFDM-based cell user communication system. Please refer to FIG. 6, which is a structural block diagram of an embodiment of an OFDM-based cell user communication system according to the present invention, which includes a packet processing unit 10 and a data transmission unit 20. The functions of the two component units are as follows: Packet processing unit 10, For performing packet processing on users in each cell in the OFDM mobile communication system; wherein the packet processing unit 10 may perform grouping processing on users in the cell according to the order of the received signal strength of each user in the cell; The signal to noise ratio of the received signal is sequentially sequenced for the users in the cell; and the users in the cell may be grouped according to the distance between the users in the cell and the central location of the base station.

The data transmission unit 20 is configured to enable different group users in the cell processed by the packet processing unit 10 to occupy different time domain symbol resources to transmit communication data.

Please refer to FIG. 7. FIG. 7 is a block diagram showing the structure of an embodiment after adding a spread spectrum processing unit in the system of the present invention. The basis of the composition of FIG. 6 above may further include a spread spectrum processing unit 30 for The communication data transmitted by the packet user falling in the cell edge area processed by the packet processing unit 10 is subjected to spreading processing to reduce user interference between cells.

Please refer to FIG. 8. FIG. 8 is a block diagram showing the structure of an embodiment of the system according to the present invention. The error correction coding processing unit 40 may further include an error correction coding processing unit 40. The communication data transmitted by the packet user falling in the cell edge region processed by the packet processing unit 10 is subjected to error correction coding processing to reduce user interference between cells.

For specific implementation details of other related technologies in the system of the present invention, refer to the related description of the corresponding technical details in the above method of the present invention, and no further description is given here.

It is apparent that those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the inventions

Claims

Rights request

A cell user communication method based on orthogonal frequency division multiplexing, comprising the steps of: performing packet processing on a user in each cell in an orthogonal frequency division multiplexing mobile communication system; and transmitting.

2. The method according to claim 1, wherein the users in the cell are grouped according to the order of magnitude of the received signal strength of each user in the cell.

The method according to claim 2, wherein the process of performing group processing on a user in a cell specifically includes:

The user in the cell receives the signal strength measured by the transmitters from different base stations; and compares the ratio of the received strongest signal strength to the second strongest signal strength and the preset respective signal strength ratio threshold values;

The user then derives the group to which the user should be classified according to the comparison result;

The result information of the packet to which it should be divided is reported to the system side.

4. The method according to claim 1, wherein the users in the cell are grouped according to the magnitude of the signal to noise ratio of the received signals of the users in the cell.

The method according to claim 4, wherein the process of performing group processing on a user in a cell specifically includes:

At least two neighboring base station receivers receive a signal to noise ratio that measures transmission signals from the same user; the system side compares the ratio of the maximum signal to noise ratio measured by the at least two neighboring base station receivers to the second largest signal to noise ratio and Comparing the set SNR ratio thresholds; and

Based on the comparison result, the packet to which the user should be divided is derived.

The method according to claim 4, wherein the process of performing group processing on a user in a cell specifically includes: Determining, respectively, a signal to noise ratio threshold value for dividing adjacent packets;

The system side compares the received signal SNR of the user feedback received by the base station receiver with the preset SNR thresholds; and

The method according to claim 1, wherein the users in the cell are grouped according to the distance between the users in the cell and the central location of the base station.

8. The method according to claim 1, wherein different group users in the cell occupy different time domain symbol resources to transmit communication data.

9. The method according to claim 1, wherein different group users in the cell occupy different time domain symbol resources in the same subframe to transmit communication data.

10. The method according to claim 9, wherein the packet user having a large signal to noise ratio of the received signal in the cell preferentially occupies the time domain symbol resource in the same subframe to transmit the communication data.

The method according to any of the preceding claims, further comprising the step of: performing spreading and/or error correction coding processing on the divided communication data transmitted by the packet user falling within the cell edge region. .

12. The method of any of claims 1 - 10, characterized in that the users in each cell are divided into two groups.

A cell user communication system based on orthogonal frequency division multiplexing, comprising: a packet processing unit, configured to perform grouping processing on users in each cell in an orthogonal frequency division multiplexing mobile communication system;

And a data transmission unit, configured to enable different group users in the cell processed by the packet processing unit to respectively use different time domain symbol resources to transmit the communication data.

The system according to claim 13, wherein the packet processing unit performs grouping processing on users in the cell according to the order of magnitude of received signal strength of each user in the cell.

The system according to claim 13, wherein the packet processing unit performs grouping processing on users in the cell according to a signal to noise ratio size of each user received signal in the cell.

16. The system of claim 13 wherein: said packet processing unit is small The distance between each user in the area from the center position of the base station is grouped and processed in the order of the users in the cell.

The system according to claim 14, 15 or 16, further comprising a frequency processing unit, configured to perform communication data transmitted by a packet user that is processed by the packet processing unit and falls within a cell edge region. Spread spectrum processing.

The system according to claim 14, 15 or 16, further comprising an error correction coding processing unit, configured to transmit, by the packet processing unit, a packet user transmission that falls within a cell edge region The data is subjected to error correction coding processing.