CN101827063A - Frequency multiplexing device and method of OFDMA (Orthogonal Frequency Division Multiplexing Access) system - Google Patents

Abstract

The present invention relates to a frequency multiplexing device and method for an OFDMA system. The device includes: a terminal-side dynamic spectrum allocation module, which is located at the system terminal side, and is used to generate services that require bandwidth setting, and simultaneously detect interference in a cell, and The bandwidth requirements, channel information, and interference information are sent to the network-side dynamic spectrum allocation module; the network-side dynamic spectrum allocation module is located on the network side, and is used to transmit information from the terminal-side dynamic spectrum allocation module and the interference of adjacent cells The levels divide the cell edge group and the cell center group into cell edge carrier subgroups and cell center carrier subgroups respectively, and generate subcarrier scheduling information. The system and method of the invention can ensure the performance of the edge users, improve the utilization rate of the frequency, and can dynamically adjust and reduce the interference suffered by the edge users according to the degree of interference between cells.

Description

Frequency multiplexing device and method for OFDMA system

technical field

The invention relates to the technical field of mobile wireless networks, in particular to a frequency multiplexing device and method for an OFDMA system.

Background technique

OFDMA (Orthogonal Frequency Division Multiple Access, Orthogonal Frequency Division Multiple Access), as a multiple access method, can enable the system to flexibly schedule resources in the frequency domain and time domain two-dimensionally, and improve the flexibility and effectiveness of resource utilization. The OFDMA system is designed for higher data transmission rates. By using frequency bands and time slots in orthogonal subcarriers to flexibly schedule system resources, the system can obtain greater multi-user and multi-frequency gains. In addition, the system It is basically not affected by frequency selective fading, and has the characteristics of high spectral efficiency and easy scalability, especially suitable for broadband communication systems. OFDMA networks will undoubtedly become an important part of future broadband wireless networks and wireless communication networks. Based on the above reasons, many standard organizations have or will use OFDMA technology as part of the transmission technology in their wireless transmission standards.

Inter-cell Interference (ICI) is an inherent problem in cellular mobile communication systems. The traditional solution is to use frequency multiplexing, and the multiplexing coefficient has only a few specific choices, such as 1, 3, 7, etc. A reuse factor of 1 means that adjacent cells use the same frequency resource, and at this time, the interference is very serious at the edge of the cell. A higher multiplexing factor (3 or 7) can effectively suppress ICI, but the spectral efficiency will be reduced to 1/3 or 1/7. Future broadband mobile communication systems have high requirements on spectrum efficiency, so it is hoped that the spectrum reuse factor will be as close to 1 as possible.

Although the OFDMA system guarantees the orthogonality between users in a cell, it cannot realize multiple access between cells well. Each cell uses the same frequency, and users at the edge of the cell have strong co-channel interference, and the performance drops sharply. Therefore, although the OFDMA technology can solve the problem of intra-cell interference better than the CDMA technology, as a price, the ICI problem caused by the OFDMA system may be more serious than that of the CDMA system. If two adjacent cells use the same frequency spectrum resource at their junction, strong ICI will be generated, affecting user use. If no additional design is adopted, the system will face severe inter-cell interference. Therefore, it is an urgent problem to be solved to design a frequency reuse structure that can not only improve the efficiency of frequency usage but also alleviate the inter-cell interference in the system.

Many mechanisms to solve the problem have been proposed. For example, Fractional Frequency Reuse (FFR), Soft Frequency Reuse (SFR). Among these mechanisms, soft frequency reuse is the most widely used. However, in the soft frequency reuse system, the frequency utilization rate at the cell edge is very low, and most of the allocated resources are not used.

In existing studies, a fractional frequency reuse cell structure is proposed, as shown in FIG. 1 . In the OFDMA system, the frequency band will be divided into a certain number of subcarriers for use (the arrow in the figure represents a subcarrier). For these subcarriers, the structure will be divided into cell edge group and cell center group for use, and they will be used in the edge area and center area of the cell respectively. The cell edge group is further divided into three subgroups: cell edge subgroup 1, cell edge subgroup 2, and cell edge subgroup 3, represented by right diagonal stripes, left diagonal stripes, and diagonal grids in the figure, respectively. This structure can significantly reduce the interference between cells. However, the frequency band division between the center of the cell and the edge of the cell in the structure is independent, resulting in the reduction of subcarriers that can be freely selected by each group, thus affecting multi-user diversity and multi-carrier. gain. For broadband communication systems, low frequency efficiency will directly reduce system throughput and support traffic, thereby reducing the performance of the impact. In addition, this structure generally does not support dynamic adjustment of the frequency usage set according to inter-cell interference conditions. Although there are still some methods in the prior art that support dynamic adjustment of the frequency usage set according to inter-cell interference conditions, the required signaling interaction is relatively large and the practicability is not strong.

Contents of the invention

(1) Technical problems to be solved

The technical problem to be solved by the present invention is to ensure the performance of edge users, improve the utilization rate of frequencies, and at the same time dynamically adjust and reduce the interference suffered by edge users according to the degree of interference between cells.

(2) Technical solution

To achieve the above object, the present invention adopts the following technical solutions:

The present invention provides a frequency multiplexing device for an OFDMA system. The device includes: a terminal-side dynamic spectrum allocation module, which is located at the system terminal side, and is used to generate a service that needs to set a bandwidth according to user requirements, and at the same time detect interference in a cell, and send the bandwidth requirement, channel information, and interference information to the network-side dynamic spectrum allocation module; The interference level of the cell divides the cell edge group and the cell center group into cell edge carrier subgroups and cell center carrier subgroups respectively, and generates subcarrier scheduling information.

Wherein, the terminal-side dynamic spectrum allocation module includes: a sending/receiving unit, configured to send bandwidth requirements, channel information, and interference information to the network-side dynamic spectrum allocation module, and receive the network-side dynamic spectrum allocation The scheduling information sent by the module; the service providing unit is used to generate services that need to set the bandwidth according to user requirements; the channel measurement unit is used to obtain its channel information in the full frequency band by decoding the downlink reference signal; the interference measurement unit is used for Detect that the terminal is interfered by adjacent cells.

Wherein, the network-side dynamic spectrum allocation module includes: a receiving/transmitting unit, configured to send scheduling information to the terminal-side dynamic spectrum allocation module, and receive bandwidth requirements and channel information sent by the terminal-side dynamic spectrum allocation module , and interference information; the interference evaluation unit is used to generate the interference level information of the cell, and send it to the adjacent cell, and receive the interference level information of the adjacent cell from the adjacent cell; the carrier group generation unit, It is used to generate cell edge carrier subgroups and cell center carrier subgroups according to the interference level information of adjacent cells; the subcarrier allocation unit is used to allocate subcarriers according to carrier subgroups, channel information, and bandwidth requirement information; information statistics The unit is used to make statistics on the channel status and bandwidth satisfaction of each terminal.

Wherein, the method comprises the steps of:

S1. System initialization, setting the initial value i=0 of the subcarrier counter of the information statistics unit, wherein, 0≤i≤N, N is the number of subcarriers;

S2. According to the carrier set that each carrier subgroup has the right to use, query the carrier subgroup that has the right to use the i-th subcarrier;

S3. The information statistics unit calculates the priority of each terminal in each carrier subgroup according to the set parameters;

S4. The subcarrier allocation unit allocates the i-th subcarrier to the terminal with the highest priority;

S5. Judging whether the subcarrier counter value of the information statistics unit reaches the maximum, if so, end the allocation and generate scheduling information, otherwise the counter counts up by 1, and returns to step S2.

Wherein, the set of carriers that each carrier subgroup has the right to use in the step S2 is generated according to the following method:

A1. The receiving/transmitting unit receives the interference assessment information of the adjacent cell and sends it to the interference assessment unit;

A2. The interference assessment unit sets the backoff level factor of the subcarrier according to the interference level of the adjacent cell and the interference assessment information;

A3. The network-side dynamic spectrum allocation module calculates the back-off ratio of the carrier subgroup in the center of the cell according to the back-off level factor;

A4. The carrier group generation unit selects the backed-off subcarrier according to the backoff ratio of the subcarrier subgroup;

A5. The carrier group generating unit respectively generates the subcarrier sets that the cell center carrier subgroup and the cell edge carrier subgroup are entitled to use according to the selection result in step A4.

(3) Beneficial effects

The device and method of the present invention achieve the goal of reducing inter-cell interference while ensuring high frequency utilization by assigning all available frequencies to two groups, the cell edge group and the cell center group. Both the edge group and the center group have all frequencies, which greatly increases the number of available frequencies for users using these groups, thereby improving the multi-user diversity and multi-carrier diversity gain of the system and the throughput of the system. The present invention also supports dynamically adjusting the frequency set of the center group of the cell according to the interference state between cells, effectively controlling the interference between cells and ensuring the performance of edge users.

Description of drawings

Fig. 1 is the structure of existing fractional frequency reuse cell;

FIG. 2 is a structure of a frequency reuse cell of an OFDMA system according to an embodiment of the present invention;

3 is a schematic structural diagram of a frequency multiplexing device of an OFDMA system according to an embodiment of the present invention;

4 is a flowchart of a frequency multiplexing method of an OFDMA system according to an embodiment of the present invention;

FIG. 5 is a flow chart of allocation of subcarriers that each carrier subgroup is entitled to use in a frequency reuse method of an OFDMA system according to an embodiment of the present invention.

Detailed ways

The frequency multiplexing device and method of the OFDMA system proposed by the present invention are described in detail as follows in conjunction with the accompanying drawings and embodiments.

The frequency multiplexing device of the OFDMA system according to an embodiment of the present invention is used to solve the subcarrier frequency allocation problem in the downlink multi-cell OFDMA system, which is realized by the frequency multiplexing structure shown in Figure 2. In the present invention In the system and method, both the cell edge group and the cell center group have the right to use all subcarriers, and the cell center group can also be divided into three subgroups for independent use. The three subgroups have the right to use most of the subcarriers. The specific range is determined by Determined by the carrier group generating unit of the dynamic spectrum allocation module at the network side. In actual resource scheduling, the subcarrier allocation unit of the network-side dynamic spectrum allocation module decides which subgroup each subcarrier is used in each scheduling (the arrow in the figure represents the result of an allocation). As shown in Figure 3, the frequency multiplexing device of an OFDMA system according to an embodiment of the present invention includes:

The dynamic spectrum allocation module on the terminal side is located on the terminal side of the system. The internal implementation of the module not only utilizes the existing functions in the terminal, but also proposes some new functions to generate services that require a certain bandwidth, and at the same time detect the interference of the cell, and Send bandwidth requirements, channel information, and interference information to the dynamic spectrum allocation module on the network side;

The dynamic spectrum allocation module on the network side is located on the side of the network (such as a base station). The internal implementation of the module not only utilizes the existing functions in the terminal, but also proposes some new functions, which are used based on the information from the dynamic spectrum allocation module on the terminal side, and The interference levels of adjacent cells divide the cell edge group and the cell center group into cell edge carrier subgroups and cell center carrier subgroups respectively, and generate scheduling information.

Among them, the terminal-side dynamic spectrum allocation module includes:

The sending/receiving unit has an existing function, and is used to send bandwidth requirements, channel information, and interference information to the network-side dynamic spectrum allocation module, and receive signaling information such as scheduling sent by the network-side dynamic spectrum allocation module;

The service providing unit has existing functions and is used to generate services that require a certain bandwidth according to user requirements;

The channel measurement unit, with existing functions, is used to obtain its channel information in the whole frequency band by decoding the downlink reference signal;

The interference measurement unit, a new function, is used to detect the interference of the terminal from adjacent cells.

The dynamic spectrum allocation module on the network side includes:

The receiving/transmitting unit is used to send signaling information such as scheduling to the terminal-side dynamic spectrum allocation module, and receive bandwidth requirements, channel information, and interference information sent by the terminal-side dynamic spectrum allocation module;

The interference evaluation unit, a new functional unit, is responsible for generating the interference level information of the cell and sending it to the adjacent cell, and receiving the interference level information of the adjacent cell from the adjacent cell;

The carrier group generation unit, a new functional unit, is used to generate a cell edge carrier subgroup and a cell center carrier subgroup according to the interference level information of adjacent cells;

The subcarrier allocation unit is a new functional module, which is used to allocate subcarriers according to the channel conditions and bandwidth satisfaction of the carrier group and the terminal;

The information statistics unit is a new function module, which is used for statistics of the channel status and bandwidth satisfaction of each terminal.

The frequency multiplexing method of the OFDMA system based on the above-mentioned device, on the basis of the mutual cooperation of the above several units, operates under a specific environment, as shown in Figure 4, the method includes steps:

S1. System initialization, the network side dynamic spectrum allocation module sets the initial value i=0 of the subcarrier counter of the information statistics unit, and starts subcarrier allocation, wherein, 0≤i≤N, N is the number of subcarriers;

S2. According to the set of subcarriers that each carrier subgroup has the right to use, query the carrier subgroup that has the right to use the i-th subcarrier;

S3. The information statistics unit calculates the priority of each terminal in each carrier subgroup that has the right to use the subcarrier according to the set parameters;

S4. The subcarrier allocation unit allocates the i-th subcarrier to the terminal with the highest priority;

S5. Judging whether the value of the subcarrier counter of the information statistics unit reaches the maximum value N, if it reaches the maximum value N, then end the allocation and generate scheduling information, otherwise the counter counts up by 1, and returns to step S2.

Through the above steps S1-S5, it is determined how to allocate the carrier of the cell, that is, in actual use, the i-th sub-carrier is allocated to a certain terminal in the carrier subgroup that has the right to use the sub-carrier.

Wherein, in the step S2, the set of carriers that each carrier subgroup has the right to use, that is, determining that each subcarrier can be used by those carrier subgroups, is determined by the network side cell and the cell according to the level of inter-cell interference and the specific conditions of the cell. , generated according to the method shown in Figure 5:

A1. The receiving/transmitting unit receives the interference assessment information of the adjacent cell and sends it to the interference assessment unit;

A2. The interference assessment unit sets the backoff level factor of the subcarrier according to the interference level of the adjacent cell and the interference assessment information;

A3. The network-side dynamic spectrum allocation module calculates the back-off ratio of the carrier subgroup in the center of the cell according to the back-off level factor;

A4. The carrier group generation unit selects an appropriate backed-off subcarrier according to the backoff ratio of the subcarrier subgroup;

A5. The carrier group generation unit generates the subcarrier sets that the cell center carrier subgroup and the cell edge carrier subgroup are entitled to use respectively according to the selection result of step A4, wherein the subcarriers that the cell edge carrier subgroup is entitled to use are fixed, According to the cell edge, it is fixedly divided into three carrier subgroups, each of which uses 1/3 of the carrier frequency.

By using the frequency multiplexing structure in the present invention, each subcarrier is owned by multiple carrier subgroups, the use of subcarriers is more detailed, and multi-carrier gains can be fully utilized. At the same time, each cell edge area is orthogonal to the frequency (subcarrier group) used by the adjacent cell edge, which ensures the degree of interference in the edge area. The introduction of multiple sectors can improve the frequency reuse rate and the throughput of the system.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all Equivalent technical solutions also belong to the category of the present invention, and the scope of patent protection of the present invention should be defined by the claims.

Claims (5)

1. A frequency multiplexing device of an OFDMA system, the device comprising: The dynamic spectrum allocation module on the terminal side is located on the terminal side of the system, and is used to generate services that require bandwidth settings according to user requirements, detect the interference of the cell at the same time, and send bandwidth requirements, channel information, and interference information to the dynamic spectrum allocation on the network side module; The network side dynamic spectrum allocation module is located on the system network side, and is used to divide the cell edge group and the cell center group into cell edge carrier subgroups according to the information from the terminal side dynamic spectrum allocation module and the interference level of adjacent cells and the cell center carrier subgroup, and generate subcarrier scheduling information. 2. the frequency multiplexing device of OFDMA system as claimed in claim 1, is characterized in that, described terminal side dynamic spectrum allocation module comprises: The sending/receiving unit is configured to send bandwidth requirements, channel information, and interference information to the network-side dynamic spectrum allocation module, and receive scheduling information sent by the network-side dynamic spectrum allocation module; The service providing unit is used to generate services that require bandwidth setting according to user requirements; The channel measurement unit is used to obtain its channel information in the whole frequency band by decoding the downlink reference signal; The interference measurement unit is used to detect the interference of the terminal by the neighboring cells. 3. the frequency multiplexing device of OFDMA system as claimed in claim 1, is characterized in that, described network side dynamic spectrum allocation module comprises: The receiving/transmitting unit is configured to send scheduling information to the terminal-side dynamic spectrum allocation module, and receive bandwidth requirements, channel information, and interference information sent by the terminal-side dynamic spectrum allocation module; An interference assessment unit, configured to generate information on the level of interference suffered by the cell, and send it to a neighboring cell, and receive information on the level of interference suffered by the neighboring cell from the neighboring cell; The carrier group generation unit is used to generate a cell edge carrier subgroup and a cell center carrier subgroup according to the interference level information of adjacent cells; A subcarrier allocation unit, configured to allocate subcarriers according to carrier subgroups, channel information, and bandwidth requirement information; The information statistics unit is used for statistics of the channel status and bandwidth satisfaction of each terminal. 4. The frequency multiplexing method based on the OFDMA system of the device described in any one of claims 1-3, is characterized in that, the method comprises the steps: S1. System initialization, setting the initial value i=0 of the subcarrier counter of the information statistics unit, wherein, 0≤i≤N, N is the number of subcarriers; S2. According to the carrier set that each carrier subgroup has the right to use, query the carrier subgroup that has the right to use the i-th subcarrier; S3. The information statistics unit calculates the priority of each terminal in each carrier subgroup according to the set parameters; S4. The subcarrier allocation unit allocates the i-th subcarrier to the terminal with the highest priority; S5. Judging whether the subcarrier counter value of the information statistics unit reaches the maximum, if so, end the allocation and generate scheduling information, otherwise the counter counts up by 1, and returns to step S2. 5. the frequency multiplexing method of OFDMA system as claimed in claim 4 is characterized in that, in described step S2, the carrier set that each carrier subgroup has the right to use generates according to the following method: A1. The receiving/transmitting unit receives the interference assessment information of the adjacent cell and sends it to the interference assessment unit; A2. The interference assessment unit sets the backoff level factor of the subcarrier according to the interference level of the adjacent cell and the interference assessment information; A3. The network-side dynamic spectrum allocation module calculates the back-off ratio of the carrier subgroup in the center of the cell according to the back-off level factor; A4. The carrier group generation unit selects the backed-off subcarrier according to the backoff ratio of the subcarrier subgroup; A5. The carrier group generation unit respectively generates the subcarrier sets that the cell center carrier subgroup and the cell edge carrier subgroup are entitled to use according to the selection result in step A4.

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