WO2009030114A1

WO2009030114A1 - Load balance method for relay-based multi-hop wireless network

Info

Publication number: WO2009030114A1
Application number: PCT/CN2008/001550
Authority: WO
Inventors: Xin Guo; Wenchao Ma
Original assignee: Lenovo (Beijing) Limited
Priority date: 2007-08-30
Filing date: 2008-08-29
Publication date: 2009-03-12
Also published as: CN101378272B; CN101378272A

Abstract

A load balance method for a relay-based multi-hop wireless network, includes steps of: obtaining a load unbalance degree of each original group; judging whether the load unbalance degree of each original group is below a pre-determined balance degree threshold, if not, selecting the original group of which the load unbalance degree exceeds the pre-determined balance degree threshold, and combining each relay station within the original group of which the load unbalance degree is the highest and its adjacent relay stations into one adjusted group; determining a target adjusted group, and adjusting the coverage range of the relay station within the target adjusted group so as to balance the load of each relay station within the original group. The load balance method can be applied to a complex relay-based multi-hop wireless network, and can effectively improve the resource utilization efficiency of the relay-based multi-hop wireless network, increase the system capacity.

Description

Load balancing method based on relay for multi-hop wireless network

The present invention relates to a load balancing method for a wireless network, and more particularly to a load balancing method for a multi-hop wideband wireless network based on a relay. Background technique

In recent years, broadband wireless communication technologies and networks have developed rapidly. Due to spectrum planning, the carrier frequencies of emerging wireless communication systems are relatively high. Although the higher frequency band can solve the frequency allocation problem, the higher the frequency band, the worse the diffraction ability of the electromagnetic wave and the worse the penetration ability. This situation poses a challenge to the coverage of the wireless signal. The current wireless access network architecture is mainly a single-hop network composed of a base station (BS, Base Station) and a mobile subscriber (MSS, Mobi le Subscriber Station). Each MSS is connected to a base station. A wireless link to access the network. Such a single-hop network is difficult to meet the requirements of a high-frequency wireless communication system, because high-frequency signals are susceptible to the shadow fading effect caused by terrain due to poor transmission and diffraction capabilities. In addition, the higher the frequency band, The faster the electromagnetic wave is attenuated under the same transmission power condition, resulting in a reduction in the coverage area of the system base station. Therefore, the wireless communication network proposes the concept of a multi-hop wireless network. The multi-hop wireless network uses a relay station (RS, Relay Station) to forward signals between the BS and the MSS, thereby forming a path of the BS-RS-MSS. Wherein, the RS may be one level or multiple stages, and a node of a multi-hop wireless network can reach the adjacent node by using a smaller transmission power, so the same power level is used compared with the single-hop network. The coverage area of the network following the network has greatly increased. Moreover, the RS location planning is flexible, which can effectively avoid the influence of terrain on the network layout.

However, the data in the relay-based multi-hop wireless network needs to be relayed one or more times between the BS and the MSS. From the signal transmission time credit or frequency occupation angle, the system resources are wasted, thus Will reduce system capacity. To this end, some new technologies attempt to use resources or other effective methods to reuse resources. The resources referred to here may be the time in a time division multiple access communication system or the frequency in a frequency division multiple access communication system. The bandwidth can also be a pseudo-random code in a code division multiple access communication system, or a combination of these resources. From the perspective of information theory, the allocation methods of different types of resources are the same. Taking a time division multiple access communication system as an example, an effective resource multiplexing method is shown in FIG. 1. The figure is a schematic diagram of a relay network downlink subframe, wherein a data transmission link between the base station and each relay station is shown. Called as a relay link, denoted as BS-RS1, BS-RS2, BS-RS3, and BS-RS4; the data transmission link between the base station, the relay station, and the user is called access. The link, which treats the BS-MSS link between the base station and all users directly communicating with it as a whole, is scheduled in units of BSs, and similarly, between any relay station and all users directly communicating with it. The RS-MSS link, also considered as a whole, is scheduled in units of RSs. Therefore, the time when the BS is serving the MSS in the figure is marked as BS on the time frame, and the time at which each RS serves the MSS is in the time frame. The above is marked as the RS, such as RS1, RS2, RS3, RS4, and the like. The resource multiplexing scheduling method does not limit the order of the relay link and the access link in the downlink subframe, and the uplink subframe can be obtained in the same manner. The A shown in FIG. 1 is a frame structure without multiplexed resource multiplexing, and the B shown in FIG. 1 is a time frame structure adjusted by resource multiplexing. The core idea is to divide the RSs that do not cause interference into the same frame. Packets, all RSs in the packet are scheduled at the same time. The RSs in the same packet are shown in the same packet as the time start of the MSS service in the coverage time frame. The RSs that interfere with each other belong to different groups, different groups. Time-sharing scheduling is required, which is displayed on the time frame as the time delay of each group scheduling.

Each RS in Figure 1 occupies different lengths on the time frame due to the different service load in the coverage area. For example, in a certain period of time, the MSS requires a large amount of resources in the coverage of an RS, that is, the RS has a large load, and the time that the RS is in the coverage of the MSS service is on the time frame. The occupied length is longer, and the shorter the occupied length.

As can be seen from FIG. 1, in the resource multiplexing method, if the difference in RS load in the same packet is larger, that is, the difference in the length occupied by each RS service time on the time frame is larger, the resource utilization ratio is lower. On the other hand, if the RSs in the same packet are balanced, the resource utilization of the method is high, and thus the system capacity can be increased. Thus, in order to be able to increase the system capacity more effectively, it is necessary to take some measures to balance the load of each RS.

In the Chinese patent application entitled "CN1355625", "Load balancing method and control system for co-frequency cells in a code division multiple access communication system", a method for balancing the BS load of an adjacent cell is proposed, and the principle of the method is proposed. As shown in FIG. 2, the adjacent two cells are the coverage areas of BS1 and BS2, respectively, and the initial load states of BS1 and BS2 are indicated by a dotted circle, the load of BS1 is too heavy and the load of BS2 is light, so by reducing The power of BS1 is reduced, so that a part of the MSS is included in the coverage of other BSs, and the power of BS2 is increased to increase its coverage, so that some MSSs in other BS coverages are included in its coverage, thereby achieving two cells. Load balancing between. The basis for judging whether the load of the BS is too light or too heavy is a predetermined threshold. When the load of the BS is greater than a predetermined overload threshold, the power is reduced, and when the load of the BS is less than a predetermined underload threshold, the power is increased. However, the method cannot solve the balanced load problem in the packet resource multiplexing method of the above-described relay-based multi-hop wireless network, because in the packet resource multiplexing method of the relay-based multi-hop wireless network, between the RSs There are cases where they interfere with each other or do not interfere with each other. RSs that do not interfere with each other belong to the same packet, and there are no adjacent edges between each other, so there is no possibility of increasing and decreasing power to achieve load balancing between adjacent cells. The RSs that do not interfere with each other cannot determine whether to increase or decrease the power of a certain RS by simple threshold judgment, because the method for resource multiplexing in packets is more important is the load between RSs in the group. Balance, not load balancing between RSs between groups. Summary of the invention

In view of this, an object of the present invention is to provide a load balancing method for a multi-hop wireless network based on a relay, which can dynamically adjust the coverage of each RS according to the load status and interference relationship of each RS, and balance the load of each RS. .

In order to achieve the above object, the technical solution adopted by the present invention is a load balancing method for a relay-based multi-hop wireless network, and the method includes the following steps: A: acquiring an imbalance of each original packet load; B, determining each Whether the original packet load imbalance is less than a predetermined balance threshold, if not, selecting the original packet whose load imbalance is greater than the predetermined balance threshold, and adjusting the packet according to the adjacent relationship between the selected original packets: C. The target adjustment packet is determined within the adjustment packet, and the coverage of the relay station within the target adjustment packet is adjusted.

In the step B, the method for forming the adjustment packet may be: adjusting the relay group by selecting the relay station in the original packet with the largest load imbalance and the adjacent relay station belonging to the original packet.

In step C, the method for determining the target adjustment group may be: selecting the adjustment group with the largest load imbalance as the target adjustment group.

In the step C, the method for determining the target adjustment packet may also be: selecting the reload relay station in the original packet with the largest load imbalance degree and the adjustment packet composed of the relay station adjacent to the selected original packet, as the target adjustment packet. .

The step C may further include: D. Repeating steps A to C until the original packet load imbalance is less than a predetermined balance threshold.

In step C, the method for adjusting the coverage of the relay station in the target adjustment packet may be: reducing the power of the relay station marked as a heavy load in the original packet in the target adjustment packet, and increasing the power of other relay stations in the target adjustment packet.

In step C, the method for adjusting the coverage of the relay station in the target adjustment packet may be: reducing the power of the relay station marked as overloaded in the original packet in the target adjustment packet, and cooperating with the relay forwarding unit to migrate the mobile user in the coverage range to The target adjusts the coverage of other relay stations within the packet. The relay forwarding unit may be a redundant relay station or a mobile user with data forwarding function.

The original packet load imbalance can be balanced by the quotient of the standard variance and the mean of the load of each relay station in the original packet.

The method may further include repeating steps A through D for a period of a specified period of time.

The load balancing method of the relay-based multi-hop wireless network provided by the present invention dynamically adjusts the coverage range of each ^ according to the load condition and the interference relationship of each RS, and has the following advantages: The load balancing method does not need to know the network topology in advance or The interference situation is determined by using the BS and RS load and interference conditions dynamically measured during network operation to determine the load balancing result; and the load balancing method can consider the load difference of each RS between each group and within the packet, thus The load balancing method can be applied to a complex relay-based multi-hop wireless network system, thereby improving resource utilization and increasing system capacity of a relay-based multi-hop wireless network. DRAWINGS

1 is a schematic structural diagram of a downlink subframe before and after using a relay-based multi-hop wireless network packet resource multiplexing scheduling method in the prior art;

2 is a schematic diagram of a method for load balancing between adjacent BSs in the prior art;

3 is a flowchart of a method for load balancing of a multi-hop wireless network based on a relay according to the present invention;

4 is a schematic diagram of a downlink sub-frame of a radio network topology structure and a packet resource multiplexing scheduling result before using a relay-based multi-hop wireless network load balancing method according to the present invention;

5 is a schematic diagram of a load adjustment scheme of a first target adjustment packet in a relay-based multi-hop wireless network load balancing method according to the present invention;

6 is a schematic diagram of a second target adjustment packet internal load adjustment scheme in a relay-based multi-hop wireless network load balancing method according to the present invention;

FIG. 7 is a schematic structural diagram of a downlink subframe before and after using a relay-based multi-hop wireless network load balancing method in the present invention. detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

The core idea of the present invention is: obtaining the load imbalance in each packet, and adjusting each of the RSs in the packet with a large load imbalance and the RSs in the other packets to adjust the coverage of the RS in the packet. Make adjustments to balance the load of each original packet. As shown in FIG. 3, the relay-based multi-hop wireless network load balancing method of the present invention includes the following steps: Step 101: Acquire a load imbalance within each packet.

The manner in which packet resources are multiplexed for each RS within a coverage of a BS is as described in the background. As shown in part A of Figure 4, in an embodiment of the present invention, the BS includes six RSs, which are respectively identified as RS1 - RS6, and the BS and the RSI-RS6 are divided into three groups according to bandwidth requirements and interference relationships for resource recovery. With scheduling, the three packets are: {BS}, {RSK RS3, RS5} and 3⁄4 {RS2, RS4, RS6}, and the downlink subframe after packet multiplexing scheduling is as shown in the Β part of FIG. In order to distinguish from the packets in the subsequent steps, these three packets are called the original packets.

After each original packet and the RS included therein are determined, the respective load conditions are obtained by the original intra-packet RS, and the load is a resource requirement in each RS coverage, which is determined by the quality of service requirements of each connection of the MSS in the RS coverage. . Then, the load unbalance degree in each original packet is obtained, and the load unbalance degree can be measured in various ways, for example, the load difference between the maximum load RS and the minimum load RS, the standard variance of each RS load in the original packet, and the like. In an embodiment, the quotient of the standard deviation and the mean of each RS load in the original packet is selected to identify the load imbalance within each original packet.

After the load imbalance of each original packet is obtained, the load condition of each RS in each original packet may be marked. The marking method selected in this embodiment is as follows: Set the reload threshold to a 0, and the light load threshold to be - Lb 0, let BW _ave denote the average value of the load of each RS in an original packet. If the load BW ^ ( 1+a ) BW _ave ^ of an RS in the original packet marks the RS as a reloaded RS, if an RS The load BW^(1+b)BW _average marks the RS as a light-duty RS, and the other RSs as a normal RS. For example, RS4 is a heavy load in the original packet {RS2, RS4, RS6}, and RS2 and RS6 are light-loaded. In addition, other marking methods can be selected, such as marking only the maximum load RS in each original packet.

Step 102: Determine whether each original packet load imbalance is less than a predetermined balance threshold BalanceDegree^, if not, select an original packet whose load imbalance is greater than a predetermined balance threshold, and select an adjacent packet between adjacent packets. Relationship composition adjustment grouping; if yes, stop this load balancing process.

For example, in this embodiment, the load imbalances of the original packets {RS1, RS3, RS5} and {RS2, RS4, RS6} are both greater than a predetermined balance threshold BalanceDegreeth, and the two original packets are selected. In order to select the original packet; and further adjust the packet according to the adjacent relationship between the selected original packets, the method for forming the adjustment packet may be various, for example, selecting one of all the original RSs and the adjacent ones thereof Others select the RS component adjustment packet within the original packet. In this embodiment, the method of selecting the RS in the original packet and combining the other RSs with the largest load imbalance is selected. For example, in this embodiment, the original group with the largest load imbalance is the original. Group {RS1, RS3, RS5}. The RSs in the original packet are grouped with the RSs belonging to the other selected original packets. For example, in this embodiment, the composition adjustment packets {RS1, RS2, RS6}, {RS3, RS2, RS4^P {RS5, RS4, RS6} are formed.

Step 103: Determine the target adjustment packet, adjust the coverage of the RS in the target adjustment packet to balance the load of each RS in the original packet.

Select an adjustment group as the target adjustment group, and there are many options. For example: Option 1: Select the adjustment group with the highest load imbalance as the target adjustment group. As in step 101, the load imbalance of each adjustment packet is obtained, and then a target adjustment packet is selected according to the load imbalance of each adjustment packet. Option 2: Select the adjustment packet consisting of the RS marked as the overloaded RS and its neighboring RS in the original packet with the largest load imbalance as the target adjustment packet.

In order to achieve the purpose of adjusting the RS load in the packet by adjusting the target, in the present invention, two adjustment targets are selected to adjust the coverage of the RS in the packet to balance the RS load in the original packet, respectively - Solution A: as shown in FIG. The power of the RS marked as a heavy load in the original packet in the target adjustment packet is reduced, the power of the other RSs of the target adjustment packet is increased, and the MSS that belongs to the reloaded RS is migrated to the coverage of other RSs in the target adjustment packet. Therefore, the load of the heavy-duty RS is reduced, and the load of the other RSs is increased. For example, in the present embodiment, to reduce the power of RS1, RS2, and an increase of power _RS6;.

Scheme B: as shown in FIG. 6, reducing the power of the RS marked as a heavy load in the original packet in the target adjustment packet, and cooperating with the relay forwarding unit to migrate the MSS that belongs to the RS to the coverage of other RSs in the target adjustment packet. Within the scope. The relay forwarding unit may be a redundant RS, such as some mobile RSs, or some other MSSs with data forwarding functions, thereby reducing the load of the overloaded RS and increasing the load of other RSs. In Figure 6, the MSSA is an MSS with data forwarding function, and the RSA is a redundant RS. The MSS1 is migrated to the coverage of the RS2 through the MSSA with data forwarding function, and the MSS2 is migrated to the coverage of the RS6 through the redundant relay RSA. Inside.

After the coverage of the RS is adjusted, the scheduling time of the BS to each RS in the relay link is also changed. For example, if the coverage of the RS1 is reduced, the length of the BS-RS1 is also shortened, and the RS2 is shortened. When the coverage of RS6 is increased, the time lengths of BS-RS2 and BS-RS6 are also extended, and the overall scheduling time of BS to RS is not changed, and the effect of the present invention is not affected. .

After performing step 103, since only one target adjustment packet is selected for load balancing, it is often impossible to implement load balancing in all original packets of the entire BS, so that steps 101 to 103 can be further cyclically executed until all the original The load imbalance of the packets is less than a predetermined balance threshold. At last, A comparison of downlink subframes before and after load balancing in the original packet is implemented as shown in FIG. 7, and part A in FIG. 7 is a frame structure in which the relay-based multi-hop wireless network load balancing method of the present invention is not employed, and Part B is the frame structure after the relay-based multi-hop wireless network load balancing method of the present invention is employed. It can be seen that by adjusting the coverage of the RS in the adjustment packet, the load of RS1 is reduced, the load of RS2 and RS6 is increased, and the load balancing of the original packet is realized.

In addition, since the network load condition changes at any time, in order to enable the dynamic adjustment process, the relay-based multi-hop wireless network load balancing method of the present invention may repeatedly perform the above steps 101 to 103 in a period of a specified period of time. And the subsequent cycle steps.

The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Those skilled in the art should be able to think of different wireless communication networks as the application background of the present invention, select different adjustments, grouping as the target adjustment group, and other parameters to represent the resource imbalance in the original group, all should be It belongs to the scope of protection of the present invention.

Claims

Claim

A load balancing method for a relay-based multi-hop wireless network, characterized in that the method comprises the following steps -

A. Obtain the imbalance of each original packet load;

B, - 'determine whether each original packet load imbalance is less than a predetermined balance threshold, if not, select an original packet whose load imbalance is greater than a predetermined balance threshold, according to the adjacent relationship between the selected original packets Composition adjustment grouping;

C. Determine the target adjustment packet in the adjustment packet, and adjust the coverage of the relay station in the target adjustment packet.

The load balancing method of the relay-based multi-hop wireless network according to claim 1, wherein in the step B, the method for adjusting the packet is: selecting the original group with the largest load imbalance The relay station in the middle of the relay station and its adjacent relay station belonging to the original group are composed of adjustment packets.

The load balancing method of the relay-based multi-hop wireless network according to claim 1, wherein in the step C, the method for determining a target adjustment packet is: selecting an adjustment packet with the largest load imbalance as the Target adjustment grouping.

The load balancing method of the relay-based multi-hop wireless network according to claim 2, wherein in the step C, the determining the target adjustment packet is: selecting the original packet with the largest load imbalance The reload relay station and the adjacent adjustment packet belonging to the relay station selected in the original packet are used as the target adjustment packet.

The load balancing method of the relay-based multi-hop wireless network according to claim 1, wherein the step C further comprises:

D. Repeat step A to step C until the original packet load imbalance is less than a predetermined balance threshold.

The load balancing method for a relay-based multi-hop wireless network according to claim 1, wherein the method for adjusting the coverage of the relay station in the target adjustment packet in the step C is: reducing the target adjustment The power of the relay station marked as a heavy load in the original packet within the packet increases the power of other relay stations in the target adjustment packet.

The load balancing method of the relay-based multi-hop wireless network according to claim 1, wherein the method for adjusting the coverage of the relay station in the target adjustment packet in the step C is: reducing the target adjustment packet intrinsic The power of the relay station marked as overloaded in the packet cooperates with the relay forwarding unit to migrate the mobile users within its coverage to the coverage of other relay stations in the target adjustment packet.

8. The load balancing method of a relay-based multi-hop wireless network according to claim 7, wherein the relay forwarding unit is a redundant relay station or a mobile user having a data forwarding function.

9. The load balancing method for a relay-based multi-hop wireless network according to claim 1, wherein the original packet load imbalance is measured by a quotient of a standard variance and an average of load of each relay station in the original packet. .

The load balancing method of the relay-based multi-hop wireless network according to claim 5, wherein the method further comprises: repeating the step A to the step by using a specified period of time as a period D.