CN1089990C - Switching control method based on dynamic priority in small region - Google Patents

Abstract

The present invention proposes the concept of dynamic priority and a handover control method based on the dynamic priority of the cell, and relates to the field of wireless mobile communication. The steps are (1) collecting data; (2) calculating the average value and power budget margin of the measurement report; (3) comparing the average value with the threshold; (4) selecting the target cell; (5) sorting the target cell. Taking into account the static priority of the cell and its resource utilization when calculating the dynamic priority, it is more reasonable and efficient than controlling switching with a simple static priority concept, avoiding the problem of low system efficiency caused by unbalanced traffic volume, and making full use of system resources , to improve the overall performance of the network.

Description

A Handover Control Method Based on Cell Dynamic Priority

The invention relates to a switching control method in the field of wireless communication, in particular to a switching control method for automatically balancing traffic in a wireless mobile communication system.

In the field of wireless communication, there are many handover methods for traffic balance control in the prior art. Reordering the handover target cells is one of the methods, because the higher the cell is, the higher the probability of being handed over. Some handover methods sort the target cells according to the power budget margin. Because there are many factors affecting the power budget margin, such as the distance between the MS and the base station, the load in the cell, the interference of the surrounding environment, etc., it is difficult to grasp the distribution of the traffic generated due to handover. Another method proposes a sorting method based on cell priority, that is, cells with high priority are preferentially switched in by MSs, while cells with low priority are less likely to be switched in by MSs. The MS cuts in and is overloaded, and the cells with low priority are starved due to insufficient traffic. Obviously, this method is an invariable priority concept, or based on a static priority concept, and it still cannot fundamentally solve the problem of low system efficiency caused by unbalanced traffic volume.

The purpose of the present invention is to propose a handover control method based on the dynamic priority of the cell, so that the network can automatically control the handover according to the actual utilization of network resources, so that the traffic can be reasonably distributed, and the system resources can be fully utilized, thereby improving the overall performance of the network .

The technical solution of the present invention is such, a kind of switching control method based on cell dynamic priority, comprises the following steps:

(1) Data collection: That is, every about 480 milliseconds, the base station controller BSC receives the data of the measurement report reported by the base transceiver station BTS, including the downlink data measured by the MS and the uplink data measured by the BTS.

(2) Calculate the average value and power budget margin of the measurement report: when the retained measurement report data exceeds the required number of samples, each time a measurement report is received, the new data and the old data falling within the sliding window are weighted average. The weights of the average distance and the average value of the levels of adjacent cells are both 1. The formula for calculating the power budget margin is

ΔPBGT(n)=PBGT(n)-HO_MARGIN(n).

(3) Compare the average value with the threshold value: when the average value retained is more than the required number, participate in the process of comparing with the threshold value. According to the priority of the switching reason, the order of the comparison process is fixed. When the The comparison process ends when a switching cause is established.

(4) Select the target cell: when the reason for the handover is inter-cell handover, the adjacent cell whose power budget margin is greater than 0 and whose average downlink level is greater than the minimum access level is selected as the target cell.

(5) Sorting of target cells: Calculate the dynamic priority of the cells according to the resource conditions of the target cells, and then sort according to the dynamic priorities of the cells, and the cells with higher priority are ranked first. If the dynamic priorities of the two target cells are the same, they are sorted according to the power budget margins of the two cells, and the cell with the higher power budget margin is ranked first. Below in conjunction with accompanying drawing, table further illustrate working principle of the present invention.

Fig. 1 is a structural block diagram of a switching device applying the switching method of the present invention; Fig. 2 is a diagram of the dynamic priority proposed in the present invention; Fig. 3 is a schematic diagram of a specific embodiment implementing the present invention; Fig. 4 is a schematic diagram of implementing the present invention Another specific embodiment shows; Table 1 is the measurement report data; Table 2 is the average value of the data in Table 1; Table 3 is the threshold in the database; Table 4 is a logarithmic table provided to avoid complex operations.

The present invention proposes a switching control method for automatic balance of business volume based on dynamic priority, and its core is the dynamic priority of cells. The dynamic priority is the result of the cell's static priority being lowered due to TCH channel resource loss. The change of dynamic priority is an adaptive process. When the resource of the cell is sufficient, the dynamic priority of the cell is close to the static priority of the cell, and the MS is easy to cut in; as the MS continuously cuts in, the resource of the cell is continuously consumed, and the TCH channel resource of the cell is also continuously reduced, so the dynamic The priority decreases, so that it is not easy for the MS to cut in; as the user hangs up, the TCH channel resources of the cell increase, and the dynamic priority of the cell increases accordingly. In addition, a cell with a high static priority has a high dynamic priority at the beginning and has a strong ability to absorb services. As the traffic continues to cut in, the dynamic priority will quickly decrease. When the dynamic priorities among the cells are similar, the ability of cells with high static priorities to absorb services is relatively weak, because the dynamic priorities of these cells decrease rapidly with resources, and the resources occupied between the two priority levels The percentage is relatively small. After the network runs stably for a long time, the traffic volume of the cell with high static priority is relatively high, but it will not be overloaded; while the traffic volume of the cell with low static priority is relatively low, but it will not be starved.

Fig. 1 is a structural block diagram of a switching device. The MSCs are connected through gateways. There is a standard A interface between MSC and BSC. Between the BSC and the BTS is the ABIS interface, which is the internal interface of the base station. There is a standard UM wireless interface between MS and BTS. Generally, one BTS corresponds to one cell. According to the difference between the source BSC and target BSC where the MS resides, there are three types of inter-cell handovers:

Inter-cell handover within the BSC, such as MS handover from BTS11 to BTS12;

Inter-cell handover between BSCs, such as MS handover from BTS21 to BTS22;

Inter-cell handover between MSCs, for example, MS handover from BTS11 to BTS22. These three handovers all need to give a handover target cell list.

Table 1 is the data sorted out according to the measurement report obtained in step (1) of the handover control method. There is only one power value for MS and BS. The uplink data, downlink data, timing advance and adjacent cell measurement values are stored in a circular queue with a length of 32, respectively. The "counter" of the queue accumulates the number of data. According to the number of data, the "current position" where the latest measurement report data is kept can be calculated. Up to 32 measurements of 16 neighboring cells were kept. The parameter AGE is used in the cell record to indicate the reliability of the record. Every time a measurement report is processed, if the record is refreshed, AGE is 0, otherwise it is incremented by 1. When a new neighbor cell is included in a measurement report, it replaces the oldest record. This old record may be an empty record, or it may be an old record that has aged. Utilize this mechanism to retain the latest and most valuable neighbor cell data.

Table 2 is the average of the data in Table 1. In step (2) of the switching control method, the sliding window parameter HREQAV is the number of samples for calculating the average value. When more than HREQAV data are retained, an average value is obtained for every HREQAV data. The calculation formula is: Among them, WEIGHT is the weight that marks the reliability of the data. When the discontinuous transmission flag DTA in the measurement report is 1, the weight of the data is 1, otherwise it is a relative weight greater than 1. The BSC calculates the average value of the uplink and downlink levels and bit error rates of the cell according to Formula 1. Since the time advance TA is proportional to the distance between the MS and the base station, the average distance between the MS and the base station can be obtained by calculating the average value of TA. When calculating the level average and distance average of adjacent cells, the relative weight is 1, because these two parameters have nothing to do with the discontinuous transmission mode. The formula for calculating the power budget margin of a cell is: ΔPBGT(n)=PBGT(n)-HO_MARGIN(n). Where PBGT(n) depends on the average level of adjacent cells. The larger the power budget margin, the smaller the path loss of the adjacent cell, and the greater the possibility of being handed over; conversely, the larger the path loss of the adjacent cell, the smaller the possibility of being handed over.

In the step (3) of the switching control method, the comparison between the average value and the threshold value is involved. Table 3 shows the threshold itself in the database. The threshold consists of 3 parts: the threshold itself, the total number of samples N and the effective number of samples P. When the average value of a certain data is more than N, compare the average value of the data with the corresponding threshold in the database to decide whether to switch. The basic principle of switching can be described as: if P out of N average values exceeds the range specified by the threshold, switching will be triggered. The order of comparison is: comparison of interference level; comparison of uplink and downlink bit error rate; comparison of uplink and downlink level; comparison of average distance; comparison of power budget. Once one of them satisfies the above switching principle, stop the comparison process immediately and give the reason for switching. The result of the interference level comparison is the internal handover, and the rest are inter-cell handovers.

In step (4) of the handover control method, if the reason for triggering the handover is not an internal handover, the BSC selects a target cell from the reserved neighboring cells. The selected target cell should meet the following conditions: the average level of the selected target cell must be greater than the minimum access level required by the target cell, and the power budget margin ΔPBGT(n) must be greater than 0.

In the step (5) of the handover control method, if there is more than one target cell meeting the above conditions, the BSC will sort all the target cells by evaluating dynamic priority. First query the resource status of the target cell, and calculate the resource percentage of the cell; then query the static priority of the cell, and then convert the two into the dynamic priority of the cell. The cells in the target cell list are sorted according to the dynamic priority calculated at this time, and the cells with higher priority are ranked first. If the dynamic priorities of the two target cells are the same, then they are sorted according to the power budget margins of the two cells, and the cell with the higher power budget margin is ranked first. Finally, the obtained handover reason and the ordered target cell list are provided to the service process.

Figure 2 can be seen as an illustration of dynamic priorities. As mentioned above, the dynamic priority mainly depends on the static priority of the cell and the resource percentage of the cell. The static priority of the cell has 8 levels from 0 to 7. The larger the level, the higher the priority. It can be set according to the statistical law of traffic. The main basis for setting the static priority is the geographical location of the cell. For example, in a micro cell in a building, the priority of adjacent cells on the same floor as this cell is set relatively high, while the priority of adjacent cells on a different floor is set relatively low, so as to ensure that the handover is basically performed on the same floor , reduce interference and improve call quality.

The resource percentage of a cell refers to the percentage of idle TCHs in the total TCH channels in the cell, ranging from 0 to 100. This is because during handover, the MS only cares about the TCH channel of the cell being cut into. The higher the resource percentage of the TCH channel, the lighter the load of the cell, which means the higher the success rate of handover. The resource lower limit is specified as SP_LOW (SP_LOW>=10). When the resource is lower than SP_LOW, the load of the cell is close to saturation, and the dynamic priority is 0. The resource percentage SP of the cell is: SP=100*(∑TCH_AVAIL)÷TCH_TOTAL In formula 2, TCH_AVAIL: the total number of idle TCH channels in the cell; TCH_TOTAL: the total number of TCH channels in the cell. It can be seen that assuming that the resource percentage of the cell at a certain moment is SP, then it is stipulated that:

SP=SP_LOW*A ^m Formula 3 where the base A satisfies the conditions:

100=SP_LOW* ^AN Formula 4N is the static priority of the cell, and the base A obtained from Formula 4 is:

图2可以认为是公式6的图解，其中假设该邻近小区的静态优先级N＝4。当m取值0到N时，Y轴得到N+1个不同的值把资源分割成N+1个区间，每个区间对应一个小区的动态优先级。明显可以看出，除了动态优先级0，其他动态优先级所在的区间从下到上依次扩大。这种资源百分比和动态优先级之间的关系是基于这样的思想：在资源还比较宽裕的时候，小区中已经接入的MS比较少，即使有新的MS切入，对小区的无线环境和网络性能的影响不大，因此小区的动态优先级降低得比较慢，鼓励MS切入；当资源比较匮乏时，接入的MS已经比较多，小区中的干扰增加，系统的性能有所下降，这时再有新的MS切入，会使小区雪上加霜，因此动态优先级降低得比较快，以减缓新的MS切入。本发明借助于指数函数模型，把小区的资源百分比折算到小区的动态优先级中，来模拟这种先缓后急的特征。从图2可见，小区的资源SP从100减少到0，相对应的动态优先级从4降低到0。假设SP_LOW为10，优先级4占据大约44％的资源，而优先级1占据大约17％的资源。根据公式6得到：M在集合[0，N]中从小到大取整数值，一旦满足条件M≥m，M就是资源百分比SP对应的动态优先级。结合公式7有：N*ln(SP÷SP-LOW)≤M*ln(100÷SP-LOW)                    公式8为了避免公式8中复杂繁琐的对数运算，本发明采用了表驱动的做法。公式8又可以写成：N*LN(SP)≤M*LN(100)                                    公式9其中LN(SP)从事先已经做好的对数表即表4中查询，资源百分比和对数表的映射关系如下：函数integer(X)是求数轴上和X最靠近的左边整数。假设SP_LOW为10，当SP为50，查询表4，LN(SP)为161。当SP为100，得到LN(SP)为228。A=(100÷SP_LOW) ^IN Formula 5 shows that A is only related to the resource lower limit SP_LOW and the static priority N of the cell. The larger N is, the smaller A is. Combining Equation 3 and Equation 5 gives:

Fig. 2 can be regarded as a diagram of Equation 6, where it is assumed that the static priority N=4 of the neighboring cell. When m takes a value from 0 to N, the Y axis obtains N+1 different values to divide the resource into N+1 intervals, and each interval corresponds to a dynamic priority of a cell. It can be clearly seen that, except for dynamic priority 0, the intervals of other dynamic priorities expand sequentially from bottom to top. The relationship between the resource percentage and the dynamic priority is based on the following idea: when resources are relatively abundant, there are relatively few MSs already connected in the cell, even if a new MS cuts in, the wireless environment and network The impact on performance is not great, so the dynamic priority of the cell decreases slowly, and MSs are encouraged to switch in; when resources are relatively scarce, there are already many MSs connected, the interference in the cell increases, and the performance of the system decreases. If a new MS cuts in, it will make the cell worse, so the dynamic priority is lowered faster to slow down the new MS cut-in. The present invention converts the resource percentage of the cell into the dynamic priority of the cell by means of an exponential function model to simulate the feature of slowing down before rushing. It can be seen from Fig. 2 that the resource SP of the cell decreases from 100 to 0, and the corresponding dynamic priority decreases from 4 to 0. Assuming that SP_LOW is 10, priority 4 occupies about 44% of resources, and priority 1 occupies about 17% of resources. According to formula 6 get: M takes an integer value from small to large in the set [0, N]. Once the condition M≥m is met, M is the dynamic priority corresponding to the resource percentage SP. Combined with Formula 7, there is: N*ln(SP÷SP-LOW)≤M*ln(100÷SP-LOW) Formula 8 In order to avoid complicated and cumbersome logarithmic operations in Formula 8, the present invention adopts a table-driven approach. Formula 8 can be written as: N*LN(SP)≤M*LN(100) Formula 9, where LN(SP) is queried from the logarithmic table that has been prepared in advance, that is, Table 4, the mapping relationship between the resource percentage and the logarithmic table as follows: The function integer(X) is to find the left integer closest to X on the number axis. Suppose SP_LOW is 10, when SP is 50, look up table 4, LN(SP) is 161. When SP is 100, LN(SP) is 228.

Fig. 3 is an embodiment of the present invention. Assuming that community A happens to have a market, the static priority of each community is set as shown in the figure. When many MSs in cell A initiate a call, some MSs must switch over. At this time, the cell with high static priority, such as cell B or D, also has high dynamic priority, and the MS starts to switch to the cell on the right; after a period of time, the resources of the cell on the right decrease, and the dynamic priority of the cell decreases. When the dynamic priorities among the cells are basically equal, the dynamic priority of the left cell may increase due to random calls in the cell, and the MS switches to the left, which also reduces the dynamic priority of the left cell. In the second year, suppose there is a market in Community B. Then setting the static priority of cell B to 0, and the static priority of cells H, I, and J to 7 can also achieve the same effect.

Fig. 4 is another embodiment of the present invention. Assume that cell A is a GSM900 macro cell, and cell B is a DCS1800 micro cell. In order to improve the access success rate of the covered area, it is hoped that the services accessed in cell A flow to cell B. During network planning, the static priority of cell A is intentionally set to 3 and cell B to 7. In this way, when the MS in cell A needs to switch, it will naturally switch to cell B. After a period of time, because cell B absorbs enough services, the dynamic priority decreases, and the ability to absorb services naturally decreases, and finally hovers near the balance point.

The present invention is a handover control method based on the dynamic priority of the cell. Since the dynamic priority takes both the static priority of the cell and the resource utilization status of the cell into consideration, it is more reasonable than the method of controlling the handover with a simple concept of static priority Efficient, can make full use of system resources, improve the overall performance of the network, and is a useful supplement to community planning.

In order to facilitate the narrative of the present invention, there are many English abbreviations in many places, and the control table is now available: (see the next page) The serial number of the number in English is full name in Chinese. Channel 4 MS1 ... N mobile station 1 ... N mobile desk 1 ... N5 DCS Digital Cellular System digital honeycomb system 6 GSM Global SystemCFOR Mobile Global Mobile Communication System 7 MSC MOBILE SWITCHING Center Mobile Exchange Center

                                                                                                                 

CHannel9           BCCH             Broadcast Control CHannel        广播控制信道10          TDMA             Time Division Multiple Access    时分多址接入11          BTS              Base Transceiver Station         基站收发信台12          PBGT             Power Budget                     功率预算13          TA               Time Advance                     时间提前量14          HO_MARGIN(n)                                      功率预算门限15 ΔPBGT(n) Power Budget Margin

Claims (8)

1. the method for handover control based on dynamic priority in small region is characterized in that comprising the steps:

(1) image data is promptly every about 480 milliseconds, and the data of the measurement report that base station controller BSC reception base transceiver station BTS reports comprise the downlink data of MS measurement and the upstream data that BTS measures;

(2) mean value of calculating measurement report and power budget nargin are after the measurement data that keeps is more than the sample number that requires, receive measurement report at every turn, new data and the old data that drop in the sliding window are weighted on average, and wherein the weights of the mean value of the level of average distance and adjacent cell are 1; The formula of the power budget nargin Δ PBGT (n) of calculation plot is:

Power budget PBGT (n) depends on the level mean value of adjacent cell in Δ PBGT (n)=PBGT (n)-HO_MARGIN (n) formula, and HO_MARGIN (n) is the power budget thresholding;

(3) with mean value and threshold values relatively when the mean value that keeps during more than the number that requires, participate in and threshold values process relatively, according to the priority of switch reasons, the order of comparison procedure is fixed, when one of them switch reasons is set up, the comparison procedure end;

(4) because minizone when switching, power budget nargin is greater than 0, and the mean value of descending level goes into to elect as Target cell greater than the adjacent cell that minimum inserts level when switch former in the select target sub-district;

(5) the Target cell ordering is according to the dynamic priority of the resource situation calculation plot of Target cell, and the dynamic priority according to the sub-district sorts then, and the sub-district that priority is high comes the front; If the dynamic priority of two Target cells is identical, according to the power budget nargin ordering of these two sub-districts, the sub-district that power budget nargin is high comes the front again.

2. method for handover control as claimed in claim 1 is characterized in that: wherein the performance number of MS and BS has only one; Upstream data, downlink data, it is in 32 the round-robin queue that Timing Advance and measurements of neighboring cells value are kept at length separately; The number of " counter " cumulative data of formation; Can extrapolate " current location " that keeps the last measurement report data according to the number of data; 32 measured values that kept 16 adjacent cells at most; Represent the degree of reliability of this record in the record of sub-district with parameter A GE, when handling measurement report, if record is refreshed, AGE is 0, otherwise adds 1 at every turn.

3. method for handover control as claimed in claim 1 or 2 is characterized in that: the computing formula of mean value is in the described step (2)

WEIGHT wherein is the weights of flag data reliability; The weights of data are 1 when the sign DTA of discontinuous transmission in the measurement report is 1, otherwise are relative weights greater than 1; BSC calculates the mean value of this sub-district up-downgoing level and the error rate according to formula 1; In the formula of the power budget nargin of described calculation plot, PBGT (n) depends on the level mean value of adjacent cell.

4. method for handover control as claimed in claim 1 is characterized in that: the threshold values in the step of described method for handover control (3) is made up of 3 parts: threshold values itself, and total sample number N and effective sample are counted P; The mean value that keeps when a certain data is during more than N, and whether the decision of comparing of corresponding threshold values in the mean value of these data and the database is switched; The basic principle of switching is: P scope that exceeds the threshold values regulation arranged in N mean value, will trigger switching; The order of described comparison is: interference level relatively; The up-downgoing error rate relatively; The up-downgoing level ratio; Average distance relatively; Power budget relatively; In case wherein certain once satisfies above-mentioned switching principle, stop comparison procedure at once, provide the reason of switching; Described switch reasons is divided into two classes: the result who is compared by interference level is inner the switching, and all the other switch for the minizone.

5. method for handover control as claimed in claim 1, it is characterized in that: in the step of described method for handover control (4), if trigger the reason of switching is not inner the switching, BSC is the select target sub-district from the adjacent cell that keeps, the condition that selected Target cell should satisfy is: the average level of the Target cell of being chosen must insert level greater than the minimum that this Target cell requires, and power budget nargin Δ PBGT (n) must be greater than 0.

6. as claim 1,2,4,5 one of any described method for handover control, it is characterized in that: the sort method in the step of described method for handover control (5) is, the resource situation of query aim sub-district at first calculates the resource percentage of sub-district; Inquire about the static priority of sub-district then, afterwards both are converted to the dynamic priority of sub-district; Sort according to the dynamic priority that calculates this moment in sub-district in the Target cell tabulation.

7. method for handover control as claimed in claim 6 is characterized in that: the formula of calculation plot resource percentage SP constantly is:

SP=SP_LOW*A ^mFormula 3 truth of a matter A wherein satisfies condition:

100=SP_LOW*A ^NFormula 4

8. method for handover control as claimed in claim 6 is characterized in that: when the dynamic priority of two Target cells was identical, then according to the power budget nargin ordering of these two sub-districts, the sub-district that power budget nargin is high came the front.

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