CN100442909C - A Method of Interlayer Handover in WCDMA Layered Network - Google Patents

Abstract

The present invention provides a method for handover between layers in a WCDMA layered network, including: measuring the moving speed of the mobile station; Higher-level cell handover; when the moving speed of the mobile station is at a normal speed, it stays at this layer; when the moving speed of the mobile station is slow and there are cells with a lower Lower-level cell handover. According to the present invention, the present invention adopts an intermittent measurement mode during interlayer switching measurement, thereby reducing the impact of starting the compressed mode on system performance. In addition, when the macro cell is handed over to the micro cell, the present invention adopts the method that the mobile station only switches to the target cell when the target cell is selected for several consecutive measurements, that is to say, the speed of the mobile station in the target cell is pre-selected. estimation, thereby avoiding ping-pong switching.

Description

A Method of Interlayer Handover in WCDMA Layered Network

technical field

The invention relates to network communication technology, in particular to an interlayer switching method in a WCDMA layered network.

Background technique

In a WCDMA (Wideband Code Division Multiple Access) mobile communication system, in order to meet the requirements of multiple high-speed data services, a large enough system service capacity is required. Generally, the system capacity per unit area is increased by reducing the cell coverage radius. In hotspot areas, the traffic is absorbed by adding micro cells; in dense urban areas with particularly high traffic, continuous coverage of small cells is realized. But for mobile stations moving at high speed, micro cells will bring many problems, such as increased call drop rate, increased system signaling load, and reduced system capacity.

In order to solve the above problems, a layered cell network structure is introduced, and a continuous coverage layer of macro cells is added on the micro cell layer. The coverage radius of the macro cell is larger than the coverage radius of the micro cell. The mobile stations of the two layers have different moving speeds. The coverage radius of the macro cell corresponds to a higher moving speed of the mobile station, and the coverage radius of the micro cell corresponds to a lower mobile table movement speed. If the concept is extended, a multi-layer stratified community can be obtained.

In order to control the mobile station to select the network layer, the network needs to estimate the moving speed of the mobile station. Usually, the moving speed of the mobile station does not refer to the actual physical moving speed of the mobile station in the network, but refers to the number of inter-cell handovers in the network. Therefore, the degree of frequent handover is reflected by the moving speed of the mobile station, so that corresponding strategies can be adopted to avoid various problems caused by frequent handover. Generally, the handover history of the mobile station is used as the basis for estimating the moving speed of the mobile station.

Switching between layers is performed according to the velocity estimation result. Speed results are usually divided into three cases: fast, slow, and normal speed. A fast mobile station needs to be handed over to a higher-level cell (such as a macro cell), a slow mobile station needs to be handed over to a lower-level cell (such as a micro cell), and a normal-speed mobile station stays in this layer. The connection between different layers is maintained through the inter-layer switching process, and the transfer of the mobile station at each layer in the network is realized. In networking, different layers generally have different frequency points, and inter-layer switching is realized through inter-frequency switching. Generally, compression mode needs to be activated during switching measurement.

The simulation shows that if the proportion of mobile stations in the compressed mode state is large in a cell, it will have a great impact on the coverage, quality and capacity of the system, so the compressed mode should be activated as little as possible.

However, in the prior art, the inter-layer handover measurement and decision scheme adopts continuous inter-frequency measurement. The inter-frequency handover measurement is triggered when the integrated quality of the active set is lower than a certain threshold, and the measurement is performed all the time. During the measurement process, if a suitable inter-frequency cell is found through measurement, it will be directly handed over to the cell; if the integrated quality of the active set is higher than a certain threshold, the inter-frequency handover measurement will be stopped.

Since continuous inter-frequency measurement is used for handover, at this time, for some situations, such as the area where the macro cell is continuously covered but the micro cell is not continuously covered, the mobile station will measure different values when the macro cell initiates the handover measurement to the micro cell. To the target cell, if the inter-frequency measurement is always enabled, not only the signal of the target cell cannot be searched, but also the transmit power of the mobile station terminal will be consumed. If the compressed mode is also enabled at the same time, the system performance will be seriously affected.

In addition, in some cases, the mobile station is estimated to be slow when it is in a macro cell, but it may be estimated to be fast again if it is handed over to a micro cell, and inter-layer ping-pong occurs. Thus, the switching frequency between layers is increased, and the communication efficiency is reduced.

Contents of the invention

The purpose of the present invention is to provide a kind of interlayer handover method in the WCDMA layered network at the shortcoming of above-mentioned prior art, thereby solved the mobile station that is in compressed mode state when realizing interlayer handover in layered network structure If the ratio is too large, it will cause the problem of degrading the system performance, and when the mobile station is handed over from the macro cell to the micro cell, it may quickly switch back to the macro cell "ping-pong" handover problem.

The present invention provides a kind of interlayer switching method in WCDMA layered network, comprising:

A. Measure the moving speed of the mobile station;

B. According to the moving speed of the mobile station, inter-layer handover is carried out by using an intermittent different-frequency measurement method. The intermittent different-frequency measurement method is: after the mobile station has different frequency measurements for a predetermined time, if no suitable target layer cell is found, Then stop the inter-frequency measurement for one cycle time, and then start the inter-frequency measurement.

The step B further includes: when the moving speed of the mobile station is fast and there is a cell with a higher layer, switching to the cell with a higher layer by means of intermittent inter-frequency measurement.

The switching to a higher-level cell by means of intermittent inter-frequency measurement further includes:

B12, select the frequency point of a higher-level cell and its adjacent cells, start inter-frequency measurement, judgment and compression mode; and start a measurement timer and a periodic timer, the duration of the measurement timer is less than the duration of the periodic timer;

B13. Judging whether there is a target cell signal that meets the handover requirement, if so

B14, select it as the target cell; and execute the switching process, switch to the target cell, stop this process,

otherwise,

B15, when the measurement timer expires, stop the inter-frequency measurement, judgment and compression mode;

B16. When the period timer expires, go to step B12.

The step B is also provided with a number of measurements, the number of measurements indicates the number of times the measurement timer is started, and when the number of measurements is equal to the maximum number of retries of the fast mobile station interlayer handover, the process is stopped.

The step B further includes: staying on the current floor when the moving speed of the mobile station is a normal speed.

The step B further includes: when the moving speed of the mobile station is slow and there is a lower-level cell, switching to the lower-level cell by means of intermittent inter-frequency measurement.

The step B further includes: when the moving speed of the mobile station is slow and there is a lower-level cell, then using intermittent inter-frequency measurement to switch to a lower-level cell that has been selected for a predetermined number of times.

Said step B further comprises:

B21, select the adjacent sub-district with lower level, and for each adjacent sub-district of the target layer, the number of times of its continuous selection as the target sub-district is cleared to 0;

B22, select the frequency points and adjacent cells of the lower level cell, start the inter-frequency measurement, judgment and compression mode, and measure the timer and the periodic timer, the duration of the measurement timer is less than the duration of the periodic timer;

B23, during inter-frequency measurement, for all adjacent cells, when the signal quality of the adjacent cell meets the handover requirement, the number of times the adjacent cell is continuously selected as the target cell is increased by 1;

B24, when the measurement timer expires, stop the inter-frequency measurement, judgment and compression mode;

B25, judging in the adjacent cells, whether there is an adjacent cell that is continuously selected as the target cell number of times and is equal to the speed pre-estimation parameter of the handover between slow user layers, if any,

B26, select it as the target cell; and execute the switching process, switch to the target cell, and stop the process;

otherwise,

B27. When the period timer expires, go to step B22.

The step B is also provided with the number of times of measurement, the number of times of measurement represents the number of times the measurement timer is started, and when the number of times of measurement is equal to the maximum number of retries of the slow mobile station interlayer handover and before performing step B27, also execute:

B28. Select the cell with the largest number of consecutive selections as the target cell among all adjacent cells as the target cell, and execute the handover process, switch to the target cell, and stop the process.

During inter-frequency measurement, for adjacent cells whose signal quality has not met the handover requirements, the number of consecutively selected target cells is cleared to 0.

Described step B28 further comprises:

B31, judge whether the continuous selection of all adjacent cells is 0 as the number of target cells, if so,

B32, then stop this process,

otherwise,

B33. Select the cell that has been continuously selected as the target cell the largest number of times as the target cell, select it as the target cell, and execute the handover process, switch to the target cell, and stop the process.

The selecting it as the target cell further includes: if there are multiple target cell signals meeting the handover requirement, selecting a cell with the best signal quality as the target cell.

According to the present invention, the present invention adopts an intermittent measurement mode during interlayer switching measurement, thereby reducing the impact of starting the compressed mode on system performance. In addition, when the macro cell is handed over to the micro cell, the present invention adopts the method that the mobile station only switches to the target cell when the target cell is selected for several consecutive measurements, that is to say, the speed of the mobile station in the target cell is pre-selected. estimation, thereby avoiding ping-pong switching.

Description of drawings

Fig. 1 is the flow chart of the handover to the macro cell of the present invention;

Fig. 2 is a flow chart of handover to a micro cell in the present invention.

Detailed ways

In order to make it easier for those skilled in the art to understand and realize the present invention, the embodiments of the present invention are described in conjunction with the accompanying drawings.

The interlayer switching measurement in the WCDMA layered network of the present invention adopts an intermittent measurement method. That is to say, after a period of measurement, if the mobile station does not find a suitable target layer cell, it can stop the measurement first, and then re-initiate the measurement after a period of time when the wireless environment has changed, and continue to search for a suitable target layer cell.

According to the present invention, the so-called inter-layer handover refers to: since each layer in the network will estimate the speed state of the mobile station, when it is found that the current estimated speed of the mobile station does not match the layer it is in, that is, the speed of the mobile station When the estimated state is fast or slow, switching between layers is required. If the mobile station is fast and there are high-level inter-frequency adjacent cells, it will try to handover to these cells; if the mobile station is slow and there are low-level inter-frequency adjacent cells, it will try to handover to these cells.

When the mobile station switches to a new level, the speed state of the mobile station defaults to normal speed. For the duration thereafter, the network evaluates the speed of the mobile station and handovers it based on the result of the speed evaluation.

The inter-layer switching process of the present invention will be described in detail below.

For the sake of illustration, first define the following constants:

TmeasFast Fast mobile station inter-layer handover measurement time length

TretryFast Fast mobile station inter-layer handover retry interval, TretryFast must be greater than TmeasFast

NretryFast Maximum number of retries for fast mobile station interlayer handover

TmeasSlow Slow mobile station interlayer handover measurement time length

TretrySlow Interlayer handover retry interval of slow mobile stations, TretrySlow must be greater than TmeasSlow

NretrySlow Maximum number of retries for interlayer handover of slow mobile stations

NhystSlow The speed pre-estimation parameter of slow mobile station interlayer handoff For the convenience of illustrating the present invention, also will define following variable and timer:

MeasNum The number of measurements that have been started

TmeasTimer measurement timer

TretryTimer cycle timer

NhystCnt(i) The number of times that adjacent cell i is continuously selected as the target cell

Firstly, the method of handing over from a micro cell with a lower hierarchy to a macro cell will be described.

Taking the mobile station in a micro cell as an example to illustrate the process of switching from a lower layer cell (micro cell) to a higher layer cell (macro cell layer) when the speed estimation state of the mobile station changes from other states to fast.

As shown in Figure 1, in step 1, MeasNum is cleared to 0.

In step 2, frequency points and adjacent cells are selected according to the target level, and measurement and judgment are started. If it is determined that the compression mode needs to be activated, the compression mode is activated at the same time. The timer TmeasTimer whose duration is TmeasFast is started, and the timer TretryTimer whose duration is TretryFast is started.

In step 3, because the interlayer handover does not require a quality comparison of the signal of the interlayer cell, as long as the pilot signal quality of the target cell (macro cell) can cover the current mobile station;

Judging whether there are multiple target cell signals meeting the handover requirements, if

Then in step 8, select a target cell with the best current signal quality; if a suitable target cell is selected through the handover decision, then start the handover execution process, switch to the target cell, stop this process, and return;

Otherwise, go to step 4.

In step 4, if the timer TmeasTimer times out, stop the measurement, judgment and compression mode, and add 1 to MeasNum.

In step 5, it is judged whether MeasNum is equal to the maximum number of measurements NretryFast, if so, then execute step 9, stop this process, and return, at this moment, it shows that there is no higher-level target cell, and handover cannot be performed.

In step 6, after another period of time (TretryFast-TmeasFast), that is, the timer TretryTimer times out, go to step 2.

When the mobile station switches from a cell with a lower layer to a cell with a higher layer, the present invention adopts an intermittent measurement method, thereby reducing the impact of starting the compressed mode on system performance.

Secondly, the method of switching from a higher-level macro cell to a lower-level micro cell will be described in detail below.

Taking the mobile station in a macro cell as an example to illustrate the handover from a higher-level cell (macro cell) to a lower-level cell (micro cell layer) when the speed estimation state of the mobile station shifts from other states to slow speed process.

As shown in FIG. 2 , in step 21 , the number of measurements MeasNum is cleared to 0. Select adjacent cells according to the priority of the target layer, and clear NhystCnt(i) to 0 for all target layer adjacent cells i.

In step 22, frequency points and adjacent cells are selected according to the priority of the target layer, and measurement and judgment are started; if it is judged that the compressed mode needs to be started, the compressed mode is started at the same time. The timer TmeasTimer whose duration is TmeasSlow is started, and the timer TretryTimer whose duration is TretrySlow is started.

In step 23, since the inter-layer handover does not require a quality comparison of the signals of the inter-layer cells, as long as the quality of the pilot signal of the target cell can cover the current mobile station. During the measurement duration of TmeasSlow, if the signal quality of the adjacent cell i meets the handover requirement, NhystCnt(i) is increased by 1.

In step 24, if the timer TmeasTimer expires, the measurement, judgment and compression modes are stopped.

In step 25, it is judged whether there is an adjacent cell with NhystCnt (i) equal to NhystSlow in the adjacent cell i, if so,

In step 27, then select this sub-district to be the target sub-district; If there are a plurality of such sub-districts, then select the one with the best current signal quality; And start the handover execution process, switch to the target sub-district, stop this process, and return;

Otherwise, in step 26, the measurement times MeasNum adds 1, and judges whether the measurement times MeasNum is equal to NretrySlow, if so,

In step 28, judge whether the NhystCnt (i) of all adjacent cells is 0, if so,

In step 29, then stop this process, and return, illustrate at this moment that there is no sub-district of lower level, can not carry out handover;

Otherwise, in step 30, select the cell with the largest NhystCnt(i) as the target cell; if there are multiple such cells, select the one with the best signal quality. If the target cell is selected, start the handover execution process, switch to the target cell, and return.

Otherwise, in step 31, during the measurement duration of TmeasSlow, NhystCnt(i) is cleared to 0 for the adjacent cell i whose signal quality has not met the handover requirement all the time.

In step 32, the timer TretryTimer times out, go to step 2.

When the mobile station is handed over from the macro cell to the micro cell, the impact of the compressed mode on the system can be reduced because of the intermittent measurement. When the macro cell is switched to the micro cell, when selecting the target cell, NhystSlow is selected consecutively for switching, which plays the role of speed estimation and can avoid the problem of ping-pong switching.

Although the present invention has been described by the embodiments, those of ordinary skill in the art know that, without departing from the spirit and essence of the present invention, the present invention can have many modifications and variations, and the scope of the present invention is defined by the appended rights Requirements to limit.

Claims (12)

1. a method for handover between layers in a WCDMA layered network, characterized in that, comprising: A. Measure the moving speed of the mobile station; B. According to the moving speed of the mobile station, inter-layer handover is carried out by using an intermittent different-frequency measurement method. The intermittent different-frequency measurement method is: after the mobile station has different frequency measurements for a predetermined time, if no suitable target layer cell is found, Then stop the inter-frequency measurement for one cycle time, and then start the inter-frequency measurement. 2. the interlayer switching method in the WCDMA layered network according to claim 1, is characterized in that, described step B further comprises: when the speed of movement of mobile station is fast, and when there is the sub-district with higher hierarchy, then Use the intermittent inter-frequency measurement method to switch to a higher-level cell. 3. the interlayer handover method in the WCDMA layered network according to claim 2, is characterized in that, described adopting intermittent inter-frequency measurement mode to hand over to the cell with higher hierarchy further comprises: B12, select the frequency point of a higher-level cell and its adjacent cells, start inter-frequency measurement, judgment and compression mode; and start a measurement timer and a periodic timer, the duration of the measurement timer is less than the duration of the periodic timer; B13. Judging whether there is a target cell signal that meets the handover requirement, if so B14, select it as the target cell; and execute the switching process, switch to the target cell, stop this process, otherwise, B15, when the measurement timer expires, stop the inter-frequency measurement, judgment and compression mode; B16. When the period timer expires, go to step B12. 4. the interlayer handoff method in the WCDMA layered network according to claim 3, is characterized in that, described step B is also provided with measurement times, and described measurement times represents the number of times that measurement timer starts, when measurement times When it is equal to the maximum number of interlayer handover retries of the fast mobile station, this process is stopped. 5. The method for handover between layers in WCDMA layered network according to claim 1, characterized in that said step B further comprises: when the moving speed of the mobile station is a normal speed, staying in the current layer. 6. The method for handover between layers in the WCDMA layered network according to claim 1, wherein said step B further comprises: when the moving speed of the mobile station is slow, and there is a cell with a lower layer , the intermittent inter-frequency measurement method is used to switch to the lower-level cell. 7. The method for handover between layers in the WCDMA layered network according to claim 6, wherein said step B further comprises: when the moving speed of the mobile station is slow, and there is a cell with a lower layer , the intermittent inter-frequency measurement method is used to switch to the lower-level cell that has been selected for a predetermined number of times. 8. the interlayer switching method in the WCDMA hierarchical network according to claim 7, is characterized in that, described step B further comprises: B21, select the adjacent sub-district with lower level, and for each adjacent sub-district of the target layer, the number of times of its continuous selection as the target sub-district is cleared to 0; B22, select the frequency points and adjacent cells of the lower level cell, start the inter-frequency measurement, judgment and compression mode, and start the measurement timer and the periodic timer, the duration of the measurement timer is less than the duration of the periodic timer; B23, during inter-frequency measurement, for all adjacent cells, when the signal quality of the adjacent cell meets the handover requirement, the number of times the adjacent cell is continuously selected as the target cell is increased by 1; B24, when the measurement timer expires, stop the inter-frequency measurement, judgment and compression mode; B25, judging in the adjacent cells, whether there is an adjacent cell that is continuously selected as the target cell number of times and is equal to the speed pre-estimation parameter of the handover between slow user layers, if any, B26, select it as the target cell; and execute the switching process, switch to the target cell, and stop the process; otherwise, B27. When the period timer expires, go to step B22. 9. the interlayer switching method in the WCDMA layered network according to claim 8, is characterized in that, described step B is also provided with measurement times, and described measurement times represents the number of times that measurement timer starts, when measurement times When it is equal to the maximum number of interlayer handover retries of the slow mobile station and before performing step B27, also execute: B28. Select the cell with the largest number of consecutive selections as the target cell among all adjacent cells as the target cell, and execute the handover process, switch to the target cell, and stop the process. 10. according to the interlayer switching method in the WCDMA layered network described in claim 8 or 9, it is characterized in that, during inter-frequency measurement, for the adjacent cell that signal quality does not satisfy switching requirement all the time, be selected as target cell number of times continuously Cleared to 0. 11. the interlayer switching method in the WCDMA hierarchical network according to claim 9, is characterized in that, described step B28 further comprises: B31, judge whether the continuous selection of all adjacent cells is 0 as the number of target cells, if so, B32, then stop this process, otherwise, B33. Select the cell that has been continuously selected as the target cell the largest number of times as the target cell, select it as the target cell, and perform a handover process, switch to the target cell, and stop the process. 12. according to the interlayer switching method in the WCDMA layered network described in claim 3 or 8, it is characterized in that, said selecting it as the target cell further comprises: if there are a plurality of target cell signals to meet the switching requirements, then select A cell with the best signal quality is the target cell.

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