[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following examples are listed to further describe the present invention in detail.
[0031] The core idea of the present invention is: in the basic process of handover, not only the quality of the downlink pilot signal measured and reported by the user terminal is good or bad, but also the external interference situation of the handover target cell is taken into consideration, according to the magnitude of the external interference value and Set the interference threshold, make a handover decision, and complete the handover process.
[0032] The method provided by the present invention can be applied to a variety of mobile communication systems, such as WCDMA, Universal Mobile Telecommunication System (UMTS), GSM, CDMA. The handover method proposed in the present invention is implemented in a WCDMA system as an example for description. This handover method is a soft handover method. The specific implementation process is as follows: the UE completes the measurement of the pilot signal strength of the neighboring cell under the control of the network side, and reports the measured value. After the RNC receives the measurement report, the RNC and the base station NodeB jointly measure the external interference value of each neighboring cell. The RNC performs a soft handover decision based on the comparison between the external interference value and the interference threshold, and the type of the current event report, and then The UE completes the handover under the control of the network side. In the present invention, the soft handover decision is to add a wireless link or replace a wireless link, respectively corresponding to 1A event report and 1C event report.
[0033]Use in specific embodiments figure 2 The 1A incident report shown is taken as an example for illustration. The specific implementation process is as follows image 3 As shown, including the following steps:
[0034] Steps 31-32: The UE completes the measurement of the pilot signal strength of neighboring cells under the control of the network side, and sends a measurement report to the RNC. The report type is 1A event report, and cell 2 is a candidate set cell. The specific measurement and measurement report sending process is the same as that in the prior art, and will not be detailed here.
[0035] Step 33: After receiving the measurement report, the RNC obtains the external interference value of cell 2 in the candidate set according to the received total wide band power (RTWP) periodically reported by the base station.
[0036] Here, the RTWP received by the base station is the superposition of the system noise floor and the uplift value. The uplift value includes the uplift value generated by the user load and external interference. Therefore, the external interference value is equal to the uplift value minus the user load generated The uplift value, the uplift value is equal to the RTWP received by the base station minus the system noise.
[0037] In practical applications, the RTWP received by the base station is the actual RTWP value currently measured by the base station. The system noise floor is the system noise when there are neither users nor external interference in the cell. This value can be measured when the system is established. The uplift value generated by the user load within the network can be based on the formula OK, where η UL Is the uplink load.
[0038] Based on the above analysis, the external interference value is equal to the RTWP value currently measured by the base station minus the system noise floor, and then minus the uplift value generated by the user load. For example, suppose that the RTWP value received by the base station is the actual RTWP value currently measured by the base station is A, the system noise floor is B, and the actual number of users supported is the uplift value C due to user load, then the outside world The interference value is ABC and the unit is decibel.
[0039] In this embodiment, the case where there is only one candidate set cell is introduced. In the case where there are actually multiple candidate set cells, the cell with the best signal quality is selected to measure the external interference value and make a handover decision.
[0040] Step 34: The RNC executes a handover decision based on the event report reported by the UE and the external interference value measured in step 33. Since the RNC in this embodiment receives the 1A event report, in this step, a handover decision is made whether to add a wireless link. When the measured external interference value is greater than the set interference threshold, the handover decision to increase the radio link is not executed, and cell 2 is not connected to the UE. At this time, the active set cell of the UE is still only cell 1, and the current Processing flow: When the external interference value is less than the set interference threshold, the handover decision to increase the radio link is executed, the radio link is added, and cell 2 is connected to the UE. The active set of UE cells include cell 1 and cell 2.
[0041] The setting of the interference threshold can be determined according to the relationship between the uplink load of the base station and the noise floor rise, which is the system noise generated by the load itself. For example, when the load is 75% in the WCDMA system, the uplink interference increases by 6dB due to the increase of the noise floor; when the load is 50%, the uplink interference increases by 3dB due to the increase of the noise floor. The uplink interference includes interference between users in the cell and external interference. Therefore, when the network design load is high, the external interference judgment threshold can be set lower, generally around 1dB; when the network design load is low, the external interference judgment threshold can be set higher, generally around 2-3dB.
[0042] Step 35: Perform handover. The processing steps are the same as those in the prior art.
[0043] When the UE sends a 1C event report to the RNC, the handover process is basically the same as the process of the 1A event report. After the UE sends the 1C event report to the RNC, the RNC obtains the external interference value of the candidate cell according to the RTWP periodically reported by the NodeB, and compares the external interference value of the candidate cell with the set interference threshold. If external interference If the value is greater than the interference threshold, the cell replacement decision is not executed; otherwise, the cell replacement decision is executed. When the UE sends a 1B event report to the RNC, the active set cell is deleted, and the original WCDMA soft handover decision is performed at this time.
