Research On The Interworking Handover Algorithm Between WCDMA And GSM

The evolution of mobile communications throughout the world is useful in orderto appreciate the enormous impact that cellular radio and Personal CommunicationServices (PCS) will have on all of us, the mobile communications system will evolveto the broadband communication network over the next several decades. Thereforehow to use wireless networks reliably and effectively to serve the users is one of thekey issues, and the research of the handover procedure has undoubtedly become a hottopic.According to the current research, the majority of the study on the handoverbetween the networks is carried out under the conditions of a given threshold value,the mobile performs a handover when the signal strength of a neighbouring cellexceeds that of the current cell with a given threshold. For example, the handoverbetween WCDMA and GSM allows the GSM network to be used to give fallbackcoverage for WCDMA technology. This means that subscribers can experienceseamless services even with a phased build-out of WCDMA. On top of that,handovers from GSM to WCDMA can be used to reduce the loading in GSM cells asthe loading in the WCDMA network increases As a result; it becomes more importantto have support for load-triggered handover in both directions. Ericsson has developedtechnologies that overcome the challenges of interworking between WCDMA (UMTS)and GSM.This paper presented the interworking handover algorithm between WCDMAand GSM and an improved algorithm: the subscriber located in the network boundaryperforms a handover according to the signal level. The improved algorithm took thenetwork blocking rate as the QoS, the algorithm test the results according to the QoSas well, and the handover only takes place when the QoS could be satisfied. TheMatlab simulation results showed that:(1)both G-W and W-G handovers exist whenthe tester wandered over the network boundary;(2)G-W handover come up more thanW-G handover；(3)both of the handovers decreased when the QoS was considered。The algorithm proposed in this paper has the following advantages:(1) the QoS of theneighbouring cell could be guaranteed better. The handover only happens when theQoS could be satisfied according to the proposed algorithm;(2) Handover successrate could be improved。As the handover comes up when the QoS of the neighbouringcell could be satisfied，the target cell could serve the users with adequate resources;(3)the system stability could be enhanced. Compared with the algorithm without QoS,the proposed one not only reduced the times of handover obviously but also saved theheadlines of the whole system. The special correlation of log-normal have been used for making the test mobilewith an island of7WCDMA cells surrounded by GSM cells and allow the mobiles tomove along the boundary on the straight red line between WCDMA cells to GSMcells in the2.5GHz (for WCDMA) and900MHz (for GSM) frequency bands.WCDMA and GSM cell, the cell radius is5km, and received current strongest GSMand WDMA networks level value every100ms.