| Summary: | 碩士 === 國立東華大學 === 資訊工程學系 === 92 ===
At 2000’s early, the new technology of UMTS was beginning to work in business and is mainly upgrade of high-speed data services. UMTS breaks through the limit of supporting voice services and low-speed data services. Our research is how to improve the network efficiency in the fuse of UMTS and GSM/GPRS when subscriber is in dual stack.
The new mobile communication generally takes advantage of the radio technology of CDMA. CDMA promotes the efficiency of radio spectrum and all subscribers share the same frequency to communicate with each other. Each node modulates data signals and the spectrum code on air. It improves the data transmission rate and is inevitably that more signals in air generate more noise and is difficult to filter the clear data signals.
In UMTS, voice services take advantage of the new codec technology of AMR. One voice call is only 12.2 kbps but one voice call in GSM/GPRS monopolizes one timeslot which can support data services in 21.4 kbps.
Based on the utilization of timeslots, our research is devoted to scheme the new the allocation of radio resource in the integrated system. In our scheme, UMTS has high priority to carry data services and voice services are carried by GSM. When UMTS is in heavy loading, the rule of allocation radio resource is modified that GPRS has high priority to carry data services and UMTS carries voice services. It can decrease the interference of UMTS to protect the decline of transmission quality. The result is improved the capacity of the integrated system and the quality of data services.
To measure our scheme, we use the simulation software of ns2 to show the performance of the integrated system. First, we measure the capacity of mobile subscribers in a stand alone cell. UMTS is the better system than GPRS when UMTS is not in heavy loading. The 90% data sessions obtain the required bandwidth, and the average loss ratio is 1%; the average delay time is qualified to support real time services except for data services in GSM/GPRS.
When UMTS is in heavy loading, the radio environment goes down with the activity of data transmission. The ratio of loss packet increases exponentially according to the data transmission rate. It causes the decrease of data transmission rate and the extension of the transfer delay time. After the implement of our scheme, UMTS and GPRS can share the traffic loading efficiently and increase the capacity of the integrated system. In each data session of 64 kbps, the increase is 7.14% in the capacity of the integrated system. In each data session of 128 kbps, the increase is 13.33% in the capacity of the integrated system. It is efficiently to management the radio resource.
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