Study On The Channel Allocation Technology Based On Handover Channel Reservation In TD-SCDMA

1. IntroductionTD-SCDMA, the third generation mobile communication standard that China puts forward and holds the independent intellectual property rights, is one of the three primary standards certificated by ITU. On April 1st 2008, TD-SCDMA began commercial in the eight cities of all the country. TD-SCDMA is put forward in China, both the international and domestic research to it is seriously lack, The country has issued relevant policy to support TD-SCDMA. The encouragement of the policy will truly have a tremendous promoting effect on the development of the whole industrial, and the study on TD-SCDMA and TD-LTE has been a hotspot in the communication field. In order to allocate resources to integrated service, which including voice service—real time service (RT) and data service—non-real time service(NRT), TD-SCDMA, one of the 3G standards, need to be able to afford an efficient resource-allocating mode .Baton Handover and DCA is very important for TD-SCDMA system.Radio resource management (RRM) can use limited wireless resources rationally and effectively, which includes call admission control (CAC), handover, power control, congestion control, pocket control and dynamic channel allocation (DCA). The TD-SCDMA system, which in order to ensure the continuity of UE, the load of network and operation maintenance, is a process making UE transform from current link layer to other cellular, and the communication service don't interrupt. The Fast-DCA algorithm is used to allocate radio resource for the user applying for connection and adjust the resource based on system state. Based on the intrinsic baton handover and DCA algorithms, we can optimize them to reduce the interrupting probability of baton handover and improve the performance of service.After the study on the domestic and overseas'baton handover and DCA algorithm, the algorithm in the fast DCA process of TD-SCDMA system has been studied and mix-data rate grouping borrowed and priority channel reservation MB DCA algorithm is introduced in this paper. The algorithm has been simulated2. MRG MB DCA algorithm in TD-SCDMA systemAccording to the UL/DL time slots rate that confirmed by Slow-DCA arithmetic, Fast-DCA arithmetic gains the usable resource list of the data service and the voice service. The movable boundary (MB) scheme is adopted when allocating the usable resource. The scheme divides the channel into two parts: data service channel and voice service channel. If the voice service channel is free and the data buffer-queue is not empty, the data service will be transmitted through the voice service channel. When a new voice call arrives and the voice service channel is not free, the voice call will grab the voice service channel which was borrowed by data service.MRG MB DCA algorithm is the improved algorithm of MB scheme. If the free BRU of voice service time slots are between 8 and 16, it can be borrowed to date service at the rate of 64kbps; If the free BRU of voice service time slots are out of 16, it can be borrowed to date service at the rate of 144kbps or two separate data service at the rate of 64kbps. The algorithm did not consider the difference between the handover voice service and the new call service, and did not consider the user's attribute and service's urgency of the handover voice service. In order to analyze the improved MRG MB DCA algorithm, a planar Markov model is founded to analyze and simulate on computer.The MRG MB DCA algorithm is analyzed under the condition of symmetrical time slots. At office area, where data service is primary, the MRG MB DCA algorithm under the condition of symmetrical time slots will be limited by DL resource and produce capability loss. So this paper studies on the MRG MB DCA algorithm under the condition of asymmetrical time slots and compares to the MRG MB DCA algorithm under the condition of symmetrical time slots.3. MRGPR MB DCA algorithm in TD-SCDMA systemBased on the research of the MRG MB DCA algorithm, the MRG MB DCA algorithm did not consider the difference between the handover voice service and the new call service, and did not consider the user's attribute and service's urgency of the handover voice service. This paper has introduced a new algorithm, mix-data rate grouping borrowed and priority channel reservation MB DCA algorithm (MRGPR MB DCA). The voice service is divided into the handover voice service and the new call service, and reserved the channels for the handover voice service priority. According to the speed of the mobile station, the handover voice service users are divided into rapid users and slow users, and according to the user's attributes, the handover voice service users are divided into VIP users and ordinary users. So the handover voice service users are divided into four Priorities, the ordinary slow users, the ordinary rapid users, the VIP slow users, the VIP rapid users. For the different priority handover voice service, the handover threshold parameters are different. According to the handover threshold parameters, the system decides whether to begin handover. The threshold parameters of higher-priority handover voice are low, and more easily satisfy the handover conditions. So high rate user can be serviced firstly. The arithmetic reduces the channel block and improves the total channel utilization efficiency.For the data service, If the free BRU of voice service time slots are between 8 and 16, it can be borrowed to date service at the rate of 64kbps; If the free BRU of voice service time slots are out of 16, it can be borrowed to date service at the rate of 144kbps or two separate data service at the rate of 64kbps. Because reserved the channels for the handover voice service, the new call service does not user these channels, so the algorithm increases the opportunity of the data service borrowing the voice channel and improve the performance of the data service. In order to analyze the improved MRGPR MB DCA algorithm, a planar Markov model is founded to analyze and simulate on computer.At office area, where data service is primary, the MRGPR MB DCA algorithm under the condition of asymmetrical time slots can work well. So this paper studies on the MRGPR MB DCA algorithm under the condition of asymmetrical time slots and compares to the MRGPR MB DCA algorithm under the condition of symmetrical time slots and MRG MB DCA algorithm under the condition of asymmetrical time slots.4. The simulation and analysis of the MRGPR MB DCA algorithmTo validate the performances of the mix-data rate grouping borrowed and priority channel reservation MB DCA algorithm, the mixed-data rate small grouping borrowed MB DCA algorithm and the mix-data rate grouping borrowed and priority channel reservation MB DCA algorithm are simulated by computer respectively. These algorithms are compared in these aspects of the handover voice call blocking probability, the voice call blocking probability, the average waiting delay of data packet, the data packet dropping probability and the total channel utilization efficiency. The result shows that, compared with the mixed-data rate small grouping borrowed MB DCA algorithm, the mix-data rate grouping borrowed and priority channel reservation MB DCA algorithm achieves the preferential access of VIP and high rate mobile user, the call failure probability resulted from the baton handover reduced 1.8%, packet maximum waiting time reduced 0.13s, the packet dropped probability reduced 6%, the channel utilization efficiency improved 4%.The MRGPR MB DCA algorithm is also simulated by computer when the time slots proportion of UL/DL is 2:4, the capability index of data service and voice service in DL are gained in the MRGPR MB DCA algorithm under the condition of time slots asymmetry and compared to the MRGPR MB DCA algorithm under the condition of time slots symmetry and the MRG MB DCA algorithm under the condition of time slots asymmetry. The result shows, at the place where the data service occupies the main proportion, the MRGPR MB DCA algorithm make big improvement on the DL data service performance.5. ConclusionOn the base of studying on the domestic and overseas'handover algorithm and fast DCA algorithm, the strategy in the BH process of TD-SCDMA system has been studied and a new algorithm called mix-data rate grouping borrowed and priority channel reservation MB DCA algorithm is introduced in this paper. The paper analyzes the theory of the algorithm and the capability of the MRGPR MB DCA algorithm under the condition of asymmetry/symmetry time slots is simulated. The result shows that the MRGPR MB DCA algorithm achieves the preferential access of VIP and high rate mobile user, reduces the call failure probability resulted from the baton handover, improves the performance of data service and increases the channel utilization efficiency. At the place where the data service occupies the main proportion, the MRGPR MB DCA algorithm make big improvement on the DL data service performance. And certain reference is provided for the research on the DCA of TD-SCDMA and TD-LTE.