Algorithm Research On Dynamic Channel Allocation Technology In2G And3G

In mobile communications system, due to spectrum resources, the time slot resources, and spreading code resources are limited, coupled with the growing traffic demand, channel allocation problem is becoming increasingly important.In2G cellular network, the way of channel allocation is mostly using fixed channel allocation (FCA), each user during a call always use the same channel, when the quality of assigned channel worsen, due to the call can’t adjust to the channel with smaller interference so that the quality of call will be reduced and call will be blocked. Dynamic channel allocation (DCA) in cellular networks starts to develop based on above problem. When new business comes, DCA will select suitable channel with minimum carrier-to-interference rate (CIR) to dynamically allocate it to new business. When the quality of assigned channel worsens, DCA algorithm will restart to select a channel with smaller interference for business. But existing research on channel allocation of cellular network mainly focused on FCA, less on DCA. Simultaneously,the model is more complicated and the algorithm has lower Rate of convergence on existing DCA. So, it is important to research on DCA of cellular network.In TD-SCDMA system, because it adopts TDD mode, it is suitable for the implementation of the DCA technology. So, TD-SCDMA can flexibly allocate resources and get the best spectrum efficiency in symmetrical and asymmetrical3G business. The DCA in TD-SCDMA includes slow DCA and fast DCA. At present, the research of fast DCA focuses on CP (complete partitioning) strategy and CS (complete sharing) strategy. The shortcoming of CP strategy is:when fewer data business of no data business in system, data time slots will be idle, Channel resource utilization will be reduced. The shortcoming of CP strategy is:it doesn’t take a variety of business into consideration in3G system, different businesses have different priorities in3G, so voice drop call rate and blocking rate will be higher.This study researches on DCA based on above. Firstly aiming at overcoming the shortages of the current dynamic channel allocation model in cellular networks, a dynamic channel allocation model based on minimizing the number of cell and channel among cells that violate electromagnetic compatibility constraints was proposed. Aiming at the mathematical model, a dynamic channel allocation algorithm in cellular networks based on genetic algorithm was proposed, obtaining a set of channel assignment with minimum interference and avoiding interference among mobile users. Simulations on several well-known twenty-one cells Philadelphia benchmark problems showed that this algorithm could get an efficient channel assignment and improved spectrum utilization and system capacity.Secondly, aiming at low utilization rate of channel resources based on complete partitioning DCA and high blocking rate of voice business based on complete sharing DCA in TD-SCDMA network, a high efficiency DCA algorithm based on resource sharing and priority is proposed. Voice and data business are assigned different priority based on resource sharing when considering different state, meanwhile, because that handoff call will bring negative effects to system performance, reserving channel for handoff call, when reserved channel is vacant, it could be borrowed for transferring data business. Simulation results show that the proposed algorithm reduces dropout rate of voice and loss rate of data packet and raise the resource utilization of the time slot and the performance of system.