Research On MAC Layer Scheduling And Resource Management For IEEE 802.16e OFDM System

Recently, with rapid development of mobile communication and urgent requirement of wireless broadband access, IEEE 802.16e comes into existance. But, compared with its mature market, IEEE 802.16e specification has many technical problems, such as MAC Layer Scheduling and Resource Management. The MAC Layer Scheduling and Resource Management refers to operation of serving BS (Base Station) to manage effectively allocable transmission resources, which involves Scheduling Services, Dynamic Frequency Selection, Sleep Mode, Handover etc. IEEE 802.16e specification only defines function modules of MAC Layer Scheduling and Resource Management, as well as the basic content and implementation rules of the function modules, but does not propose specifically the feasible schemes or implementing algorithms. Hence, studies of MAC Layer Scheduling and Resource Management, especially on how to improve utilization efficiency of system resources and how to support mobility of the terminal, have great realistic significance and economical value.This paper firstly investigates Scheduling Service algorithms by which effective management of allocable transmission resources is implemented. It proposes non-real-time, real-time and integrated scheduling service algorithms based on PF (Proportional Fairness) scheduling algorithm; according to different definitions of traffic allocation units, divides non-real-time and integrated scheduling service algorithms respectively into algorithms based on OFDM symbol and those based on subchannel; proposes a real-time scheduling service type, irtPS (Improved Real-Time Polling Scheduling), by mathematically modelling real-time traffic. Simulation results show that the proposed algorithms can satisfy QoS requirements of each scheduling service type, ensure long-time fairness at the expense of short-time fairness, and maximize utilization efficiency of system resources taking fairness into account.Secondly, this paper studies Dynamic Frequency Selection scheme which redefines allocable transmission resources. It proposes an improved Dynamic Frequency Selection scheme, in which traffic allocation unit and scheduling information delivery are selected by subchannel domain, modulation and coding domain, subcarrier domain. Simulation results show that, when IEEE 802.16e OFDM system working at unlicensed bands, the proposed scheme can improve BER performance and system capacity, but the improvement of BER performance is achieved at the expense of sytem capacity. Thirdly, this paper explores how to reduce MS's (Mobile Subscriber) occupation of allocable transmission resources through sleep mode. It proposes a method by which energy saving efficiency of the sleep mode is maximized, thus MS'soccupation of air-interface resources is reduced, and then utilization efficiency of system resources is increased; models mathetically two sleep mode states, including single Power Saving Class I and several Power Saving Classes coexisting with each other. Mathetical analysises show that energy saving efficiency of the sleep mode is maximized by optimizing time parameter configuration of the sleep mode.Finally, this paper inspects influence of handover on MAC Layer Scheduling and Resource Management. It proposes a scheme that, in order to maximize utilization efficiency of system resources, different handover mechanisms are selected depending on distinct scheduling service types, and this scheme minimizes MAC layer overhead related to handover on prerequisite of guaranteeing delay performance of scheduling services. Simulation results show that delay performance of handover is improved at the expense of more MAC overhead, and the handover mechanism with less MAC overhead can be selected on the basis of guaranteeing delay performance of scheduling services.