Research And Realization Of Radio Resource In The Protocol Of Mobile Communication

Mobile communication with wide market is one of the successes of the world scientific and economic developments in the last 20 years. Currently mobile communication is evolving from the second generation characterized by its digitalization to the third generation characterized by wireless access of wide band. In China,where the GSM holds the most proportion of the wireless network,the research and development of mobile station (MS) with the general packet radio service (GPRS,called 2.5G) not only let the vast amount of investment on GSM network continue to be profitable for a longer period,but also make the GSM network smoothly transfer to 3G. GPRS,by making better use of radio resource than GSM,is very suitable for dala service with the character of asymmetry. Protocol software of MS is very significant for the development of mobile telephone with our own property right.Our research is focused on the radio resource (RR) in the GSM protocol. As the kernel of the GSM protocol,RR is the part that distinguishes GSM from other wireless protocols. It influences the design of logical circuit. RR aims at making MS harmonically cooperate with its network,in order to provide reliable transmission on the uncertainty radio path no matter whatever telegraphic service to be asked and how (he users' movements are. After thoroughly analyzing the principle of RR,we give the precise description of the system state machine.As a way of accessing to the backbone network,the network architecture of GSM includes both aerial interface of radio path (called Um) and many circuits on the land. For example,it has a base station system (BSS),which is responsible for the distribution of radio resource,a mobile switching center (MSC),responsible for connection to external network,and a database for managing users' positions and secure strategies.High technology is applied to GSM,such as FDMA,TDM A,and frequency hopping. Many logical channels related to different services and the mapping of logical channels to physical channels are defined. GSM system is wholly digital,where voice and data at all speeds are digitized first and modulated to a serial of burst at last before transmission. The steps are as follow:PRE-LTP encoding,channel encoding,interweaving,burst forming,encrypting,and modulating.We build up the protocol architecture of MS of calss B according to two different transport mechanisms,i.e. circuit switch and packet switch. We also briefly illuminate each module of the protocol. MS of class B can be connected with GPRS and other GSM services and monitor their control channels at the same time. But only one service can be provide at the same time.The research of RR is the kernel of this paper. Timing Advance (TA) makes MS transmit signal ahead of schedule,to offset the delay of radio transmission line and thus transmit uplink signals of every MS to the BTS in their own timeslot. Power controls,including discontinuous receiving and transmission (DRX DTX). provide longer handset working without frequent alternation of battery. Frequency Hopping enhances its ability of channel anti-jamming. MS in idle mode carrys through the procedures of cell selection and reselection,and other pertinent procedures,such as PLMN selection,and register position. PLMN selection and position registration influence MS from network service provider,while cell selection and reselection from radio path. MS in idle mode has two states,i.e. one normally camped on cell and another camped on any cell,according to criteria Cl,C2,cell PRI,and access mechanism. These two states influence MS's service scope from network. Procedure of initialization assignment describes the transformation of MS from idle mode to dedicated mode,which is a typical example of timeslot aloha protocol. Authority procedure in dedicate mode checks the MS's validity,and if it is valid,a safe cipher key for the use of channel encrypting is given. Encryption procedure prevents the radio channel from being wiretapped. MS in dedicated mode not only detects the quality of radio path of...