空闲模式.docx

1、空闲模式1 Introduction没有分配到专用信道的移动台即是“空闲模式的移动台”，本功能的目的是让处于空闲模式的移动台能够接入系统，并通过网络中的其它定位算法延伸至其它系统。当移动台一开机，便立即尝试接入PLMN网络，可以人工、自动来进行网络的选择，移动台将搜寻并选择一个已选择的PLMN网络中的小区，然后锁定到一个控制信道并接收由PLMN网络所提供的有效服务。这和对小区的选择便称为Camping on。当一个移动台一直处于空模式时，它将一直试图去Camping on一个最好的小区（依信号强度算法）空闲模式下的动作是由移动台来控制的，也可以通过在BCCH信道上接收到的参数来执行控制。空闲模

2、式下的控制参数都由小区中的BCCH来传送。2 背境当一个移动台开机后且不进入任何呼叫操作，则它一直处于这样一个状态：不断选择最好的小区去Camp。读取信息并寄存LAI，以便系统知道如何建立呼叫路由。 总之：空闲模式的核心是PLMN网络选择机制，小区选择与重选算法，位置更新过程。其唯一目的是确保移动台能登寻到一个通信成功机会最大的小区。3 实现3.1 接入系统时的最强信号强度 当移动台接入系统时总是试图获得最强信号。这便是空闲模式下的小区选择与重选，这些算法将激活移动台去选择最合适去登录。最基本是信号强度。一个小区是否合适于登录，将要满足一定的算法， 4.3.2, 中详述，are satisfi

3、ed. Camping on themost suitable cell provides the MS with a high probability of goodcommunication with the system.The cell selection and reselection algorithms are governed by parametersettings. Using these parameters an operator can, on a per cell basis, make aspecific cell more or less attractive

4、to camp on for the MS. This makes itpossible for the operator to achieve similar behaviour for MSs in idle mode asin active mode. Well-designed parameter settings for cell selection andreselection in idle mode, will make the MS camp on the cell that it also wouldhave chosen if it had been in active

5、mode.3.2 Control of the paging loadIn idle mode the MS will notify the network whenever it changes location areaby the location updating procedure. Thus, the network will be kept updatedconcerning which location area the MS is presently in. When the systemreceives an incoming call it knows in which

6、location area it should page theMS, and does not need to page it throughout the whole network. This reducesthe load on the system. If the MS does not respond on the first paging, then thenetwork can do a second paging. Different paging strategies are described insection 4.7.2.The MS can also, period

7、ically and when powered on or off, notify the networkof its present status by the location updating procedure, see section 4.5.3 andsection 4.5.4. This prevents the network from doing unnecessary pagings ofMSs that have been powered off or left the coverage area. This wouldotherwise cause unnecessar

8、y load on the system.3.3 空闲模式下的低功率消耗空闲模式下，移动台间隔性地监视由当前小区专送的系统信息并测量相邻小区以决定是否要启动小区的变化，然而大部分是间下移动台处Sleep 模式? 因而节省功率，当然也可以通过不连续接收来实现（DRX）。4 技术介绍与工程指南4.1 总则空闲模式下的MS不断测量当前小区与相邻小区的BCCH载波以选择登录，必要时寄存LAI以进行位置更新。登录小区的目的是：1.激活MS去接收 PLMN系统信息,2.以便在RACH上接入网络3. 另 外 PLMN也知道MS当前的LA，（除非移动台进入限制服务状态section 4.4.3） 因而当来话知

9、道如何寻呼MS 。空闲模式下移动台工作分四个过程：1、PLMN selection,2、Cell selection,3、Cell reselection,4、Location updating.图1示：4.2 PLMN selection4.2.1 总则当移动台开机或脱离一个盲区后，它便试图去选择并登寻注册的PLMN。如果没有注册的PLMN或者注册的PLMN不存在，它将试图去选另一个PLMN（手动或自动）. If there is no registered PLMN, or if the registered PLMN is unavailable the MS will try to s

10、elect to another PLMN either automatically or manually depending on its operating mode, see sections 4.2.2 and 4.2.3. The MS normally operates on its home PLMN. However, another PLMN may be selected if, for example, the MS loses coverage. The MS will register on aPLMN if the MS finds a suitable cell

11、 to camp on and if a location updatingrequest is accepted. Registration has to be successful in order for the MS to beable to access that network. However, it does not need to perform locationupdating if it is in the same location area belonging to the same PLMN as itwas before it entered the inacti

12、ve state.The MS can select and register on another PLMN of its home country than itshome PLMN if national roaming is permitted. However, the MS will then doperiodical attempts to return to its home PLMN.There are two modes for PLMN selection; automatic and manual. Theautomatic mode utilises a list o

13、f PLMNs in an order of priority whereas themanual mode leaves the decision to the user and only indicates which PLMNsthat are available.4.2.2 Automatic modeIn automatic mode, the MS will select PLMN if available and allowable, in thefollowing order if no registered PLMN exist or is available:1) home

14、 PLMN,2) each PLMN that have been stored in the Subscriber Identity Module (SIM)in priority order,3) other PLMNs with received signal level above -85 dBm in random order,4) all other PLMNs in order of decreasing signal strength.4.2.3 Manual modeIn manual mode, the MS will first try to select the reg

15、istered PLMN or homePLMN if no registered PLMN exist. If this registration fails or if the user haveinitiated a PLMN reselection the MS will indicate to the user all availablePLMNs. The user can then select a desired PLMN which causes the MS toinitiate a registration on this PLMN. If the selected PL

16、MN is not allowable, anindication to the user to select another PLMN will be made.The user can at any time request the MS to initiate reselection and registrationonto an alternative available PLMN. This is done either using automatic ormanual mode, depending on the mode selected by the user.4.3 Cell

17、 selection4.3.1 GeneralThe cell selection algorithm tries to find the most suitable cell of the selectedPLMN according to various requirements. If no suitable cell is found and allavailable and allowable PLMNs have been tried, the MS will try to camp on acell irrespective of PLMN identity and enter

18、a limited service state enabling itto make only emergency calls if necessary. If the MS loses coverage it willreturn to the PLMN selection state and select another PLMN.Two different strategies can be used during cell selection; normal cell selectionor stored list cell selection. Stored list cell se

19、lection utilises a stored BCCHAllocation (BA) list to speed up the cell selection procedure whereas normalcell selection is performed when no such list is available.4.3.2 AlgorithmNormal cell selectionDuring normal cell selection, the MS will try to select the most suitable cell tocamp on.A cell is

20、considered suitable if:?it belongs to the selected PLMN,?it is not barred (when a cell is barred it will not be camped on by an MS in idle mode but an active MS can perform handover to it),?it does not belong to a location area which is in the list of Forbiddenlocation areas for national roaming_1 ,

21、?the cell selection criterion is fulfilled.When the MS has no information on which BCCH carriers that are used in the network, it will search all 124 RF channels in the GSM 900 system, or 374 for DCS 1800, take measurement samples of received RF signal strength and calculate the received average lev

22、el for each. The averaging is based on at least five samples per RF carrier spread evenly over a 3 to 5 second period.The MS then tunes to the carrier with the highest average signal strength leveland determines whether this carrier is a BCCH carrier by searching for thefrequency correction burst se

23、nt on the Frequency Correction Channel (FCCH).If it is a BCCH carrier, then the MS tunes to that carrier to read theSynchronisation Channel (SCH) for the BSIC parameter, and the BCCH for thesystem information messages, for example the BA list. If the data issuccessfully decoded and the cell is suita

24、ble, the MS camps on it and performsall registrations necessary. If at least the 30 strongest GSM 900 or 40 strongestDCS 1800 RF channels have been tried and no suitable cells were found, theMS will select another PLMN according to the PLMN selection procedure andsearch for suitable cells there. For

25、 multiband operation, RF channels from bothfrequency bands are evaluated during cell selection, see ref. 1.Cells can have two levels of priority; normal and low. Suitable cells that are oflow priority are only camped on if there are no other suitable cells of normal1 Only valid for mobiles supportin

26、g GSM phase 2. National roaming may be allowed only to certain location areas of a another PLMN than the homePLMN. Those location areas that are forbidden will, after an attempt to do a location updating has failed, be stored in the SIM as forbidden location areafor national roaming. This list will

27、be cleared when the mobile is powered off or the SIM is removed.priority. A priority of a cell is controlled by the Cell Bar Qualify parameter,CBQ 1 , in conjunction with the Cell Bar Access, CB, parameter, see table 1.Table 1 Behaviour of the MS for different combinations of CBQ and CB.2/1551-FCU 1

28、01 201 Uen Rev B 1996-11-07 9(If the MS finds a cell that is part of the selected PLMN but not suitable, theMS will use the BA list obtained from that cell and subsequently only searchthose BCCH carriers. This will speed up the procedure to some extent.The BA list is defined by the MBCCHNO parameter

29、. It indicates to the MSthe frequencies that must be monitored and measured both in idle and activemode. It is possible to define separate lists for idle and active mode asdescribed in Double BA-lists, ref. 2. The present document only considers theidle BA list. The BA list is sent to the MS, in idl

30、e mode, in the systeminformation messages on the BCCH. Up to 32 BCCH carriers can be definedby specifying their ARFCN using the MBCCHNO parameter.Stored list cell selectionThe MS may include optional storage of the BA list when it is powered off.This information is stored in the SIM. For example, th

31、e MS may store the BAlist in use by the PLMN selected when the MS was last active in the GSM orDCS network.If an MS includes a stored BA list of the selected PLMN, it will perform thesame measurements as for normal cell selection except that only the BCCHcarriers in the list will be scanned. The BA

32、list for a given PLMN stored in theMS will be reset and updated whenever the MS retrieves new BCCH data fromthat PLMN. If a stored list cell selection is not successful, then normal cellselection takes place.Cell selection criterionWhile in idle mode, the MS continuously calculates the cell selection quantity,C1 2 . The cell selection criterion is satisfied if C1 0.The quantity C1 is c