【正文】 and CTS fixed part selection (A/Gb mode only).In A/Gb mode, to make this initial CTS fixed part selection, the MS shall be enrolled on at least one fixed part.The relationship between these processes is illustrated in figure 1 in clause 5. The states and state transitions within each process are shown in figure 2a, figure 2b, and figure 3 in clause 5.3 Requirements and technical solutionsThe following clauses list the main requirements of idle mode operation and give an outline of the technical solution. PLMN selection and roamingThe MS normally operates on its home PLMN (HPLMN) or equivalent home PLMN (EHPLMN). However a visited PLMN (VPLMN) may be selected, ., if the MS loses coverage. There are two modes for PLMN selection:i) Automatic mode This mode utilizes a list of PLMNs in priority order. The highest priority PLMN which is available and allowable is selected.ii) Manual mode Here the MS indicates to the user which PLMNs are available. Only when the user makes a manual selection does the MS try to obtain normal service on the VPLMN.To prevent repeated attempts to have roaming service on a not allowed area (. LA or TA), when the MS is informed that an area is forbidden, the LA or TA is added to a list of forbidden LAs for roaming or forbidden TAs for roaming respectively which is stored in the MS. These list s, if existing, are deleted when the MS is switched off or when the SIM is removed. LA area restrictions are always valid for plete location areas independent of possible subdivision into GPRS routing areas. The structure of the routing area identifier (see 3GPP TS [22A]) supports area restriction on LA basis.If a message with cause value 15 (see 3GPP TS [23] and 3GPP TS [23A]) is received by an MS, then the MS shall take the following actions depending on the access technology in which the message was received:GSM, GSM COMPA。 Cell selection and reselection。 HRPD.Steering of Roaming: A technique whereby a roaming UE is encouraged to roam to a preferred roamedto work by the HPLMN.Visited PLMN: This is a PLMN different from the HPLMN (if the EHPLMN list is not present or is empty) or different from an EHPLMN (if the EHPLMN list is present).2 General description of idle modeWhen an MS is switched on, it attempts to make contact with a public land mobile work (PLMN). The particular PLMN to be contacted may be selected either automatically or manually.The MS looks for a suitable cell of the chosen PLMN and chooses that cell to provide available services, and tunes to its control channel. This choosing is known as camping on the cell. The MS will then register its presence in the registration area of the chosen cell if necessary, by means of a location registration (LR), GPRS attach or IMSI attach procedure.If the MS loses coverage of a cell, or find a more suitable cell, it reselects onto the most suitable cell of the selected PLMN and camps on that cell. If the new cell is in a different registration area, an LR request is performed.If the MS loses coverage of a PLMN, either a new PLMN is selected automatically, or an indication of which PLMNs are available is given to the user, so that a manual selection can be made.Registration is not performed by MSs only capable of services that need no registration. The purpose of camping on a cell in idle mode is fourfold:a) It enables the MS to receive system information from the PLMN. b) If the MS wishes to initiate a call, it can do this by initially accessing the work on the control channel of the cell on which it is camped.c) If the PLMN receives a call for the MS, it knows (in most cases) the registration area of the cell in which the MS is camped. It can then send a paging message for the MS on control channels of all the cells in the registration area. The MS will then receive the paging message because it is tuned to the control channel of a cell in that registration area, and the MS can respond on that control channel.d) It enables the MS to receive cell broadcast messages.If the MS is unable to find a suitable cell to camp on, or the SIM is not inserted, or if it receives certain responses to an LR request (., illegal MS), it attempts to camp on a cell irrespective of the PLMN identity, and enters a limited service state in which it can only attempt to make emergency calls.In A/Gb mode, if the CTS MS is in CTS mode only or in automatic mode with CTS preferred, it will start by attempting to find a CTS fixed part on which it is enrolled.3GPP3GPP TS (202212)10Release 11The idle mode tasks can be subdivided into five processes: PLMN selection。 HRPD.Home PLMN: This is a PLMN where the MCC and MNC of the PLMN identity match the MCC and MNC of the IMSI. Matching criteria are defined in Annex A.In A/Gb mode,...: Indicates this clause applies only to GSM System. For multi system case this is determined by the current serving radio access work.In Iu mode,...: Indicates this clause applies only to UMTS System. For multi system case this is determined by the current serving radio access work.Localised Service Area (LSA): A localised service area consists of a cell or a number of cells. The cells constituting a LSA may not necessarily provide contiguous coverage. Location Registration (LR): An MS which is IMSI attached to nonGPRS services only performs location registration by the Location Updating procedure. A GPRS MS which is IMSI attached to GPRS services or to GPRS and nonGPRS services performs location registration by the Routing Area Update procedure only when in a work of work operation mode I. Both location updating and routing area update procedures are performed independently by the GPRS MS when it is IMSI attached to GPRS and nonGPRS services in a work of work operation mode II or III (see 3GPP TS [27]). An MS which is attached via the EUTRAN performs locatio