The present document specifies the Radio sub system link control implemented in the Mobile Station (MS), Base Station System (BSS) and Mobile Switching Centre (MSC) of the digital cellular telecommunications systems GSM. Unless otherwise specified, references to GSM also include operation in any supported band (see TS 45.005).

The radio sub system link control aspects that are addressed are as follows:

• Handover;
• RF Power control in A/Gb mode, including fast power control for E-TCH and enhanced power control for TCH and O-TCH;
• RF Power control in Iu mode, including fast power control for E-TCH and enhanced power control for DBPSCH (in MAC-Dedicated and MAC-DTM states);
• Radio link Failure;
• Cell selection and re-selection in Idle mode, in Group Receive mode, in GPRS mode, in broadcast/multicast receive mode and in EC operation and PEO (see TS 43.022);
• Coverage class selection in EC operation;
• CTS mode tasks.

Handover is required to maintain a call in progress as a MS engaged in a point to point call or with access to the uplink of a channel used for a voice group call passes from one cell coverage area to another and may also be employed to meet network management requirements, e.g. relief of congestion. Handover may occur during a call from one TCH or multiple TCHs (in the case of multislot configuration) to another TCH or multiple TCHs. It may also occur from DCCH to DCCH or from DCCH to one or multiple TCH(s), e.g. during the initial signalling period at call set up. Additionally in Iu mode, handover may occur in MAC-Dedicated and MAC-DTM states:

• on PDTCH or multiple PDTCHs (in the case of multislot configuration) on DBPSCH(s) to another PDTCH or multiple PDTCHs on DBPSCH(s);
• for FLO, from one DBPSCH or multiple DBPSCHs (in the case of multislot configuration) to another DBPSCH or multiple DBPSCHs.

The handover may be either from channel(s) on one cell to other channel(s) on a surrounding cell, or between channels on the same cell which are carried on the same frequency band. Examples are given of handover strategies, however, these will be determined in detail by the network operator. For a multiband MS, the handover described is also allowed between any channels on different cells which are carried on different frequency bands, e.g. between a GSM 900/TCH and a DCS 1 800/TCH. Handover between two co located cells, carried on different frequency bands, is considered as inter cell handover irrespective of the handover procedures used. For a multi-RAT MS, i.e. an MS supporting multiple radio access technologies, handover is allowed between GSM and other radio access technologies. Adaptive control of the RF transmit power from an MS and optionally from the BSS is implemented in order to optimize the uplink and downlink performance and minimize the effects of co channel interference in the system. The criteria for determining radio link failure are specified in order to ensure that calls which fail either from loss of radio coverage or unacceptable interference are satisfactorily handled by the network. Radio link failure may result in either re establishment or release of the call in progress. For channels used for a voice group call, an radio uplink failure results in the freeing up of the uplink. Procedures for cell selection and re selection whilst in Idle mode (i.e. not actively processing a call), are specified in order to ensure that a mobile is camped on a cell with which it can reliably communicate on both the radio uplink and downlink. The operations of an MS in Idle Mode are specified in TS 43.022. Cell re-selection is also performed by the MS when attached to GPRS, except when the MS simultaneously has a circuit switched connection. Optional procedures are also specified for network controlled cell re-selection for GPRS. Cell re-selection for GPRS is defined in subclause 10.1. For a multi-RAT MS, cell selection and re-selection is allowed between GSM and other radio access technologies. An MS listening to a voice group call or a voice broadcast use cell re selection procedures to change cell. This may be supported by a list of cells carrying the voice group or voice broadcast call downlink, provided to the MS by the network. The operations of an MS in Group Receive Mode are specified in TS 43.022. Information signalled between the MS and BSS is summarized in tables 1, 2 and 3. A full specification of the Layer 1 header is given in TS 44.004, of the Layer 3 fields in TS 44.018, and of the Layer 2 fields in TS 44.060. When EC operation has been enabled, Coverage Class selection is performed by the mobile station in Idle mode to ensure that a mobile station will be able to communicate on the extended coverage common control channel (EC-CCCH). The Coverage Classes for uplink and downlink dedicated channels are assigned by the network in Packet Transfer mode to ensure that a mobile station will be able to communicate on the extended coverage packet data traffic channel (EC-PDTCH) and its associated control channel (EC-PACCH). For CTS, information signalled between the CTS-MS and CTS-FP is summarized in tables 4, 5 and 6. A full specification of the CTS Layer 3 fields is given in TS 44.056. For COMPACT, specific procedures are defined in clause 12. During the reception of an MBMS session, the mobile station is in broadcast/multicast receive mode. In this state, the MS performs autonomous cell re-selection. If the MS is a member of at least one Closed Subscriber Group, the MS may perform cell re-selection to CSG cells.