For normal service, the MS has to camp on a suitable cell, tune to that cell's control channel(s), and possibly register within the PLMN so that the MS can:

1. Receive system information from the PLMN , e.g., the cell options ;
2. Receive paging messages from the PLMN, e.g., when there is an incoming call for the MS;
3. Initiate call setup for outgoing calls or other actions from the MS (where possible, see subclause 3.5.3 and subclause 3.5.4).

The choice of such a suitable cell for the purpose of receiving normal service is referred to as "normal camping". There are various requirements that a cell must satisfy before an MS can perform normal camping on it:

1. It should be a cell of the selected PLMN or, if the selected PLMN is equal to the last registered PLMN, an equivalent PLMN;
2. It should not be "barred" (see subclause 3.5.1);
3. It should not be in an LA which is in the list of "forbidden LAs for roaming";
4. The radio path loss between MS and BTS must be below a threshold set by the PLMN operator. This is estimated as shown in subclause 3.6;
5. It should not be a SoLSA exclusive cell to which MS does not subscribe. This requirement is only valid for MSs supporting SoLSA.

Initially, the MS looks for a cell which satisfies these 5 constraints ("suitable cell") by checking cells in descending order of received signal strength. If a suitable cell is found, the MS camps on it and performs any registration necessary. Cells can have two levels of priority, suitable cells which are of low priority are only camped on if there are no other suitable cells of normal priority. (This is called "cell selection"). When camped on a cell the MS regularly looks to see if there is a better cell in terms of a cell re-selection criterion, and if there is, the better cell is selected. Also if one of the other criteria changes, (e.g., the current serving cell becomes barred), or there is a downlink signalling failure (see subclause 3.6), a new cell is selected. (This is called "cell reselection"). A MS that has enabled PEO or EC operation has relaxed requirements for how often it verifies the suitability of its serving cell and the suitability of neighbour cells for re-selection (see TS 45.008 and TS 44.018). In order to speed up these processes, a list of the RF channels containing BCCH or CPBCCH carriers of the same PLMN is broadcast in the system information messages, see subclause 4.8. Also, the MS does not need to search all possible RF channels to find a suitable cell. If, after searching the number of RF channels, given for each frequency band below, with the strongest received signal level, a BCCH or CPBCCH carrier has been found but no suitable cell of the selected PLMN has been found, the MS can stop the attempt to find a suitable cell of the selected PLMN. The number of channels to be searched are 15 for T-GSM 380, 15 for T-GSM 410, 15 for GSM 450, 15 for GSM 480, 25 for GSM 710, 25 for GSM 750, 25 for T-GSM 810, 30 for GSM 850 Band, 30 for GSM 900, 15 for T-GSM 900 and 40 for DCS 1800 and PCS 1900.

If the MS cannot find a suitable cell, it attempts to camp on any acceptable cell and enter a "limited service state", as defined in subclause 3.7. An MS attempting to camp on any acceptable cell shall not scan for CPBCCH. There are various requirements that a cell must satisfy before being considered an acceptable cell to be camped on in "limited service state":

1. It should not be "barred" (see subclause 3.5.1);
2. The radio path loss between MS and BTS must be below a threshold set by the PLMN operator. This is estimated as shown in subclause 3.6.

The PLMN operator may decide not to allow MSs to camp on certain cells. (These cells may, for example, only be used for hand over traffic, i.e. calls which need to be handed over to other cells). Barred cell information is broadcast as system information to instruct MSs not to camp on these cells. The barred cell status may in fact change dynamically; hence the MS needs to regularly check the system information for this parameter. The barred status of a cell depends on the parameters CELL_BAR_ACCESS and CELL_BAR_QUALIFY, further described in TS 45.008. For a MS that has enabled EC operation, the barred status of a cell is given by the Implicit Reject Status broadcast in EC-SCH, see TS 44.018. If a cell is barred this applies both for cell selection and reselection.

In general, cell prioritization is a means of encouraging MSs to select some suitable cells in preference to others. Since the priority comparison is only between suitable cells, prioritization does not affect coverage. Operators may prefer a certain type of cell not to be selected unless it is the only suitable type. For example, umbrella cells due to their large frequency reuse distance, or microcells because the MS could be travelling too fast for them.

Due to problems in certain areas, Network Operators may decide to restrict access from some MSs (e.g., in case of congestion on the AGCH), and for this reason the access control mechanism is provided. At subscription one or more access control classes are allocated to the subscriber and stored in the SIM. The information providing all authorized classes is broadcast as system information (together with a bit indicating whether emergency calls may be made). This information is modified dynamically and therefore the MS has to check the system information before each attempt to access. The MS ignores the Access Control information when selecting a cell to camp on, i.e. it shall not reject a cell for camping on because access on that cell is not allowed.

If the MS has received the cause "LA not allowed", it shall ignore this fact when selecting a cell to camp on, i.e. it shall not reject a cell for camping on because that cell is part of a LA where this cause has been received.

If upper layers have determined that the network has failed an authentication check (TS 24.008), the MS shall treat this cell as if the barred status broadcasted in the system information is set and reselect another cell. The MS shall treat the cell as barred for a period equal to the MM timer T3212 minus 60 seconds if the MM authentication procedure was performed or equal to the GMM timer T3302 minus 60 seconds if the GMM authentication was performed (see TS 24.008). If the timer T3212 or T3302 are disabled by the network a default value of 12 hours shall be used.