Network Entry in IEEE 802.16m

Under IEEE 802.16m, an AMS transitions between four states that are shown in Figure 5.3. These states are:

• Initialization State;
• Access State;
• Connected State; and
• Idle State.

The network entry and initial ranging procedures are performed while an AMS is in Initialization and Access States. Periodic and other (e.g., for handover) ranging procedures are performed while an AMS is in a connected state.

The procedures can be related to the states as follows. When an AMS is in the initialization state it performs the following tasks:

• a) Scanning and synchronization;
• b) Super-Frame Header Acquisition;
• c) Cell selection decision;

Once b) and c) are performed, the AMS transitions to the Access State and performs the following tasks.

• d) Ranging and uplink synchronization;
• e) Pre-authentication capability negotiation (if applicable);
• f) MS authentication, authorization and key exchange;
• g) Capability exchange and registration with serving ABS;
• h) Initial service flow establishment.

An AMS transitions to the Connected State once h) is performed.

For multicarrier operation, an AMS only attempts network entry and initial ranging with a fully configured carrier. Detecting an A-PREAMBLE, the AMS would decode the SFH and other system parameters and configuration information by which the ABS indicates its support for the multicarrier feature. Once a candidate primary carrier is selected by the AMS, network entry proceeds normally. If successful, the same carrier becomes the primary carrier for the AMS through which it may negotiate with the ABS parameters for secondary carriers. Uplink ranging may be skipped for the secondary carrier if the AMS can utilize configuration information for time, frequency and power configuration from the primary carrier, and may use adjustments in the primary carrier as an initial configuration. If applicable, an ABS may enhance the AMS's ranging in secondary carriers through assigned dedicated ranging codes. These dedicated codes would be communicated to the AMS using the primary carrier.

Figure 5.3 Transitions of an Advanced Mobile Station (AMS).

A Femtocell BS handles AMS entry and ranging procedures similar to a regular ABS. However, an AMS shall not attempt network entry (or handover, reentry from idle, or location update) to a CSG-Closed Femtocell BS except in case of emergency. Similarly with CSG-Open Femtocell BS, an AMS may only attempt such operations if it is critical to the AMS's operation, that is, the AMS connection would be otherwise terminated. An OSG Femtocell BS, on the other hand, is fully accessible to all AMSs within the Femtocell's coverage. Differentiation could be made in ranging contention for CSG-Open Femtocells, whereby CSG-members would always be granted priority over CSG-nonmembers.

An ARS transitions between three states.

• Initialization State;
• Access State;
• Operational State.

Network entry and initial ranging are performed between the Initialization and Access States, while periodic and other ranging types are performed in the Operational States.

In the Initialization State, the ARS performs the following procedures

• a) Scanning and downlink synchronization (A-Preamble Detection);
• b) Broadcast channel acquisition;
• b) Access station selection decision;

The completion of procedure c) enters the ARS into the Access State, in which the following procedures are performed.

• d) Ranging and uplink synchronization;
• e) Pre-authentication capability negotiation (if applicable);
• f) ARS authentication, authorization and key exchange (if applicable);
• g) Capability exchange and registration with servicing ABS;
• h) Neighbor station measurement report and access station selection (if required by the ABS);
• i) Configuring ARS operation parameters.

The completion of procedure i) enters the ARS into the Operational State. It is hence apparent that an ARS follows the same procedures as an AMS. An ARS, however, may additionally perform interference measurement of neighboring stations (if required by the BS), path creation, and tunnel connection establishment with the ABS.

AMS network entry may be distributed between the ARS and the ABS. This includes procedures such as capability negotiation, connection establishment, authentication and registration. Initial link adaptation is handled by the ARS.