System Access State

In the system access state, the mobile sends messages to the base station and receives messages from the base station. If the mobile receives messages on the paging chan- nel only, then it sends messages on the access channel. If the mobile receives mes- sages on the forward common control channel and broadcast control channel, then the mobile sends messages on the enhanced access channel.

There are seven substates in the system access state: (1) update overhead infor- mation substate, (2) page response substate, (3) mobile station origination attempt substate, (4) registration access substate, (5) mobile station order/message response substate, (6) mobile station message transmission substate, and (7) priority access and channel assignment (PACA) cancel substate. Figure 6.4 shows the nominal transitions among these substates. It is important to note that while in the system access state, the mobile monitors the paging channel or the forward common con- trol channel at all times [4].

6.2.3.1 Update Overhead Information Substate

In this substate, the mobile monitors for broadcast overhead messages on either the paging channel (IS-95) or the broadcast control channel (3G). These messages include:

• _{System parameters message, extended system parameters message, and}

ANSI-41 system parameters message;

• _{Access parameters message and enhanced access parameters message;} • _{Neighbor list message, extended neighbor list message, general neighbor list}

message, private neighbor list message, and universal neighbor list message;

• _{CDMA channel list message and extended CDMA channel list message.}

If the mobile receives a general page message, then it transitions from this sub- state to the page response substate.

6.2.3.2 Page Response Substate

The mobile moves to this substate after receiving a general page message. While in this substate, the mobile transmits to the base station a page response message [4]. After receiving the page response message, the base station may send a channel assignment message or extended channel assignment message to the mobile. In IS-2000, the extended channel assignment message contains parameters that the mobile uses to start receiving on a forward traffic channel. These parameters include information such as the forward and reverse traffic channel radio config- urations (FOR_RC and REV_RC), CDMA_FREQ (frequency assignment), FRAME_OFFSET (frame offset), CODE_CHAN_FCH (fundamental channel code channel), and QOF_MASK_ID_FCH (quasi-orthogonal function mask). The mobile also receives in the extended channel assignment message some power con- trol parameters. After updating its internal parameters, the mobile then enters the

IS Update overhead information substate MS idle state MS control on the traffic channel state Page response substate MS message transmission substate PACA cancel substate Registration access substate MS origination attempt substate MS order/ message response substate IS IS IS IS IS Receives order or message that requires response Performs registration access Generates data burst message Receives general page message Originates call Cancels PACA call Receives general page message Receives general page message Originates call or reoriginates PACA call Receives general page message

IS: Idle state

traffic channel initialization substate of the mobile station control on the traffic channel state.

6.2.3.3 Mobile Station Origination Attempt Substate

In this substate, the mobile transmits to the base station an origination message [4]. After receiving the origination message, the base station may send a channel assign- ment message or extended channel assignment message to the mobile. In IS-2000, the extended channel assignment message contains parameters that the mobile uses to start receiving on a forward traffic channel. The mobile also receives in the extended channel assignment message some power control parameters. After updat- ing its internal parameters, the mobile then enters the traffic channel initialization substate of the mobile station control on the traffic channel state.

6.2.3.4 Registration Access Substate

In this substate, the mobile transmits to the base station a registration message [4]. The mobile typically enters this substate from the update overhead information sub- state. For example, in performing a power-up registration (without making a call) a mobile would transition from mobile station initialization state to mobile station idle state, then to update overhead information substate and finally to registration access substate. After sending the registration message, it would then return to mobile station idle state.

In addition, while in the idle state the mobile may receive a registration request order from the base station. In performing this ordered registration, the mobile would transition to update overhead information substate and onto registration access substate. After sending the registration message, the mobile would return to mobile station idle state.

6.2.3.5 Mobile Station Order/Message Response Substate

In this substate, the mobile transmits to the base station a response or acknowledg- ment in response to an order or message received. An example of an order from the base station that requires a response is the base station challenge confirmation order. This order tells the mobile to update the shared secret data (SSD) as part of the authentication procedure. After updating, the mobile then sends back to the base station a response called SSD update confirmation order indicating a successful SSD update [4]. Other examples include a status request message from the base sta- tion; the mobile responds to this message by nominally sending a status response message back to the base station.

After sending the required response, the mobile returns to the mobile station idle state.

6.2.3.6 Mobile Station Message Transmission Substate

In this substate, the mobile transmits to the base station a data burst message. The support of this substate is optional.

6.2.3.7 PACA Cancel Substate

In this substate, the mobile transmits to the base station a PACA cancel message. A PACA call is a priority call originated by the mobile for which no traffic channel is available, so the call is queued for a priority channel assignment [4]. After receiving an origination message, the base station may send a PACA message to the mobile. This serves to inform the mobile of the queue position of the PACA call or to instruct the mobile to reoriginate the PACA call. PACA is supported for protocol revision levels greater than four.

While in queue, the user may direct the mobile to cancel the PACA call, in which case the mobile proceeds to PACA cancel substate through update overhead infor- mation substate. After sending the PACA cancel message to the base station, the mobile returns to mobile station idle state.