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The paging channel transmits all the necessary overhead parameters for the UE to register into the network [46]. Some mobile operators also transmit the BTS latitude and longitude on the paging channel, which can be exploited for navigation. The major cellular CDMA providers in the United States, Sprint and Verizon, do not transmit the BTS latitude and longitude. US Cellular used to transmit the BTS latitude and longitude, but this provider does not operate anymore. The Base Station ID (BID) is also transmitted in the paging channel, which is important to decode for data association purposes. The paging channel message encoding before transmission is illustrated in Figure 38.7.

The initial bit rate of the paging channel message is either 9.6 Kbps or 4.8 Kbps and is provided in the sync channel message. Next, the data is convolutionally encoded in the same way as that of the sync channel data. The output symbols are repeated twice only if the bit rate is less than 9.6 Kbps. After symbol repetition, the resulting frames, which are 384 symbols long, are block‐interleaved one frame at a time. The interleaver is different from the one used for the sync channel because it operates on 384 symbols instead of 128 symbols. However, both interleavers use the bit reversal method. Finally, the paging channel message is scrambled by modulo‐two addition with the long code sequence.

Figure 38.5 Forward link sync channel encoder (Khalife et al. [18]; 3GPP2 [50]).

Source: Reproduced with permission of IEEE.

Figure 38.6 Sync channel message structure (Khalife et al. [18]; 3GPP2 [50]).

Source: Reproduced with permission of IEEE.

Figure 38.7 Forward link paging channel encoder (Khalife et al. [18]; 3GPP2 [50]).

Source: Reproduced with permission of IEEE.

The paging channel message is divided into 80 ms time slots, where each slot is composed of eight half‐frames. All the half‐frames start with a synchronized capsule indicator (SCI) bit. A message capsule can be transmitted in both a synchronized and an unsynchronized manner. A synchronized message capsule starts exactly after the SCI. In this case, the BTS sets the value of the first SCI to one and the rest of the SCIs to zero. If by the end of the paging message capsule there remains fewer than 8 bits before the next SCI, the message is zero‐padded to the next SCI. Otherwise, an unsynchronized message capsule is sent immediately after the end of the previous message [46]. The paging channel structure is summarized in Figure 38.8.