13.8 PN Offset Assignment

The assignment of the PN offset for each CDMA2000 channel and/or sector utilizes the same rules that were and are used for IS-95 systems. In CDMA2000, just as with IS-95 systems, the forward pilot channel carries no data but it is used by the subscriber unit to acquire the system and assist in the process of soft handoffs, synchronization, and channel estimation. A separate forward pilot channel is transmitted for each sector of the cell site. The forward pilot channel is uniquely identified by its PN offset, or rather, PN short code that is used. The reverse pilot channel introduced in CDMA2000, however, does not utilize the Pseudorandom Number (PN) offset.

The PN sequence has some 32,768 chips that, when divided by 64, results in a total of 512 possible PN codes that are available for potential use. The fact that there are 512 potential PN short codes to pick from almost ensures that there will be no problems associated with the assignment of these PN codes. However, there are some simple rules that must be followed in order to ensure that there are no problems encountered with the selection of the PN codes for the cell and its surrounding cell sites. It is suggested that a reuse pattern be established for allocating the PN codes. The rational behind establishment of a reuse pattern lies in the fact that it will facilitate the operation of the network for maintenance and growth.

Table 13-23 shows what...