Overview

In our discussion thus far we have focused primarily on the core fundamental components involved in sending a bit stream from point A to point B using Direct-Sequence Spread-Spectrum CDMA. In fact, the previous chapter dealt mostly with what is known in CDMA parlance as the Physical Layer. We have said very little about the Network Layer, which controls all the various "global" aspects of the operation of the system (e.g., call delivery, resource assignment, hand-off exchanges, etc.). In an effort to organize the various structural components of the CDMA system, a layering scheme has been developed which divided all the various operations by function. In the Physical Layer we have all the core components that make up the structure through which we exchange messages and various types of signaling and data, i.e., the RF channel, Pilot, Sync, Access and Traffic channels, through which all of our "logical-channel" information flows. The logical channels consist of the various signaling messages (common signaling and dedicated signaling), which are then mapped onto the various physical channels as the situation dictates. For example, signaling messages may be sent over a control channel if the mobile is idle, or they may be routed to the Traffic Channel if it is on a call. Logical Channels may be permanently assigned (e.g., Sync-Channel signaling), while others may only be temporary but exclusive (e.g., Access-Channel signaling).

So far, we have spent a great deal of effort to construct the framework of our "physical channel" system,...