TABLE OF CONTENTS IS-95A is the interim standard used in North America and defines a digital cellular system based on CDMA direct sequence spread spectrum which interoperates with the analogue cellular system AMPS. The IS-95A describes an air interface and a set of protocols used between mobile terminals and the network, and can be illustrated by a three-layer stack. Layer 1 is related to the physical layer of the OSI model, layer 2 corresponds to the two sublayers of the data link layer: the Media Access Control (MAC) and the Link Access Control (LAC). In the physical layer, the IS-95A describes the transmission from the network to the mobile terminal on the forward link (down link) and the transmission from the mobile terminal to the network on the reverse link (uplink). There are two sets of channels which can be used over the forward link; broadcast channels transmitted information for the mobile units and include the pilot channel, the sync channel and the paging channels. The other forward channels are the Traffic channels carrying data to the mobile terminals. Layer 3 corresponds to the network layer.
The mobile systems built according to IS-95A are called cdmaone, which include mobile station and base station systems operating on a dual-mode (analogue and digital) cellular system. The analogue technique refers to the AMPS FM system and the digital technique refers to the cdmaone system. Consequently, IS-95A is made up of two parts; one deals with the interface to the AMPS system, and...
