This invention relates to communication systems, including but not limited to channel assignments in communication systems.
Communication systems are known to comprise an infrastructure, typically including a plurality of base stations, a controller, a home location register (HLR), and a mobile switching center (MSC), that provides communication services to communication units located in corresponding service coverage areas of the base stations. One example of such a communication system is a cellular communication system. In a cellular system, a remote unit (e.g., a mobile or portable radiotelephone) that desires to communicate, sends a channel request message to a base station serving the coverage area in which the remote unit is located. Upon receiving the channel request message, the infrastructure of the cellular system allocates a communication channel for the communication, and the remote unit begins communicating with a telephone network subscriber or another remote unit via the serving base station. Typically, multiple access wireless communication between the base station and the remote stations occurs via radio frequency (RF) channels or communication resources that provide paths over which communication signals such as voice, data, and video are transmitted.
One type of cellular communication system, Code Division Multiple Access (CDMA), utilizes spread spectrum digital technology in order to obtain higher bandwidth efficiency for a given wireless spectrum allocation. CDMA relies on processing power to extract a coded signal embedded across a broad frequency spectrum. In order to extract the desired signal from among many other overlaid unwanted signals, one utilizes the code correlated to the desired signal. The use of coding allows more channels to be derived by the overlaying of carriers one over another and greatly enhances performance in terms of derived channels per Hertz of bandwidth.
Due to the inherent interference caused by the multiple users sharing the same carrier frequency, access or call setup failures are significant in number. In other words, because of the interference caused by the user in its own and neighboring cells, it is difficult for a remote unit to obtain call setup in a reliable manner, thereby resulting in setup failure.
Accordingly, there is a need for a method of providing call setup that is more reliable manner.