A wireless digital communication system is a technique that allows people to communicate each other at a distance. In this paper we tried to explain one of the latest technologies of digital wire less communication systems - The CDMA and the application of this on cellular phones.CDMA is an acronym for code division multiple access. Each CDMA subscriber is given with a separate code for communication that reduces interferences & increases privacy. In this paper we explained about the transmission, reception of CDMA signals for cell phones, the channelising, modes of communication, features and advantages.
Code Division Multiple Access Technology emerged as an alternative to the GSM cellular architecture and has shared in the past decade’s explosive growth in the wireless market. CDMA like GSM has seen incremental improvements in capacity through out this period.
The wireless digital communication system allows people to communicate at a distance. A digital communication system mainly consists of,
1. Network components and equipment
2. The interrelationship between the components
3. Types of calls.
Wireless digital communications has dramatically increased in popularity, resulting in the need for technologies that allow multiple users share the same frequency. These are called multiple access systems. The three types of multiple access system are:
Frequency Division Multiple Access (FDMA)
Time Division Multiple Access (TDMA)
Code Division Multiple Access (CDMA)
Frequency Division Multiple Access:
Each FDMA subscriber is assigned a specific frequency channel. No one else in the same cell or a neighboring cell can use the frequency channel while it is assigned to a user. This reduces interference, but severely limits the number of users.
Time Division Multiple Access:
TDMA users share a common frequency channel, but use the channel for only a very short time. They are each given a time slot and only allowed to transmit during that time slot. When all available time slots in a given frequency are used, the next user must be assigned a time slot of another frequency.
Code Division Multiple Access (CDMA): CDMA users share a common frequency channel. All users are on the same frequency at the same. However, each pair of users is assigned with a specific code that reduces interferences while increasing privacy.
Comparison of multiple access systems: The following table summarizes some of the technical aspects of multiple access technologies. The technologyused determines the channel’s capacity. TDMA triples the capacity of FDMA, but CDMA capacity can be up to seven times that of TDMA.
Working of CDMA: This includes
1. CDMA signal generation
2. The types of codes used in CDMA
3. Forward and reverse link code channels
4. CDMA call processing