How does CDMA work?
CDMA uses the spread spectrum technique and gives each call a unique digital code. This enables several conversations to use the same radio frequency at the same time. The unique code keeps the calls separate and secure. Each conversation is spread out over the shared channel’s bandwidth allowing transmissions with the same codes to be reassembled into a conversation. That’s why, with CDMA, there’s virtually no eavesdropping, cloning or cross-talk. What are the benefits of CDMA? Increased Capacity – With CDMA, the IT&E Wireless Digital PCS Network provides a system capacity that is 10 – 20 times greater than analog systems. This means virtually no dropped calls or busy signals. Virtually no background noise or interference – Only CDMA uses a special receiver to combine multiple signals and improved signal strength. This eliminates interference and fading altogether. Background noise is filtered out by using a narrow bandwidth that corresponds to the frequency range of the human voice.
CDMA converts speech into digital information, which is transmitted as a radio signal over wireless network. What is rather unique about CDMA is that it uses a unique code to distinguish each different call, thus enabling many people to share the airwaves simultaneously; it thereby eliminates cross talk and interference. CDMA is also used in data technology apart from voice technology. What do I get? If you do not travel much (because CDMA phones do not have full roaming facility), it could be a good option for you. CDMA phones operate at 800/1900 MHz band and can have dual mode that works on both analog and digital (today’s mobile phones are primarily digital) networks. Though this technology doesn’t yet provide SMS, Call Waiting, Voice Mail, Call Line Identification, etc, these features are possible. CDMA phones also don’t have SIM cards and are unique to the network they are initiated on. So you cannot just switch networks (say from Reliance to Tata); were you to do that, you would
Signals are spread uniformly over the entire available bandwidth. Different calls are assigned different codes. Together, they appear as noise-like interference to each other. During the receiving stage, when a particular call is decoded, this noise becomes supressed. In other words, the interference is one of the limiting factors, its averaging results in increased capacity. CDMA makes full use of the processing power of the modern computers CDMA allows a channel to carry multiple con-versations at the same time by assigning each conversation at different code. A code is a pattern of bits. The receiver looks for that bit pattern. So even if there are ten conversation in a particular channel at the particular instant of time, no calls interferes with another. As long as the receiving device has the right code, it can pick up its conversation but from all the others. Since CDMA spreads multiple conversations across a wide segment of spectrum, it is known as a Spread Spectrum Technology.
Unlike GSM, CDMA can cram a large number of calls into a small band of frequencies, thus allowing more callers to use the network at the same time. The technology actually has its roots in the military where it has been used – in earlier forms – for years. Because of their similarities, Telstra has recently converted its old analogue network to CDMA; it operates on a similar radio frequency and it has been easy to upgrade analogue transmission towers for CDMA use.
