Category: CDMA

There are Four channel in Forward direction in cdma. PILOT CHANNEL (1) SYNC CHANNEL (1) FORWARD TRAFFIC + PAGING CHANNELS (62) PAGING CHANNELS ( MAXIMUM 7) PILOT CHANNEL PILOT SIGNALS…

Diversity Reception: Multiple Antennas at Base Station Each Antenna is Affected by Multipath Differently Due to Their Different Location Allows Selection of the Signal Least Affected by Multipath Fading If…

Vocoders Human voice is made up of a combination of voiced and unvoiced sounds Vocoders exploit these properties of speech production mechanism Vocoders do not respond to music, non-human sounds…

Time diversity is a technique common to most digital transmission systems.  The Rake Receiver is used to find and demodulate multipath signals that are time delayed from the main signal….

This graphically demonstrates why interleaving data improves error correction performance of data transmission systems. In the top Image, data is sequentially read out of a buffer than goes by rows….

Correlation Is a Measure of How Well a Given Signal Matches a Desired Code, The Desired Code is Compared to the Given Signal at Various Test times. Correlation is key…

Frequency diversity is inherent in a spread spectrum system.  A fade of the entire signal is less likely than with narrow band systems. Combats Fading, Caused by Multipath Fading Acts…

CDMA extends the idea of diversity reception with the concept of soft handoff.  In the slide, a mobile CDMA phone has established a call with base station one. As the…

CDMA takes advantage of quiet times during speech to raise capacity.  A variable rate vocoder is used; for the original vocoder the channel is a 9,600 bps when the user…

Closed loop power control is used to allow the power from the mobile unit to deviate from the nominal as set by open loop control. This is done with a…