CDMA: principles of spread spectrum communication
CDMA: principles of spread spectrum communication
Principles of Mobile Communication
Principles of Mobile Communication
Mobile Cellular Telecommunications Systems
Mobile Cellular Telecommunications Systems
Microwave Mobile Communications
Microwave Mobile Communications
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We consider the use of distributed antennas to increase the capacity andpeak data rate achievable in a microcellular CDMA system with limitedbandwidth. In additon to the diversity against Rayleigh fading achievable byuse of microdiversity among nearly co-located transmit or receive antennas,we exploit macrodiversity against shadow fading that more widely separatedantennas permit. We report on antenna configurations for both directionaland omni-directional antennas that provide the most uniformsignal-to-interference ratio coverage, averaged over a large number ofposition vectors drawn from a spatially uniform distribution of mobiles.Call capacities and peak transmission rates are determined for an integratedsystem carrying traffic at different constant rates, where processing gainand the transmission rate are selected to satisfy a common chip rate. Forthe downlink a 5.5 dB capacity gain can be achieved for 64 kb/s calls usingfour antennas located on the diagonals of each square cell. A bandwidth of 5MHz allows two or more calls to be simultaneously supported at data rates upto 512 kb/s, as opposed to only 128 kb/s for three co-located antennas. Onthe uplink we distinguish between the computationally simpler equal-gaincombining of the antenna signals and the possibly more complex maximum-ratiocombining. With equal gain combining we achieve a peak data rate of 128kb/s and a capacity gain of 2.5 dB relative to equal gain combining of threenearly co-located antenna signals. With maximum ratio combining the peakuplink rate can be as high as 512 kb/s and the capacity is increased by 2.0dB relative to the maximum-ratio combining of three co-located antennas.