Transmission capacity of CDMA ad-hoc networks

Spread spectrum technologies are appropriate for ad-hoc networking because they permit interference averaging and tolerate colocated simultaneous transmissions. We develop analytical results on the transmission capacity of a CDMA ad-hoc network. Transmission capacity is defined as the maximum permissible density of simultaneous transmissions that allows a certain probability of successful reception. We obtain closed-form upper and lower bounds on the transmission capacity for both frequency hopped (FH-CDMA) and direct sequence (DS-CDMA) implementations of CDMA. Our analysis shows that FH-CDMA obtains a higher transmission capacity than DS-CDMA on the order of M^1-2α/, where M is the spreading factor and α>2 is the path loss exponent. The interpretation is that FH-CDMA is generally preferable to DS-CDMA for ad-hoc networks.