Dynamic CDMA code allocation for voice and data traffic in networks of LEO satellites

Abstract

Considers a network of low-earth-orbit (LEG) satellites with integrated voice and data traffic. The uplinks and downlinks of all satellites use code-division multiple-access (CDMA) with direct-sequence spread-spectrum (DS/SS) signaling. The satellites act as bent-pipes; no on-board processing or intersatellite links are present. Dual satellite diversity is used to mitigate the effects of shadowing. The authors find an optimal CDMA code allocation policy by minimizing a cost function consisting of the weighted sum of the blocking rates of voice and data traffic subject to performance requirements (bit error rates) of the two traffic types. The relative priority of voice and data can be adjusted via a weighting factor. The activity factor of the voice traffic (talkspurts and silent periods) is taken into account to increase bandwidth efficiency. The code allocation policy has the form of a movable voice/data boundary in the CDMA code domain.