Impact of the Primary Network Activity on the Maximum Achievable Capacity of DS-CDMA/OFDM Spectrum Sharing

In this paper, the authors analyze DS-CDMA/OFDM spectrum sharing system based on Opportunistic Spectrum Access (OSA). In this system, the primary network air interface is based on DS-CDMA, in which the system performance is limited by a maximum total received interference. The total interference, among other things, is a function of the primary users' communication activity. In OSA, part of this interference is considered to be created by the secondary service, this portion is called interference threshold. Decreasing the activity of the primary user's results in a higher interference threshold, and at the same time, creates less interference at the secondary service receiver; thus the achievable capacity of the secondary service is increased.