Joint Power Adaptation and Interference Avoidance for Unlicensed Wireless Systems: A Game Theoretic Approach

In multiuser wireless systems, waveform adaptation is one of the interference management methods in which the users adaptively change their transmitting waveforms in signal space to enhance the system performance subject to some Quality-of-Service (QoS) requirements. In this paper, the uplink scenario of a Multi Carrier Code Division Multiple Access (MC-CDMA) is considered under slow and frequency selective fading. An admissibility test under maximum received power constraint is presented to check that if there exist feasiblepowers and waveforms for network users to hold the QoS constraint of each user above a predetermined level. In our set-up, a number of licensed (fixed) and unlicensed (agile) users share some orthogonal carriers to send data to a common receiver (or colocated independent receivers), subject to specific target SINRs for users. We analyze this system as a non-cooperative separable game and show the existence of Nash equilibrium point for this joint power control and codeword adaptation game.An iterative distributed algorithm based on better response strategy is presented which at the receiversresults in an ensemble of well-known Generalized Welch Bound Equality (GWBE) optimal waveforms and orthogonal waveforms for oversized users in addition to optimal transmission power for each user. We investigate the properties of fixed point and the effect of algorithm on the performance of fixed users’ network. Finally the algorithm will be confirmed by the numerical examples.

Keywords:

Unlicensed communication , interference avoidance , MC-CDMA , waveform adaptation , transmitter optimization