Spectrum sharing is an important technique to improve the spectrum efficiency of dynamic ad hoc networks. However, since the BUSY/IDLE state of the ad hoc traffic could vary quickly, it is difficult to reduce the traffic collisions between coexisting networks. This chapter investigates a spectrum-sharing scenario, where a cooperative relay network intends to access the spectral band of a dynamic ad hoc network without making too many collisions with the ad hoc traffic. Adopting a binary continuous-time Markov chain (CTMC) traffic model to characterise and predict the ad hoc traffic, the spectrum access design of the cooperative relay network is formulated as a non-convex optimisation problem. We simplify this spectrum access design problem as a convex optimisation problem, which allows us to obtain a low-complexity optimal spectrum access strategy. Moreover, owing to the dynamic nature of the ad hoc traffic, the optimal spectrum access strategy needs to be attained within a short time and under practical limitations. To this end, we generalise the spectrum access design to an ergodic setting and propose an online spectrum access strategy. This online spectrum access strategy is able to achieve the optimal ergodic performance with negligible control delay, moderate signalling overhead and little computational capability requirement for the user equipment.

Chapter Contents:

• 15.1 Introduction
• 15.2 System model
• 15.2.1 Cooperative relay network model
• 15.2.2 Ad hoc traffic prediction and interference metric
• 15.3 Frame-level spectrum sharing: optimal design
• 15.3.1 Convex reformulation of Problem (P)
• 15.3.2 Lagrangian dual optimisation solution for problem (15.14)
• 15.4 Ergodic spectrum sharing: practical online design
• 15.4.1 Problem formulation
• 15.4.2 Online spectrum access strategy
• 15.4.2.1 Online primal solution update
• 15.4.2.2 Online dual variable update
• 15.4.2.3 Merits of our online spectrum access strategy
• 15.4.3 Queueing process at the relay node
• 15.5 Simulation results
• 15.6 Conclusion
• References

Inspec keywords: telecommunication congestion control; convex programming; relay networks (telecommunication); optimal control; concave programming; Markov processes; radio spectrum management; radio equipment; cooperative communication; ad hoc networks

Other keywords: nonconvex optimisation problem; traffic collision; online spectrum band access strategy; optimal ergodic performance; optimal spectral band access; user equipment; cooperative relay network; convex optimisation problem; spectrum access design; binary CTMC traffic model; ad hoc traffic; spectrum efficiency improvement; BUSY/IDLE state; dynamic spectrum sharing; continuous time Markov chain; real-time optimal control; dynamic ad hoc network

Subjects: Markov processes; Radio links and equipment; Optimisation techniques; Optimisation techniques; Legislation, frequency allocation and spectrum pollution; Markov processes; Control applications in radio and radar