Invited Talk I Summary: Opportunistic Spectrum Access for Wireless Ad Hoc Networks: Research Challenges

Traditionally, the frequency spectrum has been rigidly allocated to users/services. This rigid allocation has led to inefficient utilization and an apparent scarcity [1]. More recently, technological advances in a number of areas (software defined radios, wideband sensing, DSP receivers and waveforms agility) have enabled the development of a new communication paradigm, namely Opportunistic Spectrum Access (OSA) that promises to eliminate the apparent scarcity problem. In OSA, wireless nodes’ spectrum usage is not pre-determined (wired in hardware) with a fixed frequency/modulation assignment, but instead radios become aware of their environment, in particular of the presence of “primary” or “protected” spectrum users, and based on this decide on a spectrum usage that is compatible with the regulatory policy in effect at the current place and time. OSA promises a significant improvement on spectrum utilization. However, while conceptually simple, OSA turns out to be a very complicated concept to realize, especially under a dynamic mobile ad hoc network where the decisions need to be taken on a distributed and autonomous manner. We revise current efforts underway to realize the OSA vision. In particular, we cover work on two enabling blocks for OSA in a distributed ad hoc network: policy-driven operation, and algorithms for coordinated spectrum allocation.