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Wireless networks are nowadays considered a founding part of the global communications and computing infrastructure that we broadly refer to as “the Internet”. Their inherent ability to support users on the move and to seamlessly interface with a variety of communications-enabled devices has opened up a number of novel research areas, including, e.g., Internet-of-Things and pervasive computing environments. At the same time, their use as de facto standard for accessing Web-based services is becoming more and more relevant with the introduction of LTE/LTE-Advanced technologies for cellular networks. In this perspective, the ability to model wireless networks at the system level and to optimise their internal functioning in various operational conditions is becoming a key factor for ensuring that the innovation pace in wireless networks technologies can be maintained.
This Special Issue of MONET contains four articles, representing extended versions of papers presented at WiOpt 2009. The 2009 edition of WiOpt represented the 7th edition of the series of Symposia on Modelling and Optimization in Mobile, Ad Hoc, Wireless Networks. The symposium took place in Seoul in June 2009 and saw the participation of more than 100 attendees. The four papers we selected for this Special Issue represent some of the most relevant research lines active in the field.
The issue starts with a paper on “Distributed Adaptive Algorithms for Optimal Opportunistic Medium Access” by S. Borst and Y. Al-Harthi. In this work, the authors deal with the design of threshold-based transmission strategies for distributed opportunistic medium access in a wireless scenario. They address the problem of setting, in an adaptive and distributed fashion, the threshold values so as to optimize the aggregate throughput utility of the various users under the proportional fairness scheme.
The second article, by W. Saad, Z. Han, T. Başar, M. Debbah and A. Hjørungnes proposes a game-theoretical approach to physical layer security in wireless networks. In particular, the authors model the physical layer security problem as a coalitional game with non-transferable utility and propose a distributed algorithm for coalition formation. Through the proposed algorithm, the wireless users can cooperate and self-organize into disjoint independent coalitions, while maximizing their secrecy rate taking into account the security costs related to information exchange. The proposed approach is applied to both decode-and-forward and amplify-and-forward schemes.
Wireless communication systems, especially those operating in unlicensed bands (WiFi, Bluetooth, ZigBee among the others) are potentially subject to denialofservice attacks caused by interference intentionally created by jammers. In “Jamming in wireless networks under uncertainty”, E. Altman, K. Avrachenkov and A. Garnaev provide a game theoretical framework for studying this problem. In particular, they deal with the case in which the user does not know whether or not the jammer is indeed present and how interference is distributed among sub-carriers. They show that the problem can be formulated as a zero-sum game and specify the equilibrium strategies in closed form.
The last article of this Special Issue deals with the performance improvements obtainable in multi-user random access wireless networks through the use of ZigZag decoding, a recently proposed receiver design that allows successful reception of packets despite collision. The authors of “Mathematical Analysis of Throughput Bounds in Random Access with ZIGZAG Decoding” (J. Paek and M. J. Neely) provide an analysis of throughput bounds in four different idealized multi-access schemes. Simulation results are presented, showing that ZigZag decoding can significantly improve the performance of random access systems.
We wish to thank all the authors and referees for their contributions toward making this Issue possible. We also thank the many authors of papers that we could not include in this Issue. Last, but not least, we would like to thank the MONET EiC (Prof. I. Chlamtac) and the Springer Publication Office for their support.