Throughput Scaling Laws in Point-to-Multipoint Cognitive Networks

Scaling Law;Cognitive Radio;Underlay Approach;Point-to-Multipoint;Co-existence;Simultaneous Operation;Least Interference Strategy;Sum of lower order statistics;largest order statistic;Interference;Electrical and Computer Engineering

Jamal, Nadia

University of Waterloo

关键词: Scaling Law;    Cognitive Radio;    Underlay Approach;    Point-to-Multipoint;    Co-existence;    Simultaneous Operation;    Least Interference Strategy;    Sum of lower order statistics;    largest order statistic;    Interference;    Electrical and Computer Engineering;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/5289/1/Jamal_Nadia.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Simultaneous operation of different wireless applications in the same geographical region andthe same frequency band gives rise to undesired interference issues. Since licensed (primary)applications have been granted priority access to the frequency spectrum, unlicensed (secondary)services should avoid imposing interference on the primary system. In other words, secondarysystem’s activity in the same bands should be in a controlled fashion so that the primary systemmaintains its quality of service (QoS) requirements.In this thesis, we consider collocated point-to-multipoint primary and secondary networks thathave simultaneous access to the same frequency band. Particularly, we examine three differentlevels at which the two networks may coexist: pure interference, asymmetric co-existence, andsymmetric co-existence levels.At the pure interference level, both networks operate simultaneously regardless of their interferenceto each other. At the other two levels, at least one of the networks attempts to mitigate itsinterference to the other network by deactivating some of its users. Specifically, at the asymmetricco-existence level, the secondary network selectively deactivates its users based on knowledgeof the interference and channel gains, whereas at the symmetric level, the primary network alsoschedules its users in the same way.Our aim is to derive optimal sum-rates (i.e., throughputs) of both networks at each co-existencelevel as the number of users grows asymptotically and evaluate how the sum-rates scale with thenetwork size. In order to find the asymptotic throughput results, we derive two propositions; oneon the asymptotic behaviour of the largest order statistic and one on the asymptotic behaviour ofthe sum of lower order statistics.As a baseline comparison, we calculate primary and secondary sum-rates for the time division(TD) channel sharing. Then, we compare the asymptotic secondary sum-rate in TD to that undersimultaneous channel sharing, while ensuring the primary network maintains the same sum-rate inboth cases.Our results indicate that simultaneous channel sharing at both asymmetric and symmetricco-existence levels can outperform TD. Furthermore, this enhancement is achievable when userscheduling in uplink mode is based only on the interference gains to the opposite network and noton a network’s own channel gains. In other words, the optimal secondary sum-rate is achievableby applying a scheduling strategy, referred to as the least interference strategy, for which only theknowledge of interference gains is required and can be performed in a distributed way.