Cognitive interference management in retransmission-based wireless networks

Abstract

Cognitive radio methodologies have the potential to dramatically increase the throughput of wireless systems. Herein, control strategies which enable the superposition in time and frequency of primary and secondary user transmissions are explored in contrast to more traditional sensing approaches which only allow the secondary user to transmit when the primary user is idle. In this work, the optimal transmission policy for the secondary user when the primary user adopts a retransmission based error control scheme is investigated. The policy aims to maximize the secondary users' throughput, with a constraint on the throughput loss and failure probability of the primary user. Due to the constraint, the optimal policy is randomized, and determines how often the secondary user transmits according to the retransmission state of the packet being served by the primary user. The resulting optimal strategy of the secondary user is proven to have a unique structure. In particular, the optimal throughput is achieved by the secondary user by concentrating its transmission, and thus its interference to the primary user, in the first transmissions of a primary user packet. The rather simple framework considered in this paper highlights two fundamental aspects of cognitive networks that have not been covered so far: (i) the networking mechanisms implemented by the primary users (error control by means of retransmissions in the considered model) react to secondary users' activity; (ii) if networking mechanisms are considered, then their state must be taken into account when optimizing secondary users' strategy, i.e., a strategy based on a binary active/idle perception of the primary users' state is suboptimal.Index Terms-Automatic retransmission request (ARQ), cognitive radios, Markov processes, reactive primary users, wireless networks. ρ Average Failure Probability J fp p J fp p min. J fp p max.

Interference management for cognitive radio systems exploiting primary IR-HARQ: A Constrained Markov Decision Process approach

“…We show that a model of CMDP can also be used to describe an IR-HARQ protocol. The main difference with the one proposed in [9] the CMDP model we propose is not discrete. Our model is based on the evolution of ACcumulated Mutual Information (ACMI) (see e.g.…”

“…This work has been extended to IR-HARQ with multiple rounds in [8] but still no power allocation is done by the secondary user. Authors of [9] propose to use ARQ protocol of the primary user in order to manage the interferences generated by the secondary user. To do so, they propose a Constrained Markov Decision Process (CMDP) to describe the state of the primary ARQ protocol.…”

Heat-aware transmission strategies

“…This study is inspired by the recent development of frame works, namely reactive cognitive networks, where the cog nition capabilities of the cognitive terminals is enhanced to control the long-tenn effect of interference on the primary users' operations [13], [14]. By modeling transmission and networking protocols and environmental variables as Finite State Machines (FSM), the reactive cognitive network frame works capture the dynamics and correlation in the tempo ral evolution of the network state.…”

Spectrum sharing with primary and secondary limited feedback in Cognitive Radio Networks

“…However, this is difficult to be implemented in practice, which motivates the recent works [4]- [12] of exploiting the imperfect channel information based on the limited feedback in cognitive radio networks.…”