Throughput, stability and fairness of carrier-sense multiple access with cooperative diversity

• Autor(a) principal: Gameiro, Atílio
• Data de Publicação: 2014
• Outros Autores: Sámano-Robles, Ramiro
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13596
• topic: Cooperative diversity; Random access; Throughput region; Stability; Markov model

Cooperative diversity has been identified as a potential candidate for boosting the physical (PHY) layer performance of future wireless networks. However, several issues remain open today in the design of an appropriate medium access control (MAC) layer for this type of system. This paper attempts to partially fill this gap by addressing the MAC-PHY cross-layer design of a class of carrier-sense multiple access protocols where collision-free transmissions are assisted by the potential cooperative retransmission of the remaining silent terminals in the network. Unlike previous works, the analysis is focused on full asymmetrical settings, where terminals experience different channel and queuing statistics. To achieve this goal, a packet reception model is here proposed for cooperative schemes where the relaying phase is activated only when the reception of previous (re)transmissions has failed. Closed-form expressions of correct reception probability are derived for Rayleigh fading channels assuming that correct reception occurs only when the instantaneous signal-to-noise ratio (SNR) exceeds a reception threshold. This reception model allows for a MAC-layer design aware of PHY-layer information, and vice versa, PHY-layer enhancement and activation using MAC-layer information. The boundary of the throughput region (i.e., the set of all achievable throughput values) is derived in a parametric closed-form expression using a multi-objective optimization approach. A method for deriving a non-parametric form was further proposed, which allows for a geometric interpretation of the two-user case. Stability features such as backlog user distribution and backlog delay are evaluated by using a novel Markov model for asymmetrical systems. Fairness is evaluated by means of the Gini index, which is a metric commonly used in the field of economics to measure income inequality. The protocol is shown to outperform its non-cooperative counterparts under diverse network conditions that are here discussed.