On the Impact of Shadowing on the Performance of Cooperative Medium Access Control Protocols

Abstract

Accurate representation of the physical layer is instrumental for a sound design and optimization of Medium Access Control (MAC) protocols for cooperative wireless networks. However, the vast majority of MAC protocols are designed and analyzed by considering simplified physical layer and channel models, which often lead to too optimistic performance predictions. In particular, even though many experimental activities have showcased the important role played by shadow-fading, most protocols are designed and evaluated by taking into account only the transmission distance (circular coverage model) or only the fast-fading. Motivated by the proved unsuitability of these models, the contribution of this paper is threefold: i) we provide important considerations on how to adequately include the effect of shadowing into the design of MAC protocols for cooperative networks; ii) we provide an analytical framework to determine the subset of active relays in order to meet a given Quality-of-Service (QoS) requirement; and iii) we study, through analysis and simulation, the performance of a promising MAC protocol for cooperative networks, which is called Persistent Relay Carrier Sensing Multiple Access (PRCSMA), by explicitly taking into account the effect of shadowing. Our study shows that shadowing can dramatically change system and protocol performance.

Impact of Correlated Log-Normal Shadowing on Two-Way Network Coded Cooperative Wireless Networks

“…(2), (3)] [9] the authors evaluate the performance of selection cooperation schemes by computing the value of the aforementioned probability, under fast fading conditions. The authors in [10], evaluated the average throughput of a MAC protocol designed for one way cooperative communications after studying the effects of uncorrelated shadowing to the [10]. This paper is a first attempt to study the effects of both fast fading and correlated shadowing in the number of relays that are suitable to participate in NC Cooperative (NCC) MAC and relay selection protocols designed for two way networks.…”

“…. , N from S j , j = 1, 2 as P Rij = P Tj h fij 2 h sij 2 [10], where: i) P Tj is the transmit-power from any source j = 1, 2 ii) h fij is the fast-fading coefficient, modeled as a Nakagami-m random variable (RV) with E h fij 2 = 1 iii) and h sij is the shadow-fading coefficient.…”

“…Pr bj2 2 , γ0 (10) where the probabilities Pr (b ij2 , γ 0 ) may be computed from eq. (4) by setting N = 2.…”

“…The authors in [eqs. (3),(5)] [10], employed the average number of relays that have correctly decoded packets transmitted by a single source in order to compute the average throughput of a cooperative MAC. Similarly, the metric presented in eq.…”

Effect of realistic channel conditions on the energy efficiency of network coding-aided cooperative MAC protocols

“…However, a fundamental limitation of the vast majority of these works is that design and analysis are usually conducted by considering very simplified physical (PHY) layer and channel models, which, on the other hand, significantly affect the actual performance of any protocol [4]. More specifically, recent simulations and experimental studies ( [5][6][7]) have clearly pointed out that long-term slow fading (shadowing) is the crucial impairment to be investigated for protocol design, analysis and optimization in distributed wireless networks.…”