Cross-layer distributed algorithm designs in wireless networks
Authors: Vahid Tarokh
Venue:  (2006)

This thesis considers the design of distributed algorithms in two scenarios: (i) rate control mechanisms that achieve quality of service guarantees in the reverse link of CDMA systems, and (ii) route discovery mechanisms that lead to energy-efficient unicast transmission in wireless sensor networks. For rate control mechanisms in the reverse link of CDMA systems, we propose two distributed algorithms that provide quality of service assurance. In the first approach, a pricing mechanism is used to derive a fair rate allocation scheme that ensures the long-term service rate received by each access terminal (AT). Furthermore, we introduce a time-varying utility function for each AT that captures the urgency of sending packets when it has been receiving low rates due to undesirable circumstances such as fading in wireless channels. In the derivation, we show that using a single common feedback from base station to ATs, and local optimizations at each ATs given specific utility functions, this pricing mechanism allows ATs to distributively find a rate allocation that (i) achieves social optimality, (ii) satisfies an interference power constraint, and (iii) exhibits desirable fairness behaviors. The derived algorithm is modified to use some design parameters adopted in the IS-856 standard, such as a single-bit reverse activity feedback and rate quantizations. Through simulations, we show that the modified algorithm has similar performance behaviors as the original algorithm with ideal assumptions. In the second approach for the rate control mechanism in the reverse link of CDMA systems, we design an algorithm that provides a means to control the relative delay that each AT experiences. For this algorithm, when each AT knows its own packet arrival statistics, which is assumed to follows a stationary Poisson distribution, it is shown through simulations that all ATs experience an equal amount of average delay when the system is underloaded, and the same packet drop probability when the system is overloaded. Furthermore, we propose a modification to the algorithm that gives priority to some desired ATs, and reduces their relative average delay. Finally, when the arrival process is not stationary, simulation results indicate that the algorithm achieves similar short-term average delay. Finally, we consider a network in which relay nodes cooperate to minimize the total energy consumed in transmitting a (unicast) packet from a source to a destination. We propose the Progressive Accumulative Routing (PAR) algorithm, which progressively performs relay discovery, relay ordering and power allocation in a distributed manner, such that each relay node only needs local information. We assume Destination Energy Accumulation, in which the destination accumulates the energy of multiple received copies of a packet, each of which is too weak to be reliably decoded by itself, while the lower-complexity relay nodes use a decode-and-forward approach. We also provide a closed-form analysis of the energy-savings achieved by the PAR when a relay node is added to an already existing DEA route. Simulations verify that the algorithm considerably reduces the total energy consumption, and can be implemented efficiently. Furthermore, it performs close to the optimal DEA route with high probability.