This paper introduces a protocol that distributively constructs a collision-free schedule for multi-hop packet radio networks in the presence of hidden terminals. As a preliminary step, each wireless station computes the schedule length after gathering information about the number of flows in its neighbourhood. Then, a combination of deterministic and random backoffs are used to reach a collision-free schedule. A deterministic backoff is used after successful transmissions and a random backoff is used otherwise. It is explained that the short acknowledgement control packets can easily result in channel time fragmentation and, to avoid this, the use of link layer delayed acknowledgements is advocated and implemented. The performance results show that a collision-free protocol easily outperforms a collision-prone protocol such as Aloha. The time that is required for the network to converge to a collision-free schedule is assessed by means of simulation.
A general discussion of this class of protocols, together with performance comparisons and protocol refinements, is offered in @cite_12 . This last paper also introduces the concepts of stickiness and variable schedule length to accommodate a larger number of contenders in slotted networks. In the present work, we will reuse both concepts in the context of multi-hop packet radio networks.
@cite_12
2033017950 2124107362 2071787409 2098222105
This paper provides a general framework for analyzing the stability of general nonlinear networked control systems (NCS) with disturbances in the setting of stability. Our presentation provides sharper results for both gain and maximum allowable transfer interval (MATI) than previously obtainable and details the property of uniformly persistently exciting scheduling protocols. This class of protocols was shown to lead to stability for high enough transmission rates and were a natural property to demand, especially in the design of wireless scheduling protocols. The property is used directly in a novel proof technique based on the notions of vector comparison and (quasi)-monotone systems. We explore these results through analytical comparisons to those in the literature, as well as through simulations and numerical comparisons that verify that the uniform persistence of excitation property of protocols is, in some sense, the ldquofinestrdquo property that can be extracted from wireless scheduling protocols. We consider a frequency-flat fading multihop network with a single active source-destination pair terminals communicating over multiple hops through a set of intermediate relay terminals. We use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the power-bandwidth tradeoff) for a simple communication protocol based on time-division decode-and-forward relaying in meaningful asymptotic regimes of signal-to-noise ratio (SNR) under a system-wide power constraint on source and relay transmissions. The impact of multi-hopping and channel fading on the key performance measures of the high and low SNR regimes is investigated to shed new light on the possible enhancements in power bandwidth efficiency and link reliability. In contrast to the common belief that in fading environments communicating over multiple hops suffers significantly in performance due to the worst link limitation, our results indicate that hopping could significantly improve the outage behavior over slow-fading networks and stabilize links against the random channel fluctuations. In particular, we prove that there exists an optimal number of hops that minimizes the end-to-end outage probability and characterize the dependence of this optimal number on the fading statistics and target energy and spectral efficiencies. This paper presents the evaluation of the multi-hop aggregate information efficiency of the slotted and unslotted ALOHA protocols. We consider a multi-hop wireless network where the nodes are spatially characterized by a Poisson point process and the traffic generation also follows a Poisson distribution. By applying the properties of stochastic geometry, we derive a closed-form lower bound on the outage probability as a function of the required communication rate, the single-hop distance, the number of hops and the maximum number of retransmissions. The results indicate that slotted ALOHA always outperforms its unslotted version, demonstrating the importance of synchronization in distributed networks. In addition, we show that it is always possible to optimize the network efficiency by properly setting the required rate for a given packet density. Finally, in the scenario considered, the use of retransmissions and multiple hops never achieves the best performance if compared to the option of single-hop links without retransmissions. This paper presents an efficient protocol for reliably exchanging information in a single-hop, multi-channel radio network subject to unpredictable interference. We model the interference by an adversary that can simultaneously disrupt up to t of the C available channels. We assume no shared secret keys or third-party infrastructure. The running time of our protocol depends on the gap between C and t: when the number of channels C =Omega(t^2), the running time is linear; when only C = t+1 channels are available, the running time is exponential. We prove that exponential-time is unavoidable in the latter case. At the core of our protocol lies a combinatorial function, possibly of independent interest, described for the first time in this paper: the multi-selector. A multi-selector generates a sequence of channel assignments for each device such that every sufficiently large subset of devices is partitioned onto distinct channels by at least one of these assignments.