Results 11  20
of
102
Performance of random medium access control: An asymptotic approach
 In Proc. ACM Sigmetrics
, 2008
"... Random MediumAccessControl (MAC) algorithms have played an increasingly important role in the development of wired and wireless Local Area Networks (LANs) and yet the performance of even the simplest of these algorithms, such as slottedAloha, are still not clearly understood. In this paper we pro ..."
Abstract

Cited by 26 (1 self)
 Add to MetaCart
Random MediumAccessControl (MAC) algorithms have played an increasingly important role in the development of wired and wireless Local Area Networks (LANs) and yet the performance of even the simplest of these algorithms, such as slottedAloha, are still not clearly understood. In this paper we provide a general and accurate method to analyze networks where interfering users share a resource using random MAC algorithms. We show that this method is asymptotically exact when the number of users grows large, and explain why it also provides extremely accurate performance estimates even for small systems. We apply this analysis to solve two open problems: (a) We address the stability region of nonadaptive Alohalike systems. Specifically, we consider a fixed number of buffered users receiving packets from independent exogenous processes and accessing the resource using Alohalike algorithms. We provide an explicit expression to approximate the stability region of this system, and prove its accuracy. (b) We outline how to apply the analysis to predict the performance of adaptive MAC algorithms, such as the exponential backoff algorithm, in a system where saturated users interact through interference. In general, our analysis may be used to quantify how far from optimality the simple MAC algorithms used in LANs today are, and to determine if more complicated (e.g. queuebased) algorithms proposed in the literature could provide significant improvement in performance.
Complexity in wireless scheduling: Impact and tradeoffs
 in Proceedings of ACM Mobihoc, Hong Kong
, 2008
"... It has been an important research topic since 1992 to maximize stability region in constrained queueing systems, which includes the study of scheduling over wireless ad hoc networks. In this paper, we propose a framework to study a wide range of existing and future scheduling algorithms and characte ..."
Abstract

Cited by 21 (8 self)
 Add to MetaCart
(Show Context)
It has been an important research topic since 1992 to maximize stability region in constrained queueing systems, which includes the study of scheduling over wireless ad hoc networks. In this paper, we propose a framework to study a wide range of existing and future scheduling algorithms and characterize the achieved tradeoffs in stability, delay, and complexity. These characterizations reveal interesting properties hidden in the study of any one or two dimensions in isolation. For example, decreasing complexity from exponential to polynomial, while keeping stability region the same, generally comes at the expense of exponential growth of delays. Investigating tradeoffs in the 3dimensional space allows a designer to fix one dimension and vary the other two jointly. For example, incentives for using scheduling algorithms with only partial throughputguarantee can be quantified with regards to delay and complexity. Tradeoff analysis is then extended to systems with congestion control through utility maximization for nonstabilizable arrival inputs, where the complexityutilitydelay tradeoff is shown to be different from the complexitystabilitydelay tradeoff. Finally, we analyze more practical models with bounded message size, and consider “effective throughput” which reflects resource occupied by control messages. We show that effective throughput may degrade significantly in certain scheduling algorithms, and suggest a mechanism to avoid this problem in light of the 3D tradeoff framework.
Optimal Control of Wireless Networks with Finite Buffers
"... This paper considers network control for wireless networks with finite buffers. We investigate the performance of joint flow control, routing, and scheduling algorithms which achieve high network utility and deterministically bounded backlogs inside the network. Our algorithms guarantee that buffers ..."
Abstract

Cited by 21 (2 self)
 Add to MetaCart
This paper considers network control for wireless networks with finite buffers. We investigate the performance of joint flow control, routing, and scheduling algorithms which achieve high network utility and deterministically bounded backlogs inside the network. Our algorithms guarantee that buffers inside the network never overflow. We study the tradeoff between buffer size and network utility and show that if internal buffers have size (N − 1)/ɛ then a high fraction of the maximum utility can be achieved, where ɛ captures the loss in utility and N is the number of network nodes. The underlying scheduling/routing component of the considered control algorithms requires ingress queue length information (IQI) at all network nodes. However, we show that these algorithms can achieve the same utility performance with delayed ingress queue length information. Numerical results reveal that the considered algorithms achieve nearly optimal network utility with a significant reduction in queue backlog compared to the existing algorithm in the literature. Finally, we discuss extension of the algorithms to wireless networks with timevarying links.
RASPberry: A Stable Reader Activation Scheduling Protocol in MultiReader RFID Systems
"... Abstract—Recent technological advances have motivated largescale deployment of RFID systems. RFID readers are often static and carefully deployed in a planned manner. However, the distribution and movements of tags are often dynamically changed and unpredictable. We study a challenging problem of sc ..."
Abstract

Cited by 19 (4 self)
 Add to MetaCart
(Show Context)
Abstract—Recent technological advances have motivated largescale deployment of RFID systems. RFID readers are often static and carefully deployed in a planned manner. However, the distribution and movements of tags are often dynamically changed and unpredictable. We study a challenging problem of scheduling the activation of the readers without collision such that the system can work in a stable way in the long term. Here a schedule is stable if at any time slot, the number of total unread tags is bounded from above with high probability under this scheduling. In this paper, we propose a stable reader activation scheduling protocol, RASPberry, in multireader RFID systems. We analytically prove that our scheduling protocol, RASPberry, is stable if the arrival rate of tags is less than the processing rate of all readers. In RASPberry, at any time slot, a reader can determine its status using only information of readers within a local neighborhood. To the best of our knowledge, this is the first work to address the stability problem of reader activation scheduling in RFID systems. Our extensive simulations show that our system performs very well. Index Terms—RFID, reader, scheduling, stability, graph. I.
Distributed Coordination with Deaf Neighbors: Efficient Medium Access for 60 GHz Mesh Networks
 in Proc. IEEE INFOCOM 2010
, 2010
"... Abstract—Multigigabit outdoor mesh networks operating in the unlicensed 60 GHz “millimeter (mm) wave ” band, offer the possibility of a quickly deployable broadband extension of the Internet. We consider mesh nodes with electronically steerable antenna arrays, with both the transmitter and receiver ..."
Abstract

Cited by 19 (7 self)
 Add to MetaCart
(Show Context)
Abstract—Multigigabit outdoor mesh networks operating in the unlicensed 60 GHz “millimeter (mm) wave ” band, offer the possibility of a quickly deployable broadband extension of the Internet. We consider mesh nodes with electronically steerable antenna arrays, with both the transmitter and receiver synthesizing narrow beams that compensate for the higher path loss at mmwave frequencies, achieving ranges on the order of 100 meters using the relatively low transmit powers attainable with lowcost silicon implementations. Such highly directional networking differs from WiFi networks at lower carrier frequencies in two ways that have a crucial impact on protocol design: (1) directionality drastically reduces spatial interference, so that pseudowired link abstractions form an excellent basis for protocol design; (2) directionality induces deafness, which makes medium access control (MAC) based on carrier sensing infeasible. Interference analysis in our prior work shows that, in such a setting, coordination between transmitters and receivers, rather than interference management, becomes the key MAC performance bottleneck. However, the question of whether such coordination can be achieved in a distributed fashion while achieving high medium utilization, was left open. In this paper, we answer this question in the affirmative, presenting a distributed MAC protocol that employs memory to achieve approximate time division multiplexed (TDM) schedules without explicit coordination or resource allocation. The efficacy of the protocol is demonstrated via packet level simulations, while a Markov chain fixedpoint analysis provides insight into the effect of parameter choices.
Distributed CrossLayer Algorithms for the Optimal Control of Multihop Wireless Networks
"... In this paper, we provide and study a general framework that facilitates the development of distributed mechanisms to achieve full utilization of multihop wireless networks. In particular, we describe a generic randomized routing, scheduling and flow control scheme that allows for a set of imperf ..."
Abstract

Cited by 18 (8 self)
 Add to MetaCart
(Show Context)
In this paper, we provide and study a general framework that facilitates the development of distributed mechanisms to achieve full utilization of multihop wireless networks. In particular, we describe a generic randomized routing, scheduling and flow control scheme that allows for a set of imperfections in the operation of the randomized scheduler to account for potential errors in its operation. These imperfections enable the design of a large class of lowcomplexity and distributed implementations for different interference models. We study the effect of such imperfections on the stability and fairness characteristics of the system, and explicitly characterize the degree of fairness achieved as a function of the level of imperfections. Our results reveal the relative importance of different types of errors on the overall system performance, and provide valuable insight to the design of distributed controllers with favorable fairness characteristics. In the second part of the paper, we focus on a specific interference model, namely the secondary interference model, and develop distributed algorithms with polynomial communication and computation complexity in the network size. This is an important result given that earlier centralized throughputoptimal algorithms developed for such a model relies on the solution to an NPhard problem at every decision. This results in a polynomial complexity crosslayer algorithm that achieves throughput optimality and fair allocation of network resources amongst the users. We further show that our algorithmic approach enables us to efficiently approximate the capacity region of a multihop wireless network.
Performance Limits of Greedy Maximal Matching in Multihop Wireless Networks
"... In this paper, we characterize the performance limits of an important class of scheduling schemes, called Greedy Maximal Matching (GMM), for multihop wireless networks. For simplicity, we focus on the wellestablished nodeexclusive interference model, although many of the stated results can be rea ..."
Abstract

Cited by 17 (1 self)
 Add to MetaCart
In this paper, we characterize the performance limits of an important class of scheduling schemes, called Greedy Maximal Matching (GMM), for multihop wireless networks. For simplicity, we focus on the wellestablished nodeexclusive interference model, although many of the stated results can be readily extended to more general interference models. The study of the performance of GMM is intriguing because although a lower bound on its performance is well known, empirical observations suggest that this bound is quite loose, and that the performance of GMM is often close to optimal. In fact, recent results have shown that GMM achieves optimal performance under certain conditions. In this paper, we provide new analytic results that characterize the performance of GMM through the topological properties of the underlying graphs. To that end, we generalize a recently developed topological notion called the local pooling condition to a far weaker condition called the σlocal pooling. We then define the localpooling factor on a graph, as the supremum of all σ such that the graph satisfies σlocal pooling. We show that for a given graph, the efficiency ratio of GMM (i.e., the ratio of the throughput of GMM to that of the optimal) is equal to its localpooling factor. Further, we provide results on how to estimate the localpooling factor for arbitrary graphs and show that the efficiency ratio of GMM is no smaller than d ∗ /(2d ∗ −1) in a network topology of maximum nodedegree d ∗. We also identify specific network topologies for which the efficiency ratio of GMM is strictly less than 1. I.
Queue BackPressure Random Access in MultiHop Wireless Networks: Optimality and Stability
"... A model for wireless networks with random (slottedAlohatype) access and with multihop flow routes is considered. The goal is to devise distributed strategies for optimal utilitybased endtoend throughput allocation and queueing stability. A class of queue backpressure random access algorithms ..."
Abstract

Cited by 17 (5 self)
 Add to MetaCart
(Show Context)
A model for wireless networks with random (slottedAlohatype) access and with multihop flow routes is considered. The goal is to devise distributed strategies for optimal utilitybased endtoend throughput allocation and queueing stability. A class of queue backpressure random access algorithms (QBRA), in which actual queue lengths of the flows in each node’s close neighborhood are used to determine the nodes ’ channel access probabilities, is studied. This is in contrast to some previously proposed algorithms, which are purely optimizationbased and oblivious to actual queues. QBRA is also substantially different from the well studied “MaxWeight ” type scheduling algorithms, which also uses backpressure. For the model with infinite backlog at each flow source, it is shown that QBRA, combined with simple congestion control local to each source, leads to optimal endtoend throughput allocation, within the network saturation throughput region achievable by random access without endtoend message passing. This scheme is generalized to the case of additional, minimum flow rate constraints. For the model with stochastic exogenous arrivals, it is shown that QBRA ensures stability of the queues as long as nominal loads of the nodes are within the saturation throughput region. Simulation comparison of QBRA and the queue oblivious optimizationbased random access algorithms, shows that QBRA performs better in terms of endtoend delays.
On Throughput Optimality with Delayed NetworkState Information
, 2008
"... We study the problem of routing/scheduling in a wireless network with partial/delayed Network (channel and queue) State Information (NSI). We consider two cases: (i) centralized routing/scheduling, where a central controller obtains heterogeneous delayed information from each of the nodes (thus, the ..."
Abstract

Cited by 17 (2 self)
 Add to MetaCart
(Show Context)
We study the problem of routing/scheduling in a wireless network with partial/delayed Network (channel and queue) State Information (NSI). We consider two cases: (i) centralized routing/scheduling, where a central controller obtains heterogeneous delayed information from each of the nodes (thus, the controller has NSI with different delays from different nodes), and makes the routing/scheduling decisions; (ii) decentralized routing/scheduling, where each node makes a decision based on its current channel and queue states along with homogeneous delayed NSI from other nodes. For each of the cases (with additional flow restrictions for the decentralized routing/scheduling case), we first characterize the optimal network throughput regions under the above described NSI models and show that the throughput regions shrinks with the increase of delay. Further, we propose channel and queue length based routing/scheduling algorithms that achieve the above throughput regions.