Browsing by Author "Ganesan, Ashwin"

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    Distributed algorithms for QoS in wireless ad hoc networks under the primary interference model
    (IEEE, 2020-08-04) Ganesan, Ashwin
    Consider a wireless network consisting of a set of wireless nodes and a set of communication links, where each communication link corresponds to a pair of nodes that are within communication radius of each other. Under the primary interference model, two communication links cannot be active at the same time if they are incident to a common node. This model of interference arises in Bluetooth networks, where transmissions between a master node and slave nodes in a piconet are scheduled by time-division duplexing, and in CDMA systems when each node is equipped with a single transceiver. Each communication link has a certain minimum bandwidth quality-of-service requirement. The admission control problem is to determine whether the network has sufficient resources to satisfy the bandwidth requirements. In this work, distributed algorithms are proposed for this admission control problem, and performance guarantees of these distributed algorithms are given. If each node has knowledge of a certain global parameter, then a distributed algorithm for flow admission control is given which has the same performance as an optimal, centralized algorithm, i.e. the distributed algorithm gives a condition that is both necessary and sufficient for a set of flow rates to be feasible.
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    On some distributed scheduling algorithms for wireless networks with hypergraph interference models
    (IEEE, 2021-05-01) Ganesan, Ashwin
    It is shown that the performance of the maximal scheduling algorithm in wireless ad hoc networks under the hypergraph interference model can be further away from optimal than previously known. The exact worst-case performance of this distributed, greedy scheduling algorithm is analyzed.
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    Performance analysis of a distributed algorithm for admission control in wireless networks under the 2-hop interference model
    (ICDCN, 2021-01-05) Ganesan, Ashwin
    A general open problem in networking is: what are the fundamental limits to the performance that is achievable with some given amount of resources? More specifically, if each node in the network has information about only its 1-hop neighborhood, then what are the limits to performance? This problem is considered for wireless networks where each communication link has a minimum bandwidth quality-of-service (QoS) requirement. Links in the same vicinity contend for the shared wireless medium. The conflict graph captures which pairs of links interfere with each other and depends on the MAC protocol. In IEEE 802.11 MAC protocol-based networks, when communication between nodes i and j takes place, the neighbors of both i and j remain silent. This model of interference is called the 2-hop interference model because the distance in the network graph between any two links that can be simultaneously active is at least 2. In the admission control problem studied in the present paper, the objective is to determine, using only localized information, whether a given set of flow rates is feasible. In the present work, a distributed algorithm is proposed for this problem, where each node has information only about its 1-hop neighborhood. The worst-case performance of the distributed algorithm, i.e. the largest factor by which the performance of this distributed algorithm is away from that of an optimal, centralized algorithm, is analyzed. Lower and upper bounds on the suboptimality of the distributed algorithm are obtained, and both bounds are shown to be tight. The exact worst-case performance is obtained for some ring topologies. While distance-d distributed algorithms have been analyzed for the 1-hop interference model, an open problem in the literature is to extend these results to the K-hop interference model, and the present work initiates the generalization to the K-hop interference model.
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    Performance analysis of distance-1 distributed algorithms for admission control under the 2-hop interference model
    (Theoretical Computer Science, 2023-02-20) Ganesan, Ashwin
    If each node in a wireless network has information about only its 1-hop neighborhood, then what are the limits to performance? This problem is considered for wireless networks where each communication link has a minimum bandwidth quality-of-service (QoS) requirement. Links in the same vicinity contend for the shared wireless medium. The conflict graph captures which pairs of links interfere with each other and depends on the MAC protocol. In IEEE 802.11 MAC protocol-based networks, when communication between nodes i and j takes place, the neighbors of both i and j remain silent. This model of interference is called the 2-hop interference model because the distance in the network graph between any two links that can be simultaneously active is at least 2. In the admission control problem studied in the present paper, the objective is to determine, using only localized information, whether a given set of flow rates is feasible. While distance-d distributed algorithms have been analyzed for the 1-hop interference model, an open problem in the literature is to extend these results to the K-hop interference model, and the present work initiates the generalization to the K-hop interference model. We show that the centralized version of the problem is NP-hard and then investigate distributed, low-complexity solutions for this problem. We propose a distributed algorithm for this problem where each node has information about only its 1-hop neighborhood. The worst-case performance of the distributed algorithm, i.e. the largest factor by which the performance of this distributed algorithm is away from that of an optimal, centralized algorithm, is analyzed. Lower and upper bounds on the suboptimality of the distributed algorithm are obtained, and both bounds are shown to be tight. The exact worst-case performance is obtained for some ring topologies. The performance of the distance-1 distributed algorithm is compared with that of the row constraints, and these two distributed algorithms are shown to be incomparable.
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    Structured Hypergraphs in Cellular Mobile Communication Systems
    (Association for Computing Machinery, 2023-01-04) Ganesan, Ashwin
    An open problem is to extend the results in the literature on unit disk graphs to hypergraph models. Motivated by recent results that the worst-case performance of the distributed maximal scheduling algorithm is characterized by the interference degree of the hypergraph, in the present work we investigate properties of the interference degree of the hypergraph and the structure of hypergraphs arising from physical constraints. We show that the problem of computing the interference degree of a hypergraph is NP-hard and we prove some properties and results concerning this hypergraph invariant. We then investigate which hypergraphs are realizable, i.e. which hypergraphs arise in practice, based on physical constraints, as the interference model of a wireless network. In particular, given the results on the worst-case performance of the maximal scheduling algorithm, a question that arises naturally is: what is the maximal value of r such that the hypergraph K1,r is realizable? We show that this value is r = 4.