This paper focuses on congestion control over multihop, wireless networks. In a wireless network, an important constraint that arises is that due to the MAC (Media Access Control) layer. Many wireless MACs use a time-division strategy for channel access, where, at any point in space, the physical channel can be accessed by a single user at each instant of time. In this paper, we develop a fair hop-by-hop congestion control algorithm with the MAC constraint being imposed in the form of a channel access time constraint, using an optimization based framework. In the absence of delay, we show that this algorithm are globally stable using a Lyapunov function based approach. Next, in the presence of delay, we show that the hop-by-hop control algorithm has the property of spatial spreading. In other words, focused loads at a particular spatial location in the network get "smoothed" over space. We derive bounds on the "peak load" at a node, both with hop-by-hop control, as well as with end-to-end control, show that significant gains are to be had with the hop-by-hop scheme, and validate the analytical results with simulation.

This paper gives a class of flow control algorithms for the adaptive allocation of bandwidths to virtual connections (VC) in high speed, wide area ATM networks. The feedback rate to the source from the network is parsimonious, with each feedback bit indicating whether the buffer at a distant switch is above or below a threshold. The service discipline at the switch is First-Come-First-Served. The important goal of adaptability aims to make all of the network bandwidth available to the active VCs, even though the number of such VCs is variable over a given range. Each VC has two parameters, one giving its minimum guaranteed bandwidth and the other is the weight for determining its share of the uncommitted bandwidth. Judicious selection of these parameters defines distinctive services, such as Best Effort and Best Effort with Minimum Bandwidth. We derive design rules for selecting the parameters of the algorithms such that the appropriate guarantees and fairness properties are exhibited ...

Abstract — In multihop wireless networks where a random access MAC scheme such as CSMA/CA is used, nodes greedily compete in a distributed manner and are unaware of the interference they cause to other surrounding nodes. In these networks, excessive interference at a receiver or a potential forwarding node causes severe blocking and reduction in throughput. In addition, the unbalanced interference experienced at a particular node can force the node to consume more time receiving packets rather than sending them, resulting in dropped packets due to buffer overflow. We discuss a novel flow control framework for regulating the transmission and improving the overall throughput of multihop wireless networks based on CSMA/CA MAC protocol. The framework prevents congestion, reduces packet loss and is attractive because per-flow information at each node is kept to a minimum. The techniques used to improve throughput include a hop-by-hop, hybrid rate and window based flow control scheme that paces the transmission of frames such that competition between frames originating from the same flow is reduced. In a general chain topology, the framework shows that throughput and energy efficiency can be increased by factors of 2.47 and 2.4, respectively, when a single flow is transmitted as fast as possible along the chain. In the high fan-in chain setup, where multiple single-hop flows are forwarded into a chain of nodes, the energy efficiency and throughput improvement factors can be as high as 5.14 and 5.58, respectively. Keywords-component; Flow control, hop-by-hop, rate control, static window, multihop wireless networks, CSMA/CA I.

We present HbH a new control paradigm in order to overcome node failure in multihop wireless ad hoc networks. HbH is an enhancement of the IEEE 802.11 protocol, that enables packet and buffer control at the MAC layer. Previous works have shown that the use of acknowledgments at the transport layer in multihop wireless networks reduces considerably the goodput achieved by connections. Instead of using end-to-end or hop-by-hop acknowledgements, with HbH wireless nodes track neighbors transmission to know if packets are correctly delivered and to detect node failures. The innovation in our work is in pushing down such control to the MAC layer which allows taking advantage of the broadcast nature of the wireless medium. HbH attempts to provide a reasonable trade-off between reliability and performance as well as complexity. Our objective is also to study the effectiveness of providing end-to-end reliability by using hop-by-hop flow control. We compare the performance of our protocol in J-Sim simulator with the traditional IEEE 802.11. We show that we can increase the reliability of a UDP flow without adding control overhead thus increasing the goodput as well. 1