[Show abstract][Hide abstract] ABSTRACT: To control congestion, either the traffic from sources should be “reduced” (traffic controlling) or the available resources
should be “increased” (resource controlling). Compared to the wired and other wireless counterparts, wireless sensor networks
usually have elastic resource availability, and the applications require a certain level of throughput called fidelity. As a result, resource control strategies cannot only alleviate congestion but also ensure the required fidelity level during
congestion by accommodating higher incoming traffic. In this paper, we first attempt to formally define the resource control
framework that adjusts the resource provisioning at the hotspot nodes during congestion. In an effort to find the optimal
resource control under the fidelity and energy constraints, we present a resource increase and decrease algorithm called Early Increase/Early Decrease (EIED) that tries to adjust the effective channel capacity quickly to suit the incoming traffic volume in an energy-efficient
manner, thereby increasing the fidelity level observed by the application. Under the energy-constrained optimization, we prove
this algorithm incurs the lowest overhead of energy consumption for the given fidelity level that is required by the application.
We also prove that the EIED algorithm performed in a distributed manner also lowers the energy consumption per packet at an
end-to-end level. The effectiveness of the EIED algorithm is verified by simulations based on realistic sensor network configurations.
[Show abstract][Hide abstract] ABSTRACT: This paper analyzes the scalability of message flooding protocols in networks with various node densities, which can be expected in vehicular scenarios. Vehicle safety applications require reliable delivery of warning messages to nearby and approaching vehicles. Due to potentially large distances and shadowing, the delivery protocol must forward messages over multiple hops, thereby increasing network congestion and packet collisions. In addition to application-layer backoff delay and duplicate message suppression mechanisms, location-based backoff techniques have been proposed for vehicular networks. We propose a new hybrid method of location-based and counterbased method, and study several variants through simulations. Our preliminary results in the various density scenarios indicate that the proposed hybrid methods outperform conventional backoff delay techniques and adaptively operate in extremely congested network condition
Mobile and Ubiquitous Systems - Workshops, 2006. 3rd Annual International Conference on; 08/2006
[Show abstract][Hide abstract] ABSTRACT: Abstract As cellular carriers start deploying packet data services such as General Packet Radio Service (GPRS) and 3G cellular networks, packet- switched voice services such as VoIP will be available over the cellular network in the near future. When the existing circuit-switched radio interface and the newly deployed packet-switched radio interface coexist in a cell, the mobile station user may have an option between the circuit-switched call and the VoIP call. While the circuit-switched voice offers a better call quality, the VoIP connection offers a better radio resource utilization. In this paper, we introduce dynamic QoS control schemes for voice traffic, where Class-A GPRS mobile station users can switch their ongoing,GSM calls to VoIP calls and vice versa seamlessly in the SIP-enabled GSM/GPRS cellular network,based on their desired quality of service. Due to the VoIP’s less radio resource demand, these schemes can also be used by the base station controller to handle the dynamically,changing,load in a cell. q 2005 Published by Elsevier B.V. Keywords: Bandwidth adaptation; QoS control; Packet cellular networks; Voice over IP (VoIP); GPRS
[Show abstract][Hide abstract] ABSTRACT: In this paper, we first attempt to formally define the re- source control framework that adjusts the resource provi- sioning at the hotspot during congestion. In an effort to find the optimal resource control under the fidelity and energy constraints, we present a resource increase and decrease al- gorithm called Early Increase/Early Decrease (EIED) that tries to adjust the effective channel capacity quickly to the incoming traffic volume in an energy-efficient manner, thereby increasing the fidelity (or accuracy) level observed by the application during congestion. Under the framework of energy-constrained optimization, we prove this algorithm incurs the lowest overhead of energy consumption for the given fidelity level that is required by the application.
Proceedings of the 11th IEEE Symposium on Computers and Communications (ISCC 2006), 26-29 June 2006, Cagliari, Sardinia, Italy; 01/2006
[Show abstract][Hide abstract] ABSTRACT: Congestion in ad hoc networks not only degrades throughput, but also wastes scarce energy due to a large number of retransmissions and packet drops. For efficient congestion control, an accurate and timely estimation of resource demands by measuring the network congestion level is necessary. Congestion level measurement in ad hoc networks is more difficult than in wired networks due to time-variant channel capacity, contention among neighboring nodes, and non-deterministic node scheduling. We propose a new congestion detection mechanism that quantifies the congestion level accurately and energy-efficiently at both a node-level (implemented at the MAC layer) and a flow-level (implemented at the routing layer) in ad hoc networks. For accurate congestion measurement, a set of metrics that decouple the measurement from various MAC protocol characteristics is defined. For energy-efficient congestion measurement, an asynchronous channel loading measurement scheme, called lazy measurement, which emulates synchronous measurement by using virtual channel sampling, is incorporated into the proposed scheme. Simulation results show that the proposed mechanism significantly cuts down the energy needed to measure congestion accurately, while maintaining the high level of accuracy needed for timely congestion control.
Wireless Communications and Networking Conference, 2005 IEEE; 04/2005
[Show abstract][Hide abstract] ABSTRACT: To avoid congestion before it happens, the traffic from the sources should be "reduced" (traffic control) or the available resources should be "increased" (resource control) in advance. While the traffic control in the context of congestion avoidance has been extensively studied mostly through the active queue management (AQM), resource control has received little attention for congestion avoidance. In this paper, we present a congestion avoidance scheme called congestion-aware packet generalized processor sharing (CPGPS) that differentiates between transient congestion and persistent congestion and takes different actions based on the type of congestion when congestion is anticipated. Unlike persistent congestion that is avoided normally by controlling the incoming traffic using the AQM algorithm, we show that transient congestion can be better handled by temporarily increasing the bandwidth available to the sources of transient congestion before packets belonging to these sources start to be dropped. To allocate bandwidth fairly among the sources of transient congestion, CPGPS is implemented on top of the packet fair queueing (PFQ) algorithm.
[Show abstract][Hide abstract] ABSTRACT: In this paper, unlike the current end-to-end congestion control mechanism such as TCP that only reduces its traffic in the presence of congestion, we propose a new wireless congestion control framework, in which a mobile station's MAC-layer tries to increase its available wireless bandwidth in the presence of incipient congestion when available bandwidth can he increased without affecting other flows in a cell. In our framework, wireless congestion is classified into channel congestion, queue congestion, and global congestion. In order to control congestion in a timely manner, the mobile station's MAC-layer decides whether available bandwidth should be increased or incoming traffic should be reduced based on the congestion type. In addition, thanks to the MAC-layer's ability to better observe the wireless channel condition, the wireless congestion, which is considered more important than the wired congestion due to its limited bandwidth, can be better handled when the path of a mobile station's connection spans wired network.
[Show abstract][Hide abstract] ABSTRACT: Congestion control in sensor networks is important not only to improve the overall throughput but also to enlengthen the network lifetime by saving the scarce energy wasted dur-ing congestion. While throttling the incoming traffic during congestion can effectively alleviate congestion, it also lowers the throughput called accuracy level observed by the appli-cation deployed in the sensor network. In this paper, we investigate how congestion can be allevi-ated by increasing the available resource amount rather than suppressing the incoming traffic. To optimally increase the available channel capacity during congestion, the end-to-end channel capacity of a flow with multiple paths and their vari-ous configurations is analyzed, which is then verified by sim-ulations. Based on the analysis and simulations, we suggest several guidelines on how to adjust the end-to-end channel capacity under the various congestion scenarios.
[Show abstract][Hide abstract] ABSTRACT: As cellular packet data services become widely deployed by the rollout of the networks such as general packet radio service (GPRS) and 3G cellular networks, packet-switched voice service such as voice over IP (VoIP) can soon be expected to be offered as an alternative to circuit-switched voice service. While circuit-switched voice offers better quality, packet-switched voice offers better resource utilization due to its multiplexing and compression techniques that can be used in packet radio principle. Therefore, the capability of having voice service over either circuit-switched network or packet-switched network provides a tradeoff between voice quality and bandwidth utilization. This paper proposes three schemes that allow users to toggle between circuit-switched voice and packet-switched voice based on the desired tradeoff. The basic idea is to allow ongoing voice traffic to alternate between circuit-switched network and packet- switched network using a 3-way calling mechanism in the SIP-enabled GSM/GPRS cellular network. We also show how these toggle schemes can be used depending on the cell load. Detailed performances of the proposed schemes are evaluated using simulation with realistic parameters of a cellular environment. The result shows our schemes can alleviate cell overloading as well as provide the smooth transition of an ongoing call between circuit-switched network and packet-switched network. Our schemes can be easily deployed in any cellular mobile network where circuit-switched network and packet-switched network coexist.
Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
[Show abstract][Hide abstract] ABSTRACT: As cellular packet data services become widely deployed by the rollout of the General Packet Radio Service (GPRS) and 3G cellular
networks, the packet-switched cellular network is emerging as an alternative to the existing circuit-switched cellular network.
While the circuit data service provides wireless bandwidth guarantees, the packet data service offers better radio resource
utilization due to its packet-switched multiplexing principle applied in the air interface. Therefore, the capability of having
a data service over either the circuit-switched radio or the packet-switched radio provides a tradeoff between the perceived
QoS and the radio utilization.
This paper proposes a novel framework for dynamic bandwidth adaptation that allows an ongoing data traffic to alternate between
the circuit data service and the packet data service using Mobile IP in the hybrid cellular network. Our approach can be used
as a tool to handle the dynamically changing load in a cell and also easily deployed in any hybrid cellular network where
the circuit and packet data services coexist
Information Networking, Networking Technologies for Broadband and Mobile Networks, International Conference ICOIN 2004, Busan, Korea, February 18-20, 2004, Revised Selected Papers; 01/2004
[Show abstract][Hide abstract] ABSTRACT: Sensor networks are being increasingly deployed for surveillance and monitoring applications. These networks will suffer from severe congestion as soon as the target events occur. During congestion, important data packets may be dropped, which can essentially nullify the purpose of sensor networks. In this paper, we propose an adaptive resource control scheme to alleviate congestion in sensor networks. The choice of resource control is necessitated by the following two factors: (1) unlike in traditional networks, we cannot simply reduce the source traffic because these data are crit-ical to the applications; and (2) sensor networks usually are densely deployed and thus have the capability of provi-sioning more resources when needed. The proposed scheme adjusts the resource provisioning based on the congestion level so that we can both increase the capacity, by having more sensor nodes forwarding data or having more rout-ing paths, to alleviate the congestion, as well as reduce the capacity after the congestion to conserve the energy con-sumption.