Charalambos Sergiou

A Comprehensive Survey of Congestion Control Protocols in Wireless Sensor Networks

Congestion control and reliable data delivery are two primary functions of the transport layer in wired and wireless networks. Wireless sensor networks (WSNs) are a special category of wireless ad hoc networks with unique characteristics and important limitations. Limitations concern their resources, such as energy, memory, and computational power, as well as their applications. Due to these limitations and characteristics, the Transmission Control Protocol (TCP), the legacy protocol that implements congestion control and reliable transmission in the Internet, cannot apply to WSNs in its traditional form. To deal with this unavailability of a standard solution, many efforts are taking place in this area. In this paper, we review, classify, and compare algorithms, protocols, and mechanisms that deal directly with congestion control and avoidance in WSNs.

Performance Study of Node Placement for Congestion Control in Wireless Sensor Networks

Performance of Wireless Sensor Networks (WSNs) can be affected when the network is deployed under different topologies. In this paper we present a performance study of congestion control algorithms in WSNs when nodes are deployed under different topologies. To perform our research we have employed algorithms SenTCP, Directed Diffusion, and HT AP. The choice of these algorithms is based on the fact that they cover two major methods used for congestion mitigation. These are: a) decreasing the load by source rate reduction (used in SenTCP) and b) increasing resources as these would help in emptying the buffers of intermediate sensor node though the creation of alternative paths (used in HTAP) or creation of multiple paths used in Directed Diffusion). We have examined the performance of these algorithms with respect to their ability to maintain low delays, to support the required data rates and to minimize packet losses under four different topologies. The topologies we have used are Simple Diffusion, Constant Placement, R-random placement and Grid placement. Results indicate that congestion control performance in sensor networks can significantly be improved, in algorithms that use multiple or alternative paths to forward their data in case of congestion (Directed Diffusion and HT AP). Performance of rate-controlled algorithms like SenTCP exhibit improvement in terms of packet latency.

Congestion control in Wireless Sensor Networks through dynamic alternative path selection

Recent applications on Wireless Sensor Networks (WSNs) demand networks with high and consistent data load. Due to the limited resources of wireless sensor nodes, high data loads can easily lead to congestion conditions. Congestion is a highly undesirable situation since its appearance creates additional overhead to the already heavily loaded environment, which, eventually leads to resource depletion. Thus, congestion control algorithms need to be applied in order to mitigate congestion. In this paper, we present a lightweight congestion control and avoidance scheme, called Dynamic Alternative Path Selection Scheme (DAlPaS). DAlPaS is a very simple but effective scheme that controls congestion while it keeps overhead to the minimum. The operation of this scheme is based on the control of resources instead of controlling the sending rate at the source. The performance of DAlPaS has been evaluated against comparable schemes with promising results.

DAlPaS: A performance aware congestion control algorithm in Wireless Sensor Networks

As Wireless Sensor Networks are evolving to applications where high load demands dominate and performance becomes a crucial factor, congestion remains a serious problem that has to be effectively and efficiently tackled. Congestion in WSNs is mitigated either by reducing the data load or by increasing capacity (employing sleep nodes). In either case due to the energy constraints and low processing capabilities of sensor nodes, congestion control and avoidance algorithms has to be kept as simple and efficient as possible while overhead must be limited. In this paper we propose a novel and simple Dynamic Alternative Path Selection Scheme (DAlPaS) attempting to face congestion by increasing capacity while attempts to maintain performance requirements. DAlPaS can efficiently and adaptively choose an alternative routing path in order to avoid congested nodes, by taking into consideration a number of critical parameters that affect the performance of a WSN while maintaining overhead in minimal levels. Simulation results show that DAlPaS algorithm can perform significant performance achievements over comparable schemes.

Energy utilization of HTAP under specific node placements in Wireless Sensor Networks

Energy utilization is a challenging task that is being encountered in low-powered Wireless Sensor Networks (WSNs) when designing an algorithm, protocol or hardware. Congestion is a factor that can affect a networks lifetime (and energy utilization), since it usually leads to packet drops or collisions in the medium followed by possible retransmissions. Forwarding data packets through alternative paths is a way to counter congestion in WSNs. Proper node placement is essential to ensure good sensing coverage and communication connectivity. Node placement could also be affected by the need to create multiple routes to the sink; therefore, it can be proven vital for the improvement of energy utilization performance of this type of congestion control algorithms. In this paper we evaluate the energy utilization performance of HTAP (Hierarchical Tree Alternative Path) a congestion control and avoidance algorithm whose operation is based on a multipath routing scheme. HTAP energy utilization is evaluated under specific node placements and in correlation with a comparable routing scheme (Directed Diffusion). Through simulations, conclusions are extracted, suggesting node placements that assist in uniform and efficient energy utilization in WSNs.

Estimating Maximum Traffic Volume in Wireless Sensor Networks Using Fluid Dynamics Principles

Studying the behavior of Wireless Sensor Networks (WSNs) is a complex task, since the effects of significant network parameters are frequently unpredictable. This, along with the fact that in most network deployments, wireless sensor nodes are densely and randomly deployed, renders the individual study of the behavior of each sensor node impractical. In this work, we attempt to analyze, model, and estimate the maximum volume of traffic than can be carried out from the sources to the sink(s) of a WSN, without the use of any congestion control algorithms. To perform our analysis we employ a macroscopic fluid dynamic model. Using this model and three fundamental traffic variables, packet density, packet flow, and spatial packet rate, we calculate the limits of the network flows, in terms of capacity, in the absence of congestion control. Calculating these limits helps us prove a relation between incoming and outgoing flow in the bottleneck nodes that can specify the optimal point at which the network should operate without the need of congestion control algorithms.

HRTC: A Hybrid Algorithm for Efficient Congestion Control in Wireless Sensor Networks

As applications in Wireless Sensor Networks (WSNs) are evolving, congestion control remains an open and, in several cases, a critical problem. A lot of research has been performed on this issue and two general approaches seem to be the most prominent for its solution: traffic control and resource control. Each of these two methods present specific advantages and disadvantages under different scenarios. In this paper we present HRTC, a dynamic scheme capable of bridging these two methods for congestion control and provide the best solution, based on the prevalent network conditions.

Study of lifetime extension in wireless sensor networks through congestion control algorithms

Energy constraints are undoubtedly a major concern in the creation of algorithms for WSNs. In this paper we examine the issue of extending a wireless sensor networks lifetime, not with the aim of providing a new algorithm, or comparing existing energy-reduction related methods, but with the aim of understanding if this problem can be inherently addressed by other types of algorithms such as those designed for congestion control and avoidance. We claim and prove that Congestion Control Algorithms can also assist in the uniform energy utilization of a Wireless Sensor Network to some extent. A number of WSN congestion control algorithms base their operation on the creation of alternative paths from the source to sink, using the plethora of the networks unused nodes. The creation of alternative paths employs several nodes which are not in the initial shortest path(s) from the source to sink and assist in safely transmitting the observed data. The use of these nodes leads to a balanced energy consumption, avoiding the creation of “holes” in the network.

Alternative path creation vs data rate reduction for congestion mitigation in wireless sensor networks

Network Congestion is a highly undesirable situation for every type of network. Especially in low powered Wireless Sensor Networks (WSNs), congestion can be proven critical for the networks proper operation. In case of congestion in a WSN, the network is programmed to react, either by reducing the data rate of the sources or by creating multiple routing paths to the sink, thus avoiding the networks congested point. In this paper we perform a comparison of these two techniques, comparing one algorithm of each category. Results depict the advantages and disadvantages of each category.

Efficient Node Placement for Congestion Control in Wireless Sensor Networks

Wireless sensor nodes are small, embedded computing devices that interface with sensors/ actuators and communicate using short-range wireless transmitters. Such nodes act autonomously, but cooperatively to form a logical network, in which data packets are routed hop-by-hop towards management nodes, typically called sinks or base stations. A Wireless Sensor Network (WSN) comprises of a potentially large set of nodes that may be distributed over a wide geographical area, indoor or outdoor. Wireless Sensor Networks (WSNs) enable numerous sensing and monitoring services in areas of vital importance such as efficient industry production, safety and security at home as well as in traffic and environmental monitoring. Traffic patterns in WSNs can be derived from the physical processes that they sense. WSNs typically operate under light load and suddenly become active in response to a detected or monitored event. Early research studies in WSNs targeted military applications, especially for battlefield monitoring. In the last few years, due to the progress of low powered units and improvements in radio technologies, wireless sensor networks technologies have gainedmomentum. WSNs are now being deployed in civilian areas and being used for habitat observation ([1], [2]), health monitoring ([3]), object tracking ([4], [5]) etc. In addition, lately, there is an emergence of mission-critical applications ([6]).