An Adaptive Virtual Queue (AVQ) Algorithm for Active Queue Management

Virtual queue-based marking schemes have been recently proposed for Active Queue Management (AQM) in Internet routers. We consider a particular scheme, which we call the Adaptive Virtual Queue (AVQ), and study its following properties: its stability in the presence of feedback delays, its ability to maintain small queue lengths, and its robustness in the presence of extremely short flows (the so-called web mice). Using a linearized model of the system dynamics, we present a simple rule to design the parameters of the AVQ algorithm. We then compare its performance through simulation with several well-known AQM schemes such as RED, REM, Proportional Integral (PI) controller, and a nonadaptive virtual queue algorithm. With a view toward implementation, we show that AVQ can be implemented as a simple token bucket using only a few lines of code

A novel real-time MAC layer protocol for wireless sensor network applications

This paper presents a comparative study of existing real-time MAC layer protocols for wireless sensor networks. Then, a new real-Time MAC protocol is presented that is based on a general purpose MAC protocol, called S-MAC. While medium access strategy in S-MAC is based on contention and back-off schemes, protocol proposed in this paper uses feedback approach as a medium access strategy. As a result of this, it increases consistency in data transmission pattern, which enables it to guarantee end-to-end delay deadlines for soft realtime applications. Proposed protocol works in continuous ON mode of operation at MAC layer and is intended to be used for randomly deployed single stream wireless sensor applications. Finally, a comparative performance analysis of proposed realtime protocol is done with other real-time and general purpose MAC protocols for wireless sensor networks

Reliable Multicast Transport for Heterogeneous Mobile IP environment using Cross-Layer Information

Reliable multicast transport architecture designed for heterogeneous mobile IP environment using cross-layer information for enhanced Quality of Service (QoS) and seamless handover is discussed. In particular, application-specific reliable multicast retransmission schemes are proposed, which are aimed to minimize the protocol overhead taking into account behaviour of mobile receivers (loss of connectivity and handover) and the specific application requirements for reliable delivery (such as carousel, one-to-many download and streaming delivery combined with recording). The proposed localized retransmission strategies are flexible configured for tree-based multicast transport. Cross layer interactions in order to enhance reliable transport and support seamless handover is discussed considering IEEE 802.21 media independent handover mechanisms. The implementation is based on Linux IPv6 environment. Simulations in ns2 focusing on the benefits of the proposed multicast retransmission schemes for particular application scenarios are presented

Power Saving MAC Protocols for WSNs and Optimization of S-MAC Protocol

Low power MAC protocols have received a lot of consideration in the last few years because of their influence on the lifetime of wireless sensor networks. Since, sensors typically operate on batteries, replacement of which is often difficult. A lot of work has been done to minimize the energy expenditure and prolong the sensor lifetime through energy efficient designs, across layers. Meanwhile, the sensor network should be able to maintain a certain throughput in order to fulfill the QoS requirements of the end user, and to ensure the constancy of the network. This paper introduces different types of MAC protocols used for WSNs and proposes S‐MAC, a Medium‐Access Control protocol designed for Wireless Sensor Networks. S‐MAC uses a few innovative techniques to reduce energy consumption and support self‐ configuration. A new protocol is suggested to improve the energy efficiency, latency and throughput of existing MAC protocol for WSNs. A modification of the protocol is then proposed to eliminate the need for some nodes to stay awake longer than the other nodes which improves the energy efficiency, latency and throughput and hence increases the life span of a wireless sensor networ

Integrated placement and routing of relay nodes for fault-tolerant hierarchical sensor networks

In two-tiered sensor networks, using higher-powered relay nodes as cluster heads has been shown to lead to further improvements in network performance. Placement of such relay nodes focuses on achieving specified coverage and connectivity requirements with as few relay nodes as possible. Existing placement strategies typically are unaware of energy dissipation due to routing and are not capable of optimizing the routing scheme and placement concurrently. We, in this thesis, propose an integrated integer linear program (ILP) formulation that determines the minimum number of relay nodes, along with their locations and a suitable communication strategy such that the network has a guaranteed lifetime as well as ensuring the pre-specified level of coverage (ks) and connectivity (kr). We also present an intersection based approach for creating the initial set of potential relay node positions, which are used by our ILP, and evaluate its performance under different conditions. Experimental results on networks with hundreds of sensor nodes show that our approach leads to significant improvement over existing energy-unaware placement schemes

Topology-aware transmission scheduling for distributed highway traffic monitoring wireless sensor networks

Wireless sensor networks have been deployed along highways for traffic monitoring. The thesis studies a set of transmission scheduling methods for optimizing network throughput, message transfer delay, and energy efficiency. Today\u27s traffic monitoring systems are centrally managed. Several studies have envisioned the advantages of distributed traffic management techniques. The thesis is based on previously proposed hierarchical sensor network architecture, for which the routing and transmission scheduling methods are derived. Wireless sensor networks have a lifetime limited by battery energy of the sensors. The thesis proposes to assign schedules for nodes to transmit and receive packets and turning off their radios during other times to save energy. The schedules are assigned to minimize the end-to-end packet delivery latency and maximize the network throughput. Conflict-free transmission slots are assigned to sensors along road segments leading to a common intersection based on locally discovered topology. The slot assignment adopts a heuristic that rotates among segments, assigns closest possible slots to neighboring nodes in a pipelined fashion, and exploits radio capture effects when possible. Based on the single-intersection approach, centralized and distributed multi-intersection scheduling methods are proposed to resolve conflicts among nodes belonging to different intersections. The centralized approach designates a controller as the leader to collect topology information of a set of contiguous intersections and assign schedules using the same single-intersection algorithm. The distributed approach has each intersection determine its own schedule independently and then exchange the topology information and schedules with its adjacent intersections to resolve conflicts locally. Based on simulation studies in ns-2, the centralized approach achieves better performance, while the distributed approach tries to approach the centralized performance at much lower communication costs. A communication cost analysis is performed to assess the trade-off between the centralized and distributed approaches