Deepesh Man Shrestha

Emerging standards for wireless mesh technology

Wireless mesh networking is a promising technology for numerous applications which appeals especially to those applications that cannot be directly supported by other wireless technologies. The commercial success of Wi-Fi and the advances in many wireless technologies have in part stimulated the development of wireless mesh networks. The persistent driving force, however, comes from the envisioned advantages of wireless mesh techniques themselves, including extended coverage, robustness, self-configuration, easy maintenance, and low cost. This article presents an overview of this emerging technology, focusing on the technical merits and related standards activities of IEEE and ZigBee that are actively applying the concept of multi-hop mesh techniques in the field of wireless networking technologies, ranging from personal area networks (PANs) to metropolitan area networks (MANs)

Mobility-Aware distributed topology control for mobile multi-hop wireless networks

In recent years mobile multi-hop wireless networks have received significant attention and one of the major research concerns in this area is topology control While topology control problem in ad hoc networks is NP-complete, several heuristic and approximation based solutions have been presented However, few efforts have focused on the issue of topology control with mobility In this paper, we introduce a new topology control scheme in the presence of mobile nodes The proposed scheme predicts future proximity of neighboring nodes and applies power control such that the network connectivity is maintained while reducing energy consumption Simulation results show that the optimal power selection based on location prediction gives better performance in terms of energy and connectivity.

An energy-efficient MAC protocol for delay-sensitive wireless sensor networks

In this paper, we propose a new medium access control protocol for wireless sensor networks, named LE-MAC (Latency and Energy aware MAC) that aims to minimize data delivery latency as well as energy consumption. To achieve both goals, we exploit a physical carrier sensing feature in CSMA/CA and combine it with a cross-layer technique. When nodes that are in routing path between source and sink become aware of the traffic based on the carrier signal, they wakeup once more during the sleep period for transmitting data over multiple hops. We evaluated the proposed scheme compared with S-MAC on the ns-2 simulator. The results show that our scheme outperforms S-MAC protocols in balancing the need of low latency and energy consumption.

EDCA-TM: IEEE 802.11e MAC Enhancement for Wireless Multi-hop Networks

In this paper, we propose the EDCA-TM, a new architecture which tunes the enhanced distributed channel access (EDCA) for multi-hop networks. In EDCA-TM, we suggest a new module for dynamic access category adaptation (DACA) over the existing channel access mechanism such as EDCA. It processes received data packets for assigning an appropriate access categories (AC) to provide delay and rate guarantee to the QoS traffic. In addition, we adopt the earliest deadline first queuing (EDF) scheme to reschedule buffered packets in the AC queues according to their urgency for actual transmission. We have simulated our proposal in the network simulator, ns-2.31, and compared it with EDCA and APHD. Results show that our schemes outperform existing protocols and provide quality service for the traffic flows within the stated requirements.

IEEE 802.11 WLAN for medical-grade QoS

In this paper, we study the problem of how to design a medical-grade wireless LAN for healthcare facilities. Unlike IEEE 802.11e MAC, which categorizes traffic primarily by delay constraint, we prioritize medical applications into access categories according to medical criticality. We design a fully-distributed contention control mechanism that can efficiently utilize wireless channel for improving medical-grade QoS. We further derive a sufficient condition for the convergence of the proposed algorithm. Our simulation result shows that our medical access categorization and the contention control mechanism significantly improve the performance of a medical network over the conventional IEEE 802.11e MAC.

A new routing protocol in ad hoc networks with unidirectional links

Most of the proposed algorithms in ad hoc networks assume homogeneous nodes with similar transmission range and capabilities. However, in heterogeneous ad hoc networks, it is not necessary that all nodes have bidirectional link with each other and hence, those algorithms may not perform well while deployed in real situations. In this paper, we propose a scheme for an ad hoc on-demand routing protocol which utilizes the unidirectional links during the data transmission. Simulation shows that it is not only possible to use unidirectional links but it is also better in terms of performance metrics we defined in different situations.

On construction of the virtual backbone in wireless mesh networks

This paper deals with the selection of backbone nodes among end-user nodes in the wireless mesh networks. Although current IEEE 802.11 standards does not allow direct client-client or wireless AP-AP communication in the infrastructure mode, new concepts on mesh networks is arising in which all types of wireless links (i.e. AP-AP, client-client and client-AP) can be formed. This leads to the connectivity between nodes across the entire network region through multi-hopping. In this context, we propose a backbone selection algorithm such that best links and nodes are used with the connectivity being preserved as long as possible. We present the preliminary simulation result of our scheme in terms of packet delivery ratio and energy consumption

Utilizing a Perceptive Technique for the Delay-Sensitive Scheduling in Wireless Sensor Networks

CSMA/CA is a well known medium access mechanism extensively used in wireless networks. By detecting the carrier sensing (CS) signal, nodes determine whether the status of the wireless medium is busy or idle. However, recent works have shown that besides detecting the channel status, these signals can be used to derive the transmitted packet size at the nodes in the CS range. In this paper, we present the feasibility of this technique using CC2420 radio. In addition, we show how we can apply larger CS range and packet size detection to solve well-known problems such as reducing latency in the wireless sensor network (WSN). To our knowledge, the proposed solution is the first trial that applies such techniques to design the delay-sensitive scheduling for WSN. Based on our ns-2 simulation, we show that our proposal reduces latency significantly compared to the existing listen/sleep scheduling based protocols.