Manikanden Balakrishnan

Impact of sleep in a wireless sensor MAC protocol

A sensor net consists of tiny devices with severe energy constraints. Employing energy efficient, sensor-specific MAC protocols is of necessity for sensor nets, and such protocols have been proposed in the literature. Sensor MAC protocols introduce sleep in sensor nodes to conserve energy and the impact of sleep on protocol performance needs a detailed investigation. In this paper, we quantify the effect of sleep on protocol performance through queueing analysis and simulation. Results demonstrate quantitatively the tradeoff between energy consumption and average latency in sensor MAC protocols.

Impact of turnaround time on wireless MAC protocols

Media access control (MAC) protocols for mobile ad-hoc networks are of interest in applications ranging from wireless local area networks (WLANs) to global skywave high-frequency radio networks. Much of the recent work in wireless MAC protocols has emphasized networks with short turnaround times (e.g., IEEE 802.11 WLANs). However, some wireless networks suffer lengthy turnaround times in the physical layer. This paper explores the interaction of turnaround time with various types of MAC protocols, and offers guidance for selecting an efficient wireless MAC protocol.

Robust token management for unreliable networks

Token passing can provide efficient medium access control in heavily loaded networks. However, it has been perceived to be too fragile for use in networks with non-negligible packet loss rates. In this paper, we present a novel token management approach that quickly recovers from common token loss and duplication scenarios, and that deals efficiently with changes in network connectivity and membership. This token management scheme was developed for use in military high frequency radio networks, and may also be appropriate for other networks that experience significant packet loss rates and relatively long link turnaround times.

Energy efficient cross-layer routing protocol in Wireless Sensor Networks based on fuzzy logic

Resources are scarce in Wireless Sensor Networks (WSN) and one of the challenges is to design a lightweight communication protocol to support efficient and uniform power consumption among nodes. In this paper, we propose an energy aware routing scheme based on a cross-layer approach for WSNs with the objective to minimize the overall consumed energy; thus, maximizing the network lifetime. The remaining battery reserve capacity, link quality and transmission power for nodes within the local communication range are taken into consideration to determine the next hop relay node to reach the network sink. Parameters from different stack layers (i.e., physical, MAC, and network) are presented to a fuzzy logic system controller which makes a next hop routing decision. The performance of the proposed cross-layer algorithm is evaluated using discrete event simulation (OMNET++ Modeler).

Fuzzy diffusion for distributed sensor networks

Distributed sensor networks (DSNs) are an emerging technology, recently finding extensive application in scientific and military surveillance. DSNs operate under severe energy constraints and are largely characterized by short-range multi-hop radio communications, which drives the need for energy-efficient routing schemes in such networks. Directed diffusion, a data-centric routing approach for application-aware DSNs has been shown to outperform traditional wireless routing schemes and achieves reasonable energy conservation through data-aggregation. However, directed diffusion ignores the energy level of sensor nodes, and we believe that incorporating the knowledge of relative energy reserves into the routing algorithm will improve energy efficiency and significantly prolong network lifetime. In this paper, we introduce fuzzy diffusion, an energy optimization on the directed diffusion scheme, and quantify its energy performance using ns-2 simulations.

Preemptive emergency medium access for wireless sensor networks: performance under realistic network conditions

The proliferation of Wireless Sensor Network (WSN) deployment in threat monitoring applications requires support for emergency-class services with tight Quality-of-Service (QoS) bounds. The CP-EDCA protocol was designed to achieve deterministic delay bounds for emergency-class traffic during distributed wireless network operation. The CP-EDCA scheme could be an ideal choice for prioritised channel access in WSNs, if the performance is demonstrated to be effective under WSN conditions. Here, we evaluate the effectiveness of CP-EDCA protocol under erroneous channel conditions and multi-hop data flow scenarios, which are distinctive features of WSNs. Mathematical and simulation analysis depicts that under typical WSN conditions, distributed preemptions accomplish deterministic delay bounds for emergency traffic even with heavy network loads. Under severe packet losses, CP-EDCA depicted perceivable improvements, relative to IEEE 802.11e standards. Analysis in multi-hop scenarios validates that the channel access preemptions have a significant impact on the end-to-end data flow performance.

Measures and Countermeasures for Null Frequency Jamming of On-Demand Routing Protocols in Wireless Ad Hoc Networks

Distributed network protocols operate similar to periodic state machines, utilizing internal states and timers for network coordination, which creates opportunities for carefully engineered radio jamming to target the protocol operating periods and disrupt network communications. Such periodic attacks targeting specific protocol period/frequency of operation is referred to as Null Frequency Jamming (NFJ). Our hypothesis is that NFJ is a pervasive phenomenon in dynamic systems, including wireless ad-hoc networks. This paper aims to test the hypothesis by investigating NFJ targeted at the on-demand routing protocols for ad-hoc networks. Our mathematical analysis and simulation results show substantial degradation in end-to-end network throughput at certain null periods/frequencies, where the jamming periodicity self-synchronizes with the route-recovery cycle. We also study an effective countermeasure, randomized route-recovery periods, for eliminating the presence of predictable null frequencies and mitigating the impact of NFJ. Our analytical model and simulation results validate the effectiveness of randomized route recovery with appropriately chosen randomization ranges.

Maximizing α-Lifetime of wireless sensor networks with solar energy sources

In this paper, using linear programming, we formulate the problem of maximizing the a-lifetime of wireless sensor networks with solar energy sources. The a-lifetime of a sensor network is defined as the duration in which a percentage of sensor data can be collected by the base station. Our formulation takes account of varying solar energy recovery rate at different sensors and jointly optimizes the transmission power of the sensors and data routing for maximizing a-lifetime. We study the break point, which marks the level of solar energy supply above which the sensor network can operate perpetually. We also study the changes in a-lifetime with the solar energy supply rate, distribution of solar energy, and the values of a. Our study provides useful guidance in practical deployment of sensor networks with renewable energy sources.

Performance of the HF token protocol

Token passing can provide efficient medium access control in heavily loaded networks. However, the management overhead required in forming and maintaining a ring of token-passing nodes is a potential liability for this protocol. In this paper, we present the results of both simulations and measurements of the HF token protocol in wireless LAN operation, and explore the range of applications that may make efficient use of token passing.

Routing in HF ad-hoc WANs

High frequency (HF) radio is commonly used to extend wireless communications beyond the line-of-sight range that limits the higher frequency bands. Despite such long-range coverage, however, indirect routing is sometimes required even in HF networks. In addition, HF radio and other wireless technologies are emerging as a means to interconnect wired subnetworks in various mobile and contingency applications. In this paper, we introduce WARRP, a wireless address resolution and routing protocol that is specifically designed to integrate single-relay route discovery with address resolution in such ad-hoc WAN.