Ad hoc networks are characterized by multihop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. We compare the performance of two prominent on-demand routing protocols for mobile ad hoc networks: Dynamic Source Routing (DSR) and Ad Hoc On-Demand Distance Vector Routing (AODV). A detailed simulation model with MAC and physical layer models is used to study interlayer interactions and their performance implications. We demonstrate that even though DSR and AODV share similar ondemand behavior, the differences in the protocol mechanics can lead to significant performance differentials. The performance differentials are analyzed using varying network load, mobility, and network size. Based on the observations, we make recommendations about how the performance of either protocol can be improved.

Piconet is a general-purpose, low-power ad hoc radio network. It provides a base level of connectivity to even the simplest of sensing and computing objects. It is our intention that a full range of portable and embedded devices may make use of this connectivity. This article outlines the Piconet system, under development at the Olivetti and Oracle Research Laboratory (ORL). The authors discuss the motivation for providing this low-level "embedded networking," and describe their experiences of building such a system. The article concludes with a commentary on some of the implications that power saving, and other considerations central to Piconet, have on the design of the system.

This paper addresses low power MAC protocols for the downlink of infrastructure wireless sensor networks. We are interested in the trade-off between power consumption and transmission delay, focusing on low traffic. We describe WiseMAC (Wireless Sensor MAC), a new protocol for the downlink of infrastructure wireless sensor networks. Another original contribution is the analysis of the performance of PTIP (Periodic Terminal Initiated Polling). Here, polling is used in the reversed direction as compared to common polling protocols. WiseMAC and PTIP are compared with PSM, the power save protocol used in both the IEEE 802.11 and IEEE 802.15.4 ZigBee standards. Analytical expressions are given for the power consumption and the transmission delay for each protocol, as a function of the wake-up period. It is shown that WiseMAC provides, for the same delay, a significantly lower power consumption than PSM. Although less energy efficient than WiseMAC and PSM, it is shown that PTIP can, thanks to its implementation simplicity, become attractive for applications tolerating large transmission delays .

Multicast/broadcast is an important service primitive in networks. The IEEE 802.11 multicast/broadcast protocol is based on the basic access procedure of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). This protocol does not provide any media access control (MAC) layer recovery on multicast/broadcast frames. As a result, the reliability of the multicast/broadcast service is reduced due to the increased probability of lost frames resulting from interference or collisions. In this paper, we propose a reliable Batch Mode Multicast MAC protocol, BMMM, which substentially reduces the number of contention phases, thus considerably reduces the time required for a multicast/broadcast. We then propose a Location Aware Multicast MAC protocol, LAMM, that uses station location information to further improve upon BMMM. Extensive analysis and simulation results validate the reliability and efficiency of our multicast MAC protocols. 1

With the progression of computer networks extending boundaries and joining distant locations, wireless sensor networks (WSN) emerge as the new frontier in developing opportunities to collect and process data from remote locations. Like IEEE 802.3 wired and IEEE 802.11 wireless networks, remote wireless sensor networks are vulnerable to malicious attacks. While wired and infrastructure-based wireless networks have mature intrusion detection systems and sophisticated firewalls to block these attacks, wireless sensor networks have only primitive defenses. WSNs rely on hardware simplicity to make sensor field deployments both affordable and long-lasting without any maintenance support. Energy-constrained sensor networks periodically place nodes to sleep in order to extend the network lifetime. Denying sleep effectively attacks each sensor node’s critical energy resources and rapidly drains the network’s lifetime. This paper analyzes the energy resource vulnerabilities of wireless sensor networks, models the network lifetimes of leading WSN medium access control (MAC) protocols, and proposes a new MAC protocol which mitigates many of the effects of denial of sleep attacks.

Deploying Wireless LAN for Industrial Control (IC-WLAN) has many benefits, such as mobility, low deployment cost and ease of reconfiguration. However, the top concern is robustness of wireless communications. Wireless control loops must be maintained under persistent adverse channel conditions, such as noise, large-scale path loss and fading. Many electro-magnetic interference sources in industrial environments, e.g. electric motor and welding, make wireless communication more challenging. The conventional IEEE 802.11 WLANs, which are designed for providing high bandwidth instead of high robustness, are therefore inappropriate for IC-WLAN. On the other hand, if the low data rate feature of industrial control is fully exploited by the state-of-the-art Direct Sequence Spread Spectrum (DSSS) technology, much higher robustness can be achieved. We hereby propose using DSSS-CDMA to build IC-WLAN, and exploiting the low data rate feature of industrial control loops for enhanced robustness. We carried out fine-grained physical layer simulations and Monte Carlo comparisons. The results show that DSSS-CDMA IC-WLAN provides much higher robustness than IEEE 802.11 WLAN, so that reliable wireless industrial control loops are made feasible. The DSSS-CDMA IC-WLAN scheme also opens up a new problem space for interdisciplinary study, involving real-time scheduling and resource management, communication, networking and control. In this paper, we study the resource management problems on maximizing robustness and minimizing control utility loss. Analytical resource optimization solutions are given. 1.

Abstract — We present an innovative MAC protocol (Q-MAC) that minimizes the energy consumption in multi-hop wireless sensor networks (WSNs) and provides Quality of Service (QoS) by differentiating network services based on priority levels. The priority levels reflect application priority and the state of system resources, namely residual energy and queue occupancies. The Q-MAC utilizes both intra-node and inter-node arbitration. The intra-node packet scheduling is a multiple queuing architecture with packet classification and weighted arbitration. We also introduce the Power Conservation MACAW (PC-MACAW)- a power-aware scheduling mechanism which, together with the Loosely Prioritized Random Access (LPRA) algorithm, govern the inter-node scheduling. Performance evaluation are conducted between Q-MAC and S-MAC with respect to two performance metrics: energy consumption and average latency. Simulation results indicate that the performance of the Q-MAC is comparable to that of the S-MAC in non-prioritized traffic scenarios; when packets with different priorities are present, Q-MAC supiors in average latency differentiation between the classes of service, while maintaining the same energy level as that of S-MAC. I.

The widespread use of mobile and handheld devices is likely to popularize ad hoc networks, which do not require any wired infrastructure for intercommunication. The nodes of mobile ad hoc networks operate as end hosts as well as routers. They intercommunicate through single-hop and multihop paths in a peer-to-peer fashion. With the expanding scope of applications of MANETs, the need to support QoS in these networks is becoming essential. This article provides a survey of issues in supporting QoS in MANETs. We have considered a layered view of QoS provisioning in MANETs. In addition to the basic issues in QoS, the report describes the efforts on QoS support at each of the layers, starting from the physical and going up to the application layer. A few proposals on interlayer approaches to QoS provisioning are also addressed. The article concludes with a discussion on the future directions and challenges in the areas of QoS support in MANETs.

authors wish to acknowledge helpful discussions with Dr. K. Venkatesh

Mobile Ad hoc Networks is an autonomous system of mobile nodes connected by multi-hop wireless links without centralized infrastructure support. As mobile communication gains popularity, the need for suitable ad hoc routing protocols will continue to grow. Efficient dynamic routing is an important research challenge in such a network. Bandwidth constrained mobile devices use on-demand approach in their routing protocols because of its effectiveness and efficiency. Many researchers have conducted numerous simulations for comparing the performance of these protocols under varying conditions and constraints. Most of them are not aware of MAC Protocols, which will impact the relative performance of routing protocols considered in different network scenarios. In this paper we investigate the choice of MAC protocols affects the relative performance of ad hoc routing protocols under different scenarios. We have evaluated the performance of these protocols using NS2 simulations. Our results show that the performance of routing protocols of ad hoc networks will suffer when run over different MAC Layer protocols.