Narrow Results

This paper introduces Neighbor Aware Adaptive Power flooding, an optimized flooding mechanism used in mobile ad hoc networks (MANETS) that employs several mechanisms (neighbor coverage, power control, neighbor awareness and local optimization) to limit the broadcast storm problem, reduce duplicate packet reception and lower power consumption in both transmission and reception. Upon receiving an optimized broadcast, a relay determines a new set of possible relays (to continue the flood) based upon local neighbor information and the previous optimized broadcast. Additionally, neighboring relays only consider the shared neighbors they are closest to. A relay may perform local optimization (to reduce power consumption and isolate broadcasts) by substituting one high power broadcast with two or more low power broadcasts, thereby introducing additional hops, We show that compared to blind flooding and multipoint relaying, NAAP in a static environment greatly reduces the problems associated with the broadcast storm problem, duplicate packet reception and power consumption.

Effective call admission control (CAC) is one of the most important techniques to provide the desired quality of service (QoS) in wireless networks. This paper investigates the call admission control problem for the power-controlled CDMA systems. With a macroscopic description for the power control problem, the call admission control for the power-constrained system is analyzed and an admissibility condition is derived. Based on the derived condition, we propose two CAC algorithms. One is an interactive method that provides the optimum performance, but requires some information exchange between base stations. The other can be implemented in a distributed manner and provide a reasonable performance. Through simulations, we show that the proposed algorithms provide an improved performance.

Ad hoc wireless networks are self-generating and self-organizing networks consisting of mobile and static nodes, which are small and have limited power resources. In a typical setup, these nodes communicate with each other through wireless medium and may act as source, destination and/or relaying nodes. As the power of the remote nodes is depleted very quickly, it is important to have a renewable energy source to support the network operations and increase lifetime. The availability of energy from the environment is unpredictable, random and uncertain, therefore energy harvesting with appropriate management plays an important role in continuous operations of ad hoc networks. In this paper, an energy harvesting and management model is presented for ad hoc networks. Along with harvesting energy, the proposed model ensures the connectivity requirements of the network for its perpetual operation.

Induction heating (IH) applications aided by power electronic control system have become very attractive in the recent past. The power electronics circuits succumb to severe switching loss, lower power density if proper switching methodology is not adhered. A state of uncertainty is indispensable in IH application as the power required by the load varies depending upon the nature of work piece. This uncertain issue makes the selection of the control algorithm and controller very vital. The mundane controllers may not be compatible to combat the uncertainties and leads to exhibit dynamic problems say transients, peak overshoot and poor response. Henceforth, the IH system requires a superlative converter topology and control scheme in order to have reduced switching loss and to improve the system performance there by negating the uncertainties. Here, in this work, a direct AC–AC boost resonant converter fed by pulse density modulation (PDM) is realized in a single stage mode. A fuzzy logic-based PDM control technique improves the efficiency and provides the versatile power control with reduced time domain specifications for dynamic changes in load. The proposed system has been studied using MATLAB/SIMULINK and validated using a hardware prototype employing dsPIC30F4011 microcontroller. The results reveal that efficient control over power can be accomplished by varying the density of the switching pulses, and thereby the efficiency is enhanced even with reduced component count. Also, the single-stage conversion is effective than its two-stage counterpart.

IEEE802.11 WLANs show increasing growth in popularity. Since these networks operate in the unlicensed ISM bands where the number of non-overlapping channels is limited, the growing number of wireless nodes leads to interference. It is well known that the interference leads to degraded performance of WLANs, especially in densely populated areas where the number of overlapping nodes is very large. Channel assignment algorithms have been proposed in recent years, in order to minimize or avoid interference between neighboring access points and hence alleviating the problem. In particular, weighted assignment algorithms have been frequently occurring in the literature. However, the effects of these algorithms are currently not well understood. In this paper, we present results, which show that weighted channel assignment algorithms that do not consider traffic categories can lead to heavy interference among WLANs with delay sensitive traffic, e.g. voice traffic. In order to overcome this, we instead propose a weighted access category channel assignment algorithm (WACCA). We present results from experiments, which show that WACCA achieves a small degree of Interference (DOI) as compared with a greedy algorithm. We also show that there is a tradeoff with convergence time. Furthermore, we propose an integration of WACCA with dynamic transmission power control and show how this combined method produces even more gain.

In this paper, we propose a fuzzy logic-based power command enhancement scheme for the mobile station in the cellular communications systems. By defining necessary linguistic terms of the power commands and corresponding fuzzy inference rules, an Embedded Fuzzy Unit (EFU) is constructed. The role of our EFU is to produce appropriate digital power commands instead of the one-bit discrete commands directly obtained from the base station. Simulations show that the EFU-based mobile station can generate considerably smoother received power at the base station. The transient overshoot and steady channel tracking error are small. Moreover, our method has the advantage of simplicity in both structure and algorithm, and is thus easy for hardware implementation.

Currently, the IEEE 802.11 standard and its distributed coordination function (DCF) access method have gained global acceptance and popularity both in wireless LANs and wireless multi-hop ad hoc environment. It has been shown that the DCF access method does not make efficient use of the shared channel due to its inherent conservative approach in assessing the level of interference. To date, various mechanisms have been proposed to improve the capacity of IEEE 802.11- based multi-hop wireless networks. These mechanisms can be broadly classified as temporal and spatial approaches depending on their focus of optimization on the channel bandwidth. The temporal approaches attempt to better utilize the channel along the time dimension by optimizing or improving the exponential bakeoff algorithm. On the other hand, the spatial approaches try to find more chances of spatial reuse without significantly increasing the chance of collisions. These mechanisms include the tuning of the carrier sensing threshold, the data rate adaptation, the transmission power control, and the use of directional antennas. This chapter is aimed specifically at providing a comprehensive survey on schemes that deploy the use of directional antenna and the schemes that consider coupling of directional antenna with power control.

In response to the asymmetry transmit power problem in Wireless Sensor Networks, the concepts of quasi-hidden node and quasi-exposed node are introduced and an interference degree criterion (IDC) is designed to ensure the feasibility of concurrent transmission in wireless sensor networks. Simulation results show that, in comparison with 802.11DCF and SB-FSMA/CA, the power control strategy based on the proposed interference degree criterion not only improves the average network throughput but also reduces the average delivery delay.