Shalinee Kishore

Wireless diversity through network coding

This paper investigates the diversity gain offered by implementing network coding (R. Ahlswede et al., 2000) over wireless communication links. The network coding algorithm is applied to both a wireless network containing a distributed antenna system (DAS) as well as one that supports user cooperation between users. The results show that network-coded DAS leads to better diversity performance as compared to conventional DAS, at a lower hardware cost and higher spectral efficiency. In the case of user cooperation, network coding yields additional diversity, especially when there are multiple users

Dynamic resource allocation schemes during handoff for mobile multimedia wireless networks

User mobility management is one of the important components of mobile multimedia systems. In a cell-based network, a mobile should be able to seamlessly obtain transmission resources after handoff to a new base station. This is essential for both service continuity and quality of service assurance. In this paper, we present strategies for accommodating continuous service to mobile users through estimating resource requirements of potential handoff connections. A diverse mix of heterogeneous traffic with diverse resource requirements is considered. The investigate static and dynamic resource allocation schemes. The dynamic scheme probabilistically estimates the potential number of connections that will be handed off from neighboring cells, for each class of traffic. The performance of these strategies in terms of connection blocking probabilities for handoff and local new connection requests are evaluated. The performance is also compared to a scheme previously proposed by Yu and Leung (see IEEE J. Select. Areas Commun., vol.15, p.1208-25, 1997). The results indicate that using dynamic estimation and allocation, we can significantly reduce the dropping probability for handoff connections.

A comparison of MAC protocols for wireless local networks based on battery power consumption

Energy efficiency is an important issue in mobile wireless networks since the battery life of mobile terminals is limited. Conservation of battery power has been addressed using many techniques. This paper addresses energy efficiency in medium access control (MAC) protocols for wireless networks. The paper develops a framework to study the energy consumption of a MAC protocol from the transceiver usage perspective. This framework is then applied to compare the performance of a set of protocols that includes IEEE 802.11, energy-conserving MAC (EC-MAC), PRMA, multiservices dynamic reservation-TDMA (MDR-TDMA), and distributed-queueing request update multiple access (DQRUMA). The performance metrics considered are transmitter and receiver usage times for packet transmission and reception. The analysis here shows that protocols that aim to reduce the number of contentions perform better from a energy consumption perspective. The receiver usage time, however; tends to be higher for protocols that require the mobile to sense the medium before attempting transmission.

Smart (in-home) power scheduling for demand response on the smart grid

This paper proposes a power scheduling-based communication protocol for in-home appliances connected over home area network and receiving real-time electricity prices via a smart meter. Specifically, a joint media access and appliance scheduling approach is developed to allow appliances to coordinate power usage so that total demand for the home is kept below a target value. Two types of appliances are considered: 1) “real-time” which consume power as they desire; and 2) “schedulable” which can be turned on at a later time. Simulation results indicate that for an appropriate target total power consumption, our scheme leads to a reduced peak demand for the home and produces a demand that is more level over time.

A Distributed Direct Load Control Approach for Large-Scale Residential Demand Response

This paper proposes a distributed direct load control scheme for large-scale residential demand response (DR) built on a two-layer communication-based control architecture. The lower-layer network is within each building, where the energy management controller (EMC) uses wireless links to schedule operation of appliances upon request according to a local power consumption target. The upper-layer network links a number of EMCs in a region whose aggregated demand is served by a load aggregator. The load aggregator wants the actual aggregated demand over this region to match a desired aggregated demand profile. Our approach utilizes the average consensus algorithm to distribute portions of the desired aggregated demand to each EMC in a decentralized fashion. The allocated portion corresponds to each buildings aforementioned local power consumption target which its EMC then uses to schedule the in-building appliances. The result will be an aggregated demand over this region that more closely reaches the desired demand. Numerical results show that our scheme can alleviate the mismatch between the actual aggregated demand and the desired aggregated demand profile.

Asymptotic analysis of amplify-and-forward relaying in Nakagami-fading environments

Amplify-and-forward (AF) relaying strategies are studied for Nakagami-fading channels in an (N + 2)-terminal wireless cooperative system where a source terminal transmits information to a destination terminal with the assistance of N relay terminals. The asymptotic outage behavior is investigated in terms of coding and diversity gains for channel-state information (CSI)-assisted AF relaying and semi-blind AF relaying in various channel profiles. It is shown that semi-blind AF relaying system achieves strictly higher average SNRs. Further, when there exists fading severity difference between the source-to-relay and relay-to-destination links, both AF strategies achieve the same diversity gain whereas semi-blind AF achieves strictly lower coding.

Battery power sensitive video processing in wireless networks

Mobile computers typically have limited energy for computing and communications due to short battery lifetimes. Encoding, decoding, and transmission of video information require significant computing and communication resources. Low power encoding and decoding schemes have been researched extensively. In this paper, we focus on processing encoded video for transmission under low battery power conditions. Such processing, while conserving battery power, attempts to reduce deterioration of video quality.

A Communication-Based Appliance Scheduling Scheme for Consumer-Premise Energy Management Systems

In this paper, a communication-based load scheduling protocol is proposed for in-home appliances connected over a home area network. Specifically, a joint access and scheduling approach for appliances is developed to enable in-home appliances to coordinate power usage so that the total energy demand for the home is kept below a target value. The proposed protocol considers both “schedulable” appliances which have delay flexibility, and “critical” appliances which consume power as they desire. An optimization problem is formulated for the energy management controller to decide the target values for each time slot, by incorporating the variation of electricity prices and distributed wind power uncertainty. We model the evolution of the protocol as a two-dimensional Markov chain, and derive the steady-state distribution, by which the average delay of an appliance is then obtained. Simulation results verify the analysis and show cost saving to customers using the proposed scheme.

A game-theoretic analysis of decode-and-forward user cooperation

A game-theoretic analysis of decode and forward cooperative communications is presented for additive white Gaussian noise (AWGN) and Rayleigh fading channels. Cooperative communications is modeled as a repeated game in which the two participating terminals are selfish and seek to maximize their own payoff, a general utility function that monotonically increases with signal-to-noise ratio. Results show a Nash Equilibrium in which users mutually cooperate can be obtained for AWGN channels when strict power control is enforced and users care about future payoff. However, such power control may not be necessary to achieve cooperative Nash Equilibrium when the game is played in Rayleigh fading channels. We study the Rayleigh fading channel as a two state Markov model in this paper. In this case, a mutually cooperative Nash Equilibrium 1) always exists when the utility function is convex and users care somewhat about future payoff; and 2) may not always exist when the utility function is concave, especially in adverse channel conditions. Examinations of several widely-used concave functions, however, demonstrate that mutual cooperation is more likely when users increase their value on future payoff. Additionally, it is shown that improving the effective uplink channel conditions of users, e.g., by using multiple transmit antennas, further encourages cooperation.

Analysis of distributed consensus time synchronization with Gaussian delay over wireless sensor networks

This paper presents theoretical results on the convergence of the distributed consensus timing synchronization (DCTS) algorithm for wireless sensor networks assuming general Gaussian delay between nodes. The asymptotic expectation and mean square of the global synchronization error are computed. The results lead to the definition of a time delay balanced network in which average timing consensus between nodes can be achieved despite random delays. Several structured network architectures are studied as examples, and their associated simulation results are used to validate analytical findings.