144 research outputs found

    On the benefits of Cross Layer Feedback in Multi-hop Wireless Networks

    Full text link
    Wireless networks operate under harsh and time-varying channel conditions. In wireless networks the time varying channel conditions lead to variable SINR and high BER. The wireless channel is distinct from and more unpredictable than the far more reliable wireline channel. {\em Cross layer feedback} is a mechanism where layers provide {\em selective} information to other layers to boost the performance of wireless networks. {\em Cross layer feedback} can lead to a tremendous increase in the performance of the TCP/IP stack in wireless networks, and an increase in the user's satisfaction level. However, it is possible that naive feedbacks (or optimizations) can work non-coherently; therefore, these can negatively effect the performance of the TCP/IP stack. In this paper, we holistically analyze each layer of the TCP/IP stack, and propose possible Cross layer feedbacks which work coherently. The proposed Cross layer feedbacks can greatly enhance the performance of the TCP/IP stack in wireless networks

    Policies for Carbon Energy Footprint Reduction of Overhead Multiple-Input Multiple-Output High Voltage Broadband over Power Lines Networks

    Get PDF
    The impact of different environmental policies on the broadband performance of overhead multiple-input multiple-output high-voltage/broadband over power lines (MIMO/HV/BPL) networks is investigated in this paper. The examined environmental policies focus on the carbon energy footprint reduction of overhead MIMO/HV/BPL networks while respecting their broadband character.The contribution of this paper is three-fold. First, the spectral and environmental performance of various configurations and topologies of overhead MIMO/HV/BPL networks is assessed with regard to respective spectral efficient (SE) and newly presented environmental efficient (EE) metrics. Second, further insights regarding the performance of overhead MIMO/HV/BPL networks highlight the better spectral and environmental performance of these networks against other today’s overhead HV/BPL networks, such as single-input single-output (SISO), single-input multiple-output (SIMO), or multiple-input single-output (MISO) ones. Third, the definition of appropriate environmental policies that optimize the coexistence of the three main sectors of concern, which are the Quality of Service (QoS) requirements, protection of existing radioservices and promotion of environmentally aware limits, is promoted. Towards that direction, the proposed SE/EE trade-off relation of this paper is expected to prove an extremely helpful SE/EE optimization technique.Citation: Lazaropoulos, A. G. (2015). Policies for Carbon Energy Footprint Reduction of Overhead Multiple-Input Multiple-Output High Voltage Broadband over Power Lines Networks. Trends in Renewable Energy, 1(2), 87-118. DOI: 10.17737/tre.2015.1.2.001

    Dynamic Topology Estimation and Resource Allocation for Power Line Communication

    Get PDF
    Power line communication (PLC), which uses existing infrastructure of power delivery for data transfer, is regarded as an economical, pervasive and extensive communication solution for smart grid and home broadband applications. One of the challenges of applying communication technologies to power line network lies in acquirement of channel state information (CSI), which is dependent on network topology. Moreover, the knowledge of topology provides a basis for the design of routing protocols and power flow optimization. Therefore, efficient approaches for dynamic topology estimation are highly demanded. While dynamic routing and resource allocation enable high-speed and multi-tasking communication services over power lines. In this thesis, a dynamic topology estimation scheme for PLC is investigated, and a cross-layer routing and resource allocation scheme assisted by dynamic topology estimation is developed to improve the system performance. In the first contribution, a high-resolution and low-complexity dynamic topology estimation scheme for time-varying indoor PLC networks is proposed. The scheme consists of three parts: a) a time-frequency domain reflectometry (TFDR) based path length estimation method, which requires measurement at a single PLC modem and achieves a much higher resolution than the frequency domain reflectometry (FDR) based method; b) a node-by-node greedy algorithm for topology reconstruction, which is much more computationally efficient than the existing peak-by-peak searching algorithm; c) an impulsive noise assisted dynamic topology re-estimation method, which results in a significant complexity reduction over fixed-frequency re-estimation. In the second contribution, a cross-layer routing and resource allocation (RA) scheme assisted by dynamic topology estimation is proposed to optimize the system throughput of indoor PLC network with heterogeneous delay requirements. The proposed scheme provides a multi-layer solution, which conducts the network layer routing based on the result of PHY layer resource allocation which is constrained by the MAC layer queuing delay. With the dynamic topology estimation proposed in the first contribution, the routing can be solved centrally at the source, which is more robust against topology changes compared to distributed solutions. The proposed cross-layer RA scheme consists of subcarrier allocation (SA) to multiple users and power allocation (PA) to subcarriers satisfying heterogeneous delay requirements. It is demonstrated that the proposed centralized routing strategy achieves a much lower packet loss rate (PLR) than a distributed routing scheme; while with optimal RA, the system throughput is significantly improved compared to the routing schemes without considering RA

    Performance Optimization Over Wireless Links With Operating Constraints

    Get PDF
    Wireless communication is one of the most active areas of technological innovations and groundbreaking research ranging from simple cellular phones to highly complex military monitoring devices. The emergence of radios with cognitive capabilities like software defined radios has revolutionized modern communication systems by providing transceivers which can vary their output waveforms as well as their demodulation methods. This adaptability plays a pivotal role in efficient utilization of radio spectrum in an intelligent way while simultaneously not interfering with other radio devices operating on the same frequency band. Thus, it is safe to say that current and future wireless systems and networks depend on their adaptation capability which in turn presents many new technical challenges in hardware and protocol design, power management, interference metrics, distributed algorithms, Quality of Service (QoS) requirements arid security issues. Transmitter adaptation methods have gained importance, and numerous transmitter optimization algorithms have been proposed in recent years. The main idea behind these algorithms is to optimize the transmitted signals according to the patterns of interference in the operating environment such that some specific criterion is optimized. In this context, the objective of this dissertation is to propose transmitter adaptation algorithms in conjunction with power control for wireless systems focusing on performance optimization based on operating constraints. Specifically, this dissertation achieves joint transmitter adaptation and power control in the uplink and downlink of wireless systems with applications to Multiple-Input-Multiple-Output (MIMO) wireless systems and cognitive radio networks. In addition, performance of the proposed algorithms are evaluated in the context of fading channels, taking into consideration the time-varying nature of wireless channels

    Lightweight mobile and wireless systems: technologies, architectures, and services

    Get PDF
    1Department of Information and Communication Systems Engineering (ICSE), University of the Aegean, 81100 Mytilene, Greece 2Department of Information Engineering and Computer Science (DISI), University of Trento, 38123 Trento, Italy 3Department of Informatics, Alexander Technological Educational Institute of Thessaloniki, Thessaloniki, 574 00 Macedonia, Greece 4Centre Tecnologic de Telecomunicacions de Catalunya (CTTC), 08860 Barcelona, Spain 5North Carolina State University (NCSU), Raleigh, NC 27695, US

    Ubiquitous Computing for Remote Cardiac Patient Monitoring: A Survey

    Get PDF
    New wireless technologies, such as wireless LAN and sensor networks, for telecardiology purposes give new possibilities for monitoring vital parameters with wearable biomedical sensors, and give patients the freedom to be mobile and still be under continuous monitoring and thereby better quality of patient care. This paper will detail the architecture and quality-of-service (QoS) characteristics in integrated wireless telecardiology platforms. It will also discuss the current promising hardware/software platforms for wireless cardiac monitoring. The design methodology and challenges are provided for realistic implementation
    corecore