This work focuses on analyses of cooperative protocols to enhance the performance of power line communication systems. Based on a measurement campaign and considering a sum power constraint, achievable data rates for amplify-and-forward (AF) and decode-and-forward (DF) protocols are analyzed. Similar investigations are performed for the maximum data rates attained using Hermitian-symmetric orthogonal frequency division multiplexing (HS-OFDM) together with equal gain combining (EGC), selection combining (SC) and maximal ratio combining (MRC) techniques. The influences of optimally and uniformly allocated transmission power and frequency bandwidth are are also analyzed and the efficiency of combination before and after equalization is compared. Results show that the relative distances among source, relay and destination nodes significantly impact system performance. Also, they reveal a range of total transmission power and bandwidth in which benefits can be verified. Among combining techniques, MRC and SC present similar results, but MRC offers a slightly better performance. In relation to computational complexity, SC is the most favorable. Maximum data rate analyses of HS-OFDM with frequency domain equalization based on zero forcing and minimum mean square error criteria show that the former scheme offers almost the same performance as the latter. Furthermore, it is shown that equalization after combination is more advantageous.

Impulse noise sources such as dimmers, halogen lamps etc., are quite common in power line networks. Hence, high-speed power line communications systems should be designed to deal effectively with them. HomePlug AV uses aggressive channel adaptation at the physical layer and efficient retransmissions at the MAC layer to deal with impulse noise. This approach can lead to very high probability (up to 20%) of Forward Error Correction (FEC) block errors under some channel conditions. HomePlug AV also has large transmission overhead to ensure reliable communication over the powerline. Transmission overhead can negatively impact the MAC efficiency on channels with high FEC Block Error Rate (BLER) due the need for a large number of retransmissions to successfully deliver packets. This paper studies the complex interaction between FEC block errors, transmission overhead, Quality of Service (QoS) requirements of a multimedia stream and its TDMA allocation requirements. Our results show that, to support low latency applications at high BLERs, the average allocation size has to be increased by one or more transmission overheads. Further, the increase in average allocation is not a strong function of application data rate. Hence, low data rate applications can suffer significant loss in efficiency at high BLERs. Our results also show that using a fixed size TDMA allocation can lead to poor utilization when the latency requirements of the application are less than four beacon periods. These results indicate that channel adaptation in HPAV should take into consideration the application QoS requirements to optimize the overall system capacity.

Mobile IPv6 (MIPv6) has been proposed to support host mobility in the Internet, yet during a handover mobile IPv6 suffers from packet disruption and packet loss. It is therefore critical to reduce or mask the handover interval from the correspondent nodes by optimizing movement detection and duplicate address detection (DAD) to reduce delays and packet loss due to handovers. In this paper, we specify a more efficient fast neighbor discovery and DAD scheme which requires each access point to execute movement detection by unicast transmission of the stored router advertisement message and implement a modified neighbor cache to handle configuration of the care-of-address (CoA) under fast DAD. We also present a performance analysis of the current IETF proposals for MIPv6 and fast mobile IPv6 relative to our proposal for enhanced mobile IPv6. Finally we demonstrate by simulation that managing the handover process in our proposed scheme greatly reduces the overall handover latency

There is industrial intent to use powerline communication (PLC) networks in the home for delivery of multimedia data, with associated challenging quality of service (QoS) requirements. Existing protocols for PLC, for wireless networks, or even for wired networks cannot meet these challenges efficiently. This paper proposes and analyzes a new protocol designed to provide the high QoS needed for delivery of multiple multimedia streams in a PLC environment. The proposed protocol, periodic contention-free multiple access (PCF/MA), directly addresses the issues of channel noise, hidden nodes and near-far effects. The proposed PCF/MA performance is analyzed theoretically and its performance is simulated. The results show that 85Mbps MAC throughput is possible with 100Mbps channel data rate, even when there are hidden nodes in the network.

Development of efficient medium access control (MAC) protocols providing both high throughput performance for data traffic and good quality of service (QoS) support for real-time traffic is the current major focus in distributed contention-based MAC protocol research. In this paper, we propose an efficient contention resolution algorithm for wireless local area networks, namely, the fast collision resolution (FCR) algorithm. The MAC protocol with this new algorithm attempts to provide significantly higher throughput performance for data services than the IEEE 802.11 MAC algorithm and more advanced dynamic tuning backoff (DTB) algorithm. We demonstrate that this algorithm indeed resolves collisions faster and reduces the idle slots more effectively. To provide good fairness performance and to support good QoS for real-time traffic, we incorporate the self-clocked fair queueing algorithm and a priority scheme into the FCR algorithm and come up with the real-time FCR (RT-FCR) algorithm, and show that RT-FCR can simultaneously achieve high throughput and good fairness performance for nonreal-time traffic while maintaining satisfactory QoS support for real-time traffic.

Design of efficient medium access control (MAC) protocols with both high throughput performance and high-degree of fairness performance is a major focus in distributed contention-based MAC protocol research. In this paper, we propose a novel and efficient contention-based MAC protocol for wireless local area networks, namely, the fast collision resolution (FCR) algorithm. This algorithm is developed based on the following innovative ideas: to speed up the collision resolution, we actively redistribute the backoff timers for all active nodes; to reduce the average number of idle slots, we use smaller contention window sizes for nodes with successful packet transmissions and reduce the backoff timers exponentially fast when a fixed number of consecutive idle slots are detected. We show that the proposed FCR algorithm provides high throughput performance and low latency in wireless LANs. The extensive simulation studies show that the FCR algorithm could significantly improve the performance of the IEEE 802.11 MAC protocol if our efficient collision resolution algorithm is used and that the fairly scheduled FCR (FS-FCR) algorithm could simultaneously achieve high throughput performance and a high degree of fairness.

Development of efficient medium access control (MAC) protocols is a fundamental research issue in high-speed wireless local area networks (LANs). We focus on the throughput efficiency of medium access algorithms for high-speed wireless LANs which use carrier sense multiple access/collision avoidance (CSMA/CA). We propose an efficient distributed contention-based MAC protocol for wireless local area networks, namely, the fast collision resolution (FCR) algorithm, and show that the proposed FCR algorithm provides high throughput and low latency in wireless LANs. The performance of FCR algorithm is compared with that of the IEEE 802.11 MAC algorithm via extensive simulation studies. The results show that FCR algorithm achieves a significantly higher efficiency than the IEEE 802.11 MAC algorithm and is easy to implement in wireless LANs.

Development of efficient medium access control (MAC) protocols which provide both high throughput performance for data traffic and good quality of service (QoS) support for real-time traffic is the current major focus in distributed contention-based MAC research. We propose an efficient contention algorithm for wireless local area networks, namely the fast collision resolution (FCR) algorithm. The MAC protocol with this new algorithm attempts to provide significantly high throughput performance for data services. To support QoS for real-time services, we incorporate the priority algorithm based on service differentiations with the FCR algorithm, and show that this prioritized FCR algorithm can simultaneously achieve high throughput and good QoS support for real-time and data services.

The HomePlug 1.0 standard allows high-speed communication on low-voltage power lines without a requirement for new wires. Effective use of the power line bandwidth requires a robust medium access control (MAC) protocol to mitigate the harsh conditions of the power line channel as well as the capability to support prioritized multimedia traffic. This paper briefly describes the HomePlug 1.0 MAC and PHY protocols, which allow prioritized channel access. It then presents field test results comparing this with the more familiar IEEE 802.11b protocol.

Development of efficient medium access control (MAC) protocols is a fundamental research issue in high-speed wireless local area networks (LANs). In this paper, we focus on the performance improvement both of MAC layer and transport layer by using a novel medium access control protocol in high-speed wireless LANs which use carrier sense multiple access/collision avoidance(CSMA/CA). We propose an efficient distributed contention-based MAC protocol, namely, the Fast Collision Resolution (FCR) algorithm, and show that the proposed FCR algorithm provides high throughput and low latency while improving the fairness performance for serving users in wireless LANs. The performance of the FCR algorithm is compared with that of the IEEE 802.11 MAC algorithm via extensive simulation studies both in MAC layer and transport layer. The results show that the FCR algorithm achieves a significantly higher efficiency than the IEEE 802.11 MAC algorithm and is well suited for transport layer protocols such as transmission control protocol (TCP) and user datagram protocol (UDP).

The Department of Electrical and Computer Engineering, University of Florida, has developed an online M.S. degree program that utilizes synchronized streaming video and audio as well as asynchronous learning networks to facilitate interactivity. In this paper, we describe some of the technical and administrative issues involved in this venture, as well as the experiences accumulated thus far in offering these courses online.

A major drawback of recursive adaptive filters based on gradient methods is that convergence to a global minimum is not always achieved. This is due to a nonconvex mean square error (MSE) performance surface. This article develops a continuous-time least mean square algorithm that converges to the global minimum with probability one.