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Multicast communication over wireless networks has many potential applications, such as real-time audiovisual content distribution or digital signage systems with multiple remote terminals. However, today’s common 802.11 networks cannot fully support such applications at the link layer due to the technical challenges in achieving both high transmission rate and high reliability for multicast data transfers. Those challenges primarily emerge from the inapplicability of immediate acknowledgment mechanisms of unicast transmissions to the multicast case and the need for finding a common transmission rate for all receivers with diverse channel conditions. The research literature in this domain mainly addresses the problem at the higher layers of the protocol stack. In this article, we present a novel approach that combines wireless link rate selection with an adaptive packet-level Forward Error Correction (FEC) mechanism in order to achieve high-rate and highly reliable multicast in 802.11 wireless networks. The integration of FEC into the 802.11 MAC layer allows direct interaction between the transmission rate and the coding scheme. As a result, potential packet losses caused by higher link rates can be compensated by the adjustable redundancy provided by FEC. In combination with an aggregated receiver feedback mechanism, this yields improved transmission efficiency and reliability for wireless multicast. We investigate this approach in a simulation environment under a realistic wireless channel model in various application scenarios with up to 50 receivers. The results represent significant performance improvements, in terms of throughput, channel utilization, and packet loss, over the state-of-the-art methods for reliable wireless multicast.

Periodic beacon messages are one of the building blocks that enable the operation of vehicular ad hoc networks (VANETs) applications. In vehicular networks environments, congestion and awareness control mechanisms are key for a reliable and efficient functioning of vehicular applications. In order to control the channel load, a reliable mechanism allowing real-time measurements of parameters like the local density of vehicles is a must. These measurements can then serve as an input to perform a fast adaptation of the transmit parameters. In this paper, considerable efforts have been directed in the recent years toward designing flexible yet robust protocols solving this problem; yet, very few have considered a proactive adaptation of the transmit parameters as a preventive measure from channel load peaks. To this end, we take the opportunity to introduce prediction and adaptation algorithm (P&A-A), a new congestion control protocol that performs a joint adaptation of the transmit rate and power, relying on an altruistic short-term prediction algorithm that estimates the vehicular density around a given vehicle within the next short while. Additionally, P&A-A adapts the transmit parameters in a way that guarantees the strict beaconing requirements and satisfies the level of awareness required for the operation of most critical VANET applications. The results of the simulations performed in a realistic scenario justify our theoretical considerations and confirm the efficiency and the effectiveness of our protocol by showing significant improvements in terms of network performance (up to 8% and 14% improvement in collision rate; and up to 10% and 20% increase in busy ratio compared to our previous scheme and the ETSI schemes, respectively) as well as the achieved level of awareness (higher coverage with higher transmission rate and power in dense scenarios, and up to 8% and 55% improvement in density perception accuracy compared to our previous scheme and the ETSI schemes, respectively). [ABSTRACT FROM AUTHOR]

Existing opportunistic network coding architectures (e.g., COPE) rely on pseudobroadcast to deliver a coded packet to multiple receivers in a single transmission. Only the primary receiver acknowledges the reception by MAC-layer acknowledgements (synchronous ACKs) and the other receivers receive the coded packet by overhearing and acknowledge the reception by asynchronous ACKs, which are usually piggybacked in outgoing data packets. In realistic wireless networks, this mechanism may cause unnecessary retransmissions if asynchronous ACKs are dropped due to packet losses or arrive late and thus compromise the throughput gain brought by network coding. In this paper, we propose a framework of joint rate control and code selection (ORC) to address this issue, aiming at improving the performance gain of opportunistic network coding in wireless networks. The framework of ORC consists of two mechanisms: (1) Rate control: the optimal transmission rate for coded packets is selected by formulating the rate control process as a Finite Horizon Markov Decision Process. (2) Code selection: based on the results of rate selection, the packet combination for forming the coded packet is determined. Numerical results show that ORC can substantially improve the performance gain of opportunistic network coding compared with COPE. [ABSTRACT FROM AUTHOR]

In this paper, we discuss issues concerned with transmission rate control in molecular communication, an emerging communication paradigm for bio-nanomachines in an aqueous environment. In molecular communication, a group of bio-nanomachines acting as senders transmit molecules, the molecules propagate in the environment, and another group of bio-nanomachines acting as receivers chemically react to the molecules propagating in the environment. In the model of molecular communication considered in this paper, senders may transmit molecules at a high rate to accelerate the receiver reactions or to increase the throughput. However, if the senders transmit molecules faster than the receivers react, the excess molecules remain in the environment and eventually degrade or diffuse away, which results in loss of molecules or degradation in efficiency. Such a potential issue associated with throughput and efficiency is in this paper discussed as an optimization problem. A mathematical expression for an upper-bound on the throughput and efficiency is first derived to provide an insight into the impact of model parameters. The optimal transmission rates that maximize the throughput and efficiency are then numerically calculated and presented, and throughput and efficiency are shown to be in trade-off relationships in a wide range of transmission rates. Further, two classes of feedback-based transmission rate control schemes are designed for autonomous bio-nanomachines to dynamically control their transmission rates, respectively based on negative and positive feedback from the receivers. The numerical evaluation of the two transmission rate control schemes is then shown to provide useful guidelines for application developers to satisfy their design goals. [ABSTRACT FROM PUBLISHER]

We propose an intervehicle communication framework for the cooperative active safety system (CASS) whose operation is based on the dissemination of each vehicle's state information through a wireless network. Such a CASS requires each subject vehicle to be aware of its surroundings, particularly of the motion and position of other vehicles in its proximity. In this paper, we assume that all vehicles are equipped with onboard communication devices. In such situations, the wireless channel is simultaneously shared by a large number of vehicles, and one of the most difficult challenges in designing CASS is to maintain real-time tracking accuracy of neighboring vehicles while avoiding network congestion and failure. To address this issue, we analyze the problem that multiple scalar linear time-invariant dynamical systems track each other over a multiaccess channel, and then, we propose a rate adaptation algorithm to distributively control the self-information broadcast behavior of each vehicle. The proposed algorithm uses a closed-loop control concept and accounts for the lossy channel. Simulation results show that, if the message generation rate is dynamically adjusted in an on-demand fashion, more accurate and robust tracking performance can be achieved under various traffic conditions. [ABSTRACT FROM PUBLISHER]

This paper addresses the resource reservation problem in a packet switching network. REBOOK, the presented algorithm, provides deterministic, fast (real-time) dynamic resource allocation and release. Based on a stateful approach, it handles faults and network errors, and recovers from route changes and unexpected flows shutdown. The distributed scheme used to store flows information avoids the need of searching for entries within the routers' control memory when packets are received and guarantees constant complexity. REBOOK can be implemented in hardware and is compatible with any packet switching network. In the Internet, it can be integrated in TCP or used with UDP to make it network friendly. Moreover, a slightly extended implementation of RSVP can be used as signalling and hosting protocol. A software implementation as standalone protocol has been developed to prove its effectiveness, robustness, and performance. [ABSTRACT FROM AUTHOR]

A data filtering scheme is proposed for transmission and error control of haptic events in haptic-based network virtual environments; this scheme is called as priority-based haptic event filtering. Because a high update rate of approximately 1 kHz is required for haptic rendering, sophisticated transmission rate control and reduction schemes are necessary for the haptic events. Although existing schemes can reduce the transmission rate without any perception impairment, they are very sensitive to packet losses. In this paper, we prioritize the haptic events according to the delay and loss effects. Utilizing the proposed haptic event prioritization, the proposed filtering scheme adapts the transmission rate and updates the predicted loss rate according to the current network state. Our simulation and experiment results confirm that the proposed scheme can effectively select important haptic events and guarantee an improved haptic interaction quality over a bandwidth-limited lossy network than existing transmission schemes tailored for networked haptics. [ABSTRACT FROM AUTHOR]