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The development of broadband transmission and ATM switching technologies opens up an opportunity for providing high bit-rate multipoint and multimedia services such as video conferencing. Also, wireless communication has the inherent advantage of multicast transmission and may be used for multipoint information services. The authors consider multicast packet switching for which an input may send the same packet to many outputs within an ATM time slot. A host of multicast queueing disciplines can be exercised. Assuming only independent head of line (HOL) service to an output from slot to slot, they derive the delay performance and saturation throughput. They then examine the accuracy of the assumption for different disciplines via extensive simulation. The FCFS HOL service discipline not only has almost completely identical results for simulation versus analysis, but also provides the best saturation throughput, fairness, and delay performance among all disciplines considered. The analysis shows that implementing packet priorities can significantly improve delay performance. >

Wireless mesh networks (WMNs) facilitate both data transfer and real-time applications over wireless medium. Owing to the shared nature of wireless frequencies, bandwidth limitation is a major challenge facing WMNs. If real-time multimedia applications, such as live video streaming, are shared among multiple clients using unicast communications, it could result in network resources starvation. Multicast transmission saves network resources by replicating live multimedia transmitted data from one source to multiple destinations using the same stream. The authors have developed a novel implementation of a multicast extension to ad hoc on-demand distance vector (MAODV) routing protocol in Linux kernel 2.6 user space, which is referred to as unidirectional link-aware MAODV (UDL-MAODV). Multicast video transmissions use user datagram protocol, which does not use implicit handshaking dialogues for guaranteeing reliability of data. Therefore the authors propose and have implemented modifications to the MAODV route discovery process to improve the reliability of multicast video transmissions. These modifications enable UDL-MAODV to ensure reliable route establishment for multimedia multicast communications over WMNs in the presence of UDLs. The authors describe in this study the software architecture of the UDL-MAODV implementation in the Linux kernel 2.6 user space, and also present multicast validation and results of performance tests using the SwanMesh WMN testbed. Furthermore, UDL-MAODV has been cross-compiled and tests are presented to compare the performance of the implementation using X86 and ARM architecture-based SwanMesh nodes. The test results show that the proposed algorithm is reliable and efficient.

As internet protocol (IP) networks in the enterprise space continue to mature, with regards to stability and availability, the desire for these networks to deliver multimedia content will grow. Although IP networks have long had enough bandwidth to support multimedia streams, the deployment of this content seems to have been somewhat limited in the enterprise. The control mechanisms for multicast traffic, both at the IP layer and the data link layer, are still the areas that have not been adopted as widely as their more common unicast counterparts. The authors examine the internet group messaging protocol (IGMP) snooping process that currently runs on enterprise switches and propose an offload hardware engine to accelerate it. Currently, many enterprise switches handle this task with a general-purpose processor within the switch. Although this process adds very little to the overall load of systems currently, as multicast transmissions become more commonplace, the need for this process to be offloaded onto specialised hardware will be a necessity, in order to maintain the stability of the switch and the surrounding network. The proposed hardware model simulations reveal significant increase in the number of packets per second that can be handled compared to software implementations.

A hybrid WDM/TDM PON architecture implemented by means of two cascaded Arrayed Waveguide Gratings (AWG) is presented. Using the Free Spectral Range (FSR) periodicity of AWGs we transmit unicast and multicast traffic on different wavelengths to each Optical Network Unit (ONU). The OLT is equipped with two laser stacks, a tunable one for unicast transmission and a fixed one for multicast transmission. We propose the ONU to be reflective in order to avoid any light source at the Costumer Premises Equipment (CPE). Optical transmission tests demonstrate correct transmission at 2.5 Gbps up to 30 km.

Forward error correction improves the performance of multicast transmissions to recover from lost packets. Common reliable multicast protocols divide the download into blocks for coding purposes; however, with present coding techniques and faster processors, it is possible to operate over complete download files. The considerable transmission performance gains of this technique are shown.

Key management is one of the challenging issues in group communications. It is generally used to secure multicast data transmission as well as preventing potential eavesdropping by malicious attackers. Group security key should be maintained for data encryption, while group key update and dissemination processes are required when a new user joins or leaves the group, which eventually lead to high communication and computation cost. Since eavesdrop activities can be initiated by capturing the disseminated keys, higher communication and computation cost due to frequent updates also increase the possibility of attack of multicast transmission. In this paper, a key management scheme for IPv6 networks is proposed to reduce communication and computation cost and therefore, fewer security risks. The obtained results from test-bed implementation show the efficiency of proposed scheme in terms of communication and computation cost, number of updated paths and security index due to key updating, while at the same time achieving both forward and backward secrecy.

We present a novel receiver-driven p2p system for delivery of multiple concurrent time constrained data streams in overlay networks. We propose an effective combination of rateless coding with intra- and inter-session network coding to efficiently exploit the path diversity in the streaming overlay. Network nodes can decide to forward rateless coded packets or to code them in intra- or inter-session mode before transmission. The transmission strategy is determined based on the availability of data sources and the demands of the children nodes. Each network node solves independently a simple flow maximization problem in order to determine the optimal coding policy. The overall system is evaluated for various networks and the results outline the advantages of the proposed approach over intra-session network coding based schemes in terms of clients' satisfaction, innovative flow rate and decoding delay.

In this paper, a hierarchical modulation scheme (known also as embedded, multi-resolution, or asymmetrical constellation) is studied for transmission of multicast and multimedia services over wireless fading channels. Specifically, we propose general design guidelines for multicast and multimedia transmission over fading channels with an adaptive hierarchical phase-shift-keying (PSK) constellation. Computer simulation results show that the proposed adaptive hierarchical M-PSK is more energy efficient than the traditional adaptive uniform M-PSK for both applications except some special cases. The energy gain of hierarchical PSK over uniform PSK depends only on the required quality parameters of the services in multimedia transmission. For multicasting, the gain depends on both the recipients' link qualities and the required quality parameters of the multicast message.

In this paper, we present a novel approach, stealth multicast, which offers a practical solution for the adoption of network-level IP multicast. Rather than focusing on a global scale such as with previous approaches, stealth multicast optimizes efficiency on a domain-wise scale. In short, stealth multicast dynamically combines redundant data payloads into virtual groups for multicast transmission across the domain. At the edge of the domain, the packets are converted back to unicast, thus keeping stealth multicast true to its namesake in that neither the user applications nor the external domain are aware of the presence of multicast. We present simulation studies to show the potential of stealth multicast.

Multimedia streaming using a multicast scheme over IEEE 802.11 multi-rate wireless local area networks (WLANs) faces many challenges owing to the heterogeneous channel conditions of receivers. Although many multicast schemes have been proposed to support multimedia streaming over multi-rate WLANs, those schemes do not deal with multicast transmission efficiently. In this paper, a new leader-based multicast scheme with a Raptor code is proposed. The proposed scheme consists of a leader selection block, a scalable video coding (SVC) block with unequal error protection (UEP), and a link adaptation block with a Raptor code. In the proposed scheme, one of the multicast group members is selected as a multicast group leader according to a leader cost, and then link adaptation operates between the multicast transmitter and the multicast group leader. In addition, SVC, UEP, and Raptor code mechanisms are applied to guarantee the minimum required performance of multicast group members. The proposed scheme aims to enhance the link utilization and guarantees the minimum quality-of-service requirement of multicast group members. Simulation results show that the proposed scheme performs better than previous multicast schemes.

This paper addresses the problem of power control in ad hoc networks supporting multicast traffic. First, we present a distributed algorithm which, given the set of multicast transmitters and their corresponding receivers, provides an optimal solution to the power control problem, if there is any. The transmit power levels obtained by solving the optimization problem minimize the network power expenditure while meeting the requirements of the SNR at the receivers. Whenever no optimal solution can be found for the given set multicast transmitters, we introduce a joint scheduling and power control algorithm, which eliminates the strong interferers thus allowing the other transmitters to solve the power control problem. The algorithm can be implemented in a distributed manner; however, it provides a sub-optimal solution since it is based on local information. Simulation results show that the obtained solution is close to the global optimum, when it exists. When there is no optimal solution, the proposed algorithm tries to maximize the number of successful multicast transmission.