Abstract-Multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. In this paper, we focus on multicast in single channel multi-access wireless local area networks (LANs) comprising several small cells. In such a system, a receiver cannot correctly receive a packet if two or more packets are sent to it at the same time, because the packets “collide. ” Therefore, one has to ensure that only one node sends at a time. We look at two important issues. First, we consider the problem of the sender acquiring the multi-access channel for multicast transmission. Second, for reliable multicast in each cell of the wireless LAN, we examine ARQ-based approaches. The second issue is important because the wireless link error rates can be very high. We present a new approach to overcome the problem of feedback colli-sion in single channel multi-access wireless LANs, both for the purpose of acquiring the channel and for reliability. Our approach involves the election of one of the multicast group members (receivers) as a ‘‘leader’ ’ or repre-sentative for the purpose of sending feedback to the sender. For reliable multicast, on erroneous reception of a packet, the leader does not send an acknowledgement, prompting a retransmission. On erroneous reception of the packet at receivers other than the leader, our protocol allows negative acknowledgements from these receivers to collide with the acknowledge-ment from the leader, thus destroying the acknowledgement and prompting the sender to retransmit the packet. Using analytical models, we demonstrate that the leader-based protocol exhibits higher throughput in comparison to two other protocols which use traditional delayed feedback-based probabilistic methods. Last, we present a simple scheme for leader election. I.

In this paper, we consider the problem of providing multicast to mobile hosts using Mobile IP for network routing support. Providing multicast in an internetwork with mobile hosts is made difficult because many multicast protocols are inefficient when faced with frequent membership or location changes. This basic difficulty can be handled in a number of ways, but three main problems emerge with most solutions. The tunnel convergence problem, the duplication problem, and the scoping problem are identified in this paper and a set of solutions are proposed.

this paper, we propose a multicast scheme known as MobiCast that is suitable for mobile 2 C.L. Tan, S. Pink / MobiCast: A Multicast Scheme for Wireless Networks

Abstract Reliable multicast is a powerful communication primitive for structuring distributed programs in which multiple processes must closely cooperate together. In this paper we propose a protocol for supporting reliable multicast in a distributed system that includes mobile hosts and evaluate the performance of our proposal through simulation. We consider a scenario in which mobile hosts communicate with a wired infrastructure by means of wireless technology. Our proposal provides several novel features. The sender of each multicast may select among three increasingly strong delivery ordering guarantees: FIFO, Causal, Total. Movements do not trigger the transmission of any message in the wired network as no notion of hand-off is used. The set of senders and receivers (group) may be dynamic. Size of data structures at mobile hosts, size of message headers, number of messages in the wired network for each multicast, are all independent on the number of group members. The wireless network is assumed to provide only incomplete spatial coverage and message losses could occur even within cells. Movements are not negotiated and a mobile host that leaves a cell may enter any other cell, perhaps after a potentially long disconnection. The simulation results show that the proposed protocol has good performance and good scalability properties. 1

We consider reliable multicast in distributed systems including mobile hosts (MHs) that communicate with a wired infrastructure by means of wireless links. Nearly all existing proposals are based on hand-off, i.e. whenever a MH switches cell, state information about this host travels across the wired network from the support station of the old cell to that of the new cell. However, we are not aware of any detailed performance analysis for hand-off based reliable multicast protocols: previous research in this area has focused mainly on correctness rather than on performance. We analyze in detail, by simulation, the performance of a proposal by Acharya and Badrinath that is based on hand-off and has been highly influential in the design of later protocols. Then, we compare this proposal with one by us that is based on an entirely different philosophy and is the only existing proposal not based on hand-off. Surprisingly, we found that our proposal outperforms the one by Acharya and Badrinath in all the aspects considered: latency, scalability, bandwidth usage efficiency and quickness in managing cell switches of MHs. Moreover, we found that this performance improvement is not obtained at the expense of increased resource requirements on MHs such as energy or memory. We believe that this performance and cost analysis allows us to gain insights into the design of reliable multicast protocols for distributed mobile systems. 1.

This paper discusses different approaches of providing multicast traffic for mobile hosts. Mobile IPv6 is used for mobility support. The network employs Protocol Independent Multicast Dense Mode (PIM--DM) for multicast routing and Multicast Listener Discovery (MLD) to collect multicast group membership information. We identify and analyze interoperation problems concerning membership control for mobile hosts and efficient multicast packet transfer from/to mobile hosts. We discuss four multicast delivery mechanisms for mobile senders and receivers, and compare them using criteria such as join delay, routing optimality, protocol overhead, network bandwidth, and system load. In particular, we suggest timer optimizations for MLD to support highly mobile receivers. 1

Flexible multi-media streaming such as advertisment insertion, location based services, mobility and wireless access are vital components that make existing Internet Radio and TV networks more attractive for the roaming users. All of these applications also provide added value to telematics, and military usage including coordination, education, situation awareness, distributed simulation, battlefield communication and multi-player games. While content distribution over a wired network can be realized by instituting proxies and gateways at several parts of the access network, providing mobility over heterogeneous wireless access need to consider many operational issues such as handoff, join and leave latency and desired level of quality of service for the mobile clients. This paper discusses some novel application layer techniques that provide a platform for Mobile E-Commerce with a multi-tiered payment and security scheme that supports a business model for a global streaming network. The proposed streaming network called MarconiNet is based on standard IETF protocols such as SIP, SAP and SDP for signaling, RTSP for stream control and RTP/RTCP for media delivery and feedback control.

Multimedia group communication emerges to focal interest at mobile devices, enriching voice or video conferencing and complex collaborative environments. The Internet uniquely provides the bene t of scalable, dynamic group communication services, vitally aiding commonly limited mobile terminals. The traditional Internet approach of Any Source Multicast (ASM) routing, though, remains hesitant to spread beyond limited, controlled environments. It is widely believed that simpler and more selective mechanisms for group distribution in Source Speci c Multicast (SSM) will globally disseminate to many users of multicast infrastructure and services. Mobility management for the recent SSM standard is under debate SSM group session initiation up until now remains unsupported by the Session Initiation Protocol (SIP). In this paper we present straightforward extensions to SIP for negotiating SSM sessions. SIP protocol speci cations and semantic are compatibly extended without adding new SIP methods. We will introduce a multimedia communication software with distributed architecture as implementation reference. Furthermore mobility management of the underlying routing layer is discussed and evaluated on grounds of real-world Internet topologies. This ongoing work is supported by the German Bundesministerium

Multicast network services advantageously complement multimedia information and communication technologies, as they open up the realm for highly scalable multicustomer applications. Mobile environments providing shared limited bandwidth to a growing number of users will emphasize the need for multicast support even further. The traditional Internet approach of Any Source Multicast (ASM) routing, though, remains hesitant to spread beyond limited, controlled environments. It is widely believed that simpler and more selective mechanisms for group distribution in Source Specific Multicast (SSM) will globally disseminate to many users of multicast infrastructure and services. However, mobility support for Source Specific Multicast is still known to be a major open problem. This paper presents a light-weight, secure implementation of the Tree Morphing protocol on the IPv6 network layer. This distributed routing algorithm allows for a continuous adaptation of multicast shortest path trees to source mobility. The approach introduced here is built upon standardized mobility signaling and includes strong authentication by means of cryptographically generated addresses. It neither requires definition of new protocol elements nor significant changes to the forwarding plane.

In this paper we present a protocol for reliable multicast within a group of mobile hosts that communicate with a wired infrastructure by means of wireless technology. The protocol assumes that the wireless coverage may be incomplete and message losses could occur even within cells, due to physical obstructions or to the high error rate of the wireless technology, for example. A novel feature of our proposal is that it tolerates failures in the wired infrastructure, i.e., crashes of stationary hosts and partitions of wired links. In particular, upon such failures mobile hosts simply observe that the covered area has shrunk. The covered area will enlarge back to its original extension when the failure recovers.