To support mobile multicasting in wireless networks, we present a new active multicasting mechanism which makes use of the state characteristic of multicast agent. In this mechanism, a multicast agent just locates the position for roaming hosts when it does not forward multicast packets. Upon reception of multicast packets, the multicast agent adjusts the service range to achieve an appropriate balance between routing efficiency and the overhead of multicast tree reconstruction. Therefore, a lot of unnecessary tree reconstructions are eliminated during the time when none multicast packet is transferred and multicast delivery path is near optimal because of the limited service range of multicast agent in the active state. To justify the effectiveness of our proposed scheme, we develop an analytical model to evaluate the signaling overhead. Our performance analysis shows that the proposed scheme can significantly reduce the system overhead and multicast routing is near optimal. The other important contribution is the novel analytical approach in evaluating the performance of mobile multicast routing protocol.

When a mobile node that subscribes to one or more multicast groups moves to another subnet, it is essential to provide a network level multicast handoff mechanism. Previous multicast handoff schemes are based on Mobile IP. However it is known that the Mobile IP is not adequate to interactive multimedia applications such as voice over IP or video conferencing due to its large handoff delay. Additionally, few researches have paid attentions on multicast handoff in infrastructure-mode WLAN environment. This paper proposes a fast inter-subnet multicast handoff method in Mobile IP based infrastructure-mode IEEE 802.11 WLAN environment. We introduce a dedicated Multicast Access Point (MAP) that works with an access points specified in standard IEEE 802.11 WLAN in order to alleviate disruption of receiving multicast datagram. Unlike previous research, our scheme does not modify Mobile IP specifications. MAP detects the completion of link-layer handoff, sends unsolicited IGMP Membership report to its local router on behalf of the mobile station and performs unicast tunneling. We evaluate the proposed method using ns-2 simulation. The simulation result shows that the proposed method can reduce the disruption period due to inter-subnet multicast handoff to about 1/12 and the packet loss rate can be reduced to about 1/4 over 20-size multicast group compared with the standard Mobile IP based IEEE 802.11 WLAN.

In this paper, we propose the design of a scalable reliable mobile multicast scheme--SRMoM. SRMoM uses well-known Scalable Reliable Multicast (SRM) in the wired networks and a NAK-based ARQ with adaptive Forward Error Correction (AFEC) in the wireless networks. In AFEC, the probability of needing retransmission of original multicast packets after FEC recovery is selectable. This selective property enables the control of channel utilization in the wireless segment for different numbers of Mobile Hosts (MHs). Using this property, the channel utilization of SRMoM is made to be virtually independent of the number of MHs, thus making it extremely scalable. The performance of SRMoM is analyzed with three adaptive FEC algorithms based on three wireless loss models, namely a Gilbert-Elliott channel, a simplified Gilbert-Elliott channel, and a binary symmetric channel, analytically as well as through simulation. Furthermore, the performance of SRMoM is compared with SRM and MRMoM (NAK-based protocol without FEC) through simulation. Using the average number of transmissions per original multicast packet, and wireless link utilization as metrics, we demonstrate that the performance of SRMoM is indeed virtually independent of the number of MHs, and that it results in the lowest number of packet transmissions and lowest channel utilization of reliable mobile multicast protocols that have been proposed to date.

Existing reliable multicast protocols are designed to perform well in wired networking environments. However, in mobile networking environments, these reliable mobile multicast protocols are not optimal as they do not take into account the limitations of power (energy), storage capacity, processing power, impairments of wireless communication channels, and the frequent changes of location and the resulting loss of network connectivity. This paper analyses four hybrid reliable multicast schemes, namely NAK-based schemes, ACK-based schemes, ACK-based schemes with FEC (Forward Error Correction), and NAK-based schemes with FEC that are suitable for mobile networking environments and quantifies their performance. These four schemes differ from the generic sender-initiated and receiver-initiated reliable multicast protocols in that they rely on a mixture of multicasting and unicasting for providing reliability. This analysis is used to show that NAK-based schemes with FEC is best suited for reliable multicasting in mobile environments as they provide excellent performance in terms of average wireless channel utilization and average processing time, independently of the number of MHs.

In this paper, we propose the Synchronized Mobile Multicast (SMM) scheme for the real-time multimedia service to achieve three most important characteristics that the traditional Home Subscription (HS) and Remote Subscription (RS) mobile schemes cannot support. First, the SMM scheme supports the scalable one-to-many and many-to-many synchronized multimedia multicast on mobile IP networks to achieves seamless playback of continuous media streams even when both the mobile sender and receivers handoff simultaneously. Second, it analyzes the minimal buffer requirements of the mobile sender, the core router, the foreign agents and the mobile receivers in the multicast tree and formulates the initial playback delay within a handoff Guarantee Region (GR). Further, combined with the fine granularity scalability (FGS) encoding approach in the MPEG-4 standard, the SMM scheme achieves superior multimedia QoS guarantees and unlimited numbers of handoffs of the mobile sender and receivers only at the cost of degraded video quality for a short period after handoff with minimal extra bandwidth.

We propose a new protocol to achieve fault recovery of multicast applications in IP internetwork with mobile participators. Our protocol uses the basic unicast routing capability of IETF Mobile IP as the foundation, and leverages existing IP multicast models to provide reliable multicast services for mobile hosts as well. We believe that the resulting scheme is simple, scalable, transparent, and independent of the underlying multicast routing facility. A key feature of our protocol is the use of multicast forwarding agent (MFA) to address the scalability and reliability issues in the reliable mobile multicast applications. Our simulation results show the distinct performance advantages of our protocol using MFAs over two other approaches proposed for the mobile multicast service, namely Mobile Multicast Protocol (MoM) and bi-directional tunneling, particularly as the number of mobile group members and home agents (HAs) increases.

The IETF Mobile IP defines two multicast options: remote subscription (RS) and bi-direction tunneling (BT). In order to synthesize the strong points of these two IETF multicast options, we propose a hybrid approach, mMOM, which selectively uses two IETF multicast options based on the mobility of mobile hosts. Whenever a mobile host requests its first registration to a certain foreign agent, the corresponding foreign agent starts the service using the BT option. Afterwards, if it requests re-registration to the same foreign agent, the foreign agent considers it to be relatively immobile and continues services using the RS option. We propose a new metric to compare heterogeneous algorithms. Simulation results show that our approach outperforms all others.

In this paper we describe a multicast routing algorithm, which builds upon mobile multicast agents of an ad-hoc network. Mobile multicast agents (MMAs) form a virtual backbone of an ad-hoc network and they provide multicast tree discovery, multicast tree maintenance and datagram delivery. First, we construct a cluster-spine hierarchy structure for an ad-hoc network. Second, we propose a multicast routing algorithm, which is inspired by Ad-hoc On-Demand Distance Vector (AODV) routing protocol. The results show that the MMA multicast algorithm can simplify the multicast tree discovery, reduce control overhead of the network, and increase the total network throughput, in comparison with general AODV multicast operation. We also overcome the deficiency of CBRP multicast routing, which places much burden on cluster heads.

In this paper, we present an alternative design, RBMoM (Range-Based Mobile Multicast), for efficiently supporting multicast for mobile hosts on the Internet. The current version of Mobile IP proposes two approaches to support mobile multicast, which are remote subscription and bi-directional tunneling. The former provides the shortest routes for delivery of multicast datagrams to mobile hosts; the latter hides host mobility from all other members of the group (therefore, no any overhead in the multicast tree maintenance). RBMoM intends to trade off between the shortest delivery path and the frequency of the multicast tree reconfiguration by controlling the service range of the multicast home agent (MHA). Actually, we will find that remote subscription and bi-directional tunneling are the extremes of RBMoM. From the point of view of the MHA and the service range concepts, RBMoM is a generalization of both approaches and a unifying mobile multicast approach. The simulation results show that RBMoM can adapt to the fluctuation of both host movement and the number of mobile group members, and has much better performance than the current two IP mobile multicast solutions.