Bandwidth-satisfied multicast trees in large-scale ad-hoc networks

The purpose of this paper is to construct bandwidth-satisfied multicast trees for QoS applications in large-scale ad-hoc networks (MANETs). Recent routing protocols and multicast protocols in large-scale MANETs adopt two-tier infrastructures to avoid the inefficiency of the flooding. Hosts with a maximal number of neighbors are often chosen as backbone hosts (BHs) to forward packets. Most likely, these BHs will be traffic concentrations/bottlenecks of the network. In addition, since host mobility is not taken into consideration in BH selection, these two-tier schemes will suffer from more lost packets if highly mobile hosts are selected as BHs. In this paper, a new multicast protocol is proposed for partitioning large-scale MANET into two-tier infrastructures. In the proposed two-tier multicast protocol, hosts with fewer hops and longer remaining connection time to the other hosts will be selected as BHs. The objective is not only to obtain short and stable multicast routes, but also to construct a stable two-tier infrastructure with fewer lost packets. Further, previous MANET quality-of-service (QoS) routing/multicasting protocols determined bandwidth-satisfied routes for QoS applications. Some are implemented as a probing scheme, but the scheme is inefficient due to high overhead and slow response. On the contrary, the others are implemented by taking advantage of routing and link information to reduce the inefficiency. However, the latter scheme suffers from two bandwidth-violation problems. In this paper, a novel algorithm is proposed to avoid the two problems, and it is integrated with the proposed two-tier multicast protocol to construct bandwidth-satisfied multicast trees for QoS applications in large-scale MANETs. The proposed algorithm aims to achieve better network performance by minimizing the number of forwarders in a tree.     

Wireless Ad Hoc Multicast Routing with Mobility Prediction

An ad hoc wireless network is an infrastructureless network composed of mobile hosts. The primary concerns in ad hoc networks are bandwidth limitations and unpredictable topology changes. Thus, efficient utilization of routing packets and immediate recovery of route breaks are critical in routing and multicasting protocols. A multicast scheme, On-Demand Multicast Routing Protocol (ODMRP), has been recently proposed for mobile ad hoc networks. ODMRP is a reactive (on-demand) protocol that delivers packets to destination(s) on a mesh topology using scoped flooding of data. We can apply a number of enhancements to improve the performance of ODMRP. In this paper, we propose a mobility prediction scheme to help select stable routes and to perform rerouting in anticipation of topology changes. We also introduce techniques to improve transmission reliability and eliminate route acquisition latency. The impact of our improvements is evaluated via simulation.     

On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks

An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.     

An Efficient Multicast Routing Protocol in Wireless Mobile Networks

Providing multicast service to mobile hosts in wireless mobile networking environments is difficult due to frequent changes of mobile host location and group membership. If a conventional multicast routing protocol is used in wireless mobile networks, several problems may be experienced since existing multicast routing protocols assume static hosts when they construct the multicast delivery tree. To overcome the problems, several multicast routing protocols for mobile hosts have been proposed. Although the protocols solve several problems inherent in multicast routing proposals for static hosts, they still have problems such as non-optimal delivery path, datagram duplication, overheads resulting from frequent reconstruction of a multicast tree, etc. In this paper, we summarize these problems of multicast routing protocols and propose an efficient multicast routing protocol based on IEFT mobile IP in wireless mobile networks. The proposed protocol introduces a multicast agent, where a mobile host receives a tunneled multicast datagram from a multicast agent located in a network close to it or directly from the multicast router in the current network. While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent may start multicast join process, which makes the multicast delivery route optimal. The proposed protocol reduces data delivery path length and decreases the amount of duplicate copies of multicast datagrams. We examined and compared the performance of the proposed protocol and existing protocols by simulation under various environments and we got an improved performance over the existing proposals.     

Location aided probabilistic broadcast algorithm for mobile Ad-hoc network routing

On-demand routing protocols are widely used in mobile Ad-hoc network (MANET). Flooding is an important dissemination scheme in routing discovering of on-demand routing protocol. However, in high-density MANET redundancy flooding packets lead to dramatic deterioration of the performance which calls broadcast storm problem (BSP). A location-aided probabilistic broadcast (LAPB) algorithm for routing in MANET is proposed to reduce the number of routing packets produced by flooding in this paper. In order to reduce the redundancy packets, only nodes in a specific area have the probability, computed by location information and neighbor knowledge, to propagate the routing packets. Simulation results demonstrate that the LAPB algorithm can reduce the packets and discovery delay (DD) in the routing discovery phase.     

Hop-by-hop Content Distribution with Network Coding in Multihop Wireless Networks

The predominant use of today's networks is content access and distribution. Network Coding (NC) is an innovative technique that has potential to improve the efficiency of multicast content distribution over multihop Wireless Mesh Networks (WMNs) by allowing intermediate Forwarding Nodes (FNs) to encode and then forward data packets. Practical protocols are needed to realize the benefits of the NC technique. However, the existing NC-based multicast protocols cannot accurately determine the minimum number of coded packets that a FN should send in order to ensure successful data delivery to the destinations, so that many redundant packets are injected into the network, leading to performance degradation. In this paper, we propose HopCaster, a novel reliable multicast protocol that incorporates network coding with hop-by-hop transport. HopCaster completely eliminates the need for estimating the number of coded packets to be transmitted by a FN, and avoids redundant packet transmissions. It also effectively addresses the challenges of heterogeneous multicast receivers. Moreover, a cross-layer multicast rate adaptation mechanism is proposed, which enables HopCaster to optimize multicast throughput by dynamically adjusting wireless transmission rate based on the changes in the receiver population and channel conditions during the course of multicasting a coded data chunk. Our evaluations show that HopCaster significantly outperforms the existing NC-based multicast protocols.     

The design, implementation, and performance evaluation of theon-demand multicast routing protocol in multihop wireless networks

Multicasting has emerged as one of the most focused areas in the field of networking. As the technology and popularity of the Internet grow, applications such as video conferencing that require the multicast feature are becoming more widespread. Another interesting development has been the emergence of dynamically reconfigurable wireless ad hoc networks to interconnect mobile users for applications ranging from disaster recovery to distributed collaborative computing. In this article we describe the on-demand multicast routing protocol for mobile ad hoc networks. ODMRP is a mesh-based, rather than conventional tree-based, multicast scheme and uses a forwarding group concept (only a subset of nodes forwards the multicast packets packets via scoped flooding). It applies on-demand procedures to dynamically build routes and maintain multicast group membership. We also describe our implementation of the protocol in a real laptop testbed     

Scalable Multicasting: The Core-Assisted Mesh Protocol

Most of the multicast routing protocols for ad hoc networks today are based on shared or source-based trees; however, keeping a routing tree connected for the purpose of data forwarding may lead to a substantial network overhead. A different approach to multicast routing consists of building a shared mesh for each multicast group. In multicast meshes, data packets can be accepted from any router, as opposed to trees where data packets are only accepted from routers with whom a tree branch has been established. The difference among multicast routing protocols based on meshes is in the method used to build these structures. Some mesh-based protocols require the flooding of sender or receiver announcements over the whole network. This paper presents the Core-Assisted Mesh Protocol, which uses meshes for data forwarding, and avoids flooding by generalizing the notion of core-based trees introduced for internet multicasting. Group members form the mesh of a group by sending join requests to a set of cores. Simulation experiments show that meshes can be used effectively as multicast routing structures without the need for flooding control packets.     

A Domain-Based Routing Protocol for SSM Source Mobility in Mobile IPv6 Networks

In Mobile IP, the signaling traffic overhead will be too high since the new Care-of-Address (CoA) of the mobile node (MN) is registered all the way with the home agent (HA) whenever the MN has moved into a new foreign network. To complement Mobile IP in better handling local movement, several IP micro protocols have been proposed. These protocols introduce a hierarchical mobility management scheme, which divides the mobility into micro mobility and macro mobility according to whether the host's movement is intra-domain or inter-domain. Thus, the requirements on performance and flexibility are achieved, especially for frequently moving hosts. This paper introduces a routing protocol for multicast source mobility on the basis of the hierarchical mobile management scheme, which provides a unified global architecture for both uni- and multicast routing in mobile networks. The implementation of multicast services adopts an improved SSM (Source Specific Multicast) model, which combines the advantages of the existing protocols in scalability and mobility transparency. Simulation results show that the proposed protocol has better performance than the existing routing protocols for SSM source mobility.     

An efficient mesh‐based multicast routing protocol in mobile ad hoc networks

Mesh‐based multicast routing protocols for mobile ad hoc networks (MANETs) build multiple paths from senders to receivers to deliver packets even in the presence of links breaking. This redundancy results in high reliability/robustness but may significantly increase packet overhead. This paper proposes a mesh‐based multicast protocol, called centered protocol for unified multicasting through announcements (CPUMA), that achieves comparable reliability as existing mesh‐based multicast protocols, however, with significantly much less data overhead. In CPUMA, a distributed core‐selection and maintenance algorithm is used to find the source‐centric center of a shared mesh. We leverage data packets to center the core of each multicast group shared mesh instead of using GPS or any pre‐assignment of cores to groups (the case of existing protocols). The proposed centering scheme allows reducing data packet overhead and creating forwarding paths toward the nearest mesh member instead of the core to reduce latency. We show, via simulations, that CPUMA outperforms existing multicast protocols in terms of data packet overhead, and latency while maintaining a constant or better packet delivery ratio, at the cost of a small increase in control overhead in a few scenarios. Copyright © 2010 John Wiley & Sons, Ltd.     

Scalable location guide overlay multicast in mobile ad hoc networks using tree partition scheme

Nodes mobility brings flinty challenges to multicast in Mobile ad hoc Networks (MANETs). To track nodes mobility, flooding messages are widely used for data delivery structure construction and maintenance in many multicast protocols. These periodic flooding messages significantly consume network resources, such as energy and bandwidth, and result in network collisions. To release data delivery structure maintenance onus, profited from GPS location service, a number of stateless location based multicast protocol were proposed, where a destination list is encapsulated into each data packet for data packet orientation. However, due to data packet capability limitation, the way of encapsulating a destination list in each data packet header restricts the protocol scalability. To solve the scalability issue of multicast protocols, we propose a Scalable Location Guide Overlay Multicast (SLGOM) for MANETs. Analysis and simulation results show that SLGOM achieves high performance in large multicast group and significantly improves the scalability of stateless multicast with respect to group size. Copyright © 2010 John Wiley & Sons, Ltd.     

Multicast support for mobile hosts using Mobile IP: Design issues and proposed architecture

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. The paper describes an architecture to support IP multicast for mobile hosts using Mobile IP. The basic unicast routing capability of Mobile IP is used to serve as the foundation for the design of a multicast service facility for mobile hosts. We believe that our scheme is transparent to higher layers, simple, flexible, robust, scalable, and, to the extent possible, independent of the underlying multicast routing facility. For example, our scheme could interoperate with DVMRP, MOSPF, CBT, or PIM in the current Internet. Where differences exist between the current version of IP (IPv4) and the next generation protocol (IPv6), these differences and any further optimizations are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Border Node Retransmission Based Probabilistic Broadcast Protocols in Ad-Hoc Networks

We propose some improvements to the flooding protocols that aim to efficiently broadcast given information in ad-hoc networks. These improvements are based on probabilistic approach and decrease the number of emitted packets. Indeed, it is more interesting to privilege the retransmission by nodes that are located at the radio border of the sender. We observe that the distance between two nodes can be approximated by comparing neighbor lists. This leads to broadcasting schemes that do not require position or signal strength information. Moreover, proposed broadcast protocols require only knowledge of one hop neighborhood and thus need only short hello message and then support high mobility.     

Reliable and efficient multicast protocol for mobile IP networks

To provide a multicasting service, several multicast protocols for mobile hosts (MHs) have been proposed. However, all of these protocols have faults, such as non‐optimal delivery routes and data loss when hosts move to another network, resulting in insecure multicast data transmissions. Thus, this paper presents a new reliable and efficient multicast routing protocol for mobile IP networks. The proposed protocol provides a reliable multicast transmission by compensating the data loss from the previous mobile agent when a MH moves to another network. In addition, an additional function allows for direct connection to the multicast tree according to the status of agents, thereby providing a more efficient and optimal multicast path. The performance of the proposed protocol is confirmed based on simulations under various conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

OFDMA‐Based Reliable Multicast MAC Protocol for Wireless Ad‐Hoc Networks

Compared with unicast, multicast over wireless ad‐hoc networks do not support reliability due to their inability to exchange request‐to‐send/clear‐to‐send (RTS/CTS) and ACK packets with multiple recipients. Although several media access control (MAC) layer protocols have been proposed to provide reliable multicast, these introduce additional overhead, which degrades system performance. A novel MAC protocol for reliable wireless multicast is proposed in this paper. By adapting orthogonal frequency division multiple access characteristics in CTS and ACK packets, the protocol achieves reliability over wireless multicast with minimized overhead.     

Scalable reliable multicast using multiple multicast channels

We examine an approach for providing reliable, scalable multicast communication, involving the use of multiple multicast channels for reducing receiver processing costs and reducing network bandwidth consumption in a multicast session. In this approach a single multicast channel is used for the original transmission of packets. Retransmissions of packets are done on separate multicast channels, which receivers dynamically join and leave. We first show that protocols using an infinite number of multicast channels incur much less processing overhead at the receivers compared to protocols that use only a single multicast channel. This is due to the fact that receivers do not receive retransmissions of packets they have already received correctly. Next, we derive the number of unwanted redundant packets at a receiver due to using only a finite number of multicast channels, for a specific negative acknowledgment (NAK)-based protocol. We then explore the minimum number of multicast channels required to keep the cost of processing unwanted packets to a sufficiently low value. For an application consisting of a single sender transmitting reliably to many receivers we find that only a small number of multicast channels are required for a wide range of system parameters. In the case of an application where all participants simultaneously act as both senders and receivers a moderate number of multicast channels is needed. Finally, we present two mechanisms for implementing multiple multicast channels, one using multiple IP multicast groups and the other using additional router support for selective packet forwarding. We discuss the impact of both mechanisms on performance in terms of end-host and network resources     

A Reliable Multicast Routing Protocol Based on Recovery Points and FEC in Mobile Ad-hoc Networks

Multicasting is an essential service for mobile ad-hoc networks. A major challenge for multicasting in mobile ad-hoc networks (MANETs) is the unstable forwarding path. This work presents a reliable multicasting protocol for mobile ad-hoc networks. A virtual backbone is used as a shared structure for multiple sessions. A lost packet recovery scheme is developed for reliable packet transmission, called the Recovery Point (RP) scheme. The RP scheme maintains the data packets received from the source for recovering lost packets for its downstream RPs. In addition, we combine the Forward Error Correction (FEC) technology with our RP scheme to enhance the reliability of our RP scheme. A mergence scheme for RP is also proposed to avoid excessive control overhead. Our RP and FEC based scheme can be used to improve the reliability and efficiency of the traditional non-acknowledged multicasting approach. Experiments were conducted to evaluate the proposed multicasting scheme. The results demonstrate that our scheme outperforms other schemes in terms of packet delivery ratio and multicast efficiency. Furthermore, the simulation results also demonstrate that our approach is stable in networks with high mobility.

Exploring mesh and tree-based multicast. Routing protocols for MANETs

Recently, it became apparent that group-oriented services are one of the primary application classes targeted by MANETs. As a result, several MANET-specific multicast routing protocols have been proposed. Although these protocols perform well under specific mobility scenarios, traffic loads, and network conditions, no single protocol has been shown to be optimal in all scenarios. The goal of this paper is to characterize the performance of multicast protocols over a wide range of MANET scenarios. To this end, we evaluate the performance of mesh and tree-based multicast routing schemes relative to flooding and recommend protocols most suitable for specific MANET scenarios. Based on the analysis and simulation results, we also propose two variations of flooding, scoped flooding and hyper flooding, as a means to reduce overhead and increase reliability, respectively. Another contribution of the paper is a simulation-based comparative study of the proposed flooding variations against plain flooding, mesh, and tree-based MANET routing. In our simulations, in addition to "synthetic" scenarios, we also used more realistic MANET settings, such as conferencing and emergency response.     

NARD: Neighbor-assisted route discovery in MANETs

Reactive routing protocols for mobile ad-hoc networks usually discover routes by disseminating control packets across the entire network; this technique is known as brute-force flooding. This paper presents NARD, which stands for neighbor-assisted route discovery protocol for mobile ad-hoc networks. In NARD, a source node floods a limited portion of the network searching not only for the destination node, but also for routing information related to other nodes (called destination-neighbors) that were near the destination node recently. Destination-neighbors can be used as anchor points where a second limited flooding takes place in search for the destination node. Because only two limited portions of the network are flooded by control packets near the source and destination nodes, NARD can significantly reduce signaling overhead due to route-discovery compared with other proposals. Simulations with NS-2 were carried out to verify the validity of our approach.     

Exploring the design space of reliable multicast protocols for wireless mesh networks

Many important applications in wireless mesh networks require reliable multicast communication, i.e., with 100% packet delivery ratio (PDR). Previously, numerous multicast protocols based on automatic repeat request (ARQ) have been proposed to improve the packet delivery ratio. However, these ARQ-based protocols can lead to excessive control overhead and drastically reduced throughput. In this paper, we present a comprehensive exploration of the design space for developing high-throughput, reliable multicast protocols that achieve 100% PDR.Motivated by the fact that 802.11 MAC layer broadcast, which is used by most wireless multicast protocols, offers no reliability, we first examine if better hop-by-hop reliability provided by unicasting the packets at the MAC layer can help to achieve end-to-end multicast reliability. We then turn to end-to-end solutions at the transport layer. Previously, forward error correction (FEC) techniques have been proved effective for providing reliable multicast in the Internet, by avoiding the control packet implosion and scalability problems of ARQ-based protocols. In this paper, we examine if FEC techniques can be equally effective to support reliable multicast in wireless mesh networks. We integrate four representative reliable schemes (one ARQ, one FEC, and two hybrid) originally developed for the Internet with a representative multicast protocol ODMRP and evaluate their performance.Our experimental results via extensive simulations offer an in-depth understanding of the various choices in the design space. First, compared to broadcast-based unreliable ODMRP, using unicast for per-hop transmission only offers a very small improvement in reliability under low load, but fails to improve the reliability under high load due to the significantly increased capacity requirement which leads to congestion and packet drop. Second, at the transport layer, the use of pure FEC can significantly improve the reliability, increasing PDR up to 100% in many cases, but can be inefficient in terms of the number of redundant packets transmitted. In contrast, a carefully designed ARQ–FEC hybrid protocol, such as RMDP, can also offer 100% reliability while improving the efficiency by up to 38% compared to a pure FEC scheme. To our best knowledge, this is the first in-depth study of high-throughput, reliable multicast protocols that provide 100% PDR for wireless mesh networks.