In this paper, we present an extended mobile backbone network topology synthesis algorithm (ETSA) for constructing and maintaining a dynamic backbone structure for mobile ad hoc wireless networks. We present and analyze the mathematical features of the proposed scheme. Using these results, we prove that: (1) The ETSA scheme converges in constant time; (2) The length of each control packet is bounded by a constant value that is independent of the number of network nodes; (3) The size of the backbone network depends only on the size of the operational area and is independent of nodal density. We compare the performance features of this scheme with those characterizing other protocols that employ clustering operations and/or use selective forwarding on demand routing methods. In addition, we present an on-demand routing protocol (MBNR) that makes use of the underlying dynamically self-configuring backbone network infrastructure and demonstrate its performance advantages when compared with an on-demand routing protocol that is based on a flat architecture, as well as with other backbone-based routing protocols.

Wireless local area network (WLAN) systems are widely implemented today to provide hot spot coverage. Operated typically in an infrastructure mode, each WLAN is managed by an access point (AP). Wireless mesh networks are employed for the purpose of extending the wireless coverage scope of the network. We synthesize a wireless mesh backbone network that serves to interconnect the underlying AP nodes. The capability of the dynamically synthesized backbone network is further enhanced by the possible use of multiple communications bands and by the employment of multiple radio modules at more capable nodes. In this paper, we present a fully distributed multi-radio backbone synthesis algorithm (MR-BSA), which serves to construct a mesh backbone network of access points. We prove mathematically that the size of the backbone network constructed by MR-BSA is bounded by a constant, so that it is independent of the number of network nodes. We also prove that the control overhead is bounded by a constant value that is independent of the number of network nodes, and the underlying backbone synthesis algorithm converges in constant time.

Wireless local area network (WLAN) systems are widely implemented today to provide hot spot coverage. Operated typically in an infrastructure mode, each WLAN is managed by an access point (AP). Wireless mesh networks are considered for implementation for the purpose of extending wireless coverage. The capability and performance behavior of the wireless mesh network can further be upgraded by using multiple communications channels and by having more capable nodes employ multiple radios modules. In this paper, we present an efficient multi-radio backbone synthesis algorithm (MR-BSA), which serves to construct a mesh backbone network of access points. We assume more capable nodes such as APs to be equipped with two radio modules while less capable nodes employ a single radio module. The presented topology construction algorithm and the associated on-demand backbone based routing mechanism are shown to improve the system's delay-throughput performance as well as its asynchronous, distributed and stable dynamic behavior

The synthesis of efficient and scalable multicasting schemes for mobile ad hoc networks is a challenging task. Multicast protocols typically construct a tree or mesh structure to distribute messages to multicast group members. Generally, these implementations impose scalability and efficiency limitations since they employ protocols that are based on a flat-topology networking architecture. We present three multicast algorithms that employ a dynamically synthesized mobile backbone network (MBN) to achieve efficient message distribution among members of multicast groups. Using the synthesized backbone network (BNet), we have a hierarchical networking architecture that enables a multicast protocol to achieve low control overhead and high transmission efficiency. The multicast algorithms under investigation are: (1) BNet flooding multicast algorithm (BFMA); (2) shared backbone multicast subnetwork (SBMS); (3) hybrid multicast algorithm (HMA). Our simulation and mathematical analysis results demonstrate the enhanced performance achieved by these MBN-based multicast algorithms when compared to ODMRP, and provide performance comparisons for these algorithms

Wireless local area network (WLAN) systems are widely implemented today to provide hot-spot coverage. Operated typically in an infrastructure mode, each WLAN is managed by an access point (AP). Wireless mesh networks (WMNs) are employed for the purpose of extending the wireless coverage scope by interconnecting the underlying AP nodes. The capability and performance behavior of the WMN can further be upgraded by using multiple communications channels and by having more capable nodes use multiple radio modules. In this paper, we present a fully distributed multiradio backbone synthesis algorithm, which serves to construct a mesh backbone network of APs. We assume more capable nodes, such as APs, to be equipped with two radio modules, while less capable nodes employ a single radio module. Multihop communications among distant client stations take place in accordance with a routing algorithm that uses the mesh backbone to establish inter-WLAN routes. The presented backbone construction algorithm and the associated on-demand backbone-based routing mechanism are shown to improve the system's delay-throughput performance, as well as its asynchronous and distributed behavior in a stable fashion

In this paper, we present an extended mobile backbone network (MBN) topology synthesis algorithm (ETSA) for constructing and maintaining a dynamic backbone structure in mobile wireless ad hoc networks. For conventional backbone formation algorithms (such as Connected Dominating Set construction algorithms) to operate correctly, perfect neighborhood knowledge is required. However, in a wireless ad hoc network, both control message losses and asynchronous timers among nodes can lead to imperfect neighborhood information. Thus, two restricting rules are introduced in this paper for the election of backbone nodes that are shown to improve asynchronous, distributed and stable operation of the algorithm. The scalability and efficiency of backbone based routing in ad hoc networks depend on the overhead introduced by the formation of a connected backbone network (BNet) and the size of the backbone network. We prove that the size of the backbone network synthesized by this algorithm is independent of nodal density. We also prove that the extended topology synthesis algorithm introduced in this paper has constant O(1) time complexity and yields a constant O(1) communication overhead factor per node.

In this paper, we present an enhanced mobile backbone network topology synthesis algorithm for constructing and maintaining a dynamic backbone structure in mobile wireless ad hoc networks. The scalability and efficiency of backbone-based routing in ad hoc networks depend on the overhead introduced by the formation of a connected backbone network and the size of the backbone network. We prove that the algorithm presented in this paper has time complexity of the order of 0(1), and yields a communication overhead factor of the order of 0(1) per node. Two rules are introduced for regulating the election of backbone nodes that are shown to enable an asynchronous, distributed and stable operation of the algorithm.

A wireless mesh network extends wireless local area network systems, which are widely implemented today to provide hot spot coverage, by implementing a reliable meshed network that serves to interconnect the access points managing each wireless local area network. The 802.11s working group has been formed recently to recommend an extended service set (ESS) that enables wider area communications among distributed clients, each of which has access to an IEEE 802.11 wireless LAN (WLAN). Such coverage can be provided by the implementation of a mesh backbone network that serves to interconnect the WLAN access points (APs). In this paper, we present a scalable, fully distributed topology control algorithm for constructing such a mesh backbone network of access points. Multi-hop communications among distant client stations take place in accordance with a routing algorithm that uses the mesh backbone to establish inter-WLAN routes. The presented topology construction algorithm and its employment by the presented routing mechanism are shown to improve the asynchronous, distributed and stable operation of the network. We prove that the topology construction and control algorithm introduced in this paper is highly scalable and efficient. The implementation complexity of the required communications control (and its associated overhead) and its temporal convergence features are independent of the number of network nodes.

In this paper, we present a novel fully distributed version of a mobile backbone network topology synthesis algorithm (MBN-TSA) for constructing and maintaining a dynamic backbone in mobile wireless ad hoc networks. The following features induce the key advantages offered by the algorithm: a) the MBN-TSA algorithm is designed to work with the unreliable natural of wireless environment; b) the backbone layout is dynamically formed and locally modified in response to communications link quality fluctuations, nodal failures and nodal mobility; c) a control mechanism employing the BN/spl I.bar/neighbor/spl I.bar/limit threshold as a key parameter, is introduced to control the size of the backbone network (BNet) and improve stability; d) analytical results show that the MBN-TSA has very little control overhead: time complexity in the order of O(l) and message complexity in the order of O(l) per node. In addition, we present an on-demand routing protocol that makes use of the underlying dynamically self-configured MBN network infrastructure. By carrying out extensive simulations, we demonstrate the performance advantages when compared to a non backbone oriented on-demand ad hoc routing protocol such as AODV.

We introduce an ad hoc wireless mobile network that employs a hierarchical networking architecture and uses high and low capacity nodes. We present a topological synthesis algorithm that selects a subset of high capacity nodes to form a backbone network (Bnet). The latter is multi-tiered and consists of interconnected backbone nodes that intercommunicate across higher power (or regular) links, and also makes use of unmanned vehicles, both airborne (UAV) and ground based (UGV). For such a mobile backbone network (MBN), we introduce a protocol, MBNP, to implement the key networking schemes. The MBNP system serves to allocate resources across the network to ensure acceptable user application QoS performance, and also a highly robust backbone-oriented networking architecture. We introduce a new class of on-demand (MBNP-OD) routing algorithms that use the backbone network for selective forwarding of route-request messages, while striving to achieve an efficient MAC layer operation. We enhance these new protocols by incorporating link stability estimates to attain a robust routing operation. To ensure service quality for admitted flows, we introduce flow admission control mechanisms. We present new power control spatial reuse based algorithms for efficient utilization of the net MAC resources through the use of time slot allocations and of CSMA/CA based (IEEE 802.11 type) protocols. We present elements of the protocol and key involved algorithms, and illustrate the advantages offered by the MBNP system.

This paper proposes an adaptive slot allocation mechanism to improve the performance of Transmission Control Protocol (TCP) in DOCSIS-based hybrid fiber coaxial (HFC) networks. The proposed mechanism is comprised of two parts: fast request transmission (FRT) and long packet deferment (LPD). FRT is designed to handle one-way TCP transfers, while LDP targets two-way transfers. Here "one-way transfers" means all active cable modems perform downloading; while "two-way transfers" indicates some perform downloading and some perform uploading. We analyze the proposed mechanism and conduct simulations using network simulator ns-2 to evaluate the performance of our mechanism. The results show that the proposed mechanism has better performance in terms of aggregate downstream throughput, access delay, and required buffer size, as compared to the original control mechanism of DOCSIS.

We have recently introduced a hierarchical structure for ad hoc wireless networks that classifies nodes into two categories: backbone capable nodes (BCNs) and regular nodes (RNs). BNCs are better equipped, have higher capacities, and have the ability to operate at multiple power levels and employ multiple radio modules. Under our protocol, identified as TBONE, when a BCN is elected to function as a backbone node (BN), it uses its high power link to communicate with other BNs, thus forming a backbone network (Bnet). To access the network, each RN or BCN must associate itself with a nearby BN (if any). The BN manages transmissions across its access network (Anet), whereby messages are transmitted to/from the BN and among Anet members at lower power levels. Our protocol dynamically initiates and maintains the configuration and association functions of such a mobile backbone network (MBN) under nodal mobility, topological changes and traffic flow variations. We further employ unmanned vehicles (UVs) to aid in maintaining the connectivity of the MBN as well as to upgrade the network capacity when required to sustain real-time and messaging flows that demand quality-of-service (QoS) performance assurance. In this paper, we present the performance features of this protocol, evaluating the number of nodes that are activated as BNs, characterizing the extent to which the system covers its client mobile station using its prescribed BCNs, and presenting the rate of various protocol interactions as a function of the mobility speed of nodal users. We also evaluate the impact of employed UVs on the system's connectivity and coverage features.

This paper studies the effect of the DOCSIS MAC layer on the performance of two-way TCP transfers in hybrid fiber coax (HFC) networks. We propose a new adaptive scheduling scheme called long packet deferment (LPD) at the headend to improve TCP performance in DOCSIS-based HFC networks. LPD reduces the frequency of transmission of long packets and, if such long packets are transmitted, they are scheduled towards the end of each transmission period. Thus, it allows the system to behave as in a symmetric network earlier, reduces the round trip delay of sending data packets, and improves the aggregate downstream throughput. We have conducted simulations using network simulator ns-2 to compare the simple first-come-first-served scheduling of DOCSIS and IEEE 802.14 like mechanism with LPD. The results show that LPD has better performance in terms of higher aggregate downstream throughput and shorter access delay.

This paper studies the effect of DOCSIS MAC layer on TCP performance in hybrid fiber coax (HFC) networks. We discuss how the DOCSIS MAC mechanism affects bandwidth asymmetry, analyze TCP behavior over DOCSIS MAC layer, and propose a new mechanism called fast request transmission (FRT) to improve TCP performance in HFC networks. We have also conducted simulations using network simulator ns-2 to compare the original control mechanism of DOCSIS with our mechanism. The results show that the proposed FRT mechanism has better performance in terms of aggregate downstream throughput, access delay, and buffer size.