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As an inexpensive, flexible, and scalable Internet-access wireless network, we have studied the architecture, protocols, and design optimizations of the Wireless Internet-access Mesh NETwork (WIMNET) that adopts multiple access-points (APs) connected through wireless links. WIMNET can improve the dependability to failures of APs and/or their links by allocating APs redundantly in the network field. Because redundant APs may increase the operational cost and degrade the throughput due to increasing radio interferences, only the necessary APs for connectivity between the hosts and the Internet gateway should be activated in communications. In this paper, we first define the active AP selection problem of selecting the minimum number of active APs, and prove the NP-completeness of its decision version through reduction from the known minimum set cover problem. Then, we propose an active AP selection algorithm of deactivating APs one by one until no more AP can be deactivated. Due to the limited transmission capacity in WIMNET, we further present an algorithm extension for throughput maximization. We verify the effectiveness of our proposal through simulations in three instances, where the number of active APs is reduced by more than 40% and the throughput is improved by more than 10% from the original in any instance. [ABSTRACT FROM AUTHOR]

Opportunistic Networks are examples of wireless, ad hoc networks where there is an absence of a continuous end-to-end path. The proliferation of mobile device usage creates opportunities for nodes to forward packets in a dynamic way, utilizing nodes as they present themselves. In more conventional, static network infrastructures, it is typical to measure efficiency of message passing between nodes. We review approaches to the measurement of efficiency in networks, and propose a qualitative and quantitative metrics framework and simulation model that would be suitable for the evaluation of performance in opportunistic networks. [ABSTRACT FROM AUTHOR]

We present Delay-Energy Aware Routing (DEAP) a novel protocol for heterogeneous wireless ad hoc networks. DEAP is a crosslayer scheme that: first, manages adaptively the energy control by controlling the wakeup cycle of sensors based on the experienced packet delay; and second, rout packet in each hoc by distributing the load a group of neighboring nodes. The primary result of DEAP is that it enables a flexible and wide range of tradeoffs between the packet delay and the energy consumption. Therefore, DEAP supports delay sensitive applications of heterogeneous networks that include sensors and actors. DEAP is scalable to the change in network size, node type, node density and topology. DEAP accommodates seamlessly such network changes, including the presence of actors in heterogeneous sensor networks. Indeed, while DEAP does not count on actors, it takes advantage of them, and uses their resources when possible, thus reducing the energy consumption of sensor nodes. Through analysis and simulation evaluations, we show that DEAP improves the packet delay and network lifetime compared to other protocols. [ABSTRACT FROM AUTHOR]

We present Geometric Broadcast for Heterogeneous Sensor Networks (GBS), a novel broadcasting protocol for heterogeneous wireless sensor and actor networks. While broadcasting is a very energy expensive protocol, it is also widely used as a building block for a variety of other network layer protocols. Therefore, reducing the energy consumption by optimizing broadcasting is a major improvement in heterogenous sensor networking. GBS is a distributed algorithm where nodes make local decisions on whether to transmit based on a geometric approach. GBS does not need any neighborhood information and imposes very low communication overhead. GBS is scalable to the change in network size, node type, node density and topology. Furthermore it accommodates seamlessly such network changes, including the presence of actors in heterogeneous sensor networks. Indeed, GBS takes advantage of actor nodes, and uses their resources when possible, thus reducing the energy consumption by sensor nodes. Through simulation evaluations, we show that GBS is very scalable and its performance is improved by the presence of actors. At the best of our knowledge, GBS is the first broadcast protocol designed specifically for heterogeneous sensor and actor networks. [ABSTRACT FROM AUTHOR]

An ad hoc network is a multi-hop wireless network of mobile nodes without fixed infrastructure. Its limited bandwidth and frequently changing topology require that its protocol should be robust, simple and energy conserving. We have proposed PDAODMRP (Passive Data Acknowledgement ODMRP) based on the passive acknowledgement function of data packets. PDAODMRP defines the adjacent un-forwarding nodes of forwarding nodes as pool nodes. With the help of pool nodes, PDAODMRP reduces its local route maintenance scope to at least one-hop. Although PDAODMRP has reduced its control overhead and data delivery delay greatly, it still selects multiple paths between a source and a member. And, its data overhead is still high. Hence, in this paper, we propose EPDAODMRP (Extended PDAODMRP) to extend PDAODMRP. Compared PDAODMRP, EPDAODMRP only selects the shortest path between a source and a member instead of all disjoint paths between a source and a member; its local route maintenance is as strong as that of PDAODMRP, which can amend all link failures. The simulation results show that EPDAODMRP has lower data overhead and lower data delivery delay. [ABSTRACT FROM AUTHOR]

Ad hoc networks are useful for providing communication support where no fixed infrastructure exists or the deployment of a fixed infrastructure is not economically profitable, and movement of communicating parties is allowed. Therefore, such networks are designed to operate in widely varying environments, from military networks to low-power sensor networks and other embedded systems. Frequent topology changes caused by node mobility make routing in ad hoc wireless networks a challenging problem. In this paper, we propose an efficient ad hoc routing algorithm, which we refer to as GZRP, a hybrid protocol that makes use of the ZRP scheme and the Global Positioning System (GPS). As opposed to the ZRP original scheme, our GZRP scheme consists of propagating the routing (query) messages only to the nodes that are further away from the query source. We discuss the algorithm, its implementation, and report on the performance of GZRP scheme, and compare it to the ZRP routing protocol using an extensive simulation experiment. Our results indicate clearly that GZRP outperforms ZRP by reducing significantly the number of route query messages, and thereby increases the efficiency of the network load. Furthermore, we show that careful GPS screening angle is an important factor in the success of the GZRP ad hoc routing protocol. [ABSTRACT FROM AUTHOR]

This paper proposes a new medium access control (MAC) protocol, called RequestTDMA/CDMA, for supporting multimedia traffic in wireless networks. In this hybrid protocol, CDMA (code division multiple access) is laid over TDMA (time division multiple access), where a time flame has two kinds of slots, namely data slots and control slots. The data slots are used to the user to transmit their data while the control slot holds the information for the next frame's slot allocation. Each data slot in a frame can be simultaneously used by multiple users with the help of uniquely assigned codes. Whenever a user needs to transmit a message, he first sends a request message to the central controller and enters the contention process. The controller takes into consideration the time of generation of a call, the bit rate requirement and the message length while reserving slots for the entire length of the message generated. The user then goes into the transmission phase if he is successful in the contention process, and continues to transmit his data till the entire message is sent. Three scheduling algorithms for the allocation of data slots are proposed and their performance are studied for four classes of traffic. We also analyze our protocol using a two-dimensional Markov chain model, and compute the state transition probabilities and derive the average waiting time for a given system load. By simulation experiments we show that our request-TDMA/CDMA protocol is able to effectively combine the orthogonality of both time and code division multiplexing. Further enhancements are also proposed to decrease the waiting time and increase the average channel utilization. [ABSTRACT FROM AUTHOR]

Introduces articles about wireless and mobile communication systems, published in the March 2001 issue of the periodical 'Journal of Interconnection Networks.' Routing problem in ad hoc mobile networks; Performance of on-demand ad hoc routing protocols; Use of global positioning systems to reduce the overhead of traffic flow.