Existing ad-hoc network routing strategies base their operations on flooding route requests throughout the network and choosing the shortest path thereafter. However, this typically results in a large number of unnecessary transmissions, which could be expensive for resource-constrained nodes such as those in a sensor network. In this paper, we propose a new mechanism HopAlert which optimizes route establishment and packet routing by limiting the number of nodes taking part in the route discovery process while achieving a low number of hops establishment. Using analysis and simulations, we show that this results in more routes with shorter hop counts than a reactive flooding protocol such as AODV while achieving higher savings.

In recent years, wireless communication technologies have been pervasive. We have many wireless options to connect to the Internet: IEEE 802.11 WLANs, GPRS, UMTS and many other competing technologies. These wireless standards were designed independently of each other. Hence, these standards do not specify a common solution to perform connection handover between two different standards. Given that each of these standards has its own advantages and disadvantages, users may want to use the best available connection for their needs. In this paper, we propose a scheme that enables seamless transitions between different wireless standards through SIP protocol. With our scheme, IP mobility across both vertical and horizontal handovers is possible without any modification to the existing applications. We define a guideline for handovers between networks, and then perform experiments with our scheme implementation to confirm the feasibility of our proposed scheme. Our results show that with our scheme, connection disruption is minimized.

The IEEE 802.11e standard has introduced specifications for service differentiation among different classes of data by specifying four service classes and a new contention resolution mechanism called EDCA. However, while the protocol shows a better performance for higher priority data such as voice and video, the performance is seen to drop drastically at high loads. In this paper, we explore the effectiveness of a multi-stage contention scheme for providing QoS differentiation among four different service classes, as specified by EDCA. From our analysis, we observe that the multi-stage with prioritization that we propose gives a much better performance than EDCA for higher priority data. Moreover, its good performance even at high network loads shows that this design is much more scalable.

In mobile ad hoc networks (MANETs), packets hop from a source to a series of forwarding nodes until they reach the desired destination. Defining the hop length to be the distance between two adjacent forwarding nodes, we observe that the two adjacent forwarding nodes tend to be farther away from each other with a higher probability in a one-dimensional MANET. We derive the probability density functions for the hop lengths to confirm our observation. Applying the developed results, we further formulate the relationship between the mean number of hops and the distance between the source and the destination.

In network mobility support for wireless ad hoc networks, mobile routers (MRs) are connected to access router (AR) by ad hoc routing. Mobile network nodes (MNNs) connect to an MR to communicate to distant correspondent nodes (CNs). Previous works on network mobility in mobile IPv6 involve packet redirection through a home agent; this redirection is costly in both bandwidth and delay. In this paper, we propose a terminal-assisted network mobility management scheme, which requires neither permanent node's IP address nor additional network servers/infrastructure support. With this scheme, IP packets redirection is not necessary; IP packets are routed directly between MNNs and CNs. Our scheme is implemented in three components: an IP-to-IP address mapping scheme on the MNN, an IPv6 header extension on each IP packet, and an IP address redirection scheme on the MRs. An MNN is located by a uniform resource identifier (URI) provided by a directory service that maps URI to IP address. Through numerical analysis, we show that our mobility management scheme exhibits better efficiency compared with that of mobile IPv6.

We propose in this paper an optimized, polymorphic, hybrid multicast routing protocol for MANET. This new polymorphic protocol attempts to benefit from the high efficiency of proactive behavior (in terms of quicker response to transmission requests) and the limited network traffic overhead of the reactive behavior, while being power, mobility, and vicinity-density (in terms of number of neighbor nodes per specified area around a mobile node) aware. The proposed protocol is based on the principle of adaptability and multibehavioral modes of operations. It is able to change behavior in different situations in order to improve certain metrics like maximizing battery life, reducing communication delays, improving deliverability, etc. The protocol is augmented by an optimization scheme, adapted from the one proposed for the optimized link state routing protocol (OLSR) in which only selected neighbor nodes propagate control packets to reduce the amount of control overhead. Extensive simulations and comparison to peer protocols demonstrated the effectiveness of the proposed protocol in improving performance and in extending battery power longevity

A new approach for modeling and performance analysis of the IEEE 802.11 medium access control (MAC) protocol is presented. The approach is based on the so-called system approximation technique, where the protocol service time distribution of the IEEE 802.11 MAC protocol is studied and approximated by an appropriate phase-type distribution, leading to the construction of a versatile queueing model which is amenable to analysis and, at the same time, general enough to allow for bursty arrival process as well as key statistical characteristics of the protocol operations. The versatility of the model is demonstrated by considering Markov modulated and on/off arrival processes as well as various data frame size distributions. The accuracy of the analytical results is verified by simulation.

In recent years, the physical layer data rate provided by 802.11 Wireless LANs has dramatically increased thanks to significant advances in the modulation and coding techniques employed. However, previous studies show that the 802.11 MAC operation, namely the distributed coordination function (DCF), represents a limiting factor: the throughput efficiency drops as the channel bit rate increases, and a throughput upper limit does indeed exist when the channel bit rate goes to infinite high. These findings indicate that the performance of the DCF protocol will not be efficiently improved by merely increasing the channel bit rate. This paper shows that the DCF performance may significantly benefit from the adoption of two separate physical carriers: one devised to manage the channel access contention, and another devised to deliver information data. We propose a scheme, referred to as out-of-band signaling (OBS), designed to reuse (and remain backward compatible with) the existing 802.11 medium access control (MAC) specification. Performance evaluation of OBS is carried out through analytical techniques validated via extensive simulation, for both saturation and statistical traffic conditions. Numerical results show that OBS improves the throughput/delay performance, and provides better bandwidth usage compared with the in-band signaling technique employed by DCF.

Quality of service support in wireless LAN is a theme of current interest. Several solutions have been proposed in literature in order to protect time-sensitive traffic from best-effort traffic. According to the EDCA proposal, which is a completely distributed solution, the service differentiation is provided by giving probabilistically higher number of channel accesses to stations involved in real-time applications. To this purpose, the MAC parameter settings of each contending stations can be tuned dynamically. In this paper, we face the problem of tuning the EDCA MAC parameters in common scenarios in which a given number of low-rate delay-sensitive traffic flows share the channel with some stations involved in data transfer. Our contribution is threefold. First, we show that, whenever possible, the delay constraints of the high priority class can be satisfied in both the cases of contention windows differentiation and inter-frame space differentiation. However, these mechanisms have different side effects in terms of bandwidth availability for the best effort stations. Second, we propose to exploit the MAC parameter dynamic settings of EDCA in order to probabilistically guarantee the delay requirements and to jointly maximize the aggregated throughput of the network. Finally, we suggest a very simple solution to automate these parameter settings in a real scenario, where traffic flows can be activated/deactivated dynamically, by simply monitoring the channel activity. The proposed solution is very robust, since it does not require any a priori traffic model or any network load estimator.

Many models have been proposed to analyze the performance of the IEEE 802.11 distributed coordination function (DCF) and the IEEE 802.11e enhanced distributed coordination function (EDCA) under saturation condition. To analyze DCF under statistical traffic, Foh and Zukerman introduce a model that uses Markovian Framework to compute the throughput and delay performance. In this paper, we analyze the protocol service time of EDCA mechanism and introduce a model to analyze EDCA under statistical traffic using Markovian Framework. Using this model, we analyze the throughput and delay performance of EDCA mechanism under statistical traffic.

In mobile ad hoc networks (MANETs), packets are forwarded by a series of nodes to the desired destination. Previously, we have studied the network connectivity of MANETs. In this paper, we study the reliability of an established route between a source to a destination. The route is considered reliable only when all links in the route remain connected for packet relaying. We analyze the link reliability under the condition that the forwarding nodes are mobile. With this analysis, we derive the time period that the established route remains reliable for packet forwarding. Simulation is conducted to validate our analysis.

With the rapid development and wide deployment of wireless local area networks (WLANs), WLAN-based positioning system employing signal-strength-based technique has become an attractive solution for location estimation in indoor environment. In recent years, a number of such systems has been presented, and most of the systems use the common nearest neighbor in signal space (NNSS) algorithm. In this paper, we propose an enhancement to the NNSS algorithm. We analyze the enhancement to show its effectiveness. The performance of the enhanced NNSS algorithm is evaluated with different values of the parameters. Based on the performance evaluation and analysis, we recommend some guidelines on optimizing the parameters of our proposed enhanced algorithm.

We propose in this paper, a polymorphic, hybrid multicast routing protocol for MANET (mobile ad hoc networks). This new polymorphic protocol attempts to take benefit of the high efficiency of proactive behavior and the low cost of network traffic of the reactive behavior. The protocol is based on the principle of adaptability and multi-behavioral modes of operations. The proposed protocol is able to change behavior in different situations in order to improve certain metrics like the battery power. Extensive simulations demonstrated the effectiveness of the proposed protocol in improving performance and in extending battery power longevity.

In this paper, we introduce a simple model for the enhanced distributed channel access (EDCA) mechanism under saturation conditions. This model captures the operation of the AIFS (arbitration inter-frame space) and contention window differentiation of the EDCA mechanism. Using this model, we analyze the throughput and delay performance of EDCA. The results of our analytical model are then verified using simulations.

In this paper, we study the performance of our earlier proposed out-of-band signaling (OBS) scheme for high speed wireless local area networks (WLANs). We employ the system approximation technique for modeling of the OBS scheme. An equivalent state dependent single server queue, that describes the OBS scheme, is constructed for the analysis of the throughput and delay performances. Moreover, we study the throughput optimization of the OBS scheme, which provides a means for optimizing the performance of the OBS scheme, given a particular network environment. Finally, we conduct several simulation experiments to validate our analytical results.