We develop a spatial framework to provide end-to-end delay estimates and guarantees in mobile multihop networks. The novel aspect of this approach is the attribution of network and MAC layer congestion to space, which enables congestion-aware routing and provides delay guarantees over a much longer duration than that achieved by the routing algorithms based on individual nodes. In a mathematically rigorous setting, first, we prove that over the duration during which the node density and the traffic pattern remain stationary, the expected values of local congestion and end-to-end delay roughly remain invariant. Second, we present an accurate method of delay estimation over geographic paths, namely path integration, and derive an upper bound for its estimation error. Further, we develop a congestion-aware routing protocol that utilizes the spatial maps of network congestion to enable delay-optimized routing of real-time applications. Through extensive QualNet simulations, we perform a detailed evaluation of the presented framework and the routing protocol in a realistic setup. The simulation studies demonstrate that the proposed scheme provides substantial improvements in the delivery of real-time applications for a wide range of node densities, velocities, and data traffic.

We present a novel framework for spatial routing through difficult terrains with possibly untrustworthy regions in tactical mobile ad hoc networks. We describe a protocol, named "Reliability Map Routing" (RMR), which uses end-to-end Quality of Service metrics that include spatial reliability and trust. The RMR protocol reactively discovers routes over spatial cells whose local reliabilities are distributed throughout the network via a fast dissemination algorithm. By using a spatial approach where reliability and trust are attributed to space rather than to nodes, RMR is able to find reliable routes that persist for longer durations than those discovered by node-centric protocols. Furthermore, RMR is capable of reliable geocasting with low overhead. Via QualNet simulation studies, we compare the performance of the RMR protocol in terms of packet delivery ratio, delay, and overhead, and quantify the effects of node density, velocity, and traffic load on protocol performance. Our results indicate that the RMR protocol performs well in high mobility, high density scenarios because of its controlled routing overhead and spatial approach to routing.

We present an empirical model of the upstream end-to-end Voice-over-IP (VoIP) delay over a mobile, multi-hop wireless network towards a single gateway. First, we define the “VoIP regime” as the regime of network operation in which a fraction 1 - ϵ of the packets are received by the gateway within the maximum tolerable VoIP networking delay y voip , and such that e is less than a maximum tolerable outage probability. We show that within the VoIP regime, the upstream VoIP delay is well-modeled by an exponential distribution whose parameter λ i depends on the number of hops i to the gateway. Second, we show that the coherence time of the VoIP regime is large enough such that the estimation of the {λ i } can be performed by the gateway, and distributed to the nodes such that each node can utilize the {λ i } in estimating the end-to-end delay from its current location for autonomous call admission decisions. Third, we validate the empirical model across scenarios that range from a flat deployment region, to a deployment region with holes, and to the case where there is background User Datagram Protocol (UDP) data traffic. The results are significant for enabling VoIP over high-mobility, multi-hop wireless networks, and in aiding node-based call admission decisions.

Wireless infrared optical code-division multiple access (W-OCDMA) is a new developing technique with many useful applications. Noting the limitation on power consumption and eye-safety requirements, wireless optical systems are power limited. Therefore control and efficient use of optical power is a key issue in analysis and design of these systems. Also, multi-user interference is the major source of impairment in these systems and power control is required to control and reduce this interference. Power control and the inevitable errors in its algorithms play an important role in design and implementation of these systems. In this article the authors study the uplink performance of W-OCDMA networks employing on–off keying (OOK) and binary pulse position modulation (BPPM) schemes without any power control algorithm. The performance improvement as a result of using perfect power control is calculated. Then, the impact of imperfect power control that is the result of channel estimation error is analysed. The results clearly illustrate that deploying a proper and accurate power control algorithm can increase network capacity and reduce network average power consumption. The authors show that systems with non-ideal power control still perform considerably better than no-power controlled systems.

This paper establishes a framework for the automated generation of networking protocols. The need for the rapid design of networking protocols in application-specific contexts has increased dramatically over the past five years. Each new application requires high performance in its own domain, as well as a rapid design cycle. Further, changes in physical layer technology quickly render previously high-performance protocols poor performance. Currently, there are no tools to automate the design of networking protocols. This paper addresses the challenge of building such tools. It proposes a methodology and a design chain for the automated generation of networking protocols, with the following novel ideas: (1) Formulation of the network protocol problem such that the exchange of protocol control information can be specified as part of the optimization program, (2) Optimal waveform generation, which specifies the optimal exchange of both control information and data, (3) Protocol Extraction: The extraction of the optimal protocol as a minimal description of the optimal waveforms. This methodology has the potential to dramatically change the future of networking protocol design by moving protocol design to a more abstract level, finding high-performance protocols not easily discovered by human intuition, and reducing the currently long protocol design cycles.

We study the uplink performance of wireless infrared code-division multiple access (CDMA) networks using OOK with optical orthogonal codes (OOC's). The analysis is performed in two cases assuming a cellular network architecture, in which all users are uniformly distributed in the cell's area. The first case is when all users transmit with the same power and no power control mechanism is used. Then, the system that deploys power control mechanism is analyzed and the performance improvements are demonstrated. The impact of imperfect power control which is caused by errors in channel estimation is also analyzed and the analytical and numerical results for all cases are included. The results clearly demonstrate the advantages of using power control algorithms for indoor infrared wireless systems that use OOC modulation techniques