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Physical-layer network coding is a high-throughput technique for communicating over the two-way relay channel, which consists of two terminals that communicate exclusively via an intermediate relay. An exchange of messages begins with both terminals transmitting binary data sequences simultaneously to the relay. The relay determines the modulo-2 sum of the sequences, which it modulates and broadcasts...
Applications operating over airborne networks are known to perform quite sub-optimally. Transmission control protocol (TCP) based applications often experience very low data throughput, while the user datagram protocol (UDP) based applications suffer high packet loss as well as out-of-order delivery. This is due to the high bit error rate (BER) nature of the wireless links and the high mobility of...
We consider a cognitive radio network in which a set of base stations make opportunistic spectrum access to support wireless subscribers within their covering cells. The spectrum of interest is divided into independent channels licensed to the primary users. Channel assignment and power control must be carried out in the cognitive network so that no excessive interference is caused to the primary...
As the world becomes increasingly dependent on dynamic and up-to-the-moment information, we recognize that broadband networks must be able to convey this information timely and wirelessly, to and from users in motion. Varieties of 802.11 compliant equipment and other types of broadband wireless equipment have been proposed for, and in some areas, being used to meet this need. There have been questions...
A future satellite communications system is envisioned that will provide a number of enhancements over predecessor satellite communication systems. It will employ high capacity packet switched service in space, high rate circuits between terminals, and utilize Dynamic Bandwidth Resource Allocation which dynamically assigns resources to terminals based on current channel conditions and traffic demand...
In this paper, we highlight the impact of variable Push-To-Talk (PTT) delays on performance of a heterogeneous Land Mobile Radio (LMR) network. We first present the PTT delay values and distributions observed for some commonly used LMR nodes. An analytical model is then developed to estimate the asymmetric throughput problem. The results obtained using this model and simulations show that a LMR node...
Military applications often require traffic to be multicast to a group of receivers. It has previously been shown that linear network coding is useful in conjunction with physical-layer multicasting for reliable multicast delivery over fading channels. Superposition coding is an effective way to deliver information to a single receiver over a fading channel. However, we have shown in previous work...
A number of large-scale applications require 10 Gbps data transport rates between high-performance computing, storage and file systems, which are connected over wide-area networks. Achieving such capability requires end-to-end optimization of all required hardware and software components including: (i) long haul SONET or 10 GigE connections; (ii) transport protocols such as TCP and UDT, (iii) encryption...
We study end-to-end delay performance of different routing algorithms in networks with random failures. Specifically, we compare delay performances of differential backlog (DB) and shortest path (SP) routing algorithms and show that DB routing outperforms SP routing in terms of throughput when the network is heavily loaded and/or the failure rate is high while SP routing achieves better delay performance...
In this paper, we investigate the packet transmission delay in a time varying satellite uplink. Specifically, we are interested in bounding the packet transmission delay within the terminal router for uplink traffic in a future satellite network. Previous work has provided delay bounds for wireline networks with a fixed transmission rate. However, these bounds do not apply to the time-varying satellite...
Cooperative hybrid-ARQ (HARQ) protocols have been widely studied because they are more efficient than cooperative protocols without HARQ. In, the throughput of a cooperative HARQ protocol based on the decode-and-forward protocol (DF-HARQ) is obtained. In this paper, the maximum achievable throughput of the DF-HARQ protocol is obtained using the asymptotic outage probability when the maximum number...
Dynamic spectrum access can enable secondary network users to access unused spectrum, or whitespace, which is found between the transmissions of primary users in a wireless network. The main design objectives for secondary user access strategy are to be able to ??scavenge?? spatio-temporally fragmented whitespace opportunities while limiting the amount of interference caused to the primary users....
The foray of wireless sensor networks into time-sensitive applications demands support for emergency services with guaranteed quality of service (QoS) bounds. We introduced CP-EDCA, a channel preemptive enhancement to the IEEE 802.11e EDCA standard, for guaranteed emergency medium access in distributed wireless environments. The performance results for emergency traffic depicted 50% uniform decrease...
Frequency hopping provides some protection against multiple access interference in random-access ad hoc networks. Power control and the use of short routing hops can further reduce interference by promoting spatial reuse. If the network is fully connected, frequency hopping and power control alone may be sufficient to allow good throughput without the use of routing. This approach is particularly...
We present a complete scenario driven component based analytic model of 802.11 MAC and OLSR routing protocols in MANETs. We use this model to provide a systematic approach to study the network performance and cross-layer analysis and design of routing, scheduling, MAC and PHY layer protocols. The routing protocol is divided into multiple components. Componentization is a standard methodology for analysis...
One of the major QoS goals for future battlefield networks (FBN) is to ensure multi-level precedence and preemption (MLPP). Ensuring MLPP is difficult, partly due to the networking architecture for FBN which consists of wired ??red?? network connected by encrypted wireless ??black?? network. The security requirements for FBN do not allow passing information from black to red networks. So when congestion...
In this paper a communication system operating over a Gilbert-Elliot channel is studied. The goal of the transmitter is to maximize the number of successfully transmitted bits. This is achieved by choosing among three possible actions: (i) betting aggressively by using a weak code that allows the transmission of a high number of bits but provides no protection against a bad channel, (ii) betting conservatively...
For wireless sensor networks (WSN) involved in geographical surveillance type applications, obtaining information from a specified region of interest is important. The information itself is dependent upon the application type specific sensors deployed within the network region. For the purpose of this study we propose a new routing protocol called swarm intelligent odour based routing (SWOB) that...
We study the use of node cooperation as a way to improve performance in multiple-source, single-destination wireless networks that use scheduled access as the channel-access method. Unlike many other studies of scheduled access, which are based on the use of a collision channel, we use a physical channel model that incorporates other-user interference, fading, and background noise. The characteristics...
Opportunistic Spatial Orthogonalization (OSO), first proposed in Shen and Fitz (2009) for the single-input-multiple-output (SIMO) system, is a cognitive radio scheme that opportunistically allows the existence of secondary users even if the primary user occupies all the frequency bands all the time. On one hand, OSO can be viewed as a multi-user diversity scheme that exploits the channel randomness...
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