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One of the crucial challenges in practical wireless networks is how to provide robust communication over fading channels. Recently, cooperative communications have emerged as a promising approach to achieve spatial diversity and thereby reduce the negative effects of fading on wireless channels. Nevertheless, a few existing works indicate that deploying cooperative relays in large-scale wireless networks...
Dynamic spectrum access has become a promising technique to fully utilize the scarce spectrum resources. However, spectrum allocation schemes with high efficiency and Quality of Service (QoS) guarantee for the primary users have yet to be designed. In this paper, two novel dynamic spectrum access schemes are proposed. The proposed schemes are based on continuous-time Markov chains (CTMC), through...
Several underwater network characteristics, including long propagation delays and a bandwidth dependent on distance, provide unique challenges to protocol designers. In this paper we present STUMP-WR, a distributed routing and channel scheduling protocol, designed for heavily loaded underwater networks. STUMP-WR selects and schedules links using a distributed algorithm to overlap communications by...
Intermittently Connected Wireless Networks (ICWN) or Delay/Disruption Tolerant Networks (DTN), have attracted attention from researchers because of their inherent characteristics, including long latency, low data rate, and intermittent connectivity. Extensive research has been conducted on ICWN, including the architecture, and routing. However, few researchers have investigated the performance of...
Random access is critical to OFDMA wireless networks. However, due to special features of an OFDMA system, how to carry out random access in an efficient manner is still an open issue for OFDMA wireless networks. In this paper, a new random access protocol is proposed for OFDMA wireless networks. It is distinguished by a novel mechanism called concurrent multi-channel carrier sense multiple access...
Existing scheduling schemes for real-time wireless video services generally focus on system throughput or delay, and do not take into account the relationship between the transmission delay and video distortion. In this paper, we develop and evaluate a delay-distortion-aware wireless video scheduling scheme in the framework of cross-layer information adaptation. At first, we construct a general video...
We consider a wireless multi-hop network with sources that are Poisson distributed and relays which are placed on the source-destination line. Given a combined TDMA/ALOHA MAC protocol, we explore the following question of optimal spatial reuse: Increasing the number of nodes that are simultaneously scheduled to transmit in a route allows nodes to transmit more often. At the same time, it results in...
In this paper, we study the problem of transmission power control and its effects on the link-scheduling performance when a set of end-to-end flows established in the network are given. This problem is approached by means of the stability region of the link-scheduling policy. The stability region is defined for link-scheduling policies as the set of input-packet rates under which the queues in the...
In recent years, along with the increasing popularity of multi-hop wireless networks, there has been a growing demand in the coupling of these networks to external ones such as the Internet. As traffic destined for external networks increases, special attention is required not only in gateway selection, but also in optimized routing and scheduling in order to maximize the network performance. In this...
Wireless communications over water may suffer from serious multipath fading due to strong specular reflections from conducting water surfaces. Cognitive radios enable dynamic spectrum access over a large frequency range, which can be used to mitigate this problem. In this paper, we study how to leverage cognitive radios for effective communications in wireless networks over water. We formally define...
Cognitive radios (CR) and cooperative communications represent new paradigms that both can effectively improve the spectrum efficiency of future wireless networks. In this paper, we investigate the problem of cooperative relay in CR networks for further improved network performance. The objective is to provide an analysis for the comparison of two representative cooperative relay strategies, decode...
In this paper, we study two fundamental issues of cooperative communications in distributed wireless networks, namely when to cooperate and whom to cooperate with. In specific, we focus on cross-layer medium access control (MAC) protocol design with beneficial node cooperation. To increase long-term network throughput, we propose an optimal grouping strategy for relay node selection, and devise a...
In a cognitive radio network, the full-spectrum is usually divided into multiple channels. However, due to the hardware and energy constraints, a cognitive user (also called secondary user) may not be able to sense two or more channels simultaneously. As different channels may have different primary user activities and time-varying channel qualities, an important task is to select which channels to...
In multihop wireless networks, end-to-end throughput is often hard to predict and is even harder to optimize due to the effect of interference. To date there is no precise result other than asymptotic bounds for this question: if there is no routing information given, what is the maximum throughput of a network using uncoordinated transmission such as IEEE 802.11 MAC? This paper attempts to address...
Heterogeneous wireless network (HWN) technology has emerged as an important option for the next generation mobile network, where mobile client (MC) are capable of simultaneously connecting to multiple access networks for better quality of services (QoS) at a lower cost. Different from a conventional HWN that uses a single connection and performs vertical handover, we observe the performance of MCs...
Relaying is a well known technique to extend coverage and improve conditions for nodes in the outer coverage region. In this paper we propose a relaying scheme that exploits the spatial separation of relay and destination pairs to improve throughput by allowing simultaneous transmissions. The proposed scheme is a cross-layer optimization for two-hop relaying that uses position information to jointly...
Wireless network operation intrinsically assumes different forms of cooperation among the network nodes, such as sharing a common wireless medium without interfering, relaying frames belonging to other nodes, controlling the transmission power for optimizing spectrum reuse, coding cooperatively multiple frames for improving information redundancy, and so on. For this reason, Game Theory has been extensively...
RFID technology is regarded as a bridge between the physical object world and the virtual digital space. In recent years, RFID system is pervading our daily life. In the RFID system, energy consumed by the reader and tags during tag identifier collection is becoming a key issue that affects the performance of the system, especially for the mobile RFID systems. In this paper, the energy consumed by...
In this paper, we propose a new quality link metric, interference and bandwidth adjusted ETX (IBETX) for wireless multi-hop networks. As MAC layer affects the link performance and consequently the route quality, the metric therefore, tackles the issue by achieving twofold MAC-awareness. Firstly, interference is calculated using cross-layered approach by sending probes to MAC layer. Secondly, the nominal...
Atmospheric scattering for ultraviolet signals enables non-line-of-sight communication of a transmitter-receiver pair on-the-move and adaptive network configuration. In this work, we first develop an experimentally validated path loss model which characterizes both multiple scattering and arbitrary pointing with noncoplanar geometry. Then we discuss how to achieve full duplexing. We suggest transmission...
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