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Cognitive radio network (CRN) users are inherently expected to experience widely-varied delays due to the uncertainty in wireless channel availability. Supporting delay sensitive real-time services through CRNs, so that visitors are allowed to experience full-scale networking services by opportunistically sharing the spectrum from a number of existing networks without impacting on the primary users,...
In this paper, we propose a channel and queue aware cross-layer algorithm for allocating power and sub-carriers to users in Orthogonal Frequency Division Multiple Access (OFDMA) networks. Our algorithm uses utility to build a bridge between the physical layer and upper layers and also to balance the efficiency and fairness of the radio resource allocation. The objective is to develop a method based...
A multichannel scheduling based on an extension of modified largest weighted delay first (M-LWDF) scheduling is proposed for heterogeneous traffic. We consider the downlink of an orthogonal frequency division multiplexing (OFDM) system where the wireless channel and queue state information are taken into account to schedule delay-sensitive and ratesensitive traffic. We propose a logarithmic notion...
In this paper, we propose a QoS control mechanism that estimates the congestion of wireless channels in the wireless LAN and evaluates the voice packet drop ratio based on the estimated congestion status. The mechanism adjusts the voice packet transmission rate according to the evaluated packet loss ratio, and thereby resolves the congestion situation. In this way, the mechanism can keep users' quality...
This paper proposes a cross-layer design (CLD) framework called channel-aware buffer unit multiple access (C-BUMA) for improving wireless local area network (WLAN) performance. In the framework, the radio propagation (i.e. PHY layer) is combined with the medium access control (MAC) protocol for packet transmissions. By sharing channel information with the MAC protocol, the approach reduced unnecessary...
Seamless handoff support is an essential issue to ensure continuous communications in wireless mesh networks (WMNs). Due to the existence of multi-hop wireless links, traditional handoff schemes designed for single-hop wireless access networks can hardly guarantee the low handoff latency requirement in WMNs. Existing solutions on reducing the handoff delay in WMNs ignore one important factor for the...
The possibility of distributing data to all interested entities connected to a mobile system is a fundamental core function in future mobile ubiquitous class based applications. Unfortunately, its realization poses many problems especially due to the typically scarce resources. With the goal of enhancing scalability, this paper presents a novel data distribution infrastructure for wireless mobile...
In this paper we develop an optimized control strategy for the connection bandwidth maximization over a time varying wireless channel, by jointly controlling the adaptive source rate and the client/playout buffering policy with constraints on the maximum connection bandwidth allowed at the Application (APP) layer, the queue-capacities available at the DataLink (DL) layer and the average and peak transmit...
The design and deployment of efficient vehicle-to-vehicle (V2V) communications systems require the knowledge of the propagation channel in which it will operate. Due to the mobility of the transmitter/receiver terminals as well as the existence of dynamic scatterers, the V2V channel is nonstationary. To account for the nonstationarity, channel characterization methods that employs the non wide-sense...
Recent advances in wireless data networks have opened many new applications including wireless monitoring and control of industrial environment. This paper presents the results of a study on the deployment of wireless network for monitoring and control in SABIC Al-Hadeed Steel Plant. Wireless channel characterization and technology evaluation are the two most critical issues in the design of wireless...
Forward error correction (FEC) is one popular error control technique to protect the video bitstream by encoding the redundancies to recover the source information errors/losses. However, the FEC redundancy trades additional bandwidth consumption to protect video data, and therefore the wireless channel properties such as burst errors and limited bandwidth impair the FEC efficiency. In this paper,...
Video smoothing techniques can be used to facilitate more effective transmission and to preserve better video quality. In this paper we develop a semi-optimal video smoothing approach to manage the transmission rates of MPEG-4 and H.264 video over a QoS-based wireless LTE network. The proposed technique utilizes a smoothing buffer with pre-defined thresholds to smooth the transmission rates while...
We derive closed form expressions for the second-order statistics of the spectral power gain of wide-band microwave indoor channels. We obtain our results within a framework general enough to be compatible with several popular channel models, such as those proposed by the IEEE 802.15.3a task group, as well as the Saleh-Valenzuela channel model. As all these models, our channel description is based...
A hierarchical routing concept with key enabling mechanisms: hierarchical neighbor and route discovery, network optimization and service discovery, are provided and evaluated in this paper. The hierarchical routing concept is novel in the sense that both physical neighbors and logical neighbors are discovered to optimize the route and service discovery process as well as enable optimization of the...
In this paper, we present AEROMAN (Architecture to Evaluate Routing Protocols for Multi-hop Ad-hoc Networks) which is designed and implemented for evaluation of routing protocols for multi-hop wireless networks. AEROMAN uses QOMET, a wireless link emulation tool, to compute parameters of wireless links, such as bandwidth, delay, packet loss rate, in contention-free conditions. In order to take into...
In this paper, wideband channel sounding for inter-level communication on board a ship have been presented. From the obtained power delay profiles for different transmitter to receiver separations, two main clusters of signals have been identified. The direct path penetrating through the ceiling and floor board of each level is the dominant signal within cluster 1. The large number of multipath signals...
Current Internet protocols like TCP have been designed to work well on channels with low channel error rates. Wireless channels on the other hand exhibit high loss rates when compared to wired channels. Current TCP implementations usually attribute packet losses caused by channel errors as being actually caused by congestion. The result is an unnecessary reduction of the sending rate which leads to...
Packet schedule is effective to improve the quality of video streaming over time-varying wireless ad-hoc networks. In this paper, we propose a time-constrained packet scheduling algorithm, which minimizes the video distortion by allocating transmission opportunities to packets under the constraint of playback delay. The problem is formulated in a constrained convex optimization framework and solved...
This report describes results from 60 GHz channel measurements and modelling in a shielded room. Final goal of this work is to investigate potential and feasibility of 60 GHz radios for very-high-data-rate short-range communications in medical applications. The measurement in a shielded room is meaningful for studying propagation characteristics in medical applications, since real surgery rooms are...
This paper presents the results of an empirical study of wireless propagation channels for vehicle-to-vehicle communications in street intersections, a scenario especially important for collision avoidance applications. The results are derived from a channel measurement campaign performed at 5.6 GHz in four different types of urban intersections. We present results on typical power delay profiles,...
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