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802.11e HCCA (Hybrid coordination function Controlled Channel Access) exhibits good QoS provisioning for constant bit rate (CBR) video streams in a single collision domain. However, its performance degrades significantly for variable bit rate (VBR) video streams particularly in multi-collision domains. In addition, HCCA has the disadvantage of high complexity. In this paper, we introduce a deterministic...
This paper proposes a space-time statistical geometric model for characterization of multipath propagation of the satellite communication, which provides some insight into the spatial properties of wideband channels. The Closed-form explicit expressions of the probability density functions (pdf) of the time of arrival (TOA) for multipath signals and the power delay profile according to the various...
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...
In this paper, we present a patent-pending type-based equalization technique to deal with non-constant group delay response commonly existing in analog/RF circuit of a communication system. Its underlying principle is that, given a modulation scheme and pulse-shaping and/or channel filter, the modulated signal has a unique statistical distribution, and any impairment in the analog/RF circuit distorts...
We show that the common approach to channel and Time-of-Arrival (ToA) estimation for Impulse-Radio Ultra WideBand (IR-UWB), where the occurrence of pulse overlap is ignored, is bound to lead to considerable estimation errors in the presence of pulse overlap. We propose the use of a low-complexity extension of the sliding correlator as a Maximum Likelihood (ML) channel estimation method that can deal...
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,...
This paper deals with relaying techniques in WiMAX communication system. Different cooperative and non-cooperative schemes are investigated and compared over a complete 802.16 WiMAX-OFDM chain. Realistic channel impulse responses are used. Measurement of some propagation conditions feeds the WINNER channel model in order to generate the channel coefficients belonging to different links. Besides, real...
Wireless infrastructure networks that provide ubiquitous connectivity to mobile nodes in metro areas are becoming increasingly popular. The nodes in such backbone networks are often equipped with multiple transceivers to allow for simultaneous transmissions in multiple non-overlapping channels. In this paper, we develop an analytical model for evaluating the throughput and delay performance of wireless...
The use of unlicensed bands, e.g., ISM (industrial, science and medical) bands is getting more and more attention nowadays due to the high scarcity and high costs of radio spectrum. Due to this, there is a high risk of interference, which degrades the performance and fails to support Quality of Service (QoS) for systems operating in these bands. Therefore, spectrum sharing between coexisting competing...
Remote patient monitoring (RPM) provides an efficient method to improve patient care in hospitals. Zigbee network technology with low-power consuming sensors has the capability to provide enhanced mobility and comfort to patients. A single Zigbee based sensor network is unable supporting all the patients on a general ward. The allocation of a ZigBee sensor network to each patient can address this...
This paper presents a new approach for a joint optimization of beamforming and temporal user scheduling for intercell interference mitigation in a multiuser multicell scenario using statistical channel knowledge. In general, the resource allocation problem considers two optimization criterions: fairness among the users in the network and a maximized sum rate of all users. The first one is achieved...
VoIP offers cheap voice communication which instigated its quick market growth. IEEE 802.11 WLANs offer cheap wireless coverage which can be used to provide VoIP service in mobile devices. But call capacity of such networks is very low compared to wired networks. To increase voice capacity in WLANs incorporation of power capture, increased data rate, and use of multiple channels are of great importance...
In this paper, a new reliable cooperative MAC protocol, which can enhance the system throughput under bad wireless channel environments, is proposed, and the protocol's performance is evaluated with a computer simulation. The system throughput and average delay, except queuing delay, are used as performance metrics. The numerical results show that the scheme proposed in this paper provides 24 more...
Underwater Acoustic Sensor Networks (UW-ASNs) is of growing research interest. This paper gives description on underwater channel model. It overviews transmission schemes in data link layer and network layer, and simulates different transmission schemes. Finally, it offers comparison and guides for future development.
In wireless cooperative networks, the asynchronism between the relays can be a source of diversity which is similar in its essence to the multipath diversity of frequency selective channels. In this context, an asynchronous two-relay cooperative wireless network using the Decode-and-Forward protocol is studied. Two strategies for relay coding are studied: independent coding and repetition coding....
The advent of efficient video compression algorithms and the increase in the data-rate handling capabilities of wireless standards facilitate multimedia streaming over wireless networks. The Quality of Service (QoS) of this application heavily depends on the number of lost packets and the end-to-end delay. Various studies have proposed solutions and analysis on the bandwidth constraints, but too little...
Due to their diverse applications, ad hoc networks are appealing for use in many domains. However, their features of open medium, absence of infrastructure, dynamic changing network topology, cooperative algorithms, lack of centralized monitoring and management point, resource constraints and lack of a clear line of defense, they are vulnerable to many attacks. Therefore, there is a major concern...
Dedicated WiMAX multimedia services are proposed for areas that lack networked infrastructure. This paper proposes multi-connection uplink video streaming for mobile WiMAX. Establishing multiple TFRC connections for a single video stream has emerged as a promising lightweight way of coping with wireless channel losses in a congestion-controlled tandem network. This study shows the impact (in terms...
This paper proposes a heartbeat radio access protocol for a mobile ad-hoc network based on a random access protocol using a high-throughput and stable single-channel Q-ary free-access collision resolution algorithm. We provide an analytical derivation of the performance of this free-access collision resolution algorithm in the presence of feedback channel errors that may be present in the mobile radio...
This paper considers network control for wireless networks with finite buffers. We investigate the performance of joint flow control, routing, and scheduling algorithms which achieve high network utility and deterministically bounded backlogs inside the network. Our algorithms guarantee that buffers inside the network never overflow. We study the tradeoff between buffer size and network utility and...
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