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Multichannel media access control (MAC) protocols can increase wireless network capacities. The rendezvous problem is the most frequently encountered challenge in developing multichannel MAC protocols. Some studies have assumed that each device is equipped with one additional antenna; however, this increases the hardware cost. Other studies have divided the timeline of each channel into several beacon...
In this paper, cognitive machine to machine (CM2M) gateway in e-healthcare systems are presented by accessing several channels via periodic sensing and spectrum handoff. An optimal energy efficient spectrum management mechanism with multiple thresholds is proposed. The developed mechanism aims to reduce energy consumption in the system by optimizing the spectrum sensing and channel switching, while...
Performing and evaluating Call Trace (CT) or also called Minimization of Drive Test (MDT) measurements entails additional expenses to the operator as well as to the users. However, by using location specific network data obtained from the measurements as additional information for self-organization procedures, we expect these procedures to perform essentially better since they can take their decisions...
In this paper a switch-stay model is proposed for spectrum access by a secondary user in the presence of a primary user, which considers the impact of spectrum handoff delay. This model is then studied to balance the trade-off between the secondary user's energy efficiency and transmission reliability in light of the probability of collision, throughput and delay constraints. Bounds on the probability...
This paper investigates cell zooming and relaying in conjunction with the use of opportunistic sleep modes to save energy at times of low load in WiMAX network deployments. It performs extensive propagation measurements in a hilly area of Covilhã, Portugal, in order to present a realistic and topographically challenging scenario in which to perform dynamic optimizations. It describes these measurements...
This paper describes an implementation of a realtime multi-user multiple-input multiple-output (MU-MIMO) communication system, with cross-layer channel-aware scheduling. The system is implemented using software reconfigurable nodes that may be configured as either user terminals, or as base stations, communicating in the GSM 1800 uplink band. Three different commonly used scheduling algorithms (based...
So far, advantages of switched beam antennas in term of signal quality enhancement for wireless communication systems have been demonstrated through computer simulations. However, the true advantages of these antenna systems cannot be reflected by computer simulations as some assumptions remain limiting factor. Therefore, this paper shows the true performance of switched beam antennas under real circumstances...
In this paper, the antenna switching scheme is proposed for Time Switched Transmit Diversity (TSTD) with ARQ (automatic repeat request) in WCDMA LCR-TDD systems, and the system performances are also investigated. The proposed TSTD system employs the ARQ scheme in which the receiver sends the acknowledgement signal (ACK or NACK) to the transmitter in order to predict the condition of the channel. For...
New applications such as high-definition (HD) video streaming are driving the data rate of wireless links from hundreds of Mbps to multi Gbps. Among a few technologies that can provide such high rates, transmission in 60-GHz bands is considered as a very promising solution. In this paper, we identify key design challenges of wireless transmission in 60-GHz bands from the perspective of medium access...
In last few years, a smart antenna has been envisaged to enhance the GPRS system implementing at Base Station. This results in the problem of complexity and expense. Alternatively, this paper considers employing switched beam antenna at Mobile Station, such as Laptop, instead. The simulation results reveal that utilizing switched beam antenna provides higher performance in term of C/I and throughput...
Directional antennas in sensor networks are receiving increasing interest and research due to the potential to increase throughput and reduce delay and interference, while requiring lower transmission power. Considering the stringent operation requirements (low duty-cycle) as MAC congestion problems in large multi-hop networks, WSN performance can benefit enormously from such directional capabilities...
In this paper, we propose an adaptive technique exploiting transmission mode switching between multiple input multiple output (MIMO) and single input multiple output (SIMO) with antenna selection to conserve mobile terminals' energy. We focus on saving uplink RF transmission energy in cellular systems supporting dynamic best effort (file transfer) traffic loads. The key idea is to judiciously slow...
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