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Resource allocation in Wireless Sensor Networks (WSNs) is certainly a challenging issue. WSNs are characterized by special features, like energy constraints and limited computing resources. Latest trends define that sensors should be able to provide Quality of Service (QoS) demanding data transmission. A modern approach in bandwidth sharing considers both the packet queue load as well as the traffic...
In this work, a cognitive cooperative communication protocol is proposed for cognitive ad-hoc networks, in which primary users and cognitive radio (CR) users may cooperate for mutual benefit. The new cooperation protocol allows active cooperation between primary users and CR users in which CR users assist to relay primary users' signals in exchange for some spectrum released from the primary users...
In this work we propose fully differential current-mode polyquaternary signaling transmitter for high-speed data transmission over chip-to-chip interconnect. Polyquaternary signaling is a bandwidth efficient signaling scheme suitable for bandwidth constrained and crosstalk prone chip-to-chip interconnect. Basic polyquaternary precoding scheme is adopted for symbol-by-symbol transmission which requires...
Deadline-driven bulk data transfers frequently occur in overlay networks running data-intensive, distributed workflow applications, such as grid and cloud environments. What distinguishes such transfers from other Internet traffic is that overlay nodes should cooperate towards the common goal of delivering all inter-dependent data timely, rather than follow individual, selfish goals. For such scenarios,...
The packet transmission rate (PTR) algorithm is an active probing algorithm, which sends several probing packets to detect background traffic. The PTR algorithm compares the time interval at the source with that of destination, and uses the time interval to estimate the available bandwidth. But the PTR algorithm cannot consider the instability of the background traffic and the losses of the probing...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
We propose a novel distributed cross-layer optimization approach for cognitive radio wireless networks. A cognitive radio is a wireless device that is capable of sensing the prevailing environmental conditions and automatically adapting its operating parameters in order to enhance the performance of both the system and potentially the whole network. Given the lack of a centralized intelligence to...
Underwater acoustic channel (UACh) requires robust techniques to get high speed data transmission for reliable communication. This paper presents the adaptive transmission technique in conjunction with the maximal ratio combining (MRC) diversity technique to adapt the UACh fluctuation based on a statistical channel model. Simulation analysis shows that we can optimize the data rate allowing the transmit...
Some communication applications, like multimedia, deliver data of different importance classes allowing unequal error protection (UEP) levels. In this paper, a multiple-input multiple-output (MIMO) system using orthogonal frequency division multiplexing (OFDM) is considered with a new UEP bit-loading algorithm based on the non-UEP algorithm by Chow, Cioffi, and Bingham. In the proposed bit-loading...
More and more users subscribing to wireless broadband services are seeking to have access to both WLAN and UMTS networks. We study individually optimal user-network association in an integrated WLAN and UMTS hybrid cell. The association problem is formulated within a non-cooperative game framework. In the formulation, mobile arrivals are assumed to follow the Poisson process and each mobile considers...
We designed and built a novel all-optical re-timing, re-amplifying, and re-shaping (3R) regeneration system based on terahertz optical asymmetric demultiplexers (TOADs) developed in our laboratory. The system is capable of parallel processing multiple wavelengths, a feature which will significantly improve the scalability of current wavelength division multiplexing (WDM) networks. Performance against...
In conventional optical data transmission schemes, electrical filters and/or optical filters are used to improve the quality of system performance. In this paper, improved design of dense wavelength division multiplexing (DWDM) optical systems is achieved by using a selective electrical filter assignment method. The methodology objective is to optimize system design and mitigate the effects of fiber...
Optical communication systems based on dense wavelength division multiplexing (DWDM) would benefit from the ability to adjust the operating wavelength of a laser transmitter. Previous attempts, including thermal adjustment, etalon based wavelength locking, and various types of optical frequency and phase locked loops such as the Pound-Drever-Hall technique suffer from weaknesses including sensitivity...
The next generation of wireless networks (4G) will use OFDMA (Orthogonal Frequency Division Multiple Access) in the reverse link. In OFDMA, the reverse link resources assigned to a user are called tiles each of which consists of a subset of consecutive subcarriers. Since at most one user is assigned to each of these tiles then reverse link transmissions within a sector are orthogonal. However, the...
This paper investigates the effective gain of antennas in indoor channels. A metric called instantaneous effective gain is proposed, and a multiple-cluster 3D channel model is used to facilitate the proposed antenna effective gain. In the multiple-cluster channel model, Laplacian and double exponential distribution are utilized to model azimuth and elevation signal power distribution respectively,...
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