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Streaming degradable content (such as video or audio) over a wireless channel presents new challenges to modern digital design, which was founded on the separation theorem of Shannon theory. Joint source-channel coding (JSCC) has recently received increasing interest to address the varying nature of the wireless channel conditions (under mobility or multicast). The conventional approach to JSCC which...
The IEEE 802.16 standard for broadband wireless access is a low cost solution for Internetaccess in metropolitan and rural areas. Although it defines five service levels to support real-time and bandwidth demanding applications, scheduling mechanisms are not specified in the standard. Due to the wireless channel variability, scheduling mechanisms widely studied for wired networks are not suitable...
Dual feedback control algorithm has proved to allow the base station to respond quickly and efficiently to the uplink bandwidth request in broadband wireless access (BWA) networks. In this algorithm the bandwidth request is calculated based on both the length of the backlogged queue and the mismatch between packet arrival and service rates. However, the physical channel quality, SNR, does not play...
60 GHz technology has been proposed recently for multi-Giga-bit/s access within different application scenarios, e.g. in crowded multi-user public transportation (PT) environments. Hence, channel sounders that are used to investigate multipath propagation and multi-user access techniques including spatial diversity and beam-forming in time-variant shadowing environments require ultra-wideband (UWB)...
Accurate Localization has gained significant interest within sensor networks recently and positioning systems based on Ultra-Wideband (UWB) technology have been considered, because the UWB signals have a very good accuracy due to the high time resolution (large bandwidth). Time of Arrival (TOA) estimation of the first path is usually used for range-based localization in realistic environments within...
To overcome the problem that the transmission rate of a multicast channel is limited by the user with the worst channel quality, which causes the total system throughput to be low, the use of both multicast and unicast channels for multicast service is considered in this paper. Unicast channels, in addition to a multicast channel, are allocated to users with signal-to-noise ratios (SNRs) lower than...
This paper focuses on the experimental aspect of short range communication between a moving vehicle and a stationary receiver. The accumulated measurements of signal to noise ratio fit a single line of site model rather well with the implication that the communications channel will function best as the distance between the radios is reduced. However, measurements of both bandwidth and packet loss...
Frequency-domain scheduling and rate adaptation enable next generation wireless cellular systems such as Long Term Evolution (LTE) to achieve significantly higher downlink throughput. LTE assigns subcarriers in chunks, called physical resource blocks (PRBs), to users to reduce control signaling overhead. To reduce the enormous feedback overhead, the channel quality indicator (CQI) report that is used...
In this paper, we consider a simple loading algorithm for Orthogonal Frequency Division Multiplexing systems in WLAN for signal spectrum optimization. The algorithm is based on the margin adaptive loading criterion and its performance over 5GHz indoor wireless channels.
In this paper, we consider a modulation scheme for a network-coded bi-directional relaying (CBR) scheme in which two different signals from mutually communicating nodes are network-coded in the relay node. It employs dual constellations as a useful means of dealing with its performance degradation in the CBR over asymmetric channel (i.e., the different signal-to-noise ratio in each link), which provide...
In this paper, we propose a joint link-adaptation and traffic control algorithm that efficiently allocates network resources to support multiple scalable video users over a capacity constrained wireless channel. Multi-rate networks, such as IEEE 802.16 or IEEE 802.11 use a link adaptation mechanism in the physical layer (PHY) and adjust the coding and modulation schemes to maintain the reliability...
In this article, we address the problem concerning the incremental construction of peer-to-peer network adopted for the distribution of multimedia contents transmitted by a single source node on asymmetric channels through an infrastructure of access points. In this paper we are introducing new algorithms based on peer-to-peer algorithm presented by G. Mazzini and R. Rovatti (2008) and compare them...
In this paper we derive closed-form expressions for the single-user capacity of selection combining diversity (SCD) system, taking into account the effect of imperfect channel estimation at the receiver. The channel considered is a slowly varying spatially independent flat Rayleigh fading channel. The complex channel estimate and the actual channel are modelled as jointly Gaussian random variables...
In a wireless regional area network (WRAN), the presence of wireless microphone (WM) signals must be detected as primary users. However, very narrow bandwidth and low power makes it difficult to sense WM signals especially when these WM signals are distributed in a wideband spectrum. In this paper, a singular value decomposition (SVD)-based approach is presented to sense and estimate multiple WM signals...
This paper proposes a decentralized adaptive soft frequency reuse scheme for the uplink of 4G long-term evolution (LTE) systems. While universal frequency reuse (UFR) is being targeted for next generation multi-cellular wireless networks, ongoing efforts supporting the LTE standard have proved that actual implementations of UFR in LTE lead to unacceptable interference levels experienced by user equipments...
Cooperation of wireless users is known to provide substantial improvements in channel reliability and in end-to-end distortion. User cooperation is especially attractive for multicast since the relays are also part of the intended recipients. In this paper, we consider a randomized distributed cooperation scheme for multicasting a source signal. Using end-to-end distortion as a performance metric...
Spectrum allocation within the fixed unlicensed band affects performance of wireless networks. Fundamental limitations of spectral efficiency on capacity of wireless local area networks (WLANs) hence needs to be studied. Recently, it was shown that the performance can be increased when both non-overlapping and partially overlapping channels are used. Unlike previous studies, this is the first known...
An OFDM system optimization for satellite communication in Ka band is estimated in terms of the Shannon theory. The analysis covers a novel closed-form expression for the optimal subcarriers, with respect to the maximization of the achieved spectral efficiency, expressed in terms of the theoretically Shannon channel capacity available to each system's user.
In this paper, we consider stationary time- and frequency-selective MIMO channels. No channel knowledge neither at the transmitter nor at the receiver is assumed to be available. We investigate the capacity behavior of these doubly selective channels as a function of one of the system parameters, the number of transmit antennas and channel parameters as delay spread, Doppler bandwidth and channel...
Orthogonal Frequency Division Multiple Access (OFDMA) is a promising technique which can provide high capacity in the wireless environments. Also cooperative communications are effectively used to achieve cooperative diversity for high reliability. In this paper, we propose the pair-based OFDMA frame structure in which cooperative users transmit their blocks in turns for achieving cooperative diversity...
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