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We consider multi-hop decode-and-forward relaying OFDM systems in this paper. All the relay nodes are assumed to be regenerative and working in half-duplex mode. We propose adaptive power allocation (PA) algorithms to maximize the overall system capacity and minimize the system outage probability, respectively. Simulation results show that the proposed algorithms outperform the existing PA algorithms...
This paper presents multipath channel parameters acquiring from wideband Multiple-Input Multiple Output (MIMO) channel measurement at 3.705GHz carrier frequency. The wideband MIMO channel sounder was used to measure MIMO radio channel characteristics. The channel measurement campaign was performed in the Seoul rail-way station where is a representative indoor hotspot region of Korea. The measurement...
Network coding (NC) and erasure coding (EC) share a common principle of encoding incoming data packets at network intermediate nodes so that destination nodes can reconstruct the original data packets using a sufficient number of encoded data packets collected at the destinations. While NC in general reduces the number of packets sent through the network, EC introduces redundancy into the packet streams...
Mobile WiMAX's scheduling service is a key factor in Radio Resource Management (RRM) in realizing Quality of Service (QoS). The choice in scheduling algorithm for Mobile WiMAX base stations, albeit outside of the scope of the standard, critically impacts the performance and robustness of Mobile WiMAX networks. This paper provides an in-depth study of four major scheduling algorithms: Round Robin (RR),...
This article analyzes a comparison of a generic digital communication and a Time Reversal communication systems. The principles and properties of Time Reversal are presented for non-impulsive waveforms. The metrics used to characterize time focusing and the measures used for the simulations are outlined. These measures are used to illustrate how the proposed metrics vary as a function of the bandwidth...
In this paper, we investigate the use of a channel shortening filter (CSF) for multiband orthogonal frequency division multiplexing ultra wideband (MB-OFDM UWB) communication systems. Indoor wideband channels are known as rich scattering environments resulting in potentially large delay spread. When the delay spread exceeds the guard interval length, intersymbol interference (ISI) and intercarrier...
In this paper, we propose an energy-efficient error correction scheme to lower the power consumption of the ADCs in the OFDM system. The proposed opportunistic error correction scheme is based on resolution adaptive ADCs and fountain codes. The key idea is to reduce the dynamic range of the channel by discarding part of the channel in deep fading. Correspondingly, the power consumption in ADCs can...
In this paper, we design the source precoding matrices and the relay amplifying matrix of an amplify-and-forward multiuser multiple-input multiple-output (MIMO) relay communication system. The minimum mean-squared error (MSE) is taken as the design criterion. We propose an alternating technique to efficiently solve the nonconvex source and relay optimization problem. It is shown that both the optimal...
In this paper, we apply General Order Statistics (GOS) theorem to multi-antenna (MIMO) dual-hop amplify-forward fixed-gain cooperative relay network. General order link, unlike the best one, is selected for the transmission/receiving at each hop. The closed-form expressions of SNR (Signal-to-Noise-Ratio) statistics such as CDF (Cumulative Distribution Function), PDF (Probability Density Function),...
Distributed antenna system (DAS) constitutes one of the most fascinating schemes to efficiently achieve the rigorous quality of service demands of next generation wireless networks. System level simulation (SLS) approach is considered since things are too complicated to be dealt only analytically and it would not be cost-effective to deploy all the real scenario to test every feature.In this paper,...
In this paper, we derive the probability density function and cumulative distribution function of packet transmission time in a spectrum sharing system. In combination with the time-out characteristics of packets, we further study the outage probability and average transmission time under peak power interference constraint over Nakagami-m fading channel. Especially, we employ the M/G/1 queuing model...
A novel iterative localization algorithm based on Particle Filter with error control is proposed in this paper. First, each node's location is estimated by a cloud of particles and their weights. Second, Degree of Inconsistency(DoI) is proposed to detect the nodes with high error. DoI makes full use of the fact that node density is high and they are randomly and uniformly distributed. The nodes with...
In this paper we present a novel distributed coding protocol for multi-user cooperative networks. The proposed distributed coding protocol exploits the existing orthogonal space-time block codes to achieve higher diversity gain by repeating the code across time and space (available relay nodes). The achievable diversity gain depends on the number of relay nodes that can fully decode the signal from...
We consider the problem faced by a passive receiver in determining the symbol stream that has been output from a wireless transmitter array encoded as Orthogonal Space-Time Block Codes (OSTBC). An informed receiver will usually be able to perform maximum likelihood channel estimation using knowledge of a symbol training sequence embedded in the transmitted data. An uninformed receiver or eavesdropper...
This paper presents methods of spectral shaping of OFDM signals to enable spectrum sharing with other transmissions. Proposed methods are based on carrier suppression algorithms, using both windowing technique and adaptation of modulating schemes on specific subcarriers. Moreover compatibility of OFDM signals generated by asynchronous transmitters, working in adjacent bandwidth is analyzed. Simulation...
This paper proposes a novel OFDM demodulation scheme, which achieves superior performance even in fast time-varying multipath fading channels where the conventional OFDM demodulator degrades seriously because of time selectivity in the channel. The proposed scheme consists of several equalizers which equalize received signals with channel impulse responses at different time instants in parallel. A...
Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM concept that uses deterministic sequences, which we call unique words, as guard intervals instead of the conventional cyclic prefixes. Since unique words represent known sequences, they can advantageously be used for synchronization, channel estimation, but also for improving the bit error ratio (BER) behavior of a...
In this paper, we propose an iteration scheme for the virtual layered space frequency communication architecture. The architecture enables the decoding of the transmitted orthogonal frequency division multiplexing (OFDM)-QPSK signals even if the number of spatial multiplexed layers is twice that of receiving antennas over multipath fading channels. In the proposed iteration scheme, the MAP decoder...
A novel 2D Mobile-to-Mobile physical model is developed in this paper by considering the underlying physics of free space propagation. When compared to existing statistical channel models, the development and application of our new model is better in terms of complexity as it requires less parameters. In addition, the proposed new model is flexible in applying to any scattering environment whereas...
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