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We present analytical tools for evaluating the performance of Reed-Solomon (RS) codes concatenated to a discrete communications system (DCS), based on the IEEE 802.11 standard, with OFDM modulation and frequency-selective fading channel. The main ideia is to model de DCS with a finite state Markov channel, more specifically the Gilbert-Elliott channel (GEC) in order to represent the successes and...
We propose a multi-band OFDM modulation for wireless VLC system together with dynamic bandwidth allocation. In addition, the proposed modulation format also can enhance the maximum VLC traffic rate to 17.8% without using blue filter.
In this reported work, the frequency diverse array concept is employed to construct an orthogonal frequency-division multiplexing (OFDM) transmitter that has the capability of securing wireless communication in free space directly in the physical-layer without the need for mathematical encryption. The characteristics of the proposed scheme in terms of its secrecy performance are validated via bit...
This work presents the system performance analysis of 2×2 space-time block code (STBC) for DFT-spread polarization division multiplexing (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems (2×2 STBC DFT-spread PDM-CO-OFDM). The optical channel impairments of random phase noise (RPN), chromatic dispersion (CD), polarization mode dispersion (PMD) and polarization dependent...
This paper presents a simple relay selection algorithm in multiuser orthogonal frequency-division multiplexing (MU-OFDM) cooperative Cognitive Radio (CR) networks to enhance normalized sum capacity of secondary users (SUs). After simplifying three node relay network to its equivalent two node network with equivalent gain on each subcarrier, a simple method for relay selection is used which considers...
This paper proposes a cooperation system jointing LDPC codes and OFDM modulation. Its principle is given in detail that the signal is encoded by LDPC and modulated with OFDM, moreover, transmit diversity is created when the relay station assists a sender by retransmitting its information signal to the destination. Furthermore, several simulation results are presented to validate the proposed approach...
In this paper, we formulate an optimization problem for resource allocation and scheduling in orthogonal frequency division multiple access (OFDMA) half-duplex decode-and-forward (DF) relay assisted networks. Our problem formulation takes into account artificial noise generation to combat a multiple antenna eavesdropper. The secrecy data rate, power, and sub-carrier allocation policies are optimized...
This paper presents the performance comparison of Single Carrier Frequency Division Multiple Access-Code Division Multiple Access (SC-FDMA-CDMA) and Orthogonal Frequency Division Multiplexing-Code Division Multiple Access (OFDM-CDMA) systems for uplink. We investigate the basic principle and the similarities and differences of these different schemes. According to these schemes, we discuss the performance...
Adaptive bit-loading algorithms can improve the performance of OFDM systems significantly. The tradeoff between the algorithms performance (optimum solution) and the computational complexity is essential for implementation of loading algorithms. In this paper, we present a low complexity non-iterative discrete bit-loading algorithm to maximize the data rate subject to specified target BER and uniform...
In this paper, a new trend of Space Time Block codes-Orthogonal Frequency Division Multiplexing (STBC-OFDM) with Convolutional and Turbo codes. The applied method is based on Alamouti's scheme. We examine the performance of two, three and four transmitters with one receiver over Nakagami-m fading channel using convolutional and turbo codes using different types of modulation such as BPSK and 64-QAM...
This survey examines the bandwidth efficiency of wireless signals, beginning with a review of the Shannon capacity and of the important differences between signal to noise ratio (snr) and individual bit energy to noise density (IBEND = Eb/N0). Recognizing that communication systems are successful only if they are profitable, value propositions that have been realized along the evolution of adopted...
In this study, we analyze the role of interleavers in OFDMA system for ensuring uniform BER performance amongst the active users and also investigate their respective PAPR properties. At first considering a generic system in a slowly changing multipath channel where high dispersion in the individual users performance exists, we apply different types of interleaving and show that they in general help...
In underwater acoustic sensor networks, the solution to augment sensor nodes' life time is crucial due to the difficulties in retrieving discharged sensor nodes. Thus, many energy efficient MAC protocols have employed mainly logical ways, such as sleep mode, hand-shaking signaling between nodes, and scheduling of transmission time, rarely using the physical characteristics of underwater acoustic channels...
There are characteristics of high noise, big attenuation, the big impedance variation and the uneven frequency response on low-voltage power line channel. Firstly, this paper proposes the combination the adaptive technology with the OFDM technology to realize the reliable and high-speed data transmission channel. It is a key to study the channel estimation of the OFDM technology and the channel allocation...
Femtocells are a promising solution for the provision of high indoor coverage and capacity. Furthermore, OFDMA-based femtocells have proven to be highly versatile when dealing with cross-layer co-channel interference; however, concerns still exist related to the impact of the different access methods to femtocells in an overlaid network. Femtocells based on a Closed Subscribers group, where only device...
Time varying channel breaks the orthogonality between the subcarriers of Orthogonal Frequency Domain Multiplexing (OFDM). This introduces Intercarrier Interference (ICI). One of the ways to mitigate ICI is to first estimate the channel and then equalize it. In this paper we propose to estimate the channel using Discrete Proplate Spheroidal Sequences (DPS) using pilot carriers interleaved with data...
This paper presents a joint timing and carrier frequency offset estimation scheme for Orthogonal Frequency Division Multiplexing (OFDM) over an Additive White Gaussian Noise (AWGN) channel, flat fading and frequency selective fading (Rayleigh channel). Estimating the correct Carrier frequency offset (CFO) minimizes the inter carrier interference (ICI). Orthogonality is maintained by using Maximum...
The problem of blind channel estimation in Multiple-Input-Multiple-Output (MIMO) Orthogonal Frequency-Division Multiplexing (OFDM) systems is investigated in this study, assuming that the transmitted symbols are independent and identically distributed. In particular, by utilizing a generalized linear non-redundant precoder, a simple blind channel estimation technique for MIMO-OFDM systems is developed...
The effect of a power amplifier nonlinearity on multi-antenna orthogonal frequency division multiplexing (OFDM) transmitters utilizing subcarrier beamforming is investigated. Theoretical analysis and simulation shows that such systems can exhibit significant performance degradation due to the power amplifier nonlinearity when there are channel state feedback errors. The SINR degradation under solely...
In this paper, we propose a novel two-stage detection framework to facilitate the coexistence detection for OFDM-based 60-GHz millimeter-wave (MMW) WLAN/WPAN. Either blind or non-blind detection scheme can be employed at both stages regarding practical concerns. Here, the “non-blind” only refers to the case that relies on the prior knowledge of the noise variance. On the other hand, the blind detection...
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