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In this paper we consider the problem of maximum-likelihood decoding of a coded orthogonal frequency-division multiplexing (OFDM) transmission plagued by the presence of narrowband interference. The presence of NBI characterizes many practical contexts, including cellular applications and emerging spectrum sharing systems, where coexistence of different types of wireless services over the same frequency...
Considering the growing demand for high-rate data services, the capacity of optical fibers has to be exploited close to its theoretical limit. In addition to techniques mitigating dispersions, coherent detection and polarization multiplexing (PolMUX) as well as forward error correction (FEC) using high-rate block codes are already applied. However, to approach channel capacity, multi-level signaling...
In this paper, we propose a new PAPR reduction using the hybrid of a partial transmit sequences (PTS) and cascade adaptive peak power reduction (CAPPR) methods with genetic algorithm (GA). These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large peak to average...
In this paper, we aim to maximize the sum rate of an Orthogonal Frequency Division Multiplexing (OFDM) system with a relay. The relay is half-duplex, and capable of decoding the message on a particular subcarrier in one time slot, and re-encoding and forwarding it on a different subcarrier in the next time slot. When the relay is active, the destination combines the signals from the source and the...
In a recent contribution, assuming pilot-only based channel estimation, we proposed an improved receiver which reduces the impact of channel uncertainty on the decoder performance. Here, we focus on semi-blind channel estimation based on expectation-maximization (EM) algorithm and propose an improved receiver design by an appropriate use of the channel estimation error statistics. This is done by...
In this paper we propose a progressive receiver for orthogonal-frequency-division-multiplexing (OFDM) transmission over time-varying underwater acoustic (UWA) channels. The progressive receiver is in nature an iterative receiver. However, it distinguishes itself from existing iterative receivers in that the system model for channel estimation and data detection is itself continually updated during...
Significant progress has been made recently on the use of multicarrier modulation in the form of orthogonal frequency division multiplexing (OFDM) for high data rate underwater acoustic communications. In this paper, we present implementation results of OFDM acoustic modems under both single-input single-output and multi-input multi-output (two transmitters and two receivers) settings. The data rates...
This paper investigates Orthogonal Frequency- Division Multiplexing (OFDM) transmission in intensity modulated, direct-detected (IM/DD) optical systems. Due to the unipolarity of the IM/DD optical channel, DC biasing and associated nonlinear clipping distortion (NLCD) is inevitable, unless an anti-periodic signal is created by limiting bit loading to only half of the available bandwidth. To generalize...
In mobile multiple-input multiple-output (MIMO) - orthogonal frequency division multiplexing (OFDM) communication systems, inter-carrier interference (ICI) and inter-antenna interference (IAI) are two crucial factors that can significantly affect detection performance. Conventionally, ICI and IAI are handled sequentially by ICI mitigation and MIMO detection. This paper proposes a novel iterative receiver...
Iterative Decision Directed Channel Estimation (DDCE) scheme is proposed in this paper for bit interleaved coded modulation (BICM)-based MIMO-OFDM systems. The proposed scheme employs Variable Step Size Normalized Least Mean Square (VSSNLMS) algorithm to implement its temporary Channel Transfer Function (CTF) Estimator and Adaptive Channel Impulse Response (CIR) predictor modules, while Fast Data...
This paper presents a low-complexity/low-latency algorithm for estimating and tracking time-varying fading channels in Orthogonal Frequency Division Multiplexing (OFDM) systems. More specifically, it is described a decision directed (DD) channel estimation (CE) method, consisting of two main steps: 1) Data detection of the current received OFDM symbol is performed by using the channel coefficients...
In this paper, we aim to maximize the weighted sum rate of Orthogonal Frequency Division Multiplexing (OFDM) relaying systems. In the considered system we jointly optimize subcarrier pairing in two consecutive time slots and power allocation on each subcarrier in each time slot. In addition, the destination combines the signals from the source and the relay pertaining to the same message in each two...
An iterative receiver for a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system is considered to jointly decode the transmitted bits and estimate the channel state. The receiver consists of the a posteriori probability (APP) algorithm, the repeat-accumulate (RA) decoder, and the least-squares (LS) channel estimator. An obvious problem, with more than two...
We consider a multi-source mesh network of static access points wherein sources use decode-and-forward to cooperate with each other. All transmissions use orthogonal frequency division multiplexing (OFDM). Our objective is to maximize the minimum achievable rate across all flows. We find a tight upper bound on the performance of the subcarrier-based cooperation and show that selecting a single relay...
This paper proposes a novel solution to cross-layer optimization for streaming of image/video over adaptive MIMO-OFDM wireless networks. Joint source-channel coding (JSCC) that includes progressive coding and adaptive modulation/code set (MCS) is applied to a singular value decomposition (SVD)-based MIMO-OFDM transmission system. Armed with a packet error rate (PER) model that considers modulation,...
This paper presents a low-complexity multiuser MIMO detection algorithm. The MIMO receiver exploits Radial space-Division Multiple Access (RDMA) principle, by paring and scheduling the MIMO multiusers with distinguishable radial space-divisions to the receiver. By exploiting the Channel State Information (CSI) and eigenvalue analysis, the MIMO receiver can selectively deploy the Linear Minimum Mean...
In this paper, we consider a broadcast transmission from a source to multiple destinations with an OFDM-based system. In order to improve the broadcast services of a cellular system, we consider the use of relays with Dynamic Decode and Forward protocols allowing the source to ignore the existence of relays in the system. A new algorithm executed at the relay is proposed. It allows for maximizing...
This paper is focused on the study of layered space-time-frequency (LSTF) architectures with channel coding for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) multiplexing systems for high speed wireless communications over a frequency-selective fading channel. In order to achieve the available spatial, temporal and frequency diversities, and also make the...
Partial transmit sequence (PTS) is a well-known peak-to-average power ratio (PAPR) reduction scheme based on the concept of multiple candidates. In this paper, we propose multiple-candidate separation at the receiver by turbo decoding. Both blind and semi-blind methods are proposed and applied to both the phase-rotation-based PTS scheme and cyclical-shift-based PTS scheme. The blind method in general...
This paper proposes an iterative receiver employing multiuser detection (MUD) and channel estimation for uplink MIMO-OFDM interleave-division multiple access (IDMA). IDMA can perform low-complexity MUD by employing a low-rate channel code and an individual interleaver for each user, and is expected to improve spectrum efficiency in mobile communications. However, an excellent channel estimator has...
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