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We propose a half-duplex cooperative scheme for a discrete memoryless channel (DMC) consisting of two users communicating with one destination. The half-duplex constraint is satisfied by performing the communication over 3 time slots with variable durations in each code block. Each user alternatively transmits and receives during the first 2 time slots, then both of them transmit during the last one...
After the initial interest caused by appearance of turbo-codes in 1993, special attention to the hardware implementation has led to many different modified algorithms for MAP decoders. The original MAP algorithm suffers from serious drawbacks in its hardware implementation. To overcome this disadvantage, Max-Log-MAP and Log-MAP algorithms have been proposed to reduce the complexity. Recently an improved...
We propose a physical layer approach to detect the relay node that injects false data or adds channel errors into the network encoder in multiple access relay networks. The misbehaving relay is detected by using the maximum a posteriori (MAP) detection rule which is optimal in the sense of minimizing the probability of incorrect decision (false alarm and miss detection). The proposed scheme does not...
Multiple-input double-output (MIDO) codes are important in future wireless communications, where the portable end-user device is physically small and will typically contain maximum two receive antennas. Especially tempting is the 4×2 channel, where the four transmitters can either be all at one station, or separated between two different stations. Such channels optimally employ rate-two space-time...
The sphere decoding algorithm for signal transmitted on multiple antennas channel is considered. In this paper, the preprocessing stage is analyzed in order to seek a reduced complexity and some improvements are made to enhance the performance. The computer simulation results show that the improved algorithm by applying Pohst Enumeration with selected initial radius is more efficient than that by...
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...
Sphere Detection (SD) method has been used as a powerful mean to find Maximum Likelihood (ML)solution to the detection problem of Multiple-Input Multiple-Output (MIMO) channels with lower complexity. This method searches closest lattice point inside a sphere. This paper discusses the effect of initial radius of the sphere on the complexity and performance of SD in different noise variances, constellation...
Space time codes (STC) have been shown to be used well with the Multiple Input Multiple Output (MIMO) channel. The Orthogonal STC (OSTC) family of codes is known to achieve full diversity as well as very simple implementation of the Maximum Likelihood (ML) decoder. However, it was proven that with a complex symbol constellation one cannot achieve a full rate code when the number of transmitting antennas...
This paper introduces a demo application toolkit, implemented using Matlab GUI, for teaching convolutional coding techniques employed in wireless communications. In this study presented, Viterbi decoding algorithm, log-MAP and SOVA Turbo decoding algorithms are performed using Matlab software. With the toolkit developed, an example image transfer application has been carried out for comparative performance...
Tailbiting convolutional codes will be used for several applications in new cellular mobile radio systems. This encoding method does not reset the encoder memory at the end of each data block, avoiding the overhead of the zero tail and improving the efficiency, especially when encoding short data blocks. Nevertheless, the absence of a known tail highly increases the complexity of the decoding process...
In this paper we introduce a new right preprocessing method for the decoding of 2 times 2 algebraic space-time codes, called algebraic reduction, which exploits the multiplicative structure of the code. The principle of the new reduction is to absorb part of the channel into the code, by approximating the channel matrix with an element of the maximal order of the code algebra. We prove that algebraic...
The use of cooperative schemes in wireless networks has recently attracted much attention in scenarios where application of multiple-antenna systems is impractical. In such scenarios, the requirement of having full channel state information (CSI) at the receiver side can be relaxed by using differential distributed (DD) transmission schemes. However, in the DD schemes proposed so far, the decoding...
Classical ML decoders for multiple input multiple output (MIMO) systems like the sphere decoder, the Schnorr-Euchner algorithm, the Fano and the stack decoders suffer from high complexity for high number of antennas and large constellation sizes. In this paper, we propose the use of parallel processing for stack decoding, to decode signals transmitted on linear MIMO channels to reduce time consumption...
One of the practical challenges of Wireless communications over Multiple-input Multiple-output (MIMO) channels is to reduce the complexity of the decoding algorithm without sacrifice in performance degradation. Geometric decoding (GD) is an emerging technique which can offer substantially lower complexity while maintaining about the same error rate as that of Maximum likelihood (ML) decoding. In this...
The golden code is a full-rate full-diversity space-time code for two transmit antennas that has a maximal coding gain. Because each codeword conveys four information symbols from an M-ary QAM alphabet, a maximum-likelihood decoder based on a conventional sphere detector has a worst-case complexity of M4. In this paper we present a new algorithm for maximum-likelihood decoding of the golden code that...
We propose a fixed-effort MIMO decoder for frequency selective indoor channels that are characterized by strong line-of-sight (LOS) components. Contrarily to the maximum likelihood (ML) approach, where all possible hypotheses are investigated by the metrics calculation, the proposed MIMO detector performs the search over a reduced set of candidates. This search set contains a reduced but representative...
Detection is one of the key technologies in multiple-input multiple-output system. In this paper we propose a new tree searching scheme which is flexible in the tradeoff between performance and complexity. Sorted QR decomposition based on minimum mean square error (MMSE) criteria is applied as a preprocessing to make the channel easier for tree searching and Fano bias, which is adjustable to achieve...
The standard approach to the design of individual space-time codes is based on optimizing diversity and coding gain. This geometric approach leads to remarkable examples, such as the Golden Code, for which the complexity of maximum likelihood (ML) decoding is considerable. Codediversity is an alternative approach where a small number of feedback bits are used to select from a family of space-time...
The single antenna user nodes at the transmitters and at the receivers share their antennas to form a virtual multiple antenna system and to realize the cooperative diversity. It can enlarge the systempsilas capacity and enhance the service quality of the ad hoc network and improve the systempsilas performance. Applying the orthogonal property of the space-time coding, we transform the vector signal...
In this paper, we consider a Time Division Multiple Access (TDMA) transmission of coded symbols over a time and frequency selective channel. We consider at the receiver a turbo-detector consisting of a Maximum A Posteriori (MAP) equalizer and a MAP decoder. We assume that the channel is unknown at the receiver. Thus, we develop a MAP iterative burst by burst channel estimation algorithm using the...
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