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This paper analyzes the effect of channel gains on the performance of signal detection in multiple-input multiple-output (MIMO) systems, and based on that proposes an intelligent MIMO signal detection algorithm. It dynamically chooses child-node number according to the gains between antennas. This algorithm is verified by simulation in the MIMO system with Matlab. While keeping the detection performance...
The main drawback of the Multi — Carrier Code Division Multiple Access (MC — CDMA) systems is the high Peak — to — Average Power Ratio (PAPR). MC — CDMA is the best candidate for the fourth generation of mobile communications. Many works present techniques to reduce the PAPR like the Partial Transmit Sequence (PTS), Selected Mapping (SLM), Clipping and Filtering and so on, but all are either increases...
A novel optimization algorithm to design a bilayer lengthened QC-LDPC code for relay channel is proposed in this paper , which combine differential evolution algorithm and bilayer graph for LDPC codes. We aim to construct QC-LDPC codes with best girth(maximum girth and minimum numbers of shortest cycles)both at relay node and destination node. Proposed algorithm is composed of two steps , first the...
In this paper, we consider a multi-relay Demodulate-and-Forward (DMF) cooperation system, in which the high order superposition modulation (SM), superposition 16-QAM modulation (16-QAM SM), is employed. For the given system, a new relay selection scheme with constellation rearrangement (CR) technique is proposed, which is based on the optimal total mutual information (MI) criterion. Firstly we find...
In this paper, a modified a posteriori probability (APP) based algorithm for the decoding of low- density parity-check (LDPC) codes is proposed. The modified APP-based algorithm utilizes an additional processing in the bit nodes to improve the accuracy instead of the check nodes normalization performed in normalized APP-based algorithm. The modified APP- based algorithm yields desirable trade-off between...
This paper addresses the joint transceiver design for uplink multiuser non-regenerative MIMO relay systems, where spatial multiplexing (SM) is applied at all users and linear processing is performed at the relay station (RS) and base station (BS). Based on the minimum mean square error (MMSE) criterion, subject to maximum power constraint at the RS, an iterative algorithm is proposed to jointly optimize...
An improved expanding window fountain code for unequal error protection is proposed in this paper. For expanding window fountain (EWF) codes, the increased performance of more important bits (MIB) is achieved at the cost of decreased performance of less important bits (LIB). On the basis of EWF codes, the proposed method uses the expanding window to cover all the input information symbols and alter...
Finding good puncturing patterns for rate-compatible non-binary LDPC codes are considered over additive white Gaussian noise (AWGN) channels in this paper. We first study several popular puncturing schemes for binary LDPC codes and generalize them to non-binary LDPC codes, where the effects of short cycles in Tanner graph are rarely investigated. By carefully studying the impacts of short cycles when...
In this paper, we focus on the design of a type of low-density parity-check (LDPC) codes called cycle codes whose parity-check matrix have exactly weight-2 columns. An approach to design nonbinary LDPC cycle codes with good performance is presented based on cycle entropy defined here. This method can obtain an elegant distribution of the nonbinary elements over the Galois Field GF(q) among the cycles...
In this paper repeat-punctured turbo trellis-coded modulation (RPTTCM) is proposed. In RPTTCM, the effect of repeat-puncture is investigated on a TTCM system, repetition of the information bits increases the interleaver size, followed by an appropriate puncturing scheme to maintain the respective code rate. The RPTTCM systems are simulated in an Additive White Gaussian Noise (AWGN) and the Rayleigh...
Under the software environment of MATLAB/Simulink, the communication system of direct sequence spread spectrum (DSSS) is dynamically modeled and simulated over a new practical Rayleigh channel, and the relationship curves of the bit error rate (BER) with the signal-to-noise ratio (SNR) of DSSS communication systems are presented. It is analyzed that DSSS system can effectively overcome multipath fading...
High-rate LDPC codes are increasingly used in transmission systems. Puncturing is a common scheme which produces a code with higher code rate starting from a base code with lower rate. This paper discusses a new method to derive a puncturing pattern, given the parity matrix of the base code. The method allows the extraction of a puncturing pattern which is optimized in terms of error floor performance...
In this paper, we investigate rate-compatible (RC) short/ moderate length irregular low-density parity-check (LDPC) codes and propose three different novel puncturing schemes to determine the preferred puncturing positions so as to achieve less performance degradation. The first one is based on a short cycle counting algorithm as well as grouping variable nodes which have the equal length of short...
Compared with the conventional one-way counterpart, two-way cooperative communications can significantly improve spectrum efficiency. When no channel state information is available at the receivers, we propose optimal non-coherent detector based on maximum likelihood rule for frequency-shift keying modulated two-way amplify-and-forward (AF) cooperative communications in Rayleigh fading channels. We...
In this paper, we consider the BER analysis of the constellation rearrangement (CoRe), which is not subject to the Gray-encoding constraint for the first transmission. This type of CoRe can be applied in a parallel transmission system such as cooperative relaying networks. Furthermore, it allow us to construct the accumulate constellation, which obtained by separating and rearranging the received...
In this paper, we propose a simplified Log-MAP algorithm that is equivalent to the Log-MAP algorithm in terms of the bit-error-rate (BER) performance, but without its implementation difficulties. The proposed algorithm is based on a linear approximation of the correction function in the Log-MAP algorithm over different signal-to-noise ratio (SNR) regions. This approximation is simple to implement...
In this paper, a turbo-coded optical interleave-division multiple-access (OIDMA) scheme is studied. A maximum a posteriori (MAP) based asynchronous on-off keying (OOK) MUD algorithm is proposed. Besides, system capacity is analyzed with an iterative technique called SNR evolution. BER is evaluated over log-normal turbulence channels, taking into consideration the effects of thermal noise and background...
Recently there has been much interest in using transmit beamforming to provide multi-antenna physical-layer multicasting. A state of the art in this context is the semidefinite relaxation (SDR) method for handling the design optimization. This paper proposes an alternative multicast transmit strategy where the transmit beams are random and time-varying. This proposed strategy consists of two key ingredients:...
Physical layer network coding (PNC) was first introduced by Zhang et al. for two-way relay channels (TWRCs). By utilizing the PNC, we can complete two-way communications within two time slots, instead of three time slots required in non- PNC systems. Recently, the upper and lower bounds for a bit error rate (BER) of PNC have been analyzed for fading channels. In this paper, we derive an exact BER...
A number of peak-to-average power ratio (PAPR) reduction techniques have been proposed for orthogonal frequency division multiplexing (OFDM) systems; however, most of them require transmitting side information and thus reduce the bandwidth efficiency. The existing constellation extension (CE) schemes do not need to transmit side information. In this paper, we propose an improved CE scheme for PAPR...
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