Performance analysis of data transmission in MC-CDMA radio interface with turbo codes

The performance of turbo codes has been shown to be near the theoretical limit in the additive while Gaussian noise channel. By using orthogonal signaling, which allows for bandwidth expansion, the performance of the turbo coding scheme can be improved even further. Since this is a low-rate code, the code is mainly suitable for spread-spectrum modulation applications. In classical turbo codes the frame length is set equal to the interleaver size, however, the codeword distance spectrum of turbo codes improves with an increasing interleaver size. It has been reported that by using repetition and puncturing the performance of turbo codes can be improved. Repeat-Punctured Turbo Codes has shown a significant increase in performance at moderate to high signal-to-noise ratios. In this paper, we study the use of orthogonal signaling and parallel concatenation together with repetition and puncturing to improve the performance of superorthogonal convolutional turbo codes for reliable and effective communications. Simulation results for the additive white Gaussian noise channel are presented together with analytical upper bounds, which have been derived using transfer function bounding techniques.

A Monte Carlo simulation was conducted to assess the performance of Multi-Carrier Code Division Multiple Access (MC-CDMA) in a sectored cell, in an indoor environment. In each sector, terminal schedule packet transmission using slotted p-persistent Inhibit Sense Multiple Access, while the packets themselves are transmitted using MC-CDMA. The simulated bit error rate performance of MC-CDMA with combining strategies maximal ratio combining (MRC) and equal gain combining (EGC) used in the frequency domain are presented. A comparison is made between analytically determined bit error probability for a single user in an additive white Gaussian noise channel using binary phase shift keying (BPSK), and simulated bit error rate for a single user using MC-CDMA with MRC and EGC. The determination of the number of sectors in a cell is also given. MC-CDMA with diversity combining outperforms BPSK in a non-fading AWGN channel. Further, as the user-number increases, EGC performs better than MRC if these combining strategies are used with MC-CDMA. Finally, the results show the basis for determining the number of sectors in a cell. When using slotted p-persistent ISMA, it is envisaged that only a single user will transmit at a time in a sector.

Turbo codes (TC) is a powerful branch of error-control coding that has exhibited performances close to the Shannon limit, whilst offering a reasonable level of computational complexity. Repeat-punctured turbo codes (RPTCs) exploit the fact that the use of larger interleavers correspond to better bit-error rate (BER) performances for the conventional turbo code, and makes use of repetition and puncturing to improve the performance of the conventional turbo code for moderate to high signal-to-noise ratios (SNRs). Motivated by turbo codes and repeat-punctured turbo codes, we study the use of a new scheme, dual-repeat-punctured turbo codes (DRPTC) in the additive white Gaussian noise (AWGN) channel. DRPTCs primarily make use of repetition and puncturing and the structure of the conventional turbo code to yield a more superior performance. The decoding in principle follows the technique of turbo decoding but needs some changes to yield the performance improvement. Simulation results for the AWGN channel is presented together with the analytical union bounds derived from transfer-function bounding techniques, and the codeword distance-spectrum for the proposed scheme is presented and evaluated.

Multi-carrier code division multiple access (MC-CDMA) technique is one of the strong candidates for next generation wireless mobile communication systems. Multi-carrier systems are very much sensitive to carrier frequency offset (CFO) results in intercarrier interference (ICI). To mitigate ICI without any spectral loss, a second order duobinary coded phase rotated conjugate cancellation algorithm is proposed in this paper. In the conventional phase rotated conjugate cancellation (PRCC) technique, one path carries the MC-CDMA signal with a phase spin of ϕ and the other path carries the conjugate of the first path signal with -ϕ phase spin. This artificial phase rotation allows the transmitter to tune the transmitted signals so that the ICI effects could be mutually cancelled at the receiver. Although the PRCC technique reduces the spectral efficiency, the limitation can be overcome by the joint second order duobinary coding scheme with PRCC technique. In the proposed method, the correlative coding between the binary symbols modulated on adjacent subcarriers is used to reduce the ICI without any spectral loss. Simulation results show that the proposed PRCC method provides better carrier to interference ratio (CIR) and bit error rate (BER) performances compared to the conventional conjugate cancellation (CC) technique.

In conventional system of wireless communication the source and the channel coding are used in different modules that increases the system complexity, cost and overall processing period. To make it more efficient, both the source and channel coding modules are combined in a single processing block, which not only decreases the system complexity but also reduces the overall processing cost. Multi Carrier Code Division Multiple Access (MC-CDMA) technique which is a combination of CDMA and Orthogonal Frequency Division Multiplexing (OFDM) provides higher capacity. The proposed approach combines joint source channel coding with MC-CDMA. Through integrity check and receiver control mechanism, our system is able to subscribe to a desired broadcast session. The proposed approach result in a capacity which is nearly equals to the upper bound of the ratio CH where C is the channel capacity and H is the entropy of the source.

For future mobile communications, an appropriately chosen multiple access scheme is a critical issue. To support robust frequency planning, multi-operator scenarios, system coexistence and hierarchical cell structures, frequency division multiple access (FDMA) and multicarrier techniques are viable choices. Further multiple access schemes presently under discussion are code division multiple access (CDMA) and time division multiple access (TDMA). A mobile radio system concept deploying a hybrid frequency and time divided code division multiple access (F/T/CDMA) scheme with a multicarrier CDMA (MC-CDMA) component, called MC/JD-CDMA, is proposed and performance results for the uplink are presented. Attractive features of the proposed system concept are the possibility to flexibly offer voice and data services with different bit rates, soft capacity, as well as inherent frequency and interferer diversity.

The multicarrier code division multiple access (MC-CDMA) technique has received considerable attention due to its high data rate for future wireless communication systems. A common problem to multiuser MC-CDMA detectors under Rayleigh fading channels is that the performance is very sensitive to the signature waveform mismatch (SWM) induced by channel estimation distortion. Besides, the disturbance of colored noise could make the performance of the system worse. In this paper, the proposed multiuser detector which utilizes the modified independent component analysis (ICA) algorithm based on approximate negentropy maximization under the second-order cone programming (SOCP) constraint can provide robustness against small-to-medium SWM over colored noise environment for a synchronous MC-CDMA system.

In this paper, we investigate in detail the performance of turbo codes in quasi-static fading channels both with and without antenna diversity. First, we develop a simple and accurate analytic technique to evaluate the performance of turbo codes in quasi-static fading channels. The proposed analytic technique relates the frame error rate of a turbo code to the iterative decoder convergence threshold, rather than to the turbo code distance spectrum. Subsequently, we compare the performance of various turbo codes in quasi-static fading channels. We show that, in contrast to the situation in the AWGN channel, turbo codes with different interleaver sizes or turbo codes based on RSC codes with different constraint lengths and generator polynomials exhibit identical performance. Moreover, we also compare the performance of turbo codes and convolutional codes in quasi-static fading channels under the condition of identical decoding complexity. In particular, we show that turbo codes do not outperform convolutional codes in quasi-static fading channels with no antenna diversity; and that turbo codes only outperform convolutional codes in quasi-static fading channels with antenna diversity

It is well known that binary error-correcting codes with iterative decoders can achieve near Shannon-limit performance on the additive white Gaussian noise (AWGN) channel, but their performance on more realistic wireless channels can become degraded due to the presence of burst errors or impulsive noise due to interference. A better performing coding scheme is the class of non-binary codes, which are known to be more effective in correcting burst errors, but interestingly there is no research reported in the literature investigating non-binary codes on impulsive noise channels. In this paper, we investigate the performance of non-binary turbo codes defined in a finite field GF(4) on symmetric alpha-stable impulsive noise channels and compare with comparable binary turbo codes. A Cauchy receiver is also employed to mitigate the effects of the channel to assist the turbo decoding. Our simulation results show that although the non-binary turbo code performs similarly to the binary turbo code on the AWGN channel, it achieves a significant coding gain over the binary turbo code as impulsiveness increases.

This correspondence analyzes the performance of concatenated coding systems and modulation schemes operating over the additive white Gaussian noise (AWGN) channel by examining the loss of capacity resulting from each of the processing steps. The techniques described in this correspondence allow the separate evaluation of codes and decoders and thus the identification of where loss of capacity occurs. Knowledge of this capacity loss is very useful for the overall design of a communications system, e.g., for evaluating the benefits of inner decoders that produce information beyond the maximum-likelihood (ML) estimate. The first two sections of this correspondence provide a general technique for calculating the composite capacity of an orthogonal or a bi-orthogonal code and the AWGN channel in isolation. The later sections examine the composite capacities of an orthogonal or a bi-orthogonal code, the AWGN channel, and various inner decoders including the decoder estimating the bit-by-bit probability of a one, as is used in turbo codes. The calculations in these examples show that the ML decoder introduces a large loss in capacity. Much of this capacity loss can be regained by using only slightly more complex inner decoders, e.g., a detector for M-ary frequency-shift keying (MFSK) that puts out the two most likely frequencies and the probability the ML estimate is correct produces significantly less degradation than one that puts out only the most likely frequency.

In the present time, there is a rapid increase in demand for faster and reliable transmission of multimedia data through wireless channels. When multimedia data specially an image is to be transferred through the wireless channel, image is highly degraded due to wireless channel errors such as fading, interference and bursty errors. Multi-Carrier Code Division Multiple Access (MC-CDMA) technique is considered as the most promising technique for efficient wireless data transmission. This paper presents the performance comparison of image transmission over MC-CDMA system with two interleaving techniques; Helical interleaving and chaotic interleaving. At the receiver, Linear Minimum Mean Square Error (LMMSE) equalization is employed. System performance is measured through Peak Signal-to-Noise Ratio (PSNR) and Root Mean square Error (RMSE) values. From results, it has been evaluated that MC-CDMA system having chaotic interleaving and LMMSE performs better instead of having helical interleaving for image transmission over wireless channels.

The multicarrier code division multiple access (MC-CDMA) technique has received considerable interest for its potential application to future wireless communication systems due to its high data rate. A common problem regarding the blind multiuser detectors used in MC-CDMA systems is that they are extremely sensitive to the complex channel environment. Besides, the perturbation of colored noise may negatively affect the performance of the system. In this paper, a new coherent detection method will be proposed, which utilizes the modified fast independent component analysis (FastICA) algorithm, based on approximate negentropy maximization that is subject to the second-order cone programming (SOCP) constraint. The aim of the proposed coherent detection is to provide robustness against small-to-medium channel estimation mismatch (CEM) that may arise from channel frequency response estimation error in the MC-CDMA system, which is modulated by downlink binary phase-shift keying (BPSK) under colored noise. Noncoherent demodulation schemes are preferable to coherent demodulation schemes, as the latter are difficult to implement over time-varying fading channels. Differential phase-shift keying (DPSK) is therefore the natural choice for an alternative modulation scheme. Furthermore, the new blind differential SOCP-based ICA (SOCP-ICA) detection without channel estimation and compensation will be proposed to combat Doppler spread caused by time-varying fading channels in the DPSK-modulated MC-CDMA system under colored noise. In this paper, numerical simulations are used to illustrate the robustness of the proposed blind coherent SOCP-ICA detector against small-to-medium CEM and to emphasize the advantage of the blind differential SOCP-ICA detector in overcoming Doppler spread.

Increasing the performances of turbo codes used in communication systems is an important issue at the moment. The method used for trellis termination influences the code performances. This paper describes and compares (in terms of bit error rate - BER and frame error rate - FER) four types of these methods: without trellis termination, termination only of the first trellis, post-interleaver flushing and dual termination. Turbo code performances are evaluated for two lengths of S-random interleaver, using binary phase-shift keying (BPSK) modulation, over Additive White Gaussian Noise (AWGN) channel. The simulations were performed for two generating matrices of the component encoders and the decoding algorithm we have used is a version of Max-Log-MAP.

In this paper, we study the effects of different ASE noise models on the performance of turbo code (TC) decoders. A soft-decoding algorithm, the Bahl, Cocke, Jelinek, and Raviv (BCJR) decoding algorithm, is generally used in TC decoders. The BCJR algorithm is a maximum a posteriori probability (MAP) algorithm, and is very sensitive to noise statistics. The Gaussian approximation of ASE noise is widely used in the study of optical-fiber communication systems, and there exist standard TCs for additive white Gaussian noise (AWGN) channels. We show that using a MAP decoding algorithm based on the Gaussian noise assumptions, however, may significantly degrade the TC decoder performance in an optical-fiber channel with non-Gaussian ASE noise. To take full advantage of TC, accurate noise statistics in optical-fiber transmissions should be used in the MAP decoding algorithm.

this paper reviews the state of the technique of field programmable gate array (FPGA) for partial Reconfiguration (PR), design methodologies of Wireless Communication System, such as Multi Carrier Code Division Multiple Access (MC-CDMA) technique has been to be suited for future wireless systems that are expected to provide higher data rates and greater flexibility for the services of voice, data, video and Internet to the users due to its property in using the bandwidth in efficient manner. The Software Defined Radio is considered as a wireless system applied by routines so as software. Consequently, the use of SDR allows vehicle manufacturers to familiarize communication applications sustained through cars to appropriate to the standards of the respected country presented in the object oriented programming. FPGAs are playing a very significant role in SDR. However, in modern wireless communication system programs, SDR and CR need to design a wide range of waveforms complex, which it is complicated in design and performance and implementation needs more time. The design of the modulation and demodulation and other signal processing application of PR technique that have the ability to modify blocks of logic dynamically by downloading partial bit files, while the remaining logic is still working without interruption; thus, power consumption and configuration time can be saved for a larger extent. The PR using was allowed to move for fewer or smaller devices as, decrease power and increase system upgradability.