Turbo receivers for interleave-division multiple-access systems (original) (raw)
Related papers
Performance and Analysis of Interleave Division Multiple access using Turbo Encoder
IJARCCE, 2017
The efficiency of CDMA system is degraded with number of user increases. CDMA is limited by (MAI) and (ISI) Hence when number of user increases the BER performance also increased. The main limitation in CDMA is that it involves separate coding and spreading operations. A method to enhance the performance of IDMA System turbo codes can be applied to IDMA system, called Turbo coded IDMA System, which is presented recently for combing the advantages of turbo and IDMA. We use regular Turbo coder is used. IDMA uses repetition code. To mitigate MAI and ISI, turbo type iterative MUD (Multi User Detection) is used. In contrast to CDMA, IDMA uses the iterative chip-By-chip (CBC) detection algorithm to overcome intra-cell Interference. An interleave-division multipleaccess (IDMA) system supports the presence of multiple users in a cell by resorting to a different interleaver per user. The results Show that the TURBO CODED IDMA is better than other FEC code like convolution code and LDPC code under the same Parameters. Turbo coded IDMA Provide high speed of communication services and low cost of receiver. Turbo codes are used in 3G/4G mobile communications. And in (deep space) satellite communications as well as other applications.
Turbo multiuser detection for turbo-coded CDMA in multipath fading channels
IEEE Transactions on Vehicular Technology, 2002
Multiuser detection and turbo coding are two of the most powerful techniques for enhancing the performance of nextgeneration wide-band code-division multiple-access (CDMA) systems. In this paper, we develop an iterative multiuser receiver for turbo-coded CDMA systems with aperiodic spreading sequences operating in multipath fading, which exploits the power of both techniques. The key innovation in the proposed receiver is a lowcomplexity soft multiuser detector which uses the same decision statistic as the conventional RAKE receiver (i.e., the outputs of the maximum ratio combiners for all the users), and performs soft-interference cancellation and instantaneous minimum mean-square error (MMSE) filtering. The soft multiuser detector has a complexity of ( 2 ) per bit per iteration, where is the number of users. A single-user receiver which employs a soft RAKE detector followed by a turbo decoder is also considered. Simulation results demonstrate that the proposed multiuser receiver offers more than 0.5-dB gain over the single-user RAKE receiver at a bit-error rate (BER) of 10 3 and even outperforms the single-user RAKE receiver operating in a single-user environment.
An Iterative Multiuser Detector for Turbo-Coded DS-CDMA Systems
Eurasip Journal on Advances in Signal Processing, 2005
We propose an iterative multiuser detector for turbo-coded synchronous and asynchronous direct-sequence CDMA (DS-CDMA) systems. The receiver is derived from the maximum a posteriori (MAP) estimation of the single user's transmitted data, conditioned on information about the estimate of the multiple-access interference (MAI) and the received signal from the channel. This multiple-access interference is reconstructed by making hard decisions on the users' detected bits at the preceding iteration. The complexity of the proposed receiver increases linearly with the number of users. The proposed detection scheme is compared with a previously developed one. The multiuser detector proposed in this paper has a better performance when the transmitted powers of all active users are equal in the additive white Gaussian noise (AWGN) channel. Also, the detector is found to be resilient against the near-far effect.
Iterative multiuser detection/decoding for turbo coded CDMA systems
IEEE Communications Letters, 2000
In this letter, we propose a novel scheme for iterative multiuser detection and turbo decoding. The multiuser detector and single-user turbo decoders are coupled such that after each turbo decoding iteration the extrinsic information of the interfering users is passed to the multiuser detector, and after each multiuser iteration, updated a posteriori probabilities are passed to the single-user turbo decoders as the soft input metrics. In synchronous systems, the proposed detector approaches the multiuser capacity limit within 1 dB in the low signal-to-noise ratio region.
Turbo multiuser detection with integrated channel estimation for differentially coded CDMA systems
2006
This thesis is concerned with iterative joint multiuser detection (MUD) and channel esti mation for the uplink of asynchronous direct-sequence code-division multiple-access (DSCDMA) systems in multipath channels. For the base station of a CDMA system, it is shown that it is possible to design a receiver tha t can recover the multiuser information symbols of all the users within its own cell without any prior knowledge of the multipath channel or the spreading codes of users outside the cell. In this thesis, for two different scenarios, we propose two receiver structures that take all the necessary signal processing operations into account simultaneously. In other words, the proposed iterative receivers can jointly perform channel estimation, channel equalization, MUD, and channel decoding. The proposed iter ative processing algorithms allow earlier stages of a receiver (e.g., the channel estimator) to refine their processing based on soft information obtained from later stages (e....
Performance of iterative multiuser receiver for turbo-coded DS-CDMA
The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring., 2003
Abstract-In this paper, a low complexity iterative multiuser receiver is analyzed for a turbo-coded CDMA system. The receiver includes a soft multiuser detector and the decoders for users. The simulation considers an uplink asynchronous transmission over a correlated frequency ...
2004
We propose an iterative multiuser detector for turbo-coded synchronous and asynchronous direct-sequence CDMA (DS-CDMA) systems. The receiver is derived from the maximum a posteriori (MAP) estimation of the single user’s transmitted data, conditioned on information about the estimate of the multiple-access interference (MAI) and the received signal from the channel. This multiple-access interference is reconstructed by making hard decisions on the users ’ detected bits at the preceding iteration. The complexity of the proposed receiver increases linearly with the number of users. The proposed detection scheme is compared with a previously developed one. The multiuser detector proposed in this paper has a better performance when the transmitted powers of all active users are equal in the additive white Gaussian noise (AWGN) channel. Also, the detector is found to be resilient against the near-far effect.
A low-complexity iterative multiuser receiver for turbo-coded MC-CDMA system
Vehicular Technology Conference. IEEE 55th Vehicular Technology Conference. VTC Spring 2002 (Cat. No.02CH37367), 2002
A low-complexity iterative multiuser receiver is proposed using groupwise maximum likelihood sequence estimation (MLSE) combined with a modified interference cancellation scheme in a turbo coded MC-CDMA system. It is based on grouping the active users according to their signal strengths and computing the log-likelihood ratios by MLSE among each group of users at the first iteration. For subsequent iterations, a modified interference cancellation scheme that can benefit from code extrinsic information available through decoding is used, for lower complexity. Simulation results are presented in a Rayleigh multipath fading environment for a typical data transmission scheme. Comparisons are made with iterative receivers using maximum a posterwri (MAP) criterion and soft interference cancellation. Performance very close to that of MAP based iterative receiver is achieved by this novel scheme within a few iterations, with much lower computational cost. This approach performs significantly well also under the near far conditions.
Iterative Multiuser Detection for Turbo Coded Cdma in Uplink Umts
In this paper, we develop an iterative multiuser receiver for decoding Turbo coded synchronous CDMA signals in both Gaussian and non-Gaussian noise. A soft-input soft-output nonlinear multiuser detector is combined with a set of single user channel decoders in an iterative detection/decoding structure. The non-linear multiuser detector utilizes the prior probabilities of each user's bits to form soft estimates used for multiple access interference cancellation. The channel decoders perform Turbo code decoding and produce posterior probabilities which are fed back to the multiuser detector for use as prior probabilities. Simulation results show that the proposed multiuser receiver performs well in both Gaussian and non-Gaussian noise. In particular, single user Turbo code performance can be approached within a few iterations with medium to low cross-correlation (0:5).
In this paper, a low-complexity multiuser receiver for turbo-coded DS-CDMA systems is presented to perform jointly iterative multiuser detection and turbo-decoding. The proposed approach consists of a new multistage partial parallel interference cancellation (NPPIC) detector and K single-user turbo decoders, where K is the number of active CDMA users. The NPPIC detector is derived based on the single-user maximum a posteriori criterion and has a similar simple structure to the conventional partial parallel interference cancellation scheme presented by Divsalar et al. A prominent feature of this detector is that it delivers interference-cancelled soft outputs to the turbo decoders and utilizes the soft information from the turbo-decoders' output. Extensive computer simulations demonstrate that the cooperation between NPPIC and turbo-decoding offers significant performance gain over the traditional non-iterative receivers and performs comparably to some existing iterative schemes of much higher complexity.