Performance of MMSE Receiver based Multi Input Multi Output-Interleave Division Multiple-Access System with Multi-user Detection over Frequency Selective Wireless Communication Channel

This paper carries comprehensive comparison of Interleave Division Multiple Access (IDMA) and Code Division Multiple Access (CDMA) systems in terms of performance (BER) and behavior to different number of users. Performance analysis of two systems whose transmitter and receiver structures are almost same are studied under Additive White Gaussian Noise (AWGN) and performance differences are illustrated by simulation results. Although Multiple Access Interference (MAI) and Intersymbol Interference (ISI) can affect the performance of the CDMA system, simulation results illustrates that IDMA system model achieves this type of problem using their interleavers. Results also show that large number of users can easily be adapted by the IDMA scheme much easier than CDMA scheme.

In this paper we investigate the detection algorithms for interleave division multiple access (IDMA) systems in the presence of carrier frequency offsets (CFOs). The existing IDMA detection algorithm is designed under the zero CFO assumption and its performance will be degraded when the CFOs are present. We first extend the existing algorithm to the nonzero CFO case by utilizing effective channel coefficients which take the CFO effects into account. Then we turn to a more practical scenario with imperfect CFO estimates. We propose an algorithm that can cope with the residual CFO effects by integrating the CFO updating into the iterative receiver. Signal-to-interference-plus-noise ratio analysis and simulations show the feasibility and superiority of our proposed algorithms.

In this treatise, we study the error-rate results of turbo coded multi-carrier interleave division multiple access (MC-IDMA) using multiple-input multiple-output (MIMO) system for up-link (UL) communications. In a multi-user system, users experience multi user interference (MUI), multi-path effects and inter antenna interference (IAI). Further, the antenna correlation reflects in the system performance. We consider sub-optimal multi-user detection techniques based on zero-forcing maximum-a-posteriori probability (MAP) Multi-user detection (MUD) and minimum mean square error (MMSE) MAP MUD in order to mitigate the effects of above mentioned interferences for our system. Further, we realize multi-carrier modulation to obviate the effects of multi-path propagations. Specifically we analyze the effects of four types of delay-spread distributions pertaining to LTE and SUI channel models in the UL MIMO MC-IDMA. Our computer simulation reveals that coded MC-IDMA with the non-linear MMSE-MAP algorithm obtain better error-rate results performance with fewer signals to noise ratio by mitigating MUI and multi-path propagations.

Interleave division multiple access (IDMA) is a potential candidate for the future fifth generation (5G) systems. In this paper, we propose a novel architecture for IDMA system with low latency while maintaining low complexity. In the conventional architecture, the IDMA receiver sequentially processes deinterleaving, despreading, spreading and interleaving for multiuser detection. The proposed architecture, which is called the interleaved domain, can perform multi-user detection directly without deinterleaving the received frame. Because of this, the interleaving is no longer needed in the interference cancellation loop resulting in the decrease of latency by half and the increase of throughput by twice. In VLSI implementation results, the proposed architecture has reduced circuit area and power consumption by 53% and 58% compared to the conventional architecture on the same throughput condition.

The main aim of massive multiuser multiple-input multiple-output (MU-MIMO) system is to improve the throughput and spectral efficiency in 5G wireless networks. The performance of MU-MIMO system is severely influenced by inter-antenna interference (IAI) and multiuser interference (MUI). The IAI occurs due to space limitations at each user terminal (UT) and the MUI is added when one UT is in the vicinity of another UT in the same cellular network. IAI can be mitigated through a precoding scheme such as singular value decomposition (SVD), and MUI is suppressed by an efficient multiuser detection (MUD) schemes. The maximum likelihood (ML) detector has optimal performance; however, it has a highly complex structure and involves the need of a large number of computations especially in massive structures. Thus, the neighborhood search-based algorithm such as likelihood ascent search (LAS) has been found to be a better alternative for mitigation of MUI as it results in near optimal performance with low complexity. Most of the recent papers are aimed at eliminating either MUI or IAI, whereas the proposed work presents joint SVD precoding and LAS MUD to mitigate both IAI and MUI. The proposed scheme can achieve a near-optimal performance with smaller number of matrix computations.

Multicarrier code division multiple access (MC-CDMA) systems are well suited for high data rate wireless multimedia services, due to their ability to convert frequency-selective fading channels to distinct flat fading channels with low complexity fast Fourier transform (FFT) devices. However, when multiple users are present, the performance of MC-CDMA systems is degraded by the multiuser interference (MUI) when the channel is frequency-selective. In order to mitigate MUI, we present a joint algorithm that combines transmit power control, antenna array processing and multiuser detection at the receiver. Interestingly, the frequency-selectivity that entails the MUI also provides multipath diversity which can help suppress the MUI. Performance of the algorithm in a number of MC-CDMA system models is evaluated in terms of the average transmit power to achieve the target signal to interference plus noise ratio (SINR). Simulations confirm the outstanding performance of this algorithm compared with the existing ones in MC-CDMA systems.

In this contribution, we consider the performance of multi-user transmitter pre-processing (MUTP) assisted interleaved division multiple access (IDMA) scheme for downlink (DL) communications. We realize MUTP using Zero Forcing (ZF)algorithm. In this paper, we consider turbo coded system to achieve high coding gain. We construct the turbo code using parallel concatenated convolutional encoder and certain bits are punctured periodically to achieve code rate ½. We construct the pre-processing matrix using channel state information of all the users. We evaluate the performance of such coded ZF-MUTP assisted IDMA system for realistic channel model based on SUI channel model specifications. From our simulations, we observe that the ZF-MUTP assisted multi-user IDMA system provides better performance in terms of bit error rate (BER) with low signal to noise ratio (SNR).

For high-speed code division multiple access (CDMA) systems, interchip interference that is caused by multipath propagation becomes severe and cannot be ignored. Together with the multiple access interference due to nonideal conditions in CDMA, they become major obstacles to overall system performance. In this paper, both batch and adaptive algorithms based on linear prediction are proposed for joint blind equalization and multiuser detection for asynchronous CDMA systems. It is shown that the new methods are insensitive to estimation error of propagation delay or chip timing. In addition, the adaptive algorithm is computationally efficient. Simulation results show that the proposed methods are also near-far resistant and compare favorably to many existing methods.

In an interleave-division multiple access (IDMA) system, interleavers have a crucial role for the system performance. This paper presents a new approach to random interleavers for traditional IDMA systems. The proposed interleaver uses a random variable which is defined by Rayleigh distribution for mapping. Simulation results demonstrate that the proposed interleaver approach improves the bit-error rate (BER) performance of the IDMA systems.

In this paper, turbo multiuser detectors in Interleave Division Multiple Access (IDMA) based systems are considered for short range underwater acoustic channels (UACs). In such long reverberant channels that demand high computational complexity, turbo detectors based on minimum mean square error (MMSE) criterion are an attractive solution to achieve a good balance between performance and complexity. Two different synchronous IDMA structures are studied and applied to signals acquired during sea trials in the North Sea; firstly, a channel estimation (CE) based IDMA with Rake reception, and secondly, an adaptive interference canceller (IC-IDMA). Both schemes include phase tracking, channel coding and are based on a chip-rate equalization and detection, which are fed in by a composite multiuser signal of the users' feedback soft information. Experimental results of three different channel ranges demonstrate that the direct adaptive receiver has better performance and additionally mitigates the errors associated with the CE based IDMA receiver while maintaining lower complexity.

This paper is concerned with the power allocation problem for practically coded interleave-division multiple-access (IDMA) systems with iterative multi-user detection (MUD) over multiple access channels (MACs). Both Additive White Gaussian Noise (AWGN) and fading channels are considered. For AWGN channels, two power allocation methods based on linear programming are discussed and compared with an interior-point method (IPM). These techniques are extended to power allocation over fading channels. Numerical results show that, with power optimization, IDMA can achieve significant performance improvements over TDMA in fading environments.

This letter analyzes the performance of complementary coded code division multiple access (CC-CDMA) systems in frequency selective fading channels. Based on the evaluation of various combining algorithms for the correlation functions of M element sequences of a CC, a per-carrier parallel interference cancellation scheme based on minimum mean square error combining (MMSEC) is proposed for CC-CDMA to achieve a frequency diversity gain and multi-user interference resistance. Both analytical and simulation results verify the superiority of the proposed scheme. It is shown that combining algorithms and correlation properties of element sequences have a significant impact on the performance of CC-CDMA systems in frequency selective fading channels.

This work proposes a novel interleave-division multiple access (IDMA) system based on cyclic shift keying (CSK) modulation, named CSK-IDMA, for multiuser underwater acoustic (UWA) communications. The CSK modulation uses a circular cyclic shift of the spreading sequence to represent the information, which can be viewed as a special $M$ -ary spread spectrum modulation. Compared with conventional direct-sequence spread spectrum (DSSS) technique, CSK overcomes the spreading gain versus data rate limitations. The proposed scheme adopts the IDMA technique to reduce the cochannel interference. At the receiver, we employ passive time reversal (PTR) technique to compress the channels and improve the signal-to-interference-noise ratio (SINR) at first. In order to perfectly incorporate with the IDMA receive structure, we propose a soft CSK demodulation which can iteratively exchange extrinsic information with a soft channel decoder to form a turbo equalization. Simulation results show the proposed CSK-IDMA scheme can offer significantly improved performance. The data processing results from a lake experiment show that the proposed scheme can support 8 users and 10 users with zero error bits for 2.3 km transmission and 2.7 km transmission, respectively. The corresponding bit error rate (BER) for 16 users are $\text{8.4} \times \text{10}^{-4}$ and $\text{9.7} \times \text{10}^{-4}$ , respectively. The data rate is 62.5 bit/s per user within 4 kHz bandwidth and spreading sequences of 256 chips. To the best of our knowledge, this is the first work which can support more than 8 users for multiuser UWA communications with a high bandwidth efficiency.

Orthogonal frequency division multiplexing (OFDM) and interleave-division multiple-access (IDMA) are both attractive technique in modern wireless communication. In this paper, we study a multi-user system, which combines OFDM and IDMA, and fortunately, inherits many advantages. In order to improve system performance, low-density parity-check (LDPC) coding is further applied. And moreover, a turbo-type iterative receiver structure is investigated to mitigate multi-use interference (MUI). Simulation results are conducted to illustrate performance improvement. It is demonstrated that MUI is canceling efficiently by means of iterative multi-user detection algorithm. The proposed scheme provides an efficient solution to high-rate multiuser communications over multipath fading channels.

Non-orthogonal multiple access (NOMA) is the solution to accommodate tremendous increase in Internet of things (IoT) applications. In interleave division multiple access (IDMA) systems, NOMA is realized using distinguished interleavers for every user. Here, we suggest a recursive successive interference cancellation (SIC)-based IDMA receiver structure for NOMA systems. With unequal optimum power distribution among multiple users, SIC has been implemented in a recursive manner. Chip-by-chip (CBC) multi-user detection (MUD)-IDMA receiver along with recursive SIC structure has been simulated under different simulation environments. The simulation results suggest the effectiveness of the receiver for dense 5G networks in future.KeywordsInterleave division multiple accessNon-orthogonal multiple accessUnequal power allocationRecursive successive interference cancellation