Multi-carrier Interleave Division Multiple Access Research Articles

Experimental demonstration of IDMA‐OFDM for visible light communications

We experimentally demonstrate a multicarrier interleave division multiple access (IDMA) scheme for bidirectional visible light communications using orthogonal frequency division multiplexing (OFDM), which has the advantages of good tolerance against multi-path, high spectral efficiency and excellent transmission performance. The generated IDMA signals are modulated on OFDM subcarriers and the different users are separated by the interleavers. When compared with orthogonal frequency domain multiple access, IDMA-OFDM offers increased transmission spans of 30 and 50 cm at a bit error rate (BER) of 10 -3 in the cases of two and four users, respectively.

Error-rate analysis of MIMO MC-IDMA system for frequency-selective channels

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.

Performance analysis of multi-carrier IDMA system for co-operative networks

In this paper, we explicate error-rate (ER) results of transmitter pre-processing (TP) aided coded multi-carrier (MC)-interleave-division-multiple-access (IDMA) scheme for co-operative downlink (DL) communication. The base station (BS) transmits the coded symbols to the relays during the first time interval. The relay decodes the symbol and then re-encodes the information so that error free communication can be achieved. Then, the coded bit stream is transmitted during the second time interval. Finally, we will obtain the user’s information at the destination using iterative decoding algorithm and achieve better ER with lower signal-to-noise ratio (SNR). We assume that each user is reinforced by at least single relay. We consider MC modulation which convert frequency-selective channel into flat-fading channel. We realize TP technique on both the BS and the intermediate relays, so that the effects of Multi-user interference and Inter-relay-interference are suppressed. To be specific, we evaluate ER performance of MC-IDMA system using TP for co-operative network with rich scattering effects based on LTE-vehicular channel environments considering both BS to relay and relay to mobile stations (MS). From our simulation results, we observe that turbo-coded co-operative aided MC-IDMA DL system with MUTP shows a substantial improvement in its ER performance with reduced amount of transmit power in terms of SNR.

Reweighted regularised variable step size normalised least mean square‐based iterative channel estimation for multicarrier‐interleave division multiple access systems

This study focuses on channel estimation scheme in multicarrier-interleave division multiple access (MC-IDMA)-based wireless communications. Specifically, a new adaptive algorithm is derived and proposed for implementation of the channel estimation in the MC-IDMA system. The proposed algorithm is named reweighted regularised variable step size normalised least mean square (R-RVSSNLMS). The proposed algorithm-based channel estimator exploits inherent sparsity in the orthogonal frequency division multiplexing channels in order to enhance its performance. Computer simulation results that show the comparison of the performance of the R-RVSSNLMS-based channel estimator with that of the channel estimators based on some families of least mean square algorithms are documented in this study. The results show that the performance of the proposed R-RVSSNLMS-based channel estimator is better than that of the other conventional estimators presented in this study. However, the proposed channel estimator exhibits negligible high computational complexity in comparison with other channel estimators considered in this study for the MC-IDMA system.

Semi-blind simplified mean value channel estimator for MC-IDMA systems

The Multi-Carrier Interleave Division Multiple Access (MC-IDMA) scheme combines Orthogonal Frequency Division Multiplexing and IDMA. The scheme combats both Inter-Symbol Interference (ISI) and Multiple Access Interference (MAI). For coherent detection of the transmitted signals at the receiver, Channel State Information (CSI) is crucial. There are several schemes that can be used to obtain CSI at the receiver, such as pilot-based schemes and decision directed scheme, semi-blind and as blind channel estimation schemes. This paper focuses on developing semi-blind channel estimation scheme for the MC-IDMA systems. The developed scheme is based on Minimum Mean Square Error (MMSE) algorithm. The estimator employs applications of the eigenvalue and eigenvector decomposition (EVD) techniques to simplify the MMSE algorithm, and is named Simplified Mean Value Estimator (SMVE). Simulation results show that the proposed SMVE-based estimator outperforms Least Mean Square (LMS) algorithm-based estimator, Modified Minimized Mean Value Estimator (MMMVE), and the Minimized Mean Value-MMSE Estimator (MMVE).

Iterative Quantum-Assisted Multi-User Detection for Multi-Carrier Interleave Division Multiple Access Systems

With the proliferation of smart-phones and tablet PCs, the data rates of wireless communications have been soaring. Hence, the need for power-efficient communications relying on low-complexity multiple-stream detectors has become more pressing than ever. As a remedy, in this paper we design low-complexity soft-input soft-output quantum-assisted multi-user detectors (QMUD), which may be conveniently incorporated into state-of-the-art iterative receivers. Our design relies on extrinsic information transfer charts. Our QMUDs are then employed in multi-carrier interleave-division multiple-access (MC-IDMA) systems, which are investigated in the context of different channel code rate and spreading factor pairs, whilst fixing the total bandwidth requirement. One of our QMUDs is found to operate within 0.5 dB of the classical maximum a posteriori probability MUD after three iterations between the MUD and the decoders, while requiring only half its complexity, at a BER of $10^{-5}$ in the uplink of a rank-deficient MC-IDMA system relying on realistic imperfect channel estimation at the receiver, while supporting 14 users transmitting QPSK symbols.

Performance of joint transmit scheme assisted multiple-input multiple-output multi-carrier IDMA system

In this paper, we present the performance of a multiple-input multiple-output multi-carrier interleave division multiple access (MC-IDMA) system assisted by combined vertical Bell Laboratories layered space–time architecture and space–time block code processing over correlated frequency-selective channels for downlink communication. In MC-IDMA system, multi-carrier is realized by orthogonal frequency division multiplexing, which can eliminate the effects of time dispersion. At the mobile station, we employ zero forcing maximum-a-posteriori and minimum mean square error MAP (MMSE/MAP) multi-user detectors (MUD) to mitigate the effects of multi stream interference and iterative chip detection to combat the effects of multiple access interference. The performance of the considered system is compared with double space–time transmit diversity (DSTTD) aided MC-IDMA system. The simulation results show that the considered scheme outperforms DSTTD MC-IDMA and MC-CDMA system with MMSE/MAP MUD in terms of achievable bit error rate.

Iterative Multiuser Detection with Soft Decision-Directed Channel Estimation for MC-IDMA and Performance Comparison with Chip-Interleaved MC-CDMA

This paper applies iterative multiuser detection employing a new channel estimation scheme to multicarrier interleave-division multiple access (MC-IDMA), called OFDM-IDMA, which is expected to offer improved spectral efficiency in mobile communications. The MC-IDMA transmitter uses both a low-rate channel code and an individual chip interleaver for each user. The MC-IDMA receiver, which this paper focuses upon, repeats the iterative multiuser detection and soft decision-directed channel estimation (SDCE) by exploiting log-likelihood ratios (LLRs) of the coded bits which the maximum a posteriori (MAP)-based channel decoders for all users provide. SDCE estimates channel impulse responses of all users by the least-mean-square (LMS) algorithm, which aims to minimize the mean squared error between the received signal and its replica. This paper investigates the performance of MC-IDMA employing SDCE and compares it with those of three MC-CDMA techniques. Computer simulations demonstrate that MC-IDMA employing SDCE outperforms time-spread MC-CDMA and frequency-spread MC-CDMA, and that it can achieve almost the same bit error rate performance as chip-interleaved MC-CDMA while requiring lower complexity.

Three Design Aspects of Multicarrier Interleave Division Multiple Access

This paper presents a novel generalized transceiver architecture, i.e., Multicarrier Interleave-Division-Multiplexing-aided Interleave Division Multiple Access (MC-IDM-IDMA). A parallel interference cancellation (PIC)-aided iterative multiuser detection (MUD) algorithm is introduced, and the convergence behavior of the system is evaluated with the aid of EXtrinsic Information Transfer (EXIT) charts under the assumption of an equal-power multiuser scenario. Three interesting design tradeoffs of the MC-IDM-IDMA system are analyzed: 1) the multiplexing versus diversity tradeoffs; 2) the coding versus spreading tradeoffs, where the achievable bandwidth efficiency of both MC-IDM and MC-IDMA are characterized, and a general design rule is provided for low-rate codes; and 3) the complexity versus performance tradeoffs and the EXIT characteristics of two different MUD algorithms are investigated, leading to a reduced-complexity hybrid MUD.