Nonorthogonal Multiple Access With Orthogonal Time–Frequency Space Signal Transmission

This paper considers an orthogonal time frequency space (OTFS)-based uplink massive multiple-input-multipleoutput (MIMO) system, in which all users transmit symbols to a base station (BS) that is equipped with an one-dimensional uniform linear array (ULA) in the delay-Doppler domain. The zero-forcing (ZF) decoding scheme is applied at the BS. Different from most existing OTFS works, this paper mainly focuses on the performance analysis. Furthermore, in contrast to the existing massive MIMO works, which assume favorable propagation (FP) conditions, here, we investigate the low but non-zero probability scenario that massive MIMO fails in providing FP. This results in a scenario where the channel matrix cannot be diagonalized with massive MIMO. Thus, to facilitate the performance analysis, a low-complexity approximation of the inverse of the Gram matrix, i.e., the Neumann series expansion, is presented. With this, a simple signal-to-noise-ratio (SNR) approximation is firstly derived, which illuminates the impact of the OTFS system parameters. Moreover, by exploiting the properties of circulant matrices, a compact expression for the OTFS multi-path correlation matrix (OTFS-MPCM) is derived.

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“…, respectively [16]. We also assume perfect knowledge of the parameters {h q,i , l q,i , k q,i } q=1,...,Ku i=1...,Mq at the BS.…”

Section: System Modelmentioning

confidence: 99%

Performance Analysis of OTFS-based Uplink Massive MIMO with ZF Receivers

Feng

Ngo

Flanagan

et al. 2021

2021 IEEE International Conference on Communications Workshops (ICC Workshops)

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“…OTFS-OMA with different interleaving patterns was proposed in [2,3]. OTFS with power-domain NOMA was explored in [4,5]. Recently, we proposed a code-domain NOMA approach for OTFS based on sparse code multiple access (SCMA), named OTFS-SCMA [6].…”

Section: A Motivationmentioning

confidence: 99%

“…• This work is the first attempt to perform channel estimation for OTFS in NOMA environment. Although OTFS was studied in the context of power-domain NOMA in [4,5,18],…”

Section: Contributionsmentioning

confidence: 99%

Convolutional Sparse Coding based Channel Estimation for OTFS-SCMA in Uplink

Thomas¹,

Deka²,

Raviteja³

et al. 2021

Preprint

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Orthogonal time frequency space (OTFS) has emerged as the most sought-after modulation technique in a high mobility scenario. Sparse code multiple access (SCMA) is an attractive code-domain nonorthogonal multiple access (NOMA) technique. Recently a code-domain NOMA approach for OTFS, named OTFS-SCMA, is proposed. OTFS-SCMA is a promising framework that meets the demands of high mobility and massive connectivity. This paper presents a channel estimation technique based on the convolutional sparse coding (CSC) approach for OTFS-SCMA in the uplink. The channel estimation task is formulated as a CSC problem following a careful rearrangement of the OTFS input-output relation. We use an embedded pilot-aided sparse-pilot structure that enjoys the features of both OTFS and SCMA. The existing channel estimation techniques for OTFS in multi-user scenarios for uplink demand extremely high overhead for pilot and guard symbols, proportional to the number of users. The proposed method maintains a minimal overhead equivalent to a single user without compromising on the estimation error. The results show that the proposed channel estimation algorithm is very efficient in bit error rate (BER), normalized mean square error (NMSE), and spectral efficiency (SE).

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“…The main idea of PD‐NOMA is to use a single frequency channel assignment to the number of users in the same cell. Henceforth, PD‐NOMA provides better connectivity compared to the OMA 15 . Moreover, the accessible bandwidth is not separated for the numerous numbers of users, and every user can share the entire accessible bandwidth for the communication.…”

Section: Introductionmentioning

confidence: 99%

An effective combination of terahertz band NOMA and MIMO system for power efficiency enhancement

Chandra

Borugadda²

2022

Int J Communication

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Terahertz (THz) band communication is extensively used to reach future communication needs for large capacity. Moreover, the multiple input multiple output (MIMO) and Non-orthogonal multiple access (NOMA) approach with multi-antenna enable users to share more data with good spectrum efficiency.Due to its various applications, different research works are done in MIMO and NOMA. But the existing approach used in NOMA-MIMO has a major limitation in power efficiency. Hence, this research work is presented for maximizing power efficiency. The power efficiency is improved effectively using the THz-NOMA-MIMO system in the presented approach. Initially, users are clustered effectively by utilizing the enhanced fuzzy c-means clustering (EFCM) approach. Afterwards, hybrid precoding with threshold orthogonal matching pursuit (TOMP) approach is presented for generating the hybrid precoding vectors. Here, optimal precoding vectors are generated using the geometric distance-based TOMP approach. This process eliminates the interference present in the data communication, thus improving power and spectral efficiency. Finally, the weight-based distributed power efficient algorithm (WDPEA) achieves the finest power allocation. These combinations of effective approaches enhance the power and spectral efficiency. The presented methodology is implemented in the working platform of MATLAB. The performance of the presented approach is examined with the different existing approaches in regards to spectral efficiency, energy efficiency, effective capacity, and the mean squared error. When the users are at 20, the sum spectral efficiency of existing zero forcing (ZF) is 21, regularized zero forcing (RZF) is 54, maximum ratio transmission (MRT) is 71, and the proposed method is 77 bit/s/Hz. When the signal to noise ratio at 25 dB, the energy efficiency of existing time division multiple access (TDMA) is 1.24, digital MIMO is 1.21, orthogonal multiple access (OMA) is 1.23, weighted NOMA is 1.35, and the proposed method is 1.38 bit/joule/Hz. The proposed method gets better results when compared to other methods.

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Nonorthogonal Multiple Access With Orthogonal Time–Frequency Space Signal Transmission

Cited by 36 publications

References 40 publications

Performance Analysis of OTFS-based Uplink Massive MIMO with ZF Receivers

Performance Analysis of OTFS-based Uplink Massive MIMO with ZF Receivers

Convolutional Sparse Coding based Channel Estimation for OTFS-SCMA in Uplink

An effective combination of terahertz band NOMA and MIMO system for power efficiency enhancement

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