Dual Relay Selection for Cooperative NOMA With Distributed Space Time Coding

Summary This paper considers cooperative non‐orthogonal multiple access (NOMA) scheme in an underlay cognitive radio (CR) network. A single‐cell downlink cooperative NOMA system has been considered for the secondary network, consisting of a base station (BS) and two secondary users, ie, a far user and a near user. The BS employs NOMA signaling to send messages for the two secondary users where the near user is enabled to act as a half‐duplex decode‐and‐forward (DF) relay for the far user. We derive exact expressions for the outage probability experienced by both the users and the outage probability of the secondary system assuming the links to experience independent, nonidentically distributed Rayleigh fading. Further, we analyze the ergodic rates of both the users and the ergodic sum rate of the secondary network. The maximum transmit power constraint of the secondary nodes and the tolerable interference power constraint at the primary receiver are considered for the analysis. Further, the interference caused by the primary transmitter (PT) on the secondary network is also considered for the analysis. The performance of the proposed CR NOMA network has been observed to be significantly better than a CR network that uses conventional orthogonal multiple access (OMA) scheme. The analytical results are validated by extensive simulation studies.

Section: Figuresupporting

confidence: 86%

“…From (23) to (25), it is clear that, when operating in the high transmit power region, the outage probability is a function of I th , , i,j and is independent of transmit power values.…”

Section: Outage Probability Ignoring Primary Interferencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Performance analysis of nonorthogonal multiple access‐based underlay cognitive relay network

Aswathi

Babu

2019

On the analysis of achievable rate for NOMA networks with cooperative users over κ‐μ shadowed fading channels

Bilim

Kapucu

2019

SummaryCooperative nonorthogonal multiple access (NOMA) system is an effective solution for the fifth generation (5G) wireless mobile communications systems. In this work, the achievable rate analysis of a NOMA communication network with decode‐and‐forward (DF) relaying under κ‐μ shadowed fading conditions is investigated. First, we develop an analytical framework for cumulative distribution function (CDF) of the considered system model. Then, the average achievable rate expressions for two different information bits namely s1 and s2 are derived based on the derived CDF for NOMA with DF relaying over κ‐μ shadowed fading channels. Furthermore, we also propose simplified average achievable rate expressions for the special cases of κ‐μ shadowed fading channels in order to facilitate the evaluation of the derived expressions. Some numerical examples on the achievable rate of the considered system are shown for different scenarios. Moreover, our derived analytical average achievable rate expressions are confirmed by the simulations results.

Space‐time block coding in millimeter wave large‐scale MIMO‐NOMA transmission scheme

Aghdam

Tazehkand

Abdolee

et al. 2020

In this paper, we introduce a new wireless system architecture using space-time block coding schemes (STBC) and non-orthogonal multiple access (NOMA) in millimeter wave (mmWave) large-scale MIMO systems. The proposed STBC mmWave large-scale MIMO-NOMA system utilizes two MIMO subarrays, transmitting data over two channel vectors to mobile users.To reduce the communication overhead and latency in the system, we utilize random beamforming with optimal coefficients at the base station and random-near random-far user pairing in implementing the NOMA scheme.Our results show that the proposed STBC mmWave large-scale MIMO-NOMA technique significantly outperforms the previous counterparts. KEYWORDSMIMO, NOMA, mmWave, STBC, optimal beamforming INTRODUCTIONDue to the growing number of mobile users and the demand by the newly introduced machine-type communications (MTC), the next generation of wireless communication systems requires to support massive connectivity, and offers low latency with ultra communication reliability. 1,2 To support massive connectivity, the use of non-orthogonal multiple access (NOMA) techniques was introduced in Kim et al. 3 By applying superposition coding and successive interference cancellation (SIC), NOMA allows multiple users to access the same time-frequency resource, leading to further improvement in the spectral efficiency (SE) and massive connectivity compared to orthogonal multiple access (OMA). 4 It has also been shown that using NOMA in conjunction of multi-input multi-output (MIMO) structure can further enhance the SE. 5 User pairing plays a key role in improving the performance of NOMA systems. Recently, several different user pairing schemes were introduced in NOMA communication systems. 6 In Beyranvand et al., 7 three random user pairing techniques were proposed, all of which were based on the random distribution of users in a cell.Although random user pairing reduces the latency, it increases the outage probability (OP) compared to other pairing methods. 1,7,8 Chopra et al. 8 derived a closed-form expression that provides the optimal number of transmit antennas to minimize the OP of such systems. One of the aims of this letter is to introduce a system architecture to further reduce the OP in MIMO-NOMA structures. Beamforming and OP in mmWave massive MIMO systems have been discussed in Zeng et al. 9 In this paper, it is shown that the proposed system outperforms the conventional massive MIMO-OMA.In recent studies, it has been shown that the combination of NOMA and conventional STBC schemes can lead to substantial performance improvement. [10][11][12][13] Toka and Kucur, 10 investigated the performance of the Alamouti code in NOMA over Nakagami-m fading channels. Arti 14 proposed a space-time transmission scheme (STTS) for large-scale MIMO communication system. Int J Commun Syst. 2020;33:e4392.wileyonlinelibrary.com/journal/dac