Enabling User Relaying In MCM-NOMA Under Doubly Selective Channels Using Iterative Interference Cancellation Schemes For Wireless IoT Networks

<div>Cell-edge users of the future cellular internet of things (IoT) with massive IoT sensors can suffer from extremely severe channel conditions, especially under very high-speed scenarios. In this paper, we present a performance improvement method for cell-edge users of multi-carrier modulation (MCM)-based non-orthogonal multiple access (NOMA) downlink systems. To this end, we consider the implementation of cooperative user relaying NOMA (CUR-NOMA) and derive its lower bound end-to-end bit error rate (E2E-BER) under doubly selective channels. In addition, the imperfect successive interference cancellation (SIC) process is analyzed, wherein two interference cancellation schemes are combined to remove the NOMA induced inter-user interference (IUI) and the doubly selective channel induced inter-carrier interference (ICI). Furthermore, numerical simulations are performed to prove the efficiency of the introduced schemes with imperfect channel state information (CSI) when compared to the theoretical perfect SIC with a perfect CSI case. </div>

Enabling User Relaying In MCM-NOMA Under Doubly Selective Channels Using Iterative Interference Cancellation Schemes For Wireless IoT Networks

<div>Cell-edge users of the future cellular internet of things (IoT) with massive IoT sensors can suffer from extremely severe channel conditions, especially under very high-speed scenarios. In this paper, we present a performance improvement method for cell-edge users of multi-carrier modulation (MCM)-based non-orthogonal multiple access (NOMA) downlink systems. To this end, we consider the implementation of cooperative user relaying NOMA (CUR-NOMA) and derive its lower bound end-to-end bit error rate (E2E-BER) under doubly selective channels. In addition, the imperfect successive interference cancellation (SIC) process is analyzed, wherein two interference cancellation schemes are combined to remove the NOMA induced inter-user interference (IUI) and the doubly selective channel induced inter-carrier interference (ICI). Furthermore, numerical simulations are performed to prove the efficiency of the introduced schemes with imperfect channel state information (CSI) when compared to the theoretical perfect SIC with a perfect CSI case. </div>

Robust Hybrid Beam-Forming for Non-Orthogonal Multiple Access in Massive MIMO Downlink

This paper presents hybrid precoding for a non-orthogonal multiple access (NOMA) transmission scheme in a millimeter wave (mmWave) massive MIMO (mMIMO) downlink. In hybrid precoding, the analog precoder is obtained by the orthogonalization of the users’ channel vectors to minimize inter-beam interference. The digital precoder consists of a zero-forcing precoder to minimize inter-user interference. In order to break the barrier of one user per beam, we utilize the NOMA within the beam for power domain multiplexing among users. Simulation results show the proposed scheme’s efficacy compared to the state-of-the-art schemes and provide 1.48 times better sum-rate performance at 10 dB received SNR.

Gyre Precoding and T-Transformation-Based GFDM System for UAV-Aided mMTC Network

In this paper, an unmanned aerial vehicle (UAV)-aided multi-antenna configured downlink mmWave cooperative generalized frequency division multiplexing (GFDM) system is proposed. To provide physical layer security (PLS), a 3D controlled Lorenz mapping system is introduced. Furthermore, the combination of T-transformation spreading codes, walsh Hadamard transform, and discrete Fourier transform (DFT) techniques are integrated with a novel linear multi-user multiple-input multiple-output (MU-MIMO) gyre precoding (GP) for multi-user interference reduction. Furthermore, concatenated channel-coding with multi-user beamforming weighting-aided maximum-likelihood and zero forcing (ZF) signal detection schemes for an improved bit error rate (BER) are also used. The system is then simulated with a single base station (BS), eight massive machine-type communications (mMTC) users, and two UAV relay stations (RSs). Numerical results reveal the robustness of the proposed system in terms of PLS and an achievable ergodic rate with signal-to-interference-plus-noise ratio (SINR) under the implementation of T-transformation scheme. By incorporating the 3D mobility model, brownian perturbations of the UAVs are also analyzed. An out-of-band (OOB) reduction of 320 dB with an improved BER of 1×10−4 in 16-QAM for a signal-to-noise ratio, Eb/N0, of 20 dB is achieved.

Performance Evaluation of Precoding Schemes for Multi User Massive MIMO System Over Nakagami-m Fading Channel

Nowadays, wireless communication system plays great roles in our dailyactivities and different improvements are requiring because the number of users increase from time to time. At the same time, users need high throughput and link reliability. The forthcoming generation of wireless communication will have to deal with some core requirements for serving large number of users simultaneously, upholdinghigh throughput for each user, assuring less energy consumption, etc. Inter-user interference has a major impact when a wireless communication link has a large number of users. To maintain a particular desired quality of service, sophisticated transmission mechanisms such as interference cancellation need be implemented. As a result, MU-massive MIMO with extremely huge antenna arrays is recommended. The term ”MU-massive MIMO” refers to a system with hundreds or thousands of antennas servicing tens of thousands of customers.Inter-user interference was greatly decreased once the channel vectors were closely orthogonal. As a result, high data rates can be supplied to multiple users at the same time. In this work, researcher investigated performance evaluation of a MU-massive MIMO utilizing different precoding schemes (like, MMSE, ZF, MRT) over nakagami-m fading channel with CSI at base station and users’ terminal. In addition, the researcher analyzed the outcome of pilot reuse factors and shaping (m) parameter.

Downlink multi-user algorithms for millimeter-wave wideband linear arrays on PD-NOMA-based squint steering beams

This article investigates using a phased linear antenna array instead of the planar array to circumvent the problem that two frequency squint steering main beams cannot cover any two beam directions simultaneously. First, we approximate the donut-shaped main beam of the linear array by means of multiple pencil-shaped main beams of a virtual planar array for matching the steering main beam of the linear array with the multi-path sparse scattering channel model mathematically and give a method for calculating the number of antenna elements of the virtual array. Second, we cope with possible inter-user interference on a single squint main beam of the linear array in some scenarios by means of the power-domain non-orthogonal multiple access (PD-NOMA) technique, making it possible to support communication with two users on a single squint main beam at the base station (BS) side. The feasible domain of PD-NOMA is given when a single antenna is used for both the BS and the user end, assuming a two-user successive interference cancellation (SIC) decoding power ratio limit. Third, three algorithms are given for serving multi-user at the BS via squint beams of the linear array. Finally, numerical results show that the second proposed algorithm supporting PD-NOMA pairing within a single donut-shaped squint main beam significantly increases the number of simultaneous users served within a single cellular system.

Inviabilidade no Afastamento da Interferência dos Próprios Usuários, no Processo de contratação de Serviços Públicos Continuados e outros Problemas afins / Inviability in the Removal of user Interference, in the Process of Hiring Continuous Public Services, and other Related Problems

De um modo geral, insta observar preocupação exclusivamente com auspícios legais, quanto à contratação dos serviços públicos, deixando de lado fatores fundamentais, em especial à qualidade e inexistindo possibilidade de participação da sociedade no processo de contratação de serviços públicos, mesmo os próprios usuários estão afastados do processo de contratação por parte do serviço público. A presente contextualização tem por finalidade evidenciar a preocupação segundaria no processo de contratação por parte do serviço público, em especial os serviços de natureza continuados, que são aqueles prestados cotidianamente, initerruptamente para população das comunidades “Municípios, Estados e Governo Federal”. Percebe-se que a estrutura das leis foram alçadas para verificação quanto enquadramento relativo à parte documental, muito pouco ou quase nada referente a qualificação propriamente dita. Embora de forma tímida exista sim previsão quanto a qualificação dos prestadores de serviços, visualizamos que estão sendo deixado de lado, quando comparadas com habilitação jurídica, fiscal, tributária e financeira. De um modo geral, às leis que tratam exclusivamente do departamento de compra dos setores público, leis de licitações, faço referência “Leis Federais Nº. 8.666 de 21 de junho de 1993” e “Lei Federal Nº. 10.520 de 19 de julho de 2002”, não estão defasadas/desajustadas, o que precisa de fato ser revisto é o posicionamento e entendimento dos aplicadores das mesmas, tanto quanto os órgãos de fiscalização. Nesse esteio, os maiores prejudicados são sem dúvida os usuários dos serviços, serviços esses que foram contratados sem parâmetro nenhum de qualidade “talvez insignificantes”, tão somente quem apresentou uma enorme lista de certidões e demais documentos alheios à qualidade do seu serviço. Por pior, nenhum objetivo é alcançado de verdade, preocupação exacerbada com legalidade, quando o País apresenta quadro jamais visto de corrupção, e por outro lado, usuários dos serviços mal atendidos por empresas apenas habilitadas documentalmente, não tendo efetiva qualificação para prestação dos serviços que foram contratadas.

Design and Analysis of Three-dimensional M-sequence Bipolar OCDMA Spectral Amplitude Code

This paper has been focused to utilize the m-sequence code in spectral/time/spatial OCDMA domain in a bipolar mode (Three Dimensional modes). The scheme has elegantly incorporated the design of an encoder and a decoder such that the system efficiently generates the code in three-dimensional bipolar mode. The decoder design is such that it effectively suppresses the multiple user interference (MUI) of three-dimensional code. System analyses are carried for defining the BER performance variation with users acceptability and received power. The observed results demonstrate that the cardinality of m-sequence three-dimensioanl bipolar code is larger than the existing 3D Pascal code, 2D -MDW,3D -PDC, 2D-PDC, 1D-CWH and 1D-MS codes. The received power in proposed system is -5.8dBm is lesser than the 3D Pascal Code at 10 -18 similarly the users adoption in system more than 210% can be accomplished as compared to 3D Pascal code.