Hailing Yang¹, Suoping Li^1,2,*, Duo Peng²

CMC-Computers, Materials & Continua, Vol.79, No.3, pp. 5273-5294, 2024, DOI:10.32604/cmc.2024.050869 - 20 June 2024

Abstract To address the problems of network congestion and spectrum resources shortage in multi-user large-scale scenarios, this paper proposes a twice random access OFDMA-NOMA-RA protocol combining the advantages of orthogonal frequency division multiple access (OFDMA) and non-orthogonal multiple access (NOMA). The idea of this protocol is that OFMDA is used to divide the entire frequency field into multiple orthogonal resource units (RUs), and NOMA is used on each RU to enable more users to access the channel and improve spectrum efficiency. Based on the protocol designed in this paper, in the case of imperfect successive interference… More >

A. Vasuki¹, Vijayakumar Ponnusamy^2,*

Intelligent Automation & Soft Computing, Vol.33, No.1, pp. 71-86, 2022, DOI:10.32604/iasc.2022.022586 - 05 January 2022

Abstract A good wireless device in a system needs high spectral efficiency. Non-Orthogonal Multiple Access (NOMA) is a technique used to enhance spectral efficiency, thereby allowing users to share information at the same time and same frequency. The information of the user is super-positioned either in the power or code domain. However, interference cancellation in NOMA aided system is challenging as it determines the reliability of the system in terms of Bit Error Rate (BER). BER is an essential performance parameter for any wireless network. Intelligent Reflecting Surfaces (IRS) enhances the BER of the users by More >

N. Manikanda Devarajan^1,*, S. Thenmozhi², K. Jayaram³, R. Saravanakumar⁴

Intelligent Automation & Soft Computing, Vol.32, No.2, pp. 1167-1178, 2022, DOI:10.32604/iasc.2022.021558 - 17 November 2021

Abstract Orthogonal Frequency Division Multiplexing (OFDM) is a wireless communication technology that is used for highly reliable and high data rate communication. In a multi-user OFDM system, the interference has occurred in the receiver side between the consecutive OFDM symbols. This interference reduces the performance of the OFDM system. To achieve good quality in received symbols the interference level should be minimized. The conventional cancellation system requires higher interference reduction time and power. These limitations of the conventional interference cancellation architectures for OFDM systems are overcome by proposing efficient and low power interference cancellation architecture. Hence,… More >

Yinghua Zhang^1,2, Jian Liu¹, Yunfeng Peng¹, Yanfang Dong², Changming Zhao^3,*

CMES-Computer Modeling in Engineering & Sciences, Vol.125, No.1, pp. 239-257, 2020, DOI:10.32604/cmes.2020.010778 - 18 September 2020

Abstract Aiming for ultra-reliable low-latency wireless communications required in industrial internet of things (IIoT) applications, this paper studies a simple cognitive radio non-orthogonal multiple access (CR-NOMA) downlink system. This system consists of two secondary users (SUs) dynamically interfered by the primary user (PU), and its performance is characterized by the outage probability of the SU communications. This outage probability is calculated under two conditions where, a) the transmission of PU starts after the channel state information (CSI) is acquired, so the base station (BS) is oblivious of the interference, and b) when the BS is aware… More >

Lei Wang¹, Jian Liu¹, Changming Zhao^{2, 3, *}, Alan Yang⁴

CMC-Computers, Materials & Continua, Vol.63, No.1, pp. 401-416, 2020, DOI:10.32604/cmc.2020.06680 - 30 March 2020

Abstract In this paper, we investigate the performance of secondary transmission scheme based on Markov ON-OFF state of primary users in Underlay cognitive radio networks. We propose flexible secondary cooperative transmission schemewith interference cancellation technique according to the ON-OFF status of primary transmitter. For maximal ratio combining (MRC) at destination, we have derived exact closed-form expressions of the outage probability in different situations. The numerical simulation results also reveal that the proposed scheme improve the secondary transmission performance compared with traditional mechanism in terms of secondary outage probability and energy efficiency. More >

Jian Liu¹, Lei Wang¹, Changming Zhao^{2, 3, *}, Alan Yang⁴

CMC-Computers, Materials & Continua, Vol.63, No.1, pp. 119-130, 2020, DOI:10.32604/cmc.2020.06074 - 30 March 2020

Abstract In this paper, we consider a three-hop relay system based on interference cancellation technique in Underlay cognitive radio (CR) network. Although underlay CR has been shown as a promising technique to better utilize the source of primary users (PUs), its secondary performance will be severely degraded. On one hand, by adapting the Underlay spectrum sharing pattern, secondary users (SUs) would observe the strict power constraints and be interfered by primary users. On the other hand, limited transmit power results in limited transmission range, which greatly degrade the secondary transmission capacity. To solve the problems above, More >

Lei Wang¹, Jian Liu^1,*, Alan Yang²

Journal of Information Hiding and Privacy Protection, Vol.1, No.3, pp. 119-133, 2019, DOI:10.32604/jihpp.2019.07296

Abstract In this paper, we study the state-dependent interference channel, where the Rayleigh channel is non-causally known at cognitive network. We propose an active secondary transmission mechanism with interference cancellation technique according to the ON-OFF status of primary network. the secondary transmission mechanism is divided into four cases according to the active state of the primary user in the two time slots. For these interference cases, numerical results are provided to show that active interference cancellation mechanism significantly reduces the secondary transmission performance in terms of secondary outage probability and energy efficiency. More >

Yinghua Zhang^1,2, Yanfang Dong², Lei Wang¹, Jian Liu^1,*, Yunfeng Peng¹, Jim Feng³

CMC-Computers, Materials & Continua, Vol.60, No.1, pp. 379-393, 2019, DOI:10.32604/cmc.2019.05790

Abstract In this paper, we propose a downlink cognitive non-orthogonal multiple access (NOMA) network, where the secondary users (SUs) operate in underlay mode. In the network, secondary transmitter employs NOMA signaling for downlink transmission, and the primary user (PU) is interfered by the transmission from SU. The expressions for the outage probabilities are derived in closed-form for both primary and secondary users in the presence of channel estimation error. Numerical simulation results show that the channel estimation error and the inter-network interference cause degradation of the downlink outage performance. Also the power allocation and the location More >