Cognitive radio network (CRN) is considered to be the future technology for the fifth generation of cellular wireless standards (5G). CRN is based on a complex spectrum allocation system, and licensed primary users (PUs) or unlicensed secondary users (SUs) are allowed to share the spectrum, provided that they do not cause significant interference. In cognitive radio, it is important to control the transmission power of SUs so that the interference should not be harmful to the quality of service of PUs. In this paper, the authors addressed the impact of system imperfections on the overall performance of multi-carrier code division multiple access (MC-CDMA)-based CRN system. A new expression of the signal-to-interference-noise ratio (SINR) for MC-CDMA-based CRN system over a Rayleigh fading channel without any power control condition among the PUs and SUs is derived and investigated. The performance of MC-CDMA-based CRN system over the frequency selective multi-path fading channel is examined by varying the number of users, the signal-to-noise-ratio (SNR) per bit, number of fading path and number of subcarriers, respectively. From the simulation results, we have seen that the SINR performance is affected by these parameters. The analysis presented in this paper shows the impact of lack of a controlling mechanism on transmitted signal power affecting the between PUs and SUs ultimately system performance. The result of the analysis will provide relevant information to design the physical layer protocol for high speed CRN system for 5G.

中文翻译：

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系统缺陷对基于 MC-CDMA 的认知无线电网络 (CRN) 系统的整体性能

认知无线电网络 (CRN) 被认为是第五代蜂窝无线标准 (5G) 的未来技术。CRN 基于复杂的频谱分配系统，许可的主要用户（PU）或未许可的次要用户（SU）可以共享频谱，前提是它们不会造成重大干扰。在认知无线电中，重要的是要控制 SU 的传输功率，以免干扰对 PU 的服务质量造成损害。在本文中，作者讨论了系统不完善对基于多载波码分多址 (MC-CDMA) 的 CRN 系统的整体性能的影响。推导和研究了基于MC-CDMA的CRN系统在PU和SU之间没有任何功率控制条件的瑞利衰落信道上的信干噪比(SINR)的新表达式。通过改变用户数、每比特信噪比 (SNR)、衰落路径数和子载波数来检查基于 MC-CDMA 的 CRN 系统在频率选择性多径衰落信道上的性能， 分别。从仿真结果可以看出，SINR 性能受这些参数的影响。本文提出的分析表明，缺乏控制机制对传输信号功率的影响最终会影响 PU 和 SU 之间的系统性能。