《電子技術(shù)應(yīng)用》
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中繼選擇協(xié)議下的認(rèn)知無(wú)線電系統(tǒng)性能研究
來(lái)源：電子技術(shù)應(yīng)用2012年第10期
唐菁敏， 龍 華， 邵玉斌， 彭 藝
昆明理工大學(xué) 信息工程與自動(dòng)化學(xué)院， 云南 昆明650500
摘要： 在保證授權(quán)用戶服務(wù)質(zhì)量（QoS）和認(rèn)知用戶峰值功率限制的前提下，推導(dǎo)出高信噪比時(shí)放大轉(zhuǎn)發(fā)中繼選擇（SAF）協(xié)議、解碼轉(zhuǎn)發(fā)中繼選擇（SDF）協(xié)議和混合中繼選擇協(xié)議（HPRS）下認(rèn)知中繼系統(tǒng)中斷概率的近似表達(dá)式。Monte Carlo仿真驗(yàn)證了三種協(xié)議下中斷概率近似表達(dá)式的合理性，理論和仿真結(jié)果表明，三種協(xié)議的中斷概率與干擾限制條件和認(rèn)知用戶峰值功率密切相關(guān)，且HPRS中斷性能要優(yōu)于SAF和SDF。
中圖分類(lèi)號(hào): TN929.53
文獻(xiàn)標(biāo)識(shí)碼: A
文章編號(hào)： 0258-7998(2012)10-0096-03
Research the outage performance of cognitive radio system based on protocols of relay selection
Tang Jingmin， Long Hua， Shao Yubin， Peng Yi
Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming 650500, China
Abstract： An approximate outage probability formulation were derived for amplify-and-forward with relay selection(SAF), decode-and-forward with relay selection(SDF) protocol and hybrid protocol with relay selection(HPRS) on the premise of guarantee primary user quality of service（QoS） and limit of maximal power in cognitive user. By Monte Carlo simulation, the rationality of the approximate outage probability formulation is validated. Theoretical analysis and simulation results show that the outage probability of three cooperative protocols is closely related to interference limit and maximal power in cognitive user. Meanwhile, the three protocols can achieve the full space diversity and the HPRS outperforms both the SAF and SDF in outage performance.
Key words : cognitive radio; relay selection; power constrained; outage probability; cooperative diversity

    認(rèn)知無(wú)線電技術(shù)能提高對(duì)頻譜資源的有效利用率，但不能克服無(wú)線環(huán)境中的信道衰落等問(wèn)題，而協(xié)同通信恰恰能有效地解決這方面的問(wèn)題。因此，融合認(rèn)知無(wú)線電技術(shù)與協(xié)同通信技術(shù)，能有效解決無(wú)線信道的衰落和頻譜資源有限這兩大問(wèn)題[1-7]。參考文獻(xiàn)[3]研究了在重疊共享（US）方式下的認(rèn)知系統(tǒng)信道容量，指出通過(guò)波束成形和中繼選擇協(xié)作可有效改善系統(tǒng)性能。參考文獻(xiàn)[4]推導(dǎo)了US方式下認(rèn)知中繼系統(tǒng)的中斷性能上界。

    本文主要研究了在US方式下認(rèn)知系統(tǒng)通過(guò)采用不同中繼選擇協(xié)議的中斷性能，分別推導(dǎo)了高信噪比時(shí)基于SAF、SDF和HPRS協(xié)議的中斷概率近似表達(dá)式。仿真結(jié)果表明，中斷概率與干擾限制條件和認(rèn)知用戶峰值功率密切相關(guān)，HPRS性能要優(yōu)于SAF和SDF的。
1 系統(tǒng)模型
    認(rèn)知系統(tǒng)傳輸模型如圖1所示，考慮一個(gè)認(rèn)知網(wǎng)絡(luò)包括一個(gè)授權(quán)用戶PU（Primary User）節(jié)點(diǎn)，一個(gè)認(rèn)知用戶SU（Secondary User）源節(jié)點(diǎn)，一個(gè)SU目的節(jié)點(diǎn)和M個(gè)SU中繼節(jié)點(diǎn)。認(rèn)知系統(tǒng)的通信過(guò)程分兩個(gè)時(shí)隙完成：第一時(shí)隙，源節(jié)點(diǎn)廣播信息, 中繼i(i=1,…,M)和目的節(jié)點(diǎn)的接收信號(hào)yi和yd,1分別為:



 

 

     

    本文理論推導(dǎo)了SAF、SDF和HPRS在高信噪比時(shí)認(rèn)知系統(tǒng)中斷概率近似表達(dá)式，并且對(duì)其中斷概率進(jìn)行了Monte Carlo仿真，結(jié)果表明，近似曲線與仿真曲線較接近，因此驗(yàn)證了近似表達(dá)式的正確性，同時(shí)對(duì)比了三種協(xié)議的性能，發(fā)現(xiàn)HPRS中斷性能始終最優(yōu)。由于認(rèn)知用戶發(fā)射節(jié)點(diǎn)同時(shí)需要滿足干擾限制及峰值功率限制，因此最終的中斷概率與這兩個(gè)限制條件密切相關(guān)。
參考文獻(xiàn)
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