Design and Analysis of Generalized Diversity Optical CDMA Systems

Abstract

中華民國一百零一年七月 I II 致謝 來到中興大學電機所碩士班兩年，很高興完成這份碩士論文，首先非常感謝 指導教授楊谷章博士的諄諄教誨，不管是在專業領域以及論文撰寫方面都給予相 當豐富的指導。讓我在通訊領域以及其他相關方面的知識得以有重大的進步，也 跟楊老師學習到更有效率的研究方法和精神，老師對於研究的專注和執著深深讓 我感受到想要有所作為，就應該付出這樣的態度。 其次感林茂昭教授、趙啟超教授和張敏寬教授對於論文初稿上的建議和指導 和口試時所提供寶貴的意見，可以使得本論文的內容和結構上更加的完善 最後我想感謝這兩年碩士班所認識的同學和朋友們，使我個人不管是在專業 領域或是心智方面甚至是解決問題的能力都有非常卓越的成長，在此感謝實驗室 的學長呈源、同學彥峰、峻丞、孝鑫、還有很多的好朋友、學弟妹以及在背後支 持我的父母親友們，讓我可以順利的從研究所畢業取得碩士學位。 III 摘要 在最新提出的光纖多樣性分碼多工系統，為以達到更好的傳送品質，每一個 使用者的每個訊號都傳送多次相同的拷貝，且每個碼在傳送前使用不同的平移， 以達到每個拷貝之間的獨立性。但是由於在短碼長且位元同步的情況下，難以僅 使用不同位移而達到獨立性，故在這篇論文，我們將結合位元非同步和拷貝之間 的獨立性這種更接近現實生活中的情況去分析光纖多樣性分碼多工系統並且推 導出一個廣義的公式，更精準的模型。最後，我們將介紹不同的位移顆粒度，用 以改善傳送品質與拷貝之間的相關系。 IV AbstractIn our recently proposed diversity O-CDMA scheme, every simultaneous user transmitted multiple copies of an optical code per data bit of one in order to achieve good code performance. To maintain performance, our analysis showed that copy independency wasessential, which was achieved by time-shifting these copies to different chip (or time-slot) positions per bit duration. However, complete copy independency is hard to achieve under the conventional chip-synchronous assumption, especially in short code length. In this paper, we combine the realistic effects of chip asynchronism and copy dependency in the analysis of such diversity O-CDMA systems and formulate a new, generalized, and more accurate performance model.

Design and Analysis of Asynchronous Incoherent Optical-CDMA Systems Using a New Code-Shifting Technique

“…As shown in Fig. 6, both theoretical and computer-simulation results match closely at various g and (w, N ) values, thus validating the accuracy of the analytical model derived in (12). Fig.…”

“…Modifying the Markov-chain chip-asynchronous analytical model [10], [25], [37], the "g-granulated" hard-limiting error probability of the proposed code-shifting technique with 1-D and 2-D λ c = 1 optical codes can now be formulated as (12) where Q k,l,g is here defined as the (hit) probability of having the periodic cross-correlation value in the preceding chip equal to k and the periodic cross-correlation value in the present chip equal to l under time-slot granularity g > 1.…”

“…As also shown in the figure, the rate of performance improvement begins to slow down when g > 3. This tendency is caused by the fact that the error probability P e,g>1 in (12) can be approximated as a function of the hit probabilities Q k,l,g (for k ∈ [0, ⌈3 − 2/g⌉], l ∈ [0, ⌈3 − 2/g⌉], (k, l) = (0, 0)), according to [11]. In general, the approximated P e,g>1 improves (or gets smaller) as these hit probabilities decrease.…”

“…In general, coherent O-CDMA supports higher spectral efficiency but is more sensitive to beat noise and physical impairments than incoherent O-CDMA [6], [14], [26]- [28]. As there exist rich collections of asynchronous unipolar optical codes, incoherent O-CDMA is more flexible in the choices of optical codes and code parameters, and potentially supports a variety of applications, such as optical-wireless, avionics communications, and multirate, multi-QoS, multimedia services [5], [10]- [12], [19], [22], [28]- [32]. Because of these reasons, this paper focuses on the asynchronous incoherent O-CDMA systems.…”

Improving Optical-Wireless CDMA System Performance in Industrial Environment with Timing Jitters

“…down (5)(6)(7)(8) . Figure 1 shows an example of an optical-wireless CDMA system model, in which optical codeword of each user (or node) is transmitted via free space for mobility and EMI immunity.…”