臺灣博碩士論文加值系統

可見光通訊個人區域網路(Visible-Light Communication Personal Area Network; VPAN)是利用光的特性來傳遞訊號，而在科技的高速發展下也使得可見光通訊(Visible-Light Communication; VLC)成為可以實現的技術。可見光個人區域網路的裝置必須隨著涵蓋範圍增大而隨之增加。然而，大量的密集配置裝置將會提高傳輸時的碰撞率，使得有效產能降低與延遲時間上升。
而在通訊協定方面，IEEE 802.15.7標準所定義之CSMA/CA機制在網路負載流量較低的環境中，會具有較高的傳輸效率。負載增加時，此種機制也會帶來傳輸時的碰撞機率上升，因此造成有效產能大量下降與延遲時間大幅提升。此外在IEEE 802.15.7標準之中，定義了免競爭週期，使得裝置可以使用保證時槽來進行資料傳送，但是保證時槽以時槽為單位使得破碎週期隨著超碼框級數增加，此種方式大幅降低了保證時槽使用率。
為了解決上述的問題，本論文提出了一種修改超碼框結構的方式，延伸了IEEE 802.15.7標準之中的競爭週期，並且針對不同優先權之訊號資料使用不同的傳輸方式，以達到有效的降低CSMA/CA所帶來的延遲時間，此外，讓保證時槽用單位後退週期來切割，降低免競爭週期的頻寬浪費。由模擬結果發現，無論是高優先權的延遲時間、有效產能或者保證時槽使用率均比IEEE 802.15.7標準的機制有較好的表現。

Visible-Light Communication Personal Area Network (VPAN) is using the characteristics of light to transmit signals, and Visible-Light Communication (VLC) can be achieved technology in the rapid development of technology. The device of the visible personal area network must be increased as the coverage increases. However, a large number of devices will increase the probability of transmission collision, and this is the main cause to decrease entire network goodput and increase delay time.
In the communication protocol, IEEE 802.15.7 standard defined the CSMA / CA mechanism will have higher transmission efficiency in the low traffic load. However, when the network device and the traffic load increase, CSMA / CA mechanism will increase the probability of transmission collision, it making a significant decrease in the goodput and a significant increase in delay time. In addition, in the IEEE 802.15.7 standard defined contention-free period (CFP) so that the device can use the guaranteed time slot (GTS) for data transmission, but GTS is using slot for unit, it makeing broken period increase with the vale of superframe oder (SO) gradually increase. This method will decrease GTS utilization.
In order to solve the above problems, this paper presents a way to modify the structure of the super-code frame, extending the competition period in the IEEE 802.15.7 standard, and using different transmission methods for different priority signal data to achieve effective reduction CSMA / CA brought about by the delay time. In addition, let GTS use the unit backoff period (UBP).In simulation results we found the delay time of high priority, good put and GTS utilization are better than IEEE 802.15.7 standard.

摘要 i
Abstract vii
誌謝 iv
目次 v
圖目次 vii
表目次 ix
第一章 緒論 1
1.1簡介 1
1.2研究動機與目的 2
1.3章節摘要 3
第二章 IEEE 802.15.7 標準概述 4
2.1 IEEE 802.15.7 標準簡介 4
2.1.1 IEEE 802.15.7標準之網路拓樸結構 5
2.1.2實體層 6
2.1.3媒體存取控制副層 10
2.1.4超碼框結構 13
2.1.5載波偵測多重存取/碰撞避免機制 (CSMA/CA機制) 14
2.1.6保證時槽分配 17
2.1.7資料傳輸模型 20
2.1.8訊框格式 25
2.2相關研究 32
第三章 研究方法 34
3.1系統基本架構 34
3.2廣播機制 36
3.3延伸競爭週期 (EXTEND CAP) 37
3.4協調者之流程 38
3.5裝置之流程 39
3.6保證時槽分配機制 41
3.6.1訊框格式修改 41
3.6.2保證時槽分配規範 42
第四章 系統模擬與結果分析 44
4.1模擬環境及參數設定 44
4.2效能評估項目 45
4.2.1產能 (Throughput) 45
4.2.2有效產能 (Goodput) 45
4.2.3平均訊框丟棄率 (Average frame drop ratio) 46
4.2.4平均傳輸延遲時間 (Average delay per frame) 46
4.2.5保證時槽使用率 (Guaranteed time slot utilization) 46
4.3模擬結果分析與比較 47
4.3.1產能(Throughput)的分析與比較 47
4.3.2有效產能(Throughput)的分析 49
4.3.3平均訊框丟棄率(Average frame drop ratio)的分析 50
4.3.4平均傳輸延遲時間 (Average delay per frame)的分析 51
4.3.5保證時槽使用率 (Guaranteed time slot utilization)的分析 53
第五章 結論與未來研究 55
參考文獻 56

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