近年來，隨著802.11相關技術的成熟，藉由無線網路來控制各項設備已成為相當普遍的應用。然而，除了802.11以外，IEEE(Institute of Electrical and Electronics Engineers)亦針對極寬頻個人無線網路發展其通訊協定IEEE 802.15.3a。802.15.3a實體層的UWB（Ultra Wide Band）技術部份一直有兩方陣營，各自擁護一套標準，一個是DS-CDMA(Direct-Sequence Code-Division Multiple Access)，另一方，則是由包括Intel及Texas Instrument等公司所組成的MBOA聯盟提出的MB-OFDM(Multi-Band Orthogonal Frequency-Division Multiplexing)。由這兩種不同方式所發展出的MAC(Media Access Control)協定差異相當大，本篇論文的研究是以DS-CDMA作為基礎，利用既有的802.15.3的MAC層協定[1]，在上層進行演算法的研究及效能的評估。
我們討論的演算法主要在於如何有效的以802.15.3 MAC為基礎，構成一個multi-piconet的網路，使得網路傳輸範圍得以不受限於單一piconet，而能傳輸至另一個piconet中的裝置，並以一個分散式的轉向排程機制作為BDEV（bridge DEV）的運作策略，盡可能地改善因802.15.3 MAC先天上的限制所容易造成的過長延遲。我們發現，若調整發送端的單位時間輸出流量，則此系統對於沒有延遲要求的資料流，即使在數個piconet所串接的網路中仍可以非常有效地完成資料的傳輸，但是由於802.15.3 MAC先天上的限制，無法避免地會造成較長的延遲，所以在multi-piconet上，很難達到多媒體的QoS需求。另外，由於802.15.3 MAC並不是利用UWB的技術作為實體層的傳輸機制，所以若直接套用相關的MAC參數，將無法充分利用UWB的高速傳輸特性。我們提出了一組較為適合UWB的MAC參數，並經由模擬驗證，發現確實可以有效地提高CAP(contention access period)時段的訊框傳輸率並降低延遲時間。最後，就我們所知，截至目前為止，以802.15.3 MAC為基礎的研究多專注於單一piconet的問題，仍無人針對multi-piconet進行任何相關研究，我們試著探索此領域的可能問題，並實現了一個multi-piconet的模擬平台，方便後續的其他相關研究有一個良好的研究基礎。

In the recent years, connecting every devices by wireless networks is a popular application as 802.11 related techniques matured. IEEE(Institute of Electrical and Electronics Engineers) not only defines 802.11, but also 802.15.3a which is a WPAN（wireless personal area network） standard based on UWB (ultra wideband) techniques. There are two groups desiring to define the physical layer of 802.15.3a. One uses DS-CDMA(Direct-Sequence Code-Division Multiple Access); the other, the union of MBOA, claims the MB-OFDM(Multi-Band Orthogonal Frequency-Division Multiplexing). The protocols of media access control of the two physical layers are very different. This paper is focused on DS-CDMA techniques and related MAC standard, 802.15.3 .
Our proposed algorithms try to efficiently transmit data among multi-piconet. A distributed strategy is employed to schedule BDEV(bridge device) to reduce delay. The proposed scheduling scheme could effectively reduce the end-to-end delay. However, due to the limitations of 802.15.3, the end-to-end delay may be too large to meet the QoS requirement of multimedia. Additionally, 802.15.3 MAC is not originally proposed for UWB technology. It may not take the advantages of UWB without modifying the relative MAC parameters. We proposed a set of MAC parameters, proven by simulation, which can efficiently raise the channel utilization and lower the transmitting delay during CAP(contention access period). Finally, as we know, there are no researches about 802.15.3 multi-piconet. The related works about 802.15.3 MAC are all focusing on single piconet. We try to explore the possible issues in this area, and realize a simulation platform for future researchers who are interested in multi-piconet UWB networks.

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