臺灣博碩士論文加值系統

近年來，由於具有低成本與低功率之優點，IEEE 802.15.4 無線個人區域網路已經越來越熱門。IEEE 802.15.4 媒體進接控制在競爭進接區間(CAP)採取的時槽式碰撞避免載波感測多重進接(slotted CSMA/CA)和傳統 IEEE802.11無線區域網路(WLAN)使用的碰撞避免載波感測多重進接不一樣。第一個不同點在於無線個人區域網路中裝置只能在連續感測到多次通道閒置之後才可以傳送封包，而不無線區域網路只要感測到一次通道閒置就可傳送封包。第二個不同點在於無線個人區域網路的後退程序就算是在通道忙碌的情況下仍然可以繼續，而在無線區域網路中，當通道忙碌時，後退程序必須凍結。因此，IEEE802.15.4的塑模也不同於IEEE802.11。我們考慮一個IEEE802.15.4信標致能的無線個人區域網路的塑模與服務差異化，其中有兩種類別的裝置同時存在。第一類別裝置的優先權高於第二類別裝置。我們藉由分配一個較低的後退指數或是重傳上限給第一類別裝置來達到不同類別的差異化。為了能接近更真實的情況，我們考慮的是非飽和流量而不是飽和流量，其中裝置佇列總是有一封包準備就緒可供存送。明確地說，每個裝置都有一個有限佇列且封包的抵達都符合波以松(Poisson)程序。我們使用二維的馬可夫鏈模型來描述考慮裝置的後退程序。此外，我們使用M/M/c/K的模型來近似裝置佇列的行為。我們研究裝置數目對於效能指標的影響。我們也研究封包抵達速率對於效能指標的影響。我們感興趣的效能指標包含成功送達率、封包遺失機率，佇列延遲和佇列溢位機率。最後但並非最不重要的，我們使用C語言來撰寫電腦模擬程式，且使用電腦模擬結果來驗證我們的數學解析結果。

In recent years, IEEE 802.15.4 WPAN networks have been popular due to their advantages in low cost and power consumption. The IEEE 802.15.4 MAC adapts the slotted carrier-sense multiple-access with collision avoidance (CSMA/CA) in the contention access period, which is different from the classical CSMA/CA used in IEEE 802.11 WLAN. The first difference is that a WPAN device can transmit only after multiple consecutive sensing of an idle channel, instead of one idle channel sensing. The second difference is that when the channel is busy, the backoff process of a WPAN device still process, instead of being frozen. Therefore, the modeling of IEEE 802.15.4 WPAN is different from that of IEEE 802.11 WLAN. We consider the modeling and the service differentiation of a beacon-enabled IEEE 802.15.4 WPAN, where two classes of devices coexist. Class-1 devices are given priority over class-2 devices. We differentiate different classes of devices by assigning a lower backoff exponent or retry limit to class-1 devices than class-2 devices. To be closer to the real-life situation, we consider the non-saturated traffic, instead of the saturated traffic ,where there is always a packet in the queue ready to transmit. Specifically, each device has a finite queue and the packet arrivals at each device follow a Poisson process. We use a 2-dimensional Markov Chain model to describe the backoff process of the considered device. Furthermore, we use M/M/c/K model to approximate the device queue behavior. We study the effect of the number of devices on the performance measures. We also study the effect of the packet arrival rate in the performance measures. The performance measures of interest are the throughput, the packet loss probability, the queueing delay, and the buffer overflow probability. Last but not least, the analytical results are validated via simulation program written in C.

摘要 I
Abstract II
Contents of Tables . IV
Contents of Figures.... . IV
Chapter 1 Introduction 1
Chapter 2 Overview of IEEE 802.15.4 3
Chapter 3 System Model 6
3.1 Service Differentiation Scheme 6
3.2 Analytical Model 8
3.3 Performance Measures 15
3.3.1 Packet Loss Probability 15
3.3.2 Queueing Delay 16
3.3.3 Average MAC Delay 17
3.3.4 Throughput 21
Chapter 4 Numerical Results 26
4.1 Equal Arrival Rate and Number of Devices 26
4.1.1 Backoff Exponent 26
4.1.2 Retry Limit 28
4.2 Fixed Arrival Rate and Number of Class-1 Devices 30
4.2.1 Backoff Exponent 30
4.2.2 Retry Limit 32
4.3 Fixed Arrival Rate and Number of Class-2 Devices 35
4.3.1 Backoff Exponent 35
4.3.2 Retry Limit 37
Chapter 5 Conclusions 51
References 52

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