隨著無線通訊技術日益進步，我們期望更便利的生活，因此需要更廣泛、更智慧化的應用服務，於是物聯網 (Internet of Things; IoT) 概念出現於我們的生活中；物聯網主要是由一群機器型態通訊裝置 (machine type communication device; MTCD) 所連接而成，其具備低功耗、低資料傳輸速率、及高覆蓋率的特點，而物聯網不只是將 MTCD 串成一個網路，更重要的是無須再透過人為協助即可實現機器間的資料自動傳遞。
為了迎接物聯網時代的來臨，第三代合作夥伴計畫 (Third Generation Partnership Project; 3GPP) 針對機器對機器 (machine-to-machine; M2M) 之間的通訊應用提出新的標準，稱為機器類型通訊的長程演進技術 (long term evolution-machine type communication; LTE-M)。而物聯網的應用多元，所以將會有大量的 MTCD 加入基地台涵蓋範圍，當這些 MTCD 和人類用戶 (user equipment; UE) 採用相同的隨機存取 (random access; RA) 機制向基地台 (evolved node B; eNB) 提出請求時，由於實體隨機存取通道 (physical random access channel; PRACH) 的資源有限，再加上 MTCD 不可以影響人類用戶通訊品質的條件下，將會造成 MTCD 的隨機存取碰撞機率提高、通道壅塞，獲得基地台回應的時間變長，甚至無回應造成服務中斷。
本論文將以改善實體隨機存取通道壅塞為首要目標，以延長 MTCD 的生命週期為次要目標，提出以分群為主、挑選群組組長為輔的機制來改善競爭存取的碰撞問題。一共提出兩種分群策略：動態角度分群策略 (dynamic angle grouping; DAG)、動態圓形分群策略 (dynamic circle grouping; DCG)；接著於每一群組中以剩餘電量及通道品質選出一群組組長 (group leader; GL)，用以代表群內的群組成員 (group member; GM) 與基地台溝通。
結果顯示，在大型賣場的模擬環境下，由於涵蓋大量的 MTCD，所以動態分群機制可有效降低競爭通道的碰撞率，由於碰撞率較低，所以節省了碰撞發生後的回退時間，所以完成所有需求的傳送時間較短，且耗電量也較未分群機制來的少，延長了 MTCD 的生命週期；對於賣場而言，同時降低 MTCD 硬體汰換成本。

Along with the wireless communication technologies progress day by day, and people expect more convenient life and need more extensive and more intelligent application. As a result, the concept of Internet of Things (IoT) is emerged in our life. It consists of a group of machine type communication devices (MTCD) which have low power, low transmission data rate and high coverage rate. IoT not only connects MTCDs for a network, but also realizes auto data transmission between MTCDs.
The generation of IoT is coming, the Third Generation Partnership Project (3GPP) brings up a new standard foe machine-to-machine (M2M) communication named long term evolution-machine type communication (LTE-M). However, application of IoT is pluralism, so a mass of MTCDs will join the coverage of evolved node B (eNB). When both of MTCDs and user equipment (UE) take the random access (RA) procedure to send request to eNB, the collision rate of MTCDs will increase. Because the physical random access channel (PRACH) is limited, and MTCD can’t affect the UE’s communication quality, the collision rate of MTCDs will increase, PRACH will congest, and the period of eNB response will be longer, even no service.
This paper will improve the PRACH congestion primary propose, to extend the life cycle of MTCD as a secondary objective, to put forward the main grouping, supplemented by the group leader (GL) selection mechanism to improve the problem of collision of RA. There are two dynamically grouping strategies are dynamic angle grouping (DAG) and dynamic circle grouping (DCG), and then according to the remaining battery and channel quality to select GL to communicate with eNB.
According to the simulation result, in the simulation environment of large indoor marketplace, due to large amount of MTCDs, the dynamically grouping strategies are useful to reduce the number of MTCDs in the PRACH, and therefor reduce the collision rate. Because of low collision rate, it saves back-off time after colliding, and the time of completing all requests is shorter. The power consumption of the dynamically grouping strategy is less than not grouping and so extend the life cycle of MTCD. For the marketplace, it reduces MTCD hardware costs by dynamically grouping strategy.

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