隨著科技日新月異，無線網路技術迅速發展，全球各個科技公司相繼推出第五代行動通訊技術(The fifth generation of mobile phone mobile communication technology standards; 5G)的產品，而物聯網、智慧城市、智慧電錶及車聯網將是未來趨勢，在不久的將來不只有人類型通訊(human-type communication; HTC)，還有機器類型通訊(machine-type communication; MTC)的需求，MTC設備具備低功耗與成本、低資料量、低或無的移動性、高覆蓋率等特性，和機器與機器之間的自動化決策與傳輸，不再需要人為控制的通訊技術，MTC設備的數量將遠高於HTC，依目前網路存取機制將無法負荷。
第三代合作夥伴計畫 (The 3rd Generation Partnership Project Agreement; 3GPP) 為了與物聯網的時代接軌，針對機器對機器 (machine-to-machine; M2M) 的通訊應用，提出機器類型通訊的長期演進技術 (Long Term Evolution-Machine type communication; LTE-M) 的新標準。而在物聯網的多元應用環境中，於一個基地台的涵蓋範圍內，可預想到除了HTC設備外，也將會有大量的MTC裝置加入其中，當這些HTC和MTC裝置採用隨機存取程序 (random access; RA) 向基地台提出請求時，由於實體隨機存取通道 (physical random access channel; PRACH) 的資源有限，大量裝置的加入將造成通道壅塞，隨機存取碰撞機率大幅提高，基地台回應時間變長、頻道利用率下降、頻道資源不足等問題。
本論文針對在實體隨機存取通道的雍塞問題進行研究，修改一般隨機存取機制，提出一種基於設備到設備(device-to-device；D2D)的分群架構，藉由設備間互相協調分配前導碼 (preamble)，有效降低碰撞問題，大幅提升頻道資源利用，大幅縮短接入時間，解決實體隨機存取通道的雍塞問題。
由模擬結果表明，在市區模擬環境，MTC設備在不均勻分布情況下，短時間內有大量MTC設備要求接入時，所提出的方法藉由裝置間溝通分配後，再依分配到的時間及位置發起隨機存取程序，有效改善實體隨機存取通道的雍塞問題，大幅提升系統效能。

With the rapid development of technology, wireless network technology has developed rapidly, and various technology companies around the world have launched the fifth generation of mobile phone mobile communication technology standards (5G) products. While the Internet of Things, smart cities, smart meters and the Internet of Vehicles will be the future trend. In the near future, there will be not only human-type communication (HTC) but also machine-type communication (MTC) requirements. MTC device has low power consumption and cost, low data volume, low or no mobility, high coverage, and other functions, and automatic decision-making and transmission between machines and machines, no need for artificially controlled communication technology, the number of MTC devices will be much higher than HTC. The current network access mechanism will not be able to load.
The 3rd Generation Partnership Project Agreement (3GPP) In order to be in line with the era of the Internet of Things, for the machine-to-machine (M2M) communication application, the long-term evolution technology of machine type communication is proposed. A new standard for Long Term Evolution-Machine type communication(LTE-M). In the multi-application environment of the Internet of Things, within the coverage of a base station, it is expected that in addition to the HTC device, a large number of MTC devices will be added, and when these HTC and MTC devices adopt random access(RA) procedures. When making a request to the base station, due to the limited resources of the physical random access channel (PRACH), the addition of a large number of devices will cause channel congestion, and the random access collision probability will be greatly increased. Delay is getting longer, channel utilization is declining, and channel resources are insufficient.
This thesis studies the congestion problem of the physical random access channel modifies the normal random access mechanism and proposes a device-to-device (D2D)-based clustering architecture. The preamble effectively reduces the collision problem, greatly improves the utilization of channel resources, greatly shortens the access delay, and solves the congestion problem of the physical random access channel.
The simulation results show that in the urban simulation environment when the MTC device is densely distributed and a large number of MTC devices are required to access in a short time, the proposed mechanism is allocated by means of communication between devices. According to the allocated time and the location initiates a random access procedure, which effectively improves the congestion problem of the physical random access channel and greatly improves the system performance.

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