隨著無線通訊技術迅速的發展，物聯網 (Internet of Things; IoT) 的概念出現於人們的生活中，並帶給我們更便利、更智慧化的應用服務。在物聯網中，機器類型通訊 (machine-type communication; MTC) 技術成為科技發展的關鍵之一，它具備低功耗與成本、低資料量、低或無的移動性、高覆蓋率等特徵，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，種種特點讓MTC在物聯網中備受關注。

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，可預想到除了用戶設備 (user equipment; UE) 外，也將會有大量的MTC裝置加入其中，當這些UE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，隨機存取碰撞機率提高，基地台回應時間變長等問題。

本論文主要是針對實體隨機存取通道的壅塞問題，提出一種不需修改競爭式隨機存取程序的改善方法，透過檢測到的碰撞因子，動態調整分群與分配不同的PRACH Configuration Index參數，將大量MTC裝置分散於三個群組後，在不同的RA-slot中發送隨機接入請求，進而減少實體隨機存取通道壅塞的問題。

由模擬結果顯示，在市區的模擬環境下，短時間內有大量的MTC裝置發送接入請求時，本論文的動態調整分群機制可以有效的將裝置分散於不同群組，並在不同的RA-slot下接收請求，達到改善實體隨機存取通道的壅塞問題。

With the rapid development of wireless communication technology, the concept of IoT has been emerge in people's lives and makes us more convenient and intelligent application services. In the Internet of Things, machine-type communication (MTC) technology has become one of the key technological development. It has several features such as low power consumption and cost, low data volume, low or no mobility, and high coverage. Automated decision-making and transmission between machine and machine eliminates the need for human-controlled communication technology. So many features make MTC receive much attention in IoT.

The 3rd Generation Partnership Project (3GPP) aims to meet the needs of the Internet of Things and proposes a new standard for Long Term Evolution-Machine type communication (LTE-M) for machine-to-machine communication applications. In the environment of the Internet of Things, within the coverage of a base station, it can be expected that in addition to user equipment (UE) and a large number of MTC devices will use random access to joining base station. When the random access procedure makes a request to the base station, due to limited resources of the physical random access channel, the addition of a large number of devices will cause channel congestion, increase the probability of random access collision, and increase the response time of the base station.

This thesis mainly focuses on the congestion problem of the random access channel of the physical entity, proposes an improved method without modifying the contention-based random access procedure, dynamically adjusts the clustering and assigns different PRACH Configuration Index parameters through the detected collision factors. After a large number of MTC devices are dispersed in three groups, random access requests are sent in different RA-slots, thereby reducing the problem of congestion of random access channels in the physical entities.

The simulation results show that in the urban area, when a large number of MTC devices send access requests in a short period of time, the proposed dynamic adjustment and grouping mechanism can effectively disperse the devices different groups and in different RA-slot, which improves the congestion problem of the physical random access channel.

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