由於科技的發展，連網技術也愈來愈普及，許多的裝置開始與網路做連結，其中機器類型通訊所占比例也大幅提升，因蜂巢式網路的覆蓋範圍及方便性，其已成為機器對機器(Machine-to-Machine, M2M)通訊的連網選擇，雖然M2M裝置一般發送的資料封包不大，但其數量龐大，在短時間內有眾多的裝置要求資源，勢必會造成競爭模式下的隨機存取發生碰撞的情形，使得成功存取的機率大幅下降，對服務品質造成影響，為此，本碩士論文著重於減緩大量M2M 裝置進行隨機存取時對系統產生的影響，將設計隨機存取控制機制，以減輕碰撞情形；並考慮到資源的使用效率，另一方面，透過前置碼使用集合的區分，讓傳送時發生碰撞的裝置能夠有機會和首次傳送的裝置分開競爭，以降低延遲，使能滿足延遲需求的裝置可以增加；最後，因為資料種類的不同，有些資料有即時性，我們進一步加入優先權的安排，事實上，在長期演進技術(Long-Term Evolution, LTE)系統中，H2H(Human-to-Human, H2H)和M2M通訊的共存也是一項議題，因此，在本碩士論文中，我們可以將H2H通訊的使用者視為高優先權的類別。透過模擬的驗證，所提機制將可達成預期的效果，除能夠在系統負載高及低時維持隨機存取效率外，也能降低平均延遲。

As the technology evolves, networking technologies become more and more popular.As an increasing amount of devices are connected to a network, the machine-to-machine (M2M) communication has become pervasive. Because of a better coverage solution provided by the cellular network, it is one of networks which can be chosen for the M2M communication. Although the data size is small, the number of M2M devices is perhaps huge. When a lot of devices are trying to access the network in a short period, collisions are inevitable, leading to communication failure and degradation of service. To address such an issue, how to alleviate collisions in the random access of the long-term evolution (LTE) system is considered when M2M devices are added. We try to propose a random access scheme to enhance efficiency. By splitting the preamble into two sets, it is able to reduce the delay for M2M devices suffering from preamble collisions. The two sets include the one of M2M devices which never tried before and the one of backlogged M2M devices. Additionally, priority is considered for devices which can not tolerate a longer delay and the others. Actually, the coexistence M2M and human-to-human (H2H) devices form an issue to be addressed. This allows us to let H2H devices have a priority higher than M2M devices. Finally, our simulation results demonstrate that our proposed scheme can achieve the goal of delay reduction and access efficiency enhancement regardless of traffic loads within the network.

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