| Summary: | 碩士 === 國立中央大學 === 資訊工程學系 === 107 === In 5G networks, the cell needs to ensure the requirement of three deployment scenarios which are Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC) and Ultra-Reliable and Low Latency Communication (URLLC). Before UE is allowed to transmit User-plane data, UE needs to perform Random Access (RA) to get its own dedicate resource. The procedure of RA contains four messages which are preamble transmission, random access response, message 3 and contention resolution. When more than one UEs select the same preamble in preamble transmission, it will lead to a $preamble\ collision$ problem which causes RA failed. The preamble collided UEs will be assigned with the same resource to transmit message 3 and this result in the cell cannot decode their data.
With more User Equipments (UE) in a cell, satisfying low latency of RA is much more challenging since the probability of $preamble\ collision$ during RA will be higher. As a result, the latency will significantly increased when there are too many of UEs join RA procedure together. To reduce the preamble collision rate, 5G comes with RA resource expanding technique. However, with more resources allocated to RA, there will be less resources for U-plane (User-plane) data transmission. As a result, in this paper, we proposed a dynamic RA resource allocation scheme for 5G network. Our proposed method not only reduces the preamble collision rate when RA loading is high, but also reserves the resource for U-plane transmission as much as possible.
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