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UE sẽ sử dụng PRACH / P cho thông tin liên lạc UL với UTRAN khi họ không có một mã channelization chuyên dụng được giao, chẳng hạn như khi tiếp cận ban đầu để UTRAN. Điều này dẫn đến khả năng va chạm (tức là nhiều UE sử dụng PRACH / P cùng một lúc). | 82 TDD Radio Interface 4.7.1.2 RRC Services and Functions The RRC offers General Control of the Broadcast type Dedicated Control of a single UE and Notification services of the Paging type to the upper layers. This is done by the RRC layer providing a signaling connection to the upper layers. This RRC signaling connection supports all the signaling requirements between the UE and a Core Network domain. Additionally the Radio Resource Control RRC layer also controls the various protocol entities of the Access Stratum via Inter-Layer procedures . The RRC services are realized via the following RRC functions Management of RRC connections between the UE and UTRAN The establishment of an RRC connection is initiated by a request from higher layers on the UE side to establish the first Signaling Connection for the UE. The establishment of an RRC connection includes an admission control function at the UTRAN as well. The release of an RRC connection can be initiated by a request from higher layers to release the last Signaling Connection for the UE or by the RRC layer itself in case of RRC connection failure. In case of connection failure the UE requests re-establishment of the RRC connection. Layer 3 Communication 83 The RRC layer also handles the assignment and reconfiguration of radio resources e.g. codes needed for the RRC connection taking into account both control and user plane needs. The RRC layer performs evaluation decision and execution related to RRC connection mobility during an established RRC connection such as handover preparation of handover to GSM or other systems cell re-selection and cell paging area update procedures based on for example measurements done by the UE. Management of Radio Bearers The RRC layer can on request from higher layers perform the establishment reconfiguration and release of Radio Bearers in the user plane. A number of Radio Bearers can be established to a UE at the same time. On establishment and reconfiguration the RRC layer .
