RAN高培资料-WCDMA无线接口物理层.ppt

* * * * * * During the cell search, the UE searches for a cell and determines the downlink scrambling code and frame synchronisation of that cell. The cell search is typically carried out in three steps: Step 1: Slot synchronisation During the first step of the cell search procedure the UE uses the SCH’s primary synchronisation code to acquire slot synchronisation to a cell. This is typically done with a single matched filter (or any similar device) matched to the primary synchronisation code which is common to all cells. The slot timing of the cell can be obtained by detecting peaks in the matched filter output. Step 2: Frame synchronisation and code-group identification During the second step of the cell search procedure, the UE uses the SCH’s secondary synchronisation code to find frame synchronisation and identify the code group of the cell found in the first step. This is done by correlating the received signal with all possible secondary synchronisation code sequences, and identifying the maximum correlation value. Since the cyclic shifts of the sequences are unique the code group as well as the frame synchronisation is determined. Step 3: Scrambling-code identification During the third and last step of the cell search procedure, the UE determines the exact primary scrambling code used by the found cell. The primary scrambling code is typically identified through symbol-by-symbol correlation over the CPICH with all codes within the code group identified in the second step. After the primary scrambling code has been identified, the Primary CCPCH can be detected.And the system- and cell specific BCH information can be read. If the UE has received information about which scrambling codes to search for, steps 2 and 3 above can be simplified. * 节点间定时关系：不同步是绝对的，解决办法是找出偏移而给予补偿 * SCH只在每个时隙的前256chip发射信息（同步码），所以是断续的。 * DSCH是和DPCH相随的，DSCH的控制信息都在下行DPCCH上发送 * * * * * 上行的DPDCH和DPCCH是平行发送的；（用不同扩频码来进行区分） 下行的DPDCH和DPCCH是串行发送的；（在扩频前要进行串并转换，并用同一个扩频码来进行扩频，所以传输数据的效率是上行的两倍） * * *