TD-LTE原理及常见优化案例预案.ppt

Code word= transport block CQI reporting referred to PDSCH Challenge in synchronization and bandwidth detection: multiple bandwidths in LTE (for system and UE). Solution: SCH and BCH are in the central part of spectrum independently of BW so UE detects the central part of the spectrum and moves to the Tx bandwidth according to UE capability. BW for SCH is 1.25 MHz (72 subcarriers) and BCH can be 1.25Mhz or 5HMz. SCH symbol timing detection can be performed by several correlation methods. UE detects correlation peaks for the P-SCH code. Radio frame timing detection can be done on SCH or obtained by decoding BCH. P-SCH: subframe level synchronization: Correlation with a sequence selected among three different sequences S-SCH: frame level synch. Cell signal carries 1 of 168 cell group identifiers (pseudo-random sequences). When UE tunes to one of this the frame is synchronized. SCH is arranged so each sequence maps to a cell group ID Cell identifiers are sent by the reference signal Before starting RACH procedure the physical layer needs to receive from higher layers the Random Access Channel Parameters (PRACH configuration and frequency position) and the parameters for determining the preamble sequences. RACH only carries the preambles (no additional signalling or user data like in WCDMA Rel 99) The eNodeB may also schedule data in the resource blocks reserved for random access channel preamble transmission. Before starting RACH procedure the physical layer needs to receive from higher layers the Random Access Channel Parameters (PRACH configuration and frequency position) and the parameters for determining the preamble sequences. RACH only carries the preambles (no additional signalling or user data like in WCDMA Rel 99) The eNodeB may also schedule data in the resource blocks reserved for random access channel preamble transmission. 停等式即对于某一个HARQ进程，在等到ACK/NACK反馈之前，此进程暂时中止，待接收到反馈后，再根据是ACK还是NACK决定发送新数据还是进行旧数据重传 等待期间，ENODEB/UE为充分利用时域资源，必须发起其他并行HARQ进程。