V2X和D2D的链路级sidelink上的区别
场景的不同：higher channel variability, lower required latency, and increased devices density
更高的信道变化、更低的时延、增加的设备密度
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The number of demodulation reference signals carried in each subframe for V2X PSBCH, PSCCH and PSSCH has increased in order to capture frequent channel changes. In standard D2D two DMRSs are used in each subframe, while in V2X PSBCH there are three DMRSs and in V2X PSCCH/PSSCH there are four.
在V2X的PSBCH，PSCCH，PSSCH的子帧中增加解调参考信号的数据，以应对信道变化。在标准D2D中，每个子帧中有两个DMRS，在V2X的PSBCH中有三个DMRS，在V2X的PSCCH和PSSCH中有四个DMRS。 -
V2X transmission control (PSCCH) and data (PSSCH) are carried in the same subframe, differently from standard D2D where control and data subframe pools are clearly distinguished. This new feature allows to decode a PSSCH immediately after a PSCCH is recovered.
V2X的PSCCH和PSSCH在同一个子帧中，而在标准的D2D中，控制和数据子帧池是明显分开的。这样的特性是使得PSCCH被接收后能够及时的解出PSSCH。 -
PSCCH and PSSCH for V2X transmission may be a