LTE V2X sidelink communication is introduced as sidelink transmission mode 3 and mode 4 in the Release 14 of 3GPP specification. V2X sidelink communication is used for direct communication between vehicle to everything. V2X comprises of vehicle-to-vehicle (V2V) communications, vehicle-to-infrastructure (V2I) communications, vehicle-to-pedestrian (V2P) communications.

V2X sidelink communication is used for low-latency safety services and out of coverage operations. It supports half duplex frequency division duplex (HD-FDD) operations as well as 10 MHz and 20 MHz channel bandwidths.

Physical Structure

Sidelink uses the single-carrier frequency-division multiple access (SC-FDMA) transmission scheme. It consists of 14 symbols in each subframe.

Note Only normal cyclic prefix is supported.

Guard Symbol

The last SC-FDMA symbol in a sidelink subframe serves as a guard period and hence not used for sidelink transmission.

Physical Channels

Physical sidelink shared channel (PSSCH) is used to carry sidelink data. Supported modulation schemes are QPSK, 16QAM, and 64QAM.

Physical sidelink control channel (PSCCH) is used to carry sidelink control information (SCI). SCI Format 1 consists of PSSCH transmission information and it is transmitted in two consecutive resource blocks (RBs). For more information on PSCCH, refer to section 5.4.3.1 of 3GPP 36.212 specification.

PSSCH and PSCCH can be transmitted in adjacent RBs or non-adjacent RBs. For more information on allocations, refer to section 14.1.1.4C and section 14.2.4 of 3GPP 36.213 specification. Both allocations types are illustrated in the following figure.

Demodulation Reference Signal

PSSCH demodulation reference signal (DMRS) and PSCCH DMRS are transmitted in 4 symbols per subframe. DMRS is transmitted on symbols 2, 5, 8, and 11 of a subframe as highlighted in the following figure. For more information on DMRS, refer to section 9.8 of the 3GPP 36.211 specification.

Retransmission

Data and control information transmitted in a subframe can be retransmitted. Frequency allocation and subframe time gap between initial transmission and retransmission can be varied. For more information on retransmission, refer to section 14.1.1.4C of 3GPP 36.213 specification.

Note
  • In RFmx Waveform Creator, set the Link Direction to Sidelink in LTE FDD to select sidelink.
  • In RFmx Waveform Creator, carrier aggregation of sidelink and other link direction carriers are not allowed.