Sidelink synchronization update

An apparatus comprising:

• at least one processor;
• and
• at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform:
• transmitting, by the apparatus, a first synchronization signal to at least one receiving user equipment with use of a sidelink, the first synchronization signal having a first frequency;
• causing transmitting, by the apparatus to the at least one receiving user equipment, an indication of a second frequency;
• and
• causing transmitting, by the apparatus to the at least one receiving user equipment, a second synchronization signal having the second frequency,
• wherein the at least one memory further stores instructions that, when executed by the at least one processor, cause the apparatus at least to perform:
• determining a frequency offset between the first frequency and the second frequency;
• and
• wherein transmitting the indication of the second frequency comprises transmitting indication of the frequency offset from the apparatus to the at least one receiving user equipment,
• wherein the indication of the frequency offset indicates a frequency offset amount in frequency units with a granularity, and
• wherein indication of the frequency offset amount in frequency units with the granularity comprises one of the following:
• 1.5 kHz with 15 kHz subcarrier spacing applied for synchronization signals or control signaling or both synchronization signals and control signaling provided by the apparatus;
• or
• 3 kHz with 30 kHz subcarrier spacing applied for synchronization signals or control signaling or both synchronization signals and control signaling provided by the apparatus.

An apparatus comprising:

• at least one processor;
• and
• at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform:
• receiving, by the apparatus from a source user equipment with use of a sidelink between the source user equipment and the apparatus, a first synchronization signal having a first frequency;
• receiving, by the apparatus from the source user equipment, an indication of a second frequency;
• and
• receiving, by the apparatus from the source user equipment, a second synchronization signal having the second frequency,
• wherein receiving the indication of the second frequency comprises receiving indication of a frequency offset from the apparatus to the at least one source user equipment,
• wherein the indication of the frequency offset indicates a frequency offset amount in frequency units with a granularity, and
• wherein indication of the frequency offset amount in frequency units with the granularity comprises one of the following:
• 1.5 kHz with 15 kHz subcarrier spacing applied for synchronization signals or control signaling or both synchronization signals and control signaling provided by the apparatus;
• or
• 3 kHz with 30 kHz subcarrier spacing applied for synchronization signals or control signaling or both synchronization signals and control signaling provided by the apparatus.