Synchronization of signals in LTE
504 different physical-layer cell ids are composed of 168 different physical-layer cell id groups each of 3 physical layer ids within the group
- primary synchronization signal – based on a frequency domain Zadoff-Chu
sequence indicating the physical layer id,
- secondary synchronization signal indicating the physical layer cell id group.
The mapping to resource elements is
- the primary synchronization signal is broadcast in the last OFDM symbol of slot 0 and slot 10. In the frequency it is located symmetrically in the centre of the configured cell bandwidth. The sequence is 62 symbols long.
- the secondary synchronization signal is shifted by one OFDM signal and thus
occupies the second last OFDM symbol of those slots.
- 5 REs are kept empty at each side of the frequency.
HI, CFI, DCI signaling
Hybrid ARQ information (HI), Control format information (CFI) and DL Control
Indicator (DCI) are signaled via PHICH, PCFICH and PDCCH.
HI is used for ACK/NACK info on UL-SCH HARQ. As there is only one TB in UL there is one bit to be signaled.
CFI is cell- and subframe specific and contains two bit where three different values are in use. DCI is existing in different formats and may combine different types of information.