This is one of the confusing and most beautiful thing in LTE.
To understand Cell Acquisition in LTE we will need help of 3gpp Spec 36.211 and 36.331 sometime.
36.211 : Physical Channel
36.331 : Radio Resource Control
1. From the primary synchronization signal(PSS), it discovers the symbol timing and gets some incomplete information about the physical cell identity.
2. From the secondary synchronization signal(SSS), it discovers the frame timing, the physical cell identity, the transmission mode(FDD or TDD) and the cyclic prefix duration (normal or extended).
3. Once PSS and SSS is acquired, the mobile starts reception of the cell specific reference signals. These provides an amplitude and phase reference for the channel estimation process, which are essential for everything that follows.
4. The mobile then receives the physical broadcast channel and reads the master information block.
5. By doing so, it discovers the number of transmit antennas at the base station, the downlink bandwidth, the system frame number and a quantity called the PHICH configuration that describes the physical hybrid ARQ indicator channel.
6. The mobile can now start reception of the physical control format indicator channel (PCFICH), so as to read the control format indicators. These indicate how many symbols are reserved at the start of each downlink subframe for the physical control channels and
how many are available for data transmissions.
7. Finally, the mobile can start reception of the physical downlink control channel (PDCCH).
8. This allows the mobile to read the remaining system information blocks (SIBs), which are sent on the physical downlink shared channel (PDSCH).
9. By doing this, it discovers all the remaining details about how the cell is configured, such as the identities of the networks that it belongs to.
To understand Cell Acquisition in LTE we will need help of 3gpp Spec 36.211 and 36.331 sometime.
36.211 : Physical Channel
36.331 : Radio Resource Control
1. From the primary synchronization signal(PSS), it discovers the symbol timing and gets some incomplete information about the physical cell identity.
2. From the secondary synchronization signal(SSS), it discovers the frame timing, the physical cell identity, the transmission mode(FDD or TDD) and the cyclic prefix duration (normal or extended).
3. Once PSS and SSS is acquired, the mobile starts reception of the cell specific reference signals. These provides an amplitude and phase reference for the channel estimation process, which are essential for everything that follows.
4. The mobile then receives the physical broadcast channel and reads the master information block.
5. By doing so, it discovers the number of transmit antennas at the base station, the downlink bandwidth, the system frame number and a quantity called the PHICH configuration that describes the physical hybrid ARQ indicator channel.
6. The mobile can now start reception of the physical control format indicator channel (PCFICH), so as to read the control format indicators. These indicate how many symbols are reserved at the start of each downlink subframe for the physical control channels and
how many are available for data transmissions.
7. Finally, the mobile can start reception of the physical downlink control channel (PDCCH).
8. This allows the mobile to read the remaining system information blocks (SIBs), which are sent on the physical downlink shared channel (PDSCH).
9. By doing this, it discovers all the remaining details about how the cell is configured, such as the identities of the networks that it belongs to.
Steps in the
cell acquisition procedure
|
||
1
|
Receive PSS
|
Symbol Timing
|
Cell Identity within Group
|
||
2
|
Receive SSS
|
Frame Timing
|
Physical Cell Identity
|
||
Transmission Mode (FDD/TDD)
|
||
Cyclic Prefix Duration (Normal/Extended)
|
||
3
|
Receive RS
|
Amplitude and phase reference for
demodulation
|
Power reference for channel quality
estimation
|
||
4
|
Read MIB from PBCH
|
Number Of Transmit Antennas
|
Downlink bandwidth
|
||
System frame number
|
||
PHICH configuration
|
||
5
|
Start Reception Of PCFICH
|
Number of control symbols per subframe
|
6
|
Read SIB’s from PDSCH
|
System information
|
No comments:
Post a Comment