Initial Network Camping:
====================
What will happen when a mobile is switched on? The first thing the mobile has to do is to find a suitable network and camp to it.
For LTE mobiles, camping happens through following steps:
1.Mobile scans the available frequency band for finding a suitable cell.First thing, mobile should know is the presence of LTE cell. It is done using some predefined sequence known as Primary Synchronisation Signal (PSS). PSS is transmitted at a specific time during specific frequencies and at specific position (To be mroe technical, PSS is transmitted at the last OFDM symbol in first and 11th slots for FDD LTE and third symbol of 3rd and 13th slots for TDD). PSS is a Zadoff-Chu sequence, There are three such sequences defined and the sequence transmitted corresposnds to cells Physial cell ID group.
2. Once the mobile has got the PSS, next level is SSS-Secondary Synchronisation Signal. SSS is transmitted in the same slots as PSS. For FDD, it is transmitted one symbol before PSS. For TDD it is transmitted 3 symbols before. 168 values for SSS are defined each corresponding to a Physical Cell ID.Once the mobile decodes SSS, it comes to know
===>Physical Cell ID (From the pattern transmitted)
===>Frame boundaries (Different patterns for slot 0/slot11, hence can know the slot in which it is transmitted,from the slot boundaries already known by PSS, Frame boundaries can be detected)
===>FDD/TDD -Since the slots in which PSS/SSS is transmitted is different, once we know the slot boundary, Duplex tech can be known
===> CP length (By blind decoding, if SSS is in symbol 5 or 6 is understood. If it is in 5, extended CP. If it is in 6 normal CP.
If you want a very much deep understanding on synchronisation sequences ,please refer the below link
http://www.steepestascent.com/content/mediaassets/html/LTE/Help/SynchSignals.html
3.Decoding of PBCH : PBCH corresponds to MIB; It gives the most important parameters like SFN,Bandwidth and CFICH format. MIB is transmitted every 40 ms,fixed scheduling
4.Decoding SIBs: SIBs contain all the required information for initial access to the cell. It gives information about the cells capabilities, common and shared channels,access restrictions etc. Once the SIBs are decoded, mobile can access the network using common channels like RACH.
5.Reference Signals: Once the UE has identified the synchronisation signals-PSS and SSS, it will use the reference signals for RSRP/RSRQ measurements and reporting.
Further Reading
1. 3gpp spec 36.101
2.LTE, the UMTS Long term evolution:From theory to Practice
http://www.amazon.com/LTE-UMTS-Long-Term-Evolution/dp/0470697164
====================
What will happen when a mobile is switched on? The first thing the mobile has to do is to find a suitable network and camp to it.
For LTE mobiles, camping happens through following steps:
1.Mobile scans the available frequency band for finding a suitable cell.First thing, mobile should know is the presence of LTE cell. It is done using some predefined sequence known as Primary Synchronisation Signal (PSS). PSS is transmitted at a specific time during specific frequencies and at specific position (To be mroe technical, PSS is transmitted at the last OFDM symbol in first and 11th slots for FDD LTE and third symbol of 3rd and 13th slots for TDD). PSS is a Zadoff-Chu sequence, There are three such sequences defined and the sequence transmitted corresposnds to cells Physial cell ID group.
2. Once the mobile has got the PSS, next level is SSS-Secondary Synchronisation Signal. SSS is transmitted in the same slots as PSS. For FDD, it is transmitted one symbol before PSS. For TDD it is transmitted 3 symbols before. 168 values for SSS are defined each corresponding to a Physical Cell ID.Once the mobile decodes SSS, it comes to know
===>Physical Cell ID (From the pattern transmitted)
===>Frame boundaries (Different patterns for slot 0/slot11, hence can know the slot in which it is transmitted,from the slot boundaries already known by PSS, Frame boundaries can be detected)
===>FDD/TDD -Since the slots in which PSS/SSS is transmitted is different, once we know the slot boundary, Duplex tech can be known
===> CP length (By blind decoding, if SSS is in symbol 5 or 6 is understood. If it is in 5, extended CP. If it is in 6 normal CP.
If you want a very much deep understanding on synchronisation sequences ,please refer the below link
http://www.steepestascent.com/content/mediaassets/html/LTE/Help/SynchSignals.html
3.Decoding of PBCH : PBCH corresponds to MIB; It gives the most important parameters like SFN,Bandwidth and CFICH format. MIB is transmitted every 40 ms,fixed scheduling
4.Decoding SIBs: SIBs contain all the required information for initial access to the cell. It gives information about the cells capabilities, common and shared channels,access restrictions etc. Once the SIBs are decoded, mobile can access the network using common channels like RACH.
5.Reference Signals: Once the UE has identified the synchronisation signals-PSS and SSS, it will use the reference signals for RSRP/RSRQ measurements and reporting.
Further Reading
1. 3gpp spec 36.101
2.LTE, the UMTS Long term evolution:From theory to Practice
http://www.amazon.com/LTE-UMTS-Long-Term-Evolution/dp/0470697164
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