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Before answering the exact question, let's go back little at once UE is switched on. When UE is switched on, it feels there are numerous signal around itself with different frequencies. So, it is now confused, with which signal he has to go with? Which is its right signal? So it starts scanning the radio signals which it supports. UE supports some specific bands. Bands contain a range of frequencies like band 7. Band: 7 Uplink Freq: 2500 - 2570 MHz Downlink Freq: 2620 - 2690MHz So it scans the frequencies which is supported by UE, and read PSS. To know more about how to read PSS and SSS, go to PSS signals  and SSS signals . So, Between UE is turned on and UE starts receiving and sending data it needs to synchronize with it's supported frequencies. This is done by PSS and SSS. Now, Where is PSS transmitted? PSS is transmitted in the last symbol of 0th and 10th slot in a frame. It gets repeated in each 5 msec time interval. [ Click here for the above image ...

As per 3GPP spec, 36.331 (RRC Protocol Spec), RRC Connection Reestablishment initiates after these conditions occur : 1. Upon detection of RLF (Radio Link Failure) 2. After Handover failure 3. Integrity check failure indication received from lower layers. 4. RRC connection Reconfiguration Failure. 5. Mobility from E-UTRA failure.

SSS stands for secondary synchronization signals. SSS comes in the symbol just before PSS comes. If you don't know, how did we detect PSS, then goto this the previous post of  PSS and SSS in LTE (Primary and secondary synchronization signals) SSS is basically an m-sequence or Maximum length sequence. Now, What is m-sequence? M-sequence is a pseudo random binary sequence. These sequence can be generated just by cycling through every possible state of a shift register of length resulting in a sequence of length . Here, Three m-sequences, each of length 31, are used to generate the secondary synchronization signals. SSS Generation Two binary sequences, each of length 31, are used to generate the SSS. Sequences  s 0 ( m 0 )  and  s 1 ( m 1 )  are different cyclic shifts of an  m -sequence,  ˜ s . The indices  m 0  and  m 1  are derived from the cell-identity group,  N ID (2)  and determine the cyclic shift. The va...