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Overal LTE Sequence


Most of us would be specialized in one or a few specific area/layer as an engineer. Technically it is understandable because not a single person can master everything, but I strongly recommend you to try to have some big picture of the whole process. Whenever you have some issues or something for you to work, try to ask your self "Where is the current issue located in the whole picture ?".

You don't have to try rote memorization for these whole process, but if you keep trying to map your current issues to specific parts within the whole picture, these whole sequence would automatically pops up in your memory. I say so often to my kid or my juniors "Don't try to memorize it, just repeat it until you automatically recall" (They are looking at me seeminly saying "What is the difference ?" -:) I just smile -:).


Following is my version of the whole LTE procedures.. but if you are trying to describe it, you would have a little bit different version.. but I think overall logic would be similar. Every now and then, just try to recall these sequence in your mind and ask your self "how in detail I can explain about each of these steps ?". Actually each of these steps can be described in a volum of a thick book.


i) UE is Off

ii) Power On UE

iii) < Frequency Search >

iv) < Timing Sync >

v) < Cell Search > : Normally a UE would find multiple cells in this process

vi) < Cell Selection >

vii) MIB decoding

viii) SIB deconding

ix) < Initial RACH Process >

x) < Registration/Authentication/Attach>

xi) < Default EPS Bearer Setup >

xii) Now UE is in IDLE Mode

xiii) <(If the current cell become weak or UE moves to another cell regisn) Cell Reselection>

xiv) <(When Paging message comes or User make a call) RACH Process>

xv) < Setup Dedicated EPS Bearer >

xv) Receive data

xvi) Transmit data

xvii)  (If UE power is percieved too weak by the network) Network send TPC command to increase UE Tx Power

xviii) (If UE power is percieved too strong by the network) Network send TPC command to decrease UE Tx Power

xix) < (If UE moves to another cell region) Network and UE perform Handover procedure >

xx) User stop call and UE gets into IDLE mode