basic call

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[url=]Overall Comparision with WCDMA[/url]

Even though overall sequence is pretty similar to WCDMA sequence, there are a couple of different points comparing to WCDMA sequence.

First point you have to look at is that in LTE 'RACH Preamble' is sent as a part of MAC Layer process. As you know RACH process was there in WCDMA, but in WCDMA it was a part of Physical layer process.

Another part I notice is that RRC Connection Setup Complete and Attach Request is carried in a single step. This is only one example. In LTE, many of NAS Message is piggybacked on RRC Messages. This would make message decoding/encoding process complicated but it would be efficient to reduce the number of message exchange between UE and eNodeB.

These are the differences you can notice just by looking at the message type, there are more differences you will find when you go into the information elements of each messages as you will see in following sections.

Next thing you will notice would be that there are much less SIBs being transmitted in LTE comparting to WCDMA. Of course there are more SIBs not being transmitted in this sequence (LTE has 10 SIBs in total), but with only these two SIBs it can transmit all the information to let UE camp on the network. In WCDMA there are a total 18 SIBs and in most case we used at least SIB1,3,5,7,11 even in very basic configurations. And some of the WCDMA SIBs like SIB5 and 11 has multipe segments. In LTE, number of SIB is small and none of them are segmented.

[url=]MIB[/url]

MIB in LTE has very minimal information (This is a big difference from WCDMA MIB) . The only information it carries are

i) BandWidth

ii) PHICH

iii) SystemFrameNumber

Of course the most important information is "BandWidth".

According to 36.331 section 5.2.1.2, the MIB scheduling is as follows :

The MIB uses a fixed schedule with a periodicity of 40 ms and repetitions made within 40 ms. The first transmission ofthe MIB is scheduled in subframe #0 of radio frames for which the SFN mod 4 = 0, and repetitions are scheduled insubframe #0 of all other radio frames.

[url=]SIB 1[/url]

SIB 1 in LTE contains the information like the ones in WCDMA MIB & SIB1 & SIB3. The important information on SIB 1 is

i) PLMN

ii) Tracking Area Code

iii) Cell Selection Info

iv) Frequency Band Indicator

v) Scheduling information (periodicity) of other SIBs

You may notice that LTE SIB1 is very similar to WCDMA MIB.

Especially at initial test case development, you have to be very careful about item v). If you set this value incorrectly, all the other SIBs will not be decoded by UE. And as a result, UE would not recognize the cell and show "No Service" message.

According to 36.331 section 5.2.1.2, the SIB1 scheduling is as follows :

The SystemInformationBlockType1 uses a fixed schedule with a periodicity of 80 ms and repetitions made within 80 ms.The first transmission of SystemInformationBlockType1 is scheduled in subframe #5 of radio frames for which the SFNmod 8 = 0, and repetitions are scheduled in subframe #5 of all other radio frames for which SFN mod 2 = 0.

This means that even though SIB1 periodicity is 80 ms, different copies (Redudancy version : RV) of the SIB1 is transmitted every 20ms. Meaning that at L3 you will see the SIB1 every 80 ms, but at PHY layer you will see it every 20ms. For the detailed RV assignment for each transmission, refer to 36.321 section 5.3.1 (the last part of the section)