Introduction to LTE...

LTE stands for Long Term Evolution. It is the evolved version of already present cellular network architecture. In general term people call it 4G also. But in fact it is NOT a 4G technology standard, it's a 3.9G. LTE-Advance is the actual 4G technology standard.

Before going further in to the brain storming architecture and call flows, we should first know the history and evolution of LTE to keep interest in it.

So the evolution of a cellular network is as follows in the diagram. As I am too lazy to draw a complete diagram, I have pulled an image of Rohde & Scewarz :
[Click on the image for zoom]

So, There are several organizations who work for cellular network architect such as 3GPP, 3GPP2, IEEE. LTE standard is defined by 3GPP. So anything you read, implement or use for LTE, it should be as per 3GPP standards.

As we are going forward day by day, we see that there are more data hungry applications. LTE will resolve this issue. In the next post we will read the motivation behind the LTE standard, the Goal set for LTE and how much LTE will be succeeded in satisfying data hungry application.

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Why does PSS & SSS synchronization need?

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

PSS and SSS in LTE (Primary and secondary synchronization signals)

In most of websites I found where do PSS and SSS come and what do these are beneficial for. The thing which most of the LTE learners want to understand is that, "What is exactly those signals?". That is the reason I started this post. PSS & SSS are two synchronization symbols in LTE which help UE (User equipment) to synchronize with network. So, PSS stands for Primary synchronization signal. SSS stands for Secondary synchronization signal. PSS is nothing but a sequence known as Zadoff-Chu Sequence . It comes in last symbol of slot 1 and slot 0. For detail info on where & how does it come, go to PSS and SSS synchronization. Now, What is Zadoff-chu Sequence ? In LTE, Zadoff chu sequence is a combination of complex sequences. These sequences have a special property, known as CAZAC webform. CAZAC stands for " C onstant A mplitude Z ero A utocorrelation". It means when we use this as a synchronization code, the correlation between the ideal sequence

SSS in LTE (secondary synchronization signals)

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 values can be read from table 6.11.2.1-1 in "Physical Cha

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