Can anyone explain how 3G LTE works?
By Stefan Constantinescu on Sunday, February 18th, 2007 at 3:48 PM PST In Ideas and rants
I’ve read about GSM, WCDMA, EVDO, HSDPA, HSUPA, WiMAX, but this new phrase "LTE" which stands for "Long Term Evolution" is still very foreign to me.
I’m trying to find more information about it, but I’m failing.
There are people out there a lot smarter than me, can you please break it down for me?
The only fact I could dig up was this:
"To obtain the all-important performance advantage for higher data rate mobile applications, the 3G LTE specifications will be based on a switch from W-CDMA to OFDM (Orthogonal Frequency Division Multiplexing) modulation technology. This represents a significant change at the lowest level of the radio communications, and achieving synchronization will be a major challenge." – RF Design
Is Nokia (NYSE: NOK) working on LTE? Will it be expensive to deploy? Time frames?
OFDM stands for Orthogonal Frequency Division Multiplexing. The current cdma based communication systems are based on a single carrier technology. OFDM breaks this single carrier into a large number of multiple sub-carriers called as tones and your entire data is sent through these tones. This has its inherent advantages.
I’m taking a course on OFDM this semester, so that I can design the LTE networks in the future!
OFDM stands for Orthogonal Frequency Division Multiplexing. The current cdma based communication systems are based on a single carrier technology. OFDM breaks this single carrier into a large number of multiple sub-carriers called as tones and your entire data is sent through these tones. This has a lot of advantages.
The technology is quite in demand and is being used by GSM and cdma carriers. I think the next next EV-DO revisions (Rev B/C) will also be OFDM based.
As far as I know, there is no specific LTE standard defined as of now (like wcdma was for 3G), perhaps WiMAX can be called as one (my professor disagrees tho).
Hopefully, I can be one of the people working on these standards in the future.
LTE is well on its way towards standardization. LTE uses OFDMA for multiple access. Very loosly speaking, its a variant of the WiMAX standards. I say loosly speaking because LTE has a different UL an DL multiple access mechanism. LTE uses OFDMA for DL and SC-FDMA (Single Carrier FDMA, or (Localised)DFT-Spread-OFDM) for UL.OFDMA works much the same way as OFDM, with the added feature that OFDM is also used for multiple access.This would mean that the different sets of subcarriers are allotted to different users in DL so that the “resource block” that they use are orthogonal to other users. In the UL, the same holds true (well, more or less) but there is an additional block of DFT sitting before the resource allocation block that, in effect, spreads the energy of the tx symbols on all the subcarriers used to tx the symbols in the UL. This reduces the PAPR at the mobile terminal but, as can be expected, leads to additional complexities regarding synchronization and channel estimation at the base station. To add to all this, LTE also supports MIMO, this means that the base station can have 2-4 antennas and the mobile terminal, at least in the baseline version has 2 antennas. Take a look at this document http://www.3gpp.org/ftp/Specs/html-info/36211.htm for a general overview of the LTE standards.
There is too much to it for me to explain in this reply. For more specific questions you can contact me at shakti.inbox@gmail.com. But I cant stress this more …*BE SPECIFIC* in your questions and I will make sure you get an answer ASAP.
Well guys,i guess i can help in that.Finally 3GPP has released Release 8 for LTE Standards,its very difficult to understand and apply i must admit but for me i got no other choice than to use those as its my graduation project.It Uses OFDM for DL, and SC-FDMA for UL at 100 Mbps DL rate and 50 Mbps UL rate.