Comments on: Can anyone explain how 3G LTE works? http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html Cell Phone News, Information, and Analysis Thu, 26 Nov 2009 08:47:50 -0600 http://wordpress.org/?v=abc hourly 1 By: Mostafa Hammam http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html/comment-page-1/#comment-164919 Mostafa Hammam Mon, 25 Feb 2008 22:04:49 +0000 http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html#comment-164919 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. 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.

]]> By: shakti http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html/comment-page-1/#comment-68836 shakti Fri, 26 Oct 2007 11:20:26 +0000 http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html#comment-68836 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. 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.

]]> By: Abhishta Paranjpe http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html/comment-page-1/#comment-11924 Abhishta Paranjpe Sun, 18 Feb 2007 23:55:06 +0000 http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html#comment-11924 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. :D 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. :D

]]> By: Abhishta Paranjpe http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html/comment-page-1/#comment-11923 Abhishta Paranjpe Sun, 18 Feb 2007 23:47:31 +0000 http://www.intomobile.com/2007/02/18/can-anyone-explain-how-3g-lte-works.html#comment-11923 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! :D 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! :D

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