Get started !
online LTE test
online C test

Updated or New
Site traffic (Aug-15)
GMSK modulation
Case of frequency correction burst
Solving modulation equations
One bit change
Normal duration burst



About
Feedback
Information Theory
Modulation
Multiple Access
OSI Model
Data Link layer
SS7
Word about ATM
GSM
GPRS
UMTS
WiMAX
LTE
Standard Reference
Reference books
Resources on Web
Miscellaneous
Mind Map
Perl resources
Magic MSC tool
Bar graph tool
C programming
ASCII table
Project Management
Simple Google box
HTML characters
Site traffic
Page view counter
5 6 9 , 6 5 9
another knowledge site

LTE - DL PHY Resource Element Group

LTE - DL PHY Resource Element Group [Under LTE]
» E-UTRA; physical channels and modulation - 36.211, Rel 8 «

Best way to understand PHY organisation would be to make an attempt in mapping physical channels onto frequency/time coordinates. Steps that can be followed are: 1) map cell specific reference signals, 2) understand and note down resource element groups, and then 3) map PSS, SSS, PBCH, PFICH, PHICH, PDCCH, and PDSCH (in that order).

Cell specific reference signals mapping works directly on resource element coordinates. Below is an example for single antenna port (p = 0) cell of ID 6.

   
   
l
0 1 2 3 4 5 6 0 1 2 3 4 5 6
1 2                        
                       
r     R     r       R    
1                        
1                        
R     r     R       r    
0                        
                       
r 0     R     r       R    
0                        
                       
R     r     R       r    
 
 
11 k
10
9
8
7
6
5
4
3
2
1
0


 R  are reference signals on antenna port 0 and  r  are reference signals on port 1. Note that even if cell has only one antenna port (like in our example), resource elements as per second antennna port configuration are kept unused (36.211:6.2.4).

Next step is to note down resource element groups. Resource elements other than those for reference signals are grouped as resource element groups, 4 REs form one group. In above example, control region is of 2 symbols with 2 REGs in first symbol and 3 in second symbol. Similarly if control region occupy 3 symbols, 3 REGs would be present in third symbol as well. If there are 4 antenna ports, four more REs from second symbol would go for reference signals reducing one REG from second symbol.

Each REG is represented as (k', l') where k' is lowest subcarrier number. l', symbol number is same for all REs within a REG. For example, first REG in second symbol would be represented as (4, 1).

This representation of REG is used for mapping PCFICH and PHICH.

Third step would be to start mapping channels as per equations specified in 36.211. In next article, we would look at examples of 6 RB and 15 RB configurations. Note that there are six configurations possible, represented as n6, n15, n25, n50, n75, and n100 (36.331:6.6.2/MIB), which correspond to channel bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz respectively (36.101:5.6).

Copyright © Samir Amberkar 2010-12§

LTE - basic PHY structure DL « LTE Index » LTE - DL PHY Structure example (6 RB, 1.4 MHz)