The Study Report of LTE
Physical Layer Documents
Sheng-Lung Cheng
Department of Communication Engineering
National Chiao Tung University
2011-10-17
Outline
•
Introduction
•
References
•
DL/UL transmission train
•
Discussible topics
Introduction
 The goal of LTE is to provide a high-data-rate, low- latency
and packet-optimized radioaccess technology supporting
flexible bandwidth deployments.
 LTE system attributes
Reference
•
•
•
•
Farooq Khan ,“LTE for 4G Mobile Broadband: Air Interface Technologies and
Performance References”, Cambridge , 2009-04-19.
Erik Dahlman, Stefan Parkvall, Johan Skold ,“4G: LTE/LTE-Advanced for Mobile
Broadband”, Academic Press , 2011-05-09.
3GPP TS 36.211: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical
channels and modulation".
van de Beek, J.J.; Sandell, M.; Borjesson, P.O.” ML estimation of time and frequency
offset in OFDM systems ”, IEEE Transactions Signal Processing, 1800 – 1805, Jul
1997.
DL/UL system model
 Frame structure(type1 for FDD and half-duplex FDD)
DL/UL system model
DL/UL system model
 Overview of
By applying different scrambling sequences for
neighboring
cells,
the interfering
signal after
downlink
physical
channel
processing.
descrambling is randomized, ensuring full utilization of
the processing gain provided by the channel code.
DL/UL system model
 Overview of uplink physical channel processing.
DL/UL system model
 Downlink layer mapping
(A)
(B)
DL/UL system model
 Downlink layer mapping
(C)
DL/UL system model
 Downlink layer mapping
The rank assignment refers to RI
DL/UL system model
 Downlink precoding
(A)
(B)
(1)
DL/UL system model
 Downlink precoding
The precode matrix assignment refers to
PMI
DL/UL system model
 Downlink precoding
(2)
Here the W(i) is not
selected by UE.
DL/UL system model
 Downlink precoding
(C) Precoding for transmit diversity
Antenna Port
Freq. Band
 x0

 x1
 x*1 
* 
x0 
DL/UL system model
 Downlink precoding
Antenna Port
Freq. Band
 x0

 x1
0

 0
0
 x*1
0
x *0
x2
0
x3
0
0 

0 
 x *3 

x*2 
Discussible topics
 Initial cell search
Discussible topics
 Initial cell search
Discussible topics
 Initial cell search
??
OFDM symbol timing synchronization
FD PSS
Radio frame timing synchronization
Cell ID determination
FD PSS
and SSS
a. Using TD PSS
The length 62 FD Zadoff–Chu (ZC) sequence has
bad TD performance when IFFT size is large.
Discussible topics
 Initial cell search
a. Using CP
Discussible topics
 Initial cell search
Downlink CRS in one antenna transmission
Some OFDM symbols may not have any data,
so the observation interval would be very large.
Discussible topics
 DCI (Downlink Control Information) blind detection
Downlink control information , DCI, provides the terminal with the
necessary information for proper reception and decoding of the
downlink data transmission.
Puncturing or repetition
Control-Channel Elements (CCEs), is a
convenient name for a set of 36 useful
resource elements. The number of
CCEs, 1, 2, 4, or 8, required for a certain
PDCCH depends on the DCI payload
channel-coding rate.
Discussible topics
 DCI blind detection
As the number of CCEs for each of the PDCCHs may vary and is not
signaled, the terminal has to blindly determine the number of CCEs used
for the PDCCH it is addressed upon.
In release 8/9, the number of blind decoding attempts is 44 per subframe,
while for release 10 with uplink spatial multiplexing the number is 60.