The Study Report of LTE Physical Layer Documents

Sheng-Lung ChengDepartment of Communication Engineering

National Chiao Tung University2011-10-17

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

Overview of downlink physical channel processing.

DL/UL system modelBy applying different scrambling sequences for neighboring cells, the interfering signal after 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

Precoding for transmit diversity(C)

0*

1

1*

0

xx

xx

Freq.

Band

Antenna Port

DL/UL system model Downlink precoding

2*

3

3*

2

0*

1

1*

0

00

00

00

00

xx

xx

xx

xxFreq.

Band

Antenna Port

Discussible topics Initial cell search

Discussible topics Initial cell search

Discussible topics Initial cell search

OFDM symbol timing synchronization

Cell ID determination

Radio frame timing synchronization

FD PSS

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.