1. Cellular Networks and Mobile Computing COMS 6998-8, Spring 2012
Instructor: Li Erran Li
1/30/2012: Cellular Networks: LTE

2. Iyappan Ramachandran Agilent Technologies May 20, 2010
A Deeper Look at LTE
Iyappan Ramachandran
Agilent Technologies
May 20, 2010

3. Cellular Comms Evolution
3GPP – collaboration for 3G based on GSM
3GPP2 – collaboration for 3G based on IS-95
GSM
GPRS
EDGE
WCDMA
HSPA
HSPA+
LTE
TD-SCDMA
TD-HSPA
TD-HSPA+
IS-95
CDMA2000
EV-DO

4. LTE PHY Basics Six bandwidths Two modes
1.4, 3, 5, 10, 15, and 20 MHz
Two modes
FDD and TDD
100 Mbps DL (SISO) and 50 Mbps UL
Transmission technology
OFDM for multipath resistance
DL OFDMA for multiple access in frequency/time
UL SC-FDMA to deal with PAPR ratio problem

5. Frame Structure Frame Structure Type 1 (FDD)
Frame Structure Type 2 (TDD)

6. Resource grid 6 or 7 OFDM symbols in 1 slot
One downlink slot, Tslot
6 or 7 OFDM symbols in 1 slot
Subcarrier spacing = 15 kHz
Block of 12 SCs in 1 slot = 1 RB
0.5 ms x 180 kHz
Smallest unit of allocation
6 or 7 OFDM symbols :
Resource block
Transmission BW
Resource element
12 subcarriers
l=0
l=6

7. 2-D time and frequency grid
#19
#18
#17
#16
1 radio frame = 10 msec ( x Ts) #5
Time #4 #3 #2
Sub-frame #1
NscRB subcarriers (=12) #0
Power
1 slot = 0.5 msec
Frequency
NBWDL subcarriers

8. DL PHY Channels and Signals
Signals: generated in PHY layers
P-SS: used for initial sync
S-SS: frame boundary determination
RS: pilots for channel estimation and tracking
Channels: carry data from higher layers
PBCH: broadcast cell-specific info
PDCCH: channel allocation and control info
PCFICH: info on size of PDCCH
PHICH: Ack/Nack for UL blocks
PDSCH: Dynamically allocated user data

9. DL Channel Mapping P-SCH - Primary Synchronization Signal
S-SCH - Secondary Synchronization Signal
PBCH - Physical Broadcast Channel
PDCCH -Physical Downlink Control Channel
PDSCH - Physical Downlink Shared Channel
Reference Signal – (Pilot)
16QAM
64QAM
QPSK
Frequency
Time

10. DL signal demo (1)
DL 5 MHz FDD signal in AWGN channel

11. DL signal demo (2)
DL 5 MHz FDD signal in frequency-selective channel

12. UL PHY Signals and Channels
Signals: generated in the PHY layer
Demodulation RS : sync and channel estimation
SRS: Channel quality estimation
Channels: carry data from higher layers
PUSCH: Uplink data
PUCCH: UL control info
PRACH: Random access for connection establishment

13. UL Channel Mapping 64QAM 16QAM QPSK
PUSCH Demodulation Reference Signal (for PUSCH)
PUCCH
Demodulation Reference Signal (for PUCCH format 0 or 1, Normal CP)
QPSK
BPSK
Time
Frequency

14. UL signal demo
UL 5 MHz FDD signal in AWGN channel

15. MIMO in LTE Rel 8 defines MIMO only for DL
1, 2 and 4 transmit antennas defined for
Transmit Diversity (TxDiv)
Spatial Multiplexing (SpMux)
Control channels undergo TxDiv based on SFBC
Data channels may undergo TxDiv or SpMux

16. Orthogonal RS locations
channel matrix needs to be known in advance for equalization

17. DL MIMOsignal demo
DL 5 MHz TDD 4x2 MIMO signal in frequency-selective channel

18. Thank you!

19. Backup slides

20. SC-FDMA