Beyond LTE: Evolving the Physical Layer

Transcription

1 Cluster of Excellence Ultra High-Speed Mobile Information and Communication Beyond LTE: Evolving the Physical Layer Helge Lüders UMIC Day Aachen, October 20, 2009 Institute of Communication Systems and Data Processing Prof. Dr.-Ing. P. Vary

2 Motivation What is? LTE = Long Term Evolution of UMTS Release 8 of 3GPP s UMTS standard Higher data rates, lower delay, increased flexibility Roll-out: ? Logo: 2

3 Motivation Why? LTE chosen by NGMN Alliance as first step towards 4G LTE is benchmark of research cluster, Area A Increase robustness Increase spectral efficiency Increase energy efficiency Decrease latency Goals in line with Logos: / 3

4 Outline Motivation LTE Physical Layer Overview LTE Coverage and Capacity The Final Frontier Breaking the Final Frontier Conclusions 4

5 LTE Physical Layer Overview System model Data from MAC Layer Segmentation CRC Channel Coding Rate Matching Mapping OFDM HARQ CRC Combining Turbo Decoding DEMUX Soft Demapping OFDM -1 Data to MAC Layer HARQ: Hybrid Automatic Repeat request 5

6 LTE Physical Layer: Resource Elements (RE) Time and frequency resources Frequency 7 12 Resource Elements (REs) = 1 Resource Block (RB) 1Time slot = 0.5 ms 1Subcarrier = 15 khz Frequency bandwidth 5 MHz 10 MHz 15 MHz Number of RBs / REs per time slot 25 / / / 6300 RE RB 20 MHz 100 / 8400 Time 6

7 Simulation: LTE Coverage and Capacity Best case goodput per resource element (RE) Error-free throughput based on CRC Includes up to 3 retransmissions Code rate: 1/3 Goodput in bit/re QPSK 16QAM 64QAM Channel quality: Signal-to-Interference-and-Noise Ratio (SINR) in db 7

8 Simulation: LTE Coverage and Capacity Best case goodput per resource element (RE) Error-free throughput based on CRC Includes up to 3 retransmissions Code rate: 1/3, 1/2, 2/3, 3/4, 4/5 Envelope Goodput in bit/re Channel quality: Signal-to-Interference-and-Noise Ratio (SINR) in db 8

9 Simulation: LTE Coverage and Capacity System-level: Channel quality and goodput/re Serving base station Adjacent interfering cells Pathloss: Cost 231, urban Signal-to-Interference-and-Noise Ratio (SINR) in db Meter Meter 9

10 Simulation: LTE Coverage and Capacity System-level: Channel quality and goodput/re Serving base station Adjacent interfering cells Pathloss: Cost 231, urban 20 or 100 user equipments (UEs) Arbitrary, uniform UE positions by Monte-Carlo simulation with 100 iterations System bandwidth: 20 MHz All UEs use same number of REs Meter Modulation and goodput in bit/re QPSK 16QAM 64QAM Meter 10

11 Simulation: LTE Coverage and Capacity Cumulative distribution of user goodput Mbit/s Best 20% near Base Station 20 Users 100 Users Percentage of users Mbit/s Weakest 20% near cell edge Sum cell goodput: 39 Mbit/s Theoretical maximum: Mbit/s (Single antenna, 20 MHz, 64QAM, code rate 1) User data rate in Mbit/s 11

12 The Final Frontier The Shannon Limit Claude E. Shannon ( ) 12

13 The Final Frontier The Shannon Physical Layer Goodput in bit/re LTE Shannon Channel quality: SINR in db 13

14 The Final Frontier Cumulative distribution of user goodput Near Base Station 20 Users 100 Users Percentage of users Near cell edge LTE Shannon User data rate in Mbit/s Sum cell goodput: LTE 39 Mbit/s Shannon 60 Mbit/s 14

15 Breaking the Final Frontier Claude E. Shannon ( ) EXCEPT MIMO 15

16 Breaking the Final Frontier The MIMO Shannon Physical Layer Goodput in bit/re 1x1 LTE 1x1 Shannon 2x2 Shannon 4x4 Shannon EXCEPT MIMO Spacial multiplexing of parallel streams Channel quality: SINR in db Moderate gains at cell edge 16

17 Breaking the Final Frontier Cumulative distribution of user goodput Near Base Station Percentage of users Near cell edge User data rate in Mbit/s 100 Users 1x1 LTE 1x1 Shannon 2x2 Shannon 4x4 Shannon EXCEPT MIMO Spacial multiplexing of parallel streams Sum cell goodput: 1x1 LTE 39 Mbit/s 1x1 Shannon 60 Mbit/s 2x2 Shannon 94 Mbit/s 4x4 Shannon 143 Mbit/s 17

18 Breaking the Final Frontier The MIMO Shannon Physical Layer Goodput in bit/re 1x1 LTE 1x1 Shannon 2x2 Shannon 4x4 Shannon EXCEPT MIMO Joint detection at Rx Channel quality: SINR in db High gains at cell edge 18

19 Breaking the Final Frontier Cumulative distribution of user goodput Near Base Station Percentage of users Near cell edge 100 Users 1x1 LTE 1x1 Shannon 2x2 Shannon 4x4 Shannon EXCEPT MIMO Joint detection at Rx User data rate in Mbit/s Sum cell goodput: 1x1 LTE 39 Mbit/s 1x1 Shannon 60 Mbit/s 2x2 Shannon 118 Mbit/s 4x4 Shannon 242 Mbit/s 19

20 Cell Edge Coverage Improvement Cooperative MultiPoint transmission (CoMP) Interference reduction / cancellation (IC) Example: perfect cancellation Percentage of users 100 Users 1x1 LTE 1x1 Shannon 2x2 Shannon 4x4 Shannon 4x4 Shannon with IC and joint detection User data rate in Mbit/s Ideal sum cell goodput: 989 Mbit/s 20

21 UMICore Physical Layer Demonstrator 21

22 Conclusions LTE is the UMIC physical layer reference Average cell goodput (SISO): 39 Mbit/s (20 MHz) At cell edge fairly close to Shannon limit Only moderate gains at cell edge by pure MIMO UMIC physical layer potentials: Significant improvement of cell edge data rates by cooperative interference management Improved energy efficiency 22

23 Cluster of Excellence Ultra High-Speed Mobile Information and Communication Questions? Thank you for your attention! Institute of Communication Systems and Data Processing Prof. Dr.-Ing. P. Vary