Prototyping with Software-defined Radio Platform NI Test Technology Forum 2015 Yonsei University, Korea April 23rd, 2015 Presenter : MinKeun Chung
TRADITIONAL WIRELESS COMMUNICATION RESEARCH
Analysis Simulation
Idea
Implement / Test
Hand over to RTL designer (C/C++/HDL)
TRADITIONAL APPROACH FOR WIRELESS COMMUNICATION
Baseband
x
y = hx h
y
Gaussian Random Base Station
User Equipment
SIMULATION IS USEFUL BUT…
•
Wireless channel is fundamentally unpredictable
•
A perfect simulation does NOT guarantee perfect system operation in real world
•
Need to prototype
NEW WIRELESS COMMUNICATION RESEARCH
Analysis Simulation
Idea
Prototyping with SDR
NEW APPROACH FOR WIRELESS COMMUNICATION Up Conversion (e.g. 2.5GHz)
Down Conversion RF
Realistic “h”
x Base Station
y User Equipment
SOFTWARE-DEFINED RADIO A radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system
Software
Hardware
WHAT IS LABVIEW? •
LabVIEW uses a patented dataflow programming model
•
NOT sequential programming architecture of text-based prgramming languages
•
The graphical code is similar to block diagrams and flowcharts
•
The flow of data between nodes determines the execution order in LabVIEW
•
Multiple blocks can execute in parallel
•
Ideal for implementation that involves multitasking and multitreading (e.g. in FPGA)
WHAT IS AN USRP?
NI USRP-2920/2922 Frequency (Hz)
50 MHz to 2.2 GHz/ 400 MHz to 4.4 GHz
Bandwidth
20MHz
DAC/ADC
DAC : 16 bit , 400 MS/s ADC : 14 bit, 100 MS/s
Output Power
17 dBm to 20 dBm
Processing
Host
WHAT IS AN USRP? Network Cable
Host Computer Network Cable
USRP Tx 1
MIMO Cable
USRP Tx 2
Gigabit Ethernet Switch
Network Cable
USRP Rx 1
MIMO Cable
USRP Rx 2
WHAT IS REAL-TIME SYSTEM?
Real-time Response The ability to reliably and, without fail, respond to an event or perform an operation within a guaranteed time period
WHAT IS PXI PLATFORM? NI PXIe-1075 Chassis
NI PXIe-8133 Controller
Power Supply / Cooling PXI Backplane (Bus technology / Timing / Synchronization)
NI 5791 RF FAM / NI PXIe-7965R FlexRIO
Transceiver ADC/DAC RF Up/Down Conversion
FPGA Module for Real-time Testbed (Xilinx Virtex-5)
Quadcore Controller Window OS LabVIEW (Software)
WHAT IS AN FPGA? •
Field Programmable Gate Array
•
A silicon chip with unconnected gates and other hardware resources
•
Enables user to define and re-define functionality Interconnect Resources
I/O Cells
Logic Blocks
WHAT IS AN FPGA? High
Microprocessors General Purpose Short design cycles
Low
Flexibility
FPGAs Reconfigurable array of fixed resources Longer design cycles than Microprocessor
Performance
Low
ASICs Specific Purpose Long design cycles
High
HOW DOES AN FPGA WORK?
•
Circuit behavior is defined using software
•
Circuit specification (gate connection, etc) is loaded into the hardware
•
No operating system is needed for execution of logic
APPLICATION: REAL-TIME FULL DUPLEX RADIOS
WHAT IS FULL DUPLEX RADIOS? Time
Time Uplink
Uplink
Downlink
Downlink
Freq.
Time Division Duplex
Freq.
Frequency Division Duplex
WHAT IS FULL DUPLEX RADIOS? Time
Uplink / Downlink Simultaneously
Full Duplex
Freq.
WHAT IS A KEY ISSUE? •
Full Duplex SIC RF Front-End (Analog Cancellation)
•
PXIe based Full Duplex Testbed (Digital Cancellation)
Full Duplex Infrastructure
Uplink RX RF Front-End
RX RF
Uplink Signal
Self-interference Cancellation Downlink Signal
TX RF Downlink TX RF Front-End
KEY FACTORS FOR SIC REQUIRED
•
Dynamic range / Resolution of ADC
•
Range of the expected signal strengths
WHAT IS THE DYNAMIC RANGE? The ratio between largest and smallest acceptable values of a variable of interest.
DR (dB) = 6.02 x n +1.76dB n: The number of bits in the DAC/ADC Resolution NI 5791 RF Transceiver: 14-bit ADC, DR (dB) = 86dB
* * *
Macro Cell TX Power: 46dBm Small Cell TX Power: 24dBm Mobile TX Power: 23dBm WiFi TX Power: 23dBm
-4dBm
14-bit ADC Dynamic Range =86dB
No Saturation
*
Saturation
HOW MUCH SIC IS NEEDED?
High PAPR = 7dB Small Cell TX Power
Gain Compression Point
Thermal Noise Floor
31dBm 24dBm
-15dBm
-90dBm
WHAT IS A GAIN COMPRESSION?
Linear Region Saturation Region
Gain Compression Point
EQUIPMENT
NI PXIe 5791 RF FAM [2pcs]
NI 7965R FlexRIO FPGA Module [4pcs]
RESOURCES & PARAMETERS (1) Center Frequency : 2.52 GHz
BW : 20MHz (Subcarrier Spacing :15kHz)
RESOURCES & PARAMETERS (2)
LTE slot : 0.5 ms (LTE downlink release 8) 15360 Samples (6 OFDM Symbols) Sampling Frequency : 30.72 MHz
CP
CP
CP
CP
66.7 us / 2048 Samples 16.7 us / 512 Samples
CP
CP
Expanded CP FFT Size : 2048
RESOURCES & PARAMETERS (3)
QPSK
16QAM
64QAM
BLOCK DIAGRAM OF A FULL DUPLEX RADIO ARCHITECTURE
SYNCHRONIZATION & CHANNEL ESTIMATION
Primary Sync Signal (Time Sync.) Root Index : 25
Primary Sync Signal (Time Sync.) Root Index : 29
Resource Element R0
R0
R0
R0
R0
R0
R0
R0
R1
Orthogonal Pilot Allocation Not allocated
R1
R1
R1
R1
R1
R1
R1
SYNCHRONIZATION & CHANNEL ESTIMATION
Time Sync. [Far-End FD] Primary Sync. Signal (Root Index : 25)
20MHz Channel Estimation [Far-End FD]
Time Sync. [Near-End FD (SI)] Primary Sync. Signal (Root Index : 29)
20MHz Channel Estimation [Near-End FD (SI)]
ANALOG SIC PERFORMANCE Analog Passive Cancellation 40MHz
-35dB (Cancellation)
2.52GHz
ANALOG SIC PERFORMANCE Analog Active Cancellation
-60dB (Cancellation) 20MHz 2.52GHz
DIGITAL SIC PERFORMANCE Calculating Digital SIC Performance Self-interference QPSK
Digital SIC (SI : QPSK)
Cancel Out
- 43dB (Avg.)
CONTELLATION RESULT THROUGH SIC Only Analog Passive SIC Desired Symbol : 64 QAM Self Interference : QPSK (Noise)
Analog Passive SIC+ Digital SIC
EXPERIMENT SETUP
Uplink Signal
Downlink Signal
Self-interference Cancellation 1.2m
EXPERIMENT SETUP @ GLOBECOM 2014 Full Duplex RF
Uplink Signal Self-interference Cancellation Downlink Signal
NI PXIe 5791 RF FAM [2pcs]
DEMO AT IEEE GLOBECOM IN AUSTIN, TX, USA, DEC. 2014
NI 7965R FlexRIO FPGA Module [4pcs]
THROUGHPUT ANALYSIS
QSPK
16QAM
64QAM
Half Duplex
21.57Mbps
43.14Mbps
64.71Mbps
Full Duplex
41.01Mbps
82.01Mbps
122.6Mbps
Throughput Gain
1.9x
1.9x
1.89x
APPLICATION: HYBRID BEAMFORMING FOR SMART SMALL CELL
WHY HYBRID BEAMFORMING? •
For many RF antennas such as massive MIMO, full digital beamforming requires considerable RF hardware cost
•
By combining analog/digital beamforming, low RF hardware cost compared to full active digital beamforming
HYBRID BEAMFORMING PROTOTYPE
HYBRID BEAMFORMING PROTOTYPE
THANK YOU ANY QUESTION?
[email protected]
https://sites.google.com/site/minkeunchung
