Download - Network Coding Testbed
Network Coding Testbed
Jeremy Bergan, Ben Green, Alex Lee
Presentation Overview
• Background Information • Project Overview
• Framework Design
• Plan & Schedule
• Prototyping
• Implementation
• Testing
Solution
• Network Coding is a scheme that has potentially larger throughput than current wired or wireless networks.
Problem
• Built a network coding testbed to implement network coding protocols and topologies.• Implement Analog Network Coding (ANC).• Utilize the Universal Software Radio Peripheral (USRP) to
send and receive the physical packet.• Implement a testing and logging layer to track testbed
performance.
Network Coding Overview
• Network Codingo Intelligently combining packets at intermediate nodes
to increase network throughput
ANC: Decoding Interfered Signals
1. Node1 and Node2 simultaneously transmito Signals interfere at intermediate node
2. Intermediate node amplifies and forwards combined signal3. Node1 can decode Node2's message based on knowledge
of the message it sent previously
Sachin Katti, Shyamnath Gollakota, Dina Kattabi, Embracing wireless interference: Analog Network Coding, in ACM SIGCOMM Computer Communication Review v.37, n.4, pp 397 – 408, October 2007
Requirements • Implement a testing framework for wireless networks
• Implement a Network coding scheme with equal or better throughput than traditional networks
• Implement ANC MAC
• Practical application to arbitrary network topologies
• Use of Universal Software Radio Peripheral (USRP) • Use of GNU Radio signal processing libraries
• Modular design
Deliverables• Network Coding Testbed
• Implement different wireless topologies & protocols
• Complete Documentation• Commented Code• Build Instructions• Repository Access
Resource Requirements• 3 USRPs
• RFX2400 Transceiver Daughterboard
• 3 Computers• Linux Operating System• GNU Radio Installed
Schedule
Design Process• Functional
Decomposition
• Prototype in Matlab
• Test in Matlab
System DesignHost:Generates and interprets data
Network:Packetizes and determines data route
MAC:Arbitrates channel access. Coordinatestransmission among nodes
Physical:Modulation/Demodulation Testing and Logging:Tools used in testing of system
Analog Network Coding Implementation• Physical Layer
o MSK modulationo ANC algorithm for decoding interfered signals
• MAC Layero Modified CSMA/CAo Allows for simultaneous interfering transmissions if they
will be able to be correctly decoded • Network Layer
o Predetermined routingo Similar packet format as 802.11
• Host Layero Random datao Predetermined patterns of data
Testing Procedure
• Implement ANC system in Matlabo Simulation in a controlled environment
• Tested Matlab simulation
• Split Matlab simulation to be implemented in GNU Radio
• Write & compile GNU Radio blocks
• Use Python to test each block
• Test entire framework over air
Matlab ANC Simulation
• Simulate a transmission and reception of interfered signal
• Decode unknown signal using ANC algorithm
• Advantages:• Debugging system
• Data Visualization
• System organization
Matlab ANC: Transmission
• Generate two signals with random data bits
• Generate a pilot sequence
• MSK Modulation
• Random overlap between two signals
Matlab ANC: Sampling
• Use pilot sequence to find start of individual signals
• Sample at optimal time for demodulation
Matlab ANC: Channel Measurements
• Variance over a sliding window• Indicator of interference
• Amplitude of individual signals• Measured at un-interfered sections
Matlab ANC: Decoding
• Use amplitude of signals to calculate possible phase pairs
• Use known phase difference to determine unknown phase difference
GNU Radio Implementation
• Determine how to port code from Matlab to C++
• Split code into blocks that deal with streams of data
GNU Radio Blocks
• Energy Detector• Uses magnitude of signal to determine beginning and
ending of signal.
• Sync Block• Uses pilot sequence to find start of individual signals• Packetizes each signal along with offset information
• Decoding Block• Runs ANC algorithm
GNU Radio Block Testing
• Non – Trivial• Must have entire block before testing• Involves two languages Python and C++
• SWIG makes C++ usable in Python• Lacking documentation
• Once compiled use Python to test C++ code• Link C++ blocks together using Python• Generate data for blocks using Python
• Use Python modules to generate packets and other inputs
Future Additions to Testbed
• Complete initial design• Add Modulation Schemes to Physical Layer
o MQAMo MPSK
• Network Layer o Implement TCP/IP
• Testing Layero Inter-node Coordinationo Single Computer Simulationo Component Benchmarking
• Other Network Coding Schemes
Lessons Learned
Conclusion
• Plan time requirements better• Gained experience outside of normal area of study• Start prototyping early in first semester
• Designed network testbed that implements ANC• Simulated ANC system in Matlab• Implementation in GNU Radio
• Wrote GNU Radio blocks• Compiled and started testing
Questions?