WINLAB

1. Cognitive Radio Rendezvous PrasanthiMaddala, Khanh Le, Craig Gutterman, Kyle Soska, Roy Yates, Ivan Seskar Motivation Rendezvous Process Rendezvous APP Modules • Develop Rendezvous Process • Interference is Asymmetric • Time Asynchronous • Use Jump Stay Based Hopping Sequence • Channel Map : • RF Filter bandwidth = 24MHz • DAC sample rate = 25MSPS • Number of Channel = 16 • Uncoordinated Cognitive Radios need to agree upon a common channel and synchronize in time • Goal: Design Rendezvous algorithm to synchronize two radios quickly as possible • subchannel width : • 25/16 = 1.5625MHz System Model • Measure interference of channel with 64-pt FFT • Determine which channels are available • Channels: C={c1,…c16) • Available Channels Radio 1:C1 ⊆ C • Available Channels Radio 2:C2⊆ C • C 1 ∩ C 2 ≠ Ø • The channel hopping sequence follows: • C1(t) є C1 • C2(t) є C2 • Transmitting: mi(t)=1 • Receiving: mi(t)=0 • Rendezvous Time: • R=min (t≥0 | C1(t) =C2(t), m1(t)= m2 ꞌ (t)) • -12.5 • 0 • 12.5 Actual number of available channel : 14 • Simulink-based APP designs : • Spectrum Sensing using 64-pt FFT • Half-duplex QPSK transceiver • Process begins by listening for a beacon • Transmits Beacon after random back-off • Continues to listen for response before switching channels • Message not recognized if on different channel • Algorithm continues until successful handshake • Rendezvous not guaranteed even if on same channel Network Algorithm • QPSK Receiver : • Carrier frequency/phase offset correction using Costas Loop • Symbol Synchronization using ML estimation • Packet detection using Barker sequence • Use a slotted networking protocol • Data Stream 1: Sends Spectrum Data to Host • Data Stream 2: Sends and Receives data packets to Host WINLAB