Harmony
Contents
Harmony
Audio used alongside WiFi to solve contention
40% gain in throughput; 27% for dense networks
Limitations of audio - frequency, penetration
Software based
1) Contention resolution over acoustic channel
2) Data transmission over wifi
Random Tone is generated - lowest tone first, while also listen
Contention resolution
Wait for DIFS
Transmit / Wait
Then repeat simultaneously
Losers subtract their RNG number by the winner
Shared flag to lock and unlock
Single Acoustic Domain
16 - 21 kHz
Reasons:
Majority of background noises go up to 12 KHz
Smart devices have high acoustic sensitivity, can capture up to 21 KHz
Propagation Delay
Takes a while to decide who wins.
Allow multiple packets to be sent
Also decide the order of the next few senders
Round-robin - parallel
- WAIT FOR DIFS -> Waits for given period of silence
Collision
Same acoustic tone, tone number
double round
length
tone
Mechanical artifacting from sudden speaker movement
Amplitude fade-in and fade-out, 5 milliseconds
Increase frequency set
gaps between frequency tone - 200 Hz gaps
26 frequencies
double round if collision occurs!! ————– 26 devices isn’t that much though
Kernel space
A-PHY - DMA; generateTone()
A-MAC - Get tone number, run Harmony, get rank, DIFS
20 meter Harmony pax
Transition
Hidden nodes