1. EECS Department University of California, Berkeley
Capture Sensing Simultaneous Access Exploiting the Capture Effect for Greater Spatial Reuse and Higher Bandwidth
Xiaofan Jiang
EECS Department University of California, Berkeley

2. Capture Effect CSMA What happens when 2 packets collide?
PREAMBLE
PAYLOAD
PACKET A
PREAMBLE
PAYLOAD
PACKET A
At R1:
What happens when 2 packets collide?
What information can we collect during a collision?
How good (bad) is CSMA?
PREAMBLE
PAYLOAD
PACKET B
PREAMBLE
PAYLOAD
PACKET B
Nothing!
At R2: A R1 A B T1 R1 T2 C R2

3. Capture Sensing Simultaneous Access
According to my table:
T2 < T1 -> OK to send
T3 > T1 -> NOT OK to send
Build a table of stronger-weaker neighbors
Propagate tables?
Packet format
Eliminating hidden-terminal ? A R1 C T1 T2 T3 R2

4. Questions or suggestions?
Status and Plan
Future Plans (winter break and spring semester)
Choose best one
Implementation
Deployment
Assessment
Dissemination
Design space in spatial reuse (spectrum)
CSMA vs CSSA vs No Carrier Sensing at all
Protocol design
Apriori vs adaptive
2nd tier tables
TTS (CSMA-EX)
RTS/CTS
Bandwidth gain / (loss) under:
Point-point
Broadcast
Low-power listening
Network layer choice
Simulation (matlab)
Questions or suggestions?