Thomas Kunz
Systems and Computer Engineering
210
HIPERLAN 1 EY-NPMA
nSeveral terminals can now have the same priority and
wish to send
–contention
phase
nElimination Burst: all remaining terminals send a burst
to eliminate contenders (11111010100010011100000110010110,
high bit- rate)
nElimination Survival Verification: contenders now sense
the channel, if the channel is free they can
continue, otherwise they have been eliminated
nYield Listening: contenders again listen in slots with a
nonzero probability, if the terminal
senses its slot idle it is free to transmit at the end of the contention phase
nthe important part is now to set the parameters for
burst duration and channel sensing
(slot-based, exponentially distributed)
–data
transmission
nthe winner can now send its data (however, a small
chance of collision remains)
nif the channel was idle for a longer time (min. for a
duration of 1700 bit) a terminal can
send at once without using EY-NPMA
–synchronization
using the last data transmission