stty -F /dev/ttyUSB0 9600
irattach /dev/ttyUSB0 -s
sysctl -w net.irda.max_baud_rate=9600
modprobe ircomm-tty
pppd call irda debug dump logfd 2 

In /etc/ppp/peers/irda set speed to 9600

ALSO! Please note that you need to change the baud rate on the client Computer/PDA/Phone too!

The rest is written in the guide IrDA Internet Sharing.