User's Manual

3 Detailed Description
28 APCD-LM043-4.0
10. If the IP address is the same as either the CCU radio or Ethernet IP address, the
packet is forwarded to the CCU application; otherwise, the CCU gets the appropriate
gateway IP address from the Routing Table and the gateway MAC address from the
ARP Table, and then sends the packet to the gateway (most likely the NAP router)
through the Ethernet port.
NOTE: The CCU and EUM pass only IP or ARP packets. All other
packets are discarded so non-IP packets, such as IPX/SPX, are
not passed over the radio link.
3.5 CCU–EUM Interface — Detailed Technical Description
This section provides a detailed description of the physical and MAC layers of the interface
between the CCU and EUM, depicted in Figure 15 on page 24.
3.5.1 Physical Layer (DSSS Radio)
Frequency Band
The LMS4000 900 MHz Radio Network operates in the 902-928 MHz Industry, Scientific, and
Medical (ISM) frequency band.
Channel Bandwidth
The channel bandwidth is 6 MHz. This channel bandwidth is used to determine the lowest and
highest allowable channel in the band. As illustrated in Figure 17, the center frequency of the
lowest and highest channels have to be set such that the signal power that falls in the bands
adjacent to the ISM band does not exceed FCC and Industry Canada limits.
Figure 17 Determination of Lowest and Highest Channel
902 - 928 MHz ISM Band
FCC limit for
emissions in
adjacent band
Lowest
Channel
905 MHz
Highest
Channel
925 MHz