805U-E Wireless Ethernet
User Manual
Man_805U-E Rev 1.5
Page 30
can decide which traffic must be forwarded between ports - it will only transfer a message
from the wired port to the wireless port if it is required.
A bridge will forward all Broadcast traffic between the wired and wireless ports. If the wired
network is busy with broadcast traffic, the radio network on the 805U-E can be unnecessarily
overburdened. Filtering may be used to reduce broadcast traffic sent over the radio. Refer
Section 3.10 for how to configure a filter.
A transparent bridge does not handle loops within the network. There must be a single path to
each device on the network. Loops in the network will cause the same data to be continually
passed around that loop. Redundant wireless links may be set up by using the Spanning Tree
Algorithm function - refer to section 3.9.
Router Operation
A router joins separate Ethernet networks together. The router has different IP addresses on
its wired and wireless ports, reflecting the different IP addresses of the separate Ethernet
networks. All the devices in the separate networks identify the router by IP address as their
gateway to the other network. When devices on one network wish to communicate with
devices on the other network, they direct their packets at the router for forwarding.
As the router has an IP address on each of the networks it joins, it inherently knows the
packet identity. If the traffic directed at the router can not be identified for any of the
networks to which it is connected, the router must consult its routing rules as to where to
direct the traffic to.
The 805U-E has one routing rule which may be configured. This routing rule is the gateway
address. The 805U-E will direct all unknown IP network traffic to this gateway IP address.
3.8
Fixed Frequency Operation
The 805U-E operates on the 869MHz band. The modules are designed to be fixed frequency
in accordance with European regulations. The 869MHz Band is split into different bands with
varying duty cycle and power limits. Generally the 2 bands used by Elpro are
500mW
869.525MHz
0.dB gain
10% Duty Cycle
5mW
869.275MHz
0dB gain
100% Duty Cycle
EC regulations are designed to either limit
a)
the time a radio can transmit, giving other systems a chance to operate, and
b)
the range of a radio, allowing more systems in a given area.
3.9
Radio Configuration Menu
The 805U-E can be configured to different radio transmission rates. A reduction in rate
increases the reliable range (transmission distance). An “automatic rate” function is provided
which automatically selects the highest data rate for reliable operation. This feature starts at
the highest rate and reduces rate if the received radio signal strength is below a user-
configurable limit.
