Using Radio Repeaters

USING RADIO REPEATERS
Application Note
12
With GroWeather Stations
INTRODUCTION
The GroWeather station with the GroWeatherLink Software version 1.1 allows the linking of several
separate weather stations to one PC through a “point-to-multipoint” radio network. The basic operation of
this network assumes that the radio at each remote site can communicate directly with the base radio.
There are situations where some (or all) of the remote sites can not communicate directly with the base radio.
For example, weather stations may be located in the next valley, or the farthest stations are out of range. In
these cases, a “repeater” radio can be used to extend the effective coverage of the base radio. The “repeater”
radio is placed between the base radio and the remote radio and can be heard by both radios. Messages sent
by the base radio that can not reach the remote are heard and rebroadcast by the repeater. The repeater will
also rebroadcast messages from the remote back to the base radio.
GENERAL CONSIDERATIONS FOR RADIO NETWORKS WITH REPEATERS
The radio used as a repeater can either be a standalone radio (i.e. a dedicated repeater), or have a weather
station attached, in addition to acting as a repeater for other radios. It is important to remember that both the
remote radio and the repeater radio must have power at the same time for communication to take place with
the base radio. We recommend running the repeater radio with AC power, or other continuous power source
so that the radio can be left on 24 hours a day. At the very least, it must be on whenever any of the remote
radios in its area of coverage are scheduled for operation.
The repeater radio must have line-of-sight and be within range of both the base radio and the intended remote
radios. The effectively limits the antenna of the repeater to the omni-directional antenna.
Make sure that you get a manual for the radio you are using. Using repeaters in a radio network increases the
complexity of the operation. The more you understand how your radios work and what their limitations are,
the greater chance you have to make the project work.
USING REPEATERS WITH YDI RADIOS
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First, design your radio network. The YDI radio will allow you to use up to 7 repeaters between the base
radio and the remote, but each one degrades performance of the system. The manufacturer recommends
using no more than 2 repeater radios in a given path. We have only tested using 1 repeater. Each remote
and repeater radio should be given a unique ID. Davis’ radio configuration program has 32 different
radio identification slots available for remote and repeater radios. Repeater radios are configured in the
same way as remote radios.
Note: If you are planning to use only 1 weather station, but require a repeater to talk to it, you must configure
the radios as “point-to-multipoint” radios, not as “point-to-point” radios with the configuration program.
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Second, install your radios and weather stations.
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Third, test the installation of the remote radios and their connection to the repeater radio. Take the base
radio and a laptop computer with the GroWeatherLink software installed to the site to the repeater radio.
Use the laptop computer to connect to each of the remote stations to verify that the signal from the
remote reaches the repeater radio.
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Fourth, test the installation of the repeater radio. Install the repeater radio at the repeater site, and attach a
weather station, even if the radio will be used as a stand-alone repeater. Install the base radio and use the
GroWeatherLink software to connect to the station attached to the repeater radio. If your network uses
more than one repeater, repeat steps three and four for each repeater radio.
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Fifth, configure the GroWeatherLink software to talk to the remote stations using the repeater. For each
weather station that requires the use of a repeater, you will have to manually specify the connection
address. In the Serial Port Settings dialog, select “Other” as the “Radio Name”. (Also select YDI Model
910 Multi-Point” as the connection type.) You will then enter the connection string in the “Phone” field
in the “Modem Settings” part of the dialog. The basic form of the connection string is: <remote ID>
“via” <repeater1 ID>”,”<repeater2 ID>.
The radio IDs are of the form “REM”<2 digit remote number>, where remote number is the number used in
the radio configuration program. For example, if the weather station is located at “Remote 6” and the
repeater is” Remote 11”, then the connect string will be “REM06 via REM11”.
USING REPEATERS WITH NEULINK RADIOS
In order to use the repeater functionality built into the RF Neulink radios, you will have to carefully consider
the design of your radio network and manually configure the radios. This note will explain the important
considerations, but Davis Instruments does not provide support for this feature of the RF Neulink radios.
According to the RF Neulink Operator Manual:
2.4 Store and Forward Repeating
The NEULINK 9600 may be configured to automatically repeat packets of data. This feature is typically used
to fill in areas of coverage where a base station cannot get far enough to talk to a particular unit. It is not
intended as a wide-area networking feature….
Each unit may be programmed with up to four different repeat TOIDs … stored in four REPEAT registers. …
When repeating is enabled the unit will watch the air for packets with a TOID matching any of the four
REPEAT registers. If it sees an ID match…it will automatically transmit the received packet again. …
The Ids that the unit is programmed to repeat may be individual Ids, groups, or all Ids. …
Some important notes concerning the repeater function are; … the automatic ACK feature of the RDXP [Radio
Data Exchange Protocol] protocol will not work in the repeat mode. If ACK is enabled [which it is for the
standard Davis configuration] then the repeat function should not be used.
4.7 Repeater Feature
… [The radio] will retransmit the packet when the carrier is not busy and it is not busy sending its own data.
The unit can only store one packet at a time. The repeater does not check the air for activity before it repeats a
packet. …Do not program two units to repeat the same Ids on the same frequency, as they will tend to transmit
at the same time, causing neither transmission to be heard by others.
These instructions impose the following restrictions on the design of a GroWeather radio network using RF
Neulink repeaters:
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Only one radio can be a repeater radio. This is because one of the Ids the repeater will repeat is the base
radio’s ID because we require 2-way communication. We cannot have two repeaters repeating the same
ID, and thus we cannot have two repeaters.
The automatic packet acknowledgement feature of the radios must be disabled, which can seriously
degrade the overall performance and reliability of the radio network. Normally, the radios will
acknowledge the receipt of each data packet, or by not acknowledging request retransmission of the
packet. This happens transparently to the weather station and software on either end. Without packet
acknowledgement, only “end-to-end” error checking is available to catch transmission errors. This also
means that “Wireless Ready” (Rev E) WeatherLinks are REQUIRED for networks with repeaters
(instead of being recommended).
To minimize the amount of extra radio traffic, the repeater ideally would repeat only packets intended for
stations that cannot be reached directly from the base radio. If the REPEAT registers are programmed
with individual radio Ids, then only 3 stations (plus the base radio) can be the recipients of repeated
packets. The radio ID numbers used by the Davis Radio Configuration program (0-32) all fall in the
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same “group”, so any use of the group Ids with the standard ID configurations will result in the repeater
repeating ALL data packets. If more than 3 radios are to be reached by the repeater, you will have to
create new groups by using other IDs.
SAMPLE NETWORK CONFIGURATIONS
The following examples show how to configure RF Neulink radios for several sample network situations.
ONE TO THREE REMOTES WITH REPEATER
This configuration has between one and three remote stations and one repeater.
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First, use the wireless configuration program to configure the radios: base, remote, and repeater.
Second, use a terminal emulation program, e.g. Windows HyperTerminal or ProComm, to modify the
programming on each of the radios.
• For the base and remote radios (but not the repeater), give the commands “ACK OFF” to turn off the
automatic ACK feature, and “EXIT” to save the changes.
• For the repeater radio, give the commands “ACK OFF”, “REPEAT 1 0000”, “REPEAT 2 <remote
ID>”, (and if there is more than one remote radio “REPEAT 3 <remote 2 ID>”, “REPEAT 4<remote
3 ID>”), “PROG 0E 1” to activate the repeater function, and “EXIT” to save changes.
Third, install the radios and weather stations.
Fourth, when configuring the communications for the remote stations, use the same “Radio Name” as the
remote radio was configured with.
MORE THAN THREE REMOTES WITH REPEATER, REPEAT EVERYTHING
This configuration can have up to 31 remote stations if you restrict yourself to the radio IDs used by the
configuration program.
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First, use the wireless configuration program to configure the radios: base, remote, and repeater radios.
Second, use a terminal emulation program, for example Windows HyperTerminal or ProComm, to
modify the programming on each of the radios. For the base radio and remote radios (not the repeater),
give the commands "ACK OFF" to turn off the automatic ACK feature, and "EXIT" to save the changes.
For the Repeater radio give the commands: "ACK OFF", "REPEAT 1 FFFF", and "EXIT" to save
changes.
Third, install the radios and weather stations.
Fourth, when configuring the communications for the remote stations, use the same "Radio Name" as the
remote radio was configured with.
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MORE THAN THREE REMOTES WITH REPEATER, REPEAT ONLY THE REMOTE RADIOS
This configuration can have as many remote radios as you want, and only those radios that require a repeater
will have their packets repeated.
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First, use the wireless configuration program to configure the radios: base, remote, and repeater radios.
For simplicity, assign all the remote radios that require the repeater to the same remote ID. We will be
changing the ID in step 2.
Second, use a terminal emulation program, for example Windows HyperTerminal or ProComm, to
modify the programming on each of the radios. For the base radio give the commands "ACK OFF" to
turn off the automatic ACK feature, and "EXIT" to save the changes.
• For the remote radios (not the repeater), you will assign a new ID number. This number will be in a
different "group" from the IDs used by the non-repeated radios. These ID's are 128 (0100 hex)
through 254 (01FE hex). For each remote radio give the commands "ACK OFF" to turn off the
automatic ACK feature, "MYID <new ID in hex>"and "EXIT" to save the changes.
• For the Repeater radio give the commands: "ACK OFF", "REPEAT 1 0000" to repeat base radio
packets, "REPEAT 2 01FF" to repeat packets for the new group, and "EXIT" to save changes.
Third, install the radios and weather stations
Fourth, when configuring the communications for the remote stations that require the repeater, use the
Radio Name "Other" and enter the ID number of the remote station in the "Phone" text box. Use the
prefix "0x" if the number is entered in hexadecimal.
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