Theory Of Operation; Server/Client Architecture; Adjustable Rf Data Rate - Laird RM024 User Manual

RM024
User Guide
T O
HEORY OF PERATION

Server/Client Architecture

The RM024 utilizes server-client network architecture to synchronize the frequency hopping. Each network must
have one radio configured as a server and all other radios configured as clients. When a radio is configured as a
server, it transmits a beacon containing timing and identification information at the beginning of each hop. The
beacon is never visible to the OEM host. Upon boot, radios configured as clients enter receive mode where they
are scanning the available frequencies listening for a beacon from a server in their network. When a client
detects the server's beacon, the client synchronizes its frequency hopping to that of the server and transition
the In Range pin Low. When the server and the client are synchronized they can begin transferring data.
Each network consists of only one server. Multiple networks can exist in the same area, provided the networks
are configured on different channels. The RM024 utilizes an intelligent Frequency Hopping algorithm which
ensures minimal interference between networks. The possible interference between collocated networks is
given by the following equation:
Maximum number of interfering bins = # of collocated servers -1
For example, with ten collocated networks, there is up to nine bins every hop cycle that are occupied by more
than one network at the same time. Although two or more networks might occupy the same hop bin at the
same time, there is truly only interference if two or more radios from alternate networks are trying to transmit
on the same bin at the same time in the same coverage area.

Adjustable RF Data Rate

The RM024's RF data rate can be adjusted to provide a trade-off between throughput and range.
Table 1: RM024 RF Data Rate
Product Model RF Profile
All RM024 0x00
125 mW versions
0x01
(RM024-X125) only
All RM024 0x03
1. Throughput is ideal, one direction, with no retransmissions. All practical RF applications should allow for
retransmission of data due to interference or less than ideal RF conditions.
Deciding which RF data rate to choose depends on the individual application. The fast RF data rate delivers much
faster throughput, but has much less range. In addition, because the lower data rate solution uses more hops, it
is better situated for collocated networks.
A rule of thumb for RF systems is every six dB of gain doubles the effective distance. The four dB increase of
receive sensitivity for the lower data rate solution means it is able to transmit almost 60% further than the
higher data rate solution.
Embedded Wireless Solutions Support Center:
http://ews-support.lairdtech.com
www.lairdtech.com/ramp
RF Data Rate Number of Hops
500 kbps 43
280 kbps 79
280 kbps 43
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Receiver Sensitivity Throughput
-94 dBm 250 kbps
-95 dBm 120 kbps
-95 dBm 120 kbps
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