MDS TransNET 900 Specifications download pdf (Page 62)

52 MDS TransNET Ref. Manual MDS 05-2708A01, Rev. E

9.0 OPERATING PRINCIPLES AND CONFIGURATION

9.1 SAF Operation with Extension Radios

The Store-and-Forward (SAF) capability operates by dividing a network into

a vertical hierarchy of two or more sub-networks. (See Figure 5 on Page 4.)

Adjacent sub-networks are connected via Extension radios operating in

“

MODE X” which move data from one sub-network to the next one.

The Store-and-Forward implementation adheres to the general polling princi-

ples used in most multiple-address systems (MAS). Polls originate from the

Master station, broadcast to all radios within the network, and travel hierar-

chically downward. All Remotes will hear the same message, but only one

Remote will respond. Messages within a hierarchy only travel in one direc-

tion at a time.

Using SAF will cut the overall data throughput in half, however, multiple

networks can be inter-connected with no additional loss in network

throughput.

Simple Extended SAF Network

The following example depicts a two-level network utilizing a single Master

(M) and an Extension (X) radio. See Figure 17.

Invisible place holder

Figure 17. Simple Extended SAF Network

Networks: J and K

In this network, messages directed to Remotes in the “K” sub-network, will

be relayed through Extension radio X

j,k

to the K-Remotes. Any response

from a Remote in sub-network “K” will pass back through Extension radio

j,k

to the Master M

. Radios in sub-network “J” operate on the same set of

frequencies and sub-network “K” but with a different radio-frequency

hopping pattern.

In the SAF operation, the Extension radios are set to

MODE X

(Details Page 36) and operate with a “dual personality”—50% of the time it

serves as a Remote station and 50% of the time as a Master for sub-network

Remotes.

J,K

Sub-Network “J”

Sub-Network “K”

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MDS TransNET 900 Specifications Page 62