Specifications

quality of shielding was required so that there would be minimum leakage of RF power. This
insures that the energy is flowing through the test bed as designed, rather then having radiation
leakage that may interfere with another portion of the test bed circuit. The IF interconnects have
to be shielded as well, but the low frequency makes it much less critical. The loss on the IF
cable is not important since the gain of the transceiver is adjusted to compensate for the cable
loss. To connect the terminals to other computer equipment via Ethernet only required the use of
standard 100Mbps cables.
Connected to each terminal we required a device to be able to send and receive IP traffic. This
requires both a PC with a capable Ethernet card as well as some form of traffic generation
software. The software also needed to be able to keep statistics on the amount of throughput that
is flowing through the system.
The last requirement of the test bed was to have some way to observe and record the system
parameters that the host terminals see. This is useful in verifying that the test bed is operating in
a reasonable manner.
3.2 Test Bed Architecture: The test bed architecture needs to be flexible so that different link
conditions can easily be simulated and tested. The basic architecture is shown below in Fig 3.1.
This figure shows that a PC is connected on each end of the link. These then connect to the
AN-50 terminals, which in turn connect to the T-58 transceiver units. The transceiver units are
then joined together through a RF link that is set to simulate some desired condition. This link
has several variations that will be considered below.
The simulated RF link has to have several different configurations for different testing situations.
The simplest architecture is just to add attenuation on the link. The attenuation will be adjusted
to simulate different link distances. The next more complex architecture is to have both
attenuation and additive white noise. The next progression is to have an interfering source. An
additional AN-50 that is sending out registration requests can be coupled into the RF link.
Figure 3.2 is shown below and shows the different configurations of the simulated RF link.
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