Technical data

JSC 36381 MARCH 30, 2000

Baseline

To immunize against RF interference and unauthorized eavesdropping, Spread

Spectrum technology (also know as “Frequency Hopping”) is employed. In Frequency

Hopping, the radio signal “hops” from frequency to frequency within a specified band

(ISM 2.4000 – 2.4825) over a set time. Both the transmitter and receiver know the

hopping pattern which is called a “channel”. Proxim RangeLAN2 products provide 15

frequency hopping sequences that are orthogonal patterns. (Consult the Proxim

RangeLAN2 Technical Reference Guide for further details.) RF connectivity depends

on RF Network Cards and RF Access Points for wireless transfer of network packets.

See Table 2-4 for RF parameter settings required for the OPS LAN.

1.4.1 RF Network Adapter

OPS LAN laptops may use a RangeLAN2 7400 PC card for RF communication

between laptops and RF access points. The network adapter is a Type II PC card

(PCMCIA) device. Attached to the Model 7400 version is an omnidirectional dipole

antenna that may be mounted to the lid of the laptop. The resulting assembly

configuration is:

7400 card + Dipole antenna = 7401 RF Card Assembly

The RangeLAN2 PC card has 2 diagnostic light emitting diodes (LEDs). A green

LED flashes whenever another station is transmitting on the channel; a yellow LED

flashes whenever the local RF station is transmitting. Appropriate drivers for the

network card, based on the laptop’s operating system, have been incorporated into

the respective software loads. See Section A.4 for technical data.

1.4.2 RF Access Point

Each RF access point is a 7520 RangeLAN2/AP-II MAC layer bridge that connects to

the coax backbone. Each unit requires a separate power source. The dipole antenna

relays RF packet communication between the backbone and RF-equipped laptops. It

filters at a rate of 14,8000 packets/sec. Access point parameters, such as channel

number and IP address are configurable through a web management tool or a null

modem cable to a laptop. All access point parameters will be preset prior to flight

and will not be changed on-orbit.

1.5 CABLED CONNECTIVITY

The OPS LAN 10BASE2 cable backbone relies on RG-58 coax cabling, BNC connectors

and terminators. Coaxial cable has several advantages, including high resistance to

electromagnetic interference (EMI), a history of reliable service, and durability.

Details concerning Ethernet cabling between ISS modules are forthcoming.