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worldwide. This presents a truly revolutionary opportunity to place convenient high-speed wireless capabilities in
the hands of users around the globe.
What is Spread Spectrum?
Spread Spectrum technology is a wideband radio frequency technique developed by the military for use in
reliable, secure, mission-critical communications systems. It is designed to trade off bandwidth efficiency for
reliability, integrity, and security. In other words, more bandwidth is consumed than in the case of narrowband
transmission, but the trade-off produces a signal that is, in effect, louder and thus easier to detect, provided that
the receiver knows the parameters of the spread-spectrum signal being broadcast. If a receiver is not tuned to
the right frequency, a spread-spectrum signal looks like background noise. There are two main alternatives,
Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS).
What is DSSS? What is FHSS? And what are their differences?
Frequency-Hopping Spread-Spectrum (FHSS) uses a narrowband carrier that changes frequency in a pattern that
is known to both transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical
channel. To an unintended receiver, FHSS appears to be short-duration impulse noise. Direct-Sequence Spread-
Spectrum (DSSS) generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip
(or chipping code). The longer the chip, the greater the probability that the original data can be recovered. Even if
one or more bits in the chip are damaged during transmission, statistical techniques embedded in the radio can
recover the original data without the need for retransmission. To an unintended receiver, DSSS appears as low
power wideband noise and is rejected (ignored) by most narrowband receivers.
Would the information be intercepted while transmitting on air?
The Bridge features two-fold protection in security. On the hardware side, as with Direct Sequence Spread
Spectrum technology, it has the inherent security feature of scrambling. On the software side, the Bridge offers a
variety of security methods, including WEP and WPA, to enhance security and access control. For more
information, refer to "Appendix B: Wireless Security."
What is WEP?
WEP is Wired Equivalent Privacy, a data privacy mechanism based on a shared key algorithm, as described in the
IEEE 802.11 standard. For more information, refer to "Appendix B: Wireless Security."
What is WPA?
WPA is Wi-Fi Protected Access, a wireless security protocol that can be used in conjunction with a RADIUS
(Remote Authentication Dial-In User Service) server. For more information, refer to "Appendix B: Wireless
Security."
Appendix A: Troubleshooting
20
Frequently Asked Questions