Unex DNMA-H92, User Manual

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Appendix A: FAQ about WLAN
1. Can I run an application from a remote computer over the wireless network?
This will depend on whether or not the application is designed to be used over a
network. Consult the application’s user guide to determine whether it supports
operation over a network.
2. Can I play computer games with other members of the wireless network?
Yes, as long as the game supports multiple players over a LAN (local area network).
Refer to the game’s user guide for more information.
3. 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).
4. 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.