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13. What is Spread Spectrum?
Spread Spectrum technology is a wideband radio frequency technique developed by
the military for use in reliable, secure, mission-critical communication 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).
14. What is WMM?
Wi-Fi Multimedia (WMM), a group of features for wireless networks that improve the
user experience for audio, video and voice applications. WMM is based on a subset of
the IEEE 802.11e WLAN QoS draft standard. WMM adds prioritized capabilities to
Wi-Fi networks and optimizes their performance when multiple concurring
applications, each with different latency and throughput requirements, compete for
network resources. By using WMM, end-user satisfaction is maintained in a wider
variety of environments and traffic conditions. WMM makes it possible for home
network users and enterprise network managers to decide which data streams are
most important and assign them a higher traffic priority.
15. What is WMM Power Save?
WMM Power Save is a set of features for Wi-Fi networks that increase the efficiency
and flexibility of data transmission in order to conserve power. WMM Power Save has
been optimized for mobile devices running latency-sensitive applications such as
voice, audio, or video, but can benefit any Wi-Fi device. WMM Power Save uses
mechanisms included in the IEEE 802.11e standard and is an enhancement of IEEE
802.11 legacy power save. With WMM Power Save, the same amount of data can be
transmitted in a shorter time while allowing the Wi-Fi device to remain longer in a
low-power “dozing” state.
16. What is GI?
GI stands for Guard Interval. It‟s a measure to protect wireless devices from cross-
interference. If there are two wireless devices using the same or near channel, and
they are close enough, radio interference will occur and reduce the radio resource
usability.
17. What is STBC?
STBC stands for Space-Time Block Coding, which is a technique used to transfer
multiple copies of data by multiple antenna, to improve data transfer performance. By
using multiple antennas, not only data transfer rate is improved, but also the wireless
stability.
