Wireless Standards Knowledge
Answers to RF Cafe Quiz #21
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This quiz test your knowledge of the modern wireless bands.
1. What are the
frequency bands for IEEE 802.11a and IEEE 802.11b/g, respectively?
IEEE 802.11a operates at 5.2 GHz
(actually parts of 5.035 through 5.825 GHz), and
IEEE 802.11b/g operates at 2.4
GHz (actually 2.412 through 2.484 GHz). Even though 'a' comes before 'b/g' and you might assume that means 802.11a
would be the lower frequency, it is not. Both are in FCC Part 15 unlicensed bands.
Which wireless router type is most likely to use three antennas?
Theoretically, average uplink throughput rates when transmitting across 40 MHz channels (two, 20-MHz bonded
channels, which the 802.11n standard allows) can be up to 40% greater in the 2x3 configuration than in the 2x2
configuration over distances of 30 to 40 feet and 20% greater in the 60- to 100-foot range.
On which frequency band does the EGSM mobile phone system operate?
The full band is 880.0 - 915.0 MHz for the uplink, and 925.0 – 960.0 MHz for the downlink.
On which frequency band does the DCS/PCS mobile phone system operate?
a) 1800/1900 MHz. The full
(Digital Communication System) band is 1710–1785 MHz for the uplink and 1805–1880 MHz for the downlink. The full
(Personal Communication System) band is 1850-1910 MHz for the uplink and 1930–1990 MHz for the downlink.
5. On which frequency band does Bluetooth operate?
c) 2.4 GHz.
Bluetooth operates within the
license-free ISM band, just like 802.11b/g/n. Various countries favor specific parts of the band, but they all
6. Which IEEE standard describes the Bluetooth system?
b) 802.15.1 to be
Bluetooth system was originally developed by
Ericsson Mobile Platforms in Lund, Sweden. The name is an anglicized version of Old Norse Blátönn or Danish
Blåtand, the name of the tenth-century king Harald I of Denmark and Norway ("Bluetooth").
7. Which type of modulation scheme does Bluetooth and WiFi employ?
d) Spread spectrum
(SS). Bluetooth uses frequency hopping spread spectrum (FHSS),
while WiFi uses direct sequence spread spectrum (DSSS).
Which of the following IEEE 802.x wireless systems currently offers the lowest data rate?
ZigBee is the simplest and lowest
power consumption system in the 802.x family, and is governed by the IEEE 802.15.4 specification. Click on the
thumbnail for a good overview.
9. What does NFC stand for?
c) Near Field
NFC is an up-and-coming system
that uses inductive or capacitive coupling between an active transceiver and an embedded 2-dimensional antenna for
passing information across a short distance. Many
beginning to incorporate NFC for exchanging information between two devices' cases that are touching each other
without actually making contact via a metal conductor.
10. Which of the following
systems has been show to cause brain cancer, sterility, skin cancer, and in some cases sever burns to the body?
d) All of the above. After collecting technical headlines on a daily basis for many years, I have discovered
many articles which claim to have conclusively proven that all of the wireless technologies with transmit powers
above a few milliwatts do cause one or more of the aforementioned maladies. Skins burns are caused not by the RF
energy, however, but by Li-Po and Li-Ion batteries catching on fire. BTW, there are as many studies that find no
health risks as those that do (except for fiery batteries, which are always found to be harmful).