- Spectrum assignments and
operational limitations are not consistent worldwide; most of Europe allows for
an additional 2 channels beyond those permitted in the US; Japan has one more on
top of that - and some countries, like Spain, prohibit use of the lower-numbered
channels. Furthermore some countries, such as Italy, used to require a 'general
authorization' for any WiFi used outside an operator's own premises, or require
something akin to an operator registration. For Europe; consult for an annual
report on the additional restrictions each European country
imposes.
- Power consumption is
fairly high compared to some other standards, making battery life and heat a
concern.
- The most common wireless
encryption standard, Wired Equivalent Privacy or WEP, has been shown to be
breakable even when correctly configured (* WiFi Access Points typically default
to an open (encryption-free) mode. Novice users benefit from a zero
configuration device that works out of the box but are unaware they are allowing
unsecured wireless access to their LAN. WPA Wi-Fi Protected Access fixes those
problems, began shipping in 2003, and is now generally available, but adoption
rates remain low.
- Many 2.4 GHz 802.11b and
802.11g Access points default to the same channel, contributing to congestion on
certain channels.
- Wi-Fi networks have
limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock
antenna might have a range of 45 m (150 ft) indoors and 90 m (300 ft) outdoors.
Range also varies with frequency band, as WiFi is no exception to the physics of
radio wave propagation. WiFi in the 2.4 GHz frequency block has better range
than WiFi in the 5 GHz frequency block, and less range than the oldest WiFi (and
pre-WiFi) 900 MHz block. Outdoor range with improved antennas can be several
kilometres or more with line-of-sight.
- Wi-Fi pollution, meaning
interference of a closed or encrypted access point with other open access points
in the area, especially on the same or neighboring channel, can prevent access
and interfere with the use of other open access points by others caused by
overlapping channels in the 802.11g/b spectrum as well as with decreased
signal-to-noise ratio (SNR) between access points. This is a widespread problem
in high-density areas such as large apartment complexes or office buildings with
many Wi-Fi access points.
WiFi networks can be
monitored and used to read and copy data (including personal information)
transmitted over the network when encryption is not enabled.
- Interoperability issues
between brands or deviations from the standard can disrupt connections or lower
throughput speeds on other user's devices within range. Wi-Fi Alliance programs
test devices for interoperability and designate devices which pass testing as
Wi-Fi CERTIFIED.
- Use of the 2.4 GHz Wi-Fi band does not require a license in most of the
world provided that one stays below the local regulatory limits and provided one
accepts interference from other sources, including interference which causes
your devices to no longer function. It is sometimes claimed that Amateur Radio
operators have permission to boost the power on their WiFi transmitters up to
the legal maximum for their Amateur Radio license class under some conditions;
this is not permitted in the US, nor in most locations.
- Legislation/regulation is not consistent worldwide; most of Europe allows
for an additional 2 channels over those allowed for b and g ;
Japan has one more on top of that - and some countries, like Spain, prohibit use
of the lower-numbered channels. Furthermore some countries, such as Italy, used
to require a 'general authorization' for any WiFi used outside the owned
premises; or required something akin to operator registration.
- The 802.11b and 802.11g flavors of Wi-Fi use the 2.4 GHz spectrum, which is
crowded with other equipment such as Bluetooth devices, microwave ovens,
cordless phones (900 MHz or 5.8 GHz are, therefore, alternative phone
frequencies one can use to avoid interference if one has a Wi-Fi network), or
video sender devices, among many others. This may cause a degradation in
performance. Other devices which use these microwave frequencies can also cause
degradation in performance.
- Power consumption is fairly high compared to other standards, making battery
life and heat a concern.
- The most common wireless encryption standard, Wired Equivalent Privacy or
WEP, has been shown to be easily breakable even when correctly configured.
Although newer wireless products are slowly providing support for the Wi-Fi
Protected Access (WPA) protocol, many older access points will have to be
replaced to support it. The adoption of the 802.11i (aka WPA2) standard in June
2004 makes available a rather better security scheme for future use — when
properly configured. In the meantime, many enterprises have had to deploy
additional layers of encryption (such as VPNs) to protect against interception.
- Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b
or 802.11g might have a range of 45 m (150 ft) indoors and 90 m (300 ft)
outdoors. 802.11a equipment, using a higher frequency, has reduced range, all
other things being equal.
- Interference of a closed or encrypted access point with other open access
points on the same or a neighboring channel can prevent access to the open
access points by others in the area. This can pose a problem in high-density
areas such as large apartment buildings where many residents are operating Wi-Fi
access points.
- WiFi equipment could be used to steal personal information (passwords,
financial information, identity information, ...) transmitted from Wi-Fi users,
if sensible protections are not used. WEP is not sensible protection for it is
easily evaded. The 802.11i standard (partially implemented in some equipment as
W(ireless)P(rotected)A(ccess) will be a substantial improvement if properly
configured at both ends.
Free access points (or improperly configured access points) may be used by a
hacker to anonymously initiate an attack that would be impossible to track
beyond the owner of the accespoints
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