Autor: Alexander Eichhorn

Wireless Networking

Using cables for network connectivity is both costly and cumbersome, hence wireless networking technologies gain traction.

Recent wireless links even surpass wired connections in net bandwith, but bear in mind that such numbers can only be achieved under best case conditions with a single sender and a single receiver.

Spectrum and Collissions

The wireless radio spectrum is by nature a shared resource that requires different access control schemes as compared to a wired network infrastructure. All consumer-grade wireless technologies subsumed under the term WiFi or WLAN use a randomized colission avoidance scheme where senders back off to cooperatively share the available spectrum. Any uncooperative high energy sender can severly degrade communication for anyone else in its vicinity. Wireless local networks cannot guarantee a stable quality of service unless interference can be eliminated by other means.


Wireless networks are less secure than wired connections because an attacker can easily receive and send signals. Unencrypted wireless networks should only be used with extreme caution. It is generally the best approach to rely on end-to-end encrypted protocols based on TLS (e.g. HTTPS, IMAPS, FTPS) when working over wireless networks, even if the wireles link itself is already encrypted.


WiFi is a packet-based wireless local area network technology (WLAN) defined by the IEEE 802.11 standard series. WLAN operates in the 2.4GHz and 5Ghz frequency bands and devides the spectrum into multiple channels. No license is required to operate a WLAN, although channel allocation limits slightly differ between countries (US 1-11, EU 1-13, JP 1-14). A WLAN signal occupies 5 adjacent channels, so to avoid interference between overlapping network installations channels 1, 6, and 11 are optimal for North America and channels 1, 5, 9 and 13 for Europe and Japan.

Wireless LANs consist of one or multiple central access points connecting to a wired network and a number of mobile wireless clients such as laptops, smartphones, tablets or other devices. Wireless routers typically combine a WLAN access point with an Ethernet switch, a WAN interface (ADSL2+), IP routing, NAT and DNS for an out-of-the box Internet experience.

Access points signal their identity by regularly broadcasting their service set identifier (SSID) and embedding them into every sent packet. Clients may be connected to at most one WLAN at a time and typically ignore packets received with a different SSID.Professional access points used in campus- and city-wide installations support roaming extensions for seamless hand-over and features to control wireless cell size and antenna configurations. Wireless range can be improved by upgrading antennas (if detachable) and capacity can be improved by increasing the access point density. WLAN networks can reach 20m indoors and distances of several kilometers outdoors. Walls, windows, ceilings and trees can easily blocked signals.

WLAN authentication and encryption has been notoriuosly weak and many public WLANs in hotels or cafe shops don't even have security features enabled to make them available as a free service. Hence, you should never trust any wireless network and instead use strong end-to-end encryption (e.g. TLS which is part of HTTPS, IMAPS, FTPS, etc) when accessing any service, even for regular Web surfing.

Performance Overview of existing WiFi standards

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