A wireless network, or a network without wires, describes a network where communication of at least two terminals is possible without requiring a wire connection. With a wireless network, the user has a certain level of mobility, as he can move freely within the covering range of the network and can maintain the connection at any place.
The connection of the wireless network is established by radio-electric waves instead of conventional cables. In this area, there are several technologies which differ from each other in certain points, e.g. the data transfer rate.
As work such as cable laying is not required when installing a wireless network, these networks are very popular, and efforts are being made for rapid further development and innovations in these technologies.
Summary of the Advantages of Wireless Networks:
- Lower expenses, as savings can be made in terms of costs and the time-intensive wiring of the network, as well as with additional devices such as printers.
- Access is possible from any location within the coverage range.
- With the correct safety installations, a wireless network offers the same high level of security with regard to the unwanted access of third parties, e.g. as in cable-bound networks. This is guaranteed through certain security functions, e.g. data encryption when information is transferred, user authentication and separate access for guests.
The three most popular Operation Modes for Wireless Networks
Infrastructure Mode
This operation mode is the most widespread. It is used especially in private households. A WLAN access point or a wireless router is in charge of coordinating all WLAN clients. This takes place through repeated transmissions of small data packets (beacons) per second to the stations in the coverage range of the network.
Among other information, these beacons include the encryption type / network names (SSID). The beacons not only facilitate the connection setup, but also monitor the reception performance. However, reception of the beacon is not yet a guarantee for a stable connection.
Ad-hoc Mode
Each participant in an ad-hoc network is of equal rank and there is no access point coordinating the others, as in the case of the infrastructure mode. Thus, at the same time, each client assumes the tasks and functions for coordination, which otherwise execute the access point.
The ad-hoc networks can be set up and installed quickly and easily in the same way as infrastructure mode networks. All participating stations in the network also use the same network name and encryption. The ad-hoc mode is only suited for a small number of stations which also have to be relatively close to each other. Otherwise, no connection is established.
An example for this would be Bluetooth or infrared connections.
Currently, stations with routing functions are being tested and researched in order to find a solution for this problem. As such, it would then be possible to exchange data or information without requiring that the stations are within a certain physical range of each other.
Wireless Distribution System (WDS)
This operation mode is mostly used with two networks operating separate from each other in infrastructure mode. Consequently, both networks have their own access point. These two access points then connect the WLANs with each other, whereby a wider network coverage is reached.
This effect can also be obtained by a repeater mode. Here, an extra access point serves as repeater, repeating and in turn, amplifying the existing signal.
Categorical Subdivision of Wireless Networks in accordance with the Coverage Range
The coverage range of a wireless network defines the space of connectivity. Wireless networks can be subdivided as follows by increasing their coverage range:
- Wireless Personal Area Network (WPAN) e.g. Bluetooth
- Wireless Local Area Network (WLAN) e.g. Wi-Fi
- Wireless Metropolitan Area Network (WMAN) e.g. Wimax
- Wireless Wide Area Network (WWAN), e.g. UMTS
Frequencies
In the WLAN standards 802.11a, b, g and h, the channel bandwidth is 20MHz. In the case of 802.11n it is 40MHz and in the case of 802.11ac, it is even 80 to 160 MHz.
Data Transfer Rates:
In the case of the data transfer rates, it is not the actual gross values but the net values which are significant. All subscribers in a network use one and the same channel bandwidth for uploads and downloads. Accordingly, the net values are more realistic in practice, and in the best case they correspond to half of the gross values.
Furthermore, a differentiation is made between two transmission types: On one hand is the transmission via individual carrier (DSSS) and on the other hand, transmission takes place via a multi-carrier (OFDM).
Security of Wireless Networks
Without measures for guaranteeing network security, wireless networks are very susceptible against attacks from outside. Two indispensable measures include encryption and authentication with passwords (in order to increase of the security of the network considerably).
Encryption
Wired Equivalent Privacy (WEP) is considered as a standard of WLAN 802.11 and this serves for encryption in accordance with an algorithm. These encryptions have a length of 64 to 256 bits. However, they are not sufficient for protection against access by third parties. This is why supplements such as WEPlus or Wi-Fi were developed. Believed to be impossible to decrypt, the new standard is 802 11i (Advanced Encryption Standard (AES). It is considered to be the successor to WEP.
Authentication
The Extensible Authentication Protocol (EAP) which can access RADIUS servers, is used to authenticate clients.