1.2.2. Wireless Coverage

Wireless Network Ranges

Wireless networks can be classified by the network topology (see Wireless Networks) and by the range or coverage. When covering wireless networks by the covered area the following three categories are common:

• Wireless Wide Area Network (WWAN) - e.g. GSM and UMTS
• Wireless Local Area Networks (WLAN) - e.g. IEEE 802.11
• Wireless Personal Area Networks (WPAN) - e.g. Bluetooth

Most WWAN and WLAN are established as infrastructure networks, thus they consist of a mobile terminal and a base transceiver station. For WWAN a structured network (backbone) of such base stations is necessary. Since every base station covers a specific area does call such network types also cellular networks . Usually the network cells for WWAN overlap only by small portions.

Wireless Wide Area Network cells covering distances of 100 meters up to 35 km. The used frequency spectrum is usually not free, which means it has to be licensed, but can also not used by somebody else. WWAN networks emerged from cell based mobile voice communication networks. Generations of wide area networks:

• Generation 0 (0G): analogue, radio cells with no handover
• Generation 1 (1G): analogue, unique calling number
• Generation 2 (2G): digital (GSM), datarate 9.6 –14 kbps
• Generation 2.5 (2.5G): digital (GPRS), datarate 20-115 kbps
• Generation 3 (3G): digital broadband (UMTS), datarate up to 2 Mbps
• Generation 4 (4G): digital, IP based, not yet available

Currently 2G and 3G communication networks are in use. Comparing existing GSM and UMTS techniques the latter network type needs much more base stations. Further the radius of UMTS cells is not constant since the coverage depends on the number of mobile clients and used data rates. A disadvantage of UMTS are higher network costs compared to G2 networks. Advantages of UMTS apart higher data rates are better data security (128bit encoding) and also better positioning capabilities (Hoffmann 2002).

Typical Mobile Phone WWAN

Wireless Local Area Networks covering distances between 10 m to 150 m (300m outdoor). They use the unlicensed spectrum and provide much higher data transfer rates (100 Mbps) than WWAN. Since WLAN technology emerged as extension to Computer LANs the network is specialized on data transfer. Mobile stations connected by WLANs can use simple infrastructures with Access Points (APs) instead of Base Stations or can connect to one another directly in ad hoc mode (Krishnamurthy et al. 2004)

Typical Home WLAN

Wireless Personal Area Networks provide short range connectivity e.g. for digital cameras or headsets. The covered area radius is about 10m but will increase up o 100m in future. The used frequency spectrum is unlicensed and data rates are about 0.5 Mbps, thus in between WWAN and WLAN. These devices connect and disconnect as needed and have therefore a so called ad hoc topology. Most WPANs are based on the Bluetooth standard. Advantages compared to WLAN are voice support and security issues (Mäs 2003).

Typical PLAN (e.g. Bluetooth)