Licensed and licence exempt free space radio links to create low bandwidth data links at distances up to 20km using bespoke aerial systems.
Point-to-point radio links are terrain independent as long as there is line of sight between the sites to be connected, or to intermediate points such as radio masts or tall buildings.
Licence exempt systems
Licence exempt systems operate in frequency bands that do not require a licence for their use. Although such systems do not incur any ongoing licence fees there are still strict regulations governing usage, hardware specifications, aerial gain and power output.
- 802.11a is an 54MBps standard for Wireless Local Area Networks (WLANs) operating in the 5.4Ghz frequency band.
- 802.11b is an 11MBps standard for WLANs operating in the 2.4Ghz frequency band.
- 802.11g is a 54MBps standard for WLANs operating in the 2.4Ghz frequency band. 802.11g is backward compatible with 802.11b, so old radio equipment can still be used with newer 802.11g radios, albeit at the slower data rate.
- 802.11n is a draft 100Mbps standard for WLAN's likely to operate in the 5GHz band.
- 802.11e is a draft standard which can provide Quality of Service (QoS)
for WLAN's .
- 802.16a is a draft specification (known as WiMAX) for wireless broadband operating on frequencies between 2-11GHz.
Effective Data Throughput
In practice the effective data throughput for wireless devices should be taken as approximately half the stated data rate due to control and encryption overheads. It should also be noted that the quoted data rate is for the system so if there are two wireless clients connected to one WAP/bridge the effective data throughput to each client will need to be further halved.
Licenced systems
Licensed radio or microwave communications are a secure, reliable and cost effective method of providing communication links for a wireless WAN to support voice, data and video applications.
The equipment uses a dedicated microwave frequency licensed for use by the Radio Agency, which controls and allocates microwave frequencies for use in the UK. Once a licence is granted, no one else can transmit at that frequency in that particular air space. This means that microwave networks rarely suffer from interference.
Microwave wireless connectivity can be used with both laser and unlicensed radio to provide a complete wireless WAN.
Features and benefits of licensed microwave communications
- Data rates of 2Mbps to 200Mbps
- Distances supported from 20 metres to 20Km
- Cost effective alternative or back up to leased lines
- Statistical availability greater than 99.99%
- Interfaces available to support voice, video and data (e.g. Ethernet)
- Ideally suited to broadband network requirements
- Secure transmissions
When installed correctly, microwave links are highly resilient to adverse weather conditions, such as rain, fog or snow.
|
|
