Small cells that support connectivity in a limited area, such as at a mine or in a rural community, or support a high density of connected devices, must be supported by effective backhaul tech- nologies to ensure that data traffic flows consistently, says telecommunications technology company Radwin SADC region MD Peter Turvey.

Cellular technologies, such as 2G, 3G and long-term evolution, vary in the consistency with which the networks can carry data, depending on the interference of signals and the number of connected devices being supported by a base station.

To provide consistent availability of a network or to support a concentration of connected devices, small-cell network architecture can be used. Radwin uses time division duplexing/time division multiple access (TDD/TDMA), orthogonal frequency-division multiplexing (OFDM) and multiple input, multiple output (Mimo) systems of its radio signals to overcome problems of interference and lack of line of sight, both of which affect signal quality.

TDD entails the separating of return signals and outbound signals into different timeframes, eliminating interference and improving availability of the connection. TDMA is a channel access method for shared media networks. It enables multiple users to share the same frequency by dividing the signal into time slots, he explains.

OFDM enables the use of multiple subcarriers, instead of a single wideband signal, while Mimo is a smart antenna solution that spreads transmission power over multiple antennas.

For example, the company provides a mobility solution, which includes high-speed point-to-multipoint connectivity to trains on the Ukraine Railway’s Lvov–Kiev– Donetzk line along 1 600 km of track. The job required Radwin to ensure downlink speeds of 30 MB/s for the length of the track, including fast handover between base stations.

“We are able to deliver high availability and consistently high throughput partly as a result of using antenna diversity, which sees the use of two antennas that have different experiences. When these two experiences are combined, they enable the radio to have multiple observations of the same signal. Other metro and train installations use our system to support security camera feeds inside the train.”

This type of security application dictates the use of very high bandwidth uplinks coupled with fast handover speeds between base stations. It results in high-quality video streaming from the train to the control centre, he says.

“This is possible because we have a configurable uplink and downlink for asymmetric traffic,” says Turvey.

“We are also providing long-distance cellular backhaul services in Mozambique for connectivity to Bazaruto Island, besides others. Radio backhaul is tricky across bodies of water, as the Fresnel zones of the line of sight radio waves can be disrupted by tidal changes. However, our system of OFDM and Mimo enables us to maintain transmission, ensuring availability,” he notes.

Radwin is able to support symmetric and asymmetric traffic, as well as a configurable uplink and downlink when using asymmetric-type radio traffic, which enables the support of applications that require either more uplink traffic, such as video streaming from security cameras installed on a train, or more downlink traffic, such as providing Internet traffic to trains or the delivery of symmetric mobile cellular traffic in very tough radio con- ditions, adds Turvey.

The company serves four key industry sectors – mobile carriers, fixed service providers and Internet service providers, security and surveillance, and public and private organisations.