Local mobile telephone operators have been quick to respond to the Office For Telecommunications Authority's (OFTA) recent ruling that allowed them to introduce dual-band services combining the GSM (global systems for mobile communications) and PCS (personal communications system) networks. Hutchison Telecom and Smartone have both launched dual-band networks just weeks after the ruling. Hutchison this month unveiled the SAR's first dual-band network two weeks after OFTA's decision. The system was built in co-operation with the operator's long-time technology partner, Motorola Cellular Infrastructure Group (CIG). Hutchison's network is Motorola's first dual-band implementation in the world. It was launched just days before the start of a similar system in Portugal. It took Hutchison and Motorola a year to implement the system. 'The main challenge was to install and upgrade the various software without deteriorating the quality of the existing services,' Cliff Woo, Hutchison Telecom's director of engineering, said. About 400,000 subscribers are using Hutchison's GSM and Everyday PCS networks. Motorola calls its network 'multiband' because of its different potential implementations. According to Bruce Duysen, CIG's Asia Pacific business operations director, Hutchison decided on a contiguous infrastructure, meaning the two networks were blended into one. One of the key advantages of merging the GSM 900 and GSM 1800 (also referred as PCS) spectrum resources is increased capacity. In the case of Hutchison Telecom's dual-band network, capacity increased 30 to 40 per cent over a separate single-band network, bringing the maximum capacity of the network to more than one million subscribers. The added capacity means there are more channels available and less chance for traffic congestion on the network, which in turn will perform more efficiently. Mr Woo said the results were a higher rate of first-time connection - by up to 99 per cent - and a lower drop call rate of less than 1 per cent. 'The two systems are backing up each other all the time, which makes the network more robust in terms of reliability,' Mr Woo said. Leveraging on the performance of a dual-band network, Motorola introduced two new technologies. Synthesised frequency hopping, which makes the network more resistant to interference, was implemented throughout Hutchison's network. Advanced load management is a traffic management system which enables the mobile operator to better control the handover mechanism of the network. The 'handover based on congestion' model selected by Hutchison detects congestion and switches the handset automatically to the best available unit, either a PCS cell or a GSM, whichever has the strongest signal. The feature enables Hutchison to adjust the responsiveness of the network on demand. It had expected a surge of traffic from Chek Lap Kok in the first few days after the airport opened, but Hutchison had been able to expand capacity to cope with the demand, Mr Woo said. Hutchison said it would invest $3.5 billion over the next three years to further enhance its dual band network. It planned to add about 200 cell sites to the existing 1,300 before the year's end. A team was looking at potential areas of development such as the upcoming West Rail track. New value-added services also would be introduced, especially in the mobile banking and Internet access areas. The network is largely targeted at business subscribers and is offered as a value-added service to Hutchison's existing GSM customers at no extra cost, apart from the purchase of a dual-band handset. The availability of the dual-band handsets is key to the development of the service, and will depend on the production strategy of mobile phone manufacturers. Only two types of dual-band handsets are now available in Hong Kong - the Nokia 6150 and the Motorola cd928, both priced at $3,380 - although more models are expected in the next few months.