Femtocells are being offered to consumers as a way of guaranteeing mobile phone-based calls and data transfer throughout a home. It is now being proposed that a type of femtocell wireless basestation could cover a much wider area.
Bath-based picoChip has announced two baseband system-on-chip devices, which it claimed will support wide area femtocells with a 2km range. One advantage of wider range femtocells to network operators is that they can be used to offload bandwidth-hungry data transfers from local fixed cells in existing mobile networks.
These fixed cells are running out of capacity, particularly data capacity, as the amount of data transferred per phone increases exponentially at the same time as the average number of phones per cell rises.
Conventional femtocells, such as Vodafone's Sure Signal, which is based on earlier picoChip silicon, cover a small area, perhaps a single house. With the new chips, the firm is aiming at femtocells for city and rural coverage.
"Compared with small femtocells, you need more mips and more square millimetres of silicon to achieve that range," picoChip CTO Doug Pulley told Electronics Weekly.
Together with increased range, the maximum user terminal speed has been boosted from 10km/h to 30km/h.
The PC313 and PC323 are complete single-chip HSPA+ femtocell SoCs for eight or 24 users respectively, both scalable to more users. Both chips mop up almost all of the femtocell silicon except for the RF chip.
For the first time at picoChip, 2x receiver and 2x transmitter diversity has been included on the devices.
According to Pulley, it is the two receive channels that make 24-user operation on one cell possible, without requiring excessive phone transmitter power.
With one antenna, the practical limit is about eight users before phone battery life becomes an issue.
"The key feature of the devices is going to be receiver diversity for eight and above active channels. You are really going to need it," said Pulley.