Femtocells are small, low-cost wireless base stations used in residential or corporate environments. Femtocells are already established in the 3G community, and now, the idea of using them is gaining ground among those working on cdma2000 and WiMAX/WiBro applications. We have noticed more activity on the femtocell front and the latest is the agreement of picoChip and Semtech to collaborate on augmenting picoChip's femtocell reference designs with Semtech's packet timing solution, ToPSynce. The two companies will concentrate on addressing the problems of synchronization, which operators typically face in implementing femtocell architectures.
Synchronization is an important issue, and there are four techniques which are typically used in 3G networks to achieve the tight timing these networks require (100ppb accuracy). Trouble is, each of them has drawbacks when it comes to femtocells. Precision crystal may be used in each network node, but this is too costly for femtocells, which must be inexpensive. GPS is also a possibility, but the technology is not very reliable inside buildings--just the environments where femtocells aim to play a big role. The femtocell may use an external cellular network to supply timing, which would be an appealing option if there is reliable cellular coverage, something which is not true everywhere. Traditional base stations may also use E1 backhaul connections to provide Stratum clocks, but this approach is unsuitable for femtocells connected over residential broadband.
Semtech says its ToPSync technology solves these problems by offering a Stratum-quality clock through an ADSL/Ethernet connection, via a packet network. The ToPSync synchronization solution thus relies on the backhaul connection, implementing synchronization over a Packet Network using IEEE1588, layering Precision Time Protocol (PTP) on top of native Ethernet (or other packet-based technologies) for transport.
For more on the picoChip-Semtech collaboration:
- see picoChip's press release
MORE: ip.access and Thomson are collaborating to bring 3G femtocells to the mass market, offering an integrated DSL residential gateway platform with a 3G femtocell to mobile operators. Report