LTE Femtocell

Many people in our industry are now of the opinion that the best way forward with LTE is to roll them out as Femtocells and then when more and more people start using them, then start deploying LTE Microcells/Marcocells

Approximately 60% of mobile usage already takes place indoors, yer providing in-building coverage is a technical problem at the giahertz frequenies used for Wimax and LTE. This is only set to get worse as the mobile continues to replace the home phone. Research indicates that, as "all you can eat" data packages become commonplace, this number of is like to reache 75% by 2011.

As transmission frequency increases, in-building penetration degrades. The additional attenuation reduces throughput for those users indoors, but there is another effect too: if the traditional macrocell allocates more power to reach the indoor user, this increases the interference for other users. Such realities inevitably have a quantifiable, negative impact on cell capacity, making it impossible to deliver 10 times the performance of 3G that is a fundamental requirement of the 4G vision.

Furthermore, the large cell approach is fundamentally less able to provide the benefits for which LTE was intended. As Cooper’s Law identifies, the best way to increase traffic density is via smaller cell sizes. A macrocell gets hit twice in this respect – it has poorer total throughput due to RF conditions and it has to spread that throughput over a much wider area.

Most operators considering the roll-out of LTE already have widespread HSPA networks. If terminal devices are going to be multimode (LTE and HSPA and GSM, for example), there is little point in deploying LTE everywhere and ensuring ubiquitous coverage, since the user experience may be no better than that provided by HSPA (or could be worse). The capital expenditure of a small cell approach need not be prohibitive. Indeed, substantial savings will be available on the back of the technological innovations that are driving down the bill of materials costs for residential femtocells.

A small cell approach also has cost implications for operating expenditure. These networks need to incorporate self-optimisting tehcnology to eliminated manual configuration during deploment and throughput the life of te equipment. These self-optimising networks(SONs) can dynamically optimise radio network performance in use and provide intelligent hackhaul capabilityies. Operators are already recoginsing these requirements and mandting the provision of SONs: the emerging residential femtocell in WCDMA is proving this capability now.

This network architecture change will produce corresponding changes throughput the infrastructure value chain. The network equipment industry will move towards a consumer market approach - in a manner similar to the use of "commerical off-the-shelf" (COTS) tehconogies in the military equipment market, infrastructue manufacturess can borrow from femtocell innovations to benfit from consumer electronics economics. This will place an onus on IC sumppliers to offer unprecedented levels of system-level expertise and support.

The tradistional marcocell approach will flounder at the next stage of network evolution: they are too expensive a solution and do not deliver the required results. It is time to femtocells for LTE.



参考：3G and 4G wireless Blog
http://gigaom.com/2008/09/15/4g-forget-cell-towers-bring-on-the-femtocells/
http://www.electronicsweekly.com/Articles/2008/09/15/44506/the-macrocell-is-dead-long-live-the-network.htm