By Stéphane Téral, Principal Analyst, Infonetics Research
There is not a single place in the telecom world where you don’t hear about small cells, but once you get into the discussions, you quickly realize that no one is tuned in to the same frequency.
There are as many views and opinions on small cells as there are mobile industry experts.
Small cells have been available to operators in the low-power node quiver for some time.
From the late 1990s throughout the first decade of this century, microcells and picocells were primarily used to address voice coverage issues as the anchor for distributed antenna systems (DAS).
But things have changed. The unabated rise of smartphones and consumer appetite for mobile data has shifted the issue from coverage to capacity.
Although linked, these are two different issues.
Coverage is a function of three variables: topography, capacity, and topology.
Topography, or the terrain and the surroundings, determines the topology, which is where and how cell sites are installed and antennas implemented.
Capacity relates to the number of users attached or communicating with the same cell site at a given time.
Existing cellular networks like GSM and CDMA were designed to cope with large coverage areas, but not capacity.
Consequently, they are not achieving the expected throughput to ensure seamless mobile broadband in the uplink as users move away from the macro base station.
This is primarily due to an increase in the inter-cell interference (ICI) as well as constraints on the transmit power of the handsets.
In addition, topographic constraints in urban areas such as wall thickness and number of floors in buildings generate poor in-building penetration.
This directly leads to two additional issues or use cases: indoor versus outdoor for both coverage and capacity.
Consequently, there are four distinct use cases that do not necessarily require the same strategy:
- Indoor coverage
- Outdoor coverage
- Indoor capacity
- Outdoor capacity
As the macro network is essentially built out mainly for coverage and for zoning and environmental issues -- and acquiring new sites is difficult and even impossible in places like California -- there is urgency to develop solutions that address the four use cases.
The problem is: there is no one-size-fits-all solution.
Each use case is so different that it takes a full quiver of low-power node ammunition to address specific situations, including femtocells, picocells, microcells, WiFi access points, and remote radio heads (RRHs) combined with ad hoc spectrum.
As a result, there are many camps and schools of thoughts and the network densification that uses high counts of small cells tend to dominate the headlines nowadays.
That too does not necessarily address all use cases at once.
Put another way, densifying a macrocell site consists of dividing it into a larger number of added smaller cells.
The smaller the cell, the higher the number of small cells required.
For example, in public space deployments, it could take twice as many non-consumer femtocells as picocells to do the job.
High numbers of small cells look attractive to would-be small cell players, but the reality is that interference management and backhaul issues remain a major barrier to deploying them, particularly for mobile operators who only have a limited spectrum portfolio, not to mention scarce human resources.
So, while the Small Cell Forum is working on use cases, here at Infonetics global operators we have interviewed believe DAS will remain a fundamental tool for malls, airports, stadiums, etc.
Yes, small cells are poised to play a major role in 3G and 4G network expansion, but operators are going to pick the right tool for their needs and small cells aren't always the right solution.
When the rubber finally meets the road we will know whether the high expectations small cells have generated were warranted.
The bottom line is, small cells – I'm not talking about residential femtocells here – remain a tiny market compared to macrocells, and will take time to reach meaningful penetration.
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