Author: Scott Wakelin
Much has been written in the trade press recently about how mobile network operators, like Verizon Wireless and AT&T in the U.S., Orange in France, or China Mobile in, well, China) are looking at a new architecture for how they build their networks, which is called C-RAN, or Centralized Radio Access Network.
All subscribers of mobile services should care about C-RAN, and here are my 5 reasons why.
Before I get into it, here’s a quick overview of C-RAN. I’m sure everyone reading this has seen a cell tower, which holds the antennas that are transmitting and receiving information to the subscribers for a particular company in the area served by the tower. At the bottom of that cell tower is a relatively small building that looks a bit like a shed, which holds a bunch of equipment, including:
- Cellular processing equipment (called the baseband unit),
- “Transport” equipment that is used to connect the cell site to the rest of the mobile operators’ network,
- Air conditioning to keep the temperature of the equipment in the room within their operating range, and
- Power supplies to power the transmitters on the tower as well as the above equipment.
This is the “traditional architecture.” In the new C-RAN architecture, there’s no longer an equipment room at each cell site. Instead, this equipment is centralized in a nearby location (central office or data center), which also houses the equipment for multiple cell-sites over a given region—hence the “C” in C-RAN stands for centralized.
Now back to what this mean to all of us and the 5 reasons why you should care (in no particular order):
Reason #1: A Greener Environment
With an increasing subscriber base and more cell towers to service those subscribers with faster and faster connections, greenhouse gas emissions from mobile communication networks are increasing. Ericsson predicts that the worldwide mobile communication industry will contribute 0.5% of the worlds’ total greenhouse gas (GHG) emissions in 2020 – up from 0.2% in 2007.
Don’t get me wrong, this is already an incredibly good number. Mobile operators are considered “light intensity” in their environmental impact, but this is still 178 MTonnes of CO2.
How does C-RAN help? Take China Mobile, the worlds’ largest mobile network operator, as an example. In their white paper on C-RAN, they report that 72% of their power consumption is at the cell site. And of that, a whopping 46% is consumed by the air conditioners!
If all existing and future cell sites were to (magically) evolve to a C-RAN model, leveraging the already present air conditioners in existing central offices, there would be 59 MTonnes less CO2 in the atmosphere in 2020. And that’s just 2020 — imagine the number in 2030…
Since it’s impractical to move all existing cell sites to C-RAN, how about we shoot for all new cell sites? This is still important when one considers that, in China alone in 2015, there will be around one million new cell sites constructed.
But there’s more: most mobile operators proactively service each and every one of their cell sites on a regular basis, called “truck rolls,” focusing in particular on the equipment in the equipment room. With C-RAN, you can envision a future where the operator no longer has to drive out to 10’s or 100’s of thousands of cell sites each month, resulting in a reduction in vehicle emissions.
Reason #2: Faster Downloads
In order to deliver the massive increase in connection speeds that subscribers demand (my data usage increased to over 450MB in just six days versus 35MB in the preceding 24 days after upgrading to a new Apple IPhone 6plus from Blackberry), mobile network operators need to deploy more capacity—essentially more cell sites.
The problem is, as they deploy more and more of these cell-sites, they start to interfere with each other, particularly in the boundary areas between one cell site and another. To the user downloading, for instance a YouTube video (shameless self-promotion), this interference is seen as a reduction in data rate and perhaps even buffering. And no one likes buffering, right?
Mobile network operators have a solution to this interference problem, called CoMP or coordinated multipoint. CoMP has been shown to increase mobile network performance at cell boundaries by up to 100%. The problem is, CoMP is not really effective or possible with the traditional network architecture because it requires that multiple cell sites’ processing equipment be very closely coordinated with each other.
The best way to achieve this coordination is by having the baseband equipment for multiple cell sites located in the same place. This is precisely what C-RAN does.
Reason #3: Reduced Visual Impact
With C-RAN, new radio transmitters can be added into the network without also having to identify a place with enough space for the equipment room. Not having an equipment room is already a visual improvement. But what’s more, C-RAN allows the industry to come up with inventive new ways to reduce, if not eliminate, the visual impact of the radios as well. As an example, it’s easy to see a future where the radios are integrated into innovative new building materials.
Reason #4: Reduced Cell Site Noise
This one is relevant to those living in apartments and other multi-dwelling units that have cellular antennas on the roof. In these cases, the cellular processing equipment might be housed in the buildings attic, with fans and other air conditioning equipment generating noise. Noise is also generated when the operator needs to perform maintenance on the equipment. C-RAN helps reduce if not eliminate all of this noise. Sounds good right?
Reason #5: Lower Costs for Mobile Operator and Subscribers
Mobile operators are faced with a daunting challenge: they need to increase the capacity of their network at a faster rate than their revenue is growing. Much faster. Perhaps 11x faster. If they don’t, they risk losing their customers to their competitors. We’ve all seen how fierce the competition is between rival mobile operators.
C-RAN allows operators to save money in operating their networks in several ways:
- Reduced power consumption
- Reduced maintenance costs
- Reduced site lease expenses
It also allows them to save on building their networks through:
- More efficient utilization of cellular processing equipment. Did you know that on average, the baseband equipment at a cell site is only 30% utilized? This is because they need to have enough processing capability to handle the peak load for the area served. With C-RAN, they can pool their baseband equipment so they only need to have enough processing capacity to handle the average load. Pretty cool!
- Eliminating the equipment room. China Mobile estimates the cost related to this activity at around 8% of the total budget to build a new site.
- Reduced air conditioning and power supplies.
Overall, in their trials to date, China Mobile has found CAPEX (new construction) savings of 30% and OPEX (operating) savings of 53% by going to C-RAN.
Will this translate into lower fees for subscribers? One can only hope. If anything, C-RAN should allow your friendly neighborhood mobile operator to keep your subscription fees down while they deliver the mobile bandwidth we all desire.
One Question Remains
You may be asking: if C-RAN is so powerful, why isn’t it the typical architecture today? The answer is three-fold:
- Until 4G/LTE came along there wasn’t a strong technical motivation
- It needs fiber, which isn’t universally available particularly at older cell-sites
- A lack of solutions to address how to connect the radios at the cell-site to the processing equipment in the central office or data center.
For (1), we know that almost all mobile operators are currently deploying 4G/LTE networks and are beginning to think about what 5G looks like. To address (2), fiber access is now an important consideration for the location of new cell sites, and is already available at most if not all cell sites in many parts of the world. Finally, new technology is becoming available to address (3).
My next post will look at this new technology, including the requirements for a fronthaul network and how OTN-based fronthaul can reduce operators’ total cost of ownership.
C-RAN is an important technology that should be embraced by every mobile operator as they look to 4G and beyond to the 5G future. It’s a way to deliver a higher capacity, lower cost network with the minimum possible environmental footprint.
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