Small cell base stations have become one of the leading solutions to address the imbalance in supply and demand of mobile network capacity. Further, they have been identified as a key technology to enable spectrum sharing schemes.

The subject of small cells is not one of “why,” but rather “how.” Specifically: “How to deploy small cell base stations cost effectively.” This paramount question is far encompassing and cuts across the myriad of issues at the core of small cell base station deployments such as site acquisition, installation, and backhaul.

Hence, the question of cost is not singularly unique to any one specific function – rather, a comprehensive approach is required to solve the small cell cost challenge.

Taking this holistic approach, I like to highlight the advantages of integrating the backhaul function with the small cell base station. By definition, small cells are mounted at a relatively low height above ground, cover a small area and are mainly targeted for locations wheretraffic density is high. This makes small cells visible to people on the street; consequently, one can expect adverse public response to large and obtrusive form factors mounted at close proximity to the public.

Thus, the installation process must be quick and the deployment visually discreet. Therefore, integrating the backhaul function with the small cell base station is a key element to enable small cell deployments.

Integration serves to reduce operational expenses since attachment cost could constitute a major cost driver that would be reduced by up to 50 percent with integration. The cost of leasing space on a pole or building sidewall varies significantly on a regional and municipal basis and even within the same municipality. In the US, the FCC (News - Alert) and some states regulate what utility companies (except for municipal utilities) can charge cable companies for systems attached to poles, which averages to roughly $7 per year.

However, this is not the case for pole attachments on municipal assets where small cells are to be deployed and where reported rates in some areas reach several hundred of dollars per month. Obviously, such high rates are detrimental to the small cell business case.  

By integrating the small cell base station with the backhaul solution, costs are cut by half. For example, consider a pole attachment rate of $50 per month for a module. This adds up to about $4,000 over a 10-year period comprising anywhere between 15-20 percent of the total cost of ownership of the backhaul solution.

Integrating the small cell with the backhaul module eliminates this cost.

Integration reduces capital expenditures since the combined small cell base station and backhaul module have a lower cost. Depending on the level of integration, it’s not uncommon to realize 28 percent savings using the combined module over two separate modules. Integration alsoeliminates some ancillary components such as cables and mounting brackets, thereby reducing deployment and installation time – a prerequisite to scalable and mass deployments.

Integration also reduces the visual footprint, lessening public objections to wirelesssystem deployments.

Integrating the backhaul and small cell solution can take different forms, each with its own advantages and corresponding cost benefit. For example, integration can range from a pure mechanical packaging exercise, to a more complex one where the baseband processor supportsboth access and backhaul functionality, to anything in between. Certain functions that are necessary for the operation of both the small cell base station and backhaul system can be implemented in a single instance instead of being duplicated on both modules.

An example of this is combining the power sub-systems to save space and obtain a smaller overall form factor. Another example is synchronization, which can be aggregated into a single function to synchronize both systems.

Because non-line-of-sight wireless backhaul systems operate in the sub 6 GHz bands, they can leverage the same ecosystem as LTE (News - Alert) and other access technologies. This further increases the opportunity for cost effective integration of the small cell and backhaul modules. Greatereconomies of scale are therefore expected in this scenario leading to more attractive cost points for the combined solution.

Regardless of how one chooses to integrate small cell and backhaul systems, one key contributing factor to the combined form factor is the antenna of the backhaul system – it is directional, unlike the omni-directional one typically seen on small cell base stations. Since the antenna impacts the deployment and installation process this is where competing backhaul options differentiate themselves.

For example, line-of-sight wireless backhaul systems typically implement a parabolic antenna that must be precisely aligned with the paired transceiver endpoint. Thus, for simplicity of installation and antenna alignment, the antenna must remain free from constraints, which reduces the level of integration possible. On the other hand, non-line-of-sight wireless backhaul systems typically rely on flat panel antennas that do not require alignment with the serving hub module, thereby greatly increasing the backhaul solution flexibility and level of integration possible.

In the quest to solve the small cell deployment challenge, integration of the backhaul and small cell becomes important for the potential cost savings that can be achieved. I estimate cost savings to be at least 15 percent of the total cost of ownership for the combined small cell and backhaul solution. Furthermore, of the different types of backhaul solutions, NLOS wireless is the most amenable to integration with the small cell base station, as it provides the highest potential costsavings among the competing backhaul options.

Frank brings over 17 years of experience in the wireless industry with a thorough knowledge and experience in access and backhaul technologies. He has defined a line of innovative compact base stations and established strategic alliances at Redline Communications (News - Alert) where he led product management for 4G wireless access networks. At Ericsson, Frank worked extensively with mobile network operators to deploy three networks in the Americas, after which he defined sales and market entry strategies at Metawave Communications for a GSM smart antenna system. Frank holds a BS in Electrical Engineering from Case Western Reserve University, Cleveland, OH, and a MASc in Electrical Engineering and an MBA from the University of Toronto, Canada.

Edited by Braden Becker