Reader Forum: Optimizing heterogeneous networks via advanced SON technology

Editor’s Note: Welcome to our weekly Reader Forum section. In an attempt to broaden our interaction with our readers we have created this forum for those with something meaningful to say to the wireless industry. We want to keep this as open as possible, but maintain some editorial control so as to keep it free of commercials or attacks. Please send along submissions for this section to our editors at:dmeyer@rcrwireless.com ortford@rcrwireless.com.
As major carriers around the world are starting to roll out 4G networks, there is broad agreement that these networks require a heterogeneous topology in order to bridge the exponentially growing radio access network RAN gap between mobile data demand and actual network capacity. Heterogeneous networks, which augment existing macrocell network infrastructure with smaller cells (femtocells, picocells, microcells, etc.), will be required to successfully surf the mobile data tsunami.
Peter Jarich, analyst at Current Analysis, recently surveyed key decision makers in the femtocell vendor ecosystem and found that 56% believe residential femtocells will be a critical part of operator LTE deployments, while 94% believe small cells other than resident femtocells will be critical.
The new “heterogeneous” macrocell/small cell topology, however, introduces three new and significant RAN complexities: 1) many of the small cells will be transient in nature, i.e., moving around, coming on and off-line in an ad-hoc manner, etc.; 2) there will be a lot of them; and 3) many of them will interfere with each other, in some cases with 100% overlap (e.g. a femtocell nested entirely within a macrocell footprint). Managing the associated challenges, such as inter-cell interference and spectrum re-use, will become a major hurdle, and will require advanced, real-time, fully-automated RAN intelligence.
In early deployments, some carriers have partitioned separate frequency bands for their macrocell and small cell networks (and even within their small cell networks) with some success. But even if/when all of the related bugs are worked out, this is not scalable given a fixed amount of spectrum and the impending large scale deployment of small cells.  In order for heterogeneous networks to work properly (and cost-effectively), carriers must find a way to actively manage interference and other related inter-cell challenges, rather than to avoid them.
Self-organized networking is an industry vision for implementing automated RAN planning, provisioning and other related algorithms that enable features such as “plug-and-play.” The 3GPP SON standard specifies these algorithms to enhance network planning, as well as to begin to address deployment, operation and optimization considerations.
But this standard for SON doesn’t go far enough – it connects the user small cell with the network upon startup, but does not actively manage that connection once made. Advanced SON technology is being developed, which integrates RAN management and advanced RAN intelligence to dynamically manage a heterogeneous network’s base stations via real-time inter-cell communication and coordination.
At Mobile World Congress 2010 and International CTIA Wireless 2010, AirHop demonstrated the practical implications of small cell interference and how advanced SON technology can help solve the problem. Using two live UMTS base stations broadcasting video over the air to commercial USB UE devices, we simulated an actual user experience of, say, an apartment resident and neighbor, both with a residential femtocell. Without the advanced SON enabled, the video playback experience was frustrating, with long load times and stuttering playback/buffering. Once enabled on the base stations, the advanced SON allowed both videos to play smoothly, with the software nearly doubling the available bandwidth through intelligent RAN management, which eliminated the interference. A video of this demonstration is available at http://www.airhopcomm-web.com/solution.html.
What the demonstration showed, and what carriers have learned from their initial trials, is that to make the small cells work properly, they will have to actively manage inter-cell interaction to mitigate interference. Advanced SON technology provides an “active” approach to interference management via distributed algorithms and real-time coordination among the cells, with a flexible architecture capable of supporting centralized, distributed and hybrid deployments.
Advanced SON solves the RAN gap problem by enabling the deployment of unplanned small cells via not only auto-configuration and maintenance but, more importantly, dynamic optimization while they are in operation. With the use of advanced SON, networks can achieve the performance required by 3G/4G standards without traditional planning or when traditional planning is not viable.
Some in the industry have said that the smart phone-driven “mobile Internet era” will necessitate a significant shift away from the traditional macrocell network design. Certainly, the shift toward packet-based 4G networks makes the transition to heterogeneous networks easier. But it also means that the next-generation network may not be about a dramatic improvement in air interface performance and capacity, as much as about enhancing the ability to build and deploy heterogeneous networks.
Advanced SON technology advances this paradigm by enabling the successful merging of unplanned small cell deployments into existing macrocell topologies.