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Scalable Indoor Small Cells vs. Extending Macro Cells Indoors
August 31, 2015

Large macro base stations companies have a seemingly attractive offer for wireless operators – “Just use our macro base stations indoors! We can offer you new indoor radio heads that connect to the baseband/digital units you love, and you will be on your merry way.” The problem with this offer is that it is trying to force-fit technology designed for towers and other outdoor environments – called CPRI – into an enterprise environment.

CPRI is a standard designed to carry baseband I/Q samples from the baseband unit to a radio head. CPRI was developed so that base station OEMs could source radio transceiver units from multiple suppliers. Over time, CPRI made it possible for the radio transceivers (radio heads) to be moved from the base station chassis to the tower top, with a fiber optic cable in between. This move to remote radio heads reduced cable losses, and boosted the coverage of macro base stations. All good things.

However, CPRI was never designed to be bandwidth efficient.  A single 20 MHz LTE carrier with 2x2 MIMO requires 4.9152 Gbps of bandwidth to carry CPRI between the baseband unit and each radio head*. Considering that a 20 MHz LTE carrier can deliver up to 150 Mbps on the downlink and 50 MHz on the uplink, CPRI’s bandwidth efficiency is less than 3%. In practice, it is even lower. Some vendors compress CPRI, but compression adds cost and barely increases CPRI efficiency by a factor of 3.

The CPRI approach works fine when there is dedicated fiber between the base station and each radio head, but is not appropriate for buildings. Networks inside buildings are built with switched Ethernet. Enterprises want to connect all kinds of equipment to their Ethernet LAN – from computers and printers to Wi-Fi APs and small cells. The Ethernet LAN is the “neutral host” network infrastructure for the enterprise, and all these devices need to share the bandwidth on the LAN. Over the last 20 years, a wide range of technologies have been developed to share the LAN, from QoS to VLAN, and they were developed for a good reason: it does not make sense for enterprises to go around deploying custom cable infrastructure for every new technology they need.

Some vendors are proposing non-CPRI approaches that split baseband processing between the baseband unit and the radio head,  and are able to work on Ethernet instead of fiber. Such approaches require slightly less than 1 Gbps per radio head to carry a 20 MHz channel. Still, the throughput required on LAN increases linearly with the number of radio heads connected to the baseband unit, making it unfeasible to share the enterprise LAN.

SpiderCloud’s scalable small cell system is the only system that can serve thousands of subscribers in buildings as large as 1.5 million square feet and works on a shared enterprise LAN. In a SpiderCloud system, all baseband processing is done by its small cells, called radio nodes. Up to hundred dual carrier radio nodes are connected to SpiderCloud’s small cell controller, Services Node. The Services Node is responsible for anchoring all the user sessions, managing mobility and interference, and SON. This architecture ensures that the only traffic between SpiderCloud’s small cell and Services Node is actual user traffic, and some few hundred kbps of overhead. In other words, deploying a SpiderCloud small cell system on an Enterprise LAN is no different than deploying an enterprise Wi-Fi system. SpiderCloud’s ability to share the enterprise LAN is one of the main reasons why Cisco selected SpiderCloud to build 3G and LTE modules that clip on to Cisco’s market-leading Aironet Wi-Fi access points.

Finally, let’s consider what happens in the future with LTE-Advanced and 5G. With LTE-Advanced and 5G, operators are looking for ways to use more spectrum and more antennas. The amount of bandwidth required for CPRI scales linearly with channel bandwidth, number of channels and number of antennas. If CPRI-based approaches are struggling to, but are unable to offer 20 MHz LTE on Enterprise LANs, how will they offer LTE-Advanced and 5G? Perhaps, this is the reason why NGMN and many other organizations looking at the future of mobile networks, believe that densification using small cells is the way forward.

* This is how the math works:  30.72Msps (sampling rate) * 15b (sampling width) * 2 (I/Q) * 16/15 (1 control word per 15 data words) * 10/8 (CPRI line coding of 10b/8b) * [2 (for 2 Tx antennas) + 2 (for 2 Rx antennas)] = 4.9152 Gbps. Assuming peak cell throughput of 150Mbps in DL and 50Mbps in UL, the best-case efficiency of CPRI (bandwidth on CPRI link / actual throughput delivered by cell) is less than 3%!

- Amit Jain, Vice President of Marketing & Product Management
Twitter: @SpiderCloud_Inc

Fact Check: Adding Capacity in an E-RAN System
August 24, 2015

We have encountered a number of incorrect opinions about how to add capacity to an E-RAN installation. It’s time to clarify the concerns, and set the record straight.

Adding capacity to an E-RAN installation is done by increasing the size of backhaul connecting it to the mobile core. Further, the contemporary Ethernet Network Termination Equipment “NTE” that are implemented by Tier One operators, adding capacity is performed by an OSS system by increasing the logical rate on a 1Gbps Ethernet physical port. There is no need to visit the building, add additional Radio Nodes and cabling, or install new cards in a chassis.   

In the balance of this post, we review the E-RAN technical characteristics that support the approach of increasing backhaul to add capacity to an E-RAN.

E-RAN Technical

  • Each SpiderCloud Radio Node (SCRN-310) offers 2 cells (sectors) of capacity, and supports up to 128 active users.
  • Up to 100 SCRN-310s can be connected to a Services Node. The Services Node supports over 10,000 subscribers.
  • The number of Radio Nodes in a building is based on coverage. Each radio node covers 750-1000 sq. m. (7,500-10,000 sq. ft.).
  • A single 20Mhz wide LTE carrier can deliver up to 150Mbps of downlink to a mobile device.
  • The fronthaul network supporting the cloud of Radio Nodes associated with a Services Node is typically a 1Gb PoE+ link to an Ethernet VLAN with a 10Gbps backbone that interconnects the switches.

To make sense of this, typical commercial structures in the USA and Europe allocate anywhere from 15-25 sq. m. per person (150-250 sq. ft.) and, for purposes of this Fact Check, we’ll use a density of 10 sq. m. per person. This means that the maximum population supported by a single RN-310 with 750 sq. m. of coverage will be 75 people - of which only a small amount will be consuming capacity from their serving Radio Node at any moment in time.

Clearly, there is a huge amount of RF link capacity available to serve the mobile devices in this example. Note that each RN provides more capacity to a 1,000 sq. m. area than many DAS (or remote radio head systems) provide to a 10,000 sq. m. building. We shared, in this post, our view of spectrum re-use and how the E-RAN is analogous to the wired network revolution that was led by the emergence of 10Base-T and Ethernet switches.

In our experience, there is rarely a situation in which an operator has to add a Radio Node due to RF resource contention.

Now, let’s look at the backhaul that connects the Services Node to the mobile core. When an E-RAN system is viewed from end to end, the sizing of the backhaul is generally the bottleneck in any performance scenario. What limits the capacity of an E-RAN system is the backhaul that the operator delivers. If the operator delivers 100 Mbps of backhaul to an E-RAN with 20 RNs, it will operate at <5% of its capacity. If an operator wants to add capacity to an E-RAN, all they need to do is to increase the backhaul coming into the building.

Fact Check Recap:
Question: How do you add capacity to an E-RAN?
Answer: Increase the size of the backhaul as-needed. No truck rolls or on-site work required.

To our readers, if you have additional questions or areas of interest around implementation, please contact us. We’re happy to Fact Check what you may have been told.

- Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies

Twitter: @EMobilityInside
Visit our Enterprise IT site @ http://SpiderCloud.com/EInsider

Enterprise Small Cells are Measurably Visible Now
August 17, 2015

The study, The Potential for Small Cells Infrastructure-as-a-Service in the U.S., sponsored by Cisco, Intel, and SpiderCloud was published by iGR last week. If you think back, it was not that long ago that Enterprises were not only unaware of Small Cells, but there was little drive to improve mobile services indoors beyond Wi-Fi upgrades. This study clearly illustrates the awareness of Enterprise IT leaders willingness to move to managed services, and the need to enable mobile devices to be fully functional indoors. For those in the Small Cells market for more than a few years, the results shared in the study are phenomenal in that Enterprise awareness of the technology is minimally 50% across the different sized firms responding to the study.

More importantly, the results of Interest in Enterprise Small Cell Solutions as a Managed Service question (page 17) point to a significant amount of Enterprise IT people willing to participate in funding a resolution to their poor indoor mobile coverage and capacity. For firms of 5,000+ employees, 30% are interested, with an additional 40% neutral. If we assume that neutral means “our enterprise could potentially fund this, if the price is right”, the Total Addressable Market of Enterprises who could fully or partially fund their indoor RAN deployment is potentially 70%!

We are seeing the continued acceleration of the move to a mix of managed services as the foundation of Enterprise communications. The willingness of Enterprises to entertain the family of IaaS offerings, as called out in this study, illustrate the shift from just a few short years ago when Enterprise IT leadership wanted to buy, build and run everything inside their data centers. One of the core factors that the study also calls out is the need to provide much direct control and reporting to the enterprise as part of IaaS platforms. From the study: “To an IT manager, the phrase managed solution means that they retain some control, and have a secure environment while benefiting from a solution that reduces IT Overhead and capital expense.”

In the competitive business environment we live in today, IT leaders are being challenged to invest both capital and salary funds into initiatives that yield competitive advantage. For IT services that every corporation must have to operate, they are judged as commodities by most CIO’s compared to vital Line of Business systems such as the Supply Chain environment.

In case you missed it, a few posts we have done on Enterprise mobility trends:

Enjoy the study. It’s great to see that Small Cells have broken through into the thought processes of so many Enterprise IT people who must supply fully functional wireless communications environments to their clamoring employees.

- Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies

Twitter: @EMobilityInside
Visit our Enterprise IT site @ http://SpiderCloud.com/EInsider

Why Capacity and User Experience Matters
August 10, 2015

In our last posting on Single Cell Architectures vs. Scalable Small Cells, we explored the importance of handovers between cells as a key component of scaling capacity. We’ll now review a project that set out to explore the claimed benefits of SpiderCloud Wireless E-RAN scalable small cells system in a live network setting and share the results.

Let’s setup the context of the project:

  • Three-story building with installed LTE DAS system.
  • About 200 employees per floor.
  • No complaints of service or performance issues.
  • Operator offered one floor to disable DAS and implement the E-RAN in its place to prove the viability of the technology.

In order to proceed with the project, a walk of the candidate floor was conducted to collect our baseline DAS performance data. For the overall floor, we measured an average of 23.9 Mbps on the LTE downlink.

The project proceeded forward by disabling the DAS infrastructure on the candidate floor, and replacing with an E-RAN. The system supported the LTE needs of the users on that floor for the trial period. Data and metrics were continuously collected so the overall system performance could be evaluated at end of the project.

At end of project, and before the DAS system was returned to service on the floor, a second walk of the floor was conducted to collect our E-RAN performance data. The same path and collection tool was used to re-survey for average throughput. For the overall floor, we measured an average of 60.9 Mbps on the LTE downlink. That is a 255% increase in average downlink rate based on the measured DAS downlink average of 23.9 Mbps.

Finally, the daily consumption data was collected and charted. Our operator was both surprised and pleased by the results. Why? The data consumption on the E-RAN equipped floor was 57% higher than with the DAS system. As the chart below illustrates, the single E-RAN floor was driving more traffic than the other two floors combined.

Conclusions

  • Faster downlink performance increased data consumption by over 50%. Customer satisfaction with the performance improvement encouraged more usage by mobile owners.   
  • For mobile operators, increases in data consumption can either raise customer loyalty or translate into revenue.
  • Just because a DAS system appears to be operating normally, there can be significant financial and performance improvements by replacing it with scalable small cells. For DAS owners planning for re-design driven by LTE needs, it is wise to consider adding scalable small cells alongside the legacy technology instead of making additional DAS capital investments.

- Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies

Twitter: @EMobilityInside
Visit our Enterprise IT site @ http://SpiderCloud.com/EInsider