22 Nov 2012

Small Cell Architecture Approaches

Ronny Haraldsvik of SpiderCloud Wireless looks at the different small cell architecture approaches and how they affect coverage, capacity, scalability & services.

Demand for mobile data capacity is doubling every year.

Mobile operators need small cell system flexibility as they transition to support both multiple mobile access technologies and enterprise customers who increasingly rely on mobility for productivity.

Mobile operators must be able to control 10s to 100s of multi-mode 3G/Wi-Fi/LTE small cells in each and all of the deployments inside enterprise or mixed indoor/outdoor venue such as stadiums, malls and transport hubs - with one touch-point and without interference to other small cells or the macro cellular network.

That’s a tall order. So, is that not possible today with small cells? Yes and no. It depends on the architecture approach.

Several consumer femtocell suppliers are positioning their existing products in the enterprise small cell market, often with slightly higher capacity and proprietary extensions to their core network based femtocell controllers.

Though these offerings enable consumer femtocell suppliers to leverage their investment, they do not meet the performance expectations of enterprises or the business requirements of mobile operators. Enterprises expect small cell systems to provide seamless voice coverage, LAN- comparable mobile data throughput, and integration with local applications.

Mobile operators need a solution that can be rapidly deployed, minimizes operating costs, is easy to manage, and scales - from small offices to huge multi-story buildings.

A different approach is to create a system capable of managing a scalable small cell system to meet the performance expectations of enterprises and the business requirements of mobile operators.

Key functions of a scalable small cell system must include: - Seamless voice coverage, with make before break handovers

  • Consistently high data throughput, by managing inter-small cell interference

  • Policy-based integration with Enterprise Intranet and voice applications

  • Rapid deployment, with self-organizing and self-optimizing algorithms

  • Enterprise-centred management

  • Lower operating costs through efficient use of backhaul

  • Scalability – from small enterprises to very large

Why is small cell system scalability Important?

Employees of mid-to-large sized enterprises constitute 15% of subscribers at major mobile operators, and contribute as much as 30% of their revenue. These enterprise customers are not only the most loyal and profitable customers that mobile operators have, but also the most demanding. They expect the mobile operator to deliver seamless wireless coverage in their facilities, to stay ahead of the rapidly growing demand for wireless capacity, and to offer innovative ways to solve business problems.

Small cells offer one of the best ways for carriers to deliver wireless coverage and capacity, as well as new services to customers. Analysts such as Gartner, Dell’Oro and Goldman Sachs expect small cells to drive 18% of RAN investment by 2016. Infonetics Research expects enterprise small cells to be the fastest growing small cell category, comprising over 50% of small cell investment by 2016.

ABI Research expects enterprise small cell equipment to reach the $2 billion mark by 20161. Not only are enterprise small cells the only economically viable option to provide coverage in small to medium enterprises, they are expected to take market share from distributed antenna systems (DAS) in the mid- to-large enterprise market. The growth in enterprise small cell systems is primarily due to the system’s flexibility and ability to tie into an operator’s overall HetNet.

Enterprise small cell systems cannot be built by merely increasing the transmit power and user count of residential small cells (also known as femtocells). Single high-power femtocells may be able to cover as much as 1,000-1,500 square meters. However, over 80% of commercial buildings are larger than 1,000 square meters, each with hundreds or sometimes, thousands of subscribers. These offices need multiple small cells for coverage and capacity.

The standard femtocell architecture (in which femtocells connect to a core-based gateway using a 3GPP defined protocol called Iuh) does not offer coordination, interference management or handovers between femtocells. Enterprise femtocell suppliers are approaching this problem by adding functionality to their femtocell gateways. Trials conducted by operators demonstrate that this approach does not scale. The largest commercially deployed enterprise small network that relies on a centrally located gateway for mobility and interference coordination has 7 small cells.

Design Considerations

Mobile operators want to win or retain enterprise customers, and to sell them new services. To accomplish these goals, an in-building 3G wireless system should provide seamless voice coverage, with practically no call drops. Data throughput should be comparable to the LAN. A small cell system must be able to measure system performance and offer service level guarantees. The systems should be secure, easy to deploy and inexpensive to operate. Plus, it should easily integrate with the enterprise’s local network. This section discusses each of these design considerations in some detail.

  1. Seamless Mobility – Users in enterprise environments are not stationary. People are moving throughout the day in an enterprise. SpiderCloud’s experience shows that in a building with 800+ subscribers, subscribers cross small cell boundaries over 20,000 times an hour.

  2. Consistently high throughput – Customers are now accustomed to a multi-megabit data experience on their smartphones, and they will not be satisfied with an in-building wireless system unless it provides them such rates. Further, customers are unlikely to tolerate wide variations in data rates as they move throughout their offices.

  3. Enterprise-centered management – An operator should be able to manage each enterprise small cell system as one unit, rather than managing individual small cells. Not only does this reduce operational costs, it also allows the operator to differentiate by offering SLAs to its enterprise customers.

  4. Self-organizing and rapidly deployable – Speed of deployment is important, both for reducing deployment expenses and increasing revenue. Enterprise systems are often deployed after work hours when the operator (or enterprise) is paying overtime wages. Further, the sooner an operator can deploy, the sooner it can acquire new customers and start receiving revenue.

  5. Efficient use of Backhaul – Backhaul (the connection between the small cell system and the operator’s core network) is a very large recurring expense and must be minimized. To do so, all small cells in an enterprise should share a single backhaul link. Traffic on this link should be prioritized, and overhead minimized.

  6. Local switching of voice and data traffic – Enterprise users want to securely access their Intranet and PBX, without installing special client software. An enterprise small cell system should make this possible, without breaking basic features like mobility.

  7. Scalability – Since it is expensive for operators to commercialize new technologies, an ideal enterprise small cell system should be able to cost-effectively cover multi-story buildings and campuses that are as large as 50,000 square meters (500,000 square feet), or offices as small as 1,000 square meters (10,000 square feet). Offices smaller than 1,000 square meters can be addressed by consumer or enterprise femtocells.

Broadly, there are two ways of building enterprise small cell systems.

  1. Using a core-network based controller: This approach, favored by residential femtocell companies, involves adding new functionality to the femtocell gateway (also known as Femto Concentrator, HNB gateway and Iuh gateway) to address basic requirements such as inter-small cell mobility and consistent throughput.

  2. Using a local controller in the enterprise: This approach, pioneered by SpiderCloud Wireless, uses a small controller in the enterprises that aggregates all the small cells in an enterprise, manages mobility and interference across them, integrates them with the enterprise’s Intranet, and provides a single interface to the core network.

Local Controller approach

Without the presence of a local control point on an enterprise customer’s Ethernet network, a mobile operator cannot effectively coordinate small cells or inter-small cell signaling (soft Handover signaling in the case of 3G, and X2 signaling interface for LTE).

Without the presence of a local control point, small cells have to connect back to the mobile operator’s core network-based gateways, slowing down handovers and increasing the rate of interference coordination inside buildings. A local control point is essential for Local IP Access (LIPA), also known as local switching and local breakout, which is needed to ensure inter-small cell mobility. LIPA enables content caching, access to content-based and localized services.

A local Controller enables seamless small cell-to-small cell mobility and manages interference between the small cell system and the macro cellular network and significantly increases average mobile data throughput for small cells, capacity, and the overall performance of a small cell network. This can improve the small cell economics for a mobile operator significantly.

One small cell system must be able to handle over 100,000 data sessions and handoffs on a daily basis while providing reliable voice and data coverage for hundreds to thousands of employees with just one connection to the mobile core network.

Mobile operators must be able to co-deploy 3G, 3G+Wi-Fi and LTE/4G small cell Radio Nodes, all managed by a single control point. A local controller makes it possible to ‘densify’ an in-building network without impacting the rest of the network. It aggregates all the small cells deployed inside and makes the overall system appear as a single node to the mobile network.

Benefits to Mobile Operators’ Enterprise Customers

Beyond basic coverage and capacity with stand-alone small cells, with a local control point inside the deployment which controls all small cells, mobility and such, mobile operators can offer enterprise customers with reliable Mobile Applications and Cloud Services (MACS) to help mobilize people and move expenses from the Capex to the Opex side of the equation with clientless and effortless communications services enabled by the system.

Scalable System Example

SpiderCloud Wireless enables mobile operators to build very dense small cell networks to address their own network coverage and capacity needs, and offer enterprise customers with reliable mobile, application and cloud services as they transition from a wireless to a mobile connected enterprise.

The system, sold direct to mobile operators, is called an E-RAN (Enterprise Radio Access Network) system consists of a Services Node (SCSN) that can control over 100 self-organizing and multi-access 3G, Wi-Fi and LTE/4G small cells that can be installed in just days using an enterprise Ethernet Local Area Network (LAN).

One E-RAN delivers unprecedented capacity and coverage to over 10,000 connected smartphones and tablets, with just one connection to the mobile operator’s core network. The scalable system architecture simplifies deployment and overall network configuration for mobile operators as they address pent-up demand for reliable mobile services from enterprise and large venue customers.

The SCSN significantly increases average mobile data throughput for small cells, capacity and the overall performance of a small cell network, improving the small cell economics for a mobile operator.

A SpiderCloud system is proven to handle over 100,000 data sessions and handoffs on a daily basis while providing reliable voice and data coverage for hundreds to thousands of employees with just one connection to the mobile core network.

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About the author

Ronny Haraldsvik, Senior Vice President and CMO at SpiderCloud Wireless. Ronny joined SpiderCloud Wireless from BelAir Networks where he was Senior Vice President/Chief Marketing Officer (BelAir Networks was acquired by Ericsson in April, 2012). A Silicon Valley veteran, Ronny has more than 23 years of global strategic marketing and industry experience from a range of technology segments including Radio Access Networks, Small Cells, Wi-Fi, web and video optimization, wire-line networking and IP services, RFID, personal computing, wafer fabrication, software, and consumer devices.

SpiderCloud Wireless is the innovator behind a breakthrough, small-cell managed services platform that allows mobile operators to deliver scalable and unprecedented cellular and Wi-Fi coverage, capacity and cloud services to medium to large enterprises, wherever there's a LAN.

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