Small Cells' and 5G - Small Cell Forum Workshop

Small Cell Forum recently held a workshop on the role of small cells' in 5G. Each speaker had 10 minutes to present their view/vision. The presentations are available here and combined PDF embedded below.

Small Cells Deployment Stories

I recently got an opportunity to hear about the small cell deployment studies, organised as SCWS pre-conference workshop. The combined slides from the presentation are embedded below and available to download from Small Cell Forum page here.

Summary of Small Cell Forum Champions day

Small Cell forum held its champions day in Rome this month. There were some interesting case studies and presentations (details below). I have embedded some presentations and provided links to others. Interested people, feel free to explore further.

The Small Cell Forum has identified six key work items where they will be focusing their energies. These are:

• Small cells in Enterprise
• License Exempt Spectrum
• HetNet & SON
• Virtualization of small cells
• Multi operator support
• The role of small cells in 5G, IOT & M2M

Spidercloud did a presentation on Enterprise small cells. They were also one of the sponsors for a study by analyst firm iGR that showed strong demand among Enterprises for Managed Services based on Small Cells.

Cisco shared a case study from a university campus deployment where existing WI-FI APs were ‘upgraded’ to add a small cell capability.

Quortus demonstrated the range of architectures possible with virtualized small cell core networks including the on site MEC server supporting small cells across an enterprise and mission critical small cells supporting public safety applications. See presentation below:

iBwave showed how deployment within the enterprise had improved, with a case study which reduced indoor small cell planning down to one site visit.

MVNO TalkTalk outlined their plans to add LTE small cells to their home routers enriching customer experience as well increasing traffic offload from the macro network. The residential 4G small cells use a dedicated 3.3MHz carrier frequency already compatible with existing 4G handsets to provide good coverage indoors and in the surrounding streets.

Nokia demonstrated the importance of 3D thinking when planning small cell HetNets in dense urban indoor and outdoor environments due to building and user topography.

Qualcomm described how their SON technology provides zero touch integration for both the small cells and the macros, optimizing handovers in both directions.

Huawei shared their vision for small cell evolution, incorporating emerging technologies which leverage license exempt spectrum. Their demonstration of LAA mobility with Vodafone notching up 600Mbps peak rates clearly showing the potential of a joined-up approach to spectrum.

Airspan trials with SoftBank demonstrated an early nFAPI implementation working in a virtualized small cell / macro HetNet. The small cells filled in coverage gaps, and their densification increased capacity. Centralised CoMP and eICIC were demonstrated over a pre-standard nFAPI which works over commonly available packet based transport with significantly less stringent performance requirements than required with CPRI based C-RAN.

Dynamic Spectrum Access (DSA) techniques for Small Cells and Wi-Fi

Picture Source: Analysis Mason

There is a lot of spectrum which is used sparingly or is kept reserved for unlicensed or shared access. Any party that wishes and is allowed to use this spectrum has to co-ordinate with the license holders or others in similar situations. Hence we have different access mechanisms which are collectively called as Dynamic Spectrum Access (DSA) techniques.

An article by Analysis Mason on this topic suggests the following:

The term DSA has come to encompass a number of different approaches and techniques that aim to increase the utilisation of the radio frequency spectrum. At its most ambitious, it is hypothesised that cognitive and software-defined radios could intelligently choose when to transmit, so as to avoid other radio transmissions and also to avoid causing undue interference to fellow frequency users. Short-term propositions include near-real-time spectrum assignment in certain bands and greater use of long-term secondary spectrum leasing to authorised spectrum partners.

DSA is therefore all about making better use of radio spectrum through re-use of 'idle' bandwidth, being either frequencies that are not used in all locations, in which other systems could be deployed, or frequencies that are only used intermittently, and which could therefore be re-used outside these times. These 'gaps' in utilisation, which provide opportunities for DSA, arise for a number of reasons.

• Coverage: a licence holder might not be using its allotted licence in a specific region.
• Time: an area of spectrum might by less-frequently required at different times during a day (or on longer timescales).
• Lack of service users: there may be a limited number of subscribers taking advantage of a service.
• Licence technical parameters: the regulator may have mandated that a piece of spectrum can only be used for a specific purpose, while other technologies emerge during the life of a licence that can use the same spectrum.
• Pragmatic under-utilisation to prevent interference: empty guard bands are placed between spectrum bands to stop transmission leakage to prevent interference, which could be re-used by systems that have the appropriate characteristics to avoid interference.

One of the overarching drivers for DSA is to help overcome spectrum shortages – particularly noting that under-utilised bands may exist across a relatively wide range of the spectrum. Even in the economies where wireless communications have developed the most and usage restrictions have been removed, thus making spectrum use as flexible as possible, spectrum under-utilisation is still considered to be widespread.

The Cisco vision on the other hand seems far too optimistic and suggests the following:

TV White Spaces (TVWS) are spectrum allocated to TV broadcasts, but not being used in a given geographic location. TVWS radios allow for use of white space spectrum for unlicensed wireless access.

Authorized Shared Access (ASA) or Licensed Shared Access (LSA) allow a secondary licensee to use the “shared” spectrum when the primary licensee is not using it.

The United States Federal Communications Commission (FCC) has proposed a three-tier model for shared access in the 3.5-GHz band. Tier 1 would be for incumbent federal agencies, including military radar users. Tier 2 would be authorized prioritized access similar to ASA and LSA. Tier 3 would be generalized authorized access, which is similar to unlicensed access.

A number of DSA technologies already exist or are in exploration.

Geo-location, database-based spectrum sharing techniques have the most traction as a practical approach to spectrum sharing. Devices that want to use shared spectrum must geo-locate themselves and consult a database to determine what spectrum is available.

The geo-location database manages the spectrum resource allocation based on predefined policies and availability to ensure the primary licensee is not impacted. An enhanced version of the geo-location database system—called a Spectrum Access System (SAS)—is the basis for the FCC spectrum-sharing proposal in the 3.5-GHz band.

A second technology is cognitive radio, which senses and monitors the radio environment. This includes knowing the location and policies for self-regulation. Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) are cognitive radio techniques that allow co-existence with radar and satellite systems.

Another technology is Software-Defined Radio (SDR), which allows devices to adapt to local radio conditions and use the appropriate radio frequencies.

I came across this very interesting whitepaper by MIT that details all the DSA techniques and its progress. Paper embedded below:

New Models for Protected Shared Access - Toward More Efficient Spectrum Management from Zahid Ghadialy

We will discuss in the future post how the DSA techniques could be useful for using Small Cells in the unlicensed spectrum (a.k.a. LTE-U).