To hear first-hand about overcoming spectrum challenges, come and hear Robindhra Mangtani, Principal Advisor- Mobile, Strategy & Technology Group, Ofcom, UK, who is taking part in a panel discussion on the subject on Day Two of the LTE World Summit, the premier 4G event for the telecoms industry, is taking place on the 23rd-26th June 2014, at the Amsterdam RAI, Netherlands.
What are the main practical challenges of making effective use of shared -spectrum?
The benefits of spectrum sharing have in the past been constrained by the difficulty associated with managing interference between services, which can limit the overall range and quality of service that can be achieved. Technology developments will include the use of databases and cognitive sensing to help devices decide which frequencies and time slots to use, based on a better understanding of how other are using the same spectrum band in their location. These approaches have the potential to improve the quality of service that can be provided by the different services sharing spectrum and are sometimes collectively referred to as Dynamic Spectrum Access (DSA) technologies.
Spectrum sharing databases are sometimes referred to as geo-location databases. They make it easier for devices to identify spectrum that is available for sharing, while protecting the operation of existing services. This will be an important enabler for access to shared spectrum. While the current focus in the UK is on the use of databases to manage access to TV white spaces (i.e. within the frequency range 470 – 790MHz) (TVWS), the fundamental principle is not frequency specific. The database concept could be extended to manage access to spectrum across a broader range of frequencies. This could enable a tiered access model, where licensed and licence exempt use could be permitted in the same band to meet the needs of different spectrum users.
Such DSA technologies are enabling devices sharing the same spectrum band to dynamically select a frequency and/or time slot to avoid causing interference to other nearby devices. Devices can gather the information needed to avoid causing interference using approaches, including:
– Database control: An extension of the geo-location database approach to provide devices with information and dynamically updating them on not only what spectrum is available, but also on how the spectrum can be used to prevent interference to other devices; and
– Sensing: here devices detect and avoid using the radio frequencies emitted by other devices.
An example of DSA is the TVWS (incumbent users of this spectrum are DTT and PMSE) where new database-assisted devices access and share different frequencies dynamically in response to the dynamic nature of incumbent PMSE allocations. Enhancements of TVWS databases will also assist in coordinating sharing between new devices (as well as sharing with incumbents).
Is shared spectrum a magic bullet for capacity crunch issues?
No, but do we see spectrum accessed on a shared basis providing an important and complementary approach to the use of dedicated spectrum bands. Sharing can occur geographically, where spectrum is unused in a particular location, or on a temporal basis, or both such as in TVWS where spectrum is only being used at certain times. Under both approaches, the same spectrum band is accessed by more than one service, which can provide a number of benefits:
– It can increase access to spectrum for use by new services;
– It can reduce barriers to spectrum access, acting as enabler for growth and innovation in new wireless services; and
– It can allow consumers and businesses to more easily access spectrum and deploy their own wireless infrastructure where it is needed.
– Public authorities may enable sharing of bands that they may still need some geographical and temporal access to, or may wish to keep open the possibility that they may recover for use at a subsequent date.
Could LTE in unlicensed spectrum and small cells be a way forward to solve capacity crunch concerns?
One particularly attractive potential use of shared spectrum is to allow deployment of low power smaller sized cells to provide coverage in areas of concentrated demand in cities and towns alongside cleared spectrum. Small cells reduce the number of users accessing the spectrum available in each cell, effectively increasing the capacity available to each user. The reduced coverage range also makes it easier to manage interference with other small cells sharing access to the same spectrum band.
In Europe, a Licensed Shared Access (LSA) approach is being considered to enable mobile broadband services to share access with incumbent spectrum users, with a particular focus on using this approach in the 2.3GHz band. In the US, the Federal Communications Commission is taking steps to enable shared access to the 3.5GHz military band for use by small cells.
The use of modified LTE-like technologies in the licence exempt Wi-Fi spectrum is also an interesting possibility. It should be noted that in addition to solving capacity issues, small cell technology has the potential to provide full functionality mobility in the area immediately around a home or workplace, even if this is in a sparsely-populated area which might have poor mobile coverage.
The 10th annual LTE World Summit, the premier 4G event for the telecoms industry, is taking place on the 23rd-26th June 2014, at the Amsterdam RAI, Netherlands. Click here to download a brochure for the event.
What are the latest developments in the use of white spaces for spectrum?
‘White space’ refers to frequencies that are not being used by existing licensees at a specific time or location. Location-aware wireless devices assisted by ‘geo-location’ databases, providing information on white space availability and taking other existing licensed use into account, (e.g. PMSE use) offer one new way of sharing spectrum. We have been exploring opportunities to enable access to TV white-spaces (TVWS) in the UHF bands. The latest step in this process has been our work with stakeholders to implement pilot tests consisting of a number of trial deployments of white space devices and databases by stakeholders, and a programme of coexistence testing led by Ofcom. During 2014 Ofcom will complete the pilot and then, subject to the pilot confirming the feasibility of the policy, to move forward to permit white space devices access the UHF band on a commercial basis.
We will also look to extend the geo-location database approach to other frequency bands beyond TV white spaces in the UHF band, where this is feasible and will deliver benefits to citizens and consumers
What predictions can you make on how 5G will use spectrum compared to how it’s used today for 4G?
Over the next 10 years mobile technologies will evolve towards 5G. Today, there are different visions for the defining characteristics of 5G. These include the need to provide ever increasing data rates, the ability to cater for different applications, including M2M/IoT, the flexibility to access spectrum where and when needed in a dynamic way, the ability to combine the provision of very high network capacity in dense population areas with ubiquitous coverage, and reliability for specific applications that will require them. Depending on future technology trajectories, 5G spectrum use and requirements could differ significantly from that of 3G and 4G technologies making wider use of Carrier Aggregation across both frequency bands and radio technologies, dark fibre, cloud-based RAN, licensed and unlicensed spectrum assets, in order to achieve higher throughput, deliver adaptive QoS, low power IoT applications and improved latency.
Other predictions on technologies that might be part of a 5G story on spectrum might be:
– Bands above 20GHz which will provide high bandwidth capacity in dense urban areas
– Whether there needs to be a band identified as the initial 5G band below 6GHz, which could bring the advantages of low latency etc. in a new RAT to semi-urban and rural areas
– Variable aggregation in-band
– Soft handover between licensed and unlicensed bands
– Network deciding which RAT and bandwidth to be used for optimum E2E QoS rather than device
– Google constellation succeeding (commercially) where Iridium didn’t
Can more be done to encourage spectrum harmonisation for today’s networks?
Yes, we will continue our work with stakeholders to ensure industry needs and UK government objectives for spectrum including the pan EU allocation at 700MHz. LTE roaming is in its infancy and in contrast to 2G and 3G roaming is an example that harmonisation is important. It shows that the fragmentation of band plans worldwide affects both the use by device and the ability of end users to access new services.
Could we see further release of spectrum in the UK in the near future years for data use?
The government published an update to its Public Sector Release (PSSR) Programme in which it has confirmed its commitment to the release 500MHz of Public sector spectrum by 2020 for private sector (non-Crown) uses. Sharing of spectrum of between the Public sector and other uses will form an important aspect of this programme.
The first key milestone in the PSSR Programme will be the release of 40MHz in the 2.3GHz band (2350 – 2390MHz), and 150MHz in the 3.4GHz band (from 3410 to 3600MHz) by the Ministry of Defence (MoD). We also have carried out a recent consultation on the future of the 700MHz band and extension of Wi-Fi band at 5GHz
Why is important for Ofcom to be represented at the LTE World Summit?
Ofcom seeks to enable and encourage investment in high technology infrastructure so that UK citizens and consumers benefit from the new services and subsequent economic growth etc. Our hope is that the LTE World Summit will provide us with additional knowledge and insight that will enable us to adapt our future strategy accordingly.