Spectrum Sharing (Part 1): Great idea… right?

by Jussi Kahtava

We are delighted to introduce Jussi Kähtävä to readers of the 'Our Views' blog. This blog post is the first of two posts on the topic of spectrum sharing. Jussi's main area of interest is spectrum sharing through TV White Space technologies and Authorised Shared Access. He is also helping a major ICT company in developing LTE-based solutions for M2M applications. 

There is a lot of recent noise in some quarters of wireless industry around the shared use of spectrum. However, spectrum sharingit is not a new topic. For decades the ITU-R has allocated primary, co-primary and secondary uses of spectrum bands that have since become various assignments by national administrations. For example, PMSE (Programme Making and Special Events) shares UHF (Ultra High Frequency) spectrum with over-the-air television broadcast. Moreover, the licence-exempt nature of the ISM (Industrial, Scientific and Medical) bands is based on shared use – supporting applications such as Wi-Fi, Bluetooth, and NFC (Near Field Communications).

These days, spectrum sharing has gained renewed attention in policy circles with discussion about LSA (Licenced Shared Access, also known as ASA or Authorised Shared Access) and TVWS (Television White Space) and the approaches for accessing non-exclusive spectrum. 

Figure: Alternative approaches to spectrum licencing

MNOs are concerned about spectrum sharing…

We recognise that MNOs (Mobile Network Operators) are concerned about spectrum sharing and this view will not change easily. MNOs are worried that spectrum sharing is a two-way street. Changes in the regulatory framework, to allow mobile broadband services to share underutilised spectrum in other frequency bands, may easily mean that those other services may have to share underutilised mobile broadband spectrum. My personal impression is that this threat of encroachment on MNO spectrum is a larger concern than the lack of good QoS (Quality of Service) in shared bands.

…but should they worry about it?!

It is easy to say that the MNOs should not worry, but it is very difficult to ease their concerns on sharing spectrum where another party has similar statutory rights of use as the incumbent.

Some of the factors on MNOs’ side would certainly be that:

  • Spectrum use should be as harmonized as possible and independent decisions by administrations on sharing need to be avoided
  • CEPT level elaboration on how to best tap into underutilized spectrum avoids knee-jerk reactions on spectrum that temporarily lies fallow

I do not think that TVWS needs MNOs, nor do MNOs need TVWS.

If TVWS is to happen, it will move forward without MNO presence, and that may actually be for the best! Fairly narrow (8 MHz) spectrum bands (which are different depending on time and location of the device) in sub-1 GHz spectrum are not suitable for offloading heavy data traffic  in the way that Wi-Fi is (Wi-Fi has hundreds of MHz of contiguous spectrum) in the ISM bands. Furthermore, being licence-exempt, these narrow bands are not really suitable for deploying LTE in the first place. The LTE standard was not designed with licence exempt operation in mind, and only reaches its full potential in large bandwidths, e.g 20MHz.  

Figure: TVWS developments worldwide (Q2 2013)

In theory, LSA is more attractive to MNOs than TVWS

Existing business models, as they function today on licensed (exclusive) operator spectrum, may not translate to shared use of spectrum. However, LSA is spectrum sharing on terms that may be more amiable to MNOs. It provides:

  • Predictable Quality of Service (it is there, or it is not, but that is known a priori)
  • A type of licence very similar to those assigned to MNOs today
  • The global benefits of scale, for instance, with the first LSA band in Europe (2.3 GHz TDD band)

However, my conversations with MNOs indicate that they are, for the most part, not hankering after LSA spectrum.

My discussions with operators indicate that they are still not sold on LSA. The fundamental reason may be more the concern of reciprocity (on spectrum sharing) rather than QoS issues or concerns over the short license durations been talked about for LSA. The approach in Brussels to look into spectrum sharing in more generic terms under the EU Radio Spectrum Policy Programme (RSPP). It has commendable aspirations but it also further muddles the position that MNOS may see themselves in. For example, the EC (European Commission) has formulated the concept of Beneficial Sharing Opportunities (BSO) under its Communication on Promoting the Shared Use of Radio Spectrum Resources, which is expected to develop a coherent and consistent process for finding spectrum sharing opportunities in the European Union. Ironically, it is this very concept that makes MNOs suspicious of spectrum sharing.

What about smaller, tier 3 and tier 4 operators?

Small operators in particular would be sorely challenged if they cannot compete at similar availability and QoS as larger MNOs. Shared spectrum cannot offer them the same opportunities as exclusive spectrum.

Ultimately, MNOs are confident that they will be able to access adequate exclusive, licenced spectrum

All operators are optimistic about getting more licensed spectrum! Recent spectrum auctions over the past two or three years have made great progress towards fulfilling Digital Agenda targets for releasing exclusive access spectrum to operators. Given this situation, it is difficult to see MNOs deigning to show significant interest in spectrum sharing- at least until after WRC-15 (the World Radiocommunication Conference 2015) and the outcome of the IMT agenda item (where further IMT allocations will be discussed and expected to be accepted)

So, in terms of today's business models, MNOs won’t necessarily see a benefit in LSA. Consequently for the foreseeable future, they will not push device manufactures to support LSA bands. However, that support is not really needed as long as the LSA bands are expanding on already existing IMT bands - for example, there are already TD-LTE chipsets supporting 2.3 GHz and the handset market is developing outside Europe. The situation would be very difficult should we expect to have new spectrum bands (not currently in 3GPP LTE band plans) to be introduced only through LSA. In this scenario, there would be no pressure on OEMs from MNOs to support extraneous LSA bands.