Address for Correspondence:
2 Evelyn Avenue
Aldershot
Hants, GU11 3QB
Tel: +44 (0)7711 490702
Email: [email protected]
Mr K. Sithamparanatham
Chairman FM WG54
C/O Ofcom
Riverside House
2a Southwark Bridge Road
London
Dear Kuha,
FM WG54 – Points following Mtg. 7th & 8th September 2015.
I am writing to you immediately following the FM54 meeting because I believe a significant number
of serious issues arose during the meeting and I felt it may be helpful to capture the industry
perspective on these.
I am taking this initiative because I firmly believe that the PMR industry will soon need to have a
robust solution for data service in addition to the voice service.
At present, many people are looking at LTE in all its forms. However, in the UK, deploying such
service in either of the UHF bands appears challenging to the point of actual impossibility in the
current situation. But, other regulatory authorities may well have a better opportunity.
Nevertheless, having such solutions available elsewhere may provoke the development of a portfolio
of suitable products that could be used in other bands in the UK. Thus this work may well eventually
result in a better position for the UK BR industry in another band.
Obviously, the UK situation is rather different from the rest of the region due to the 410-430MHz
band being less available for reasons of exclusion and the 450-470MHz band being congested and
the opposite transmit and receive arrangements. Nevertheless, I feel that much of the complexity is
widely applicable.
In this letter I am simply listing the issues with a sentence or two of explanatory text. However, I do
intend to provide a paper on the Data Channel Access Protocol Euro-Norm Standard. In listing these
points I have attempted to list them in order of impact to the work of WG54. This is not intended to
represent an indication of priority. I note in the list which I believe to be the priorities
1. There are some CEPT countries that differentiate in their terminology between PMR
technologies used for civilian use and the same technology used for Government use. Thus
when asked for PMR usage they may not include figures for government use. Hence the
amount of PMR used may be understated.
2. The need for a new report on coexistence with other services is clear. However, my
understanding from the meeting was that the proposers of LTE in the 450-470MHz band
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actually were not considering co-existence at all. Instead they appeared to consider that LTE
would be the exclusive use in the entire band in the future. Other users being cleared from
the band. The guard band necessary to protect neighbours in other bands was to be
provided from within the 450-470MHz range.
3. The necessity of point (2) above was reinforced by a paper located on the 450 Alliance
website which appears to indicate that the spectrum arrangement was for two 5MHz
frequency blocks in the 450-470MHz band. All the rest of the band being needed for guard
band. See the bottom of page 3 on the attached document (reproduced here below).
4. The differences between Report 240 and the proposed situation are brought to greater
attention by the proposed served population. In the case of Report 240 the served user
population was very small indeed from a single site. However, due to the range at 450MHz,
the coverage area is 7500 sq km (see Ovum report page 4). Considering a rural population of
1000 persons per sq km, this means that the population within the coverage area is up to
7,500,000. If we were to assume that this service attracts only a very small 0.1% population
penetration, this appears to mean that even at the best data rate (taken as roughly half the
uplink figure in the above chart to allow for a 5MHz channel instead of a 10MHz channel),
each person can expect a fairly slow payload data rate service of around 1kB/s1. It appears
that the assumption must therefore be for a much lower population penetration and/or
lower coverage area per site or alternatively a completely different usage model.
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6.5MB of capacity shared by 7500 persons using it concurrently in the busy periods equates to an average payload capacity of 1kB/s. A
7500 concurrent users figure is far higher than the assumed concurrent use in report 240 (approx 1 UE per sq km). The apparent need for
half the available spectrum to be taken by guard band means that 10MHz carriers are not possible in the 450-470MHz band.
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5. Reducing the coverage area to improve traffic capacity (the introduction of a cellular plan
rather than a radio-isolated area) may be challenging due to the adjacent channel
interference level implied by the apparent need for large guard bands.
6. The current release of LTE does not contain a number of mission-critical (M-C) servicerelated features. These are currently in progress within 3GPP but the dates for the
introduction of the outcome of that work appears uncertain and whether the final standard
will include these features as mandatory. Under that condition, the use of LTE may not be
acceptable to many users currently occupying the band and who would wish to include M-C
data features in their operational communications portfolio. This point, whilst extremely
important in the long term, may be less important today as users already use non-missioncritical public communications for many data systems. However, as these data systems
continue to increase in operational importance, the transition to mission-critical variants
becomes more desirable over time.
7. The use of a sharing strategy may provide a viable solution for every regulatory authority
faced with assignment congestion in PMR bands. Whilst it is not suggested that all the
channels are declared as shared, having a pool of shared channels is potentially helpful. It is
noted here that the sharing strategy is extremely simple to implement as no coordination
between users is required. Caution is required however, because sharing of this type
assumes light loading. Thus sharing merely addresses congestion of licence assignment not
actual air-traffic congestion in the field.
8. Sharing assumes traffic that is structured in such a manner that other users can utilise the
gap between transmissions. Thus data presents a problem if that data is effectively a
continuous stream of transmission with no usable gap between. Thus sharing in a data-rich
environment implies a strategy of accompanying shared spectrum with shared data-only
channels and those data-only channels would require the mandatory application of an
Interface regulation (under the R&TTE Directive and late RED) to control channel access. Key
features of such a Euro-Norm would include (not necessarily an exhaustive list):
a. Channel testing for power on-channel (not a simple matter)
b. Synchronisation with the detected power to determine the gaps (also not a simple
matter)
c. Durations and other controls
d. Checks for algorithm stability
e. Capacity limits as part of the access
f. Essential requirements to meet the regulatory authorisation of the access (channel
occupied bandwidth per user, channelization, block edge masks, transitory power
side-lobes, Tx power, Receiver characteristics relating to detection and protection,
data rate, sectoring etc.)
g. Unit identification
h. Clear-down for over-use
i. Fault detection and clear-down
j. Assumptions for the essential characteristics for technology (for example, the
designers of the standards could decide that spread spectrum would not be included
in the technology list).
k. Others
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I hope you find this contribution helpful
Kindest regards
Tim Cull
CC: Thomas Weber, Secretary to FNWG54.
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