Discussion paper

Spectrum options for control channels in wireless television outside broadcast cameras

Disclaimer

The opinions contained in this document are those of the Ministry of Economic Development and do not reflect official government policy. Readers are advised to seek specific legal advice from a qualified professional person before undertaking any action in reliance on the contents of this publication. The contents of this discussion paper must not be construed as legal advice. The Ministry does not accept any responsibility or liability whatsoever whether in contract, tort, equity or otherwise for any action taken as a result of reading, or reliance placed on the Ministry because of having read, any part, or all, of the information in this discussion paper or for any error, inadequacy, deficiency, flaw in or omission from the discussion paper.

Introduction

Invitation for submissions

Posting and release of submissions

Glossary

1. Objective

2. Current situation

    2.1 Licensing

    2.2 Frequency availability

3. Options

    3.1 Sharing with amateur radio and short range devices (SRDs) in the frequency range 434.1375-434.4625 MHz

    3.2 Sharing with SRDs in the 821-822 MHz band

    3.3 Other options?

4. Next steps 

Introduction

Television Outside Broadcast (TVOB) operations make use of portable wireless cameras to deliver content from a live event site to a nearby control room or associated mobile station. The camera systems use separate radio frequency channels for transmission of a video signal (at microwave frequencies) and a control signal (generally in the lower UHF band), which enables remote operation of the camera.

Manufacturers provide different configuration choices for both the video channel and the control channel, according to user requirements and local regulations.

Some degree of international uniformity exists for the selection of the microwave video channels (i.e. 2.7 GHz, 5 GHz and 7 GHz). However, the control channel frequency ranges are less specific and vary for different jurisdictions. As New Zealand is largely a technology importer, this has implications for the availability of suitable equipment.

Generally, the UHF control channels used by TVOB wireless camera systems employ low transmit powers to carry remote control signals across short distances (approximately 50 metres). Low output power emissions (e.g., up to 25 mW e.i.r.p.) enable frequency-sharing with other services because of the low risk of interference. These power limits are specified for various frequency ranges in New Zealand under General User Licences (GULs).

However, some TVOB operations, such as broadcast of outdoor sporting events, require higher transmission powers (e.g. up to 300 mW e.i.r.p.) in order for camera systems to be remotely operated at greater distances (500 metres to 1 kilometre).

UHF channel plans in New Zealand are well established and designed to host services including land mobile, fixed links, television, telemetry and amateur radio. It has been identified that high power TVOB control channel emissions are generally wider than traditional UHF land mobile and fixed services channels, thereby falling outside current channel plans. So the use of TVOB systems in existing fixed service bands is likely to result in the spectrum utilisation within these bands being less than optimal.

In addition, the ubiquitous nature of the incumbent land mobile service makes the coordination and licensing of high power control channels necessary in order to avoid harmful interference to existing licensees.

Therefore, the Ministry wishes to consult with industry and spectrum stakeholders on appropriate licensing frameworks for higher power control channels in TVOB wireless cameras.Top

Invitation for submissions

Comments on the proposals contained in this paper and on any related issues are invited from interested parties. Written submissions should be sent no later than 23 July 2009 to:

or email to:

radiospectrum@med.govt.nz (preferred option)

Posting and release of submissions

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Glossary

 Top

1. Objective

This paper discusses the technical issues and possible licensing options for high power control channels, specifically used in television broadcasting operations involving longer range (up to approximately 1 kilometre) outdoor communication and control of wireless cameras. It has been identified that there is currently some demand in New Zealand for such an application but the specific level of demand is not known.
There is currently no radio spectrum band designated for high power control channels at present. In order to address the spectrum efficiency issues described in the introduction, the Ministry considers that there is a need to identify a suitable band for such high power control channels.

Question 1

What is your view of the likely demand for high power control channel services?

2. Current situation

2.1 Licensing

Overseas administrations employ a GUL-type approach for licensing low power control channels, while high power control channels are subject to frequency coordination and short-term licensing by the regulator, typically for the duration of the event being televised. The availability of channels therefore cannot be guaranteed by the spectrum management agency. There is no internationally harmonised band designated for high power control channels.

In New Zealand, a GUL for low power control channels (25 mW maximum e.i.r.p.) is available in the 433.05-434.79 MHz range.

At present, emissions outside the GUL limits are coordinated and licensed by the Radio Spectrum Management (RSM) group at the Ministry on a short-term, case-by-case basis in the 400 MHz bands. However, ad hoc short-term licensing of this service would appear to be of limited effectiveness, noting that:

• UHF channel plans in the 400 MHz bands are not strictly the same in every country, therefore TVOB control equipment designed for other administrations may not be technically compatible with the New Zealand channel plan and incumbent services; and
• Most bands in the 400 MHz spectrum are heavily used in New Zealand by land mobile and fixed services¹, making the licensing and coordination of TVOB control with these services difficult.

TVOB wireless camera users may also find it unacceptable that channel availability cannot be guaranteed.

The Ministry therefore considers that a band should be identified to allocate for high power control channels. Preferably, the prospective band should not be heavily used by other services with narrower channel bandwidths.

Question 2

Do you agree with the Ministry’s assessment about the need to designate a band for high power control channels?

2.2 Frequency availability

TVOB control channels transmit digital commands using a single frequency, omnidirectional, UHF link between the control station and the wireless camera. The camera transmits the video content using a microwave channel. Most manufacturers provide off-the-shelf solutions with control channels available in the 430-438 MHz band (restricted to low power), while high power solutions (approximately 300 mW) are available around 456 MHz using 80 kHz channels.

The latter technology, although suitable for the intended TVOB purpose discussed here, does not conform to the existing New Zealand analogue land mobile channel plans in this part of the UHF spectrum (25 kHz trunked land mobile C band and 12.5 kHz simplex CNX band).

Frequency coordination between land mobile and higher power digital control channels is impractical due to the ubiquitous nature of the C band mobile receive component (455.325-458.235 MHz). C band mobile receivers would suffer interference when in range of high power control channels. Simplex services in this band would also be affected in the same way.

Sharing with the fixed service bands (I, JL and J bands) has also been considered. The fixed service bands in the 420-470 MHz range comprise the following ranges: I band (420-430 MHz), JL band (440-449 MHz) and J band (450-470 MHz). These bands are used by point-to-point and point-to-multipoint networks employed in narrow-band communication applications. The greater directivity of fixed link antennas implies an increased risk of interference from line-of-sight omnidirectional control emissions, thereby limiting the options for channel-sharing with this service. Further, point-to-multipoint networks occupy multiple receivers spread out over large areas, which increases the complexity of channel re-use.

It has also been identified that camera manufacturers can customise the RF units (generally in the VHF and UHF ranges) to suit local regulations (i.e. re-tuning to a different frequency or adopting conventional land mobile narrow-bandwidth channels). However as discussed above, these solutions are only viable if:

• Wide-band devices (80 kHz) are tuned to operate in bands where there is no sharing involved with the mobile receive component of the C and CNX band land mobile services, or
• Narrow-band transceivers (less than 80 kHz) are designed to fit current channel plans of suitable land mobile or fixed point-to-multipoint bands.

Customisation of the RF units also incurs additional production costs.

Question 3

Are there any other frequency-sharing alternatives in the VHF or UHF bands that should be considered?

Question 4

From the equipment supplier’s perspective, how feasible is it to customise high power control channel transmitters to suit New Zealand channel plans?

Top

3. Options

3.1 Sharing with amateur radio and short range devices (SRDs) in the frequency range 434.1375-434.4625 MHz

The band 430-440 MHz is allocated to the radiolocation service on a primary basis, and the amateur and amateur satellite services on a secondary basis². Further, the New Zealand Radiocommunications Regulations (GURL for Amateur Radio Operators³ note 2) specify that the band 430-440 MHz is allocated on a shared basis with other services. In addition, amateurs share the band 433.05-434.79 MHz⁴ with SRDs (GURL).

The current use of the UHF band 434.1375-434.4625 MHz by the amateur service is low (three licences only) in comparison to adjacent bands. This suggests that the band could potentially be shared with higher power camera control channels on a permanent basis. This option would provide four contiguous control channels of 80 kHz each and would require coordination of channel use according to the user’s operational requirements (short-term or long-term licensing). Permanent licences could be created for ongoing events at fixed locations in conjunction with the requirement to coordinate channel use. One-off events at ad-hoc locations could be licensed on a short-term basis, but this would depend on frequency availability at the time.

Some manufacturers have indicated that they are able to make modifications to their 400 MHz band RF modules in order to support specific requirements for high power emissions. This option is likely to represent a reduced cost alternative in comparison to the potential cost of producing fully customised transmitters designed to operate in other bands.

Question 5

How feasible is it to allocate the high power control channel service on a shared basis with the existing amateur service in the 434.1375-434.4625 MHz frequency range?

Question 6

Is it feasible to source TVOB control channel (high output power) equipment in the 434.1375-434.4625 MHz frequency range? How does the cost of this option compare to an ‘off-the-shelf’ solution?

3.2 Sharing with SRDs in the 821-822 MHz band

The frequency band 819-824 MHz is allocated to SRDs under a General User Licence⁵. Devices operating in this band are limited to a maximum output power of 100 mW e.i.r.p. The use of this band is relatively low in comparison to other SRD bands and its primary use involves the operation of wireless microphones.

Higher power control channels could potentially share a portion of this band, comprising the 821-822 MHz range. The use of this range would minimise the risk of interference to adjacent licensed services, i.e. land mobile radio services below (812-819 MHz) and cellular services above (825-840 MHz).

The advantages of this option are the availability of an increased number of channels (twelve 80 kHz channels), and fewer issues arising from sharing with other services, compared to shared allocations in the lower UHF band. However, this option would require users to purchase customised control channel units designed specially for this band, which is likely to result in higher costs than an off-the-shelf solution or the solution in Option 1.

Question 7

Is it feasible to share spectrum between SRDs and high power control channels in the 821-822 MHz frequency range?

Question 8