3. Sharing with New SRD Services

The band 918 to 921 MHz is currently allocated to STL and shared with low power (3 mW) Short Range Devices (SRDs) in New Zealand. This band is allocated to higher power (4 W) SRDs in North and South America and 1 Watt SRD in Australia. As a result the majority of the SRD equipment available internationally for operation in this band uses higher power than that currently permitted in New Zealand.

Interference calculations show that there is a significant risk of harmful interference if a 1 Watt SRD is operated on the same channel within line of site and within the beamwidth of an STL receiver antenna.

Digital STLs will tolerate greater in-band interference signal levels. However this improvement is not sufficient to fully resolve the potential interference from higher powered SRDs.

In a recent review of spectrum allocations for SRDs there was interest in expanding the utility of the 915-921 MHz SRD band but current STL licence holders were apprehensive about the disruption to a significant number of licences. A summary of submissions is available on the Ministry's website at Review of Spectrum Allocations for Short Range Devices: Summary of Submissions and Conclusions.

If higher powered SRDs are permitted then it is anticipated that there will be significant growth in systems which take advantage of the superior propagation characteristics of the band. Examples include data networks between buildings and long range cordless phones with external antennas.

In addition many retail Radio Frequency Identification (RFID) systems are planned to be deployed in the 900 MHz ISM band. If these become ubiquitous then the RFID interrogating equipment could contribute to the noise floor in metropolitan areas.

The Ministry wishes to minimise any barriers to new services such as SRDs while also protecting established investment. It is therefore likely that higher powered SRDs will be introduced in New Zealand in the near future and to accommodate such SRD introduction it is necessary to protect existing STL functionality. As SRDs are generally ubiquitous consumer products traditional geographic mechanisms for co-frequency sharing SRD with fixed STL transmissions are limited. Therefore, it is necessary to develop a system of band segmentation that accommodates SRD introduction whilst transitioning existing STL licences to nearby radio-frequency bands whilst minimising costs for both SRD and STL operators. General options for transition planning include:

1. SRD User Driven Transition:
   

   A user driven transition where the incoming technology, SRDs, drives the timing of STL migration, could have the following form;
   

1. 1. A GURL for SRD operation in the band 915 - 921 MHz is created;
   2. A condition could be added to all STL licences in the band 915 to 921 MHz noting that after a specified date there would be no protection from interference due to transmitters operating in the same band under a GURL for SRD;
   3. Existing STL licensees can choose if and when to apply for licences in alternative bands at their own discretion. Under this option an incentive to transition is created, but because of the unknown rate of introduction of SRD, the migration of STLs would be uncontrolled and demand for new licences would be difficult to predict. Thus, there could not be any guarantee that replacement licences would be available in high use or metropolitan areas.

2. STL User Driven Transition:

   A user driven transition where the incumbent technology, STLs, controls the timing of migration, could have the following form;
   1. A GURL for SRD operation in the band 915-921 MHz is created. SRD operation is licensed on a non-interference basis with respect to licensed STL operation;
   2. Existing STL licensees can choose if and when to apply for licences in alternative bands at their own discretion;
   3. A nominal termination date on STL licences could be applied to incentivise the transition.
      
   Under this option the unknown rate of migration of STLs means the demand for new STL licences is difficult to predict. Also, significant compliance action to ensure that SRD introduction did not unduly compromise STL operation may be required and then would only provide a reactive solution with respect to interference issues.

3. Multi-lateral Managed Rationalisation and Transition:

   A planned transition managed by the Ministry with input from STL licensees, could have the following form;
   1. This would involve the Ministry inviting licensees to identify licences, and associated timings, they wish to migrate out of the 915 to 921 MHz band, to the current alternative bands 849 to 851 MHz and 929 to 935 MHz;
   2. The Ministry would then develop a migration plan and manage the implementation of the plan;
   3. Those licensees who chose not to migrate under the plan could apply for replacement licences at a later date but licences would not be reserved for this purpose.
   The migration plan would involve many of the licensees changing channels at pre-agreed deadlines to optimise the STL assignment plan at these sites. The new licences would be assigned channels within the current bands 849 to 851 MHz and 929 to 935 MHz. It has been shown that at the busiest sites most channels in the band 915 to 921 MHz could be migrated to the other 2 bands under this plan. More details of this migration are provided in Appendix C.

4. Uni-lateral Managed Rationalisation and Transition:

   A planned transition whereby the Ministry exercises Regulation 15 or the Radiocommunications Regulations 2003 to achieve migration of STL licences. Under this option the Ministry would develop the migration plan from the 915 to 921 MHz band to other STL bands. All licensees would be assured of replacement licences.

Licensees may also have the option of migrating to the new bands 846 to 849 MHz and 935 to 938 MHz using digital STL equipment. In addition those licensees which have several analogue licences for the same path may be required to seek more spectrum efficient solutions as part of their migration strategy.

Question 8: Of the 4 options identified, which is the preferred solution to ensure STL licensees are protected from interference if higher powered SRD are permitted in the band 915 to 921 MHz?

Question 8a: If higher powered SRDs are to be permitted in the band 915 to 921 MHz what timeframe would be required to migrate all STL licences from the band?

In order to minimise costs of transitioning STL transmissions from one licensed frequency to another, an analogue STL to analogue STL transition is considered above. That is, it is assumed that the currently used analogue STL transmitter can cheaply and simply be returned to the new required frequency. Considering wider environmental and business factors may show that such a transition is not the most economical and a different type of transition plan may better suit the STL licensee e.g. a one step transition from one or more analogue STLs to one or more digital STLs.