4.1.1 New fixed link band at 841-849 MHz and long-term SRD harmonisation at 915-929 MHz

The Ministry’s base proposal is to allocate the unused spectrum at 841-849 MHz for fixed links, particularly STLs, and to harmonise the lower edge of the 921-929 MHz SRD band with that of Australia (915 MHz) in the longer term, as illustrated in Figure 4 (page 34). Harmonisation with the Australian band would also include permitting 4 watt RFIDs in 920 926 MHz, with the same out-of-band emission limits¹¹.

Table 2: Allocation changes for new fixed link band and SRD harmonisation

Under this proposal, there will be a new interface between SRDs and adjacent GSM/W CDMA services at 915 MHz. The Kordia report provides a conservative analysis of this interface. The analysis shows that there is a requirement for considerable distance separation (8.2 km) between these services on outdoor line-of-sight paths to reduce interference risks. Concern is raised in particular about the potential impact of multiple SRD devices such as future check-out scanners impacting on nearby GSM/W CDMA base station receivers. However, the most likely scenario for SRD deployment is indoor use, which provides a significant increase in obstruction and multipath losses, with the consequent reduction of potential interference. The Ministry notes that the Australian Communications and Media Authority (ACMA) has allocated SRDs adjacent to cellular services at 915 MHz without a guard band. ACMA has not recorded any interference issues to date.

Similarly, Kordia’s supplementary analysis of potential interference between 4 watt RFIDs operating in 920-926 MHz (with out-of-band emission limits as specified in the Australian class licence) and the cellular interface at 915 MHz suggests that the devices are likely to have negligible impact on base station receivers at GSM cell sites. In the case of W CDMA base station receivers, while the conservative analysis suggests that a significant distance separation (12 km) would be required, in reality filter performance similar to that of GSM base station receivers, combined with the 5 MHz frequency separation and the likely operation of RFIDs indoors, will mean that there should be little impact on these base station receivers.

The analysis also suggests that 4 watt RFIDs should be able to operate in the 920 926 MHz band without causing unacceptable degradation to STLs operating in the band above 929 MHz.

Question 9

Is the band 841-849 MHz a viable option for STL use? If not, please explain.

Question 10

Are there services or applications other than STLs for which the spectrum at 841-849 MHz would be better allocated? If so, please provide details.

Question 11

Is the proposed expansion of the SRD allocation to 915-929 MHz, along with an increase in power from 1 watt to 4 watts for RFIDs operating at 920-926 MHz, viable and appropriate in New Zealand? If not, please explain.

Question 12

In regards to the interface between GSM/W-CDMA and SRDs at 915 MHz, would you suggest any mitigation measures for this interface? If so, please provide details.

Footnote

¹¹ Emissions below 917.75 MHz must be no greater than -37 dBm e.i.r.p. and emissions above 926 MHz must be no greater than -33 dBm e.i.r.p..