New CH for UHF CB From 40-80ch From ACMA
Posted: Thu May 15, 2008 10:06 am
There are a number of options relating to the technical framework for licensing use of the 400 MHz band that are being explored. In broad terms these can be grouped into options related to:
reduced channel bandwidth and re-packing;
increased spectrum sharing; and
facilitating change of use of the spectrum.
Each is discussed below. The options are not mutually exclusive. It may be optimal to pursue some of the options to increase spectrum sharing and options to reduce channel bandwidth and re-pack the spectrum.
Reduced channel bandwidth and re-packing
Use of analog FM radio equipment requiring 25 kHz channels is well established in the 400 MHz band and has been for many years. Overall, around 70 per cent of the frequency assignments in the 400 MHz band are to systems using 25 kHz or greater bandwidth.
Use of the 400 MHz band is dominated by the land mobile and fixed (point-to-point) services. Table 2 shows the percentage of assignments above and below or equal to 12.5 kHz bandwidth for these service types.
Table 2: Bandwidth percentage – Land Mobile and Fixed (Point-to-Point) Assignments
For the land mobile service, 63.1 per cent of frequency assignments are to 25 kHz channels, implying that around this percentage of equipment in use requires a bandwidth of 25 kHz. There appears to be scope to significantly decrease the amount of spectrum used for the land mobile service by moving towards increased use of 12.5 kHz equipment. Land mobile equipment using 12.5 kHz channels is readily available and offers virtually identical performance to 25 kHz equipment.
For the fixed (point-to-point) service, 25 kHz equipment dominates, accounting for 97.7 per cent of assignments. A justification for a 25 kHz (or greater) bandwidth requirement for point-to-point links is to support higher data rates for digital signals.
Table 3 shows the type of emission carried by these links: analog telephony or a digital signal. It shows that 72 per cent carry analog voice and 28 per cent of them carry digital information. The digital systems are potentially unable to move to narrower bandwidths due to data rate requirements. The analog systems, however, have the potential to reduce bandwidth to 12.5 kHz.
Table 3: Breakdown of emission types for land mobile and fixed (point-topoint) assignments
Overall growth in the number of radio systems in congested areas can be achieved by freeing up more spectrum. There appears to be scope for a migration of all land mobile and most fixed (point-to-point) systems from 25 kHz to 12.5 kHz.
A process of ‘channel splitting’, whereby an occupied 25 kHz channel is converted to two 12.5 kHz channels, may be used to make new channels available.1 This practice is evident in Sydney and Brisbane where growth in the overall number of land mobile systems operating in accordance with the 400 MHz Plan has occurred despite congestion of the band.2
Figure 4 shows spectrum use for land mobile services in south eastern Australia in Segment K of the 400 MHz Plan.3
The figure on the left represents the current deployment, where both 12.5 kHz and 25 kHz services are in operation. The figure on the right demonstrates the reduction in licence congestion in the event that all existing 25 kHz services were converted to 12.5 kHz bandwidth.
1 Although the splitting of 25 kHz channels is not consistent with the 400 MHz plan, accredited persons are able to assign 12.5 kHz services in segments of the band designated for 25 kHz channelling. This is possible because the 400 MHz plan is an administrative band plan, and therefore lacks the statutory obligations associated with Frequency Band Plans.
2 In Melbourne, growth in the number of assignments in congested parts of the band seems to have been provided by the increased use of low power services.
3 See Attachment 2 for information on the part of the band referred to as segment K.
Figure 4: Spectrum use for land mobile services in south eastern Australia in Segment K of the 400 MHz Plan. The vertical shaded scale denotes the number of channels allocated (from zero to all).
Information is sought on the issues that a migration to 12.5 kHz systems will raise. What are the costs? How much time would be needed for such a migration?
Migrating from 25 kHz to 12.5 kHz
In the replanning processes for the VHF bands that occurred in the 1990s, a strategy of on-channel bandwidth reduction was used to optimise the availability of spectrum while minimising disruption to users (see Figure 5). Licensees using 25 kHz equipment on a particular channel migrate to a 12.5 kHz system on that channel. Base equipment needs to be updated at the time of migration, but mobiles can be incrementally replaced or upgraded. Over time, the spaces between channels open up and other 12.5 kHz assignments can be made. For the VHF land mobile bands this process took around ten years.
ACMA is considering imposing restrictions on the assignment of new frequencies to 25 kHz analog FM systems within the frequency ranges 403–420 MHz and 450–520 MHz. Existing 25 kHz systems would still be able to operate and expand for a limited time, but new analog systems requiring 25 kHz channels would not generally be permitted.
In time, measures would be imposed to create incentives to reduce and possibly to remove 25 kHz analog FM assignments in this spectrum. Such measures could include pricing incentives to encourage users to move from 25 kHz to 12.5 kHz assignments. Alternatively administrative action by ACMA to not renew 25 kHz assignments after a certain date is an option.
A transition from 25 kHz to 12.5 kHz channelling would appear to be a good candidate for a geographically based phased approach where measures to enforce bandwidth reductions are delayed in areas with lower congestion.
ACMA seeks comments on the factors that should be taken into account in seeking to reduce and ultimately remove 25 kHz analog FM land mobile equipment from the band.
ACMA seeks comments regarding the proposal to migrate to 12.5 kHz assignments.
What type of approaches should be considered by ACMA to facilitate migration away from the use of 25 kHz analog FM systems in the 400 MHz band?
Potential options for migration
A number of options are available to support a migration from 25 kHz to 12.5 kHz channels:
The ‘Interleave’ method (see Figure 5) which interleaves 12.5 kHz channels with the existing 25 kHz raster. A new 12.5 kHz channel is assigned to the same centre frequency as the current 25 kHz channel. When an adjacent channel is converted to 12.5 kHz, an extra 12.5 kHz channel can be inserted between the two on the 12.5 kHz raster.
This option would offer a relatively soft migration path for users as the mobile fleet can be upgraded over time. A disadvantage is that additional channels are not available immediately because new channels are only released when two or more adjacent channels become clear.
The ‘Offset’ method (Figure 6) which divides a current 25 kHz channel in two so that two 12.5 kHz channels can immediately be inserted with centre frequencies offset by 6.25 kHz to the 25 kHz raster.
This method would provide simple splitting, but causes more complexity in the channel raster definition as centre frequencies are not reused. Base equipment and mobiles would usually need to be replaced and/or retuned all at once, to avoid interference issues from the adjacent channel. Some accredited persons have advised that they are already using this option occasionally for clients when adjacent channels are not available.
Another option is for a group of 25 kHz channels to migrate into a block of 12.5 kHz channels (Figure 7), thus freeing up contiguous blocks of spectrum for other purposes.
This option would require extensive retuning and replacement of equipment as well as a complete re-coordination of systems. The advantage of this approach is that it would create blocks of unencumbered spectrum that could be easily and efficiently re-farmed.
Figure 7: Block channel bandwidth reduction migration path.
If ACMA concludes that a migration to 12.5 kHz operation of 25 kHz analog FM systems within the frequency ranges 403–420 MHz and 450–520 MHz is important to the replanning of this spectrum, what are the implications for stakeholders of the different approaches discussed above?
What would be the preferred bandwidth reduction migration path if ACMA decided to mandate a migration to 12.5 kHz channelling?
UHF Citizen Band—increase in available channels
The UHF Citizen Band (CB) comprises forty 25 kHz channels. Use of UHF CB is supported by a class licence. Anyone may operate UHF CB equipment provided that operation and the equipment used is in keeping with the conditions of the licence. Users do not have to apply for a licence and no fees are payable by CB radio users.
UHF CB equipment is cheap compared to typical land mobile equipment. Eight repeater channels are available, increasing the potential range of use to tens of kilometres. Australians are enthusiastic users of UHF CB for business and personal purposes. The main disadvantage to users is that no protection from interference is offered and therefore channels may be subject to congestion.
In light of the overall considerations in the band outlined in this paper, including the possibility of a reduction in channel bandwidth elsewhere in the band, it may be desirable to extend this potential bandwidth reduction to UHF CB. The existing 25 kHz channel bandwidth would be reduced to 12.5 kHz via an appropriate migration scheme.
For an environment such as UHF CB, where there is a very large quantity of existing equipment in use, a scheme where the old and new equipment have a degree of compatibility is desirable. This may suggest that the interleave method of yielding more channels could be the most appropriate.1
If an 80 channel UHF CB band is to be implemented, ACMA anticipates that there would be a period of time during which existing equipment using 25 kHz bandwidth would be permitted to continue operation, and new 80 channel 12.5 kHz equipment would also be permitted to operate. After the phase-out date only the use of 12.5 kHz channel equipment would be authorised. Use of 25 kHz bandwidth UHF CB equipment would not be supported.
It is acknowledged that arrangements would need to be addressed to preserve the utility of the emergency channels throughout any transitional period.
ACMA seeks views on increasing the number of UHF CB channels from 40 to 80 by the implementation of 12.5 kHz channelisation, with a corresponding phase-out of 25 kHz channel equipment.
Accommodating more digital land mobile
Overseas trends and research indicate that there will be a significant increase in the use of digital modulation schemes for land mobile equipment in the future. Generally digital land mobile equipment uses the spectrum at least as, and in many cases more, efficiently than analog systems.
There are a number of digital technologies in use by land mobile equipment around the world. TETRA equipment requires an RF channel bandwidth of 25 kHz, but uses Time Division Multiple Access (TDMA) techniques so that up to four communications channels are supported within this bandwidth. TETRA usually employs a frequency split of 10 MHz (with 5, 7 and 8 MHz also part of the TETRA standard for 400 MHz).
APCO equipment is able to support a wide range of frequency splits,2 with 9 MHz being commonly used in the United States.
Current Australian arrangements effectively prevent the operation of TETRA in the 403–420 MHz and 450–500 MHz ranges as the available frequency splits for duplex operation are not compatible.
ACMA seeks comments on the future requirement for digital land mobile operation and ways that ACMA can facilitate greater use of this more spectrally efficient technology.
1 See discussion above in section Migrating from 25 kHz channels to 12.5 kHz channels.
2 For example the Metropolitan Mobile Radio (MMR) network in Victoria is an APCO network employing frequency splits of 4, 5.5, 6 and 9.5 MHz.
Here is a (Eg Frequency on UHF CB)
Right now user 25khz Stepped
476.425.0 Mhz
476.450.0 Mhz
New 12.5 khz Stepped
476.425.0 Mhz
476.437.5 Mhz
476.450.0 Mhz
NOTE This Post Will Delete By 18/07/2008
reduced channel bandwidth and re-packing;
increased spectrum sharing; and
facilitating change of use of the spectrum.
Each is discussed below. The options are not mutually exclusive. It may be optimal to pursue some of the options to increase spectrum sharing and options to reduce channel bandwidth and re-pack the spectrum.
Reduced channel bandwidth and re-packing
Use of analog FM radio equipment requiring 25 kHz channels is well established in the 400 MHz band and has been for many years. Overall, around 70 per cent of the frequency assignments in the 400 MHz band are to systems using 25 kHz or greater bandwidth.
Use of the 400 MHz band is dominated by the land mobile and fixed (point-to-point) services. Table 2 shows the percentage of assignments above and below or equal to 12.5 kHz bandwidth for these service types.
Table 2: Bandwidth percentage – Land Mobile and Fixed (Point-to-Point) Assignments
For the land mobile service, 63.1 per cent of frequency assignments are to 25 kHz channels, implying that around this percentage of equipment in use requires a bandwidth of 25 kHz. There appears to be scope to significantly decrease the amount of spectrum used for the land mobile service by moving towards increased use of 12.5 kHz equipment. Land mobile equipment using 12.5 kHz channels is readily available and offers virtually identical performance to 25 kHz equipment.
For the fixed (point-to-point) service, 25 kHz equipment dominates, accounting for 97.7 per cent of assignments. A justification for a 25 kHz (or greater) bandwidth requirement for point-to-point links is to support higher data rates for digital signals.
Table 3 shows the type of emission carried by these links: analog telephony or a digital signal. It shows that 72 per cent carry analog voice and 28 per cent of them carry digital information. The digital systems are potentially unable to move to narrower bandwidths due to data rate requirements. The analog systems, however, have the potential to reduce bandwidth to 12.5 kHz.
Table 3: Breakdown of emission types for land mobile and fixed (point-topoint) assignments
Overall growth in the number of radio systems in congested areas can be achieved by freeing up more spectrum. There appears to be scope for a migration of all land mobile and most fixed (point-to-point) systems from 25 kHz to 12.5 kHz.
A process of ‘channel splitting’, whereby an occupied 25 kHz channel is converted to two 12.5 kHz channels, may be used to make new channels available.1 This practice is evident in Sydney and Brisbane where growth in the overall number of land mobile systems operating in accordance with the 400 MHz Plan has occurred despite congestion of the band.2
Figure 4 shows spectrum use for land mobile services in south eastern Australia in Segment K of the 400 MHz Plan.3
The figure on the left represents the current deployment, where both 12.5 kHz and 25 kHz services are in operation. The figure on the right demonstrates the reduction in licence congestion in the event that all existing 25 kHz services were converted to 12.5 kHz bandwidth.
1 Although the splitting of 25 kHz channels is not consistent with the 400 MHz plan, accredited persons are able to assign 12.5 kHz services in segments of the band designated for 25 kHz channelling. This is possible because the 400 MHz plan is an administrative band plan, and therefore lacks the statutory obligations associated with Frequency Band Plans.
2 In Melbourne, growth in the number of assignments in congested parts of the band seems to have been provided by the increased use of low power services.
3 See Attachment 2 for information on the part of the band referred to as segment K.
Figure 4: Spectrum use for land mobile services in south eastern Australia in Segment K of the 400 MHz Plan. The vertical shaded scale denotes the number of channels allocated (from zero to all).
Information is sought on the issues that a migration to 12.5 kHz systems will raise. What are the costs? How much time would be needed for such a migration?
Migrating from 25 kHz to 12.5 kHz
In the replanning processes for the VHF bands that occurred in the 1990s, a strategy of on-channel bandwidth reduction was used to optimise the availability of spectrum while minimising disruption to users (see Figure 5). Licensees using 25 kHz equipment on a particular channel migrate to a 12.5 kHz system on that channel. Base equipment needs to be updated at the time of migration, but mobiles can be incrementally replaced or upgraded. Over time, the spaces between channels open up and other 12.5 kHz assignments can be made. For the VHF land mobile bands this process took around ten years.
ACMA is considering imposing restrictions on the assignment of new frequencies to 25 kHz analog FM systems within the frequency ranges 403–420 MHz and 450–520 MHz. Existing 25 kHz systems would still be able to operate and expand for a limited time, but new analog systems requiring 25 kHz channels would not generally be permitted.
In time, measures would be imposed to create incentives to reduce and possibly to remove 25 kHz analog FM assignments in this spectrum. Such measures could include pricing incentives to encourage users to move from 25 kHz to 12.5 kHz assignments. Alternatively administrative action by ACMA to not renew 25 kHz assignments after a certain date is an option.
A transition from 25 kHz to 12.5 kHz channelling would appear to be a good candidate for a geographically based phased approach where measures to enforce bandwidth reductions are delayed in areas with lower congestion.
ACMA seeks comments on the factors that should be taken into account in seeking to reduce and ultimately remove 25 kHz analog FM land mobile equipment from the band.
ACMA seeks comments regarding the proposal to migrate to 12.5 kHz assignments.
What type of approaches should be considered by ACMA to facilitate migration away from the use of 25 kHz analog FM systems in the 400 MHz band?
Potential options for migration
A number of options are available to support a migration from 25 kHz to 12.5 kHz channels:
The ‘Interleave’ method (see Figure 5) which interleaves 12.5 kHz channels with the existing 25 kHz raster. A new 12.5 kHz channel is assigned to the same centre frequency as the current 25 kHz channel. When an adjacent channel is converted to 12.5 kHz, an extra 12.5 kHz channel can be inserted between the two on the 12.5 kHz raster.
This option would offer a relatively soft migration path for users as the mobile fleet can be upgraded over time. A disadvantage is that additional channels are not available immediately because new channels are only released when two or more adjacent channels become clear.
The ‘Offset’ method (Figure 6) which divides a current 25 kHz channel in two so that two 12.5 kHz channels can immediately be inserted with centre frequencies offset by 6.25 kHz to the 25 kHz raster.
This method would provide simple splitting, but causes more complexity in the channel raster definition as centre frequencies are not reused. Base equipment and mobiles would usually need to be replaced and/or retuned all at once, to avoid interference issues from the adjacent channel. Some accredited persons have advised that they are already using this option occasionally for clients when adjacent channels are not available.
Another option is for a group of 25 kHz channels to migrate into a block of 12.5 kHz channels (Figure 7), thus freeing up contiguous blocks of spectrum for other purposes.
This option would require extensive retuning and replacement of equipment as well as a complete re-coordination of systems. The advantage of this approach is that it would create blocks of unencumbered spectrum that could be easily and efficiently re-farmed.
Figure 7: Block channel bandwidth reduction migration path.
If ACMA concludes that a migration to 12.5 kHz operation of 25 kHz analog FM systems within the frequency ranges 403–420 MHz and 450–520 MHz is important to the replanning of this spectrum, what are the implications for stakeholders of the different approaches discussed above?
What would be the preferred bandwidth reduction migration path if ACMA decided to mandate a migration to 12.5 kHz channelling?
UHF Citizen Band—increase in available channels
The UHF Citizen Band (CB) comprises forty 25 kHz channels. Use of UHF CB is supported by a class licence. Anyone may operate UHF CB equipment provided that operation and the equipment used is in keeping with the conditions of the licence. Users do not have to apply for a licence and no fees are payable by CB radio users.
UHF CB equipment is cheap compared to typical land mobile equipment. Eight repeater channels are available, increasing the potential range of use to tens of kilometres. Australians are enthusiastic users of UHF CB for business and personal purposes. The main disadvantage to users is that no protection from interference is offered and therefore channels may be subject to congestion.
In light of the overall considerations in the band outlined in this paper, including the possibility of a reduction in channel bandwidth elsewhere in the band, it may be desirable to extend this potential bandwidth reduction to UHF CB. The existing 25 kHz channel bandwidth would be reduced to 12.5 kHz via an appropriate migration scheme.
For an environment such as UHF CB, where there is a very large quantity of existing equipment in use, a scheme where the old and new equipment have a degree of compatibility is desirable. This may suggest that the interleave method of yielding more channels could be the most appropriate.1
If an 80 channel UHF CB band is to be implemented, ACMA anticipates that there would be a period of time during which existing equipment using 25 kHz bandwidth would be permitted to continue operation, and new 80 channel 12.5 kHz equipment would also be permitted to operate. After the phase-out date only the use of 12.5 kHz channel equipment would be authorised. Use of 25 kHz bandwidth UHF CB equipment would not be supported.
It is acknowledged that arrangements would need to be addressed to preserve the utility of the emergency channels throughout any transitional period.
ACMA seeks views on increasing the number of UHF CB channels from 40 to 80 by the implementation of 12.5 kHz channelisation, with a corresponding phase-out of 25 kHz channel equipment.
Accommodating more digital land mobile
Overseas trends and research indicate that there will be a significant increase in the use of digital modulation schemes for land mobile equipment in the future. Generally digital land mobile equipment uses the spectrum at least as, and in many cases more, efficiently than analog systems.
There are a number of digital technologies in use by land mobile equipment around the world. TETRA equipment requires an RF channel bandwidth of 25 kHz, but uses Time Division Multiple Access (TDMA) techniques so that up to four communications channels are supported within this bandwidth. TETRA usually employs a frequency split of 10 MHz (with 5, 7 and 8 MHz also part of the TETRA standard for 400 MHz).
APCO equipment is able to support a wide range of frequency splits,2 with 9 MHz being commonly used in the United States.
Current Australian arrangements effectively prevent the operation of TETRA in the 403–420 MHz and 450–500 MHz ranges as the available frequency splits for duplex operation are not compatible.
ACMA seeks comments on the future requirement for digital land mobile operation and ways that ACMA can facilitate greater use of this more spectrally efficient technology.
1 See discussion above in section Migrating from 25 kHz channels to 12.5 kHz channels.
2 For example the Metropolitan Mobile Radio (MMR) network in Victoria is an APCO network employing frequency splits of 4, 5.5, 6 and 9.5 MHz.
Here is a (Eg Frequency on UHF CB)
Right now user 25khz Stepped
476.425.0 Mhz
476.450.0 Mhz
New 12.5 khz Stepped
476.425.0 Mhz
476.437.5 Mhz
476.450.0 Mhz
NOTE This Post Will Delete By 18/07/2008