[wireless-regdb] [PATCH] wireless-regdb: Update regulatory rules for Singapore (SG)

[Sven Eckelmann]

On Mittwoch, 23. August 2017 15:52:40 CEST Seth Forshee wrote:
[...]
> > +# Source
> > +# https://www.imda.gov.sg/~/media/imda/files/regulation%20licensing%20and%20consultations/ict%20standards/telecommunication%20standards/radio-comms/imdatssrd.pdf?la=en
> > +# page 12-14
> > +# The EIRP for 5250 – 5350 can be increased by 3dB if TPC is implemented.
[...]
> > +	# 5470 - 5725 is only allowed when TPC is implemented
> > +	# (5470 - 5725 @ 160), (30), DFS
> 
> I'm not sure that the lack of a specific provision for operating without
> TPC in this range means that it cannot be used. As I understand it, TPC
> would only result in a reduction in EIRP of 3 dB, so as long as we use
> a power limit of half of the maximum allowed we will be safe.
> 
> If this is incorrect I'd appreciate it if someone more knowledgable on
> the topic could chime in.

I would also be happy about feedback regarding this part. But my current 
settings are based on the document [1] mentioned in this change.

Let us look at the range 5250 – 5350 on page 13. There are two entries for the 
same frequency range.

 * 28:
   - up to 200 mW
   - requires TPC for 5250 – 5350 Mhz
 * 29:
   - up to 100 mW
   - requires *no* TPC for 5250 – 5350 Mhz

This is exactly the 3(.01029995...) dB difference which you've talked about. 
Now to the frequency range 5470 - 5725 MHz on page 14. 

 * 30:
   - up to 1000 mW
   - requires TPC for 5470 - 5725 MHz

There is no extra exception rule for non-TPC mode.

Now let us check what IEEE 802.11h-2003 [2] says about TPC.

* 5.4.4.1 TPC:
  - doesn't say anything about 3dB but mentions adaption based on different 
    criteria
* 7.3.2.16 Power Capability element
  - nothing regarding 3 dB here (just allows 5 dB tolerance)
* 7.3.2.17 TPC Request element
  - only describes the element
  - nothing relevant regarding the usage
* 7.3.2.18 TPC Report element
  - only describes the element
  - nothing relevant regarding the usage
* 7.4.1.3 TPC Request frame format
  - only describes the element
  - nothing relevant regarding the usage
* 7.4.1.4 TPC Report frame format
  - only describes the element
  - nothing relevant regarding the usage
* 10.3.16 TPC request
  - nothing relevant regarding the limits
* 11.5 TPC procedures
  - refers to 11.5.4 for the power adaption
* 11.5.4 Adaptation of the transmit power
  - has some suggestions to the power reduction methods
  - doesn't go into details
  - nothing about a 3dB only reduction

Ok, where is the 3 dB then coming from? My guess is the mitigation 
requirement. This should be 3 dB as *default* value (page 59). "11.5 TPC 
procedures" says following:

"Potential methods to ensure regulations are met even if TPC is not employed
include using a transmit power that is below the legal maximum (including any 
mitigation factor).".

It informs us also in "11.5.2 Specification of regulatory and local maximum 
transmit power levels" that the mitigation factors are defined in each 
regulatory domain:

"Any calculation of the local maximum transmit power for the channel shall 
ensure the mitigation requirements for the channel in the current regulatory 
domain can be satisfied. The conservative approach is to set the local maximum 
transmit power level equal to the regulatory maximum transmit power level 
minus the mitigation requirement. However, it may be possible to satisfy the 
mitigation requirement using a higher local maximum transmit power level. A 
lower local maximum transmit power level may be used for other purposes (e.g., 
range control, reduction of interference)."

It is therefore now relevant to know how these these statements from 802.11h 
and the statements from the the Singapore document have to be combined 
correctly. My current change now assumes following strict interpretation:

 * Singapore provides a mitigation factor of 3 dB for 5250 – 5350 Mhz (see 
   table entry 28 + 29)
 * Singapore provides now mitigation factor for 5470 - 5725 MHz and requires 
   TPC

I am currently unsure whether it is now valid to say that the default 
mitigation factor would be 3 dB and thus there is an implicit table entry (let 
us call it 30b) which would be:

 * 30b:
   - up to 500 mW
   - requires *no* TPC for 5470 - 5725 MHz

Countries like AU or regions like ETSI (ETSI EN 301 893) seem to have this 
mitigation factor always specified in their rules. But Singapore is missing it 
for this specific frequency range.

Kind regards,
	Sven

[1] https://www.imda.gov.sg/~/media/imda/files/regulation%20licensing%20and%20consultations/ict%20standards/telecommunication%20standards/radio-comms/imdatssrd.pdf?la=en
[2] http://standards.ieee.org/getieee802/download/802.11h-2003.pdf
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