I'm coming up on a new Tait P25 system soon, and I'm wondering if there are any standardized DAQ tests yet for portables, mobiles, and base stations. I've done drive tests in the past for govt P25 systems using STI equipment. But, that just benchmarks the system after it is built as part of the acceptance testing. It doesn't test the individual radios, and sooner or later I will need to test them. Those of you who are daily hand-on with a P25 system, what are you guys doing to test your subscriber equipment and PM your stations?
Thx
DAQ testing
Moderator: Queue Moderator
Re: DAQ testing
Digital mode testing of portable, mobile, and base station equipment is generally done using BER since the TIA has determined BER to DAQ relationships. TIA TSB-88 contains a table of projected channel performance to DAQ for various modulation types for both faded reference sensitivity and static reference sensitivity. Static reference sensitivity is what we are used to measuring on the bench [e.g. 0.35uv/12dBS].
Also, TIA-102-CAAA and TIA-102-CAAB contain test equipment requirements and procedures for testing P25 including measurement of faded sensitivity.
Directly comparing DAQ performance of various products is an interesting challenge. Analog FM radio performance can be evaluated with traditional audio quality test measurements such as signal-to-noise, distortion, SINAD, AF power output, etc. DAQ on the other hand is by definition subjective. This has also been a problem for the telecommunications industry [VOIP & cell phone] where the term MOS [Mean Opinion Score] is often used. DAQ and MOS use a similar scale.
The need to test audio quality without the cost of groups of persons serving as evaluators has resulted in the development of methods to automate the estimation of voice quality. Examples are PSQM, PSQM+ and PAMS. More recently PESQ has been developed to overcome some issues with earlier methods. P25 manufacturers have been moving toward the use of PESQ as a standardized tool for VOCODER performance evaluation.
Although PESQ testing has been incorporated into some Agilent and R&S instruments designed for the "wireless" industry, it does not appear to have yet made it into instruments designed for the two-way field. Stand-alone VQT [Voice Quality Test] instruments are available - for example the Agilent Telegra VQT - but they are rather spendy.
The Institute for Telecommunication Sciences [NTIA] has done considerable research in the area of VQT. They have numerous documents available for interested parties. Some of their reports are:
99-358 Delivered Audio Quality Measurements on Project 25 Land Mobile Radios
98-347 Objective Estimation of Perceived Speech Quality ....
01-386 Voice Quality Assessment of Vocoders in Tandem Configuration
Also, they publish an annual Technical Progress Report. There are summaries of their tests and programs in each of these. The reports can all be downloaded at:
http://www.its.bldrdoc.gov/
[It appears to me that these people are having entirely too much fun to be getting paid to work there.]
Also, TIA-102-CAAA and TIA-102-CAAB contain test equipment requirements and procedures for testing P25 including measurement of faded sensitivity.
Directly comparing DAQ performance of various products is an interesting challenge. Analog FM radio performance can be evaluated with traditional audio quality test measurements such as signal-to-noise, distortion, SINAD, AF power output, etc. DAQ on the other hand is by definition subjective. This has also been a problem for the telecommunications industry [VOIP & cell phone] where the term MOS [Mean Opinion Score] is often used. DAQ and MOS use a similar scale.
The need to test audio quality without the cost of groups of persons serving as evaluators has resulted in the development of methods to automate the estimation of voice quality. Examples are PSQM, PSQM+ and PAMS. More recently PESQ has been developed to overcome some issues with earlier methods. P25 manufacturers have been moving toward the use of PESQ as a standardized tool for VOCODER performance evaluation.
Although PESQ testing has been incorporated into some Agilent and R&S instruments designed for the "wireless" industry, it does not appear to have yet made it into instruments designed for the two-way field. Stand-alone VQT [Voice Quality Test] instruments are available - for example the Agilent Telegra VQT - but they are rather spendy.
The Institute for Telecommunication Sciences [NTIA] has done considerable research in the area of VQT. They have numerous documents available for interested parties. Some of their reports are:
99-358 Delivered Audio Quality Measurements on Project 25 Land Mobile Radios
98-347 Objective Estimation of Perceived Speech Quality ....
01-386 Voice Quality Assessment of Vocoders in Tandem Configuration
Also, they publish an annual Technical Progress Report. There are summaries of their tests and programs in each of these. The reports can all be downloaded at:
http://www.its.bldrdoc.gov/
[It appears to me that these people are having entirely too much fun to be getting paid to work there.]
Re: DAQ testing
Thanks. Those boil to the top in a search pretty quick. In your experience then, is DAQ just an acceptance test? That is, it's only important during implementation to satisfy the contract, but from a maintenance POV, you do not test each radio to ensure it meets a 3.4 spec?
Interesting article by some Coast Guard techs trying to develope standardized tests for maintaining their equipment - http://www.uscga.edu/uploadedFiles/Acad ... 0Paper.pdf
Interesting article by some Coast Guard techs trying to develope standardized tests for maintaining their equipment - http://www.uscga.edu/uploadedFiles/Acad ... 0Paper.pdf
Re: DAQ testing
No, we don't test incoming radios for DAQ. Static bench sensitivity test is really all that's practical.
During the RFP process that resulted in our State purchasing a new statewide P25 trunked system, the State radio folks initially wanted to develop a testing plan to compare various makes and models of mobiles and portables to certify ones that would be acceptable for agency purchase. That did not prove to be achievable.
The P25 CAP is supposed to offer end user assurance that radios meet the P25 specs but doesn't offer a way to compare different units. Although field-testing would be desirable - it is not a simple matter - as discovered by the authors of that Coast Guard paper. A couple of their observations are revealing:
"...so it turned out that there was much more going on between a VHF transmission and the reception of that transmission than a gain and some additive noise."
"A DAQ-SINAD relationship is going to be harder to develop than originally conceived."
They certainly went to a lot of work conducting tests but I think they may not have done enough preliminary research.
Their failure to achieve conclusive results is probably due to oversimplification. Radio channel behavior is much more complex than can be emulated by the simple addition of Gaussian noise. The paper makes no reference to faded sensitivity testing, to TIA-102-CAAA, or to TIA-TSB-88.
Channel fading emulation is incorporated into some high tier signal generators such as the R&S SMU200A or stand-alone units such as the Spirent SR5500 Wireless Channel Emulator are available.
If you really want to test P25 radio's DAQ performance, it should be possible to configure a testing lab consisting of a P25 signal source such as an Aeroflex 3920, a channel emulator such as the Spirent, the P25 radio, and finally a PESQ analyzer such as the Agilent Telegra or the R&S UPV. If you are going to make the tests acoustically, you'll also need an ISO 3745 acoustic chamber.
Let me know if you put that together - I'll want to make a field-trip!
Actually, ITS has all the gear and the expertise - that's where we should make a field-trip.
In their 2009 TPR, ITS has an article about their Fading Characteristics Verification program [pg 38-39].
It will be interesting to see their results and to see if they recommend any revisions of the TIA-CAAA faded reference sensitivity testing procedure.
During the RFP process that resulted in our State purchasing a new statewide P25 trunked system, the State radio folks initially wanted to develop a testing plan to compare various makes and models of mobiles and portables to certify ones that would be acceptable for agency purchase. That did not prove to be achievable.
The P25 CAP is supposed to offer end user assurance that radios meet the P25 specs but doesn't offer a way to compare different units. Although field-testing would be desirable - it is not a simple matter - as discovered by the authors of that Coast Guard paper. A couple of their observations are revealing:
"...so it turned out that there was much more going on between a VHF transmission and the reception of that transmission than a gain and some additive noise."
"A DAQ-SINAD relationship is going to be harder to develop than originally conceived."
They certainly went to a lot of work conducting tests but I think they may not have done enough preliminary research.
Their failure to achieve conclusive results is probably due to oversimplification. Radio channel behavior is much more complex than can be emulated by the simple addition of Gaussian noise. The paper makes no reference to faded sensitivity testing, to TIA-102-CAAA, or to TIA-TSB-88.
Channel fading emulation is incorporated into some high tier signal generators such as the R&S SMU200A or stand-alone units such as the Spirent SR5500 Wireless Channel Emulator are available.
If you really want to test P25 radio's DAQ performance, it should be possible to configure a testing lab consisting of a P25 signal source such as an Aeroflex 3920, a channel emulator such as the Spirent, the P25 radio, and finally a PESQ analyzer such as the Agilent Telegra or the R&S UPV. If you are going to make the tests acoustically, you'll also need an ISO 3745 acoustic chamber.
Let me know if you put that together - I'll want to make a field-trip!
Actually, ITS has all the gear and the expertise - that's where we should make a field-trip.
In their 2009 TPR, ITS has an article about their Fading Characteristics Verification program [pg 38-39].
It will be interesting to see their results and to see if they recommend any revisions of the TIA-CAAA faded reference sensitivity testing procedure.
Re: DAQ testing
Thanks. Kinda what I thought. Kinda what I gathered from all my reading. The DAQ concept has been out since the mid 90's and yet not a single test equipment manufacturer has a machine for DAQ certification. I'll do my best to steer the customer from forcing their maintenance personnel to perform what hasn't been done by folks who wear pocket protectors for a living. They are all about the procedure, and if nobody else can develope a procedure, then they can't.
Re: DAQ testing
One of the amazing things I've discovered is how DAQ has crept into local laws. During my search I kept running into sections of city code requiring building owners to ensure radio coverage within the building, parking structures, and stairwells. Okay. We have similar requirements here, and it has been good business for us designing and installing BDA's in several of the larger buildings and subterranean parking structures. But, we have a region-wide analog 800 trunking system that will eventually go P25 where DAQ is applicable. I'm also finding cities requiring BDAs for their conventional UHF systems, and applying a DAQ 3 as the criteria citing the TIA docs as the source for the standard. With DAQ being a high level concept with no tangible, reproducible tests, how do building owners do that? (rhetorical question) Are these requirements misapplying DAQ? (not so rhetorical - doing a sanity check on my understanding of DAQ and not arguing whether cities should or should not write code for BDAs)
Re: DAQ testing
"...With DAQ being a high level concept with no tangible, reproducible tests..."
--------------------------------------------------------------------------------------------
You are missing the whole point of TSB-88 which is the establishment of standardized methods of channel performance prediction and verification.
TSB-88 defines DAQ and the relationship between DAQ and Cf/(I+N) [Faded Carrier to Interference plus noise].
These definitions are given for wideband and narrowband analog FM as well as for all of the common and emerging digital modulation formats.
TSB-88 further establishes methods for determination of interference and noise based on transmitter SPD, receiver ENBW, adjacent channel performance, ambient noise, etc. Thus, providers of coverage prediction software and coverage verification tools can develop their products to a common standard, customers can specify their requirements in standardized terms, and vendors can engineer systems that will meet the customer's requirements on equal footing.
There is a presentation, TSB-88 Managing Intersystem Interference for Dissimilar Modulations, that gives an overview of TSB-88 and its relationship to TIA-603 and TIA-102:
http://www.apcointl.org/frequency/docum ... -olson.ppt
--------------------------------------------------------------------------------------------
You are missing the whole point of TSB-88 which is the establishment of standardized methods of channel performance prediction and verification.
TSB-88 defines DAQ and the relationship between DAQ and Cf/(I+N) [Faded Carrier to Interference plus noise].
These definitions are given for wideband and narrowband analog FM as well as for all of the common and emerging digital modulation formats.
TSB-88 further establishes methods for determination of interference and noise based on transmitter SPD, receiver ENBW, adjacent channel performance, ambient noise, etc. Thus, providers of coverage prediction software and coverage verification tools can develop their products to a common standard, customers can specify their requirements in standardized terms, and vendors can engineer systems that will meet the customer's requirements on equal footing.
There is a presentation, TSB-88 Managing Intersystem Interference for Dissimilar Modulations, that gives an overview of TSB-88 and its relationship to TIA-603 and TIA-102:
http://www.apcointl.org/frequency/docum ... -olson.ppt
Re: DAQ testing
I'm a readin ...
Re: DAQ testing
I realize that the document I referenced deals primarily with the adjacent channel aspects of TSB-88, but it does contain [on Pg 20] the TSB-88 table of DAQ definitions and signal relationships and can be freely downloaded [TSB-88 is available for purchase].