Subject: [NEXTEL-1] APCO's-Draft Determination of the Local Median

From: [email-masked]
Date: Tue, 29 Jul 2003 23:13:17 -0400

APCO's-Draft Determination of the Local Median

Determination of the Local Median

The purpose of this paper is to propose a method of measurement to determine the
value of a desired signal median value over a prescribed area.  The goal is to
determine if a user has provided a prescribed median signal level sufficient to be
guaranteed resolution by local interferers without any additional system changes
on the victim’s part in the post refarming environment.

This is being discussed in the Consensus Group to the 800 MHz Rebanding NPRM FCC
02-55 and is located in Appendix F.  This test is the key to gaining true
consensus as to signal levels and who pays.

Thought process and Consensus member inputs: The simpler the test, the better the
chance that it will be used. It has to have a scientific basis.Results should be
repeatable (although they may change over longer periods of time) After measured
data collection is completed the benchmark values can be determined by software
evaluation of the captured data.

 Testing should cause minimal disruption of commercial services and be conducted
during periods of normal to high traffic conditions.

To minimize the number of tests, a first test to determine if additional tests
will even be required will be conducted.  It will measure the RSSI (C+I+N).  If
victim radios operate (unmutes) in the local area being tested, then it can be
concluded that the value of C is greater than (I+N). A test tone or some audio
signal should be provided so that the receiver unmute is verified. Since the
maximum difference between C and (I+N) has to be large enough to allow the radio
to unmute, then the error in measuring the composite will be less than
approximately 2 dB .  Therefore if the ensemble median exceeds the target value by
2 dB then the criterion has been met.  However, if it doesn’t meet the target,
then a second test of (I+N) may be conducted to permit a more accurate
determination of the local median value of the desired signal.  If the median
value of C is within 2 dB of the target a second (I+N) test may be optionally
performed to determine that the value of (I+N) hasn’t changed during the testing.

This sequence of tests allows a preliminary determination of the median desired
signal level without requiring base transmit frequencies from being taken out of
service.  More exhaustive troubleshooting testing may require that the interfering
emitters be turned off.  This normally requires late night testing and may not be
appropriate as the interfering emitters may not be active due to reduced traffic
loading during late night testing.  The (I+N) testing can be done during normal
business hours, as only one channel needs to be taken out of service on the
victim’s system.

Draft of the test.

1. Determine the size of area to be tested.  A minimum area of 3 arc seconds by 3
arc seconds .  Local obstructions may determine the size as well as how large the
reported affected area is.  If the affected area is quite large, a location of
reported problems should be selected.

a. It needs to be large enough to be consistent with coverage predictions and FCC,
dBu, contours limitations.

b. The data points need to be relatively uniformly distributed across the area
being tested.

c. A constant velocity along the route should be maintained to prevent over-
sampling in any given location.

2. A low or band pass filter should be inserted between the test receiver and its
antenna.
a. The purpose is to differentiate between IMR and OOBE noise by attenuating
potential IMR signals from the CMRS portion of the band.
b. The filter’s loss on the desired frequency needs to be included in the
calibration.

3. With all appropriate channels transmitting constantly, gather “continuous” data
over a route that covers the prescribed area .  This is measuring (C+I+N)

a. Gather data points at a constant speed following a route that covers the
prescribed area.  See Figure 1.

b. From the data, determine the median (C+I+N).

c. A constant velocity along the route should be maintained to prevent over-
sampling in any given location.

4. Modulate the desired channel with a test signal to verify that if the radio is
unmuted.

a. Digital radios this is approximately 5 dB C/(I+N)

b. Analog radios should have their manual squelch setting set for a C/(I+N) of 5
dB.

5. If the median (C+I+N) is greater than 2 dB than the median target value and the
receiver was unmuted, then the “threshold test” is considered a pass.

6. If the median (C+I+N) is not greater than 2 dB than the median target value,
the following optional additional testing can be conducted as part of a
troubleshooting process.

7. Repeat the test following the same route with the desired carrier not keyed.
The RSSI now captures only (I+N).  This test should be run as soon as possible to
be sure conditions are similar to the initial test.

a. Gather data points at a constant speed following a route that covers the
prescribed area.  See Figure 1.

b. If test receiver has AFC, disable it so it remains on the test frequency and is
not pulled toward the interfering emitters signal..

c. From the data, determine the median (C+I+N)

8. The value of N should be a constant
a. The thermal noise of the receiver.  All else is I.   If OOBE noise is present
it will be captured in this data.

9. Determine the median C based on the median (C+I+N) and (I+N)
10. If the calculated median C is close to the target value, a third test,
repeating the (I+N) test can optionally be performed to ensure that the (I+N) has
not changed.  The route would be the same as used in step 5).

Example: calculation to determine the median value of C from the alternative
testing.

 Median (C+I+N) = -98 dBm [2.815E-09]
 Median (I+N)      = -110 dBm [7.071E-10]
 N is constant     = -124 dBm [1.411E-10]

From this data, the value of I can be calculated:

I+N = -110 dBm (7.071E-10)
N =    -124 dBm (1.411E-10)
I = 7.071E-10 -1.411E-10) = 5.660E-10 (-110.18 dBm).  This step isn’t really
necessary, but may add additional information about the interfering emitter(s).
C = 2.815E-09 - 7.071E-10 = 2.108E-09 = -98.28 dBm

Additional Notes

The (I+N) may not be constant due to interfering emitters being intermittently
active.  This is the reason for the short time difference between the (C+I+N)
measurement and the (I+N) measurement.

The purpose of the external test receiver’s filter is to eliminate receiver IMR
from being included in the measured data.  This allows various test receivers to
be utilized.  Note that a minimum receiver IMR specification of ? 70 dB is
recommended.  If a lower IMR value is used, additional attenuation of potential IM
generating signals may be required.
If the measured value of C is within 2 dB of the prescribed value, the (I+N) test
may optionally be rerun over the same route to confirm that the measured median
(I+N) is still valid (no significant change).

The median value rather than the mean value is used due to potential RSSI upper
and lower limits.  These limits would invalidate a mean value.  Reference TSB88A,
§ 7.8.1.
Receiver calibration methodology is documented in TSB88A , § 7.8.3 - 7.8.4.  See
also TIA/EIA 845, “RADIOWAVE PROPAGATION - PATH LOSS - MEASUREMENT, VALIDATION,
AND PRESENTATION”, § 4, “Signal Strength Measurement” and its associated sub
clauses.

Figure 1 - Route for Measurement

Figure 1 is a simplified route.  Local obstructions and access may limit the
route.  It is important to develop the route so that no one portion is overly
represented in the measured data.

Some alternative approaches may be considered.  They are however, more useful in
trouble shooting root causes .  They are documented here for future inclusion into
a Revised Best Practices Guide.

Alternate 1) Including BER% measured values .

If the system is digital, both (C+I+N) RSSI and BER% can simultaneously be
captured.  This then provides addition data as to what the median C/(I+N) really
is.  This is more complex.  Different receivers of the same model and manufacturer
may have slightly different characteristics.

The static BER% of the test receiver can be measured using normal test equipment.
The difference between the static C/N and faded C/N for the necessary faded BER%
can be used.  For example, if the 5% static BER is -120 dBm and the 2% static BER%
is 2.2 dB higher (-117.8 dBm) then the C/N for 2% static BER is 2.2 dB greater
than the value in TSB88A, Table A-1.  If the modulation is C4FM that would be 7.6
dB + 2.2 dB = 9.8 dB.  The value of faded 2% BER is 17.7 dB, 7.9 dB above the
static value.  Thus the C for 17.7 dB requires a desired of -117.8 dBm + 7.9 =
-109.9 dBm.

If the criterion is a 20 dB C/(I+N) The 1% faded BER can be used for C4FM.

The process of determining if 1% BER can be achieved in the local area will
determine if the desired C/(I+N) is being achieved.

This test provides a better understanding of the interference mechanism.  If
(C+I+N) is large, but the BER% increases, the (I+N) component is increasing.

Alternate 2) Proactive Determination

Using a receiver with a calibrated RSSI, approach local areas of potential
interference with the desired frequency not active.  If the RSSI (I+N) indicates a
value that is X dB less than the local desired signal level, known from previous
measurements, a determination of interference zones can be quickly determined.
Note however that the (I+N) may vary with time and activity of various emitters.
Also the desired may be different due to hardware issues.

This method can proactively determine potential trouble areas before they affect
users.  It is not really intended to be the determination of who must fund a fix.
It does however; provide warnings to potential interference situations that may
occur in the future.
--
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---

From: "Harry Ekelund" <[email-masked]>
Date: Wed, 30 Jul 2003 08:23:54 -0700

An interesting application for RFID that perhaps the anti-technology
activists can accept.

Harry J. Ekelund, P.E.   - AE7NY
Marketing Manager
Kathrein - Scala Division

---

From: [email-masked]
Date: Wed, 30 Jul 2003 11:37:30 -0400

Thanks Harry I have seen a similar program.
One of the anti-RFID  advocates here sent me a 3 page letter when I posted this to
Nextel-1 back on 7/18/03 :

"RFID to be Used for Baggage Tracking in Japan
A new organization in Japan, the Advanced Airport Systems Technology
Research  Consortium (ASTREC), was formed to further the use of technology in
airports."

http://groups.yahoo.com/group/NEXTEL-1/message/9482

When the article mentioned that JFK was part of the system, the guy went
ballistic. Reminds me of the bird nuts.......

Harry Ekelund wrote:

>  An interesting application for RFID that perhaps the anti-technology activists
> can accept.
>
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>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

---

From: "Harry Ekelund" <[email-masked]>
Date: Wed, 30 Jul 2003 08:50:24 -0700

I pay some attention to the RFID business. If there is continued interest on
the subject, I can post on it. Cast your ballot if you want more on RFID.

Harry
  -----Original Message-----
  From: [email-masked] [mailto:[email-masked]]
  Sent: July 30, 2003 8:38 AM
  To: [email-masked]
  Subject: Re: [NEXTEL-1] An alternative use for RFID

  Thanks Harry I have seen a similar program.
  One of the anti-RFID  advocates here sent me a 3 page letter when I posted
this to Nextel-1 back on 7/18/03 :
  "RFID to be Used for Baggage Tracking in Japan
  A new organization in Japan, the Advanced Airport Systems Technology
  Research  Consortium (ASTREC), was formed to further the use of technology
in  airports."

  Harry Ekelund wrote:

---

From: [email-masked]
Date: Wed, 30 Jul 2003 11:55:22 -0400

I'm always interested.

How do you thing this privacy issue will play out. I'm of the opinion that RFID's
strength will be on the commercial level and not the consumer.

Also if you have any info on interference being used to counter RFID an FBI agent
is looking for a "White Paper" on the subject.

Thx
Marcel

Harry Ekelund wrote:

> the subject, I can post on it. Cast your ballot if you want more on RFID.Harry
>
>      One of the anti-RFID  advocates here sent me a 3 page letter when I
>      posted this to Nextel-1 back on 7/18/03 :
>
>      Research  Consortium (ASTREC), was formed to further the use of
>      technology in  airports."
>
>      When the article mentioned that JFK was part of the system, the guy
>      went ballistic. Reminds me of the bird nuts.......
>
>
>      Harry Ekelund wrote:
>
                        ADVERTISEMENT
                         [click here]

---

From: "Todd Ellis" <[email-masked]>
Date: Wed, 30 Jul 2003 12:02:31 -0400

Sounds interesting.  I wonder if the Bureau would fund a study.

Todd Ellis

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] 
Sent: Wednesday, July 30, 2003 11:55 AM
To: [email-masked]
Subject: Re: [NEXTEL-1] An alternative use for RFID

I'm always interested.

How do you thing this privacy issue will play out. I'm of the opinion that
RFID's
strength will be on the commercial level and not the consumer.

Also if you have any info on interference being used to counter RFID an FBI
agent
is looking for a "White Paper" on the subject.

Thx
Marcel

---

From: [email-masked]
Date: Wed, 30 Jul 2003 12:14:11 -0400

Good luck-He's lurking here and on WFHSG-
All  I get is cryptic messages that I need a "Secrete Decoder Ring" to figure out.

Also are you familiar with the:

General Director for regulation and quality of service
Ministry for communications
Italy
XXXXX54442191
[email-masked]

I 'm still trying to figure out the chain of command there.
He is another Fan..........

---

From: Rick Parrish <[email-masked]>
Date: Wed, 30 Jul 2003 11:51:57 -0500

[email-masked] wrote:

>Also if you have any info on interference being used to counter RFID an FBI agent is looking for a "White Paper" on the subject.
>  
>
Marcel;

Didn't you post some info on a whitepaper and/or research project 
related to GPS jamming? Seems like much of the work there would carry 
over to the low power nature of RFID.

-rick

---

From: [email-masked]
Date: Wed, 30 Jul 2003 13:19:13 -0400

I think some of it would transfer but the technology employed by the RFID devices is different. The jammer was just a broad band device generating
noise.  With RFID I think it would require very a specific signal to "Null" the device. I will take a look at the jammer doc and see if it is remotely
applicable.

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---

From: [email-masked]
Date: Wed, 30 Jul 2003 13:25:54 -0400

If some one wants to look over my shoulder on this one.......
 Search GPS Jammer revealed-

 http://groups.yahoo.com/group/NEXTEL-1/message/6031

 http://groups.yahoo.com/group/NEXTEL-1/message/5961

 http://groups.yahoo.com/group/NEXTEL-1/message/5958

 http://groups.yahoo.com/group/NEXTEL-1/message/5956

 http://groups.yahoo.com/group/NEXTEL-1/message/5554

---

From: Rick Parrish <[email-masked]>
Date: Wed, 30 Jul 2003 12:38:31 -0500

>noise.  With RFID I think it would require very a specific signal to "Null" the device. I will take a look at the jammer doc and see if it is remotely
Okay, the "jammer" would need to be specific to the family of RFID 
devices being circumvented (eg. 125/250 kHz, 13 MHz, or 900 Mhz). An 
active jamming device is going to have the side effect of energizing the 
RFID tag.

Dumb tags - you want the jamming signal to compete with the weaker RFID 
reply at the reader. The tag replies but the reader can't distinguish 
the reply from the noise.

Smart tags - the jamming signal competes with the reader's "query" or 
"polling" message. If the tag does not receive the correct poll message, 
it won't respond.

Instead of a wideband noise maker like the GPS application, it's (most 
likely) a narrowband noise maker with less power than an FRS 2-way radio.

An interesting feature for the manufacturers of RFID readers is the 
ability to detect the presence of an interfering signal - like a jammer 
or another nearby reader.

Hmmm ... a few more emails and you'll have your whitepaper off this list!

-rick

(and speaking of FRS 2-way radios, I saw a 22 channel model for sale at 
a drug store, I thought FRS was only 14 channels).

---

From: [email-masked]
Date: Wed, 30 Jul 2003 16:30:08 -0400

> active jamming device is going to have the side effect of energizing the

What modulation technique? or would you use and un modulated carrier?
What bandwidth?  As you can tell I have not done my DD yet. I'm buried in OFMD
beta project. I just saw the 1st OFMD, Wi-Fi, WCDMA phone. They are waiting for an STA for 3 sites. The say you can do full motion video conferencing at 60
Mph. FYI- Tomorrow I get to (see and hear) Moto's new iDEN vocoder. I should be interesting!

> the reply from the noise.
That's easy-

> "polling" message. If the tag does not receive the correct poll message,

Easy-

> or another nearby reader.
Not so easy, but do able

> a drug store, I thought FRS was only 14 channels).

Sometimes the qualify "Pl" tone as a channel...... Go figure, unless it's a GMRS 
radio. I defer to Alan D. on the FRS/GMRS issues.

---

From: Rick Parrish <[email-masked]>
Date: Wed, 30 Jul 2003 15:54:00 -0500

>What modulation technique? or would you use and un modulated carrier?
PM or narrow FM ... the low frequency stuff (125 khz) may by AM ... I'd 
have to look.

>What bandwidth?  
Pretty narrow stuff (low bit rate) - maybe 3khz - way less than 30khz. 
The point of couse is that such a device is pretty low-tech stuff.

>As you can tell I have not done my DD yet. I'm buried in OFMD
>beta project. I just saw the 1st OFMD, Wi-Fi, WCDMA phone. They are waiting for an STA for 3 sites. The say you can do full motion video conferencing at 60 Mph. FYI- Tomorrow I get to (see and hear) Moto's new iDEN vocoder. I should be interesting!
>
Marcel you're always interesting, [ and the iDEN vocoder demo should be 
interesting too ;^) ] !

>Sometimes the qualify "Pl" tone as a channel...... Go figure, unless it's a GMRS radio. I defer to Alan D. on the FRS/GMRS issues.
>
I've seen units advertise the 38 CTCSS tones and "channels" - this was 
different. It listed 7 GMRS channels, 7 FRS-only channels - and 8 more 
"extra" GMRS channels. *shrug* I dunno.

-rick

---

From: "marcel_rf1" <[email-masked]>
Date: Wed, 30 Jul 2003 21:30:19 -0000

I was told there will be money available under DARPA.

http://www.darpa.mil/

> From: Marcelrf@B... [mailto:Marcelrf@B...]

---

From: [email-masked]
Date: Thu, 31 Jul 2003 03:32:50 -0400

I trying to trace the Manufact the new chip. I have a few leads but today we will reverse eng this puppy and find out who makes the chip.

---

From: [email-masked]
Date: Thu, 31 Jul 2003 03:36:05 -0400

Let me try this again

I'm trying to trace the Manufacture of the new chip. I have a few leads but today we will reverse enigineer this puppy and find out who makes the
chip.