**REPORT ON EMWIN TESTING AT WALLOPS CDAS**

**November 1 and 2, 2005**

**Prepared by**

**Peter Woolner**

**Mitretek Systems**

**November 23, 2005**

**SUMMARY**

The tests described in this report were performed on November 1^st^ and
2^nd^, 2005 at the Wallops CDA Station by Philip Whaley of NOAA/WCDAS,
Dana Irvin of Avtec, and Peter Woolner of Mitretek. They were witnessed
by Angelo Wade of NESDIS/OSD. These tests were performed using the same
Avtec software and IF Adapter as was used for similar tests in February,
2005, but using the deliverable hardware from the Avtec EMWIN contract.

The test results confirmed the EMWIN system performance that was
demonstrated in the February tests for the prototype receiver. In
addition, the close grouping of 11 of the measurements made during
February and November provide a significantly higher confidence level
that they accurately represent the true back-to-back system performance.
They also provide a reasonable statistical justification for classifying
three other measurements that were well removed from this group, as "out
of family" and could therefore be discarded. (See the chart on page 4 of
this report.)

All the tests were made with the Avtec transmit and receive equipment
connected back-to-back on the bench, but with the real GOES East receive
signals added to prove the receiver could tolerate that level of
interference. This was a close approximation of the level of
interference that is expected from the GOES N/P satellites, and
duplicates the test set-up used for the previous tests in February.

Note that the new EMWIN signal format, using OQPSK and a pulse shaping
filter, and operating at a nominal 19.2 kbps data rate, has not yet been
tested through its allocated transponder on a GOES N/P series satellite.
Therefore the amount of degradation caused by non-linearities or other
imperfections in that transponder is still unknown.

In addition, at the end of these tests, data from the new 19.2 kbps
channel into WCDAS through an RS-232 port, was passed through the test
transmitter and receiver, thus proving the data path is ready for
service when GOES N becomes available for use.

**TEST DESCRIPTION**

All tests were performed with the equipment configured as shown figure
1.

![](media/image1.wmf)**Figure 1. Block Diagram of Test Configuration**

All tests were made in the same way as for the February tests. The test
signal used OQPSK modulation at 19.2 kbps user data rate, but with the
start and stop bits removed and the Attached Sync Marker and frame
header bits added. The FEC coding used was a rate ½ Convolutional inner
code concatenated with a RS (255,223) outer code. The modulator output
was shaped to meet the requirements of IESS 308e, figures 7 and 8, using
a 6^th^ order Butterworth bandpass filter to shape the incoming pulses.
The level of the test EMWIN signal into the receiver was set at -55 dBm
and, for tests 1 to 5, the signal received from GOES East was combined
with the test signal out of the EMWIN modulator so that the level of the
EMWIN-I signals from GOES East were equal to the level of the test EMWIN
signal. The noise generator output level was then adjusted as necessary
to provide the desired E~B~/N~0~ value. For tests 6 and 7, the signals
received from GOES East were increased as much as possible (to a level
12.25 dB above the test EMWIN signal) to show this did not degrade the
Frame Error Rate (FER) performance to any measurable extent.

For all tests, the frame sync parameters were set to Search Threshold =
0, Lock Threshold = 6, Check Frames = 0, and Flywheel Frames = 4.

Prior to the start of the FER tests, the power out of the modulator when
unmodulated, was compared to its output power when modulated. In each
condition, the modulator output was fed directly into a Boonton
wattmeter. The power when modulated was found to be 0.6 dB greater than
when not modulated. That 0.6 dB correction has been applied to all
measurements recorded herein.

At the start of each test the C/N~0~ was measured for an unmodulated
carrier using a spectrum analyzer with internal averaging set at 100.
The offset for the N~0~ part of the measurement was chosen at the
frequency that produced the lowest noise. The C/N~0~ was also measured
at the end of each FER test and averaged with the start value to provide
the reference for that test. The E~B~/N~0~ values were then calculated
as:

E~B~/N~0~ = C/N~0~ + 0.6 -- 10\*LOG(15400) = C/N~0~ -- 41.3 dB/Hz

In each FER test, the carrier was modulated with a recorded EMWIN data
set, then the receiver was locked and allowed to run for a
pre-determined period of time. The numbers of frames transmitted and
received were recorded, plus the numbers of frames that are
uncorrectable by the RS code, Viterbi sync errors, frames missing, and
data frame sequence errors. This last item was used as a way to measure
the number of separate error events that had occurred.

The count of missing frames included the uncorrectable frames, as well
as those frames that were missed because the Attached Sync Marker could
not be correctly identified. Since either event will result in a frame
that is omitted from the data passed to the user, it was the total
number of missing frames that was recorded and used to derive the FER.
The FER was calculated by dividing the total number of missing frames by
the total number of transmitted frames. Frames transmitted count was
derived from the receiver monitor values by subtracting from the
received frames count the number of fill frames (if any) then adding the
total number of missing frames minus the uncorrectable frames.

The timing of the start of each test was controlled by manually setting
the receive monitor parameters to zero, after the system had shown it
was in lock. Each test was ended by freezing the receive monitor display
at the pre-determined time and capturing the values of the parameters
described above. They are shown in the table below.

**TEST RESULTS**

The following table shows the results of the tests of November 1 and 2,
2005, arranged in order of increasing E~B~/N~0~.

  ------ --------- ------------- ----------- ------------- --------- ---------
  Test   Eb/No     Total Frames  Number of   Missing or    FER       Errors
  Nbr    (dB/Hz)   Transmitted   Events      Error Frames            per Event

  2      2.6       1934          67          71            3.7E-02   1.06

  6      2.7       3917          55          85            2.2E-02   1.55

  3      2.85      3836          24          26            6.8E-03   1.08

  7      3.05      6022          16          17            2.8E-03   1.06

  5      3.15      125901        5           62            4.9E-04   12.40

  1      3.3       11005         14          133           1.2E-02   9.50
  ------ --------- ------------- ----------- ------------- --------- ---------

The following chart is a plot of these results for E~B~/N~0~ versus FER,
plus the results from the February tests. (The February test result
table is provided in Appendix A for easy reference if desired.)

![](media/image2.wmf){width="6.0in" height="5.469291338582678in"}

**Chart 1. Back-to-Back Frame Error rate Test Results**

**DISCUSSION OF TEST RESULTS**

1.  The two points shown in the lower right of the chart actually
    experienced no errors or missing frames during their test periods.
    One error was artificially added to the result for each of these
    tests in order to produce the points plotted on the chart. The
    actual error rates for these points are unknown. It is probable, but
    not certain, that they lie some unknown distance below these plotted
    points.

2.  The 11 points nearest the left edge of the chart are considered
    "in-family", i.e. together they fall close to a curve that would
    match the theoretical shape, and their displacement from that curve
    can be considered within the bounds of experimental error.

3.  The three points between these two groups do not meet this criterion
    and do have recorded errors. Also, they do not seem to form a
    different curve that might also match the theoretical shape but with
    greater implementation losses. They are therefore considered
    out-of-family.

4.  The 11 in-family points tend to indicate the long term average
    performance for this system would most likely cross the FER line of
    10^-4^ at E~B~/N~0~ values between about 3.0 and 3.5 dB/Hz.

5.  This is a significant improvement for the probable worst-case limit,
    3.5 compared to 4.5 dB/Hz that was indicated by the February tests
    alone.

6.  The two tests run with maximum interference from GOES East are
    interleaved between the three tests for which the interference was
    approximately equal to the desired signal level. All five tests fit
    the came curve within the probable experimental error, indicating no
    significant change in performance due to the presence of the
    increased levels of the other signals from the GOES satellite.

Although these results are considered a good indication, it is important
to remember that there have still been no tests made with the EMWIN
signal passing through the actual satellite transponder. Since this
transponder was not designed to carry a signal that uses a pulse shaping
filter as is done for this EMWIN signal, more than usual degradation due
to the satellite transponder is expected to occur. The actual
performance of the EMWIN link cannot be known for sure until the link is
tested through an actual GOES N series satellite.

**APPENDIX A. FEBRUARY 2005 RESULTS**

  ------ ----------- -------------- -------- -------------- --------- -----------
  Test   E~B~/N~0~   Total Frames   No. of   Missing or     FER       Errors per
  Nbr    dB/Hz       Transmitted    Events   Error Frames             Event

  3      2.3         3160           31       58             1.8E-02   1.87

  1      2.6         904            48       75             8.3E-02   1.56

  9      2.8         24042          54       113            4.7E-03   2.09

  4      2.9         115504         82       645            5.6E-03   7.87

  2      3.0         10000          15       15             1.5E-03   1.00

  8      3.1         23554          2        2              8.5E-05   1.00

  5      3.95        23237          6        34             1.5E-03   5.67

  7      4.25        116023         1        79             6.8E-04   79.00

  6      4.3         24104          0        1              4.1E-05   0.00

  10     5.0         120012         0        1              8.3E-06   0.00
  ------ ----------- -------------- -------- -------------- --------- -----------

The following chart is a plot of these results for E~B~/N~0~ versus FER,
with some additional annotations that are discussed in the following
section.

> ![](media/image3.wmf){width="5.67007874015748in"
> height="5.034645669291338in"}

**Chart A1. Back-to-Back Frame Error Rate Test Results**

**APPENDIX B. LINK CALCULATIONS**

  --------------- ------------------------------------------- ------------ -----------
  **EMWIN LINK                                                             
  CALCULATIONS                                                             
  FOR 19200 bps                                                            
  NOMINAL RATE**                                                           

                  **Parameter**                               **Units**    **Value**

                  Data Rate (before framing and coding)       bps          15514

                  Modulation Type                                          OQPSK

                  FEC Coding Type                                          Conv+RS

                  FEC Coding Rate                                          0.437

  **Ground Uplink                                                           
  Transmitter**                                                            

                  Uplink Frequency                            MHz          2034.70

  Transmit EIRP                                               dBmi         76.7

  Antenna                                                     dB           0.5
  Pointing Loss                                                            

  **Earth - To -                                                            
  Space**                                                                  

                  Path Distance (for 5 deg elevation)         km           41127

  Free Space Loss                                             dB           190.9

  Atmospheric                                                 dB           0.4
  Attenuation                                                              

  **S/C Receive                                                             
  Performance**                                                            

  Polarization                                                dB           0.2
  Loss                                                                     

  U/L Incident                                                dBmi         -115.3
  Power                                                                    

                  Antenna Gain (from 5 deg elevation)         dBi          14.8

  G/T (incl cable                                             dB/K         -14.2
  losses)                                                                  

  Boltzmann                                                   dBm/Hz/K     -198.6
  constant                                                                 

  Uplink Thermal                                              dB/Hz        69.1
  C/No                                                                     

  **S/C Transmit                                                            
  Performance**                                                            

                  Downlink Frequency                          MHz          1692.70

  Transmit EIRP                                               dBmi         44.8
  (to 5 deg                                                                
  elevation)                                                               

  **Space - To -                                                            
  Earth**                                                                  

                  Path Distance (for 5 deg elevation)         km           41127

  Free Space Loss                                             dB           189.3

  Atmospheric                                                 dB           0.4
  Attenuation                                                              

  **Ground                                                                  
  Downlink                                                                 
  Receiver**                                                               

  Downlink                                                    dBmi         -144.9
  Incident Power                                                           

                  Pwr Flux Density Rqmt (EOC in 4 kHz)        dBW/m2       -154

                  Power Flux Density (EOC in 4 kHz)           dBW/m2       -159.0

  E/S G/T                                                     dB/K         -0.3

  Polarization                                                dB           0.2
  Loss                                                                     

  Boltzmann                                                   dBm/Hz/K     -198.6
  constant                                                                 

  Downlink                                                    dB/Hz        53.2
  Thermal C/No                                                             

  **Eb/No Overall                                                           
  Calculation**                                                            

  Overall                                                     dB/Hz        53.1
  Composite C/No                                                           

  Data Rate in dB                                             dB-Hz        41.9

  Eb/No                                                       dB           11.2
  Calculated                                                               
  --------------- ------------------------------------------- ------------ -----------

  ---------------- ------------------------------------------- ------------ -----------
  **Required Eb/No                                                           
  Adjustments**                                                             

                   Required BER                                             1E-06

  Theoretical                                                  dB           10.6
  Eb/No with no                                                             
  coding                                                                    

  Theoretical                                                  dB           8.0
  coding gain                                                               

  Theoretical                                                  dB           2.6
  Eb/No with FEC                                                            
  coding                                                                    

  Ground Segment                                               dB           1.9
  Implementation                                                            
  Loss                                                                      

  Satellite                                                    dB           4.7
  Segment                                                                   
  Degradations                                                              

  Required Eb/No                                               dB           9.2

  **Eb/No MARGIN**                                             **dB**       **2.0**
  ---------------- ------------------------------------------- ------------ -----------