VDL Frequency assignment planning criteria



AERONAUTICAL MOBILE COMMUNICATIONS PANEL

Working Group B

14th Meeting

Montreal, Canada, 13 to17 January 2003

VDL FREQUENCY PLANNING ASSIGNMENT CRITERIA

1. Interference thresholds

1. The interference threshold for the VDL is specified (Annex 10, Volume III, Part I, paragraph 6.3.5.1) as follows:

i) VDL Mode 2 Maximum corrected bit error rate (BER) is 1 in 103104

Note: The uncorrected BER value of 1 in 103 is to be used in the testing of equipment. The forward error calculation used in VDL Mode 2 (Annex 10, Volume III, Part I, paragraph 6.4.3.1.2.1 refers) translates an uncorrected BER of 1 in 103 into a corrected BER of 1 in 104

ii) VDL Mode 3 Maximum uncorrected bit error rate is 1 in 103

iii) VDL Mode 4 Maximum bit error rate is 1 in 104

Note: The BER value for VDL Mode 4 corresponds to a message error rate (MER) of approximately 1 in 2 times 10-2 using the formula [MER=1-(1-BER)216 ] and assuming a one slot message with 216 bits of data. VDL Mode 4 does not provide forward error correction of the data.

2. R/F signal parameters

2.1 The values for the R/F signal in Table 1 were used in the testing of equipment and the development of separation criteria for VDL.

3. Testing parameters (source: Appendix D and E to the report of WG B12/13).

3.1. Interfered Station (receiver): DSB-AM (air and ground receiver)

minimum (desired) signal level at receiver input: ground stations -94 93 dBm

aircraft stations -85 82 dBm

|Interfering station |DSB-AM |VDL M2 |VDL M3 23) |VDL M4 |

|S/P ratio 5) |N/A |6 dB |18 dB 2) |12 dB |

|S+N/N |N/A |6 dB |not measured |6 dB 4) |

|Channel load interferer |N/A |2% |1 timeslot 1) |Various (see table below)|

| | | |4 timeslots 1) | |

Table 2

1) maximum loading of timeslots; with four timeslots operating on VDL Mode 3, only the squelch break for the DSB-AM receiver was tested. However, this is not longer mentioned in Appendix E.

2) only aircraft DSB-AM receivers were considered.

3) measured against audio voice “Non sens measurement”

4) not tested; the SINAD reduction corresponding to a 6 dB S/P was checked. S/P is the best criteria to reflect the audio perception of the interference

(SINAD is the signal + noise + distortion to noise + distortion ratio. (S+N+D)/(N+D)

5) Accepted values after evaluation of audio samples of interference.

|Parameter |DSB-AM |DSB-AM |VDL-M2 |VDL-M2 |VDL-M3 |VDL-M3 |VDL-M$4 |VDL-M4 |

|TRANSMITTER |Airborne |Ground |Airborne |Ground |Airborne |Ground |Airborne |Ground |

|Output power transmitter |44 dBm |50 dBm |42 dBm |42 dBm |44 dBm |44 dBm |43 dBm |45 dBm |

| |(25 W) |(100 W) |(16 W) |(16 W) |(25 W) |(25 W) |(20 W) |(32 W) |

|Feeder loss (assumed) |-3 dB |-3 dB |-3 dB |-3 dB |-3 dB |-3 dB |-3 dB |-3 dB |

|Antenna gain (assumed) |0 dB |2 dB |0 dB |2 dB |0 dB |2 dB |0 dB |2 dB |

|EIRP |41 dBm |49 dBm |39 dBm |41 dBm |41 dBm |43 dBm |44 dBm |44 dBm |

| |(12.5 W) |(80 W) |(8W) |(12.5 W) |(12.5 W) |(20 W) |(10 W) |(25 W) |

|Adjacent channel emission (Transmitter) |

|1st adj ch.(16kHz) | | |-18 dBm |-18 dBm |-18 dBm |-18 dBm |-18 dBm |-18 dBm |

|2nd adj ch. | | |-28 dBm |-28 dBm |-28 dBm |-28 dBm |-28 dBm |-28 dBm |

|4th adj ch. | | |-38 dBm |-38 dBm |-38 dBm |-38 dBm |-38 dBm |-38 dBm |

|8thadj ch. | | |-43 dBm |-43 dBm |-43 dBm |-43 dBm |-43 dBm |-43 dBm |

|16th adj ch. | | |-48 dBm |-48 dBm |-48 dBm |-48 dBm |-48 dBm |-48 dBm |

|32nd adj ch. | | |-53.dBm |-53.dBm |-53.dBm |-53.dBm |-53.dBm |-53.dBm |

|RECEIVER |

|Min signal at receiver antenna |75 (V/m |20 (V/m |75 (V/m |20 (V/m |75 (V/m |20 (V/m |75 35 (V/m |35 (V/m |

|Annex 10, Vol. III |(-82 dBm) |(-93 dBm) |(-82 dBm) |(-93 dBm) |(-82 dBm) |(-93 dBm) |(-82 88 *dBm) |(-88 dBm) |

| |part II |part II |part I |part I |part I |part I |part I |part I |

|Min. signal at antenna as per App. C |2.3.2.2.1 |2.2.2.2 |6.2.2. |6.3.5.2 |6.2.2. |6.3.5.2 |6.9.5.1.1.21 |6.9.5.1.1.1 |

|(WG/B13) |75 (V/m |20 (V/m |20 (V/m |20 (V/m |20 (V/m |20 (V/m |35 (V/m |35 (V/m |

| |(-82 dBm) |(-93 dBm) |(-93 dBm) |(-93 dBm) |(-93 dBm) |(-93 dBm) |(-88 dBm) |(-88 dBm) |

|Feeder loss |3 dB |3 dB |3 dB |3 dB |3 dB |3 dB |3 dB |3 dB |

|Antenna gain |0 dB |2 dB |0 dB |2 dB |0 dB |2 dB |0 dB |2 dB |

|Min. signal at receiver input |-85 dBm |-94 dBm |-85 dBm |-94 dBm 1) |-85 dBm |-94 dBm |-85 dBm |-89 dBm |

|Min. signal at receiver input as per | | | | | | | | |

|App. D (B/13) |-82 dBm |-93 dBm |-82 dBm |-82 dBm* | | |-88 dBm |-88 dBm |

|Min. signal at receiver input as per | | | | | | | | |

|App. E (B/13) |-82 dBm |-93 dBm |-82 dBm |-93 dBm |-82 dBm |-93 dBm |-88 dBm |-88 dBm |

|Adjacent channel rejection (Receiver) |

|1st adj. Ch | | |-40 dB |-40 dB |-40 dB |-40 dB |-40 dB |-40 dB |

|3rd 4th adj. Ch | | |-60 dB |-60 dB |-60 dB |-60 dB |-60 dB |-60 dB |

Table 1

1) Since the required value of the SARPs could not be measured, a value of -85 dBm (equivalent to 75 (V/m) is to be used in the testing.

* Aircraft can receive from another aircraft

Note Secr.: the differences between values in Annex 10 and the appendices in the Report of WG B12/13 need to be clarified.

3. Testing parameters

3.1. Interfered Station (receiver): DSB-AM (air and ground receiver)

minimum (desired) signal level at receiver input: ground stations -94 dBm

aircraft stations -85 dBm

|Interfering station |DSB-AM |VDL M2 |VDL M3 2) |VDL M4 |

|S/P ratio 5) |N/A |6 dB |18 dB 2) |12 dB |

|S+N/N |N/A |6 dB |not measured |6 dB 4) |

|Channel load interferer |N/A |2% |1 timeslot 1) |Various (see table below)|

| | | |4 timeslots 1) | |

Table 2

1) maximum loading of timeslots; with four timeslots operating on VDL Mode 3, only the squelch break for the DSB-AM receiver was tested. However, this is not longer mentioned in Appendix E.

2) only aircraft DSB-AM receivers were considered.

3) measured against audio voice

4) not tested; the SINAD reduction corresponding to a 6 dB S/P was checked.

(SINAD is the signal + noise + distortion to noise + distortion ratio. (S+N+D)/(N+D)

5) Accepted values after evaluation of audio samples of interference.

3.2 Interfered Station (receiver) VDL Mode 2 (air and ground receiver)

minimum (desired) signal level at receiver input: ground stations: -94 93 dBm (see note 1) to Table 1)

aircraft stations: -825 dBm

channel load 20% (for testing with VDL Mode 4: 100%**)

bit error rate for VDL Mode 2: 1 in 103 (uncorrected)

|Interfering station |DSB-AM |VDL M2 |VDL M3 |VDL M4 |

|Channel load interferer |100% |2% | |100%1) |

Table 3

1)correction factors need to be applied. These are under development.

3.3 Interfered Station (receiver) VDL Mode 3 (air and ground receiver) 1)

minimum (desired) signal level at receiver input: ground stations: -94 dBm (see note 1) to Table 1)

aircraft stations: -85 dBm

bit error rate for VDL Mode 3: 1 in 103 (uncorrected)

|Interfering station |DSB-AM |VDL M2 |VDL M3 |VDL M4 |

| | | | | |

| | | | | |

| | | | | |

Table 4

1) No testing had been carried out on VDL Mode 3 equipment.

3.4 Interfered Station (receiver) VDL Mode 4 (air and ground receiver)

minimum (desired) signal level at receiver input: ground stations -89 88 dBm

aircraft stations --8885 dBm

channel load: 100 % (only aircraft stations were considered)

message error rate (MER): 2 in 102 which corresponds to a uncorrected bit error rate of 1 in 104.

| Interfering station |DSB-AM |VDL M2 |VDL M3 |VDL M4 |

|Channel load interferer | |100%(?) 1) | |Various 1) (see |

| | | | |Paragraphs 3.5 and 3.6 |

| | | | |below) |

Table 5

1) correction factors need to be applied

Note: MER = 1-(1-BER)216 where 216 equals to maximum number of data bits in a VDL-Mode 4 message.

3.5 VDL Mode 4 interferer channel loading

| |Channel loading of interferer |

|Channel type | |

| |Scenario 1 |Scenario 2 |Scenario 4 |

| |Aircraft on ground vs |Aircraft on ground vs ground station |Aircraft vs aircraft both |

| |aircraft on ground | |airborne |

| | |Case A – ground station as |Case B – aircraft as | |

| | |interferer |interferer | |

|ADS-B |6.7 % |3.3 % |6.7 % |0.44 % |

| |5 x 1-slot per second |3 x 1-slot plus 1 x 2-slot |5 x 1-slot per second |1 x 1-slot per three seconds|

| | |per two seconds | | |

|Point-to-poin|1.7 % |40 % |1.7 % |0.33 % |

|t comms | | | | |

| |5 x 1-slot and 5 x 2-slot |10 x 1-slot plus 20 x 2-slot|5 x 1-slot and 5 x 2-slot |1 x 1-slot and 1 x 2-slot |

| |per 12 seconds |per second |per 12 seconds |per 12 seconds |

|TIS-B |0 % |90 % |0 % |0 % |

| |- |22 x 3-slot per second |- |- |

Table 6

3.6 Summary of VM4 victim loadings

| |Channel loading of victim |

|Channel type | |

| |Scenario 1 |Scenario 2 |Scenario 4 |

| |Aircraft on ground vs |Aircraft on ground vs ground station |Aircraft vs aircraft both |

| |aircraft on ground | |airborne |

| | |Case A – aircraft as victim |Case B – ground station as | |

| | | |victim | |

|ADS-B |1.3 % |1.3 % |3.3 % |0.44 % |

| |1-slot per second |1-slot per second |3 x 1-slot and 1 x 2-slot |1 x 1-slot per three seconds|

| | | |per two seconds | |

|Point-to-poin|0.33 % |0.33 % |40 % |0.33 % |

|t comms | | | | |

| |1 x 1-slot and 1 x 2-slot |1 x 1-slot and 1 x 2-slot |10 x 1-slot and 20 x 2-slot |1 x 1-slot and 1 x 2-slot |

| |per 12 seconds |per 12 seconds |per second |per 12 seconds |

|TIS-B |0 % |0 % |90 % |0 % |

| |- |- |22 x 3-slot per second |- |

Table 7

4. Test methods

[pic]

4.1 Impact of VDL signal on DSB-AM receiver (measuring of D/U ratio)

4.1.1 The test methods in 4.1.1.1, and 4.1.1.2 below can be used to asses the impact of VDL signals into a DSB-AM receiver and are based on measuring the ratio of power of the interfered (desired) and interfering (undesired) signal levels at the receiver input.

4.1.2. Tests on adjacent channel were made with 25 kHz increments. On the basis of a theoretical comparison of the R/F front end of receivers designed for 25 kHz and 8.33 kHz channel spacing, it was shown that measurements made with 25 kHz equipment would also comply with 8.33 kHz equipment. The results are presented with reference to the adjacent channel number, rather that the adjacent channel frequency and are equally applicable when assigning frequencies in an 8.22 and 25 kHz environment. Special attention needs to be given when the DSB-AM system is operating in a mixed (25/8.33 kHz) environment.

4.1.1.1 Test procedure for measuring the squelch break

a. No desired DSB-AM signal is present

b. Co-channel operation. The undesired VDL signal source is tuned to the same frequency as the DSB-AM receiver and the undesired VDL signal level is increased until the squelch is broken. The level is recorded.

c. Adjacent channel operation. The undesired VDL signal source is tuned to the 1st, 2nd, 3rd, 4th, 5th, 10th, 20th and 40th adjacent channel with increments of 25 kHz for DSB-AM equipment with a channel spacing of 25 kHz and 8.33 kHz for DSB-AM equipment with a channel spacing of 8.33 kHz. The undesired VDL signal level is increased until the squelch is broken. The level is recorded.

4.1.1.2 Test procedure for measuring on-channel interference. (Evaluation of the effect of the interference on the audio output of the receiver)

a. The desired DSB-AM signal source is set to produce a signal level of

-85dBm (for aircraft receiver testing) or -94dBm (for ground equipment testing) at the DSB-AM receiver input, 30% amplitude modulated and with ATC phrases at the input of the DSB-AM receiver

b. The undesired VDL signal source is set to give a 30 dB D/U (VDL mode 3 only) the center frequency of the desired AM signal. The DSB-AM receiver is tuned to the same frequency. And a recording is made of the audio output from the receiver [for each adjacent channel].

c. The undesired VDL signal is then increased to give a 30 dB D/U (VDL mode 3 only) in the pass band of the receiver on the first and subsequent adjacent channels and a recording made of the audio output from the receiver for each adjacent channel.

d. A listening panel then assesses the quality of the audio results recorded, scoring each.

4.2 Test procedure for measuring the impact of VDL signal on DSB-AM receiver. (Measuring of (Signal + Noise) to Noise ratio ((S+N)/N and Signal to Pulse (S/P) ratio).

4.2.1 The test methods in 4.2.1.1, 4.2.1.2 and 4.2.1.3 below can be used to assess separately the effects of a digital signal on a DSB-AM receiver. By separating the effects of the pulse [modulation] and [continuous] modulation of a digital signal on the audio signal, these two objective parameters can be separately measured and tested. In the presence of a desired signal, the signal + noise to noise ((S+N)/N) ratio and signal to pulse (S/P) ratio as specified in Table 2 are considered [at the output of the receiver]. The level of acceptability of these (S+N)/N ratios and S/P ratios was established through varying the ratios level and through conducting subjective tests with audio samples.

4.2.1.2 Test method for measuring the (S+N)/N radio degradation.

a. The desired DSB-AM signal source is set so as to produce either a signal level of –85dBm (for airborne DSB-AM receiver) or –94dBm (for ground DSB-AM receiver) at the DSB-AM receiver input, 30% amplitude modulated with a 1kHz tone. The DSB-AM receiver is tuned to the same frequency as the desired DSB-AM signal source.

b. Co-channel operation. The undesired VDL signal source is set in continuous mode 1) with a center frequency equal to that of the DSB-AM receiver. The level of undesired VDL signal source at the input of the DSB-AM receiver is varied until a (S+N)/N degradation on the audio output of 6 dB (VDL modes 2 & 3 only) is measured at the audio output of the receiver. The level of the undesired VDL signal source at the receiver input is noted.

c. 1st adjacent channel operation. The undesired VDL signal source is set in continuous mode with a center frequency offset by one RF channel (first adjacent channel) from the frequency to which the DSB-AM receiver is tuned. The level of the undesired VDL signal soured at the input of the DSB-AM receiver is varied until a (S+N)/N degradation at the audio output of the DSB-AM receiver of 6 dB (VDL modes 2 & 3 only) is measured The level is noted.

d. 2nd adjacent channel operation and beyond. The undesired VDL signal source is then tuned to the next adjacent channel (second adjacent channel) and the level of the signal of the undesired VDL signal source at the input of the DSB-AM receiver is varied until a (S+N)/N degradation at the audio output of the receiver of 6 dB is measured. The level is noted. The audio distortion is checked to ensure that it is less than 10%. If this is not the case then the undesired VDL signal which is level required to achieve 10% audio distortion is measured and noted.

d. This is repeated for the 3rd, 4th, 5th, 10th, 20th & 40th adjacent channel

1) Continuous mode refers to a continuous transmission of data. This is obtained by removing the ramp up and ramp down sequences in the VDL, which results in VDL Mode 3 having the same continuous mode characteristics as VDL Mode 2 since these two systems have the same physical layer.

4.2.1.3 Test method for measuring the signal-to-pulse (S/P) ratio.

a. The desired DSB-AM signal source signal is set so as to produce either a signal level of –82dBm (for airborne DSB-AM receiver) or –93dBm (for ground DSB-AM receiver), 30% modulated 1kHz tone at the input of the victim receiver. The DSB-AM receiver is tuned to the same frequency as the desired DSB-AM signal.

b. Co-channel operation. The undesired VDL signal source is set in pulse (burst) mode with a center frequency equal to that of the DSB-AM receiver. The level of the undesired VDL signal source at the input of the DSB-AM receiver is varied until the level of the audio pulses 1) is 6 dB (VDL modes 2 & 3 only) below the nominal audio peak level (the audio pulse level being half of the nominal audio peak level). This level is noted.

c. Adjacent channel operation. The undesired VDL signal source is set in pulse (burst) mode with a center frequency offset by one channel (first adjacent 25 or 8.33 kHz channel) from the frequency to which the DSB-AM receiver is tuned and the level of the undesired VDL signal source at the input of the DSB-AM receiver is varied until level of the audio pulses 1) is 6 dB (VDL modes 2 & 3 only) below the nominal audio peak level (the audio pulse level being half of the nominal audio peak level). This level is recorded.

d. The undesired VDL signal source is then set to the 2nd, 3rd, 4th, 5th, 10th, 20th & 40th adjacent channel and the level of signal at the input of the DSB-AM receiver is varied until the audio pulse 1) level is 6 dB below the nominal audio peak level and the level noted.

1) Audio pulses are the remaining pulses on the interfered audio signal and are caused through the ramp up and ramp down sequences of the VDL.

Note: when testing the interference from VDL Mode 2 into the DSB-AM receiver, it was observed that the adjacent channel rejection (ACR) obtained when measuring the (S+N)/N ratio is within the same range when measuring the S/P ratio. Therefore only the channel rejection characteristics obtained when measuring S/P ratios were considered

4.3. Test procedure for assessing the impact of either a undesired DSB-AM signal or undesired VDL signal on a VDL Mode 2 or Mode 3 receiver.

4.3.1 Test method for measuring the bit error rate of the VDL.

a. The desired VDL signal source is set so as to produce either a signal level of –82 dBm (for airborne VDL receiver) or –93 dBm (for ground VDL receiver)at the input of the VDL receiver input. The VDL receiver is tuned to the same frequency as the desired VDL signal source.

b. Co-channel operation. The undesired VDL or DSB-AM signal source is tuned to the same frequency as the VDL receiver. The level of the undesired signal VDL or DSB-AM source is increased until the bit error rate, as specified in section 3 is below the required value. The level of the undesired signal source at the input of the VDL receiver is noted. The characteristics of the undesired signal source are as specified in section 3.

c. Adjacent channel operation. The undesired VDL or DSB-AM signal source is tuned to the 1st, 2nd, 3rd, 4th, 5th, 10th, 20th, and 40th adjacent channel of the VDL receiver. The level of the undesired signal VDL or DSB-AM source is increased until the bit error rate, as specified in section 3 is below the required value. The level of the undesired signal source at the input of the VDL receiver is noted. The characteristics of the undesired signal source are as specified in section 3.

4.4. Test procedure for assessing the impact of an undesired VDL Mode 4 signal on VOR or ILS receiver. (Source: Report WG B12/13, Appendices I and J.)

4.4.1 VOR receiver testing (see test setup below).

a. Characteristics of the VOR

(i) Channel spacing for VOR receiver is 50 kHz

ii) Co- and adjacent channel interference shall be measured (1st, 2nd, 3rd

and 4th adjacent VDL Mode 4 channel with 25 kHz increments).

(iii) A change in the VOR bearing of 0.3o due to the interference of VDL Mode 4 shall be considered as interference threshold. (A change of 0.3o in the selected VOR bearing corresponds to a deviation in the VOR course indicator of 4.5 (A).

(iv) VOR frequencies 112 MHz, 115 MHz and 117.975 MHz shall be tested.

(v) The level of the VOR signal at the input of the VOR receiver shall be set at –79 dBm.

b. Characteristics of the VDL Mode 4 signal.

(i) The VDL Mode 4 interference source shall be incremented in steps of 25 kHz.

ii) The following VDL Mode 4 duty cycles shall be investigated:

1. 1.3% duty cycle (one sync burst in one slot every second), simulating the worst case co-site (on-board an aircraft) scenario).

2. 2.7% duty cycle (two slot burst transmissions in every second slot), simulating the worst case co-site (on-board) scenario for transmission of e.g. TCP-information.

3. 50% duty cycle (sync burst transmissions in very second slot), simulating a medium dense scenario of interferers at equal distance

4. 50% duty cycle (two slot transmissions in every other two slots), simulating a medium dense scenario of interferers at equal distance.

The undesired VDL Mode 4 signal is then increased to produce a change in the VOR bearing of 0.30.

5. The undesired VDL Mode 4 signal is then increased to produce a change in the VOR bearing of 0.30. This corresponds to a change in the course deflection current of 4.5 (A.

Note: 50% duty cycle leads to a beat frequency of 37 Hz. VOR’s are rather sensitive against low beat frequencies in the order of 30 Hz. This scenario should be considered as a medium dense scenario with interferes at equal distance.

4.4.2 ILS-Localizer receiver testing (same test setup as for VOR)

a. Characteristics of the ILS-Localizer

(i) Channel spacing for ILS-Localizer receiver is 50 kHz

iii) Co- and adjacent channel interference shall be measured (1st, 2nd, 3rd

and 4th adjacent VDL Mode 4 channel with 25 kHz increments).

(iii) A change in the ILS-Localizer difference in depth of modulation (DDM) of 0.093 due to the interference of VDL Mode 4 shall be considered as interference threshold. (A change of 0.093 in the DDM corresponds to a deviation in the ILS course indicator of 4.5 (A).

(iv) ILS-Localizer frequencies 111.95 MHz shall be tested.

(v) The level of the ILS-Localizer signal at the input of the Localizer receiver shall be set at –86 dBm.

b. Characteristics of the VDL Mode 4 signal.

(i) The VDL Mode 4 interference source shall be incremented in steps of 25 kHz.

iii) The following VDL Mode 4 duty cycles shall be investigated:

1. 1.3% duty cycle (one sync burst in one slot every second), simulating the worst case co-site (on-board an aircraft) scenario).

2. 2.7% duty cycle (two slot burst transmissions in every second slot), simulating the worst case co-site (on-board) scenario for transmission of e.g. TCP-information.

3. 50% duty cycle (sync burst transmissions in very second slot), simulating a medium dense scenario of interferers at equal distance

4. 50% duty cycle (two slot transmissions in every other two slots), simulating a medium dense scenario of interferers at equal distance.

5. The undesired VDL Mode 4 signal is then increased to produce a change in the ILS-Localizer bearing of 0.093 DDM. This corresponds to a change in the course deflection current of 4.5 (A..

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Notes

1. Throughout this document, the minimum signal levels at the receiver input have been amended, compared with the Report of WG B12/13 for the following reasons

1.1 Annex 10 stipulates that the minimum field strength by an airborne transmitter shall be at least 20 (V/m at the antenna of the DSB-AM ground station. This converts to an isotropically received power of -93 dBm and with an antenna gain of 3 dB and feeder losses of 2 dB, the signal level at the ground receiver input shall be at least -94 dBm. Similarly, the minimum signal level at the airborne receiver shall be at least -85 dBm.

(Re. Annex 10, Volume III, Part II, paragraph 2.3.2.2.1)

1.2. For VDL Mode 2/3, the minimum signal levels, following the same methodology as above, shall be -94 dBm at the ground receiver and -85 at the airborne receiver.

(Re. Annex 10, Volume III, Part I, paragraph 6.2.2.and 6.3.2)

1.3 For VDL Mode 4, the minimum signal levels at the receiver input shall be -85 dBm for the airborne receiver and -89 dBm at the ground receiver.

Throughout this paper, these values have been used. In the various parts of the Report of WG B, other values have been identified and their use may need further clarification

See the attached paper

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

5. Protection requirements.

Note: When this paragraph reference is made to adjacent channels, this refers to the actual adjacent channel number. The actual frequency separation of the adjacent channel may vary depending on the channel separation in use (i.e. 25 kHz or 8.33 kHz) for DSB-AM systems. No information is currently available when the DSB-AM channel separation is 50 kHz or more.

5.1 VDL Mode 2

5.1.1 VDL Mode 2 and DSB-AM systems

The following interference scenarios have been analyzed:

(Source: WG B/11, WP5)

(i) interference from VDL Mode 2 into DSB-AM systems

(ii) interference from DSB-AM systems into VDL Mode 2

5.1.1.1 Interference caused by VDL Mode 2 into DSB-AM systems

5.1.1.1.1 Co-channel interference

No measurements addressing the co-channel interference from DSB-AM into VDL Mode 2 and from VDL Mode 2 into DSB-AM have been presented. Although in general, VDL Mode 2 and DSB-AM systems may not operate within the same or overlapping designated operational coverage (DOC), a co-channel protection requirement needs to be developed in order to assess co-channel assignments in not overlapping airspace (e.g. to assess co-frequency assignments between different ICAO Regions).

5.1.1.1.2 Adjacent channel interference

5.1.1.1.2.1 Annex 10, Volume III, Part II contains the immunity criteria for DSB-AM receiving systems against interference from any VDL station as follows:

…….

|2.3.2.8    VDL C Interference immunity |

|performance |

| |

|2.3.2.8.1    For equipment intended to be used in independent operations of services applying DSB-AM and VDL technology on board the same |

|aircraft, the receiving function shall provide an adequate and intelligible audio output with a desired signal field strength of not more than|

|150 microvolts per metre (minus 102 dBW/m2) and with an undesired VDL signal field strength of at least 50 dB above the desired field strength|

|on any assignable channel 100 kHz or more away from the assigned channel of the desired signal. |

| |

|Note.C This level of VDL interference immunity performance provides a receiver performance consistent with the influence of the VDL RF |

|spectrum mask as specified in Volume III, Part I, 6.3.4 with an effective transmitter/receiver isolation of 68 dB. Better transmitter and |

|receiver performance could result in less isolation required. |

……..

This provision would require the assigned (desired) DSB-AM channel (frequency) to function properly with a desired signal level of -76 dBm a the DSB-AM receiver input and a (undesired) VDL signal of -26 dBm at 100 kHz or more away from the desired DSB-AM channel (frequency) and corresponds with a 50 dB adjacent channel rejection of any such VDL signal at 100 kHz. It is assumed that the 50 dB adjacent channel rejection applies also under the condition when the desired signal field strength equals 75 (V/m (-82 dBm).

5.1.1.1.2.2 This Standard is not specific about adjacent channel rejection with a frequency separation less than 100 kHz (for 25 kHz DSB-AM systems) and furthermore needs to be amended for 8.33 kHz systems. It may be better to refer to the adjacent channel number.

5.1.1.1.2.3. An adjacent channel reduction (ACR) of -50 dB would require in the air-to-air interference mode a geographical separation of about 500 meters between aircraft. The operational scenario is not expecting geographical separation distances of less than 600 m (vertical separation) between aircraft.

5.1.1.1.2.4 Measurements on a number of aircraft DSB-AM receivers (in accordance with the test method in paragraph 4.2.1.3) demonstrated the following ACR.

|channel |A1 |B1 |C1 |D1 |E1 |F1 |G1 |I1 |worst |

| | | | |GS | | | | |case |

|1 |52 |41 |55 |32 |42 |53 |55 |42 |32 |

|2 |72 |59 |63 |52 |52 |62 |62 |68 |52 |

|3 |76 |63 |61 |60 | |70 |70 |71 |60 |

|4 |78 |70 |69 |61 |60 |73 |75 |74 |61 |

|5 |80 |75 |68 |68 | |75 |75 |76 |68 |

|10 |80 |77 |69 |69 |68 |80 |75 |81 |68 |

|20 |79 |78 |68 |74 |71 |90 |74 |86 |69 |

|40 |81 |78 |69 |73 |75 |93 |73 |84 |69 |

Table 8 Adjacent channel rejection test results S/P=6dB; f-136 MHz

Note: ACR test results for lower frequencies give slightly better ACR.

5.1.1.2 Interference caused by VDL Mode 2 into DSB-AM systems

5.1.1.2.1 Co-channel interference

No measurements addressing the co-channel interference from DSB-AM into VDL Mode 2 and from VDL Mode 2 into DSB-AM have been presented. Although in general, VDL Mode 2 and DSB-AM systems may not operate within the same or overlapping designated operational coverage (DOC), a co-channel protection requirement needs to be developed in order to assess co-channel assignments in not overlapping airspace (e.g. to assess co-frequency assignments between different ICAO Regions).

5.1.1.2.2 Adjacent channel interference

5.1.1.2.2.1 Annex 10, Volume III, Part I contains the immunity criteria for VDL aircraft receiving systems against interference from any source (VDL or DSB-AM) as follows:

………

|6.3.5.3    Out-of-band immunity performance. The receiving function shall satisfy the specified error rate with a desired signal field |

|strength of not more than 40 microvolts per metre (minus 114 dBW/m2) and with an undesired DSB-AM D8PSK or GFSK signal on the adjacent or any |

|other assignable channel being at least 40 dB higher than the desired signal. |

| |

|6.3.5.3.1    After 1 January 2002, the receiving function of all new installations of VDL shall satisfy the specified error rate with a |

|desired signal field strength of not more than 40 microvolts per metre (minus 114 dBW/m2) and with an undesired VHF DSB-AM, D8PSK or GFSK |

|signal at least 60 dB higher than the desired signal on any assignable channel 100 kHz or more away from the assigned channel of the desired |

|signal. |

|Note.C This level of interference immunity performance provides a receiver performance consistent with the influence of the VDL RF spectrum |

|mask as specified in Volume III, Part I, 6.3.4 with an effective isolation transmitter/receiver isolation of 69 dB. Better transmitter and |

|receiver performance could result in less isolation required. Guidance material on the measurement technique is included in Annex 10, Volume |

|V, Attachment A, section 7. |

|……………. |

| |

|6.3.5.4    Interference |

|immunity performance |

| |

|6.3.5.4.1    The receiving function shall satisfy the specified error rate with a desired field strength of not more than 40 microvolts per |

|metre, and with one or more out-of-band signals, except for VHF FM broadcast signals, having a total level at the receiver input of minus 33 |

|dBm. |

| |

|Note.C In areas where adjacent higher band signal interference exceeds this specification, a higher immunity requirement will apply. |

……

5.1.1.2.2.2. This Standard requires the assigned (desired) VDL channel (frequency) to function properly with a desired signal level of -88 dBm at the VDL receiver input and a (undesired) DSB-AM signal of -48 dBm (or any other VDL signal) at the first, second and third adjacent channel (in a 25 kHz assignment environment) or -28 dBm at the fourth and beyond adjacent channels. These adjacent channel characteristics correspond with a 40 dB adjacent channel rejection between 0 - 100 kHz and 60 dB beyond. It is assumed that the adjacent channel rejection applies also under the condition when the desired signal field strength equals 75 (V/m (-82 dBm).

5.1.1.2.2.3. Measurements on one aircraft VDL Mode 2receiver (in accordance with the test method in paragraph 4.3.) demonstrated the following ACR.

|channel |Annex 10 |A3 |

|1 |40 |32 |

|2 |40 |60 |

|3 |40 |60 |

|4 |60 |66 |

|5 |60 |69 |

|10 |60 |71 |

|20 |60 |74 |

|40 |60 |78 |

Table 9 Adjacent channel rejection test results BER 1 in 103; f=128 MHz

5.1.1.3 It was concluded that the ACR for VDL being interfered with DSB-AM systems is (slightly) better that when DSB-AM systems are being interfered with VDL. Therefore, the calculation of minimum geographical separation distances concentrates on the protection of DSB-AM systems.

Note: It is recommended to re-write the immunity requirements for VDL Mode 2 and DSB-AM systems in order to provide for the specific signal characteristics of the interferer. The following ACR figures are proposed (for the airborne stations)

|channel |DSB-AM interfered by VDL |VDL Mode 2 |

| |Mode 2 |interfered by |

| | |DSB-AM |

| |Annex 10 | |Annex 10 | |

| |(current) | |(current) | |

|1 | |32 |40 |32 |

|2 | |52(50?) |40 |60 |

|3 | |60 |40 |60 |

|4 |50 |60 |60 |60 |

|5 |50 |60 |60 |60 |

|10 |50 |60 |60 |60 |

|20 |50 |60 |60 |60 |

|40 |50 |60 |60 |60 |

Table 10 Proposed revised adjacent channel characteristics for DSB-AM and VDL Mode 2 systems

5.1.1.3 Squelch break

The squelch break for DSB-AM receivers was measured with VDL Mode 2 signal levels greater than 0 dBm. on the second and beyond adjacent channel. It was therefore considered that squelch break is not a parameter to be considered in frequency assignment planning.

Note: no information is available on the squelch break characteristics with VDL Mode 2 signals on the first adjacent channel.

6. Frequency assignment planning criteria

6.1 Propagation model

Separation distances shall be calculated on the basis of free space propagation.

The transmission loss (path loss) using free space propagation characteristics can be calculated as follows:

Transmission loss (dB) = 20log(f) + 20 log(d) +32.4 (Re. ITU R Recommendation.525-2) (1)

f = MHz

d = km

2 Interference model

[pic]

Pd - Pu = D/U = Pd - {(Tu +Lu + Gu) -Lbf} where: Pd, Pu and Tu are expressed in dBm (2)

Lu, Gu and Lbf are expressed in dB

From (1) and (2) the separation distance can be calculated by:

20log(d) = D/U - Pd +Tu + L + Gu - 20log(f) - 34.2

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