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exceeds this specification, a higher immunity requirement
will apply.
6.3.5.4.2 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 VBF FM
broadcast signals having a total level at the receiver input of
minus 5 dBm.
6.4 PHYSICAL LAYER
PROTOCOLS AND SERVICES
The aircraft and ground stations shall access the physical
medium operating in simplex mode.
6.4.1 Functions
6.3.5.2 Sensitivity. Thc receiving function shall satisfy 6.4.1.1 The physical layer shall provide the following
the specified error rate with a desired signal strength of not functions:
more than 20 microvolts per metre (minus 120 d13w/m2)
(minus 87 dBm). a) transmitter and receiver frequency control;
Note.- The required signal strength at the edge of the
service volume rakes into account the requirements of the
system and signal losses within the system, and considers
environmental noise sources.
6.3.5.3 Undesired signal rejection. 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 d ~ ~ / (mmin~us) 81 dBm) and with an undesired signal
on the adjacent or any other assignable channel at least 40 dB
higher than the desired signal.
6.3.5.3.1 Recommendation.- The receiving furzction
should satisfy the specwed error rate with a desired signal
field strength of not more than 40 microvolts per metre (minus
114 dBw/m2) (minus 81 dBm) and with an undesired signal on
the adjacent or any other assignable channel at least 60 dB
higher than the desired signal.
Note.- Guidance material on the measurement technique
is included in Annex 10, Volume Y 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
b) data reception by the receiver;
c) data transmission by the transmitter; and
d) notification services.
6.4.1.1.1 Transmitter/receiver frequency control. The
VDL physical layer shall set the transmitter or receiver
frequency as commanded by the link management entity
(LME).
Note.- The LME is a Link layer entity specified in 6.5.
6.4.1.1.2 Data reception by the receive^ Signals
received shall be decoded so that they may be accurately read
at the higher layers.
6.4.1.1.3 Data transmission. The VDL physical laycr
shall appropriately encode the data received from the data link
layer and transmit it over the RF channel.
6.4.1.1.4 NbtBcation services. The operational parameters
of the equipment shall be monitored at the physical
layer. Signal quality analysis shall be performed on the
demodulator evaluation process and on the receive evaluation
process; this analysis shall be normalized between a scale of
0 and 15, where 0 to 3 is considered poor, 4 to 12 is adequate,
and 13 to 15 is excellent.
-6/11WI
No. 72
Annex 10 - Aeronautical Telecommunications Volume 111
Note.- Processes that may be evaluated in the demodu- Note.- It is not necessary to transmit all 128 ones. The
lator irlclude BER, SNR, and riming jitter: Processes that may next phase of the training sequence should begin as soon as
be evaluated in the receiver include received signal level and the transmitter has reached 90 per cent power output.
group delay.
6.4.2.1.3.2 Continuous wave tone. After the transmitter
6.4.1.1.4.1 Recommendation.- The signal quality has stabilized, a CW tone consisting of 88 binary ones, shall
analysis should be based on received signal strength. be transmitted,
6.4.2 Mode 1 frames
6.4.2.1 To transmit a sequence of frames, a station shall
insert the bit numbers and flags (as per 6.5.3.3.1), prepend the
training sequence (as per 6.4.2.1.3) and finally encode and
modulate the RF signal (as per 6.4.2.1.1, 6.4.2.1.1.1 and
6.4.2.1.4).
6.4.2.1.1 Modulation scheme. Mode 1 shall use an
amplitude-modulated minimum shift keying (AM-MSK) modulation
scheme, which is a constant-phae, frequency shift
keying technique using two tones. The presence of the lower
tone of a tone pair shall indicate a bit change from the
previous bit. The presence of the higher tone shall indicate that
there is no bit change. The phases of the two tones shall be
chosen so that the minimum phase discontinuity occurs at the
interface with the preceding bit and so that the amplitude of
each tone is zero at the bit transition. The slope of the
waveforms at the and of a bit cell shall be positive for a
binary one and negative for a binary zero.
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