曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
the receiver include received signal level and group delay.
6.9.5.3.1 Estimation of naiseftoor A VDL Mode 4 station
6.9.5.1 S.2 Arrival time. The arrival time of each received shall estimate the noise floor based on power measurements of
transmission shall be measured with a two-sigma enor of 5 the channel whenever a valid training sequence has not been
microseconds. detected.
6.9.5.1.5.3 Recommendation.- The receiver should be 6.9.5.3.2 The algorithm used to estimate the noise floor
capable of the arrival time within a wo-sigma shall be such that the estimated noise floor shall be lower than
error of I microsecond. che maximum power value measured on the channel over the
last minute when the channel is regarded as idle.
Note.- The VDL Mode 4 receiver uses an energy sensing
6.9.5.2 PROTOCOL DEFINITION FOR GFSK algorithm as one of fhe means to determine the state of the
chunnel (idle or busy). One algorithm that can be used to
6'9.5.2.1 Modulation scheme. The modulation scheme estimate the noise floor is described in the Manual on VDL
shall bc GFSK. The first bil transmitted (in the training Mode 4 Technical S~ecificutionssequence)
shall be a high tone and the transmitted tone shall
be toggled before transmitting a 0 (i.e. non-return to zero 6.9.5.3.3 Channel idle to busy detection. A VDL Mode 4
inverted encoding). station shall employ the following means to determine the
channel idle to busy transition ar the physical layer.
6.9.5.2.2 Modtilafion mte. Binary ones and binary zcros
shall be gentrated with a modulation index of 0.25 2 0.03 and 6.9.5.3.3.1 Detection of a training sequence. The channel
a BT producc of 0.28 ? 0.03, producing data Iransmission at a shall be declared busy if a VDL Mode 4 station detects a valid
bit rate of 19 200 bits/s r 50 ppm. training sequence followed by a frame flag.
1/11/01
No. 76
Annex 10 - Aeronautical Telecommunications Volume III
6.9.5.3.3.2 Measurement of charznel power; Regardless of
the ability of the demodulator to detect a valid training
sequence, a VDL Mode 4 station shall consider thc channel
busy with at least a 95 per cent probability within 1 ms after
on-channel power rises to rhe equivalent of at least four times
the estimated noise floor for at least 0.5 milliseconds.
Note.- Nominal performcmce is defined as u bit error rate
(BER) of 1 om".
6.9.5.5 PHYSICALLA YER SYSTEM PARAMETERS
6.9.5.5.1 Parameter PI (minimum transnzission length)
6.9.5.3.4 Ch,atznel busy to idle detection
6.9.5.3.4.1 A VDL Mode 4 station shall employ the
following means to detennine the channel busy to idlc
transition.
6.9.5.3.4.2 Mcasuremen,t of transmission length. Whcn
the training sequence has been detected, the channel busy
state shall be held for a period of time at least equal to
5 milliseconds, and subsequently allowed to transition to the
idle state based on measurement of channel power.
6.9.5.3.4.3 Meusurem~nt of channel power: When not
otherwise held in the channel busy state, a VDL Mode 4
station shall consider the channel idle with ar lcast a 45 per
cent probability if on-channel power falls below the equivalent
of twice the estimated noise floor for at least 0.9 milliseconds.
6.9.5.4 RECEIVER~TRANSMIINTTTEERRAC TION
6.9.5.4.1 Receiver ID ~ransrnittertu rnaround time. A VDL
Mode 4 station shall be capable of beginning the transmission
of the transmitter power stabilization sequence within
16 microseconds after terminating the receiver function.
6.9.5 -4.2 Frequency change during tmnsmission. The
phase acceleration of the carrier from the start of the
synchronizarion sequence to the data end flag shall be less than
300 Hz per second.
6.9.5.4.3 Transmitter to receiver turnaround time. A VDL
Mode 4 station shall be capable of receiving and demodulating
with nominal performance an incoming signal within I ms
after completing a rransmission.
6.9.5.5.1.1 A receiver shall be capable of demodulating a
transmission of minimum length PI without degradation of
BER.
6.9.5.5.1.2 The value of P1 shall be 19 200 bits.
6.9.5.5.2 Parumeter P2 (nominal co-channel interference
pe$onnance)
6.9.5.5.2.1 The parameter P2 shall be the nominal
co-channel interference ar which a receiver shall be capable of
demodulating without degradation in BER.
6.9.5.5.2.2 The value of P2 shall be 12 dB.
6.9.6 Link layer
Note.- Details on link layer functions are contuined in the
Manual on VDL Mode 4 Technical Specifications.
6.9.7 Subnetwork layer and SNDCF
Note.- Details on subnetwork layer finctions and SNDCF
are contained in the Manual on VDL Mode 4 Technical
SpecijTca tions.
6.9.8 ADS-B applications
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
附件10--航空电信an10_v3_1ed_amend_76(36)
