Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 1929

b) synchronization and ambiguity resolution. 6.4.4.3.1.1 Transmitter ramp-up and power stabilization. This shall be as specified in 6.4.4.1.1.1. 6.4.4.3.1.2 Synchronization and ambiguity resolution. The second component of the training sequence shall consist of the synchronization sequence, known as S2, as follows: 000 111 011 010 000 100 001 010 100 101 011 110 001 110 101 111 and shall be transmitted from left to right. 6.4.4.3.2 Header. The header segment shall consist of 8 transmitted symbols. The 24 transmitted bits shall be encoded as 12 bits of header information and 12 parity bits, generated as a single (24, 12) Golay code word. The encoding of the (24, 12) Golay code word shall be as defined in 6.4.4.1.2. 6.4.4.3.3 User information. The user information segment shall consist of 192 3-bit symbols. When transmitting voice, FEC shall be applied to the analysis output of the vocoder specified in 6.8. The vocoder shall provide satisfactory performance in a BER environment of 10–3 (with a design goal of 10–2). The overall bit rate of the vocoder including FEC is 4 800 bits/s (except when in the truncated mode in which the bit rate is 4 000 bits/s). 6.4.4.3.3.1 When transmitting user data, the 576 bits shall be encoded as a single Reed-Solomon (72, 62) 28–ary code word. For user data input to the Reed-Solomon encoder of length less than 496 bits, input data shall be padded with zeroes at the end to a full length of 496 bits. The field defining the primitive polynomial of the code shall be as described in 6.4.3.1.2.1. The generator polynomial shall be as follows: i 120 ( ) = −α ∏ i x Note.— The Reed-Solomon (72, 62) code is capable of correcting up to five 28-ary (code word) symbol errors in the received word. 6.4.4.3.4 Transmitter ramp-down. This shall be as defined in 6.4.4.1.3. 6.4.4.4 Interleaving. There shall be no interleaving in Mode 3 operation. 6.4.4.5 Bit scrambling. Under Mode 3 operation, bit scrambling, as specified in 6.4.3.1.4 shall be performed on each burst, starting after the training sequence. The scrambling sequence shall be reinitialized on each burst effectively providing a constant overlay for each of the Mode 3 fixed length bursts. Annex 10 — Aeronautical Communications Volume III 22/11/07 I-6-16 6.4.4.6 Receiver/transmitter interaction. The switching times in this subsection will be defined as the time between the middle of the last information symbol of one burst and the middle of the first symbol of the synchronization sequence of the subsequent burst. Note.— This nominal time will be shortened by considerations such as the finite width of each symbol due to Nyquist filtering and the ramp up and power stabilization sequence. Such alternative definitions could yield switching times up to 8 symbol periods shorter. 6.4.4.6.1 Receiver to transmitter switching time. An aircraft radio shall be capable of switching from reception to transmission within 17 symbol periods. This time can be relaxed to 33 symbol periods for aircraft radios which do not implement functions requiring discrete addressing. Note 1.— The shortest R/T switching time for an aircraft radio occurs when the reception of an uplink M channel beacon is followed by a V/D transmission in the same slot. In certain instances where aircraft radios do not implement functions requiring discrete addressing, the R/T switching time can be increased since the last two Golay words of the uplink M channel beacon need not be read. Note 2.— The minimum turnaround time assumes that in configurations 3V1D, 2V1D, and 3T (as contained in Section 5.5.2.4 of the Manual on VDL Mode 3 Technical Specifications), the aircraft radios will be provided with software that will prevent them from transmitting a downlink M channel message in a slot following the reception of a voice message from another aircraft with a long time delay. 6.4.4.6.2 Transmitter to receiver switching time. An aircraft radio shall be capable of switching from transmission to reception within 32 symbol periods. Note.— The worst case T/R switching time for an aircraft radio occurs when it transmits a downlink M channel message and receives a V/D message in the same slot. 6.4.4.7 Fringe coverage indication 6.4.4.7.1 Recommendation.— Indication of near edge-of-coverage should be provided to the VDL Mode 3 aircraft. 6.5 LINK LAYER PROTOCOLS AND SERVICES 6.5.1 General information 6.5.1.1 Functionality. The VDL link layer shall provide the following sublayer functions:

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