Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 1915

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 as contained in the Manuals on VDL Mode 2 and VDL Mode 3 Technical Specifications. 6.4.1.1.2 Digital reception by the receiver. The receiver shall decode input signals and forward them to the higher layers for processing. 6.4.1.1.3 Digital transmission. The VDL physical layer shall appropriately encode and transmit information received from higher layers over the RF channel. 6.4.2 Modes 2 and 3 common physical layer 6.4.2.1 Modulation scheme. Modes 2 and 3 shall use differentially encoded 8 phase shift keying (D8PSK), using a raised cosine filter with α = 0.6 (nominal value). The information to be transmitted shall be differentially encoded with 3 bits per symbol (baud) transmitted as changes in phase rather than absolute phase. The data stream to be transmitted shall be divided into groups of 3 consecutive data bits, least significant bit first. Zeros shall be padded to the end of the transmissions if needed for the final channel symbol. 6.4.2.1.1 Data encoding. A binary data stream entering a differential data encoder shall be converted into three separate binary streams X, Y, and Z so that bits 3n form X, bits 3n + 1 form Y, and bits 3n + 2 form Z. The triplet at time k (Xk, Yk, Zk) shall be converted to a change in phase as shown in Table 6-1*, and the absolute phase φk is the accumulated series of Δφk, that is: φk = φk-1 + Δφk 6.4.2.1.2 Transmitted signal form. The phase-modulated baseband signal as defined in 6.4.2.1.1 shall excite the pulse shape filter. ( ) ( , ) +∞ =−∞ = φ − ∑k k s s t h t kT where: h is the complex impulse response of the pulse shape filter; k is defined in 6.4.2.1.1; φ is defined by the equation in 6.4.2.1.1; t is time; Ts is time duration of each symbol. The output (function of time) of the pulse shape filter (s(t)) shall modulate the carrier frequency. The pulse shape filter shall have a nominal complex frequency response of a raised-cosine filter with α =0.6. * All tables are located at the end of this chapter. Part I Annex 10 — Aeronautical Communications I-6-9 22/11/07 6.4.2.2 Modulation rate. The symbol rate shall be 10 500 symbols/second, resulting in a nominal bit rate of 31 500 bits/s. The modulation stability requirements for Modes 2 and 3 are provided in Table 6-2. 6.4.3 Mode 2 specific physical layer Note.— The Mode 2 specific physical layer specification includes a description of the Mode 2 training sequence, forward error correction (FEC), interleaving, bit scrambling, channel sensing, and physical layer system parameters. 6.4.3.1 To transmit a sequence of frames, a station shall insert the bit numbers and flags (per the data link service description for Mode 2 as contained in the Manual on VDL Mode 2 Technical Specifications), compute the FEC (per 6.4.3.1.2), interleave (per 6.4.3.1.3), prepend the training sequence (per 6.4.3.1.1), carry out bit scrambling (per 6.4.3.1.4) and finally encode and modulate the RF signal (per 6.4.2.1). 6.4.3.1.1 Training sequence. Data transmission shall begin with a demodulator training sequence consisting of five segments:

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