SCS P4dragon DR-7800, Руководство по установке

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3. The PACTOR Modes
52
3.3 PACTOR-4 (P4)
As over the years the computation power of the Digital Signal Processors being available has
dramatically increased, it seemed possible also to increase the transfer speed and robustness of
PACTOR-3 by at least factor two, while maintaining the bandwidth being occupied. The
development of PACTOR-4 begun in the year 2006 on a new DSP chipset from Freescale
which was called “
StarCore
”. The PACTOR modes including PACTOR-4 have finally been
implemented into the
P4
dragon
modem using a 400 MHz quad “
StarCore
” 64 bit DSP system.
PACTOR-4 (P4) is designed for superior performance under adverse multipath channel
conditions. The demodulator utilizes a powerful adaptive equalizer compensating for channel
distortions. P4 provides a wider useful adaptation range compared to PACTOR-3 (P3). The
ARQ protocol is even more adaptive and flexible.
Compatibility:
P4 modems are fully capable of P1-P3 and thus fully backward compatible to
older P1-P3 systems.
ARQ-Protocol:
Similar to P3 but faster adaptivity.
Modulation:
10 speed levels, DBPSK/DQPSK (non-coherent, spreading factor 16), BPSK-
32QAM (coherent), adaptive equalizing.
1800 symbols/second (compatible to HF “amateur” transceivers).
Bandwidth:
2400 Hz @ -40 dB.
Crest Factor:
Always < 4 dB.
Data speed:
Max. 5512 bps (compression off, @ ca. +17 dB on AWGN channel, after all
protocol overhead). Max. raw bit rate prior to protocol overhead:
9000 bps (uncoded) / 7500 bps (coded)
Compression: PMC
(compression factor: 1.9 on plain text data),
AMC
(compression factor: 4.5 on plain text data; ca. 2.0 on average “binary”
data). (Remark: AMC, Adaptive Markow Compression, is still under
development.)
Minimum SNR:
-19 dB required for maintaining a connection on AWGN channel.
Throughput
Comparison:
Compared to P3 (compression off):
Ca. factor 2 on AWGN channel above 0 dB, ca. 1.5 below 0 dB.
Ca. factor 2.5-5 on ITU “good / moderate / poor” channels above 0 dB.
Ca. factor 1.5-2.5 below 0 dB.