Comtech EF Data CDM-Qx Especificações descarregar pdf (Página 133)

6–1

Chapter 6. FORWARD ERROR

CORRECTION OPTIONS

6.1 Introduction

As standard, the Modem is equipped with three Forward Error Correction

encoders/decoders – Viterbi, concatenated Reed-Solomon and Trellis (which is available

with the 8-PSK FAST option). The constraint lengths and encoding polynomials are not

only Open Network compatible (IESS-315), but are also Closed Network compatible

with the vast majority of existing modems from other manufacturers. Comtech EF Data

has performed compatibility testing to ensure inter-operability.

Turbo Coding represents a very significant development in the area of FEC, and

optionally, the modem may be fitted with a Turbo Product Codec. They are plug-in

daughter cards (SIMM modules) that are field upgradeable. The codec provides data rate

capability up to 20 Mbps, and code rates of:

• Rate 5/16 (BPSK

• Rate 21/44 (BPSK, QPSK)

• Rate 3/4, and 7/8 (QPSK, 8-PSK, and 16-QAM)

• Rate 17/18 (QPSK and 8-PSK)

Turbo Product Coding provides one of the best Forward Error Correction technologies

currently available, and is now offered with a sufficient range of code rates and

modulation types that link performance can be optimized under any conditions.

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Comtech EF Data CDM-Qx Especificações Página 133