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B.3 Return Service
B.3.1 General
The customer/SN end-to-end system functional configuration for return service is shown
in Figure B-5. Return data generated in the customer platform undergoes various
baseband data conditioning operations (i.e., data format conversion, data
demultiplexing for alternate bits on the I and Q channels, convolutional encoding,
symbol format conversion, and symbol interleaving) and RF signal processing
(spectrum spreading, modulation, I/Q-channel power weighting, and frequency
upconversion) prior to transmission to the TDRSS. At the WSC, the inverse RF signal
processing (frequency downconversion, despreading, and demodulation) and baseband
signal processing (symbol synchronization, symbol format conversion, symbol
deinterleaving, Viterbi decoding, data format conversion, and data interleaving of the I-
and Q-channel data bits) are performed. The return service data at the WSC/SN data
interface will always be treated as NRZ-L. For example, if NRZ-M data formatting is
scheduled, the SN will perform NRZ-M to NRZ-L data format conversion. If SN
customers would like their data format to be unaltered by the SN (i.e., in the example
just given, they would like to receive NRZ-M data rather than NRZ-L data at the SN data
interface), then customers need to schedule through the SN as if their data format is
NRZ-L; then the SN will not perform any data format conversion. Refer to Section 3,
paragraph 3.6, for information concerning data interface capabilities and restrictions.
Data
Sources
NRZ
or
Bi
Customer Platform
Data
Conditioning
Operations
Transponder
Configuration
SN RF Interface
TDRSS
WDISC
DAS
MDM
SN Ground Local
Terminal Interface
IF
High Data
Rate
Customer
MOC
Figure B-5. Return Service End-to-End System Functional Configuration
Revision 10 B-8 450-SNUG
TDRS
SN Data Interface