Does repeating a data transmission constitute spreading?

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SUMMARY

Repeating a data transmission can indeed be classified as a form of spreading, particularly in the context of spread spectrum techniques. The discussion highlights that even TCP/IP, through its retransmission of packets upon receiving a NACK, qualifies as a spreading scheme. In Orthogonal Frequency-Division Multiplexing (OFDM), interleaving data across subcarriers increases spectrum occupancy without altering total bandwidth. This method involves inserting zeros between data symbols, leading to repetition in the time domain, which is a critical distinction from traditional diversity schemes.

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  • Understanding of spread spectrum techniques
  • Familiarity with TCP/IP protocols
  • Knowledge of Orthogonal Frequency-Division Multiplexing (OFDM)
  • Basic concepts of interleaving and IFFT operations
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  • Research TCP/IP NACK mechanisms and their implications on data transmission
  • Explore the principles of Orthogonal Frequency-Division Multiplexing (OFDM)
  • Learn about frequency-domain interleaving techniques and their effects on signal processing
  • Investigate diversity schemes and their differences from spreading techniques
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Network engineers, telecommunications professionals, and anyone involved in signal processing or data transmission optimization will benefit from this discussion.

Tybalt
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TL;DR
This is a question about defining spread spectrum. It seems that spreading should involve more than just repeating data symbols.
Generally, spread spectrum is defined as using more spectrum (or bandwidth) than is needed to transmit a signal. But according to this definition, even TCP-IP would be a spreading scheme because it retransmits packets upon receiving a NACK. In OFDM, if you interleave data across the subcarriers instead of using a contiguous block of subcarriers, you increase the spectrum occupancy, but the total bandwidth (= number of subcarriers x subcarrier bandwidth) is the same. Some people call this spreading. Interleaving involves inserting zeros between data symbols that are operated upon by the IFFT, so this frequency-domain interleaving causes repetition in the time domain, i.e., the output of the IFFT repeats Z times, where Z is the number of zeros you insert between the data symbols.
 
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Thanks. This is helpful.
 

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