DTMB Single Frequency Network (SFN) Adaptor

Advantages of SFN over MFN

• Higher bandwidth efficiency - For the same coverage, MFN requires three different frequency bands or more, while in SFN only one frequency band is needed.
• Lower transmission power
• Re-modulating identical information onto different transmitters can be avoided.
• More reliable reception and better coverage - A receiver in SFN can achieve potential diversity gain.

Synchronization is a Key Function of SFN Adaptor

Transmitters shall radiate:

• over the same frequency band
• at the same time
• the same signals.

Solution of SFN Adaptor

• Frequency Synchronization
  - Same working frequency from each transmitter
  - Same frequency for each carrier in multi-carrier system
  - Can be achieved by using common reference frequency (GPS10M for example) to control the modulation
• Time Synchronization
  - Use GPS as reference timing (1pps, 10M)
  - Achieved through SFN Adaptor
• Guard Interval (GI)
  - The length of GI determines the maximum delay spread the system can manage - the longer the GI, the longer the allowed distance among the transmitters, but the lower the transmission efficiency.