Patent ID: 8165173

Claim:
A data transmission method, being applicable to a semi-duplex Ethernet Passive Coaxial-cable Network and the network comprising a CLT, Coaxial-cable Line Terminal, and at least one CNU, Coaxial-cable Network Unit; the CLT transmitting downlink data to each CNU in a preset downlink transmission period and each CNU transmitting uplink data to the CLT in a preset uplink transmission period; the preset uplink transmission period being shorter or equal to the period that clock synchronization can be kept by the CNU; the method comprising: sending, by the CLT, clock information to the CNU before the expiration of the period that the clock synchronization can be kept by the CNU, the clock information being adapted to make the clocks of the CNU and CLT be kept synchronized with each other within a period; wherein the preset downlink transmission period comprises at least one preset minimum time slice which is shorter than or equal to the period that the clock synchronization can be kept by the CNU; the sending the clock information to the CNU before the expiration of the period that the clock synchronization can be kept by the CNU comprises: determining, by the CLT, whether there is a to-be-transmitted data frame at the starting point of each minimum time slice of the downlink transmission period, and if there is a to-be-transmitted data frame, sending the data frame which carried the clock information to each CNU; otherwise sending an idle signal which carried the dock information to each CNU in the minimum time slice.