| 摘要 |
<p>The invention discloses a spread spectrum communication system for framed data. It may be used to improve satellite broadcasting, e.g. DVB-S2 broadcasts. Payload data 222 of a frame is passed through a modulator to map the data onto modulation symbols. The output from this modulator is spread using a selected first spreading code S1 selected from a plurality of first spreading codes which have mutually different spreading factors. This allows payload data to be transmitted with a variable spreading factor. A header of the frame contains 231 physical layer signaling data (PLS) and an indication of the selected first spreading code. At least a portion of this header is spread using a second spreading code S2. The spreading factor of the second spreading code is greater than or equal to the spreading factor of each of the first spreading codes. This ensures that the header can always be received, even when the SNR is poor. The header may additionally include a start of frame (SOF) indication 203, spread using a third spreading code S3. The frame is modulated onto an RF carrier for transmission. There are transmitter and receiver embodiments.</p> |
