Transmission method and apparatus for transmitting low-speed SDH signals using a high-speed SDH frame

A transmission apparatus which transmits low-speed SDH signals using high-speed SDH frames, comprising:

• a multiplexer unit which multiplexes the low-speed SDH signals into a first high-speed SDH frame, the first high-speed SDH frame including an information payload, a line overhead and a section overhead, the section overhead being divided into a first section overhead SOH and a second section overhead SOH, the first SOH carrying regenerator SOH bytes and the second SOH carrying multiplex SOH bytes;
• a multiplex SOH generating unit which generates the multiplex SOH bytes in the second SOH of the first high-speed SDH frame without changing the line overhead and the payload before the first high-speed SDH frame is transmitted by the transmission apparatus;
• wherein said multiplex SOH generating unit causes stuffing bytes to be added to the second SOH of the first high-speed SDH frame when the first high-speed SDH frame is generated, the stuffing bytes being larger in number than a product of an allowed clock frequency error and a total number of line-related bytes contained in one of the low-speed SDH signals;
• and
• a multiplex SOH detecting unit which detects multiplex SOH bytes in a second SOH of a second high-speed SDH frame without changing a line overhead and a payload of the second high-speed SDH frame when the second high-speed SDH frame reaches the transmission apparatus.