The BT experience of implementing 140 Mbit/s 8-PSK carriers for transatlantic cable restoration purposes

For many years, the satellite communications fraternity has grappled with the problem of squeezing carriers with an information rate of 140 Mbit/s into a transponder bandwidth of 72 MHz, which has a practical transmission rate limit of around 60 MBaud (i.e. 120 Mbit/s when using the 4-phase PSK modulation technique). This paper describes the BT experience in implanting the solution agreed upon with AT&T and France Telecom for the restoration via satellite of failed transatlantic cable systems. The paper charts progress from the decision to use 8-phase Phase Shift Keying (PSK) with rate-5/6 Forward Error Correction (FEC) encoding through to successful operation, including details of system design, implementation, performance evaluation and operational experiences