Constellation shaping
Constellation shaping is an energy efficiency enhancement method for digital signal modulation that improves upon amplitude and phase-shift keying and conventional quadrature amplitude modulation ) modulation by transmitting low-energy signals more frequently than high-energy signals.
A constellation is a pattern of the possible signal combinations. In a static constellation, all of the combinations are used equally. In practice, however, the transmission media distorts the signal unevenly; some combinations require lower energy and resist channel noise more than others.
A shaped constellation transmission sends some signal combinations more often and others less frequently to optimize the signal quality at the destination, or to maintain the same quality using less transmission energy.Probabilistic constellation shaping
Probabilistic constellation shaping changes the shaping parameters based on predefined terms. This allows a significant capacity increase. This technique gathered more interest in September 2016 when Nokia Bell Labs demonstrated working 1 Tbit/s data transmission channels between German cities. In October 2016, Alcatel-Lucent and Bell Labs claimed to have achieved 65 Tbit/s transmission over a 6,600 km single mode fiber in laboratory trials.
