Optimization of hierarchical modulation for use of scalable media
EURASIP Journal on Advances in Signal Processing
Nonequiprobable signaling on the Gaussian channel
IEEE Transactions on Information Theory
IEEE Transactions on Information Theory
Optimal nonuniform signaling for Gaussian channels
IEEE Transactions on Information Theory
Superposition of Broadcast and Unicast in Wireless Cellular Systems
IEEE Communications Magazine
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The problem of constellation shaping for broadcast transmission in degraded channels remains a challenge. This is especially so when a single source communicates simultaneously with two receivers using a finite dimension constellation. This paper focuses on a practical situation where unicast service to each user is transmitted over broadcast channels. We investigate the optimization of an achievable rate closure region by using non-uniform constellations issued from superimposition of high-rate information on low-rate information and by using a nonequiprobable distribution of the transmitted symbols. The achievable rate region is derived for a two-user additive white Gaussian noise (AWGN) broadcast channel and for finite input pulse amplitude modulation (PAM) constellations. A noticeable shaping gain up to 3.5 dB maximum was shown on signal-to-noise ratio (SNR), compared with the equiprobable distribution of transmitted symbols obtained for a 4-PAM constellation when achievable rates are maximized over the probability distribution of channel input signals and the constellation shape. © 2012 Alcatel-Lucent. © 2012 Wiley Periodicals, Inc.