Practical LDPC coded modulation schemes for the fading broadcast channel with confidential messages
This addresses the lack of practical schemes for secure communication in fading broadcast channels, but it appears incremental as it builds on existing theoretical work with specific coding methods.
The paper tackles the design of practical coding and modulation schemes for a fading broadcast channel with confidential messages, aiming to achieve fixed levels of reliability and security, and shows that feasibility conditions exist and some outage probability must be tolerated.
The broadcast channel with confidential messages is a well studied scenario from the theoretical standpoint, but there is still lack of practical schemes able to achieve some fixed level of reliability and security over such a channel. In this paper, we consider a quasi-static fading channel in which both public and private messages must be sent from the transmitter to the receivers, and we aim at designing suitable coding and modulation schemes to achieve such a target. For this purpose, we adopt the error rate as a metric, by considering that reliability (security) is achieved when a sufficiently low (high) error rate is experienced at the receiving side. We show that some conditions exist on the system feasibility, and that some outage probability must be tolerated to cope with the fading nature of the channel. The proposed solution exploits low-density parity-check codes with unequal error protection, which are able to guarantee two different levels of protection against noise for the public and the private information, in conjunction with different modulation schemes for the public and the private message bits.