The state-dependent K-user memoryless broadcast channel (BC) with state feedback is investigated. We propose a novel transmission scheme and derive its corresponding achievable rate region, which, compared with some general schemes that deal with feedback, has the advantage of being relatively simple and thus is easy to evaluate. In particular, we show that the proposed scheme achieves the capacity region of the symmetric erasure BC with an arbitrary input alphabet size. For the fading Gaussian BC, numerical results show that the proposed scheme outperforms existing schemes in terms of symmetric rate. Our analysis also proves its optimality at high signal-to-noise ratio, in terms of degrees of freedom.

In this paper, we investigate the two-user erasure broadcast channel in which only one of the receivers feeds the output back to the transmitter. We propose a transmission scheme based on joint source-channel coding and show that the achievable rate region can be strictly larger than the ones previously known for this channel. In particular, the proposed scheme is partially optimal in the sense that the boundary of the achievable region overlaps in part with the boundary of the capacity region of the same channel with two-sided feedback. Thus, we identify a condition under which one-sided feedback is as good as two-sided feedback. Our result also demonstrates the limitation of bit-wise linear transmission schemes previously used for such channels.

This paper investigates the two-user Erasure Broadcast Channel (EBC), where the Channel State Information (CSI) is fully known at the destination, while the transmitter is only aware of the strictly causal CSI by state feedback and an estimate of the instantaneous CSI. We propose a novel transmission scheme that exploits both the delayed and the instantaneous CSI. Our scheme includes both the case with full CSI and the case with delayed CSI as special cases. We also derive a new outer bound region for this channel. For the symmetric EBC, we show that our scheme is capacity achieving in some nontrivial cases. Since both the inner and outer bound regions are characterized with linear constraints, numerical evaluation can be done easily.

In this paper, we investigate the fast fading broadcast relay channel (BRC) with one source (macrocell BS), one relay (smallcell BS), and two destinations (mobile users). We assume that the instantaneous channel state information (CSI) is known only at the receivers' side, whereas the relay can obtain a noiseless CSI feedback from the destinations about the source-destination channels (with delay). An inner bound on the capacity region of this channel is derived based on a partial-decode-compress-forward (PDCF) scheme. The main idea is to let the relay decode a significant portion of the source messages and then generate and forward to the receivers some useful side information using both the decoded messages and the CSI feedback. Numerical results show that, thanks to the feedback, the proposed scheme provides a non-negligible gain over conventional decode-forward/compress-forward schemes in terms of sum-rate performance, especially in the high SNR regime. Quite remarkably, we show that overall transmit power of the macrocell network can be significantly reduced owing to the feedback from users to the smallcell BS.