When does Partial Noisy Feedback Enlarge the Capacity of a Gaussian Broadcast Channel?

Ravi, Aditya Narayan; Pillai, Sibi Raj B.; Prabhakaran, Vinod M.; Wigger, Michèle

doi:10.1109/isit44484.2020.9174173

Cited by 2 publications

(4 citation statements)

References 14 publications

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“…1 becomes relevant. Furthermore, the model generalizes the existing passive feedback models in [10], [11] and [12], and effectively subsumes the results there. While our proof techniques build on [12], for both achievability as well as converse, the generalizations here necessitate additional steps and different analytical computations, which are more involved.…”

Section: Introductionsupporting

confidence: 75%

“…The computational details are omitted here. While capacity enlargements were shown here for small values of P , this can be easily extended to higher powers, similar to [11].…”

Section: Zero-forcing Achievable Scheme For Theoremmentioning

confidence: 52%

“…Our idea of achievability is to use the simple linear feedback coding scheme suggested in [11], [12], and show a capacity enlargement whenever feasible. However, the specific parameters of the scheme have to be tuned differently to obtain the results here.…”

Section: Zero-forcing Achievable Scheme For Theoremmentioning

confidence: 99%

“…However, in the asymmetric situation, where one user is stronger compared to other, it was shown in [10] that with noisy feedback only from the strong receiver, no such enlargement is possible when the feedback noise variance is above a threshold. A sharp characterization of the feedback noise threshold for capacity enlargement with onesided feedback was presented in [11]. A tight characterization of the noise variances for which two-sided noisy feedback is SRBP acknowledges the support from DST India IMPRINT grant 001280.…”

Section: Introductionmentioning

confidence: 99%

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On the Capacity Region of Gaussian Broadcast Channels under Two-Sided Noisy Feedback

Ravi

Pillai

Prabhakaran

et al. 2021

2021 IEEE International Symposium on Information Theory (ISIT)

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The capacity region of several multiuser models in information theory can be enlarged by utilizing feedback of the received symbols. This is in contradiction to the discrete memoryless case, where feedback is known not to change the capacity. In this paper, we consider two broadcast models with noisy feedback from both the receivers. The models are derived from a standard memoryless scalar GBC, where two intermediate passive nodes are assumed to be observing the transmissions via separate noisy links corrupted by independent AWGN. In our first model, the scalar output from each intermediate node is passed through two additional independent AWGN links, called feedback and forward links. The output of the feedback link is observed by the transmitter as feedback, whereas only the forward link is observed by the corresponding decoder. We derive conditions that are both necessary and sufficient for feedback to enlarge the capacity region. In the second model, the two outputs of a standard GBC are observed by the respective decoders, but the transmitter observes the sum of the symbols at the receivers using causal feedback. We show that such a feedback has no effect on the capacity region.

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Section: Introductionsupporting

confidence: 75%

“…The computational details are omitted here. While capacity enlargements were shown here for small values of P , this can be easily extended to higher powers, similar to [11].…”

Section: Zero-forcing Achievable Scheme For Theoremmentioning

confidence: 52%

Section: Zero-forcing Achievable Scheme For Theoremmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On the Capacity Region of Gaussian Broadcast Channels under Two-Sided Noisy Feedback

Ravi

Pillai

Prabhakaran

et al. 2021

2021 IEEE International Symposium on Information Theory (ISIT)

Self Cite

View full text Add to dashboard Cite

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On the Capacity Enlargement of Gaussian Broadcast Channels With Passive Noisy Feedback

Ravi

Pillai

Prabhakaran

et al. 2021

IEEE Trans. Inform. Theory

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It is well known that the capacity region of an average transmit power constrained Gaussian Broadcast Channel (GBC) with independent noise realizations at the receivers is enlarged by the presence of causal noiseless feedback. When the noise variances at the receivers are identical, even passive feedback via independent memoryless Gaussian links can lead to a capacity region enlargement. The last fact remains true even when the feedback noise variance is very high, and available only from one of the receivers. While such capacity enlargements are feasible for several other feedback models in the Gaussian BC setting, it is also known that feedback does not change the capacity region for physically degraded broadcast channels. In this paper, we consider a two user GBC with independent noise realizations at the receivers, where the feedback links from the receivers are corrupted by independent additive Gaussian noise processes. We investigate the set of four noise variances, two forward and two feedback, for which no capacity enlargement is possible. A sharp characterization of this region is derived, i.e., any quadruple outside the presented region will lead to a capacity enlargement, whereas quadruples inside will leave the capacity region unchanged. Our results lead to the conclusion that when the forward noise variances are different, too noisy a feedback from one of the receivers alone is not always beneficial for enlarging the capacity region, be it from the stronger user or the weaker one, in sharp contrast to the case of equal forward noise variances.

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When does Partial Noisy Feedback Enlarge the Capacity of a Gaussian Broadcast Channel?

Cited by 2 publications

References 14 publications

On the Capacity Region of Gaussian Broadcast Channels under Two-Sided Noisy Feedback

On the Capacity Region of Gaussian Broadcast Channels under Two-Sided Noisy Feedback

On the Capacity Enlargement of Gaussian Broadcast Channels With Passive Noisy Feedback

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