We investigate a K-user parallel packet-erasure broadcast channel. There is an ongoing effort to harness millimeter-wave bands, which are known to be unstable having high outage probabilities, by combining them with stable legacy bands. Motivated by this effort, we consider a heterogeneous scenario in which the parallel subchannels are categorized into two classes having different outage probabilities. For the two-user case, we characterize the sum capacity by developing an explicit achievable scheme and deriving a matching upper bound. In contrast to suboptimal schemes that apply coding on a per-subchannel basis only, our scheme applies coding across subchannels to exploit coding opportunities that arise from asymmetric outage probabilities more efficiently, thereby achieving optimality. By extending our scheme systematically to be applicable for the K-user case, we show that it can provide significant gains over existing schemes. Compared to the K-user scheme currently employed in practice, which allocates chunks of subchannels to users exclusively, we demonstrate the performance improvement attainable by our scheme to be substantial, as the multiplicative gain scales with K. Moreover, we find that our scheme outperforms a per-subchannel extension of state-of-the-art K-user schemes by large margins, further reducing the optimality gap. Our results suggest a potential coding scheme that can be employed in future wireless systems to meet ever-growing mobile data demands.
Bibliographical noteFunding Information:
Manuscript received January 20, 2020; revised July 3, 2020 and October 23, 2020; accepted January 2, 2021. Date of publication January 13, 2021; date of current version April 16, 2021. The work of Soheil Mohajer was supported by the National Science Foundation under Grant CCF-1749981. The work of Changho Suh was supported by the Air Force Office of Scientific Research under Award number FA2386-19-1-4050, Korea Advanced Institute of Science and Technology (KAIST) Grand Challenge 30 (KC30) Project in 2019 (1711100603) funded by KAIST and Korea Government (MSIP), and National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (NRF-2018R1A1A1A05022889). This article was presented in part at the 2017 IEEE International Symposium on Information Theory, Aachen, Germany, June 2017. The associate editor coordinating the review of this article and approving it for publication was G. Durisi. (Corresponding author: Changho Suh.) Sunghyun Kim was with the Electronics and Telecommunications Research Institute, Daejeon 34129, South Korea. He is now with the Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02142 USA (e-mail: firstname.lastname@example.org).
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- Broadcast channels
- communication systems
- information theory
- millimeter wave communication
- state feedback