CIF: Small: Collaborative Research: Communications in Ultra-Low-Rate Regime: Fundamental Limits, Code Constructions, and Applications

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Wireless networks have become an integral part of our society by connecting billions of users around the globe. The next generation wireless networks, known as 5G, are expected to deliver orders of magnitude higher data rates to an ever-increasing number of devices. The fundamental limits on how much networks can be pushed towards these advancements are determined by the amount of available wireless bands. To this end, two extremes of wireless communications have become increasingly important, namely, narrowband and wideband. The narrowband communication, using a small band of frequencies, enables connectivity of thousands of devices, such as everyday objects in Internet-of-Things (IoT) networks, to a single cell tower. Wideband communications, using large swaths of frequencies, at extremely high frequencies is the key enabling technology for delivering ultra-high data rates to 5G mobile users. In both of these scenarios, individual bits of information are assigned extremely low power for communication resulting in bit-wise wireless channels with low capacity. This introduces a new array of fundamental problems with respect to communications over low-capacity channels that is the focus of this project. The results of this project will contribute to the foundation of information and coding theory as well as the development of wireless networks that can achieve the ultimate limits of narrowband and wideband communications.Recently, the wireless standards entity, 3GPP, has introduced new protocols into the standard in order to integrate IoT into the cellular network. A major feature of these protocols is to deploy ultra-low-rate communications in order to address diverse requirements of IoT networks. Such low-rate communication is enabled in the standard by simply allowing a large number of block repetitions, which could be extremely suboptimal from the channel coding perspective. A similar situation arises in wideband scenarios. Wideband channels can essentially provide high data rates, in terms of bits per second. However, individual coded bits experience extremely low signal-to-noise ratios, due to limited signal power and larger attenuations in higher frequencies. In light of the emerging applications in these two extremes of wireless communications, the investigators aim at a comprehensive investigation of channel coding in the low-capacity regime. The specific objectives in this project are as follows: (1) Provide a precise framework for channel coding at low capacity, and characterize fundamental non-asymptotic laws for channel coding in this regime; (2) Develop techniques for the non-asymptotic analysis of wireless wideband and millimeter wave systems; (3) Investigate state-of-the-art codes, including their construction, performance, and efficient decoding, for adaptation to low-rate regimes; (4) Construct efficient concatenated coding schemes including coded repetition and concatenation with low-rate algebraic codes, given diverse requirements of low-capacity applications. Consequently, this project develops a formal connection between information theory, coding theory, and wireless communications resulting in a mathematically precise interface between these areas to address the challenges of narrowband and wideband wireless systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.