Optimization and Applications of Modern Wireless Networks and Symmetry

Due to the future demands of wireless communications, this book focuses on channel coding, multi-access, network protocol, and the related techniques for IoT/5G. Channel coding is widely used to enhance reliability and spectral efficiency. In particular, low-density parity check (LDPC) codes and polar codes are optimized for next wireless standard. Moreover, advanced network protocol is developed to improve wireless throughput. This invokes a great deal of attention on modern communications

Cellular, Wide-Area, and Non-Terrestrial IoT: A Survey on 5G Advances and the Road Towards 6G

The next wave of wireless technologies is proliferating in connecting things among themselves as well as to humans. In the era of the Internet of things (IoT), billions of sensors, machines, vehicles, drones, and robots will be connected, making the world around us smarter. The IoT will encompass devices that must wirelessly communicate a diverse set of data gathered from the environment for myriad new applications. The ultimate goal is to extract insights from this data and develop solutions that improve quality of life and generate new revenue. Providing large-scale, long-lasting, reliable, and near real-time connectivity is the major challenge in enabling a smart connected world. This paper provides a comprehensive survey on existing and emerging communication solutions for serving IoT applications in the context of cellular, wide-area, as well as non-terrestrial networks. Specifically, wireless technology enhancements for providing IoT access in fifth-generation (5G) and beyond cellular networks, and communication networks over the unlicensed spectrum are presented. Aligned with the main key performance indicators of 5G and beyond 5G networks, we investigate solutions and standards that enable energy efficiency, reliability, low latency, and scalability (connection density) of current and future IoT networks. The solutions include grant-free access and channel coding for short-packet communications, non-orthogonal multiple access, and on-device intelligence. Further, a vision of new paradigm shifts in communication networks in the 2030s is provided, and the integration of the associated new technologies like artificial intelligence, non-terrestrial networks, and new spectra is elaborated. Finally, future research directions toward beyond 5G IoT networks are pointed out.Comment: Submitted for review to IEEE CS&

Capacity-Achieving Coding Mechanisms: Spatial Coupling and Group Symmetries

The broad theme of this work is in constructing optimal transmission mechanisms for a wide variety of communication systems. In particular, this dissertation provides a proof of threshold saturation for spatially-coupled codes, low-complexity capacity-achieving coding schemes for side-information problems, a proof that Reed-Muller and primitive narrow-sense BCH codes achieve capacity on erasure channels, and a mathematical framework to design delay sensitive communication systems. Spatially-coupled codes are a class of codes on graphs that are shown to achieve capacity universally over binary symmetric memoryless channels (BMS) under belief-propagation decoder. The underlying phenomenon behind spatial coupling, known as “threshold saturation via spatial coupling”, turns out to be general and this technique has been applied to a wide variety of systems. In this work, a proof of the threshold saturation phenomenon is provided for irregular low-density parity-check (LDPC) and low-density generator-matrix (LDGM) ensembles on BMS channels. This proof is far simpler than published alternative proofs and it remains as the only technique to handle irregular and LDGM codes. Also, low-complexity capacity-achieving codes are constructed for three coding problems via spatial coupling: 1) rate distortion with side-information, 2) channel coding with side-information, and 3) write-once memory system. All these schemes are based on spatially coupling compound LDGM/LDPC ensembles. Reed-Muller and Bose-Chaudhuri-Hocquengham (BCH) are well-known algebraic codes introduced more than 50 years ago. While these codes are studied extensively in the literature it wasn’t known whether these codes achieve capacity. This work introduces a technique to show that Reed-Muller and primitive narrow-sense BCH codes achieve capacity on erasure channels under maximum a posteriori (MAP) decoding. Instead of relying on the weight enumerators or other precise details of these codes, this technique requires that these codes have highly symmetric permutation groups. In fact, any sequence of linear codes with increasing blocklengths whose rates converge to a number between 0 and 1, and whose permutation groups are doubly transitive achieve capacity on erasure channels under bit-MAP decoding. This pro-vides a rare example in information theory where symmetry alone is sufficient to achieve capacity. While the channel capacity provides a useful benchmark for practical design, communication systems of the day also demand small latency and other link layer metrics. Such delay sensitive communication systems are studied in this work, where a mathematical framework is developed to provide insights into the optimal design of these systems

On Signal Constellations and Coding for Long-Haul Fiber-Optical Systems

Motivated by the realization that even the enormous bandwidth available in an optical fiber is finite and valuable, the design of spectrally efficient long-haul fiber-optical communication systems has become an important research topic. Compared to other wireline technologies, e.g., transmission over coaxial cables, the main challenge comes from the inherent nonlinearity of the underlying communication channel caused by the relatively high signal intensities. In this thesis, we study the design of spectrally efficient fiber-optical systems for both uncoded and coded transmission scenarios.We consider the problem of designing higher-order signal constellations for a system that is severly impaired by nonlinear phase noise. By optimizing amplitude phase-shift keying constellations, which can be seen as the union of phase-shift keying constellation with different amplitude levels, gains of up to 3.2 dB at a symbol error probability of 10^(−2) are shown to be achievable compared to conventional constellations. We also illustrate a somewhat counterintuitive behavior of optimized constellations for very high input powers and nonlinear distortions. In particular, sacrificing a constellation point or ring may be beneficial in terms of the overall performance of the constellation.Furthermore, we study polarization-multiplexed transmission, where spectral efficiency is increased by encoding data onto both polarizations of the light. For a memoryless fiber-optical channel, we introduce a low-complexity detector which is based on an amplitude- dependent phase rotation and subsequent threshold detection. The complexity compared to the four-dimensional maximum likelihood detector is considerably reduced, albeit at the expense of some performance loss.Lastly, we consider the design of a coded fiber-optical system operating at high spectral efficiency. In particular, we study the optimization of the mapping of the coded bits to the modulation bits for a polarization-multiplexed fiber-optical system that is based on the bit-interleaved coded modulation paradigm. This technique, which we refer to as bit mapper optimization, is extended to the class of spatially coupled low-density parity- check codes, which have shown outstanding performance over memoryless binary-input channels. For a transmission scenario without optical inline dispersion compensation, the results show that the transmission reach can be extended by roughly up to 8%, without significantly increasing the system complexity

On Signal Constellations and Coding for Long-Haul Fiber-Optical Systems

Motivated by the realization that even the enormous bandwidth available in an optical fiber is finite and valuable, the design of spectrally efficient long-haul fiber-optical communication systems has become an important research topic. Compared to other wireline technologies, e.g., transmission over coaxial cables, the main challenge comes from the inherent nonlinearity of the underlying communication channel caused by the relatively high signal intensities. In this thesis, we study the design of spectrally efficient fiber-optical systems for both uncoded and coded transmission scenarios.We consider the problem of designing higher-order signal constellations for a system that is severly impaired by nonlinear phase noise. By optimizing amplitude phase-shift keying constellations, which can be seen as the union of phase-shift keying constellation with different amplitude levels, gains of up to 3.2 dB at a symbol error probability of 10^(−2) are shown to be achievable compared to conventional constellations. We also illustrate a somewhat counterintuitive behavior of optimized constellations for very high input powers and nonlinear distortions. In particular, sacrificing a constellation point or ring may be beneficial in terms of the overall performance of the constellation.Furthermore, we study polarization-multiplexed transmission, where spectral efficiency is increased by encoding data onto both polarizations of the light. For a memoryless fiber-optical channel, we introduce a low-complexity detector which is based on an amplitude- dependent phase rotation and subsequent threshold detection. The complexity compared to the four-dimensional maximum likelihood detector is considerably reduced, albeit at the expense of some performance loss.Lastly, we consider the design of a coded fiber-optical system operating at high spectral efficiency. In particular, we study the optimization of the mapping of the coded bits to the modulation bits for a polarization-multiplexed fiber-optical system that is based on the bit-interleaved coded modulation paradigm. This technique, which we refer to as bit mapper optimization, is extended to the class of spatially coupled low-density parity- check codes, which have shown outstanding performance over memoryless binary-input channels. For a transmission scenario without optical inline dispersion compensation, the results show that the transmission reach can be extended by roughly up to 8%, without significantly increasing the system complexity

one6G white paper, 6G technology overview:Second Edition, November 2022

6G is supposed to address the demands for consumption of mobile networking services in 2030 and beyond. These are characterized by a variety of diverse, often conflicting requirements, from technical ones such as extremely high data rates, unprecedented scale of communicating devices, high coverage, low communicating latency, flexibility of extension, etc., to non-technical ones such as enabling sustainable growth of the society as a whole, e.g., through energy efficiency of deployed networks. On the one hand, 6G is expected to fulfil all these individual requirements, extending thus the limits set by the previous generations of mobile networks (e.g., ten times lower latencies, or hundred times higher data rates than in 5G). On the other hand, 6G should also enable use cases characterized by combinations of these requirements never seen before, e.g., both extremely high data rates and extremely low communication latency). In this white paper, we give an overview of the key enabling technologies that constitute the pillars for the evolution towards 6G. They include: terahertz frequencies (Section 1), 6G radio access (Section 2), next generation MIMO (Section 3), integrated sensing and communication (Section 4), distributed and federated artificial intelligence (Section 5), intelligent user plane (Section 6) and flexible programmable infrastructures (Section 7). For each enabling technology, we first give the background on how and why the technology is relevant to 6G, backed up by a number of relevant use cases. After that, we describe the technology in detail, outline the key problems and difficulties, and give a comprehensive overview of the state of the art in that technology. 6G is, however, not limited to these seven technologies. They merely present our current understanding of the technological environment in which 6G is being born. Future versions of this white paper may include other relevant technologies too, as well as discuss how these technologies can be glued together in a coherent system

Adaptive rate allocation scheme for joint source-channel coding based on double protograph LDPC codes

Although the joint source and channel coding (JSCC) system based on double protograph low-density paritycheck (DP-LDPC) codes shows excellent error performance in wireless communications systems, there still is some space left for the improvement of error rate performance and the robustness of this JSCC system as it suffers high sensitivity to source statistics. In this paper, an adaptive rate allocation scheme under fixed bandwidth is presented for joint sourcechannel coding，which allocates rate adaptively between the source and channel codes according to channel state information and source statistics. The simulation results show that the proposed scheme can possess excellent error performance of both water-fall region at low signal to noise ratio (SNR) and error-floor region at high SNR. In addition, it is helpful to reduce the influence of source statistics to this system and improve the robustness