Centralized and partial decentralized design for the Fog Radio Access Network

Fog Radio Access Network (F-RAN) has been shown to be a promising network architecture for the 5G network. With F-RAN, certain amount of signal processing functionalities are pushed from the Base Station (BS) on the network edge to the BaseBand Units (BBU) pool located remotely in the cloud. Hence, partially centralized network operation and management can be achieved, which can greatly improve the energy and spectral efficiency of the network, in order to meet the requirements of 5G. In this work, the optimal design for both uplink and downlink of F-RAN are intensively investigated

Signal Processing and Learning for Next Generation Multiple Access in 6G

Wireless communication systems to date primarily rely on the orthogonality of resources to facilitate the design and implementation, from user access to data transmission. Emerging applications and scenarios in the sixth generation (6G) wireless systems will require massive connectivity and transmission of a deluge of data, which calls for more flexibility in the design concept that goes beyond orthogonality. Furthermore, recent advances in signal processing and learning have attracted considerable attention, as they provide promising approaches to various complex and previously intractable problems of signal processing in many fields. This article provides an overview of research efforts to date in the field of signal processing and learning for next-generation multiple access, with an emphasis on massive random access and non-orthogonal multiple access. The promising interplay with new technologies and the challenges in learning-based NGMA are discussed

Analysis and design of physical-layer network coding for relay networks

Physical-layer network coding (PNC) is a technique to make use of interference in wireless transmissions to boost the system throughput. In a PNC employed relay network, the relay node directly recovers and transmits a linear combination of its received messages in the physical layer. It has been shown that PNC can achieve near information-capacity rates. PNC is a new information exchange scheme introduced in wireless transmission. In practice, transmitters and receivers need to be designed and optimized, to achieve fast and reliable information exchange. Thus, we would like to ask: How to design the PNC schemes to achieve fast and reliable information exchange? In this thesis, we address this question from the following works: Firstly, we studied channel-uncoded PNC in two-way relay fading channels with QPSK modulation. The computation error probability for computing network coded messages at the relay is derived. We then optimized the network coding functions at the relay to improve the error rate performance. We then worked on channel coded PNC. The codes we studied include classical binary code, modern codes, and lattice codes. We analyzed the distance spectra of channel-coded PNC schemes with classical binary codes, to derive upper bounds for error rates of computing network coded messages at the relay. We designed and optimized irregular repeat-accumulate coded PNC. We modified the conventional extrinsic information transfer chart in the optimization process to suit the superimposed signal received at the relay. We analyzed and designed Eisenstein integer based lattice coded PNC in multi-way relay fading channels, to derive error rate performance bounds of computing network coded messages. Finally we extended our work to multi-way relay channels. We proposed a opportunistic transmission scheme for a pair-wise transmission PNC in a single-input single-output multi-way relay channel, to improve the sum-rate at the relay. The error performance of computing network coded messages at the relay is also improved. We optimized the uplink/downlink channel usage for multi-input multi-output multi-way relay channels with PNC to maximize the degrees of freedom capacity. We also showed that the system sum-rate can be further improved by a proposed iterative optimization algorithm

Distributed Cooperative Spatial Multiplexing System

Multiple-Input-Multiple-Output (MIMO) spatial multiplexing systems can increase the spectral efficiency manyfold, without extra bandwidth or transmit power, however these advantages are based on the assumption that channels between different transmit antenna and receive antenna are independent which requires the elements in antenna array be separated by several wavelengths. For small mobile devices, the requirement is difficult to implement in practice. Cooperative spatial multiplexing (C-SM) system provides a solution: it organizes antennas on distributed mobile stations to form a virtual antenna array (VAA) to support spatial multiplexing. In this thesis, we propose a novel C-SM system design which includes a transmitter with two antennas, a single antenna receiver and a relay group with two single antenna relays. In this design, we assume that the transmitter tries to transmit two coded independent messages to the receiver simultaneously but the transmitter-receiver link is too weak to support the transmission. Thus a relay group is introduced to help with the transmission. After relays receive the messages from the transmitter via a $2\times 2$ MIMO link, they first detect and quantize the received messages, then compress them independently according to the Slepian and Wolf theorem, the compressed messages are sent to the receiver simultaneously where de-compression and de-quantization are performed on the received messages. After that the resulting messages are combined to estimate the original coded messages. The estimated coded messages are decoded to produce the original messages. The basic system structure is studied and an analytical bit error rate expression is derived. Several transmission protocols are also introduced to enhance the system BER performance. The merit of this design is focus on the relay destination link. Because the Slepian and Wolf theorem is applied on the relay-destination link, messages at the relays can be compressed independently and de-compressed jointly at the receiver with arbitrarily small error probability but still achieve the same compression rate as a joint compression scheme does. The Slepian and Wolf theorem is implemented by a joint source-channel code in this thesis. Several schemes are introduced and tested, the testing results and performance analysis are given in this thesis. According to the chief executive officer (CEO) problem in the network information theory, we discover an error floor in this design. An analytical expression for this error floor is derived. A feedback link is also introduced from the receiver to the relays to allow the relays to cooperatively adapt their compression rates to the qualities of the received messages. Two combination schemes at the receiver are introduced, their performances are examined from the information theory point of view, the results and performance analysis are given in this thesis. As we assume that the relay destination link is a multiple access channel (MAC) suffers from block Rayleigh fading and white Gaussian noise, the relationship between the MAC channel capacity and the Slepian and Wolf compression rate region is studied to analyse the system performance

Summary of Research 1994

The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government.This report contains 359 summaries of research projects which were carried out under funding of the Naval Postgraduate School Research Program. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, and technical reports. The research was conducted in the areas of Aeronautics and Astronautics, Computer Science, Electrical and Computer Engineering, Mathematics, Mechanical Engineering, Meteorology, National Security Affairs, Oceanography, Operations Research, Physics, and Systems Management. This also includes research by the Command, Control and Communications (C3) Academic Group, Electronic Warfare Academic Group, Space Systems Academic Group, and the Undersea Warfare Academic Group