Low-complexity iterative detection techniques for Slow-Frequency-Hop spread-spectrum communications with Reed-Solomon coding.

Slow-frequency-hop (SFH) spread-spectrum communications provide a high level of robustness in packet-radio networks for both military and commercial applications. The use of a Reed-Solomon (R-S) code has proven to be a good choice for use in a SFH system for countering the critical channel impairments of partial-band fading and partial-band interference. In particular, it is effective when reliability information of dwell intervals and individual code symbols can be obtained and errors-and-erasures decoding (EE) can be employed at the receiver. In this dissertation, we consider high-data-rate SFH communications for which the channel in each frequency slot is frequency selective, manifesting itself as intersymbol interference (ISI) at the receiver. The use of a packet-level iterative equalization and decoding technique is considered in conjunction with a SFH system employing R-S coding. In each packet-level iteration, MLSE equalization followed by bounded distance EE decoding is used in each dwell interval. Several per-dwell interleaver designs are considered for the SFH systems and it is shown that packet-level iterations result in a significant improvement in performance with a modest increase in detection complexity for a variety of ISI channels. The use of differential encoding in conjunction with the SFH system and packet-level iterations is also considered, and it is shown to provide further improvements in performance with only a modest additional increase in detection complexity. SFH systems employing packet-level iterations with and without differential encoding are evaluated for channels with partial-band interference. Comparisons are made between the performance of this system and the performance of SFH systems using some other codes and iterative decoding techniques

Non-Coherent Cooperative Communications Dispensing with Channel Estimation Relying on Erasure Insertion Aided Reed-Solomon Coded SFH M-ary FSK Subjected to Partial-Band Interference and Rayleigh Fading

The rationale of our design is that although much of the literature of cooperative systems assumes perfect coherent detection, the assumption of having any channel estimates at the relays imposes an unreasonable burden on the relay station. Hence, non-coherently detected Reed-Solomon (ReS) coded Slow Frequency Hopping (SFH) assisted M -ary Frequency Shift Keying (FSK) is proposed for cooperative wireless networks, subjected to both partial-band interference and Rayleigh fading. Erasure insertion (EI) assisted ReS decoding based on the joint maximum output-ratio threshold test (MO-RTT) is investigated in order to evaluate the attainable system performance. Compared to the conventional error-correction-only decoder, the EI scheme may achieve an Eb/N0 gain of approximately 3dB at the Codeword Error Probability, Pw , of 10-4 , when employing the ReS (31, 20) code combined with 32-FSK modulation. Additionally, we evaluated the system’s performance, when either equal gain combining (EGC) or selection combining (SC) techniques are employed at the destination’s receiver. The results demonstrated that in the presence of one and two assisting relays, the EGC scheme achieves gains of 1.5 dB and 1.0 dB at the Pw of 10-6 , respectively, compared to the SC arrangement. Furthermore, we demonstrated that for the same coding rate and packet size, the ReS (31, 20) code using EI decoding is capable of outperforming convolutional coding, when 32-FSK modulation is considered, whilst LDPC coding had an edge over the above two schemes

Multicarrier Frequency Hopping Spread Spectrum Techniques With Quasi-Cyclic Low Density Parity Check Codes Channel Coding

This work presents a new proposed Multicarrier Frequency Hopping Spread Spectrum (MCFH-SS) system employing Quasi-Cyclic Low Density Parity Check (QC-LDPC) codes instead of the conventional LDPC codes. A new technique for constructing the QC-LDPC codes based on row division method is proposed. The new codes offer more flexibility in terms of high girth, multiple code rates and block length. Moreover, a new scheme for channel prediction in MCFH-SS system is proposed. The technique adaptively estimates the channel conditions and eliminates the need for the system to transmit a request message prior to transmitting the packet data. The ready-to-use channel will be occupied with a Pseudonoise (PN) code and use for transmission or else, it will be banned

Coherent peak detection algorithms for utra first stage code acquisition

The first stage of UTRA code acquisition is the most crucial stage of the cell search process because it has to deal with the largest amount of uncertainty. We assume that the cell search starts when the mobile station is turned on with no prior information about the base station(s) that may be in the vicinity of the mobile station. The mobile station must acquire slot boundaries in order to obtain timing information of the detected base station. Therefore, this large amount of uncertainty gives longer mean acquisition time. In this thesis, we have devised four new peak detection algorithms for first stage code acquisition. We utilize the available base stations with few multipath signals along with the standard oversampling and pipelining utilization. We compare different coherent and non-coherent combining techniques and run simulations for different carrier frequency errors. We have developed simulation software using MATLAB, to simulate the performance of these algorithms. Our simulation results show that coherent combining for some of the new algorithms provide results close if not better than its non-coherent counterpart even at moderate carrier frequency errors especially at low signal to interference ratio

Design guidelines for spatial modulation

A new class of low-complexity, yet energyefficient Multiple-Input Multiple-Output (MIMO) transmission techniques, namely the family of Spatial Modulation (SM) aided MIMOs (SM-MIMO) has emerged. These systems are capable of exploiting the spatial dimensions (i.e. the antenna indices) as an additional dimension invoked for transmitting information, apart from the traditional Amplitude and Phase Modulation (APM). SM is capable of efficiently operating in diverse MIMO configurations in the context of future communication systems. It constitutes a promising transmission candidate for large-scale MIMO design and for the indoor optical wireless communication whilst relying on a single-Radio Frequency (RF) chain. Moreover, SM may also be viewed as an entirely new hybrid modulation scheme, which is still in its infancy. This paper aims for providing a general survey of the SM design framework as well as of its intrinsic limits. In particular, we focus our attention on the associated transceiver design, on spatial constellation optimization, on link adaptation techniques, on distributed/ cooperative protocol design issues, and on their meritorious variants

On the theoretical aspects of multi-carrier spread spectrum systems.

by Tsan-Fai Ho.Thesis (M.Phil.)--Chinese University of Hong Kong, 1996.Includes bibliographical references (leaves 64-68).Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Review on spread spectrum communications --- p.1Chapter 1.2 --- The spread spectrum techniques --- p.2Chapter 1.2.1 --- Direct Sequence (DS) Systems --- p.2Chapter 1.2.2 --- Frequency Hopping (FH) Systems --- p.2Chapter 1.2.3 --- Time Hopping (TH) Systems --- p.4Chapter 1.2.4 --- Hybrid Systems --- p.4Chapter 1.3 --- Existing Applications of the spread spectrum systems --- p.5Chapter 1.4 --- Organization of the thesis --- p.6Chapter 2 --- The Concept of Duality --- p.7Chapter 2.1 --- Multi-Carrier Systems - An Overview --- p.7Chapter 2.2 --- Orthogonal Frequency Division Multiplexing --- p.8Chapter 2.2.1 --- Bandwidth Efficiency --- p.9Chapter 2.2.2 --- Spectral Efficiency --- p.10Chapter 2.2.3 --- Effects of fading --- p.11Chapter 2.3 --- Applications of OFDM in multiple access --- p.13Chapter 2.3.1 --- ST-CDMA --- p.13Chapter 2.3.2 --- MC-DS-CDMA --- p.14Chapter 2.3.3 --- OFDM-CDMA --- p.15Chapter 2.4 --- Duality - Time-Frequency Interrelation --- p.16Chapter 3 --- Performance of Multi-Carrier CDMA System --- p.17Chapter 3.1 --- System Model --- p.17Chapter 3.2 --- Performance Analysis --- p.20Chapter 3.2.1 --- Gaussian Channel --- p.20Chapter 3.2.2 --- Fading Channel --- p.24Chapter 3.3 --- Performance with Pulse Shape --- p.33Chapter 3.4 --- Appendix --- p.34Chapter 4 --- Signal Design Criteria for MC-CDMA System --- p.36Chapter 4.1 --- Existence of Signal Distortion --- p.37Chapter 4.2 --- Measures of the Signal Envelope Fluctuation --- p.38Chapter 4.3 --- Complementary Sequences --- p.41Chapter 4.4 --- Crest Factors --- p.42Chapter 4.4.1 --- Time-limited Pulse --- p.43Chapter 4.4.2 --- Ideally Band-Limited Pulses --- p.43Chapter 4.4.3 --- Shaped Pulses --- p.45Chapter 4.5 --- Spectrally Efficient Complementary (SEC) Sequences --- p.48Chapter 4.6 --- Construction of Spectrally Efficient Complementary(SEC) Sequences --- p.50Chapter 4.7 --- Generalized Multiphase Spectrally Efficient Complementary Sequences --- p.55Chapter 5 --- Summary and Future Extensions --- p.58Chapter 5.1 --- Summary of the Results --- p.58Chapter 5.2 --- Topics for Future Research --- p.59AppendixChapter A --- Exhaustive search of MPSEC sequences --- p.61Chapter B --- Papers derived from this thesis --- p.63Bibliography --- p.6

Low-resolution ADC receiver design, MIMO interference cancellation prototyping, and PHY secrecy analysis.

This dissertation studies three independent research topics in the general field of wireless communications. The first topic focuses on new receiver design with low-resolution analog-to-digital converters (ADC). In future massive multiple-input-multiple-output (MIMO) systems, multiple high-speed high-resolution ADCs will become a bottleneck for practical applications because of the hardware complexity and power consumption. One solution to this problem is to adopt low-cost low-precision ADCs instead. In Chapter II, MU-MIMO-OFDM systems only equipped with low-precision ADCs are considered. A new turbo receiver structure is proposed to improve the overall system performance. Meanwhile, ultra-low-cost communication devices can enable massive deployment of disposable wireless relays. In Chapter III, the feasibility of using a one-bit relay cluster to help a power-constrained transmitter for distant communication is investigated. Nonlinear estimators are applied to enable effective decoding. The second topic focuses prototyping and verification of a LTE and WiFi co-existence system, where the operation of LTE in unlicensed spectrum (LTE-U) is discussed. LTE-U extends the benefits of LTE and LTE Advanced to unlicensed spectrum, enabling mobile operators to offload data traffic onto unlicensed frequencies more efficiently and effectively. With LTE-U, operators can offer consumers a more robust and seamless mobile broadband experience with better coverage and higher download speeds. As the coexistence leads to considerable performance instability of both LTE and WiFi transmissions, the LTE and WiFi receivers with MIMO interference canceller are designed and prototyped to support the coexistence in Chapter IV. The third topic focuses on theoretical analysis of physical-layer secrecy with finite blocklength. Unlike upper layer security approaches, the physical-layer communication security can guarantee information-theoretic secrecy. Current studies on the physical-layer secrecy are all based on infinite blocklength. Nevertheless, these asymptotic studies are unrealistic and the finite blocklength effect is crucial for practical secrecy communication. In Chapter V, a practical analysis of secure lattice codes is provided