OFDM modulation

Ultra-wideband (UWB) technology enables high-data-rate communications and centimeter-accurate indoor localization but suffers severe degradation in multipath fading channels due to dense multipath components, narrowband interference (NBI), and low signal-to-noise ratios (SNR). Conventional energy-based detection methods, including Rake receivers, fail under these conditions due to amplitude sensitivity. This paper introduces a phase congruency (PC)-based selective Rake (S-Rake) receiver that exploits phase alignment across frequencies rather than signal magnitude for robust feature detection. The proposed method computes PC metrics via Hilbert transforms and sub-band decomposition to identify phase-aligned multipath components, guiding S-Rake finger selection (4, 8, and 128 fingers) and time-of-arrival (TOA) estimation. Simulations using 6th-derivative Gaussian pulses over IEEE 802.15.3a CM4 channels (NLOS, 4-10 m) with AWGN and IEEE 802.11a interference (SIR=-30 dB to 0 dB) demonstrate that PC-based S-Rake achieves 4 dB SNR gain at BER=10⁻⁴ over conventional Rake under high interference. DS-UWB with PC outperforms TH-UWB by 3× lower BER at SIR=-30 dB. Increasing Rake fingers from 4 to 128 reduces BER by >40% and improves TOA accuracy by 62% (RMSE: 1.8 ns → 0.68 ns). PC maintains BER=10⁻³ at SIR=0 dB where conventional methods fail. Results establish PC as a transformative paradigm for interference-resilient UWB applications including IoT localization and 5G-coexistent communications.

Control signaling strategies for scheduling information in cellular OFDM systems are studied. A single-cell multiuser system model is formulated that provides system capacity estimates accounting for the signaling overhead. Different scheduling granularities are considered, including the one used in the specifications for the 3G Long Term Evolution (LTE). A greedy scheduling method is assumed, where each resource is assigned to the user for which it can support the highest number of bits. The simulation results indicate that the cost of control signaling does not outweigh the scheduling gain, when compared with a simple round-robin scheme that does not need signaling of scheduling information. Furthermore, in the studied scenario, joint coding and signaling of scheduling information over all selected users is found to be superior to separate coding and signaling for each user. The results also indicate that the scheduling granularity used for LTE provides better performance than the full granularity.

This paper considers transmission of scheduling information in OFDMA-based cellular communication systems such as 3GPP long-term evolution (LTE). These systems provide efficient usage of radio resources by allowing users to be scheduled dynamically in both frequency and time. This requires considerable amounts of scheduling information to be sent to the users. The paper compares two basic transmission strategies: transmitting a separate scheduling message to each user versus broadcasting a joint scheduling message to all users. Different scheduling granularities are considered, as well as different scheduling algorithms. The schemes are evaluated in the context of the LTE downlink using multiuser system simulations, assuming a full-buffer situation. The results show that separate transmission of the scheduling information requires a slightly lower overhead than joint broadcasting, when proportional fair scheduling is employed and the users are spread out over the cell area. The results also indicate that the scheduling granularity standardized for LTE provides a good trade-off between scheduling granularity and overhead.

Various Orthogonal Frequency Division Multiplexing (OFDM)-based wireless communication standards have raised more stringent requirements on throughput and flexibility of Fast Fourier Transformation (FFT), a kernel data transformation task in communication systems. Application-specific instruction set processor (ASIP) has emerged as a promising solution to meet these requirements. In this paper, we propose a novel ASIP design tailored for FFT computation. We reconstruct the FFT computation flow into a scalable array structure based on an 8-point butterfly unit (BU). Any-point FFT computation can be carried out in the array structure which can easily expand along both the horizontal and vertical dimensions. We incorporate custom register files to reduce memory access. The data address for custom registers in each FFT stage is changed accordingly, and we derive a regular address changing (AC) rule. With the microarchitecture modifications, we extend the instruction set with three custom instructions correspondingly. Our FFT ASIP implementation achieves great performance improvement over the standard FFT software implementation, one TI DSP processor, and one commercial Xtensa ASIP, with the data throughput improvement as 866.5X, 5.9X, 2.3X, respectively. Meanwhile, the area and power consumption overhead of the custom hardware is negligible.

Fig. 1. Computation of weight combining and its combining process Recovered data demod CI 0 *(0) CI 0 *(1) CI 0 *(N-1) FFT Channel Estimation Weight Computation WN-2 W1 W0 WN-1 WN-1 Fig. 1. Computation of weight combining and its combining process Recovered data demod CI 0 *(0) CI 0 *(1) CI 0 *(N-1) FFT Channel Estimation

The use of discrete Hartley transform (DHT) precoding was recently shown to achieve peak to average power (PAPR) reduction for OFDM. In this paper, we show that DHT precoding also achieves full diversity. We consider the sparse matrix formed by the combination of DHT and the discrete Fourier transform (DFT) and propose a receiver configuration that minimizes complexity. Furthermore, we present a detailed account of the system complexity to show that it is slightly more than uncoded conventional OFDM. Also, since this system saves the complexity required for achieving diversity gain and reducing the peak to average power (PAPR), it reduces the system complexity when the PAPR reduction and diversity techniques are taken into account for conventional OFDM. We analytically show that this system achieves full diversity and then verify it using simulation results. Simulations results also show that the system has a substantial improvement in bit error performance over conventional OFDM.

The primary subject of this paper is the sekction of a pulse-shaping wavefom for in-home power line communications. As system performance is also determined by other parameters affecting the length and shaping of the OFDMsymbol, the problem formulation is expanded to also include the simultaneous selection of guard i n t e n d length and Hunning window length, creating a joint optimization problem. Given the constraints of allowing no transmit notch Flters, and adequate receive side mitigation of narrow band jammers, we jointly optimize the selection of guurd intend length, transmit pulse-shuping and receive side windowing for throughput petfiormance on the average power line channel. Throughput perfotmance is inferred from SNR duta and associated p a r d interval overhead. We also present resulfs of pe gormance assessment and parameter selection, for the average power line channel, based on U collection of 120 measured power line channel impulse responses.

This paper describes the security mechanisms provided in the HomePlug AV specification. It highlights the AV approach for solutions to problems in detection of other nodes with which to form a network, efficient transmission of the initialization vector (IV), reducing risks of key and IV reuse, and implementing "push-button" security for casual users. A novel key agreement protocol based on channel adapted powerline communications is described and analyzed. It also describes mechanisms to allow extensibility for higher layer key distribution protocols.

Unequal Error Protection (UEP) is the key to future multi-layer and scalable data and video transmission. This paper presents a novel bit-loading and channel adaptation technique to realize UEP properties in the physical transport using greedy and sub-optimal bit-loading algorithms. In this case, we exploited the power minimization approach developed by the greedy algorithm to allow for an arbitrary number of classes, arbitrary SNR margins between the classes, and arbitrary numbers of bits per class. We achieved similar results using a fast sub-optimum power minimization bit-loading algorithm based on Campello's algorithm. Our results show the suitability of this technique to realize UEP for a single user case using orthogonal frequency division multiplexing (OFDM). Additionally, we extended the results to demonstrate the performance of allocating resources to two users with different quality of service (QoS), each of which requires data of different priorities.

Radio over fiber (RoF) can be assessed as a system of most convenient combination of optical fiber and radio signals. The technique of orthogonal frequency division multiplexing (OFDM) considers as a data distribution over a huge number of carriers having spaced from each other with specific frequencies at overlap bands. Hence incorporates OFDM with the optical fiber, OFDM-RoF system can be increased the modulation RF access capacity besides high-speed data transmission, it considers a broadband communication trend of the current and future applications specifically for 5G mobile. The optical network scenarios of various RF can be model with optisystem software, and OFDM in addition to use a section of the orthogonal multiplex frequency of 16-quadrature amplitude modulation (QAM) RF modulating signal. In the optical domain, Mach-Zehnder modulator (MZM) optical modulators are used to carry out different results with different fiber lengths. An OFDM-RoF wireless communication system considers as advanced data rate transmission achievement by minimum delays. The essential goal of this paper is for identifying the minimum bit error rate (BER) for the 16-QAM modulation with varying fiber length. The OFDM-RoF system can be able for realizing a fiber length 100 km with a restricted decreasing in the received power so that the constellation noise is became greater despite of applying electrical amplification and optical amplification.

This project over the last four years is by far, the most significant accomplishment of my life and it would be impossible without people who supported and believed in me. My utmost gratitude goes to the ancient of days, the Almighty God, the author of life who has enabled and provided me with the opportunity to embark on this journey of acquisition of knowledge. May His name be forever praised. My heartfelt appreciations and deepest thanks goes to my amiable supervisor, Professor Predrag Rapajic for his expert guidance. His approach to research work is professional and his support throughout my PhD was phenomenal and tremendous. His vast knowledge in Engineering, especially wireless communications, and his skills in research paper writing is overwhelming. His belief in me and the various privileges he had given to me have helped to bring me to this end. He found time to proffer invaluable suggestions and advice towards the realization of this research work. It will be an understatement to say I have gained immensely from his pool of knowledge and persistent encouragement during the course of my PhD work. I would like to express my heartfelt gratitude to the only love of my life, my angel, sweet Uzomaka Goretti ENEH for her understanding and total support at every stage of this PhD work. You are more than a wife to me. Thank you very much. Special appreciation to my lovely twins (Terry and Bliss) whom have continued to shower their love and disturbances throughout my PhD work. I wish to express my special thanks to Mr Emeka Eneh (Akwaeke), Mr Obi Chime and Prof. Ezeugwu of University of Southbank Uk for their candid support from the start to the finish of this work.

We propose a CDMA-OFDM access mechanism for Multihop Cellular Networks (MCN). We construct groups within the MCN, where each group comprises of a source node, a destination node, their intermediate relay nodes and assign a correlated PN sequence to each such group. Within a particular group, a single carrier is assigned to each intermediate hop. The sub carriers assigned to the intermediate hops in a given group are mutually orthogonal. Hence the proposed OFDM is FDMA in nature. The sub carriers and transmit power levels to the relay nodes are assigned in such a way as to maximize the end-to-end throughput. The end-to-end throughput is formulated by assuming a Rayleigh flat fading channel between nodes. We present a method to reuse the PN codes assigned to the groups in a particular cell. We also introduce a novel architecture for MCN. Simulation results show that the proposed access mechanism achieves better end-to-end throughput and bit error rate (BER) performance as compared to ...

In our previous work [1], we have analysed Multiuser Interference (MUI) by considering synchronous and asynchronous transmission under multiuser case for DS-CDMA based OFDM system. In [1] we have considered MUI at receiver from N-1 active users. In this paper we have examine MUI by considering packet based transmission with Impulse radio. In this situation MUI is generated due to collision of UWB pulses, which are used to define single bit under UWB transmission. This type of interference will take place in UWB based network due to organization of information bits into packets by higher layers. Here we have considered the TH-PAM and TH-PPM based Impulse radio systems for evaluating MUI.

Traditionally, analog and/or digital predistortion is used to linearize power amplifiers (PAs), at the cost additional hardware. We here present a novel lineariztion method using segmented non-linear RF-DACs to linearize PAs at no additional hardware cost. Through the DAC bias, we are able to control the expanding non-linearity, bringing a large flexibility. Through simulations, we have demonstrated the robustness and flexibility with this approach, achieving excellent overall linearity over a large range of DAC and PA bias conditions.

Communication systems are continued to improve over the time span with main objective to enhance the quality of service (QoS) for multiple users at same time. Multiplexing techniques re used to emerge the set of users into the channel one the account of time or frequency. That made restricted band or disturbs the communication period (time). Alternatively, OFDM channels are made to utilize so-called orthogonality of users to ensure full band full time. The main challenge to this approach is the noise that hits the user payload (signals). In order to overcome the problem of noise, it was necessary to understand the SNR that channel. This paper proposed four optimization algorithms for optimizing the channel capacity using optimum SNR. The Greedy algorithm has made a 90Mbps of channel capacity in lesser convergence time of 0.1 seconds.

In this paper, a OFDM transceiver system including aDepth-first Stack based Sequential decoding solution that isbased on Schnorr-Eucner by Maximum likelihood method andthe SNR loss compensation method due to the insertion of cyclicprefix in the OFDM transceiver system to solve the inter symbolinterference and inter carrier interference has beenimplemented. The analysis and algorithms are general in nature

Long Term Evolution (LTE) uses different techniques to achieve high throughput required, such as the HARQ techniques, Multiple-Input Multiple-Output (MIMO) transmission schemes and estimation techniques. In the present paper, research focuses on Downlink LTE channel estimation which is based on the interpolation to estimate channel coefficients. Thus, we propose an adaptive method for polynomial interpolation based on Lagrange polynomial. We perform the Downlink LTE system for Single-Input SingleOutput (SISO) and MIMO transmission then compare the obtained results with linear and Sinus Cardinal Interpolations. The simulation results show that the Lagrange method outperforms the linear interpolation in term of Block Error Rate (BLER) and throughput vs. Signal to Noise Ratio (SNR). Keywords-LTE; MIMO; SISO; Interpolation; Lagrange

A high data rate multi-carrier receiver employing orthogonal frequency division multiplexing (OFDM) for mobile communications requires joint low-power VLSI design optimization of the channel equalizer and demodulator. Although the multi-carrier receiver structure can be greatly simplified by use of the Fast Fourier Transform (FFT) for demodulation, the physical hardware complexity of the FFT is still significant. By introducing a powerful channel equalizer, reduction in FFT complexity can be achieved while maintaining sufficient reception quality. This paper analyzes the performance and hardware complexity of the receiver structure in a multipath communications environment. VTC2000