Combinatorial FSK modulation for power-efficient high-rate communications

Deep-space and satellite communications systems must be capable of conveying high-rate data accurately with low transmitter power, often through dispersive channels. A class of noncoherent Combinatorial Frequency Shift Keying (CFSK) modulation schemes is investigated which address these needs. The bit error rate performance of this class of modulation formats is analyzed and compared to the more traditional modulation types. Candidate modulator, demodulator, and digital signal processing (DSP) hardware structures are examined in detail. System-level issues are also discussed

FPGA Based Efficient OFDM Based Design and Implementation for Data and Image Transmission for Healthcare

Enormous growth in telecommunication industry demands for high speed data transmission with better quality of service (Qos). The telecommunication networks are offering the services which is from 1 Mbps to several Mbps of speed. However, most of the existing techniques address to assure the very high speed data for multimedia communication. The multimedia data may find a suitable application in healthcare system. The OFDM modulation technique promises to provide the multimedia services at rather high speed using the spectrum more efficient compared traditional scheme like TDMA, FDMA. The orthogonality of carriers eliminates the interference among the closely packed carriers and offers comparatively efficient bandwidth. The OFDM design requires choosing proper parameter selection. Important feature of OFDM is that the multipaths are effectively eliminated by choosing a higher cyclic prefix values which, gives significant results but causing more energy loss. This paper presents an efficient design for OFDMtransceiver by using FPGA. The design is modeled and simulated using Matlab Simulink and finally the design is coded using Verilog RTL and simulated in modelsim and synthesizing and implementation is done using in Xilinx EDA tool. The image type of data is taken for transmission in the proposed OFDM transceiver system. The received image type data achieves PSNR value of 29.920dB and the binary input data achieves 36.06% improvement in power utilization and less area overhead. The paper also shows the improvement in area and power compared to existing authors.Published By: Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP) © Copyright: All rights reserved

Transmission Experiment of Bandwidth Compressed Carrier Aggregation in a Realistic Fading Channel

In this paper, an experimental testbed is designed to evaluate the performance of a bandwidth compressed multicarrier technique termed spectrally efficient frequency division multiplexing (SEFDM) in a carrier aggregation (CA) scenario1. Unlike orthogonal frequency division multiplexing (OFDM), SEFDM is a non-orthogonal waveform which, relative to OFDM, packs more sub-carriers in a given bandwidth, thereby improving spectral efficiency. CA is a long term evolution-advanced (LTE-Advanced) featured technique that offers a higher throughput by aggregating multiple legacy radio bands. Considering the scarcity of radio spectrum, SEFDM signals can be utilized to enhance CA performance. The combination of the two techniques results in a larger number of aggregated component carriers (CCs) and therefore increased data rate in a given bandwidth with no additional spectral allocation. It is experimentally shown that CA-SEFDM can aggregate up to 7 CCs in a limited bandwidth while CA-OFDM can only put 5 CCs in the same bandwidth. In this work, LTE-like framed CA-SEFDM signals are generated and delivered through a realistic LTE channel. A complete experimental setup is described together with error performance and effective spectral efficiency comparisons. Experimental results show that the measured BER performance for CA-SEFDM is very close to CA-OFDM and the effective spectral efficiency of CA-SEFDM can be substantially higher than that of CA-OFDM

Nyquist-SEFDM: Pulse shaped multicarrier communication with sub-carrier spacing below the symbol rate

A new waveform design which simultaneously compresses bandwidth and suppresses out-of-band power leakage is studied in this work considering future 5th generation (5G) requirements. Thus, doubly created interference, coming from less than symbol rate packed sub-carriers and pulse shaping filters, is introduced. Therefore, this work, through using specially designed detectors, deals with the doubly created interference problem. It paves the way to non-orthogonal signal detection and non-orthogonal carrier aggregation (CA) system designs; both of importance to future wireless and wired communication systems

Fast TCM Decoding: Phase Quantization and Integer Weighting

TCM, combining modulation and coding, achieves coding gains over conventional uncoded multilevel modulation without the attendant bandwidth expansion. Since TCM was proposed Ungerboeck (1982, 1987) substantial work has done in this area. A large portion of the TCM work has been in the area of high-speed data transmission over voice grade modems using quadrature amplitude modulation, QAM. QAM, not having a constant envelope, is unattractive for employing a TWT with its nonlinear behavior as the power stage. Additional work has been done in utilizing M-ary PSK with TCM. Simulations by Taylor and Chan (1981) utilizing a 4-state convolutional code demonstrated the coding gain of a rate 2/3 coded 8-PSK modulation scheme. Wilson et. al. (1984) obtained results for 16-PSK TCM using codes with 4 to 32 states and achieved coding gains of 3.5 to 4.8 dB respectively, over 8-PSK and demonstrated that small memory codes achieved good gains with simple design procedures

Spectrally Efficient FDM over Satellite Systems with Advanced Interference Cancellation

For high data rates satellite systems, where multiple carriers are frequency division multiplexed with a slight overlap, the overall spectral efficiency is limited. This work applies highly overlapped carriers for satellite broadcast and broadband scenarios to achieve higher spectral efficiency. Spectrally efficient frequency division multiplexing (SEFDM) compresses subcarrier spacing to increase the spectral efficiency at the expense of orthogonality violation. SEFDM systems performance degrades compared to orthogonal signals, unless efficient interference cancellation is used. Turbo equalisation with interference cancellation is implemented to improve receiver performance for variable coding, compression and modulation/constellation proposals that may be applied in satellite communications settings. Such parameters may be set to satisfy pre-defined spectral efficiency values for a given quality index (QI) or associated application. Assuming LDPC coded data, the work proposes two approaches to receiver design; a simple matched filter approach and an approach utilising an iterative interference cancellation structure specially designed for SEFDM. Mathematical models and simulations studies are presented indicating promising gains to be achieved for SEFDM transmission with advanced transceiver architectures at the cost of increased complexity at the receiver

Timing-Error Tolerance Techniques for Low-Power DSP: Filters and Transforms

Low-power Digital Signal Processing (DSP) circuits are critical to commercial System-on-Chip design for battery powered devices. Dynamic Voltage Scaling (DVS) of digital circuits can reclaim worst-case supply voltage margins for delay variation, reducing power consumption. However, removing static margins without compromising robustness is tremendously challenging, especially in an era of escalating reliability concerns due to continued process scaling. The Razor DVS scheme addresses these concerns, by ensuring robustness using explicit timing-error detection and correction circuits. Nonetheless, the design of low-complexity and low-power error correction is often challenging. In this thesis, the Razor framework is applied to fixed-precision DSP filters and transforms. The inherent error tolerance of many DSP algorithms is exploited to achieve very low-overhead error correction. Novel error correction schemes for DSP datapaths are proposed, with very low-overhead circuit realisations. Two new approximate error correction approaches are proposed. The first is based on an adapted sum-of-products form that prevents errors in intermediate results reaching the output, while the second approach forces errors to occur only in less significant bits of each result by shaping the critical path distribution. A third approach is described that achieves exact error correction using time borrowing techniques on critical paths. Unlike previously published approaches, all three proposed are suitable for high clock frequency implementations, as demonstrated with fully placed and routed FIR, FFT and DCT implementations in 90nm and 32nm CMOS. Design issues and theoretical modelling are presented for each approach, along with SPICE simulation results demonstrating power savings of 21 – 29%. Finally, the design of a baseband transmitter in 32nm CMOS for the Spectrally Efficient FDM (SEFDM) system is presented. SEFDM systems offer bandwidth savings compared to Orthogonal FDM (OFDM), at the cost of increased complexity and power consumption, which is quantified with the first VLSI architecture

Non-Orthogonal Narrowband Internet of Things: A Design for Saving Bandwidth and Doubling the Number of Connected Devices

IEEE Narrowband IoT (NB-IoT) is a low power wide area network (LPWAN) technique introduced in 3GPP release 13. The narrowband transmission scheme enables high capacity, wide coverage and low power consumption communications. With the increasing demand for services over the air, wireless spectrum is becoming scarce and new techniques are required to boost the number of connected devices within a limited spectral resource to meet the service requirements. This work provides a compressed signal waveform solution, termed fast-orthogonal frequency division multiplexing (Fast-OFDM), to double potentially the number of connected devices by compressing occupied bandwidth of each device without compromising data rate and bit error rate (BER) performance. Simulation is firstly evaluated for the Fast-OFDM with comparisons to single-carrier-frequency division multiple access (SC-FDMA). Results indicate the same performance for both systems in additive white Gaussian noise (AWGN) channel. Experimental measurements are also presented to show the bandwidth saving benefits of Fast-OFDM. It is shown that in a line-of-sight (LOS) scenario, Fast-OFDM has similar performance as SC-FDMA but with 50% bandwidth saving. This research paves the way for extended coverage, enhanced capacity and improved data rate of NB-IoT in 5th generation (5G) new radio (NR) networks

Variable-Rate VLSI Architecture for 400-Gb/s Hard-Decision Product Decoder

Variable-rate transceivers, which adapt to the conditions, will be central to energy-efficient communication. However, fiber-optic communication systems with high bit-rate requirements make design of flexible transceivers challenging, since additional circuits needed to orchestrate the flexibility will increase area and degrade speed. We propose a variable-rate VLSI architecture of a forward error correction (FEC) decoder based on hard-decision product codes. Variable shortening of component codes provides a mechanism by which code rate can be varied, the number of iterations offers a knob to control the coding gain, while a key-equation solver module that can swap between error-locator polynomial coefficients provides a means to change error correction capability. Our evaluations based on 28-nm netlists show that a variable-rate decoder implementation can offer a net coding gain (NCG) range of 9.96-10.38 dB at a post-FEC bit-error rate of 10^-15. The decoder achieves throughputs in excess of 400 Gb/s, latencies below 53 ns, and energy efficiencies of 1.14 pJ/bit or less. While the area of the variable-rate decoder is 31% larger than a decoder with a fixed rate, the power dissipation is a mere 5% higher. The variable error correction capability feature increases the NCG range further, to above 10.5 dB, but at a significant area cost