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

Demonstration of Negative Impedance Conversion for Bandwidth Extension in VLC

This work proposes and demonstrates the utility of a negative impedance converter (NIC) circuit, based on a common collector (CC) amplifier, for the generation of negative capacitance. The design principle of the proposed NIC is introduced, then a negative capacitance equals -200 pF is demonstrated using discrete devices constructed on a printed circuit board (PCB). The designed NIC is applied for the bandwidth extension of LEDs to enhance the achievable data rates in visible light communication (VLC) systems. The paper includes analytical derivations of the obtained negative capacitance as a function of circuit parameters and verifies this by both simulation and experimentally. Measurements show significant bandwidth extension by neutralising the bandwidth-limiting effect of the LED diffusion capacitance through the introduction of a parallel negative capacitance

Energy and Spectrally Efficient Signalling for Next Generation IoT

This work proposes an energy and spectrally efficient signalling technique for the next generation internet of things (IoT). The signalling method employs the bandwidth compressed fast-orthogonal frequency division multiplexing (FOFDM) scheme with the single dimensional pulse amplitude modulation (PAM) as well as the frequency orthogonal filtering technique using Hilbert transform (HT) pair. The proposed HT-FOFDM system is designed and modelled based on the narrowband IoT (NB-IoT) specifications. To investigate the designed signalling method of different spectral efficiencies, we conducted simulations for HT-FOFDM with comparisons to single-carrier frequency division multiple access (SC-FDMA). We show that the proposed PAM modulated HT-FOFDM signalling increases the data rate effectively while maintaining reliable transmission within the same bandwidth of 180kHz. Comparative results of the bit error rate (BER) performance in additive white Gaussian noise (AWGN) channel and constellation diagrams of received noisy signals are presented. Furthermore, we show that HT-FOFDM with PAM modulation schemes comprehensively outperforms SC-FDMA that achieves the same spectral efficiencies with significant power advantages

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

FPGA design of low complexity SEFDM detection techniques

This paper presents for the first time the hardware design of low complexity detection algorithms for the recovery of Spectrally Efficient Frequency Division Multiplexing (SEFDM) signals. The work shows that a practical design is feasible using Field Programmable Gate Arrays (FPGAs). Two detection techniques can be implemented using the proposed system architecture, namely Zero Forcing (ZF) and Truncated Singular Value Decomposition (TSVD), demonstrating that our hardware design is flexible. TSVD offers a significant reduction in complexity compared to optimal detection techniques, such as Maximum Likelihood (ML) while outperforming ZF, in terms of Bit Error Rate (BER). Results show excellent fixed-point performance and are comparable to existing floating-point computer-based simulations

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

A Joint Waveform and Precoding Design for Non-orthogonal Multicarrier Signals

In the spectrally efficient frequency division multiplexing (SEFDM) non-orthogonal multicarrier signal, higher spectral efficiency can be achieved at the expense of self-created inter carrier interference (ICI). The effective interference, which is contributed by all sub-carriers, has to be minimized and this results in a receiver of significant complexity. In order to mitigate the interference and simplify the receiver design, in this work, a precoding technique, based on eigenvalue decomposition of the sub-carrier correlation matrix, is utilised. Briefly, the technique is based on modifying the data sent on individual sub-carriers according to the signal quality of each, which is based on the sub-carrier to interference ratio (ScIR) of such sub-carrier as estimated from eigenvalue decomposition. A full system model is presented in this paper and simulations show that the precoding of SEFDM results in either better bit error rate (BER) performance compared to that of an orthogonal frequency division multiplexing (OFDM) system of the same spectral efficiency or in higher effective bit rate relative to an OFDM system with the same BER performance. Modelling is done in simple Gaussian noise channels and in a static frequency selective channel and for different modulation formats. Results show that for the same bandwidth a 128QAM precoded SEFDM system outperforms a 16QAM OFDM one by offering 75% bit rate increase. Furthermore, Turbo coding assisted BER performance comparisons are investigated in this work. Using 64QAM modulated symbols, the precoded SEFDM outperforms the typical OFDM by several dBs

Prototyping of Singular Value Reconstruction Precoding for Reliable Non-Orthogonal IoT Signals

Massive connectivity is one of the main research directions for beyond 5G. The cellular based narrowband IoT (NB-IoT), enabled by the orthogonal frequency division multiplexing (OFDM) signal, is an important technique. To evolve into the beyond 5G era, non-orthogonal concepts are preferred to re-shape the NB-IoT to provide higher spectral efficiency, wider coverage and lower power consumed services. This work investigates a non-orthogonal waveform in next generation IoT (NG-IoT) scenarios. Previous work has verified the advantages of zero forcing (ZF) precoding in interference mitigation but with some limitations. This work proposes a singular value reconstruction (SVR) precoding method, which can improve the precoding reliability and greatly reduce noise sensitivity. Simulations show significant spectral efficiency gain when compared with the previous work. An experiment platform is then configured in an over-the-air multiuser multiple input multiple output (MIMO) scenario to verify the practical feasibility of the precoding algorithm

Bandwidth Enhancement Technique for Bipolar Single Stage Distributed Amplifier Design

This work reports a novel approach to extending the bandwidth of single stage distributed amplifiers (SSDAs). The three-stepped technique involves scaling down the inductance on the input artificial transmission line (ATL); creating a high frequency resonance peak by the addition of shunt capacitance on the input ATL; and compensating for the resulting increased reflection with adapted negative resistance attenuation compensation techniques. Compared with the inductive-peaked cascode technique applied in the SSDA which currently has the highest reported bandwidth, simulation results, based on full foundry transistor models, predict up to 30% improvement in gain-bandwidth (GBW) performance for the same active device at the same bias. In addition, the reduction in the length of the input ATL effectively reduces transmission line losses, thereby improving the overall gain performance