Square-root Nyquist filter design for QAM-based filter bank multicarrier systems

Filter bank multicarrier systems with quadrature amplitude modulation (FBMC/QAM) have drawn attentions to get the advantage of complex symbol transmission, as well as very low out of band radiation and relaxed synchronization requirements for asynchronous scenarios. In order to make this system viable for practical deployment, the biggest challenge is designing appropriate filters to minimize the interference between adjacent subcarriers, while maintaining the Nyquist property of the filter. We show that the deviation from the Nyquist property can be compensated through the fractional shift of the filtered symbols, which provides flexibility to optimize the stopband of the filter. The proposed design method shows advantages over the state of the art designs, and provides guidance for the filter design in practical FBMC/QAM systems

Improved Nyquist pulse shaping filters for generalized frequency division multiplexing

Generalized Frequency-Division Multiplexing (GFDM) is one of the multicarrier modulation schemes currently under study for next generation 5G cellular networks. One of the main characteristics of GFDM is the low out of band emission that is achieved by means of a flexible time-domain pulse shaping of individual subcarriers. In the paper, we propose to use improved Nyquist pulse shaping filters which have been originally introduced in the context of single-carrier modulation schemes for reducing the sensitivity to symbol timing error due to their higher eye opening and smaller maximum distortion. Here we consider their use in GFDM and evaluate their symbol error rate (SER) performance in case of 16-QAM transmission over an additive white Gaussian noise channel. Moreover, we also considered the concept of the wavelet for better time-frequency localization of the pulse shaping filters by using the Meyer auxiliary function. Numerical results are reported to demonstrate the superior SER performance achieved by the proposed improved Nyquist pulse shaping filters in comparison to that achieved with conventional Nyquist pulse shaping filters

Frequency Spreading Equalization in Multicarrier Massive MIMO

Application of filter bank multicarrier (FBMC) as an effective method for signaling over massive MIMO channels has been recently proposed. This paper further expands the application of FBMC to massive MIMO by applying frequency spreading equalization (FSE) to these channels. FSE allows us to achieve a more accurate equalization. Hence, higher number of bits per symbol can be transmitted and the bandwidth of each subcarrier can be widened. Widening the bandwidth of each subcarrier leads to (i) higher bandwidth efficiency; (ii) lower complexity; (iii) lower sensitivity to carrier frequency offset (CFO); (iv) reduced peak-to-average power ratio (PAPR); and (iv) reduced latency. All these appealing advantages have a direct impact on the digital as well as analog circuitry that is needed for the system implementation. In this paper, we develop the mathematical formulation of the minimum mean square error (MMSE) FSE for massive MIMO systems. This analysis guides us to decide on the number of subcarriers that will be sufficient for practical channel models.Comment: Accepted in IEEE ICC 2015 - Workshop on 5G & Beyond - Enabling Technologies and Application

Doctor of Philosophy

dissertationThe demand for high speed communication has been increasing in the past two decades. Multicarrier communication technology has been suggested to address this demand. Orthogonal frequency-division multiplexing (OFDM) is the most widely used multicarrier technique. However, OFDM has a number of disadvantages in time-varying channels, multiple access, and cognitive radios. On the other hand, filterbank multicarrier (FBMC) communication has been suggested as an alternative to OFDM that can overcome the disadvantages of OFDM. In this dissertation, we investigate the application of filtered multitone (FMT), a subset of FBMC modulation methods, to slow fading and fast fading channels. We investigate the FMT transmitter and receiver in continuous and discrete time domains. An efficient implementation of FMT systems is derived and the conditions for perfect reconstruction in an FBMC communication system are presented. We derive equations for FMT in slow fading channels that allow evaluation of FMT when applied to mobile wireless communication systems. We consider using fractionally spaced per tone channel equalizers with different number of taps. The numerical results are presented to investigate the performance of these equalizers. The numerical results show that single-tap equalizers suffice for typical wireless channels. The equalizer design study is advanced by introducing adaptive equalizers which use channel estimation. We derive equations for a minimum mean square error (MMSE) channel estimator and improve the channel estimation by considering the finite duration of channel impulse response. The results of optimum equalizers (when channel is known perfectly) are compared with those of the adaptive equalizers, and it is found that a loss of 1 dB or less incurs. We also introduce a new form of FMT which is specially designed to handle doubly dispersive channels. This method is called FMT-dd (FMT for doubly dispersive channels). The proposed FMT-dd is applied to two common methods of data symbol orientation in the time-frequency space grid; namely, rectangular and hexagonal lattices. The performance of these methods along with OFDM and the conventional FMT are compared and a significant improvement in performance is observed. The FMT-dd design is applied to real-world underwater acoustic (UWA) communication channels. The experimental results from an at-sea experiment (ACOMM10) show that this new design provides a significant gain over OFDM. The feasibility of implementing a MIMO system for multicarrier UWA communication channels is studied through computer simulations. Our study emphasizes the bandwidth efficiency of multicarrier MIMO communications .We show that the value of MIMO to UWA communication is very limited

MULTICARRIER TRANSMISSION TECHNIQUES

In this thesis, multicarrier transmission techniques envisioned for the fifth-generation wireless networks are studied. First, three basic techniques, namely orthogonal frequency-division multiplexing (OFDM), filter-bank multicarrier offset quadrature amplitude modulation (FBMC-OQAM), and generalized frequency-division multiplexing (GFDM) are reviewed in detail. In particular, the block-based structure and cyclic prefixing of OFDM are discussed and its bit error rate (BER) performance is analyzed. Then it is demonstrated that with offset QAM the orthogonality between subcarriers in FBMC-OQAM is preserved. Next, the roles of tail biting technique and circular convolution in GFDM are explained. An efficient implementation of GFDM is also described. Second, circular filterbank multicarrier offset QAM (CFBMC-OQAM), a technique which combines the block-based structure of GFDM and offset QAM of FBMC-OQAM, is presented. Then a precoded scheme is proposed, in which the Walsh-Hadamard (WH) transform is applied to CFBMC-OQAM system, resulting in a precoded scheme called WH-CFBMC-OQAM. The proposed system has a block-based structure and can be implemented efficiently using fast Fourier transform (FTT) and inverse FFT (IFFT). In addition, a cyclic prefix can be inserted to facilitate simple equalization at the receiver. WH-CFBMC-OQAM exploits the frequency diversity by averaging the signal-to-noise ratios (SNRs) over all subcarriers. A theoretical approximation for the bit error rate performance of WH-CFBMC-OQAM over a frequency-selective channel is derived. Under the same system configuration, simulation results demonstrate the excellent performance of the proposed scheme when compared to the performance of other techniques. Simulation also verifies that the theoretical results match perfectly with simulation results for any SNR value

PAPR and BER Analysis in FBMC/OQAM System with Pulse Shaping Filters and Various PAPR Minimization Methods

Filter Bank Multicarrier with Offset Quadrature Amplitude Modulation(FBMC/OQAM) system design based on frequency sampling prototype filter takes into account the low frequency utilization of Orthogonal Frequency Division Multiplexing(OFDM)  caused by adding Cyclic Prefix(CP). The CP decreases spectral efficiency and increases Peak to Average Power Ratio(PAPR). FBMC is an OFDM enhancement. In this paper to reduce the PAPR, we explained companding methods. We have proposed an FBMC that makes use of prototype pulse shaping filters which can be adjusted to meet system requirements in order to defeat these limitations. Due to its significant effect on the performance of FBMC-OQAM, choosing the right filter is crucial. Different prototype filters are used to investigate the performance of the FBMC-OQAM in this paper. Using the validated system, it was found that frequency utilization is more and good out-band suppression as well as an excellent application value in 5G technology. By using ?-law companding method, FBMC/OQAM provides better performance. It produces low PAPR, low out of band(OoB), high BER performance, less computational complexity and high spectral efficiency as compared to other methods

Doctor of Philosophy

dissertationThe use of multicarrier techniques has allowed the rapid expansion of broadband wireless communications. Orthogonal frequency division multiplexing (OFDM) has been the most dominant technology in the past decade. It has been deployed in both indoor Wi-Fi and cellular environments, and has been researched for use in underwater acoustic channels. Recent works in wireless communications include the extension of OFDM to multiple access applications. Multiple access OFDM, or orthogonal frequency division multiple access (OFDMA), has been implemented in the third generation partnership project (3GPP) long- term evolution (LTE) downlink. In order to reduce the intercarrier interference (ICI) when user's synchronization is relaxed, filterbank multicarrier communication (FBMC) systems have been proposed. The first contribution made in this dissertation is a novel study of the classical FBMC systems that were presented in 1960s. We note that two distinct methods were presented then. We show that these methods are closely related through a modulation and a time/frequency scaling step. For cellular channels, OFDM also has the weakness of relatively large peak-to-average power ratios (PAPR). A special form of OFDM for the uplink of multiple access networks, called single carrier frequency division multiple access (SC-FDMA), has been developed to mitigate this issue. In this regard, this dissertation makes two contributions. First, we develop an optimization method for designing an effective precoding method for SC-FDMA systems. Second, we show how an equivalent to SC-FDMA can be developed for systems that are based on FBMC. In underwater acoustic communications applications, researchers are investigating the use of multicarrier communication systems like OFDM in underwater channels. The movement of the communicating vehicles scales the received signal along the time axis, which is often referred to as Doppler scaling. To undo the signal degradation, researchers have investigated methods to estimate the Doppler scaling factor and restore the original signal using resampling. We investigate a method called nonuniform fast Fourier transform (NUFFT) and apply that to increase the precision in the detection and correction of the Doppler scaling factor. NUFFT is applied to both OFDM and FBMC and its performance over the experimental data obtained from at sea experiments is investigated

Improving GFDM Symbol Error Rate Performance using Better than Nyquist Pulse Shaping Filters

Fourth generation (4G) cellular systems have been optimized to provide high data rates and reliable coverage to mobile users. New waveforms at the physical layer are needed. Generalized frequency division multiplexing (GFDM) is a candidate modulation for the fifth generation (5G) standard based on multi-branch multicarrier filter bank approach. A main characteristic of GFDM is its low out of band emission, achieved by means of a flexible time-domain pulse shaping of individual subcarriers. In this paper, the influence of the improved Better than Nyquist pulse shaping filters on symbol error rate (SER) performance of the GFDM system in the case of zero forcing (ZF) receiver is investigated. We considered their use in GFDM to evaluate the impact on SER performance in case of 16-QAM transmission over an additive white Gaussian noise channel. Moreover, we also considered the concept of the wavelet for better time-frequency localization of the pulse shaping filters by using the Meyer auxiliary function. Numerical results are reported to demonstrate the superior SER performance achieved