S. Kamilah Syed-Yusof

Bio: S. Kamilah Syed-Yusof is an academic researcher from Universiti Teknologi Malaysia. The author has contributed to research in topics: Additive white Gaussian noise & EXIT chart. The author has an hindex of 1, co-authored 1 publications receiving 13 citations.

Soft-feedback MMSE equalization for non-orthogonal frequency division multiplexing (n-OFDM) signal detection

Abstract: A frequency division multiplexing technique, nonorthogonal frequency division multiplexing (n-OFDM), is proposed in [1]– [2] to enhance the efficiency of bandwidth utilization. This paper reveals that the smaller the frequency separation, the larger sum capacity can be achieved compared with the conventional OFDM technique. However, n-OFDM system introduces inter-carrier interference (ICI) at the transmitter because the orthogonality between the subcarriers no longer holds. Moreover, since the channel covariance matrix of n-OFDM has high condition number when the overlapping factor, 1 − α, is large, conventional linear detectors suffers from severe noise enhancement. To solve this problem, this paper proposes the use of soft cancellation- minimum mean-squared error (SCMMSE) turbo equalization. Binary constellation constrained mutual information (CCMI) is calculated by utilizing the area property for the EXtrinsic Information Transfer (EXIT) chart of the SC-MMSE equalizer. Results of the EXIT chart analysis and bit-error-rate (BER) simulations in additive white Gaussian noise (AWGN) channel are presented.

The First 15 Years of SEFDM: A Brief Survey

Abstract: Spectrally efficient frequency division multiplexing (SEFDM) is a multi-carrier signal waveform, which achieves higher spectral efficiency, relative to conventional orthogonal frequency division multiplexing (OFDM), by violating the orthogonality of its sub-carriers. This survey provides the history of SEFDM development since its inception in 2003, covering fundamentals and concepts, wireless and optical communications applications, circuit design and experimental testbeds. We focus on work done at UCL and outline work done other universities and research laboratories worldwide. We outline techniques to improve the performance of SEFDM and its practical utility with focus on signal generation, detection and channel estimation.

Spectrally efficient FDM: Spectrum saving technique for 5G?

Abstract: Spectrally efficient frequency division multiplexing (SEFDM) improves spectral efficiency relative to the well known orthogonal frequency division multiplexing (OFDM) Optimal detection of SEFDM, to recover signals corrupted by inter carrier interference (ICI), has major drawbacks in the exponential growth of detection complexity with the enlargement of system size and modulation level This poses several challenges to SEFDM practical implementations In this work, we present and compare practicable detection algorithms for both uncoded and coded SEFDM systems In the case of the uncoded system, we discuss a multi-band architecture termed block-spectrally efficient frequency division multiplexing (B-SEFDM) which subdivides the signal spectrum into several blocks, allowing each block to be detected separately The other system discussed in the paper utilizes convolutional coding with an appropriate receiver comprising a fast Fourier transform (FFT) based demodulation and detection working alongside a standard Bahl-Cocke-Jelinek-Raviv (BCJR) decoder Mathematical modelling results show the suitability of the detector for use in large size non-orthogonal multicarrier systems In the presence of multipath frequency selective channel, system modelling results show that this coded system with 1024 sub-carriers can save up to 45% of bandwidth compared to an otherwise equivalent OFDM

Concentric UCAs based low-order radio vortex wireless communications with co-mode interference

Abstract: To meet the rapidly capacity-growing requirements, orbital angular momentum (OAM) based Radio vOrtex Wireless COMMunications (RowComm) has received much attention in recent years. The uniform circular array (UCA) is an efficient and convenient antenna structure to transmit/receive OAM beams with multiple OAM modes simultaneously. However, for high-order OAM modes, the OAM beams are divergent with severe attenuations. Thus, it is difficult to directly utilize high-order OAM modes to achieve high capacity for wireless communications. In this paper, we transform the high-order singular UCA into the low-order concentric UCAs to increase the capacity. In particular, we propose the mode-decomposition scheme and the co-mode successive interference cancellation algorithm to mitigate co-mode interference and decode the transmit signals. Then, we formulate the capacity maximization problem and convert it into an equivalent convex optimization problem. We solve the capacity maximization problem and derive the corresponding optimal power allocation scheme. Numerical simulations are presented to validate and evaluate that our developed low-order concentric UCAs based RowComm can significantly increase the capacity as compared with the high-order singular UCA based RowComm.

Bandwidth compressed waveform and system design for wireless and optical communications : theory and practice

Abstract: This thesis addresses theoretical and practical challenges of spectrally efficient frequency division multiplexing (SEFDM) systems in both wireless and optical domains. SEFDM improves spectral efficiency relative to the well-known orthogonal frequency division multiplexing (OFDM) by non-orthogonally multiplexing overlapped sub-carriers. However, the deliberate violation of orthogonality results in inter carrier interference (ICI) and associated detection complexity, thus posing many challenges to practical implementations. This thesis will present solutions for these issues. The thesis commences with the fundamentals by presenting the existing challenges of SEFDM, which are subsequently solved by proposed transceivers. An iterative detection (ID) detector iteratively removes self-created ICI. Following that, a hybrid ID together with fixed sphere decoding (FSD) shows an optimised performance/complexity trade-off. A complexity reduced Block-SEFDM can subdivide the signal detection into several blocks. Finally, a coded Turbo-SEFDM is proved to be an efficient technique that is compatible with the existing mobile standards. The thesis also reports the design and development of wireless and optical practical systems. In the optical domain, given the same spectral efficiency, a low-order modulation scheme is proved to have a better bit error rate (BER) performance when replacing a higher order one. In the wireless domain, an experimental testbed utilizing the LTE-Advanced carrier aggregation (CA) with SEFDM is operated in a realistic radio frequency (RF) environment. Experimental results show that 40% higher data rate can be achieved without extra spectrum occupation. Additionally, a new waveform, termed Nyquist-SEFDM, which compresses bandwidth and suppresses out-of-band power leakage is investigated. A 4th generation (4G) and 5th generation (5G) coexistence experiment is followed to verify its feasibility. Furthermore, a 60 GHz SEFDM testbed is designed and built in a point-to-point indoor fiber wireless experiment showing 67% data rate improvement compared to OFDM. Finally, to meet the requirements of future networks, two simplified SEFDM transceivers are designed together with application scenarios and experimental verifications.

Experimental validations of bandwidth compressed multicarrier signals

Abstract: We comprehensively summarize experimental validations 1 of bandwidth compressed multicarrier waveforms for future 5th generation (5G) applications. The proposed waveforms are derived from an existing non-orthogonal multicarrier concept termed spectrally efficient frequency division multiplexing (SEFDM) where sub-carriers are non-orthogonally packed at frequencies below the symbol rate. This improves the spectral efficiency at the cost of self-created inter carrier interference (ICI). In this work, experiments are reported and testing is carried out in three scenarios including long term evolution (LTE)-like wireless link; millimeter wave radio-over-fiber (RoF) link and optical fiber link. In the first scenario, for a given 25 MHz bandwidth, the SEFDM testbed can provide 70 Mbit/s gross data rate while only 50 Mbit/s can be achieved for an OFDM system occupying the same bandwidth. For the millimeter wave experiment, occupying a 1.125 GHz bandwidth, the gross bit rate for OFDM is 2.25 Gbit/s and with 40% bandwidth compression, 3.75 Gbit/s can be achieved for SEFDM. Two experimental optical fiber links are described in this work; a 10 Gbit/s direct detection optical SEFDM system and a 24 Gbit/s coherent detection SEFDM system. The LTE-like signals and millimeter wave technologies are well suited to provide last mile communications to end users as both can support mobility in wireless environments. The lightwave signals delivered by optical fibers would offer higher data rates and support long-haul communications. The reported techniques, used individually or combined, would be of interest to future wireless system designers, where bandwidth saving is of importance, such as in 5G networks, aiming to provide high capacity and high mobility, simultaneously while saving spectrum.