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A novel channel estimator for Zero-Tail DFT-spread-OFDM
... This technique, termed UW DFT-S OFDM, uses the pulse forming structure of the DFT-S OFDM to decrease the energy consumed by accommodating a UW in the queue. In the same manner to the ZT DFT-S OFDM, information symbols are matched to the center of DFT spread blocks [30,31]. Also, in place of putting zero redundant symbols at both ends of the DFT spreading blocks, non-zero redundant symbols are used which repress the leaky energy in the queue. ...
A novel concatenated Lifting Wavelet Transform (LWT) and Walsh Hadamard Transform (WHT) with Universal Filtered Multi Carrier (UFMC) waveform is suggested as an alternative to Orthogonal Frequency Division Multiplexing (OFDM) waveform for the next generation wireless telecommunication systems in this paper. The suggested waveform is composed of LWT and WHT with UFMC waveform. Both the elimination the disadvantages of OFDM and the improvement the achievement of UFMC waveform, from the fifth generation waveform candidates, has been aimed with the suggested waveform. In order to verify the performance of the suggested waveform and compare with the traditional OFDM, UFMC, and LWT‐UFMC waveform computer simulation studies are performed in additive white Gaussian noise and flat Rayleigh fading channel environments. The acquired computer simulation results exhibit that the achievement of the suggested waveform has better than the achievement of the traditional OFDM, UFMC, and LWT‐UFMC waveform. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
... Further, the non-cyclic distorted versions also generate mutual interference when transmitted simultaneously, causing significant crosscorrelation. 1) Proposed channel estimator: We present here a channel estimator for ZT DFT-s-OFDM which aims at overcoming the aforementioned drawbacks [30]. The principle of the proposed channel estimator is to correlate the received signal against the original reference sequence rather than its zero-padded version, provided specific arrangements to restore cyclicity are ℎ ′ Fig. 8. Usage of the OLA principle for emulating a cyclic fading. ...
This article deals with Generalized Discrete Fourier Transform - spread - Orthogonal Frequency Division Multiplexing (G-DFT-s-OFDM) waveforms, that replace the Cyclic Prefix (CP) of traditional OFDM/DFT-s-OFDM with an internal guard period. Such waveforms feature significant benefits in terms of flexibility, spectral containment and low Peak-to-Average Power Ratio (PAPR). Aspects related to reference sequence design and mapping for channel estimation are thoroughly addressed, and a new estimator for the specific Zero-Tail (ZT) DFT-s-OFDM case is proposed. Further, we address the opportunity of exploiting the internal guard period at each symbol for frequent channel state information updates, thus enabling the possibility of tracking rapidly varying propagation conditions.
... Berardinelli et al. [32] have used zero tail DFT in order to substitute cyclic prefix in OFDM. Applicability of similar technique to improve and make OFDM suitable for 5G network was discussed by same authors in [33] and [34]. The authors have adopted analytical approach in order to mitigate the overhead as well as propagation delay. ...
Orthogonal frequency-division multiplexing (OFDM) is one of unbeatable multiplexing technique till date. However with increasing version of next generation mobile standards like 5G, the applicability of OFDM is quite questionable. The prime reason behind this is in order to offer higher data rates and extensive networking services in 5G, OFDM will be required to overcome some inherent problems of spectral leakage, power consumption, less supportability of increased channel capacity. The reason community still believes that there is positive scope of OFDM to be applicable in 5G network provided it undergoes certain changes. This paper reviews some of the complimentary waveforms that have been theoretically proven to be adding edge to OFDM system. The paper reviews different waveforms as well as multiple access techniques to be used in designing 5G technology and assess their effectiveness in viewpoint of research applicability and effectiveness towards leveraging 5G.
Orthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channels at different frequencies. CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimising the use of available bandwidth. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end.
Multi-Carrier (MC) CDMA is a combined technique of Direct Sequence (DS) CDMA (Code Division Multiple Access) and OFDM techniques. It applies spreading sequences in the frequency domain.
Wireless communications has witnessed a tremendous growth during the past decade and further spectacular enabling technology advances are expected in an effort to render ubiquitous wireless connectivity a reality.
This technical in-depth book is unique in its detailed exposure of OFDM, MIMO-OFDM and MC-CDMA. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context.
Divided into three main parts:
Part I provides a detailed exposure of OFDM designed for employment in various applications
Part II is another design alternative applicable in the context of OFDM systems where the channel quality fluctuations observed are averaged out with the aid of frequency-domain spreading codes, which leads to the concept of MC-CDMA
Part III discusses how to employ multiple antennas at the base station for the sake of supporting multiple users in the uplink
• Portrays the entire body of knowledge currently available on OFDM
• Provides the first complete treatment of OFDM, MIMO(Multiple Input Multiple Output)-OFDM and MC-CDMA
• Considers the benefits of channel coding and space time coding in the context of various application examples and features numerous complete system design examples
• Converts the lessons of Shannon’s information theory into design principles applicable to practical wireless systems
• Combines the benefits of a textbook with a research monograph where the depth of discussions progressively increase throughout the book
This all-encompassing self-contained treatment will appeal to researchers, postgraduate students and academics, practising research and development engineers working for wireless communications and computer networking companies and senior undergraduate students and technical managers.
Zero padding (ZP) of multicarrier transmissions has been proposed as an appealing alternative to the traditional cyclic prefix (CP) orthogonal frequency-division multiplexing (OFDM) to ensure symbol recovery regardless of the channel zero locations. In this paper, both systems are studied to delineate their relative merits in wireless systems where channel knowledge is not available at the transmitter. Two novel equalizers are developed for ZP-OFDM to tradeoff performance with implementation complexity. Both CP-OFDM and ZP-OFDM are then compared in terms of transmitter nonlinearities and required power backoff. Next, both systems are tested in terms of channel estimation and tracking capabilities. Simulations tailored to the realistic context of the standard for wireless local area network HIPERLAN/2 illustrate the pertinent tradeoffs.
From the editors of the highly successful LTE for UMTS: Evolution to LTE-Advanced, this new book examines the main technical enhancements brought by LTE-Advanced, thoroughly covering 3GPP Release 10 specifications and the main items in Release 11. Using illustrations, graphs and real-life scenarios, the authors systematically lead readers through this cutting-edge topic to provide an outlook on existing technologies as well as possible future developments. The book is structured to follow the main technical areas that will be enhanced by the LTE-Advanced specifications. The main topics covered include: Carrier Aggregation; Multiantenna MIMO Transmission, Heterogeneous Networks; Coordinated Multipoint Transmission (CoMP); Relay nodes; 3GPP milestones and IMT-Advanced process in ITU-R; and LTE-Advanced Performance Evaluation. Key features: Leading author and editor team bring their expertise to the next generation of LTE technology. Includes tables, figures and plots illustrating the concepts or simulation results, to aid understanding of the topic, and enabling readers to be ahead of the technological advances.
5G, the mobile communication technology for beyond 2020, will provide access to information and the sharing of data anywhere and anytime for anyone and anything. This paper describes the current status of the processes moving toward 5G, or "IMT for 2020 and beyond," in ITU-R. We also provide a view of 5G opportunities, challenges, requirements and technical solutions.
In the existing scheduled radio standards using Orthogonal Frequency Division Multiplexing (OFDM) or Discrete Fourier Transform-spread-OFDM (DFT-s-OFDM) modulation, the Cyclic Prefix (CP) duration is usually hard-coded and set as a compromise between the expected channel characteristics and the necessity of fitting a predefined frame duration. This may lead to system inefficiencies as well as bad coexistence with networks using different CP settings. In this paper, we propose the usage of zero-tail DFT-s-OFDM signals as a solution for decoupling the radio numerology from the expected channel characteristics. Zero-tail DFT-s-OFDM modulation allows to adapt the overhead to the estimated delay spread/propagation delay. Moreover, it enables networks operating over channels with different characteristics to adopt the same numerology, thus improving their coexistence. An analytical description of the zero-tail DFT-s-OFDM signals is provided, as well as a numerical performance evaluation with Monte Carlo simulations. Zero-tail DFT-s-OFDM signals are shown to have approximately the same Block Error Rate (BLER) performance of traditional OFDM, with the further benefit of lower out-of-band (OOB) emissions.
The 5th generation (5G) of mobile radio access technologies is expected to become available for commercial launch around 2020. In this paper, we present our envisioned 5G system design optimized for small cell deployment taking a clean slate approach, i.e. removing most compatibility constraints with the previous generations of mobile radio access technologies. This paper mainly covers the physical layer aspects of the 5G concept design.
It has been proposed recently to replace the cyclic prefix (CP) in OFDM transmission by zero-padding (ZP); this guarantees symbol recovery even when channel s are located on a subcarrier. This, though, has the disadvantage that the simple DFT-based receiver does not perform well, but results have shown that if much higher complexity turbo demodulation is used, ZP-OFDM outperforms CP-OFDM. However, by viewing N-carrier OFDM as multicode CDMA with complex spreading codes from the N-PSK alphabet, one can apply to ZP-OFDM the numerous suboptimum multiuser receivers developed for CDMA. The performance of these receivers is dictated by the correlation properties of the IDFT matrix. Therefore, we propose to "modify" the IDFT matrix used to modulate the data in ZP-OFDM so that the resulting matrix possesses better correlation properties, and hence improved performance over multipath channels can be achieved. Simulation results verify the large gains in the uncoded performance of ZP-OFDM with modified IDFT matrix compared to CP-OFDM and ZP-OFDM with the IDFT matrix.
Broadband wireless access systems deployed in residential and
business environments are likely to face hostile radio propagation
environments, with multipath delay spread extending over tens or
hundreds of bit intervals. Orthogonal frequency-division multiplex
(OFDM) is a recognized multicarrier solution to combat the effects of
such multipath conditions. This article surveys frequency domain
equalization (FDE) applied to single-carrier (SC) modulation solutions.
SC radio modems with frequency domain equalization have similar
performance, efficiency, and low signal processing complexity advantages
as OFDM, and in addition are less sensitive than OFDM to RF impairments
such as power amplifier nonlinearities. We discuss similarities and
differences of SC and OFDM systems and coexistence possibilities, and
present examples of SC-FDE performance capabilities
In this paper, we investigate pilot-symbol-aided parameter
estimation for orthogonal frequency division multiplexing (OFDM)
systems. We first derive a minimum mean-square error (MMSE)
pilot-symbol-aided parameter estimator. Then, we discuss a robust
implementation of the pilot-symbol-aided estimator that is insensitive
to channel statistics. From the simulation results, the required
signal-to-noise ratios (SNRs) for a 10% word error rate (WER) are 6.8 dB
and 7.3 dB for the typical urban (TU) channels with 40 Hz and 200 Hz
Doppler frequencies, respectively, and they are 8 dB and 8.3 dB for the
hilly-terrain (HT) channels with 40 Hz and 200 Hz Doppler frequencies,
respectively. Compared with the decision-directed parameter estimator,
the pilot-symbol-aided estimator is highly robust to Doppler frequency
for dispersive fading channels with noise impairment even though it has
some performance degradation for systems with lower Doppler frequencies
A new general class of polyphase sequences with ideal periodic
autocorrelation function is presented. The new class of sequences is
based on the application of Zadoff-Chu polyphase sequences of length
N = sm 2, where s and m are
any positive integers. It is shown that the generalized chirp-like
sequences of odd length have the optimum crosscorrelation function under
certain conditions. Finally, recently proposed generalized P4 codes are
derived as a special case of the generalized chirp-like sequence