430 research outputs found
Time-Frequency Warped Waveforms
The forthcoming communication systems are advancing towards improved
flexibility in various aspects. Improved flexibility is crucial to cater
diverse service requirements. This letter proposes a novel waveform design
scheme that exploits axis warping to enable peaceful coexistence of different
pulse shapes. A warping transform manipulates the lattice samples non-uniformly
and provides flexibility to handle the time-frequency occupancy of a signal.
The proposed approach enables the utilization of flexible pulse shapes in a
quasi-orthogonal manner and increases the spectral efficiency. In addition, the
rectangular resource block structure, which assists an efficient resource
allocation, is preserved with the warped waveform design as well.Comment: 4 pages, 5 figures; accepted version (The URL for the final version:
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8540914&isnumber=8605392
Low Correlation Interference OFDM-NLFM Waveform Design for MIMO Radar Based on Alternating Optimization.
The OFDM chirp signal is suitable for MIMO radar applications due to its large time-bandwidth product, constant time-domain, and almost constant frequency-domain modulus. Particularly, by introducing the time-frequency structure of the non-linear frequency modulation (NLFM) signal into the design of an OFDM chirp waveform, a new OFDM-NLFM waveform with low peak auto-correlation sidelobe ratio (PASR) and peak cross-correlation ratio (PCCR) is obtained. IN-OFDM is the OFDM-NLFM waveform set currently with the lowest PASR and PCCR. Here we construct the optimization model of the OFDM-NLFM waveform set with the objective function being the maximum of the PASR and PCCR. Further, this paper proposes an OFDM-NLFM waveform set design algorithm inspired by alternating optimization. We implement the proposed algorithm by the alternate execution of two sub-algorithms. First, we keep both the sub-chirp sequence code matrix and sub-chirp rate plus and minus (PM) code matrix unchanged and use the particle swarm optimization (PSO) algorithm to obtain the optimal parameters of the NLFM signal's time-frequency structure (NLFM parameters). Next, we keep current optimal NLFM parameters unchanged, and optimize the sub-chirp sequence code matrix and sub-chirp rate PM code matrix using the block coordinate descent (BCD) algorithm. The above two sub-algorithms are alternately executed until the objective function converges to the optimal solution. The results show that the PASR and PCCR of the obtained OFDM-NLFM waveform set are about 5 dB lower than that of the IN-OFDM
Empirical Comparison of Chirp and Multitones on Experimental UWB Software Defined Radar Prototype
This paper proposes and tests an approach for an unbiased study of radar waveforms' performances. Using the ultrawide band software defined radar prototype, the performances of Chirp and Multitones are compared in range profile and detection range. The architecture was implemented and has performances comparable to the state of the art in software defined radar prototypes. The experimental results are consistent with the simulations
Non-continuous piecewise nonlinear frequency modulation pulse with variable sub-pulse duration in a MIMO SAR radar system
This paper proposes an implementation of non-continuous piecewise nonlinear frequency modulation (N-PNLFM) signals in MIMO radar which are composed of a sequence of N-PNLFM subpulses. The N-PNLFM subpulse can be divided into three segments, the first and third segment are composed of linear frequency modulation (LFM) waveforms. The LFM waveforms in each N-PNLFM subpulse will be orthogonal in one sequence of our new N-PNLFM signal. A non-linear frequency modulation (NLFM) waveform is in the central component of each N-PNLFM subpulse, the bandwidths of each NLFM waveforms are distributed randomly. Each subpulse can be controlled by different variable parameters in both auto-correlation and cross-correlation functions. In order to suppress the high sidelobes in the new N-PNLFM signal and increase the diversity of signals, each subpulse duration is also distributed randomly. Our proposed PNLFM signals are optimized by applying a particle swarm optimization (PSO) algorithm. Comparing with other PNLFM signals, numerous simulations illustrate that our implementation achieves better performance
Multitones’ Performance for Ultra Wideband Software Defined Radar
This chapter proposes and tests an approach for an unbiased study of radar waveforms’ performances. Through an empirical performance analysis, the performances of Chirp and Multitones are compared with both simulations and measurements. An ultra wideband software defined radar prototype was designed and the prototype has performances comparable to the state of the art in software defined radar. The study looks at peak-to-mean-envelope power ratio, spectrum efficiency, and pulse compression as independent waveform criteria. The experimental results are consistent with the simulations. The study shows that a minimum of 10 bits resolution for the AD/DA converters is required to obtain near-optimum performances
Frequency Diverse Array Radar: Signal Characterization and Measurement Accuracy
Radar systems provide an important remote sensing capability, and are crucial to the layered sensing vision; a concept of operation that aims to apply the right number of the right types of sensors, in the right places, at the right times for superior battle space situational awareness. The layered sensing vision poses a range of technical challenges, including radar, that are yet to be addressed. To address the radar-specific design challenges, the research community responded with waveform diversity; a relatively new field of study which aims reduce the cost of remote sensing while improving performance. Early work suggests that the frequency diverse array radar may be able to perform several remote sensing missions simultaneously without sacrificing performance. With few techniques available for modeling and characterizing the frequency diverse array, this research aims to specify, validate and characterize a waveform diverse signal model that can be used to model a variety of traditional and contemporary radar configurations, including frequency diverse array radars. To meet the aim of the research, a generalized radar array signal model is specified. A representative hardware system is built to generate the arbitrary radar signals, then the measured and simulated signals are compared to validate the model. Using the generalized model, expressions for the average transmit signal power, angular resolution, and the ambiguity function are also derived. The range, velocity and direction-of-arrival measurement accuracies for a set of signal configurations are evaluated to determine whether the configuration improves fundamental measurement accuracy
Fractional fourier transform based waveform for a joint radar-communication system
The increasing demand of spectrum resources and the need to keep the size, weight and power consumption of modern radar as low as possible, has led to the development of solutions like joint radar-communication systems. In this paper a novel Fractional Fourier Transform (FrFT) based multiplexing scheme is presented as joint radar-communication technique. The FrFT is used to embed data into chirp sub-carriers with different time-frequency rates. Some optimisation procedures are also proposed, with the objective of improving the bandwidth occupancy and the bit rate and/or Bit Error Ratio (BER). The generated waveform is demonstrated to have a good rejection to distortions introduced by the channel, leading to low BER, while keeping good radar characteristics compared to a widely used Linear Frequency Modulated (LFM) pulse with same duration and bandwidth
Integrated Sensing and Communication Signals Toward 5G-A and 6G: A Survey
Integrated sensing and communication (ISAC) has the advantages of efficient
spectrum utilization and low hardware cost. It is promising to be implemented
in the fifth-generation-advanced (5G-A) and sixth-generation (6G) mobile
communication systems, having the potential to be applied in intelligent
applications requiring both communication and high-accurate sensing
capabilities. As the fundamental technology of ISAC, ISAC signal directly
impacts the performance of sensing and communication. This article
systematically reviews the literature on ISAC signals from the perspective of
mobile communication systems, including ISAC signal design, ISAC signal
processing algorithms and ISAC signal optimization. We first review the ISAC
signal design based on 5G, 5G-A and 6G mobile communication systems. Then,
radar signal processing methods are reviewed for ISAC signals, mainly including
the channel information matrix method, spectrum lines estimator method and
super resolution method. In terms of signal optimization, we summarize
peak-to-average power ratio (PAPR) optimization, interference management, and
adaptive signal optimization for ISAC signals. This article may provide the
guidelines for the research of ISAC signals in 5G-A and 6G mobile communication
systems.Comment: 25 pages, 13 figures, 8 tables. IEEE Internet of Things Journal, 202
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