Radar-Communications Systems Coexistence and Agile Multicarrier Radars

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2018-09-21
Degree programme
83 + app. 67
Aalto University publication series DOCTORAL DISSERTATIONS, 156/2018
Rigid allocation policies can no longer satisfy the growing demand for spectrum. There is a great need for flexible and efficient use of spectral resources. Spectrum sharing between different wireless systems is one approach to solve this problem. This requires that the systems are fully adaptive and cognitive. Consequently, these can take advantage of their operational environment knowledge such as the state of the radio spectrum. For such demanding task, multicarrier waveforms provide a convenient and flexible way of generating and designing waveforms. Thanks to their multiple degrees of freedom in time, frequency and code domain, multicarrier waveforms allow for performance optimization as well. In this thesis, theories, methods and justifications for coexistence and spectrum sharing among radar and wireless communication systems are developed. A generalized multicarrier radar (GMR) model is proposed to enable the required flexible use of spectrum and adaptation to different target scenarios and operational environments. It allows for conveniently representing most of the known radar waveforms as well as designing and optimizing new ones. Using the developed model novel multicarrier waveforms are proposed. These waveforms relax the subcarrier orthogonality constraint for an improved ambiguity function and consequently better radar performance. Constrained radar waveform optimization using the GMR model and a mutual information (MI) based objective function is proposed. Several examples of waveforms employing fast frequency hopping, which are special cases of the GMR model, are also provided. The problems of radar waveform optimization and adaptation are addressed in the coexistence context using multicarrier waveforms, in particular OFDM. The optimization problems are formulated for different radar tasks, i.e. target characterization, target detection and target parameter estimation. The optimization is performed using information theoretic criteria such as mutual information (MI) or criteria stemming from detection and estimation theory, for example, Neyman-Pearson (NP) criterion or Cramer-Rao bound (CRB). The optimization problems proposed in this thesis are formulated by imposing constraints on the total transmitted radar power and an interference mask provided by the communication system. This interference mask ensures that a desired rate for the communication users can be achieved. The solutions to the optimization problems represent power allocations over the available subcarriers. The performance of the proposed optimized waveforms in this thesis is evaluated in simulations using receiver operating characteristic or root mean squared error plots, for the detection and estimation tasks respectively. Recommendations on which optimization objective functions produce the best performing waveforms are given. It is also demonstrated that exploiting the communication signal reflected off the target can improve the radar performance for all considered tasks.
Supervising professor
Koivunen, Visa, Prof., Aalto University, Department of Signal Processing and Acoustics, Finland
Thesis advisor
Koivunen, Visa, Prof., Aalto University, Department of Signal Processing and Acoustics, Finland
multicarrier radar, waveform design, coexistence, optimization, estimation, detection
Other note
  • [Publication 1]: Marian Bica, Visa Koivunen. Generalized Multicarrier Radar: Models and Performance. IEEE Transactions on Signal Processing, vol. 64, no. 17, pp. 4389-4402, September 2016.
    DOI: 10.1109/TSP.2016.2566610 View at publisher
  • [Publication 2]: Marian Bica, Visa Koivunen. Frequency Agile Generalized Multicarrier Radar. In 2014 48th Annual Conference on Information Sciences and Systems (CISS), Princeton, NJ, pp. 1-6, March 2014.
    DOI: 10.1109/CISS.2014.6814069 View at publisher
  • [Publication 3]: Marian Bica, Visa Koivunen. Waveform Optimization for Target Parameter Estimation in Cooperative Radar-Communication Systems. Submitted to IEEE Transactions on Aerospace and Electronic Systems, 2018.
  • [Publication 4]: Marian Bica, Kuan-Wen Huang, Visa Koivunen, Urbashi Mitra. Mutual information based radar waveform design for joint radar and cellular communication systems. In 2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Shanghai, pp. 3671-3675, March 2016.
    DOI: 10.1109/ICASSP.2016.7472362 View at publisher
  • [Publication 5]: Marian Bica, Kuan-Wen Huang, Urbashi Mitra, Visa Koivunen. Opportunistic Radar Waveform Design in Joint Radar and Cellular Communication Systems. In 2015 IEEE Global Communications Conference (GLOBECOM), San Diego, CA, pp. 1-7, December 2015.
    DOI: 10.1109/GLOCOM.2015.7417624 View at publisher
  • [Publication 6]: Marian Bica, Visa Koivunen. Delay Estimation Method for Coexisting Radar and Wireless Communication Systems. In 2017 IEEE Radar Conference (RadarConf), Seattle, WA, pp. 1557-1561, May 2017.
    DOI: 10.1109/RADAR.2017.7944455 View at publisher
  • [Errata file]: P1, P2, P6