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Open Access Publications from the University of California

Scholarly Works (135 results)

  • Article
  • Peer Reviewed
UC Riverside Previously Published Works (2019)
This paper examines the role of full-duplex radio for securing wireless network from a new perspective. It first studies the secrecy capacity of two single-antenna full-duplex users against a multi-antenna eavesdropper (Eve) who has the perfect knowledge of the channel state information (CSI) from users to Eve. It is shown that if Eve uses a basic matched-filtering, the probability of zero secrecy (or outage) can be made small by a large jamming power from both users and a small gain of residual self-interference (RSI) power. But if Eve uses the optimal matched-filtering, the probability of outage grows rapidly as either the jamming power from the users increases or the number of antennas on Eve increases, regardless of the RSI gain. To prevent any Eve from obtaining its CSI, this paper then proposes a novel anti-eavesdropping channel estimation (ANECE) method, which allows users to obtain their own CSI while keeping all Eves in handicap. This method also prevents Eves from colluding with each other at any layer. The design of ideal pilots for ANECE for multiple multi-antenna users and multiple broadband multi-antenna users is discussed. It is also shown that the capacity of Eve with any number of antennas but without its CSI can be virtually eliminated over a time window corresponding to the number of antennas at the transmitter for each realization of the CSI.
    Cover page: Advanced Properties of Full-Duplex Radio for Securing Wireless Network
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (1996)
    This paper develops a fast maximum likelihood method for estimating the impulse responses ofmultiple FIR channels driven by an arbitrary unknown input. The resulting method consists of two iterative steps, where each step minimizes a quadratic function. The two-step maximum likelihood(TSML) method is shown to be high-SNR efficient, i.e., attaining the Cramer-Rao lower bound (CRB) at high SNR. The TSML method exploits a novel orthogonal complement matrix of the generalized Sylvester matrix. Simulations show that the TSML, method significantly outperforms the cross-relation (CR) method and the subspace (SS) method and attains the CRB over a wide range of SNR. This paper also studies a Fisher information (FI) matrix to reveal the identifiability of the M-channel system. A strong connection between the FI-based identifiability and the CR-based identifiability is established
      Cover page: Fast maximum likelihood for blind identification of multiple FIR channels
      • Article
      • Peer Reviewed
      UC Riverside Previously Published Works (1992)
      A new method, called the matrix enhancement and matrix pencil (MEMP) method, is presented forestimating two-dimensional (2-D) frequencies. In the MEMP method, an enhanced matrix is constructed from the data samples, and then the matrix pencil approach is used to extract out the 2-D sinusoids from the principal eigenvectors of the enhanced matrix. The MEMP method yields theestimates of the 2-D frequencies efficiently, without solving the roots of a 2-D polynomial or searching in a 2-D space. It is shown that the MEMP method can be faster than a 2-D FFT method if the number of the 2-D sinusoids is much smaller than the data set. Simulation results are provided to show that the accuracy of the MEMP method can be very close to the Cramer-Rao lower bound
        • Article
        • Peer Reviewed
        UC Riverside Previously Published Works (2023)
          Cover page: Generalized Channel Probing and Generalized Pre-Processing for Secret Key GenerationCreative Commons 'BY' version 4.0 license
          • Article
          • Peer Reviewed
          UC Riverside Previously Published Works (2004)
          Subspace computation is fundamental for many signal processing applications. A well-known tool for computing the principal subspace of a data matrix is the power method. During the iterations of the power method, a proper normalization is essential to avoid numerical overflow or underflow. Normalization is also needed to achieve desirable properties such as orthonormalized subspacematrices. A number of normalization techniques for the power method is reviewed, which include the conventional as well as nonconventional ones. In particular, a new method of normalization is introduced to achieve asymptotical orthonormalization of subspace matrices without the use of squareroot. This method is among a class of normalization methods that allow a simple adaptive implementation of the power method for subspace tracking.
            Cover page: Asymptotical Orthonormalization of Subspace Matrices Without Square Root
            • Article
            • Peer Reviewed
            UC Riverside Previously Published Works (1994)
              Cover page: High resolution imaging of continuously moving object using stepped frequency radar
              • Article
              • Peer Reviewed
              UC Riverside Previously Published Works (2010)
              This paper provides an overview of the design of transmit and receive beamformers and transmit power allocation for MIMO relays. Soft and hard methods for interference cancelation are presented, which play a critical role for all MIMO relays whether they are full-duplex or half-duplex, regenerative or non-regenerative, one-way relay or two-way relay. A perspective of MIMO relays in a network of many hops is illustrated. A distinction is made between feedback loop of energy and feedback loop of noise. Subspace computation and a generalized water-filling (GWF) algorithm are shown as important building blocks for the design.
                Cover page: AN OVERVIEW OF BEAMFORMING AND POWER ALLOCATION FOR MIMO RELAYS
                • Article
                • Peer Reviewed
                UC Riverside Previously Published Works (1994)
                  Cover page: The most efficient implementation of the IQML algorithm
                  • Article
                  • Peer Reviewed
                  UC Riverside Previously Published Works (2011)
                  In this paper, we consider a channel estimation scheme for a two-hop nonregenerative MIMO relay system without the direct link between source and destination. This scheme has two phases. In the first phase, the source does not transmit while the relay transmits and the destination receives. In the second phase, the source transmits, the relay amplifies and forwards, and the destination receives. At the destination, the data received in the first phase are used to estimate the relay-to-destination channel, and the data received in the second phase are used to estimate the source-to-relay channel. The linear minimum mean-square error estimation (LMMSE) is used for channel estimation, which allows the use of prior knowledge of channel correlations. For phase 1, an algorithm is developed to compute the optimal source pilot matrix for use at the relay. For phase 2, an algorithm is developed to compute the optimal source pilot matrix for use at the source and the optimal relay pilot matrix for use at the relay.
                    Cover page: Optimal Design of Source and Relay Pilots for MIMO Relay Channel Estimation 
                    • Thesis
                    • Peer Reviewed
                    UC Riverside Electronic Theses and Dissertations (2022)

                    Physical layer security (PLS) is an approach that provides secrecy based on information-theoretic model which does not account for any computation capability assumption or pre-installed standardized secret key generation algorithm and it is a good additional protection on the top of the existing security scheme.

                    This work includes two different topics for improving PLS with full-duplex radio.

                    In the first topic, we study the secrecy performance of several schemes for multi-antenna transmission to single-antenna users with full-duplex (FD) capability against randomly distributed single-antenna eavesdroppers (EDs). These schemes and related scenarios include transmit antenna selection (TAS), transmit antenna beamforming (TAB), artificial noise (AN) from the transmitter, user selection based their distances to the transmitter, and colluding and non-colluding EDs. The locations of randomly distributed EDs and users are assumed to be distributed as Poisson Point Process (PPP). We derive closed form expressions for the secrecy outage probabilities (SOP) of all these schemes and scenarios. The derived expressions are useful to reveal the impacts of various environmental parameters and user's choices on the SOP, and hence useful for network design purposes. Furthermore, we have investigated the secrecy performance of the scheme where multiple legitimate users are randomly located. Examples of such numerical results are discussed.

                    For the second topic, we present a secure downlink communication system where a transmitter sends information to multiple single antenna users under ultra reliable and low-latency communication (uRLLC) system requirement. To meet uRLLC requirement and provide secrecy against multi-antenna eavesdropper (Eve), transmitter adopts a special channel training scheme called anti-eavesdropping channel estimation (ANECE) as well as a standard transmit beamforming to send secret information in short blocklength regime. Using ANECE, two or more cooperative full-duplex radio devices obtain their receive channel state information (CSI) with respect to each other while preventing Eve from obtaining any consistent estimate of its receive CSI, which improves the secrecy of subsequent transmission of information between the devices. We derive the closed form expression of average secrecy throughput (AST) of ANECE assisted transmission. Our closed form expression of approximated AST in terms of blocklength and various controllable parameters provides useful insights to maximize AST under uRLLC requirement. In another chapter, we investigate the uplink communication system where multiple single antenna users send secret information to multi-antenna access point (AP) under ultra reliable and low-latency communication (uRLLC) system requirement. Finally, numerical results are discussed.

                      Cover page: Secrecy Enhancement with Full-Duplex Radio in Wireless Networks
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