L.B. Milstein

University of California, Davis, Davis, California, United States

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Publications (212)88.6 Total impact

  • Arash Vosoughi · P.C. Cosman · L.B. Milstein
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    ABSTRACT: We consider the joint source-channel coding (JSCC) problem of 3-D stereo video transmission in video plus depth format over noisy channels. Full resolution and downsampled depth maps are considered. The proposed JSCC scheme yields the optimum color and depth quantization parameters as well as the optimum forward error correction code rates used for unequal error protection (UEP) at the packet level. Different coding scenarios are compared and the UEP gain over equal error protection is quantified for flat Rayleigh fading channels.
    No preview · Article · Jan 2015 · IEEE Signal Processing Letters
  • Madushanka Soysa · P.C. Cosman · L.B. Milstein
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    ABSTRACT: We examine the performance of a cognitive radio system in a hostile environment where an intelligent adversary tries to disrupt communications by minimizing the system throughput. We investigate the optimal strategy for spoofing and jamming a cognitive radio network with a Gaussian noise signal over a Rayleigh fading channel. We analyze a cluster-based network of secondary users (SUs). The adversary may attack during the sensing interval to limit access for SUs by transmitting a spoofing signal. By jamming the network during the transmission interval, the adversary may reduce the rate of successful transmission. We present how the adversary can optimally allocate power across subcarriers during sensing and transmission intervals with knowledge of the system, using a simple optimization approach specific to this problem. We determine a worst-case optimal energy allocation for spoofing and jamming, which gives a lower bound to the overall information throughput of SUs under attack.
    No preview · Article · Aug 2014 · IEEE Transactions on Communications
  • Ning Kong · Larry B. Milstein
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    ABSTRACT: For an AWGN channel, the required SNR-increase-per-bit-increase (SNR_inc/bit_inc), in bits per symbol, to maintain the same symbol error rate (SER) for one or two dimension modulation schemes, such as MPSK and MQAM, is known. In this paper, we present similar results for a Rayleigh fading channel. It is found that the required SNR_inc/bit_inc in a fading channel consists of two parts-one is the same as that for an AWGN channel, and the other one is the extra SNR increase due to the fading. The latter is large (over 2dB) for a small constellation size (M) and negligible with a large M. It also decreases as the diversity order (DO) increases. In addition, we present simple closed-form expressions for the SNR penalty of using MPSK over QAM signals for Rayleigh fading. It is found that the extra penalty due to fading increases and approaches a constant as M increases. It decreases as the DO increases. Simulation results match the theoretical analysis.
    No preview · Conference Paper · Nov 2013
  • Source
    Dawei Wang · Laura Toni · P.C. Cosman · L.B. Milstein
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    ABSTRACT: We consider a multiuser OFDM system in which users want to transmit videos via a base station. The base station knows the channel state information (CSI) as well as the rate distortion (RD) information of the video streams and tries to allocate power and spectrum resources to the users according to both physical layer CSI and application layer RD information. We derive and analyze a condition for the optimal resource allocation solution in a continuous frequency response setting. The optimality condition for this cross layer optimization scenario is similar to the equal slope condition for conventional video multiplexing resource allocation. Based on our analysis, we design an iterative subcarrier assignment and power allocation algorithm for an uplink system, and provide numerical performance analysis with different numbers of users. Comparing to systems with either only physical layer or only application layer information available at the base station, our results show that the user capacity and the video PSNR performance can be increased significantly by using cross layer design. Bit-level simulations which take into account the imperfection of the video coding rate control, the variation of RD curve fitting, as well as channel errors, are presented.
    Preview · Article · May 2013 · IEEE Transactions on Communications
  • Yichao Shen · Wenwen Zhou · Peizhi Wu · L. Toni · P.C. Cosman · L.B. Milstein
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    ABSTRACT: To increase spectrum efficiency, researchers envision a device-to-device (D2D) communication system in which a closely located mobile device pair may share the same spectrum with a cellular user. By opportunistically choosing the frequency, the D2D pair may increase the spectrum efficiency in terms of data rate per Hertz, at the price of additional interference to that cellular user. In previous models, users either stop cellular transmission and switch to D2D transmission or vice versa. However, if the cell is fully loaded, a D2D pair will not be able to switch back to the conventional mode because no extra resource is available. In this paper, we propose a D2D assisted model, where a D2D link is enabled to assist transmission, while keeping the conventional cellular transmission. In this way, the D2D link can be turned on and off according to the link quality. We also propose a PHY-layer study for the transmission scheme in such a way that the system throughput and the video reception quality is always improved compared to a conventional link.
    No preview · Conference Paper · Jan 2013
  • L. Toni · Dawei Wang · P.C. Cosman · L.B. Milstein
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    ABSTRACT: We address channel code rate optimization for transmission of non-scalable coded video sequences over orthogonal frequency division multiplexing networks for scenarios with arbitrary mobility. A slice loss visibility (SLV) model is used to evaluate the visual importance of each H.264 slice. In particular, taking into account both the visibility scores available from the bitstream and the channel state information, we optimize the channel code rate for each GOP and the mapping of video slices within 2-D time-frequency resource blocks, in order to better protect more visually important slices. Results demonstrate that the proposed algorithm outperforms baseline ones which do not take into account the SLV in the video transmission.
    No preview · Conference Paper · Jan 2012
  • Qihang Peng · Dingyong Hu · Qicong Peng · P.C. Cosman · L.B. Milstein
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    ABSTRACT: The optimal sensing-deception strategy by a power-limited intelligent adversary of a cognitive radio network is analyzed in this paper. The average number of false detections of the secondary users is maximized when the adversary employs noise spoofing signals, and each such signal experiences multipath-induced fading. The global optimal solution to what turns out to be a nonlinear, non-convex optimization is obtained through a two-step transformation. Numerical results show that, under i.i.d. Rayleigh fading, the optimal sensing-deception strategy for the adversary corresponds to equal-power, partial-band spoofing.
    No preview · Conference Paper · Jan 2012
  • Source
    Dawei Wang · P.C. Cosman · L.B. Milstein
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    ABSTRACT: We study an uplink video communication system with multiple users in a centralized wireless cell. The multiple access scheme is Orthogonal Frequency Division Multiple Access (OFDMA). Both physical layer channel state information (CSI) and application layer rate distortion (RD) information of video streams are collected by the base station. With the goal of minimizing the average video distortion across all the users in the system, we design an iterative resource allocation algorithm for subcarrier assignment and power allocation. Based on the physical layer resource allocation decision, the user will adapt the application layer video source coding rate. To show the advantage of this cross layer algorithm, numerical results are compared with two baseline resource allocation algorithms using only physical layer information or only application layer information. Bit-level simulation results are presented which take into account the imperfection of the video coding rate control, as well as channel errors.
    Preview · Conference Paper · Jan 2011
  • Liwen Yu · L.B. Milstein · J.G. Proakis · B.D. Rao
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    ABSTRACT: We consider a convolutionally coded orthogonal frequency-division multiple access (OFDMA) based cognitive radio system where each user achieves perfect synchronization for its own signal, while different users are asynchronized due to random timing offsets. The presence of asynchronous secondary users introduces potential multiple access interference (MAI) to each primary user's receiver. The strength of the MAI is determined by the secondary users' transmission powers, and their distances and frequency separations to the primary user. Expressions for the primary user's pairwise error probability and average probability of error are derived, and an error floor prediction method is presented. Finally, the trade-off between the MAI to the primary user and the secondary users' performances are investigated through numerical examples and simulations.
    No preview · Conference Paper · May 2010
  • Source
    Qihang Peng · P.C. Cosman · L.B. Milstein
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    ABSTRACT: This paper addresses the design of the power-limited intelligent adversary for sensing deception in a cognitive radio network. The average number of successfully spoofed bands by the adversary is analyzed, which can be expressed in terms of the individual spoofing probability on each band. The worst-case sensing deception strategy is obtained by maximizing the average number of successfully spoofed bands, under the adversary's power constraint. Specifically, for a cognitive radio network where energy detection is utilized by secondary users, it is shown that the worst-case deception strategy is equal-power, partial-band spoofing.
    Preview · Conference Paper · Jan 2010
  • Qihang Peng · P.C. Cosman · L.B. Milstein
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    ABSTRACT: We are interested in determining the sensitivity of a tactical cognitive radio (CR) system to intentional spoofing. That is, we assume the existence of an intelligent adversary whose goal is to attack the CR system by deceiving the secondary users into believing that as many frequency bands as possible are occupied by primary users, thus minimizing the number of bands in which the secondary users attempt to transmit. We refer to this operation by the adversary as "spoofing", and the specific spoofing signal we choose is a partial-band noise waveform. That is, for a given total power level that is available to the adversary, we maximize the average number of false detections incurred by secondary users as a result of the spoofing. We consider a channel such that each band experiences flat Rayleigh fading, whereby the fading is independent from band to band, and derive the average number of false detections by the secondary users due to the spoofing. The results obtained for the fading channel are compared to similar results for an additive white Gaussian noise channel (AWGN). They are also compared to a physically unrealizable scenario whereby the spoofing knows the instantaneous fade gains of the spoofing waveform at the victim CR receiver. This latter result is presented as a "worst-case" perspective as to how well the spoofing operation can be expected to perform.
    No preview · Conference Paper · Jan 2010
  • Ning Kong · Laurence B. Milstein
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    ABSTRACT: The paper introduces a new concept of groupwise generalized selection combining (GGSC), denoted by GGSC(n, m, L) , in which there are n groups of generalized selection combining GSC(m, L) where the largest m (in SNR) elements are selected from L independent elements. The paper proves that GGSC(n, m, L) has the same diversity order (DO) as that of MRC with nL elements, denoted by MRC(nL) and GSC(nm, nL) which selects the same number of branches globally from the same total of nL elements. The paper quantifies the performance differences among GGSC(n, m, L) , GSC(nm, nL) and MRC(nL). The paper shows the SNR loss of GGSC(n, m, L) relative to GSC(nm, nL) is less than 2.59 dB for arbitrary m, n and L. For diversity orders of practical interest (<12), the loss is less than 0.6 dB.
    No preview · Conference Paper · Nov 2009
  • Source
    A.H. Djahanshahi · L.B. Milstein · P.H. Siegel
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    ABSTRACT: In this paper, we explore a novel approach to evaluate the inherent UEP (unequal error protection) properties of irregular LDPC (low-density parity-check) codes over BECs (binary erasure channels). Exploiting the finite-length scaling methodology, suggested by Amraoui et. al., we introduce a scaling approach to approximate the bit erasure rates of variable nodes with different degrees in the waterfall region of the peeling decoder. Comparing the bit erasure rates obtained from Monte Carlo simulation with the proposed scaling approximations, we demonstrate that the scaling approach provides a close approximation for a wide range of code lengths (between 1000 and 8000). In view of the complexity associated with the numerical evaluation of the scaling approximation, we also derive simpler upper and lower bounds.
    Preview · Conference Paper · Aug 2009
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    Conference Paper: Wireless relay placement
    J. Cannons · L.B. Milstein · K. Zeger
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    ABSTRACT: An algorithm is given for placing relays at spatial positions to improve the reliability of communicated data in a sensor network. The network consists of many power-limited sensors, a small set of relays, and a receiver. The receiver receives a signal directly from each sensor and also indirectly via a single-hop relay path. The relays rebroadcast the transmissions in order to achieve diversity at the receiver. Both amplify-and-forward and decode-and-forward relay networks are considered. Channels are modeled with Rayleigh fading, path loss, and additive white Gaussian noise. The main results of the paper are geometric descriptions of sets of locations in the plane in which sensors are assigned to given, fixed-location relays, and the analysis of system performance.
    Preview · Conference Paper · Feb 2009
  • Source
    S.S. Tan · M.J. Rim · P.C. Cosman · L.B. Milstein
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    ABSTRACT: This paper addresses the use of adaptive modulation in progressive image transmission with multiple description coding in conjunction with an Orthogonal Frequency Division Multiplexing (OFDM) system. Specifically, two adaptive systems are considered: variable rate with fixed power, and variable rate with variable power. An algorithm is proposed to allocate power and constellation size at each subchannel by maximizing the throughput. Simulation results confirm that cross-layer optimization with adaptive modulation enhances system performance.
    Preview · Conference Paper · Jan 2009
  • Ning Kong · Larry B. Milstein
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    ABSTRACT: This paper derives closed-form asymptotic symbol error rates (ASERs) for MPSK and MQAM signals with selection combining (SC) over Nakagami-m fading channels. It also presents a closed-form expression for the power loss of SC compared to maximal ratio combining (MRC) over a Nakagami-m fading channel. It is found that this power gap is a function of only the number (X) of independent Nakagami-m channels and the fading parameter m. For a fixed m, the gap monotonically increases with L. For a fixed L, the gap monotonically increases with m and approaches <sup>10</sup>log<sub>10</sub> L dn (the asymptotic gap between MRC and SC in an AWGN channel) as m rarr infin . In addition, numerical results show the accuracy of the ASERs obtained from closed-form expressions for both MRC and SC with MPSK and MQAM signals for large SNRs. They also show that the SNR gap is identical to that predicted by the analysis for arbitrary L and m.
    No preview · Conference Paper · Jan 2009
  • Source
    K. Raghunath · A. Chockalingam · L.B. Milstein
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    ABSTRACT: In uplink OFDMA, timing offsets (TO) and/or carrier frequency offsets (CFO) of other users with respect to a desired user can cause multiuser interference (MUI). In practical uplink OFDMA systems, effect of this MUI is made acceptably small by requiring that timing/frequency alignment be achieved at the base station (BS) receiver with high precision. Alternatively, an ability to handle large TOs and CFOs using interference cancellation techniques at the BS receiver can offer the benefits of i) allowing low-cost transmit carrier frequency oscillators to be used at all the mobiles in an open-loop mode which can reduce the mobile cost and complexity, and ii) dropping the cyclic prefix (CP), which increases the throughput. In this paper, we first analytically characterize the degradation in the average output signal-to-interference ratio (SIR) due to the combined effect of both TOs as well as CFOs in uplink OFDMA without CP, and subsequently propose a parallel interference canceller (PIC) to mitigate the effect of interferences due to no CP and large TO/CFO. We illustrate the bit error performance of the proposed PIC for the cases of with and without CP. Simulation results show that performance close to that of 'with CP' can be achieved 'without CP' using increased number of PIC stages.
    Preview · Conference Paper · Apr 2008
  • Source
    A.H. Djahanshahi · P.H. Siegel · L.B. Milstein
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    ABSTRACT: This paper proposes a new approach for decoding LDPC codes over MISO channels. Since in an n<sub>T</sub> times 1 MISO system with a modulation of alphabet size 2<sup>M</sup>, n<sub>T</sub> transmitted symbols are combined and produce one received symbol at the receiver, we propose considering the LDPC-coded MISO system as an LDPC code over 2<sup>MnT</sup>-ary alphabet. Consequently, we propose a modified Tanner graph to introduce belief propagation for decoding MISO-LDPC systems. As a result, the MISO symbol detection and binary LDPC decoding steps are merged into a single message passing decoding. We also propose an efficient method that significantly reduces the complexity of belief propagation decoding in MISO-LDPC systems. Furthermore, we show that our proposed decoder outperforms the conventional decoder for short length LDPC codes in unknown channel scenarios.
    Preview · Conference Paper · Jan 2008
  • Diego Piazza · L.B. Milstein
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    ABSTRACT: Research in recent years has been focusing on the role of multiuser diversity in enhancing the throughput of wireless networks. Channel fading is now seen as a source of randomization that can be exploited by a smart scheduler with partial channel information, for example, in terms of data rates requested by the users. In this paper, we analyze the performance of a multiuser diversity system, taking into account the feedback errors due to channel variability. Channel estimation errors are modeled as Gaussian random variables with variance depending on the Doppler spread. Based on a block fading channel model, we present an expression for the throughput, both as a function of the key system parameters, such as packet length and data rate thresholds, and channel characteristics, such as Doppler spread. From the analysis of the performance, we present a tradeoff between multiuser diversity and mobility, and also between rate adaptivity and channel estimation errors. It is shown that multiuser diversity gain is reduced for increasing receiver mobility, and that the throughput loss depends also on the distribution of the data rate thresholds. Finally, we use the expressions derived in the paper in order to adaptively reduce the loss due to feedback errors. Given a set of possible data rates, the users can choose the most suitable one based not only on the set of thresholds and signal strength, but also on mobility conditions and system parameters, such as packet length.
    No preview · Article · Jan 2008 · IEEE Transactions on Wireless Communications
  • Qi Qu · L.B. Milstein · D.R. Vaman
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    ABSTRACT: In this paper, we investigate the issue of cooperative node selection in MIMO communications for wireless ad hoc/sensor networks, where a source node is surrounded by multiple neighbors and all of them are equipped with a single antenna. Given energy, delay and data rate constraints, a source node dynamically chooses its cooperating nodes from its neighbors to form a virtual MIMO system with the destination node (which is assumed to have multiple antennas), as well as adaptively allocates the power level and adjusts the constellation size for each of the selected cooperative nodes. In order to optimize system performance, we jointly consider the optimization of all these parameters, given the aforementioned system constraints. We assume that the source node either has CSI, or has no CSI. Heuristic algorithms, such as maximal channel gain (MCG) and least channel correlation (LCC) algorithms are proposed in order to exploit available system information and to solve the constrained optimization problem.
    No preview · Conference Paper · Jan 2008

Publication Stats

3k Citations
88.60 Total Impact Points

Institutions

  • 2013
    • University of California, Davis
      Davis, California, United States
  • 1992-2013
    • University of California, San Diego
      • Department of Electrical and Computer Engineering
      San Diego, California, United States
    • University of San Diego
      San Diego, California, United States
  • 1988-2006
    • California State University
      • Department of Electrical & Computer Engineering
      Long Beach, California, United States
  • 2004
    • Broadcom Corporation
      Irvine, California, United States
  • 1992-2001
    • CSU Mentor
      • Department of Electrical & Computer Engineering
      Long Beach, California, United States
  • 1999
    • National University (California)
      San Diego, California, United States
  • 1998
    • University of Colorado Colorado Springs
      • Department of Electrical and Computer Engineering
      Colorado Springs, CO, United States
  • 1997
    • Northwestern University
      • Department of Electrical Engineering and Computer Science
      Evanston, IL, United States
  • 1989-1997
    • University of Florida
      • Department of Electrical and Computer Engineering
      Gainesville, Florida, United States
  • 1996
    • Signal Processing Inc.
      Maryland, United States
  • 1995
    • The University of Hong Kong
      • Department of Electrical and Electronic Engineering
      Hong Kong, Hong Kong
    • Naval Medical Center San Diego
      San Diego, California, United States
  • 1994-1995
    • Politecnico di Milano
      • • Department of Electronics, Information, and Bioengineering
      • • Department of Electrical Engineering
      Milano, Lombardy, Italy
    • Georgetown University
      Washington, Washington, D.C., United States
  • 1993-1994
    • George Washington University
      • Department of Electrical & Computer Engineering
      Washington, D. C., DC, United States
    • Newport Corporation
      Irvine, California, United States
  • 1991
    • CUNY Graduate Center
      New York City, New York, United States
    • Virginia Polytechnic Institute and State University
      • Department of Electrical and Computer Engineering
      Blacksburg, VA, United States
  • 1990
    • City College of New York
      • Department of Electrical Engineering
      New York City, NY, United States