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Heath R.,University of Texas at Austin | Peters S.,Kuma Signals, LLC | Wang Y.,Huawei | Zhang J.,Huawei
IEEE Communications Magazine | Year: 2013

Providing uniformly high capacity in cellular systems is challenging due to fading, path loss, and interference. A partial solution to this problem is the deployment of distributed antenna systems, where transmission points are distributed throughout the cell using coax cable or fiber, instead of being centrally located on a single tower. This article reviews how distributed antenna systems are evolving to provide higher performance on the downlink in cellular systems. Research trends in distributed antennas for the downlink of cellular systems are described along with current progress on their integration into commercial wireless cellular standards. A key observation is that distributed antenna systems are tightly integrated into the cellular architecture, and incorporate physical layer technologies like MIMO communication and multiuser MIMO to provide higher data rates. © 1979-2012 IEEE.


El Ayach O.,University of Texas at Austin | Peters S.,Kuma Signals, LLC | Heath R.W.,University of Texas at Austin
IEEE Wireless Communications | Year: 2013

Interference alignment is a revolutionary wireless transmission strategy that reduces the impact of interference. The idea of interference alignment is to coordinate multiple transmitters so that their mutual interference aligns at the receivers, facilitating simple interference cancellation techniques. Since interference alignment's inception, researchers have investigated its performance and proposed several improvements. Research efforts have been primarily focused on verifying interference alignment's ability to achieve the maximum degrees of freedom (an approximation of sum capacity), developing algorithms for determining alignment solutions, and designing transmission strategies that relax the need for perfect alignment but yield better performance. This article provides an overview of the concept of interference alignment as well as an assessment of practical issues including performance in realistic propagation environments, the role of channel state information at the transmitter, and the practicality of interference alignment in large networks. © 2013 IEEE.


Lee N.,University of Texas at Austin | Lin X.,University of Texas at Austin | Andrews J.G.,University of Texas at Austin | Andrews J.G.,Kuma Signals, LLC | And 2 more authors.
IEEE Journal on Selected Areas in Communications | Year: 2015

This paper proposes a random network model for a device-to-device (D2D) underlaid cellular system using stochastic geometry and develops centralized and distributed power control algorithms. The goal of centralized power control is twofold: ensure that the cellular users have sufficient coverage probability by limiting the interference created by underlaid D2D users, while scheduling as many D2D links as possible. For the distributed power control method, the optimal on-off power control strategy is proposed, which maximizes the sum rate of the D2D links. Expressions are derived for the coverage probabilities of cellular, D2D links, and the sum rate of the D2D links in terms of the density of D2D links and the path-loss exponent. The analysis reveals the impact of key system parameters on the network performance. For example, the bottleneck of D2D underlaid cellular networks is the cross-tier interference between D2D links and the cellular user, not the D2D intratier interference when the density of D2D links is sparse. Simulation results verify the exactness of the derived coverage probabilities and the sum rate of D2D links. © 1983-2012 IEEE.


Daniels R.C.,University of Texas at Austin | Daniels R.C.,Kuma Signals, LLC | Heath Jr. R.W.,University of Texas at Austin
IEEE Transactions on Wireless Communications | Year: 2012

Wireless communication networks use link adaptation to select physical layer parameters that optimize the transmission strategy as a function of the wireless channel realization. In the vehicle-to-vehicle (V2V) networks considered in this letter, the short coherence time of the wireless channel makes link adaptation based on the impulse response challenging. Consequently, link adaptation in V2V wireless networks may instead exploit the large-scale characteristics of the wireless channel (i.e. path loss) since they evolve slowly and enable less frequent feedback. Large-scale channel information may be captured through channel or} position/motion measurements. We show, through the definition of new large-scale coherence expressions, that channel measurements render large-scale coherence as a function of time-change while the position/motion measurements render coherence as a function of velocity-change. This letter is concluded with highway simulations of modeled and measured channels to demonstrate the advantage of position/motion information for feedback reduction in V2V link adaptation. © 2012 IEEE.


Grant
Agency: National Science Foundation | Branch: | Program: STTR | Phase: Phase I | Award Amount: 225.00K | Year: 2016

The broader impact/commercial potential of this project is the production of high-fidelity intelligent transportation systems at lower costs to increase automotive safety globally without wasting wireless spectrum to be used for other humanity improvement technologies. Successful completion of the work plan in this project enables opportunity for wireless communication device vendors and automotive original equipment manufacturers (OEMs) in the vehicular RADAR sensor market through structured target estimation (SSTE). Preliminary studies have suggested that SSTE may reduce the device cost requirements for vehicular RADAR to automotive OEMs by one order of magnitude. The availability of RADAR processing on standard wireless communication devices also enables dual-purpose wireless devices, leading to further reduced costs as well as increased security. Reduced costs and increased security in vehicular RADAR not only presents an attractive business opportunity, but also leads to safer transportation globally. Preliminary studies have also shown that SSTE requires 87% fewer spectrum resources. More efficient spectrum usage yields more spectrum availability for other applications like cellular communications and simultaneously increases the opportunity for license-free public spectrum. This Small Business Technology Transfer Research (STTR) Phase I project will validate a new framework for RADAR through a suite of signal processing functions known as successive structured target estimation (SSTE). In contrast to standard RADAR waveform processing, SSTE uses channel impulse response estimates available on wireless communication devices. SSTE exploits newly-discovered target structure to substantially improve performance in terms of ranging accuracy and spectrum consumption. The work plan will evaluate ranging accuracy and spectrum consumption through over-the-air radio frequency (RF) testing with moving vehicles. These tests must show that: (1) SSTE enables RADAR applications that use much less spectrum than required by current RADAR devices (2) SSTE functions adequately in all relevant vehicular environments (3) SSTE is able to track a sufficient number of targets for vehicular applications (4) wireless communication devices may service RADAR applications through SSTE without sacrificing performance in relevant vehicular environments.


Grant
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase II | Award Amount: 499.96K | Year: 2011

Kuma Signals proposes to prototype and test the Dillo fractional bit mapping framework investigated in the Phase I work plan. The Dillo system is designed to enable orthogonal frequency division multiplexing (OFDM) in high Doppler, low SNR, long delay spread environments with impulsive noise. The framework utilizes an innovative holistic approach to the physical layer design, focusing on cancellation of inter-carrier interference combined with powerful channel coding and adaptive spreading for peak-to-average power ratio reduction.


Grant
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 99.33K | Year: 2010

Kuma Signals proposes the DILLO fractional bit mapping framework with three candidate waveform designs to investigate in Phase I. The DILLO system is designed to enable orthogonal frequency division multiplexing (OFDM) in high Doppler, low SNR, long delay spread environments with impulsive noise. The framework utilizes an innovative holistic approach to the physical layer design, focusing on cancellation of inter-carrier interference combined with powerful channel coding and spreading for low peak-to-average power ratio reduction. The framework is designed to operate at SNRs of -20 to 0 dB and offer 4.8-64 kbps data rates under stressed conditions.


Grant
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 79.99K | Year: 2012

Kuma Signals LLC, in partnership with Rockwell Collins, propose to leverage our experience in HF multiple-input multiple-output (MIMO) communications, networking, and waveform design, to develop a new wideband HF (WBHF) waveform for high-rate Marine communications. The new waveform will allow trade-offs between a 4x data rate increase, 100x reliability increase, and 3x range increase over the current state-of-the-art in WBHF designs. Using 2-channel near vertical incidence skywave (NVIS) MIMO provides a 2x data rate increase. We will also investigate the use of low-complexity equalizers that have proven successful in enabling wide bandwidths at UHF in commercial broadband standards. In particular, low-complexity equalizers enable a 2x bandwidth increase over the currently proposed 24kHz channels. To increase reliability and connectivity, two existing HF networking protocols will be compared for suitability for Marine operations. Further, by designing our waveform to have adaptable bandwidths, we will work with our partners and spectrum regulatory bodies to ensure a 48kHz waveform does not impede existing traffic. The result of our Phase I Option will be a TRL 4 prototype utilizing our Karma MIMO software defined radio platform.


Grant
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase I | Award Amount: 99.95K | Year: 2015

Kuma Signals, LLC (Kuma) proposes to produce and prototype a practical mobile ad hoc networking (MANET) wireless protocol that features interference alignment (IA), multi-user MIMO (MU-MIMO), and single-user MIMO. While SU-MIMO and MU-MIMO is market-proven, IA is not. Many of the technical hurdles to accomplish IA have been overcome, including time and frequency synchronization and CSI distribution, but several practical challenges related to modulation, transceiver calibration, and medium access control (MAC) remain. In the work plan contained in this proposal, Kuma proposes to solve these remaining problems, finally proving that IA is market ready. In phase 2, Kuma proposes to partner with the University of Texas at Austin, architects of the most advanced IA prototyping efforts to date.


Grant
Agency: NSF | Branch: Standard Grant | Program: | Phase: STTR PHASE I | Award Amount: 225.00K | Year: 2016

The broader impact/commercial potential of this project is the production of high-fidelity intelligent transportation systems at lower costs to increase automotive safety globally without wasting wireless spectrum to be used for other humanity improvement technologies. Successful completion of the work plan in this project enables opportunity for wireless communication device vendors and automotive original equipment manufacturers (OEMs) in the vehicular RADAR sensor market through structured target estimation (SSTE). Preliminary studies have suggested that SSTE may reduce the device cost requirements for vehicular RADAR to automotive OEMs by one order of magnitude. The availability of RADAR processing on standard wireless communication devices also enables dual-purpose wireless devices, leading to further reduced costs as well as increased security. Reduced costs and increased security in vehicular RADAR not only presents an attractive business opportunity, but also leads to safer transportation globally. Preliminary studies have also shown that SSTE requires 87% fewer spectrum resources. More efficient spectrum usage yields more spectrum availability for other applications like cellular communications and simultaneously increases the opportunity for license-free public spectrum.

This Small Business Technology Transfer Research (STTR) Phase I project will validate a new framework for RADAR through a suite of signal processing functions known as successive structured target estimation (SSTE). In contrast to standard RADAR waveform processing, SSTE uses channel impulse response estimates available on wireless communication devices. SSTE exploits newly-discovered target structure to substantially improve performance in terms of ranging accuracy and spectrum consumption. The work plan will evaluate ranging accuracy and spectrum consumption through over-the-air radio frequency (RF) testing with moving vehicles. These tests must show that: (1) SSTE enables RADAR applications that use much less spectrum than required by current RADAR devices (2) SSTE functions adequately in all relevant vehicular environments (3) SSTE is able to track a sufficient number of targets for vehicular applications (4) wireless communication devices may service RADAR applications through SSTE without sacrificing performance in relevant vehicular environments.

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