Patents by Inventor Georgios Giannakis

Georgios Giannakis has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20080037685
    Abstract: Techniques are described for space-time block coding for single-carrier block transmissions over frequency selective multipath fading channels. Techniques are described that achieve a maximum diversity of order NtNr (L+1) in rich scattering environments, where Nt (Nr) is the number of transmit (receive) antennas, and L is the order of the finite impulse response (FIR) channels. The techniques may include parsing a stream of information-bearing symbols to form blocks of K symbols, precoding the symbols to form blocks having J symbols, and collecting consecutive Ns blocks. The techniques may further include applying a permutation matrix to the Ns blocks, generating a space-time block coded matrix having Nt rows that are communicated through a wireless communication medium. The receiver complexity is comparable to single antenna transmissions, and the exact Viterbi's algorithm can be applied for maximum-likelihood (ML) optimal decoding.
    Type: Application
    Filed: March 6, 2007
    Publication date: February 14, 2008
    Applicant: Regents of the University of Minnesota
    Inventors: Georgios Giannakis, Shengli Zhou
  • Publication number: 20070253496
    Abstract: In general, linear complex-field encoding techniques are proposed For example, transmitter of a wireless communication system includes an encoder and a modulator. The encoder linearly encodes a data stream to produce an encoded data stream. The modulator to produce an output waveform in accordance with the encoded data stream for transmission through a wireless channel. The modulator generates the output waveform as a multicarrier waveform having a set of subcarriers, e.g., an Orthogonal Frequency Division Multiplexing (OFDM) waveform. The encoder linearly encodes the data stream so that the subcarriers carry different linear combinations of information symbols of the data stream.
    Type: Application
    Filed: April 21, 2003
    Publication date: November 1, 2007
    Inventors: Georgios Giannakis, Yan Xin, Zhengdao Wang
  • Publication number: 20060083338
    Abstract: Techniques are described that provide noncoherent demodulation via correlating “dirty” templates in wireless communication systems. In particular, the described techniques cross-correlate dirty templates that are adjacent symbol-long segments of the received noisy waveform. Unlike transmitted reference (TR) and differential templates that are noisy, i.e., propagate through the wireless communication channel, these dirty templates are both noisy and offset in time and, thus, are dirty. As a result, the described techniques enable noncoherent demodulation without timing synchronization and channel estimation. Symbol demodulation may be performed utilizing a maximum likelihood (ML) sequence detector or, alternatively, conditional ML demodulation may be performed to reduce receiver complexity. The described techniques may also be applied to a TR scheme to improve performance in the presence of mistiming.
    Type: Application
    Filed: October 3, 2005
    Publication date: April 20, 2006
    Applicant: Regents of the University of Minnesota
    Inventors: Georgios Giannakis, Liuqing Yang
  • Publication number: 20060083319
    Abstract: Techniques are described that provide inter-symbol interference—(ISI) and multi-user interference—(MUI) resilient blind timing synchronization and low complexity demodulation in wireless communication systems. A nonzero mean symbol is transmitted with a predetermined period in a stream of zero mean symbols during a synchronization phase. Only nonzero mean symbols are transmitted outside of the synchronization phase. Blind or non-data aided synchronization is performed at the receiver while bypassing channel estimation. The techniques enable timing synchronization via energy detection and low-complexity demodulation by matching the received waveform to a synchronized aggregate template (SAT). The SAT is recovered by averaging samples of the received waveform during the synchronization phase.
    Type: Application
    Filed: October 4, 2005
    Publication date: April 20, 2006
    Applicant: Regents of the University of Minnesota
    Inventors: Georgios Giannakis, Xiliang Luo
  • Publication number: 20050220200
    Abstract: Techniques are described for multicarrier multiple access wireless transmission, e.g. orthogonal frequency-division multiple access (OFDMA) transmissions, over frequency selective fading channels. The techniques are designed to maintain constant modulus transmissions for uplink while effectively mitigating intersymbol interference. Specifically, the techniques utilize non-redundant unitary precoding across OFDMA subcarriers to maintain constant modulus transmissions for uplink communications. For example, the techniques involve precoding a block of information symbols and assigning a different subcarrier for each symbol of the block. The subcarriers are selected to be equi-spaced and may be selected, for example, from a phase-shift keying constellation. The number of symbols per block is equal to the number of subcarriers assigned per user. Importantly, even with multiple subcarriers per user, the techniques enable constant modulus transmissions for uplink.
    Type: Application
    Filed: March 2, 2005
    Publication date: October 6, 2005
    Inventors: Georgios Giannakis, Shengli Zhou, Pengfei Xia
  • Publication number: 20050135314
    Abstract: Techniques are described for performing block equalization on a received wireless communication signal formed according to interleaved chips generated from sub-blocks of symbols. For example, a one-step block equalization process is described which produces estimates of the information-bearing symbols from a wireless communication signal received from two or more transmitters in a soft handoff environment. The techniques provide improved performance in high load, soft handoff environments with low complexity, highly flexible equalization. The wireless communication signal may be a CIBS-CDMA signal in which a symbol block is divided into sub-blocks and spread by a user-specific block-spreading matrix. The CIBS signal is received through M subchannels and a de-spreading matrix is applied to produce a multi-user interference (MUI) free sub-block output for the mth channel.
    Type: Application
    Filed: May 7, 2004
    Publication date: June 23, 2005
    Inventors: Georgios Giannakis, Shengli Zhou
  • Publication number: 20050105594
    Abstract: The invention provides an ultra-wideband (UWB) transmitter and various techniques for generating digitally filtered UWB pulses that substantially maximize power and bandwidth in one or more frequency bands while allowing narrow-band interference (NBI) to be avoided, e.g. interference to and from wireless local area networks (WLANs). In particular, the UWB transmitter utilizes a digital filter to generate digitally filtered UWB pulses to substantially maximize power and bandwidth in the Federal Communications Commission (FCC) spectral mask for UWB communications. In one embodiment, the invention provides a method comprising generating digitally filtered ultra-wide band (UWB) pulses to substantially maximize power in one or more frequency bands of a UWB spectrum and to substantially reduce power in one or more NBI frequency bands of the UWB spectrum. The invention may be implemented without modifying the analog components of existing UWB transmitters.
    Type: Application
    Filed: September 29, 2004
    Publication date: May 19, 2005
    Inventors: Georgios Giannakis, Liuqing Yang, Xiliang Luo
  • Publication number: 20050105631
    Abstract: A wireless communication system is described that generates FDFR transmissions with any number of transmit and receive antennas through flat-fading channels and frequency- or time-selective channels. In particular, the system utilizes layer-specific linear complex-field (LCF) coding with a circular form of layered space-time (ST) multiplexing to achieve FDFR wireless communications with any number of transmit and receive antennas through flat-fading and frequency- or time-selective channels. Additionally, the described techniques provide flexibility for desirable tradeoffs among performance, rate, and complexity.
    Type: Application
    Filed: September 30, 2004
    Publication date: May 19, 2005
    Inventors: Georgios Giannakis, Xiaoli Ma
  • Publication number: 20050105588
    Abstract: Techniques are described for generating digital carrier multi-band user codes for a baseband ultra-wideband (UWB) signal. The digital carrier multi-band user codes comprise spreading codes that enable multiple access in a UWB system. The user codes are digital, lead to baseband operation, and provide flexibility in handling narrow band interference (NBI) within the UWB system. In one embodiment, the invention provides a method comprising generating digital carrier multi-band user codes for a baseband ultra-wideband (UWB) signal of a user in an UWB system.
    Type: Application
    Filed: September 29, 2004
    Publication date: May 19, 2005
    Inventors: Georgios Giannakis, Liuqing Yang
  • Publication number: 20050002325
    Abstract: Techniques are described for space-time-frequency (STF) coding of multi-carrier transmissions over frequency-selective fading channels. In particular, techniques for STF coding of MIMO-OFDM systems are described that provide maximum diversity, high coding gains, and low decoding complexity are described. A set of generally correlated OFDM subcarriers are divided into groups of subcarriers creating a set of group STF (GSTF) subsystems, within which STF coding is applied to each GSTF subsystem. Subcarrier grouping preserves maximum diversity gains and simplifies both the code construction within each GSTF and decoding complexity. ST coding techniques are used in designing STF block (STFB) and STF trellis (STFT) codes which are applied within GSTF subsystems.
    Type: Application
    Filed: April 20, 2004
    Publication date: January 6, 2005
    Inventors: Georgios Giannakis, Zhiqiang Liu, Yan Xin
  • Publication number: 20050002461
    Abstract: Techniques are described for channel estimation of block transmissions over time- and frequency-selective wireless fading channels. A wireless transmitter forms blocks of symbols that include at least two blocks of training symbols separated by at least one information-bearing symbol. Each block of training symbols comprises a first block of zero symbols and a second block of zero symbols separated by at least one training symbol. Each block of training symbols is equally long and equally spaced between information-bearing symbols. The training and information-bearing symbols are transmitted with equal power, respectively. A wireless receiver receives a wireless transmission signal formed according to the blocks of symbols and forms an estimate of a wireless communication channel based on the training symbols within the received signal.
    Type: Application
    Filed: May 21, 2004
    Publication date: January 6, 2005
    Inventors: Georgios Giannakis, Xiaoli Ma