Patents by Inventor Anand Narasimhan

Anand Narasimhan 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).

  • Patent number: 6252968
    Abstract: A method of enhancing the audio quality in a reproduction medium having unknown characteristics. With this method a predetermined finite set of single frequency tones are generated and these tones are then passed through the reproduction medium to generate an output signal, which in turn is passed through a set of sub-band filters. Each of the sub-band filters pass at least a frequency corresponding to one of the tones in the set of tones. The characteristics of the reproduction medium is then estimated as a result of passing the output signal through the set of sub-band filters. Based on the estimated characteristics of the reproduction medium, a set of sub-band inverse filters are constructed. Finally before passing the audio signal through the reproduction medium the signal is passed through the set of inverse filters to improve the quality of the audio signal after it passes through the reproduction medium.
    Type: Grant
    Filed: September 23, 1997
    Date of Patent: June 26, 2001
    Assignee: International Business Machines Corp.
    Inventors: Anand Narasimhan, Ganesh Nachiappa Ramaswamy
  • Patent number: 6173044
    Abstract: A gateway enables point to multipoint connectivity from voice, data, or SVD clients over voice and data networks. The gateway connects one or more known voice networks (e.g. telephone networks) and one or more data networks (e.g. LANs, WANs, and internet) so that clients on either network may access any of the networks via various devices like analog telephones, data modems, SVD modems, or direct data network connections (e.g., ethernet, token ring). The gateway has connections to both the data network(s) as well as the voice network(s). The gateway is capable of splitting a signal with both voice and data streams and routing either and/or both of these streams over the voice network alone, the data network, or both. A process, executing on the gateway enables the gateway to establish connections on gateway paths and to control and direct a flow of voice and data information between the destinations on these networks.
    Type: Grant
    Filed: February 6, 1996
    Date of Patent: January 9, 2001
    Assignee: International Business Machines Corporation
    Inventors: Peter Dirk Hortensius, Leon Lumelsky, Anand Narasimhan
  • Patent number: 6073165
    Abstract: A message processing and forwarding system for processing electronic messages in a digital format received over a computer communication path or network, and forwarded over a telephone circuit switched network to a user's receiver, such as a pager. A content processor in a message server processes the received digital message in accordance with knowledge of the receiver's capabilities and user-configured message filtering information to create a customized second message suitable for handling by the user's receiver at a remote physical location. Also, the system defines a distributed architecture for global paging, including multiple redundancy, to yield a robust system. In a preferred embodiment, the original digital message is part of an e-mail message received and forwarded through a conventional computer communication network such as the Internet.
    Type: Grant
    Filed: July 29, 1997
    Date of Patent: June 6, 2000
    Assignee: Jfax Communications, Inc.
    Inventors: Anand Narasimhan, Yaacov Shemesh, Jude M. Flannery, Jason Thaxter
  • Patent number: 5613206
    Abstract: This invention discloses a method and apparatus for acquiring and maintaining a cellular wireless communications subnetwork on an Ad Hoc basis, where mobile units within a cellular network communicate with each other using only a single communications channel of the entire cellular wireless communications network.
    Type: Grant
    Filed: April 6, 1995
    Date of Patent: March 18, 1997
    Assignee: International Business Machines Corporation
    Inventors: David F. Bantz, Anand Narasimhan
  • Patent number: 5574665
    Abstract: The present invention is a system and method for resolving closely spaced frequencies in frequency patterns used to tag objects. The system comprises a base station transceiver and one or more objects that send the base station a unique frequency pattern that identifies the respective object and/or provides information about the object. The base station performs a method by which an estimate of a received signal from an object is compared to one or more known frequency patterns in a frequency pattern set stored at the base station. One test frequency pattern at a time is selected and a distance is determined between the estimated received frequency pattern and the selected test frequency pattern. Iterative modifications are done to the test frequency pattern to minimize the distance.
    Type: Grant
    Filed: April 29, 1994
    Date of Patent: November 12, 1996
    Assignee: International Business Machines Corporation
    Inventor: Anand Narasimhan
  • Patent number: 5515366
    Abstract: Direct communication between a primary portable unit initiating the communication and a secondary portable unit is established utilizing two handshaking operations. The first handshaking operation is performed in the base station channel to establish initial contact between the primary and secondary portable units. After initial contact is made, the second handshaking operation is performed to establish communication in an unoccupied channel. The base station channel and the unoccupied channel may be a TDMA/TDD channel or a TDMA/FDD channel.
    Type: Grant
    Filed: November 17, 1994
    Date of Patent: May 7, 1996
    Assignee: International Business Machines Corporation
    Inventors: Trieu C. Chieu, Anand Narasimhan, Gary E. O'Neil, Li-Cheng R. Zai
  • Patent number: 5448569
    Abstract: Methods for handoff in a wireless communication network including a local area network connected to a plurality of base stations, each of which has a geographic area, defined as a cell, within which mobile stations can communicate with a base station, with each such base station being capable of performing bidirectional wireless communication with one or more of said mobile stations under control of a controller, with communication between base stations and mobile stations being performed by frequency hopping, with there being n available frequency hopping channels in a fixed frequency band, with each channel being of a same fixed duration and having a fixed frequency different than another channel.
    Type: Grant
    Filed: April 12, 1994
    Date of Patent: September 5, 1995
    Assignee: International Business Machines Corporation
    Inventors: Chia-Chi Huang, David F. Bantz, Frederic Bauchot, Kadathur S. Natarajan, Anand Narasimhan, Michele M. Wetterwald
  • Patent number: 5285480
    Abstract: A TDMA RF received signal is demodulated by first being filtered with a fixed transversal filter having a characteristic selected for matching a fixed square root raised cosine pulse characteristic of the received signal. The filtered signal is then adaptively filtered for compensating for a time varying impulse response of the channel. The adaptive filtering is performed initially during a synchronizing portion (preamble) of the filtered signal in accordance with a fast recursive least squares algorithm. Subsequent filter adaptation to a data portion of the filtered signal is accomplished in accordance with a computationally less expensive normalized least mean square procedure. The adaptive filter repetitively applies a modified Viterbi algorithm to blocks of 2D symbols, such that D symbols are released for adapting the adaptive filter means during the data portion of the filtered signal and the signal.
    Type: Grant
    Filed: September 3, 1991
    Date of Patent: February 8, 1994
    Assignee: General Electric Company
    Inventors: Sandeep Chennakeshu, Anand Narasimhan, John B. Anderson
  • Patent number: 5283811
    Abstract: An adaptive Decision Feedback Equalizer (DFE) (40) for a digital cellular mobile radio channel demodulator (30) employs a Complex Fast-Kalman Adaptation algorithm (56) to track channel variations. Sensitivity to sample timing jitter is reduced by providing the DFE with fractionally spaced feed-forward taps (50'). Deficiencies inherent in using a reduced precision implementation are overcome by adding a dither signal to sets of operations in the algorithm, the dither signal comprising an appropriately selected Gaussian random variable. For small delay spreads of approximately one third of a symbol duration or less, a resulting degradation in Bit Error Rate is avoided by switching the DFE out of the circuit or by reducing the number of taps of the DFE. For delay spreads of less than 40 microseconds and greater than approximately 10 microseconds, a (2,3) fractionally spaced DFE provides an adequate compromise between complexity and performance.
    Type: Grant
    Filed: September 3, 1991
    Date of Patent: February 1, 1994
    Assignee: General Electric Company
    Inventors: Sandeep Chennakeshu, Anand Narasimhan, John B. Anderson
  • Patent number: 5249205
    Abstract: A received time division multiple access (TDMA) signal having a time slot comprised of a plurality of symbols including at least one sequence of synchronizing symbols and a plurality of data symbols is demodulated by adaptively filtering the received signal to minimize inter-symbol interference due to an effect of channel signal propagation delay. The adaptive filtering step is performed by processing the received signal with a multi-stage lattice decision feedback equalizer having (M=N.sub.1 -N.sub.2) stages followed by (N.sub.2 -1) two-dimensional stages. A metric is next formed for each of the stages in accordance with a predetermined mathematical relationship between the output signals of each of two stages. A plurality of the formed metrics are next accumulated over a plurality of time slots.
    Type: Grant
    Filed: September 3, 1991
    Date of Patent: September 28, 1993
    Assignee: General Electric Company
    Inventors: Sandeep Chennakeshu, Anand Narasimhan, John B. Anderson