Patents by Inventor Ashok Agrawala

Ashok Agrawala 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: 20070201412
    Abstract: Disclosed is a protocol used by wireless stations sharing a single wireless channel. When a local station senses a communication between remote stations using the channel, the local station estimates whether its local transmissions would disrupt this on-going remote communication. To estimate, the local station forms capture models of the remote stations. From the capture models, the local station determines if its local transmission would prevent each remote station from capturing the signal from the other remote station. If the local transmission would not disrupt the remote communications, the local station transmits its message over the channel at the same time the remote stations use the channel. The local station performs the estimation using parameters of the remote stations. The stations could share their parameters by including them in headers of frames. The protocol can be implemented as an enhancement to the IEEE 802.11 standard.
    Type: Application
    Filed: February 28, 2006
    Publication date: August 30, 2007
    Inventors: Lusheng Ji, Jonathan Russell Agre, Tamer Nadeem, Ashok Agrawala
  • Publication number: 20070058564
    Abstract: A Cyclone Network Synchronization algorithm is presented that does not depend on highly stable and expensive clocks or hardware, yet it can synchronize nodes in a network with a very high degree of accuracy. It is very light-weight since no clock synchronization is performed, and subsequently does not incur any overhead in message passing. Instead, synchronization is done solely by listening to the regular network traffic. Finally, the amount of padding or time overhead incurred by the CNS algorithm is extremely small, even when used with system clocks that have high drift rates (e.g. 1000 PPM or more).
    Type: Application
    Filed: July 21, 2006
    Publication date: March 15, 2007
    Applicant: University of Maryland
    Inventors: Ashok Agrawala, Michael Trinh
  • Publication number: 20050243936
    Abstract: In a wireless communication network, the location of an addressable receiver relative to the locations of a plurality of addressable sources of electromagnetic radiation is found using probabilistic models of the signal strength measured at the addressable receiver. The inventive method provides location determination on a finer spatial scale than was heretofore available. A region of interest is calibrated via a discrete-space radio map storing probability distributions of received signal strength at the measurement locations. The stored probability distributions are compensated for temporal variability and biases, such as through temporal correlations of the sampled received signal strength.
    Type: Application
    Filed: March 26, 2004
    Publication date: November 3, 2005
    Inventors: Ashok Agrawala, Moustafa Youssef
  • Publication number: 20050055568
    Abstract: A system for detecting the presence of an intruder in a protected area utilizes a received signal strength indicator (RSSI) value of signals broadcast from transmitting stations deployed in the protected area. The system includes monitoring points for receiving broadcast signals, measuring the RSSI values of the received signals, and transmitting the measured RSSI values to a security system server. The security system server analyzes the RSSI values, and initiates security measures when the physical security of the protected area is violated which is detected when the measured RSSI values deviate from a predetermined strength of the broadcast signals. The security system also has the ability to track objects in the protected area and keep track of their movement in real time and report such movement. The system may be based on a Wi-Fi infrastructure in the protected area.
    Type: Application
    Filed: August 12, 2004
    Publication date: March 10, 2005
    Inventors: Ashok Agrawala, Moustafa Amin Youssef, Layla Shahamat
  • Publication number: 20050020275
    Abstract: An asset positioning method and system (700) rapidly and accurately determine the special location of wireless nodes distributed in three-dimensional space. Furthermore, as a by-product, every node also determines the relative offset and drift of every other node's clock, so that it is possible for all nodes to carry out a precise synchronized action (708). The positioning and synchronization protocol has significant implications for a broad range of wireless networking infrastructure and applications. For instance, the rapid availability of accurate location information greatly simplifies and optimises the implementation of ad-hoc networks and sensor-based applications (716). Additionally, the synchronized node operations facilitate the development of new applications, such as phase-locked arrays, in which several low power transmitters coordinate to form a powerful group transmitter.
    Type: Application
    Filed: August 15, 2001
    Publication date: January 27, 2005
    Inventors: Ashok Agrawala, Ronald Larsen, A. Udaya Shankar, Douglas Szajda