University System of Maryland

Ashok Kumar Agrawala

Amitabh Varshney

A Udaya Shankar

Christopher A Landauer

Matthew Mah

Moustafa Youssef

Sung Lee

Christian B Almazan

Ronald L Larsen

Douglas C Szajda

A system and method are provided for adaptive synchronization of timing information provided in communications messages transmitted between independently clocked communication nodes of a wireless communications network. The system and method include measures for collecting timestamps of messages generated by a plurality of the nodes, each timestamp being generated by one of the nodes relative to a local time reference thereof. A pairwise clock error is computed for at least one pair of nodes based upon a plurality of network messages passed therebetween. A global time reference is adaptively established for the timestamps responsive to the pairwise clock error. A plurality of mapping factors are defined each for translating from one local time reference to the global time reference. The mapping factors are selectively applied to corresponding ones of the timestamps.

Method and system for adaptive synchronization of timing information generated by independently clocked communication nodes

A multifunctional interaction system which is capable of spatio-temporal context localization of users and of communication of audio/video streams to an entity of interest defined by the user, includes a communication domain supporting a predefined localization service, a server associated with the communication domain, client devices, and a dynamically changing context database which is customized in accord with the dynamics of interaction sessions of client devices with the server. The client communicates with the system to either request services therefrom or to send a message to the entity of interest. The system is provided with a panic alert mechanism which, upon actuation, transmits an audio/video data stream along with the client location tag, time stamp, and client ID, to a police precinct for prompt action.

System and method for adaptive context aware interaction of user with entity of interest

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. A measurement of the signal strength at the addressable receiver from each of the plurality of addressable sources is used in conjunction with the discrete-space radio map to identify one of the coordinates thereof that maximizes the conditional probability P(xls), where x is the radio map location and s is a vector of measured signal strengths.

Method and system for determining user location in a wireless communication network

An asset positioning method and system () 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 (). 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 (). 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. Since the positioning protocol yields rapid responses and positional accuracy in the range of a few centimeters, the positioning protocol permits mobile nodes to be tracked while they are moving.

Method, system and computer program product for positioning and synchronizing wireless communications nodes

Nodes in a network transmit information among one another without the need for identifying headers. A calendar is maintained, indicating the times at which various data chunks are to be sent. When a request is made, the calendar is checked to see whether resources are free to accommodate the request. If so, the calendar is revised to reserve resources for the request.

Growing community of inventors

Ashton, MD, United States of America

Ashok Kumar Agrawala