Vsis, Inc.

Cisco Technology, Inc.

James Sun

Vijay K Nagasamy

Mohammad Usman

Harish Ramamurthy Devanagondi

A data packet parser, for determining packet format, is substantially software controlled, to readily accommodate new or different formats, without the need for using a microprocessor for parsing. Comparisons are performed under the control of data stored in a database. By storing new or different data in the database, new or different packet formats can accommodated without the need for making hardware changes. In one embodiment, comparisons performed on various fields of the data packet result in setting or clearing bits of a signature word which identifies the packet format. The signature word can be used directly or indirectly such as forming the input argument of a ternary CAM, to provide a pointer to microcode which appropriately handles the data packet in the identified format.

Programmable data packet parser

Systems and methods are disclosed for ionospheric correction in a system employing a single GPS frequency receiver for determining the geographic location of an object on the earth's surface. The receiver receives signals transmitted at the GPS L,frequency from at least first, second and third GPS satellites, the first, second and third satellites having respective orbital positions relative to the receiver such that the total electron count (TEC) contribution to ionoshperic interference to signals transmitted by the respective satellites and received by the receiver is approximately the same. Respective measured distances of the three satellites to the receiver are determined based on the actual signal transmission times. True distances of the respective satellites are then calculated based on the assumption that the TEC contribution to the interference from each satellite is approximately the same.

Ionospheric correction for single frequency GPS receivers using three satellites

Systems and methods are disclosed for ionospheric correction in a system employing a single GPS frequency receiver for determining the geographic location of an object on the earth's surface. The receiver receives signals transmitted at the GPS L.sub.1 frequency from at least first and second GPS satellites, the first and second satellites having respective orbital positions relative to the receiver such that the total electron count (TEC) contribution to ionoshperic interference to signals transmitted by the respective satellites and received by the receiver is approximately the same. Respective measured distances of the two satellites to the receiver are determined based on the actual signal transmission times. True distances of the respective satellites are then calculated based on the assumption that the TEC contribution to the interference from each satellite is approximately the same.

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Mountain View, CA, United States of America

James Sun