Symbol Technologies, LLC

Gregory B Ennis

LaRoy Tymes

Frances Lee

An apparatus and a method route information to a mobile unit in a data communications system having a home network and a remote network. Each of the home and remote networks supports one or more mobile units and one or more stationary access points. The mobile unit has a unique address and may roam from the home network to the remote network. The mobile unit associates with one access point which serves as a home agent. When the mobile unit roams and is away from its home network, the apparatus discovers a physical location of the mobile unit by sending an agent advertisement packet from the access point. If the location of the mobile unit is not at the home network, the apparatus associates the mobile unit with one of the access points on the foreign network which serves as a foreign agent. Next, the apparatus registers the mobile unit with the home agent, encapsulates original data received by the home agent which is destined for the mobile unit, forwards encapsulated data to the foreign agent, and converts the encapsulated data to the original data and delivers the original data to the mobile unit via the foreign agent.

Mobile internet communication protocol

A packet data transmission system is used to link a number of remote hand-held data-gathering units such as bar code readers to a central computer. Data packets are sent from the remote units by an RF link to intermediate base stations, then sent by the base stations to the central computer by a serial link. Direct sequence spread spectrum modulation is used for the RF link. The remote hand-held units initiate an exchange using RF transmission to and from the base stations, receiving only during a rigid time window following a transmission from the remote unit. The base stations cannot initiate an exchange with the remote units, but instead send data to the remote units only as part of the exchange. To alert a remote unit when a message is waiting at a base station to be sent to a particular unit, some of the acknowledge (base-to-remote) packets sent by the base station may contain an identification such as a list of all remote units (identified by ID number) which have messages waiting. Alternatively, a bit map can be used to identify these remotes. These base-to-remote packets with the identification of remotes with messages waiting are called 'announcements.' Each remote unit (if not engaged in regular exchanges for a time interval) periodically listens (activates its receiver) to receive an announcement packet containing such a list or bit map and decodes this announcement to see if it has a message waiting. If so, this remote unit then sends a transmit packet so the base can send the waiting message in an acknowledge packet.

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Los Gatos, CA, United States of America

Gregory B Ennis