Motorola Corporation

Michael A Stepien

Thomas A Freeburg

Timothy J Wilson

Steven D Upp

Manohar A Joglekar

Stephen Michael Bench

James R Engel

James C Secora

William W Milleker

William R Dirkes

Keith J Glidewell

Methods and apparatus for facilitating mobility of the mobile stations in a wireless local area network (WLAN) allows uninterrupted communications as the mobile station moves. The method includes associating () a MNIP address () with the mobile station; establishing () a communications link between the mobile station and a first WLAN AP () in a first subnet () and associating () a first WLAN IP () address with the mobile station. Then using () the first WLAN IP address for an application that benefits from a persistent connection. Further included is establishing () a second communications link between the mobile station and a second WLAN APin a second subnet (). When the mobile station is using the application, continuing to use the first WLAN IP address for communicating with the second subnet; and requesting () a second WLAN IP address in the second subnet when the persistent connection is no longer needed.

Mobile station mobility in a wireless LAN

In a data message communication system, certain messages require a return acknowledgement signal. The present invention contemplates a method and means which are activated whenever an outbound message is received. Each portable unit which receives a message then monitors the outbound communication channel to determine if the inhibit signal is currently active. If the inhibit is not currently active, the particular unit will transmit its acknowledgement message immediately. If the inhibit signal is active, each portable unit will maintain a count of the number of outbound messages, addressed to other units requiring an acknowledgement, since that particular portable received its message. At the termination of the inhibit signal, each portable unit will pause for a period equivalent to the product of the acknowledgement message time slot multiplied by count of messages accumulated since the receipt of the particular portable units message. Each portable unit will then transmit an acknowledgement signal at the termination of its unique pause period.

Inbound acknowledgement stack

Data muting apparatus is described that mutes variable-length data signals communicated between a central station and mobile and portable radios in a dispatch radio communications system. The central station includes a base station transceiver, a dispatcher console, a general communications controller (GCC), a digital communications computer and a display terminal. The base station transmitter and receiver communicate over an RF duplex channel to the transceiver of the mobile and portable radios. The dispatcher console provides for voice communications and is coupled by a transmit signal line and a receive signal line to the base station transceiver. The GCC provides for data communications and is also coupled to the transmit signal line and is interposed between the dispatcher console and the base station transceiver in the receive signal line. The GCC and mobile and portable radios include data muting apparatus enbodying the present invention. The data muting apparatus includes a detector for detecting the presence of a carrier signal and muting circuitry for muting the transceiver output for a predetermined time interval when a carrier signal has been detected. During the predetermined time interval, other circuitry may detect a synchronization word in a received data signal and mute the receiver output until still other circuitry detects the last bit of a following information word in the received data signal and unmutes the transceiver output. Thus, data signals at the beginning of each communication are muted without impairing voice communications.

Data muting method and apparatus for radio communications systems

A data communication system for use in the control and monitoring of mobile stations, for example, in a bus monitoring system, from a central station over a communication channel carrying both data and voice information. Information is encoded into digital messages having a start code followed by one or more data blocks. The start code identifies the beginning of the data block that follows and enables synchronization of clock circuitry to the received data frequency. The data blocks have N digital words with M binary bits where one word is a parity word and N-1 words are data words. Each of the data words has a data portion and parity portion coded for correction of at least one error. Reliability is enhanced by a data detector which discriminates between data and noise or voice to provide an indication of the presence of data. In transmitting the digital messages, the bits of the N words in each data block are interleaved to provide protection against error bursts.

Data communication system with random and burst error protection and

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Hoffman Estates, IL, United States of America

Michael A Stepien