Synchronized paging system

• US 5,663,715 A
• Filed: 07/19/1996
• Issued: 09/02/1997
• Est. Priority Date: 09/22/1994
• Status: Expired due to Term

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Glenayre Electronics Incorporated (EDCI Holdings Incorporated)
• Inventors: Godoroia, Andrei
• Primary Examiner(s): ZIMMERMAN, BRIAN A
• Application Number:
  US08/687,788
• Time in Patent Office: 410 Days
• Field of Search: 340/825.2, 340/825.44, 455/38.1, 370/95.1, 379/57
• US Class Current: 340/4.2
• CPC Class Codes: G08B 3/1066 with other provisions not elsewhere provided for, e.g. turn-off protection
• CPC Class Codes: H04B 7/18567 Arrangements for providing additional services to the basic mobile satellite telephony service
• CPC Class Codes: H04M 11/022 Paging systems personal calling arrangements or devices G08B3/1008; selective calling networks H04W84/022
• CPC Class Codes: H04W 84/022 One-way selective calling networks, e.g. wide area paging
• CPC Class Codes: H04W 84/025 with acknowledge back capability

Abstract

A two-way paging system includes a paging terminal and one or more transmitters and receivers. The paging terminal, transmitter and receiver are synchronized to a common clock reference which is derived from the global positioning satellite system. The transmitter transmits paging signals in sequential frames having a predefined start time and duration. A paging unit is instructed to transmit its acknowledge signal during a predefined time slot. By synchronizing the paging terminal transmitters and receivers to a common clock the receivers are able to determine the frame number and time slot during which an acknowledge signal is transmitted based on the time of reception of the acknowledge signal. If the acknowledge signal is transmitted during the correct flame and time slot, the paging system can determine that the paging unit has received the paging message correctly.

Claims

1. A circuit for decoding a paging signal received on a reverse channel from a remotely located paging unit which was transmitted in response to a paging message transmitted on a forward channel from a paging transmitter, comprising:

a register for storing a synchronize code;

a correlator circuit that samples the paging signal received on the reverse channel and analyzes the sample to determine if the received paging signal matches the synchronize code;

a timing circuit for providing an indication of the current time;

means for storing an indication of the time at which a beginning of the paging signal was received; and

means for updating the register with a new synchronize code based on the time since the paging signal was received and the current time.

2. The circuit as in claim 1, wherein the timing circuit is synchronized to timing signals produced by a global positioning satellite system.

3. A paging reception system for decoding paging signals transmitted at a predefined time on a reverse channel from a remotely located paging unit, the paging signals including a synchronized code and at least one other code having a defined bit pattern transmitted at a known time within the paging signal, the reception system comprising:

an antenna for receiving;

a receiver circuit coupled to the antenna for receiving paging signals transmitted on the reverse channel, wherein the receiver creates a digitized version of the received paging signal;

a memory circuit that stores the digitized paging signal;

an adaptive decoder circuit that includes a register for storing a code that when detected indicates a symbol edge in the digitized paging signal;

a symbol timing circuit that compares the digitized paging signal with the code stored in the register, the symbol timing circuit providing an indication whether or not the digitized paging signal matches the code in the register;

a clock circuit that provides an indication of the current time; and

a central processing unit that receives the signal produced by the symbol timing circuit and updates the code stored in the register if the symbol timing circuit cannot match the digitized paging signal with the code stored in the register, wherein said code is updated at the predefined time at which the code having the defined bit pattern is expected.

4. The paging reception of claim 3, wherein the clock is synchronized to timing signals produced by a global positioning satellite system.

5. A method of operating a paging receiver to receive paging signals of the type having a synchronized code that marks the beginning of the paging signal and at least one other code having a known bit pattern transmitted at a predefined time in the paging signal, comprising the steps of:

synchronizing the receiver to a common time source used by a remote paging unit to determine when a paging signal should be transmitted on the reverse channel;

storing a digitized version of the paging signals transmitted on the reverse channel; and

programming a symbol timing circuit to analyze the digitized paging signals for the synchronized code that marks the beginning of the paging signal and, if the synchronized code cannot be found, reprogramming the symbol timing circuit to analyze the digitized paging circuit with the code having the defined bit pattern at the predefined time when the code is to be transmitted.