MXPA94005547A - Circuit and method for operating an inalambr communication system - Google Patents

Abstract

A wireless communication system for use with a public telephone system network, characterized by: at least one remote device adapted to transmit and receive radiofrequency communication signals, a series of base stations adapted to transmit radio frequency communication signals and for receiving radio frequency communication signals from at least one remote device, a communication link joining each base station with a telephone line of this public telephone system network for transmitting communication signals between the telephone line and the series of base stations, and connect each of the base stations of the series of base stations, to transmit information signals between this series of stations

Description

CIRCUIT AND METHOD FOR OPERATING A WIRELESS COMMUNICATION SYSTEM ** L JAMES MIELKE, US citizen, with INVENTOR: residence at: 319 Old Country Way, Wauconda, Illinois, 60084, E. U. A.

MOTOROLA, INC., American entity, with APPLICANT: address: 1303 East Algonquin Road, Sc au burg, Illinois, 60196, E. U. A.

SUMMARY OF THE INVENTION A circuit and a method for operating a wireless communication system (10) having multiple base stations (11) allows the transfer of a radio frequency communication between a base station (11) and a remote device (12) towards another base station (11), without the use of a separate controller that regulates the base stations. The base stations (11) communicate with each other by means of the tip and nape line of the public network of the telephone system (18), at a frequency of approximately 30 KHz. Consequently, the communication signals transferred between the base stations (11) are outside the audible range of the user and will be filtered by the public network of the telephone system (18). The base station (11) which is in active communication with a remote device (12) will determine if any other base station (11) is receiving a more powerful radio frequency communication signal from the remote device (12) and will transfer the link from the remote device (12). communication to another base station (11).

FIELD OF THE INVENTION The present invention relates in general to a wireless communication system, and more particularly to a circuit and method for connecting a wireless remote device to a base station, in a wireless communication system.

BACKGROUND OF THE INVENTION In the past, wireless communication systems provided communication between one or more remote devices and a series of remote base stations that included a controller to regulate communication between a remote device and the base stations. The control generally provided the transfer of transmissions between the base stations when necessary. An example of a wireless communication system having a series of base stations is a cellular telephone system. Generally, the base stations of the cellular telephone system are controlled by a cellular control station. A cordless telephone system is another example of a wireless communication system that could operate with a series of base stations. Currently, cordless telephone systems include one or more remote devices or microphones that are related to a single base station. Each of the remote devices can communicate with the base station on a different frequency. Therefore, communication between the various remote devices and the only base station can be accommodated. However, cordless telephone systems do not currently include multiple base stations. As in any wireless communication system having multiple base stations, there is a need to regulate the communication between the remote device and the base stations of a cordless telephone system having multiple bases. In particular, there is a need to regulate which base station will communicate with a particular remote device. In addition, because the power of the radio frequency communication signals between the remote device and the base stations can vary with time and the relative location of the remote device with respect to the base stations, it is useful to link each remote device with the station base that has the most powerful radiofrequency communication link. In a cordless telephone system, it is beneficial to regulate communication between a remote device and the base stations without employing a separate controller from the base stations. Eliminating any requirement of a separate controller will reduce the cost and complexity of the system. Accordingly, there is a need to create a circuit and method for operating wireless communication systems having multiple base stations such as a cordless telephone system that eliminates any requirement of a separate controller from the base stations.

SUMMARY OF THE INVENTION The present invention accompanies a wireless communication system for use in a public telephone system network comprising at least one remote device adapted to transmit radiofrequency communication signals and to receive signals from radio frequency communication, from a series of base stations. An example of a remote device could be a remote cordless phone device. A data link also connects each base station with a telephone line to transmit communication signals and to receive communication signals from the telephone line. A base station is the "active" base station and provides communication signals to the telephone line by means of a data link and radio frequency communication signals to the remote device. The data link also links the base stations together to allow communication between them. Each base station provides information signals that are transmitted to the other base stations by means of data links. The information signals include a signal indicating the power of the radio frequency communication signal received from the remote device. The active base station processes the information signals of each base by indicating the power of the radio frequency communication signal received by each base, to determine which base station should be active. For a wireless communication system that has multiple remote devices, a separate base station will be the active base station for each remote device. Each base will transmit an information signal indicating the power of the radio frequency communication signal received from each remote device. Accordingly, each active base station will determine which base station is receiving the most powerful radio frequency communication signal. The present invention also includes a method for operating a wireless communication system having a series of base stations and at least one remote device. The method initially establishes a radio frequency communication link between a remote device and one of the base stations, called the "main" base station or initial active base station. The remote device also provides radio frequency communication signals to the remaining base stations. Each of the base stations generates an information signal that * indicates the signal strength of the radio frequency communication signals received from the remote device. The main base station performs an investigation for the other base stations in relation to the information signals, to determine which base station is receiving the most powerful radio frequency communication signal from the remote device. Finally, a radiofrequency communication link is established between the remote device and the base station that has the most powerful radio frequency communication signal. The method of the present invention also contemplates a portable communication system having multiple remote devices. The method is similar to a wireless communication system that has a remote device. However, each base station that is in communication with a remote device will act as an active base station. Consequently, each base station # active will challenge the other base stations to determine which base station has the strongest radio frequency communication signal. Each active base station will transfer the radio frequency communication link to a non-active base station, if a non-active base station is receiving a more powerful radio frequency communication signal.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a horizontal projection of a wireless communication system 10 having multiple stations base 11 and multiple remote devices 12 for employing the circuit and the method of the present invention. Figure 2 is a block diagram of the circuit for operating a wireless communication system in accordance with the present invention. Figure 3 is a circuit diagram of the preferred signal transceiver circuit 24 shown in the block diagram of Figure 2. Figure 4 is a flow diagram of the method for operating a portable communication system according to the present invention. invention.

DESCRIPTION OF THE PREFERRED MODALITY Referring to Figure 1, a # Horizontal projection of a wireless communication system 10 having a series of base stations 11 and a series of remote devices 12, which employ the circuit and method of the present invention. The base stations 11 are linked by data links 14 to a single line 16 of a public telephone system network (PSTN) 18. Although any number of remote devices can be incorporated in the wireless communication system, only one is required • a remote device. The remote devices 12 may include any device capable of establishing a radio frequency communication with the base stations 11. An example of a base station and an associated remote device includes a cordless telephone. A cordless telephone that could employ the circuit and method of the present invention is set forth in U.S. Patent No. 5,140,635, assigned to Motorola, Inc., the entire patent of which is incorporated herein by reference. As shown in Figure 1, each base station 11 is in communication with the other base stations by means of data links 14 (indicated by the solid lines between the base stations). Preferably, the data link can incorporate the standard tip and nape lines of the public telephone system network, joining each base station with the same telephone line 16 of the public telephone system network. Alternatively, the * communication between the base stations can be achieved by a separate radio frequency communication circuit. Finally, each remote device 12 communicates with each base station 11 by means of radiofrequency communication signals (illustrated by dotted lines in Figure 1). Referring now to Figure 2, a block diagram for station 10 shows the portions Important # of the base station to provide information signals between the base stations by means of data links. Each base station generally includes a radio transceiver 20 for transmitting radiofrequency communication signals and receiving radio frequency communication signals from each remote device 12. Radio transceivers are well known in the art and can be employed in the present invention. Preferably, the radio transceiver circuit set forth in the aforementioned United States Patent 5,140,635 is employed. The radio frequency communication signals include the frequency or channel occupied by the remote device, a security code assigned to the remote device to allow it to operate in the wireless communication system 10 and any message signals. The message signals may depend on the remote device, but may include voice signals, facsimile data or computer data. The radio transceiver 20 provides communication signals on a line 22 that is connected to a signal transceiver circuit 24. The signal transceiver circuit 24 includes a standard telephone company interface (Telco) circuit 26 for transmitting communication signals. The standard Telco circuits are well known in the art and provide communication signals to the tip and nape lines of the public telephone system network. The radio transceiver 20 also generates a signal d information on the line 22. The information signal can include a signal indicating the reception power of the signal (RSSI) and the security code associated with a remote device. The RSSI signal indicates the power of the radio frequency communication signals received from the remote device 12. In a system having multiple remote devices, an RSSI signal is generated for each remote device 12 and is identified by the security code associated with the remote device. The RSSI signal can be an on / off indicator or it can represent a discrete level within a range of predetermined levels, which represents the strength of the signal. The information signals that include an RSSI signal are supplied to a microprocessor 28. The microprocessor 28 in each base station 10 maintains an RSSI signal that indicates the signal strength of the radio frequency communication signal received from each remote device 12. The microprocessor 28 also communicates with a signal transceiver circuit 24 to transmit the RSSI signals to the other base stations and to receive the RSSI signals from the other base stations • by means of data links 14. As will be described in detail with reference to the operation of the circuit of the present invention, the microprocessor 28 of each active base station compares the RSSI signals associated with a given remote device of each base station, to determine if another base station is receiving a more powerful radio frequency communication signal. The signal transceiver circuit 24 generally includes a transmitter circuit 30 and a receiver circuit 32. The microprocessor 28 provides an RSSI signal to the signal transceiver circuit 24 for connecting signals to the tip and neck lines of the public telephone system network PSTN 31 by means of data links 14. Preferably, the transmitting circuit 30 transmits information signals at a frequency of approximately 30 KHz '. A frequency of 30 KHz is selected to optimize the transmission of information signals. In particular, a signal of 30 KHz is outside the audible range and therefore can not be heard by the user of the remote device. A frequency signal of 30 KHz is also the lowest frequency outside the audible range and therefore allows the greatest signal amplitude in the Telco line. Finally, a signal of 30 KHz will be filtered by the public network of the telephone system. Although a signal of 30 KHz is preferred, any other frequency that is outside can be used # of the audible interval and that is going to be filtered with the public telephone system network. The signal transceiver circuit 24 also includes a receiver circuit 32 for receiving information signals from other base stations by means of data links 14. Preferably, the receiver circuit 32 includes a useful frequency band filter to pass d 30 KHz signals transmitted on the data link by transmitting circuits of other base stations. The information signals are connected to the microprocessor where they are stored. Because each base station will receive the information signals from other base stations, any of the base stations will be able to function as an active base station and determine which base station is receiving the most powerful radio frequency communication signal from a particular remote device. Finally, an answering machine 33 can be incorporated into one of the base stations. From • preference, the answering machine will be a digital answering machine. Referring now to Figure 3, the preferred signal transceiver circuit 24 (illustrated in block form in Figure 2) which is located in each base station 11 is shown in detail. The transmitter circuit 30 includes a Y (AND) gate. 34 having a first input 36 connected to receive a rectangular wave of 30 # KHz and a second input 38 connected to receive data. The data includes information signals describing the remote device, the channel or frequency of operation, and the RSSI signal generated by the radio transceiver as described above. The data will be transmitted as a 30 kHz rectangular wave, conjuncting them with the 30 kHz rectangular wave signal data. Alternatively, the data can be provided by the microprocessor as a 30 KHz signal. The output 40 of the AND (AND) gate 34 are connected by means of a capacitor 42 to the drop line. Preferably, the capacitor 42 is approximately 200 picofarads. The output 40 of the Y (AND) gate 34 is also connected to an inverter 44. The output 46 of the inverter 44 is connected by means of a capacitor 48 to the neckline. The capacitor 48 is also preferably of 200 picofarads. The Telco circuit 26 is also shown in detail in Figure 3. The Telco circuit 26 includes a transformer 52 for transmitting and receiving audio signals from the radio transceiver. The transformer is connected to a relay 54. The relay 54 is controlled by a transistor 56 that is turned on or off with a voltage on a control electrode 58 connected to an input resistor 60. The relay 54 is connected to a circuit in # branch 62 on node 64. The nodes 66 and 68 of branch circuit 62 are connected to the tip and nape lines. Shunt circuit 62 also receives signals from the tip and neck lines at nodes 66 and 68. Finally node 70 is connected to transformer 52 to transmit signals from the tip and neck lines to the radio transceiver. Finally, the signal transceiver circuit 24 includes a receiver circuit 70. The receiver circuit 70 acts as a useful frequency band filter to pass the information signals of the other base stations, and block the signals of the public telephone system network . Preferably, the receiver circuit 70 will pass the 30 KHz information signals that are transmitted by the transmitter circuits 30 of the other base stations. The receiver circuit 70 includes a differential amplifier circuit 72 having a positive input 74 and a negative input 76. The positive input 74 is connected to the neckline by the capacitor 78 and the resistor 80 which forms a low pass filter. Preferably capacitor 78 is 620 pf and resistor 80 is 10 KO. The input 74 is also connected to a parallel resistance-capacity network comprising a capacitor 82 and a resistor 84 to form a high-pass filter. Preferably, capacitor 82 is 20 pf and resistor 84 is 220 KO. The negative input 76 to the differential amplifier is also connected to a capacitor 86 in series with a resistor 88 to form a low pass filter. Preferably, the capacitor 86 is 620 pf and the resistor 88 is 220 KO. Also, a parallel configuration of a capacitor 90 and resistor 92 is connected between the negative input 76 and the output 94 of the differential amplifier. Preferably, capacitor 90 is 90 pf and resistor 92 is 220 KO.

The detailed signal transceiver circuit 24 shown in Figure 3 is an example of a circuit that can be employed. However, it will be understood that other signal transceiver circuits may be employed to transmit and receive information signals of approximately 30 KHz in the data link within the scope of the present invention.

Operation Now the circuit operation will be described in detail. In general, in a system that has multiple remote devices, each remote device that is in use will be in active radio frequency communication with a single base station. The active communication of radio frequency is considered as a transfer of communication signals between a remote device and a base station. Although each base station receives radio frequency communication signals from a remote device for purposes of determining an RSSI signal for each remote device, only one base station (ie the active base station) will return the radio frequency communication signal. Similarly, each base station will be in active radio frequency communication with only one remote device. Each active base station may be able to transfer the radio frequency communication link to the remote device associated with one of the remaining (ie non-active) base stations if one of the base stations is receiving a more powerful radio frequency communication signal . The microprocessor of the active base station will determine which base station is receiving the most powerful radio frequency communication signal from the associated remote device. If another base station that is not active is receiving a more powerful radio frequency communication signal from the remote device, the microprocessor of the active base will provide command signals to the transmit circuit 30 which is shown in detail in Figure 3. The command signals will be transmitted to the non-active base station to transfer the radio frequency communication link to the non-active base station. Referring now to Figure 4, the method for operating a portable communication system is described in detail with refee to flow chart 100. E flow chart 100 is directed to a radio frequency communication link between a remote device and an active base station. However, it will be understood that the flow diagram 100 is applied to all active communication links in the system. In the initial step 102, the remote device is on. The remote device sends a radiofrequency communication signal indicating the identification code or security code assigned to the remote device. The remote device will not be able to communicate with the base stations of the system unless the base stations have the security code in a list. A method for assigning security codes to base stations is described in the United States patent application (Proxy refee number CE765R) invented by James Francis Goedken, Thomas Perszyk and Charles John Malek and entitled METHOD FOR OPERATING A SYSTEM D COMMUNICATION WITH MULTIPLE BASE STATIONS, application that was also assigned to Motorola, Inc. and that is presented on the same date as this one, being incorporated herein by refee. The remote device will make a radio frequency communication link with the last bas station with which the remote device was communicated, called the main base station in step 104. It will be understood that The first active base station that has a link d * radio frequency communication with the remote device will be called the main base station for purposes of convenience. The main base station is of no importance after the radiofrequency communication link has been established. The main base station then generates an RSSI signal in step 106. The main base station also requests from the other base stations in step 108 an RSSI signal indicating the power of the radiofrequency communication link. The microprocessor of the main base station will then determine in step 110 whether another base is receiving a more powerful radio frequency communication signal, evaluating the RSSI signals from those received from the base stations. If no other base station has a stronger RSSI signal, the main base station will check if the RSSI signal is low in step 112. If the RSSI signal is low, the main base station returns to step 108 to interrogate the other base stations Regarding the RSSI signals. If the RSSI signal is not low, the home base will continue normal operation for a certain period of delay time set in step 114. After the delay period, the new base station checks if RSSI is low in step 112. However, if the main base station determines that some other base station has an RS signal? more powerful in step 110, the main base station will determine if another base station has a radio frequency communication link with another remot device in step 116. If one or more of the base stations that have a stronger RSSI signal do not have a communication link with another remote device, the main bas station will transfer the radio frequency connection to the base station having the most powerful RSSI in step 118. This base station will become the new active base station. The base station will then determine whether the RSSI signal is low in step 112 to either continue normal operation in step 114 or interrogate the other base stations in step 108. If all base stations have a higher RSSI signal in step 116 already have an RF communication link with a remote device, the main base station will determine whether the signal RS? I is low in step 112 to continue normal operation in step 114 or interrogate the other bases in step 108. In summary, the circuit and method for operating a wireless communication system allows base stations to transfer information signals between stations to determine which base station is receiving the most powerful radio-frequency communication signal from a remote device. . The circuit and the method reduce cost and complexity by eliminating the requirement of a separate controller from the base station.

NOVELTY OF THE INVENTION Having described the present invention, it was considered as a novelty and, therefore, it is claimed as property.

Claims (10)

1. what is contained in the following CLAIMS; A wireless communication system for use with a public telephone system network, characterized by: at least one remote device adapted to transmit and receive radiofrequency communication signals; a series of base stations adapted to transmit radio frequency communication signals and to receive radiofrequency communication signals from at least one remote device; a communication link joining each base station with a telephone line of this public telephone system network for transmitting communication signals between the telephone line and the series of base stations, and connecting each of the base stations of the series of base stations , to transmit information signals between this series of base stations.
2. 2. The wireless communication system d according to claim 1, wherein each bas station is further characterized by a circuit indicating the power of the received signal, for generating a signal d information indicating the power of a radio frequency communication signal received from the at least one remote device.
3. 3. The wireless communication system according to claim 1, wherein the information signals d are transmitted between a series of base stations at a frequency of approximately 30 KHz. The wireless communication system according to claim 1, wherein the information signals are characterized by a security code assigned to at least one remote device that allows communication with the series of base stations. The wireless communication system according to claim 1, wherein each base station is characterized by a transmitter circuit for transmitting the information signals to a series of base stations and their receiving circuit to receive these information signals from the series of base stations. 6. A wireless telephone system for use with a public network of the telephone system characterized by: at least one remote device adapted to transmit and receive radiofrequency communication signals; a series of base stations adapted to transmit radio frequency communication signals to receive radiofrequency communication signals from at least one remote device; a communication link connecting each base station to a telephone line of the public network of the telephone system, to transmit communication signal between each base station of the series d base stations, and where this telephone line is connected with each of the base stations of the series of base stations for transmitting signals between this series of base stations, wherein one of the base stations of the series of base stations, provides communication signals to the telephone line by means of a communication link, and signals of radio frequency communication to at least one of the remote devices; each of the base stations has a power indicator circuit of the reception of the signal to generate an information signal indicating the signal strength of the radio frequency communication signals received from at least one remote device; and each base station has a transmitter for transmitting the information signal to the series of base stations and a receiver for receiving these information signals from the series of base stations by means of a data link. 7. A method for operating the wireless communication system having a series of base stations adapted to communicate with a public telephone system network by means of a telephone line, adapted to communicate with at least one remote device by means of signaling signals. radiofrequency communication; characterized by the steps of: providing a communication link between the series d base stations and a telephone line of the public telephone system network, wherein the communication link allows communication between the base stations and allows communication between each base station and this telephone line; transmit information signals between this series of base stations; and providing a radio frequency communication link between at least one remote device and at least one of the base stations of the series of base stations. 8. A method for operating a wireless communication system having a series of base stations and at least one remote device, characterized by the steps of: establishing a radiofrequency communication link between at least one remote device one of the series of the base stations; generating a signal for each base station, indicating the signal strength of the radiofrequency communication signals received from at least one remote device; interrogated from the selected base station of the base station series, to the other base stations, with respect to the signal generated in each of the base stations, indicating the power of the radio frequency communication signals; determining which base station is receiving the most powerful radio frequency communication signal from the at least one remote device; and establishing a radiofrequency communication link with the base station which has the most powerful signal strength of this radio frequency communication signal. The method for operating the wireless communication system having a series of base stations and at least one remote device, according to claim 8, wherein the step of generating a signal for each base station, indicating the power of the radio frequency communication signal, is characterized in that it provides a communication link between this series of base stations. The method for operating the wireless communication system having a series of base stations and at least one remote device, according to claim 8, wherein the signals transmitted on the communication link are transmitted at a frequency d approximately 30 KHz . In testimony of which I sign the present in this City of Mexico, D. F., on July 20, 1994. P1313 / 94MX +