WO2019024251A1

WO2019024251A1 - System and method for a mobile device to interface with the public switched telephone network

Info

Publication number: WO2019024251A1
Application number: PCT/CN2017/106016
Authority: WO
Inventors: Chiwah LO; Hwaisian TSAI
Original assignee: Wivo Limited
Priority date: 2017-08-01
Filing date: 2017-10-13
Publication date: 2019-02-07

Abstract

What is disclosed is a system to couple a mobile device to a public switched telephone network (PSTN), said system comprising: an interface subsystem coupled to said PSTN using a first coupling, and the mobile device using a second coupling, wherein said interface subsystem receives one or more incoming calls from said PSTN over said first coupling, redirects said received one or more incoming calls to said mobile device over said second coupling, receives one or more outgoing calls from said mobile device over said second coupling, and redirects said received one or more outgoing calls to said PSTN over said first coupling.

Description

SYSTEM AND METHOD FOR A MOBILE DEVICE TO INTERFACE WITH THE PUBLIC SWITCHED TELEPHONE NETWORK

FIELD OF THE INVENTION

The present disclosure relates to gateways to connect mobile devices with the public switched telephone network using a data network.

BRIEF SUMMARY

A system to couple a mobile device to a public switched telephone network (PSTN) , said system comprising: an interface subsystem coupled to said PSTN using a first coupling, and the mobile device using a second coupling, wherein said interface subsystem receives one or more incoming calls from said PSTN over said first coupling, redirects said received one or more incoming calls to said mobile device over said second coupling, receives one or more outgoing calls from said mobile device over said second coupling, and redirects said received one or more outgoing calls to said PSTN over said first coupling.

A method for coupling a mobile device to a PSTN comprising receiving one or more incoming calls from said PSTN over a first coupling； redirecting said received one or more incoming calls to a mobile device over a second coupling； receiving one or more outgoing calls from said mobile device over said second coupling； and redirecting said received one or more outgoing calls from said mobile device over said second coupling.

An application for a mobile device to receive one or more incoming calls from a PSTN via a first coupling and an interface subsystem； and transmit one or more outgoing calls via a second coupling and the interface subsystem.

The foregoing and additional aspects and embodiments of the present disclosure will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments and/or aspects, which is made with reference to the drawings, a brief description of which is provided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the disclosure will become apparent upon reading the following detailed description and upon reference to the drawings.

FIG. 1 is an illustration of an example implementation of the system and method described below.

FIG. 2 is an illustration of an example implementation of an interface subsystem.

FIG. 3 is an illustration of an example sequence for receiving an incoming call from a public switched telephone network (PSTN) and redirecting the incoming call to a mobile device.

FIG. 4 is an illustration of an example sequence for receiving an outgoing call from a mobile device and redirecting the incoming call to a PSTN.

FIG. 5 is an illustration of an example implementation of an interface subsystem comprising a power harvest circuit.

While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments or implementations have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of an invention as defined by the appended claims.

DETAILED DESCRIPTION

For a very long time, most telephone voice calls took place using the Public Switched Telephone Network (PSTN) . Users connected to the PSTN using Plain Old Telephone System (POTS) copper pair wires, also known as "landlines" . However landlines require telecommunications providers to provide fixed phone lines for all users. Furthermore these landlines are not mobile.

In recent years, wireless or mobile phones and devices have grown in importance to consumers. These devices connect to cellular base stations via wireless communication, which are the "last mile" of the connection to telecommunication companies. Wireless connections provide mobility and eliminate the need of installing fixed phone lines for every user. However, the quality of service of wireless connections is not always good. The quality is highly dependent on factors such as:

- the quality of the wireless channel, which in turn is dependent on factors such as:

o coverage by the base station,

o environmental factors, and

o location of the user using the channel；

- the interference； and

- the traffic load at the connected cellular base station.

Mobile phones can also make calls over WiFi networks using, for example, Voice-Over-IP technology (VOIP) , but the quality of service is even more difficult to maintain because:

- the connection is going through a packet switched network instead of a circuit switching network, and

- the quality of the data channel still relies on the quality of connection between cellular device and base station.

By contrast, the quality of service over the PSTN is usually better and more consistent.

The system and method detailed below mitigates the problem of quality of service faced by wireless or mobile devices via utilizing the PSTN. It also allows a user to answer calls directed to a landline number using his or her mobile device, thus reducing the constraint of mobility inherent to a landline.

FIG. 1 shows an example implementation of the system and method. In FIG. 1, the mobile device 101 is connected via a mobile network 103 to a base station 105 which is in turn connected to PSTN 107. Mobile device 101 is, for example, a smartphone or a tablet or a laptop. Application 102 runs on mobile device 101. Mobile device 101 is coupled to interface subsystem 109 via a coupling 108. In one embodiment, the coupling 108 is achieved via network 110. Network 110 is created using technology known to one of skill in the art. In one embodiment, network 110 is a packet switched network. This is, for example, Bluetooth, Zigbee or WiFi. In another embodiment, network 110 is comprised of a plurality of subnetworks. In additional embodiments mobile network 103 is also coupled with network 110. As would be appreciated by one of skill in the art, coupling 108 takes place in some of these additional embodiments via base station 105, mobile network 103 using data connections and technologies such as Long Term Evolution (LTE) , and network 110. This gives the user of mobile device 101 the ability to answer telephone calls directed to the user’s landline via mobile device 101 and application 102, thereby enhancing the mobility of the landline.

In a further embodiment, coupling 108 comprises

–an uplink channel from the mobile device 101 to interface subsystem 109, and

-a downlink channel from interface subsystem 109 to mobile device 101.

Interface subsystem 109 is coupled to the PSTN 107 via coupling 106. In one embodiment, coupling 106 is implemented using POTS copper lines.

Interface subsystem 109 couples mobile device 101 to the PSTN 107 via coupling 108 and coupling 106. It serves as a gateway device between coupling 108 and coupling 106. Interface subsystem 109 performs the following functions:

- receives incoming calls from the PSTN 107 over coupling 106, and directs these calls to mobile device 101 over coupling 108, and

- receives outgoing calls from mobile device 101 over coupling 108, and directs these calls to PSTN 107 over coupling 106.

Typically, the data within the calls are transmitted using different formats and protocols in coupling 108 and coupling 106. For example, data is transmitted over coupling 108 using a "digital" format and using packet-switching protocols such as the Real-Time Protocol (RTP) , the Real-Time Control Protocol (RTCP) , the Session Initiation Protocol (SIP) ； and over coupling 106 using "analog" formats and circuit-switching protocols such as Dual Tone Multi Frequency (DTMF) and Signaling System 7 (SS7) .

Interface subsystem 109 receives incoming calls from the PSTN and converts the data within the incoming call from an analog format used in PSTN 107 to an appropriate digital format before redirecting the call to mobile device 101 over coupling 108. Similarly interface subsystem 109 converts the data within outgoing calls from the digital format used in coupling 108 to an analog format for use over PSTN 107, before redirecting the call to PSTN 107.

As explained above, application 102 runs on mobile device 101. Application 102 is responsible for enabling the mobile device 101 to receive and make calls over coupling 108. In some embodiments, application 102 is downloaded from sites such as the

PLAY STORE or the

APP

The connection between mobile device 101 and the interface subsystem 109 is implemented using protocols known to those of skill in the art. These protocols are used to, for example, to maintain appropriate maximum allowable voice delay and good voice quality by trading off, for example, packet drop and packet latency.

Interface subsystem 109 can be implemented in many ways. In one embodiment, it is implemented as part of a fixed line device connected to PSTN 107. Then, the fixed line device is modified to connect to both PSTN 107 and network 110. In one embodiment, interface subsystem 109 is implemented using a combination of hardware and software. In another embodiment, interface subsystem 109 is implemented as a stand-alone device.

FIG. 2 shows an example implementation of interface subsystem 109. The communication interface 201 connects to network 110 and is capable of receiving and transmitting signals using, for example, Bluetooth, WiFi, Zigbee or other wireless communication technologies, or the combination of two or more of them. In a further embodiment, communication interface 201 receives and transmits packetized voice data. Communication interface 201 is also capable of implementing protocols such as SIP, RTP and RTCP. It is also compliant with standards necessary for voice communication such as G. 711.

Processor 202 performs the role of managing the operation of interface subsystem 109. In addition, processor 202 controls hook switch 206.

Analog-to-digital (A/D) conversion subsystem 204 performs the role of converting the data within incoming calls from, for example, a typical analog format used in PSTN 107 to a digital format for use in over coupling 108.

Digital-to-analog (D/A) conversion subsystem 203 performs the role of converting the data within outgoing calls from, for example, a digital format used for transmissionover coupling 108 to a typical analog format used in PSTN 107.

Telephone line hybrid device 205 is responsible for 2-4 wires conversion and isolation. In some embodiments this is an active circuit. Hook switch 206 is turned on if the system goes "off-hook" and enables an off hook load 207 to be introduced across the POTS line. Protection circuit 208 is necessary to protect the interface subsystem 109 from damages caused by excess high voltage such as lightning. This is important if the POTS line is long and runs over ground.

Power unit 209 supplies power to interface subsystem 109. Power unit 209 is coupled to the components 201 –204 of interface subsystem 109 so as to supply power to these components. In embodiments where telephone line hybrid device 205 is an active circuit, power unit 209 is coupled to telephone line hybrid device 205 as well. In some embodiments, power unit 209 comprises an alternating current (AC) adapter for connection to a mains supply. In some embodiments, power unit 209 comprises one or more batteries. In some embodiments, the one or more batteries comprise at least one rechargeable battery. In embodiments where power unit 209 comprises at least one rechargeable battery, In the embodiments where power unit 209 comprises at least one rechargeable battery, power unit 209 additionally comprises subsystems to charge the at least one rechargeable battery. These subsystems are based on, for example:

- wired charging techniques known to those of skill in the art； or

- wireless charging techniques known to those of skill in the art, such as the Qi protocol.

In further embodiments, power unit 209 comprises one or more batteries and an AC adapter. Then, if power unit 209 is not connected to a mains supply, interface subsystem 109 is powered by the one or more batteries. However, if power unit 209 is connected to a mains supply then the interface subsystem 109 stops being powered by the one or more batteries. In some of the embodiments where the one or more batteries comprises a rechargeable battery, when power unit 209 is connected to a mains supply the rechargeable battery is then charged. In some embodiment, power unit 209 comprises a power or energy harvest circuit, which extracts power from the copper line to provide all or partial power for running interface subsystem 109. Such a power or energy harvest circuit will be described in further detail below.

In FIG. 2, coupling 106 is represented by POTS copper line 216, which couples interface subsystem 109 to PSTN 107.

An example sequence for receiving an incoming call from PSTN 107 and redirecting the incoming call to mobile device 101 will be explained below with reference to FIGS. 2 and 3. In FIG. 3, in step 301 when an incoming call arrives over PSTN 107, hook switch 206 is switched on by, for example, processor 202. Then, in step 302 the incoming call is received at A/D conversion subsystem 204 and the voice data within the received incoming call is converted to, for example, an appropriate digital format for transmission over coupling 108. The processing comprises steps such as:

- Performing appropriate signal processing on the received data as necessary, prior to compressing the data；

- compressing the data by using lossy or lossless compression algorithms employing either fixed or variable bit rate techniques； and

- performing interlacing and adding error correction/detection code either before and/or after packetizing the voice data, that is, putting the voice data into packets or,

o Packetization parameters such as size of packets are based on factors such as

■ voice delay caused by the packet transmission latency,

■ voice quality degradation caused by packet loss,

■ hardware cost,

■ power consumption required for computation,

■ transmission power requirements,

■ desired voice quality, and

■ the maximum allowed delay.

as necessary. One of skill in the art would also recognize that the steps above are covered by one or more protocols and standards such as the G. 711 standard, the Real-time Protocol (RTP) , the Real-Time Control Protocol (RTCP) and other applicable standards and protocols.

In step 303, the packetized voice data is sent to communication interface 201, which sets up a call with mobile device 101 using, for example, SIP. The packetized voice data is then transmitted to mobile device 101 over the downlink channel in coupling 108. In one embodiment, communication interface 201 applies one or more encryption techniques during transmission of the packetized voice data so as to ensure and enhance user security. In some embodiments, the components of interfacing subsystem 109 changes some parameters in real-time to respond to the channel condition. For example, the digital to analog conversion subsystem 204 increases the redundancy and reduces the data rate associated with the voice data transmitted over the downlink channel, if the drop rate over the downlink channel is increased.

An example sequence for receiving an outgoing call from mobile device 101, and redirecting the outgoing call to the PSTN 107 will be explained below with reference to FIGS. 2 and 4. In FIG. 4, in step 401 a call is initiated from mobile device 101 from, for example, application 102 via SIP. In step 402, the processor 202 switches on hook switch 206 so that the system goes off-hook. The mobile device 101 then sends voice data in a digital format appropriate for transmission over the uplink channel in coupling 108 to communication interface 201. In step 403, the processor 202 receives the digital formatted voice data from communication interface 201 and sends it to D/Aconversion subsystem 203. In step 404, this voice data is converted by D/Aconversion subsystem 203 from the digital format used in coupling 108 to an analog format for usage in PSTN 107. The D/Aconversion process comprises, for example:

- decrypting the received packetized voice data；

- depacketizing the decrypted packetized voice data；

- decompressing the depacketized voice data； and

- performing necessary signal processing steps prior to transmission over the PSTN 107 as known to those of skill in the art.

One of skill in the art will recognize that the above embodiments are meant as exemplary embodiments, and some of the steps may be omitted or altered as necessary. One of skill in the art would also recognize that the steps above are covered by one or more protocols and standards such as the G. 711 standard, RTP, RTCP and other applicable standards and protocols.

In one embodiment, the techniques used to transmit voice data in the uplink channel over coupling 108 may be different to the techniques used to transmit voice data in the downlink channel, depending on the differences in uplink and downlink channel characteristics. In an example embodiment, if the uplink channel is much faster than the downlink channel, then the encryption algorithm used for the downlink channel is simpler than the one used for the uplink channel.

In step 405, interface subsystem 109 transmits the analog formatted voice data over coupling 108 to PSTN 107.

As explained previously, in one embodiment power unit 209 on interface subsystem 109 comprises a power harvest circuit. An example embodiment of a power unit comprising an power harvest circuit is shown in FIG. 5.

FIG. 5 shows an example interface subsystem 529. Communication interface 501, processor 502, A/D conversion subsystem 504, D/Aconversion subsystem 503, telephone line hybrid device 505, off hook load 507, hook switch 506, POTS copper line 516 and protection circuit 508 are similar to communication interface 201, processor 202, A/D conversion subsystem 204, D/Aconversion subsystem 203, telephone line hybrid device 205, off hook load 207, hook switch 206, POTS copper line 216 and protection circuit 208 respectively. Interface subsystem 529 is powered by power unit 519. As shown in FIG. 5, power unit 519 comprises power harvest circuit 509, charging circuit 510, battery 511 and power circuit 512. In an embodiment, power harvest circuit 509 is coupled to processor 202.

In the embodiments where coupling 106 is a POTS copper line such as POTS copper line 516 in FIG. 5, this implementation harvests the power from the POTS loop current 513 to charge one or more batteries 511 to power the interface subsystem 109. The POTS line changes from "on-hook" to "off-hook" based on the loop current 513 flowing through the POTS wire pair. When the loop current 513 flowing through the POTS copper line 516 is higher than a certain threshold, then the POTS copper line 516 changes status from "on-hook" to "off-hook" .

In one embodiment, when the POTS copper line 516 is on hook and there is no ringing the power harvest circuit 509 does not draw sufficient current from POTS copper line 516 for the POTS loop current 513 to exceed the threshold, and change the status of POTS copper line 516 from on hook to off hook.

In FIG. 5, in an embodiment, the off-hook load 507 is adjusted compared to a prior art off hook load so that when the hook switch 506 is turned on, the off-hook load 507 is insufficient for the POTS loop current 513 to exceed the threshold. Then, the power harvest circuit 509 creates part or all of the required loading such that the POTS loop current 513 exceeds the threshold. Therefore the combination of the adjusted off-hook load and the power harvest circuit 509 emulates a prior art off hook load. The power harvest circuit 509 then harvests power from the POTS loop current 513. Power harvest circuit 509 then supplies the charging circuit 510 which charges the one or more batteries 511. The one or more batteries 511 powers the power circuit 512 which supplies necessary power to the rest of

system including components

501, 502, 503, 504, and also 505 in case it is an active circuit.

In one embodiment, there is no off-hook load 507. Then when hook switch 506 is turned on, power harvest circuit 509 supplies sufficient loading for the POTS loop current 513 to exceed the threshold. This is achieved by, for example, a command sent from processor 202 to power harvest circuit 509. Power harvest circuit 509 then charges one or more batteries 511 as explained previously.

In another embodiment, when the POTS copper line 516 is on hook and there is ringing, the power harvest circuit 509 draws some current from POTS copper line 516 to charge up the battery 511, but not enough for the POTS loop current 513 to exceed the threshold and change the status from on hook to off hook.

In another embodiment, the power harvest circuit 509 continues to draw sufficient current even when the battery 511 is fully charged up, so as to ensure that the the POTS loop current 513 continues to exceed the threshold, and the status of the POTS copper line 516 does not change to on-hook,

Other implementations are also possible. In one embodiment, when mobile device 101 connects to interface subsystem 109, the application 102 attempts to "check-in" with the interface subsystem 109. If this attempt is successful, then mobile device 101 is able to make calls over PSTN 107 via network 110 and interface subsystem 109. Interface subsystem 109 is also able to direct calls received from the PSTN 107 to mobile device 101 via network 110.

In one embodiment, as part of the check-in process the application 102 prompts the user to accept or not accept whether to continue with the connection. This is useful if, for example, an expensive data connection to interface subsystem 109 is made over a network such as mobile network 103 of FIG. 1, rather than a cheaper alternative such as network 110. In one embodiment, this involves the application detecting whether the connection is taking place over a WiFi network rather than a mobile network. Then, the application 102 warns the user accordingly. In a further embodiment, application 102 only allows coupling 108 to be made if mobile device 101 connects via a networking technology implemented in network 110 such as Bluetooth or WiFi.

In another embodiment, interface subsystem 109 is connected to a voicemail answering system so as to allow callers to leave messages for the user. Then, interface subsystem 109 sends either the voicemails or links to the voicemails to the user so as to allow the user to pick up the voicemail.

In yet another embodiment, application 102 records input from a plurality of users for different geographic locations to indicate whether it would be better for a user in a geographic location to connect to, for example mobile network 103 or interface device 109 to make a call from mobile device 101. In a further embodiment, application 102 detects the strength of mobile coverage by mobile network 103 to estimate the quality of a voice call, and compares this to the quality of a voice call made over network 110 via, for example, WiFi. Then application 102 selects the better path to create coupling 108.

In a further embodiment, application 102 is able to connect to other applications running on mobile device 101. These include, for example, address book or contact list applications. Then, mobile device 101 uses the information stored in these other applications to make outgoing calls.

In yet another embodiment, the application 102 allows the user to specify the networks available for coupling 108. This is useful if, for example, the user does not want calls either made from mobile device 101 or redirected to mobile device 101 over certain networks.

It will be known to one of skill in the art that variations are possible to the embodiments described above. For example, in one embodiment, if digital PSTN lines such as T1 lines are used, then A/D conversion substem 204 and D/Aconversion subsystem 203 of FIG. 3 are not needed.

While particular implementations and applications of the present disclosure have been illustrated and described, it is to be understood that the present disclosure is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations can be apparent from the foregoing descriptions without departing from the spirit and scope of an invention as defined in the appended claims.

Claims

A system to couple a mobile device to a public switched telephone network (PSTN) , said system comprising:

an interface subsystem coupled to said PSTN using a first coupling, and the mobile device using a second coupling, wherein said interface subsystem

receives one or more incoming calls from said PSTN over said first coupling,

redirects said received one or more incoming calls to said mobile device over said second coupling,

receives one or more outgoing calls from said mobile device over said second coupling, and

redirects said received one or more outgoing calls to said PSTN over said first coupling.
The system of claim 1, wherein said interface subsystem comprises an analog-to-digital conversion subsystem, wherein

said one or more incoming calls comprises voice data formatted in an analog format； and

said analog-to-digital conversion subsystem converts said voice data from said analog format to a digital format before being redirected to said mobile device.
The system of claim 1, wherein said interface subsystem comprises a digital-to-analog conversion subsystem, wherein

said one or more outgoing calls comprises voice data in a digital format； and

said digital-to-analog conversion subsystem converts said voice data from said digital format to an analog format before being redirected to said PSTN.
The system of claim 1, wherein said second coupling is achieved using Bluetooth.
The system of claim 1, wherein said second coupling is achieved using WiFi.
The system of claim 1, wherein

an application is installed on said mobile device； and

said mobile device receives said one or more incoming calls and transmits said one or more outgoing calls via said application.
The system of claim 1, wherein said first coupling comprises POTS copper lines.
The system of claim 7, wherein said interface device comprises a power harvest circuit.
The system of claim 8, wherein said power harvest circuit is used to harvest power from a loop current associated with said POTS copper line.
The system of claim 9, wherein said harvested power is used to charge at least one battery to power said interface subsystem.
A method for coupling a mobile device to a PSTN comprising

receiving one or more incoming calls from said PSTN over a first coupling；

redirecting said received one or more incoming calls to a mobile device over a second coupling；

receiving one or more outgoing calls from said mobile device over said second coupling； and

redirecting said received one or more outgoing calls from said mobile device over said second coupling.
The method of claim 11, wherein said one or more incoming calls comprise voice data formatted in an analog format, said method further comprising converting said voice data from said analog format to a digital format before said redirecting to said mobile device.
The method of claim 11, wherein said one or more incoming calls comprise voice data formatted in an analog format, said method further comprising converting said voice data from said digital format to an analog format before said redirecting to said mobile device.
The method of claim 11, wherein said second coupling is achieved using at least one of Bluetooth and WiFi.
The method of claim 11, wherein

an application is installed on said mobile device； and

said mobile device receives said one or more incoming calls and transmits said one or more outgoing calls via said application.
The method of claim 11, wherein said first coupling comprises POTS copper lines.
The method of claim 16, further comprising harvesting power from a loop current associated with said POTS copper line.
The method of claim 17, wherein said harvested power is used to charge a battery.
The method of claim 17, wherein said harvesting is achieved using a power harvest circuit； and

said power harvest circuit draws insufficient current so as to change a status of said POTS copper lines from on-hook to off-hook.
An application for a mobile device to

receive one or more incoming calls from a PSTN via a first coupling and an interface subsystem； and

transmit one or more outgoing calls via a second coupling and the interface subsystem.