Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/18—Service support devices; Network management devices
  • H04W88/181—Transcoding devices; Rate adaptation devices
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/16—Gateway arrangements

Definitions

• the present invention relates to telecommunications. More particularly, the present invention relates to a method and system for interfacing a digital network with a public switched telephone system.
• Fig. 1 is a block diagram of typical telephone network.
• Local calling area 90(a) is comprised of public switched telephone network (PSTN) 100(a) and wireless telephone system 106(a)
• local calling area 90(b) is comprised of PSTN 100(b) and wireless telephone system 106(b).
• Wireless telephone systems 106 provide mobile telephone service and PSTN's 100(a) and (b) provide stationary telephone service within their respective local calling areas 90.
• Long distance network 102 and asynchronous transfer mode (ATM) network 104 are coupled to PSTN's 100(a) and (b) as well as wireless telephone systems 106(a) and (b ) , and provide long distance telecommunication service between local calling areas 90(a) and (b).
• ATM network 104 provides long distance telecommunication service via high speed packet based connections
• long distance network 102 provides long distance telecommunication service via dedicated connections.
• any audio information associated with the telephone calls carried by wireless telephone systems 106 is digitally encoded via a process called vocoding
• any audio information associated with telephone calls carried by PSTN's 100 is digitally encoded via a process called pulse code modulation (PCM).
• Vocoding is far more efficient than PCM, but requires substantially greater signal processing resources to perform. The signal processing resources are required during both the initial vocoding of the audio information, and when the audio information is devocoded for purposes of regeneration of that audio information.
• Wireless telephone systems 106(a) and (b) utilize vocoding because they conduct telephone calls using radio frequency (RF) signals and the amount of RF bandwidth available for conducting these telephone calls is limited. Therefore, efficiency within wireless telephone systems 106 is critical.
• RF radio frequency
• PSTN's 100 have no such bandwidth limitation, and therefore the cost of the additional signal processing resources required by vocoding is usually not justified.
• the digitally encoded audio information must be exchanged between the two systems.
• the encoding method must be converted from vocoding to PCM, and vice-versa, so that each system will be able to properly regenerate the audio information.
• this conversion is performed within the wireless telephone systems 106 just before, and just after, the data crosses over between the two systems, depending on the direction of the data flow.
• the conversion is performed within wireless telephone systems 106 because that is where the necessary signal processing resources are located, and because PSTN's 100 generally do not possess such signal processing resources.
• vocoded audio information leaving wireless telephone system 106(a) is devocoded before being introduced into one of the other telecommunication systems for purposes of routing.
• These other telecommunication systems include PSTN 100(a), which is used for local telephone calls, as well as long distance network 102 and ATM network 104, which are used for long distance telephone calls. Long distance telephone calls may also be introduced into long distance network 102 or ATM network 104 by way of PSTN 100(a).
• PCM encoded audio information from a PSTN 100 arriving at wireless telephone system 106(a) via one of these other telecommunication systems is converted to vocoded audio information before being further processed within wireless telephone system 106(a).
• the method of processing the associated audio information described above is inefficient. This is because the digitally encoded audio information is encoded via the less efficient PCM method for the majority of path through which it travels, and therefore is encoded via less efficient PCM for a majority of the time. This is especially true for long distance telephone calls which are carried outside wireless telephone systems 200 for almost the entire transmission.
• An improved method of processing a telephone call would allow the audio information to remain in vocoded format for a greater portion of the time, thereby decreasing the amount of network resources consumed by the telephone call and reducing the cost. Therefore, a need exists for an improved method and system for interfacing a wireless telephone system with other telephone networks.
• the present invention is a novel and improved method and system for interfacing a digital network with a public switched telephone network.
• a first wireless telephone system determines if a telephone call is directed to a public switched telephone network (PSTN) located within a local calling area having another wireless telephone system. If so, an asynchronous transfer mode (ATM) or other packet based link is established between the two wireless telephone systems, and vocoded audio information is transmitted over that ATM link.
• ATM asynchronous transfer mode
• the vocoded audio information is converted by the second wireless telephone system into pulse code modulation (PCM) encoded audio information, and introduced into the PSTN.
• PCM pulse code modulation
• PCM formatted data from the receiving PSTN is converted into vocoded audio information by the second wireless telephone system, and then transmitted to the first wireless telephone system via the ATM or other packet based link.
• Fig. 1 is a block diagram of a telephone network
• Fig. 2 is a block diagram of a telephone network illustrating the routing of telephone calls in accordance with one embodiment of the invention
• Fig. 3 is a block diagram of a cellular telephone system configured in accordance with one embodiment of the invention.
• ATM asynchronous transfer mode
• PSTN public switched telephone network
• the present invention is described in the context of a wireless telephone system. It will be apparent to one skilled in the art that the present invention may be used within other digital networks that encode audio and other information in a highly efficient manner when compared to the systems with which they interact. In other cases throughout the disclosure, well known systems are shown in block form. This is done in order to avoid unnecessarily obscuring the disclosure of the present invention.
• Fig. 2 is a block diagram of a telephone network configured in accordance with one embodiment of the invention.
• Local call area 190(a) is comprised of PSTN 200(a) and wireless telephone system 206(a)
• local calling area 190(b) is comprised of PSTN 200(b) and wireless telephone system 206(b).
• Local calling area 190(c) is comprised of PSTN 200(c).
• Wireless telephone systems 206 provides mobile telephone service and PSTN's 200 provide stationary telephone service within their respective local calling areas 190.
• Long distance network 202 and ATM network 204 are coupled to PSTN's 200(a), (b) and (c), as well as wireless telephone systems 206(a) and (b), and provide long distance communication services between local calling areas 190(a) - (c).
• ATM network 204 provides long distance telecommunications, services using high speed data packets and long distance network 202 provides long distance telecommunications services via dedicated connections.
• a local calling area 190 is defined by physical proximity, however, other definitions are contemplated including area code, reduced cost for exchanging information, and ability to transfer information without the use of a long distance telecommunications service.
• Dashed line (A) illustrates an exemplary telephone call between wireless telephone system 206(a) and PSTN 200(a), which is a local telephone call. Audio information from wireless telephone system 206(a) is encoded via vocoding while it is transported within wireless telephone system 206(a).
• the method of encoding is converted from vocoding to PCM within wireless telephone system 206(a) and the PCM vocoded audio information is passed into PSTN 200(a) where it is used to generate audio information.
• audio information from PSTN 200(a) is encoded via PCM and the PCM encoded audio information is transmitted via path (A) into wireless telephone system 206(a).
• the PCM encoded audio information is converted into vocoded audio information for further transport within wireless telephone system 206(a).
• Dashed line (B) indicates the path of an exemplary long distance telephone call between wireless telephone system 206(a) and PSTN 200(c).
• vocoded audio information generated within wireless telephone system 206(a) is converted into PCM encoded audio information before being introduced into long distance network 202.
• Long distance network 202 then passes the PCM encoded audio information to PSTN 200(c) where it is used to generate audio information.
• PCM encoded audio information from PSTN 200(c) is transmitted via long distance network to wireless telephone system 206(a).
• Wireless telephone system 206(a) converts the PCM encoded audio information to vocoded audio information for further transport and processing within wireless telephone system 206(a).
• wireless telephone system 206(a) To set up the telephone call indicated by dashed line (B), wireless telephone system 206(a) first determines that the telephone call is directed to local calling area 190(c). Additionally, wireless telephone system 206(a) determines that another wireless telephone system 206 is not located within local calling area 190(c). In response to these determinations, wireless telephone system 206(a) elects to convert the vocoded audio information into PCM encoded audio information before introducing the audio information into long distance network 202, so that is may be properly processed when received by PSTN 200(c). Additionally, wireless telephone system 206(a) selects long distance network 202 to route the telephone call to PSTN 200(c).
• the call may also be routed through PSTN 200(a) and long distance network 202 to PSTN 200(c), or via ATM network 204.
• Dashed line (C) indicates the path of a second exemplary long distance telephone call between wireless telephone system 206(a) and PSTN 200(b).
• vocoded audio information from wireless telephone system 206(a) is transmitted via ATM network 204 to wireless telephone system 206(b) where it is used to generate audio information.
• Wireless telephone system 206(b) converts the vocoded audio information to PCM encoded audio information and transmits the PCM encoded audio information to PSTN 200(b).
• PCM encoded audio information from PSTN 200(b) is transmitted to wireless telephone system 206(b).
• Wireless telephone system 200(b) converts the PCM encoded audio information to vocoded audio information and transmits the vocoded audio information to wireless telephone system 206(a) via ATM network 204 for further transmission and processing.
• wireless telephone system 206(a) To setup the call indicated by dashed line (C) wireless telephone system 206(a) first determines that the call is directed to a PSTN 200 located with local calling area 190(b), and that wireless telephone system 206(b) is also located within local calling area 190(b) . In response to these determinations, wireless telephone system 206(a) elects to transmit vocoded audio information to wireless telephone system 206(b). Additionally, wireless telephone system 206(a) selects to route the call through ATM network 204 and wireless telephone system 206(b) to PSTN 200(b) .
• wireless telephone system 206(a) notifies wireless telephone system 206(b) of the call directed to PSTN 200(b) and instruct wireless telephone system 206(b) to convert the vocoded audio information into PCM encoded audio information which and to transmitted to PSTN 200(b).
• This instruction can be implied as part of the notification procedure, or can be performed via the transmission of additional data.
• Fig. 3 is block diagram of wireless telephone system 206(a) configured as a cellular telephone system in accordance with one embodiment of the invention.
• Subscriber units 300(a) and (b) interface with base stations 302(a) and (b) via radio frequency (RF) signals and transmit and receive digitally encoded audio information.
• Base stations 302(a) and (b) are coupled to cellular interconnect subsystem (CIS) 304 within base station controller (BSC) 306.
• Call control processor (CCP) 308 is coupled to CIS 304 and home location register (HLR) 310.
• Selector system 312 selects between the multiple signals that arrive from a subscriber unit 300 in a soft hand-off situation and is coupled to CIS 304 and signal processing system 314.
• PSTN interface 316 is coupled to PSTN 200(a) of Fig. 2 and ATM interface 318 is coupled to ATM network 204 of Fig. 2 and both interface systems are coupled to signal processing system 314.
• HLR 310 is a data base that stores information about the various local calling areas 190. In the preferred embodiment this information including the area code of each local calling area and whether another wireless telephone systems 206 or other telecommunications signal processing system having compatible vocoding capability is located within that local calling area 190. HLR 310 may also contain information regarding the various exchange codes located within each local calling area and the proximity of the associated exchanges to another wireless telephone system 206.
• CCP 308 first determines if the telephone call is local or long distance. Secondly, CCP 308 determines if the call is directed to a PSTN 200 or to a another wireless telephone system 206. If the call is long instance and directed to a PSTN 200 then CCP 308 further determines if a wireless telephone system 206 is located within the same local calling area 190 as the receiving PSTN 200. Based on these determinations, CCP 308 takes a variety of actions during call setup in order to establish a telephone call in accordance with the present invention.
• CCP 308 determines that wireless subscriber unit 300(a) is requesting a long distance call directed to a PSTN 200 and that a second wireless telephone system 206 is located within the same local calling area as the receiving PSTN 200, it establishes a link to that wireless telephone system 206 via ATM network 204. Additionally, CCP 308 instructs the second wireless telephone system 206 to establish a connection with the receiving PSTN 200, and to prepare to receive vocoded audio information and to convert that vocoded audio information into PCM encoded information before transmitting that PCM encoded audio information to PSTN 200.
• CCP 308 instructs the second wireless telephone system 206 to convert PCM encoded audio information from the receiving PSTN 200 into vocoded audio information before transmitting that vocoded audio information over to ATM network 204. As described above, this instruction can be implied as part of the notification procedure, or can be performed via the transmission of additional data.
• CCP 308 also configures CIS 304, selector system 312 and signal processing system 314 to pass vocoded audio information from subscriber unit 300(a) to ATM interface 318 which in turn directs the vocoded audio information to ATM network 204.
• Vocoded audio information received via ATM interface 318 associated with the exemplary telephone call is passed through signal processing system 314, selector system 312, and CIS 304 before being passed to subscriber unit 300(a) via base transceiver station 302(a).
• CCP 308 determines that wireless subscriber unit 300(a) is requesting a long distance call that is directed to a PSTN 200 within a local calling area 190 lacking a wireless telephone system 206, a connection to the receiving PSTN 200 is established through long distance network 202 of Fig 2.
• CCP 308 configures CIS 304 to pass the audio information to signal processing system 314 via selection system 312.
• CCP 308 also configures signal processing system 304 to convert the vocoded audio information into PCM encoded audio information and to transmit that PCM encoded audio information into long distance network interface 320.
• signal processing system 314 may be configured to pass the vocoded audio information to pass the PSTN interface 316 which routes the data to long distance network 202 through PSTN 200(a) of Fig 2.
• PCM encoded audio information from the receiving PSTN 200 is transmitted through long distance network 202 of Fig. 2 and long distance network interface 320 to signal processing system 314.
• Signal processing system 314 is further configured by CCP 308 to convert the PCM encoded audio information into vocoded audio information, and to transmit that data to subscriber unit 300(a) via selector system 312, CIS 304, and ⁇ ise transceiver station 302(a).
• CCP 308 determines that a local call to PSTN 200(a) has been requested by wireless subscriber unit 300(a) (Fig. 2) it configures signal processing system 314 to convert the vocoded audio information from subscriber unit 300(a) to PCM encoded audio information and to transmit that PCM encoded audio information to PSTN interface 316.
• PSTN interface 316 proceeds to transmit the PCM encoded audio information to PSTN 200(a).
• PCM encoded audio information from PSTN 200(a) is received by PSTN interface 316 which transmits the data to signal processing system 314.
• Signal processing system 314 converts the PCM encoded audio information into vocoded audio information and transmits that vocoded audio information to subscriber unit 300(a) via selector system 312, CIS 304, and base transceiver station 302(a).
• selector system 312, CIS 304, and base transceiver station 302(a) When another wireless telephone system 206 initiates a telephone call directed to PSTN 200(a), and notification of that telephone call is received by wireless telephone system 206(a), that notification is directed to CCP 308.
• CCP responds by establishing a connection to PSTN 200(a) via PSTN interface 316, and configuring ATM interface 318 to direct vocoded audio information from the requesting wireless telephone system associated with the telephone call to signal processing system 314.
• CCP 308 configures signal processing system 314 to convert the vocoded audio information received from ATM interface 318 and associated with the telephone call to PCM encoded audio information and to pass the PCM encoded audio information to the receiving PSTN 200 via PSTN interface 316.
• PCM encoded audio information from the receiving PSTN 200 is transmitted to signal processing system 314 via PSTN interface 316.
• CCP also configures signal processing system 314 to convert the PCM encoded audio information into vocoded audio information, and to pass that vocoded audio information to ATM interface 318 which transmits the vocoded audio information to the requesting wireless telephone system 206 via ATM network 204 of Fig. 2.
• wireless telephone system 206(a) By processing telephone calls in the above described manner, wireless telephone system 206(a) more efficiently interfaces with other telephone networks. This is because data is transmitted over the long distance ATM network 204 in the more efficient vocoded format for long distance telephone calls directed a PSTN 200 located within a local calling area 190 also having a wireless telephone system 206, and therefore conserves long distance network resources. Additionally, by transmitting this vocoded audio information over ATM network 204, or another packet based network, the benefit of using the more efficiently vocoded audio information format is realized to a greater extent. This is because ATM network 204 is a packet based network which more efficiently allocates the available network resources between the various telephone calls and other communication sessions it carries.

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• Engineering & Computer Science (AREA)
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• Signal Processing (AREA)
• Data Exchanges In Wide-Area Networks (AREA)
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• 1996
  • 1996-05-28 ZA ZA964331A patent/ZA964331B/xx unknown
  • 1996-06-04 IL IL11856496A patent/IL118564A/xx not_active IP Right Cessation
  • 1996-06-07 CN CN96196058A patent/CN1203005A/zh active Pending
  • 1996-06-07 KR KR1019970709180A patent/KR19990022738A/ko not_active Application Discontinuation
  • 1996-06-07 BR BR9609481A patent/BR9609481A/pt active Search and Examination
  • 1996-06-07 EP EP96921423A patent/EP0832540A1/en not_active Withdrawn
  • 1996-06-07 AU AU62651/96A patent/AU715374B2/en not_active Ceased
  • 1996-06-07 RU RU98100450A patent/RU2147771C1/ru not_active IP Right Cessation
  • 1996-06-07 WO PCT/US1996/009683 patent/WO1996042176A1/en not_active Application Discontinuation
  • 1996-06-07 JP JP09503199A patent/JP3083852B2/ja not_active Expired - Fee Related
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