Abstract:
A method of automatic response and loop-backing is developed for remotely measuring the quality of the Internet telephone by IP phone. When a quality measuring instrument is requested to measure the quality of Internet telephone, a request call is placed to an IP phone for quality measurement. The method of automatic response and loopback is enable the IP phone to handle the call for quality measuring without interrupting the user of IP phone without affecting utilization of supplementary Internet telephone services.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an automatic response and loopback method for remote quality measurement in Internet telephony and, more particularly, to an automatic response and loopback method for remote quality measurement in Internet telephony wherein a quality measurement instrument wishing to measure Internet telephony quality can place a call to an Internet phone without causing inconvenience to the user of the Internet phone and without affecting utilization of supplementary Internet telephony services. 
     2. Related Prior Art 
     In recent years, Internet phones (IP phones) that deliver voice and video calls through the Internet have been rapidly popularized. 
     Unlike standard telephones using public switched telephone networks (PSTN) based on circuit switching, IP phones use IP networks (IP addresses) based on packet switching. 
     IP phones may be divided into wired VoIP (Voice over Internet Protocol) phones and wireless Wi-Fi (wireless fidelity) phones. Reduction in network investment costs due to integration of telephone networks and data networks, reduction in management costs and increase in efficiency owing to construction of integrated networks, and easy adoption of Internet-based multimedia services such as video conferencing are expected to rapidly increase the number of IP phones in the near future. 
     Unlike the PSTN using dedicated lines, IP networks using flexible lines may experience high packet loss and significant delay depending upon network traffic. In comparison to PSTN telephony, IP telephony tends to be poor in terms of quality of service (QoS) and hence needs more accurate QoS measurement. 
     That is, VoIP services requiring strict real-time properties may experience significant quality degradation owing to real-time limitations of IP networks. Hence, it is necessary for VoIP service providers to continuously perform quality measurement and failure analysis to resolve customer dissatisfaction due to quality degradation in voice communication and to ensure an effective level of voice communication quality for customers. 
     As part of an effort to ensure IP telephony quality, in a related art method for measuring IP telephony quality, a maintenance technician carrying a measurement instrument is dispatched to a site where a quality problem has occurred and measures IP telephony quality using the measurement instrument. This method is inefficient in terms of time and cost. 
     In another related art method for remote real-time quality measurement, a quality measurement instrument is installed in a management center and a measurement function is realized in IP phones. Later, to measure IP telephony quality in real-time, the quality measurement instrument installed in the management center may send a quality measurement request to a particular IP phone and analyze looped back results from the IP phone. 
     SUMMARY OF THE INVENTION 
     For remote quality measurement, the IP phone must automatically respond to the quality measurement request without human intervention and loop back received data to the quality measurement instrument. This process should not cause inconvenience to the user and not interrupt various supplementary services in use. 
     However, the related art quality measurement method may fail to specify how to measure quality using automatic responses. In addition, the related art method based on loopback may have to usepackets having a size larger than that of standard real-time transport protocol (RTP) packets used in IP telephony to measure two-way quality. This may produce measurement results incommensurate with actual situations owing to the increased RTP data size. When the standard RTP data size is used, the related art method may produce incomplete measurement results covering not two-way quality but one-way quality only. 
     The present invention is conceived to solve the above problems, and one aspect of the present invention is to provide an automatic response and loopback method for remote quality measurement in Internet telephony that implements automatic response and loopback functions for an IP phone so that remote quality measurement may be conducted to produce two-way quality results without causing inconvenience to the user of the IP phone, without interrupting supplementary IP telephony services and without violating the RTP standard for IP telephony. 
     In accordance with one aspect of the invention, an automatic response and loopback method for remote quality measurement in Internet telephony includes: (A) receiving, by a first IP phone  200   a , a call requesting quality measurement from a measurement instrument  290  (S 310 ), and analyzing the received call to check whether the received call is a call for remote quality measurement (S 320 ); (B) responding to, by the first IP phone  200   a , the call requesting quality measurement by sending a connection signal having a loopback indication and a loopback mode indication without sending a ring signal (S 350 ); (C) sending, by the measurement instrument  290 , an RTP packet to the first IP phone  200   a  (S 360 ), and checking, by the first IP phone  200   a , whether a loopback mode set during call reception for remote quality measurement and connection signal transmission is IP packet loopback or media loopback (S 370 ); (D) immediately sending, when the loopback mode is IP packet loopback between a jitter buffer  201  and an IP network  270 , by the first IP phone  200   a , a loopback RTP packet whose header is a newly created RTP header and whose payload is a copy of the payload of the received RTP packet to the measurement instrument  290  (S 373 ); and (E) terminating, when a regular call is received or is placed during handling of the call for quality measurement, by the first IP phone  200   a , the call for quality measurement and processing the regular call first (S 380 ). 
     Preferably, the automatic response and loopback method further includes (A1) deactivating, when the received call is a call for remote quality measurement after checking in (A), by the first IP phone  200   a , a ring generator  211 , which notifies call reception, and a caller number display  213 , which displays a caller number associated with a received call (S 330 ). 
     Preferably, the automatic response and loopback method further includes (A2) deactivating, when the received call is a call for remote quality measurement after checking in (A), by the first IP phone  200   a , a voice activity detector  207 , which transmits silence packets, and an echo remover  209 , which detects and removes echo in a voice signal, so as to successfully loop back data for the call received from the measurement instrument  290  to the measurement instrument  290  (S 340 ). 
     Preferably, the automatic response and loopback method further includes (D1) sending, when the loopback mode is media loopback between an encoder/decoder  203  and a POTS network  205  after checking in (C), by the first IP phone  200   a , a loopback RTP packet whose header is a newly created RTP header and whose payload is a copy of the decoded payload of the received RTP packet after passing through the encoder/decoder  203  to the measurement instrument  290  (S 375 ). 
     Preferably, in (E), when a call for quality measurement is received during a regular call, the first IP phone  200   a  rejects the call for quality measurement by returning a cause code other than a cause code corresponding to “busy” so as not to disrupt supplementary services like “call waiting”. 
     According to the automatic response and loopback method for remote quality measurement in Internet telephony, when an IP phone receives a call for quality measurement from a quality measurement instrument, the IP phone may disable ring signaling and calling number identification so as not to cause inconvenience to the user of the IP phone. 
     Even when the user of the IP phone uses a supplementary service such as a ringback tone service, it is possible to accurately measure IP telephony quality without disrupting the supplementary service by forcing the IP phone to immediately send a connection signal (for example, SIP  200  (ok) response) instead of a ring signal (for example, SIP  180  (ringing) response). Here, SIP refers to the Session Initiation Protocol that can be used for creating, modifying and terminating multimedia sessions between intelligent terminals on the Internet. 
     It is possible to increase quality measurement accuracy by forcing the IP phone to deactivate a voice activity detection (VAD) function and by preventing loopback data from being removed through an echo cancellation function, which may recognize loopback data as echo. 
     When a regular call is placed by the user or is received during quality measurement, the call for quality measurement is terminated. When a call for quality measurement is received during a regular call, the call for quality measurement is rejected with a cause code other than a cause code corresponding to the SIP  486  (busy) response. Hence, it is possible to perform quality measurement without disrupting supplementary services in use and without interrupting call handling of the user. 
     In addition, as the size of loopback RTP payload is identical to that of standard RTP payload, it is possible to perform quality measurement in an actual service environment. 
    
    
     
       The above and other aspects, features and advantages of the invention will be more clearly understood from the following detailed description of exemplary embodiments taken in conjunction with the accompanying drawings. 
         FIG. 1  illustrates a system configuration supporting an automatic response and loopback method for remote quality measurement in Internet telephony according to an embodiment of the present invention; 
         FIG. 2  illustrates a detailed configuration of an IP phone used in the present invention; and 
         FIG. 3  is a flowchart of an automatic response and loopback method for remote, quality measurement in Internet telephony according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an automatic response and loopback method for remote quality measurement in Internet telephony of the present invention will be described in detail with reference to the accompanying drawings. 
     First, a description is given of a system employed for the automatic response and loopback method for remote quality measurement in Internet telephony of the present invention. 
       FIG. 1  illustrates a system configuration supporting an automatic response and loopback method for remote quality measurement in Internet telephony according to an embodiment of the present invention, and  FIG. 2  illustrates a detailed configuration of an IP phone used in the present invention. 
     As shown in  FIG. 1 , the system, which implements the automatic response and loopback method for remote quality measurement in IP telephony according to an embodiment of the present invention, includes a first IP phone  200   a , a second IP phone  200   b , session border controllers  230   a  and  230   b , IP private branch exchanges  250   a  and  250   b , an IP network  270  and a measurement instrument  290 . 
     More specifically, the first IP phone  200   a  and the second IP phone  200   b  send and receive multimedia data such as voice and video data through the IP network  270 . 
     As shown in  FIG. 2 , each of the first IP phone  200   a  and the second IP phone  200   b  includes a jitter buffer  201  for temporarily buffering RTP data such as voice and video data received through the IP network  270  from the measurement instrument  250 , an encoder/decoder  203  for decompressing IP data from the jitter buffer  201 , a POTS network  205  for receiving the data decompressed by the encoder/decoder  203 , a voice activity detector  207  for sending silence packets when a voice signal is not present in the data from the POTS network  205 , an echo remover  209  for detecting and cancelling echo in a voice signal from the POTS network  205 , a ring generator  211  for generating an alert indicating reception of a call requesting quality measurement coming from the measurement instrument  290 , a caller number display  213  for displaying a caller number associated with a call requesting quality measurement coming from the measurement instrument  290 , and an automatic response unit  215  for automatically responding to a call coming from the measurement instrument  290 . 
     The jitter buffer  201  and the encoder/decoder  203  constitute a loopback that sends voice and video data received from the measurement instrument  290  back to the measurement instrument  290 . Here, loopback performed between the jitter buffer  201  and the IP network  270  is referred to as IP packet loopback, and loopback performed between the encoder/decoder  203  and the POTS network  205  is referred to as media loopback. Loopback is preferably performed at a point near to the POTS network  205  in order to loop back a signal, which is nearly identical to a signal sent to the first IP phone  200   a  or the second IP phone  200   b , to the measurement instrument  290 . 
     Specifically, in IP packet loopback, the first IP phone  200   a  or the second IP phone  200   b  sends an RTP (real-time transport protocol) packet received from the measurement instrument  290  performing quality measurement back to the measurement instrument  290  before the RTP packet passes through the jitter buffer  201  or the encoder/decoder  203 . Here, the header of the loopback RTP packet is a new RTP header and the payload thereof is a copy of the payload of the received RTP packet. To measure bidirectional quality, the measurement instrument  290  should send an RTP packet that contains sequence number information other than regular voice data as payload data. 
     That is, upon reception of the loopback RTP packet, the measurement instrument  290  computes RTP loss, delay and jitter (variation of packet delay with time) along the loopback section by analyzing sequence number information in the payload, and computes loss and jitter in the reception direction. As delay and jitter in the transmission direction can be computed on the basis of the loss, delay and jitter along the loopback section and the delay and jitter in the reception direction, the measurement instrument  290  can compute bidirectional qualities. 
     In media loopback, an RTP packet is looped back after passing through the encoder/decoder  203 . Here, as in IP packet loopback, the loopback RTP packet is formed by replacing the header of the received RTP packet with a new RTP header. Media loopback is not applicable to bidirectional quality measurement. The loopback data may be recorded and compared with original voice data to examine the level of distortion. 
     Referring back to  FIG. 1 , each of the session border controllers (SBC)  230   a  and  230   b  converts signaling data and media data transmitted between the first IP phone  200   a  and the second IP phone  200   b , and acts as a private network interface. 
     The IP private branch exchanges (IP-PBX)  250   a  and  250   b  act as telephony exchanges for the first IP phone  200   a  and the second IP phone  200   b , and conduct PSTN and PBX interworking functions. 
     The IP network  270  connects the first IP phone  200   a  and the second IP phone  200   b  for communication so that the first IP phone  200   a  and the second IP phone  200   b  may send and receive multimedia data such as voice and video data. 
     Here, the IP network  270  includes RTP protocol packets  272  to transport multimedia data such as voice and video data between the first IP phone  200   a  and the second IP phone  200   b , and RTCP protocol packets  274  to control the RTP packets  272 . 
     The measurement instrument  270  places calls for quality measurement to the first IP phone  200   a  and the second IP phone  200   b  using an IP data loopback mode to measure quality. 
     Next, a description is given of an automatic response and loopback method for remote quality measurement in Internet telephony of the present invention with reference to  FIG. 3 . As the same procedure is applied among the IP phone  200   a , the IP network  270  and the measurement instrument  290  and among the second IP phone  200   b , the IP network  270  and the measurement instrument  290 , the method is described using only the first IP phone  200   a , the IP network  270  and the measurement instrument  290 . 
       FIG. 3  is a flowchart of the automatic response and loopback method for remote quality measurement in Internet telephony according to another embodiment of the present invention. 
     Referring to  FIG. 3 , the measurement instrument  290  transmits a call requesting quality measurement to the first IP phone  200   a  (S 310 ). Upon reception of a call from the measurement instrument  290 , the first IP phone  200   a  checks whether the received call is a call for remote quality measurement (S 320 ). 
     Here, for quality measurement, the measurement instrument  290  transmits a call requesting quality measurement that contains an indicator indicating loopback test and another indicator indicating loopback mode (IP packet loopback or media loopback). 
     When the received call is a call for remote quality measurement, so as not to cause user inconvenience, the first IP phone  200   a  deactivates the ring generator  211  (which indicates call reception) and the caller number display  213  (which displays a caller number associated with a received call) (S 330 ). 
     Additionally, to successfully loop back data as to the received call from the measurement instrument  290 , the first IP phone  200   a  deactivates the voice activity detector  207  (which transmits silence packets) and the echo remover  209  (which detects and removes echo in a voice signal) (S 340 ). 
     When the user uses a ringback tone service, to prevent a ringback tone transmitted during quality measurement from affecting quality measurement, the first IP phone  200   a  immediately sends a connection signal (for example, SIP  200  (ok) response) as a response without a ring signal (for example, SIP  180  (ringing) response) (S 350 ). 
     That is, when the received call is a call for remote quality measurement, the first IP phone  200   a  skips transmission of a ring signal (for example, SIP  180  (ringing) response) and sends a connection signal (for example, SIP  200  (ok) response) having a loopback indicator and a loopback mode indicator (IP packet loopback or media loopback) through the automatic response unit  215 . Alternatively, the first IP phone  200   a  may send a tentative response signal (for example, SIP  100  (trying) response). 
     Upon reception of the connection signal from the first IP phone  200   a , the measurement instrument  290  sends an RTP packet to the first IP phone  200   a  (S 360 ). The first IP phone  200   a  checks whether the loopback mode set during call reception for remote quality measurement and connection signal transmission is IP packet loopback between the jitter buffer  201  and the IP network  270  or media loopback between the encoder/decoder  203  and the POTS network  205  (S 370 ). 
     When the loopback mode is IP packet loopback between the jitter buffer  201  and the IP network  270 , the first IP phone  200   a  immediately sends a loopback RTP packet whose header is a newly created RTP header and whose payload is a copy of the payload of the received RTP packet to the measurement instrument  290  so that quality measurement is performed in an environment identical to the standard RTP environment (S 373 ). 
     When the loopback mode is media loopback between the encoder/decoder  203  and the POTS network  205 , the first IP phone  200   a  sends a loopback RTP packet whose header is a newly created RTP header and whose payload is a copy of the decoded payload of the received RTP packet after passing through the encoder/decoder  203  to the measurement instrument  290  so that quality measurement is performed in an environment identical to the standard RTP environment (S 375 ). 
     Here, in the event that the first IP phone  200   a  is located on a private network with network address translation (NAT), as an RTP packet sent by the measurement instrument  290  may be unable to reach the first IP phone  200   a  unless the first IP phone  200   a  sends an RTP packet first, the first IP phone  200   a  sends a dummy RTP packet until a first RTP packet is received. 
     Thereafter, so as not to disrupt call handling of the user, when a regular call is received or is placed by the user during handling of the call for quality measurement, the first IP phone  200   a  terminates the call for quality measurement and processes the regular call first. 
     In other words, loopback mode operation may be terminated when the user of the first IP phone  200   a  picks up the handset to place a call, when a regular call not for quality measurement is received, or when the measurement instrument  290  sends a termination signal. 
     When a call for quality measurement is received during a regular call, the first IP phone  200   a  rejects the call for quality measurement by returning a cause code (for example,  406 ) other than a cause code corresponding to “busy” response (for example,  486 ) so as not to disrupt supplementary services like “call waiting” (S 380 ). 
     Although some embodiments have been described herein, it should be understood by those skilled in the art that various modifications, changes, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be limited only by the accompanying claims and equivalents thereof.