Abstract:
Following initial call establishment negotiation to build a call context between a network and a remote unit, the base processes the header of the data packets. The base acts as an intermediate nodal point to establish call contexts with the endpoints on the traffic channels, wherein the processing of the header of the data packets is terminated at the base. The base processes only the header field that needs to be transmitted along the payload, and transfers the processed portion along with the payload. A session is then established between the remote unit and the network, and the traffic resumes from both ends.

Description:
TECHNICAL FIELD 
     The present invention relates to data communications. More particularly, the invention relates to reducing the bandwidth requirement to transmit data packets. 
     BACKGROUND OF THE INVENTION 
     Users may place and receive internet-based calls using voice over Internet protocol (VoIP) via the customer&#39;s existing plain old telephone service (POTS) telephone equipment operating in its current fashion. Such a configuration allows a user to utilize existing POTS telephones to place and receive public switched telephone network (PSTN)-based calls as well as VoIP-based calls, thus avoiding the need to purchase redundant telephone hardware equipment. 
     In placing and receiving a call, data packets are transmitted and received between a network and a remote terminal. In transmitting the data packets, headers may be processed, such as by compression, to reduce the bandwidth requirement to transmit the data packets. 
     SUMMARY OF THE INVENTION 
     In accordance with the exemplary embodiments of this invention, narrowband links, such as wireless links, are used in transmitting data packets. In wireless communications, in accordance with various exemplary embodiments, following initial call establishment negotiation to build a call context between a network and a remote unit, the processing of the header of the data packets is terminated at the base. The base then transfers only the associated payload and payload type to the remote unit via the established traffic channel. 
     In various exemplary embodiments of this invention, in wireless communications, during the initial part of the call establishment, the base intrudes into the call establishment messages to establish a context identification for the remote unit. Following the initial call establishment negotiation, a session is established between the remote unit and the network, and the traffic resumes from both ends. 
     Based on initial negotiation, the base uses various header fields to associate the identified context with the call as established during the initial negotiation phase. In accordance with various exemplary embodiments, only the header field that needs to be transmitted along with a payload is compressed and transmitted with the payload. 
     In accordance with various exemplary embodiments, in wireless communications, the base acts as an intermediate nodal point to establish call contexts with the endpoints on the traffic channels, wherein the processing of the header of the data packets is terminated at the base. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a packet transmission network; 
         FIG. 2  shows an exemplary header to be processed in accordance with this invention; 
         FIG. 3  shows an exemplary embodiment of a context processor in accordance with this invention; and 
         FIG. 4  is a flowchart illustrating a call context establishing process in accordance with this invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an illustration of a packet transmission network. As shown in  FIG. 1 , terminals  102  and  104  are connected to a network  100 , which in turn is connected to base  200  of remote unit  202 . In an exemplary embodiment, terminals  102  and  104  are plain old telephone terminals (POTS), and the network  100  is a public switched telephone network (PSTN). As shown in  FIG. 1 , the remote unit  202  is connected to the network  100  via a wireless airlink access. 
     It should be appreciated that this invention is not limited to the packet transmission network as shown in  FIG. 1 . In accordance with the various exemplary embodiments of this invention, any packet transmission network that provides transmissions via narrowband access may be applied to this invention. That is, it should be appreciated that this invention may be applied to wireline communications as well as wireless communications. Further, though  FIG. 1  shows only two terminals  102  and  104 , and one remote unit  202 , it should be appreciated that any number of terminals and remote units may be applied. 
     In the exemplary embodiment of  FIG. 1 , in transmitting a data packet from the network  100  to the remote unit  202  over the airlink access, call establishment is made through initial call establishment between the network gateway of the network  100  and the remote unit  202 . Using the initial call establishment negotiation, a call context is established for establishing the call between the network  100  and the remote unit  202 . After the call context is built, the data packet is transmitted from the network  100  and the header of the data packet is processed, and relevant portions of the data packet are transferred to the remote unit  202  via the established airlink channel. 
     In an exemplary embodiment, a media gateway control protocol (MGCP) is used to establish the call context. However, it should be appreciated that any initial call establishment negotiation protocol for establishing a call context may be applied in the exemplary embodiments of this invention. 
       FIG. 2  shows an exemplary header to be processed in accordance with this invention, such as an RTP, UDP, IP header for a voice internet protocol (VoIP) data packet. As shown in  FIG. 2 , an RTP, UDP, IP header  1000  consists of an internet protocol (IP) header portion  1100 , a user datagram protocol (UDP) header portion  1200  and a real-time transport protocol (RTP) header portion  1300 . IP header portion  1100  includes constant header fields  1120  and context identification associating header fields  1140 . UDP header portion  1200  includes constant header fields  1220  and context identification associating header fields  1240 . RTP header portion  1300  includes constant header fields  1320 , flow regulation header fields  1340 , and transmitted header fields  1360 . 
     In accordance with the exemplary embodiments of this invention, the processing of the header of the data packets is terminated at the base  200 . As shown in  FIG. 1 , a context processor  2000  is provided in the base  200  to process the headers  1000  of the data packets. In accordance with various exemplary embodiments of this invention, the context processor  2000  transfers only the transmitted header portions  1360  and the associated data of the data packets to the remote unit  202  via the established traffic channel in a loss-less manner. 
     Based on initial negotiation, the context processor  2000  can use header fields in the header, such as the source IP address and the destination IP address fields from the context identification associating header fields  1140  of the IP header portion  1100 , and the source port and destination port information fields from context identification associating header fields  1240  of the UDP header portion  1200 , to associate the destination terminal identification, line identification context with the call as established during the initial call establishment phase. 
     In particular, in various exemplary embodiments, during the initial part of the call establishment through the call establishment negotiation between the network gateway of the network  100  and the remote unit  202 , the context processor  2000  intrudes into the initial call establishment messages at the network  100  to process a create connection message (CRCX) and the associated session data protocol (SDP) header. In these exemplary embodiments, the context processor  2000  extracts the line identification to the remote unit  202  from the SDP header. The context processor  2000  also extracts information such as the source IP address and the destination address from the IP header portion  1100 , the source port and destination port information from the UDP header portion  1200 . The processor  2040  then processes the extracted information to establish context identification for the remote unit  202 . 
     Following the initial call establishment negotiation, a real-time transport protocol (RTP) session is established between the remote unit  202  and the network gateway of the network  100 , and traffic resumes from both the remote unit  202  and the network gateway. 
       FIG. 3  shows an exemplary embodiment of the context processor of  FIG. 1 . As shown in  FIG. 3 , the context processor  2000  includes a header extractor  2020 , a header compressor  2040  and an identification module  2060 . The header extractor  2020  extracts information from the initial call establishment messages, and separates the header  1000  from the payload. The header compressor  2040  receives the header  1000  from the header extractor  2020 , and compresses the relevant portions of the header  1000 . The compressed header is then input to the identification module  2060  along with the payload to associate the identified context with the airlink channel of the call established from the initial call establishment messages. 
     In accordance with the various exemplary embodiments of this invention, only the relevant portions of the header  1000 , such as the transmitted header field  1360  of the RTP header portion  1300 , are compressed. That is, header fields that remain constant over the life of the connection, such as IP version, IP header length, type of service, IP identification, flags, fragment offset, time to live, protocol type of the constant header fields  1120  in the IP header portion  1100 , and the RTP version, padding, extension, CSRC count bits of the constant header fields  1320  in the RTP header portion  1300 , are not required by the remote unit  202  for channel processing. Further, the constant header fields  1220  of the UDP header portion  1200 , such as UDP Checksum, are not used in channel processing in the embodiments of this invention. 
     The flow regulation header fields  1340  of the RTP header portion  1300 , such as the RTP sequence number field and RTP timestamp field, are used in the base  200  for flow regulation and synchronization and jitter calculation, and are not required to be transmitted over the airlink for channel processing. Similarly, the context identification associating header fields  1140  and  1240  of the IP header portion  1100  and the UDP header portion  1200 , respectively, are used to associate the context identification with the established call, and are not required to be transmitted over the airlink for channel processing. 
     Accordingly, by compressing and transmitting only the relevant fields of the header  1000  that is required to be transmitted along with the payload, such as the payload type field in the transmitted header field  1360  of the RTP header portion  1300 , a significant degree of compression may be obtained. Thus, the bandwidth requirement to transmit the data packet over the airlink access may be limited, and the transmission may be performed in a loss-less manner. 
       FIG. 4  is a flowchart illustrating a call context establishment process in accordance with an exemplary embodiment of this invention. As shown in  FIG. 4 , the process begins with step  400 , and continues to step  410 , where the information is extracted by the base. That is, in this step, the context processor intrudes into the initial call establishment messages at the network to extract information such as the IP source and destination address, RTP source and destination port information, and line identification information. Control then continues to step  420 . 
     In step  420 , header information is extracted from the extracted information. Next, in step  430 , relevant portions of the header are compressed. For example, header fields which remain constant or are used for flow regulation and synchronization and jitter calculation, and are not required to be transmitted over the airlink for channel processing, are not compressed. Accordingly, only the relevant fields of the header that are required to be transmitted along with the payload, such as the payload type field, is compressed. Control then continues to step  440 . 
     In step  440  the context identification is formed. Then, in step  450 , the call session is established by switching to the identified context. That is, the identified context is associated with the bearer channel of the call session established from the initial call establishment negotiation. Control then continues to step  460 , where the process ends. 
     While the present invention is disclosed in the context of a presently preferred embodiment, it will be recognized that a wide variety of implementations may be employed by persons of ordinary skill in the art consistent with the above discussion and the claims which follow below.