Abstract:
Disclosed herein is a method of processing an error frame that occurs in packet data communication between a mobile station and a communication server which exchanges packets with the mobile station over a radio network. The method carried out by the mobile station includes the steps of: a) detecting an error having occurred in received packet data during communication in a radio network; and b) requesting the communication server to retransmit the packet data without reducing the congestion window size. In addition, the method carried out by a communication server includes the steps of: a) detecting an error having occurred in transmitted packet data during communication in a radio network; and b) retransmitting the packet data without reducing the congestion window size.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application claims the priority of Korean Patent Application No. 2004-011357, filed on Feb. 20, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
         [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a data communication technique used in a mobile communication network and, more particularly, to a method of processing an error frame that occurs in packet data communication between a mobile communication terminal and a communication server which exchanges packets with the mobile communication terminal over a radio network (RN).  
         [0004]     2. Description of the Related Art  
         [0005]      FIG. 1  is a block diagram showing a well-known 3GPP2 network topology. A mobile station (MS)  10  is indicative of a mobile communication terminal, such as a personal computer with wireless adapters, a mobile handset, a Wireless Application Protocol (WAP) terminal, or a mobile communication modem.  
         [0006]     A radio network (RN)  20 , also called a radio core network, is comprised of a base transceiver system (BTS)  21 , a base station controller (BSC)  23 , and a packet control function (PCF)  25 . The RN  20  manages the mobility of the MS  10  and may authenticate the MS  10  using a Visitor Location Register (VLR) and a Home Location Register (HLR), which are connected to a mobile switching center (MSC)  30 . The RN  20  controls data transmission between the MS  10  and a packet data serving node (PDSN)  40 , and performs data buffering between the MS  10  and the PDSN  40 . Furthermore, the RN  20  performs a paging process when data is transferred to the MS  10  over an Internet Protocol (IP) network.  
         [0007]     Once a basic authentication process of a data call has been completed, a Generic Routing Encapsulation (GRE) protocol establishes a virtual connection between the RN  20  and the PDSN  40 .  
         [0008]     The BSC  23  provides call control and signaling function in addition to providing remote management function and hand-off function between BTSs and BSCs.  
         [0009]     The BSC  23  communicates to the PDSN  40  through the PCF  25  over the GRE tunnel. The PCF  25  and the PDSN  40  communicate with each other using a standard interface known as the RN-to-PDSN interface (R-P interface), which has two components: the A11 interface, used for control messages, and the A10 interface, used for user data. The PCF  25  provides data buffering and packet segmentation functions so that link layer packets received from the PDSN  40  can be transmitted to the MS  10  over an air interface. While the PCF  25  may be incorporated in the BSC  23 , the PCF  25  is usually configured as a separate system.  
         [0010]     The PDSN  40  provides access to the Internet, intranets, and WAP servers for the MSs that use the RN  20 . The Point-to-Point Protocol, or PPP, is commonly used to establish a direct connection between the PDSN  40  and the MS  10 . The PDSN  40  uses a Remote Authentication Dial-In User Service (RADIUS) server  50  for user authentication and traffic management, then forwards traffic to a gateway router/home agent at the designated IP network.  
         [0011]     The RADIUS server  50  interacts with the PDSN  40  to perform AAA (Authentication, Authorization, Accounting) functions. That is, the RADIUS server  50  verifies that a user is a valid subscriber, determines what services are available for the user, and tracks usage for billing.  
         [0012]     A Home Agent (HA)  60  maintains mobile user registrations and tunnels packets destined for the mobile client to the PDSN  40 . The HA can perform dynamic home address assignment for the MS  10  from address pools configured locally, through Dynamic Host Configuration Protocol (DHCP), or from the RADIUS server  50 . Upon receiving a registration request message from the MS  10 , the HA  60  allows a corresponding IP address to be used when a method of statically assigning the IP address is employed. On the other hand, when a method of dynamically assigning the IP address is employed, the HA  60  allows an IP address to be used by assigning the IP address and transmitting a registration reply message. When the MS  10  moves to another PDSN area, it notifies the HA  60  of the PDSN area.  
         [0013]     A Dynamic Host Configuration Protocol (DHCP) server/Domain Name System (DNS) server  70  is indicative of a server capable of automatically assigning users IP addresses. The DHCP server/DNS server  70  is used for establishing an IP address, a domain name, etc.  
         [0014]     The DNS server is used for converting a host name into an IP address and vice versa. The DNS server may update an IP address for a specific host name upon receiving a DNS update message according to the RFC2136 protocol.  
         [0015]     When the MS  10  capable of using a packet data service over the above-mentioned mobile communication network requests the packet data service, the BSC  23  and PCF  25  determine which PDSN should transmit packet data. At this time, a radio traffic channel and a radio link protocol (RLP) are established between the MS  10  and the BSC  23 . The A8 interface is used to provide a path for user traffic between the BSC  23  and the PCF  25  for packet data services. In addition, the A10 interface is used to provide a path for user traffic between the PCF  25  and the PDSN  40  for packet data services. In this case, the packet data service in an ‘active’ state implies that the MS  10  occupies a radio traffic channel, maintains the RLP link and the A8 link, and transmits/receives packet data.  
         [0016]      FIG. 2  is a schematic diagram showing a protocol stack for data call transfer in a conventional mobile communication system. The protocol stack includes a physical layer, a Radio Link Protocol (RLP), a Point-to-Point Protocol (PPP), an Internet Protocol (IP), a Transmission Control Protocol (TCP), a User Datagram Protocol (UDP), etc.  
         [0017]     The physical layer is the lowest layer of the Open System Interconnection Reference Model (OSI Reference Model), an International Standards Organization (ISO) standard for worldwide communications that defines a framework for implementing protocols in seven layers. The physical layer, which is implemented in hardware, defines all electrical and physical specifications for devices. IS-95B/2000 protocol  109  corresponds to the physical layer.  
         [0018]     The RLP  107  is used to provide reliable data service over the air interface between the MS  10  and a base station. The RLP  107  also employs an Automatic Repeat Request (ARQ) scheme to request retransmission of messages which have errors or fail to arrive in order to ensure reliable transfer of data.  
         [0019]     The PPP  105  is a method of connecting a computer to the Internet using a phone line. Working in the data link layer of the OSI Reference Model, the PPP  105  sends the computer&#39;s TCP/IP packets to a server that puts them onto the Internet.  
         [0020]     The IP  103  is a data-oriented protocol used by source and destination hosts for communicating data across a packet-switched internetwork. The IP  103  specifies the format of packets, also called datagrams, and the addressing scheme.  
         [0021]     The TCP is a connection-oriented, reliable delivery byte-stream transport layer protocol. Whereas the IP  103  protocol deals only with packets, the TCP enables two hosts to establish a connection and exchange streams of data. The TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.  
         [0022]     The UDP is an alternative to the TCP and, together with IP, is sometimes referred to as UDP/IP. Like the TCP, the UDP uses the IP  103  to actually get packets from one computer to another. Unlike TCP, the UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically, the UDP does not provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. Network applications that want to save processing time because they have very small data units to exchange may prefer UDP to TCP.  
         [0023]     The MS  10  establishes a session with a communication network connection unit such as the PCF  25  using the physical layer and the RLP. The MS  10  establishes a PPP session with the PDSN  40 .  
         [0024]     The MS  10  establishes a session with a supplementary service unit, which is provided in a mobile communication service system, using the TCP/IP or UDP/IP. Wireless data communications using the TCP/IP or UDP/IP is available only when a PPP connection is established between the MS and the PDSN.  
         [0025]     Examples of applications required for accessing the Internet via the mobile communication terminal include a browser and a software platform such as JAVA, Binary Runtime Environment for Wireless (BREW), or Graphics Virtual Machine (GVM).  
         [0026]     In the case when the MS or a communication server detects one or more errors during TCP communication in the above-mentioned communication network, a congestion control scheme widely used in typical wireline network communications has been used for error processing. Specifically, in the case when a communication error is detected from a received TCP packet or an acknowledgement (ACK) response to a transmitted packet is not received until a TCP&#39;s retransmission timer expires, the MS or the communication server determines the packet to have been lost due to congestion, and reduces the congestion window size of a transmission side to retransmit the packet.  
         [0027]     The reduction in congestion window size leads to a significant decrease in the effective transfer rates of the transmission side. The occurrence of packet losses in a typical wireline network is mainly caused by a waiting time based on a priority logic mechanism in a routing process. However, in case of the radio network, the packet losses may occur due to a high bit error rate (BER) compared to that of the wireline network, or multi-path fading. In addition, the packet losses in the radio network may occur due to the rerouting of packets during handoff. Consequently, determining the packet losses in the radio network to have occurred due to congestion causes a problem in terms of transmission efficiency.  
       SUMMARY OF THE INVENTION  
       [0028]     The present invention provides a method of improving transmission efficiency in a mobile communication network in which a transmission error has occurred.  
         [0029]     The present invention also provides a method of processing a transmission error having occurred in a radio network in a different manner from a transmission error having occurred in a wireline network.  
         [0030]     In accordance with an aspect of the present invention, there is provided a packet data communication method carried out by an MS connected to a communication server over a mobile communication network, the method comprising the steps of: a) detecting an error having occurred in received packet data during communication in a radio network; and b) requesting the communication server to retransmit the packet data without reducing the congestion window size.  
         [0031]     The step a) may comprise the step of detecting, by the MS, a frame error in a physical layer or a link layer associated with the radio network and notifying a TCP (Transmission Control Protocol) layer of the occurrence of the frame error.  
         [0032]     The step b) may comprise the step of transmitting a dummy segment having a TCP header with a certain flag set.  
         [0033]     In accordance with another aspect of the present invention, there is provided a packet data communication method carried out by an MS connected to a communication server over a mobile communication network, the method comprising the steps of: c) detecting an error having occurred in transmitted packet data during communication in a radio network; and d) retransmitting the packet data without reducing the congestion window size.  
         [0034]     The method may further comprise the steps of: detecting an error having occurred in transmitted packet data during communication in a wireline network; and retransmitting the packet data after reducing the congestion window size.  
         [0035]     In the step c), the MS may determine a transmission error to have occurred if the MS is notified by the communication server of the error occurrence in the radio network or if the MS does not receive within a predetermined time from the communication server an ACK (acknowledgement) message for acknowledging the receipt of the packet data.  
         [0036]     The communication server may notify the MS of the error occurrence by sending a dummy segment having a TCP header with a certain flag set.  
         [0037]     In accordance with another aspect of the present invention, there is provided an MS connected to a communication server over a mobile communication network, comprising data communication means which retransmits or requests to retransmit packet data without reducing the congestion window size when an error is detected by the MS in the packet data transmitted or received during communication in a radio network.  
         [0038]     The data communication means comprises a data transmitter and a data receiver, wherein the data transmitter including: a radio network transmission error detector for determining whether an error has occurred in the transmitted packet data during communication in the radio network; and a radio network retransmitter for retransmitting the packet data without reducing the congestion window size when the occurrence of the error is detected by the radio network transmission error detector, and the data receiver including: a radio network reception error detector for determining whether an error has occurred in the received packet data during communication in the radio network; and a radio network retransmission requester for requesting the communication server to retransmit the packet data without reducing the congestion window size when the occurrence of the error is detected by the radio network reception error detector.  
         [0039]     The radio network reception error detector may detect a frame error in a physical layer or a link layer associated with the radio network and notifying a TCP layer of the occurrence of the frame error.  
         [0040]     The radio network retransmission requester may transmit a dummy segment having a TCP header with a certain flag set.  
         [0041]     The radio network transmission error detector may determine the error to have occurred in the transmitted packet data when the radio network transmission error detector is notified by the communication server of the error occurrence or does not receive within a predetermined time from the communication server an ACK message for acknowledging the receipt of the packet data.  
         [0042]     The radio network transmission error detector may detect the notification of the communication server by checking a certain flag in the TCP header.  
         [0043]     In accordance with another aspect of the present invention, there is provided a packet data communication method carried out by a communication server which performs data communication with a plurality of MSs, the method comprising the steps of: e) detecting an error having occurred in received packet data during communication in a radio network; and f) requesting the MSs to retransmit the packet data without reducing the congestion window size.  
         [0044]     The step e) may comprise the step of detecting, by the communication server, a frame error in a physical layer or a link layer associated with the radio network.  
         [0045]     The step f) may comprise the step of transmitting a dummy segment having a TCP header with a certain flag set.  
         [0046]     In accordance with another aspect of the present invention, there is provided a packet data communication method carried out by a communication server which performs data communication with a plurality of MSs, the method comprising the steps of: g) detecting an error having occurred in transmitted packet data during communication in a radio network; and h) retransmitting the packet data without reducing the congestion window size.  
         [0047]     The method may further comprise the steps of: detecting an error having occurred in transmitted packet data during communication in a wireline network; and retransmitting the packet data after reducing the congestion window size.  
         [0048]     In the step g), the communication server may determine a transmission error to have occurred if the communication server is notified by the MS of the error occurrence in the radio network or if the communication server does not receive within a predetermined time from the MS an ACK message for acknowledging the receipt of the packet data.  
         [0049]     The MS may notify the communication server of the error occurrence by sending a dummy segment having a TCP header with a certain flag set.  
         [0050]     It should be noted that the term “MS” described in the present invention is indicative of a data communication terminal capable of accessing a mobile communication network, such as a mobile communication terminal, a communication server, and a notebook computers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0051]     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0052]      FIG. 1  is a block diagram showing a well-known 3GPP2 network topology;  
         [0053]      FIG. 2  is a schematic diagram showing a protocol stack for data call transfer in a conventional mobile communication system;  
         [0054]      FIG. 3  is a flowchart showing downstream data communication in accordance with an embodiment of the present invention;  
         [0055]      FIG. 4  is a flowchart showing upstream data communication in accordance with another embodiment of the present invention; and  
         [0056]      FIG. 5  is a block diagram showing the configurations of the MS in accordance with another embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0057]     Exemplary embodiments of the present invention will be described in detail with reference to the annexed drawings, where the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings.  
         [0058]      FIG. 3  is a flowchart showing downstream data communication in accordance with an embodiment of the present invention. A packet data communication method in an MS connected to a communication server over a mobile communication network is initiated by establishing a data call between the MS and the communication server (steps S 251  and S 211 ). Call setup processes are well known in the art.  
         [0059]     While the communication server is typically indicative of the PDSN  40  serving as an Internet interface unit shown in  FIGS. 1 and 2 , it should be noted that the communication server is not limited to the PDSN  40 . That is, the communication server may be an Internet server in a wireline network connected to the Internet interface unit or radio network equipment  20 , which is capable of processing the physical and link layers.  
         [0060]     Subsequently, the communication server transmits packet data (step S 213 ). The MS  10  receives the packet data (step S 253 ). In this case, the packet data communication method in the MS  10  includes the step of detecting errors having occurred in received packet data during communication in a radio network (steps S 255  and S 257 ) and the step of requesting the communication server to retransmit the packet data without reducing the congestion window size (step S 259 ).  
         [0061]     In accordance with a preferred embodiment of the present invention, in steps S 255  and S 257 , the MS  10  detects a frame error in a physical layer or a link layer associated with the radio network and notifies the TCP layer of the occurrence of the frame error. In more detail, it is determined whether packets received from either the IS-95B/2000 layer  109  as a physical layer or the RLP layer  107  as a link layer, among the communication protocols incorporated in the MS  10  shown in  FIG. 2 , include the frame error (step S 255 ). If the received packets are determined to include the frame error, the IS-95B/2000 layer  109  or the RLP layer  107  including the frame error notifies a TCP layer incorporated in the MS of the occurrence of the frame error (step S 257 ).  
         [0062]     In accordance with another preferred embodiment of the present invention, in step S 259 , the retransmission request is made by transmitting a dummy segment having a TCP header with a certain flag set. In more detail, when a frame error is detected in a lower layer, the TCP layer is notified of the occurrence of TCP packet losses, then notifies a TCP layer on a transmission side of the occurrence of TCP packet losses by use of the dummy segment. Here, the dummy segment indicates a segment of 20-60 bytes which has only a header without data. One of six reserved bits contained in a flag field of a TCP header is used to indicate the dummy segment.  
         [0063]     Steps S 257  and S 259  are skipped when the frame error is not detected at step S 255 .  
         [0064]     On the other hand, in accordance with another embodiment of the present invention, a packet data communication method in a communication server communicating with a plurality of MSs includes the steps of detecting errors having occurred in transmitted packet data during communication in a radio network (step S 215 ) and of retransmitting the packet data without reducing the congestion window size (step S 217 ).  
         [0065]     In accordance with another preferred embodiment of the present invention, in step S 215 , the communication server determines a transmission error to have occurred if the communication server is notified by the MS of the error occurrence or if the communication server does not receive within a predetermined time from the MS an acknowledgement (ACK) message for acknowledging the receipt of the packet data. In more detail, when the communication server receives a dummy packet having a TCP header with a certain flag set, which implies the error occurrence, from the MS at step S 259 , the communication server determines a transmission error to have occurred in the radio network while the packet data is being transmitted to the MS. Furthermore, when the communication server transmits packet data and does not receive an ACK message from the MS until a retransmission timer expires, a transmission error is determined by the communication server to have occurred in the radio network while the packet data is being transmitted to the MS.  
         [0066]     In the case when the communication server receives the dummy segment and thus determines a transmission error to have occurred, the communication server does not retransmit the packet data until the retransmission timer expires. Otherwise, the packet data is retransmitted once again when no ACK message is received from the MS. Alternatively, the communication server may re-initialize the retransmission timer and retransmit the packet data.  
         [0067]     As described above, upon detecting errors having occurred in transmitted packet data during communication in a radio network, the communication server retransmits the packet data without reducing the congestion window size (step S 217 ).  
         [0068]     On the other hand, when the MS detects a transmission error in the IP or TCP layer rather than the physical and link layers, the detected transmission error is determined to have occurred in a wireline network (step S 261 ). In this case, the IP or TCP layer does not send an ACK message for acknowledging the receipt of the packet data (step S 263 ).  
         [0069]     In accordance with another preferred embodiment of the present invention, a packet data communication method in the communication server further includes the steps of detecting errors having occurred in transmitted packet data during communication in a wireline network (step S 219 ) and of retransmitting the packet data after reducing the congestion window size (step S 221 ). In more detail, the communication server determines a transmission error to have occurred in the wireline network if the communication server does not receive from the TCP layer on a reception side an ACK message for acknowledging the receipt of the packet data until a retransmission timer of the TCP layer expires (step S 219 ). In this case, the communication server reduces the congestion window size in accordance with a solution to packet losses in a typical wireline network, and retransmits corresponding data to a destination MS (step S 221 ). Step S 221  is skipped if the communication server receives the ACK message in step S 219  and thus no error is determined to have occurred in the wireline network.  
         [0070]     The MS and the communication server determine whether the communication has terminated after completion of the data transmission (step S 265 ). If necessary, a call is released (step S 267 ).  
         [0071]      FIG. 4  is a flowchart showing upstream data communication in accordance with another embodiment of the present invention. A packet data communication method in an MS connected to a communication server over a mobile communication network is initiated by establishing a data call between the MS and the communication server (steps S 511  and S 551 ).  
         [0072]     The MS transmits packet data (step S 513 ). The communication server receives the packet data (step S 553 ). In this case, the packet data communication method in the communication server includes the steps of detecting errors having occurred in received packet data during communication in a radio network (step S 555 ) and of requesting the MS to retransmit the packet data without reducing the congestion window size (step S 559 ).  
         [0073]     In accordance with a preferred embodiment of the present invention, in step S 555 , the communication server detects a frame error in a physical layer of a link layer associated with a radio network and notifies the TCP layer of the occurrence of the frame error. In more detail, it is determined whether packets received from either the IS-95B/2000 layer  109  as a physical layer or the RLP layer  107  as a link layer, among the communication protocols incorporated in the radio network shown in  FIGS. 1 and 2 , include the frame error (step S 555 ). A protocol associated with only the radio network is present between the MS and the radio network equipment, but not present between the radio network equipment and a wireline Internet server. Thus, the radio network equipment is needed for the wireline Internet server to detect errors in the radio network. Consequently, the communication server in accordance with the embodiment of the present invention may be one of radio network equipment  20 . Alternatively, the communication server may be a wireline Internet server in the case where the radio network equipment  20  detects and notifies an error in the radio network to the wireline Internet server.  
         [0074]     In accordance with another preferred embodiment of the present invention, in step S 559 , the retransmission request is made by transmitting a dummy segment having a TCP header with a certain flag set. When a frame error is detected in a lower layer of a radio communication network, the communication server recognizes that the frame error has been detected, and requests the MS to retransmit packet data by sending a fixed dummy packet to the MS. Here, the dummy segment indicates a segment of 20-60 bytes which has only a header without data. One of six reserved bits contained in a flag field of a TCP header is used to indicate the dummy segment.  
         [0075]     On the other hand, in accordance with another embodiment of the present invention, a packet data communication method in the MS communicating with the communication server includes the steps of detecting errors having occurred in transmitted packet data during communication in a radio network (step S 515 ) and of retransmitting the packet data without reducing the congestion window size (step S 517 ).  
         [0076]     In accordance with another preferred embodiment of the present invention, in step S 515 , the MS determines a transmission error to have occurred if the MS is notified by the communication server of the error occurrence or if the MS does not receive within a predetermined time from the communication server an acknowledgement (ACK) message for acknowledging the receipt of the packet data. In more detail, when the MS receives a dummy packet having a TCP header with a certain flag set, which implies the error occurrence, from the communication server at step S 559 , the MS determines a transmission error to have occurred in the radio network while the packet data is being transmitted to the communication server. Furthermore, when the MS transmits packet data and does not receive an ACK message from the communication server until a retransmission timer expires, a transmission error is determined by the MS to have occurred in the radio network while the packet data is being transmitted to the communication server.  
         [0077]     In the case when the MS receives the dummy segment and thus determines a transmission error to have occurred, the MS does not retransmit the packet data until the retransmission timer expires. Otherwise, the packet data is retransmitted again when no ACK message is received from the communication server. Alternatively, the MS may re-initialize the retransmission timer and retransmit the packet data.  
         [0078]     As described above, upon detecting errors having occurred in transmitted packet data during communication in a radio network, the MS retransmits the packet data without reducing the congestion window size (step S 517 ). On the other hand, step S 517  is skipped when the frame error is not detected in the radio network at step S 515 .  
         [0079]     On the other hand, when the communication server detects a transmission error in the IP or TCP layer rather than the physical and link layers, the detected transmission error is determined to have occurred in a wireline network (step S 561 ). In case of the TCP layer, a transmission side determines a transmission error to have occurred if a reception side does not notify the occurrence of the transmission error to the transmission side and does not send an ACK message until a retransmission timer expires (step S 563 ). A server which uploaded data finally reaches through the wireline network, such as a content server on the wireline Internet, determines whether or not the transmission error has occurred.  
         [0080]     In accordance with another preferred embodiment of the present invention, a packet data communication method in the MS further includes the steps of detecting errors having occurred in transmitted packet data during communication in a wireline network (step S 519 ) and of retransmitting the packet data after reducing the congestion window size (step S 521 ). In more detail, the MS determines a transmission error to have occurred in the wireline network if the MS does not receive from the TCP layer on a reception side an ACK message for acknowledging the receipt of the packet data until a retransmission timer of the TCP layer expires (step S 519 ). In this case, the MS reduces the congestion window size in accordance with a solution to packet losses in a typical wireline network, and retransmits corresponding data to the communication server (step S 521 ). Step S 521  is skipped if the communication server receives the ACK message in step S 519  and thus no error is determined to have occurred in the wireline network.  
         [0081]     The communication server and the MS determine whether the communication has terminated after completion of the data transmission (steps S 523  and S 565 ). If necessary, a call is released (steps S 525  and S 567 ).  
         [0082]      FIG. 5  is a block diagram showing the configurations of the MS in accordance with another embodiment of the present invention. The MS comprises a communication processing unit  100 , a system control unit  400 , a display unit  600 , a voice input/output (I/O) circuit  700 , a key input unit  800 , and a radio frequency (RF) module  900 .  
         [0083]     The RF module  900  is one used for detecting voice and data signals from radio signals transmitted or received via an antenna. The voice I/O circuit  700  is one for inputting/outputting voice signals, which are received from the RF module  900 , via a microphone/speaker.  
         [0084]     The configurations of the key input unit  800  and the display unit  600  are well-known in the art, and thus their detailed description is omitted here. The RF module  900  comprises an antenna and an RF circuit to communicate with a base station. The RF module  900  is designed to be available in all cellular systems such as TDMA, CDMA, PDC, and GSM. The voice I/O circuit  700 , which comprises well-known circuits such as an audio amplifier and a filter, converts digital into analog voice signals and vice versa.  
         [0085]     A baseband circuit of the RF module  900 , the communication processing unit  100 , and the system control unit  400  are integrated into a single chip, which is commercially available. This IC chip, which is called a mobile station modem (MSM) chip, includes a hardware dedicated for communication processing, a digital signal processor, and a general-purpose microprocessor. Logically, the IC chip includes the communication processing unit  100  for controlling voice and data communications, and the system control unit  400  for controlling the overall system according to input signals from the key input unit  800 . The communication processing unit  100  includes a typical voice communication module  300  for processing voice communication.  
         [0086]     In accordance with another embodiment of the present invention, the MS can be connected to the communication server over a mobile communication network. The MS includes a data communication module  500  which retransmits or requests to retransmit packet data without reducing the congestion window size when an error is detected in the packet data transmitted or received during communication in a radio network.  
         [0087]     In accordance with a preferred embodiment of the present invention, the data communication module  500  includes a data transmitter  510  and a data receiver  530 . The data transmitter  510  includes a radio network transmission error detector  511  and a radio network retransmitter  513 . The radio network transmission error detector  511  determines whether an error has occurred in transmitted packet data during communication in the radio network. The radio network retransmitter  513  retransmits the packet data without reducing the congestion window size when the occurrence of the error is detected by the radio network transmission error detector  511 . The data receiver  530  includes a radio network reception error detector  531  and a radio network retransmission requester  533 . The radio network reception error detector  531  determines whether an error has occurred in received packet data during communication in the radio network. The radio network retransmission requester  533  requests the communication server to retransmit the packet data without reducing the congestion window size when the occurrence of the error is detected by the radio network reception error detector  531 .  
         [0088]     In this case, the radio network reception error detector  531  detects a frame error in packet data received from either the IS-95B/ 2000  layer as a physical layer or the RLP or PPP layer as a link layer, as shown in  FIG. 2 , and notifies the TCP layer in the MS of the occurrence of the frame error. On the other hand, the radio network retransmission requester  533  requests retransmission of the packet data by transmitting a dummy segment having a TCP header with a certain flag set. A transmission error is determined by the radio network transmission error detector  511  to have occurred if the radio network transmission error detector  511  is notified by the communication server of the error occurrence or receives no ACK message within a predetermined time from the communication server. Further, the radio network transmission error detector  511  detects the error occurrence by checking a predetermined flag in the TCP header.  
         [0089]     According to the present invention, it is possible to increase transfer rate by processing transmission errors occurred in the radio network and the wireline network in different schemes.  
         [0090]     Further, it is possible not to reduce transmission efficiency during communication in the radio network. In addition, it is possible efficiently determine whether the transmission error has occurred in the wireline network or in the radio network.  
         [0091]     While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the present invention as defined by the following claims.