KR100879149B1 - Operating method and terminal apparatus of tcp well adapting to vertical hand-off in heterogeneous wireless network with congestion control - Google Patents

Abstract

The present invention relates to a congestion control terminal device and a method for operating vertical handoff in a heterogeneous wireless network, and more particularly, to a terminal including a 3G radio unit, a WLAN radio unit, a TCP unit, and a control unit, wherein the 3G radio unit and the WLAN radio unit are received. Detects and analyzes signal strength to determine vertical handoff, transmits data with CWND value set at receiver, detects, records and computes ACK signal status and RTT variable value received from receiver, controls and monitors to set and operate as timer value A control unit; A TCP unit configured to set the last recorded variable of the vertical handoff system under the control of the control unit, to process the data with the CWND variable value by TCP, and to record and manage the last time value at which the ACK signal is received from the receiving side; And a timer unit configured to update the time value under the control of the controller and count the TIMEOUT. Characterized in that the configuration, the vertical handoff is selected, there is an effect to quickly adapt to a given wireless environment to efficiently transmit data, and to facilitate congestion control on the transmitting side.

Mobile Communication, 3G, WLAN, Congestion Control, CWND, ACK, RTT

Description

Congestion Control Terminal and Operation Method of Vertical Handoff in Heterogeneous Wireless Networks

1 is a functional configuration diagram illustrating a congestion control concept of vertical handoff in a heterogeneous wireless network according to the present invention;

2 is a block diagram of a congestion control system function of vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention;

3 is a functional diagram of a terminal device for congestion control of vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention;

4 is a detailed block diagram of a TCP portion of a terminal for congestion control of vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention;

5 is a flowchart illustrating a congestion control terminal data transmission method of vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention;

6 is a flowchart illustrating a method for returning a congestion control terminal device in a vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention.

          ** Description of the symbols for the main parts of the drawings **

10, 15: terminal 20: base station

30: base station controller 40: core network

50: public communication network 60: Internet

70: AP 90: wireless network

100: 3G wireless unit 110: control unit

120: memory unit 130: timer unit

140: keyboard portion 150: display portion

160: TCP section 161: WLAN variable module

162: 3G variable module 163: management module

164: variable setting module 163: TCP operation module

170: IP unit 180: WLAN wireless unit

The present invention adapts quickly to a given communication environment without degrading TCP performance in a vertical handoff of a heterogeneous wireless network. In particular, when the interworking of heterogeneous wireless networks having different data rates occurs, The present invention relates to a congestion control terminal device and a method for operating vertical handoff in a heterogeneous wireless network that efficiently utilizes allocated bandwidth without removing transmission and reception data loss.

In the mobile communication system, a mobile terminal freely moving in a service area communicates with a desired party at any time and anywhere by wireless connection, and the service area is formed in a circle of a predetermined size by a base station. The size is determined in consideration of variables such as, for example, the radius varies from several tens of meters to several kilometers, and since the base stations are continuously repositioned at regular intervals so that the service area is continuous, the mobile communication service is used anywhere in the country.

Early 1st generation (1G) mobile communication systems transmitted voice signals in an analog manner, and 2nd generation (2G) mobile communication systems developed digitally to transmit text messages. The communication system is capable of high speed data communication, thereby enabling video communication.

In general, the mobile terminal for mobile communication is relatively small, and it is always carried in order to solve a communication desire such as a call or reception from the other party, which may occur at a time. Therefore, the utilization rate or utilization rate is low. For example, a text message service, a video message service, an email service, an online game, an internet search, a notification service, and the like, and a new additional service is continuously developed and provided.

The Internet is widely used as an important communication network means by searching and sending a large amount of information to and from the other party. However, the Internet has been solved to solve the problem of wired connection.

There are two methods of accessing the Internet through a mobile communication system and a method of accessing through a local area network (WLAN). The advantage of being able to send and receive e-mails and search a large amount of information through a mobile terminal while moving. There is this.

The Internet uses the TCP (TRANSMISSION CONTROL PROTOCOL) protocol structure and the IP (INTERNET PROTOCOL) protocol structure. The TCP protocol ensures error-free data transmission between transmission and reception by checking that digital data has been transmitted without error and retransmitting if the data is damaged by transmission errors.

The method of accessing through a mobile communication system has a merit that the service area is formed nationwide and can be accessed immediately anytime and anywhere, but the communication cost is high, and the method of accessing via WLAN has a very low communication cost, but the service area is limited. . In addition, in general, WLANs have advantages in that data transmission speeds or bandwidths are wider than in mobile communication systems.

Therefore, when a mobile terminal is connected to the Internet in a mobile state, it is common to connect to a WLAN in an area where WLAN access is possible and to access and communicate through a mobile communication system in an area where WLAN access is not possible.

As such, the mobile communication system is connected to a WLAN system, which is a heterogeneous system with a different wireless environment, while the mobile terminal is connected to the Internet while maintaining a state of being connected to the Internet, or a mobile communication system that is a heterogeneous system with a different wireless environment, while connected to a WLAN system. Connecting to the system is called vertical handoff (HAND-OFF), which must be done unconditionally to maintain the current communication state, and handoff because vertical handoff is to select a better wireless environment or a lower communication cost. In case of failure, communication is not lost.

In the data communication using TCP, there may be a case in which the data processing capability of the transmitting terminal and the receiving terminal is different or the transmission capability on the transmission path is different. In particular, a data processing capability difference occurs in a vertical handoff situation. It is CONGESTION CONTROL to adjust the difference of different data transmission and processing capacity on the transmitting side.

Congestion control in the TCP protocol has a problem in that it cannot suddenly increase from a low transmission rate to a high transmission rate and also suddenly decrease from a high transmission rate to a low transmission rate.

According to the present invention, when vertical handoff occurs between a heterogeneous wireless network by a third-generation mobile communication system and a WLAN system having a different wireless environment, a TCP performance is quickly adjusted so that TCP performance is not degraded. It provides congestion control terminal equipment and operation method of vertical handoff in heterogeneous wireless networks that quickly responds to rapid transmission band change by eliminating TCP performance degradation factor by storing the congestion control variable and reusing it when vertical handoff occurs. To do that.

In addition, even if vertical handoff occurs between heterogeneous wireless systems, it adapts quickly to the most suitable conditions for the communication environment. Therefore, the vertical handoff in heterogeneous wireless networks improves data communication reliability and preferences by transmitting data without error. It is an object of the present invention to provide an off congestion control terminal apparatus and an operation method.

In order to achieve the above object, the present invention is a terminal including a 3G radio, a WLAN radio, a TCP, and a control unit, and detects and analyzes the received signal strength of the 3G radio and the WLAN radio, and performs vertical handoff. A control unit for determining and transmitting the data with the CWND value set at the receiving side, and detecting and recording the ACK signal state and the RTT variable value received from the receiving side and calculating and calculating the operation value as a timer value; A TCP unit configured to set the last recorded variable of the vertical handoff system under the control of the control unit, to process the data with the CWND variable value by TCP, and to record and manage the last time value at which the ACK signal is received from the receiving side; And a timer unit configured to update the time value under the control of the controller and count the TIMEOUT. Present a configuration that includes.

In addition, the present invention devised to achieve the above object, in the data transmission operation method of a terminal including a 3G radio unit, WLAN radio unit, TCP unit, control unit, the final handoff is confirmed by the control unit Starting the counting of the timer by setting the value of the corresponding variable recorded and transmitting data with the CWND value set in the counterpart; Setting and recording sRTT and RTTvar to a predetermined one step down value and setting the timer when the ACK signal is returned once from the counterpart receiving the transmitted data, and recording and calculating sRTT and RTTvar to one down step value; Checking whether data transmission is completed, and if the transmission is completed, managing the last recorded variable value in the variable module of the system; This presents the included configuration.

In addition, the present invention devised to achieve the above object, in the terminal comprising a 3G wireless unit, WLAN wireless unit, TCP unit, the control unit, by detecting the received signal strength of the 3G wireless unit and WLAN wireless unit vertically A controller which determines a handoff, analyzes a signal transmitted from a transmitter, returns an ACK signal if it is received without error, and returns a plurality of ACK signals if there is an error that can be recovered, and returns no ACK signal if it cannot recover; A TCP unit configured to set the last recorded variable of the vertical handoff system under control of the control unit, combine the received data into TCP processing, and record and update the updated variable value; And a timer unit configured to update the time value under the control of the controller and to count TIMEOUT. Present a configuration that includes.

In addition, the present invention devised in order to achieve the above object, in the data receiving operation method of the terminal including a 3G radio, a WLAN radio, a TCP, the control unit, if the control unit confirms the vertical handoff, the final A receiving process of setting the corresponding variable value recorded and confirming that data is received; Returning an ACK signal when it is determined that data is received and there is no error, and returning a plurality of ACK signals when it is determined that a recoverable error is included; And terminating if the received data is found to be irrecoverable; This presents the included configuration.

Hereinafter, the congestion control apparatus and method for vertical handoff in a heterogeneous wireless network will be described in detail with reference to the accompanying drawings.

1 is a functional block diagram illustrating a congestion control concept of vertical handoff in a heterogeneous wireless network according to the present invention, and FIG. 2 is an example of the present invention. 3 is a functional block diagram of a congestion control system of vertical handoff, FIG. 3 is a functional diagram of a terminal device for congestion control of vertical handoff in a heterogeneous wireless network, and FIG. FIG. 5 is a detailed block diagram of a TCP portion of a terminal for congestion control of vertical handoff in a heterogeneous wireless network. FIG. 5 is a flowchart illustrating a congestion control terminal data transmission method of vertical handoff in a heterogeneous wireless network. 6 shows an example of the present invention in a heterogeneous wireless network. Jikjeok a congestion control terminal equipment replying method flowchart of the handoff.

In describing an example of the present invention, drawings and descriptions which are not directly related to the present invention and well-known technical contents are omitted from the drawings, so that the gist of the present invention is clearly transmitted without obscuring the gist of the present invention.

Referring to FIG. 1, a concept of congestion control of vertical handoff in a heterogeneous wireless network according to the present invention will be described. The first terminal 10 wirelessly connects to the second terminal 15 through the wireless network 90 and establishes TCP. Communicate data using protocols.

The TCP protocol is used with the IP protocol to send data in the form of messages between terminals or computers on the Internet. IP manages the address (ADDRESS) for data delivery processing and TCP tracks and manages each packet divided into packet unit of the transmitted data, and the packet is efficiently routed through the Internet. It is a piece of what is divided into several small pieces of a certain size to make it possible.

For example, when transmitting a video file (FILE) or a large amount of data files from the first terminal 10 on the receiving side to the second terminal 15 on the receiving side, the TCP protocol program provided in the first terminal 10. The LAYER divides the file into multiple packets of a certain size, assigns a serial number to each packet, passes it to the IP protocol program layer, and adds an address to each packet to be transmitted to the second terminal by the IP protocol. Is given. The first terminal 10 transmits to a wireless network 90 by a wirelessly connected 3G or WLAN system and a second terminal wirelessly connected in a 3G or WLAN manner by switching of a wireless network 90 including the Internet. Is sent to. At this time, even if each packet has the same transmission destination address (IP address), it may be transmitted through different paths of the wireless network 90 including the Internet. TCP of the second terminal 15 waits until all packets are normally received in order to reassemble each packet in sequence by serial number, thus forming one complete file.

TCP is a connection-oriented protocol and means that the connection is maintained while the data is processed by each application program. The TCP protocol transmits the data by dividing the data into several unit packets accurately so that the IP protocol can be processed. On the side, packets are reassembled in order and reconstructed into complete data. In the OSI communication model, they belong to the transport layer, which is a layer 4 (LAYER).

This TCP uses a retransmission technique in the event of an error or damage to the transmitted data to ensure that no transmission error of data occurs between the first terminal 10 on the sending side and the second terminal 15 on the receiving side. Transport protocol. For example, when the first terminal 10 transmits data, the second terminal 15 receives the error from the second terminal 15 to check whether an error occurs. If an error is not detected in the received data, an ACK signal is returned as an acknowledgment signal. Is detected, the data of the frame or packet is retransmitted so that an error does not occur in the final reassembled data. That is, the TCP protocol is not installed in the equipment on the network path but is installed and configured in each end terminal of the first terminal 10 on the transmitting side and the second terminal 15 on the receiving side.

Data loss between the first terminal 10 and the second terminal 15 is transmitted by the first terminal 10 beyond the processing capacity of the second terminal 15 or the transmission path to the second terminal 15. Occurs when data is transmitted beyond the data transmission processing capacity by each device of the wireless network 90 including the Internet constituting the network, and it is congested to adjust the data transmitted from the first terminal 10 on the transmitting side. It is CONGESTION CONTROL, and the present invention records a congestion control variable value previously used and reuses it in the same wireless environment, so that the present invention can quickly adapt to changes in the data transmission environment.

Among these congestion control variables, the CWND (CONGESTION WINDOW) variable is a value that changes the size of data transmitted in one packet, and the RTT (ROUND TRIP TIME) variable transmits data and confirms normal reception from the other party (ACKNOWLEDGE). The time or response time before the signal is returned. Since the value of the RTT variable changes from time to time, especially in a wireless environment, it is generally expressed in sRTT to distinguish it from the RTTvar representing the VARIANCE value.

Referring to FIG. 2, a congestion control system for vertical handoff in a heterogeneous wireless network will be described with reference to FIG. 2. A computer (PC), a mobile terminal (MOBILE PHONE), a PDA, a portable computer are used to transmit and receive data. (TABLET PC), an end terminal (hereinafter referred to as a terminal) including a data terminal (10, 15) is a position where the radio signal reception signal strength (RSSI) of the 3G mobile communication system base station (BS) 20 is strong In the 3G method to wirelessly connect to the base station 20, wireless access signal strength (RSSI) of the WLAN access point (ACCESS POINT: AP) 70 is wirelessly connected to the AP 70 in a WLAN manner This wireless connection is automatically handled by manual selection or set control commands.

In general, a 3G mobile communication system is suitable for high-speed data transmission using CODE DIVISION MULTIPLE ACCESS (CDMA), and is allocated with a radio frequency of about 1.8 GHz and has a data transmission rate of about 150 Kbps.

Early mobile communication systems began with communication systems that used analog voice signals, and in digitalized mobile communication systems, technology developed to enable data communication at a data rate or bandwidth of 9.6 Kbps or 14.4 Kbps. As a result, 64.4 Kbps data communication is possible, and in the recent 3G method, data communication of 144 to 153 Kbps (described at 153 Kbps transmission rate for convenience of explanation) is enabled. Also referred to as standard CDMA2000 1x system of synchronous mobile communication system.

WLAN (WIRELESS LAN) is based on the international standard "IEEE 802.11-1999," which connects the AP 70 to a wired LAN network and wirelessly connects the mobile terminals 10 and 15 to the Internet. This is how you connect.

The Institute of Electrical and Electronic Engineers (IEEE) 802 standard is a set of LAN connection method and protocol standards developed by the IEEE 802 committee that promotes standardization of computer networks.

The reference model of the IEEE 802 standard protocol is based on the layering concept of the OSI reference model, and mainly standardizes the lower two layers among the seven layers of the OSI model, and the WLAN service conforms to the IEEE 802.11b / g international standard. ISM radio band (unlicensed band) or 5GHz radio band of 2.400 to 2.483 GHz is used, so there is no radio frequency interference with other communication services and a narrow service area or coverage with low output power.

In general, the wireless LAN (WLAN) service of the 2.4 GHz radio band is used locally in indoor and narrow coverage hotspots. Wireless LAN system can be easily interworked with the Internet network and is produced and supplied in the system specification according to international standard, so the device price is low and its use is spread by the advantages such as high speed data transmission, and now it is higher speed data transmission or wider frequency. The IEEE 802.11g specification is discussed for the band. There is also a method using the 2.3 GHz band, the method according to the IEEE 802.11a standard of 54 Mbps transmission rate or bandwidth and the IEEE 802.11n standard of 100 Mbps transmission rate or bandwidth. Hereinafter, the data transmission rate of the WLAN will be described as 54 Mbps for convenience of description.

That is, in the 2.4 GHz frequency band wireless LAN scheme, high-speed data transmission can be performed using the ISM band. For example, the service area is limited to indoors and hotspots due to narrow coverage and frequency interference of several tens of meters, and 2.3. The WLAN system in the GHz frequency band uses a licensed band of portable Internet service, and thus transmits high-speed data while maintaining wider coverage. The hotspot region is, for example, a large bookstore, a fast food store, a coffee shop, an airport, a university, and the like. . Initial coverage was only a few tens of meters in radius, but recently it is possible to reach a radius of 200 meters and is gradually expanding due to technology development.

For example, when the terminals 10 and 15 to transmit data are connected to the 3G base station 20, the terminal 10, 15 is connected to the core network 40 through the base station controller (BSC) 30, AAA (AUTHENTICATION AUTHORIZATION ACCOUNTING) equipment When the service is authenticated by the mobile station, the mobile switching center (MOBILE SWITCHING CENTER: MSC) or the data exchange station (PACKET DATA SERVING NODE: PDSN) is connected to request the switching of the communication path with the other receiving terminal 10, 15, and HA ( Data is transmitted to the receiving terminal (10, 15) that is located through the HOME AGENT. At this time, the other party's receiving terminal (10, 15) is the Internet (60), public communication network (PUBLIC SWITCHING TELEPHONE NETWORK: PSTN) 50, the terminal 10 connected via the AP 70 of the WLAN or through the 3G base station , 15). In the following description of the present invention, for convenience of description, it will be described as terminals 10 and 15 which can be selectively connected to both 3G mobile communication system and WLAN system.

When the transmitting terminal 10, 15 transmits data to the receiving terminal 10, 15, it is confirmed whether it is connected to the base station 20 of the 3G system or the AP 70 of the WLAN system, and confirmed The device transmits data at the data rate or bandwidth by vertical handoff using the access method, and transmits the data to the receiving terminal. In this case, as an example, the transmitting terminal 10, 15 and the receiving terminal 10, 15 are connected through a path including the core network 40 and the base station controller 30.

For example, when the transmitting terminal 10, 15 is connected to the 3G system, it can transmit data at a maximum transmission rate of 153 Kbps, and when the transmitting terminal 10, 15 is connected to the WLAN system, it can transmit data at a maximum 54 Mbps transmission rate.

In addition, when the receiving terminal 10 or 15 is connected to the 3G system, it can receive data at a maximum transmission rate of 153 Kbps, and when it is connected to a WLAN system, it can receive data at a transmission rate of up to 54 Mbps.

Therefore, congestion control occurs when data is transmitted between the transmitting side and the receiving side terminals 10 and 15, and a wider bandwidth or a faster transmission speed at the transmitting side than the data transmission and processing capability of the equipments on the transmitting side and the receiving side path. In case of transmitting more data, a loss of part of the transmitted data occurs (LOSS). To detect this, a transmitter uses a timer and a data acknowledgment signal from the receiver. Receive an ACK (ACKNOWLEDGE) signal. The timer is set for a time longer than the usual time at which the transmitting terminal can transmit data and receive the ACK signal from the receiving terminal. In general, if an ACK signal is not received until the timeout time set in the timer is completed, the data of the corresponding frame or packet is lost.

The terminals 10 and 15 receive or transmit data at a maximum of 153 Kbps when connected to a 3G system, and receive or transmit data at a maximum of 54 Mbps when connected to a WLAN system.

Rather than unilaterally determining the data transmission rate at the sending terminal and sending it, checking the data reception status of the receiving terminal and adjusting the data transmission rate at the sending terminal, that is, congestion control and transmitting the data, causes a data transmission error. Can be sent without occurrence.

The 3G wireless system and the WLAN wireless system are called heterogeneous wireless systems, and the wireless environment between heterogeneous systems is randomly selected by the user because wireless networks of different types are overlapped in one region. It can be selected or automatically selected to determine the wireless network and use the service. This selection is called VERTICAL HAND-OFF, and handoff is made unconditionally to maintain the communication status of the terminal, and vertical handoff is a method that selects a method with a lower communication cost or a higher data transmission quality. In this case, the communication in progress is not interrupted even if the unconditional handoff is not made and fails.

In general, when the TCP protocol has a vertical handoff in such a heterogeneous wireless network environment, the data transmission performance due to the TCP may drop rapidly due to a sudden change in the data transmission band or transmission rate of 153 Kbps and 54 Mbps. In the case of vertical handoff from a 153 Kbps low data transmission network by 3G to a 54 Mbps high data transmission network by WLAN, sudden data throughput in TCP congestion control increases linearly (LINEAR). Since it is impossible to increase, the disadvantage of failing to efficiently use a high data transmission band occurs.

In addition, when a vertical handoff occurs from a 54 Mbps high data rate network using a WLAN scheme to a 153 Kbps low data rate network using a 3G scheme, more data than the data transmission and processing capability on the path with the receiving side occurs. Because of the situation of transmitting the data, congestion (CONGESTION) the network congestion (loss of data) occurs, a problem that adversely affects the transmission of other data in the chain.

When the vertical handoff occurs, the present invention reuses the congestion control variable that was finally used in the previous congestion control process so that the transmitting terminal 10, 15 controls the data rate vertically.

Referring to FIG. 3, a terminal device for congestion control of vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention will be described. The 3G wireless unit 100 wirelessly transmits and receives data by wirelessly connecting to a 3G base station; A WLAN wireless unit 180 for wirelessly transmitting and receiving data by wirelessly connecting to a WLAN type AP; Connect to 3G radio and WLAN radio, detect and analyze received signal strength to determine vertical handoff, transmit data with set CWND value, and control received ACK signal status and RTT variable value as detection record and timer value And a control unit 110 for monitoring; A memory unit 120 for recording the operation and application programs and operation data of the terminal; A timer unit 130 for counting the timeout according to a value set by the controller and control; A keyboard unit 140 for inputting a command signal for operating and controlling the terminal; A display unit 150 for outputting and displaying data transmitted and received with operation information of the terminal; A TCP unit 160 for recording the last-operated variable value of each system, setting by vertical handoff and dividing the transmitted data into packet-sized units by CWND variable values; An IP unit 170 for allocating a receiving side address to a transmitted packet unit is included.

Referring to FIG. 4, the TCP unit 160 of a terminal for congestion control of vertical handoff in a heterogeneous wireless network will be described with reference to FIG. 4. The operation is activated by the vertical handoff notification of the controller 110. A WLAN variable module 161 for updating and recording the variable values of the sRTT, the RTTvar, and the CWND to be provided and managing the last recorded values; A 3G variable module 162 for updating and recording the variable values of sRTT, RTTvar, and CWND that are activated and operated by vertical handoff notification of the controller 110, and manage them as the last recorded values; The controller 110 activates the variable recording module of the vertical handoff system, sets the last updated recorded variable to be applied, provides the calculated and provided sRTT and RTTvar variable values to be updated and recorded, and analyzes the provided ACK signal. If there is no error, the management module 163 provides to update and record the CWND variable value by one predetermined step; A variable setting module 164 for receiving, setting and operating the last recorded variable of the vertical handoff system under the control of the management module 163; And a TCP operation module 165 for dividing and transmitting data into unit sizes determined by variables provided by the variable setting module 164. This is the configuration that is included.

The control unit 110 monitors the 3G radio unit 100 and the WLAN radio unit 180 and performs a vertical handoff to a system having a high signal strength and notifies the TCP unit 160, and is provided from the TCP unit 160. Counting is started by setting the TIMEOUT value of the sRTT and RTTvar variables to the timer unit 130, providing the ACK signal received from the receiving side to the TCP unit 160, and the RTT variable value is calculated using the sRTT and RTTvar variable values. It receives the data in the size of the CWND variable value set by the TCP unit 160 to control and monitor the radio transmission to the receiving side.

The management module 163 analyzes the receiving side ACK provided from the control unit 110, and if it is confirmed that a plurality of times, for example, three times (DUPLICATE) is received, the CWND variable value is an intermediate step value between the initial setting value and the currently set value. If it is notified that the receiving side did not provide the ACK signal during the set TIMEOUT time from the control unit 110, the variable values of sRTT and RTTvar are updated to a predetermined value and updated (UPDATE), and the CWND variable is set. The value is updated to the initial value. The variable includes sRTT, RTTvar and CWND values.

Hereinafter, a congestion control terminal device for vertical handoff in a heterogeneous wireless network will be described in detail with reference to FIGS. 3 and 4.

The controller 110 analyzes the command signal input from the keyboard unit 140 and loads the corresponding program and operation data from the memory unit 120 to enter an operation standby state, and outputs current operation state information to the display unit 150. For the user to confirm.

The controller 110 in the standby state monitors the 3G radio unit 100 and the WLAN radio unit 180 to detect and analyze the strength of each received signal and output the detected signal strength to the display unit 150. In the state in which a command signal for automatically connecting to a system having a large received signal strength is input from the keyboard unit 140, a vertical handoff is automatically performed to connect to the corresponding system. In the state in which the automatic connection command signal is not input, A vertical handoff is performed to connect to the system selected by the manually input command signal.

The controller 110 notifies the TCP 160 of the vertical handoff situation, the TCP 160 is notified by the management module 163, and the management module 163 is a variable module of the handoff system. For example, in the case of vertical handoff to the WLAN system, the CWND, sRTT, and RTTvar variable values recorded in the WLAN variable module 161 are read and recorded in the variable setting module 164, and the variable setting module 164 is set. The TCP operation module 165 is controlled to set the data size in packet units by the CWND variable value. In addition, the management module 163 provides variable information of sRTT and RTTvar recorded in the variable setting module to the control unit, and the control unit sets the determined TIMEOUT time value to the timer unit 130.

When it is confirmed by the controller 110 that a command signal for transmitting a large amount of data from the keyboard unit 140 to the designated counterpart is input, the controller 110 divides the data into the CWND variable value that was used by providing the data to be transmitted to the TCP unit 160. Packet unit, and provide the packet unit data thus configured to the IP unit 170 to allocate the address of the designated receiver side, and to the WLAN radio unit 180 to wirelessly transmit to the designated counterpart The control unit 130 controls the set TIMEOUT time.

The controller 110 monitors the WLAN radio unit 180 and checks whether an ACK signal, which is an acknowledgment signal of receiving the packet data transmitted from the counterpart receiver, is returned. If the ACK signal is returned before being timed out from the other party's receiver, the number of reply of the ACK signal is checked and the timer unit 130 is controlled to check the RTT (ROUND TRIP TIME) time required from data transmission to reply and sRTT. , The RTTvar variable value is calculated and updated and recorded in the TCP unit 160.

When the ACK signal is returned from the counterpart once, it means that the transmitted packet unit data is well transmitted without error, and if it is returned 3 times, it means that some of the transmitted packet unit data has been lost or error has occurred. If the ACK signal is not returned until the TIMEOUT count is completed, it means that a loss has occurred in all the transmitted packet unit data.

For example, if it is determined by the controller 110 that the ACK signal is returned once, it is determined that the current wireless environment, the equipment on the path, and the data processing capability of the receiving side are relatively good, and thus, the TCP unit 160 is controlled to control the CWND variable. Increase the value by one level. That is, the data size of the packet unit to be transmitted in the next order is adjusted to send as much as the predetermined size. In addition, the TCP unit 160 is controlled to update the sRTT and RTTvar variable values by one step down (UPDATE), and the timer unit 130 records the TIMEOUT time counted in the following order by the RTT variable value calculation. Set to reduce by a predetermined size.

As another example, when it is confirmed by the control unit 110 that the ACK signal is returned a plurality of times, that is, three times, it is an indication that a part of the data received at the receiving side is lost but recoverable, so that the equipment in the surrounding wireless environment and path And a slight problem in the data processing capability of the receiving side. The controller 110 controls the TCP 160 to select the CWND variable value as an intermediate value between the current value and the initial value so that the downward value is updated and recorded. It is reduced by a predetermined size. In addition, in the case of the sRTT and RTTvar variable values, the intermediate value between the present value and the initial value is selected so that the upward value is updated and recorded, thereby increasing the TIMEOUT time counted in the following order by a predetermined size.

In addition, when the ACK signal is not returned until the control unit 110 completes the counting of the TIMEOUT time set in the timer unit 130, the CWND recorded in the WLAN variable module 161 by controlling the TCP unit 160. Updates and records the congestion control variable values of sRTT and RTTvar to initial values and retransmits the corresponding packet unit data.

Referring to the data radio reception state of the terminals 10 and 15, the control unit 110 monitors the 3G radio unit 100 and the WLAN radio unit 180 in the standby state to confirm the signal strength and signal by automatic or manual. When the vertical handoff to the system with strong strength and notifying the vertical handoff state to the TCP unit 160, the TCP unit 160 reads the last recorded variable value from the corresponding variable module and sets the operating state. Data can be transmitted and received through the connected system.

The controller 110 checks whether data is received from the other party through the connected system, and if the data is received, analyzes the received packet unit data to determine whether an error has occurred.

If it is confirmed by the control unit 110 that no error occurs in the received packet unit data, the controller returns an ACK signal once to the sender, and if it is confirmed that a recoverable error has occurred in the received packet unit data, the ACK signal is set to a large number. Reply 3 times as many times as an example. In the case where a recoverable error occurs, the number of replies of the ACK signal may be specified a plurality of times, such as two, three or four or more times. However, the present invention will be described by designating three times as an example for convenience of description. In addition, if an unrecoverable error is detected or confirmed not to be received, an ACK signal is not returned.

In other words, if an error-free data is received normally, an ACK signal is returned once, and if a recoverable error is detected from the received packet unit data, the ACK signal is repeated three times, and an unrecoverable error is detected or data is returned. If not received, no ACK signal is returned. Therefore, the reception side adjusts the congestion control variable value on the transmission side.

Referring to FIG. 5, a method of transmitting a congestion control terminal device data of vertical handoff in a heterogeneous wireless network will be described with reference to FIG. 5. The terminal device includes a 3G radio unit, a WLAN radio unit, a TCP unit, and a controller. A method of operating a data transmission, the method comprising: setting a last recorded variable value when starting from a vertical handoff by a controller to start counting a timer and transmitting data as a CWND value; Setting and recording the CWND value up one step and setting the sRTT and RTTvar to the predetermined down step value and setting the timer when the ACK signal is returned from the counterpart; If data transmission is completed, storing and managing the last recorded variable value in a variable module of a corresponding system; It is configured to include.

Referring to FIG. 6, a method of returning a congestion control terminal device for vertical handoff in a heterogeneous wireless network according to an embodiment of the present invention will be described. Data of a terminal device including a 3G radio unit, a WLAN radio unit, a TCP unit, and a controller In the reception operation method, if it is confirmed by the vertical handoff by the control unit to set the last recorded variable value and confirming whether the data is received; If the data is received and confirmed that there is no error, returning the ACK signal a set number of times; if a recoverable error is included, returning the ACK signal a plurality of times or more; Terminating if the received data is found to be unrecoverable or not received; It is configured to include.

Hereinafter, a congestion control terminal device data transmission method of vertical handoff in a heterogeneous wireless network will be described in detail with reference to the accompanying drawings, wherein the 3G radio is controlled by the controller 110 of the terminals 10 and 15. The unit monitors the WLAN unit and the WLAN radio unit, and determines whether to vertically handoff by a manual control or an automatic control command signal (S100). That is, the control unit analyzes the command signal input from the keyboard unit and checks whether the vertical handoff is set to be automatically performed by the received signal strength analysis of each system or by manual selection. By hand or automatically vertical to the selected system.

If it is determined that the vertical handoff is in progress, the controller controls the TCP unit and reads the congestion control variables CWND, sRTT, and RTTvar values recorded as the last operation in the system connected to the vertical handoff and resets the operation state (S110). ). At this time, if the congestion control variable is not recorded as the last operated value, it is set and operated as the initial value.

If it is confirmed by the control unit to analyze the command signal input from the keyboard unit and transmit a large amount of data to the specified counterpart (S120), the data is configured in a packet unit of the size according to the set CWND variable value and transmitted to the designated counterpart ( In step S130, the timer unit is controlled to start counting the set TIMEOUT time (S140).

After receiving the data transmitted from the other party and confirming whether to return the ACK signal, which is a response signal, and confirming that the ACK signal is returned one time, the set number of times (S150), the controller controls the TCP unit to set the CWND value one step higher. Since the data is set to send more data of a predetermined size (S160), since the sRTT and RTTvar are recorded one step down and calculated and set to the timer unit, the TIMEOUT time is shortened by a predetermined size (S170).

The control unit checks whether the transmission of the corresponding data is completed to the other party, and if the data transmission is not completed, returns to the transmission process (S120). If transmission is completed, the CWND, sRTT, and RTTvar variables, which are the last recorded congestion control variables, are transmitted. The value is stored and managed in the allocated area and the process proceeds to the end (S190).

In the setting process, if it is confirmed by the control unit that the ACK signal is returned more than the set number of times, for example, three times (S200), the current CWND value and the initial value are set to the calculated intermediate value and updated and recorded. S210), the currently set sRTT and RTTvar variable values and initial values are upwardly set to the calculated intermediate values and updated and recorded (S220), and the process proceeds to the management process (S180).

In other words, if the ACK signal is returned more than the set number of times, a recoverable error is detected in the data received at the receiving side. Therefore, the CWND variable value at the transmitting side is set downward to reduce the size of data configured in packet units. The transmission rate is lowered by a predetermined size, or the downward setting for reducing the data transmission bandwidth is set, and the upward setting for increasing the time required for data transmission is performed.

In addition, if it is determined that the ACK signal is not returned from the receiver until the count of the set TIMEOUT time is completed (S230), the controller receives unrecoverable data or no data at all. The CWND, sRTT, and RTTvar values, which are congestion control variables, are updated, set, and recorded to initial values, and are fed back to the transmission process S120 to retransmit the corresponding packet unit data.

For example, when expressed by the TCP algorithm of the transmitting terminal as described above, it can be expressed as follows.

That is, when the transmitting terminal receives an ACK signal indicating that the receiving terminal has received the error without error after transmitting the data, the transmitting terminal increases the data transmission rate by a predetermined size and updates the congestion control variable value by reducing the allocated time by the predetermined size. When receiving the repeated ACK signal indicating that a recoverable error has been detected from the receiver, updating and setting the current congestion control variable value as an intermediate value from the initial value, setting and recording, and acknowledging during the TIMEOUT time set in the timer unit. If no signal is returned, the congestion control variable value is updated and set to the initial value and operated at the lowest data rate and the maximum transfer time.

In addition, referring to the accompanying drawings, a method of returning a congestion control terminal apparatus for vertical handoff in a heterogeneous wireless network will be described in detail. The 3G radio unit is controlled by the controller 110 of the terminals 10 and 15. The WLAN wireless unit monitors and checks whether to vertically handoff by manual control or automatic control command signal (S300). If it is confirmed that the vertical handoff is in progress, the controller controls the TCP unit and reads the congestion control variables CWND, sRTT, and RTTvar values recorded as the last operation in the system connected to the vertical handoff, and sets them back to the operational state (S310). ). At this time, if the congestion control variable is not recorded as the last operated value, it is set and operated at a predetermined initial value.

The controller checks whether data is received from the system connected by the vertical handoff (S320), and if it is determined that the data is received, analyzes the received data and checks whether it is received without error (S330).

When it is confirmed that there is no error in the received data, the ACK signal is returned to the transmitting terminal once, which is a set number of times (S340), and when it is confirmed that there is an error in the received data, it is checked whether it is a recoverable error (S350), If it is determined that the error is recoverable, the ACK signal is returned more than the number of times set by the transmitting side. For example, the ACK signal is repeated three times (S360). If it is confirmed as an unrecoverable error, the process proceeds to the end without returning the ACK signal. S370).

For example, when expressed by the TCP algorithm of the receiving terminal as described above, it can be expressed as follows.

That is, the terminal receiving the data returns an ACK signal to the sender once when there is no error in the received data, and returns a plurality of ACK signals when a recoverable error is included. If an impossible error is included, no ACK signal is returned.

Therefore, the present invention having the above configuration has the advantage of efficiently using the allocated bandwidth that adapts quickly to a given wireless environment because the terminal reuses the congestion control variable value last used in the corresponding wireless environment when it is vertically handed off. have.

In addition, the receiving terminal analyzes an error occurrence state in the received data and returns the error-free state, a recoverable error, and an unrecoverable error. Therefore, the receiving terminal facilitates congestion control to reduce the data transmission error to a minimum. There is this.

Although the present invention has been described as an example, the present invention is not necessarily limited to this example, and various modifications can be made without departing from the spirit of the present invention. Therefore, one example disclosed in the present invention is not intended to limit the technical spirit of the present invention but to explain, and the scope of the technical spirit of the present invention is not limited by the one example. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

According to the present invention having the above-described configuration, when the transmitting terminal selects vertical handoff in the wireless region of the 3G system and the wireless region of the WLAN system, for example, it rapidly adapts to a given wireless environment and transmits data, thereby increasing the efficiency of the system. There is an industrial use effect.

In addition, the present invention having the configuration described above has a convenient effect in that the receiving terminal analyzes the received data and returns an error occurrence status to the transmitting side, thereby facilitating congestion control at the transmitting side.

Claims (18)

In the terminal device including a 3G radio unit, WLAN radio unit, TCP unit, control unit, Determining and analyzing the received signal strength of the 3G radio and the WLAN radio to determine the vertical handoff, transmit data with the CWND value set at the receiver, detect and record the ACK signal state and the RTT variable value received from the receiver, A control unit for controlling and monitoring the setting value to a timer; A TCP unit configured to set the last recorded variable of the vertical handoff system under the control of the control unit, to transmit the data by TCP processing the CWND variable value, and to record and manage the last time value at which the ACK signal is received from the receiving side; And A timer unit configured to update a time value under the control of the controller to count TIMEOUT; Congestion control terminal of the vertical handoff in a heterogeneous wireless network comprising a. The method of claim 1, wherein the control unit, The 3G radio unit and the WLAN radio unit monitor and vertically handoff to a system having a high signal strength, notify the TCP unit, and set the TIMEOUT value calculated from the sRTT and RTTvar variables provided from the TCP unit to the timer unit to start counting. The ACK signal received from the receiver is provided to the TCP unit, and the RTT variable value is calculated and provided as the sRTT and RTTvar variable values, and the data is received at the size of the CWND variable value set by the TCP unit. Congestion control terminal device of the vertical handoff in a heterogeneous wireless network, characterized in that configured to control and monitor the transmission. The method of claim 1, wherein the TCP unit, A WLAN variable module which updates and records the sRTT, RTTvar, and CWND variable values activated and operated by vertical handoff notification of the controller, and manages them as the last recorded values; A 3G variable module for updating and recording the sRTT, RTTvar, and CWND variable values activated and operated by vertical handoff notification of the controller, and managing them as the last recorded values; If the control unit is activated by the vertical handoff notification and it is confirmed that a plurality of received by analyzing the receiving side ACK provided from the control unit calculates and sets the CWND variable value as the intermediate step value between the initial setting value and the currently set value, and If there is a notification that the receiving side has not provided the ACK signal during the set TIMEOUT time, the control unit updates the variable values of sRTT and RTTvar to a predetermined one step larger (UPDATE) and the CWND variable value is updated and recorded to the initial value. module; A variable setting module for receiving, setting and operating the last recorded variable of the vertical handoff system under the control of the management module; And A TCP operation module for dividing and transmitting data into unit sizes determined by variables provided by the variable setting module; Congestion control terminal of the vertical handoff in a heterogeneous wireless network, characterized in that consisting of the configuration. The method of claim 1, A 3G radio unit connected to the control unit and wirelessly transmitting and receiving data in a 3G manner; A WLAN radio unit connected to the controller and wirelessly transmitting and receiving data in a WLAN manner; A memory unit for recording an operation program and data under control of the controller; An IP unit for generating and analyzing a destination address of data transmitted and received by the controller through the Internet; A keyboard unit directly connected to the controller and directly inputting a command signal for operation and control; And A display unit which displays operation state information and data information transmitted / received by the control unit; Congestion control terminal of the vertical handoff in a heterogeneous wireless network further comprises. The method of claim 3, wherein In the heterogeneous wireless network, the management module is configured to set a CWND variable value as an intermediate step value between an initial setting value and a currently set value when it is confirmed that a plurality of repetitions are received by analyzing a receiving side ACK provided from the control unit. Congestion control terminal of vertical handoff. The method according to claim 3 or 5, The management module updates and records the variable values of the sRTT and the RTTvar to a larger value by one step and the CWND variable value is updated to the initial value when a notification that the receiving side has not provided the ACK signal for the set TIMEOUT time from the controller. Congestion control terminal device of the vertical handoff in a heterogeneous wireless network, characterized in that consisting of. delete In the data transmission operation method of the terminal device including a 3G radio unit, WLAN radio unit, TCP unit, control unit, If it is determined by the controller to be a vertical handoff, starting the counting of a timer by setting the last recorded value of the variable and transmitting data with a CWND value set in the counterpart; Setting and recording sRTT and RTTvar to a predetermined one step down value and setting the timer to a predetermined one step down value when the ACK signal is returned from the counterpart receiving the transmitted data. And Checking whether the transmission of the data is completed, and if the transmission is completed, storing and managing the last recorded variable value in a variable module of the corresponding system; Congestion control terminal device operating method of vertical handoff in a heterogeneous wireless network included. The method of claim 8, If it is confirmed that the ACK signal is continuously returned more than the set number of times in the setting process, the CWND value is set downward to the middle value of the currently set value, and the sRTT and RTTvar are upwardly recorded to the calculated intermediate value and the timer value An error process of calculating and setting with; An initial process of setting and updating sRTT, RTTvar, and CWND variable values to initial values when it is determined that the ACK signal is not returned during the TIMEOUT time; It further includes a congestion control terminal operation method of the vertical handoff in heterogeneous wireless network. The method of claim 8 or 9, wherein the transmission process, Confirming whether the vertical handoff is performed by the controller; Setting the sRTT, RTTvar, and CWND variable values last recorded in the previous process to be applied when it is determined that the vertical handoff is performed; Setting a TIMEOUT value of a timer with a calculated value of the applied sRTT and RTTvar variable and starting counting; And Dividing and transmitting data in units of the applied CWND value; Congestion control terminal device operating method of the vertical handoff in a heterogeneous wireless network comprising a. The method of claim 8 or 9, wherein the setting process, Confirming, by the controller, whether an ACK signal is returned from a receiving side; If the ACK signal is returned, setting and recording the current CWND value by one step upward; And Recording and setting the sRTT and RTTvar variable values by one step and setting them in a timer; Congestion control terminal device operating method of the vertical handoff in a heterogeneous wireless network comprising a. The method of claim 9, wherein the error process, Confirming, by the controller, whether a plurality of ACK signals are returned from a receiving side; If a plurality of ACK signals are returned, setting the current value and initial value of CWND to a calculated intermediate value and updating and writing the result to a corresponding variable module; Setting the current value and the initial value of the sRTT and the RTTvar recorded in the corresponding variable module upward to the calculated intermediate value, updating and recording, and setting the timer; Congestion control terminal device operating method of the vertical handoff in a heterogeneous wireless network comprising a. The method of claim 12, And a plurality of ACK signals are returned more than a predetermined number of times, the method of operating a congestion control terminal of vertical handoff in a heterogeneous wireless network. In the terminal device including a 3G radio unit, WLAN radio unit, TCP unit, control unit, Detects and analyzes the received signal strength of the 3G radio unit and the WLAN radio unit to determine the vertical handoff, and analyzes the signal transmitted by the transmitter to return a set number of times of the ACK signal if received without error. A control unit which repeatedly returns a plurality of signals over a set number of times and does not return an ACK signal if it cannot recover; A TCP unit configured to set the last recorded congestion control variable value of the system which is vertically handed off under the control of the controller, combine the received data into TCP processing, and record and update the updated variable value; And A timer unit configured to update a time value under the control of the controller and to count TIMEOUT; Congestion control terminal of the vertical handoff in a heterogeneous wireless network comprising a. The method of claim 14, wherein the TCP unit, And separately recording and managing the congestion control variable values set in the environment where the 3G radio unit and the WLAN radio unit respectively connect, and reuse the last recorded congestion control variable values in the vertical handoff state. Congestion control terminal of vertical handoff in heterogeneous wireless network. The method of claim 14, The set number of times is a one time and the number of times the number of repetition is a congestion control terminal device of the vertical handoff in heterogeneous wireless network, characterized in that the configuration. In the data receiving operation method of the terminal device including a 3G radio unit, WLAN radio unit, TCP unit, control unit, A reception step of confirming whether or not data is received by setting the last recorded value of the corresponding variable when the controller determines the vertical handoff; Returning an ACK signal a set number of times when the data is received and confirming that there is no error, and returning a plurality of ACK signals more than the set number of times when it is determined that a recoverable error is included; And Terminating if the received data is found to be unrecoverable; Congestion control terminal device operating method of vertical handoff in a heterogeneous wireless network included. The method of claim 17, wherein the reply process, Analyzing the received data by the controller and confirming that the received data is received without errors; If there is no error in the received data, returning a set number of times of an ACK signal to a transmitter; And If there is a recoverable error in the received data, returning a plurality of ACK signals to the sender more than a set number of times; Congestion control terminal device operating method of the vertical handoff in a heterogeneous wireless network comprising a.

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