KR20030013757A - System for supporting handoff/roaming in the short distance radio network based on bluetooth - Google Patents

Abstract

PURPOSE: A system for supporting a hand-off/roaming in a local area wireless network based on a Bluetooth is provided to expand a service area in the local area wireless communication network using a Bluetooth technique. CONSTITUTION: A BlueWIN-AP(Bluetooth Wireless Indoor Network-Access Point) performs a LAN(Local Area Network) connection of a BlueWIN-DT(Data Terminal), and performs a proxy function for informing information such as a Bluetooth device address and a clock offset of the BlueWIN-DT to a BlueWIN-RA(Roaming Agent), receiving a command of the BlueWIN-RA, setting up a connection, and relaying a PPP(Point-to-Point Protocol) diagram. The BlueWIN-RA performs a PPP server function for processing PPP connection with the BlueWIN-DT in a sub-network composed as NAPs(Network Access Points). After a hand-off is completed, the BlueWIN-RA recovers the PPP connection through a tunnel end point redirection so that a conventional PPP connection state is maintained during the hand-off/roaming irrespective of disconnection with a Bluetooth link.

Description

SYSTEM FOR SUPPORTING HANDOFF / ROAMING IN THE SHORT DISTANCE RADIO NETWORK BASED ON BLUETOOTH}

The present invention relates to a short range wireless communication network based on Bluetooth technology, and more particularly, to a system supporting handoff / roaming for expanding a service area in a short range wireless communication network using such a Bluetooth technology.

Bluetooth, one of short-range wireless data communication standards such as Infrared Data Association (IrDA), Wireless LAN (IEEE 802.11), and Shared Wireless Access Protocol (SWAP), uses radio frequency without the need for physical cables for communication between various electronic devices. As a communication standard that can exchange data at high speed, Ericsson, Nokia, IBM, Toshiba, and Intel will be the center members and formed a consortium called Bluetooth Special Interest Group (SIG) in May 1998. The "Bluetooth Spec. 1.0" standard was specified in the first forum held in the UK. Bluetooth 1.0 has a data transfer rate of 1 Mbps and a transmission distance of 10 to 100m, and the number of member companies has increased to 1,900 in just over a year. This Bluetooth technology uses frequency hopping spread spectrum technology that sets 79 channels with 1MHz bandwidth in the 2.4GHz band and changes the channel 1600 times per second, so it can transmit / receive radio waves to notebook computers, mobile phones, PDAs, digital cameras, printers, and MP3s. Due to the advantages of being able to connect wirelessly to players, home network devices, etc., stable data exchange, and low cost / low power, its adoption and use are expected to increase. However, compared to the IEEE 802.11b wireless LAN, which is another short-range wireless technology using the 2.4 GHz band like Bluetooth, the transmission distance is about 10 m and the wireless device has a distance restriction of up to 100 m even when using an output amplifier. In order to guarantee user mobility and usage area comparable to a LAN, it is necessary to expand service area through handoff / roaming as in a broadband wireless communication network. However, Bluetooth, which was created with the wires of a portable device removed or with a PAN (Personal Area Network) in mind, is currently spec. Until 1.1 handoff / roaming is not handled.

Therefore, while the present invention accommodates the Bluetooth specification standardized by the Bluetooth SIG and IEEE 802.15, it eliminates the problem of use occurring during the frequent inquiry / connection process of the universal Bluetooth user equipment, and also uses one of the weak points of Bluetooth. This is to solve the distance constraint by extending the service area through the handoff / roaming support method of the present invention.

1 is a diagram illustrating a system for supporting handoff / roaming with a Bluetooth-based short range wireless network of the present invention.

2 illustrates PPP termination in a roaming agent.

3 shows an initial connection setup.

4 shows the measurement of a clock offset.

5 shows pre-paging.

6 illustrates a RSSI based link loss detection and handover mechanism.

7 illustrates a link watchdog timer based link loss detection and handover mechanism.

<Description of Main Abbreviations of the Present Invention>

AP: access point

RA: Roaming Agent

BlueWIN ^TM: Bluetooth wireless indoor network (Bluetooth Wireless IndoorNetwork)

BlueWIN-AP: BlueWIN Access Point

BlueWIN-RA: BlueWIN Roaming Agent

DT: Data Terminal

LAP: Lan Access Profile

NAP: Network Access Point

NAT: Network Address Translation

In order to achieve the object of the present invention, the present invention provides a system for supporting handoff / roaming on a Bluetooth-based short-range wireless network,

BlueWIN-AP, a network access point (NAP) for LAN connection of Bluetooth user devices, and BlueWIN-DT with Bluetooth client application software for handoff / roaming support. And a BlueWin-Roaming Agent (BlueWIN-RA) that manages handoff / roaming support and all Bluetooth devices in the service area on a wired backbone, wherein the BlueWIN-Network Access Point (BlueWIN-AP) The win-data terminal makes a LAN connection, and information such as a Bluetooth device address (BD＿ADDR, Bluetooth Device Address) and a clock offset (clock＿offset) of the data terminal is transmitted to the roaming agent between the blue win-roaming agent and the data terminal. Relays and PPP diagrams, such as setting up connections and receiving commands from roaming agents. When acting as a proxy, the BlueWIN-Roaming Agent (BlueWIN-RA) serves as a PPP server that handles PPP connections with data terminals in a subnetwork composed of network access points when supporting handoff / roaming. After the handoff is completed, the PPP connection is restored through tunnel end point redirection, so that the existing PPP connection state is maintained even during handoff / roaming regardless of disconnection of the Bluetooth link. do.

In addition, the present invention is to perform packet buffering for each PPP session in consideration of the time delay and transmission rate caused by the handoff when changing the tunnel endpoint direction in order to eliminate the packet loss and increase the efficiency of packet delivery. It is characterized by.

In addition, the present invention is characterized by processing commands and events using the Blue Win protocol such as Table 1 and Table 2 attached between the Blue Win access point and the roaming agent.

In addition, the present invention is the information of the clock offset between the data terminal (DT) and the newly connected access point (AP2) for determining the paging / access time between the data terminal and the Blue Win access point (AP), the data The clock offset between the terminal and the existing connected access point AP1 and the clock offset between the AP1 and AP2 stored in the roaming agent through an inquiry between the access points in advance are used. It is characterized by the relative clock offset.

In addition, in the present invention, the BlueWin access point (AP) includes two Bluetooth modules (first Bluetooth module and second Bluetooth module), the first Bluetooth module is used for general data communication, the second Bluetooth module It is used to pre-page to determine the position of the data terminal closer to the AP, characterized by reducing the handoff time.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings of FIGS. 1 to 7.

1 is a diagram illustrating a basic configuration of a system for supporting handoff / roaming on a Bluetooth-based short range wireless network according to the present invention. As shown in the figure, the basic configuration of the system according to the present invention is a Bluetooth access point (BlueWIN-AP), which is a network access point (NAP) for LAN connection of a Bluetooth user device, and a Bluetooth client application for handoff / roaming support. BlueWIN data terminal (BlueWIN-DT), a data terminal equipped with software, and BlueWIN-RA, a roaming agent that manages all Bluetooth devices in the service area and handoff / roaming support on the wired backbone. Is done.

The BlueWin AP of the present invention includes two Bluetooth modules, wherein the first Bluetooth module enables the data terminal DT to make a LAN connection. The secondary Bluetooth module is used for pre-paging for locating a data terminal closer to an access point (AP). The description of the pre-paging will be described below with reference to FIG. do). In addition, the BlueWin access point is located between the data terminal and the roaming agent (RA) to inform the roaming agent of information such as BD_ADDR, clock_offset of the data terminal, and establishes a connection by receiving a command from the roaming agent. It acts as a relay.

The BlueWin Roaming agent of the present invention serves as a PPP server that handles PPP connections with data terminals in a subnetwork consisting of network access points (NAPs). Tunneling sends the data from the Internet to the appropriate NAP. When the data terminal moves to another NAP, it buffers the IP packets and redirects them to the moved NAP. It also stores and manages information (status, location, BD_ADDR, clock_offset) of data terminals in the subnetwork. It manages handovers and issues NAPs to the appropriate commands. For example, if a data terminal connected to one NAP is far away, the data terminal is located by issuing a command to pre-page the NAPs in the vicinity thereof. If it is disconnected, the NAP close to the data terminal is determined, and an instruction is made to access the NAP. In addition, a data terminal having a fixed IP also serves as a foreign agent in mobile IP.

The BlueWin DT of the present invention uses a PPP-compliant Serial Cable Emulation Protocol (RFCOMM) model defined in the Bluetooth LAN Access Profile (LAP). If you use dynamic IP, you can use the IP assigned by the PPP server. If you use static IP, you can use mobile IP.

In addition, BlueWin data terminals have some additional functionality to support handover. That is, when the connection is disconnected during the handover, the PPP session must be maintained until the end of the handover, and the continuous page scan mode is used to accept the connection request from the new AP. It has a function to enter (continuous page scan mode). A data terminal that satisfies these conditions may be referred to as a blue win data terminal.

Bluetooth Spec. In the case of LAP, the standard of network connection in 1.1, network connection is made through PPP on RFCOMM, a serial communication emulation layer in Bluetooth, so every time a user changes the connection from the current NAP to another NAP as the user moves. In addition to performing the inquiry / access process, a new PPP connection must be attempted. In this case, all the information related to the existing connection is lost due to the new PPP connection in addition to the time required for inquiry / connection. That is, in addition to the time delay caused by handoff, packet loss due to disconnection of the PPP connection is accompanied.

Therefore, regardless of disconnection of the Bluetooth link, the existing PPP connection should be maintained even during handoff / roaming. To this end, the BlueWIN access point of the present invention (BlueWIN-AP) is designed to operate in a dual mode (dual mode) is divided into a case of supporting a universal LAP (Lan Access Profile) and the case of handoff / roaming. That is, when the blue win access point of the present invention does not use a roaming agent, it operates as a universal network access point (NAP) having a PPP server and a network address translation (NAT), and supports handoff / roaming. In PAP server, the PPP server is located on the roaming agent, not the NAP, and the NAP managed by the roaming agent serves only as a proxy for relaying the PPP diagram through tunneling as shown in FIG. 2. Accordingly, the PPP connection on the roaming agent becomes valid even when the NAP handoff of the user equipment is performed, and the roaming agent recovers the PPP connection through tunnel end point redirection after the handoff is completed.

In addition, the roaming agent performs packet buffering in consideration of the time delay and transmission speed that occur due to handoff when changing the tunnel endpoint direction in order to increase the packet loss and packet transmission efficiency. From the point of view of the user device, the PPP service is not detected by the roaming agent, not by the NAP to which the connection is made.

3 shows an initial connection setup according to the invention.

A data terminal that wants to access the network basically makes an initial connection according to the LAP (Lan Access Profile). That is, the data terminal makes an inquiry and page to the network, and uses a master / slave switch to make a piconet called a Bluetooth network, which is composed of a master and a slave device corresponding thereto. piconet) is entered as a slave whose AP is the master.

After the connection is completed, the AP determines whether the data terminal DT is a blue win data terminal or a general data terminal. In this case, when the data terminal is a Blue Win data terminal, when the connection is disconnected, the data terminal enters the R0 page scan mode. The time bw_pagescan_to is determined.

4 shows the measurement of the clock offset according to the invention.

When a data terminal connected to one AP (AP1) is disconnected from an existing AP and connected to a new AP (AP2), in order to paging AP2, a clock offset (clock_offset) between the data terminal and AP2 is required. I need information.

In order to obtain this, the Bluetooth module of the AP has a clock offset between the AP1 and AP2 stored in the roaming agent through a clock offset between the AP1 and AP1 previously connected. The relative clock offset can be calculated.

Of course, the clock offset is also obtained through inquiry between two Bluetooth modules in one AP. Since the data communication cannot be performed during the inquiry, the second Bluetooth module is used. In order to be able to obtain information of distant APs, it is necessary to increase the transmission strength of the inquiry response packet of the Bluetooth module to the class 1 level.

In fact, since the top 5 bits (1.28 sec resolution) of the 15 bits of the clock offset value are used for the page, even when considering the clock drift, the clock offset value calculated once does not need to be updated for a very long time. none.

5 shows a pre-paging according to the present invention.

The NAP of the present invention for handoff / roaming support has two Bluetooth modules. The first Bluetooth module is used for general data communication, while the second Bluetooth module is used for pre-paging.

In case of pre-paging, when the radio signal strength indication (RSSI) value of the data terminal connected to the AP falls below a predetermined value (PrePage_th), adjacent APs page the data terminal to determine the relative position of the data terminal in advance. To make it possible. If adjacent APs simultaneously page the same data terminal, the interference can be large, and is adjusted by the roaming agent to pre-page sequentially. Among the HCI commands, there are no commands that execute only pages, but the HCI_remote_name_request may be used to effectively perform pre-pages.

The time it takes for the AP to pre-page one data terminal depends on the page_scan_repetition mode of the data terminal. That is, the time to be paged with a certain probability is determined between 0 and 1.28 seconds in the R1 mode, and may take up to 2.56 seconds in the R2 mode. In order to perform efficient pre-page, it is necessary to reduce page_scan_interval by adjusting page_scan_activity of data terminal by using HCI_write_page_scan_activity command. have.

6 is a diagram illustrating a link loss detection and handover mechanism based on radio signal size indication (RSSI).

When the wireless signal size measurement value read from the AP AP1 connected to the data terminal DT becomes lower than a predetermined value Link_lost_th, the AP forces the data terminal by using an HCI_disconnect_command. Disconnect from At this time, if the connection is disconnected due to authentication failure or the like by using Low Resource (0x14) as the reason code, which is one of the arguments of the HCI_Disruption_Command (In this case, User Ended Connection? 0x13- ). The disconnected data terminal enters the R0 page scan mode and performs a continuous page scan. The roaming agent then uses the information obtained from the pre-page to issue a command to connect to one of the neighboring APs (AP2) (BW_HANDOVER_COMMAND). In this case, the connection is performed using the first Bluetooth module instead of the second Bluetooth module. While the connection is made, AP1 cannot communicate with existing data terminals, but if the data terminal is in the R0 page scan mode, it responds in the first page train (10ms). The time is very short.

If there is no pre-page information or the AP2 selected by the pre-page fails to connect, the roaming agent instructs other APs around AP1 to sequentially find and connect to the data terminal.

7 illustrates a link watchdog timer based link loss detection and handover mechanism.

If it is difficult to use the radio signal strength indication (RSSI), handover cannot be performed by the pre-page method described above. In this case, the link watchdog timer should be used to detect link loss. The default value of the link monitoring timeout is 20 seconds. However, after the connection between the data terminal and AP1 is made, change this value shortly (about 1 second) using the HCI_write_link_supervision_timeout command. Over time delay can be reduced. When using the link watchdog timer, when the timer expires, the data terminal and AP1 receive an HCI_disconnect_complete event (reason code: Connection timeout 0x08). The data terminal then enters the R0 page scan mode, and AP1 notifies the roaming agent of the disconnection. Since the roaming agent cannot use the pre-page information, the roaming agent instructs APs near AP1 to try to connect to the data terminal sequentially.

In this case, the link monitoring timeout should be shortened, which may limit the number of slaves that can enter the park mode.

In both of the above methods, it is assumed that the data terminal operates in the R0 page scan mode after disconnection occurs. The BlueWin data terminal is configured to perform a continuous page scan for a certain amount of time (bw_page_scan_timeout: default is 2.56 seconds) after disconnecting.

On the other hand, if the data terminal does not work because it is not a BlueWin terminal (check with the AP after initial connection setup), the page for making a new connection can take a long time. In addition, if the pre-page information is not available or the pre-page information is inaccurate, the interrupt time of the existing connection due to the page may be very long because several APs must page. In such a case, before the first module pages, the second module pages, checks that the second module enters its area, and connects using the first module to minimize the interrupt time.

To prevent the connection between the data terminal and the AP being disconnected during the handover during the movement of the data terminal, the ppp session is maintained and the RFCOMM connection only needs to be reconnected after the data terminal is connected to the new AP. In the present invention, for this purpose, Bluewin data terminal software exists between RFCOMM and PPP of the data terminal to maintain a PPP session.

In addition, the delay can be very large due to packet loss due to handover, so the roaming agent stores a buffer for each session to store incoming packets during the disconnection time and transmit them after handover to minimize the delay. Do it. At this time, the size of the buffer is determined by the transfer rate x handover time.

For the BlueWin handover described above, the BlueWin protocol is defined between the AP and the roaming agent. The BlueWin protocol can be divided into roaming agent-to-AP commands (BlueWin commands) and AP-to-roaming agent events (BlueWin events), which are delivered as XML data for extensibility.

In addition, the commands and events for determining whether the data terminal supports the Blue Win service extension between the AP and the data terminal are defined in Tables 1 and 2 below.

BlueWin commands BW Command type Arguments Direction Return event BW_READ_DT_TYPE_COMMAND AP-> DT BW_TYPE_EVENT BW_READ_CLOCK_OFFSET_COMMAND Agent-> AP BW_AP_CLOCK_OFFSET_EVENT BW_PREPAGE_COMMAND DTBD_ADDR, clock offset Agent-> AP BW_PREPAGE_SUCCESS_EVENT, BW_PREPAGE_FAIL_EVENT BW_HANDOVER_COMMAND DTBD_ADDR, clock offset Agent-> AP BW_HANDOVER_SUCCESS_EVENT, BW_HANDOVER_FAIL_EVENT

BlueWin events BW Event type Data Direction BW_DT_TYPE_EVENT DT type (BlueWin DT, non-BlueWin DT) DT-> AP BW_NEW_DT_EVENT DT type AP-> Agent BW_AP_CLOCK_OFFSET_EVENT relative clock offsets between AP's AP-> Agent BW_DT_CLOCK_OFFSET_EVENT clock offset between AP and DT, ID of DT, ID of AP AP-> Agent BW_LINK_LOW_POWER_EVENT ID of DT AP-> Agent BW_PREPAGE_SUCCESS_EVENT, BW_PREPAGE_FAIL_EVENT ID of AP, ID of DT AP-> Agent BW_DISCONNECT_EVENT ID of DT AP-> Agent BW_LINK_LOST_EVENT ID of DT AP-> Agent BW_HANDOVER_SUCCESS_EVENT, BW_HANDOVER_FAIL_EVENT ID of DT, ID of AP AP-> Agent

As described above, while the present invention accommodates the Bluetooth specification standardized by the Bluetooth SIG and IEEE 802.15, the present invention eliminates the problem of usage occurring during the frequent inquiry / connection process of the universal Bluetooth user equipment, and also one of the weak points of Bluetooth. Can be solved by extending the service area through the handoff / roaming support method of the present invention.

Claims (5)

A system for supporting handoff / roaming on a Bluetooth based local area network, BlueWIN-AP, a network access point (NAP) for LAN connection of Bluetooth user devices, BlueWIN-DT with Bluetooth client application software for handoff / roaming support, and Includes BlueWIN-Roaming Agent (BlueWIN-RA), which supports handoff / roaming on the wired backbone and manages all Bluetooth devices in the service area. The BlueWIN-AP allows the BlueWin-Data terminal to make a LAN connection, and transmits information such as BD \ ADDR and clock＿offset of the data terminal to a roaming agent between the BlueWin-Roaming Agent and the data terminal. It acts as a proxy to relay relays and PPP diagrams, such as alerts, commands from roaming agents to set up connections, The BlueWIN-Roaming Agent (BlueWIN-AP) acts as a PPP server that handles PPP connections with a data terminal in a subnetwork consisting of a network access point (NAP). After handoff is completed, the tunnel endpoint direction is changed. end point redirection to recover the PPP connection, so that the existing PPP connection state is maintained during handoff / roaming regardless of disconnection of the Bluetooth link. System to support it. The method of claim 1, The blue win-roaming agent performs packet buffering for each PPP session in consideration of the time delay and transmission speed caused by the handoff when changing the tunnel endpoint direction in order to eliminate packet loss and improve packet transmission efficiency. A system for supporting handoff / roaming on an based local area wireless network. The method according to claim 1 or 2, A system for supporting handoff / roaming on a Bluetooth-based short-range wireless network, which processes commands and events using the Bluewin protocol as shown in Tables 1 and 2 between the BlueWin access point and the roaming agent. . The method according to claim 1 or 2, The BlueWin access point includes two Bluetooth modules (a first Bluetooth module and a second Bluetooth module), where the first Bluetooth module is used for general data communication, and the second Bluetooth module is used to determine the location of the data terminal closer to the AP. A system for supporting handoff / roaming on a Bluetooth-based short range wireless network, characterized by reducing handoff time by using to pre-page to determine in advance. The method according to claim 1 or 2, The information of the clock offset between the data terminal DT for determining the paging / connection time between the data terminal and the BlueWin access point and the newly connected access point AP2 is the previously connected access to the data terminal. It is calculated as a relative clock offset between the data terminal (DT) and AP2 by using the clock offset with the point (AP1) and the clock offset between the AP1 and AP2 stored in the roaming agent through the inquiry between the access point in advance. A system for supporting handoff / roaming on a Bluetooth based local area network.