WIRELESS LOCAL AREA NETWORK SYSTEM BASED ON AN ACCESS POINT (AP) SUPPORTING WIRELESS TERMINAL ROAMING

A wireless local area network (WLAN) system is disclosed. The WLAN system includes a first access point (AP), and a second AP which has a same service set identifier (SSID) as that of the first AP, wherein the first AP and the second AP are configured to respectively perform a network address translation (NAT) and have a same virtual media access control (MAC) address. The WLAN system according to the present disclosure supports successful roaming between APs which belong to different networks regardless of the type of the wireless terminal.

BACKGROUND

1. Technical Field

Exemplary embodiments relate to a wireless local area network, and more particularly, to a wireless local area network system which supports roaming to another network while moving regardless of the type of a wireless terminal.

2. Description of Related Art

As wireless terminals are widely distributed and mobile communication networks are developed, the amount of use of mobile Internet, which connects to a website or a blog using a mobile wireless terminal, is rapidly increasing. A wireless short range network or a wireless local area network (WLAN) environment, which allows mobile Internet, requires seamless communication with a user. As such, the importance of roaming in a WLAN based on IEEE 802.11 standards is being highlighted. The IEEE 802.11 standards are marketed under the brand name Wi-Fi, which is an abbreviation of “wireless fidelity”. Wi-Fi or WLAN refers to a LAN that is wireless, and thus there is a limit in distance covered by the LAN. The communication speed decreases as the wireless terminal gets farther from an access point (AP), and if the wireless terminal completely deviates from the range, a disconnection occurs. Roaming is a function of moving connection from one AP to another AP while maintaining network connection of the wireless terminal. A plurality of APs, which provide the same service set ID (SSID) so that the SSIDs may sufficiently overlap, need to be distributed for seamless, flexible roaming. In the WLAN connection service, which uses a conventional AP and wireless terminal, even though AP cells overlap, if the wireless terminal is moved between the AP cells, the Internet is disconnected because each AP forms one sub-network in the current network address. That is, the network areas of AP1 and AP2 are different. If the wireless terminal is allocated an IP address from the AP1 and moves to the area of the AP2, the network address of the AP1 is not processed in the area of the AP2, and thus the connection to the Internet is not made.

FIG. 1is a block diagram illustrating a WLAN system according to a related art. Referring toFIG. 1, a conventional WLAN system100includes a first AP110, a second AP112, a switch120, and a router140. In detail, the first AP110and the second AP112are connected to the router140via the switch120, and is connected to an Internet company network (KORNET)160through the router140. The first AP110operates in a bridge scheme, and the second AP112operates in a network address translation (NAT) mode. The first AP110and the second AP112have a unique media access control (MAC) address allocated by each manufacturing company. Generally, the AP operates in a bridge scheme or a NAT scheme. The bridge scheme operates as a simple switching hub. Hence, a service, such as a dynamic host configuration protocol (DHCP) which is set in a MODEM or upper L3 equipment, is only transmitted to the wireless terminal. The AP, which operates as the bridge scheme receives the network setting from, for example, a 3-layer router or an L3 switch, which is upper-end equipment, and thus the AP performs a function of only changing the signals into wireless signals. That is, the wireless terminal, which is connected to the first AP110that operates in the bridge mode, is allocated an IP address by the router140. That is, the router140becomes a DHCP server, and the first AP110becomes a DHCP client. Furthermore, according to the NAT scheme, the AP itself serves as a DHCP server, which receives a public IP and provides the public IP to wireless terminals, as the private IP. That is, the AP becomes the DHCP server, and wireless terminals become the DHCP client. Consequently, the AP, which operated in the NAT mode, becomes a kind of router which connects to different networks. The wireless terminal, which is connected to the second AP112that operates in the NAT mode, is allocated the IP address from the second AP112. Consequently, the first AP110and the second AP112are connected to the same router140, but the second AP112is in the NAT mode, and thus the WLAN system100ofFIG. 1is allocated the IP address by different DHCP servers. The first AP110and the second AP112belong to different networks and the wireless terminal moves during connection to the first AP110, and thus a new IP address needs to be allocated to maintain connection in order to connect to the second AP112. A new IP address needs to be allocated to connect to a new network other than a current network while the wireless terminal is moving. If the wireless terminal requests a new IP address (broadcasts a DHCP discover) when roaming between adjacent APs, which belong to different networks, an IP address in a new network is allocated, and thus successful roaming becomes possible. However, when the wireless terminal requests an Internet connection with the existing IP address without requesting a new IP address, the existing IP address is not processed in a new network, and thus a disconnection occurs and roaming fails. Consequently, the success of roaming in the WLAN system is determined according to whether a function of requesting an IP address allocation is automatically supported if the wireless terminal tries connection with an AP, which belongs to another network. As, a result, this causes a problem that the user of a particular wireless terminal cannot be provided a seamless mobile communication service. Hence, there is a need for a WLAN system which may support successful roaming regardless of the type of the wireless terminal.

SUMMARY

Exemplary embodiments provide a wireless local area network system which supports roaming to another network regardless of the type of a wireless terminal.

According to an aspect of an exemplary embodiment, there is provided a wireless local area network system which successfully supports roaming between APs that belong to different networks regardless of the type of the wireless terminal by applying the NAT mode to the AP.

According to a wireless local area network system according to an exemplary embodiment, seamless roaming may be possible and the problem of lack of IP may be resolved by applying a NAT mode to an access point. Furthermore, a separate DHCP server is not necessary, and thus the investment costs for the DHCP server may be reduced. Roaming at the access point end is realized, and thus AP equipment is not necessary. Also, a change in the circuit configuration of the conventional wireless network is not necessary.

According to one or more exemplary embodiments, a wireless local area network (WLAN) system based on an access point (AP) includes: a first AP; and a second AP which has a same service set identifier (SSID) as that of the first AP, wherein the first AP and the second AP are configured to respectively perform a network address translation (NAT) and have a same virtual media access control (MAC) address.

The first AP and the second AP may be configured to generate the virtual MAC address according to a predetermined scheme.

The virtual MAC address may be generated based on an original MAC address which has been set at a time of manufacturing.

The first AP and the second AP may be connected to a first router via a first switch.

The first AP may be connected to a first router via a first switch, and the second AP may be connected to the first router via a second switch.

The first AP may be connected to a first router via a first switch, and the second AP may be connected to a second router via a second switch.

The first router may be configured to function as a dynamic host configuration protocol (DHCP) server having an internet protocol (IP) address pool of a first class or a second class.

The first AP and the second AP may be respectively configured to function as a DHCP server having the IP address pool of the first class and the second class.

The first router and the second router may be respectively configured to function as a DHCP server having the IP address pool of the first class and the second class.

DETAILED DESCRIPTION

The attached drawings for illustrating exemplary embodiments are referred to in order to gain a sufficient understanding of the exemplary embodiments, the merits thereof, and the objectives accomplished by the implementation of the exemplary embodiments.

The exemplary embodiments may be modified in various different forms, and the scope of the present invention is not limited to the exemplary embodiments described below. Rather, the exemplary embodiments are provided to complete the present disclosure and completely let those of ordinary skill in the art understand the concept of the present invention.

Hereinafter, exemplary embodiments will be described in detail with reference to the attached drawings.

FIG. 2is a block diagram of a wireless local area network (WLAN) system200according to an exemplary embodiment. Referring toFIG. 2, the WLAN system200includes a first access point (AP)210, a second AP212, a switch220, and a router240.FIG. 2illustrates a case where a wireless terminal performs roaming within the same data link of the same network. In detail, the first AP210and the second AP212are connected to the router240via the switch220, and are connected to an Internet company network260(KORNET) through the router240. The first AP210and the second AP212have the same service set identifier (SSID). The first AP210and the second AP212operate in a network address translation (NAT) mode. The first AP210and the second AP212have a unique media access control (MAC) address allocated by each manufacturing company. For example, the MAC address of the first AP210may be 00:25:A6:A0:AA:1B, and the MAC address of the second AP220may be 00:25:A6:A0:10:83. The first AP210and the second AP212have the same virtual MAC address. For example, the first AP210and the second AP220may have the same virtual MAC address 00:25:A6:11:00:00. The MAC address is a physical address. However, the MAC address is obtained through software, and thus the MAC address may be generated by software, and the wireless terminal may be set to recognize the MAC address of the first AP210and the second AP212as the same by the virtual MAC address. The virtual MAC address may be generated based on the original MAC address. The first AP210and the second AP212may have a virtual MAC address, which is generated in a predetermined scheme. In other words, the WLAN system200according to an exemplary embodiment allocates the same virtual MAC address between the first and second APs210and212having different MAC addresses, and thus even though the connection of the wireless terminal is changed from the first AP210to the second AP212, the wireless terminal belongs to the same network, and thus the IP address, which is provided at the time of connecting to the first AP210for the first time, for example, 172.30.1.1, is still valid even after connecting to the second AP212. This is because the first AP210and the second AP212, which function as a DHCP server for the wireless terminal, have the same virtual MAC address, and thus the DHCP server is the same to the wireless terminal and there is no need for being allocated a new IP address. Hence, even if the IP address is not updated, the network connection is maintained. Consequently, the WLAN system200according to an exemplary embodiment may support successful roaming even if the wireless terminal does not request an update of the IP address when the connection of the wireless terminal is changed from the first AP210to the second AP212. Furthermore, the roaming may be simply performed by software in the AP without a complicated circuit operation.

In the WLAN system200according to an exemplary embodiment, the first AP210and the second AP212may be configured to be allocated an IP address of class B or class C. The router240may function as a DHCP server having the IP address pool of class B or class C. The first AP210and the second AP212may be allocated the IP address of class B or class C by the router240, wherein IP addresses allocated for the first AP210and the second AP212from B class or C class are different. The first AP210and the second AP212may have the DHCP server function having the IP address pool of class B or class C. The method of making the MAC address of the first AP210and the second AP212, which is detected by the wireless terminal, the same, by introducing the virtual MAC address concept, may cause a collision between IP addresses. If the IP address pool allocated by the router240is class C, the IP address of the first AP210and the second AP212has an IP address of the same class C, and the number of IP addresses, which may be held by the wireless terminal connected to the first AP210and the second AP212, is merely 253. That is, the IP address, which the wireless terminal has been allocated from the first AP210, may have already been allocated to another wireless terminal by the second AP212and may be used. The IP address pool, which is allocated by the router240to prevent a collision of a private IP address allocated to the wireless terminal, may be extended from class C to class B. In this case, the first AP210and the second AP212may now be allocated the IP address of a different class B by the router240. For example, the IP addresses, which may be held by the first AP210, may be 172.30.1.1 to 253. The IP addresses which may be held by the second AP212may be 172.30.2.1 to 253. The IP address (third octet is “1”) allocated to the wireless terminal by the first AP210cannot be the same as the IP address (third octet is “2”) allocated to the wireless terminal by the second AP212. Hence, even if the first AP210and the second AP212have the same MAC address, there is no possibility of a collision of the IP address at the time of roaming.

The switch120may be a layer-2 (L2) switch, which is located in a data link layer and is connected to a different data link. The L2 switch performs switching with the MAC address. The L2 switch processes the wireless terminal of an area narrower than that of the router240, performs a role of transmitting a packet, and transmits the packet to the wireless terminal by using the MAC address of the wireless terminal in the MAC layer. Furthermore, the L2 switch transmits the packet to the wireless terminal by using the mapping information of the physical connection port between the MAC address of the wireless terminal and the AP, which accepts the wireless terminal. The MAC address is also called an Ethernet hardware address, an adapter address, or a physical address. The MAC address is used only when the wireless terminals communicate via the AP, and is not used when disconnecting from the Internet. When disconnecting from the Internet, the MAC is substituted by the MAC address of a sharer.

The router240may distinguish the network as the layer-3 router and provide the IP address to the wireless terminal according to the request of the wireless terminal. As such, the wireless terminal within the area belongs to the same network area. That is, the first AP210and the second AP220belong to the network area of the router240. The router240may accept the L2 switch and transmit packets within the network. The router240is a representative layer 3 (L3: network layer) device, checks the destination address of the packet using the routing function and transmits the packet to the destination, and has a routing function of selecting the path to use as the optimal path at the time of transmission. The router240may accommodate a plurality of L2 switches.

FIG. 3is a block diagram of a WLAN system according to another exemplary embodiment. Referring toFIG. 3, the WLAN system300includes a first AP310, a second AP312, a first switch320, a second switch322, and a router340. The first AP310is connected to the router340via the first switch320, and the second AP312is connected to the router340via the second switch322. Unlike the exemplary embodiment ofFIG. 2, the first AP310and the second AP312are connected to different switches. The exemplary embodiment ofFIG. 3may be a case where the wireless terminal performs roaming to another data link which is distinguished by the first and second switches320and322within the same network. The first AP310and the second AP312include the same SSID. The first AP310and the second AP312operate in a NAT mode. The first AP310and the second AP312have a unique MAC address allocated by each manufacturing company. The first AP310and the second AP312have the same virtual MAC address.

In the WLAN according to another exemplary embodiment, the first AP310and the second AP312may be configured to be allocated the different IP addresses from classes B and C. The router340may function as a DHCP server having the IP address pool of class B or class C. The first AP310and the second AP312may be allocated the different IP addresses from classes B and C by the router340. The first AP310and the second AP312may have a function of the DHCP server having the IP address pool of class B or class C. A detailed description of the exemplary embodiment ofFIG. 3is omitted here because it has already been described with reference toFIG. 2.

FIG. 4is a block diagram of a WLAN system400according to another exemplary embodiment. Referring toFIG. 4, the WLAN system400includes a first AP410, a second AP412, a first switch420, a second switch422, a first router440, and a second router442. The first AP410is connected to the first router440via the first switch420, and the second AP412is connected to the second router442via the second switch422. Unlike the exemplary embodiments ofFIGS. 2 and 3, the first AP410and the second AP412are connected to different routers via different switches. The exemplary embodiment ofFIG. 4describes a case where a wireless terminal performs roaming to another network which is distinguished by the router440.

In the WLAN system400according to another exemplary embodiment, the first AP410and the second AP412may be configured to be allocated the IP address of different classes B and C. The router400may function as a DHCP server having the IP address pool of class B or class C.

In the case of the exemplary embodiment ofFIG. 4, the first AP410and the second AP412are connected to different routers440and442, and thus the exemplary embodiment ofFIG. 4is different from the exemplary embodiments ofFIGS. 2 and 3. Such a difference merely causes a result that the IP address of the DHCP server of the first AP410becomes different from the IP address of the DHCP server of the second AP412. As such, as in the exemplary embodiments ofFIGS. 2 and 3, as long as the first AP410and the second AP412operate in a NAT method, and the virtual MAC address of the first AP410becomes the same as the virtual MAC address of the second AP412, the wireless terminal determines the first AP410and the second AP412as the same. Hence, a detailed description thereof is omitted because it has been described above with reference toFIG. 2.

The case of applying a virtual MAC address concept, and applying a technical concept of allocating the same virtual MAC address between APs and a technical concept of extending the IP address pool for preventing an IP address collision between wireless terminals at the time of roaming, with respect to the AP, has been described above. However, the exemplary embodiments are not limited thereto, and those of ordinary skill in the art may modify the exemplary embodiments and apply the modified embodiments to the network equipment having a routing function and a DHCP server function.