Method of delivering multicast packets in a mesh network

In a mesh network, when a wireless mesh link exists between a first mesh access point and a second mesh access point, the first mesh access point can deliver a multicast packet to the second mesh access point through the wireless mesh link. When the second mesh access point determines that the multicast packet from the first mesh access point is a redundant packet, the second mesh access point will send a multi-path notice to the first mesh access point. After receiving the multi-path notice, the first mesh access point stops delivering the multicast packet through the path.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of delivering multicast packets in a mesh network, and more particularly, to a method of delivering multicast packets and preventing multi-paths in a mesh network.

2. Description of the Prior Art

Wireless mesh network (WMN) is a key technology for next-generation wireless networks. The wireless mesh network supports ad-hoc networking and has the self-organization and self-configuration properties. The wireless mesh network serves as an access network that employs multi-hop wireless forwarding by non-mobile nodes to relay data to and from Internet. It was announced that the wireless mesh network could provide data transmission rate up to 134.4 mbps, which satisfies the requirement of the next-generation high-speed wireless networks.

Please refer toFIG. 1.FIG. 1is a schematic diagram of a wireless mesh network according to the prior art. The wireless mesh network comprises two kinds of mesh nodes, a mesh portal (MB)12and mesh access points (MP)14. The mesh portal12is a gateway between the Internet and the wireless mesh network, for delivering data from the wireless mesh network to the Internet, or from the Internet to the wireless mesh network. The mesh access point14provides a wireless network service directly to a mobile station (MS)16through a wireless access link. When the radio of the mesh access points14can cover each other, a wireless mesh link exists between the two mesh access points14and each of two mesh access points14can deliver the data through the link. The mesh access points14and the mesh portal12construct a mesh distribution system. In other words, the mesh access points14communicates with the mesh portal12through a mesh network protocol, and the mesh access point14communicates with the mobile station16through many protocols, such as IEEE 802.11 and mobile telecommunication network.

When the mobile station16enters the service range of the mesh access point14, the mobile station16performs an association procedure to establish a wireless mesh link with the mesh access point14. The mesh access point14is a serving mesh access point of the mobile station16. Through the wireless mesh network, the mobile station16can communicate with other mobile stations16in the wireless mesh network or other hosts in the Internet. For example, the data delivering to the mobile station16are relayed between different mesh access points14, and the data are delivered to the serving mesh access point of the mobile station16finally. In the wireless mesh network, each mesh access point14delivers not only the data of the mobile station16in the service range but also the data from other mesh access point14. In addition, the wireless communication uses the broadcast transmission. If the transmission between each mesh access point14is not scheduled effectively, the transmission of the mesh access point14may collide so as to reduce the performance of the wireless mesh network. Thus, there is a protocol to control the period or frequency of the transmission of each mesh access point14, which is the medium access control (MAC) protocol of the wireless network. In addition, before delivering the data to the mobile station16, the mesh access point14has to determine which mesh access point14is the serving mesh access point of the mobile station16. The mobile station16can move so it may associate with different serving mesh access point. Thus, a mobility management and a routing mechanism are specified in the network layer of the protocol of the wireless network.

Please refer toFIG. 2andFIG. 3.FIG. 2toFIG. 3are schematic diagrams of mesh access points delivering a multicast packet according to the prior art. The wireless mesh network comprises four mesh access points, and between each mesh access point has a wireless mesh link. A first mesh access point121(source terminal) uses a multicast transmission to break a frame into multiple unicast packets and deliver the packets to each peer mesh access point respectively. On receipt of the packet, the mesh access point forwards the packet to each peer mesh access point using same mechanism. The same packet will be delivered many times since multi-paths exist in the mesh network. As shown inFIG. 2, the first mesh access point121delivers a multicast packet to the second, third, and fourth mesh access point122,123,124. As shown inFIG. 3, the second, third, and fourth mesh access point122,123,124forward the multicast packet to the peer mesh access point. Accordingly, the forwarding multicast packets are unnecessary and waste the channel resource.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a method of delivering multicast packets for a mesh network comprises: establishing a first wireless mesh link between a first mesh access point and a second mesh access point; establishing a second wireless mesh link between the second mesh access point and a third mesh access point; the second mesh access point receiving a multicast packet from the first mesh access point through the first wireless mesh link; the second mesh access point receiving the multicast packet from the third mesh access point through the second wireless mesh link; and the second mesh access point sending a multi-path notice to the third mesh access point.

According to another embodiment of the present invention, a method of delivering multicast packets for a mesh network comprises: a first mesh access point delivering a multicast packet to a second mesh access point; when the second mesh access point determines the multicast packet from the first mesh access point as a redundant, the second mesh access point sending a multi-path notice to the first mesh access point; and the first mesh access point stopping delivering the multicast packet to the second mesh access point after receiving the multi-path notice.

DETAILED DESCRIPTION

Please refer toFIG. 4toFIG. 8.FIG. 4toFIG. 8are schematic diagrams showing an embodiment of mesh access points delivering a multicast packet according to the present invention. To prevent the mesh access point from delivering the duplicate multicast packet that results in resource waste, the present invention provides a simple and efficient method for detecting the redundant paths and notifying the peer mesh access points to stop delivering the multicast packet through the path for a predetermined period. The predetermined period can prevent the path from blocking permanently. The network will be detected again after the predetermined period. In this embodiment, the wireless mesh network comprises four mesh access points, and between each mesh access point has a wireless mesh link. As shown inFIG. 4, the first mesh access point21delivers a multicast packet to the second, third, and fourth mesh access point22,23,24. As shown inFIG. 5, after receiving the multicast packet from the first mesh access point21, the third mesh access point23delivers the same multicast packet to the peer mesh access point, the second mesh access point22and the fourth mesh access point24. However, the second mesh access point22and the fourth mesh access point24have received the multicast packet from the first mesh access point21already. Thus, the second mesh access point22sends a multi-path notice MPN to the third mesh access point23to indicate that the path is unnecessary. Similarly, the fourth mesh access point24sends a multi-path notice MPN to the third mesh access point23to indicate that the path is unnecessary. As shown inFIG. 6, after receiving the multicast packet from the first mesh access point21, the second mesh access point22delivers the same multicast packet to the peer mesh access points, the third mesh access point23and the fourth mesh access point24. However, the third mesh access point23and the fourth mesh access point24have received the multicast packet from the first mesh access point21already. Thus, the third mesh access point23sends a multi-path notice MPN to the second mesh access point22to indicate that the path is unnecessary. Similarly, the fourth mesh access point24sends a multi-path notice MPN to the second mesh access point22to indicate that the path is unnecessary. As shown inFIG. 7, after receiving the multicast packet from the first mesh access point21, the fourth mesh access point24delivers the same multicast packet to the peer mesh access points, the second mesh access point22and the third mesh access point23. However, the second mesh access point22and the third mesh access point23have received the multicast from the first mesh access point21already. Thus, the fourth mesh access point24sends a multi-path notice MPN to the second mesh access point22to indicate that the path is unnecessary. Similarly, the fourth mesh access point24sends a multi-path notice MPN to the third mesh access point23to indicate that the path is unnecessary. As shown inFIG. 8, after the peer mesh access points of the first mesh access point21have determined the multi-path, the first mesh access point21has the best path for delivering the multicast packet in the wireless mesh network.

According to the present invention, each mesh access point can determine where the source terminal of the received multicast packet is. For example, the second, third, and fourth mesh access point22,23,24receive the multicast packet delivered from the first mesh access point21(source terminal). For the second mesh access point22, when the second mesh access point22receives the same multicast packet from the third mesh access point23, since the second mesh access point22has received the multicast packet from the first mesh access point21, the second mesh access point22determines that the multicast packet from the third mesh access point23is a redundant packet. That is, the path of delivering the multicast packet generated by the first mesh access point21through the third mesh access point23is a redundant path. Thus, the second mesh access point22sends a multi-path notice MPN to the third mesh access point23to indicate that the path is unnecessary. After receiving the multi-path notice MPN, third mesh access point23stops delivering the multicast packet generated by the first mesh access point21to the second mesh access point22for a predetermined period. The predetermined period is about several minutes. In addition, when the second mesh access point22receives the same multicast packet from the fourth mesh access point24, the second mesh access point22can determine than the multicast packet from the fourth mesh access point24is a redundant packet. Thus, the second mesh access point22sends a multi-path notice MPN to the fourth mesh access point24to indicate that the path is unnecessary. Similarly, the third mesh access point23and the fourth mesh access point24can determine the path of the multicast packet according to the same mechanism so as to have the best path for the multicast packet.

Please refer toFIG. 9.FIG. 9is a table of a multi-path notice according to an embodiment of the present invention. The mesh access points of the present invention use the multi-path notice to stop the delivering path of the multicast packet so as to increase the efficiency when the mesh access points deliver the multicast packet. In the embodiment, the format of the multi-path notice comprises six columns. The first column31represents 802.11 Header. The second column32represents Mesh Header. The first column31and the second column32refer to IEEE 802.11 and 802.11s specification. The third column33represents the category. The length of the third column33is 8 bits. The third column33defines the data types. For example, the data is notice type. The fourth column34represents the action code. The length of the fourth column34is 8 bits. The fourth column34defines the function of the data. For example, the data is for multi-path notice. The fifth column35represents the flag. The length of the fifth column35is 8 bits. The fifth column35defines if the multicast packet is enabled. “0” indicates disable, and “1” indicates enable. The sixth column36represents the medium access control (MAC) address of the source. The length of the sixth column36is six 8 bits. The sixth column36records the MAC address of the mesh access point generating the multicast packet. In the embodiment ofFIG. 4toFIG. 8, the sixth column36of the multi-path notice MPN records the MAC address of the first mesh access point21. The mesh access point delivers the multi-path notice according toFIG. 9to the peer mesh access point to notify that the path for the multicast packet is redundant, so the multicast packet delivered through the path is unnecessary.

In conclusion, the method of delivering multicast packets for a mesh network according to the present invention can improve the efficiency when mesh access points deliver the multicast packets. In a mesh network, when a wireless mesh link exists between a first mesh access point and a second mesh access point, the first mesh access point can deliver a multicast packet to the second mesh access point through the wireless mesh link. When the second mesh access point determines that the multicast packet from the first mesh access point is a redundant packet, the second mesh access point will send a multi-path notice to the first mesh access point. After receiving the multi-path notice, the first mesh access point stops delivering the multicast packet through the path. Thus, the present invention prevents the mesh access point delivering the duplicate multicast packet resulting in the resource waste.