WO2014092545A1

WO2014092545A1 - A system and method for path selection in a wireless mesh network

Info

Publication number: WO2014092545A1
Application number: PCT/MY2013/000250
Authority: WO
Inventors: Ahmad Zaki BIN ABU BAKAR; Azmi BIN YAACOB; Shariq Haseeb; Muhammad Faheem BIN MOHD EZANI; Mohd Ariff BIN ABDULLAH
Original assignee: Mimos Berhad
Priority date: 2012-12-12
Filing date: 2013-12-11
Publication date: 2014-06-19
Also published as: MY157065A

Abstract

The present invention relates to a system and method for path selection in a wireless mesh network. The wireless mesh network includes a default gateway (10), at least two gateways (100) and a plurality of access points (200). Each gateway (100) is able to determine cost of its backhaul link with reference to other gateways (100) in the wireless mesh network. The cost of backhaul link is determined based on link capacity and congestion information of each gateway (100) in the wireless mesh network. The cost of backhaul link is used by each access point (200) to compute a routing cost. The access point (200) selects a path having the least routing cost in its routing table (240) for transmitting a data packet to the backhaul network (20).

Description

A SYSTEM AND METHOD FOR PATH SELECTION IN A WIRELESS MESH

NETWORK

FIELD OF INVENTION

The present invention relates to a system and method for path selection in a wireless mesh network and more particularly to a system and method for selecting a path based on link capacity of a gateway.

BACKGROUND OF THE INVENTION

Typically, path selection in a wireless mesh network is based on Layer 2 information such as hop count, link quality, and etc. However, such path selection does not consider bandwidth of a gateway leading to a destination or source node. Thus, an optimal path may not be selected when another gateway is provided. Moreover, the bandwidth of the network may not be fully utilized.

In view of this, US Patent No. 8,036,144 B2 discloses a gateway selection method for wireless mesh network. The gateway selection method is provided for selecting an optimal gateway includes building a spanning routing tree to a given network. Reference factors of routers are calculated regarding the network to total network capacity in association with the spanning routing tree. A router is selected which has the greatest reference factor as being an optimal gateway of the network. However, such method does not consider congestion information of a path in selecting the optimal path. Moreover, the method selects one of the mesh nodes as an optimal router gateway based on the distance from the gateway to the other nodes. The capacities of the gateways are not considered in selecting an optimal router gateway.

Therefore, there is a need to provide a system and method for selecting a path in a wireless mesh network based on bandwidth and congestion information of gateways in the wireless mesh network.

SUMMARY OF INVENTION

The present invention provides a system for path selection in a wireless mesh network. The system comprises a default gateway (10) connected to a backhaul network (20), at least two gateways (100) connected to said default gateway (10), wherein each gateway (100) includes an egress module (110), a backhaul module (120), and a plurality of access points (200), wherein each access point (200) includes a mesh module (210) and a routing table (240). Each gateway (100) further includes a peer gateway detection module (130) for receiving announcements from other gateways (100) in the wireless mesh network; a link capacity calculation module (140) for determining the link capacity and congestion of the gateway (100); a cost calculation module (150) for computing cost of a backhaul link of the gateway (100), wherein the cost calculation module (150) is connected to the peer gateway detection module (130), and the link capacity calculation module (140); a link capacity storage module (160) for storing link capacity information of the at least two gateways (100), wherein the link capacity storage module (160) is connected to the cost calculation module (150); a gateway link capacity announcement module (170) for broadcasting link capacity information of the gateway (100) over the wireless mesh network, wherein the gateway link capacity announcement module (170) is connected to the egress module (110) and the link capacity calculation module (140); and a cost announcement module (180) for broadcasting the computed cost from the cost calculation module (150) to the access points (200), wherein the cost announcement module (180) is connected to the egress module (110) and the cost calculation module (150). Each access point (200) further includes a cost announcement receiver module (220) for receiving the computed cost from the gateways (100); a new cost calculation module (230) for computing routing costs with respect to each gateway (100), wherein the new cost calculation module (230) is connected to the cost announcement receiver module (220), the routing table (240) and a routing table updater module (250); and the routing table updater module (250) for updating routing cost in said routing table (240) with the routing cost computed by the new cost calculation module (230).

The present invention also provides a method for selecting a path by an access point (100) in a wireless mesh network. The method is characterised by the steps of receiving a cost of the gateway's backhaul link from each gateway (100) in the wireless mesh network; computing new routing costs with respect to each gateway (100), wherein a new routing cost with respect to a particular gateway (100) is computed by dividing current cost with respect to the particular gateway (100) with the cost received from the particular gateway (100); and updating routing costs in a routing table (240) with the new routing costs; selecting a path having the least routing cost in the routing table (240) for transmitting a data packet to the backhaul network (20).

Preferably, the cost of backhaul link of a gateway is computed by a gateway (100) using the steps of receiving link capacity and congestion information broadcasted by other gateways (100) in the wireless mesh network; storing the link capacity and congestion information; computing cost of backhaul link by dividing the gateway's link capacity with the highest link capacity among the gateways (100) in the wireless mesh network; and broadcasting the computed cost to the access points (200).

Preferably, the link capacity and congestion information is determined by a gateway (100) using the steps of transmitting a train of packets to a random node in a backhaul network (20); determining the link capacity and congestion of the gateway (100) by transmitting a train of packets to random access points (200) and computing the transmission rate of the transmitted train of packets; and broadcasting the determined link capacity and congestion information to the other gateways (100) in the wireless mesh network. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. FIG. 1 shows a wireless mesh network.

FIG. 2 shows a block diagram of a gateway (100) according to an embodiment of the present invention. FIG. 3 shows a block diagram of an access point (200) according to an embodiment of the present invention.

FIG. 4 shows a flowchart of a method for determining link capacity according to an embodiment of the present invention. FIG. 5 shows a flowchart a method for computing cost of backhaul link of a gateway in a wireless mesh network according to an embodiment of the present invention.

FIG. 6 shows a flowchart of a method for selecting a path in an access point (200) based on cost of backhaul link of each gateway (100) in a wireless mesh network according to an embodiment of the present invention.

DESCRIPTION OF THE PREFFERED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.

Referring to FIG. 1 , there is shown a wireless mesh network. The wireless mesh network comprises of a default gateway (10), two gateways (100) and a plurality of access points (200). Although the network is shown as having only two gateways (100), it is appreciated that the network may include any suitable number of gateways (100) connected to the default gateway (10). The default gateway (10) is used for connecting the wireless mesh network to the backhaul network (20) such as the Internet. Preferably, the default gateway (10) is an internet router. In order for a computing device (300) to transmit or receive data packets to/from a backhaul network (20) via the default gateway (10), the data packets are routed through the access points (200) to/from either one of the gateways (100). There are multiple paths that can be used for routing the data packets. For instance, a computing device (300) connected to a first access point (200a) may transmit a data packet to the backhaul network (10) through the first access point (200a), second access point (200b), third access point (200c), fourth access point (200d), fifth access point (200e), and a first gateway (100a); or through the first access point (200a), second access point (200b), sixth access point (200f), seventh access point (200g), and a second gateway (100b); or through the first access point (200a), second access point (200b), third access point (200c), sixth access point (200f), seventh access point (200g), and the second gateway (100b); or through the first access point (200a), second access point (200b), third access point (200c), seventh access point (200g), and the second gateway (100b); or through the first access point (200a), second access point (200b), sixth access point (200f), third access point (200c), fourth access point (200d), fifth access point (200e), and the first gateway (100a); or through the first access point (200a), second access point (200b), sixth access point (200f), seventh access point (200g), third access point (200c), fourth access point (200d), fifth access point (200e), and the first gateway (100a). The best route for the computing device (300) to transmit the data packet to the backhaul network (20) is selected based on link capacity and congestion information of each gateway (100).

Referring to FIG. 2, there is shown a block diagram of a gateway (100) according to an embodiment of the present invention. The gateway (100) is used for connecting the access points (200) to the default gateway (10) for accessing the backhaul network (20). Moreover, the gateway (100) is used for determining cost of its backhaul link in reference to other gateways in the wireless mesh network. The term "backhaul link" herein below refers to the link between the gateway and the default gateway. Preferably, the gateway (100) is a mesh gateway. The gateway (100) includes an egress module (110), a backhaul module (120), a peer gateway detection module (130), a link capacity calculation module (140), a cost calculation module (150), a link capacity storage module (160), a gateway link capacity announcement module (170), and a cost announcement module (180). The egress module (110) is used to transmit and receive data packets to/from at least one neighbouring access point (200). The egress module (110) is connected to the gateway link capacity announcement module (170) and cost announcement module (180). The backhaul module (120) is used to relay data packets from the access points (200) to the backhaul network (20) such as the Internet, an Ethernet, local area network (LAN), wide area network (WAN) or any other appropriate network via the default gateway (10). The backhaul module (120) is virtually connected to the egress module (110) through the gateway's operating system, wherein the operating system forwards the data packets from the egress module (110) to the backhaul module (120).

The peer gateway detection module (130) is used for receiving announcements from other gateways (100) in the network. The announcements are received in the form of signalling packets and it includes link capacity and congestion information of the other gateways (100). The congestion information refers to transmission rate and packet latency. The peer gateway detection module (130) is connected to the cost calculation module (150) to send the link capacity and congestion information of the other gateways.

The link capacity calculation module (140) is used for determining the link capacity and congestion of the gateway (100) by transmitting a train of packets to random access points (200) and computing the transmission rate of the transmitted train of packets. The link capacity calculation module (140) is connected to the cost calculation module (140) and gateway link capacity announcement module (170) to send the link capacity and congestion information which includes throughput of the backhaul link, latency of the backhaul link and packet loss.

The cost calculation module (150) is used to compute cost of the gateway (100) with reference to other gateways (100). The term "cost" refers to a likelihood value of selecting the gateway's backhaul link, wherein the higher the cost of the gateway (100), the least desirable the gateway's backhaul link is. The cost is computed by dividing the gateway's link capacity and congestion with the highest link capacity and congestion among the gateways (100) in the network. The cost calculation module (150) is also used to store link capacity information of the gateway (100) and other gateways (100) in the link capacity storage module (160). The cost calculation module (150) is connected to the link capacity storage module (160), the peer gateway detection module (130), the link capacity calculation module (140) and the cost announcement module (180).

The gateway link capacity announcement module (170) is used for announcing the link capacity information of the gateway (100) to the other gateways (100) by broadcasting the link capacity information over the network. The gateway link capacity announcement module (170) sends the link capacity information to the other gateways (100) via the egress module (110). The gateway link capacity announcement module (170) is connected to the egress module (110) and the link capacity calculation module (140).

The cost announcement module (180) is used for announcing the computed cost from the cost calculation module (150) to the access points (200). The computed cost is announced to the access points (200) by encapsulating the cost in a packet and broadcasting the packet over the network. Thus, an access point (200) updates its routing table with the cost encapsulated in the packet whenever the access point (200) receives the packet. The cost announcement module (180) is connected to the egress module (110) and the cost calculation module (150).

Referring to FIG. 3, there is shown a block diagram of an access point (200) according to an embodiment of the present invention. The access point (200) is interconnected to at least one neighbouring access point (200) via a wireless communication technology such as but not limited to WiFi, WiMax, IEEE 802.11 based communications and etc. The access point (200) is used to relay data packets to/from its neighbouring access points (200) and to communicate with at least one computing device (300) such as but not limited to laptop, mobile phone, personal computer, handheld communication device, handheld computing device, wireless modem card or any other device suitable for communicating wirelessly within the wireless mesh network. Moreover, the access point (200) is used to determine paths to the gateways (100) in the network and selecting the best path based on the routing cost for each path. The access point (200) includes a mesh module (210), a cost announcement receiver module (220), a new cost calculation module (230), a routing table (240) and a routing table updater module (250).

The mesh module (210) is used for connecting to at least one neighbouring access point (200) or a gateway (100). The cost announcement receiver module (220) is used for receiving the costs from the gateways (100). The cost announcement receiver module (220) is connected to the new cost calculation module (230) for transmitting the costs received from the gateways (100). The new cost calculation module (230) is used for computing the new routing costs by dividing the current costs with the costs received from the gateways (100). The new cost calculation module (230) is connected to the cost announcement receiver module (220), routing table (240) and routing table updater module (250). The routing table (240) is used for storing route information which includes gateway address, next hop address and routing cost. The routing table (240) is connected to the new cost calculation module (230) and the routing table updater module (250).

The routing table updater module (250) is used for updating the costs in the routing table (240) with the new routing costs computed by the new cost calculation module (230). Referring to FIG. 4, there is shown a flowchart of a method for determining link capacity by the gateway (100). Initially, as in step 401, a train of packets is transmitted to a random node in the backhaul network (20) by the link capacity calculation module (140). The train of packets transmitted is a series of dummy User Datagram Protocol (UDP) traffic.

In step 402, the link capacity calculation module (140) determines the link capacity and congestion of the gateway (100) by transmitting a train of packets to random access points (200) and computing the transmission rate of the transmitted train of packets. The determined link capacity and congestion information are then transmitted to the gateway link capacity announcement module (170) and the cost calculation module (150).

In step 403, the gateway link capacity announcement module (170) sends the link capacity to the other gateways (100) in the network through the egress module (110).

Referring to FIG. 5, there is shown a flowchart of a method for computing cost of backhaul link of a gateway in a wireless mesh network. Initially, as in step 501 , the peer gateway detection module (130) detects the link capacity and congestion announcements broadcasted by other gateways (100) in the network.

Once the peer gateway detection module (130) receives the announcement from the other gateways (100), the peer gateway detection module (130) extracts and sends the link capacity and congestion information of the other gateways (100) in the network to the cost calculation module (150) as in step 502. In step 503, the cost calculation module (150) stores the link capacity and congestion information of all the gateways (100) in the link capacity storage module (160).

In step 504, the cost calculation module (150) computes the cost of the gateway's backhaul link by dividing the gateway's link capacity with the highest link capacity among the gateways (100) in the network. For example, with reference to FIG. 1 , assuming that the first gateway (100a) has a link capacity of 5MB and the second gateway (100b) has a link capacity of 10MB; the computed cost of the backhaul link of the first gateway (100a) is 0.5 as a result of the link capacity of the first gateway (100a) divided by the link capacity of the second gateway (100b). Meanwhile, the computed cost of the backhaul link of the second gateway (100b) is 1 as a result of the link capacity of the second gateway (100b) divided by the highest link capacity among the gateways (100) which is the link capacity of the second gateway (100b).

In step 505, the cost calculation module (150) sends the computed cost of the gateway's backhaul link to the cost announcement module (180).

In step 506, the cost announcement module (180) broadcasts the computed cost to the access points (200).

Referring to FIG. 6, there is shown a flowchart of a method for selecting a path by an access point (200) based on cost of backhaul link of each gateway (100). After the gateways (100) in the network have computed its cost of backhaul link by using the method as shown in FIG. 5, the cost announcement receiver module (220) receives the computed costs of the gateway's backhaul link broadcasted from each gateway (100).

The costs are then forwarded to the new cost calculator module (230) from the cost announcement receiver module (220) as in step 602.

In step 603, the new cost calculator module (230) computes new routing costs with respect to each gateway (100), wherein a new routing cost with respect to a particular gateway (100) is computed by dividing the current cost with respect to the particular gateway (100) with the cost received from the particular gateway (100). As an example, with reference to FIG. 1, assuming that the third access point (200c), the fourth access point (200d), the fifth access point (200e), and the seventh access point (200g) have a current cost with respect to the first gateway (100a) of 3, 2, 1 and 4 respectively, and a current cost with respect to the second gateway (100b) of 2, 3, 4 and 1 respectively, while the cost from the first gateway (100a) is 0.5 and the cost from the second gateway (100b) is 1 ; the new routing costs with respect to the first gateway (100a) for the third access point (200c), the fourth access point (200d), the fifth access point (200e) and the seventh access point (200g) are computed as 6, 4, 2 and 8 respectively as a result of the current cost divided by the cost received from first gateway (100a). Meanwhile, the new routing costs with respect to the second gateway (100b) for the third access point (200c), the fourth access point (200d), the fifth access point (200e) and the seventh access point (200g) are computed as 2, 3, 4 and 1 respectively as a result of the current cost divided by the cost received from second gateway (100b).

In step 604, the new cost calculator module (230) sends the new routing costs to the routing table updater module (250).

In step 605, the routing table updater module (250) updates routing costs in the routing table (240) with the new routing costs computed by the new cost calculation module (230). Thereon, the access point (200) selects a best path for transmitting a data packet to the backhaul network (20) based on the routing costs in its routing table (240), wherein the path having the least routing cost is selected as the best path. As an example, with reference to FIG. 1 , assuming that the third access point (200c), the fourth access point (200d), the fifth access point (200e), and the seventh access point (200g) have a new routing cost with respect to the first gateway (100a) of 6, 4, 2 and 8 respectively, and a new routing cost with respect to the second gateway (100a) of 2, 3, 4 and 1 respectively; the third access point (200c) selects a path to the second gateway (100b) via the seventh access point (200g) as the new routing cost with respect to the second gateway (100b) is lesser than the new routing cost with respect to the first gateway (100a), the fourth access point (200d) selects a path to the first gateway (100a) via the fifth access point (200e) as the new routing cost with respect to the first gateway (100a) is lesser than the new routing cost with respect to the second gateway (100b), the fifth access point (200d) selects a path to the first gateway (100a) as the new routing cost with respect to the first gateway (100a) is lesser than the new routing cost with respect to the second gateway (100b), and the seventh access point (200g) selects a path to the second gateway (100b) as the new routing cost with respect to the second gateway (100b) is lesser than the new routing cost with respect to the first gateway (100a)

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

1. A system for path selection in a wireless mesh network comprising:

a default gateway (10) connected to a backhaul network (20), at least two gateways (100) connected to said default gateway (10), wherein each gateway (100) includes an egress module (110), a backhaul module (120), and

a plurality of access points (200), wherein each access point (200) includes a mesh module (210) and a routing table (240);

wherein said system is characterised in that:

each gateway (100) further includes:

a peer gateway detection module (130) for receiving announcements from other gateways (100) in the wireless mesh network,

a link capacity calculation module (140) for determining the link capacity and congestion of said gateway (100),

a cost calculation module (150) for computing cost of a backhaul link of said gateway (100), wherein said cost calculation module (150) is connected to said peer gateway detection module (130), and said link capacity calculation module (140),

a link capacity storage module (160) for storing link capacity information of said at least two gateways (100), wherein said link capacity storage module (160) is connected to said cost calculation module (150),

a gateway link capacity announcement module (170) for broadcasting link capacity information of the gateway (100) over the wireless mesh network, wherein said gateway link capacity announcement module (170) is connected to said egress module (110) and said link capacity calculation module (140), and a cost announcement module (180) for broadcasting the computed cost from the cost calculation module (150) to said access points (200), wherein said cost announcement module (180) is connected to said egress module (110) and said cost calculation module (150); and each access point (200) further includes

a cost announcement receiver module (220) for receiving the computed cost from said gateways (100),

a new cost calculation module (230) for computing routing costs with respect to each gateway (100), wherein said new cost calculation module (230) is connected to said cost announcement receiver module (220), said routing table (240) and a routing table updater module (250), and

said routing table updater module (250) for updating routing cost in said routing table (240) with the routing cost computed by said new cost calculation module (230).

A method for selecting a path by an access point (100) in a wireless mesh network is characterised by the steps of:

a) receiving a cost of the gateway's backhaul link from each gateway (100) in the wireless mesh network;

b) computing new routing costs with respect to each gateway (100), wherein a new routing cost with respect to a particular gateway (100) is computed by dividing current cost with respect to the particular gateway (100) with the cost received from the particular gateway (100); and

c) updating routing costs in a routing table (240) with the new routing costs;

d) selecting a path having the least routing cost in the routing table (240) for transmitting a data packet to the backhaul network (20).

The method as claimed in claim 2, wherein the cost of backhaul link of a gateway is computed by a gateway (100) using the steps of:

a) receiving link capacity and congestion information broadcasted by other gateways (100) in the wireless mesh network;

b) storing the link capacity and congestion information;

c) computing cost of backhaul link by dividing the gateway's link capacity with the highest link capacity among the gateways (100) in the wireless mesh network; and

d) broadcasting the computed cost to the access points (200). The method as claimed in claim 3, wherein the link capacity and congestion information is determined by a gateway (100) using the steps of:

a) transmitting a train of packets to a random node in a backhaul network (20);

b) determining the link capacity and congestion of the gateway (100) by transmitting a train of packets to random access points (200) and computing the transmission rate of the transmitted train of packets; and

c) broadcasting the determined link capacity and congestion information to the other gateways (100) in the wireless mesh network.