Patent Application
20080080388
As shown in the drawings for purposes of illustration, the invention is embodied in an apparatus and method for wireless networks and wireless mesh networks that suppress probe responses. The embodiments disclosed aid, among other things, a client device in maintaining an association with an access point or access node of a wireless network. Maintenance of associations is desirable because it helps prevent client devices from roaming excessively.
The access points of
More than one access point, such as, access points 220, 222, 224, 226 receive probe requests from a client device 250. Each access point that receives the probe estimates a quality of the wireless link between the client device 250 and the receiving access point. For each receiving access point, the quality of the link can be determined, for example, by measuring the received signal strength of the probe request. That is, the signal strength of the probe request is to at least some extent dependent upon the quality of the transmission link between the client device transmitting the probe request, and the device receiving the probe request. Generally, the greater the received signal strength, the better the quality of the link between the client device and the receiving device.
Wireless network parameters, however, can also influence the desirability of one network device (gateways, access node or access point) over another network device. For example, data throughput, latency, backhaul bandwidth and stability of the access point can also be useful in determining which probe request receiving access point should be connected to the probe request transmitting client device. Therefore, the link quality that is communicated from an access point (or access node) can additionally include one or more network parameters associated with the access point. An embodiment includes the link quality (for example, an RSSI measurement) being modified to reflect one or more network quality parameters associated with the access point.
As previously stated, the access points 220, 222, 224, 226 can receive a probe request from the client device 250. Each access point can estimate a link quality between the access point and the client device 250 by measuring, for example, a receive signal strength of the probe request. The link quality can be communicated to the neighboring access points be broadcasting a received signal strength indicator (RSSI) to the neighboring access points. For example, as shown in
If, for example, the link quality indicator of the access node 222 is determined to be the best, the access node 222 responds to the probe request with a probe response 260. As indicated above, the determination of best link quality can be based on the RSSI as determine by each individual access point. Additionally, the best link quality can also include network quality parameters as previously discussed. The network quality parameters can be communicated directly to the neighboring access point, or the network quality parameters can be used to modify, for example, the RSSI to reflect the quality of the network quality parameters.
As previously described, the quality of the link can be determined by a receive signal strength of the probe response. The link quality can be additionally based on a network quality parameter of the access point.
The access point communicates the quality of the link between the access point and the client device. This allows the access points of the network to determine which of the access points has the best link quality. The access point with the best link quality can respond to the probe request. The process allows the client device to make a better selection than if all of the access points were to respond with a probe response. Additionally, the method reduces the number of probe responses, which improves air-time usage of the available transmission channels.
As will be described, the access nodes 420, 422, 424, 426 select route to the gateways 410, 411. As shown in
As will be described, the gateways 410, 411 and the access nodes 420, 422, 424, 426 can all provide a client device (such as, client device 450) with wireless access to the wired network 400. The methods of probe response suppression described for access node are applicable for gateways as well. The term “access node” is used here for nodes within a wireless mesh network as opposed to the “access points” of the wireless network of
Initial link quality estimates of the wireless mesh network of
Mesh Network Quality Parameter
One example of a mesh network quality parameter is an indicator of a path quality of the access node to a gateway of the mesh network. As shown in
The path quality can include both an upstream direction path quality (towards the default gateway) and a downstream direction path quality (away from the default gateway). As will be described, the downstream link quality can be determined by a persistence of successfully received routing packets.
Another wireless network quality parameter that can be useful includes an indicator of a bandwidth of a backhaul connection. If the connecting device is a gateway or an access point, the backhaul is typically the connection between the connecting device and the wired network. If the connecting device is an access node, the backhaul is the connection between the default gateway of the access node and the wired network.
Mesh networks can include fixed and mobile access nodes. Mobile access nodes are typically less reliable because of the changing condition of their wireless links (upstream and/or downstream). Therefore, another useful mesh network quality parameter is an indicator of whether the access node is a mobile access node or a fixed access node.
Mesh networks include some form of latency between, for example, an access node of the mesh network and the corresponding default gateway. More specifically, the latency can be for the data path between the access node and its default gateway. The latency can vary form one access node to another. Once the access node knows its latency, it can indicate the latency through the latency indicator, which can be include as or within the mesh network quality parameter.
Routing Selections
As previously described, the quality of an upstream path from an access node to a default gateway can be determined during routing selection by the access node. An embodiment of the mesh network includes gateways originating and broadcasting routing beacons at a predetermined rate (such as 4 beacons per second). Each first level access node (such as access nodes 420, 422, 424, 424) receive routing beacons from at least one of the gateways 410, 411. By knowing the original rate in which the beacons are broadcast from the gateways, and the rate at which routing beacons are successfully received, the receiving access node can determined the persistence of successfully received routing beacons. An embodiment includes each first level access node selecting an upstream gateway based on a persistence of successfully received routing beacons.
Each first level access node can then rebroadcast the successfully received routing beacons. The rebroadcast beacons can include additional information allowing second level access nodes (not shown) that receive the rebroadcast routing beacons to determine a routing path back to a gateway. The additional information can include identification (for example, an address) of the first level access node or a hop count (hop count indicates the number of wireless links an access node is from a gateway).
The mesh network can include any number of gateways and any number of access nodes. The number of wireless hops include within the wireless mesh network is not limited.
As previously stated, the persistence of received routing beacons can be used to select a routing path to a gateway. The persistence reflects that quality of the routing path to a gateway, and can be used to provide routing path quality within probe responses transmitted by each access node.
The routing path quality can be determined in both the downstream direction (away from the default gateway) and the upstream direction (towards the default gateway). The downstream quality can be determined by receiving routing beacons as described. The upstream quality can be determined by an upstream device (access node or gateway) receiving routing beacons from the access node, determining the persistence of successfully received beacons, and then including this information in the beacons that the upstream device broadcasts, and are received by the access node.
More than one access node, such as, access nodes 420, 422, 424, 426 receive probe requests from a client device 450. Each access node that receives the probe estimates a quality of the wireless link between the client device 450 and the receiving access node. For each receiving access node, the quality of the link can be determined, for example, by measuring the received signal strength of the probe request. That is, the signal strength of the probe request is to at least some extent dependent upon the quality of the transmission link between the client device transmitting the probe request, and the device receiving the probe request. Generally, the greater the received signal strength, the better the quality of the link between the client device and the receiving device.
Wireless network parameters, however, can also influence the desirability of one network device (gateway or access node) over another network device. For example, data throughput, latency, backhaul bandwidth and stability of the access node can also be useful in determining which probe request receiving access node should be connected to the probe request transmitting client device. Therefore, the link quality that is communicated from an access node can additionally include one or more network parameters associated with the access node. An embodiment includes the link quality (for example, an RSSI measurement) being modified to reflect one or more network quality parameters associated with the access node. That is, the value of the RSSI can be modified to reflect the quality of the one or more network quality parameters.
As previously stated, the access nodes 420, 422, 424, 426 can receive a probe request from the client device 450. Each access node can estimate a link quality between the access node and the client device 450 by measuring, for example, a receive signal strength of the probe request. The link quality can be communicated to the neighboring access nodes by broadcasting a received signal strength indicator (RSSI) to the neighboring access nodes. For example, as shown in
As previously described, the quality of the link between the access node and the client device can be determined based on the probe request by measuring a received signal strength of the probe request. The link quality can be communicated to neighboring access node be transmitting the RSSI of the probe request. Additionally, a wireless mesh network quality parameter can be communicated to the neighboring access nodes. Exemplary wireless mesh network quality parameters include a path quality of the access node to a wireless mesh network gateway, a latency of the access node, and/or a backhaul bandwidth of the access node.
Each access node of a wireless network that operating as described, ensures that the proper probe request receiving access node responds to the probe request of the client device. Transmission channel air-time usage is minimized because only a single access node responds to the probe request.
The communication between access nodes can be directly between the access nodes, or the communication can be routed through the gateways of the wireless mesh network.
Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The invention is limited only by the appended claims.
