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A Few WLAN Enhancements Disclosure Number: IPCOM000235426D
Publication Date: 2014-Feb-26
Document File: 33 page(s) / 3M

Publishing Venue

The Prior Art Database

Related People

Annie Wang: ATTORNEY


1) Method to Avoid Hidden Node Problem Automatically; 2) Cross-Channel Affiliate Marketing Using Wi-Fi Access Point Location, Online Activity, and User Identification; 3) Wireless Client QoS Monitoring from Client to Internet; 4)An Apparatus to Employ Reliable Multicast in Large Enterprise Wireless Networks; 5) Dynamic Offload of IEEE 802.11 Encapsulation and De-Capsulation Operations to the Radio Hardware for Distributed Security; 6) Shared VLAN Network Elements Auto Discovery; 7) Use of Trusted Group Keys in Wireless Enterprise Deployments to Increase Scalability; 8) Dynamic Update for External Captive Portal; 9) PoE Prioritization and Auto MTU Adjustment.

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Page 01 of 33

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Page 02 of 33

Method to Avoid Hidden Node Problem Automatically

Ying Lu, Guangzhi Ran, Kangchang Huang

Hidden nodes in a wireless network refer to nodes that are out of range of other nodes or a collection of nodes. It affects not only the level of performance degradation, but also the fairness of channel access and link's stability. It is a problem and always exists at mesh networks because of long distance topology, using different antenna type, none Wi-Fi interference and so on. At the mesh forming stage, if two nodes are hidden from each other, the two nodes can't join the same radio group at the same channel. This invention can avoid this case, see below.

Figure 1 hidden node topology

Need to avoid hidden node working in the same radio group on multi-radio mesh networks.


Hidden node can be judged by SNR, if that heard from is too low, or even can't hear , and are hidden from each other. In the outside field, asymmetric carrier cense and/or interference always happen, so if one direction of two node's SNR is low enough, we consider them as hidden nodes from each other.

Referring to Figure 1, when starts to connect with by sending associate request frame, the 's connected-neighbor- list which report the neighbor-list information (SNR, etc) of and will be contained in this frame, so will check both direction of each radio's SNR in connected-neighbor-list to find whether hidden problem exist or not.

In multi-radio mesh networks, different channel can be used to form the whole networks, the radios that connect through one- hop or more-hop in one channel forms a radio group.


WiFi, mesh networks, hidden nodes



Page 03 of 33

Below is an example (see Figure 2). There are seven routers in the mesh networks, each of which has two radios. Each color presents a radio cloud in different channel, there are four radio groups exist in the networks.

Figure 2: Radio Groups

In this example, there are four radio groups in the mesh networks:

Radio groups / channel


1 / Channel=161

{R10 ,R40 ,R51 }

2 / Channel 149

{R11 ,R30 }

3 / Channel 149

{R51 ,R61 ,R21}

4 / Channel 165

{R31 ,R20 ,R60}

Although the radios in group 2 and group 3 are wo...