CN111656736A

CN111656736A - Method and apparatus for detecting hidden node

Info

Publication number: CN111656736A
Application number: CN201880087499.0A
Authority: CN
Inventors: E·佩伦达; H·加卡宁
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Oyj; Nokia Solutions and Networks Oy
Priority date: 2018-02-13
Filing date: 2018-02-13
Publication date: 2020-09-11
Anticipated expiration: 2038-02-13
Also published as: WO2019157627A1; CN111656736B

Abstract

According to an embodiment, a networked device (121) for detecting a hidden node (100) in a wireless mesh network (130), WMN, having a plurality of active nodes (100-102) is disclosed, the networked device (121) comprises a processing unit (120), the processing unit (120) being configured to collect operational parameters for a first active node (101) and a second active node (102) of the active nodes (100) operating in the same channel, and calculating respective channel utilization performance indicators for the first active node (101) and the second active node (102) based on the operating parameters, and calculating a difference between the respective channel utilization performance indicators, and when the difference exceeds a first predefined threshold, the hidden node (100) is detected as a third active node operating on the same channel and hidden from the first active node (101) or the second active node (102) (101).

Description

Method and apparatus for detecting hidden node

Technical Field

The present invention relates generally to the field of detecting hidden nodes in a wireless mesh network.

Background

The wireless mesh network WMN is a communication network comprising a plurality of nodes organized in a mesh topology. Each of these nodes wirelessly exchanges data with other nodes and/or associated devices in the WMN. Because of their rapid and easy deployment, WMNs are widely installed in private and public environments, such as residential areas, businesses, and offices, particularly where cables are unavailable or undesirable. However, when the WMN is extended, every other node therein will reduce the end-user throughput. To alleviate this problem, a node may be equipped with multiple radios, and then different channels may be allocated to different nodes. However, in an unmanaged environment, such as in an apartment building, and even in offices that include different companies, different competing nodes share channels, resulting in the hidden node problem in WMNs. Such hidden node problems have a very severe impact on the quality of experience of the end user.

The hidden node problem occurs when the first node is within the transmission range of the second node but outside the transmission range of the third node. The first node is then hidden with respect to the third node and vice versa. Both the first node and the third node may actively transmit data to the second node because they cannot sense that the medium in which the data is transmitted is busy. As a result, collision of data packets may occur at the second node, resulting in a high error rate. Therefore, it is important to detect hidden nodes in WMNs to avoid such high error rates.

One way to detect hidden nodes is by so-called active hidden node detection mechanisms in the network, such as described by fatma m. et al in the detection technique of hidden nodes in wireless Ad Hoc networks published in london 2011 in WCE 2011 at the second world engineering convention. By means of this mechanism, if a node wants to detect a potential hidden node in the network, it sends a detection request to all its one-hop neighbors. Next, the one-hop neighbor nodes that receive the request begin sending unicast probe packet sequences to the neighbors within the time interval specified in the detection request. The detecting node then measures the traffic of its neighbors and based on the received packets, builds a complete list of hidden nodes.

Hidden nodes may also be detected in a passive manner by a request-to-send/clear-to-send mechanism. These are based on sniffing or listening to all data transmissions on the medium and detecting lost data packets in the data stream.

Another technique is disclosed in US20140036709a1, in which hidden nodes are detected based on analysis of reports received from multiple nodes. A hidden node is detected if it is observed that a transmission at one node is not observed by another node.

Document US20170026819a1 discloses a method for out-of-band hidden node detection. The method includes transmitting an out-of-band signal and considering both the node and the associated device. The node or associated device transmits a first out-of-band signal and updates a first list of neighboring devices based on receipt of a second out-of-band signal from the neighboring devices. The node may then receive a second list of neighboring devices from its associated device. By comparing the first list and the second list, the node may detect a hidden node and thereby change the operation mode before transmitting the data packet.

Disclosure of Invention

However, the above-described method for detecting a hidden node is to introduce an additional signal such as a detection request in the network or to detect the hidden node retroactively. The former method affects network operation, thereby interrupting user service, while the latter method detects hidden nodes only later, so the detection may have become obsolete.

It is therefore an object to disclose an apparatus and a system for detecting hidden nodes in WMNs without interrupting the user service and at the same time avoiding the risk of detection being outdated.

In a first aspect, the object is achieved by a networked device for detecting hidden nodes in a WMN having a plurality of active nodes, the networked device comprising a processing unit configured to:

-collecting operating parameters for a first one and a second one of the active nodes operating in the same channel; and

-calculating respective channel utilization performance indicators for the first active node and the second active node based on the operating parameters; and

-calculating a difference between the respective channel utilization performance indicators; and

-detecting the hidden node as a third active node operating on the same channel and hidden from the first active node or the second active node when the difference exceeds a first predefined threshold.

First, the processing unit collects operating parameters of active nodes in the WMN. These operating parameters are parameters that are available to the networked devices, i.e., parameters that do not interfere with WMN operation. Thus, no requests are sent to the nodes, nor are there any changes in the configuration of the nodes, e.g., switching them to the scanning mode. Furthermore, since the purpose is to detect hidden nodes in WMNs, the collection targets a pair of nodes, i.e., a first active node and a second active node operating in the same channel.

Such as channel utilization parameters, activity factors, noise levels, received signal strength indicator RSSI levels, bit error rates, and/or retransmission rates.

Second, the processing unit calculates respective channel utilization performance parameters for both the first node and the second node. Thus, the collected operating parameters are converted into performance parameters that express, for each node, its performance with respect to its channel used to send and receive packets.

Third, the processing unit of the networked device calculates a difference between the channel utilization performance indicators of the first node and the second node. Subsequently, in a fourth step, the difference is checked in order to detect hidden nodes.

When the difference exceeds a first predefined threshold, the processing unit detects the hidden node as a third active node operating on the same channel as the first node and the second node. The detected node is then hidden from the first active node or the second active node.

Several advantages over the prior art have been identified. First, only the active nodes are considered in the detection. It is superfluous to take inactive hidden nodes into account, since they, although they are hidden, do not affect the user performance. Second, by focusing on a pair of nodes, the WMN is described at the location of these nodes, thus eliminating the need to consider the entire WMN. This reduces the complexity of subsequent calculations. Third, since the calculations and associated detection are performed using operational parameters, WMNs are not affected and WMNs are described when collecting parameters. Thus, there is no need for any service interruption by the node, nor for channel switching that would cause delays and thus reduce the overall network capacity. In other words, the detection in the present disclosure is performed at zero cost compared to the prior art. Finally, since only the operating parameters are collected, the networked device is suitable for implementation in WMNs in a fast and straightforward manner.

According to an embodiment, the additional condition is checked when the difference does not exceed a first predefined threshold. In the latter case, the processing unit performs further calculations when the respective channel utilization performance indicators are represented similarly or differently, or when the already calculated difference is approximately equal to zero. Thus, the difference is, for example, less than the error tolerance. The processing unit then calculates respective bit error rate performance indicators for the first active node and/or the second active node. The latter calculation is again based on the collected operating parameters.

Next, the processing unit also detects a third active node as a hidden node when one of the respective error performance indicators exceeds a predefined error threshold. Thus, hidden nodes are detected when they are located on both sides of the first node and the second node.

According to an embodiment, the channel utilization performance indicator indicates a channel busy time during the predefined time period.

In this way, the channel utilization performance indicator is calculated by observing only the channel busy time, thereby calculating the indicator in a fast and straightforward manner. Furthermore, by simply adjusting the predefined time period, the networked device may easily accommodate WMNs that are highly dynamic or non-dynamic.

According to an embodiment, the first node and the second node are manageable by the networking device.

This not only means that the operating parameters are collected in an efficient manner, but also means that, for example, the possibility of introducing errors in collecting the parameters is reduced.

According to an embodiment, the networked device further comprises a knowledge base KB comprising channel utilization performance indicators, and the processing unit is further configured to update the KB after calculating the channel utilization performance indicator for each active node.

In addition to storing channel utilization performance indicators, KB may also be used to describe WMNs. Advantageously, the first predefined threshold may then be dynamically adapted to refine the detection, wherein each pair of first and second nodes performs the refinement.

According to a second aspect, the present disclosure relates to a method for detecting hidden nodes in a WMN having a plurality of active nodes, the method comprising the steps of:

According to an embodiment, the method further comprises the steps of: when the difference does not exceed a first predefined threshold, and when the respective channel utilization performance indicators are similar:

-calculating respective error rate performance indicators based on operational parameters of the first active node and/or the second active node; and

-detecting the third active node as a hidden node when one of the respective error rate performance indicators exceeds a predefined error threshold.

According to a third aspect, the present disclosure relates to a computer program product comprising computer executable instructions for performing the method according to the second aspect when the program is run on a computer.

According to a fourth aspect, the present disclosure relates to a computer readable storage medium comprising the computer program product according to the third aspect.

Drawings

Fig. 1 illustrates a wireless mesh network including a networking device for detecting hidden nodes, according to an embodiment of the invention; and

FIG. 2 shows steps performed by a networked device for detecting hidden nodes in accordance with an embodiment of the present invention; and

FIG. 3 illustrates steps for updating a knowledge base including channel utilization performance indicators computed by networked devices according to an embodiment of the invention; and

FIG. 4 illustrates a suitable computing system for performing steps according to embodiments of the invention.

Detailed Description

According to an embodiment, the invention relates to a networking device for detecting hidden nodes in a wireless mesh network WMN. Fig. 1 shows such a WMN 130 and such a networked device 121. Fig. 2 shows the steps performed by the networking device 121 for detecting hidden nodes.

The WMN 130 shown in fig. 1 comprises four

nodes

100 and 103, only three of which 100 and 102 are active. Each active node transmits and receives data packets within its respective range. This is illustrated by

ranges

110 and 112, each range corresponding to an active node. In particular, range 110 relates to node 100, range 111 relates to node 101, and range 112 relates to 102. Since node 103 is inactive in this exemplary illustration, the relevant scope is not shown.

The

active nodes

100 and 102 within the WMN 130 all operate on the same channel. The channel is for example in the 2.4GHz or 5GHz band.

In the representation of fig. 1, the range is represented by a circle, but it should be clear that the range of the node in a real-world situation may differ from a circle and depend on, for example, obstacles (such as walls and ceilings of the location in which the node operates).

Nodes

100 and 102 are within range 111 of node 101 and node 100 is outside range 112 of node 102, and thus node 102 is outside range 110 of node 100. Thus, node 102 is a hidden node with respect to node 100, and the same reasoning applies from the perspective of node 102, i.e., node 100 is a hidden node with respect to node 102.

The networking device 121 detects these hidden

nodes

100 and 102 in WMN 130. To this end, the networking device 121 comprises a processing unit 120 and, according to an embodiment, a knowledge base KB 122.

In the illustration of fig. 1,

nodes

100 and 103 are manageable nodes, i.e., are manageable by the networking device 121. This is illustrated, for example, by connection 123, which connection 123 is a connection between the networking device 121 and the networking device 121. In this way, the networking device 121 may collect data from the node and may also change the settings of the node, e.g., switching of operating channels.

Alternatively, the networked device 121 may include a receiving unit or radio receiver to collect data from the

nodes

100 and 102 in the WMN 130.

In a first step 200, the processing unit 120 collects the operation parameters from the

active nodes

100 and 102. These operating parameters are parameters that are collected without interfering with the WMN 130. Such as a channel utilization parameter, an activity factor, a noise level, a received signal strength indicator, RSSI, level, a bit error rate and/or a retransmission rate, or any other parameter suitable for describing the operation of the active node 100-102. Since the operational parameters are collected 200 without interfering with the WMN 130, the operational parameters are collected 200 at zero cost. The collection 200 of parameters is performed periodically at predefined time intervals (e.g., every few seconds).

In a next step 201, the collected 200 operating parameters are converted into a channel utilization performance indicator. The channel utilization performance indicators identify a network state and detect hidden nodes based on the channel utilization performance indicators.

For example, the channel utilization performance indicator is based on the channel busy time and is calculated as:

wherein

Is a channel utilization indicator for node x operating in channel h, where node x corresponds to node 100. Thus, when node y corresponds to node 101, the channel utilization indicator for node 101 corresponds to

Since they all operate in the same channel h that has been highlighted.

For each active node 100 in the WMN 130, 102, a channel utilization performance indicator may be calculated 201. Next, the KB of the networked device 121 is updated 202 with the calculated 201 channel utilization performance indicator.

Next, the processing unit 120 verifies 203 whether the difference between the channel utilization performance indicators of two neighboring nodes (e.g. nodes 100 and 101) exceeds a first predefined threshold u_hn，thr. In other words, therefore, if the absolute value of the difference exceeds the threshold, the following condition is verified 203:

when the difference exceeds a threshold, a hidden node is detected, and thus in this exemplary illustration, a node 102 that is hidden with respect to node 100 is detected.

Passes verification 203 of the difference and is by node 100 or node 101 when the difference exceeds a first predefined thresholdThe edge detects a node. However, when hidden nodes will be present on both sides of the neighboring

nodes

100 and 101, one hidden node is within the range 110 of node 100 but not within the range of node 101, and the other hidden node is within the range 111 of node 101 but not within the range of node 100, and both nodes have similar data traffic, corresponding channel utilization performance indicators

And

will have approximately the same value.

Thus, when the condition verified in step 203 does not exceed the first predefined threshold u_hn，thrThe processing unit 120 utilizes the given value. Thus, when the performance indicator is utilized

And

the difference between is about zero and, in addition, a hidden node will also be detected when the error rate of the packets sent at node 100 or node 101 is above a predefined error threshold, i.e. the following conditions are verified 205:

since hidden nodes introduce high errors.

When a hidden node is detected, the inference phase 204 is triggered by the processing unit 120. This may be, for example, notifying the user of the hidden node 102 and suggesting steps to take, such as, for example, switching of a channel of one of the

nodes

100 and 102.

The steps performed by the processing unit 120 can also be illustrated according to FIG. 3, in which steps for updating the KB122 are shown. In a first step, data 200 is collected, which corresponds to the same steps shown in fig. 2. Next, the operating parameters are sent 310 and then interpreted in the sensing stage 300, in other words converted into channel utilization performance indicators. These calculated performance indicators are sent 311 for use in the intermediate learning stage 301, which intermediate learning stage 301 updates 312KB122 on its behalf.

In the inference phase 302 (which is based on data received from the perception phase 300 or from the KB122 itself), it is determined when a hidden node is detected or not. Next, when a hidden node is detected, the detection is sent 313 to the decision stage 303. In decision phase 303, an optimization phase 304 is triggered to remedy the hidden node problem. The optimization stage 304 further exchanges 314 data with the KB such that the KB122 is further optimized in the subsequent sensing stage 300 and/or inference stage 302.

Fig. 4 shows details of a networked device 121 according to a further embodiment of the present invention. The networking device 121 is adapted to perform the steps according to the above embodiments. The networking device 121 may also be incorporated into or serve as a node. The networking device 121 may generally be formed as a suitable general purpose computer and includes a bus 410, a processor 402, a local memory 404, one or more optional input interfaces 414, one or more optional output interfaces 416, a communication interface 412, a storage element interface 406, and one or more storage elements 408. The bus 410 may include one or more conductors that allow communication among the components of the networking device 121. Processor 402 may include any type of conventional processor or microprocessor that interprets and executes programmed instructions. Local memory 404 may include a Random Access Memory (RAM) or another type of dynamic storage device that stores information and instructions for execution by processor 402 and/or a Read Only Memory (ROM) or another type of static storage device that stores static information and instructions for execution by processor 402. Input interface 414 may include one or more conventional mechanisms that allow an operator to input information to networked device 121, such as a keyboard 420, a mouse 430, a pen, voice recognition and/or biometric mechanisms, and so forth. Output interface 416 may include one or more conventional mechanisms for outputting information to an operator, such as a display 440. The communication interface 412 may include any transceiver-like mechanism, such as, for example, one or more ethernet interfaces that enable the networked device 121 to communicate with other devices and/or systems (e.g., with the node 100 and 103). The communication interface 412 of the networking device 121 may be connected to such networking device by means of a Local Area Network (LAN) or a Wide Area Network (WAN) such as, for example, the internet. The storage element interfaces 406 may include a storage interface, such as, for example, a Serial Advanced Technology Attachment (SATA) interface or a Small Computer System Interface (SCSI), for connecting the bus 410 to one or more storage elements 408, such as one or more local disks, e.g., SATA disk drives, and controlling writing data to and/or reading data from these storage elements 408. Although the storage element 408 is depicted as a local disk, in general any other suitable computer readable medium may be used, such as a removable disk, an optical storage medium such as a CD or DVD, a ROM disk, a solid state drive, a flash memory card, and so forth. The networking device 121 described above may also run as a virtual machine on top of physical hardware.

Although the present invention has been described with reference to specific embodiments, it will be clear to a person skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that various changes and modifications may be effected therein without departing from the scope of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, readers of the present patent application will understand that the word "comprising" or "comprises" does not exclude other elements or steps, that the words "a" or "an" do not exclude a plurality, and that a single element, such as a computer system, a processor or another integrated unit, may fulfil the functions of several means recited in the claims. Any reference signs in the claims shall not be construed as limiting the respective claim concerned. The terms "first," "second," "third," "a," "b," "c," and the like, when used in the specification or claims, are introduced to distinguish between similar elements or steps and not necessarily to describe a sequential or chronological order. Also, the terms "top," "bottom," "above," "below," and the like are introduced for descriptive purposes and not necessarily for relative positioning. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention are capable of operation in other sequences and in other orientations than described or illustrated herein.

Claims

1. A networked device (121) for detecting hidden nodes (100) in a wireless mesh network (130), WMN, having a plurality of active nodes (100-102), the networked device (121) comprising a processing unit (120), the processing unit (120) being configured to:

-collecting operation parameters for a first (101) and a second (102) of said active nodes (100-102) operating in the same channel; and

-calculating respective channel utilization performance indicators for the first active node (101) and the second active node (102) based on the operating parameters; and

-detecting the hidden node (100) as a third active node operating on the same channel and hidden from the first active node (101) or the second active node (102) (101) when the difference exceeds a first predefined threshold.

2. The networking device (121) of claim 1, wherein the processing unit (120) is further configured to, when the difference does not exceed the first predefined threshold and when the respective channel utilization performance indicators are similar:

-calculating respective error rate performance indicators based on the operating parameters for the first active node (101) and/or the second active node (102); and

-detecting the third active node as the hidden node (100) when one of the respective bit error rate performance indicators exceeds a predefined error threshold.

3. The networking device (121) of claim 2, wherein the channel utilization performance indicator indicates a channel busy time during a predefined time period.

4. The networking device of claim 3, wherein the respective channel utilization performance indicators are similar when the difference is less than an error tolerance.

5. The networking device (121) of claim 4, wherein the first node (101) and the second node (102) are manageable by the networking device (121).

6. The networking device (121) of claim 5, wherein the operational parameter comprises at least one of:

-a channel utilization parameter; and

-an activity factor; and

-a noise level; and

-a received signal strength indicator, RSSI, level; and

-a bit error rate; and

-retransmission rate.

7. The networking device (121) of claim 6, further comprising a knowledge base (122), the knowledge base (122) comprising a channel utilization performance indicator; and wherein the processing unit is further configured to update the knowledge base (122) after calculating the channel utilization performance indicator for each active node (100-102).

8. A method for detecting a hidden node (100) in a wireless mesh network (130), WMN, having a plurality of active nodes (100-102), the method comprising the steps of:

9. The method of claim 8, further comprising the steps of: when the difference does not exceed the first predefined threshold and when the respective channel utilization performance indicators are similar:

10. A computer program product comprising computer executable instructions for performing the method according to claim 8 or 9 when the program is run on a computer.

11. A computer readable storage medium comprising the computer program product of claim 10.