WO2014023872A1 - Network discovery and neighbour database - Google Patents

Network discovery and neighbour database Download PDF

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Publication number
WO2014023872A1
WO2014023872A1 PCT/FI2012/050773 FI2012050773W WO2014023872A1 WO 2014023872 A1 WO2014023872 A1 WO 2014023872A1 FI 2012050773 W FI2012050773 W FI 2012050773W WO 2014023872 A1 WO2014023872 A1 WO 2014023872A1
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WO
WIPO (PCT)
Prior art keywords
network cluster
database
wireless device
neighbour
apparatus
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PCT/FI2012/050773
Other languages
French (fr)
Inventor
Enrico-Henrik Rantala
Markku Turunen
Kari LEPPÄNEN
Mika Kasslin
Sami Virtanen
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Nokia Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Priority to PCT/FI2012/050773 priority Critical patent/WO2014023872A1/en
Publication of WO2014023872A1 publication Critical patent/WO2014023872A1/en

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W8/00Network data management
    • H04W8/005Discovery of network devices, e.g. terminals
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00Routing or path finding of packets in data switching networks
    • H04L45/46Cluster building
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W40/00Communication routing or communication path finding
    • H04W40/24Connectivity information management, e.g. connectivity discovery or connectivity update

Abstract

A method, apparatus, and computer program for facilitating reassociation of a wireless device in a wireless network are provided. The wireless device stores a first neighbour database comprising information on neighbouring wireless devices. Upon changing association from a first network cluster to a second, older network cluster, the wireless device uses the stored first neighbour database as an initial neighbour database in the second network cluster.

Description

Network Discovery and Neighbour Database

Field

The invention relates to the field of wireless communications and, particularly, to discovering a wireless network and providing a neighbour database. Background

In a mobile networking environment, a wireless device may be configured to scan for available wireless networks and select a wireless network with which to establish association for data transfer. The wireless device may also be configured to continue the scanning after the association and, upon discovery of another wireless network, the wireless device may change the association to the newly discovered wireless network.

Brief description

The invention is defined by the independent claims.

Embodiments of the invention are defined in the dependent claims. List of drawings

Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which

Figure 1 illustrates a wireless network to which embodiments of the invention may be applied;

Figure 2 illustrates a flow diagram of a process for changing association of a wireless device and managing a neighbour database in that context according to an embodiment of the invention;

Figure 3 illustrates an embodiment for triggering forced scanning in the wireless device according to an embodiment of the invention;

Figures 4 and 5 illustrate embodiments for reassociating wireless devices according to an embodiment of the invention; and

Figure 6 illustrates a block diagram of an apparatus according to an embodiment of the invention.

Description of embodiments

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

Figure 1 illustrates a wireless communication scenario to which embodiments of the invention may be applied. The wireless communication scenario may be realized by a wireless network comprising wireless devices 104, 108, 1 10, 1 12, 1 14, 1 16. The wireless network may be a mobile ad hoc network having no fixed infrastructure. The wireless network may be based in IEEE 802.1 1 specification or another standard enabling the creation of the mobile ad hoc networks.

In an embodiment, the wireless devices 104, 108, 1 10, 1 12, 1 14, 1 16 share the same network identifier.

The wireless network may maintain time synchronization between the wireless devices 104, 108, 1 10, 1 12, 1 14, 1 16. The wireless devices may also broadcast awareness information comprising information on neighbouring devices. The beacon messages may be used for synchronization and, additionally, the beacon messages may contain the awareness information. Each wireless device may be provided with a functionality that manages and controls the synchronization, and the functionality may be divided into two functional entities: A medium access control (MAC) layer and awareness networking control (ANC). The MAC layer controls generation of beacon messages, handling of received beacon messages and maintaining a synchronization function based on the received beacons. In order to have an always-on awareness system, usage of energy-efficient radio resources is an advantage. An example of such a usage is to provide two operation modes. In the first operation mode, the wireless device tries to detect other devices as soon as possible. In this mode a device may use standard beaconing mode and operate on a single channel. In the second operation mode, operations are focused on data transfer with an(other) device(s). In this mode the wireless device may use a diluted beaconing mode and multichannel operation. The ANC may determine when to switch between the operation modes. The ANC may use the first mode when the wireless device has no neighbouring devices, e.g. by using the standard beaconing mode and the single channel operation. When the wireless device has neighbouring device(s), the ANC may use the second operation mode, e.g. by using the diluted beaconing mode and multi-channel operation. An example of such a system is Awarenet.

The wireless devices 104, 108, 1 10, 1 12, 1 14, 1 16 may form a group or a network cluster of one or more wireless devices. In a network cluster, the wireless devices are awake approximately at the same time. This may be realized by providing close time synchronization between the wireless devices. When two clusters come to proximity of each other, the devices form a larger cluster having the same time synchronization. As a synchronization reference, a cluster having an earlier time of establishment is used. The wireless devices may broadcast the age of their respective network cluster(s), e.g. time elapsed from the establishment of the network cluster in a beacon message. In order to make synchronization faster, a wireless device may emit an additional beacon in one of the following exemplary situations: if a wireless device receives, during the scanning, a beacon indicating a time of establishment that is later than the time of establishment of the network cluster of the wireless device itself minus a determined constant; If the wireless device receives during an awake period a beacon indicating a time of establishment which is later than the time of establishment of the network cluster of the wireless device itself minus a determined another constant; or whenever the wireless device receives a beacon indicating a time of establishment which is earlier than the time of establishment of the network cluster of the wireless device itself plus a determined another constant. The wireless device may make a random decision whether to emit an additional beacon or not, or a wireless device may emit an additional beacon if it did scanning during the latest scanning opportunity. The first and second case may be understood such that the wireless device announces its presence to another network cluster having a sufficiently later time of establishment, in order to announce its presence to wireless devices of the other network cluster. The third case may be understood such that the wireless device announces the earlier network cluster establishment time to the other network cluster having a later network cluster establishment time. Devices may use these additional beacons for synchronization.

The wireless devices 104 to 1 16 of the wireless network of Figure 1 may be divided into a plurality of network clusters, wherein the devices within the same network cluster are synchronized with each other. The synchronization may be understood such that sleep periods and awake periods of wireless devices belonging to the same network cluster are mutually synchronized. As a consequence, the wireless devices of the same network cluster are dormant substantially at the same and awake substantially at the same time. The awake periods may be shorter than the doze periods in order to save battery. There may also be at least coarse synchronization between different clusters of the wireless network, e.g. awake periods of the different network clusters may overlap at least partially.

In addition to the doze and awake periods, each wireless device may have a periodic scanning opportunity, wherein the wireless device may make a decision whether or not to use the scanning opportunity. The decision may be based on randomization, e.g. each wireless device may make a random decision of whether or not to carry out scanning during the scanning opportunity.

The clusters may share the same network identifier, as shown in Figure 1 . The network identifier may be any identifier that identifies the network. However, different network clusters may be identified by different time values, wherein each time value indicates a moment of establishment of a corresponding network cluster. This time value may be called a timing synchronization function (TSF) timestamp. The time value may be a progressing counter value counted and broadcasted by the wireless devices of the network cluster. The time value may increase constantly, as counted by the wireless devices of the network cluster, and time values of different network cluster may increase at the same rate to enable comparison between the different time values. It should be appreciated that in some embodiments the time value may be fixed and indicate explicitly a timing of the establishment of the network cluster, and a wireless device may determine that a network cluster having a time value indicating the earliest timing has been established first.

In an embodiment, the network identifier is also a time value indicating a moment of establishment of the wireless network. As a consequence, the network identifier is in one embodiment a fixed identifier and in another embodiment a time value, e.g. a time counter value.

Figure 1 illustrates two network clusters belonging to the same wireless network. Wireless devices 104, 1 10, 1 12, 1 16 belong currently to a first network cluster 100, while wireless devices 108, 1 14 belong to a second network cluster. The network clusters 100, 102 share the same network identifier X but different time values: time value Y for the first network cluster 100 and time value Z for the second network cluster 102. Let us assume that Z > Y which means that the second network cluster 102 has been established before the first network cluster 100.

An operating principle of the wireless network may be to provide synchronization between all the devices of the wireless network. Therefore, the wireless devices 104 to 1 16 may be configured to attempt to minimize the number of different network clusters, because synchronization within a network cluster may be more accurate than between different network clusters. The wireless devices 104 to 1 16 may be configured to synchronize to the network cluster having a time value indicating the earliest establishment. As a consequence, if a wireless device discovers a network cluster that has been established prior to the network cluster with which the wireless device is currently synchronized, the wireless device may be configured to change the synchronization to the older network cluster by adopting a timing synchronization value of the older network cluster.

The wireless devices 104 to 1 16 may also be configured to maintain a neighbour database comprising identities and parameters of detected neighbouring wireless devices. The neighbour database may comprise at least one of the following parameters for each neighbouring wireless device: a medium access control (MAC) address, a radio distance between the wireless device and the neighbouring wireless device, a reliability value representing reliability of the information on the respective neighbouring wireless device, a traffic value indicating the amount of transmitted traffic per a time unit, speed, context-related parameters such indoors/outdoors environment, etc. The MAC address may be used to identify a neighbouring wireless device in the neighbour database. The radio distance may be used to determine the quality of a communication link between the wireless device and each neighbouring wireless device. The radio distance may be represented in the form of a received channel power indicator (RCPI), received signal strength indicator (RSSI), path loss, or any other indicator proportional to the radio distance or signal attenuation between the wireless device and each neighbouring wireless device. The reliability value may be provided in a form of counter or time value indicating duration from the last update of the parameters for a given neighbouring wireless device. Any other reliability metric representing the reliability of the information on the neighbouring wireless device is naturally possible.

The neighbour database may also contain categorization of other wireless devices, based on, for example, how regularly the other wireless devices have transmitted messages or how long other wireless devices have been present as a neighbour. As an example a wireless device may categorize another wireless device as "stable", if the time period of the latest received transmission is less than (or equal to) a threshold value Tactive and the number of received messages is greater than (or equal to) a threshold value Nactive- The wireless device may categorize another wireless device as "known" if the time period of the latest received transmission is less than (or equal to) the threshold value Tactive but number of received messages is less than the threshold value Nactive- The wireless device may categorize another wireless device as "potentially-known", if the time period of the latest received transmission is greater than the threshold value Tactive but less than a given expiration time period threshold TeXpiration- If the time period of the latest received transmission is greater than or equal to the expiration time period threshold TeXpiration, then the wireless device removes the other device from the neighbour database. The wireless device may determine that the neighbouring wireless devices that have been categorized as "stable" will share the same knowledge of network clusters in proximity. An embodiment of the invention provides a procedure for optimizing a change of association from the first network cluster 100 to the second network cluster 102 in terms of managing the neighbour database. The association may be understood as a wireless device connecting or being connected to a network cluster or to a wireless device of the network cluster. In the embodiments using the NIC, the association may comprise synchronization to a given network cluster, while reassociation may comprise switching synchronization from the first network cluster 100 to the second network cluster 102. In some embodiments, the association may also comprise authentication of the wireless device, sharing at least one encryption key, etc.

In an embodiment, the neighbour database comprises or consists of single-hop neighbours. A single-hop neighbour may be defined as a neighbouring wireless device with which a wireless device may communicate directly, while a multi-hop neighbour is a wireless device with which the wireless device may communicate indirectly via at least one other neighbouring wireless device. Referring to Figure 1 , the wireless device 1 16 may receive message transmissions originating from the wireless devices 104 and 1 12, but not from 1 10. As a consequence, the neighbour database of the wireless device may comprise entries for the neighbouring wireless devices 104 and 1 12 but not for the wireless device 1 10. The neighbor database may comprise "first hand" information the wireless device 1 16 is able to acquire directly from the neighbouring devices 104, 1 12. The first hand information may be defined for the wireless device 104 as information acquired directly from the wireless device 104. The wireless device 1 16 may also store a neighbourhood database comprising "second hand" information acquired as the awareness information, e.g. information on the wireless device 104 the wireless device 16 received from the wireless device 1 12 but not directly from the wireless device 104. The neighbourhood database may comprise entries for the same set of neighbouring wireless devices as the neighbor database.

In an example, a neighbouring wireless device 104 may broadcast awareness information about its neighbour wireless devices 1 10 and 1 12. Such information may include radio distance measurements, estimated positions, and/or calculated neighbourhood map. The wireless device 1 16 may construct its own neighborhood map based on information measured on its own and information exchanged with single-hop neighbouring wireless devices 104, 1 12. If the wireless device 1 16 receives an awareness information message from any wireless device, it may update the neighborhood database for the wireless devices 104 and 1 12 listed in the neighbour database, but not for 1 10 because there is no corresponding entry for 1 10 in the neighbor database.

The neighbour database consisting of the single-hop neighbours may be used to detect fast situations when neighbours disappear due to reassociation with another older cluster, for example. This database may be used to trigger detection of a better cluster with more wireless devices. Thus, the single-hop neighbour database is filled with information on only those neighbouring devices from which the wireless device is able to receive transmissions.

In an embodiment, the wireless devices may maintain in the same or in another neighbour database multi-hop neighbours in order to monitor a larger network or network cluster topology, locations of the neighbouring wireless devices, etc.

In an embodiment, the wireless device 1 16 constructs and maintains the neighbour database and/or the neighbourhood database on its own. In another embodiment, the neighbour database and/or the neighbourhood database is managed in a server or a corresponding entity and transferred over a cellular connection or similar to the wireless device 1 16.

Figure 2 illustrates a flow diagram of a procedure carried out in a wireless device of the first network cluster, e.g. the wireless devices 1 16. Referring to Figure 2, the wireless device 1 16 has been associated the first network cluster 100 identified by a first time value indicative of a moment of establishment of the first network cluster 100 (block 200). The wireless device 1 16 stores in block 202 a first neighbour database comprising information on neighbouring wireless devices 104, 1 10, 1 12 associated with the first network cluster 100.

In block 204, the wireless device 1 16 detects the presence of the second network cluster 102 identified by a second time value indicative of a moment of establishment of the second network cluster 102. In block 206 the wireless device analyses the time values of the network clusters 100 and 102 and determines from the first time counter value and the second time counter value that the second network cluster 102 has been established before the first network cluster 100. As a consequence, the wireless device changes association from the first network cluster 100 to the second network cluster 102. After association with the second network cluster 102, the wireless device 1 16 uses contents of said first neighbour database as an initial neighbour database for the wireless device 1 16 in the second network cluster 102 (block 208).

The wireless device 1 16 may adopt the first neighbour database as the initial neighbour database as such, or it may change some of the contents of the first neighbour database when adopting the first neighbour database as the initial database in the second network cluster. In an embodiment, the wireless device 1 16 changes the categorization of at least some of the neighbouring devices listed in the first neighbour database. For example, a neighbouring wireless device categorized as "stable" in the first neighbour database and in the first network cluster 100 may be re-categorized as "known" or "potentially-known" because the wireless device 1 16 may expect that previously "stable" devices share the same neighbourhood information and thus will appear soon as neighbours in the second network cluster. The wireless device 1 16 may re-categorize a "known" neighbouring wireless device in the first neighbour database as "potentially-known" or it may even be removed from the initial neighbour database. The wireless device 1 16 may remove "potentially-known" wireless devices when adopting the first neighbour database as the initial neighbour database in the second network cluster.

According to this embodiment, the wireless device 1 16 maintains the neighbour database comprising the neighbouring devices 104, 1 10, 1 12 the wireless device 1 16 had in the first network cluster 100. Momentarily, the neighbour database may not be up-to-date because the neighbouring devices 104, 1 10, 1 12 may still be in the first network cluster. However, because of the inherent tendency of the network to reduce the number of network clusters, it is probable that the other wireless devices 104, 1 10, 1 12 will also appear the second network cluster 102 soon. Therefore, maintaining the old "stable" and also possibly "known" neighbouring devices 104, 1 12, 1 14 in the database reduces the need for reconstructing the database. This reduces the processing requirements in the wireless device 1 16 and improves the connectivity of the wireless device 1 16.

In an embodiment, the first neighbour database used as the initial database consists of single-hop neighbours. In an embodiment, the first neighbour database used as the initial database comprises one or both of the above-described neighbour database and the neighbourhood database. The neighbourhood database comprising the second-hand information on the neighbours may be used in the initial database, if both the neighbouring wireless device that transmitted the second-hand information and the neighbouring wireless device referred by the second-hand information are or are expected to be present in the second network cluster. In an example where the neighbourhood database comprises the above-described neighbour map information, the wireless device 1 16 may copy into the initial database the neighbour map information containing those neighbouring wireless devices that have already detected to be present or are expected to be present in the second network cluster 102.

In an embodiment, the wireless device 1 16 uses contents of said first neighbour database as the initial neighbour database in the second network cluster without verifying validity of the contents of the first neighbour database when changing the association. It may be understood that the association with a new network cluster does not necessitate a validation of the contents of the neighbour database, and the contents of the previous neighbour database may be taken for use in the new network cluster without such a validation. However, the re-categorization may be carried out as a default operation in the above-described manner, depending on the embodiment. As a result of this feature and the fact that probably the neighbouring wireless devices of the first network cluster will also transfer to the second network cluster soon after the wireless device 1 16, the neighbouring database will be updated over time through conventional operation of the wireless device 1 16, and no special validity check in connection with changing the association is necessary. The wireless device may update the neighbour database on the basis of neighbour information received in connection with scanning opportunities and/or awake periods in the second network cluster 102.

In another embodiment, the wireless device 1 16 verifies the validity of the first neighbour database in connection with changing the association from the first network cluster 100 to the second network cluster before employing the first neighbour database as the initial database in the second network cluster 102. The wireless device may carry out the verification during its next one or more scanning opportunities in which the wireless device 1 16 scans for the presence of neighbouring wireless devices in the second network cluster 102. If the wireless device 1 16 detects at least one neighbouring wireless device comprised in both the second network cluster and in the first neighbour database, the wireless device 1 16 may employ the first neighbour database as the initial database. As a consequence, the parameters of said at least one detected neighbouring wireless device need not to be determined from a scratch. In an embodiment, the wireless device 1 16 may be configured to use a condition that at least a determined number of neighbouring devices comprised in the first neighbour database must be detected in the second network cluster 102 before using the first neighbour database as the initial database in the second network cluster 102. The determined number may be higher than one. If the wireless device 1 16 detects no neighbouring wireless devices in the second network cluster 102 that are also listed in the first neighbour database, the wireless device 1 16 may rebuild the neighbour database from the scratch.

Let us now describe some embodiments for causing the change of the association from one network cluster to another with reference to Figure 3. The procedure may be carried out between blocks 202 and 204 of Figure 2. In an embodiment, the wireless device 1 16 still associated with the first network cluster 100 executes a forced scanning for other network clusters upon detecting a determined event in the wireless device 1 16 (block 300). The determined event may be at least one of the following: a significant amount of entries of the neighbour database are about to expire; the neighbour database is about to become empty; the number of received messages drops; an application has requested for an immediate scanning. The exhaustion of the entries in the neighbour database may be detected by determining that the number of neighbouring devices listed in the neighbour database decreases or is about to decrease within a determined time interval below a threshold. The decreases in the number of received messages may be detected by determining that the amount of traffic in the network cluster decreases below a traffic threshold. This may be carried out through a simple traffic monitoring procedure. The block 300 may be carried out by the above-described ANC. In block 302, the ANC configures the MAC function to carry out a forced scanning and to use modified scanning parameters that may differ from scanning parameters used during regular scanning of the wireless device 1 16 to ensure that the wireless device maintains synchronization with neighbouring wireless devices.

The modified scanning parameters used during the forced scanning may comprise at least one of an extended scanning duration and forced use of a preset scanning opportunity. As a consequence of extending the scanning duration, the wireless device 1 16 increases the probability of discovering a neighbouring wireless device and/or a neighbouring network cluster. The forced use of a scanning opportunity may comprise skipping the randomness related to making the decision of whether or not using the prescheduled scanning opportunity. If the wireless device always uses the scanning opportunities scheduled to it, e.g. periodic scanning opportunities, the forced use of the scanning opportunity is in use by default. In some embodiments, the forced scanning is executed in time periods that do not overlap or overlap partially with the scanning opportunities.

The MAC may realize the forced scanning in the scanning phase or in the awake period(s) of the wireless device. With respect to the scanning phase, the ANC may invoke a MAC command "immediate_scan". The command may also define the modified scanning parameters but, in another embodiment, the modified scanning parameters have been predetermined and stored in a memory unit, and the ANC does not need to compute and provide them separately. When the MAC function receives the command, it saves active scanning parameters currently in use and sets the modified scanning parameters as active parameters for the duration of the forced scanning. After the MAC has completed the forced scanning, it restores the saved configuration parameters and resumes normal operation. If MAC detects a transmission of a message, e.g. a beacon or data message, from a neighbouring network cluster during the scanning it may carry out normal synchronization with the neighbouring network cluster after the reception of the message or soon after the scan provided that the neighbouring network cluster is older than the network cluster with which the MAC is currently synchronized.

With respect to carrying out the forced scanning during the awake periods, the MAC may use an extended awake period functionality as the discovery method. The ANC may invoke a MAC command "stay_awake". When the MAC receives the command, it saves the current active configuration parameters for the awake period and sets the modified parameters as active parameters for the next awake period. The modified awake parameters may comprise an extended awake duration. Then, the MAC starts the extended awake and, after the extended awake period, the MAC restores the saved configuration parameters and resumes the normal operation. If the MAC detects beacons from a neighbouring network cluster during the scanning it may carry out normal synchronization with the neighbouring network cluster, provided that the neighbouring network cluster is older than the network cluster with which the MAC is currently synchronized. Let us now consider two examples of using the forced scanning with reference to Figures 4 and 5. Let us in both examples assume an initial situation where the wireless devices 1 12 and 1 16 belong to the first network cluster 100, while the wireless device 108 belongs to the second network cluster 102. Referring to Figure 4, the devices 1 12 and 1 16 carry out data transfer during their mutually synchronized awake periods (400, 402). In block 404, the wireless device determines to use its scanning opportunity to carry out normal scanning. During the scanning period 404, the wireless device 108 detects a beacon message transmitted by the wireless device 1 12 during its next awake period 406. The beacon message may comprise the time value representing the age of the first network cluster 100. The detection of the scanning message may trigger comparison of the time value in the beacon message with a corresponding time value of the second network cluster 102 in the wireless device 108. Upon detecting that the time value comprised in the beacon message indicates that the first network cluster 100 is younger than the second network cluster 102, the wireless device 108 may cause transmission of an additional beacon message comprising the time value of the second network cluster 102. The wireless device 108 may transmit the additional beacon message immediately within its scanning period 404 and within the awake period 406 of the wireless device 1 12. Upon detecting the additional scanning message from the wireless device 108, the wireless device 1 12 also carries out the comparison between the time values of the network clusters 100, 102 and detects that the second network cluster is older. This detection triggers the wireless device to change the association from the first network cluster 100 to the second network cluster 102 and to synchronize with the second network cluster. As a consequence, the awake periods of the wireless device 1 12 will become synchronized with the awake periods of the second network cluster 102, as shown by awake periods 410, 412. The wireless device 1 12 also maintains its neighbour database unaffected during the transition. After being associated with the second network cluster 102, the wireless device continues normal detection of neighbouring devices in the new network cluster, and the neighbour database will be updated inherently.

Let us assume that the wireless device 1 16 does not detect the beacon message from the second network cluster in block 408, and so it maintains its synchronization with the first network cluster. Since the awake periods of the wireless devices 1 12 and 1 16 are now not mutually synchronized, the wireless device 1 16 will no longer detect the transmissions by the wireless device 1 12, e.g. in its awake period 414. After a time period, the wireless device 1 16 determines that a forced scanning is needed as a result of detecting decreasing amount of traffic or absence of neighbours, and the wireless device 1 16 carries out the forced scanning in 416. The forced scanning may be realized during the scanning period and/or awake period of the wireless device 1 16. Because of the extension of the scanning period, the scanning period more probably overlaps with the awake periods 418, 420 of the second network cluster 102. During the forced scanning, the wireless device 1 16 detects a beacon message from the wireless device 1 12 that now broadcasts the time value of the second network cluster 102. As a consequence, the wireless device 1 16 also gains knowledge about the older second network cluster 102 and changes its association from the first network cluster 100 to the second network cluster. The wireless device 1 16 may also maintain its neighbour database acquired and updated during the association with the first network cluster. As a consequence, the wireless devices 1 12, 1 16 have one another's parameters readily available, and no neighbour detection is necessary before starting the data transfer between the wireless devices 1 12, 1 16 in the second network cluster 102 (awake periods 422, 424, 426). If the wireless devices 1 12, 1 16 store in the neighbour database entries for neighbouring wireless devices belonging to neighbouring network cluster(s) as well, the wireless devices 1 12, 1 16 may have the parameters of other wireless devices of the second network cluster 102 also readily available after the reassociation. When all the wireless devices of the first network cluster 100 have changed the associations to the second network cluster 102, the first network cluster 100 may cease to exist.

In the embodiment of Figure 4, the wireless device 1 12 changes the association immediately upon detecting the older network cluster. This may cause some delay in the detection of the older network cluster by other wireless devices of the younger network cluster, e.g. wireless device 1 16. In the embodiment of Figure 5, upon detecting the older network cluster the wireless device 1 12 maintains synchronization with its current network cluster at least for the next awake period in order to transmit the beacon comprising the time value of the older network cluster. In this manner the other wireless devices of the younger network cluster become immediately aware of the other network cluster, and the delay in transferring all the devices to the older network cluster may be reduced. In Figure 5, the same reference numbers as used in Figure 4 have the same function. Now, upon detecting the beacon from the wireless device 108 (having an awake period 500) in its scanning period 502, the wireless device does 1 12 not change the association immediately for the next awake period 512 of the second network cluster 102 but, instead, maintains the association with the first network cluster 100. However, the wireless device 1 12 may already modify its beacon message to comprise at least the time value of the second network cluster. The wireless device 1 12 transmits a beacon comprising the time value of the second network cluster in 504. In 504, the wireless device 1 12 thus uses the awake period of the first network cluster 100 to transmit a beacon comprising the time value of the second network cluster 102. Thereafter the wireless device 1 12 synchronizes with the second network cluster 102, as represented by 514, 506, while the wireless device 1 16 receiving the beacon in 508 maintains the synchronization with the first network cluster 100 for the next awake period 510 in order to transmit the beacon comprising the time value of the second network cluster 102 to the remaining wireless devices of the first network cluster 100, if any. Thereafter, all the devices 108, 1 12, 1 16 are associated with the second network cluster, as shown by 516, 518, 520. Again, the wireless devices 1 12, 1 16 may maintain the neighbour database intact in connection with the change of the association from the first network cluster 100 to the second network cluster 102. Therefore, the database is readily available.

In an embodiment, the wireless device 1 12, 1 16 may make a random decision between instant synchronization with the second network cluster and maintaining the synchronization with the first network cluster 100 for the next awake period 510 in order to transmit the beacon comprising the time value of the second network cluster 102. Accordingly, some wireless devices of the first network cluster 100 may synchronize instantly upon discovery of the second network cluster 102, while other wireless devices first announce the presence of the second network cluster 102 to the remaining devices of the first network cluster 100 before synchronizing with the second network cluster 102.

In another embodiment, the wireless device may make a deterministic decision between instant synchronization with the second network cluster and maintaining the synchronization with the first network cluster 100 for the next awake period 510 in order to transmit the beacon comprising the time value of the second network cluster 102. For example, if the wireless device 1 16 will have a scanning opportunity within a determined time interval, it may choose to maintain the current synchronization and use the scanning opportunity to transmit the additional beacon. On the other hand, if the wireless device 1 16 does not have a scanning opportunity within the determined time interval, it may choose to synchronize immediately to the second network cluster 102.

It should be noted that the wireless device 1 12 does not necessarily broadcast in block 504 the same time value it received in block 502 from the second network cluster 102. For example, when the time value is a counter value, the wireless device 1 12 may add a value proportional to the duration between blocks 502 and 504 to the time value comprised in the beacon received in block 502. The same applies to the wireless device 1 16. In another embodiment, if the duration between blocks 502, 504 is considered negligible and the counter value is incremented with periodicity that is higher than the duration between blocks 502 and 504, the wireless devices 1 12, 1 16 may, at least in some situations, transmit the same time value received from the second network cluster.

Obviously, the forced scanning of Figure 4 may be applied to the embodiment of Figure 5 as a safety mechanism for wireless devices of the first network cluster 100 that do not detect the beacons transmitted (for example because of interference) in steps 500, 504, 510.

Figure 6 illustrates a block diagram of a structure of an apparatus according to an embodiment of the invention. The apparatus may comply with specifications of an IEEE 802.1 1 network and/or an Awarenet network. The wireless apparatus may also be a cognitive radio apparatus capable of realizing ad hoc networks and adapting its operation to a changing radio environment and network configurations. The apparatus may be the above-described wireless device and it may be comprised in a computer (PC), a laptop, a tablet computer, a cellular phone, a palm computer, or any other apparatus provided with radio communication capability. In another embodiment, the apparatus carrying out the above-described functionalities of the wireless 1 16 device is comprised in such a wireless device 1 16, e.g. the apparatus may comprise a circuitry, e.g. a chip, a processor, a micro controller, or a combination of such circuitries in the wireless device 1 16.

Referring to Figure 6, the apparatus may comprise a communication controller circuitry 50 configured to control wireless communications in the wireless device 1 16. The communication controller circuitry 50 may comprise a control part 52 handling control signalling communication with respect to transmission, reception, and extraction of control or management frames including the beacon messages, as described above. The control part 52 may also realize the above- described MAC function related to the sleep, awake, and scanning periods of the wireless device 1 16 and the association and reassociation of the wireless device with network clusters. The communication controller circuitry 50 may further comprise a data part 56 that handles transmission and reception of payload data during the awake periods of the wireless device 1 16. The communication controller circuitry 50 may further comprise a network discovery processor 55 configured to carry out discovery and information management related to neighbouring wireless devices and neighbouring network clusters. The network discovery processor 55 may comprise a forced scanning controller 54 configured to monitor the operation of the wireless device 1 16, the operation network cluster with which the wireless device 1 16 is currently associated, and the contents of the neighbour database 62 stored in a memory 60. Upon detecting an event in the monitored instances, or upon receiving a request through a user interface of the apparatus, the forced scanning controller 54 may choose to execute the above- described forced scanning by invoking the control part 52 with an appropriate forced scanning command. As a consequence, the forced scanning controller 54 may carry out the above-described functionality of the ANC.

The network discovery processor 55 may further comprise a neighbour database manager 58 configured to maintain and update the neighbour database 62. The neighbour database manager 58 may acquire parameters of discovered neighbouring wireless devices of own and neighbouring network clusters from beacon messages received by the control part 52. On the basis of the information on the neighbouring wireless devices contained in the received beacon messages, the neighbour database manager may add entries for new neighbouring wireless devices and update the entries of those neighbouring wireless devices already contained in the neighbour database 62. The neighbour database manager may also add a reliability value for each entry. Upon reception of new beacon message associated with an entry in the neighbour database, the neighbour database manager 58 may reset the reliability value of that entry to show that the entry provides reliable information on the corresponding neighbouring wireless device. On the other hand, when a reliability value of an entry shows sufficient unreliability, the neighbour database manager 58 may delete that entry. In this manner, the neighbour database manager 58 may keep the neighbour database 62 up-to-date. The operation of the neighbour database manage may be independent of the changes in the association of the wireless device 1 16. In some embodiments, the neighbour database manager 58 is not even aware of the current association of the wireless device 1 16.

The circuitries 52 to 58 of the communication controller circuitry 50 may be carried out by the one or more physical circuitries or processors. In practice, the different circuitries may be realized by different computer program modules. Depending on the specifications and the design of the apparatus, the apparatus may comprise some of the circuitries 52 to 58 or all of them. The apparatus may further comprise the memory 60 that stores computer programs 64 (software) configuring the apparatus to perform the above- described functionalities of the wireless device. The memory 60 may also store the neighbour database 62 and other information needed for the wireless communications. The apparatus may further comprise radio interface components 70 providing the apparatus with radio communication capabilities within its wireless network and/or within at least one network cluster. The radio interface components 70 may comprise standard well-known components such as an amplifier, filter, frequency-converter, (de)modulator, and encoder/decoder circuitries and one or more antennas. The apparatus may further comprise a user interface enabling interaction with the user of the communication device. The user interface may comprise a display, a keypad or a keyboard, a loudspeaker, etc.

In an embodiment, the apparatus carrying out the embodiments of the invention in the wireless apparatus comprises at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the functionalities of the wireless device 1 16 according to any one of the processes of Figures 2 to 5. Accordingly, the at least one processor, the memory, and the computer program code form processing means for carrying out embodiments of the present invention in the wireless device 1 16.

As used in this application, the term 'circuitry' refers to all of the following: (a) hardware-only circuit implementations such as implementations in only analog and/or digital circuitry; (b) combinations of circuits and software and/or firmware, such as (as applicable): (i) a combination of processor(s) or processor cores; or (ii) portions of processor(s)/software including digital signal processor(s), software, and at least one memory that work together to cause an apparatus to perform specific functions; and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor, e.g. one core of a multi-core processor, and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular element, a baseband integrated circuit, an application-specific integrated circuit (ASIC), and/or a field-programmable grid array (FPGA) circuit for the apparatus according to an embodiment of the invention.

The processes or methods described in Figures 2 to 5 may also be carried out in the form of a computer process defined by a computer program. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include transitory and/or non-transitory computer media, e.g. a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package. Depending on the processing power needed, the computer program may be executed in a single electronic digital processing unit or it may be distributed amongst a number of processing units.

The present invention is applicable to wireless networks defined above but also to other suitable wireless systems. The protocols used, the specifications of the systems, and their network elements develop rapidly. Such development may require extra changes to the described embodiments. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

Claims
1 . A method comprising:
associating, by a wireless device, with a first network cluster identified by a first time value indicative of a moment of establishment of the first network cluster; storing in the wireless device a first neighbour database comprising information on neighbouring wireless devices associated with the first network cluster; detecting by the wireless device a presence of a second network cluster identified by a second time value indicative of a moment of establishment of the second network cluster; determining from the first time value and the second time value that the second network cluster has been established before the first network cluster; causing the wireless device to change association from the first network cluster to the second network cluster as a result of said determination; after association with the second network cluster, using contents of said first neighbour database as an initial neighbour database for the wireless device in the second network cluster. 2. The method of claim 1 , wherein the first network cluster and the second network cluster share the same network identifier.
3. The method of claim 1 or 2, wherein the contents of said first neighbour database are used as the initial neighbour database in the second network cluster without verifying validity of the contents of the first neighbour database when changing the association.
4. The method of any preceding claim, wherein the first neighbour database consists of single-hop neighbours.
5. The method of any preceding claim, further comprising changing categorization of at least some of the neighbouring wireless devices comprised in the first neighbour database when adopting the first neighbour database as the initial neighbour database in the second network cluster.
6. The method of any preceding claim, further comprising updating the initial neighbour database on the basis of neighbour information received in connection with periodic scanning opportunities in the second network cluster.
7. The method of any preceding claim, wherein the first time value and the second time value are counter values broadcasted by devices of first network cluster and second network cluster, respectively.
8. The method of any preceding claim, wherein the first neighbour database comprises at least one of the following for each neighbouring wireless device: a medium access control address, a radio distance between the wireless device and the neighbouring wireless device.
9. The method of any preceding claim, further comprising while the wireless device is still associated with the first network cluster: upon detecting a determined event in the wireless device, causing the wireless device to execute a forced scanning for other network clusters, wherein scanning parameters used during the forced scanning differ from scanning parameters used during regular scanning of the wireless device.
The method of claim 9, wherein the determined event is at least one of the following: the number of neighbouring devices listed in the first neighbour database decreases or is about to decrease within a determined time interval below a threshold, the amount of traffic in the first network cluster decreases below a traffic threshold, and an application executed in the wireless device requests for the forced scanning.
The method of claim 9 or 10, wherein the different scanning parameters used during the forced scanning comprise at least one of an extended scanning duration and forced use of a scanning opportunity. 12. The method of any preceding claim 9 to 1 1 , wherein the wireless device is configured to alternate between a doze mode and an awake mode, and wherein the forced scanning is realized by extending an awake time of the wireless device.
13. The method of any preceding claim, further comprising in connection with changing the association from the first network cluster and second network cluster: after determining to change the association to the second network cluster, maintaining synchronization with the first network cluster so as to transmit a beacon message in the first network cluster, wherein the beacon message comprises a time value of the second network cluster.
14. The method of any preceding claim, further comprising verifying validity of the first neighbour database before employing the first neighbour database as the initial database in the second network cluster.
15. The method of claim 14, wherein the verification comprises: determining whether or not the second network cluster comprises at least one neighbouring wireless device listed in the first neighbour database; if the second network cluster comprises at least one neighbouring wireless device listed in the first neighbour database, employing the first neighbour database as the initial database in the second network cluster; and if no neighbouring wireless device listed in the first neighbour database is detected in the second network cluster, creating a new neighbour database for the second network cluster.
16. The method of any preceding claim, further comprising storing in the wireless device a neighbour database comprising first hand information on at least one neighbouring device and a neighbourhood database comprising second hand information on said at least one neighbouring device, wherein the first neighbour database used as the initial database in the second network cluster comprises at least one of said neighbour database and said neighbourhood database.
17. An apparatus comprising:
at least one processor; and
at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: associate with a first network cluster identified by a first time value indicative of a moment of establishment of the first network cluster; store in the at least one memory a first neighbour database comprising information on neighbouring wireless devices associated with the first network cluster; detect a presence of a second network cluster identified by a second time value indicative of a moment of establishment of the second network cluster; determine from the first time value and the second time value that the second network cluster has been established before the first network cluster; cause change of association from the first network cluster to the second network cluster as a result of said determination; after association with the second network cluster, use contents of said first neighbour database as an initial neighbour database for the wireless device in the second network cluster.
18. The apparatus of claim 17, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to utilize the same network identifier in the first network cluster and the second network cluster.
19. The apparatus of claim 17 or 18, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to use contents of said first neighbour database as the initial neighbour database in the second network cluster without verifying validity of the contents of the first neighbour database when changing the association.
20. The apparatus of any preceding claim 17 to 19, wherein the first neighbour database consists of single-hop neighbours.
21 . The apparatus of any preceding claim 17 to 20, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to change categorization of at least some of the neighbouring wireless devices comprised in the first neighbour database when adopting the first neighbour database as the initial neighbour database in the second network cluster.
22. The apparatus of any preceding claim 17 to 21 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to update the initial neighbour database on the basis of neighbour information received in connection with periodic scanning opportunities in the second network cluster.
23. The apparatus of any preceding claim 17 to 22, wherein the first time value and the second time value are counter values broadcasted by devices of first network cluster and second network cluster, respectively.
24. The apparatus of any preceding claim 17 to 23, wherein the first neighbour database comprises at least one of the following for each neighbouring wireless device: a medium access control address, a radio distance between the wireless device and the neighbouring wireless device.
25. The apparatus of any preceding claim 17 to 23, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the following while being still associated with the first network cluster: upon detecting a determined event in the apparatus, causing execution of a forced scanning for other network clusters, wherein scanning parameters used during the forced scanning differ from scanning parameters used during regular scanning of the apparatus.
26. The apparatus of claim 25, wherein the determined event is at least one of the following: the number of neighbouring devices listed in the first neighbour database decreases or is about to decrease within a determined time interval below a threshold, the amount of traffic in the first network cluster decreases below a traffic threshold, and an application executed in the apparatus requests for the forced scanning.
27. The apparatus of claim 25 or 26, wherein the different scanning parameters used during the forced scanning comprise at least one of an extended scanning duration and forced use of a scanning opportunity. 28. The apparatus of any preceding claim 25 to 27, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to alternate between a doze mode and an awake mode, and to realize the forced scanning by extending an awake time of the apparatus.
29. The apparatus of any preceding claim 17 to 28, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the following in connection with changing the association from the first network cluster and second network cluster: after determining to change the association to the second network cluster, maintain synchronization with the first network cluster so as to transmit a beacon message in the first network cluster, wherein the beacon message comprises a time value of the second network cluster. 30. The apparatus of any preceding claim 17 to 29, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to verify validity of the first neighbour database before employing the first neighbour database as the initial database in the second network cluster.
31 .The apparatus of claim 30, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the verification by: determining whether or not the second network cluster comprises at least one neighbouring wireless device listed in the first neighbour database; if the second network cluster comprises at least one neighbouring wireless device listed in the first neighbour database, employing the first neighbour database as the initial database in the second network cluster; and if no neighbouring wireless device listed in the first neighbour database is detected in the second network cluster, creating a new neighbour database for the second network cluster.
32. The apparatus of any preceding claim 17 to 31 , wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: storing in the at least one memory a neighbour database comprising first-hand information on at least one neighbouring device and a neighbourhood database comprising second-hand information on said at least one neighbouring device, wherein the first neighbour database used as the initial database in the second network cluster comprises at least one of said neighbour database and said neighbourhood database.
33. An apparatus, comprising means for carrying out all the steps of any preceding claim 1 to 16.
34. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute the method according to any preceding claim 1 to 16.
PCT/FI2012/050773 2012-08-07 2012-08-07 Network discovery and neighbour database WO2014023872A1 (en)

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