KR20070072364A - Method for beacon exchange between devices with asymmetric links and system thereof - Google Patents

Abstract

A method for exchanging beacons between devices having asymmetric links and a system using the method are provided to classify the devices into a normal power device and a low power device based on a transmission range, so that the low power device can forward beacons to the normal power device through at least one relay device, thereby effectively reducing beacon collision. When a low power device(L) receives beacons of a normal power device(N), the device(L) checks whether an asymmetric link with the device(N) exists on the basis of the received beacons. If so, the device(L) negotiates with at least one relay device(R) to demand relay for the asymmetric link. Based on the negotiated results, the device(R) notifies the device(L) and the device(N) which the device(L) wants to communicate with of the negotiated results.

Description

METHOD FOR BEACON EXCHANGE BETWEEN DEVICES WITH ASYMMETRIC LINKS AND SYSTEM THEREOF}

1 is an exemplary diagram for describing a wireless private network according to an embodiment of the present invention.

2 is an exemplary diagram for describing an asymmetric link between devices according to an embodiment of the present invention.

3 is an exemplary view for explaining the structure of a superframe according to an embodiment of the present invention.

4 is an exemplary diagram for describing a system for exchanging beacons between devices having an asymmetric link according to an embodiment of the present invention.

5 is an exemplary diagram illustrating a method for exchanging beacons between devices having an asymmetric link according to an embodiment of the present invention.

6 is a first exemplary diagram for describing fields of an asymmetric link information element according to an embodiment of the present invention.

7 is a second exemplary diagram for describing fields of an asymmetric link information element according to an embodiment of the present invention.

8 is a third exemplary diagram for describing fields of an asymmetric link information element according to an embodiment of the present invention.

9 is an exemplary diagram for explaining an asymmetric link relay request command / information element according to an embodiment of the present invention.

10 is an exemplary view for explaining a beacon forward information element according to an embodiment of the present invention.

11 is an exemplary diagram for explaining a system for exchanging beacons between devices having an asymmetric link according to another embodiment of the present invention.

TECHNICAL FIELD The present invention relates to a wireless personal area network, and more particularly, to exchange beacons between devices having an asymmetric link in a wireless private network that can efficiently reduce beacon collisions or distributed reservation protocol (DRP) collisions. It relates to a method and a system using the same.

In general, a wireless private network is defined to operate within a range of private operating space, eg, approximately 10 meters. Some protocols that define the physical and data link layers of wireless private devices are determined by the Institute of Electrical and Electronics Engineering (IEEE) standards committee. In these private operating spaces, UWB technology can provide data rates in excess of hundreds of Mbps.

In a wireless private network, the medium is shared between all devices for communication. Medium Access Control (MAC) mechanisms for devices include how to connect to the network, how each device provides information to the network, how to transfer data at the data rate required by other devices, how the medium is used to the maximum, and so on. It is inevitable to be able to manage a wide range of media connections. MAC for a wireless private network can be designed in two approaches, a centralized approach and a distributed approach. The centralized approach operates for one device to manage the media access function for all devices for the entire network. All other devices then request the assistance of a centralized coordinator for media access functions such as connecting to the network and reserving channel time. The distributed approach is that the media access function is distributed evenly among all the devices in the network, and all devices share the burden of managing the media access function for each other.

Wireless private networks do not have a centralized coordinator, and devices use a distributed approach for MAC. All devices work together to share information with each other to allow new devices to connect, to allocate channel time to send data to other devices, or to perform MAC tasks such as synchronization mechanisms. Distributed wireless private network systems are formed in an ad-hoc form. The devices are activated to broadcast their ID and capabilities through a control frame called Beacon.

The distributed MAC approach relies on a timing concept called superframe. Superframes have a fixed length of time and are divided into a plurality of time windows called time slots. Some time slots are used by the device to send their beacons and some time slots are used by the devices to send data. Slots through which beacons are sent are called beacon slots and slots through which data is sent are called data slots. The length of the beacon slot may be smaller than the length of the data slot. Beacon slots typically appear together at the beginning of a superframe. In addition, the number of beacon slots may be fixed or changed depending on other configurations of the distributed MAC mechanism.

A superframe consists of a plurality of medium access slots (MAS) (eg, the number is shown as 256). Some medium access slots constitute a beacon period, and the beacon period may be comprised of beacon slots used by a plurality of devices to send a beacon frame. The remaining medium access slots constitute a data period, which may be comprised of data slots used by several devices to transmit data to other devices in the network. Typically, the superframe duration is 64 ms and the duration of media access slots is 256 μs. Information about the device's characteristics and superframe usage is broadcast by each device in a beacon frame sent during the beacon period, and the device's neighbors can use that information for better processing. The start time of the superframe is determined by the start of the beacon period and is defined as BPST (Beacon Period Start Time). In each device, the MAC layer maintains information about each device's individual neighbors. The neighbor of each device is defined by its transmit and receive range. All MAC protocol mechanisms are expressed for this individual neighbor.

MAC protocol algorithms attempt to identify a beacon slot that sends the device's ID and a unique beacon. In one beacon period, beacons of all devices are defined to belong to one beacon group. A device may not know the beacons of all devices in its beacon group. However, individual neighbor information of each device is included in its beacon. Thus, devices can still get information about other devices two hops apart.

In today's MBOA MAC Version 0.98 protocol as well as other wireless MAC protocols, it is assumed that devices on the network have the same transmit and receive capabilities. Therefore, it is assumed that the range of each device in the network is the same. All links in the wireless network are considered to be bidirectional.

However, in a typical WPAN or WLAN, heterogeneous devices make up a network. The beacon frame must be sent by all devices using the maximum power described so that all devices within the 10 meter range can receive the beacon and update their neighbor table. However, some devices, such as headphones, microphones, etc. may have limited power capability and cannot transmit at the maximum power described, so their transmission range is reduced. The beacons transmitted by these Lower Power Devices are unknown to some Normal Power Devices. However, beacons transmitted by normal power devices may be known to low power devices.

Low power devices are used to define devices that can only use low transmit power to transmit their beacon frames and other frames. Low power devices are not intentionally indicative of devices that reduce transmit power or that lower battery power. Here, device N is a device with normal transmit power capability, while device L is only a device capable of transmitting at low power. Thus, even if the beacon of device N reaches device L, the beacon of device L does not reach device N. Thus, the link between device N and device L is referred to as asymmetric.

Single-hop bidirectional communication is not possible between two devices with an asymmetric link between them. Since the beacons of device L do not reach device N, some of the neighbors of device N may reuse the beacon slots or data slots used by device L. This can cause beacon slot collisions and DRP impulse problems in device L. There is no mechanism by which device L can communicate by means of a reservation made for an application for devices with an asymmetric link. This can lead to resource depletion and unfairness due to the use of wireless media in low power devices. Currently in MBOA MAC Protocol Version 0.98, there is no mechanism provided to solve the problems caused by asymmetric links.

Multi-hop hybrid networks can help to provide high bandwidth and wide coverage for wireless data networks. Multi-hop hybrid networks focus on CSMA / CA-based networks, using IEEE 802.11 as a specific example and integrating three basic functions: synchronization, routing, and energy savings. The solution is based on the periodic calculation of the connectivity tree between nodes reporting to the same access point, starting from the access pointer. Nodes, the highest points of the tree relaying data packets and control packets (also referred to as beacons), are applied to the system to establish a simple convergent algorithm for computing distributed neighbor search protocols and connection trees. Analysis and simulation results show that the proposed solution has low protocol overhead with regard to message passing and execution time. And the proposed solution performs well even if the node moves.

The method described above applies periodic calculation of the connection tree between nodes reporting to the same access point, starting from the access pointer. This method describes the use of nodes, the highest points of the tree, relaying data packets and control packets (beacons). This multi-hop communication helps to reduce the energy consumption of mobile nodes and allows for lower interference and increased coverage. However, this method does not describe the use of relaying nodes in the case of asymmetric links.

The present invention has been made to solve the above problems, and in order to effectively reduce the beacon collision or DRP (Distributed Reservation Protocol) collision caused by the asymmetric link, low power device and normal power device based on the transmission range It is an object of the present invention to provide a method and a system for exchanging beacons between devices having an asymmetric link that allows a low power device to forward a beacon with a normal power device through at least one relay device.

In order to achieve the above object, a method for exchanging beacons with any one of a plurality of normal power devices in the wireless network by a low power device having an asymmetric link to connect to a wireless network according to an embodiment of the present invention When the low power device receives the beacon of the normal power device, determining whether the low power device has an asymmetric link with the normal power device based on the received beacon, and if the low power device has an asymmetric link with the normal power device, A device negotiating with at least one relay device for requesting relay for the asymmetric link, and based on the negotiation result, the relay device informs the normal power device to which the low power device and the low power device are to communicate. To announce the outcome of the negotiations It characterized in that it comprises a system.

In order to achieve the above object, a system for exchanging beacons with any one of a plurality of devices in the wireless network by a device having an asymmetric link to connect to the wireless network according to an embodiment of the present invention A normal power device, if the beacon of the normal power device is received, checks whether it has an asymmetric link with the normal power device based on the received beacon, and if it has an asymmetric link with the normal power device, relays to the asymmetric link And a relay device for notifying a result of the request to a normal power device to which the low power device communicates with the low power device according to a request of the low power device.

Hereinafter, with reference to the accompanying drawings and the contents described in the accompanying drawings will be described in detail preferred embodiments of the present invention, but the present invention is not limited or restricted by the embodiments. Like reference numerals in the drawings denote like elements.

The present invention facilitates identification of an asymmetric link in a wireless private network resulting from low power devices and proposes a method for performing beacon exchange between devices having an asymmetric link.

Current medium access control (MAC) protocols exclude low power devices from joining the network. The present invention enables low power devices to join a network. By using the present invention, identification of the asymmetric link and forwarding beacon information of the low power device to the low power device and other devices having the asymmetric link is made.

If beacon information is not forwarded, beacon slots and data slots used by low power devices may be reused by other devices that are neighbors of the normal power device, causing beacon collisions and Distributed Reservation Protocol (DRP) collisions. .

Accordingly, the present invention provides a method for eliminating the case of beacon collision and DRP collision caused by asymmetric links. The latency associated with low power devices joining the network is reduced, and the rate reduction caused by DRP collisions is also avoided. In addition, the present invention proposes to classify devices into two types, INHERENTLY_LOW_POWER_DEVICE and NORMAL_RANGE_DEVICE. This classification reduces the time for the device to join the wireless network because it helps to quickly identify asymmetric links and avoid unnecessary beacon slot switches.

An information element called an asymmetric link information element lists all the asymmetric links that make up the device. The structure is defined so that the receiver can easily check the list of low power devices and the list of normal power devices. The technique used to operate asymmetric links is backwards compatible with MBOA MAC Version 0.98 without requiring significant changes to the MBOA MAC protocol. The system defined in the present invention identifies some devices as relay devices for forwarding beacon frames between devices with an asymmetrical link. The method of the present invention also describes a procedure for easily identifying a relay device.

If no relay device is found in the network, the present invention provides a method for controlling a beacon and data slot collision to reduce beacon and data loss in a wireless network in which a low power device of the identified asymmetric link is described with reference to FIGS. Explain.

1 is an exemplary diagram for describing a wireless private network according to an embodiment of the present invention.

As shown in Fig. 1, a wireless private network without a centralized coordinator is described. Various devices that have their range in large circles are shown as dark circles. Devices share information in cooperation with each other to perform a MAC function. This network is an extremely simplified representation, assuming all devices have the same transmission capability. Thus their communication range looks the same.

However, this assumption is not always valid because devices can have a variety of capabilities and can have a variety of communication ranges for their broadcast communication.

2 is an exemplary diagram for describing an asymmetric link between devices according to an embodiment of the present invention.

As shown in FIG. 2, an asymmetric link is described between two devices having different power levels transmitting beacons. The beacon sent by device N is received by device L. Device L has transmit power but can only transmit at low power. Beacons sent by device L do not reach device N. Because of this asymmetric link, device N will be listed as a neighbor in the neighbor table maintained by device L, but device L is unknown to device N.

The present invention proposes to assign different types to devices such as INHERENTLY_LOW_POWER_DEVICE and NORMAL_RANGE_DEVICE based on the transmission range.

Devices that can transmit their beacons at the maximum power described by the MAC PHY interface, either as beacon transmission power or maximum transmission power, are classified as NORMAL_RANGE_DEVICE and can only uniquely use transmit power below the transmit power given by the MAC PHY specification. The device is classified as INHERENTLY_LOW_POWER_DEVICE. This information, which can be maintained at the MAC layer, is useful for quickly identifying asymmetric links. By default, the device transmission range type will be set to NORMAL_RANGE_DEVICE.

3 is an exemplary view for explaining the structure of a superframe according to an embodiment of the present invention.

As shown in Fig. 3, the structure of the beacon slot and the data slot in the superframe is described. The numbers in the figures indicate, for example, the superframe duration, the number of beacon slots, and the number of data slots. Changes in these numbers do not affect the function of the present invention. Control information is transmitted by the devices in beacon frames in the selected beacon slots. Data slots used for communication are reserved using the Distributed Reservation Protocol.

While creating the network, the device in active mode will send beacons in the beacon period in every superframe and know the neighboring beacons in all beacon slots described by the length of the beacon period. The device will begin transmitting the beacon frame at the start of the beacon slot. Devices must transmit a beacon using the pBeaconTransmitRate, a predefined rate, and the transmission must not exceed the mMaxBeaconLength, a predefined length. To determine beacon transmission, if the beacon slot used in the last mMaxLostBeacons superframe is not marked as occupied by the Beacon Period Occupancy Information Element (BPOIE) transmitted or received by the device, the device shall consider whether the beacon slot is available. . In order to detect beacon collisions, the device must randomly skip beacon transmissions to know that neighbors are trying to use beacon slots. If a device does not receive a beacon from a neighbor in one superframe, it must use the information in the beacon received in the previous superframe from the neighbor as if it received the current superframe. If a device does not receive a beacon from another device while transmitting consecutive superframes above mMaxLostBeacons, which is a predefined number of losses, then the other device should not be considered a neighbor for communication purposes.

A device watching beacons during the beacon period confirms that a beacon collision has occurred. If a beacon slot is reported occupied by a BPOIE within any beacon, the device ID of the beacon slot received in the current superframe is not its device ID. Alternatively, while skipping beacon transmission, the device checks the beacon in the current superframe or after skipping beacon transmission, the device checks the beacon in the next superframe that the beacon slot is occupied by some other device in the BPOIE. Beacon collision is an important problem that can occur in networks with asymmetric links. If the device detects a beacon collision, it will stop beaconing the current beacon slot, select a new beacon slot other than the maximum used beacon slot in the beacon cycle, and send its beacon through the selected beacon slot. If the asymmetric link is not identified, this beacon shifting process will have to be done several times by the low power device.

Also, devices involved in DRP negotiation may attempt to reserve the same MAS slot or because of mobility the devices may have the same slots marked as reserved. If the same slot sets are marked as reserved in two DRP-IE messages of different device pairs, then a DRP collision exists. DRP conflicts must be resolved, but otherwise, data loss can occur on both links. DRP collisions will occur more easily in a wireless network with some asymmetric links because the DRP-IE of the low power device does not know that the normal power device is out of range.

This beacon and DRP collision phenomenon can be reduced and avoided in networks with asymmetric links, as the information contained in the beacons of low power devices is forwarded to devices with asymmetric links. The method described herein describes the critical steps taken before declaring a link asymmetrically, and further provides a method for use to avoid problems arising due to link asymmetry.

4 is an exemplary diagram for describing a system for exchanging beacons between devices having an asymmetric link according to an embodiment of the present invention.

As shown in FIG. 4, a system for exchanging beacons between devices having an asymmetric link is described. All devices except device L can transmit at the same maximum power as that authorized by the MBOA MAC PHY specification. Device L is a device with low power performance. Thus, beacons are only received by devices C and R. Although the beacons of devices N and Q are received by device L, the beacons of device L do not reach devices N and Q. An asymmetric link exists between devices N, L and devices L, Q.

A method for exchanging beacons between devices having an asymmetric link according to an embodiment of the present invention configured as described above will be described with reference to FIG. 5.

5 is a flowchart illustrating a method for exchanging beacons between devices having an asymmetric link according to an embodiment of the present invention.

As shown in FIG. 5, a sequence of control frames exchanged between devices in a wireless network is described to identify a relay device capable of forwarding beacons for a low power device. The asymmetric link relay request and response message is used to determine the relay device used between two devices having an asymmetric link.

In the detailed description provided below, a device with a smaller transmission range is referred to as device L, and a peer device with an asymmetric link is referred to as device N. The following steps are performed by these two devices to first verify that an asymmetric link exists.

Scenario 1 : Consider the case where device N is already in the network and device L starts non-corning.

1. Device L receives the beacons of all its neighbors including device N and decides to use a new slot that is not used by any device in its beacon group.

2. Device L continues to receive beacons of its neighbors, and recognizes that the BPOIE sent by device N did not include the device ID and beacon slot of device L. The beacon slot used by device L is marked as free in the BPOIE of device N. It is an important situation to check before determining whether a link is asymmetric. In case of beacon collision device N will reflect the broadcast address or other device's ID in the beacon slot used by device L. Thus, device L does not consider the beacon slot as a case of beacon collision when the beacon slot is marked as free in the BPOIE of another device. This same BPOIE response will be seen from another device with an asymmetric link with device L, such as device Q.

3. Device L must continue to beaconed in the same slot. If device L is INHERENTLY_LOW_POWER_DEVICE, then at the end of the mMaxLostBeacons superframe, device L will determine that it has an asymmetric link with device N. However, if device L is NORMAL_RANGE_DEVICE, device L must continue to beaconed in the same slot for a new superframe count of mIdentifyALCount. mIdentifyALCount At the end of the superframe, if device N still continues to reflect the free beacon slot used by device L, device L will determine that it has an asymmetric link with device N.

Beacon shift is not required, as in this scenario, which does not constitute a beacon collision as defined in MBOA MAC Version 0.98. If there is a change in information in the BPOIE slot state until the mMaxLostBeacons and mIdentifyALCount superframes are reached, the scenario changes to that described below.

Scenario 2 : Consider the case where device N is already in the network and device L starts non-corning.

1. Device L receives the beacons of all its neighbors including device N and decides to use a new slot that is not used by any device in its beacon group.

2. In the next superframe, device L receives the beacon of device N, and recognizes that the beacon slot of device L is marked for use by another device in the BPOIE of the beacon. This is the case of a beacon slot collision between device L and another neighboring device N outside the range of device L.

3. If device L is INHERENTLY_LOW_POWER_DEVICE, it should continue to beaconed in the slot and process the BPOIE received from device N for the mMaxLostBeacons superframe. If device N continues to reflect the device ID of another device in the BPOIE, it is not a situation of beacon collision. Thus, device L determines that it has an asymmetric link with device N. Device L's ability to continue sending beacons to slots marked as occupied by its neighbors is a departure from MAC MBOA Version 0.98 and is only done by devices authorized as INHERENTLY_LOW_POWER_DEVICE.

4. If device L is NORMAL_RANGE_DEVICE, device L will consider the situation in step 2 as a beacon collision and move to another free beacon slot depending on the beacons received. This step continues until a unique beacon slot is found by device L and the device ID is reflected in the BPOIE of device N or the situation changes to scenario 1. And device L determines that it has an asymmetric link with device N.

Scenario 3 : Consider the case where device N is already in the network and device L starts non-corning.

1. Device L receives the beacons of all its neighbors including device N and decides to use a new slot that is not used by any device in its beacon group.

2. In the next superframe, device L receives the beacon of device N and recognizes that the beacon slot used by device L in the BPOIE is marked for use by the broadcast device. This is the case of a beacon slot collision between device L and another neighboring device N outside the range of device L. Thus, for this situation, device L will function as in MBOA MAC Version 0.98 and move to a new beacon slot as possible in its neighbor. After the beacon slot move, the beacon logic will change to either scenario 1 or scenario 2 to identify the asymmetric link.

If there is no asymmetric link between the two devices, the BPOIE of all participating devices after beacon collision determination will show respective beacon slot and device ID information.

The benefit of qualifying devices with the INHERENTLY_LOW_POWER_DEVICE and NORMAL_RANGE_DEVICE groups is that low-power devices can identify asymmetric links at the maximum time duration of the mMaxLostBeacons superframe and they need to switch beacon slots for situations that are not identified as beacon collisions. There is no. Devices classified as NORMAL_RANGE_DEVICE will try to change the beacon slot for as long as the beacon collision is determined or an asymmetric link is identified.

As such, it can be determined that there is an asymmetric link between the low power device and the normal power device. The asymmetric link information element transmitted to all devices having an asymmetric link will be described with reference to FIGS. 6 to 8.

6 to 8 are exemplary diagrams for describing fields of an asymmetric link information element according to an embodiment of the present invention.

6 to 8, fields of an asymmetric link information element (ALIE) according to an embodiment of the present invention will be described. This information element is transmitted by all devices having an asymmetric link. The general format of the information element is shown in FIG. 6, which may include the number of asymmetric links, the device IDs of the plurality of low power devices, and the device IDs of the plurality of normal power devices. The format transmitted by the low power device is shown in FIG. 7, which may include the number of asymmetric links, the device ID of the low power device, and the device IDs of the plurality of normal devices. The format transmitted by the normal device is shown in FIG. 8, which may include the number of asymmetric links, the device IDs of the plurality of low power devices, and the normal power device ID.

At this time, if the device ID of the transmitting side in the ALIE is included in the second field in the information element, it is an ALIE transmitted by the low power device, otherwise it is an ALIE transmitted by the normal device. This format conveys that the device is a low power device and also contains information of all asymmetric links of the device in one information element.

The present invention introduces a new information element called ALIE as described in FIG. The low power device will include an ALIE as depicted in FIG. 7, and the normal device will include an ALIE described in FIG. 8. The ALIE is updated when a device sees more asymmetric links with other devices. In an asymmetric link, the normal power device N will also have to send an ALIE to recognize that their neighbors have a unidirectional link with the device L and this information can be used by the routing algorithm so that bidirectional traffic is not forwarded over the asymmetric link. .

The systems and methods described herein also provide a method for the beacons of low power devices to be known to the normal range diabis of the asymmetric link. The present invention proposes a new idea that a beacon control frame is forwarded to devices so that consistent information about neighbors is maintained at all devices in the beacon group. The present invention proposes the use of a relay device called an asymmetric link relay device represented by an AR device. The low power device will choose a common neighbor as a relay device between itself and the low power device having an asymmetric link. The negotiation process is initiated between the low power device and the AR device.

If a normal power device has an asymmetric link, the low power device negotiates with the relay device to request relay on the asymmetric link, for example, asymmetric used when negotiating with the relay device with a relay request beacon and a relay response beacon. The link relay request command / information element will be described with reference to FIG.

9 is an exemplary diagram for explaining an asymmetric link relay request command / information element according to an embodiment of the present invention.

As shown in FIG. 9, in a new command frame or information called an asymmetric link relay request command / information element (ARR IE) used by a low power device negotiating with a neighboring device to request to operate as a relay device. Describes the fields of. The ARR IE includes the device ID of the low power device, the device ID of the normal device, and the status code.

An information element called a new command frame or asymmetric link relay request command / IE (ARR IE) is used by the low power device to negotiate with a neighboring device requesting to function as a relay device. If the relay device is willing to forward the beacons of the low power device, it will send an ARR IE with a status flag to allow the relay. However, the neighbor device may also select a relay reject with a status flag to reject the relay in response to the relay request message. The low power device must also negotiate with some other common neighboring devices.

If the AR device accepts the forward of beacon information of the low power device, it will include the beacon of the low power device in BEACON_FWD_IE and broadcast BEACON_FWD_IE like the beacon of the low power device.

Based on the negotiation result, the relay device announces the negotiation result to the low power device and the normal power device to which the low power device communicates. For example, a beacon used when the relay notification beacon informs the normal power device of the negotiation result. The forward information element will be described with reference to FIG.

10 is an exemplary view for explaining a beacon forward information element according to an embodiment of the present invention.

As shown in Fig. 10, the fields in the beacon forward information element, BEACON_FWD_IE, are described. This new information element adds its beacon by the relay device to forward the beacon information of the low power device to the normal device. The first field of the beacon forward information element describes the number of asymmetric links the device has. Secondly, BEACON_FWD_IE lists the device IDs of all normal devices for which the beacon is to be forwarded. The last field is received at the relay device and is the beacon frame of the low power device. BEACON_FWD_IE writes the device IDs of all devices for which the beacon is forwarded. Devices not written to BEACON_FWD_IE cannot process forwarded beacon information. BEACON_FWD_IE need not be included in every beacon of the relay device. The relay device may choose to include BEACON_FWD_IE periodically, but at least once per mMaxLostBeacons. Since the beacons are only forwarded periodically, the normal device must maintain the beacon slot information of the low power device while receiving a larger number of superframes (called mLargeMaxLostBeacons). In addition, new relay devices must be negotiated in the case of relay devices that are out of range of the neighbor.

11 is an exemplary diagram for explaining a system for exchanging beacons between devices having an asymmetric link according to another embodiment of the present invention.

As shown in FIG. 11, a system for exchanging beacons between devices having an asymmetric link is described. If the topology of the network is that there are no common neighbors between the devices in the asymmetrical link, for example, if there is no response after several relay request attempts, the low power device will try to find a common device within two hop distances. To this end, low power devices attempt to broadcast a beacon limited to two hops. Because of the distance limitation of two hops, unnecessary broadcast overhead will be reduced.

For example, the following topology situation is considered. The first relay device R1 does not have a connection with the device N. Thus, device L seeks to find another device capable of conveying the relevant information within a range of two hops. From this process, the device L may provide its beacon slot information to the device N through the first relay device R1 and the second relay device R2.

The present invention defines a method for identifying an asymmetric link in a wireless private network. The MBOA MAC protocol is used in the specification to describe the proposed method. The present invention also provides a mechanism for generating a robust list of network neighbor information in devices that are part of asymmetric links.

Devices that implement the MBOA MAC protocol must match the MAC and MAC PHY interface specifications. Any low power termination devices such as headphones, speakers, microphones may be part of the UWB network and may not use MAC except their physical layer limits, which may not be able to transmit frames at full power as required by the MBOA MAC PHY interface. Performs well. This limitation reduces the transmission range of these devices. The current MBOA MAC does not allow such devices to be part of the UWB MBOA wireless private network. The system and method described in the present invention provide a method by which such low power devices can join a UWB network and communicate with other devices to their neighbors.

An embodiment of the present invention may include a computer readable medium including program instructions for performing various computer-implemented operations. The computer readable medium may include program instructions, local data files, local data structures, or the like, alone or in combination. The media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical recording media such as CD-ROMs, DVDs, magnetic-optical media such as floppy disks, and ROM, RAM, flash memory, and the like. Hardware devices specifically configured to store and execute the same program instructions are included. Examples of program instructions may include high-level language code that can be executed by a computer using an interpreter as well as machine code such as produced by a compiler.

Although specific embodiments of the present invention have been described so far, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As can be seen from the above description, a method for exchanging beacons between devices having an asymmetric link and a system using the same according to an embodiment of the present invention classify devices into low power devices and normal power devices based on a transmission range. Therefore, the low power device forwards the beacon to the normal power device through the at least one relay device, thereby effectively reducing the beacon collision or the Distributed Reservation Protocol (DRP) collision caused by the asymmetric link.

Claims (24)

A method for a low power device having an asymmetric link to connect to a wireless network to exchange beacons with any one of a plurality of normal power devices in the wireless network, the method comprising: When the low power device receives the beacon of the normal power device, determining whether the low power device has an asymmetric link with the normal power device based on the received beacon; If the normal power device has an asymmetric link, the low power device negotiating with at least one relay device to request relay for the asymmetric link; And Based on the negotiation result, the relay device notifying the negotiation result to the normal power device to which the low power device and the low power device communicate; Beacon exchange method comprising a. According to claim 1, The wireless network, Including a normal power device capable of transmitting beacons at the maximum power described in the MAC PHY interface classified by transmission range and a low power device capable of transmitting beacons at or below the maximum power described in the MAC PHY interface Beacon exchange method characterized in that. According to claim 1, The checking step, When the low power device receives beacons of neighboring devices that include the normal power device, selecting one beacon slot that is not used by the neighboring devices; The low power device transmitting a beacon through the preselected beacon slot; And If the low power device receives a beacon from the normal power device, determining whether the low power device has an asymmetric link with the normal power device based on the received beacon Beacon exchange method comprising a. The method of claim 3, wherein Checking the received beacons, Determining, by the low power device, whether to use the pre-selected beacon slot and whether to include the device ID of the low power device based on a beacon period occancy information element (BPOIE) field in the received beacon. Beacon exchange method characterized in that. According to claim 1, The negotiating step, The low power device generating a relay request beacon for an asymmetric link relay request as a result of the checking and transmitting the generated relay request beacon to the at least one relay device; Beacon exchange method comprising a. The method of claim 5, The relay request beacons, A beacon including an information element consisting of a device ID of the low power device, a device ID of the normal power device, and a status code for the asymmetric link relay request Beacon exchange method characterized in that. According to claim 1, The known step, When the relay device receives the relay request beacon, transmitting a relay response beacon for permission to relay to the low power device in response to the received relay request beacon; And Forwarding, by the relay device, a relay notification beacon including the beacon received from the low power device after transmitting the relay response beacon to the stationary power device; Beacon exchange method characterized in that. The method of claim 7, wherein The relay response beacons, A beacon including an information element consisting of a device ID of the low power device, a device ID of the normal power device, and a status code for the asymmetric link relay permission Beacon exchange method characterized in that. The method of claim 7, wherein The relay notification beacons, A beacon comprising an information element comprised of the number of asymmetric links, the device ID of the plurality of normal power devices, and the beacon received from the low power device Beacon exchange method characterized in that. According to claim 1, If the stationary power device has an asymmetric link with the low power device, the low power device broadcasts a beacon including an information element consisting of the number of the asymmetric links, the device ID of the low power device, and the device IDs of a plurality of normal power devices Steps to Beacon exchange method further comprising. According to claim 1, If the low power device has an asymmetric link with the low power device, the normal power device broadcasts a beacon including an information element consisting of the number of the asymmetric links, a device ID of a plurality of low power devices, and a device ID of the normal power device. Steps to Beacon exchange method further comprising. According to claim 1, The low power device sending a beacon to the stationary power device via at least one relay device after the negotiation result is known to the stationary power device Beacon exchange method further comprising. A system for exchanging beacons with any one of a plurality of devices in a wireless network, the device having an asymmetric link trying to connect to a wireless network, the system comprising: A stationary power device within the wireless network; Receiving a beacon of the stationary power device, based on the received beacons to determine whether the asymmetric link with the stationary power device, and if it has a non-symmetrical link with the stationary power device low power requesting relaying for the asymmetric link device; And A relay device for notifying a result of the request to a normal power device to which the low power device communicates with the low power device according to a request of the low power device; System comprising a. The method of claim 13, The wireless network, Including a normal power device capable of transmitting beacons at the maximum power described in the MAC PHY interface classified by transmission range and a low power device capable of transmitting beacons at or below the maximum power described in the MAC PHY interface System characterized in that. The method of claim 13, The low power device, Receiving beacons of neighboring devices including the normal power device, selecting one beacon slot not used by the neighboring devices, and then transmitting a beacon through the selected beacon slot System characterized in that. The method of claim 15, The low power device, When receiving the beacon from the normal power device, checking whether the pre-selected beacon slot is used and whether the device ID of the low power device is included based on a BPOIE (Beacon Period Occupancy Information Element) field in the received beacon System characterized in that. The method of claim 13, The low power device, Generating a relay request beacon for the asymmetric link relay request and transmitting the generated relay request beacon to the at least one relay device if the stationary power device has an asymmetric link with the normal power device System characterized in that. The method of claim 17, The relay request beacons, A beacon including an information element consisting of a device ID of the low power device, a device ID of the normal power device, and a status code for the asymmetric link relay request System characterized in that. The method of claim 13, The relay device, Upon receiving the relay request beacon, a relay response beacon for relay permission is sent to the low power device in response to the received relay request beacon, and the relay notification beacon including the beacon received from the low power device is received. Forward to a power device System characterized in that. The method of claim 19, The relay response beacons, A beacon including an information element consisting of a device ID of the low power device, a device ID of the normal power device, and a status code for the asymmetric link relay permission System characterized in that. The method of claim 19, The relay notification beacons, A beacon comprising an information element comprised of the number of asymmetric links, the device ID of the plurality of normal power devices, and the beacon received from the low power device System characterized in that. The method of claim 13, The low power device, Broadcasting a beacon comprising an information element comprised of the number of the asymmetric links, the device ID of the low power device, and the device ID of a plurality of normal power devices, if it has an asymmetric link with the normal power device; System characterized in that. The method of claim 13, The normal power device, Broadcasting a beacon comprising an information element comprising a number of the asymmetric links, a device ID of a plurality of low power devices, and a device ID of the normal power device, if the device has an asymmetric link with the low power device; System characterized in that. According to claim 1, The low power device, Sending a beacon to the stationary power device via at least one relay device after the relay device announces the request result to the stationary power device System characterized in that.

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