KR100667493B1 - Method for supporting voice channel on scatternet - Google Patents

Abstract

A method for supporting a voice channel on a scatternet is provided to enable a slave device, connected to two maser devices, to synchronize a clock of one of the two master devices with a clock of the other master device, thereby removing guard slots necessary for connection with the two master devices. A method for supporting a voice channel on a scatternet comprises the following steps of: enabling a slave device, connected to the first master device(M1) and the second master device(M2), to synchronize clocks of the two master devices(M1,M2)(522); and enabling the slave device to designate a time slot, which will be used for supporting a voice channel with the first master device(M1) and the second master device(M2), according to the synchronized clock(528).

Description

Method for supporting voice channel on scatternet}

1 is a view showing a form of a general scatternet appearance,

2 is a diagram illustrating a time division duplex (TDD) communication scheme over a Bluetooth network;

3 is a view showing transmission of a high-quality voice (HV) packet used in Bluetooth,

4 is a view showing a form of the guard slot formed on the scatternet,

5 is a view showing a voice channel support method on a scatternet according to a first embodiment of the present invention;

FIG. 6 is a diagram illustrating a state in which a time slot to be used for voice channel support according to the present invention is designated;

7 is a diagram illustrating a voice channel support method on a scatternet according to a second embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

100, 102: piconet

The present invention relates to a voice channel support method on a scatternet, and to a slave channel connected to two master devices and a voice channel support method between two master devices.

Bluetooth is a short-range wireless communication technology standard developed to enable free wireless communication between various devices in a relatively small area (10-100m) at low cost and low power consumption. In 1994, Ericsson Mobile Communication Group began researching low-power, low-cost radio interfaces between mobile phones and peripherals.In February 1998, Ericsson, Nokia, IBM, Toshiba, and Intel The Bluetooth Special Interest Group (SIG) was established, and the version 1.0 Bluetooth specification was released in August 1999 by the SIG, and the official international standards organization was the IEEE 802.15 workgroup to establish international standards based on the Bluetooth standard. Is working closely with SIG.

Bluetooth can be installed in all information devices used in homes and offices, and it is possible to configure a wireless network between them and to interwork with any wired / wireless network. Therefore, when the wireless network using Bluetooth is completed, data exchange between all information devices, especially laptops, PDAs, and mobile phones, is free. When the Internet bridge is configured using Bluetooth, it reaches the desktop computer through optical cable, ADSL, modem, etc. Internet information can be reached in the user's hand. In other words, by using Bluetooth, the ultimate goal of wireless communication can be reached at anytime, anywhere, anyone, and any type of information exchange.

The Bluetooth network is composed of a master / slave. A master device can have up to seven slave devices. The Bluetooth network composed of one master device is called a piconet, and a Bluetooth network to which a plurality of piconets are connected is called a scatternet.

1 is a view showing a form of a general scatternet, wherein the first master device M1 is connected to the Sl and A slave devices to form a piconet 100, and the second master device M2 is S2 and FIG. 2 illustrates a scatternet form in which two piconets 100 and 102 are connected through the A device while forming another piconet 102 through connection with the slave device A. FIG.

Bluetooth channels include SCO (Synchronous Connection-Oriented) channels and Asynchronous Connection-Less (ACL) channels.

The SCO channel exchanges data through time slots reserved at regular time intervals of 625us. SCO data packets transmitted once again are not retransmitted. Therefore, the SCO channel is suitable for data transmission where time factors are important and reliability is not required, and is mostly used as a voice channel (actually, one time slot length of 625us corresponds to the voice signal speed of 64 kbps) and piconet. The master device on the PC can set up SCO channels with up to three slave devices.

ACL channels, on the other hand, do not have a reserved time slot. In addition, point-to-multipoint connection is possible, but only one ACL channel can be established between one master device and a slave device.

Accordingly, the first master device M1 can set up to three SCO channels as the S1 device or the A device and the voice channel existing on its piconet 100, and of course, two devices A and S1 All of them can finally form three SCO channels. Similarly, the second master device M2 may form an SCO link with the S1 device or the A device existing on its own piconet 102.

However, referring to the case of the A device connected to the first master device M1 and the second master device M2 as slave devices, the SCO channel is formed separately from the first master device M1 or the second master device. It is possible to form the SCO channel with M2, but it is impossible to form the SCO channel simultaneously with both the first master device M1 and the second master device M2.

Every Bluetooth device has a native free-running counter that controls its timing and operation, and the clock generated by the self-oscillation counter is called a native clock (CLKN). It is called). Then, when a given Bluetooth device operates as a master device, the device controls slave devices belonging to its piconet and uses its CLKN as its internal reference timing. In order for the slave device to synchronize with the master device, a predetermined clock offset value is added to its CLKN to change the clock of the master device to the CLKN and use it for controlling its own operation.

Therefore, since the slave device of each piconet is made to operate according to the clock of its own master device, the device A uses the clock used when operating as the slave device of the first master device M1 and the slave of the second master device M2. The timing of the clocks used when operating as a device is different so that it supports a voice channel with one master device and cannot acquire a channel for transmitting a voice signal with another master device.

Therefore, the present invention has been made to solve the above problems, and provides a voice channel support method on a scatternet that allows a slave channel connected to two master devices on a scatternet and a voice channel formed between the two master devices. There is a purpose.

In order to achieve the above object, a voice channel supporting method on a scatternet according to the present invention comprises the steps of: a slave device connected to a first master device and a second master device to synchronize the clocks of the two master devices; And specifying, by the slave device according to the synchronized clock, a time slot to be used for voice channel support with each of the first master device and the second master device.

The clock synchronization of the first master device and the second master device may include requesting a clock change so that the slave device is equal to the clock of the second master device to the first master device or the second master device. Requesting a clock change to be equal to a clock of one master device; And changing the clock of the first master device or the second master device according to the request.

And transmitting, by the first master device or the second master device which has changed its clock according to the request, its changed clock information to the slave device.

The clock synchronization of the first master device and the second master device may be performed by the second master device not forming a voice channel when the slave device has already formed a voice channel with the first master device. Requesting a clock change to be equal to the clock of the first master device; And changing, by the second master device, its clock according to the request, wherein the second master device, which has changed its clock according to the request, sends the changed clock information to the slave device. Transmitting; may further comprise.

In the present invention, the clock change request may be performed by transmitting a clock change message having any one of a form of a Link Manager Protocol (LMP) and a Logical Link Control and Adaptation Protocol (L2CAP) message.

The time slot designation to be used for supporting the voice channel with the first master device and the second master device may include a time slot to be used by the slave device performing a sniff request to each of the first master device and the second master device. It is characterized by specifying.

In addition, when a time slot to be used for voice channel support with the first master device and the second master device is designated, the slave device may be used as a voice channel and a data channel with each of the first master device and the second master device. Specify a time slot.

However, when the slave device has already formed a voice channel with the first master device, when the time slot to be used for supporting the voice channel with the first master device is designated, only the time slot to be used as the data channel is additionally specified. It is characterized by.

In this case, the voice channel is a SCO (Synchronous Connection-Oriented) channel, and the data channel is an Asynchronous Connection-Less (ACL) channel.

According to the present invention, when the slave device designates a time slot to be used as a voice channel with each master device, the slave device is designated to use two time slots every six time slots, and a time to be used as a data channel with the master device. In designating a slot, two time slots are used for every 12 time slots.

In addition, in the present invention, the slave device may perform a sniff request twice to the first master device and the second master device to designate a time slot to be used as the voice channel and a time slot to be used as the data channel. have.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating a time division duplex (TDD) communication scheme over a Bluetooth network. Referring to the drawings, a length of each channel allocated to a time slot is 625us. The number of time slots is determined according to the Bluetooth clock of the piconet master device.

Due to the time slot, the master device and the slave device alternatively transmit packets. That is, the master device transmits the packet only in the even numbered time slots, and the slave device transmits the packet only in the odd numbered time slots. In addition, a packet transmitted by a master device or a slave device must be implemented within 5 time slots. Here, the packet refers to a data unit transmitted in the piconet channel.

In more detail, a packet used in Bluetooth includes a common packet, a SCO packet for voice data communication, an ACL packet for non-voice data communication, and a SCO packet for voice data communication according to the present invention. There are high quality voice (HV) 1, HV 2, and HV 3 packets.

The HV1 packet is a packet for transmitting 10 bytes of voice data. In addition, the error is protected by a 1/3 forward error correction (FEC) code. The payload is 240 bits long and there is no header in the payload. When transmitting 64 kbps of voice data using this packet, it is possible to transmit at 1.25 ms period. That is, the voice data is transmitted every two time slots.

Next, the HV2 packet is a packet for transmitting 20 bytes of voice data. And 2/3 FEC code protects against errors. The payload length is 240 bits equal to HV1, and there is no header in the payload. When using this packet to transmit 64kbps of voice data, 2.5ms cycle is possible. That is, the voice data is transmitted every four time slots.

The HV3 packet is a packet for transmitting voice data of 30 bytes. There is no error correction with the FEC code, and the payload length is 240 bits equal to HV1, and there is no header in the payload. When using this packet to transmit voice, transmission of 3.75ms period is possible. That is, the voice data is transmitted every six time slots.

3 is a diagram illustrating the transmission of an HV packet used in Bluetooth. As described above, the HV1 packet is transmitted every two time slots, the HV2 packet is transmitted every four time slots, and the HV3 packet is transmitted every six time slots. When transmitting voice data using the HV1 packet, only one SCO channel is used by the master device. When transmitting voice data using the HV2 packet, two SCO channels are used and the HV3 packet is used. In the case of transmitting voice data, up to three SCO channels can be supported.

4 is a diagram illustrating a form of a guard slot formed on a scatternet, in which a master device 1 transmits voice data of an HV3 packet every six time slots to its slave device 1, and transmits one voice channel with the slave device 1; Forming.

At this time, the slave device 1 is connected to the master device 2 again. When the slave device 2 is operated as the slave device 2, the slave device 1 operates according to the clock timing of the master device 2.

Accordingly, it can be seen that the slave device operates with the master device 1 and the master device 2 and the timing is not corrected as the clocks of the two master devices are different.

Therefore, although the slave device forms one voice channel with the master device 1 and can use the remaining four time slots, the slave device operates as the slave device 2 of the master device 2 and uses the time slot that is set according to the operation clock of the master device 2. Only two time slots are available for data communication with the master device2. And as shown in the figure it can be seen that guard slots (Guard Slots) are required so that collision does not occur in communication with the two master devices.

Therefore, the slave device forms a voice channel with the master device 1 as the slave device 1 of the master device 1, and can simultaneously perform data communication using two time slots that can be used as the slave device 2 of the master device 2. There is no time slot that can be used for voice signal transmission with device 2. As a result, the devices operating as slaves of the master device 1 and the master device 2 cannot support voice channels simultaneously with each master device.

In the present invention, the slave devices connected to the master devices of the two piconets adjust the clock timing of the two master devices by changing the clock so that one master device clock has the same offset as the other master device clock. This eliminates the need for Guard Slots and enables two voice channels.

5 is a diagram illustrating a voice channel support method on a scatternet according to a first embodiment of the present invention. Referring to FIG. 5, the first master device M1 is connected to the S1 device, the second master device M2 is connected to the S2 device (500), and the A device is the first master that is the master device of the piconet 100. It is connected to the slave device of the device M1 (502), and forms a voice channel (SCO channel) between each other and receives a voice signal from the first master device (M1) (504,506).

In this situation, when the second master device M2, which is the master device of another piconet 102, performs paging to the device A (508) and requests a connection, the device A transmits a response signal (510). 2 may be connected to the slave device of the master device (M2) (512).

Here, the packet used when the device A receives a voice signal from the first master device M1 is an HV3 packet of the SCO channel.

When the device A receives a request for forming a voice channel from the second master device M2 or otherwise has a request to establish a voice channel with the second master device M2 in order to provide a predetermined function (514). In operation 516, the clock change message is transmitted to the second master device M2.

Here, the clock change message transmitted from the device A to the second master device M2 is a message for requesting the offset adjustment to have the same timing as the clock of the first master device M1. Requests that the clock of the second master device M2 be set to the clock of the first master device M1.

The clock change message defines a message that performs a function of requesting a clock offset change in the form of a Bluetooth Link Manager Protocol (LMP) message or a Logical Link Control and Adaptation Protocol (L2CAP) message.

The second master device M2 checks whether it is currently possible to change its clock (518). If the clock cannot be changed, the second master device M2 transmits a notification message to the device A (520) and requests it again when the clock change is possible. If the clock change is possible, the clock is changed by adjusting the offset of its operation clock through the clock change message received from the device A (522), and information about the changed clock is transferred to the device A, which is its slave device. The data is transmitted to the S2 device (524).

The A device and the S2 device that receive the changed clock information of the second master device M2 perform an operation according to the changed clock of the second master device M2 (526). When operating as the slave device of M1) and the second master device M2, it is possible to operate according to the timing of the same clock.

Accordingly, the device A can connect to the first master device M1 and the second master device M2 at the same time and thus do not need the guard slot, which can be used for communication.

Device A then requests two sniffs (528, 530) to second master device (M2) and one sniff to first master device (M1) (532). The sniff request of the device A limits the currently available time slots to the time slots capable of communicating with the first master device M1 and the time slots capable of communicating with the second master device M2, respectively. A specific time slot is allocated so that the first master device M1 and the second master device M2 are simultaneously connected and a voice channel can also be formed with the second master device M2.

In Bluetooth, each device has four modes of operation: Active, Hold, Sniff, and Park to efficiently manage channels and links between devices and minimize power consumption. It can work.

The active mode is a mode in which the master device performs normal communication with the slave device, and the hold mode is a typical mode used when it is not necessary to send data for a relatively long time. Sniff mode is only available for slave devices and specifically limits the time slots that can be communicated between the master device and the slave device. That is, due to the limited duty cycle of the slave device, communication with the master device is possible only in a specific time slot. The park mode is a mode in which the slave device intermittently communicates with the master device and the slave device in order to maintain synchronization with the master device and to switch the active mode.

Here, since the device A has already formed a voice channel with the first master device M1 and receives a voice signal from the first master device M1, the device A requests the first sniff to the second master device M2. Specify a start time slot so that a voice channel can be formed with the second master device M2 through a time slot not in use with the first master device M1 at a time, and a few time slots based on the start time slot Each time, a sniffer request is made to the second master device M2 by specifying a period of time to use the corresponding time slot and a time slot length of how many time slots to use at a time (528).

At this time, the A device forms an SCO channel with the second master device M2 and a voice channel, and transmits voice data using the HV3 packet of the SCO channel, thereby requesting a sniff to the second master device M2. In this case, the period of the time slot to be used is set to 6.

Therefore, the time slot is reserved for the SCO channel so that the voice data packet can be transmitted using two time slots once every six time slots with the second master device M2.

The device A uses a time slot to be used to provide an ACL channel, which is a data channel required to transmit control data and a general data packet with the second master device M2 at the second sniff request to the second master device M2. Reserve (534).

Similarly, the device A also makes a sniff request with the first master device M1 to provide a data channel for transmitting control data and general data packet with the first master device M1, and reserves a time slot to use. As shown in FIG. 6, two time slots are provided for each six time slots so that the A device supports the SCO channel, which is a voice channel, to the first master device M1 and the second master device M2 as shown in FIG. 6. It is used to transmit voice packets.

As a result, only two time slots remain in each available time slot every six time slots, so that data can be transmitted to the ACL channel of the first master device M1 at one time, and the second time slot of the second master device M2 is next. By enabling data transmission through the ACL channel, both master devices and voice channels are supported and control data can be transmitted and received.

As a result, in the sniff request for the ACL channel with each of the first master device M1 and the second master device M2, corresponding time slots are designated to use two time slots as ACL channels every 12 time slots.

When the time slot to be used as the voice channel and data channel with each master device is completed by the sniff request of the device A as described above, the device A uses the designated time slot to establish a voice channel with the first master device M1. At the same time, a new voice channel can be established with the second master device M2 (534).

FIG. 6 shows that each time slot is designated to be used as an SCO channel, which is a voice channel of a first master device M1 and a second master device, and an ACL channel, which is a data channel, through a sniff request. Is showing.

Through the above process, the A device operates as a slave device of two master devices, the first master device M1 and the second master device M2, and simultaneously forms a voice channel with the two master devices.

Accordingly, as an example to which the present invention is applicable, when handoff occurs to the second master device M2 while the device A is making a call through the voice channel with the first master device M1 on the Bluetooth communication network, In the past, only hard handoff was possible, but according to the present invention, soft handoff may also be used to improve call quality.

7 is a diagram illustrating a voice channel support method on a scatternet according to a second preferred embodiment of the present invention, wherein the first master device M1 and the second master device M2 are master devices of an S1 device and an S2 device, respectively. Are connected to form piconets 100 and 102 (700).

In this situation, the device A transmits a response signal for paging of the first master device M1 to establish a connection with the first master device M1 (702, 704, 706), and responds to the paging of the second master device M2. The signal is transmitted and connected to the second master device M2 (708, 710, 712) to form one scatternet connected to the two piconets (100, 102).

Then, on the scatternet, the device A operates as a slave device of the first master device M1 and the second master device M2, and requests a voice channel formation request from the first master device M1 and the second master device M2. When there is a request to establish a voice channel with each of the first master device M1 and the second master device M2 in order to receive an input or to provide a predetermined function (714), the device A receives a first request. The clock change message is sent to either the master device M1 or the second master device M2 (716).

As described above with reference to FIG. 5, the clock change message is defined by using a message that performs a function of requesting a clock change in the form of an LMP message or an L2CAP message of Bluetooth.

When the device A sends a clock change message to the first master device M1, the second master device requests the clock offset adjustment so that the clock change message has the same timing as the clock of the second master device M2. When the clock change message is sent to M2, a message is generated and transmitted to request the clock offset adjustment so that the clock change message has the same timing as the clock of the first master device M1.

Thus, through this clock change message, the device A causes the M1 clock to have the same timing as the M2 clock or the M2 clock to have the same timing as the M1 clock.

As a result, when communicating with the first master device M1 or communicating with the second master device M2, the guard slots required by the clock offsets of each other are removed.

In FIG. 7, the device A transmits the clock change message to the first master device M1 as an example. If the device A transmits the clock change message to the first master device M1, the first device may be changed. When receiving the message that the clock change is impossible from the master device (M1), it can be made to send a clock change message to the second master device (M2) and request the clock change. However, if the second master device M2 also cannot change the clock, the device A waits for a time when the clock of either device can be changed, and then sends a clock change message to request the clock change again.

In this case, when the clock change of the first master device M1 or the second master device M2 is impossible, the case where the clock is changed by receiving a clock change request from another slave device may be representative.

As shown in FIG. 7, after receiving the clock change message from the device A, the first master device M1 checks whether the current clock can be changed (718), and if not, transmits a notification message to the device A. If it is possible to change the clock, the clock is changed by adjusting the clock offset through the received clock change message (722), and the information about the changed clock is transferred to the slave device A and the S1 device. Transmit (724).

The device A and the device S1 receiving the changed clock information of the first master device M1 perform an operation according to the changed clock of the first master device M1 (726). Accordingly, the device A is the first master device. When operating as the slave device of M1 and the second master device M2, it is possible to operate at the same timing.

As described with reference to FIG. 5, the device A uses a sniff request to the first master device M1 and the second master device M2, and each of the M1 and second master devices M2 and the voice channel SCO channel. And time slots to be used as data channels (ACL channels) (728, 730, 732, and 734).

In the case of the embodiment illustrated in FIG. 5, since the device A has already formed a voice channel with the first master device M1, the first master device M1 may make a first sniff request through a single sniff request. Although a time slot for a data channel with () is specified, in the embodiment shown in FIG. 7, device A does not currently form a voice channel with both the first master device M1 and the second master device M2. As shown in FIG. 6, each device can be used for each voice slot (SCO channel) and data channel (ACL channel) with the first master device M1 and the second master device M2 for each time slot. It is specified in two sniff requests.

The description of the sniff request of the device A is the same as that described with reference to FIG. 5 and will be omitted here.

On the other hand, device A is referred to as performing two sniff requests to the master device to designate time slots for the voice channel and the data channel to the master device. However, if you add a new parameter as the sniff's input parameter to make this possible with a single sniff request, you can specify a time slot for each master device, voice channel, and data channel with a single sniff request. can do.

Referring to FIG. 6, the time slot used by the device A as a voice channel and a data channel with the first master device M1 uses time slots 0 to 4 time slots, and the next two time slots Do not use it, and again use two timeslots for the voice channel and then the next four timeslots. And it can be seen that it is repeated in a cycle of 12 time slots.

Accordingly, if you define a parameter that informs the time slot usage information as the new input parameter of sniff, one sniff request is performed when the sniff request is performed to the first master device M1. Also, a time slot to be used as a voice channel and a data channel with the first master device M1 can be specified. Of course, the same may be applied to the sniff request to the second master device M2.

When the above sniff request is completed, a time slot to be used as a voice channel and a data channel with the first master device M1 and the second master device M2 is designated, and the device A is assigned a time slot designated with each master device. And form a voice channel (736,738).

The present invention is not limited to the above-described embodiments and can be variously modified and implemented by those skilled in the art without departing from the technical spirit of the present invention.

According to the present invention, a slave device connected between two master devices on a scatternet changes a clock of one of the two master devices to be the same as the clock of the other master device, so that a guard previously required when connecting to the two master devices is required. Allows you to remove the slot.

As time slots, which could not be used as guard slots, can be used to communicate with two master devices, time slots can be obtained to form a voice channel with the two master devices. Enables sending and receiving.

Claims (13)

Synchronizing clocks of the two master devices by slave devices connected to the first master device and the second master device; And Designating a time slot to be used by the slave device for supporting the voice channel with each of the first master device and the second master device according to the synchronized clock. The method of claim 1, The clock synchronization of the first master device and the second master device, Requesting, by the slave device, a clock change to be equal to the clock of the second master device to the first master device or requesting a clock change to be equal to the clock of the first master device to the second master device; And And changing the clock by the first master device or the second master device in response to the request. The method of claim 2, And transmitting the changed clock information of the first master device or the second master device to the slave device according to the request. How channels are supported. The method of claim 1, The clock synchronization of the first master device and the second master device, If the slave device has already formed a voice channel with the first master device, requesting a clock change to be equal to the clock of the first master device to the second master device not forming a voice channel; And And changing the clock by the second master device in response to the request. The method of claim 4, wherein And transmitting, by the second master device which has changed its clock according to the request, its changed clock information to the slave device. The method according to claim 2 or 4, The clock change request is performed by transmitting a clock change message having any one of a form of a Link Manager Protocol (LMP) and a Logical Link Control and Adaptation Protocol (L2CAP) message. . The method of claim 4, wherein In designating a time slot to be used for supporting a voice channel with the first master device that has already formed a voice channel, the slave device additionally specifies only a time slot to be used as a data channel. How to apply. The method of claim 1, The time slot designation to be used for the voice channel support with the first master device and the second master device designates a time slot to be used by the slave device performing a sniff request to each of the first master device and the second master device. Voice channel support method on a scatternet, characterized in that. The method of claim 1, When a time slot to be used for voice channel support with the first master device and the second master device is designated, a time for the slave device to use as a voice channel and a data channel with each of the first master device and the second master device. Voice channel support method on a scatternet characterized in that the slot is specified. The method of claim 9, The voice channel is a SCO (Synchronous Connection-Oriented) channel, the data channel is an Asynchronous Connection-Less (ACL) channel, characterized in that the voice channel on a scatternet. The method of claim 9, And assigning two time slots for every six time slots when the slave device designates a time slot to be used as a voice channel with each master device. The method of claim 9, And assigning two time slots to every 12 time slots when the slave device designates a time slot to be used as a data channel with each master device. The method of claim 9, Scatternet characterized in that the slave device performs a sniff request twice to the first master device and the second master device to designate a time slot to be used as the voice channel and a time slot to be used as the data channel. To support voice channels on Windows.

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