DE10310522A1 - Procedures to transfer interruption free data e.g. for Bluetooth communication network, constructing a connection between a base station and a mobile station and transferring data if connection parameter is met - Google Patents

Abstract

The method involves constructing a first connection (2) between a first base station (4) and a mobile station (7). Constructing a second connection (3) between a second base station (5) and the mobile station, whereby data is transferred from the mobile station to the first base station (4), if at least one connection parameter, in particular the connection quality corresponds to a given range of values. The data will handover to a second basestation, if the connection parameters fall outside the given range of values.

Description

The invention relates to a method for uninterrupted transmission of data between a mobile station and a first and / or a second base station in a Bluetooth communication network with one application layer each, one protocol layer each, one connection layer each and one physical layer each.

In cellular networks, the cellular Mobile stations can be built with one base station per cell be called on the network without the caller knowing their exact Location, i.e. knows their current cell network cell. In addition, mobile stations switch from one cell of the network to another cell. This possibility is called "roaming" or "handover". "Roaming" means that spatial Movement of a mobile device from one radio cell to another without an active connection (Voice or data connection) exists. "Handover" is a change of radio cell during an active one Connection. The handover therefore creates a new physical connection established, an existing, old physical connection will be dismantled shortly afterwards.

The possibility of roaming and handover will not in the Bluetooth standard in its current version 1.1 described, but is left to the network suppliers.

Two interconnected stations form a piconet in which one station (master) of the other (Slave) logically higher is. In addition, the networking of several piconets is also possible possible, that one station is connected to several others at the same time. Several piconets form a scatternet. Every piconet has only one master station, but one slave station can have multiple piconets belong.

Such scatternet structures of a Bluetooth communication network include known from WO0197448, where an ad hoc network is built up, consisting of several newly formed ones Subnets exist in which the number of individual connections is minimized, so that between a first and a second Station an optimized connection is created.

Furthermore, WO0069186 is a communication system known which consists of a number of local radio networks, e.g. Pico Networks is composed. The local radio networks are not related to each other synchronized, and a radio interface is used, the has no broadcast channel, e.g. a Bluetooth radio interface. A control unit is included in the basic configuration of the system connected to any local radio network. About the radio units can over the each radio node set up a connection to the control unit and be maintained. The radio units are also roaming, Handover, the implementation of measurements and fast connection setups possible in the system.

In the known systems however, there is a risk of building a second piconet for the handover the connection of a mobile station to a second base station takes place quickly enough and thereby the connection to the mobile station is interrupted becomes.

The object of the invention is a Procedure for implementation by handover in a Bluetooth multi-cell radio system, that a greater security the connection to the mobile station guaranteed.

This object is achieved by the Method according to claim 1 solved. Preferred embodiments the invention are the subject of the dependent claims.

Essential element of the method according to the invention is it that additionally to the normal connection of the mobile station to a first Bluetooth base station Another (auxiliary) connection to a second Bluetooth base station established to which a quick change (handover) takes place if necessary can. This ensures that the connection when reached does not break the range limit of the first base station, but passes to the second base station.

The method according to the invention for uninterrupted transmission of data between a mobile station and a first and / or a second base station in a Bluetooth communication network with one application layer each, one protocol layer each, one connection layer each and one physical layer each, comprises the steps: establishing a first connection between the first base station and the mobile station, building a second Connection between the second base station and the mobile station, the data being transmitted from the mobile station to the first base station if at least one connection parameter, in particular the connection quality corresponds, lies in a predetermined value range, and the data are transmitted from the mobile station to the second base station, if the at least one connection parameter lies outside the specified value range.

Preferably the first and the second connection is an asynchronous connection for a transmission of data and a synchronous connection for a transmission of voice data.

In a further preferred embodiment the invention is from the first asynchronous connection to the second asynchronous connection depending on a first connection parameter changed.

In particular, the first synchronous connection becomes the second synchronous connection change depending on a second connection parameter.

The assembly is preferably carried out the second asynchronous connection between the second base station and the mobile station by a page request from the mobile station.

Alternatively, building the second asynchronous connection between the second base station and the mobile station, however, also by an instruction from a network center respectively.

The first preferably corresponds and / or the second connection parameter of the connection quality, both can independently from each other or together by the network center.

It is particularly advantageous if the logical assignment between the application layers of the mobile station and the first and / or a second base station when changing is maintained from the first connection to the second connection.

To save electricity, is preferred the second connection until the change in an idle state (park mode) held.

An advantage of the invention is that the connection when the range limit of the first is reached Base station can be switched quickly.

Other features and advantages of Invention emerge from the following description of preferred Embodiments, reference is made to the accompanying drawings.

1 shows a Bluetooth network with a Piconet set up according to the prior art.

2 shows the Bluetooth network 1 with a first and a second piconet connection according to the invention.

3 shows the Bluetooth network 2 after changing the base stations.

4 shows the layers that are involved in a change of connection according to the invention.

5 shows an embodiment of the method according to the invention.

A multi-cell radio system according to the Bluetooth standard, as in 1 shown and generally with 1 is used for communication via wireless connections 2 between at least one of several Bluetooth access points (AP, Access Point) or base stations 4 . 5 . 6 and one or more mobile terminals (MS, Mobile Station) or mobile stations 7 , Generally every base station has 4 . 5 . 6 the role of a master in a connection to a mobile station 7 , Accordingly, the mobile stations assume the role of the slave in the connections. One or more connections that are established with a specific base station are also known as Bluetooth piconets.

The individual base stations 4 . 5 . 6 are with a central control unit or network center 8th connected via a network (e.g. LAN, Local Area Network). The network center 8th includes a special handover control unit 9 for controlling the change of the mobile station 7 from one base station to another, if this becomes necessary due to a decrease in the connection quality, for example. Even the mobile stations 7 can each have an additional handover control unit (not shown).

The establishment of the connections between the mobile station and a base station is described below with reference to 2 and 3 explained.

The mobile station 7 establishes a first connection to a suitable base station, which in 1 and 2 the base station 4 (BS1) is. This connection is an asynchronous connection (Asynchronous Connection-Less Link, ACL Link). Via this connection, any data between the mobile station 7 and base station 4 exchanged, for example access to a LAN (Local Area Network) is possible.

That first connection 2 is the main connection and is referred to below as the R (root) ACL.

If a voice connection is also required, a synchronous connection (Synchronous Connection-Oriented Link, SCO Link) is also set up. Via the synchronous connection between the mobile station 7 and the base station 4 transmit synchronous voice data.

In order to increase the security of the first connection and to avoid the connection being broken off and the mobile station then having to start a new, time-consuming connection setup again, the mobile station creates a second connection according to the invention 3 set up to another base station, in 2 this is the base station 5 (BS2). This connection is initially also an asynchronous connection, over which no application data or language can be exchanged, since the software protocol layers required for this are not activated.

The second connection 3 is a purely auxiliary connection that is intended to speed up a handover / roaming procedure so that when the first connection is interrupted 2 a second connection is quickly available as a replacement. The second connection is hereinafter referred to as A- (Aux-) ACL.

Since there is no connection via the second connection data transfer takes place and therefore no permanently active connection is required, it can be switched to an idle state (Park Mode) to minimize the power consumption of the mobile station.

The mobile station 7 is now in two different piconets 2 and 3 in which it takes on the role of the slave. In the Bluetooth standard, such a constellation is referred to as "Scatternet".

As long as the connection quality of the first connection 2 is sufficient, the data on the first connection 2 transfer. The connection quality of the first connection 2 and possibly also the second connection 3 permanently through the handover connection control unit 9 in the network center 8th supervised. The reception field strength of the connection is preferably used as a parameter for the connection quality. This received field strength is supplied by the Bluetooth hardware as an RSSI value (Received Signal Strength Indication).

Already during communication via the first connection 2 care is taken that the second connection 3 has a sufficiently good connection quality. If the second connection 3 if it deteriorates, this connection is cleared down and an alternative second connection to another base station is established as soon as possible. It must be ensured that this new base station is neither the "old" base station to which the second connection was broken, nor the base station 4 with which the first connection 2 already exists. In the latter case, this would mean that the first as well as the second connection 2 and 3 would be the same and thus run counter to the goal of greater security of the connection.

As soon as a handover becomes necessary, for example because the connection quality drops below a permissible level, the data exchange from the first connection 2 on the second connection 3 relocated. The second connection 3 is now the main connection of the mobile station 7 with the rest of the network 1 , The first connection 2 will be dismantled if this is still necessary or possible. Then the "second" connection 3 between mobile station 7 and base station 5 rededicated to the "new" first connection. This is in 3 shown.

In 3 is originally with 3 designated second connection between the mobile station 7 and base station 5 now the new first connection 10 , It repeats between the mobile station 7 and the base stations 5 and 6 in 3 now what in 2 already with the stations 7 . 4 and 5 The mobile station builds next to the first connection to secure the connection to the rest of the Bluetooth network 10 with the base station 5 a second connection 11 with the base station 6 BS3 on. The second connection 11 is again initially only an asynchronous connection, which is preferably switched to the idle state, since for the time being no data is transmitted via it.

In 4 the Bluetooth protocol layers involved in the method according to the invention are shown. In the following it is assumed that the protocol layers to the mobile station 7 belong. At the logically highest level is an application layer 12 arranged, which contains the application programs that run on the mobile station. The protocol layer 13 includes protocols like SDP 13a , TCS 13b and RFCOMM 13c described in the Bluetooth standard. Furthermore, there is a logical connection layer in the Bluetooth standard 14 provided, which is generally referred to as L2CAP. This connection layer 14 makes contact with a hardware 17 for sure.

According to the invention, a handover control unit is additionally implemented in the software. It is based on a handover protocol 13d in the protocol layer 13 and a handover connection unit 15 below the connection layer 14 together. Both are logical via a direct connection 18 directly connected to each other, if necessary, the connection layer 14 bypass, as explained below.

The new base station for the second connection can be selected in various ways:
In a first embodiment of the invention, the mobile station searches 7 with a page request for suitable base stations nearby and then connects to a suitable base station.

The mobile station connects at a second base station 7 directly with a suitable base station as it is from the network center 8th is specifically informed about base stations in the neighborhood. This information is through the handover protocol 13d between the central control unit 8th and the mobile device 7 replaced. Such a method speeds up the connection establishment to the new access point.

The following is a handover between the mobile station 7 and the base stations 4 . 5 and 6 explained in detail.

• 1. Die Handover-Steuereinheit 13d und 15 der Mobilstation 7 stellt fest, dass die Verbindungsqualität der ersten Verbindung 2 in einen kritischen Bereich gerät, so dass ein Handover erforderlich ist.
• 2. Das Handover-Protokoll 13d der Mobilstation 7 sendet der Handover-Steuerungseinheit 9 der Netzzentrale 8 eine Nachricht, die einen Handover auf die Basisstation 5, zu welcher die zweite Verbindung 3 bereits besteht, ankündigt.
• 3. Die L2CAP-Verbindung wird sowohl auf der Seite der Mobilstation 7 als auch auf der Seite der Basisstation 4 blockiert. Alle noch nicht über die Luftschnittstelle übertragenen Daten-Pakete werden versendet, neue Daten-Pakete werden nicht mehr bearbeitet und werden in der L2CAP Sende-Warteschlange eingereiht. Somit ist sichergestellt, dass keine Daten-Pakete durch das Handover verloren gehen.
• 4. Die im Ruhezustand befindliche zweite Verbindung wird aktiviert und in den aktiven Modus geschaltet. Diese Aufgabe kann sowohl die Basisstation 5 als auch die Mobilstation 7 erledigen. Zum Aktivieren wird ein Bluetooth- Standardbefehl (HCl_Exit_Park_Mode) verwendet. Sowohl die Mobilstation 7 als auch die Basisstation 5 erhalten daraufhin die HCl- Mitteilung "Mode Change Event" von ihrer jeweiligen Bluetooth- Hardware 17.
• 5. Anschließend werden in der Mobilstation 7 die internen Datenstrukturen in der L2CAP- Schicht 14 derart geändert, dass die logischen Kanäle nun nicht mehr über die erste Verbindung 2 laufen, sondern über die zweite Verbindung 3. Dadurch findet ein Handover zwischen erster und zweiter Verbindung 2 und 3 statt, also zwischen Basisstation 4 und 5. Die alte zweite Verbindung 3 wird nun als erste Verbindung (über Basisstation 5) geführt, und die alte erste Verbindung 2 ist die neue zweite Verbindung (über Basisstation 4). Für die zweite Verbindung muss allerdings eine neue Basisstation gefunden werden, da die Verbindung zu der Basisstation 4 ja bekanntlich keine ausreichende Qualität mehr bietet (siehe Punkt 9 unten).
• 6. Zeitgleich übergibt die erste Basisstation 4 den logischen L2CAP- Kanal inklusive der Sende-Warteschlange an die Basisstation 5. Die Kommunikation zwischen erster Basisstation 4 und zweiter Basisstation 5 findet über die zentrale Steuereinheit 8 statt.
• 7. Besteht außerdem eine synchrone Verbindung für die Sprachübertragung (SCO Link) zwischen der Mobilstation 7 und der Basisstation 4, so wird diese abgebaut und anschließend sofort über die neue Basisstation 5 wieder aufgebaut. Die logischen Verknüpfungen zu der synchronen Verbindung werden ebenfalls von der ersten an die zweite Basisstation übergeben, so dass Sprach-Applikationen, wie z.B. das Cordless Telephony Profile (CTP), ungestört weiterlaufen.
• 8. Die Blockade der L2CAP-Verbindung wird nun in der Mobilstation 7 und in der neuen Basisstation 5 aufgehoben. Zwischen der Mobilstation 7 und der neuen Basisstation 5 besteht nun eine vollwertige Verbindung, über die Daten und Sprache übertragen werden können.
• 9. Anschließend beendet die Handover Verbindungs-Steuereinheit der Mobilstation 7 die Verbindung zur ersten Basisstation 4 und baut eine neue "Aux Link"-Verbindung zu einer geeigneten zweiten Basisstation auf, z.B. zu BS3.

First there is a first connection between the mobile station 7 and the base station 4 , There is also a "parked" second connection 3 to the base station 5 , The following handover comprises the following individual steps:

• 1. The handover control unit 13d and 15 the mobile station 7 notes that the connection quality of the first connection 2 gets into a critical area, so a handover is required.
• 2. The handover protocol 13d the mobile station 7 sends the handover control unit 9 the network center 8th a message that is a handover to the base station 5 to which the second connection 3 already exists, announces.
• 3. The L2CAP connection is both on the side of the mobile station 7 as well as on the base station side 4 blocked. All data packets that have not yet been transmitted via the air interface are sent, new data packets are no longer processed and are placed in the L2CAP send queue. This ensures that no data packets are lost due to the handover.
• 4. The second connection, which is idle, is activated and switched to active mode on. This task can be done by both the base station 5 as well as the mobile station 7 take care of. A standard Bluetooth command (HCl_Exit_Park_Mode) is used for activation. Both the mobile station 7 as well as the base station 5 will then receive the HCl message "Mode Change Event" from their respective Bluetooth hardware 17 ,
• 5. Then be in the mobile station 7 the internal data structures in the L2CAP layer 14 changed so that the logical channels are no longer on the first connection 2 run, but over the second connection 3 , This creates a handover between the first and second connection 2 and 3 instead of between the base station 4 and 5 , The old second connection 3 is now the first connection (via base station 5 ) led, and the old first connection 2 is the new second connection (via base station 4 ). However, a new base station must be found for the second connection, since the connection to the base station 4 yes, as is well known, no longer offers sufficient quality (see point 9 below).
• 6. The first base station transfers at the same time 4 the logical L2CAP channel including the send queue to the base station 5 , Communication between the first base station 4 and second base station 5 takes place via the central control unit 8th instead of.
• 7. There is also a synchronous connection for voice transmission (SCO Link) between the mobile station 7 and the base station 4 , it is dismantled and then immediately via the new base station 5 rebuilt. The logical links to the synchronous connection are also transferred from the first to the second base station, so that voice applications, such as the Cordless Telephony Profile (CTP), continue to run undisturbed.
• 8. The blockage of the L2CAP connection is now in the mobile station 7 and in the new base station 5 canceled. Between the mobile station 7 and the new base station 5 there is now a full connection through which data and voice can be transmitted.
• 9. The handover connection control unit of the mobile station then ends 7 the connection to the first base station 4 and establishes a new "Aux Link" connection to a suitable second base station, for example to BS3.

The corresponding method according to the invention can be in a preferred embodiment as in 5 shown as a flow chart. First in step 19 established a first connection R-ACL and R-SCO between the mobile station and a first base station. Immediately afterwards, a second connection (auxiliary connection) A-ACL and A-SCO is set up in step 20 between the mobile station and a further base station, which is not identical to the first base station.

In the following step 21, a relevant connection parameter is permanently monitored. This is especially the connection quality, but it can also be from the outside (e.g. through the network center 8th ) a parameter is set for other reasons, based on which a handover must take place.

As soon as the connection parameter changes, branches the method from step 21 to step 22, in which the data / voice transmission from the first to the second connection, i.e. by R-ACL and possibly R-SCO on A-ACL and A-SCO.

In the following step 23 then the second connection A-ACL and A-SCO, over which data is already transmitted are "explained" to the first connection, and the procedure jumps back to a point between step 19 and step 20 at which again a second connection to secure communication via the first connection is established.

As long as none in step 21 If there is any reason for a handover, the procedure repeats the query of the connection parameter to step 24, in which the test is carried out, whether the auxiliary connection "Aux-Link" is still sufficient Quality. If this is the case, the method jumps back to a point before step 21, and the sequence of the test the connection quality for the main connection and the auxiliary connection starts from front.

However, if it is determined in step 24 that the connection quality If the auxiliary connection is no longer sufficient, this will be done in step 25 dismantled. Subsequently the process returns before step 20, in which a new auxiliary connection is established becomes.

1

Bluetooth communication network

2

first Root Connection

3

first Aux connection

4

first base station

5

second base station

6

third base station

7

mobile station

8th

Network Central Station

9

handover control

10

second Root Connection

11

second Aux connection

12

application layer

13

Protocol layer, 13a SDP, 13b TCS, 13c RFCOMM, 13d handover

control

14

L2CAP layer

15

control layer for handover

16

interface between software and hardware

17

hardware

18

additional connection between handover control layer and handover

control 13d

19

construction a root connection between the mobile station and the first base station

20

construction an aux connection between the mobile station and the second base station

21

Query, whether quality of root connection is sufficient

22

change from root to aux connection

23

reclassification from aux connection to new root connection

24

Query, whether quality of aux connection is sufficient

25

reduction the aux connection

Claims (9)

Method for the uninterrupted transmission of data between a mobile station ( 7 ) and a first ( 4 ) and / or a second ( 5 ) Base station in a Bluetooth communication network ( 1 ) with one application layer each ( 12 ), one protocol layer each ( 13 ), one connection layer each ( 14 ) and one physical layer ( 17 ), which includes the steps: establishing a first connection ( 2 ) between the first base station ( 4 ) and the mobile station ( 7 ), Establishing a second connection ( 3 ) between the second base station ( 5 ) and the mobile station ( 7 ), the data from the mobile station ( 7 ) to the first base station ( 4 ) are transmitted if at least one connection parameter, which corresponds in particular to the connection quality, lies in a predetermined value range, and the data from the mobile station ( 7 ) to the second base station ( 5 ) are transmitted if the at least one connection parameter lies outside the predetermined value range. The method of claim 1, wherein the first ( 2 ) and the second ( 3 ) Connection each comprise an asynchronous connection (R-ACL, A-ACL) for the transmission of data and a synchronous connection (R-SCO, A-SCO) for the transmission of voice data. Method according to Claim 2, in which the first asynchronous connection (R-ACL, 2 ) to the second asynchronous connection (A-ACL, 3 ) is changed depending on a first connection parameter. Method according to Claim 2 or 3, in which the first synchronous connection (R-SCO, 2 ) to the second synchronous connection (A-SCO, 3 ) is changed depending on a second connection parameter. Method according to one of the preceding claims, in which the establishment of the second asynchronous connection (A-ACL, 3 ) between the second base station ( 5 ) and the mobile station ( 7 ) through a page request from the mobile station ( 7 ) he follows. Method according to one of Claims 1 to 4, in which the establishment of the second asynchronous connection (A-ACL, 3 ) between the second base station ( 5 ) and the mobile station ( 7 ) by an instruction from a network center ( 8th ) he follows. Method according to one of claims 3 to 6, in which at least one of the connection parameters by the network center ( 8th ) is set. Method according to one of the preceding claims, in which the logical assignment between the application layers ( 13 ) the mobile station ( 7 ) and the first ( 4 ) and / or the second ( 5 ) Base station when changing from the first connection ( 2 ) to the second connection ( 3 ) is maintained. Method according to one of the preceding claims, in which the second connection ( 3 ) is kept in an idle state (park mode) until the change.