HK1069490A

HK1069490A - Mobile communication system, radio network controller and method of transferring data employed therefor

Info

Publication number: HK1069490A
Application number: HK05101794.1A
Authority: HK
Inventors: 柴田和子; 植田佳央
Original assignee: 日本电气株式会社
Priority date: 2003-03-19
Filing date: 2005-03-01
Publication date: 2005-05-20

Description

Mobile communication system, radio network controller and data transmission method thereof

Technical Field

The present invention relates to a mobile communication system, a radio network controller, and a data transmission method employed therefor, and more particularly, to a technique for realizing data transmission between node bs (radio base stations) during high-speed packet communication by HSDPA (high speed downlink packet access) based on an IMT (international mobile telecommunications) -2000 system.

Background

HSDPA has recently become a fundamental consideration for the industry to achieve faster IMT-2000 system-based packet transmission, with the main goals of improving downlink peak data rate, reducing transmission time delay, achieving high throughput, etc.

HSDPA is a system that provides high-speed packet transmission of 8Mbps in the downlink, in which HS-DSCH (high speed downlink shared channel) is used as a downlink transport channel.

Fig. 5 shows a configuration of a mobile communication system which employs the packet transmission method as described above. The mobile communication system shown here includes a mobile station (UE: user equipment) 11, base stations (node bs) 4-1 and 4-2 operable to manage cells 40-1 and 40-2, respectively, an RNC (radio network controller) 12 operable to control the base stations 4-1 and 4-2, and a CN (core network: mobile switching center) 14 operable to switch a mobile switching network. RNC 12 has MDC (macro diversity Combining) 13, which is responsible for copying and distributing data as well as Combining and selecting data.

In the described mobile communication system the protocol stack of the HS-DSCH comprises MAC-HS (high speed medium access control) functions in the node B, as shown in fig. 6.

Referring to fig. 6, an interface between an RNC [ CRNC (controlling RNC)/SRNC (serving RNC) ] and a base station is referred to as Iub, and an interface between a base station and a mobile station is referred to as Uu.

The protocol stack of the mobile station includes a MAC-d (dedicated MAC) layer, a MAC-HS layer, and a PHY (physical) layer, and the protocol stack of the base station includes a MAC-HS layer, a PHY layer, a HS-DSCHFP (high speed downlink shared channel frame protocol) layer, and a TNL (transport network layer). Furthermore, the protocol stack of the RNC includes a MAC-d layer, a HS-DSCHFP layer and a TNL.

A transport channel for voice calls, such as a dedicated channel, may allow soft handover (soft handover) by virtue of the function of the MDC in the RNC, which copies the data and distributes it to different base stations. However, the HSDPA system cannot achieve handover between base stations because the base stations are provided with MAC-hs functions.

Therefore, when high-speed packet communication by HSDPA is performed, if handover between base stations occurs, the RNC is required to switch the destination of downlink packet data from a handover source base station (serving node B) to a handover destination base station (target node B) (for example, TS25.401, v.5.2.0(2002-03), section 11.2.7 proposed by 3GPP (third generation partnership project)).

During this handover, the MAC-hs function in the handover source base station is reset to clear the data stored in the queue, resulting in data loss.

If the upper RLC (radio link control) layer is delivery acknowledgement (AM: acknowledged mode), data involved in data loss is recovered, whereas in delivery unacknowledged (UM: unacknowledged mode), packets cleared in the upper protocol are not retransmitted.

Therefore, when handover between base stations occurs due to movement of a user who is performing HSDPA-based high-speed packet communication using RLC-UM or the like, the conventional data transmission method causes a problem that data loss of high-speed packets occurs at a mobile station.

In order to prevent such data loss, high-speed packet data must be transmitted between base stations at the time of handover of the base stations. In addition, the handover destination base station needs to transmit the high-speed packet data transmitted from the RNC and the handover source base station to the mobile station in the correct order.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and has an object to provide a mobile communication system, a radio network controller, and a data transmission method employed thereby, which are capable of realizing high-speed packet data transmission without causing any data loss in handover between base stations during high-speed packet communication.

Disclosure of Invention

The present invention relates to a mobile communication system comprising a radio network controller for controlling base stations. The mobile communication system includes means for transmitting packet data from a handover source base station to a handover destination base station when a handover occurs between base stations, the handover being caused by movement of a mobile station in high-speed packet communication between the base station and the mobile station.

The present invention also relates to a radio network controller for controlling base stations, which includes means for transmitting packet data from a handover source base station to a handover destination base station when a handover occurs between base stations, the handover being caused by movement of a mobile station in high-speed packet communication between the base station and the mobile station.

The invention also relates to a data transmission method for a mobile communication system comprising a radio network controller for controlling a base station. The method includes the step of transmitting packet data from a handover source base station to a handover destination base station when a handover occurs between the base stations, the handover being caused by movement of a mobile station in high-speed packet communication between the base station and the mobile station.

Specifically, in an RNC (radio network controller) of an IMT (international mobile telecommunications) -2000 system, when handover occurs between base stations during high-speed packet communication based on HSDPA (high speed downlink packet access), the mobile communication system of the present invention enables continuous reception of high-speed packets without any data loss by routing using an IP (internet protocol) address or by establishing AAL2 ATM (asynchronous transfer mode) adaptation layer type 2 between base stations to transmit data.

HSDPA is a system that provides high-speed packet data transmission of 8Mbps in the downlink, in which HS-DSCH (high speed downlink shared channel) is used as a downlink transport channel.

The protocol stack of the HS-DSCH (see fig. 6) comprises MAC-HS (high speed medium access control) functions in the base station. A transport channel for voice calls, such as a dedicated channel, allows soft handover by means of an MDC (macro diversity combining) function provided in the RNC responsible for copying and distributing the data to different base stations. However, the HSDPA system cannot achieve soft handover between base stations because the base stations are provided with MAC-hs functions.

Therefore, when high-speed packet communication by HSDPA is being performed, if handover between base stations occurs, the RNC is required to switch the destination of downlink packet data from the handover source base station (serving node B) to the handover destination base station (target node B). During this handover, the MAC-hs function in the handover source base station is reset to clear the data stored in the queue, resulting in data loss.

If an upper RLC (radio link control) layer is a delivery acknowledged type (AM: acknowledged mode), data involved in data loss is recovered, whereas in a delivery unacknowledged type (UM: unacknowledged mode), data cleared in an upper protocol is not retransmitted.

Therefore, when handover between base stations occurs while HSDPA-based high speed packet communication is being performed using RLC-UM, data loss of high speed packet data may occur at a mobile station (UE: user equipment).

In order to prevent such data loss of high-speed packet data, when handover occurs across different base stations during high-speed packet communication by HSDPA, the mobile communication system of the present invention transfers data from a handover source base station to a handover destination base station according to the following two techniques.

First, in the case of an IP-RAN (internet protocol-radio access network), the RNC notifies the handover source base station of the transport layer address (IP address) and the binding ID [ UDP (user datagram protocol) ] port number of the handover destination base station, so that the handover source base station can transmit data to the handover destination base station.

Next, in the case of the ATM-based RAN, the RNC notifies the handover source base station of the AAL2 endpoint address of the handover destination base station, so that the handover source base station can transmit data to the handover destination base station. At this time, an AAL2 connection is newly established to use its link so that high-speed packet data transmission can be completed.

The mobile communication system of the present invention is configured such that a sequence number is added to the HS-DSCH protocol so that when handover between base stations occurs, a handover destination base station can control the order of transmitting downlink high-speed packet data to a mobile station. This allows the handover destination base station to transmit the high-speed packet data received from the RNC and the handover source base station to the mobile station in the correct order.

Accordingly, the mobile communication system of the present invention realizes high-speed packet communication in which packets can be transmitted in a controlled order without detecting data loss.

Drawings

Fig. 1 is a block diagram showing a configuration of an RNC according to an embodiment of the present invention;

fig. 2 is a sequence diagram illustrating a process of data transmission through IP routing in an IP-RAN network according to the embodiment of the present invention;

fig. 3 is a block diagram showing a configuration of an RNC according to another embodiment of the present invention;

fig. 4 is a sequence diagram illustrating a procedure for transmitting high-speed packet data using an AAL2 connection in an ATM-based network according to the another embodiment of the present invention;

fig. 5 is a block diagram showing a configuration of a conventional mobile communication system; and is

Fig. 6 shows the protocol for the HS-DSCH.

Detailed Description

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram showing a configuration of an RNC (radio network controller) according to an embodiment of the present invention, and schematically showing a data transmission mechanism in an IP (internet protocol) -based network.

As shown in fig. 1, RNC1 includes an IP routing processor 2 and a recording medium 3, and is connected to base stations (node B #1 to node B # N)4-1 to 4-N, wherein the recording medium 3 stores therein a program (computer-executable program) executed at IP routing processor 2. The IP routing processor 2 includes a call control unit 21, a data transmission unit 22, a sequence number storage unit 23, and a transmission destination IP address storage unit 24.

The RNC1 includes an Iu interface protocol processor, a radio interface processor, etc. in addition to the IP routing processor 2, which are not directly related to the present invention, and thus a description of the configuration and operation thereof will be omitted.

Meanwhile, the radio interface processor includes a PDCP (packet data convergence protocol) processing unit, an RLC (radio link control) [ UM (unacknowledged mode), AM (acknowledged mode) ] protocol processing unit, a MAC-d (dedicated medium access control) protocol unit, an HS-DSCHFP (high speed downlink shared channel frame protocol) protocol processing unit, and the like.

Referring again to fig. 1, the operation of the RNC1 will be described below. First, when an HS-DSCH (high speed downlink shared channel) is handed over from a handover source base station (serving node B)4-1 to a handover destination base station (target node B)4-N, RNC1 receives an RRC (radio resource control) measurement report, which represents a measurement report, sent from a mobile station (UE: user equipment) (not shown).

The IP route processor 2 stores the sequence number (sequence number) of the HS-DSCHFP at the time of receiving the RRC measurement report in the sequence number storage unit 23.

The call control unit 21 transmits "RL (radio link) reconfiguration prepare" to the handover source base station 4-1 to delete the HS-DSCHFP resources therein. Also, the call control unit 21 transmits "RL reconfiguration prepare" to the handover destination base station 4-N to add the HS-DSCHFP resource thereto.

Then, the handover destination base station 4-N sends "RL reconfiguration ready" containing its own IP address and UDP (user datagram protocol) port number to the RNC 1. The call control unit 21 stores the IP address and UDP port number in the message transmitted from the handover destination base station 4-N in the transfer destination IP address storage unit 24.

The call control unit 21 transmits "RL reconfiguration commit (commit)" to the handover source base station 4-1, which contains the sequence number stored upon reception of the RRC measurement report, in the sequence number storage unit 23, and the IP address and UDP port number of the handover destination base station 4-N.

The data transmission unit 22 transmits data from the handover source base station 4-1 to the handover destination base station 4-N based on the IP address and UDP port number of the handover destination base station 4-N.

Fig. 2 is a sequence diagram illustrating a process of data transmission through IP routing in an IP-RAN (internet protocol-radio access network) according to an embodiment of the present invention. Referring to fig. 1 and 2, an IP routing data transmission procedure in the IP-RAN network in this embodiment of the present invention will be described below.

In the following description, "transport layer address" and "binding ID" in "NBAP (node B application part): RL reconfiguration ready" indicate an IP address and a UDP (user datagram protocol) port number of the handover destination base station 4-N, respectively.

During the high-speed packet communication, upon receiving a message (measurement report) requesting activation of handover between base stations from the mobile station (a 1 in fig. 2), the RNC1 stores the HS-dsch fp sequence number (a 2 in fig. 2) that has been transmitted to the base station by that time.

RNC1 includes the transport layer address and the binding ID contained in the "NBAP: RL reconfiguration ready" message from the base station into the "NBAP: RL reconfiguration commit" to be transmitted to the handover source base station 4-1, thereby notifying the handover source base station 4-1 of the destination of the data (a 7 in fig. 2).

Upon receiving the "NBAP: RL reconfiguration commit", the handover source base station 4-1 accesses the transport layer address (IP address) and the binding ID (UDP port number) in the "NBAP: RL reconfiguration commit", and then transmits all high-speed packet data starting from the sequence number contained in the "NBAP: RL reconfiguration commit" to the Time when the "NBAP: RL reconfiguration commit" is received, to the RNC1, with neither operation being performed later than an Activation Time (Activation Time) (CFN: connection frame number), after which it switches to another cell (a 9, a10 in fig. 2).

After sending "NBAP: RL reconfiguration commit" through the route, RNC1 starts to transmit data from the handover source base station 4-1 to the handover destination base station 4-N (a 11 in fig. 2).

Furthermore, RNC1 also holds station data (station data) indicating the correspondence between the transport layer address (IP address) and each base station in advance, and reads out this station data when RNC1 is restarted, thereby preparing a transport layer address/base station number conversion table.

The RNC1 uses this transport layer address/base station number conversion table upon receiving high-speed packet data sent from the handover source base station 4-1, and converts the transport layer address contained in the sent packet data into a base station number, and then transmits the data to the relevant base station (i.e., handover destination base station 4-N).

Thus, according to the present embodiment, even if handover occurs across different base stations during high-speed packet communication by HSDPA, data loss of high-speed packet data can be prevented by transferring data from the handover source base station 4-1 to the handover destination base station 4-N. In addition, even if the movement of the mobile station from one base station to another occurs in the RNC1, high-speed packet communication can be realized without any data loss.

Specifically, in the case of an IP-RAN network, the RNC1 notifies the handover source base station 4-1 of the transport layer address (IP address) and the binding ID (UDP port number) of the handover destination base station 4-N, so that the handover source base station 4-1 can transmit data to the handover destination base station 4-N.

Therefore, the present embodiment prevents data loss of high-speed packet data, and can achieve high-speed packet communication without data loss even if movement of a mobile station from one base station to another occurs in the RNC 1.

Fig. 3 is a block diagram showing a configuration of an RNC according to another embodiment of the present invention, and schematically showing a data transmission mechanism in an ATM (asynchronous transfer mode) network.

As shown in fig. 3, the RNC 5 includes an AAL2(ATM adaptation layer type 2) switch processor 6 and a recording medium 7, the recording medium 7 having stored therein a program (computer executable program) executed at the AAL2 switch processor 6, and the RNC 5 is connected to each of the base stations (node B #1 to node B # N)4-1 to 4-N. The AAL2 switching processor 6 includes a call control unit 61, a data transmission unit 62, a sequence number storage unit 63, and an address mapping table 64 (hereinafter simply referred to as an address mapping table) for node bs and endpoints.

The RNC 5 includes, in addition to the AAL2 switching processor 6, AAL2 terminal devices, Iu interface protocol processors, radio interface processors, and the like, which are not directly related to the present invention, and thus, description of the configuration and operation thereof will be omitted.

The operation of the RNC 5 will be described below with reference to fig. 3. First, when the HS-DSCH is handed over from the handover source base station (serving node B)4-1 to the handover destination base station 4-N (target node B), the RNC 5 receives an RRC measurement report indicating a measurement report, which is transmitted from the mobile station (not shown).

The AAL2 switching processor 6 stores the sequence number of the HS-DSCHFP at the time of receiving the RRC measurement report in the sequence number storage unit 63.

The call control unit 61 locates the endpoint address of the handover destination base station 4-N from the address mapping table 64. The call control unit 61 also sends "RL reconfiguration prepare" containing the endpoint address of the handover destination base station 4-N to the handover source base station 4-1 to clear the HS-DSCHFP resources of the handover source base station 4-1.

The handover source base station 4-1 transmits "ALCAP (access link control application part): ERQ (establishment request message)" to the RNC1, and sets the endpoint address of the handover destination base station 4-N as the destination endpoint address for this message. The call control unit 61 transmits the received "ALCAP: ERQ" to the handover destination base station 4-N based on the destination endpoint address contained in the "ALCAP: ERQ".

The call control unit 61 transmits "RL reconfiguration prepare" to the handover destination base station 4-N to add HS-DSCHFP resources thereto. The handover destination base station 4-N then sends "RL reconfiguration ready" to the RNC 1.

Subsequently, the call control unit 61 transmits "RL reconfiguration commit" containing the sequence number retrieved from the sequence number storage unit 63 to the handover source base station 4-1. The data transmission unit 62 then transmits data from the handover source base station 4-1 to the handover destination base station 4-N based on the destination endpoint address obtained from the handover source base station 4-1.

Fig. 4 is a sequence diagram illustrating a procedure for transmitting high-speed packet data using an AAL2 connection in an ATM-based network according to another embodiment of the present invention. Referring to fig. 3 and 4, a high-speed packet data transmission process using an AAL2 connection in an ATM-based network according to another embodiment of the present invention will be described below.

In the following description, "AAL 2 endpoint address" and "binding ID" in "NBAP: RL reconfiguration ready" indicate the AAL2 endpoint address and UDP port number of the handover destination base station 4-N, respectively.

In the case of RAN (radio access network), RNC 5 includes the AAL2 endpoint address of handover destination base station 4-N in "NBAP: RL reconfiguration prepare" to be transmitted to handover source base station 4-1 to notify the destination of data to handover source base station 4-1 (b 3 in fig. 4).

After sending "NBAP: RL reconfiguration ready" to RNC 5, handover source base station 4-1 sends "ALCAP: ERQ" to RNC 5, for which message the destination endpoint address is set to the AAL2 endpoint address received with "NBAP: RL reconfiguration ready" to establish an AAL2 connection for high speed packet data transmission.

The RNC 5 transmits the "ALCAP: ERQ" message to the handover destination base station 4-N based on the destination endpoint address contained in the "ALCAP: ERQ".

Upon receiving the "ALCAP: ERQ" message, the handover destination base station 4-N transmits the "ALCAP: ECF" (setup confirm message) received through the RNC 5 to the handover source base station 4-1. Thus, an AAL2 connection for high-speed packet data transmission is established between the handover source base station 4-1 and the handover destination base station 4-N.

Subsequently, when the handover source base station 4-1 receives "NBAP: RL reconfiguration commit", it transmits all high-speed packet data starting from the sequence number in "NBAP: RL reconfiguration commit" until the reception of "NBAP: RL reconfiguration commit" to the handover destination base station 4-N (b 9 to b13 in fig. 4) during the activation time (CFN) before handover to another cell by using the AAL2 connection.

Therefore, in the present embodiment, even if handover occurs across different base stations during high-speed packet communication based on HSDPA, data loss of high-speed packet data can be prevented by transferring data from the handover source base station 4-1 to the handover destination base station 4-N, and in addition, high-speed packet communication can be realized without any data loss even if the RNC 5 detects that the mobile station moves from one base station to another.

Specifically, in the case of an ATM-based RAN network, the RNC 5 notifies the handover source base station 4-1 of the AAL2 endpoint address of the handover destination base station 4-N, so that the handover source base station 4-1 can transmit data to the handover destination base station 4-N. At this time, an AAL2 connection is newly established to use its link, thereby realizing high-speed data transmission.

Therefore, the present embodiment prevents data loss of high-speed packet data, and can obtain high-speed packet communication without any data loss even if the RNC 5 detects that the mobile station moves from one base station to another.

As described above, the present invention has the aforementioned structure and operation, and thus provides an advantage that high-speed packet data transmission can be achieved without data loss during handover between base stations in the middle of high-speed packet communication.

Claims

1. A mobile communication system comprising a radio network controller for controlling a base station, wherein

The radio network controller includes means for transmitting packet data from a handover source base station to a handover destination base station when a handover occurs between base stations, the handover occurring due to movement of a mobile station during high-speed packet communication performed by an HSDPA system between a base station and the mobile station.

2. The mobile communication system according to claim 1, wherein the means for transmitting packet data transmits data from the handover source base station to the handover destination base station by routing using an IP address.

3. The mobile communication system according to claim 2, wherein the means for transmitting packet data notifies the handover source base station of an IP address and a UDP port number of the handover destination base station.

4. The mobile communication system according to claim 1, wherein the means for transmitting packet data establishes an AAL2 connection between the handover-source base station and the handover-destination base station to transmit data from the handover-source base station to the handover-destination base station.

5. The mobile communication system according to claim 4, wherein the means for transmitting packet data notifies the handover source base station of the AAL2 endpoint address of the handover destination base station.

6. The mobile communication system of claim 1, wherein a sequence number is added to the HS-DSCH frame protocol so that the handover destination base station controls an order of transmitting downlink high speed packet data when the handover occurs between base stations.

7. A radio network controller for controlling a base station, comprising:

means for transmitting packet data from a handover source base station to a handover destination base station when handover occurs between base stations, the handover occurring due to movement of a mobile station during high-speed packet communication performed by an HSDPA system between a base station and the mobile station.

8. The radio network controller of claim 7, wherein the means for transmitting packet data transmits data from the handover source base station to the handover destination base station by routing using an IP address.

9. The radio network controller of claim 8, wherein the means for transmitting packet data notifies the handover source base station of an IP address and a UDP port number of the handover destination base station.

10. The radio network controller of claim 7, wherein the means for transmitting packet data establishes an AAL2 connection between the handover source base station and the handover destination base station to transmit data from the handover source base station to the handover destination base station.

11. The radio network controller of claim 10, wherein the means for transmitting packet data notifies the handover source base station of an AAL2 endpoint address of the handover destination base station.

12. The radio network controller of claim 7 wherein sequence numbers are added to the HS-DSCH frame protocol such that when the handover occurs between base stations, the handover destination base station controls the order in which downlink high speed packet data is transmitted.

13. A data transmission method of a mobile communication system including a radio network controller for controlling a base station, the method comprising:

a step of transmitting packet data from a handover source base station to a handover destination base station when a handover occurs between base stations, the handover occurring due to movement of a mobile station during high-speed packet communication performed by an HSDPA system between a base station and the mobile station, the step being performed by the radio network controller.

14. The method of claim 13, wherein the step for transmitting packet data comprises transmitting data from the handover source base station to the handover destination base station by routing using an IP address.

15. The method of claim 14, wherein the step for transmitting packet data includes notifying the handover source base station of an IP address and a UDP port number of the handover destination base station.

16. The method of claim 13, wherein the step for transmitting the packet data comprises establishing an AAL2 connection between the handover source base station and the handover destination base station to transmit data from the handover source base station to the handover destination base station.

17. The method of claim 16, wherein the step for transmitting the packet data comprises informing the handover source base station of an AAL2 endpoint address of the handover destination base station.

18. The method of claim 13, wherein a sequence number is added to an HS-DSCH frame protocol so that the handover destination base station controls an order of transmitting downlink high speed packet data when the handover occurs between base stations.

19. A program of a method for transmitting data for a mobile communication system including a radio network controller for controlling a base station, wherein the program causes a computer to execute the steps of:

a step of transferring packet data from a handover source base station to a handover destination base station when a handover occurs between base stations, the handover occurring due to movement of a mobile station during high-speed packet communication performed by an HSDPA system between a base station and the mobile station.