JP2007081885A - Data transmission system, data transmission method, radio controller, base station and mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce deterioration in signal quality on the service boundary of MBMS in a data transmission system where an identical MBMS content is distributed in an OFDM system from one or more base stations. <P>SOLUTION: In the data transmission system, identical user common data are distributed in the OFDM system spread by a scramble code from a plurality of base stations to one or more mobile station. A radio network controller (RNC) comprises a means for storing received user common data, and a means for notifying a scramble code common to a plurality of base stations connected with the RNC. Each of the plurality of base stations comprises a means for spreading the user common data by a notified common scramble code and transmitting them to one or more mobile stations by radio, and a means for notifying the common scramble code to one or more mobile stations. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention generally relates to the technical field of wireless data transmission, and more particularly, to a data transmission system, a base station, and a data transmission method for transmitting content of a multimedia broadcast / multicast service (MBMS).

  In recent mobile communication systems, not only circuit-switched voice services but also large-capacity multimedia services using packet switching systems are being performed. In the third generation standardization mechanism (3GPP), MBMS in a packet switching type system is standardized, and related architectures and configurations related to radio channels have been published (see Non-Patent Document 1).

  A mobile station, a base station, and a radio network controller (RNC: Radio Network Controller) constitute a radio access network (RAN). From the viewpoint of delivering MBMS content, the RNC may be referred to as an MBMS server. The MBMS server is connected to the broadcast multicast service center (BM-SC) through some network.

A mobile station (UE) under the control of a base station or Node B (Node B) receives an MBMS notification indicator (NI) that prompts the user to join MBMS. The mobile station selects a service of interest (for example, news broadcast) from the received NI, notifies the base station of the service, and executes a procedure for joining the service. . In this type of conventional system, a cell group identifier (Cell Group Id) is assigned to each MBMS content transmitted between one MBMS server, and one PDCP and RLC are shared within the group. When combining or soft combining is performed at a cell or sector boundary, each of MBMS contents distributed from a plurality of asynchronous cells is specified by MBMS Neighboring Cell Information. Are synthesized by using L1 combining timing.
3GPP interface standard, 3GPP “TS25.346”, “TS25.331”, Internet <URL: http://www.3gpp.org>

  In future mobile communication systems that have started discussions at the 3rd Generation Standardization Organization (3GPP), an orthogonal frequency division multiplexing (OFDM) scheme is promising as a downlink transmission scheme. The OFDM scheme has a feature that delayed waves that arrive within a guard interval (GI) can be combined without interfering with each other. For this reason, MBMS content is simultaneously transmitted from a plurality of cells using the OFDM method, and MBMS content is synthesized at the cell edge to improve performance. In this case, the MBMS service area that distributes the same content is covered by one or more cells, and the cell boundary and the MBMS service boundary are not necessarily the same. In addition, there are many services that a mobile station (UE) may subscribe to, and each MBMS server generally distributes different contents. Therefore, especially in the vicinity of the service boundary, different MBMS contents may interfere with each other, resulting in signal quality degradation.

  The present invention has been made in order to address at least one of the above-mentioned problems, and the problem is that in an MBMS system in which the same MBMS content is distributed from one or more base stations based on the OFDM scheme, The present invention provides a data transmission system, a data transmission method, a radio control apparatus, a base station, and a mobile station that at least reduce signal quality degradation at the service boundary.

  In the present invention, a radio control apparatus, a plurality of base stations, and one or more mobile stations are provided, and the same user common data is code-spread with a spreading code (scramble code) from the plurality of base stations to one or more mobile stations. A data transmission system that uses the OFDM method is used. The radio control apparatus includes means for storing received user common data, and means for notifying the plurality of base stations of a common scramble code common to a plurality of base stations connected to the radio control apparatus. Each of the plurality of base stations includes means for spreading user common data with the notified common scramble code and wirelessly transmitting to one or more mobile stations, and means for notifying one or more mobile stations of the common scramble code. Have.

  According to the present invention, in a data transmission system in which the same MBMS content is distributed from one or more base stations by the OFDM method, it is possible to at least reduce signal quality degradation at the MBMS service boundary.

  According to an aspect of the present invention, a radio network controller (RNC) or an MBMS server determines a common scrambling code that is common to a plurality of subordinate base stations. The common scramble code is prepared separately from the scramble code prepared for each cell. User common data (MBMS content) is transmitted from a plurality of base stations to one or more mobile stations by the OFDM method spread with a common scramble code. Since the common scrambling code is different for each RNC (for each MBMS service), the mobile station at the cell edge can easily determine whether or not it is at the service boundary and can share MBMS content coming from multiple adjacent cells in phase. It is possible to easily determine whether or not to perform synthesis (soft combining).

  A common scramble code may be prepared for each MBMS content. In this way, it is possible to synthesize the MBMS content of all cells that are delivering the same service.

  The common scramble code may be determined by a management server connected to the radio network controller and managing the scramble code, by an agreement with an adjacent radio network controller, or by external input as station data.

<Communication system>
FIG. 1 shows a communication system assumed in an embodiment of the present invention. The communication system includes a core network (CN) and a radio access network (RAN). The CN includes a route control device (Access Router) and a control station (BM-SC: Broadcast / Multicast-Service Center) that controls delivery of MBMS content. On the other hand, the RAN communicates with a plurality of radio base stations (Node B), a radio network controller (RNC) or MBMS server that controls a plurality of Node Bs, and a plurality of base stations (Node B) via a radio interface. It consists of a mobile station (UE). The interface between the routing device and the RNC is expressed as Iu. The interface between RNC and base station is expressed in Iub. The interface between RNCs is expressed in Iur. Each interface name assumed in this embodiment is an example, and the present invention is not limited to this.

  In the downlink radio interface between the Node B and the UE, an OFDM scheme that is code-spread using a spreading code (scramble code) is used. Cell identification is usually performed using a spreading code called a scramble code. As will be described later, in the present invention, in addition to the scramble code for each cell, a common scramble code that is commonly used for a plurality of cells is prepared, and the difference in service or the difference in content is distinguished by using the common scramble code. In the illustrated example, base stations of cells A and B are connected to one MBMS server, and the same MBMS content is distributed in cells A and B. The base station of cell C is connected to another MBMS server, and content that is generally different from the content distributed in cells A and B is distributed in cell C. Accordingly, a service boundary is formed between the cells A and B and the cell C.

  If the present invention described below is not used, the mobile station (UE) located near the service boundary (the boundary between the cell A and the cell C and the boundary between the cell B and the cell C) has different contents. There is a concern that the received signal quality is greatly deteriorated. Since the mobile station located near the boundary between the cell A and the cell B can receive the same content from both cells, soft combining can be performed well. This is due to the fact that the UE can determine whether or not it is located at the cell edge, but cannot determine whether or not it is located at the service boundary. It is assumed that the transmission timings of all base stations are synchronized with each other at least for the delivery of MBMS content.

<MBMS server>
FIG. 2 shows a functional block diagram of an MBMS server according to an embodiment of the present invention. The MBMS server includes a control unit, a wired transmission unit, a scramble code setting unit, a server communication unit, an MBMS server communication unit, an external input unit, and a storage unit.

  The control unit controls each functional entity included in the MBMS server and controls the operation of the entire MBMS server device. The wired transmission unit has a function of notifying the base station (Node B) of the scramble code determined by the scramble code setting unit, a function of communicating with a management server on the network (NW), and a function of communicating with an adjacent MBMS server. . The scramble code setting unit has a function of determining a scramble code of Node B connected to itself (under the MBMS server) when distributing MBMS content. This scramble code is prepared for each MBMS server, and is distinguished from a normal scramble code prepared for each cell. The server communication unit has a function of communicating with a management server arranged on the NW, and the management server has a function of managing a scramble code of Node B under the MBMS server. The MBMS server communication unit has a function of communicating with an adjacent MBMS server via an Iur interface. The external input unit has a function of manually inputting a scramble code such as station data when distributing MBMS content from the outside. The storage unit has a function of storing information used in the RNC, and particularly stores MBMS content received from a host device.

  For convenience of explanation, the MBMS server is illustrated as including all of the server communication unit, the MBMS server communication unit, and the external input unit. However, this is not essential to the present invention, and at least one of these functions is provided. That's fine. In this case, the wired transmission unit may have a function corresponding to the server communication unit, the MBMS server communication unit, and the external input unit provided for the MBMS server.

A normal scramble code C _CELL prepared for each cell and a scramble code C _MB prepared for each MBMS server are prepared separately. These may be set completely independently or may have some relationship.

<Node B>
FIG. 3 shows a functional block diagram of a base station (Node B) according to an embodiment of the present invention. Node B includes a control unit, a wireless transmission unit, a wired transmission unit, an MBMS content identification unit, and a scramble code setting unit.

  The control unit controls each functional entity included in Node B and controls the overall operation of Node B. The wireless transmission unit has a function of distributing MBMS content to mobile stations, and the MBMS content is spread with a scramble code designated by the MBMS server. In this embodiment, the downlink radio channel may be transmitted by an OFDM-CDMA (also called MC-CDMA or OFCDM) method as an example. However, the present invention is not limited to this, and transmission may be performed by an OFDM method in which spreading processing is performed using a spreading code (scramble code). The wired transmission unit has a function of receiving notification of a scramble code designated by the MBMS server and a function of receiving MBMS content distributed from the MBMS server. The MBMS content identification unit stores data transmitted from the MBMS server and has a function of identifying whether or not it is MBMS content. The scramble code setting unit has a function of setting a scramble code for MBMS content distribution designated by the MBMS server in order to create a downlink radio channel.

<MBMS server operation flow>
FIG. 4 shows an example of the operation flow of the MBMS server according to an embodiment of the present invention. This operation example is performed when the MBMS service is started. The MBMS server determines whether or not to start the MBMS content distribution service (step S1). This determination may be made based on whether the MBMS server has received MBMS content from a higher-level device (BM-SC or the like), for example. If No in step S1, the flow ends. If YES, the flow proceeds to step S2, and an MBMS content distribution service is started.

  In step S2, it is determined whether or not to make an inquiry to a management server (for example, an O & A server) arranged on the network (NW). As described above, such a management server has a function of managing scramble codes. The MBMS server may or may not be configured to communicate with the management server to determine the scramble code. In the former case, the determination result in step S2 is YES, and the MBMS server inquires the management server and acquires information on the scramble code. In the latter case, the determination result in step S2 is NO, and the flow proceeds to step S3.

  In step S3, it is determined whether or not to make an inquiry to a neighboring MBMS server. The MBMS server may or may not be configured to negotiate with neighboring MBMS servers when determining the scramble code. In the former case, the determination result in step S3 is YES, and the MBMS server makes an inquiry to a neighboring MBMS server and acquires information on the scramble code. For example, one RNC acquires scramble code information that is not used by the other RNC. In the latter case, the determination result in step S3 is NO, and the flow proceeds to step S4.

  In step S4, it is determined whether or not the scramble code can be artificially input as station data. The MBMS server may or may not be set so that the scramble code is externally input as station data. In the former case, the MBMS server receives external input and obtains information on the scramble code. In the latter case, information on the scramble code is acquired by some other method (step S41).

  In step S5, information on the scramble code acquired in each procedure of step S2, S3, S4 or S41 is notified to the scramble code setting unit in FIG. Based on this information, the scramble code used under the MBMS server is determined. The determined scramble code is notified to a plurality of Node Bs connected to the MBMS server (step S6), and the flow ends.

  For convenience of explanation, the flow is drawn so that the MBMS server can execute all the steps S2, S3, S4 and S41, but this is not essential to the present invention. This is because it is only necessary to set a scramble code for the service by some method after the start of the service is determined in step S1. When step S2 or S3 is used, the system can autonomously set the scramble code under the MBMS server, so it can be set automatically. In steps S2 and S3, an additional function is required to set a scramble code, but in the case of step S4, no additional function is required. Further, when two or more of steps S2, S3, S4, and S41 can be executed, the order in which the procedures are executed is not limited to the illustrated order, and the order in which the steps are executed may be changed. Information obtained from steps S2, S3, S4 or S41 or a combination thereof may relate to one scramble code, or may be a plurality of candidates for usable scramble codes. In the latter case, it is determined in step S5 which scrambling code should be used finally.

<Operation flow of Node B>
FIG. 5 is a flowchart showing an operation example of the base station (Node B) according to one embodiment of the present invention. This operation example is performed when the MBMS service is started.

  In step S1, it is determined whether or not a scramble code related to MBMS is notified from the MBMS server to which Node B belongs. As a result of the determination in step S1, if the scramble code is not notified from the MBMS server, the flow ends, and if it is notified, the flow proceeds to step S2. In step S2, Node B sets the designated scramble code in the wireless transmitter. The mobile station (UE) is notified by broadcast information that the scramble code is used for delivery of MBMS content. As an example, it is assumed that notification is made with broadcast information, but the present invention is not limited to this, and a method of notifying by signaling or the like at the start of MBMS service may be used. In step S3, it is determined whether there is MBMS content to be transmitted to the UE. If there is MBMS content to be transmitted as a result of the determination in step S3, the MBMS content is transmitted using the scramble code set for that purpose (step S4). If the result of determination in step S3 is that there is no MBMS content to be transmitted and there is user data to be transmitted, user data is transmitted using a normal scramble code set for each cell ( Step S5). It should be noted that the normal scramble code set for each cell and the scramble code notified in step S1 are not the same.

  FIG. 6 shows a functional block diagram of a mobile station (UE) according to an embodiment of the present invention. The UE includes a control unit, a radio transmission unit, a broadcast information analysis unit, a data analysis unit, and a scramble code setting unit.

  A control part performs control with respect to each functional entity with which UE is equipped, and manages operation | movement of UE whole. The wireless transmission unit has a function of receiving broadcast information in a serving cell, and a function of despreading and receiving MBMS content with a specified scramble code. In the present embodiment, the downlink radio channel is transmitted by an OFDM method in which spreading processing is performed using a spreading code (scramble code). The broadcast information analysis unit has a function of analyzing a common scramble code for MBMS broadcast by broadcast information. The data analysis unit has a function of analyzing data transmitted on the data channel. As an example, the data analysis unit analyzes the data type by analyzing the coded identifier on the SCCH attached to the data channel. The scramble code setting unit has a function of setting a scramble code according to the data type transmitted on the data channel. More specifically, if the transmitted data is MBMS content, a “common scramble code” common to a plurality of cells according to the present invention is used. If the transmitted data is not MBMS content, a scramble code for each cell is used. Is used.

  FIG. 7 is a flowchart showing an operation example of a mobile station (UE) according to an embodiment of the present invention.

  In step S1, it is determined whether or not the mobile station has received broadcast information. As a result of the determination in step S1, if the broadcast information has not been received, the flow ends. If it has been received, the flow proceeds to step S2. In step S2, the UE sets the designated scramble code in the radio receiver. In step S3, the UE determines the type of data transmitted on the data channel. If the result of the determination in step S3 is that the data type is MBMS content, the MBMS content is received using the common scramble code set for that purpose (step S4). If the result of determination in step S3 is normal user data whose data type is not MBMS content, user data is received using a normal scramble code set for each cell (step S5).

  According to this embodiment, a common scramble code is prepared for each MBMS server (for each service area). Accordingly, the mobile station (UE) located at the cell edge determines whether the common scramble code is different, and if it is the same, the UE is in the same service area and executes soft combining. If the common scramble code is different, the cell edge is also a service boundary, so the UE does not perform soft combining. By performing such an operation, the UE can effectively avoid unnecessary combining processing of received signals at the service boundary.

  In the first embodiment, a scramble code is prepared for each MBMS server. In the second embodiment, a scramble code is prepared for each MBMS content to be distributed.

<MBMS server>
FIG. 8 shows a functional block diagram of an MBMS server according to an embodiment of the present invention. The MBMS server includes an MBMS content identification unit in addition to the control unit, the wired transmission unit, the scramble code setting unit, the server communication unit, the MBMS server communication unit, the external input unit, and the storage unit described with reference to FIG.

  The control unit controls each functional entity included in the MBMS server and controls the operation of the entire MBMS server device. The wired transmission unit has a function of notifying the base station (Node B) of the scramble code determined by the scramble code setting unit, a function of communicating with a management server on the network (NW), and a function of communicating with an adjacent MBMS server. . The scramble code setting unit has a function of determining a scramble code of Node B connected to itself (under the MBMS server) when distributing MBMS content. This scramble code is determined for each MBMS content. The server communication unit has a function of communicating with a management server arranged on the NW, and the management server has a function of managing a scramble code of Node B under the MBMS server. The MBMS server communication unit has a function of communicating with an adjacent MBMS server via an Iur interface. The external input unit has a function of manually inputting a scramble code such as station data when distributing MBMS content from the outside. The storage unit has a function of storing information used by the MBMS server, and particularly stores MBMS content received from a host device. The MBMS content identification unit has a function of identifying MBMS content to which UEs under the MBMS server are subscribed. In other words, the MBMS server knows which UE subscribes to which service and which service contains which content.

<Node B>
The base station (Node B) used in the present embodiment has the same function as that of the base station (FIG. 3) used in the first embodiment, but the scrambling code setting method is mainly different. Node B has a control unit, a wireless transmission unit, a wired transmission unit, an MBMS content identification unit, and a scramble code setting unit as shown in FIG.

  The control unit controls each functional entity included in Node B and controls the overall operation of Node B. The wireless transmission unit has a function of distributing MBMS content to mobile stations, and the MBMS content is spread with a scramble code designated by the MBMS server. Also in this embodiment, the downlink channel is transmitted by the OFDM method in which spreading processing is performed using a spreading code (scramble code). The wired transmission unit has a function of receiving notification of a scramble code designated by the MBMS server and a function of receiving MBMS content distributed from the MBMS server. The MBMS content identification unit stores data transmitted from the MBMS server and has a function of identifying whether or not it is MBMS content. The scramble code setting unit has a function of setting a scramble code for MBMS content distribution designated by the MBMS server for each MBMS content in order to create a downlink radio channel.

  According to this embodiment, a scramble code is set for each content. As described above, if the MBMS server is different, the content distributed from there is generally different. Therefore, the UE can distinguish between different contents using the scramble code, and can avoid unnecessary combining processing of received signals at the service boundary. This is the same as in the first embodiment. However, in this embodiment, a scramble code is prepared for each content, not for each MBMS server. Therefore, even if the UE is at the service boundary, if the same content happens to be distributed from both service areas (MBMS server), those scramble codes are the same, and both distribution contents are appropriately combined. It turns out that they can be done and they can be soft combined. That is, according to the present embodiment, the mobile station can synthesize signals coming from all cells that distribute the same content.

1 is a diagram illustrating a data transmission system according to an embodiment of the present invention. 1 shows a functional block diagram of an MBMS server according to an embodiment of the present invention. FIG. FIG. 2 shows a functional block diagram of a base station according to an embodiment of the present invention. It is a flowchart which shows the operation example performed with a MBMS server. It is a flowchart which shows the operation example performed in a base station. 1 shows a functional block diagram of a mobile station according to one embodiment of the present invention. It is a flowchart which shows the operation example performed with a mobile station. It is a functional block diagram of an MBMS server according to an embodiment of the present invention.

Explanation of symbols

UE mobile station
Node B base station
RNC wireless network controller
RAN radio access network
CN core network

Claims (9)

A data transmission system having a radio controller, a plurality of base stations, and one or more mobile stations, and distributing the same user common data from a plurality of base stations to one or more mobile stations by the code spread OFDM method. And
The radio control apparatus has means for storing received user common data, and means for notifying the plurality of base stations of a common scrambling code common to a plurality of base stations connected to the radio control apparatus,
Each of the plurality of base stations spreads user common data with the notified common scramble code and wirelessly transmits the data to one or more mobile stations, and notifies the set common scramble code to one or more mobile stations. And a data transmission system. A radio control apparatus connected to the plurality of base stations, used in a data transmission system for distributing the same user common data from a plurality of base stations to one or more mobile stations using the code spread OFDM method,
Means for storing user common data;
Means for distributing common user data to the plurality of base stations;
Means for notifying the plurality of base stations of a common scramble code common to the plurality of base stations;
A wireless control device comprising: A means for determining whether or not the received data is user common data;
The radio control apparatus according to claim 2, wherein the common scramble code is prepared for each user common data.   3. The radio control apparatus according to claim 2, wherein the common scramble code is determined by a management server that manages the scramble code, by an agreement with an adjacent radio network controller, or by external input as station data. A base station used in a data transmission system that distributes the same user common data from a plurality of base stations connected to a radio network controller to one or more mobile stations by code-spread OFDM method,
Means for receiving information of a common scramble code common to a plurality of base stations from the radio control device;
Means for spreading user common data with a common scramble code notified from the radio control device, and wirelessly transmitting to one or more mobile stations;
Means for notifying one or more mobile stations of a common scramble code;
A base station characterized by comprising: The base station according to claim 5, wherein the common scramble code is prepared for each user common data. The base station according to claim 5, further comprising means for spreading user data different from the user common data with a scramble code prepared for each cell and wirelessly transmitting the data to one or more mobile stations. A mobile station used in a data transmission system that distributes data by an OFDM scheme code-spread from a plurality of base stations connected to a radio network controller,
Means for receiving broadcast information including information of a common scramble code common to the plurality of base stations;
Means for determining whether the data type is user common data common to one or more users;
If the data type is user common data, the data is despread with the common scramble code. If the received data type is not user common data, the data is scrambled for each base station. Means for despreading;
A mobile station characterized by comprising: An OFDM system that has a radio controller, a plurality of base stations, and one or more mobile stations, in which the same user common data is code-spread with a spreading code (scramble code) from the plurality of base stations to one or more mobile stations. A data transmission method for distribution,
The radio control apparatus stores received user common data, and notifies the plurality of base stations of a common scramble code common to a plurality of base stations connected to the radio control apparatus,
Each of the plurality of base stations spread user common data with the notified common scramble code, and wirelessly transmit to one or more mobile stations,
A data transmission method characterized in that at least one of the one or more mobile stations despreads and demodulates user common data received from one or more base stations with a common scramble code notified from the one or more base stations .

Images