KR20050094691A - Uplink scheduling method of mobile communication system - Google Patents

Abstract

The present invention provides an effective uplink scheduling method for retransmission in a mobile communication system in which a terminal transmits data to a base station through an enhanced transmission dedicated channel (E-DCH). In the uplink scheduling method for retransmission according to the present invention, a terminal requests control information from a radio network controller based on response signals transmitted from a plurality of base stations, and one base station controlling the terminal is transmitted from the radio network controller. Uplink scheduling for retransmission of the terminal is performed by using the control information.

Description

Uplink scheduling method of mobile communication system {UPLINK SCHEDULING METHOD OF MOBILE COMMUNICATION SYSTEM}

The present invention relates to a scheduling method of a mobile communication system, and more particularly, to an effective downlink scheduling method for retransmission when a terminal in soft handover transmits data through an enhanced transmission dedicated channel (E-DCH).

UMTS (Universal Mobile Telecommunications System) is a third generation mobile communication system that has evolved from the European standard Global System for Mobile Communications (GSM) system.It is based on GSM Core Network and Wideband Code Division Multiple Access (WCDMA) access technologies. The aim is to provide an improved mobile communication service.

1 is a diagram illustrating a network structure of a UMTS applied to the prior art and the present invention.

As shown in FIG. 1, a UMTS system is largely composed of a terminal, a UMTS Terrestrial Radio Access Network (UTRAN), and a Core Network (CN).

The UTRAN consists of one or more Radio Network Sub-systems (RNS), each of which is a Radio Network Controller (RNC) and one or more base stations managed by the RNC. It is composed of

The Node B is managed by the RNC, and receives the information transmitted from the physical layer of the terminal in the uplink, and transmits data to the terminal in the downlink, and serves as an access point of the UTRAN for the terminal.

The RNC is in charge of allocating and managing radio resources and serves as an access point with the CN. In addition, the RNC includes a path attenuation of each UE to Node-Bs (or path attenuation of serving UEs and neighboring cells of each UE) and an amount of uplink interference amount of the serving cell and neighboring cells of each UE. Manage your information. In particular, the RNC manages path attenuation information for Node Bs in handover of UEs in soft handover situations. Through such management, the RNC can more accurately know the amount of interference for neighbor cells generated by the UE, which is a handover situation. Accordingly, the RNC informs the Node B of the information, and the Node B performs scheduling using management information provided from the RNC.

2 is a diagram illustrating a connection structure between a UTRAN and a terminal in a UMTS network.

2, in order to receive a service provided by UMTS, a terminal must be connected to a core network, and information on the terminal and the core network is transmitted via the UTRAN. The core network and the RNC are connected through the Iu interface to exchange data and control messages. Each terminal connected to the UMTS network is managed by a specific RNC in the UTRAN. At this time, the RNC managing the terminal is called a SRNC (Serving RNC). That is, the SRNC refers to an RNC serving as an access point with a core network for data transmission of a specific terminal.

The SRNC serves as a second layer of OSI (Open System Interface) for data received through the air interface or transmitted to the terminal, and allocates a radio resource suitable for providing a service. The radio resource management function of the SRNC includes all control functions related to a specific terminal such as transmission channel setting, handover decision, and open loop power control. And, at a specific point in time, the terminal connected to the core network through the UTRAN has only one SRNC.

Normally, one RNC is used for the connection between the UE and the RNC. However, when the UE moves to an area in which another RNC is in charge, the UE connects to the SRNC via the RNC of the moved area.

That is, as shown in Figure 2, when the terminal is initially connected through R1 (RNC 1), but later moved to a cell managed by R2 (RNC 2), the terminal is connected to R1 via the Iur interface via R2 do. The management of the terminal and the role of the access point between the core network are still performed by R1, and R2 performs a partial function of simply routing user data or allocating a code that is a common resource.

In the UMTS network, like R2, all RNCs connected to the UE except for SRNC are called DRNC (Drift RNC). As such, one terminal may not have a DRNC according to a connection state, and may have one or several DRNCs.

Currently, the next generation mobile communication, especially 3GPP communication system is considering the application of the enhanced uplink dedicated channel (E-DCH) in accordance with the demand for uplink speed.

As shown in FIG. 3, an uplink dedicated channel (DCH) and an enhanced uplink dedicated channel (E-DCH) are all transport channels dedicated to one UE. In particular, the E-DCH is used by the UE to transmit uplink data to the UTRAN, and has an advantage of transmitting uplink data at high speed compared to the DCH. In order to transmit data at high speed, the E-DCH uses techniques such as Hybrid ARQ (HARQ), Node B Controlled Scheduling (hereinafter abbreviated to Node B scheduling), and a fast DCH configuration method.

For the E-DCH, Node B transmits downlink control information for controlling the E-DCH transmission of the terminal to the terminal. The downlink control information includes response information (ACK / NACK) for HARQ, E-DCH transmission rate allocation information for Node B scheduling, E-DCH transmission start time and transmission time interval allocation information, and transport block size information (Transport Block Size). Information).

In particular, as packet data services have been introduced, one of the methods for securing the reliability of data transmission has been used, and a method of requesting retransmission by detecting an error with demodulated data on the receiving side has been used. In a system considering retransmission, the acknowledgment information (ACK) indicates to the sender that the receiver has successfully received data, and the NACK indicates that the receiver does not receive data properly or that there is an error in the received packet. To judge. When the ACK signal is received, the transmitter determines that the receiver has properly received the packet and transmits the next packet. When receiving the NACK signal, the transmitter determines that the receiver has not properly received the packet and retransmits the previous packet.

Meanwhile, the terminal transmits uplink control information to the Node B. The uplink control information includes E-DCH Rate Request Information, UE Buffer Status Information, and UE Power Status Information for Node B scheduling. The uplink control information and the downlink control information for the E-DCH are transmitted through a physical control channel such as a dedicated physical control channel (E-DPCCH).

4 is a diagram illustrating a protocol model for an E-DCH.

As shown in FIG. 4, the MAC-e sublayer supporting the E-DCH exists under the MAC-d sublayer of the UTRAN and the UE. The MAC-e sublayer of the UTRAN is located in Node B, and there is also a MAC-e sublayer in each terminal. On the other hand, the MAC-d sublayer of the UTRAN is located in the SRNC that manages the corresponding terminal, and the MAC-d sublayer also exists in each terminal. And the function or location of the new MAC-e for EDCH control is still under discussion and there is a possibility of change.

As described above, in order to transmit uplink data at high speed through the E-DCH, various techniques such as HARQ (Hybrid ARQ) and Node B control scheduling and fast DCH configuration have been proposed.

Conventional scheduling and rate control for the uplink was performed by the scheduler of the radio network controller (RNC). However, the RNC scheduler does not quickly cope with the change in the load of the uplink. That is, the RNC scheduler cannot quickly control the amount of uplink load on each user equipment (UE), and when retransmission is required, the retransmission is determined after transmission to the upper RNC. There was a problem that a transmission delay occurred. Therefore, Node B scheduling has been introduced as a more efficient uplink scheduling method for uplink speed.

In the time-rate scheduling scheme for the uplink E-DCH, Node B effectively adjusts the total amount of uplink interference by controlling the packet transmission time and transmission data rate through the uplink E-DCH for each UE. do. Through such control, the base station maximizes utilization of uplink radio resources.

On the other hand, in the time-rate scheduling scheme for the uplink E-DCH, the UE transmits its packet within the transmission data rate (or transmission rate) range only at the moment when the transmission is allowed from the base station, and this scheduling In the scheme, the UE is scheduled by one Node B (serving Node B) that controls itself.

In addition, UEs in soft handover state with multiple Node Bs are similarly scheduled by one serving Node B scheduling uplink of the UE. Accordingly, among the Node-Bs in which the terminal is in soft handover, other Node-Bs except the serving Node-B may receive a packet through the E-DCH transmitted by the terminal even if the terminal is in soft handover with the terminal. none.

On the other hand, in the conventional system for transmitting a packet using an uplink channel, all Node Bs in soft handover receive the packet transmitted by the terminal, and selectively combines a packet without a reception error in the RNC. To achieve diversity gain.

However, in the current Node B scheduling scheme, this diversity effect cannot be obtained because only one serving Node B receives and manages information transmitted from the terminal. Therefore, various methods for obtaining the diversity effect have been discussed. In this method, all Node Bs in the soft handover area can receive data transmitted by the UE, and the UE signals TFC (Transport Format Combination) information to all Node Bs in the soft handover area. A method for allowing all Node Bs to receive a packet has been proposed.

As described above, when all Node Bs in the soft handover area are able to receive data transmitted by the UE, the UE receiving the response signal (ACK / NACK) generated by the Node B is through its own algorithm, that is, By combining or selecting the response signals, it is determined whether the transmitted data has been properly received.

In the conventional wireless system, since the RNC knows Node B information (path attenuation information and transmission data rate, etc.) for each UE whenever the UE transmits data, the RNC could reflect the information when requesting retransmission. . However, in the E-DCH system scheduled for Node B control, since the UE and Node B exchange information under the control of Node B and transmit the information, the UE cannot request or obtain control information from the RNC every time data is transmitted. Node B cannot get information about each other.

Therefore, when the UE determines whether the previously transmitted packet is successfully received based on response signals received from several Node Bs, and then retransmits the packet, the UE has a disadvantage in that it unnecessarily allocates transmission power to the retransmitted data. That is, in the related art, since the terminal cannot obtain control information from the RNC, there is a problem of increasing uplink interference rather than performing proper scheduling.

Accordingly, an object of the present invention is to provide a method for reducing the amount of unnecessary uplink interference and more effectively performing retransmission when a UE in a soft handover region performs retransmission.

In order to achieve the above object, in a mobile communication system for transmitting data from a terminal to a base station through an enhanced dedicated uplink channel, the terminal transmits control information to a wireless network controller based on response signals transmitted from a plurality of base stations. One base station for requesting and controlling the terminal performs uplink scheduling for retransmission of the terminal using control information provided from the radio network controller according to the request of the terminal.

Preferably, the terminal is a terminal in a soft handover area, and the plurality of base stations are all base stations in a soft handover area.

Preferably, the response signal transmitted by the base station is a reception acknowledgment signal, that is, a NACK / ACK signal including information on whether or not the received data error.

Preferably, the dedicated uplink channel is an enhanced uplink dedicated channel (E-DCH).

Preferably, the terminal requests control information from the radio network controller when retransmission of data is required.

Preferably, when the control signal is requested from the terminal, the radio network controller transmits radio link information for all base stations in the soft handover area of the terminal to one base station controlling the terminal.

Preferably, the base station controlling the terminal is a serving node B.

The present invention is implemented in a mobile communication system such as a universal mobile telecommunications system (UMTS) developed by 3GPP. However, the present invention can also be applied to communication systems operating according to other standards. Hereinafter, preferred embodiments of the present invention will be described in detail.

According to the present invention, in a wireless system in which a terminal transmits data through an enhanced uplink dedicated channel E-DCH, when a base station (hereinafter referred to as Node B) transmits a response signal to a received signal to the terminal, the terminal Determine whether to request information of the RNC based on the response signal.

That is, the data (signal) transmitted by the terminal in the soft handover area is received by all Node Bs in the handover area, and the corresponding Node Bs generate a response signal for the received data and transmit it to the terminal. When receiving a NACK signal exceeding a predetermined threshold based on the received response signal, the RNC requests information about Node Bs. Accordingly, the RNC informs the terminal of Node B information about the terminal in the soft handover area to reduce uplink interference when data is retransmitted, so that the information can be used for scheduling of the serving Node B transmitting the next new packet. do.

The UTRAN consists of a plurality of RNCs and a plurality of Node Bs managed by each RNC, and each Node performs scheduling on an uplink channel to implement an E-DCH for transmitting uplink data at high speed.

In the conventional wireless system, each RNC managing a specific Node B performs flow control, acceptance and control of radio links, and traffic control for Node Bs, path attenuation information with a terminal, and information about a terminal and neighbor cells. Manage path attenuation information and uplink interference information. In addition, the RNC measures and manages the amount of interference due to the UE in the handover area by managing path attenuation information for various Node Bs in soft handover for the UEs in the soft handover area.

Meanwhile, in order to secure the reliability of packet data transmission and reception, the E-DCH considers a technique for requesting retransmission by detecting an error with demodulated data at the receiving side. In the E-DCH, the UE transmits data to Node B. Since the process is not yet clearly defined, Node B generates a response signal and transmits the response signal to the UE, thereby determining whether the UE transmits the packet by determining the response signal. Or the RNC determines the response signal to determine whether the packet is successfully transmitted.

In the case where the Node B generates a response signal and transmits the response signal to the terminal, in particular, when all the Node Bs in the soft handover region transmit the response signal in the soft handover region, the terminal is based on the received response signal. It is determined whether the packet transmission is successful. For example, the terminal may determine whether to retransmit by the ratio of the ACK / NACK of the received response signal, may be determined by applying the weight for each Node B to the received response signal, and receives only one ACK signal If so, you may be able to determine that the packet transmission was successful.

In this situation, the terminal may predict path information of each Node B for the previously transmitted packet through the received response signal. That is, the UE can predict that the Node B that received the NACK response is in a bad channel condition or a point where transmission and reception are difficult in the handover region. However, since there is no method for exchanging information between Node Bs, it is unnecessary for the Node B which cannot receive successfully even if the serving Node B retransmits the transmission power without any information for the Node B, or if the UE retransmits or retransmits. In this case, retransmission is performed at high power, causing large uplink interference to neighbor cells.

This problem is because information cannot be obtained from the RNC every transmission time when Node B control scheduling is performed to reduce transmission delay and improve uplink speed for the E-DCH.

Therefore, in the present invention, when the UE in the soft handover area receives a NACK response of a predetermined threshold or more to reduce uplink interference due to retransmission, when the RNC requests information on each Node B from the RNC, the RNCs manage information about each UE. Notify Node B to perform the procedure to perform scheduling required for retransmission.

5 is a flowchart illustrating an uplink scheduling method for retransmission according to the present invention. It is assumed that n Node Bs are included in the soft handover area.

Referring to FIG. 5, when the terminal enters the soft handover area, the RNC notifies the terminal of the soft handover area (S1). If it is known that the UE has entered the soft handover area, the UE transmits data to all Node Bs in the soft handover area (S11).

The Node Bs receiving the data transmitted by the terminal generate a response signal (ACK / NACK) and then transmit it to the terminal (S12), and the terminal receiving the response signal performs an internal algorithm, that is, the NACK signal is In step S13, it is determined whether or not the received packet has been successfully received by checking whether it is equal to or greater than the threshold value, and more specifically, whether or not the data is retransmitted.

As a result of determination, if the number of NACK is less than the threshold, the terminal proceeds to step S11 and transmits the next data. If the number of received NACK is greater than or equal to the threshold, the terminal determines that radio link information is required and requests uplink information to the RNC. Send signaling (S14).

The RNC informs the serving Node B of control information about Node Bs in the soft handover area of the terminal at the request of the terminal. Accordingly, the serving Node B performs scheduling for retransmission of the terminal using the corresponding control information (S15), and the terminal prevents an increase in interference to the uplink by performing data retransmission according to the scheduling of the serving Node B. The efficiency and coverage of the uplink may be increased (S16).

As described above, in case of Node B control scheduling for the E-DCH, control information cannot be obtained from the RNC every time data is transmitted. Therefore, conventionally, when Node B scheduling is performed in the E-DCH, the UE may increase uplink interference due to retransmission or Node B scheduling may be inefficiently performed.

According to the present invention, a terminal in a soft handover area transmits data to all Node Bs in the soft handover area, and determines the situation of a radio link based on the response signals received from the Node Bs, and then controls the information to the RNC. Determine whether to request. That is, when the radio link situation is not good, and it is necessary to obtain control information from the RNC, the UE requests control information from the RNC so that the Node B (serving Node B) which performs scheduling by link information to the Node Bs for each UE is performed. Can be obtained from RNC.

Therefore, in the present invention, the serving Node B performs uplink scheduling so that the UE can retransmit data at an appropriate transmission power and transmission rate using the obtained control information, thereby efficiently controlling the uplink noise increase while controlling the uplink load. There is a controllable effect.

In addition, although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary and will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a diagram showing a network structure of a UMTS applied to the prior art and the present invention.

2 is a diagram illustrating a connection structure between a UTRAN and a terminal in a UMTS network.

3 is a diagram showing the structure of DCH and E-DCH.

4 illustrates a protocol model for an E-DCH.

5 is a flowchart illustrating an uplink scheduling method of a mobile communication system according to an embodiment of the present invention.

Claims (15)

In a mobile communication system in which a terminal transmits data to a base station through a dedicated uplink channel, and the base station transmits a response signal to the terminal, The terminal according to claim 2, characterized in that the request for control information to the radio network controller based on the response signal transmitted from a plurality of base stations. The method of claim 1, wherein the terminal The method of claim 1, wherein the base station is a terminal in a soft handover area, and the plurality of base stations are all base stations in a soft handover area. The method of claim 1, wherein the response signal transmitted by the base station is The uplink scheduling method as claimed in claim 1, wherein the reception link signal comprises a reception acknowledgment signal including information on whether or not the received data is in error. The method of claim 3, wherein the acknowledgment signal is The uplink scheduling method according to claim 1, characterized in that the NACK / ACK signal. The method of claim 1, wherein the dedicated uplink channel is An uplink channel scheduling method characterized in that the enhanced uplink channel (E-DCH). The method of claim 1, wherein the terminal If retransmission of data is required uplink scheduling method characterized by requesting the control information to the radio network controller. In a wireless system in which a terminal transmits data to a base station through a dedicated uplink channel, and the base station transmits a response signal to the terminal, Determining whether data is retransmitted using a plurality of response signals; Requesting control information from a wireless network controller when retransmission is necessary; And performing uplink scheduling for retransmission by a base station controlling the terminal by using the control information provided by the radio network controller. The method according to claim 7, further comprising the step of performing data retransmission according to the scheduling by the base station controlling the terminal. The method of claim 7, wherein the terminal is The method of claim 1, wherein the base station is a terminal in a soft handover area, and the plurality of base stations are all base stations in a soft handover area. The method of claim 7, wherein the response signal transmitted by the base station is The uplink scheduling method as claimed in claim 1, wherein the reception link signal comprises a reception acknowledgment signal including information on whether or not the received data is in error. The method of claim 10, wherein the acknowledgment signal is The uplink scheduling method according to claim 1, characterized in that the NACK / ACK signal. 8. The method of claim 7, wherein the dedicated uplink channel is An uplink channel scheduling method characterized in that the enhanced uplink channel (E-DCH). The method of claim 7, wherein the wireless network controller If a control signal is requested from the terminal, the uplink scheduling method for transmitting the radio link information for all the base stations in the soft handover area of the terminal to the base station controlling the terminal. The method of claim 7, wherein the base station for controlling the terminal Serving node B characterized in that the uplink scheduling method. 8. The method of claim 7, wherein the retransmission is The uplink scheduling method, characterized in that performed when the reception failure signal is greater than the threshold.