KR20030042846A - Packet Scheduling method for High Speed Data Packet Access system - Google Patents

Abstract

PURPOSE: A method of performing packet scheduling for an HSDPA(High Speed Downlink Packet Access) system is provided to additionally consider delay time and related information of data while operating a scheduler assigning wireless resources, thereby enabling scheduling in consideration of the delay time as well as priorities of the data. CONSTITUTION: A timer(209) transmits delay time information of data to a storage device(201)(S211). A scheduler(207) receives state information of a buffer with the delay time information(S212). The scheduler(207) receives channel state information from a physical layer(205)(S213). The scheduler(207) determines size of a data block and an MAC-hs SDU, and the determined data block is transmitted to an HARQ(Hybrid Automatic Repeat request) block(203), and is transmitted through the physical layer(205)(S214,S215). If the storage device(201) receives a transmission result of success(S216), the storage device(201) deletes the data, and sends transmission information of the data to the timer(209)(S218). If the transmission fails, the HARQ block(203) informs the scheduler(207) of a transmission result of failure, and retransmits the data(S217).

Description

Packet Scheduling Method for High Speed Downlink Packet Access (HSDPA) System {Packet Scheduling method for High Speed Data Packet Access system}

The present invention relates to a scheduler operation for allocating radio resources in a base station node of a High Speed Downlink Packet Access (HSDPA) system. In particular, the present invention relates to scheduling by reflecting data delay time information as a parameter of scheduling. The present invention relates to a packet scheduling method of a high speed downlink packet access system capable of providing a service according to a characteristic and a type of a service.

UMTS (Universal Mobile Terrestrial 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 technology. In order to provide a more improved mobile communication service. For the standardization of UMTS, in December 1998, ETSI in Europe, ARIB / TTC in Japan, T1 in the US and TTA in Korea were referred to as the Third Generation Partnership Project (hereinafter abbreviated as 3GPP). The project has been organized and is currently developing a detailed specification of UMTS.

In 3GPP, UMTS standardization work is divided into 5 Technical Specification Groups (hereinafter, abbreviated as TSG) in consideration of the independence of network components and their operation for the rapid and efficient technology development of UMTS. I'm going. Each TSG is responsible for the development, approval, and management of standards within the relevant areas, among which the Radio Access Network (hereinafter referred to as RAN) group (TSG-RAN) supports WCDMA access technology in UMTS. To develop a specification for the function, requirements high speed, and interface of the UMTS radio network (Universal Mobile Telecommunications Network Terrestrial Radio Access Network, hereinafter referred to as UTRAN).

The TSG-RAN Group is again composed of a Plenary Group and four Working Groups. Working Group 1 (WG1) develops standards for the Physical Layer (WG1), while the second Working Group (WG2) works with the Data Link Layer (2nd Layer) and Network Layer (WG2). Role of the third tier). In addition, the third operation group defines standards for interfaces between base stations, radio network controllers (hereinafter referred to as RNCs) and core networks in the UTRAN, and the fourth operation group relates to radio link performance. Discuss requirements and requirements for radio resource management.

1 is a diagram showing the structure of a 3GPP UTRAN to which the prior art and the present invention is applied.

Referring to FIG. 1, the UTRAN 110 includes one or more Radio Network Sub-systems (hereinafter referred to as RNS) 120 and 130, and each RNS 120 and 130 is connected to one RNC 121 and 131. It consists of one or more base stations (Node Bs) 122, 123, 132, 133 managed by the RNCs 121, 131. The RNCs 121 and 131 are connected to a mobile switching center (MSC) 141 for circuit-switched communication with a GSM network, and SGSN (for packet-switched communication with a general packet radio service (GPRS) network). Serving GPRS Support Node) 142.

The base station (Node B) 122, 123, 132, 133 is managed by the RNC (121, 131), and receives the information sent from the physical layer of the terminal 150 in the uplink, and the terminal 150 in the downlink It is responsible for the role of an access point of the UTRAN to the terminal transmitting to. The RNCs 121 and 131 are in charge of allocating and managing radio resources. The RNC, which is responsible for the direct management of the base station Node B, is called a control RNC (CRNC), and is in charge of managing a common radio resource. A place that manages dedicated radio resources allocated to each terminal is called a serving RNC (SRNC). The control RNC and the responsible RNC may be the same, but when the terminal moves out of the area of the responsible RNC to the area of another RNC, the control RNC and the responsible RNC may be different. The various components in the UMTS network can be in different locations, so an interface is needed to connect them. The base station Node B and the RNC are connected by an Iub interface, and the RNC is connected through an Iur interface. The interface between the RNC and the core network is called Iu.

2 illustrates a structure of a radio access interface protocol between a terminal and a UTRAN based on the 3GPP radio access network standard. The wireless access interface protocol of FIG. 2 consists of a physical layer (PHY), a data link layer, and a network layer horizontally, and vertically transmits a control plane for transmitting control signals and data information transmission. It is divided into user planes. The user plane is an area in which user traffic information is transmitted, such as voice or IP packet transmission, and the control plane is an area in which control information is transmitted, such as network interface or call maintenance and management.

The protocol layers of FIG. 2 are based on the lower three layers of the Open System Interface (OSI) reference model, which are well known in communication systems. The first layer (L1), the second layer (L2), and the third layer (L3).

The first layer L1 performs a role of a physical layer (PHY) for the wireless interface, and a transport channel with a medium access control layer (hereinafter abbreviated as MAC) layer on the upper layer. Are connected via Data transmitted to the physical layer through a transport channel is transmitted to a receiver by using various coding and modulation methods suitable for a wireless environment. The transport channel existing between the physical layer and the MAC layer is a dedicated transport channel and a common transport channel, respectively, depending on whether the terminal can be used exclusively or shared by multiple terminals. Are distinguished.

The second layer L2 serves as a data link layer, and allows multiple terminals to share radio resources of the WCDMA network. The second layer (L2) is the MAC layer, Radio Link Control (hereinafter referred to as RLC) layer, Packet Data Convergence Protocol (hereinafter referred to as PDCP) layer, and broadcast / multicast control (Broadcast / Multicast Control; hereinafter abbreviated as BMC) is divided into layers.

Here, the MAC layer transfers data through an appropriate mapping relationship between logical channels and transport channels. Logical channels are provided with various logical channels according to the type of information transmitted to the channels connecting the upper layer and the MAC layer. In general, a control channel is used to transmit control plane information, and a traffic channel is used to transmit information of the user plane. The MAC layer is divided into two sublayers according to the function performed again. These are the MAC-d sublayer located in the SRNC while managing the dedicated transport channel, and the MAC-c / sh sublayer located in the CRNC while managing the shared transport channel.

The RLC layer configures an appropriate RLC PDU suitable for transmission by a segmentation and concatenation function of an RLC SDU transmitted from an upper layer, and performs an automatic repeat request for retransmitting an RLC PDU lost during transmission. ARQ) function can be performed. The RLC SDU or RLC descended from the upper layer operates in three ways: transparent mode, unacknowledged mode, and acknowledgment mode, depending on the method of processing the RLC SDU from the upper layer. There is an RLC buffer for storing PDUs.

The PDCP layer is located on top of the RLC layer and makes data transmitted through a network protocol such as IPv4 or IPv6 suitable for transmission in the RLC layer. In particular, a header compression technique that compresses and transmits header information of a packet may be used for efficient transmission of an IP packet.

The BMC layer enables a message transmitted from a cell broadcast center (CBS) to be transmitted through an air interface. The main function of the BMC is to schedule and transmit a cell broadcast message transmitted to a terminal, and generally transmits data through an RLC layer operating in an unresponsive mode.

For reference, since the PDCP layer and the BMC layer use a packet switching scheme, the PDCP layer and the BMC layer are connected to the SGSN and are only located in the user plane because only user data is transmitted. Unlike these, the RLC layer may belong to the user plane or to the control plane depending on the layers connected to the upper layer. In case of belonging to the control plane, it corresponds to a case of receiving data from a radio resource control layer (hereinafter, referred to as RRC) layer, and otherwise corresponds to a user plane. In general, a service of transmitting user data provided to the upper layer by the second layer L2 in the user plane is defined as a radio bearer (RB), and the upper layer by the second layer L2 in the control plane. The transmission service of the control information provided by is defined as a signaling radio bearer (SRB). In addition, as shown in FIG. 2, in the case of the RLC layer and the PDCP layer, several entities may exist in one layer. This is because one terminal has several radio carriers, and generally only one RLC entity and PDCP entity are used for one radio carrier. Entities of the RLC layer and the PDCP layer may perform independent functions in each layer.

The RRC layer located at the bottom of the third layer L3 is defined only in the control plane, and is responsible for control of transport channels and physical channels in connection with setting, resetting, and releasing radio carriers. In this case, the setting of the wireless carrier means a process of defining characteristics of a protocol layer and a channel necessary to provide a specific service and setting each specific parameter and operation method. It is also possible to transmit control messages transmitted from a higher layer through an RRC message.

The WCDMA system described above aims at a transmission rate of 2Mbps in a indoor and pico-cell environment and 384kbps in a general wireless environment. However, as the wireless Internet is becoming more common and the number of subscribers is increasing, more various services are emerging, and higher transmission speeds are required to support them. Therefore, in 3GPP, a research is being conducted to provide a high transmission speed by evolving a WCDMA network, and a representative system is HSDPA (High Speed Downlink Packet Access).

Based on WCDMA, the HSDPA system can support up to 8-10Mbps in downlink, and can provide shorter latency and improved capacity. The techniques employed in the HSDPA system to provide improved transmission rates and capacities include Link Adaptation (LA), Hybrid Automatic Repeat Request (HARQ), and fast cell selection. Fast Cell Selection (hereinafter referred to as FCS), and Multiple Input Multiple Output (hereinafter referred to as MIMO) antenna techniques.

The link adaptation technique (LA) uses a modulation and coding scheme (abbreviated as MCS) according to the state of the channel. If the channel state is good, a high modulation such as 16QAM and 64QAM is used. In case the channel condition is not good, a low modulation method such as QPSK is used.

In general, the low-modulation method has a smaller amount of transmission than the high-modulation method, but it shows excellent transmission success rate when the channel environment is not good. Therefore, it may be considered to be advantageous when the influence of fading or interference is large. . On the other hand, high modulation methods have much higher frequency utilization efficiency than low modulation methods, and can provide a transmission rate of 10Mbps using the 5MHz bandwidth of WCDMA. However, it is very sensitive to the effects of noise and interference. Therefore, when the terminal is located close to the base station, it is possible to increase the transmission efficiency by using 16QAM or 64QAM, and when the terminal is located at the cell boundary or the influence of fading is low, a low modulation method such as QPSK is useful. Do.

The HARQ method is a retransmission method having a different concept from that of a packet retransmission performed in the RLC layer. This ensures higher decoding success rates by combining data used and retransmitted in conjunction with the physical layer with previously received data. In other words, it is a method of decoding by combining the retransmitted packet with the previous step of decoding while storing the packet which failed to be transmitted without discarding it. Therefore, when used together with the LA technique, the packet transmission efficiency can be greatly increased.

The FCS method is similar to the conventional soft handover. Although the terminal may receive data from multiple cells, the terminal may receive data from a cell having the best channel state in consideration of the channel state of each cell. Conventional soft handover has been a method of receiving data from multiple cells and increasing the transmission success rate using diversity, but the FCS method receives data from only one specific cell in order to reduce interference between cells.

MIMO antenna technique is a method that can improve the data transmission speed by using several independent channels in a channel environment where scattering is high. It is a system that is composed of several transmitting antennas and several receiving antennas to obtain diversity gain by reducing the correlation between radio waves received for each antenna.

Meanwhile, the HSDPA system is based on the existing WCDMA network and tries to introduce a new technology while keeping the WCDMA network as it is. However, some modifications are inevitable to incorporate new technologies. Representatively, the example is an improvement of the existing base station (Node B) function. That is, in the WCDMA network, most of the control functions are located in the RNC, but most of the new technologies for the HSDPA system are managed by the base station (Node B) in order to adapt to the channel situation more quickly and reduce the delay time to the RNC. However, the extended function of the base station (Node B) is not a function of replacing the RNC, and from the standpoint of the RNC, it can be seen that the functions for the high speed data transmission are in charge of the auxiliary function added.

Therefore, unlike the existing WCDMA system, the base station Node B has been modified to perform a part of the MAC function, and a layer for performing this is called a MAC-hs sublayer.

The MAC-hs sublayer may be located above the physical layer to perform packet scheduling or HARQ and LA functions. In addition, a transport channel called HS-DSCH (High-Speed Downlink Shared Channel), which is different from the existing transport channel, is used for data transmission for HSDPA. This channel is used to transmit data from the MAC-hs sublayer of the base station Node B to the physical layer.

3 shows a radio access protocol structure for supporting the HSDPA system. As shown, the MAC-hs sublayer is located above the physical layer (PHY) of the base station Node B.

The MAC-c / sh and MAC-d sublayers are located in the CRNC and SRNC, respectively, as in the conventional system, and HS-DSCH FP for transmission of data for HSDPA between the RNC and the Node B or between the RNCs. It uses a transport protocol called (Frame Protocol).

In this case, the MAC-c / sh sublayer, the MAC-d sublayer, and the RLC layer located above the MAC-hs sublayer perform the same functions as the current system. Therefore, the RNC to support HSDPA is enough to add only a little software in the current system.

The structure of the MAC layer used in the HSDPA system is shown in detail in FIG. 4.

As shown in FIG. 4, the MAC layer is divided into three sublayers: the MAC-d sublayer 161, the MAC-c / sh sublayer 162, and the MAC-hs sublayer 163. The MAC-d sublayer 161 manages dedicated logical channels for a specific terminal while in the SRNC, and the MAC-c / sh sublayer 162 manages common transport channels located in the CRNC and the MAC-hs sublayer 163 is located in the base station (Node B) to manage the HS-DSCH. However, it can be said that there is almost no function performed by the MAC-c / sh sublayer 162 in the HSDPA system. That is, the MAC-c / sh sublayer 162 has been responsible for allocating and processing common resources shared by multiple terminals in the existing system. However, in the HSDPA system, the MAC-c / sh sublayer 162 is simply transferred from the MAC-d sublayer of SRNC. It performs only a flow control role of delivering the data to the MAC-hs sublayer 163 of the base station Node B.

Referring to FIG. 4, flow control, HARQ, scheduling, and TFC selection, which are functions performed in the MAC-hs sublayer, will be described.

The flow control function controls the flow of data in consideration of the transmission capability according to the interface of the network. This function is used to prevent the discard of data that may be caused by congestion on the interface when data is transmitted through the HS-DSCH or to reduce the delay time of the signaling signal in the second layer (L2). In this case, the flow control may be independently performed according to the priority of data transmitted through each HS-DSCH channel.

As described briefly above, the HARQ function is a method used to increase data transmission efficiency. An HARQ block exists in the MAC-hs sublayer 163 to support the HARQ function. One HARQ block exists for each UE, and several HARQ processes exist in each HARQ block. The HARQ process is in charge of controlling according to the HARQ operation and is used for transmitting specific data. The HARQ process can share and use multiple data, but only one is processed at a time. Therefore, if the data transmission is successful, the process becomes empty and can be used for transmission of other data. If the transmission fails, the data is stored until the data is successfully transmitted or discarded. Data transmitted by each HARQ process is called a data block, and the data block is composed of one or several MAC-hs SDUs. For reference, the size of each MAC-hs SDU is not variable and has a fixed size. The number of MAC-hs SDUs constituting the data block may vary depending on the state of the radio channel. That is, because a good channel can transmit a large amount of data, as many MAC-hs SDUs are included. At this time, the determination of the data block is performed in the scheduling block that receives the report on the channel state from the physical layer.

Scheduling determines the transmission order according to the priority of data to be transmitted. In addition, the size of the data block to be processed in the HARQ process is determined, and the priority class identifier (Priority Class Identifier) and serial number (Transmission Sequence Number (hereinafter abbreviated as TSN)) of this block is attached to the HARQ block. The HARQ block retransmits the same data block upon retransmission.

The TFC selection function is responsible for informing the format of each HS-DSCH when several HS-DSCHs are used for data transmission.

Referring to FIG. 4, let's see how the data from the RLC layer is transferred to the HS-DSCH in the MAC layer. The RLC PDUs transmitted from the RLC layer through a dedicated traffic channel (DTCH) or a dedicated control channel (DCCH) are routed through a channel switching function in the MAC-d layer. When transmitted on a dedicated channel (DCH: Dedicated Channel), the relevant header is attached to the MAC-d sublayer 161 and transferred to the physical layer through a dedicated channel (DCH), and the HS-DSCH channel of the HSDPA system is used. If so, the RLC PDU is transmitted to the MAC-c / sh sublayer 162 through transport channel multiplexing by a channel switching function. Transport channel multiplexing adds identification information of a logical channel to each data when several logical channels use one transport channel. The MAC-c / sh sublayer 162 receiving the RLC PDU simply transfers a packet from the MAC-d sublayer 161 to the MAC-hs sublayer 163. Data delivered to MAC-hs sublayer is stored in buffer of MAC-hs sublayer 163, and is composed of data block of appropriate size for channel status by scheduling block, and priority information and TSN are added to the data block. It is delivered to the HARQ block in a timely manner. At the time of transmission, a TFC (Transport Format Combination) suitable for the transmission format of the HS-DSCH is selected and transmitted.

FIG. 5 illustrates an operation of a scheduling block in the MAC-hs sublayer. The configuration and operation of the scheduling block will be described.

Referring to FIG. 5, the storage device 171 generally corresponds to a soft memory that can easily erase and write data, and stores MAC-hs SDUs transmitted from an upper layer.

The scheduler 174 receives buffer status information such as priority and data amount of the stored data from the storage device 171 (S101), and receives channel state information from the physical layer 173 (S102). The scheduler 174 determines the size of the data block to be transmitted and the corresponding MAC-hs SDU based on the information, and then controls the operations of the storage device 171 and the HARQ block 172 (S103 and S104). The determined data block is transmitted to the HARQ block by adding the priority identifier and TSN and transmitted through the physical layer.

In addition, identification information about data successfully transmitted in the HARQ block 172 is transmitted to the storage device 171 in the HARQ block 172 to delete the corresponding data from the storage device (S105). The data block successfully transmitted in the HARQ block 172 notifies the transmission result to be deleted from the MAC buffer, and if the transmission fails, the data block is reported to the scheduler 174 so that the scheduler can consider retransmission of the corresponding data (S106). ).

In general, in most communication systems, including high speed downlink packet access (HSDPA) systems, the overall efficiency and transmission characteristics of the system are highly dependent on the scheduling algorithm used. Therefore, in order to guarantee the quality related to the transmission rate or the delay time of a specific service, an appropriate scheduling algorithm is required for each service. Scheduling to be used can be implemented in various ways according to the purpose of use, a representative case is to maximize the transmission efficiency of the system and to ensure fairness (fairness) between terminals. The first method is a method of maximizing system throughput by allocating most of radio resources to a terminal having the best channel state. However, even if the channel state is poor, even if there is a lot of data to be transmitted, there is a disadvantage in that it may not be properly serviced because radio resources are not allocated. The second method is to distribute the radio resources evenly to all terminals, and to allocate the radio resources to all the terminals fairly regardless of the channel state. That is, the UTRAN gives each terminal an equal opportunity regardless of the location or channel state. However, there is a disadvantage in that the overall utilization efficiency of the system may be lowered by allocating a large amount of resources to the terminal having a poor channel state.

In the HSDPA system, the scheduling function of data is performed in a scheduling block of a base station Node B. The information used for the scheduling may include quality information of the current radio channel, traffic amount in the cell, and priority information of each data transmitted using the HS-DSCH FP in the MAC-d sublayer. Among these, the priority of the packet is transmitted using the Common Channel Priority Indicator (CmCH-PI) field transmitted through the HS-DSCH FP and has a value of 16 steps from 0-15. In this case, the data with priority 0 means the lowest priority, and the data with priority 15 becomes the data with the highest priority.

Currently, the most important factor in the scheduling algorithm used in the HSDPA system is data priority. Therefore, the scheduler observes the data of the various terminals in the storage device in the MAC-hs layer to determine the amount of data that can be transmitted in consideration of the state of the channel, and then configures the data block for the highest priority data. The transmission will be timely. Although the specific scheduling algorithm may vary depending on the operator, the information for scheduling that they can use in common is almost the same. That is, the scheduling block of the HSDPA system should configure an algorithm using only the priorities of the data transmitted from the Node B level and the data transmitted from the RNC.

However, since the HSDPA system is expected to provide various multimedia services, it is necessary to satisfy various requirements according to the characteristics of the service. Therefore, in some cases, the service may be sensitive to delay time. In other words, after a certain delay, they are no longer valuable as data. Examples of these services are real-time services such as voice services and video telephony, which typically discard data after a certain delay. Even if it is not a real-time service, even when transmitting TCP / IP traffic using the HSDPA system, the effect of delay time may be large. This case is caused by the application of Slow Start, a function that controls the flow of data in the TCP layer. When the delay time of the data exceeds the threshold, the amount of data transmitted is significantly reduced. Therefore, although the priority of data is important, in some cases, scheduling in consideration of data delay time is also necessary. Of course, high priority can be assigned to these latency-sensitive services, but simply assigning a low priority does not satisfy the latency requirement.

Although the delay time of data generally occurs in a backbone network, most transmission delay times can be considered to occur in UTRAN using a radio channel. Therefore, the delay time in the UTRAN can be used as important data in the implementation of the scheduling algorithm. However, since most of the time the data stays in the UTRAN includes the delay time in the RLC layer as well as the MAC-hs sublayer, these data can be received from the RNC in which the RLC layer is located. However, in the current system, since there is no method of notifying the Node B of the delay time in the RLC, a modification for this is necessary.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In the case of dynamically distributing radio resources by a scheduler in a high-speed downlink packet access (HSDPA) system, scheduling reflecting not only the priority but also the data delay time It is an object of the present invention to provide a packet scheduling method for a high speed downlink packet access system.

Another feature is to provide a packet scheduling method for a high speed downlink packet access system for transmitting a packet delay time in an RLC layer from an RNC in which an RLC layer is located to a base station so that a packet scheduler located in a base station can know a delay time of each data. The purpose is to provide.

Another feature is that the data received from the RLC layer together with the time the data stays in the RLC layer, and the delay information that adds the delay time and the delay time in the MAC layer can be used as a parameter of the scheduling of the data. An object of the present invention is to provide a packet scheduling method for a high speed downlink packet access system.

It is another object of the present invention to provide a packet scheduling method for a high speed downlink packet access system in which data and delay information of the data can be transmitted through a lub interface or a lur interface of a UMTS network.

It is another object of the present invention to provide a packet scheduling method for a high speed downlink packet access system in which a scheduler located in a base station can receive a maximum delay time value necessary to perform scheduling considering a delay time from an RNC layer. .

It is another object of the present invention to provide a packet scheduling method for a high speed downlink packet access system that controls packet transmission by considering packet priority and delay time.

1 is a structure of a 3GPP UTRAN.

2 is a protocol structure of a radio access interface.

3 is a radio access protocol structure for a high speed downlink packet access system.

4 is a structure of a MAC layer for supporting a high speed downlink packet access system.

5 is a scheduler structure in the conventional MAC-hs sublayer.

6 is a packet scheduler method for an HSPDA system according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

161 ... MAC-d sublayer 162 ... MAC-c / sh sublayer

163 MAC-hs sublayer 171,201 Storage device

172,203 ... HARQ blocks 173,205 ... Physical layer

174,207 scheduler 209 timer

A packet scheduling method for a high speed downlink packet access system according to the present invention for achieving the above object,

Informing a scheduler of channel state information of a physical layer, status information of a buffer, and delay information of data to be transmitted for downlink packet transmission in a high speed downlink packet access system;

The media access control layer transmits the data transmitted from the radio link control layer through the physical layer through the schedule reflecting the channel state information, the buffer state information and the delay information of the data in the scheduler.

Preferably, the media access control layer is characterized by receiving data and information related to the delay time of the data from the upper layer.

Preferably, the upper layer is a radio link control layer, and the radio link control layer is characterized in that the data and the data transfer the delay time in the radio link control layer to the media access control layer.

Preferably, the delay time in the radio link control layer is characterized by using a discard timer value for measuring an elapsed time of a service data unit in each radio link control layer.

Preferably, the delay time in the radio link control layer is received as an average delay time of data transmitted to the medium access control layer.

Preferably, the delay information includes the data and the delay information of the corresponding data when the data is transmitted through the Iub interface or the Iur interface of the UMTS network.

Preferably, when the media access control layer receives an RLC PDU from an upper layer, it operates a corresponding timer for measuring a delay time in the media access control layer.

Preferably, the delay information is calculated as the sum of the delay time received from the radio link control layer and the delay time stayed in the media access control layer.

Preferably, the initial value of the timer running in the medium access control layer is driven by setting the delay time received from the radio link control layer to an initial value, or counting from the initial value separately from the delay time received from the radio link layer. Characterized in that.

Preferably, when the data is successfully transmitted to the physical layer, the driving of the timer is stopped.

Preferably, the packet transmission is performed by reflecting the priority of the packet and the delay time of the data.

Preferably, the packet having a long delay time is preferentially transmitted to a packet having the same priority.

In a packet scheduling method for a high speed downlink packet access system according to another embodiment of the present invention, in a high speed downlink packet access (HSDPA) system, a radio network controller (RNC) transmits a packet of a base station for efficient transmission of a packet to a downlink. Transmitting various information necessary for the operation of the scheduler;

A scheduler located in the base station uses a media access control layer through scheduling by using channel state information, buffer state information, data priority, data delay information, and the like, using various information necessary for the operation of the scheduler received from the wireless network controller. And transmitting data transmitted from the radio link control layer through the physical layer.

A packet scheduling method for a high speed downlink packet access system according to an exemplary embodiment of the present invention configured as described above is as follows.

The types of services provided by the UMTS system can be divided into delay-sensitive services and services that are not sensitive to latency. Latency-sensitive services are services that are less valuable as data when they exceed a predetermined maximum delay time, such as voice services or video on demand (VOD) services.

On the other hand, latency-insensitive services include Internet services such as web browsing services. These services are not sensitive to transmission time, but may have priority based on importance on a service-by-service basis. Therefore, the priority among services is important in these services.

First, the data delay time in UTRAN considers both the time elapsed after being delivered from the MAC-hs sublayer and the time spent in the RLC layer of the RNC. That is, when each data is transferred from the RLC layer to the MAC layer, the data including the delay time of each data is transferred along with the data.

In addition, since the MAC-d sublayer and the MAC-hs sublayer are also located in the RNC and the base station Node B, respectively, it is necessary to transfer data delay information together with the data between the sublayers in the MAC layer. Since the delay time in the RLC layer is not transmitted from the system to the MAC layer in the conventional system, the delay information may be received from the RLC layer.

6 is a scheduler structure in the MAC-hs sublayer according to the present invention.

Referring to FIG. 6, in the MAC-hs sublayer, a timer 209 indicating a delay time of each data when each MAC-hs SDU is transferred from the RLC layer to the MAC layer in order to measure a time spent in the MAC layer. ) Drives.

At this time, the initial value of each timer 209 is initialized by the delay time information transmitted from the RLC layer. In one embodiment, the timer 209 drives the delay information transmitted from the RLC layer as an initial value (delay time in the RLC layer), and in another embodiment, the delay time transmitted from the RLC layer. There is a method of driving from the initial value (0) after storing the information separately. For example, if the delay information transmitted from the RLC layer is 5 seconds, the timer in the above embodiment starts from 5 seconds or stores the 5 seconds separately and counts the delay time from 0.

The timer 209 transmits the delay information of the corresponding data to the storage device 201 (S211). The delay information transmitted at this time measures the delay time information transmitted from the RLC layer and the time the data stays in the MAC layer. It is the sum of one delay information.

Each MAC-hs SDU is buffered and stored in the storage device 201 together with delay information according to the driving of the timer 209.

When the scheduler 207 receives the state information of the buffer through the storage device 201, the scheduler 207 receives the delay time information of each data (S212). That is, the buffer status information includes delay time information of the corresponding data along with data priority, data amount, size information of the SDU, and the like, and the scheduler 207 receives the channel status information from the physical layer 205. (S213).

When the scheduler 207 receives the buffer status information and the channel status information, the scheduler 207 performs scheduling for data transmission control based on the buffer status information and the channel status information to determine the size of the data block to be transmitted and the corresponding MAC-hs SDU. . The determined data block is transmitted to the HARQ block 203 by adding the priority identifier and the TSN and transmitted through the physical layer 205 (S214 and S215).

At this time, when the storage device 201 receives a transmission result indicating that a specific data block is successfully transmitted from the HARQ block 203 (S216), the storage device 201 deletes the corresponding data in the device and is associated with the data. In order to stop driving of the timer 209, the transmission information of the corresponding data is sent to the timer (S218).

If the transmission fails, the HARQ block 203 notifies the scheduler 207 of the transmission result so that the corresponding data can be retransmitted during the scheduler operation (S217).

Referring to the data transmission control operation by the scheduling of the scheduler 207, data having a longer delay time is preferentially transmitted to data having the same priority. In this case, since only the data for one terminal can be transmitted, the terminal selects a terminal having data with a longer delay time from among terminals having data having the same priority.

In addition, depending on the type of service, the weight for the delay time may be higher than the priority of the data. In this case, the control is performed to consider the priority of the data and the delay time.

In addition, there may be a service in which only priorities are defined according to the type of service, and there may be a service in which only a delay time limit is defined. In the former case, each service is scheduled according to priority, and in the latter case, the service is scheduled according to the delay condition of each service.

The RLC layer measures the delay time for each data to inform the MAC layer of the data delay time. A separate timer for measuring the delay time in the RLC layer may be driven, but in some cases, a timer that is already used may be used. As a representative example, in the RLC layer, a discard timer (Timer_Discard) for measuring a time elapsed after each RLC SDU is delivered to the RLC layer may be used. The value of the timer may be used.

The purpose of the discard timer is to measure the length of time they stay in the RLC layer for each RLC SDU delivered from the upper layer, and discard the data if the RLC SDU is not being transmitted for a long time. That is, if the RLC SDU is not successfully transmitted until the discard timer expires, the RLC SDU is discarded. Accordingly, the discard timer information may be recognized as a delay time of the RLC SDU in the RLC layer, and transmits the discard timer information together with the RLC PDU when the RLC PDUs are transmitted to the MAC layer. The delay time in the radio link control layer is transmitted as an average delay time of data transmitted to the medium access control layer.

Also, in the HSDPA system, since the RLC layer and the sublayers of the MAC layer are connected through various interfaces, the delay time in the RLC layer should be informed to the MAC-hs sublayer through the Iur interface or the Iub interface.

Therefore, the information on the timer timer (Timer_Discard) is added to the frame of the HS-DSCH FP that transmits data through the Iub or Iur interface.

In the case of information whose priority is important according to the type of service, the data and priority information of the data are informed through HS-DSCH FP. In case of the service where the delay time information is important, the data and delay time information (RLC delay) Time) through the HS-DSCH FP. At this time, the format of the HS-DSCH FP for each service may be different.

In some cases, a method of informing the amount of data stored in the RLC buffer as the delay time information may be used. This is because a larger amount of data in the buffer means more delay time. In addition, since a lot of capacity may be wasted when delivering the value of the discard timer, there may be a method of informing the average delay time of the transmitted data or discretizing the delay time.

As described above, in the present invention, when services that are sensitive to transmission delay time are provided by the scheduler of the HSDPA system, when controlling the transmission of data, in order to further transmit data in consideration of the delay time in the UTRAN, the RLC layer The delay time, which is the sum of the delay time information and the delay time information in the MAC layer, is considered along with other transmission control parameters.

Therefore, in order to efficiently transmit a packet in downlink in a high speed downlink packet access (HSDPA) system, a radio network controller (RNC) transmits various information necessary for the operation of a packet scheduler of a base station, and a scheduler located in the base station The media access control layer is transferred from the radio link control layer through scheduling using the state information, the buffer state information, the priority of the data, the delay information of the data, and various information necessary for the operation of the scheduler received from the radio network controller. Enables data to be transmitted through the physical layer.

As described above, according to the packet scheduling method for the high-speed downlink packet access (HSDPA) system according to the present invention, the base station of the high-speed downlink packet access (HSDPA) system of the data when the scheduler for allocating radio resources By considering the delay-related information additionally, scheduling can be performed in consideration of the data priority as well as the data priority, so that the scheduling of the delay-sensitive data service is possible, which can guarantee the quality of service. It has an effect.

Claims (21)

In order to transmit packet data from the high speed downlink packet access (HSDPA) system to the downlink, the quality information of the physical channel, the buffer status information in the media control layer, the priority of the data, and the delay information of the media are included in the media access layer. Informing the scheduler of the; Transmitting, by the media access control layer, data transmitted from the radio link control layer through the physical layer through scheduling by reflecting channel quality status information, buffer status information, data priority, data delay information, and the like in the scheduler; Packet scheduling method for a high speed downlink packet access system comprising a. The method of claim 1, The media access control layer is a packet scheduling method for a high speed downlink packet access system, characterized in that for receiving data and information related to the delay time of the data from a higher layer. The method of claim 2, The upper layer is a radio link control layer, and the radio link control layer is a medium access control layer for the fast downlink packet access system, characterized in that the data transfers the delay time in the radio link control layer together with the data. Packet scheduling method. The method of claim 3, wherein The delay time in the radio link control layer is a packet scheduling method for a fast downlink packet access system, characterized in that using a discard timer value for measuring the elapsed time of a service data unit in each radio link control layer. The method of claim 4, wherein And applying the value of the discard timer as the elapsed time of the protocol data unit in the radio link control layer. The method of claim 5, A packet scheduling method for a high speed downlink packet access system, characterized in that when a plurality of service data units are included in one protocol data unit, a value of the largest discard timer is used. The method of claim 3, wherein And a delay time in the radio link control layer is set to an average delay time of data simultaneously transmitted to a medium access control layer. The method of claim 2 or 3, The data delay information in the upper layer is a packet for a high speed downlink packet access system, characterized in that the data is transmitted along with the delay information of the data and the data transfer through the Iub interface or the Iur interface of the UMTS network Scheduling Method. The method of claim 8, The delay information is a packet scheduling method for a high speed downlink packet access system, characterized in that the transmission using the HS-DSCH Frame Protocol used for the transmission of data for HSDPA in the Iub or Iur interface. The method of claim 1, The delay information used for scheduling a packet in the media access control layer is calculated by the sum of the delay time received from the radio link control layer and the delay time stayed in the media access control layer. Packet scheduling method. The method of claim 1, The delay information used for scheduling a packet in a medium access control layer is a packet scheduling method for a high speed downlink packet access system, characterized in that the delay time only stays in the medium access control layer. The method according to claim 10 or 11, wherein When the medium access control layer receives an RLC PDU from an upper layer, runs a corresponding timer for measuring a delay time in the medium access control layer. The method of claim 12, The initial value of the timer running in the medium access control layer is a packet scheduling method for a high speed downlink packet access system, characterized in that for driving by setting the delay time received from the radio link control layer to an initial value. The method of claim 12, The initial value of the timer running in the medium access control layer packet scheduling method for a high speed downlink packet access system, characterized in that counting from the initial value, apart from the delay time received from the radio link layer. The method of claim 12, And stopping the driving of the timer when data is successfully transmitted to the receiving medium access control layer. The method of claim 15, The delay information used for scheduling the packet is a packet scheduling method for a high speed downlink packet access system, characterized in that the amount of data in the RLC buffer. The method of claim 15, The amount of data in the RLC buffer packet transmission method for a high-speed downlink packet access system, characterized in that included in the data transfer through the Iub interface or Iur interface of the UMTS network. The method of claim 1, Packet scheduling method for a high speed downlink packet access system, characterized in that the scheduling by reflecting the priority of the packet and the delay time of the data when transmitting the packet. The method of claim 13, The packet scheduling method for the high speed downlink packet access system, characterized in that for transmitting the packet with a high delay for the same priority packet. Transmitting, by a radio network controller (RNC), various information necessary for the operation of a packet scheduler of a base station for efficient transmission of packets on a downlink in a high speed downlink packet access (HSDPA) system; A scheduler located in the base station uses a media access control layer through scheduling by using channel state information, buffer state information, data priority, data delay information, and the like, using various information necessary for the operation of the scheduler received from the wireless network controller. And transmitting the data transmitted from the radio link control layer through a physical layer. The method of claim 20, The wireless network controller is a packet scheduling method for a high speed downlink packet access system, characterized in that the base station informs the maximum delay time information for the service while establishing a connection between the terminal and the core network for a particular service.