Patent Application
20050207343
This application claims the benefit under 35 U.S.C. 119(a) of an application entitled “METHOD FOR PERFORMING EFFICIENT FLOW CONTROL OF PACKET DATA TRANSMISSION BETWEEN A RADIO NETWORK CONTROLLER AND ANODE-B IN A MOBILE COMMUNICATION SYSTEM USING A HIGH-SPEED DOWNLINK PACKET ACCESS TECHNIQUE”, filed in the Korean Intellectual Property Office on Mar. 17, 2004 and assigned Ser. No. 2004-17986, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to technology for efficiently transmitting packet data in a wideband code division multiple access (WCDMA)-based mobile communication system. More particularly, the present invention relates to a flow control system and method for efficiently transmitting packet data between a radio network controller (RNC) and a Node-B.
2. Description of the Related Art
Mobile communication systems have developed into high-speed, high-quality wireless data packet communication systems for providing data service and a multimedia service as well as voice service. The 3rd generation (3G) mobile communication system is divided into an asynchronous system (3rd Generation Partnership Project (3GPP)) and a synchronous system (3rd Generation Partnership Project 2 (3GPP2)). According to Release 5, the standardization for a high-speed, high-quality wireless data packet service in the 3G mobile communication system is ongoing. For example, the standardization for high-speed downlink packet access (HSDPA) is ongoing in the 3GPP, and the standardization for 1× Evolution Data and Voice (1×EV-DV) is ongoing in the 3GPP2. The purpose of the standardization is to provide high-quality wireless data packet transfer service at more than 2 Mbps in the 3G mobile communication system. The 4th generation (4G) mobile communication system serves to provide a high-speed, high-quality multimedia service. An enhanced uplink dedicated channel (E-DCH) or uplink for transmitting high-speed, high-quality wireless data packets is discussed in Release 6.
A factor causing a high-speed, high-quality data service to be degraded in the conventional communication system is a wireless channel environment. The environment of a wireless communication channel may be affected by white noise, signal power variations due to fading, shadowing, the Doppler effect due to the mobility or frequent speed variations of a terminal, interference associated with other users and a multipath signal, and so on.
A need exists for advanced technology capable for improving an adaptive capability to channel variations in addition to technology for providing high-speed wireless data packet service in the existing 2G or 3G mobile communication system. A high-speed power control technique adopted in the conventional system may improve the adaptive capability to channel variations. An adaptive modulation & coding scheme (AMCS) and a hybrid automatic repeat request (HARQ) scheme are commonly mentioned in the 3GPP and 3GPP2 for standardizing a high-speed data packet transmission system.
Referring to
A RNS includes a radio network controller (RNC) and one or more Node-Bs. The RNC is classified as a serving RNC (SRNC), a drift RNC (DRNC), or a controlling RNC (CRNC) according to its function. The SRNC 140 manages information of the UE 110, and is responsible for data communication with the CN. The CRNC 130 controls a Node-B 120 communicating with the UE 110.
In this case, the UE 110 and a universal terrestrial radio access network (UTRAN) are connected through a Uu interface, and the CRNC 130 and the SRNC 140 are connected through an lur interface. The Node-B 120 communicating with the UE 110 and the CRNC 130 are connected through an Iub. The interfaces are defined by the 3GPP, and may be changed.
A higher layer structure and each layer defined by the 3GPP will be described with reference to
The physical layer performs channel coding/decoding, modulation/demodulation, and channelization/dechannelization functions, and so on. The physical layer converts data to be transmitted into a radio signal, and converts a received radio signal into data. After transport channel data transmitted to the physical layer is appropriately processed, the processed data is transmitted to the UE or RNC by physical channels. The physical channels include a primary common control physical channel (P-CCPCH) on which a broadcast channel (BCH) is transmitted, a secondary common control physical channel (S-CCPCH) on which a paging channel (PCH) and a forward access channel (FACH) are transmitted, a dedicated physical channel (DPCH) on which a dedicated channel (DCH) is transmitted, a physical downlink shared channel (PDSCH) on which a downlink shared channel (DSCH) is transmitted, a high-speed physical downlink shared channel (HS-PDSCH) on which a high-speed downlink shared channel (HS-DSCH) is transmitted, and a physical random access channel (PRACH) on which a random access channel (RACH) is transmitted. Other physical channels not used to transmit higher layer data or a control signal comprise a pilot channel, a primary synchronization channel, a secondary synchronization channel, a paging indicator channel, an acquisition indicator channel, a physical common packet channel, etc.
The physical layer and the L2/MAC layer are connected through a transport channel. The transport channel defines a technique for processing specific data in the physical layer. The processing technique includes a channel coding technique, an amount of data that can be transmitted in a unit of time, that is, a transport block set size, and so on. The following Table 1 describes types or functions of transport channels.
The L2/MAC layer performs a function for transferring data from the L2/RLC layer using a logical channel to the physical layer through a proper transport channel, and a function for transferring data from the physical layer using the transport channel to the L2/RLC layer through a proper logical channel. The L2/MAC layer inserts additional information into data received through the logical channel or transport channel, or analyzes inserted additional information to perform an appropriate operation according to a result of the analysis. The logical channel is divided into a dedicated channel serving as a channel for a specific UE and a common channel serving as a channel for a plurality of UEs. Moreover, the logical channel is divided into a control channel and a traffic channel according to message type. The following Table 2 describes types or functions of logical channels.
The L2/RLC layer receives a control message transmitted for the UE and appropriately processes the received control message while taking into account characteristics of the control message, such that the processed control message is transmitted to the L2/MAC layer using a logical channel. Moreover, the L2/RLC layer processes data in an appropriate wireless resource control form, and transmits the processed data to the L2/MAC layer using the logical channel. The number of RLC entities in the L2/RLC layer depends upon the number of radio links between at least one UE and the RNC.
The Node-B associated with the High Speed Downlink Packet Access (HSDPA) service additionally configures a high-speed medium access control (MAC-hs) layer and a frame protocol (FP) layer.
The MAC-hs layer supports scheduling for UEs according to the HSDPA service and the HARQ technique. The MAC-hs layer determines the priorities of UEs receiving the HSDPA service.
On the other hand, the FP layer controls a frame for generating the HS-DSCH. That is, the HS-DSCH FP layer generates and transmits the HS-DSCH. The MAC-hs layer controls an operation for allocating packet data of the UE supporting the HSDPA service to a specific slot for the generated HS-DSCH. Accordingly, the CRNC 130 connected to the Node-B 120 configures a common/shared MAC (MAC-c/sh) layer and an FP layer. The MAC-c/sh layer stores the HS-DSCH frame.
The SRNC 140 connected to the CRNC 130 through the Iur interface configures a dedicated MAC (MAC-d) layer and an FP layer to support the HSDPA. In the above structure, the HS-DSCH FP layer performs a flow control function for transmitting a HS-DSCH data frame between the Node-B 120 and the CRNC 130, and performs a flow control function for transmitting a HS-DSCH data frame between the CRNC 130 and the SRNC 140. When a MAC-c/sh layer is not present in the CRNC 130, the flow control function for transmitting an HS-DSCH data frame is performed between the FP layer of the Node-B 120 and the HS-DSCH FP layer of the SRNC 140.
The flow control process and the control messages defined in the 3GPP standard will be described with reference to
In step 310, an RNC 302 sends, to a Node-B 301, a HS-DSCH CAPACITY REQUEST message, which is a request for transport channel capacity required for the HSDPA service when a packet to be transmitted to the Node-B 301 is present. In step 320, the Node-B 301 includes channel resource allocation information in a HS-DSCH CAPACITY ALLOCATION message and sends the HS-DSCH CAPACITY ALLOCATION message in response to the request message 310. In steps 330 and 340, the RNC 302 receiving the response message can transmit, to the Node-B 301, packet data of the HSDPA service according to the channel resource information.
Referring to
Referring to
Accordingly, the RNC transmits packet data of the number of PDUs set in the HS-DSCH credits field 520 during the interval set in the HS-DSCH interval field 530 according to the PDU size set in the maximum MAC-d PDU length field 510. When a value of the HS-DSCH repetition period field 540 is greater than 1, a transmission operation is repeated by the set number of repeated transmissions.
The HS-DSCH CAPACITY ALLOCATION message can be sent in the following cases.
Referring to
Accordingly, the Node-B can receive a control message of the HS-DSCH CAPACITY REQUEST and the HS-DSCH data frame to perform capacity allocation.
Packet data of the maximum MAC-d PDU length is divided and repeatedly transmitted according to the number of HS-DSCH credits during the interval set in the HS-DSCH interval field. In this case, repeated transmissions vary with a value set in the HS-DSCH repetition period field.
Referring to
Accordingly, to send data within a range in which overflow does not occur, the sender computes an allowable amount of transmission data (Credit_Balance) to send data within the computed Credit_Balance.
That is, the sender can send data while preventing overflow in the receiver by making use of the control information (Fwd_Cnt) from the receiver.
The flow control process based on the credit information in the wired network illustrated in
In the 3GPP standard, the FP layer inside the Node-B determines the number of credits using the user buffer size information associated with the accumulated amount of user data in the RNC and the user buffer size information in the Node-B. Accordingly, the RNC can send, to the Node-B, only packet data of the capacity allocated by the Node-B.
When the RNC sends the packet data to the Node-B through a link interface, an overflow may occur in a link buffer that temporarily stores the packet data, resulting in congestion. That is, because channel capacity based on the HSDPA service is allocated using only an amount of buffering in the Node-B, an overflow in the Node-B can be prevented. However, because a buffer state of the link interface within the RNC is not taken into account, the overflow occurs in the link buffer of the RNC.
In other words, when only the amount of buffering in the Node-B is taken into account in a state in which the overflow in the link interface of the RNC is not taken into account, the RNC may not transmit MAC-d PDUs of the number of HS-DSCH credits during the HS-DSCH interval due to congestion.
When updated capacity allocation is performed in a state in which the Node-B does not identify a congestion state of the RNC link buffer, the congestion state of the RNC link buffer becomes continuously worse. When the Node-B continuously allocates a significant amount of capacity, the RNC transmits data regardless of the allocated capacity.
The conventional flow control function can prevent a buffer overflow of the Node-B, but has a problem in that an overflow of the RNC link buffer continues because the conventional flow control function does not take into account a state of the RNC link buffer, such that link efficiency between the RNC and the Node-B becomes degraded.
Accordingly, the present invention has been designed to solve the above and other problems occurring in the prior art. Therefore, it is an aspect of the present invention to provide a system and method for efficiently transmitting packet data between a Node-B and a radio network controller (RNC) in a mobile communication system using a high-speed downlink packet access (HSDPA) technique.
It is another aspect of the present invention to provide a system and method by which a Node-B identifies a link buffer state of a radio network controller (RNC) in a mobile communication system using a high-speed downlink packet access (HSDPA) technique.
It is another aspect of the present invention to provide a system and method by which a Node-B allocates accurate capacity by taking into account a link buffer state of a radio network controller (RNC) in a mobile communication system using a high-speed downlink packet access (HSDPA) technique.
It is yet another aspect of the present invention to provide a system and method by which a Node-B controls an amount of packet data according to a link buffer state of a radio network controller (RNC) in a mobile communication system using a high-speed downlink packet access (HSDPA) technique.
The above and other aspects of the present invention can be achieved by a system and method for performing efficient flow control between a Node-B and a radio network controller (RNC) in a mobile communication system using a high-speed downlink packet access (HSDPA) technique. The system and method comprise receiving, from the RNC, a request message for resource capacity allocation required to transmit high-speed downlink packet data in the Node-B and identifying the number of packet data units capable of being allocated by the RNC; comparing the number of packet data units requested from the RNC and the number of packet data units acceptable to the Node-B, and determining packet data for the flow control using a minimum value between the requested number of packet data units and the acceptable number of packet data units; and allocating the resource capacity according to the determined packet data, and notifying the RNC of the allocated resource capacity through a response message.
The above and other aspects of the present invention can be achieved by a system and method for controlling an amount of packet data according to a link buffer state of a radio network controller (RNC) in a Node-B provided in a mobile communication system using a high-speed downlink packet access (HSDPA) technique. The system and method comprise considering a buffer size of the Node-B and an amount of packet data requested from the RNC to determine resource capacity in the Node-B, and notifying the RNC of the determined resource capacity; counting the number of times when an amount of packet data transmitted from the RNC during a designated period is less than the determined resource capacity; and when the counted number of times is greater than the number of control flows set for total packet data transmission, allocating to the RNC less resource capacity than the determined resource capacity, and notifying the RNC of the allocated resource capacity.
The above and other aspects and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Throughout the drawings, the same element is designated by the same reference numeral or character.
Embodiments of the present invention will be described in detail herein below with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted for conciseness. It is to be understood that the phraseology and terminology herein are exemplary and should not limit the scope of the invention.
The embodiments of the present invention provide a method for efficiently preventing a congestion state of a link buffer occurring in a high-speed downlink packet access (HSDPA) flow control process in a wideband code division multiple access (WCDMA) system defined in the 3rd Generation Partnership Project (3GPP) standard, thereby improving link efficiency. Moreover, the embodiments of the present invention provide a method for preventing the congestion state of the link buffer without requiring an additional message between a Node-B and a radio network controller (RNC).
Referring to
The RNC 902 serving as the SRNC and the CRNC provides the HSDPA service to the UE. A main controller 950 of the RNC 902 controls a traffic processor 970 to allocate packet data (traffic) for the UE. The packet data is received when an interface 980 supports the HSDPA service from the CN. The traffic processor 970 transfers the packet data stored according to capacity allocated from a frame protocol (FP) entity 910 of the Node-B 901 to a line interface 940 through a switch 960. The line interface 940 transfers the packet data received from the traffic processor 970 to a line interface 930 of the Node-B 901.
The FP entity 910 of the Node-B 901 determines if an amount of data received through a switch 920 and the line interface 930 of the Node-B 901 is equal to that of data of the previously allocated capacity. According to a result of the determination, the FP entity 910 allocates new resource capacity to the traffic processor 970, such that the flow of the packet data is controlled.
In accordance with an embodiment of the present invention, the FP entity 910 identifies a buffer congestion state within the line interface 940 of the RNC 902 by comparing the amount of packet data transmitted through the line interface 940 of the RNC 902 with the previously allocated resource capacity. In this case, the FP entity 910 differentiates the buffer congestion state through the normal allocation mode and the virtual congestion allocation mode to allocate different resource capacities.
Referring to
The normal allocation mode indicates that a link buffer state of the Node-B and a link buffer state of the RNC are normal. In the normal allocation mode, resource allocation for the HSDPA is performed normally. Accordingly, the Node-B takes into account an internal reception buffer size (Rx_Buffer_Size) and an amount of data requested from the RNC through a CAPACITY REQUEST message to perform the resource allocation.
In the virtual congestion allocation mode, the Node-B takes into account congestion in an interface buffer in relation to an interface between the RNC and the Node-B, and performs resource allocation based on the congestion state. That is, the Node-B predicts congestion in the line interface of the RNC for actually transmitted packets, and allocates less capacity in the virtual congestion allocation mode than in the normal allocation mode.
As mentioned above, the Node-B determines the line interface state of the RNC. If it is determined that the line interface state of the RNC corresponds to the normal allocation mode 1001, the Node-B considers a reception buffer state of the Node-B, and sends capacity allocation information to the RNC. In this case, when information of the line interface state of the RNC indicates a virtual congestion state (Virtual_Congestion_Flag=1), the resource allocation stops. After the line interface state of the RNC is switched to the virtual congestion allocation mode 1002, the Node-B performs resource allocation based on the virtual congestion allocation mode. Less capacity is allocated in the virtual congestion allocation mode as compared with the normal allocation mode, such that the RNC load is reduced.
However, if it is determined that the line interface state of the RNC corresponds to the normal allocation mode (Virtual_Congestion_Flag=0) when a predetermined time has elapsed, the Node-B allocates resource capacity corresponding to the normal allocation mode. That is, the Node-B performs the resource allocation by considering the line interface state of the RNC, thereby efficiently transmitting packet data according to the HSDPA service.
Referring to
Accordingly, the FP entity of the Node-B performs resource allocation by taking into account the line interface state of the RNC, thereby reducing the RNC load.
However, if the ratio of the virtual congestion count value (Virtual_Congestion_Counter) to the total number of control flows is not greater than the reference ratio (Virtual_Congestion_Determination_Ratio) in step 1130, the FP entity of the Node-B proceeds to step 1150 to perform resource allocation based on the normal allocation mode.
Referring to
However, if the ratio of the virtual congestion count value (Virtual_Congestion_Counter) to the total number of control flows is not less than the reference ratio (Virtual_Congestion_Determination_Ratio) in step 1230, the FP entity of the Node-B proceeds to step 1240 to maintain the virtual congestion allocation mode.
The resource allocation in the normal allocation mode is computed using the following Equation 1. Alternatively, the resource allocation in the normal allocation mode may be performed by means of other methods.
In the above Equation 1, “BBTS,i,Threshold
The resource allocation in the virtual congestion allocation mode is computed using the following Equation 2. Alternatively, the resource allocation in the virtual congestion allocation mode may be performed by means of other methods.
In terms of resource capacity allocation, HS-DSCH credits in the normal allocation mode are similar to those in the virtual congestion allocation mode. Only, when a ratio (Allocation_Ratio_Virtual_CongestionK) according to the congestion state is taken into account, allocation capacity in the virtual congestion allocation mode is smaller than that in the normal allocation mode. The ratio (Allocation_Ratio_Virtual_CongestionK) according to the congestion state is used to ensure credits according to a priority K of a user as in the normal allocation mode.
Because a control message is sent only when new resource capacity is allocated, the total system load does not increase.
As described above, the embodiments of the present invention have a number of advantageous effects.
For example, an embodiment of the present invention provides a basic technique capable of performing normal flow control according to the 3GPP standard. More specifically, the embodiment of the present invention can prevent abnormal flow control by performing a flow control process by considering a buffer state of the RNC line interface.
Because the flow control process is performed by considering a congestion state of the RNC line interface, the efficiency of using a line interface between the RNC and the Node-B improves.
Although embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the present invention. Therefore, the present invention is not limited to the above-described embodiments, but is defined by the following claims, along with their full scope of equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17986/2004 | Mar 2004 | KR | national |
