CN100574174C - The control method that radio link control layer buffer area overflows - Google Patents

The control method that radio link control layer buffer area overflows Download PDF

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Publication number
CN100574174C
CN100574174C CNB2005100027749A CN200510002774A CN100574174C CN 100574174 C CN100574174 C CN 100574174C CN B2005100027749 A CNB2005100027749 A CN B2005100027749A CN 200510002774 A CN200510002774 A CN 200510002774A CN 100574174 C CN100574174 C CN 100574174C
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rlc
sdu
bo
buffering area
pdu
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CNB2005100027749A
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CN1812313A (en
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童颖
王成毅
许佰魁
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华为技术有限公司
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Abstract

The present invention relates to the control method that a kind of radio link control layer buffer area overflows, comprising: A. presets RLC buffer threshold value, and initialization Bo value is 0; B.RLC carries out pre-segmentation to the SDU that receives, calculates current Bo value according to the result; Whether the Bo that C. judges RLC less than RLC buffer threshold value, if, carry out the RLC function treatment, carry out the MAC function treatment again; Otherwise deletion SDU upgrades current Bo value, and carries out the MAC function treatment.The invention still further relates to another kind of control method, not being all of this method and said method:, directly carry out the RLC function treatment to the SDU segmentation in advance of receiving; Search for the PDU that first does not send sign SDU in addition, and delete all PDU of this SDU, all the other steps are the same.The present invention controls the SDU of RLC buffering area, effectively reduces time delay end to end, improve response speed and end-to-end between quality services.

Description

The control method that radio link control layer buffer area overflows

Technical field

The present invention relates to the communications field, particularly relate to the control method that a kind of radio link control layer buffer area overflows

Background technology

Along with development of Communication Technique, the particularly development of 3G technology, data, services will become one of important service of mobile communication system.This wireless data service will be provided to the seamless link of Internct for the terminal use, can allow the user obtain information more easily by wireless system.And the existing Internet network mainly carries out networking and finishes transfer of data by TCP/IP.

Described transmission control protocol (TCP, Transmit Control Protocol) is a kind of reliable transmission technology, guarantees the transmission performance of transmission control protocol TCP in existing cable network by adopting methods such as startup slowly, Congestion Avoidance and fast quick-recovery.The realization of these methods is exactly to have increased a congestion window (cwnd) and threshold values (ssthresh) in the TCP of transmit leg, and the initial value of described congestion window when connection begins to set up is a tcp data bag size, upgrades by described method subsequently; Described threshold values has then reflected the Flow Control thresholding of transmitting terminal.In data transmission procedure, when congestion window during less than threshold values, TCP enables and starts method slowly; When congestion window during, adopt the Congestion Avoidance method greater than threshold values; There is when losing to adopt quick recovery method in data.And described employing quick recovery method is accompanied by startup and Congestion Avoidance slowly constantly, and avoiding has loss of data when transmission.

Described startup method slowly is meant the speed of transmitting terminal according to the affirmation speed decision transmission new data packets of receiving terminal.Transmission control protocol TCP sends a tcp data bag when beginning, wait for the receiving end affirmation then, after receiving the affirmation bag, congestion window is increased to 2 packet sizes from 1 tcp data bag, can send 2 tcp data bags this moment, after these 2 packets obtained confirming, congestion window was increased to 4 packet sizes from 2 tcp data bags, and can send 4 tcp data bags this moment.The rest may be inferred, and sending data volume is to increase by progression when beginning, and the packet that sends up to congestion window starts the Congestion Avoidance method during greater than the threshold values set.Described Congestion Avoidance method is meant after the affirmation of whenever receiving a new tcp data bag of making a start just to be increased congestion window, its increment multiply by tcp data bag size according to tcp data bag size determines divided by a congestion window byte (congestion window CWND and packet size all are unit count with the byte) that again the data volume that this moment, transmitting terminal can send slowly increases along with the restriction of current congestion window.This growth rate is a kind of linear growth process with respect to startup method slowly.

When TCP technology and cordless communication network seamless link, wireless network can be set up a bearing link for the connection of an IP address, a Radio Link control (RLC, Radio Link Control) carrying entity, all various TCP from this IP address connect or data all transmit on this entity.And the wireless network protocol buffer memory ability of this entity without limits, therefore the TCP on all entities connects just as a router that receiving ability is infinite, but the transmission rate of wireless network is limited, the bulk data that sends the startup stage of causing TCP slow all can be buffered in the rlc layer of wireless network, especially even more serious when a plurality of TCP connections send data simultaneously, make that TCP can not be satisfactory in the transmission performance of wireless network.Such as the user when opening a plurality of connection, when sending some service request (as open new web page or stop certain request of operating), the TCP response message is blocked in after the data to be sent such as a large amount of, and the time delay of introducing is impatient at sometimes, often be interpreted as network congestion by TCP, thereby it is seriously limited to trigger the TCP flow, the transmission performance variation.Therefore, improve Transmission Control Protocol and on radio bearer, obtain best transmission performance, reduce effectively that propagation delay time is very urgent end to end in the global system for mobile communications (UMTS, Universal Mobile Telcommunications System).

At present, improve the transmission performance of data, the control method that the radio link control layer buffer area of end-to-end propagation delay time overflows in the reduction UMTS system mainly contains following several:

First method is according to agreement RFC3481 and RFC3449, for improving the data transmission performance of TCP on wireless network, the corresponding strategies that the reduction propagation delay time is made respectively, comprises respectively: the tcp window size of adjusting transmit leg and recipient; Increase the initialization window of transmit leg; The transmission rate of restriction transmit leg; Adjust the size of MTU (MTU, Maximum Transmit Unit); Enable the path mtu testing mechanism at transmit leg; Enable selectivity ACK at transmit leg and recipient; Enable direct congestion notification mechanism; Enabling time is stabbed mechanism; Do not use the head compression method of TCP/IP; Revise the mechanism of recipient's backspace ACK.These parameters and mechanism all are that existing Transmission Control Protocol is adjusted accordingly, though improved the performance of the transfer of data of TCP in wireless network to a certain extent, reduced propagation delay time end to end, but the unified effective result of above adjustment neither one has different parameter combinations just can reach this effect at different environment often; In the wireless network of reality was used, the main frame of last each service node of Internet was uncontrollable.Particularly in real commercial system, the terminal of another IP is a mobile phone, setting and association that above method needs the user to grasp the TCP parameter utilize the mobile phone daemon software that advanced parameters is set, could improve the performance of the transfer of data of TCP in wireless network, reduced propagation delay time end to end, these also are unpractical for domestic consumer.In addition, some above-mentioned adjustment measure need redesign TCP/IP, and such as the mechanism of revising recipient's backspace ACK, this is impossible implement to existing service network.

Second method is to abandon trigger mechanism according to the Service Data Unit (SDU, Service Data Unit) that rlc protocol 25.322 has defined based on timer.This method makes the SDU discard insensitive to the variation of channel speed, and the explication of maximum delay is provided.Described method comprises:

At first, when the data service carrying is set up, create Radio Link control rlc layer.This Radio Link control rlc layer bufcreates again, and described buffering area is used to receive and deposit the tcp data bag from high level, and this packet is called as Service Data Unit SDU.Rlc layer obtains SDU from upper strata control protocol radio resource control layer RRC and abandons timer value, and by local specified transmission rate, data block number and data block size PDU the transmission data is sent.Described PDU (Protocol Data Unit) is a protocol Data Unit.

Secondly, when Radio Link control rlc layer is received a tcp data bag, start SDU and abandon timer, monitor the transmission time of this SDU.Rlc layer is according to the transmission rate and the data block size requirements of this locality then, and cutting apart SDU is a plurality of PDU, and begins to send PDU.

Once more, when Radio Link control rlc layer has collected the affirmation bag of all PDU of described SDU correspondence, stop this SDU and abandon timer.

At last, control rlc layer when SDU abandons timer expiry,, then abandon this SDU if also do not collect the affirmation bag of all PDU of described SDU correspondence when Radio Link.

Therefore, as can be seen, the shortcoming of existence is from above-mentioned disclosed method: can cause synchronization to have a plurality of tcp data bags to arrive the buffering area of rlc layers because TCP starts effect slowly, so the timer of these SDU can start at synchronization.And, will cause these a collection of all follow-up SDU to abandon timer expiry because so in a single day the transmission mechanism according to the order of sequence of wireless network has a SDU overtime, this moment, SDU was abandoned by collective, can cause the rlc layer free of data to send out, reduce the RLC throughput, influence the quality services between end-to-end.

Summary of the invention

The technical problem that the present invention solves provide a kind of simply, the radio link control layer buffer area control method of overflowing efficiently, guaranteeing under the prerequisite that default data rate (RLC throughput) of eating dishes without rice or wine and the actual data rate of eating dishes without rice or wine are complementary, can effectively reduce time delay end to end, improve response speed and end-to-end between quality services Qos.

For addressing the above problem, the invention provides the control method that a kind of radio link control layer buffer area overflows, the described buffering area of this method is used to receive and deposit the Service Data Unit SDU from the upper strata, and this method comprises the steps:

Default RLC buffer threshold value, and initialization to represent the controlling value Bo of current RLC data volume that buffering area is preserved be 0;

Wireless chain control layer RLC carries out pre-segmentation to the SDU that receives, and calculates the RLC buffering area controlling value Bo of current business amount according to the result of pre-segmentation;

Whether the RLC buffering area controlling value Bo that judges the current business amount less than RLC buffering area control gate limit value, if, directly carry out the RLC function treatment, carry out the MAC function treatment again; Otherwise, directly delete SDU, upgrade the RLC buffering area controlling value Bo of current business amount, trigger TCP and stop to send the new business data to RLC, till arriving the thresholding that TCP retransmits fast and recovery algorithms sets, and carry out the MAC function treatment.

Described wireless chain control layer RLC carries out pre-segmentation to the SDU that receives, and according to the detailed process that the result of pre-segmentation calculates the RLC buffering area controlling value Bo of current business amount be: RLC carries out pre-segmentation according to the data block of the PDU size of control protocol parameter appointment to the SDU that receives, calculate the RLC buffering area controlling value Bo of current business amount according to pre-segmentation result, its computing formula is: the data volume of all PDU that the original Bo+ of Bo=increases newly, wherein, described Bo be in any time RLC buffering area all etc. data volume to be sent.

The process of the described RLC of carrying out function treatment is: the data block that SDU is divided into protocol Data Unit PDU size, and be inserted in the PDU formation by the order of first in first out, for each PDU is provided with SDU sequence number under it, and for being changed to not, the transmission sign of this SDU sequence number correspondence sends sign, the PDU piece number that writes down this SDU simultaneously and separated;

The process of the described MAC of carrying out function treatment is: the most preceding data send the MAC layer in the PDU formation to coming, and more according to SDU sequence number that this PDU write down, the transmission sign of this SDU sequence number correspondence of notice RLC is set to send, notifies RLC to upgrade the RLC buffering area controlling value Bo of current business amount simultaneously.

The formula that described RLC upgrades the RLC buffering area controlling value Bo of current business amount is: the PDU data volume that the original Bo-of Bo=has sent, wherein, described Bo be in any time RLC buffering area all etc. data volume to be sent.

The computing formula of the RLC buffering area controlling value Bo of described renewal current business amount is: the deleted PDU data volume of Bo-that Bo=is original, wherein, described Bo be in any time RLC buffering area all etc. data volume to be sent.

Described TCP retransmits fast and recovery algorithms comprises:

When a SDU when rlc layer is dropped, cause that then the opposite end retransmits identical affirmation bag, when TCP receives the affirmation bag of the 3rd repetition, the big or small summation of the actual unacknowledged data packet of threshold value=TCP/2 are set, congestion window=threshold value+3 * tcp data bag;

When the affirmation bag of another repetition arrived, congestion window increased the size of a tcp data bag, when unacknowledged data packet summation during less than congestion window, began to transmit next new data packets;

When the next one confirms that the affirmation bag of new data arrives, congestion window=threshold value is set, finish quick re-transmission and recovery algorithms, enter Congestion Avoidance.

The control method that the present invention also provides a kind of radio link control layer buffer area to overflow, described buffering area is used to receive and deposit the Service Data Unit SDU from the upper strata, comprising:

Pre-set RLC buffer threshold value, and initialization to represent the controlling value Bo of current RLC data volume that buffering area is preserved be 0;

Wireless chain control layer RLC directly carries out the RLC function treatment with the SDU that receives, and calculates the RLC buffering area controlling value Bo of current business amount according to RLC function treatment result;

Whether the RLC buffering area controlling value Bo that judges the current business amount is less than default RLC buffering area control gate limit value, if directly carry out the MAC function treatment, and notice RLC upgrades the RLC buffering area controlling value Bo of current business amount; Otherwise, when searching the PDU data of first SDU that does not send, delete all PDU data relevant with described SDU, and the RLC buffering area controlling value Bo of renewal current business amount, trigger TCP and stop to send the new business data to RLC, in the time of till arriving the thresholding that TCP retransmits fast and recovery algorithms sets, carry out the MAC function treatment.

The process of the described RLC of carrying out function treatment is: the data block that SDU is divided into protocol Data Unit PDU size, and be inserted in the PDU formation by the order of first in first out, for each PDU is provided with SDU sequence number under it, and for being changed to not, the transmission sign of this SDU sequence number correspondence sends sign, the PDU piece number that writes down this SDU simultaneously and separated;

The formula of the RLC buffering area controlling value Bo of described calculation current business amount is: the data volume of all PDU that the original Bo+ of RLC buffering area controlling value Bo=is newly-increased, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.

The process of the described MAC of carrying out function treatment is: the most preceding data send the MAC layer in the PDU formation to coming, and more according to SDU sequence number that this PDU write down, the transmission sign of this SDU sequence number correspondence of notice RLC is set to send, notifies RLC to upgrade the RLC buffering area controlling value Bo of current business amount simultaneously; Wherein,

The formula that described RLC upgrades the RLC buffering area controlling value Bo of current business amount is: the PDU data volume that the original Bo-of Bo=has sent, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.

The computing formula of the RLC buffering area controlling value Bo of described renewal traffic carrying capacity is: the deleted PDU data volume of Bo-that Bo=is original, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent;

Described TCP retransmits fast and recovery algorithms comprises:

When a SDU when rlc layer is dropped, cause that then the opposite end retransmits identical affirmation bag, when TCP receives the affirmation bag of the 3rd repetition, the big or small summation of the actual unacknowledged data packet of threshold value=TCP/2 are set, congestion window=threshold value+3 * tcp data bag;

When the affirmation bag of another repetition arrived, congestion window increased the size of a tcp data bag, when unacknowledged data packet summation during less than congestion window, began to transmit next new data packets;

When the next one confirms that the affirmation bag of new data arrives, congestion window=threshold value is set, finish quick re-transmission and recovery algorithms, enter Congestion Avoidance.

Compared with prior art, the present invention has following beneficial effect: the present invention is on the basis of not changing original transmission control protocol TCP, come from the realization of global mobile communication UMTS agreement and mobile device, improve itself and the cooperating of Transmission Control Protocol, guaranteeing under the prerequisite that default data rate (RLC throughput) of eating dishes without rice or wine and the actual data rate of eating dishes without rice or wine are complementary, shorten time delay end to end, improve response speed and Qos end to end.

Description of drawings

Fig. 1 is the flow chart of a kind of radio link control layer buffer area of the present invention control method of overflowing;

Fig. 2 is the flow chart of quick re-transmission of the present invention and fast restoration algorithm;

Fig. 3 is the flow chart of the another kind of radio link control layer buffer area of the present invention control method of overflowing;

Fig. 4 is the schematic diagrames of embodiments of the invention at the control simulation result of the different RLC buffering area controls of the single-threaded download of 64k.

Embodiment

The present invention is applicable to the telecommunication transmission system that adopts air interface protocol, such as global system for mobile communications (UMTS, Universal Mobile Telcommunications System).The architecture of described air interface protocol, it mainly is divided into three layers, lowermost layer be physical layer (PHY) L1, being positioned on the physical layer is data link layer L2, being positioned on the data link layer is network layer L3.See that vertically protocol architecture is divided into the control plane and a user plane that is used to send data message of be used to transmit control signal (signaling).

Data link layer is divided into several sublayers, from control plane, it comprises media access control layer (MAC) and wireless chain control layer (RLC), from user plane, it also comprises the packet data protocol convergence sublayer (PDCP) of handling Packet Service and is used to handle the broadcast/multi broadcast control sublayer (BMC) of broadcast/multi broadcast business.Network layer mainly comprises radio resource control layer (RRC).

Physical layer provides the service of transmission by transmission channel to MAC, and transmission information is feature with the transmission means of data, and designation data is to transmit in which way.

MAC provides the service of transmission by logic channel to RLC.Logical message is a feature with the type that sends data, and which kind of type is the data of indication transmission be.

RLC provides the foundation of data link and discharges service.At control plane, the business on RLC carrying upper strata be referred to as Signaling Radio Bearer (Signal radio bearer, SRB), the data of transmitting on Signaling Radio Bearer are signalings; At user plane, if when PDCP and BMC are not used by business, the business on RLC carrying upper strata be referred to as radio bearer (radio bearer, RB), otherwise RB is by PDCP and BMC carrying, the data of transmitting on radio bearer are user profile.Signaling and user profile are all transmitted by RLC.Transmits data packets is drawn together and is sent data and receive data, and data packets for transmission is drawn together signaling and user profile.

In order to guarantee in the impregnable SDU time delay that reduces simultaneously of the throughput of rlc layer data, need control the size of traffic carrying capacity RLC buffering area, after buffering area reaches certain thresholding, abandon SDU, utilize TCP to retransmit fast and Restoration Mechanism, suppress to start slowly the SDU progression growth effect that causes.According to the difference of the deletion mode of SDU, the control method of RLC buffering area is also different.

Seeing also Fig. 1, is the control method that a kind of radio link control layer buffer area provided by the invention overflows, and this method is applicable to that the SDU data of last arrival RLC of deletion are fast.When data service carrying was set up, radio resource control layer RRC created wireless chain control layer RLC and MAC layer MAC, and described RLC bufcreates, and was used to receive and deposit the Service Data Unit SDU from the upper strata, comprising:

Step S11: default RLC buffer threshold value, and initialization to represent the controlling value Bo of current RLC data volume that buffering area is preserved be 0;

Step S12: wireless chain control layer RLC carries out pre-segmentation to the SDU that receives, and calculates the RLC buffering area controlling value Bo of current business amount according to pre-segmentation result;

Step S13: whether the RLC buffering area controlling value Bo that judges the current business amount less than RLC buffering area control gate limit value, if, directly carry out the RLC function treatment, carry out MAC function treatment (step S14) again; Otherwise, directly delete SDU, upgrade the RLC buffering area controlling value Bo of current business amount, trigger TCP and stop to send the new business data to RLC, till arriving the thresholding that TCP retransmits fast and recovery algorithms sets, and carry out MAC function treatment (step S15).

In step S11, when data service is initially set up, wireless network at first is rlc layer of this data business establishment, this layer is according to radio management resource RRC specified transmission rate and delay requirement, initialization RLC buffering area control thresholding, it is the threshold value of PDU formation, and initialization to represent the controlling value Bo of current RLC data volume that buffering area is preserved be 0, wherein, the value of thresholding is provided with according to the emulation comparing result, as shown in table 1 below, generally can adjust by data configuration according to the delay requirement of network.

Table 1:

When rlc layer receives that Service Data Unit SDU is when (also claiming the tcp data bag here), calculate the RLC buffering area controlling value Bo when described SDU is divided into the data block of protocol Data Unit PDU size of radio resource control layer RRC parameter appointment in advance, its computing formula is: the data volume of all PDU that the original Bo+ of Bo=is newly-increased, wherein said Bo be in any time RLC buffering area all etc. data volume (step S12) to be sent.

Judge that whether current budget RLC buffering area controlling value Bo is less than RLC buffering area control gate limit value, if the Bo value of institute's budget less than RLC buffering area control gate in limited time, described Service Data Unit SDU is carried out the RLC function treatment, be about to the data block that Service Data Unit SDU is divided into the PDU size of radio resource control layer RRC parameter appointment, and in the order insertion PDU formation according to first in first out, and SDU is set sends and to be masked as not transmit status, wait for that the MAC layer sends.When the MAC layer will come top data when sending in the PDU formation, the SDU relevant with this PDU sends sign and is set to transmit status, and notice RLC upgrades traffic carrying capacity Bo value, its formula is: the PDU data volume that the original Bo-of Bo=has sent, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.

If the Bo value of institute's budget is more than or equal to RLC buffering area control gate in limited time, the SDU that direct deletion is received at last, and upgrade traffic carrying capacity Bo value, its computing formula is: the deleted PDU data volume of Bo-that Bo=is original.After this SDU deletion, trigger TCP and temporarily stop to send new data, till reaching the thresholding that TCP retransmits fast and recovery algorithms is set to rlc layer.Carry out the MAC function treatment then, promptly will come top data when sending in the PDU formation when the MAC layer, the SDU relevant with this PDU sends sign and is set to transmit status, and notice RLC renewal traffic carrying capacity Bo value, and its formula is: the PDU data volume that the original Bo-of Bo=has sent.

Described TCP retransmits fast and recovery algorithms is an intrinsic algorithm of Transmission Control Protocol.Wherein, re-transmission and recovery algorithms are that the present invention adopts control of RLC buffer size and SDU to abandon the consideration basis of the strategy that combines fast.After buffering area reaches certain thresholding, abandon SDU, thereby cause the TCP congestion mechanism, suppress to start slowly the SDU progression growth effect that causes.TCP is defined in when being subjected to an out of order packet and produces the affirmation bag of a repetition immediately and send to the opposite end, if when transmit leg is received the affirmation bag that repeats more than three, shows this message dropping and retransmits, and do not need that retransmission timer is overtime by the time.Described quick re-transmission and quick the re-transmission and recovery algorithms as shown in Figure 2, comprising:

Step H11: when a SDU when rlc layer is dropped, cause that then the opposite end retransmits identical affirmation bag, when TCP receives the affirmation bag of the 3rd repetition, the big or small summation of the actual unacknowledged data packet of threshold value=TCP/2 are set, congestion window=threshold value+3 * tcp data bag

Step H12: when the affirmation bag of another repetition arrived, congestion window increased the size of a tcp data bag, when unacknowledged data packet summation during less than congestion window, began to transmit next new data packets

Step H13: when the next one confirms that the affirmation bag of new data arrives, congestion window=threshold value is set, finishes quick re-transmission and recovery algorithms, enter Congestion Avoidance.

Wherein, the process of described quick re-transmission and quick re-transmission and recovery algorithms is: when TCP began transmits data packets, the state of re-transmission and quick re-transmission and recovery algorithms was considered as not starting fast, and duplicate acknowledgment bag statistical number is zero.After reaching certain thresholding, buffering area abandons SDU, thereby cause the TCP congestion mechanism, judge whether to start quick re-transmission and quick the re-transmission and recovery algorithms, if not, when TCP receives that is confirmed a bag, judge that whether described affirmation bag is the affirmation bag of the 3rd repetition of receiving, if, threshold value is set to 1/2nd of the actual unacknowledged data packet size of TCP summation, congestion window is set to threshold value+3 * tcp data bag, and the tcp data bag of retransmission of lost retransmits with re-transmission and recovery algorithms are set to start the repeat counter zero clearing fast then fast to wireless chain control layer RLC; Otherwise when the affirmation bag of receiving repetition was no more than three times, congestion window was set to original congestion window and tcp data bag sum, then continued to send next new tcp data bag.

When quick re-transmission with retransmit fast and recovery algorithms when having started, TCP receives one when confirming bag, and elder generation judges whether described affirmation bag is the affirmation bag of repetition, and if not, congestion window is set to threshold value, retransmits fast with recovery algorithms to be set to not start.If, whether judge congestion window again greater than actual unacknowledged data packet summation, if greater than, then continue to send next new tcp data bag, if be not more than, then congestion window is set to original congestion window and tcp data bag sum, and does not send data;

According to this algorithm as can be known, when SDU is dropped, the actual unacknowledged data packet size of RLC buffer size=TCP summation.And the actual unacknowledged data packet size of congestion window (cwnd)=TCP this moment summation/2+3 * tcp data bag, whenever receive later the affirmation bag of a repetition, cwnd increases tcp data bag size, set up up to the actual unacknowledged data packet size of cwnd>TCP summation, TCP could send the new data section.That is to say that TCP can be in the SDU that the retransmits data of confirming not send out any before bag is received, but after the data in the RLC buffering area sent half, TCP can issue new data.Therefore generally speaking, the Bo value can not be 0.It is too poor to remove the non-wireless network aerial transmission quality, and this situation generally can not take place under the good situation of the network coverage.

In addition, also seeing also Fig. 3, is the control method that another kind of radio link control layer buffer area provided by the invention overflows, and this method is applicable to that first SDU data that arrive RLC of deletion are fast.When data service carrying was set up, radio resource control layer RRC created wireless chain control layer RLC and MAC layer MAC, and described RLC bufcreates, and was used to receive and deposit the Service Data Unit SDU from the upper strata, comprising:

Step M11: pre-set RLC buffer threshold value, and initialization to represent the controlling value Bo of current RLC data volume that buffering area is preserved be 0;

Step M12: wireless chain control layer RLC directly carries out the RLC function treatment with the SDU that receives, and calculates the RLC buffering area controlling value Bo of current business amount according to RLC function treatment result;

Step M13: whether the RLC buffering area controlling value Bo that judges the current business amount is less than default RLC buffering area control gate limit value, if directly carry out the MAC function treatment, and notice RLC upgrades the RLC buffering area controlling value Bo (step M14) of current business amount; Otherwise, when searching the PDU data of first SDU that does not send, delete all PDU data relevant with described SDU, and the RLC buffering area controlling value Bo of renewal current business amount, trigger TCP and stop to send the new business data to RLC, in the time of till arriving the thresholding that TCP retransmits fast and recovery algorithms sets, carry out MAC function treatment (step M15).

Described step M11 is identical with the implementation procedure of above-mentioned steps S11, when initially setting up according to data service, upper strata specified transmission rate and delay requirement are provided with RLC buffer threshold value, and initialization to represent the controlling value Bo of current RLC data volume that buffering area is preserved be 0.In addition, the value of thresholding also can be provided with according to the emulation comparing result, as above shown in the table 1, generally can adjust (not giving unnecessary details) here by data configuration according to the delay requirement of network.

When rlc layer receives that Service Data Unit SDU is when (also claiming the tcp data bag here), carry out the RLC function treatment, described Service Data Unit SDU is divided into the data block of the PDU size of RRC parameter appointment, and be inserted in the PDU formation according to the order of first in first out, and SDU is set sends and to be masked as not transmit status, wait for the processing of MAC layer function, the data volume of all PDU that the original Bo+ of RLC buffering area controlling value Bo=this moment is newly-increased, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.

Judge then whether described Bo controls thresholding less than the RLC buffering area of initial setting up, when Bo prescribes a time limit less than the RLC buffering area control gate of initial setting up, then directly carry out the MAC function treatment, promptly will come top data when sending in the PDU formation when the MAC layer, the SDU relevant with this PDU sends sign and is changed to transmit status, and notice RLC renewal traffic carrying capacity Bo value, its computing formula is the PDU data volume that the original Bo-of Bo=has sent; Otherwise, just when Bo value more than or equal to RLC buffering area control gate in limited time, in the PDU formation, begin search, if the affiliated pairing transmission of SDU sequence number of PDU is masked as and sends then continue next PDU in the search queue from first PDU; The PDU number of the separation of writing down according to this SDU if the pairing transmission of SDU sequence number under the PDU is masked as not transmission is deleted the PDU data continuously, till next PDU does not belong to this SDU.Promptly all PDUs relevant with this SDU are all deleted.Upgrade the RLC buffering area controlling value Bo of current business amount simultaneously, its computing formula is the deleted PDU data volume of the original Bo-of Bo=.After this SDU deleted, triggering TCP stopped to send the new business data to RLC, and in the time of till the thresholding that arrives the fast quick-recovery setting of TCP, quick re-transmission of described TCP and recovery algorithms are not here being given unnecessary details as previously mentioned.

For clearer explanation the present invention, now technical scheme of the present invention is described further.At the WCDMA wireless network layer, should finish the initial foundation of user data service earlier, radio resource control layer RRC creates RLC, MAC layer, and specified transmission rate, and transmission data block PDU size and number, such as, transmission rate is 64Kbit/s, whether for additional poll sign, user answer mode also are non-response modes or the like to transmission means.Data service with the same IP of all these users address all is carried on the same rlc layer then.For descending tcp data bag, through GTPU (GPRS Tunnel Protocol, GPRSTunneling Protocol), PDCP (PDCP, Packet Data ConvergenceProtocol), RLC, MAC, physical layer arrive portable terminal through air interface Uu transmission, the TCP acknowledgment bag that portable terminal sends also is to arrive physical layer by air interface, through MAC, RLC, the contrary processing procedure of PDCP, GTPU is received by TCP at last again.Wherein, GTPU is actual to be to have set up a tunnel for described mobile phone users, is used for the transparent transmission tcp data; PDCP is actual to be that tcp data bag IP head is encoded or decoded, and the packet that becomes rlc layer or GTPU layer understanding is issued corresponding protocol layer; Physical layer mainly is to be data-modulated that wireless signal sends with the demodulation wireless signal and issues MAC for the MAC layer data;

The present invention mainly realizes at Radio Link control RLC and media interviews control MAC.The major function of described rlc layer is the data that buffer memory PDCP sends, PDU size and number according to control protocol RRC appointment, data are divided into the data block of PDU size, and all these PDU data blocks are arranged in the formation according to the order of first in first out, wait for the transmission of MAC layer.When obtaining new tcp data, RLC recomputates traffic carrying capacity Bo value, and its computing formula is the data volume (calculating with byte) of the newly-increased PDU of the original Bo+ of Bo=.When data need retransmit, RLC update calculation traffic carrying capacity Bo value, the Bo+ PDU data volume (calculating) to be retransmitted that Bo=is original with byte.

Described MAC layer mainly is to dispatch according to the RRC specified transmission rate, sends data block to physical layer.When having PDU to be sent out away, MAC layer notice RLC upgrades traffic carrying capacity Bo value, and its computing formula is the PDU data volume (calculating with byte) that the original Bo-of Bo=has sent.Therefore traffic carrying capacity Bo value representation in arbitrary moment RLC buffering area all etc. data volume to be sent, the present invention utilizes this parameter value to realize the control of RLC buffering area.

The actual transmission of the slowstart algorithm that adopts in Transmission Control Protocol data volume increases by progression, TCP sends out pine a large amount of message segment but go on a fishing expedition earlier to receiving terminal, only send the message segment of some, be generally 1 and 2, by the time receiving terminal is just confirmed bag ACK to one of transmitting terminal feedback after receiving a message segment, transmitting terminal receives that the number that sends message segment behind the correct affirmation bag doubles, promptly send two, transmitting terminal just increases a MSS value with congestion window after whenever receiving the affirmation bag of a new message segment, so go down, reach certain thresholding until send data volume, when promptly reaching the threshold value (ssthresh) of congestion avoidance algorithm, TCP will enable congestion avoidance algorithm then.And congestion avoidance algorithm traffic volume with respect to slowstart algorithm is a linear growth process.This mechanism of TCP has caused the startup stage that TCP is slow, and the data volume that rlc layer receives from the upper strata causes more tcp data bag to be trapped in the RLC buffering area greater than the transmitting capacity of itself.And in the TCP congestion avoidance phase, TCP sends data volume and slows down, whenever receive that an affirmation just can only send a tcp data bag, this moment, RLC was from upper strata rate of received data and RLC transmission rate basically identical, so the RLC buffering area is detained the tcp data bag of some all the time.If data volume is bigger in the RLC buffering area, and the speed of eating dishes without rice or wine of distributing is when relatively low, and then the time delay of tcp data bag is bigger.Such one recently newly to the tcp data bag if certain request of user (such as initiating to stop certain request of operating in the downloading process), must wait until that then other SDU could send response after sending in the buffering area, the too slow reason of user face data response that Here it is.Adopt TCP to retransmit fast and recovery algorithms (as previously mentioned, not giving unnecessary details) here to this present invention, thereby suppress to start slowly the SDU progression growth effect that causes.In fact the RLC buffering area situation that Bo equals 0 promptly do not occur as long as there are data to send out all the time, then can guarantee throughput.If the RLC buffering area that is provided with down is more little meeting this requirement, the loopback delay that tcp data wraps in wireless network layer is just more little.TCP time delay=internal transmission time delay+tcp data wraps in the loopback delay of wireless network layer end to end, and it is little to reduce the SDU time delay, just can reduce the end-to-end time delay of transfer of data greatly, improves the TCP/RLC performance.

For furthermore bright beneficial effect of the present invention, please refer to following application example.Suppose that the TCP MTU that network connects is 1460 (Ethernet), during BLER=10%, do not adopt RLC buffering area control algolithm and adopt the test result that 3 thread TCP download under this algorithm to see the following form 2.

Table 2

Assignment speed RLC buffering area algorithm RLC buffering area (byte) The transmission rate of eating dishes without rice or wine (Kbps) Corresponding SDU time delay (ms) ??64K Adopt ??8~12K ??58.3 ??1,220~1,653

Do not adopt ??- ??58.5 ??10,490 ??144K Adopt ??16~20K ??126.5126.6 ??1,020~1,243 Do not adopt ??- ??126.5 ??7,089 ??256K Adopt ??32K ??228.0 ??1,117 Do not adopt ??- ??228.4 ??4,649 ??384K Adopt ??40K~48K ??341.7341.9 ??9621,091 Do not adopt ??- ??342 ??3,950

Control the setting up procedure of thresholding below with the transfer of data simulation result shows buffering area of 64K bit/s:

1, carries out single-threaded TCP under the transmission rate of wireless network 64kbit/s when downloading, different RLC buffer size simulation results such as table 3

Table 3

RLC buffering area (byte) The probability of Bo=0 The transmission rate of eating dishes without rice or wine (Kbps) TCP time delay (s) The SDU maximum abandons number ??4K ??14.3% ??52776 ??0.552 ??1 ??8K ??0.7% ??58196 ??0.995 ??1 ??12K ??0.1% ??58362 ??1.389 ??1 ??16K ??0.0% ??58445 ??1.763 ??1 ??24K ??0.1% ??58510 ??2.559 ??1 ??32K ??0.0% ??58529 ??4.369 ??0 Do not limit ??0.0% ??58494 ??4.30 ??0

L3 submits the comparative result of speed and time delay under the different RLC buffering area controls of the single-threaded download of its 64k, as shown in Figure 4.

2, carry out 3 thread TCP under the transmission rate of wireless network 64kbit/s and download simultaneously, different RLC buffer size simulation results (mode of overflowing adopts first SDU that is untreated in the deletion formation) as shown in table 4

Table 4

RLC buffering area (byte) The probability of Bo=0 The transmission rate of eating dishes without rice or wine (Kbps) TCP time delay (s) The SDU maximum abandons number ??8K ??0.5% ??58349/7,608 ??1.187 ??1.139 ??1.158 ??1 ??12K ??0.0% ??58349/9,351 ??1.603 ??1.530 ??1.545 ??1

??24K ??0.1% ??58307/8,137 ??3.056 ??3.043 ??3.036 ??1 ??32K ??0.0% ??58440/7,854 ??3.940 ??3.932 ??3.493 ??1 Do not limit ??0.0% ??58531/9,373 ??9.424 ??9.444 ??7.344 ??0

From the above, carry out the single-threaded TCP simulation result when downloading under the transmission rate of wireless network 64kbit/s, when TCP receives buffering area and is 32K, after the limits value of RLC buffering area is more than or equal to 32K, does not have SDU and abandon because of overflowing the RLC buffering area.And when 3 threads are downloaded, set up 3 TCP/IP to connect, it is 32K that each TCP receives buffering area, and TCP receives the buffering area summation much larger than 32K, and promptly the 32KRLC buffering area still has SDU and overflows and abandon.

Therefore, RLC buffering area control gate limit value is effective when receiving the buffering area summation less than current opposite end TCP, and inoperative when being worth more than or equal to this, transfer of data is controlled by the TCP Flow Control directly.For 64K business datum amount,, guarantee that simultaneously throughput do not suffer a loss substantially no matter single-threaded or multithreading when the RLC buffer size is restricted to 8K~12K, can obviously reduce SDU and TCP RTT time delay.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (9)

1, a kind of RLC buffering area of wireless chain control layer control method of overflowing, described buffering area are used to receive and deposit the Service Data Unit SDU from the upper strata, it is characterized in that, comprising:
A, default RLC buffer threshold value, and initialization to represent the RLC buffering area controlling value Bo of current RLC data volume that buffering area is preserved be 0;
B, Radio Link control rlc layer carry out pre-segmentation to the SDU that receives, and calculate the RLC buffering area controlling value Bo of current business amount according to the result of pre-segmentation;
C, judge the current business amount RLC buffering area controlling value Bo whether less than RLC buffer threshold value, if, directly carry out the RLC function treatment, carry out the MAC function treatment again; Otherwise, the SDU that direct deletion is received at last, upgrade the RLC buffering area controlling value Bo of current business amount, trigger TCP and stop to send new SDU to RLC, wherein, when a SDU when rlc layer is deleted, then cause the identical affirmation bag of opposite end repeating transmission, when TCP receives the affirmation bag of the 3rd repetition, the actual unacknowledged SDU size of threshold value=TCP summation/2 are set, congestion window=threshold value+3 * SDU, when the affirmation bag of another repetition arrived, congestion window increased the size of a SDU, when unacknowledged SDU summation during less than congestion window, begin the next new SDU of transmission to RLC, and successively carry out RLC function treatment and MAC function treatment, when the next one confirms that the affirmation bag of new SDU arrives, congestion window=threshold value is set, finish quick re-transmission and recovery algorithms, enter Congestion Avoidance.
2, method according to claim 1, it is characterized in that, the detailed process of described step B is: RLC carries out pre-segmentation according to the PDU size of control protocol parameter appointment to the SDU that receives, calculate the RLC buffering area controlling value Bo of current business amount according to the result of pre-segmentation, its computing formula is: the data volume of all PDU that the original Bo+ of Bo=increases newly, wherein, described Bo be in any time RLC buffering area all etc. data volume to be sent.
3, method according to claim 2 is characterized in that, among the step C
The process of the described RLC of carrying out function treatment is: the data block that SDU is divided into protocol Data Unit PDU size, and be inserted in the PDU formation by the order of first in first out, for each PDU is provided with SDU sequence number under it, and for being changed to not, the transmission sign of this SDU sequence number correspondence sends sign, the PDU piece number that writes down this SDU simultaneously and separated;
The process of the described MAC of carrying out function treatment is: the most preceding data send the MAC layer in the PDU formation to coming, and according to SDU sequence number that this PDU write down, the transmission sign of this SDU sequence number correspondence of notice rlc layer is set to send, notifies rlc layer to upgrade the RLC buffering area controlling value Bo of current business amount simultaneously.
4, method according to claim 3, it is characterized in that, the formula that described rlc layer in the MAC function treatment process upgrades the RLC buffering area controlling value Bo of current business amount is: the PDU data volume that the original Bo-of Bo=has sent, wherein, described Bo be in any time RLC buffering area all etc. data volume to be sent.
5, method according to claim 1 is characterized in that, among the step C
The computing formula of the RLC buffering area controlling value Bo of described renewal current business amount is: the deleted PDU data volume of Bo-that Bo=is original, wherein, described Bo be in any time RLC buffering area all etc. data volume to be sent.
6, a kind of RLC buffering area of wireless chain control layer control method of overflowing, described buffering area are used to receive and deposit the Service Data Unit SDU from the upper strata, it is characterized in that, comprising:
A, pre-set RLC buffer threshold value, and initialization to represent the RLC buffering area controlling value Bo of current RLC data volume that buffering area is preserved be 0;
B, Radio Link control rlc layer directly carry out the RLC function treatment with the SDU that receives, and calculate the RLC buffering area controlling value Bo of current business amount according to RLC function treatment result;
C, judge that whether the RLC buffering area controlling value Bo of current business amount is less than default RLC buffer threshold value, if directly carry out the MAC function treatment; Otherwise, when searching the PDU data of first SDU that does not send, delete all PDU data relevant with the described SDU that first does not send, and the RLC buffering area controlling value Bo of renewal current business amount, trigger TCP and stop to send new SDU to RLC, wherein, when a SDU when rlc layer is deleted, then cause the identical affirmation bag of opposite end repeating transmission, when TCP receives the affirmation bag of the 3rd repetition, the actual unacknowledged SDU size of threshold value=TCP summation/2 are set, and congestion window=threshold value+3 * SDU is when the affirmation bag of another repetition arrives, congestion window increases the size of a SDU, when unacknowledged SDU summation during, begin the next new SDU of transmission, and successively carry out RLC function treatment and MAC function treatment less than congestion window, when the next one confirms that the affirmation bag of new SDU arrives, congestion window=threshold value is set, finishes quick re-transmission and recovery algorithms, enter Congestion Avoidance.
7, method according to claim 6 is characterized in that, among the step B
The process of the described RLC of carrying out function treatment is: the data block that SDU is divided into protocol Data Unit PDU size, and be inserted in the PDU formation by the order of first in first out, for each PDU is provided with SDU sequence number under it, and for being changed to not, the transmission sign of this SDU sequence number correspondence sends sign, the PDU piece number that writes down this SDU simultaneously and separated;
The formula of the RLC buffering area controlling value Bo of described calculating current business amount is: the data volume of all PDU that the original Bo+ of RLC buffering area controlling value Bo=is newly-increased, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.
8, method according to claim 7 is characterized in that, among the step C
The process of the described MAC of carrying out function treatment is: the most preceding data send the MAC layer in the PDU formation to coming, and according to SDU sequence number that this PDU write down, the transmission sign of this SDU sequence number correspondence of notice rlc layer is set to send, notifies rlc layer to upgrade the RLC buffering area controlling value Bo of current business amount simultaneously; Wherein,
The formula that described rlc layer in the MAC function treatment process upgrades the RLC buffering area controlling value Bo of current business amount is: the PDU data volume that the original Bo-of Bo=has sent, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.
9, method according to claim 7 is characterized in that, among the step C
When deleting relevant with described SDU all PDU data, the computing formula of the RLC buffering area controlling value Bo of described renewal traffic carrying capacity is: the deleted PDU data volume of Bo-that Bo=is original, wherein said Bo be in any time RLC buffering area all etc. data volume to be sent.
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