KR20060041305A - Data flow control for multi-layered protocol stack - Google Patents

Abstract

The invention relates to a system, a device, a method and a computer program product for controlling the flows of a plurality of Data Units (DUs) over logical links, said system comprising at least two first-type Link Control (LC) means (40-1a.. 40- 8a), wherein each first-type LC means transforms a first-type DU into a second-type DU and vice versa, and provides a first interface (43-1.. 43- 8a) for said first-type DUs and a second interface for said second type DUs, and a second-type LC means (5a) with interfaces (50-1a.. 50-8a) for said second-type DUs, wherein the second interface of each of said first- type LC means (40-1a.. 40-8a) is directly connected to one respective interface (50-1a.. 50-8a) of said second-type LC means (5a), and wherein said second-type LC means (5a) comprises means (52a) for separately controlling the respective flows of the second-type DUs, which are transferred over its respective interfaces (50-1a.. 50-8a).

Description

Data flow control for multi-layered protocol stack}

The present invention relates to a system and apparatus for controlling the flows of a plurality of data units (DUs) over logical links. The invention also relates to a method and a computer program product for controlling the flows of a plurality of data units via a logical link.

Data transmission in cellular wireless systems such as mobile communication globalization system (GSM) or universal mobile communication system (UMTS) is growing and more complex with the advent of a mixture of advanced multi-media applications and services. . For the optimal use and fair distribution of scarce radio resources, more complex data flow control techniques are needed, and "flow control" is the management of data flow between nodes in a cellular radio system, for example mobile stations and base stations. As will be appreciated, data can be processed at an effective rate. Too much data arriving before the device at one of the nodes can process the data will cause a data overflow, which means that the data must be lost or retransmitted. An example of complex data flow control techniques is the introduction of priority-based data flow control, in which data is assigned a quality of service (QoS) parameter and / or a pre-defined class of service and then, for example, the highest QoS requirements. In order to optimize the transmission of the carried data, the data flow is processed taking into account the QoS parameters and / or class of service. Lack of proper priority-based data flow control results in resources being wasted for low priority services and ultimately dissatisfied with the mobile subscriber.

1 illustrates a portion of a protocol stack of a General Packet Radio Service (GPRS) integrated into the GSM protocol stack in the scope of GSM Phase 2+ development to use GSM radio resources more efficiently. The GPRS protocol stack controls the communication of a mobile station (MS) 1 and a serving GPRS support node (SGSN) 2 via a base station subsystem (BSS) 3.

After all, as shown in Fig. 1, the Logical Link Control (LLC) layer 4 of the GPRS protocol stack will be of primary interest. This layer and its functions are standardized by the European Telecommunications Standards Institute (ETSI) and described in technical document 3GPP TS 04.64 (December 2001, version 8.7.0).

The LLC layer 4 is regarded as a sub-layer of layer-2 in the ISO / OSI 7-layer reference model and is layer-3 entities in the MS 1 and layer-3 equivalent entities in its associated SGSN 2. It operates over a Radio Link Control (RLC) layer 5 and a base station subsystem GPRS protocol (BSSGP) layer 6 to provide logical links between them. Above the LLC layer 4, i.e. in the network layer (layer-3 of the ISO / OSI model) 7, Tunnelling of Messages (TOM) protocol 7-1, GPRS mobility management (GMM) : GPRS Mobility Management (7-2) protocol, Sub-Network Dependent Convergence (SNDC) layer 7-3 and SMS protocol 7-4 are located.

In cooperation with Medium Access Control (MAC) protocol 8, the RLC protocol 5 operates on top of a GSM radio frequency (RF) channel (physical layer) 9 and is available for GPRS in a radio cell. Statistical multiplexing of several logical connections on packet data channels (PDCHs) enables reliable packet-oriented transmission between MS 1 and BSS 3. RLC / MAC already includes an Automatic Repeat Request (ARQ) scheme for handling transmission errors over the air interface, while the LLC protocol 4 is a link such as Integrated Services Digital Network (ISDN). Applying flow control and error handling mechanisms known from the layer protocols provides a reliable encrypted logical link between the MS 1 and the SGSN 2. The ARQ scheme in the LLC is not designed to handle transmission errors over the air interface, but is designed to handle frame loss and errors in a fixed network or for link recovery after cell change. BSSGP 6 operating on top of network service 10, such as Frame Relay (FR) and lower layer-1 (L1) protocol 11, controls flow between BSS 3 and SGSN 2. In charge. The conversion between the RLC protocol 5 and the BSSGP protocol 6 is performed via a relay 12 in the BSS 3.

The TOM protocol 7-1 is a general protocol layer used for the exchange of TOM protocol envelopes between the MS 1 and the SGSN 2. The GMM protocol 7-2 transmits messages between the MS 1 and the SGSN 2 using the services of the LLC layer 4. It includes functions such as attachment and authentication, and includes sending session management messages for functions such as PDP context activation and deactivation. Network layer protocols are intended to enable services derived from a wide variety of sub-networks and data links. GPRS supports several network layer protocols that provide protocol transparency to users of the services. Therefore, all functions related to the transmission of network layer PDUs are performed in a transparent way by the GPRS network entities. SNDCP 7-3 provides the application of different network layers to the logical link by mapping different packet data protocols (eg, Internet Protocol (IP) data packets) to the services provided by the LLC layer. . The SMS protocol 7-4 transmits short messages between the MS 1 and the SGSN 2 using the services of the LLC layer 4.

FIG. 2 provides a more detailed view of the structure of the LLC layer 4 as shown at the MS 1 side, where signaling transmissions between the elements of FIG. 2 are provided in dashed lines and joint signaling and data transmissions are solid lines. Is provided. The LLC layer 4 is composed of a plurality of LLC entities (LLEs) 40-1... 40-8, an LLC management entity 41, a multiplexer 42, and a plurality of LLC-SAPs 43-1. 43-9). Through the SAPs 43-1 .. 43-8, the services of the LLEs 40-1 .. 40-8 are the protocols of the network layer 7, i.e. the SMS protocol 7-1. ), The GMM protocol 7-2, the SNDCP 7-3 and the TOM protocol 7-4. There is also a pure signaling link between the GMM protocol 7-2 and the LLC management entity 41 via the SAP 43-9. Below the LLC layer 4, the RLC layer 5 and the MAC layer 8 are located. LLC frames from the multiplexer 42 are delivered to the RLC layer 5 via one single RLC-SAP 50-1.

The LLC layer 4 provides four LLC-SAPs 43-2 .. 43-5 to the SNDCP 7-3, and the SNDCP 7-3 manages the actual data packet transmission. . In GPRS, four radio priority levels are defined. Correspondingly, four LLC-SAPs are needed for packet data transmission, and an SAP identifier (SAPI) identifies by the LLC entity the point at which LLC services are provided to the network layer entity. SAPIs for the four radio priority levels are SAPI = 3, 5, 9 and 11, respectively. Services made available through the LLC-SAPs 43-2 .. 43-5 are provided by the LLEs 40-2 .. 40-5. Each LLE is an information flow of N-PDUs transmitted as LLC service data units (LLC-SDUs) in LLC-PDUs, respectively, via LLC links / connections between equivalent LLEs in MS 1 and SGSN 2 To control. The N-PDUs are transmitted between the LLE and the SNDCP 7-3 via a corresponding LLC-SAP. LLEs provide unconfirmed / confirmed information transfer, flow control (in asynchronous balanced mode) and frame error detection to the SNDCP 7-3. Each LLC connection is identified by a Data Link Connection Identifier (DLCI) consisting of a SAPI and a Temporary Logical Link Identifier (TLLI). As already explained, the SAPI is used to identify the SAP on the SGSN 2 side and on the MS 1 side of the LLC interface, the SAPI is carried in the address field of each LLC frame. The TLLI is used to identify a particular MS 1. TLLI allocations are controlled by the GMM. TLLI is not carried in LLC frames.

The multiplexer 42 multiplexes the LLC connections of the respective LLEs 40-1 .. 40-8 and LLC frames (LLC-PDUs) that are delivered to an equivalent multiplexer entity in the remote SGSN 2 LLC layer 4. S). When transmitting an LLC frame, the multiplexer 42 generates and inserts a frame check sequence (FCS), performs a frame encryption function, and various LLEs 40-1 .. 40-8 in which connections are multiplexed. Provide a SAPI-based LLC layer contention solution. Upon receipt of the LLC frame, the multiplexer 42 performs a frame decoding function and checks the FCS. If the frame passes the FCS check, the multiplexing procedure distributes the LLC frame to an appropriate LLE. For the encryption function, an encryption key is generated using an encryption algorithm, starting with, for example, an unpredictable random number and an identification key generated by the authentication center. The FCS typically consists of a 24-bit cyclic redundancy check (CRC) code. CRC-24 is used to detect bit errors in the frame header and information fields.

When delivered to the RLC layer 5 via the RLC-SAP 50-1, the LLC frames from the multiplexer 42 are divided into RLC data blocks. In the RLC layer 5 and the MAC layer 8, an optional ARQ between the MS 1 and the network provides for retransmission of erroneous RLC data blocks. If a complete LLC frame is successfully transmitted across the RLC layer, it is sent to an equivalent LLC entity in the SGSN 2.

By multiplexing connections of different LLEs 40-1... 40-8 into LLC frames, the multiplexer 42 can (through the single RLC-SAP 50-1) for all signaling and data transmissions. ) Provides a common interface between the LLC layer 4 and the RLC layer 5. However, the multiplexer also represents a bottleneck for smooth data flow of different LLC connections controlled by the respective LLEs 40-1 .. 40-8. This means that the RLC layer has a good view of the radio resources available for the transmission of RLC data blocks of the RLC layer, the data of different LLC connections through the single RLC-SAP 50-1 due to the multiplexing procedure. This is due to the fact that it does not have the possibility to control the flows individually. Thus, it is not possible for the RLC layer 5 to adapt the flows of different LLC connections with different QoS requirements to the transmission state of the lower radio resource, and the overall data flow of the LLD-PDUs over the LLC links and thus the LLC Deteriorate the flow of N-PDUs included as LLC-SDUs in PDUs.

It is therefore an object of the present invention to provide improved control of the flow of data units over logical links in a communication system operating in a multi-layer protocol stack.

A system for controlling the flows of a plurality of data units (DUs) over logical links is proposed, the system comprising at least two first-type link control (LC) means, each first-type LC The means converts the first-type DU into a second-type DU and converts the second-type DU into a first-type DU, the first interface to the first-type DUs and the second type DUs. And a second type LC means having interfaces to the second type DUs, wherein the second interface of each of the first type LC means is the second type. Directly connected to each interface of one of the LC means, the second-type LC means individually carrying respective flows of the second-type DUs, which are transmitted via respective interfaces of the second-type LC means Means for controlling.

Compared with the prior art, the invention multiplexes the respective second-type DUs, which are transmitted over the second interfaces of the respective first-type LC means, and the multiplexed via the single interface of the second LC means. Omit the use of a multiplexer for transmitting the second-type DUs. Instead, the present invention proposes a second-type LC means with several interfaces, each of which is connected directly to each respective second interface of each of the at least two first-type LC means. The second-type LC means is provided with means for controlling the flows of the second-type DUs via respective interfaces. As a result, the present invention allows to individually control the flow of each second-type DUs converted from each first-type DUs in each first-type LC means. Due to the one-to-one relationship of the first-type DUs and the second-type DUs converted by the same first-type LC means, the second-type LC means are also defined by the respective first-type LC means. It is possible to control the flows of respective first-type DUs transmitted through respective first interfaces. That is, according to the present invention, the flows of the respective first-type DUs delivered to the respective first interfaces of the respective first-type LC means may be controlled by the second-type LC means. .

According to the system of the present invention, the first-type LC means converts the first-type DU into a second-type DU and performs the at least a frame checking function and an encryption function and converts the second-type DU into the first type. -Conversion to type DU is preferred. The omission of a prior art multiplexer requires a partial function of the multiplexer, which requires at least the insertion and inspection of the frame check sequence and the encryption and decryption of the frames, which will be integrated into each of the first-type LC means. Then converting the first-type DUs into the second-type DUs includes inserting and encrypting a frame check sequence, while converting the second-type DUs into the first-type DUs at least the frame check. Decoding and checking of sequences. According to the system of the present invention, it is still possible to have the prior art configuration with the first-type DUs which do not perform a frame check function and an encryption function, wherein the DUs transmitted over respective second interfaces Note that it is multiplexed by a multiplexer performing a function and an encryption function and transmitted through separate interfaces of the second-type LC means. The present invention only needs to have at least two first-type LC means with frame checking and encryption functions and the second-type LC means are exclusive to the second interfaces of the at least two first-type LC means. It is necessary to have interfaces to be connected. The interface of the multiplexer can thus be connected to an additional interface of the second-type LC means, but individual flow control is only possible for DUs converted by the first-type LC means without being multiplexed later, while The flow of the multiplexed DUs can only be controlled jointly.

According to the system of the present invention, at least two first-type LC means can also be distinguished by the characteristics of the first-type DUs transmitted over respective first interfaces, and the second-type LC means Means for individually controlling respective flows of the second-type DUs, transmitted over the respective interfaces of the second-type DUs, are converted into the first-type DUs or the second-type It is desirable to control the flows of each of the second-type DUs in consideration of the characteristics of the first-type DUs in which DUs are converted from the first-type DUs. The at least two distinguishable first-type LC means are thus suitable for the transmission and conversion of at least two different types of first-type DUs, and each first with a respective interface of the second-type LC means. The at least two distinctions due to the direct connection between the second interfaces of the type LC means and the ability of the second type LC means to individually control the flows of the second type DUs transmitted over the respective interfaces The flow of the first-type DUs transmitted over the first interfaces of possible first-type LC means may be controlled by the second LC means. It is likewise possible to have as many distinguishable first-type LC means (and corresponding first-type DUs) as there are interfaces of said second-type LC means.

According to the system of the invention, the second-type LC means preferably comprise at least one data unit (DU) buffer for buffering the second-type DUs transmitted over respective interfaces. The data unit (DU) buffer stores the second-type DUs to be transmitted over a common transmission link that can be at least partially controlled by the second-type LC means.

According to the system of the present invention, means for individually controlling respective flows of the second-type DUs, which are transmitted via the respective interfaces of the second-type LC means, are characterized in that the second-type DUs are Consider the characteristics of the first-type DUs converted into first-type DUs or the second-type DUs from the first-type DUs and the state of the at least one data unit (DU) buffer To control the flows of each of the second-type DUs. Then respective flows of the second-type DUs through respective interfaces of the second-type DU may be adapted to the state of the buffer. The state of the buffer may describe information about the number of stored DUs, the number of empty storage units, the speed of the buffer or the storage and clearance. For example, if the buffer is only slowly cleared, the second-type LC means may reduce the flow of all second-type DUs, or through the one of each of the two-type DUs Only flow can be reduced.

According to the system of the invention, the second-type LC means also preferably comprises means for evaluating the status of the physical transmission links over which the second-type DUs are transmitted. The second-type DUs may be transmitted directly or indirectly via the physical transmission link, ie it is also possible for there to be additional LC means located between the second-type LC means and the physical transmission link. Correspondingly, the second-type DUs may or may not be further converted before being transmitted on the physical transport channel. The state of the physical transmission link may be determined by any parameter related to data transmission, such as available transmission bandwidth, error characteristics, delay characteristics, signal to noise or carrier to interference ratio, or a combination thereof. Can be characterized.

According to the system of the present invention, means for individually controlling respective flows of the second-type DUs, which are transmitted via the respective interfaces of the second-type LC means, are characterized in that the second-type DUs are Characteristics of the first-type DUs converted into first-type DUs or the second-type DUs are converted from the first-type DUs, and of the physical transmission link through which the second-type DUs are transmitted. It is more desirable to control the flows of each of the second-type DUs in consideration of the state. Thus both the characteristics of the distinguishable first-type DUs and the state of the physical transport link determine the flow control.

According to the system of the present invention, the means for individually controlling the flows of each of the second-type DUs, transmitted through respective interfaces of the second-type LC means, means for operating a flow control protocol. More preferably. The flow control protocol controls the respective flows of the second-type DUs via respective interfaces of the second-type LC means and can be stored in additional second-type LC means buffers. In order to require type DUs or to block further transmission of the second-type DUs from the buffers of the first-type LC means, it may be communicated with the respective first-type LC means by control commands.

According to the system of the present invention, the flow control protocol is more preferably an XOn / XOff flow control protocol. In this regard, the receive data buffer sends an XOff command to the transmit data buffer when the receive buffer is full, and issue an XOn command to the transmit data buffer when the receive buffer is ready for further data buffering. Send. Other flow control protocols are also possible.

According to the system of the present invention, the characteristics are more preferably the quality of service (QoS) requirements of the first-type DUs. The first-type DUs converted by the first-type LC means to the second-type LC means may be differentially prioritized by the second-type LC means. For example, if the buffer of the second-type LC means is increasingly filled, the second-type LC means may be configured to include the second-type DUs corresponding to the first-type DUs with the lowest QoS requirements. Flow can be reduced, so that the second-type DUs with at least higher QoS requirements can be further processed by means following the buffer in the second-type LC means, the means following the buffer May be for example a transmitter / receiver of the physical transmission link or additional LC means for controlling the physical transmission link. QoS requirements may include information about the utilization, throughput (effective data rate), packet loss, latency (delay) and jitter (latency variation) of the network.

According to the system of the present invention, the system preferably further comprises link management means for controlling the first-type LC means. The control may include, for example, parameter initialization, error handling, and access flow control calls.

According to the system of the present invention, the logical links are preferably logical links between a serving GPRS support node (SGSN) and a mobile station (MS) of a mobile radio system operating according to the General Packet Radio Service (GPRS) standard or its derivative services. Wherein the first-type LC means are logical link control (LLC) entities of the GPRS logical link control (LLC) protocol with additional sequence-based frame checking and encryption functionality, and wherein the first interfaces are of the LLC entities. Service access points (LLC-SAPs), the second-type DUs are LLC frames, the interfaces of the second-type LC means are radio link control (RLC) -SAPs, and the first-type DUs are The LLCs, which are N-PDUs of a GPRS network layer protocol, wherein the second-type LC means implements the functionality of the GPRS RLC protocol and is transmitted over the respective RLC-SAPs Further comprising means for individually controlling respective flows of the frame.

N-PDUs with different QoS requirements, for example representing N-PDUs of the SNDCP, encapsulate the N-PDUs as LLC-SDUs in LLC-PDUs transmitted over logical links between equivalent LLEs, respectively, It must be transmitted between the MS network layer and equivalent entities in the SGSN network layer. According to the present invention, the connections between the LLEs made available to the network layer in the LLC-SAPIs can now be controlled individually for each LLC-SAPI, because according to the system of the present invention, the LLC connection This is because they are no longer multiplexed before using the RLC connection service in single RLC-SAPs and use each of the RLC connections that are available in several respective RLC-SAPs separately. Due to the omission of the prior art LLC multiplexer, there is substantially no flow disturbance between the RLC entities and the network entities, for example the SNDCP entities. Therefore, the RLC layer can perform complete data flow control of data to be transmitted through each LLC-SAP. The RLC layer communicates directly with the LLEs for both uplink and downlink data flows, for example by an XOn / XOff flow control protocol, the LLEs having their own small buffers. In the event of a problem with the RLC buffers or the radio link, flow control may stop the transmission of low priority SNDCP PDUs and instead maintain the transmission of high priority SNDCP PDUs. Apart from the fact that the number of primitives between the entities is significantly reduced, resulting in reduced MCU load and buffer usage, the multiplexer itself and its expensive buffers can be omitted.

Also proposed is an apparatus for controlling the flows of a plurality of data units (DUs) over logical links of a communication system, the apparatus comprising at least two first-type link control (LC) means, The first-type LC means converts a first-type DU into a second-type DU and converts a second-type DU into a first-type DU, a first interface to the first-type DUs and the first Providing a second interface for two type DUs, wherein the apparatus comprises a second type LC means with interfaces for the second type DUs, and the second of each of the first type LC means An interface is directly connected to each respective interface of the second-type LC means, and the second-type LC means are individually transmitted through respective interfaces of the second-type DUs. Individually control each flow of DUs And it means for. The device may, for example, represent a mobile terminal, in particular equipped with a mobile phone, a personal digital assistant (PDA) or a network card in a communication system operated according to the General Packet Radio Service (GPRS) standard or a derivative service thereof. It may be a computer or may form part of such a terminal.

Also proposed is a method for controlling the flows of a plurality of data units (DUs) via logical links, the method comprising a first method via respective first interfaces of at least two first-type link control (LC) means. Sending type data units (DUs); Converting the first-type DUs into second-type DUs and converting the second-type DUs into the first-type DUs in the respective first-type LC means; Transmitting the second-type DUs over respective second interfaces of the first-type LC means; Transmitting the second-type DUs over respective interfaces of the second-type LC means, wherein the second interface of each of the first-type LC means is one respective interface of the second-type LC means Directly connected to; And individually controlling the respective flows of the second-type DUs, which are transmitted through respective interfaces of the second-type LC means.

According to the method of the present invention, converting the first-type DUs into second-type DUs and converting the second-type DUs into the first-type DUs comprises at least a frame check function and an encryption function. It is preferable to include.

According to the method of the present invention, at least two first-type LC means can be distinguished by the characteristics of the first-type DUs conveyed through respective first interfaces, and through the respective interfaces. Individually controlling the flows of the two-type DUs, wherein the second-type DUs are converted into the first-type DUs or the second-type DUs are converted from the first-type DUs. It is preferable that the characteristics of the first-type DUs are considered.

According to the method of the invention, the method further comprises buffering the second-type DUs transmitted over respective interfaces of the second-type LC means in at least one data unit (DU) buffer. Do.

According to the method of the present invention, in the step of individually controlling respective flows of the second-type DUs through the respective interfaces, the second-type DUs are converted into the first-type DUs or the first ones. Preferably, the characteristics of the first-type DUs and the state of the at least one data unit (DU) buffer in which two-type DUs are converted from the first-type DUs are considered.

According to the method of the present invention, the method further comprises evaluating a state of a physical transmission link through which the second-type DUs are transmitted.

According to the method of the present invention, in the step of individually controlling respective flows of the second-type DUs through the respective interfaces, the second-type DUs are converted into the first-type DUs or the first ones. It is desirable to take into account the characteristics of the first-type DUs from which the two-type DUs are converted from the first-type DUs and the state of the evaluated transmission link.

According to the method of the present invention, the step of individually controlling the respective flows of the second-type DUs through the respective interfaces preferably includes the steps necessary for operating the flow control protocol.

According to the method of the present invention, the flow control protocol is preferably an XOn / XOff flow control protocol.

According to the method of the present invention, the characteristics are preferably the quality of service (QoS) requirements of the first-type DUs.

According to the method of the invention, the method preferably further comprises controlling said first-type LC means by link management means.

According to the method of the present invention, preferably, the logical links are logical links between a serving GPRS support node (SGSN) and a mobile station (MS) of a mobile radio system operated according to the General Packet Radio Service (GPRS) standard or its derivative services. Wherein the first-type LC means are logical link control (LLC) entities of the GPRS logical link control (LLC) protocol with additional sequence-based frame checking and encryption functionality, and wherein the first interfaces are of the LLC entities. Service access points (LLC-SAPs), the second-type DUs are LLC frames, the interfaces of the second-type LC means are radio link control (RLC) -SAPs, and the first-type DUs are N-PDUs of a GPRS network layer protocol, wherein the second-type LC means implements the functionality of the GPRS RLC protocol and wherein the LLC frames are converted or overlaid onto the N-PDUs. Individually controlling respective flows of the LLC frames, which are transmitted on at least two RLC-SAPs of the RLC-SAPs, taking into account the characteristics of the N-PDUs from which the LLC frames are converted from the N-PDUs It is preferable to carry out further steps.

Also proposed is a computer program product, wherein the computer program product is directly loadable into an internal memory of a digital computer, the software code for performing the method steps of the above-mentioned method claims when the computer program product is executed on a computer. Include the parts.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described below.

1 shows an overview of the lower three protocol layers of a prior art protocol stack of a general packet radio service (GPRS) system.

2 is a detailed diagram of the structure of the prior art LLC and RLC layers of the GPRS protocol stack as seen from the mobile station (MS) side.

3 is a detailed view of the structure of the LLC and RLC layers of the GPRS protocol stack as seen from the MS side in accordance with the present invention.

4 is a detailed view of the structure of the RLC layer as seen from the MS side according to the present invention.

FIG. 3 shows Logical Link Control (LLC) 4a and Radio Link Control (RLC) of the GPRS protocol stack as seen from the MS 1 side, including changes according to the present invention. 5a shows the structure of the layers. Changes in the prior art protocol stack as shown in FIGS. 1 and 2 only affect the LLC layer 4a and the RLC layer 5a. For a description of the network layer 7 above the LLC layer 4a and the medium access control (MAC) layer 8 below the RLC layer 5a, the corresponding of the prior art in FIGS. Reference is made to the description.

In contrast to the prior art protocol stack of FIG. 2, the protocol stack according to the present invention includes a modified LLC layer 4a, which is deprived of the multiplexer 42. Multiplexer functionality has been moved to modified LLC entities (LLEs) 40-1a .. 40-8a, each connected to one LLC service access point (LLC-SAPs) 43-1 .. 43-8, respectively. . The modified LLEs 40-1a... 40-8a are no longer connected to the multiplexer 42 of the prior art, but are connected to MAC-SAPs 50-1a .. 50-8a, respectively. The modified LLEs 40-1a... 40-8a are still controlled by the LLC management entity 41.

User data packets, for example Internet Protocol (IP) data packets, are adapted to the services provided by the LLC layer 4a via sub-network dependent convergence protocol (SNDCP). The SNDCP transmits information of user data packets between network layer equivalent entities using network protocol data units (N-PDUs). Transmission of N-PDUs between network entities is provided by modified LLEs 40-2a .. 40-5a and available to the network layer via the LLC-SAPs 43-2 .. 43-5 QoS-dependent LLC connections are made. In the LLC layer 4a, N-PDUs are transmitted as LLC service data units (LLC-SDUs) that are part of LLC-PDUs (LLC frames). The LLC PDUs are transmitted between equivalent LLC entities of the MS 1 and SGSN 2, respectively, using connections provided by lower RLC layers. Once again, the LLC-PDUs are sent as LLC-SDUs as part of the RLC-PDUs.

Due to the omission of the prior art multiplexer 42, the LLC frames are no longer multiplexed, so that one RLC-SAP 50-1a .. 50-8a for each modified LLE 40-1a .. 40-8a. ) Exists. Frame checking and encryption, which was a task of the prior art multiplexer 42, is now performed by the modified LLEs 40-1a... 40-8a, that is, insertion of a frame check sequence and transmission of a frame during frame transmission. When the frame is received, the frame check sequence is decoded and checked.

Advantageously the modified RLC layer 5a now controls the flow of LLC frames corresponding to different QoS requirements of the respective N-PDUs. This is accomplished by operating an XOn / XOff protocol between the modified RLC layer 5a and the modified LLEs 40-1a .. 40-8a. Thus, the modified RLC layer 5a may thus transmit XOn ("send more LLC frames") or XOff ("send more LLC frames") to the modified LLEs 40-1a .. 40-8a. By sending messages, one can choose which modified LLE buffer to receive additional LLC frames from. The modified RLC layer 5a includes at least one buffer for buffering RLC frames to be passed to the MAC layer 8 for transmission on a physical propagation channel 9 and the physical transport channel 9 Has the means to assess the current state of The status of the physical transport channel 9, the QoS requirement of each LLC frame that can be polled separately from each of the buffers in each of the modified LLEs 40-1a. By recognizing the state, the modified RLC layer 5a can now adapt the transmission of LLC frames on the physical transport channel 9 to the QoS requirements of the LLC frames. If the channel is poor and the buffer starts to fill more and more, it is reasonable to stop transmitting LLC frames with low QoS requirements and focus on the transmission of LLC frames with high QoS requirements. Flow control of each of the LLC frames of this type is performed for both uplink and downlink. It helps to reduce the MCU load by reducing the number of service primitives needed for communication between the protocol entities. Moreover, buffer usage is reduced. Flow control of N-PDUs transmitted between network entities in MS 1 and SGSN 2 under the use of QoS-specific LLC connections is due to improved flow control between LLC 4a and RLC layer 5a. It is more granular and more adaptive to the state of the physical transmission link 9.

4 provides a more detailed view of a possible implementation of the RLC layer 5a of the GPRS protocol stack according to the present invention. Within the modified RLC layer 5a, RLC buffers 51-2a... 51-5a are provided for buffering RLC frames (including the LLC frames) to be passed to the MAC layer 8. In this example implementation, RLC buffers 51-2a... 51-5a in turn provide services to the SNDCP 7-3 via respective LLC-SAPs 43-2 .. 43-5. Is provided for each RLC-SAP 50-2a... 50-5a providing services to the respective modified LLEs 40-2a... 40-5a. The RLC buffers 51-2a... 51-5a are controlled by the flow control instance 52a. The flow control instance 52a activates an XOn / XOff protocol between the RLC buffers 51-2a... 51-5a and the respective modified LLEs 40-2a. The RLC layer 5a relies on knowledge of the state of the physical transport channel 9, which is provided to the flow control instance by the channel state instance 53a, to determine from which modified LLE to receive additional LLC frames. You can choose. The channel state instance 53a may determine the state of the physical transport channel by itself or may receive information about the state of the physical transport channel from upper or lower layers.

The present invention has been described above through only one of a number of possible embodiments. It should be noted that there are alternative methods and variations that will be apparent to those skilled in the art and may be implemented without departing from the scope and spirit of the appended claims, for example the present invention overcomes the bottleneck of the multiplexer in a multi-layer protocol stack. To other, non-essential wireless communication systems. Various types of flow control mechanisms between protocol layers of interest are possible. In particular, it is also possible to have hybrid systems in which separate flow control of both multiplexed bundles of LLC frames and non-multiplexed LLC frames is performed.

Claims (26)

A system for controlling the flows of a plurality of data units (DUs) over logical links, the system comprising: At least two first-type link control (LC) means 40-1a .. 40-8a, wherein each first-type LC means 40-1a .. 40-8a removes the first-type DU. Converts a 2-type DU and converts a 2-type DU to a first-type DU, a first interface 43-1 .. 43-8 and the second type DU for the first-type DUs; At least two first-type link control (LC) means 40-1a .. 40-8a providing a second interface to the devices; And A second-type LC means 5a having interfaces 50-1a... 50-8a to the second-type DUs, the first-type LC means 40-1a. Each second interface is directly connected to one respective interface 50-1a... 50-8a of the second-type LC means 5a, and the second-type LC means 5a is Means 52a for individually controlling the flows of each of the second-type DUs, which are transmitted via respective interfaces 50-1a... 50-8a of the second-type LC means. A system comprising two-type LC means (5a). 2. The apparatus of claim 1, wherein the first-type LC means 40-1a .. 40-8a convert the first-type DU into a second-type DU by performing at least a frame checking function and an encryption function. And convert the second-type DU into the first-type DU. The method according to claim 1 or 2, wherein the at least two first-type LC means (40-1a. 40-8a) are the respective first interfaces (43-1) of the first-type LC means. 43-8), distinguished by the characteristics of the first-type DUs transmitted through Means 52a for individually controlling the respective flows of the second-type DUs, which are transmitted through respective interfaces 50-1a... 50-8a of the second-type LC means 5a. Is considered in consideration of characteristics of the first-type DUs in which the second-type DUs are converted into the first-type DUs or the second-type DUs are converted from the first-type DUs. System for controlling the flows of each of the type DUs. 4. The method of claim 3, wherein the second-type LC means 5a buffers the second-type DUs transmitted over respective interfaces 50-1a .. 50-8a of the second-type LC means. At least one data unit (DU) buffer (51-2a... 5. A means according to claim 4, for individually controlling the flows of each of said second-type DUs, which are transmitted via respective interfaces 50-1a .. 50-8a of said second-type LC means. 52a indicates the characteristics and characteristics of the first-type DUs in which the second-type DUs are converted into the first-type DUs or the second-type DUs are converted from the first-type DUs; Controlling the flows of each of the second-type DUs in consideration of the state of one data unit (DU) buffer (51-2a ... 51-5a). 4. System according to claim 3, characterized in that the second-type LC means 5a comprises means 53a for evaluating the state of the physical transport link 9 over which the second-type DUs are transmitted. . The control of claim 6 individually controlling flows of the second-type DUs, which are transmitted via respective interfaces 50-1a... 50-8a of the second-type LC means 5a. Means 52a for converting the characteristics of the first-type DUs in which the second-type DUs are converted into the first-type DUs or the second-type DUs are converted from the first-type DUs. And control respective flows of the second-type DUs in consideration of the state of the physical transmission link (9) in which the second-type DUs are transmitted. The second-type DU according to any one of claims 1 to 7, which is transmitted via respective interfaces 50-1a .. 50-8a of the second-type LC means 5a. Means (52a) for individually controlling the respective flows of the apparatus comprises means for operating a flow control protocol. 9. The system of claim 8, wherein the flow control protocol is an XOn / XOff flow control protocol. 10. The system of any of claims 3-9, wherein the characteristics are quality of service (QoS) requirements of the first-type DUs. 11. The system according to any one of the preceding claims, further comprising link management means (41) for controlling said first-type LC means (40-1a .. 40-8a). 12. The Serving GPRS Support Node (SGSN) of any one of claims 3 to 11, wherein the logical links operate according to a General Packet Radio Service (GPRS) standard or a derivative service of the General Packet Radio Service. (2) and logical links between the mobile station (MS) 1, wherein the first-type LC means 40-1a .. 40-8a are GPRS logical link controls with additional sequence-based frame checking and encryption functions. Logical link control (LLC) entities of a (LLC) protocol, and the first interfaces 43-1... 43-8 are service access points () of the LLC entities 40-1a. LLC-SAPs), the second-type DUs are LLC frames, and the interfaces 50-1a... 50-8a of the second-type LC means are radio link control (RLC) -SAPs, 1-type DUs are N-PDUs of the GPRS network layer protocol 7 and the second-type LC means 5a is the GPRS RLC Pro. Means 52a for implementing the functionality of a call and individually controlling respective flows of the LLC frames, which are transmitted over the respective RLC-SAPs 50-1a... 50-8a. System characterized. An apparatus for controlling flows of a plurality of data units (DUs) over logical links of a communication system, the apparatus comprising: At least two first-type link control (LC) means 40-1a .. 40-8a, wherein each first-type LC means 40-1a .. 40-8a removes the first-type DU. Converts a 2-type DU and converts a 2-type DU to a first-type DU, a first interface 43-1 .. 43-8 and the second type DU for the first-type DUs; At least two first-type link control (LC) means 40-1a .. 40-8a providing a second interface to the devices; And A second-type LC means 5a having interfaces 50-1a... 50-8a to the second-type DUs, the first-type LC means 40-1a. Each second interface is directly connected to one respective interface 50-1a... 50-8a of the second-type LC means 5a, and the second-type LC means 5a is Means 52a for individually controlling the flows of each of the second-type DUs, which are transmitted via respective interfaces 50-1a... 50-8a of the second-type LC means. Apparatus characterized in that it comprises a two-type LC means (5a). A method for controlling flows of a plurality of data units (DUs) over logical links, the method comprising: The first-type data units (through the first interfaces 43-1 .. 43-8) of at least two first-type link control (LC) means 40-1a .. 40-8a. Transmitting DUs); Converting the first-type DUs into second-type DUs and converting the second-type DUs into the first-type DUs in the respective first-type LC means 40-1a. Converting to; Transmitting the second-type DUs over respective second interfaces of the first-type LC means 40-1a... 40-8a; Transmitting the second-type DUs through the respective interfaces 50-1a... 50-8a of the second-type LC means 5a, wherein the first-type LC means 40-1a. 40-8a) each second interface directly connected to one respective interface 50-1a... 50-8a of the second-type LC means 5a; And Individually controlling respective flows of the second-type DUs, which are transmitted through respective interfaces 50-1a... 50-8a of the second-type LC means 5a. How to feature. 15. The method of claim 14, wherein converting the first-type DUs into second-type DUs and converting the second-type DUs into the first-type DUs comprises at least a frame check function and an encryption function. Characterized in that. The method according to claim 14 or 15, At least two first-type LC means 40-1a.. 40-8a may be distinguished by the characteristics of the first-type DUs conveyed through respective first interfaces of the first-type LC means. Can, Individually controlling the respective flows of the second-type DUs through the respective interfaces 50-1a... 50-8a, the second-type DUs to the first-type DUs. Characteristics of the first-type DUs converted or the second-type DUs are converted from the first-type DUs are taken into account. 17. The apparatus according to claim 16, wherein the second-type DUs transmitted over respective interfaces 50-1a .. 50-8a of the second-type LC means 5a are buffered at least one data unit. Buffering at (51-2a .. 51-5a). 18. The method of claim 17, wherein in the step of individually controlling respective flows of the second-type DUs through the respective interfaces 50-1a .. 50-8a, The at least one data unit (DU) buffer 51-2a and the characteristics of the first-type DUs converted into 1-type DUs or the second-type DUs are converted from the first-type DUs. 51-5a) the condition of which is taken into account. 17. The method according to claim 16, further comprising evaluating the state of the physical transport link (9) in which the second-type DUs are transmitted. 20. The method of claim 19, wherein in the step of individually controlling respective flows of the second-type DUs through the respective interfaces 50-1a. The characteristics of the first-type DUs converted into 1-type DUs or the second-type DUs are converted from the first-type DUs and the state of the evaluated transmission link 9 are taken into account. How to. 21. The method according to any one of claims 14 to 20, wherein individually controlling the respective flows of the second-type DUs through the respective interfaces 50-1a .. 50-8a is flow control. And the steps necessary for operating the protocol. 22. The method of claim 21 wherein the flow control protocol is an XOn / XOff flow control protocol. 23. The method of any of claims 16-22, wherein the characteristics are quality of service (QoS) requirements of the first-type DUs. 24. The method according to any one of claims 14 to 23, further comprising the step of controlling the first-type LC means 40-1a .. 40-8a by the link management means 41. How to. 25. The Serving GPRS Support Node (SGSN) of any of claims 16-24, wherein the logical links operate according to a General Packet Radio Service (GPRS) standard or a derivative service of the General Packet Radio Service. (2) and logical links between the mobile station (MS) 1, wherein the first-type LC means 40-1a .. 40-8a are GPRS logical link controls with additional sequence-based frame checking and encryption functions. Logical link control (LLC) entities of a (LLC) protocol, and the first interfaces 43-1... 43-8 are service access points () of the LLC entities 40-1a. LLC-SAPs), the second-type DUs are LLC frames, and the interfaces 50-1a... 50-8a of the second-type LC means are radio link control (RLC) -SAPs, 1-type DUs are N-PDUs of the GPRS network layer protocol 7 and the second-type LC means 5a is the GPRS RLC Pro. The RLC-SAPs 50-1a implement the functionality of a protocol and take into account the characteristics of the N-PDUs in which the LLC frames are converted to the N-PDUs or the LLC frames are converted from the N-PDUs. 50-8a) further controlling the respective flows of the LLC frames, which are transmitted on at least two RLC-SAPs. A computer program product loadable directly into an internal memory of a digital computer, comprising: software code portions for performing the method steps of any one of claims 14 to 25 when the computer program product is executed on a computer. Computer program product.

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