KR19990084387A - Error Correction Method for Asynchronous Transmission Mode Cell in Asynchronous Transmission Mode Wireless Network - Google Patents

Abstract

The present invention discloses an error correction method for an ATM cell in an asynchronous transmission mode (ATM) wireless communication network including at least a mobile station and a base station forming a radio link. The traffic attribute determination unit of the base station determines the traffic attribute of the ATM cell transmitted from the mobile station during call setup with the mobile station and determines the priority of the traffic using the determined result. When the priority of the traffic is determined, the error correction unit performs an error correction operation according to a forward error control (FEC) function or an automatic repeat request (ARQ) function for the transmitted ATM cell according to the determined priority. The present invention can correct burst errors caused by an increase in the bit error rate (BER) in a wireless environment with a large amount of noise such as fading and propagation delay. Can be solved.

Description

Error Correction Method for Asynchronous Transmission Mode Cell in Asynchronous Transmission Mode Wireless Network

The present invention relates to an asynchronous transmission mode wireless communication network, and more particularly, to an error correction method for an asynchronous transmission mode cell transmitted in a wireless environment.

Early communication systems provided only voice to subscribers. However, as technology advances, communication systems are being developed to provide more services to subscribers. That is, today's communication systems are developing not only voice but also multimedia services such as data and video.

A method of connecting a wireless personal communication network and a broadband communication network based on optical transmission such as Broadband Integrated Services Digital Network (B-ISDN) or Asynchronous Transfer Mode (ATM) for such a multimedia service. This is being studied. For example, US Patent No. 5,638,371, entitled "MULTISERVICES MEDIUM ACCESS CONTROL PROTOCOL FOR WIRELESS ATM SYSTEM", registered June 10, 1997, illustrates an example of a wireless personal network connected to an ATM network. That is, the patent discloses a concept of a communication network in which wired and wireless links are integrated. As such, the future personal communication network will be developed in the form of integrated wired and wireless links to provide broadband multimedia services, and ATM transmission technology will be used for effective service provision.

On the other hand, when transmitting an ATM cell in a wireless environment, unlike in a wired environment, a bit error rate due to fading, jamming, multi-path, channel encoding and decoding should be considered. In case of transmitting ATM cell in wired environment, error correction is not considered. However, since compressed data is transmitted as well as voice, these data should not cause errors. Therefore, Forward Error Control (FEC) is adopted as an option. Here, the FEC function means a HEC (Header Error Control) function in the ATM cell header.

However, since only one bit error can be corrected by the HEC function, in a wireless environment where noise such as fading and propagation delay are large, correction of burst error due to an increase in a bit error rate (BER) This is impossible. If burst errors cannot be corrected, the ATM cell discard rate on the radio link will be much larger than that of wired links with random errors. As such, when transmitting an ATM cell in a wireless environment such as an ATM wireless communication network, a function of burst error correction is additionally required. This request is due to the fact that in the case of error correction for an ATM cell in a wireless environment, it is necessary to correct voice and data separately in the case of error correction for an ATM cell in a wired environment. Therefore, since the HEC function, which is an error correction method used when transmitting ATM cells in a wired environment, cannot be applied to a wireless environment as it is, it is required to implement an error correction method that can replace the HEC function.

Accordingly, an object of the present invention is to provide an error correction method suitable for ATM cells transmitted in a wireless environment.

Another object of the present invention is to provide a method for correcting a burst error occurring when an ATM cell is transmitted in a wireless environment.

Another object of the present invention is to provide a method for minimizing ATM cell discard rate in a radio link.

The present invention for achieving these objects discloses an error correction method for an ATM cell in an ATM wireless communication network including at least a mobile station and a base station forming a radio link. The traffic attribute determination unit of the base station determines the traffic attribute of the ATM cell transmitted from the mobile station during call setup with the mobile station and determines the priority of the traffic using the determined result. When the priority of the traffic is determined, the error correction unit performs an error correction operation according to a forward error control (FEC) function or an automatic repeat request (ARQ) function for the transmitted ATM cell according to the determined priority.

The present invention can correct burst errors caused by an increase in the bit error rate (BER) in a wireless environment with a large amount of noise such as fading and propagation delay. Can be solved.

1 is a view showing a connection configuration of a general asynchronous transmission mode wireless communication network.

2 is a view showing a configuration according to the present invention of the base station shown in FIG.

3 is a format diagram of an asynchronous transmission mode (ATM) traffic indexer transmitted and received between a base station and a mobile station in an asynchronous transmission mode wireless communication network.

4 is a diagram showing a processing flow of an error correction operation performed by the error correction unit shown in FIG.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. The terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of the user or chip designer, and the definitions should be made based on the contents throughout the present specification.

1 is a view showing a connection configuration of a wireless ATM network (WIRELESS ATM COMMUNICATION NETWORK) to which the present invention is applied, this configuration is shown in FIG. The configuration is the same as the network configuration shown in FIG. This ATM wireless communication network consists of a wireless ATM network consisting of a mobile station (MS) 10 and a base station (BS) 20, a base station 20, an ATM switch (SWITCH) 30, and an ATM network (NETWORK). It consists of a fixed ATM network consisting of 40. At this time, each component supports a hierarchical structure for operating a broadband multimedia service.

Referring to FIG. 1, the mobile station 10 includes a user application layer (USER APPLICATION LAYER), an asynchronous transmission mode adaptation layer (AAL: ATM ADAPTATION LAYER), an asynchronous transmission mode layer (ATM LAYER), a physical layer (PHY: PHYSICAL LAYER), wireless RALO ACCESS LAYER (RAL) protocol is supported. The base station 20 supports protocols of the ATM layer, the RAL layer, and the PHY layer. ATM switch 30 supports the ATM layer and PHY layer protocols. ATM network 40 supports protocols of user application layer, ATM adaptation layer, ATM layer, and PHY layer. The base station 20 is wirelessly connected to the mobile station 10 through the RAL layer protocol, and is also connected to the ATM switch 30 through the PHY layer protocol. The ATM switch 30 is connected to the base station 20 and the ATM network 40 through the PHY layer protocol.

In FIG. 1, the base station 20 includes an antenna ANT, a network interface unit (NIU) 21, a resource allocation unit 22, a WATM / ATM header conversion unit 23, an ATM signal & mobile unit, as shown in FIG. (Signalling & Mobility) 24, traffic attribute determination unit 25, error correction 26, ATM network interface 27 and interconnection network (Interconnection Network) 28. Here, antenna ANT, WATM NIU 21, WATM resource allocation unit 22, WATM / ATM header conversion unit 23, ATM signal & mobile unit 24, ATM network interface 27 and interconnection network 28 are general components as disclosed in the above-mentioned US patent. admit. Therefore, detailed description of each component will be omitted here. However, the base station 20 further includes a traffic attribute determination unit 25 and an error correction unit 26 for the operation of error correction according to the present invention.

The present invention provides a parameter for the quality of service and the traffic exchanged between them in a call set-up between a mobile station 10 and a base station 20 in an ATM wireless communication network configured as described above. Determining the attribute of the traffic by using and performs error correction suitable for the determined traffic. Here, determining the nature of the traffic is to determine whether the priority of the loss and delay of the ATM cell is high (HIGH PRIORITY) or low (LOW PRIORITY). The nature of this traffic is determined differently depending on whether the ATM cell being transmitted is voice, data or video.

3 is a diagram illustrating the format of ATM traffic descriptor information exchanged between a mobile station 10 and a base station 20 when a call is set up in an ATM wireless communication network. The base station 20 uses the classifier to determine the attributes of an ATM cell. Done. The ITU-T Recommendation I.411 defines the User Network Interface (UN) signaling, which specifies the format of the ATM traffic classifier information as described above.

Referring to FIG. 3, each element of ATM traffic classifier information is structured based on 8 bits (Bits), and includes header information having a size of 1 octets to 4 octets. ATM traffic classifier information includes not only the header information but also various parameters that enable the determination of traffic attributes. The 5 octets of ATM traffic classifier information include the Forward Peak Cell Rate (CLP = 0) parameter, and the 6 octets contain the Forward Peak Cell Rate (CLP = 0) parameter, and 7 octets. Includes a Forward Peak Cell Rate (CLP = 0 + 1) parameter, and an 8 octet includes a Backward Peak Cell Rate (CLP = 0 + 1) parameter. The 9 octets contain the Forward Sustainable Cell Rate (CLP = 0) parameter, the 10 octets contain the Forward Sustainable Cell Rate (CLP = 0) parameter, and the 11 octets contain the Forward Sustainable Cell Rate (CLP = 0) parameter. The Sustainable Cell Rate (CLP = 0 + 1) parameter is included, and the 12 octet includes the Backward Sustainable Cell Rate (CLP = 0 + 1) parameter. The 13 octets contain the Forward Maximum Burst Size (CLP = 0) parameter, the 14 octets contain the Forward Maximum Burst Size (CLP = 0) parameter, and the 15 octets contain the forward maximum burst size (CLP = 0) parameter. The Forward Maximum Burst Size (CLP = 0 + 1) parameter is included, and the 16 octets contain the Backward Maximum Burst Size (CLP = 0 + 1) parameter. The 17 octets contain the Best Effort Indicator parameter, the 18 octets contain the Traffic Management Options Identifier parameter, and the 18.1 octets are reserved. The last two bits of the 18.1 octets include a tagging backward parameter and a tagging forward parameter.

In FIG. 3, forward indicates a direction from a calling user to a called user, and backward indicates a direction from a called user to a calling user.

As described above, during the call setup in the ATM wireless communication network, the ATM traffic classifier information structured as shown in FIG. 3 is exchanged between the mobile station 10 and the base station 20. The base station 20 first receives an ATM cell from the mobile station 10 on the CAI (Common Air Interface) (step S41 of FIG. 4). Since the received ATM cell includes ATM traffic classifier information structured as shown in FIG. 3, the base station 20 determines the attributes of the ATM cell using the ATM traffic classifier information included in step S42. ). In this case, when it is determined that both the loss priority and the delay priority are high, the base station 20 determines that the traffic attribute is "1". If it is determined that the loss priority is high and the delay priority is low, the base station 20 determines that the traffic attribute is "2". The base station 20 determines that the traffic attribute is "3" when it is determined that the loss priority is low and the delay priority is high. If it is determined that both the loss priority and the delay priority are low, the base station 20 determines that the traffic attribute is "4" (step S42).

After determining the traffic attribute of the ATM cell transmitted from the mobile station 10, the base station 20 performs an error correction operation using the determination result (step S43). When it is determined that the traffic attribute is "1", the base station 20 performs error correction on the ATM cell according to the Forward Error Control (FEC) function, and also the automatic repeat request (ARQ) function. Correct the error accordingly. When it is determined that the traffic attribute is "2", the base station 20 performs error correction on the ATM cell according to the ARQ function. When it is determined that the traffic attribute is "3", the base station 20 performs error correction on this ATM cell according to the FEC function. When it is determined that the traffic attribute is "4", the base station 20 does not perform any error correction on this ATM cell.

As described above, the error correction is performed differently according to the result of the determination of the traffic attribute to perform the optimal error correction for the currently transmitted ATM cell. This error correction is performed for ATM cells transmitted in a wireless environment. When a voice ATM cell is transmitted, error correction is performed according to the same method as that performed for a wired environment ATM cell, that is, FEC function. In contrast, when data ATM cells are transmitted, error correction is performed differently from voice ATM cells. In addition to the FEC function, the error correction operation according to the ARQ function is further added to perform the error correction operation. At this time, although there are various types of ARQ functions, it is preferable to adopt and use a selective repeat ARQ function having the best throughput.

For reference, error correction using the FEC function has the advantage of reducing the transmission delay time, eliminating the need to copy the transmission packet at the receiving side, and performing the operation only by hardware. However, there is a disadvantage that an extra bandwidth must be used for error correction operation using the FEC function even without an error. On the other hand, error correction using the ARQ function has a disadvantage of lengthening the transmission delay time.

Therefore, the present invention focuses on the fact that the error correction according to the FEC function and the error correction according to the ARQ function have the above advantages and disadvantages, and the loss priority and the delay priority are high (the traffic attribute is "1"). Case) performs both error correction operations according to the FEC and ARQ functions. On the other hand, when the loss priority is high and the delay priority is low (when the property of the traffic is "2"), error correction is performed using the ARQ function, and when the loss priority is low and the delay priority is high (the property of the traffic). If "3"), error correction is performed using the FEC function. If the loss priority and the delay priority are low, no error correction is performed.

As described above, the present invention determines the traffic attribute of the ATM cell transmitted in the wireless environment and performs error correction according to the determination result. This operation, unlike error correction for ATM cells transmitted in a wired environment, performs optimal error correction according to traffic characteristics. Therefore, there is an advantage that the burst error caused by the increase of the bit error rate (BER) can be corrected in a wireless environment in which noise such as fading and propagation delay are large. In addition, since the burst error can be corrected, there is an advantage to solve the disadvantage that the ATM cell discard rate in the wireless link is significantly larger than the wire link.

Claims (4)

An error correction method for an ATM cell in an asynchronous transmission mode (ATM) wireless communication network including at least a mobile station and a base station forming a radio link, the method comprising: A decision process of determining the traffic attribute of an ATM cell transmitted from the mobile station upon call setup of the mobile station and the base station, and determining the priority of the traffic using the determined result; And an error correction process for performing error correction on the transmitted ATM cell according to the determined priority. The method of claim 1, wherein the determining process, A first step of determining a loss priority and a delay priority of traffic by using a traffic indexer included in an ATM cell transmitted from the mobile station during call setup of the mobile station and the base station; And a second step of determining the priority of the traffic according to the loss priority and the delay priority of the traffic determined in the first step. 3. The method of claim 2, wherein the priority of the traffic determined in the second step is a case in which both a loss priority and a delay priority are high as the first priority, and a case in which the loss priority is low and the delay priority is high. 3. The error correction method of claim 1, wherein the loss priority is high and the delay priority is low as the third priority, and when the loss priority and the delay priority are both low, the fourth priority is determined. The method of claim 3, wherein the error correction process comprises: The first priority ATM cell performs error correction according to an automatic repeat request (ARQ) function along with error correction according to a forward error control (FEC) function, An error correction operation according to the automatic repeat request function is performed on the ATM cell of the second priority; An error correction operation according to the forward error control function is performed on the third priority ATM cell; And an error correction operation is not performed on the fourth priority ATM cell.