KR20090032219A - Apparatus and methode for allcating uplink resource in broadband wireless communication system - Google Patents

Abstract

An apparatus and a method for allocating uplink wireless resources in a broadband wireless communication system are provided to automatically allocate an uplink wireless resource, thereby reducing a transmission delay time and increase a transmission rate. A classifier(302) checks a downlink packet of a bidirectional class received from a upper level. A downlink scheduler(306) performs downlink scheduling about the downlink packet. And the downlink scheduler determines whether to perform uplink scheduling corresponding to the downlink packet A communication unit(320) transmits the downlink packet to a terminal.

Description

Device and method for allocating uplink radio resource in broadband wireless communication system {APPARATUS AND METHODE FOR ALLCATING UPLINK RESOURCE IN BROADBAND WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a broadband wireless communication system, and more particularly, to an apparatus and method for allocating uplink radio resources in a broadband wireless communication system.

The 4th Generation (hereinafter referred to as '4G') communication system provides users with services of various quality of service (QoS) using a transmission rate of about 100 Mbps. There is active research going on. Particularly, in 4G communication systems, studies are being actively conducted to support high-speed services in a form of guaranteeing mobility and QoS in a broadband wireless access (BWA) communication system such as a wireless local area network system and a wireless urban area network system. Is going on. In addition, the representative communication system is the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.

According to the IEEE 802.16 standard, there are UGS, rtPS, ertPS, nrtPS, BE, and the like as an uplink radio resource allocation method. Uplink radio resource allocation is performed by scheduling of the base station, and the base station allocates the uplink radio resource according to the information promised when receiving a request from the terminal or establishing a call. The method of requesting uplink radio resource allocation by the terminal includes a code ranging method and a piggyback method.

Referring to FIG. 3, the code ranging method is as follows.

The terminal transmits a bandwidth request ranging code using a code division multiple access (CDMA) code to the base station (step 101). Accordingly, the base station transmits to the terminal using an information element (IE) named 'CDMA_Alloc_IE'. Allocating a small amount of resources that can make a bandwidth request (step 103). Upon receiving the 'CDMA_Alloc_IE', the UE requests a required band (step 105). The base station allocates an uplink radio resource according to the request of the terminal and transmits a resource allocation message informing of this (step 107). In operation 109, the terminal transmits uplink data through the allocated uplink radio resource.

Looking at the piggyback method with reference to Figure 4 as follows.

In step 201, the base station to which the uplink radio resource is allocated is transmitted to the terminal through the procedure as shown in FIG. Accordingly, the terminal transmits the uplink data and the piggyback band request message through the allocated uplink radio resource (step 203). Upon receiving the piggyback band request message, the base station allocates an uplink radio resource again according to the piggyback band request, and transmits a resource allocation message indicating the uplink radio resource (step 205). Subsequently, the terminal transmits uplink data through the allocated uplink radio resource (step 207). As such, in the case of the piggyback scheme, the terminal may be allocated an uplink radio resource within a short time without performing code ranging.

Among the listed uplink radio resource allocation schemes, the BE scheme is a representative scheme for performing uplink radio resource allocation by the request. The BE service includes a Transmission Control Protocol (TCP), and more than 90% of Internet traffic is included in the TCP. Looking at one of the characteristics of the TCP, when the TCP segment (segment) is delivered, the ACK (ACKnowledgement) message indicating whether the reception is successful in the reverse direction is delivered. When the ACK message is delivered, the next segment of the TCP window is transmitted in the reverse direction. In other words, traffic by TCP is bidirectional. Accordingly, the terminal receiving the TCP segment should transmit an ACK message to the base station. In addition, the terminal receiving the ACK message should transmit the next TCP segment to the base station. However, due to the allocation of uplink radio resources according to the above-described procedure, an uplink transmission delay of an ACK message or a TCP segment occurs every time. Therefore, a problem occurs that the throughput of a service using TCP is reduced.

The terminal may select and use a bandwidth request and a piggyback band request using a ranging code according to the presence of uplink radio resources. However, since the bandwidth request using the ranging code has more procedures than the piggyback band request, there is a problem that more transmission delay occurs. Since bidirectional traffic such as TCP always requires uplink data transmission within a predetermined time after downlink data transmission, it is possible to design a piggyback band request at all times. However, in the current IEEE 802.16 standard, the uplink traffic and the downlink traffic are scheduled completely independently, and the correlation between the two is not considered.

Accordingly, an object of the present invention is to provide an apparatus and method for improving a transmission rate of a Transmission Control Protocol (TCP) service in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for reducing time consumption due to an uplink radio resource allocation procedure in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for automatically allocating uplink radio resources according to characteristics of downlink data in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for automatically allocating an uplink radio resource for a service belonging to a specific class in a broadband wireless communication system.

According to a first aspect of the present invention for achieving the above object, a base station apparatus in a broadband wireless communication system, a classifier for identifying a downlink packet of the bidirectional class received from the upper end, and downlink scheduling for the downlink packet And a downlink scheduler for determining whether to perform uplink scheduling corresponding to the downlink packet, and a communication unit for transmitting the downlink packet to a terminal.

According to a second aspect of the present invention for achieving the above object, a method of operating a base station in a broadband wireless communication system includes the steps of identifying a downlink packet of a bidirectional class received from an upper end, and downlinking the downlink packet The method includes performing a link scheduling, determining whether to perform uplink scheduling corresponding to the downlink packet, and transmitting the downlink packet to a terminal.

In a broadband wireless communication system, by automatically allocating an uplink radio resource for a bidirectional service that requires an immediate response to data transmission, such as Transmission Control Protocol (TCP), it is possible to reduce a transmission delay time and increase a transmission rate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, a description will be given of a technique for automatically allocating uplink radio resources according to characteristics of downlink data in a broadband wireless communication system. The present invention is described by taking an orthogonal frequency division multiplexing (hereinafter referred to as "OFDM") wireless communication system as an example, and may be equally applicable to other wireless communication systems.

The present invention, such as TCP (Transmission Control Protocol), uplink for traffic requiring uplink ACK (ACKnowledgement) message response to the downlink data or traffic required for uplink data transmission according to the downlink ACK message, To allocate radio resources quickly. To this end, the base station should determine which of the downlink packets provided from the upper end is traffic having the characteristics described above. The present invention defines a class for traffic having the characteristics described above for packet division. The class is a delimiter for applying a scheduling policy according to the characteristics of a service. In the IEEE (Institute of Electrical and Electronics Engineers) 802.16 communication system, there are classes such as UGS, rtPS, ertPS, nrtPS, and BE. For convenience of explanation below, the newly defined class is referred to as a "bidirectional class".

The class is classified using the information included in the packet header. That is, the base station can check the type of the information included in the header of the packet provided from the upper end, and check the class mapping information according to the type of the information to know the class of the packet. Accordingly, the base station according to the present invention classifies packets having a bidirectional class and allocates uplink radio resources to the classified packets without request of the terminal. Details of an uplink radio resource allocation procedure of the base station will be described with reference to the accompanying drawings.

3 is a block diagram of a base station in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the base station includes a packet classifier 302, a log recording unit 304, a downlink scheduler 306, an uplink scheduler 308, a packet buffer 310, and a message. A generator 312, an encoder and modulator 314, a subcarrier mapper 316, an OFDM modulator 318, and a radio frequency (RF) transmitter 320 are included.

The packet classifier 302 classifies packets received from the upper end to the base station by class. That is, the packet classifier 302 checks the class of the packet through the header of the received packets. In particular, according to the present invention, the packet classifier identifies the bidirectional class packets and provides them to the DL scheduler 306.

The log recording unit 304 stores a downlink transmission history for packets of a bidirectional class according to the present invention. That is, the log recorder 304 receives the downlink scheduling result for the packet of the bidirectional class from the DL scheduler 306 and stores the last downlink packet transmission time information for each terminal. In addition, the log recorder 304 stores minimum resource amount information and automatic time allocation information for automatic uplink radio resource allocation for uplink radio resource allocation for downlink packets of a bidirectional class. The information of the bidirectional class stored in the log recording unit 304 is called a scheduling parameter, which is summarized in Table 1 below.

 Parameter name  meaning   T   Minimum time difference between previous downlink packet transmission time and current downlink packet transmission time to enable automatic uplink radio resource allocation.  F   Frame interval of uplink radio resources that are automatically allocated after downlink packet transmission.  X   Minimum allocation size for automatic uplink radio resource allocation.

The DL scheduler 306 performs scheduling for downlink packets. In other words, the DL scheduler 306 determines which radio resource of which frame to transmit the downlink packet to the terminal. In addition, according to the present invention, when scheduling the downlink packet of the bidirectional class, the DL scheduler 306 checks scheduling parameters of the bidirectional class stored in the log recorder 304, and checks the downlink packet of the bidirectional class. It is determined whether a corresponding uplink scheduling should be performed. Here, the downlink packet of the bidirectional class includes a data or ACK message. In detail, the DL scheduler 306 calculates a time difference between a previous downlink transmission time to a corresponding UE and a current downlink transmission time due to the scheduling after performing scheduling of the downlink packet of the bidirectional class. do. The DL scheduler 306 checks 'T' among the parameters shown in Table 1 and checks whether the time difference is greater than the 'T'. If the time difference is greater than 'T', the DL scheduler 306 determines automatic uplink scheduling and provides scheduling parameters 'F', 'X' and information of the corresponding UE to the UL scheduler 308. .

The UL scheduler 308 transmits scheduling for uplink transmission of the terminal according to the request or class characteristics of the terminal. In particular, according to the present invention, when the scheduling parameters 'F', 'X' and information of the corresponding UE are provided from the DL scheduler 306, the UL scheduler 308 may store X bytes of resources of the frame after the F frame. bytes) size of the uplink radio resource is allocated to the corresponding terminal.

The packet buffer 310 stores the packet to be transmitted and outputs the packet to the encoder and modulator 314 according to the scheduling result of the DL scheduler 306. The message generator 312 generates a control message to be sent. For example, the message generator 312 generates a map (MAP) message including the scheduling result information provided from the DL scheduler 306 and the UL scheduler 308 to the encoder and modulator 314. Output

The encoder and modulator 314 encodes a bit string provided from the packet buffer 310 and the message generator 312 according to a corresponding coding scheme, and then modulates the complex sequence according to the corresponding modulation scheme. Convert to The subcarrier mapper 316 maps the complex symbols provided from the encoder and the modulator 314 to corresponding frequency resources. The OFDM modulator 318 converts the complex symbols mapped to the frequency resource into a time domain OFDM symbol through an inverse fast fourier transform (IFFT) operation, and inserts a cyclic prefix (CP). The RF transmitter 320 converts the OFDM symbols provided from the OFDM modulator 318 into analog and upconverted RF signals into RF band analog signals and transmits them through an antenna.

4 is a flowchart illustrating an operation procedure of a base station in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the base station determines whether a downlink packet of a bidirectional class is received from an upper end in step 401. That is, the base station checks the header of the packets received from the upper end, and determines whether the class of the received packet is a bidirectional class. Here, the downlink packet of the bidirectional class includes a data or ACK message.

When the downlink packet of the bidirectional class is received, the base station determines the scheduling parameters of the bidirectional class in step 403. The scheduling parameters are shown in Table 1 below.

In step 405, the base station performs downlink scheduling on the downlink packet received in step 401. In other words, the base station determines which radio resource of which frame to transmit the downlink packet to the terminal.

After performing the downlink scheduling, the base station proceeds to step 407 to calculate a time difference between the previous downlink transmission time to the terminal and the current downlink transmission time due to the scheduling of step 405. The previous downlink transmission time is confirmed through stored downlink transmission log information of the terminal.

After calculating the time difference, the base station proceeds to step 409 and checks whether the time difference is greater than the parameter 'T' identified in step 403. That is, the base station determines whether the terminal has an available uplink radio resource. If the time difference is less than or equal to 'T', the base station proceeds to step 413.

On the other hand, if the time difference is greater than 'T', the base station proceeds to step 411 and allocates uplink radio resources of size X bytes of the resources of the frame after the F frame to the terminal. In this case, when the downlink map (MAP) message indicates a resource of a frame after the F frame, step 411 is a resource allocation operation. If not, step 411 is an operation of determining whether to allocate resources in the future, not actual resource allocation.

In step 413, the base station transmits the downlink packet received in step 401 to the terminal. In other words, the base station performs coding, modulation, frequency mapping, OFDM modulation, CP insertion, analog conversion, RF conversion, and the like on the downlink packet, and then transmits the data through an antenna. In this case, the base station also transmits a map message including downlink and uplink scheduling information.

5 compares the performance of the present invention with the prior art. 5 illustrates a transfer rate according to a time change when using a FTP (File Transfer Protocol) download service. FIG. 5 (a) shows a case of allocating an uplink radio resource according to the prior art, and FIG. 5 (b) shows a case of allocating an uplink radio resource according to the present invention.

As shown in FIG. 5A, when the conventional technology is used, it may be confirmed that the data rate is not uniform and fluctuates. This is because an additional transmission delay occurs while requesting uplink radio resource allocation. On the contrary, as shown in (b) of FIG. 5, when the present invention is used, the variation of the transmission rate is relatively insignificant, and the overall transmission rate is also high.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a diagram illustrating an example of signal exchange when allocating uplink radio resources using a code ranging method in a general broadband wireless communication system;

FIG. 2 is a diagram illustrating an example of signal exchange when assigning a piggybacked uplink radio resource in a general broadband wireless communication system; FIG.

3 is a block diagram of a base station in a broadband wireless communication system according to an embodiment of the present invention;

4 is a flowchart illustrating an operation procedure of a base station in a broadband wireless communication system according to an embodiment of the present invention;

5 is a diagram comparing the performance of the present invention and the prior art.

Claims (19)

A base station apparatus in a broadband wireless communication system, A classifier for identifying a downlink packet of a bidirectional class received from an upper end; A downlink scheduler for performing downlink scheduling on the downlink packet and determining whether to perform uplink scheduling corresponding to the downlink packet; Apparatus comprising a communication unit for transmitting the downlink packet to the terminal. The method of claim 1, And the classifier identifies the downlink packet of the bidirectional class based on the type of information included in the header of the downlink packet received from the upper end. The method of claim 1, The downlink packet comprises a data or ACK (ACKnowledgement) message. The method of claim 1, The bidirectional class is an apparatus for distinguishing traffic requiring uplink data transmission for a downlink ACK message response or downlink ACK message for downlink data. The method of claim 1, The downlink scheduler calculates a time difference between the last downlink packet transmission time to the terminal and the downlink packet transmission time due to the downlink scheduling, and performs the uplink scheduling when the time difference is greater than a threshold. Device for determining what to do. The method of claim 1, The apparatus may further include an uplink scheduler for performing uplink scheduling corresponding to the downlink packet according to the determination of the downlink scheduler. The method of claim 6, And the uplink scheduler performs uplink scheduling according to a scheduling parameter of the bidirectional class. The method of claim 7, wherein The scheduling parameter may include at least one of a frame interval of an uplink radio resource automatically allocated after downlink packet transmission and a minimum allocation size for automatic uplink radio resource allocation. The method of claim 7, wherein And a storage unit for storing the scheduling parameter. The method of claim 1, The communication unit, An encoder and a modulator for encoding the bit string of the downlink packet according to a corresponding coding scheme, and then modulating the bit string of the downlink packet into complex symbols; A mapper for mapping the complex symbols provided from the encoder and the modulator to corresponding frequency resources; An OFDM modulator for converting complex symbols mapped to the frequency resource into an orthogonal frequency division multiplexing (OFDM) symbol through an inverse fast fourier transform (IFFT) operation, and inserting a cyclic prefix (CP); And a transmitter for analog-converting and up-converting the OFDM symbol provided from the OFDM modulator to convert the RF symbol into an RF band analog signal and transmitting the same through an antenna. A method of operating a base station in a broadband wireless communication system, Checking a downlink packet of a bidirectional class received from an upper end; Performing downlink scheduling on the downlink packet; Determining whether uplink scheduling corresponding to the downlink packet is performed; And transmitting the downlink packet to a terminal. The method of claim 11,  The downlink packet of the bidirectional class is identified through the type of information included in the header of the downlink packet received from the upper end. The method of claim 11, The downlink packet, characterized in that it comprises a data or ACK (ACKnowledgement) message. The method of claim 11, The bidirectional class is a class for classifying traffic requiring uplink data transmission for a downlink ACK message response or downlink ACK message for downlink data. The method of claim 11, The process of determining whether to perform uplink scheduling corresponding to the downlink packet, Calculating a time difference between the last downlink packet transmission time to the terminal and the downlink packet transmission time due to the downlink scheduling; Determining that the uplink scheduling is to be performed when the time difference is greater than a threshold. The method of claim 11, And performing uplink scheduling corresponding to the downlink packet according to the determination of the downlink scheduler. The method of claim 16, The uplink scheduling is performed according to a scheduling parameter of the bidirectional class. The method of claim 17, The scheduling parameter may include at least one of a frame interval of an uplink radio resource automatically allocated after downlink packet transmission and a minimum allocation size for automatic uplink radio resource allocation. The method of claim 11, The process of transmitting the downlink packet, Encoding a bit string of the downlink packet according to a corresponding coding scheme, and then modulating the bit string of the downlink packet into complex symbols; Mapping the complex symbols provided from the encoder and the modulator to corresponding frequency resources; Converting the complex symbols mapped to the frequency resources into time-domain Orthogonal Frequency Division Multiplexing (OFDM) symbols through an Inverse Fast Fourier Transform (IFFT) operation, and inserting a CP (Cyclic Prefix); And converting the OFDM symbols provided from the OFDM modulator into analog and upconverted RF signals to RF band analog signals and transmitting them through an antenna.

Images