Patent Publication Number: US-2010118816-A1

Title: Apparatus and method for transmitting data in wireless communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority of Korean Patent Application No. 10-2008-0111740, filed on Nov. 11, 2008, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and method for transmitting data in a wireless communication system; and, more particularly to an apparatus and method for transmitting data in a wireless communication system. 
     2. Description of Related Art 
     Communication systems mean a system for voice communications and data transfer between long distance terminals, they can be categorized into wired communication systems and wireless communication systems. The wired communication system guarantees stable transfer of data and signal because systems are connected through wires, but the mobility of the user is limited. On the other hand, a wireless communication system guarantees mobility, but data transfer condition is unstable and data transmission rate is slower than transmission rate in a wire communication system. 
     Not like the existing wireless communication which was mostly used for voice communication service, recent wireless communication services are increasingly used in data service area. Also, needs for multimedia services that can satisfy various applications are increasing. To satisfy these various applications, transferring various types of data is required. These various types of data include large capacity multimedia packets. Accordingly, a wireless communication system that can provide high speed data transmit service is required. Also, each service has various specific characters and makes different Quality of Service (QoS). In this reason, techniques for wireless communication systems that have a wide bandwidth for transferring large capacity multimedia packet and can provide suitable QoS for users&#39; need are being developed. 
     Techniques that simultaneously transmit data through a plurality of antennas in order to transfer multimedia packets and to improve QoS are used. These techniques can increases data transfer speed and obtain profit based on diversity. A representative example to transfer data through multiple antennas is Multiple Input Multiple Output (MIMO). Also, multiple frequency band technology which transfer data through various frequency bands in order to broaden the transmission frequency band is being developed and practically being used. 
     MIMO system will be described hereinafter. 
     MIMO system is a wireless communication technology broadening the transmit/receipt frequency band by combining multiple antennas. MIMO is a method of transmitting different signal simultaneously through different antenna and combining signals transmitted from the antennas together at the receiver, which enables to use broad band and increase communication speed. Theoretically, the MIMO system has the effect that use of 2 antennas widens 2 times of its data rate, and use of 3 antennas widens 3 times of its data rate. 
     In case of wireless LAN, since available frequency band is limited, it is difficult to increase transmission speed or range by widening the available frequency band for a user. In this reason, MIMO system allows to broaden the frequency band by using multiple antennas in the limited space by increasing the access points. Also, since the multiple antennas receive the signals transmitted through various routes, transmission and receipt of signals are stable and communication efficiency can be increased in an obstacle surrounded condition. 
     The multiple frequency band technique widens the frequency band by using more than one frequency band and can transmit large capacity data simultaneously. Also, compared to the single frequency band technique, the multiple frequency band technique can reduce burst errors occurred during communication in a bad communication condition by sending dispersed data through diverse frequency band. 
     The MIMO system which uses multiple frequency bands and multiple antennas can transmit one and more data stream simultaneously by using diverse transmitting routes. Because MIMO system uses diverse transmitting routes, burst errors in each transmit route can occur in a different rate. To control the error rate, in the MIMO system using the multiple frequency bands and the multiple antennas, a type that the physical layer uses the same transmission method for the multiple frequency bands and the multiple antennas, and a type that the physical layer uses different modulation and coding method for each antenna in a different way from MAC layer in order to increase system transmit efficiency. 
     An apparatus for transmitting data using the multiple frequency bands and the multiple antennas mentioned above will be described referred to the attached drawings hereinafter. 
       FIG. 1  is diagram illustrating a wireless communication system diagram using multiple frequency bands and multiple antennas. 
     A base station  120  includes multiple antennas and transmits data to terminals  131  and  132  through the multiple frequency bands and the multiple antennas. Also, the base station  120  receives data transmitted from the terminal  131  and  132  through the multiple frequency bands and the multiple antennas. The base station  120  can be connected to a data communication equipment or a data communication network  110  either by wire or wireless. In  FIG. 1 , it is presumed that the base station  120  is connected to the data communication equipment or the data communication network  110  by the wire. Also, the terminal  131  and  132  can be connected to a different data communication equipment or a data communication network  141 ,  142  or be connected to the same data communication equipment or the data communication network  141 ,  142 . The communication equipment/data communication network  141 ,  142  can be connected to the terminal  131 ,  132  either by wire or wireless. In  FIG. 1 , it is presumed that the data communication equipment or the data communication network  141 ,  142  is connected to the terminal  131 ,  132  by wire. 
     Operation procedures of  FIG. 1  will be described. The base station  120  which receives digital data from the data communication equipment or the data communication network  110  transmits the data to the terminal  131 ,  132  through multiple frequency bands and multiple antennas. The transmitted data are received through the multiple frequency bands and the multiple antennas at the terminal  131 ,  132  and transmitted to the data communication equipment or a data communication network  141 ,  142 . 
     The data communication equipment or the data communication network  141 ,  142  which is connected to the terminal  131 ,  132  transmits the data, and the terminal  131 ,  132  transmits the data to the base station  120  through the multiple frequency bands and the multiple antennas. The base station  120  transmits the data received through the multiple frequency bands and the multiple antennas to the data communication equipment or the data communication network  110  which is connected to the base station  120 . 
       FIGS. 2A and 2B  are block diagrams showing data transmitting/receiving apparatus.  FIGS. 2A and 2B  show the base station  120  and the terminal  131 ,  132  of the data transmitting/receiving apparatus in  FIG. 1  on the basis of a layer. 
     With reference to  FIG. 2A , data transmitting procedure at the transmitting unit will be described on the basis of operation in each layer. A service data matching unit  211  receives the data from the data communication equipment or the data communication network and transmits the data to a MAC layer transmitting unit  212 . The MAC layer transmitting data process unit  212  receives the data from the service data matching unit  211 . A frame generator  212   a  generates an appropriate frame for the transmission type and sends the data to a physical layer transmitting unit  213 . The physical layer transmitting unit  213  receives frames generated at the MAC layer transmitting unit  212 . A modulator  213   a  modulates the received data with an appropriate modulation type for the data, and an encoder  213   b  encodes the data to be optimized to the wireless communication surrounding and transmit speed. A transmitter  213   c  decides the frequency in order to transmit the data and sends the data to a data transmitting antenna  214 . The data transmitting antenna  214  transmits the data. Descriptions of general functions processed in the physical layer which is not required in the present invention will be omitted. 
     With reference to  FIG. 2B , data receiving procedure at the receiving unit will be described on the basis of operation in each layer. The physical layer receiving unit  222  receives the data from a data receiving antenna  221 . A receiver  222   c  of the physical layer receiving unit  222  collects data from the receiving antenna, and a decoder  222   b  decodes data which is encoded at the encoder  213   b  of the physical layer transmitting unit  213 . A demodulator  222   a  of the physical layer receiving unit  222  demodulates the modulated signals at the modulator  213   a  of the physical layer transmitting unit  213  and transmits the data to a MAC layer receiving unit  223 . The MAC layer receiving unit  223  receives data from the physical layer receiving unit  222 . An error checking unit  223   a  checks the error of the received data and a packet scheduler  223   b  sorts the data and sends the sorted data to a service data matching unit  224 . The service data matching unit  224  receives data from the MAC layer receiving unit  223  and determines whether the destination of the data is a terminal of a user or a data communication equipment or data communication network. If the destination of the data is a terminal of the user, information is sent to the user by a upper layer application unit  226 . If the destination of the data is a base station or a relay station to transmit the data to another network, data is sent to a designated communication equipment or a data communication network through a data transmitting unit  225 . 
     In the communication method described above, MAC layer does not send data packets by an appropriate scheduling method for the multiple frequency bands or the multiple antennas but by the same scheduling method. Accordingly, if channel status gets worse and error rate of transmission path through some frequency bands and some antennas abruptly increases, packet loss rate abruptly increases. Therefore, it is needed a data transmitting apparatus and method that prevents from burst error by transmitting each of data packets in the MAC layer using independent frequency band and a scheduling method which fits to the independent frequency band, to thereby increase the transmission efficiency. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention is directed to an apparatus and method for transmitting data to improve a data transfer speed. 
     Another embodiment of the present invention is directed to an apparatus and method for transmitting data to avoid burst errors. 
     Another embodiment of the present invention is directed to an apparatus and method for transmitting data to provide QoS to the user. 
     In accordance with an embodiment of the present invention, an apparatus for transmitting in a wireless communication system, includes: a frame generating unit configured to generate a frame based on user data and to transmit the frame and frame information; a scheduling unit configured to generate a schedule of the frames to be transmitted on a frame-by-frame basis based on the frame information and to transmit the schedule; and a data matching unit configured to match the frames based on the schedule so as to transmit the frames at a time. 
     In accordance with another embodiment of the present invention, a method for transmitting data in a wireless communication system, includes: generating a frame based on user data and to transmit the frame and frame information; generating a schedule of the frames to be transmitted on a frame-by-frame basis based on the frame information and to transmit the schedule; and matching the frames based on the schedule so as to transmit the frames at a time. 
     Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art to which the present invention pertains that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a wireless communication system diagram using multiple frequency bands and multiple antennas. 
         FIGS. 2A and 2B  are block diagrams showing data transmitting/receiving apparatus. 
         FIG. 3  is a detailed block diagram of a transmitting apparatus in accordance with an embodiment of the present invention. 
         FIG. 4  is a detailed block diagram of a transmitting apparatus in accordance with another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be constructed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention. The drawings are not necessarily to scale and in some instances, proportions may have been exaggerated in order to clearly illustrate features of the embodiments. 
       FIG. 3  is a detailed block diagram of a transmitting apparatus in accordance with an embodiment of the present invention. 
     The MAC layer transmitting unit and the physical layer transmitting unit using the multiple frequency bands and the multiple antennas will be explained with reference to  FIG. 3 . The multiple frequency bands and the multiple antennas are also called as transmission media for transmitting the data. The MAC layer transmitting unit includes a timing signal generating unit  310 , a MAC frame generating unit  320 , a transmitting data scheduling unit  330 , a 1 st  transmission memory  340 , a transmitting data matching unit  350 , a 2 nd  transmission memory  360  and a physical layer control signal generating unit  370 . A physical layer transmitting unit  380  receives the data from the MAC layer transmitting unit  300  and sends the data to the transmitting antenna  214 . Since the physical layer transmitting unit  380  has the same structures as the physical layer transmitting unit  213  described with reference to  FIG. 2A , and detailed description on the physical layer transmitting unit  380  is omitted herein. 
     Functions of blocks in  FIG. 3  will be described hereinafter. 
     The timing signal generating unit  310  generates timing signals needed for transmitting the MAC frame and provides the timing signals to each functional block. The MAC frame generating unit  320  forms a MAC frame that meets the frame specification based on the input data from the service data matching unit  211  and stores the MAC frame in the 1 st  transmission memory  340 . The MAC frame generating unit  320  sends the MAC frame control information of each MAC frame to the transmitting data scheduling unit  330 . The MAC frame control information includes frame length, a sequence number of the MAC frame and address of 1 st  transmitting memory in which the MAC frame is stored. 
     The transmitting data scheduling unit  330  includes a plurality of schedulers, and each scheduler operates for one of frequency bands and antennas. The transmitting data scheduling unit  330  provides the MAC frame control information received from the MAC frame generating unit  320  to the schedulers. Each scheduler of the transmitting data scheduling unit  330  generates a MAC frame list describing MAC frames that can be sent for a predetermined time through the corresponding frequency band or the corresponding antenna, and sends the MAC frame list to the transmitting data matching unit  350 . 
     The transmitting data matching unit  350  reads the MAC frame based on the transmitted data memory address which is included in the MAC frame control information on each of the antenna, and sends the MAC frame to the 2 nd  transmission memory  360 . The 2 nd  transmission memory  360  may be a First Input First Output (FIFO) memory. For easy description, it is supposed that the 2 nd  transmission memory  360  is the FIFO memory hereinafter. 
     The 2 nd  transmission memory  360  stores the MAC frame received from the transmitting data matching unit  350  at the corresponding FIFO for each frequency band or antenna. The physical layer transmitting unit  380  calls the MAC frame from FIFO according to the transmit time and transmits the MAC frame through antenna after the modulation and coding procedure. 
       FIG. 4  is a detailed block diagram of a transmitting apparatus in accordance with another embodiment of the present invention. 
     Comparing  FIG. 4  with  FIG. 3 , the transmitting apparatus in  FIG. 4  further includes a wireless environment quality testing unit  410 . The wireless environment quality testing unit  410  may be a receiver in general. For example, the receiver checks the signal quality received from the transmitter and sends the signal quality information back to the transmitter. It is supposed that the wireless environment quality testing unit  410  is the receiver hereinafter. In addition, the wireless environment quality testing unit  410  may be also separate equipment that can test the wireless communication quality. The difference between  FIG. 3  and  FIG. 4  will be explained in detail hereinafter. 
     The wireless environment quality testing unit  410  for providing the QoS collects channel quality information of each frequency band and antenna and transmits the channel quality information to a transmitting data scheduling unit  420 . The transmitting data scheduling unit  420  receives the channel quality information decides the priority between MAC frames and amount of data to be sent based on the channel quality information. The wireless environment quality testing equipment  410  which checks the channel status is located in the physical layer transmitting unit or the MAC layer transmitting unit. 
     The transmitting data scheduling unit  420 , which receives data for QoS from the wireless environment quality testing unit  410 , applies a different scheduling according to a network or QoS which the user wants based on the MAC frame control information of the MAC frame generating unit  440 . MAC frames that requires high QoS, e.g., video data and audio data, are transmitted through the frequency bands and/or antennas having good channel quality, and allocated to the scheduler that are in charge of the decided frequency band and/or antenna. MAC frames that requires low level of QoS, e.g., FTP data, is transmitted through the frequency bands and/or antennas having a relatively low channel quality, and allocated to the scheduler that are in charge of the decided frequency and/or antenna. 
     As explained in the embodiment of the present invention, high speed and reliable transmission of data can be performed by using multiple frequency bands and multiple antennas. Also, the QoS that meets the needs of the network or the user can be provided by checking the quality of the wireless channel by the wireless environment quality testing unit  410  and forwards the wireless channel quality information. 
     While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.