Abstract:
A data communication method for a mobile communication system reduces the consumption of resources when a desirable half-duplex data connection is provided. The data communication method includes the steps of: a) determining whether data communication is needed between at least two MSs (Mobile Stations) located in a service area of one BTS (Base Transmit Subsystem); b) if the data communication between the MSs is needed, assigning one physical half-duplex data channel to the MSs in common; and c) if data is transmitted to the MSs over a downlink channel of the half-duplex data channel, adding a header to the data to create data, and transmitting the data to the MSs.

Description:
PRIORITY 
   This application claims priority to an application entitled “DATA COMMUNICATION METHOD FOR MOBILE COMMUNICATION SYSTEM”, filed in the Korean Intellectual Property Office on Jan. 10, 2003 and assigned Serial No. 2003-01696, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a mobile communication system, and more particularly to a data communication method for a mobile communication system. 
   2. Description of the Related Art 
     FIG. 1  is a view illustrating a schematic diagram of a conventional mobile communication system. Referring to  FIG. 1 , mobile stations (MSs)  110  and  112  are connected to a BTS (Base Transmit Subsystem)  120  over an air interface, and a MS  114  is connected to a BTS  122  over the air interface. The BTSs  120  and  122  are wirelessly connected to the MSs  110  and  112 , and the other BTS  122  is wirelessly connected to the MS  114 . Upon receiving each incoming call for MSs of corresponding service areas from a BSC (Base Station Controller), the BTSs transmit the incoming call to a corresponding MS. Then, if the MS transmits an outgoing call to the BTS, the BTS transmits the outgoing call to the BSC  130 . The BSC  130  manages the overall call control processes such as a voice call process, circuit call process, and packet call process, etc., of each MS. Also, the BSC  130  performs signaling with a MSC (Mobile Switching Center), and performs a handover operation. 
   The MSC  140  is connected to a HLR (Home Location Register)  150 . The MSC  140  performs a call connection/switching function for processing incoming/outgoing request signals entering the MSs  110 ,  112  and  114 , and performs a network-interworking function with other MSCs. HLR (Home Location Register)  150  is a database for storing/managing data of mobile phone subscribers. The HLR  150  registers or deletes a subscriber&#39;s location, and inquires about subscriber information. 
   Multiple-access wireless communication between the BTSs  120  and  122  and the MSs  110 ,  112 , and  114  in such a mobile communication system is established over RF (Radio Frequency) channels for providing the mobile communication system with physical paths to transmit a plurality of communication signals such as an audio signal, a data signal, and an image signal, etc. Uplink channels, indicated as dotted lines in  FIG. 1 , are adapted to establish a call connection state among the BTSs  120  and  122  and the MSs  110 ,  112  and  114  or adapted to answer a message received from a paging channel. The downlink channel, indicated as solid lines in  FIG. 1 , is adapted to transmit voice or data signal information to the prescribed MSs  110 ,  112  and  114  at the BTSs  120  and  122 . That is, one wireless channel is composed of one uplink channel and one downlink channel. 
   For instance, in the case where two MSs  110  and  112  connected to the BTS  120  are interconnected to each other such that data is interchangeable between the MSs  110  and  112  over the BTS  120 , one wireless channel composed of one uplink channel and one downlink channel is assigned between the MS  110  and the BTS  120 , and the other wireless channel is assigned between the MS  112  and the BTS  120 . In conclusion, two uplink channels and two downlink channels are used between the MSs  110  and  112  to establish data communication between the MSs  110  and  112 . 
   The aforementioned connection scheme for the conventional mobile communication system is indispensable for a full-duplex connection requiring two-way simultaneous data transmission. However, if only one-way data transmission is required at a prescribed time, for example, if one MS sends a file to a counterpart MS in the range of short distance (i.e., within a service area of one BTS), two-way channels assigned each MS are adapted to interchange signaling command/response messages for establishing a wireless access state with others, but there is little traffic on such two-way channels, resulting in unnecessary consumption of most of channel capacities. 
   SUMMARY OF THE INVENTION 
   Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a data communication method for a mobile communication system for reducing the consumption of resources when a desirable half-duplex data connection is provided. 
   In accordance with the present invention, the above and other objects can be accomplished by the provision of a data communication method for a mobile communication system, including the steps of a) determining whether data communication is needed between at least two MSs (Mobile Stations) located in a service area of one BTS (Base Transmit Subsystem); b) if the data communication between the MSs is needed, assigning one physical half-duplex data channel to the MSs in common; and c) if data is transmitted to the MSs over a downlink channel of the half-duplex data channel, adding a header to the data to create data, and transmitting the data to the MSs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a view illustrating a schematic diagram of a conventional mobile communication system; 
       FIG. 2  is a view illustrating a schematic diagram of a mobile communication system in accordance with a preferred embodiment of the present invention; 
       FIG. 3  is a flow chart illustrating a half-duplex data connection procedure in accordance with a preferred embodiment of the present invention; and 
       FIG. 4  is a view illustrating the appearance of transmission/reception data formats on a data channel in accordance with a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. 
   According to the present invention, in the case where a data communication is established between at least two MSs within one BTS service area, the BTS allocates one physical channel between the two MSs. Provided that data transmission is established over one downlink channel while the BTS transmits data to at least two MSs, these MSs only receive the data without any operation. Therefore, the BTS divides transmission data in block units, and displays a receiver of a corresponding data block on a header of each data block. In this case, a candidate for the receiver may be one or more than two MSs. In the case where the MSs transmit data to the BTS over one uplink channel, only a qualified MS having authority to transmit the data to the BTS is able to perform such data transmission. Typically, in case of receiving uplink traffic data other than signaling information, the BTS transmits the same traffic data in a downlink direction. In this way, the BTS serves as an amplifier between at least two MSs at a short distance. 
     FIG. 2  is a view illustrating a schematic diagram of a mobile communication system in accordance with a preferred embodiment of the present invention. A plurality of MSs  212 ,  214 ,  262  and  264  shown in  FIG. 2  are designed to establish a half-duplex data connection service according to the present invention. For this purpose, the MSs  212 ,  214 ,  262  and  264  are registered to the half-duplex data connection service in a mobile communication system. The MSs  212 ,  214 ,  262  and  264  are implemented to control half-duplex data. That is, the MSs  212 ,  214 ,  262  and  264  generate data format for a half-duplex data communication on a core network  200 . The MSs  212 ,  214 ,  262  and  264  receive arbitrary data appropriate for the half-duplex data connection service from the core network  200 . 
   Referring to  FIG. 2 , the MSs  212  and  214  receive a mobile communication service from a BTS  220 , and the MSs  262  and  264  receive a mobile communication service from a BTS  222 . The BTSs  220  and  222  are connected to a MSC  240  over a BSC  230 . The MSC  240  performs a call connection/switching function for processing incoming/outgoing request signals entering the MSs  212 ,  214 ,  262  and  264 . HLR  250  is a database for storing/managing data of mobile phone subscribers. The HLR  250  registers or deletes a subscriber&#39;s location, and inquires about subscriber information. 
   According to the present invention, the BTS, the BSC, the MSC and the HLR for providing such MSs with such a mobile communication service are defined as a core network. In other words, a network for providing mobile phones with a mobile communication service is defined as a core network according to the present invention. 
   The MS  212  connected to one BTS  220  requests the BTS  220  to establish a half-duplex data connection between itself  212  and another MS. The half-duplex data connection request of the MS  212  is created in the same manner as in a typical mobile communication system; that is, the MS  212  uses a common channel. It should be noted, however, that a predetermined service code for the half-duplex data connection service is prescribed between the MS  212  and the core network  200 . So, the MSs  212 ,  214 ,  262  and  264  transmit a predetermined counterpart MS information and the predetermined service code to the core network  200  in such a way that such a half-duplex data connection request to the BTS is established. 
   In the case where the MS  212  transmits to a core network  200  such a half-duplex data connection request to other MS  214  connected to the BTS  220  (also connected to the MS  212 ), the core network  200  searches a database contained in either the HLR  250  or a VLR (Visitor Location Register) (not shown) to determine whether the MS  214  receiving the half-duplex data connection request gains access to the same BTS (i.e.,  220 ). Then, the core network  200  determines whether the MS  214  is capable of performing the half-duplex data connection service by determining whether the MS  214  is registered to the half-duplex data connection service in a mobile communication system. In other words, all the MSs must inform the mobile communication system of prescribed information for indicating whether or not they support the half-duplex data connection service at a prescribed time at which they are registered to a network. As described above, it is necessary for the MS  214  to generate a data format for a half-duplex data communication on the core network  200 , receive data appropriate for the half-duplex data connection service from the core network  200 , and process the data. Provided that there is no information for indicating that the half-duplex data connection service is available, the BTS may check whether the half-duplex data connection service is available in a counterpart MS over an additional common channel after substantially paging the counterpart MS. This condition check procedure may be different in individual mobile communication systems. 
   If the MS  214  does not gain access to the same BTS  220 , the half-duplex data connection request transmitted from the MS  212  to the MS  214  is denied. For example, in the case where the MS  212  transmits to the core network  200  a half-duplex data connection request to other MS  262  or  264  connected to other BTS  222  instead of the BTS  220 , the core network  200  denies the half-duplex data connection request from the MS  212 . 
   With reference to  FIG. 2 , in the case where the MS  214  receiving the half-duplex data connection request message from the MS  212  is located in a service area  202  of the same BTS  220  and the half-duplex data connection service is available, one physical channel is assigned the MSs  212  and  214 . Prior to such a physical channel assignment, it is noted that the core network  200  must page the MS  214  and transmit half-duplex data connection channel information to the MS  214 . 
   The half-duplex data channel is shared with an uplink channel and downlink channel, respectively, and has the following characteristics. After performing such a half-duplex data channel allocation, the concept of a caller (i.e., the MS  212  in the present invention) and a callee (i.e., the MS  214  in the present invention) is of little importance, but discrimination between a sender and a receiver is of importance. In this case, a sender is defined as an arbitrary MS with uplink authority as follows. 
   Referring back to  FIG. 2 , if the core network  200  assigns one physical half-duplex data channel to the MSs  212  and  214 , the MSs  212  and  214  serve as one virtual MS  210  for the BTS  220  (or the core network). Therefore, the MSs  212  and  214  simultaneously receive all the data transmitted from the BTS  220  to the half-duplex data channel in the downlink direction of the half-duplex data channel between the virtual MS  210  and the BTS  220 . The downlink channel information between the virtual MS  210  and the BTS  220  includes a traffic data block for a receiver, and a signaling data block between a sender and the receiver. 
   The BTS  220  divides data to be transmitted into a plurality of data blocks, and indicates a receiver of a corresponding data block on a header of each data block. In this case, a candidate for the receiver may be one or more than two MSs. Such receiver information is transmitted using either a unique number for indicating a corresponding MS, or bitmap information. The MSs  212  and  214  in case of signal reception reply to corresponding traffic and signal only when they are indicated as a destination in a data block header. Similarly, the MSs  212  and  214  ignore the corresponding traffic and signals when they are not indicated as a destination in a data block header. 
   In the meantime, if the core network  200  assigns one physical half-duplex data channel to the MSs  212  and  214 , the MSs  212  and  214  serve as one virtual MS  210  for the BTS  220  (or the core network). Therefore, only one of the MSs  212  and  214  is able to transmit a data block to the BTS  220  in the uplink direction of the half-duplex data channel between the virtual MS  210  and the BTS  220 . 
   Uplink channel information between the virtual MS  210  and the BTS  220  includes a sender&#39;s traffic data block, a sender&#39;s signaling data block, and a receiver&#39;s signaling data block, etc. Here, the signaling data block includes a traffic data ACK (ACKnowledgement) and a signaling data ACK. The ACK information is adapted to indicate success or failure of corresponding data block reception and, if necessary, is also adapted to induce data retransmission. 
   If the MSs  212  and  214  receive the traffic and signal, they should inform the BTS  220  of ACK information of the received traffic and signal, i.e., success or failure of corresponding data block reception, in order to establish stable data communication. In this case, the MS receiving the data block has no authority to use an uplink channel as a receiver. Only a qualified MS having authority to use such an uplink channel can transmit data to the BTS  220  in the uplink direction. Therefore, one or more receiver MSs among a plurality of MSs making a half-duplex data connection state must have periodic uplink authority. 
   In more detail, in order to allow the MS  214  receiving the data block to transmit reporting ACK data of the received data block to the core network  200 , a mobile communication system of the present invention periodically assigns a small-sized uplink space to the MS  214 . As a result, the MS  214  receiving the data block can transmit the reporting ACK data, i.e., success or failure information of the data block&#39;s reception, to the core network  200 . 
   Such a reporting ACK data is important when establishing synchronization with a receiver. For example, a GSM (Global System for Mobile communications) system needs to successively update necessary TA (Timing Advance) information with change in geographical locations involving a corresponding MS therein. But, unless the GSM system successively updates the TA information, it cannot establish a stable uplink transmission. For this stable uplink transmission, the receiver needs to perform a periodic uplink function, such that even the receiver can easily function as a sender without additional synchronization. 
   For this operation, such an uplink channel is divided into a plurality of sub-channels on a time domain to allow the MSs to be individually assigned sub-channels, such that the MSs share the uplink channel with one another. Likewise, in the case where a sender finishes transmission of all the traffic information, additional signaling information is transmitted to the core network  200  according to the authority to use the uplink channel, such that a request to return the authority to use the uplink channel is transmitted to the core network  200 . In this case, the core network  200  transmits all the traffic to the receiver, and gives the receiver the requested uplink channel use authority using additional signaling information. Therefore, if an arbitrary MS defined as a new sender has no transmission information, the arbitrary MS transfers its own uplink channel use authority to a counterpart MS in the same manner as the above. Such a transfer of the uplink channel use authority is repeated until one MS attempting to complete such data connection status, among a plurality of MSs using the half-duplex data channel, generates a termination request via additional signaling information. 
   If the traffic data other than signaling information is received in an uplink direction, the core network  200  transmits the same traffic data in a downlink direction. Likewise, the core network  200  serves as an amplifier between all MSs located within a short distance range. 
     FIG. 3  is a flow chart illustrating a half-duplex data connection procedure in accordance with a preferred embodiment of the present invention, and  FIG. 4  is a view illustrating the appearance of transmission/reception data formats on a data channel in accordance with a preferred embodiment of the present invention. 
   Referring to  FIGS. 2˜4 , the MS  212  transmits a half-duplex data connection request to the MS  214  over the core network  200  at step  302 . Upon receiving the half-duplex data connection request from the MS  212 , the core network  200  determines on the basis of the half-duplex data connection request whether the MS  214  is located in a service area of the BTS  220  connected to the MS  212  at step  304 , and also determines whether the MS  214  is able to perform a half-duplex data connection service at step  304 . As stated above, such determination at step  304  is based on prescribed information indicating whether the MS  214  is registered to the half-duplex data connection service in a mobile communication system. If the MS  214  is disconnected from the BTS  220  of the MS  212  or the half-duplex data connection service is not available at step  304 , a mobile communication system informs the MS  212  of a failure of the half-duplex data connection service at step  306 . 
   Otherwise, if the MS  214  is connected to the BTS  220  of the MS  212  and the half-duplex data connection service is available at step  304 , the core network  200  adapts the MS  212  and the MS  214  to be one virtual MS and assigns one physical half-duplex data channel to the one virtual MS at step  308 . Thereafter, the core network  200  transmits to the MSs  212  and  214  a data block in a downlink direction of the half-duplex data channel at step  310 . In this case, the core network  200  divides transmission data into block units, and indicates the receiver of a corresponding data block on a header of each data block. In this case, a candidate for the receiver may be one or more than one MS. A data block format  400  transmitted to the MSs  212  and  214  is depicted in  FIG. 4 . The data block is composed of a header  402  and a traffic or signal data  404 . The header  402  may indicate a receiver of a corresponding data block as aforementioned. So, the MSs  212  and  214  receiving the data block reply to a corresponding traffic or signal data  404  only when they are indicated as destination information in the data block header  402 . Similarly, the MSs  212  and  214  ignore the corresponding traffic and signal data  404  when they are not indicated as the destination in the data block header  402 . 
   In addition, the core network  200  allows only one of the MSs  212  and  214  to transmit such a data block to the BTS  220  in the uplink direction of the half-duplex data channel between the virtual MS  210  and the BTS  220  at steps  312  and  314 . The dotted line of  FIG. 3  indicates that uplink of MS 2  can be limited. A data block format  410  transmitted from the MSs  212  and  214  to the core network  200  is also depicted in  FIG. 4 . The data block is composed of a reporting ACK data  412  and a sender&#39;s traffic or signal data  414 . As stated above, a small-sized uplink space  412  is periodically assigned the MS  212  or  214  receiving the data block, such that the MS  212  or  214  can transmit the reporting ACK data  412  of the received data block to the core network  200 . As a result, the MS  212  or  214  receiving the data block can transmit the reporting ACK data  412  of recently received data block, i.e., success or failure information of the current reception data block, to the core network  200 , therefore, if necessary, the MS  212  or  214  may request the core network  200  to retransmit the necessary data block. The MS  212  or  214  having authority to use an uplink channel is assigned an uplink space  414  through which data transmission to a counterpart MS is performed. Therefore, the MS  212  or  214  transmits traffic or signal data to the core network  200  as a sender. 
   As apparent from the above description, in accordance with the present invention, in the case where data communication between at least two MSs located in a service area of one BTS is established, the BTS assigns one physical channel between the MSs, thereby preventing unnecessary consumption of resources and making it possible for a mobile communication system to make effective data transmission on the condition that it is determined that a short distance half-duplex data connection service is preferable. 
   Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.