Abstract:
A base transceiver station in a mobile communication system, includes a GPS time frequency unit for outputting a synchronized time which is received from at least one GPS satellite and frequency information; a BTS main processing unit for generating a control command to control one BTS; an ATM interface unit for interfacing with an asynchronous mode communication device; a packet routing unit for providing routing information used for setting path of packet data; a multi-rate channel unit for processing an inter-channel communication, each channel having a different data rate; a signal transformation unit for transforming and modulation/demodulation of an input signal; and a wireless unit for wireless communication with a mobile station.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a base transceiver station; and, more particularly, to a base transceiver station in a mobile communication system for increasing capacity two times or more than that of a conventional base station by supporting direct spread and multi-carrier, and for making a high speed data processing possible.  
         DESCRIPTION OF THE PRIOR ART  
         [0002]    Generally, a mobile communication system includes a mobile station which is a communication terminal, lots of base transceiver stations (BTS) for wireless relaying arrival and sending signals of the communication means which is located in a predetermined region, a base station controller (BSC) for controlling the BTS, a mobile switching center (MSC) for performing a switching function of a call which is transmitted through the BSC and a home location register for transmitting information when there exists requirement of user information.  
           [0003]    Especially, the BTS includes a BTS control processor (BCP) for performing general management of the BTS, a digital unit (DU) for performing signal processing function of a channel, a time &amp; frequency unit (TFU) for providing a standard frequency and timing to the BTS, a radio frequency (RF) unit for processing a RF signal and a BTS interconnection network (BIN) for performing a packet routing function with the control unit.  
           [0004]    In a conventional BTS system, a bandwidth of a transmitting/receiving carrier is conflicted to 1.25 MHz so hard to provide multimedia services such as video service and wireless internet service.  
           [0005]    For example, when transmitting a predetermined information about 1.25 MHz band through a radio channel, the conventional BTS processes only narrow banded single carrier of 1.25 MHz. Moreover, the conventional BTS cannot process multi-carrier so it cannot support speedy data service.  
           [0006]    Therefore, a BTS system of treating wide-banded frequency for speedy data service and supplying wide banded multi-carrier for adapting in a mixture in proportion to IS-2000 and IS-95 originated BTS, according to a network evolution to IMT-2000, is required.  
         SUMMARY OF THE INVENTION  
         [0007]    It is, therefore, an object of the present invention to provide a base station system in a mobile communication system for making a single carrier, multi carrier and direct spread possible by selecting bandwidth between 1.25 MHz and 5 MHz and in case of evolving to CDMA2000 3X system, uses RF switches and SAW filters of a transceiver unit without amendment and increasing capacity more than two times than that of conventional BTS.  
           [0008]    Another object of the present invention is to divide a multi-carrier by an allocated frequency for accepting a multi-carrier in a analog down-converter card assembly (ADCA).  
           [0009]    In accordance with an aspect of the present invention, there is provided a base transceiver station in a mobile communication system, comprising: a GPS time frequency unit for outputting a synchronized time which is received from at least one GPS satellite and frequency information; a BTS main processing unit for generating a control command to control one BTS; an ATM interface unit for interfacing with an asynchronous mode communication device; a packet routing unit for providing routing information used for setting path of packet data; a multi-rate channel unit for processing an inter-channel communication, each channel having a different data rate; a signal transformation unit for transforming and modulation/demodulation of an input signal; and a wireless unit for wireless communication with a mobile station. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, in which:  
         [0011]    [0011]FIG. 1 is a block diagram illustrating a base transceiver station in mobile communication system in accordance with the present invention;  
         [0012]    [0012]FIG. 2 is a block diagram showing a forward link constitution of a base transceiver station in accordance with the present invention;  
         [0013]    [0013]FIG. 3 is a block diagram showing a reverse link constitution of a base transceiver station in accordance with the present invention;  
         [0014]    [0014]FIG. 4 is a graph showing a total RF output level compared to frequency of TXFU in FIG. 1;  
         [0015]    [0015]FIG. 5 is a block diagram specifically showing an interfacing part with a RF device of a base station system in accordance with the present invention;  
         [0016]    [0016]FIG. 6 is a block diagram showing a switching form of a SAW filter in FIG. 5; and  
         [0017]    [0017]FIG. 7 is a block diagram showing another switching form of a SAW filter in FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    Hereinafter, a base transceiver station in a mobile communication system according to the present invention will be described in detail referring to the accompanying drawings.  
         [0019]    [0019]FIG. 1 is a block diagram illustrating a base transceiver station in mobile communication system in accordance with the present invention. A GPS time frequency unit  10 , which outputs location information received from at least one GPS satellite, includes a GPS receiver  12  for receiving a GPS signal and a distribution board  14  for distributing received information from the GPS receiver  12  to each device which requires synchronization in time and frequency.  
         [0020]    The GPS time frequency unit  10  is connected to an IS-2000 BTS main processor card assembly (IBPA)  16  which generates a control signal for managing each structural element of the BTS. The IBPA  16  includes an alarm &amp; status collector  20  for collecting the BTS status and issuing an alarm signal when the status is over a predetermined limit and a main processor  18  which generates a control signal for controlling the BTS.  
         [0021]    Also, the IBPA  16  is connected to an asynchronous transfer interface card assembly (AICA)  22  for interfacing with asynchronous transfer mode devices and an inter packet router card assembly (IPRA)  24  for routing a packet data.  
         [0022]    The IBPA  16  is also respectively connected to a multi rate channel card assembly (MCCA)  26  for processing an inter-channel data having different rate and a digital down &amp; up converter card assembly (DDCA &amp; DUCA)  28  for up/down converting a digital signal.  
         [0023]    In here, the MCCA  26 , the DDCA  28  and the DUCA  28  are connected to a receive ASIC for receiving data from the IBPA  16 , an analog up converter card assembly (AUCA)  30  for up converting an analog signal and to an analog down converter, respectively.  
         [0024]    The ADCA  30  is connected to a RX front end unit (RXFU)  32 , which is low noise amplifying the received signal, and the AUCA  30  is connected to a TX front end unit (TXFU)  34  which restricts band of a transmitting signal and transmits it to an antenna.  
         [0025]    Also, two receiving antennas and one transmitting antenna include the RXFU  32  and the TXFU  34 , respectively.  
         [0026]    An operation flow of the BTS is accounted by emphasizing a wireless transmitting/receiving unit and is divided into two cases—a forward link which emits a radio signal through an antenna and a reverse link which receives a wireless signal from the outside.  
         [0027]    [0027]FIG. 2 is a block diagram showing a forward link constitution of a base transceiver station in accordance with the present invention.  
         [0028]    One DUCA is connected with three of AUCA and three of AUCA are connected with one combiner. Each of combiner is connected with each of TXFU and each of TXFU interfaces antenna.  
         [0029]    In here, each of TXFU includes a linear power amplifier, a band pass filter and directional coupler, and the combiner, inputted signal is transmitted to the antenna via the linear power amplifier, the band pass filter and the directional coupler, consecutively.  
         [0030]    On the contrary, the reverse link case that receives a signal from the outside is as below.  
         [0031]    [0031]FIG. 3 is a block diagram showing a reverse link constitution of a base transceiver station in accordance with the present invention. One RXFU interfaces one receiving antenna and each of RXFU has one path. That is, one RXFU has one independent module and each module is being one path. The module includes a band pass filter, a low noise amplifier and a power divider.  
         [0032]    Therefore, each of band pass filter of the RXFU is connected with each of receiving antenna and each of power divider is connected with each of ADCA.  
         [0033]    The base transceiver station system in a mobile communication system in accordance with the present invention satisfies recommendation of IS 2000 and CDMA 2000.  
         [0034]    [0034]FIG. 4 is a graph showing a total RF power level compared to frequency of the TXFU in FIG. 1. An interface part of RF in the BTS is as below.  
         [0035]    [0035]FIG. 5 is a block diagram specifically showing an interfacing part with a RF device of a base transceiver station in accordance with the present invention. An input signal of the TXFU is inputted from the last amplifier  62 , via a band pass filter  60 , a mixer  58 , a saw filter  56 , a second amplifier  54 , flower attenuator  52  and a fist amplifier  50 .  
         [0036]    An input signal of the DDCA is inputted from a variable amplifier  76 , via a band pass filter  74 , an amplifier  72 , a mixer  70 , a flower attenuator  68  and a low noise amplifier  66 .  
         [0037]    The base transceiver station in accordance with the present invention can select bandwidth by using the RF switch  80   a  and  80   b.    
         [0038]    [0038]FIG. 6 is a block diagram showing a switching form of a SAW filter in FIG. 5. A first SAW filter  56   a  and a second SAW filter  56   b  which provide 1.25 MHz of bandwidth and 5 MHz bandwidth are interfaced and a first and a second switch  80   a ,  80   b  are connected with the end of each filter  56   a ,  56   b  for changing the bandwidth of the signal according to a predetermined control signal.  
         [0039]    As described above, a bandwidth can be composed by using the first and the second switch, and it can also be composed to support the 5 MHz bandwidth in FIG. 7.  
         [0040]    When the conventional system and the present system is mixed, selective bandwidth operation in FIG. 6 is convenient, but if the network evolution is already completed, then a mono bandwidth operation in FIG. 7 is preferred.  
         [0041]    Specific characteristics of the base transceiver station elements are as below.  
         [0042]    1) AUCA  
         [0043]    The AUCA performs forward direct frequency conversion and the ADCA performs reverse direct frequency conversion.  
         [0044]    2) MCCA  
         [0045]    The MCCA is located in a digital shelf and performing call processing function in the cell, and interfaced with the DUCA/DDCA unit, so in case of the forward/backward link, gives and takes a digital sampling signal from the DUCA/DDCA.  
         [0046]    Also, the MCCA is communicated with IBPA and HDLC through an internal bus and all status information of the MCCA are transmitted to the IBPA through the path. The MCCA is usually interfaced with a cell controller and gives and takes a call setup, a call cutting and hand-off related information. The MCCA has a data transmission path of 32 channels, at least, and has a Walsh code length of 4 bits to 256 bits according to a wireless environment and data rate. The MCCA supports all the synchronous and asynchronous communication and if it provides data service, it has speed of 2 Mbps.  
         [0047]    Also, in case of a reverse link, the MCCA has a continued pilot signal and when a data rate is over 14400 bps, supports highly efficient FEC coding, and supports quadrature phase shift keying (QPSK) instead of conventional binary phase shift keying (BPSK) as a double forward link Walsh channel.  
         [0048]    3) IBPA  
         [0049]    The IBPA is a control unit that wholly operates and manages the base transceiver station. The IBPA generates a control signal for call processing and maintenance and controls the DUCA/DDCA and a RF unit, respectively and is interfaced with the BTS to transmit and receive traffic and control information.  
         [0050]    The IBPA has a wireless resources managing function, a packet routing, an error detecting, a statistical information selecting and reporting function. That is, the IBPA allots and manages CDMA frequency, a channel and a frame offset resources and connects traffic control information to a BTS controller and the ATM, and routes traffic and control information which are received from the BTS controller and the ATM to a corresponding PBA unit. The IBPA detects an error within a BTS device and reports the error to a BTS maintenance unit, collects statistical information about a call and reports the information to the BTS maintenance unit and reports an alarm of the BTS device.  
         [0051]    Also, the IBPS has a call processing function. That is, the IBPS processes a general call, which includes arrival and sending signal, a softer hand-off call, a soft hand-off call and a hard hand-off call.  
         [0052]    The IBPS has a system optical information management function between a mobile station and the BTS. That is, it receives and manages GPS optical information and provides system optical information within the mobile station and the BTS.  
         [0053]    Also, the IBPA performs a forward and a reverse link power control function and a wireless signal transmit and receive function. That is, it performs a wireless signal transmit and receive function which includes allotting of a pilot channel, a synchronous channel, an access channel, a paging channel and a traffic channel.  
         [0054]    4) DUCA/DDCA unit  
         [0055]    The DUCA/DDCA unit performs a function of minimizing signal difference of a clock signals and the forward/reverse links and is located between the channel card ADCA and AUCA to transform a digital signal of the channel card to medium frequency signal then applies it to the AUCA, or transform a medium frequency signal to a digital signal then applies it to the channel card.  
         [0056]    5) STFU  
         [0057]    The STFU includes a PBA form that adds GPS, which receives related data from a GPS satellite, and TFCA function, which receives the data and provides time information and standard clock to the BST.  
         [0058]    According to the preferred embodiment as described above, in a wireless channel of a mobile communication system, a structure planning technology of CDMA 2000 3X BTS, which has 5 MHz bandwidth for supporting a multi-carrier and a direct spread method and be able to carry out high rate data service, may be utilized to a fundamental technology for an improved BTS design and has two times of a CDMA capacity than a conventional cellular and a personal communication services (PCS) system, therefore, a multimedia service is possible.  
         [0059]    Although the preferred embodiments of the 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.