Abstract:
A method and apparatus for controlling a forward direction power ratio in a W-CDMA wireless base station including the steps of: recognizing a variation in number of traffic channels; recognizing a data transfer speed; computing a power ratio of each channel according to the number of traffic channels and the data transfer speed; and re-adjusting an existing power ratio according to the computed power ratio of each channel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wireless communication system, and more particularly, to a W-CDMA (Wide band-Code Division Multiple Access) wireless communication system. 
     2. Background of the Related Art 
     Generally, a wireless communication system such as a WLL (Wireless local loop) adopts a CDMA multi-connection method that has a large accommodation capacity for subscribers compared to other connection methods. Unlike the existing narrow band CDMA method, a wide band CDMA method is capable of implementing an ISDN (integrated services data network) service and a packet communication network, as well as transferring a call, a facsimile, and data. 
     FIG. 1 is a schematic block diagram of the W-CDMA WLL system, which includes an RIU (radio interface unit)  20  for receiving a signal from a subscriber terminal  10  of a user and wirelessly transferring it to a base station via antennas. The base station includes a RP (radio port)  30  for handling connection and release of a signal wirelessly with the RIU  20 . An RPC (radio port controller)  40  connects a call link between the RP  30  and a WLL switching system  50 , and a WLL switching system  50  establishes a call link with an existing PSTN (public switch telephone network)  60 . 
     In the WLL system constructed as described above, a forward direction power from the RP  30  to the RIU  20  includes a pilot channel, a synchronization channel, a paging channel, a traffic channel and a signal channel. Accordingly, the RP  30  is able to heighten a communication efficiency by adequately controlling a power ratio between the channels with a limited forward direction power. 
     Generally, there is a standard for constantly maintaining and using the ratio of each channel that constructs the forward direction power or a reverse direction power in the CDMA wireless communication system. For example, a forward direction power defined in an international standard, IS-97-A, presented by Qualcomm Co., is constructed such that 20% is occupied by a pilot channel and the remaining 80% is occupied by the synchronization channel, paging channel and traffic channel (total forward direction power equals 100%). 
     The power ratio of IS-97-A must be altered in a W-CDMA system to account for the power of the signal channel. In this respect, the power value of the signal channel is defined to be different depending on the data speed of the traffic channel. 
     The RP  30  of the background W-CDMA WLL system determines a power ratio of each channel on the basis of the entire traffic channel that it can receive, and controls the forward direction power of each channel by applying these power ratios to the fixed power value. 
     However, the background art has a problem in that, since the previously established power ratio is used for each channel, an actual power ratio is determined differently depending on the number of individual traffic channels currently connected to the RP  30 . For example, if the power ratio of each channel is determined based on the assumption that 30 individual traffic channels in total are connected, a relative power ratio of each individual traffic channel actually received by the RIU  20  would be much different when 10 individual traffic channels are actually connected to be operated. 
     Thus, a problem arises in that the power ratio would unavoidably offend the standard as defined, and thus, the smaller the number of actual individual traffic channels becomes, the smaller the power ratio of the traffic channel to the other channels becomes, which negatively affects its communication quality. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter. 
     An object of the present invention is to improve the power ratio. 
     Another object of the present invention is to improve the power ratio in a forward direction. 
     A further object of the present invention is maintain a constant power ratio. 
     Still another object of the present invention is to provide a method for controlling the forward direction power ratio in a W-CDMA wireless base station in which the power ratio of each channel is adjusted according to the number of traffic channels so that a constant power ratio is maintained regardless of the number of the traffic channels. 
     To achieve these and other advantages and, in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for controlling a forward direction power ratio of a plurality of channels in a wireless base station including the steps of: recognizing a variation in the number of traffic channels; recognizing a data transfer speed of the traffic channel; determining a power ratio for each channel according to the number of traffic channels and the data transfer speed; and re-adjusting an existing power ratio according to the determined power ratio for each channel. 
     To further achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a wireless communication system including: a remote system that receives and transmits information data; and a base station that receives and transmits information data, wherein communication between the remote system and the base station is established by a plurality of channels including a first channel, a power ratio for the plurality of channels being based on a number of individual first channels and a data transfer rate of the first channel. 
     To still further achieve these and other advantages and in accordance with the purpose of the present invention, as is embodied and broadly described herein, there is provided a base station including: a radio frequency device that converts signals to and from a wireless signal; an antenna that transmits and receives the wireless signal; and a controller that digitizes a signal to be transferred to the radio frequency device, spreads it, and converts to an analog signal, and controls a first channel power and a second channel power according to a power ratio determined based on a number of individual it first channels. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
     FIG. 1 is a schematic block diagram of a general W-CDMA WLL system in accordance with background art; 
     FIG. 2 shows an example of a construction of internal hardware of a wireless base station (that is, a radio port (RP)  30 ) of a W-CDMA WLL system in accordance with the present invention; and 
     FIG. 3 is a flow chart of a process of controlling a forward direction power ratio in the RP of the W-CDMA WLL system in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The basic construction of a W-CDMA WLL system in accordance with the present invention is similar to that of the background art shown in FIG.  1 . FIG. 2 shows an example of internal hardware of a wireless base station (RP  30 ) of the W-CDMA WLL system in accordance with a preferred embodiment of the present invention. FIG. 3 is a flow chart of a process of controlling a forward direction power ratio in the RP  30  of the W-CDMA wireless base station. 
     As shown in FIG. 2, an example of the radio port  30  of the W-CDMA WLL system in accordance with the present invention includes a processor  31  for computing a power ratio of each channel according to the number of traffic channels that are currently connected, accordingly controlling the power of a pilot channel, a synchronization channel and a paging channel. The radio port  30  also outputs a power control signal for the traffic channel and the signal channel. The radio port  30  also includes a channel board  32  for digitalizing a signal to be transferred to the RIU  20 , spreading it and converting it to an analog signal, and controlling the power of the traffic channel and the signal channel according to the signal provided from the processor  31 . The radio port  30  further includes an RF unit  33  for converting the signals provided from the processor  31  and the channel board  32  to a high frequency wireless signal and transferring it to the RIU  20  through an antenna  34 . 
     Based on the international standard IS-97-A, 20% of the entire power is allotted to a pilot channel, and the remaining 80% is allotted to the synchronization channel, the paging channel, the traffic channel and the signal channel. Further, the power value of each channel on the basis of the traffic channel is expressed in detail by the following Table 1. 
     [Table 1] 
     Pilot channel power=20% 
     Paging channel power+synchronization channel power+traffic channel power+signal channel power=80% 
     paging channel power=2×the number of channels×traffic channel power; 
     synchronization channel power=(the number of channels×traffic channel power)/2 
     traffic channel power=the number of channels×individual traffic channel power 
     signal channel power=individual traffic channel power/correction value 
     In this respect, since the power of the signal channel is varied according to the transfer speed of the traffic channel, the correction value is set as a predetermined proportional constant. 
     For example, in the W-CDMA WLL system of the present invention, when the transfer speed of the traffic channel is 32 Kbps, the correction value is set so that the power of the traffic channel is 7.258 times as much as the power of the signal channel. Namely, for a given data transfer speed of the traffic channel, the power of the traffic channel is increased proportionally to the power of the signal channel. Based on the criteria of Table 1, the processor  31  begins operation in a previously programmed state in which the power ratio of each channel is computed. 
     In FIG. 3, the processor  31  determines a forward direction power only with the pilot channel, the synchronization channel and the paging channel at the initial state of the operation in step S 1 . When a traffic channel is generated with the RIU  20  through the channel board  32 , the channel board  32  identifies the number of currently connected traffic channels and sends this information to the processor  31  in step S 2 . Upon receipt of the number of traffic channels, the processor  31  judges the kind of service of the formed traffic channel to thereby obtain a predetermined proportional constant (correction value) of the power of the signal channel according to the data transfer speed in step S 3 . The forward direction power ratio of each channel is computed according to Table 1 in step S 4 , and the existing power ratios are re-set in step S 5  according to the power ratios computed in step S 4 . 
     Accordingly, the processor  31  controls and outputs each of the power values of the pilot channel, synchronization channel and paging channel. The processor  31  also outputs to the channel board  32  a control signal for controlling the power of the traffic channel and the power of the signal channel. 
     Then, the channel board  32  controls the power of the traffic channel and the power of the signal channel to the RIU  20  according to the control signal inputted from the processor  31  and transfers it to the RIU  20  along with a signal to be transferred thereto. The signal outputted from the processor  31  and the channel board  32  is converted to a high frequency wireless signal through the RF unit  33  and then wirelessly transferred to the RIU  20 . 
     As so far described, the W-CDMA wireless base station of the present invention recognizes the number of currently connected traffic channels, adjusts each power value according to the number of traffic channels, and constantly maintains the power ratio of each channel, so that in any environment it can satisfy the standard of the forward direction power ratio as defined by the international standards, and accordingly, the communication quality can be improved. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.