Abstract:
A data transmitting/receiving apparatus and method in a wireless system are provided to enhance a performance by coupling a transmission power controlling method and an erasure-error correction method. If a channel environment is not good, transmission power is not allocated to prevent unnecessary transmission power consumption, and allowing each user to independently control transmission power and reduces multiple access interference. A channel state may be determined through a channel gain so that if a channel state is not good, a corresponding data symbol is regarded as an erasure symbol, and accordingly, a receiving end performs a demodulation by an erasure-error correction technique to restore data. Thus, a correction capability of a block code can be improved.

Description:
[0001]    This disclosure claims priority from Korean Patent Application No. 14101/2003, filed Mar. 6, 2003, the subject matter of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    Embodiments of the present invention may relate to a wireless system. More particularly, embodiments of the present invention may relate to a data transmitting/receiving apparatus and method in a wireless system that combines a transmission power controlling method and an erasure-error correcting method.  
           [0004]    2. Background of Related Art  
           [0005]    In a wireless system, when data is transmitted and received between a sending end and a receiving end, the received data is frequently damaged when a transmission channel state becomes bad (or damaged) due to a time difference according to geographical features or in each path and spatial environment factors. In order to compensate for such damage occurring at the channel in data transmission and reception, a transmission power controlling method or an error correcting method may be used.  
           [0006]    In the transmission power controlling method, the sending end and the receiving end may raise or drop the transmission power according to a channel situation (or based on channel performance) so that every terminal user can receive a same strength of a radio wave. This may help guarantee a uniform quality of service (QoS). More specifically, if the channel is in a good state (hereafter also called good), the transmission power may be lowered, whereas if the channel is not in a good state (hereafter also called bad), the transmission power may be raised.  
           [0007]    The error correcting method may restore damaged received data as it occurs at the receiving end, for which a turbo-coding method or a block encoding method may be used.  
           [0008]    However, since either the transmission power adjusting method or the error correcting method are separately used, advantages and disadvantages of both methods are not suitably adopted.  
         SUMMARY OF THE INVENTION  
         [0009]    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.  
           [0010]    Embodiments of the present invention may provide a data transmitting/receiving apparatus and method in a wireless system capable of enhancing performance by coupling (or combining) a transmission power controlling method and an erasure-error correction method.  
           [0011]    A data transmission apparatus in a wireless system may be provided that includes a Q-ary encoding unit to block-encode data to be transmitted and a modulating unit to receive each Q-ary symbol from the Q-ary encoding unit. The Q-ary encoding unit may modulate and output a modulated Q-ary symbol. An amplifying unit may amplify each modulated data to as high a target power for a channel gain and output the amplified data.  
           [0012]    A data transmitting method may also be provided in a wireless system. This may include comparing channel gains in each sub-channel of transmission data with a prescribed (or predetermined) reference value to classify a channel as ‘good’ or ‘bad’. If the channel is classified as ‘bad’, the corresponding data symbol is erased and transmission power is controlled to be ‘0’to stop data transmission, whereas if the channel is classified as ‘good,’ transmission power of all the sub-channels is controlled to be ‘P,’ for example.  
           [0013]    Embodiments of the present invention may also provide a data receiving apparatus in a wireless system that includes a demodulating unit for demodulating a signal received by each sub-channel and outputting a Q-ary symbol. A Q-ary decoding unit may perform a block decoding on a Q-ary symbol of each sub-channel output from the demodulating unit.  
           [0014]    A data receiving method may also be provided in a wireless system that includes comparing channel gains of transmission data for each sub-channel with a prescribed (or predetermined) reference value to classify a channel as ‘good’ or ‘bad’. If the channel is in the ‘bad’ state, it may be determined that a corresponding data symbol has been erased and the symbol is stored. On the other hand, if the channel is in a ‘good’ state, a demodulation may be performed on the data symbol and the demodulated symbol may be stored. The stored symbols may be collected to form a packet unit. A demodulation may be performed according to an erasure-error correction method to restore data.  
           [0015]    The channel gain value may be shared by channels, detected by a receiving end and informed to a sending end through a feedback channel, or estimated through a value detected in a previous data transmission.  
           [0016]    Additional advantages, objects, features and embodiments of the present invention may be set forth in part in the description that 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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The following represents brief descriptions of the drawings in which like reference numerals refer to like elements and wherein:  
         [0018]    [0018]FIG. 1 illustrates a construction of a data transmitter in a wireless system in accordance with an example embodiment of the present invention;  
         [0019]    [0019]FIG. 2 is a flow chart of a data transmitting method in a wireless system in accordance with an example embodiment of the present invention;  
         [0020]    [0020]FIG. 3 illustrates a data receiving apparatus in a wireless system in accordance with an example embodiment of the present invention; and  
         [0021]    [0021]FIG. 4 is a flow chart of a data receiving method in a wireless system in accordance with an example embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 illustrates a construction of a data transmitter in a wireless system in accordance with an example embodiment of the present invention. Other embodiments and configurations are also within the scope of the present invention.  
         [0023]    As shown in FIG. 1, a data transmitting apparatus in a wireless system may include a Q-ary encoding unit  10 , a modulating unit  20  and an amplifying unit  30 . The Q-ary encoding unit  10  may block-encode data to be transmitted. The modulating unit  20  may modulate each Q-ary symbol output from the Q-ary encoding unit  10  and output sub-channel data. The amplifying unit  30  may amplify each modulated sub-channel data to as high a target power for a channel gain and output the amplified data.  
         [0024]    The Q-ary encoding unit  10  may include a Q-ary block encoder  11 , an interleaver  12  and a serial-to-parallel converter  13 . The Q-ary block encoder  11  may add a redundancy to an information sequence block of to-be-transmitted data and map the data to a code sequence block having a greater number of bits. The interleaver  12  may interleave the mapped data symbol to prevent an error on a channel. The serial-to-parallel converter  13  may convert the interleaved serial Q-ary code symbol into an M-parallel bit and output the bits to each sub-channel. ‘Q’ may be a multiple of ‘2’ and ‘M’ is log 2 Q and indicates a number of sub-channels. For example, in an 8-ary in which Q is 8, since ‘M’ is log 2 8=3, the number of sub-channels may be 3.  
         [0025]    The modulating unit  20  may include a modulator for each of the sub-channels to modulate Q-ary symbols of each Q-ary symbol and output them.  
         [0026]    The amplifying unit  30  may include an amplifier for each of the sub-channels to amplify each sub-channel to a target power for a channel gain and output the amplified signals.  
         [0027]    [0027]FIG. 2 is a flow chart of a data transmitting method in a wireless system in accordance with an example embodiment of the present invention. Other operations, orders of operations and embodiments are also within the scope of the present invention.  
         [0028]    [0028]FIG. 2 shows that a sending end detects channel gains (γ i ) of to-be-tramsmitted data for each sub-channel (step S 10 ). The channel gains (γ i ) are obtained through a feedback channel by a receiving end, obtained by being shared between channels, or estimated from a value detected in a previous data transmission.  
         [0029]    The detected channel gains (γ i ) may be compared with a certain (or predetermined) reference value (γ 0 ) (step S 20 ). If one channel gain for all the sub-channels is smaller than the reference value (γ 0 ), then a corresponding channel is determined to be in a bad state and classified as ‘BAD’ (step S 30 ). A corresponding data symbol is erased (step S 40 ) and data transmission may be interrupted by making the transmission power ‘0’ (step S 50 ). In other words, it may be determined that there would be an error in data transmission, so therefore the data transmission is not even made. Even though the sending end does not transmit data, the receiving end can estimate the data that has not been transmitted through sharing information among wireless channels.  
         [0030]    If, however, all the channel gains (γ i ) in every sub-channel are greater than or the same as the reference value (γ 0 ), the corresponding channel is determined to be in a good state and classified as ‘GOOD’ (step S 60 ). The transmission power of the corresponding channel is set as ‘P’ (step S 70 ). ‘P’ may be a constant or a function related to the channel gain (γ i ) and may include a target power value calculated as the receiving end feeds back a measured channel gain to the sending end. The above process may be simplified as follows:  
         [0031]    (γ i )&lt;(γ 0 )→BAD→erasing corresponding symbol and transmission power= 0  (for some, i, iε{1, 2, . . . , M})  
         [0032]    (γ i )≧(γ 0 )→GOOD→not erasing corresponding symbol and transmission power=P (for all i, iε{1, 2, . . . M}), wherein ‘P’ is a constant or a function of γ i .  
         [0033]    Namely, in consideration of an ON-OFF channel inversion power control method, if a channel condition is not good, the transmission power may be allocated to ‘0’ to prevent data transmission, and for an error generated in this case, the corresponding symbol may be designated as an erasure symbol to thereby enhance a correction capability of a block code. The erasure-error correction may be better than a general error correction, and the block code can correct double erasure symbols of the error.  
         [0034]    [0034]FIG. 3 illustrates a data receiving apparatus in a wireless system in accordance with an example embodiment of the present invention. Other embodiments and configurations are also within the scope of the present invention.  
         [0035]    As shown in FIG. 3, a data receiving apparatus in the wireless system may include a demodulating unit  100  and a Q-ary decoding unit  200 . The demodulating unit  100  may demodulate a signal received by each sub-channel and output a Q-ary symbol. A Q-ary decoding unit  200  may perform a block decoding on the Q-ary symbol of each sub-channel output from the demodulating unit  100 .  
         [0036]    The demodulating unit  100  may include a plurality of demodulators for all of the sub-channels so as to demodulate signals received by each sub-channel and appropriately output the signals.  
         [0037]    The Q-ary decoding unit  200  may include a parallel-to-serial converter  201  for converting Q-ary symbols that are input in parallel bits for the plurality of sub-channels into serial bit Q-ary symbols. The parallel-to-serial converter  201  may output the bits to a deinterleaver  202  for performing a deinterleaving on the Q-ary symbols. A Q-ary block decoder  203  may perform an erasure-error correction on the deinterleaved symbol data to restore transmission data.  
         [0038]    [0038]FIG. 4 is a flow chart of a data receiving method in a wireless system in accordance with an example embodiment of the present invention. Other operations, orders of operations and embodiments are also within the scope of the present invention.  
         [0039]    In FIG. 4, channel gains (γ) of received data in each sub-channel are detected (step S 110 ). The detected channel gains (γ i ) are compared with a prescribed (or predetermined) reference value (γ 0 ) (step S 1   20 ).  
         [0040]    If even one channel gain of the plurality of sub-channels is smaller than the reference value (γ 0 ), a corresponding channel is determined to be in a bad state and classified as ‘BAD’ (step S 130 ). If, however, all the channel gains (γ i ) of every sub-channel are greater than or the same as the reference value (γ 0 ), the corresponding channel is determined to be in a good state and classified as ‘GOOD’ (step S 140 ).  
         [0041]    If the classified channel state is ‘BAD’, it is determined the corresponding data symbol has been erased and data is stored (step S 150 ). If the classified channel state is ‘GOOD’, a demodulation is performed on a corresponding data symbol and the data is stored (step  160 ).  
         [0042]    Thereafter, when data are collected to form a packet (step S 170 ), a demodulation is performed according to the erasure-error correction to restore data in the packet unit (step S 1   80 ).  
         [0043]    The above-described data transmitting/receiving apparatus and method in the wireless system has many advantages. For example, by considering the ON-OFF channel inversion power controlling method, if a channel is in a bad state, transmission power can be saved, and because each user controls transmission power independently with respect to other users, an average multiple access interference can be reduced.  
         [0044]    In addition, since a symbol having a high error occurrence probability is designated as an erasure symbol through channel gains and the receiving end restores data through demodulation according to the erasure-error correction method, the correction capability of the block code can be enhanced.  
         [0045]    The foregoing embodiments, advantages and objects 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 above description 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.