Patent Publication Number: US-2007115796-A1

Title: Method and apparatus for transmitting/receiving channel quality information in a wireless communication system

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
      This application claims the benefit under 35 U.S.C. §119(a) of a Korean Patent Application filed in the Korean Industrial Property Office on Aug. 29, 2005 and assigned Serial No. 2005-79687, the entire disclosure of which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention:  
      The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and an apparatus for providing channel quality information in a wireless communication system.  
      2. Description of the Related Art:  
      Current communication systems can be largely divided into wire communication systems and wireless communication systems. The wireless communication systems can be divided according to their multiplexing schemes, for example, a Time Division Multiplexing (TDM) scheme, a Code Division Multiplexing (CDM) scheme, and an Orthogonal Frequency Division Multiplexing (OFDM) scheme. With the current remarkable and rapid development of technologies, the CDM scheme is now most widely used. The CDM scheme can be divided into a synchronous scheme and an asynchronous scheme and is being developed into various schemes capable of providing relatively high-speed data communication.  
      However, since the CDM scheme uses orthogonal codes in order to identify channels, the CDM scheme has now caused shortages in resources due to the limited quantity of orthogonal codes. Therefore, as a replacement for the CDM scheme, the OFDM scheme is now strongly gathering attention. The OFDM scheme, which transmits data using multiple carriers, is a special type of a Multiple Carrier Modulation (MCM) scheme in which an input serial symbol sequence is converted into parallel symbol sequences, and the parallel symbol sequences are modulated with a plurality of mutually orthogonal sub-carriers. The parallel symbol sequences are modulated into a plurality of sub-carrier channels, which are then transmitted.  
      This type of MCM system was first applied to a high-frequency wireless communication for use in the High Frequency (HF) radio in the late 1950&#39;s, and an OFDM scheme for overlapping between a plurality of orthogonal sub-carriers was first studied in the 1970&#39;s. This OFDM scheme implements an orthogonal modulation between multiple carriers, resulting in limited system application. However, in 1971, Weinstein et al. announced that efficient modulation and demodulation can be achieved by using the Discrete Fourier Transform (DCT). Since this announcement, the technology for the OFDM scheme has rapidly developed. Known use of a guard interval and insertion of a cyclic prefix in the art has made it possible to further decrease the negative influence of the OFDM system in relation to the multi-path and delay spread. As a result of such technological development, the OFDM scheme is now widely applied to digital transmission technologies, which include Digital Audio Broadcasting (DAB) and digital television, Wireless Local Area Network (WLAN), and a Wireless Asynchronous Transmission mode (WATM), among others.  
      More specifically, after introduction of use of the DFT, the OFDM has not been widely used due to the complexity in the hardware. However, recent developments in various digital signal processing technologies including Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) have realized actual use of the OFDM.  
      The OFDM scheme is similar to the conventional Frequency Division Multiplexing (FDM). However, the OFDM scheme can achieve optimum transmission efficiency during high-speed data transmission by maintaining the orthogonality between multiple sub-carriers in the transmission. Further, the OFDM scheme has superior frequency-use efficiency and is very resistive to a multi-path fading, which results in an optimum transmission efficiency during high-speed data transmission. Since the OFDM scheme uses an overlapped frequency spectrum, it can effectively use a frequency, is very resistive to a frequency selective fading and a multi-path fading, reduces an Inter-Symbol Interference (ISI) using a guard interval, and provides an equalizer composed of simple hardware. Also, the OFDM scheme is very resistive to an impulse noise, such that it is widely used in communication system architecture.  
      Meanwhile, factors degrading a high speed and high quality data service in wireless communication are usually caused by the channel environment. In the wireless communication, the channel environment is frequently changed by power change of received signals due to fading and the Additive White Gaussian Noise (AWGN), shadowing, Doppler Effect due to movement or frequency speed change of a User Equipment (UE), interference by other users or multi-path signals, among others. Therefore, in order to support a high speed and high quality data service in wireless communication, it is necessary to efficiently overcome such degrading factors. One of the important methods used in order to overcome fading in a wireless communication system is an Adaptive Modulation and Coding (AMC) scheme, which will be discussed below.  
      The AMC scheme is a scheme for adaptively adjusting the modulation scheme and the coding scheme according to channel change in the wireless link. The Channel Quality Information (CQI) of the wireless link is usually detected by measuring a Signal to Noise Ratio (SNR) of a received signal. For example, in a downlink, a UE measures CQI of the downlink and feeds the measured CQI back to a node B through an uplink. The node B estimates the channel status of the downlink based on the CQI of the downlink that is fed back and adjusts the modulation scheme and the coding scheme in accordance with the estimated channel status. According to the AMC scheme, a high order modulation scheme and a high coding rate are applied when there is relatively good channel status. A low order modulation scheme and a low coding rate are applied when there is relatively bad channel status. In comparison with the existing scheme depending on high-speed power control, the AMC scheme can enhance the adaptability to temporally variable characteristics of the channel, thereby improving the average performance of the system.  
      In general, broadband systems simultaneously operate a plurality of AMC channels, instead of operating a single AMC channel. Specifically, a broadband system divides the entire frequency band into a plurality of sub-bands, receives individual CQI for each sub-band fed back from a UE, and independently applies the AMC scheme to each sub-band. This occurs since the broadband system has higher frequency selectivity than a narrowband system. Hereinafter, application of the AMC technology to a broadband OFDM system will be described.  
       FIG. 1  is a graph illustrating an example of a typical broadband OFDM system which uses the AMC technology. The graph shown in  FIG. 1  has an ordinate axis according to orthogonal frequencies and an abscissa axis according to time.  
      In  FIG. 1 , reference numeral  101  denotes one sub-carrier and reference numeral  102  denotes one OFDM symbol. In an OFDM system as shown in  FIG. 1 , the entire frequency band is divided into N sub-carrier groups, that is, N sub-bands, and AMC operation is performed for each sub-carrier group. Hereinafter, one sub-carrier group is called one “AMC sub-band.” Specifically, sub-carrier group #1  103  is referred to as AMC sub-band #1, and sub-carrier group #N  104  is referred to as AMC sub-band #N.  
      In a typical OFDM system, allocation of resources (such as scheduling) is performed with a reallocation period including a plurality of OFDM symbols as noted by reference numeral  105 .  
      As described above, the AMC operation (modulation and coding) is independently performed for each AMC scheduling in the OFDM system. Therefore, each UE feeds back CQI information for each scheduling, and a node B receives the CQI information for each scheduling, performs scheduling for each sub-band, and transmits user data for each sub-band. As an example of the scheduling, the node B selects a UE comprising the best channel quality for each sub-band and transmits data to the selected UE, thereby maximizing the system capacity.  
      According to the characteristics of the AMC operation, it is better for the multiple sub-carriers which are necessary for transmission of data to one UE to be closer. This is because adjacent sub-carriers have similar channel response characteristics while distanced sub-carriers may have largely different channel response characteristics when there is frequency selectivity due to multi-path wireless channels in a frequency domain. Further, the object of the AMC operation is to maximize the system capacity by collecting adjacent sub-carriers comprising good channel responses and transmitting data through the collected adjacent sub-carriers. Therefore, it is preferable to have a structure that can collect adjacent sub-carriers with good channel responses and transmit data through the collected adjacent sub-carriers.  
      Therefore, the AMC technology as described above is proper for data transmission to a specific user. This is because it is preferred that a channel transmitted to a plurality of users, such as a broadcast channel or a common control channel, not be adapted to the channel status of only one user. Further, the AMC is proper for transmission of traffic that is less sensitive to delay, because the AMC technology is basically intended for data transmission to UEs in good channel conditions, and it is impossible to wait until the channel condition of a corresponding user becomes good enough to transmit delay-sensitive traffic, such as real-time traffic including Voice over IP (VoIP) traffic and video conference traffic. In other words, it may be necessary to transmit data in a bad channel condition, in order to guarantee a limit in delay for the users of real-time traffic.  
      Accordingly, there is a need for an improved system and method for adaptively transmitting and receiving channel quality information of each AMC sub-band in application of an AMC technology in a broadband OFDM-based system.  
     SUMMARY OF THE INVENTION  
      An aspect of exemplary embodiments of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of exemplary embodiments of the present invention is to provide a method and an apparatus for adaptively transmitting and receiving channel quality information of each AMC sub-band in application of an AMC technology in a broadband OFDM-based system.  
      An exemplary embodiment of the present invention provides a method and an apparatus in which a UE either transmits or does not transmit channel quality information according to channel conditions, thereby reducing the overhead due to the transmission of the channel quality information.  
      It is still another object of an exemplary embodiment of the present invention to provide a method and an apparatus, which define a speed status of a UE as one of multiple levels and measures and reports channel quality information of the UE according to each level.  
      It is still another object of an exemplary embodiment of the present invention to provide a method and an apparatus, in which information about a channel quality information transmission mode of a UE is transmitted to a node B controlling the target cell during handover of the UE, thereby continuously supporting an adaptive transmission of the channel quality information.  
      According to an exemplary embodiment of the present invention, a method and an apparatus are provided to provide efficient and exact channel quality information by applying an AMC technology in a broadband OFDM system.  
      It is still another object of an exemplary embodiment of the present invention to provide a method and an apparatus, which can improve the system capability by providing exact and efficient channel quality information of each AMC sub-band according to the AMC technology in a broadband OFDM system.  
      In order to accomplish this object, a method for receiving channel quality information of a User Equipment (UE) in a wireless communication system which divides an entire frequency band into multiple sub-bands and uses each of the multiple sub-bands in communication is provided. A speed status of the UE is determined. The determination is made based on a determined speed status as to whether to receive the channel quality information of the UE. A channel quality information transmission mode is reported which indicates a type of the channel quality information, to the UE when a determination is made to receive the channel quality information of the UE. The channel quality information is received from the UE according to the channel quality information transmission mode. Radio resources are allocated to the UE in consideration of the received channel quality information.  
      In accordance with another aspect of an exemplary embodiment of the present invention, a method for transmitting channel quality information of a UE in a wireless communication system which divides an entire frequency band into multiple sub-bands and uses each of the multiple sub-bands in communication is provided. A speed status of the UE is determined and the determined speed status is reported to a node B when the determined speed status is different from a previous speed status. Information from the node B is received, which indicates a channel quality information transmission mode according to the determined speed state. At least one of an average channel quality value of the sub-bands and channel quality information of each of the sub-bands is transmitted to the node B.  
      In accordance with another aspect of an exemplary embodiment of the present invention, an apparatus for transmitting and receiving channel quality information of a User Equipment (UE) in a wireless communication system which divides an entire frequency band into multiple sub-bands and uses each of the multiple sub-bands in communication is provided. The UE determines a speed status of the UE and transmits the determined speed status to a node B when the determined speed status is different from a previous speed status. The node B determines whether to receive the channel quality information of the UE based on the determined speed status. The node B reports a channel quality information transmission mode, which indicates a type of the channel quality information, to the UE when a determination to receive the channel quality information of the UE is made. The node B also receives the channel quality information from the UE according to the channel quality information transmission mode, wherein the received channel quality information is used in order to allocate radio resources to the UE.  
      Other objects, advantages and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other exemplary objects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a graph illustrating an example of a typical broadband OFDM system which uses the AMC technology;  
       FIG. 2  is a block diagram of a node B for determining a channel quality information transmission mode for the AMC operation according to an exemplary embodiment of the present invention;  
       FIG. 3  is a block diagram of a UE for transmitting channel quality information according to an exemplary embodiment of the present invention;  
       FIG. 4  is a flowchart of a process for determining a channel quality information transmission mode in a wireless communication system according to an exemplary embodiment of the present invention;  
       FIG. 5  is a message flowchart illustrating a change in the transmission mode by a request from a UE according to an exemplary embodiment of the present invention;  
       FIG. 6  is a message flowchart illustrating a change in the transmission mode by a command of the node B according to an exemplary embodiment of the present invention;  
       FIG. 7  illustrates channel quality information transmission modes which can be determined based on a speed status of the UE according to an exemplary embodiment of the present invention;  
       FIG. 8  is a message flowchart which illustrates a process for transmitting channel quality information for a speed status of the UE according to a first exemplary embodiment of the present invention;  
       FIGS. 9A and 9B  illustrate a message flowchart of a process for transmission of channel quality information according to the second exemplary embodiment of the present invention;  
       FIG. 10  is a flowchart illustrating an operation of a node B for determining a channel quality information transmission mode according to an exemplary embodiment of the present invention;  
       FIGS. 11A and 11B  illustrate a flowchart of an operation of a UE for determining the speed status of the UE according to the first exemplary embodiment of the present invention;  
       FIGS. 12A and 12B  illustrate a flowchart of an operation of a UE for determining the speed status of the UE according to the second exemplary embodiment of the present invention; and  
       FIGS. 13A and 13B  illustrate a flowchart of an operation of a UE for determining the speed status of the UE according to the third exemplary embodiment of the present invention. 
    
    
      Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures.  
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
      First, several points to be considered for an OFDM system according to an exemplary embodiment of the present invention will be discussed. The following points must be taken into important consideration in design and operation of an OFDM system operating with a plurality of sub-bands.  
      It is necessary to determine the number of sub-bands into which the entire system band will be divided. That is, it is necessary to determine the number N, which is the number of divided sub-bands. Second, it is necessary to determine whether to feedback the channel quality information for all of the N sub-bands to each UE, or to feedback the channel quality information for only a part of the N sub-bands to each UE, or to feedback only an average value for all or only a part of the N sub-bands to each UE.  
      The number of sub-bands into which the entire system band will be divided is important in order to use the frequency selectivity of a channel as much as possible. Specifically, this is because it is most efficient to select sub-carriers with good channel conditions and transit data by using the selected sub-carriers. In order to achieve such selection and transmission, it is best to make the value N as large as possible. In an extreme case, it is beneficial to make N as large as the number of entire sub-carriers. However, when N is too large, the UE may have too much channel quality information to feedback, which results in an uplink load that is too large.  
      If four bits are necessary for transmission of channel quality information for one sub-band by a UE, 40 bits are required in order to transmit channel quality information for ten sub-bands. Such an overhead may be considerably large, in view of the fact that the transmission period of the channel quality information is very short in order to catch up with the fast fading.  
      When the entire system band is divided into a small number N of sub-bands, it may be impossible to properly utilize the frequency selectivity of the channels, so that the gain obtainable from the AMC operation is reduced. The problem of how many sub-bands into which the entire system band will be divided establishes a trade-off relation between the downlink performance and the downlink load. Therefore, the value N must be determined without any bias between the two incompatible objects, the downlink performance improvement and the downlink load reduction.  
      Second, it is necessary to determine whether to feed the channel quality information back for all of the N sub-bands to each UE, or to feed the channel quality information back for only a part of the N sub-bands to each UE, or to feed only an average value back for all or only a part of the N sub-bands to each UE. This issue relates to how to feed the channel quality information back to each UE when the entire system band has been divided into N sub-bands. For example, when the entire system band has been divided into four sub-bands, the UE can feed the channel quality information back according to the following methods.  
      According to the first method, the UE always feeds corresponding channel quality information of all the four sub-bands back, respectively. According to the second method, the UE selects an instantly best sub-band from the four sub-bands and feeds back only the channel quality information of the selected sub-band together with an identifier of the selected sub-band. According to the third method, the UE selects k number of instantly best sub-bands from the four sub-bands (k cannot exceed four) and feeds only the channel quality information of the k selected sub-bands back together with identifiers of the k selected sub-bands. According to the fourth method, the UE always feeds back average channel quality information for the four sub-bands. According to the fifth method, the UE selects k number of sub-bands from the four sub-bands (k cannot exceed four) and feeds back average channel quality information for the k selected sub-bands.  
      Further to the five above-mentioned methods, there may be various additional methods for feeding back the channel quality information for the four sub-bands. Hereinafter, each of the above-mentioned methods will be referred to as a “channel quality information transmission mode.” The channel quality information transmission mode may include a case of transmitting no channel quality information as an enlarged concept. Various channel quality information transmission modes, which will be described below, also have two incompatible aspects, the downlink performance improvement and the downlink load reduction.  
      From among the above methods, when the UE always feeds back the corresponding channel quality information of all four sub-bands, the uplink load may increase, while the node B can recognize the channel quality information of all four sub-bands, for all UEs. In contrast, when the UE feeds back channel quality information of only selected sub-bands, the uplink load decreases. However, the node B can recognize the channel quality information of only the selected sub-bands and cannot recognize the channel quality information of the other sub-bands. It is necessary to take this problem into consideration in order to more efficiently transmit channel quality information in an OFDM system.  
      According to an exemplary embodiment of the present invention, an optimum mode is selected from various modes as illustrated in Table 1 below.  
                   TABLE 1                           Channel quality           information transmission       Environment   mode                                               Downlink load   High   1 out of N, 2 out of N           Low   N − 1 out of N, N out of N       Uplink load   High   1 out of N, 2 out of N, Average               value           Low   N − 1 out of N, N out of N       Speed   High speed   Average value           Low speed   Selection according to other               conditions       Service type   Sensitive/High   N − 1 out of N, N out of N       (service delay   Sensitive/Low   1 out of N, 2 out of N       sensitiveness/   Generous/High   N − 1 out of N, N out of N       required average   Generous/Low   1 out of N, 2 out of N       transmission speed)                  
 
      Table 1 illustrates situations in which environmental conditions can determine the most advantageous channel quality information transmission mode. In Table 1, “k out of N” implies that the UE selects k sub-bands comprising good channel conditions from N sub-bands and feeds back channel quality information of the k selected sub-bands. In Table 1, k denotes an integer which is larger than or equal to 1 and smaller than or equal to N. Further, in Table 1, “average value” implies transmission of average channel quality information of all the sub-bands or a part of all the sub-bands, instead of individual feedback of the channel quality information of each sub-band.  
      Hereinafter, the most advantageous channel quality information transmission modes according to various environmental conditions will be described with reference to  FIG. 1 .  
      When the downlink load is low, there are not many users requiring the service within the system and it is highly probable that multiple sub-bands will be allocated to one user. Therefore, it is preferable to require channel quality information of all the sub-bands from each UE. In contrast, when the downlink load is high, there are many users requiring the service within the system and it is less probable that multiple sub-bands will be allocated to one user. Therefore, a transmission mode, in which each UE feeds back channel quality information of a part of all the sub-bands, is selected. That is, the UE selects only a part of the total N sub-bands and feeds back the channel quality information of only the selected sub-bands, thereby reducing the uplink load.  
      Further, when the uplink load is low, feedback of a large quantity of channel quality information by the UE does not create a big problem. Therefore, in order to send as much information as possible to a node B, a transmission mode for transmitting channel quality information of as many sub-bands as possible is selected. In contrast, when the uplink load is high, increase in the quantity of channel quality information fed back by the UE causes further increase in the uplink load. Therefore, a transmission mode is selected to make the load as small as possible.  
      Meanwhile, when the UE moves at a high speed, it is difficult to efficiently perform the AMC operation because the high speed of the UE implies that the channel status of the UE rapidly changes. Even though the UE has already measured and fed back channel quality information, the channel status may have changed and the UE has a low adaptability to the channel at the time point at which AMC data determined based on the fed back information are actually transmitted. Therefore, when the UE moves at a high speed, instant channel quality information is not highly available, and transmission of an average value of the channel quality information over the fast channel change shows no big difference in the AMC performance from transmission of instant channel quality information. Therefore, when UE moves at a high speed, it is preferable to select a mode which causes the uplink load to be as small as possible.  
      When the UE moves at a low speed, which corresponds to an environment suitable for use of the AMC, it is preferable to determine the transmission mode in consideration of other conditions. It is possible to achieve an optimum determination in view of the service benefit. This may be done by selecting a transmission mode in which high-class UEs, such as users paying large amounts or UEs desired to be assigned priorities in view of the system policy, feed a large quantity of channel quality information back to a UE despite taking up a rather large quantity of uplink load. It is preferable to select a transmission mode that results in a relatively small uplink load for low class UEs.  
      Further, the channel quality information transmission mode may change according to service types. For example, in the case of providing real-time traffic sensitive to delay, if the transmitted data like the VoIP is not large, there is no problem in supporting a service while satisfying a required Quality of Service (QoS) when the UE selects one sub-band with the best channel condition from the N sub-bands and feeds back the channel quality information of the selected sub-band. It is not necessary to increase the uplink load by feeding back channel quality information of multiple sub-bands for such traffics.  
      For real-time traffic requiring a relatively large number of bands, such as traffic for a video conference, it is preferable to increase the number of sub-bands, and the channel quality information of which is to be feed back. For traffic comprising a relatively generous sensitivity to service time delay, it is possible to freely determine the transmission mode in consideration of additional conditions as well as the average required data rate as for the real-time traffic.  
      Hereinafter, structures of a node B and a UE for the above-discussed operation will be briefly described. Next, a process for setup and change of a channel quality information transmission mode in order to apply the AMC according to an exemplary embodiment of the present invention will be discussed.  
       FIG. 2  is a block diagram of a node B for determining a channel quality information transmission mode for the AMC operation according to an exemplary embodiment of the present invention. Hereinafter, an operation of a node B according to an exemplary embodiment of present invention will be described.  
      An upper layer interface  213  is connected to an upper node, such as a core network node, and processes data for transmission/reception of the data to/from the upper node. Specifically, the upper layer interface  213  receives various signaling signals and data signals, provides a data processor  214  with data to be transmitted to a UE from among the received signals, and provides a control unit  211  with the signaling signals (the connection is not shown). Further, the upper layer interface  213  converts the format of the received data from the data processor  214  and transfers the converted data to the upper node. The data processor  214  outputs the data received from the upper layer interface  213  to a multiplexer  215  under the control of the control unit  211 .  
      The control unit  211  performs scheduling, controls various operations of the node B, determines a channel quality information transmission mode according to an exemplary embodiment of the present invention, and generates and outputs a corresponding message to the multiplexer  215 . Further, the control unit  211  can acquire load information of uplink and downlink from a Radio Frequency (RF) unit  216  and/or the data processor  214  in order to receive channel quality information about a channel status. As described above, various methods can be used in order to acquire the load information of the uplink and downlink. A database  212  provides the control unit  211  with information necessary in order to determine the channel quality information transmission mode. The database  212  may store the information necessary in order to determine the channel quality information transmission mode, such as class information of each UE, and service quality information of data provided by each UE, among others. The database  212  may also provide the stored information to the control unit  211 . Further, a database  212  may store only the information of the user currently using the service, while the other information is managed by a specific node of an upper network.  
      The multiplexer  215  multiplexes received data from the data processor  214  and the control unit  211  and outputs the multiplexed data to the RF unit  216 . Then, the RF unit  216  processes the data into a transmission format corresponding to each system and then up-converts the processed data into a signal of an RF band. Specifically, in an OFDM system, the multiplexer  215  modulates input data, performs Inverse Fast Fourier Transform (IFFT) on the modulated data, adds a Cyclic Prefix (CP) to the IFFTed data, converts the CP-added data to data of an RF band, and then transmits the RF band data.  
       FIG. 3  is a block diagram of a UE for transmitting channel quality information according to an exemplary embodiment of the present invention.  
      An RF unit  312  down-converts an RF band incoming signal and provides the down-converted signal to a baseband processor  313 . Then, the baseband processor  313  converts the down-converted incoming signal to data symbols according to a scheme provided by the system. For example, in the case of an OFDM system, the baseband processor  313  eliminates the CP from the down-converted incoming signal, performs Fast Fourier Transform (FFT) on the CP-eliminated incoming signal, and then demodulates the FFTed incoming signal. When the baseband processor  313  transmits data, the baseband processor  313  performs a process similar to the transmission process as in  FIG. 2 . The incoming data that has been processed by the baseband processor  313  is input to a control unit  311 .  
      Meanwhile, the RF unit  312  provides a portion of the incoming signal to a channel quality measurement unit  314 . The channel quality measurement unit  314  measures or obtains channel quality information from the incoming signal and provides the channel quality information to the control unit  311 . Then, the control unit  311  selects necessary channel quality information from the entire channel quality information according to either a negotiation with the node B or a request from the node B, and then transmits only the selected channel quality information in the uplink direction. At this time, the control unit  311  performs the uplink transmission of the selected channel quality information by generating a message for transmission of the selected channel quality information and then outputting the message to the baseband processor  313 .  
      Meanwhile, the UE includes a memory  315  for storing user data and control data, among others. The UE also includes a key input unit  317  for generating a key signal according to user&#39;s input for interfacing with the user and then providing the key signal to the control unit  311 , and a display unit  316  for reporting the status of the UE to the user through letters, pictures, and characters, among others.  
      The UE further includes a mobility measurement unit  318  for measuring the mobility of the UE. The mobility measurement unit  318  manages timers either controlled by the node B or set by the UE itself. The mobility measurement unit  318  also measures and stores the mobility values of the UE, which are expressed as the number of cells through which the UE has passed while each timer operates, and the standard deviation or numerical average speed of signal intensities for the entire frequency bands or downlink pilot channels, among others. The control unit  311  determines the speed status of the UE by referring to the mobility values measured by the mobility measurement unit  318 , reports the determined speed status to the node B, and then reports channel quality information according to a channel quality information transmission mode determined by the node B based on the speed status.  
      The most advantageous channel quality information transmission mode may change according to environmental conditions. First, a process for determining a channel quality information transmission mode according to an exemplary embodiment of the present invention will be described with reference to  FIG. 4 .  
       FIG. 4  is a flowchart of a process for determining a channel quality information transmission mode in a wireless communication system according to an exemplary embodiment of the present invention. As described above, the wireless communication system may take various channel quality information transmission modes.  
      When a node B performs communication with a UE, the node B determines one channel quality information transmission mode from among the various channel quality information transmission modes in step  400 . That is, based on the contents of Table 1, the node B selects one channel quality information transmission mode. Such selection of one channel quality information transmission mode may be achieved through negotiation between the UE and the node B. The UE performs channel quality information according to the transmission mode determined in step  400 . Then, in step  410 , the node B receives channel quality information from the UE according to the determined channel quality information transmission mode. Then, the node B selects the best channel (such as at least one sub-band) from the received channel quality information, and then transmits data to the UE through the selected channel.  
      Meanwhile, it may become necessary to change the channel quality information transmission mode while the UE or the node B determines the channel quality. For example, when the UE determines that it is necessary to change the channel quality information transmission mode in step  420  during call connection according to change in the status (for example channel environment) of the UE, the UE can request change of the current channel quality information transmission mode to another channel quality information transmission mode. Also, when the node B determines that the uplink or downlink channel environment has changed, the node B requests the UE to change the channel quality information transmission mode to another mode. In step  430 , the channel quality information transmission mode is changed through re-negotiation between the node B and the UE. Otherwise, if the node B determines that it is necessary to change the channel quality information transmission mode, the node B commands the UE to change the channel quality information transmission mode being used to another one without re-negotiation. The command is given according to one of the following methods: 
      (1) the node B commands a specific UE to change the channel quality information transmission mode or changes the channel quality information transmission mode through re-negotiation;     (2) the node B commands some UEs within the system to change the channel quality information transmission mode; and     (3) the node B commands all UEs within the system to change the channel quality information transmission mode.    

      The command is carried by common control information transmitted from the node B to the UEs. It should be noted that all of the above-mentioned steps may be performed by one system or some of them may be omitted. For example, change of the transmission mode is limited during the call connection.  
      According to one of the channel quality information transmitting methods proposed by an exemplary embodiment of the present invention, each node B selects one channel quality information transmission mode from various channel quality information transmission modes according to a situation of the node B itself, so that all UEs can use the selected channel quality information transmission mode.  
      In other words, although various channel quality information transmission modes are arranged for one system, the node B uses one channel quality information transmission mode during one transmission period. That is, all UEs controlled by the node B use the same transmission mode instead of using multiple transmission modes during one transmission period. To this end, the node B must report the very channel quality information transmission mode being used from among the various channel quality information transmission modes to the UEs controlled by the node B. If the node B wants to change the transmission mode, the node B reports the changed transmission mode to all UEs controlled by the node B through a broadcast message. That is, the node B uses the broadcast message so that all the UEs can share the information about the changed transmission mode.  
       FIG. 5  is a message flowchart illustrating change in the transmission mode by a request from a UE according to an exemplary embodiment of the present invention.  
      Referring to  FIG. 5 , when it is determined that it is necessary to change the channel quality information transmission mode with reference to Table 1 described above (for example, when the channel status of the UE has been changed to a high-speed channel), the UE transmits a “channel quality information transmission mode change request” message to the node B in step  500 . It is preferred that the channel quality information transmission mode change request message includes “preferred mode” information which indicates a transmission mode which the UE desires. Upon receiving the channel quality information transmission mode change request message including the preferred mode information, the node B determines an approval or a denial of the channel quality information transmission mode change request in consideration of various conditions as shown in Table 1, generates an approval or denial message containing a result of the determination, and then transmits the approval or denial message to the UE in step  502 .  
      When the request has been approved, the transmitted approval message includes information about a mode change time point as well as the information about the determined mode. Upon receiving the mode change approval or denial message from the node B, the UE transmits an “Acknowledgement (ACK) message” to the node B in order to report successive reception of the message (step  504 ). Then, in step  506 , the UE sets the changed mode and transmits the channel quality information in the changed mode at the mode change time point appointed in the approval message.  
       FIG. 6  is a message flowchart illustrating change in the transmission mode by a command of the node B according to an exemplary embodiment of the present invention. The signal flow in  FIG. 6  corresponds to a case in which the node B commands change of the channel quality information transmission mode or broadcasts a changed channel quality information transmission mode.  
      The node B determines the transmission mode of the UE based on Table 1, and transmits a “channel quality information transmission mode change command” message to the UE (step  600 ). The channel quality information transmission mode change command message includes transmission mode information, which indicates a new transmission mode, and mode change time point information. Upon receiving the channel quality information transmission mode change command” message from the node B, the UE transmits an “Acknowledgement message” to the node B in order to report successive reception of the message (step  602 ). Then, the UE changes the transmission mode to a new transmission mode indicated by the node B at the time point appointed in the channel quality information transmission mode change command” message (step  604 ).  
      Hereinafter, exemplary embodiments of the present invention in relation to speed of the UE from among the factors for determining the channel quality information transmission mode will be described. As described above, factors determining the channel quality information transmission mode include downlink/uplink load, service type/QoS, speed of the UE, class of the UE, etc., among which representative information which can have changeability is the speed of the UE. Therefore, specific exemplary embodiments of the present invention of the determination of the channel quality information transmission mode and exemplary embodiments of the present invention relating to support for the channel quality information transmission mode in consideration of the mobility of the UE such as handover will be described while focusing on the speed of the UE. The following description is based on an assumption that the entire frequency band is divided into N number of sub-bands for the AMC (that is, AMC sub-bands). Each sub-band includes one or more continuous or discontinuous sub-carriers.  
       FIG. 7  illustrates channel quality information transmission modes which can be determined based on a speed status of the UE according to an exemplary embodiment of the present invention. Hereinafter, three levels of the speed status are defined, and use of different channel quality information transmission modes according to the levels of the speed status will be described.  
      Referring to  FIG. 7 , reference numeral  701  denotes a Low Speed Status (LSS) of the UE. The LSS  701  implies that it is highly probable that the channel environment of the UE does not rapidly change but is stable. At this time, the UE feeds back an average value of the channel quality of the entire N sub-bands and channel quality information of each of K sub-bands (K=N−M; M is an integer smaller than N and larger than 0; and K is an integer larger than or equal to 1 and smaller than or equal to N). In other cases, the UE feeds back only the channel quality information for each of the K sub-bands in the LSS  701 .  
      If the channel quality information transmission mode is not limited by factors other than the speed of the UE, it is possible to feedback the channel quality information of the K sub-bands in the LSS  701 . For example, even when the UE is in the LSS  701 , if it is impossible to allocate a sub-band due to the downlink load or the QoS of the service requested by the UE, the UE can feed back only an average value of the channel quality information for the N sub-bands instead of feeding back the channel quality information of the K sub-bands.  
      That is to say, the LSS  701  refers to a low speed movement of the UE. At this time, the UE may feed back an average value of the channel quality information for the N sub-bands and/or the channel quality information for each of the K sub-bands. In determining the channel quality information transmission mode, it is of course possible to consider other factors in addition to the speed of the UE. That is, in the LSS  701 , the channel quality information can be transmitted as long as the transmission of the channel quality information is not limited by other factors.  
      The average value of the channel quality for the N sub-bands can be used to determine a coding rate of a Distributed Resource Channel (DRCH), which does not belong to one sub-band but is distributed over all the bands, when the node B allocates the DRCH to the UE. Further, the average value of the channel quality for the N sub-bands can be used for power control, among others in communication with the UE. The channel quality information of each of the K sub-bands is used when each sub-band is allocated to the UE, and the number K of the sub-bands to be reported can be determined through negotiation with the UE and the node B either when the UE starts the service or during the service. The negotiation is performed in consideration of the class of the UE, the service requested by the UE and the QoS of the service, and the downlink/uplink load, among others.  
      Reference numeral  703  denotes a High Speed Status (HSS) of the UE. In the HSS  703 , the channel quality information cannot be used in allocation of the DRCH or each sub-band or power control since the channel environment of the UE can rapidly change. This is because the channel quality information at the rapidly changing channel environment of the HSS  703  has no reliability and is not stable. Therefore, in the HSS  703 , it is unnecessary to feed back the average value of the channel quality for the N sub-bands and the channel quality information of the K sub-bands. In the HSS  703 , the UE does not perform the transmission of the channel quality information. Therefore, the radio resources saved due to the non-transmission of the channel quality information can be used in another signaling or data transmission.  
      Reference numeral  702  denotes an Unknown Speed Status (USS) which is neither the HSS  703  nor the LSS  701 . The USS  702  may be an intermediate speed which is neither the high speed nor the low speed. Or, the USS  702  may be a status which is an instantly high or low speed but cannot satisfy conditions such as speed maintenance time required for the LSS  701 . That is, the USS  702  implies that the UE moves at a continuous intermediate speed or at a discontinuous high or low speed that cannot be determined to be the HSS or the LSS. At the USS  702 , the UE feeds back only the average value of the channel quality for the N sub-bands as the channel quality information. This is because the channel quality information for each of the K sub-bands at a status in which the speed status of the UE is not exactly known does not have enough reliability and stability to be used for allocation of the sub-bands based on the channel quality information.  
      The three speed status levels  701  to  703  shown in  FIG. 7  are used to determine the channel quality information transmission mode. The speed status of the UE described above are indispensable for determination of the channel quality information transmission mode, and it is possible to reduce the overhead of the channel quality information fed back from the UE to the node B by the three levels of speed status  701  to  703 . If only one or two speed status levels are used, information needed to determine the channel quality information transmission mode is insufficient, and it is thus impossible to efficiently determine the channel quality information transmission mode. When more sub-divided levels are used, the complexity in the calculation of the speed of the UE increases, and the overhead of the information fed back to the node B from the UE according to the sub-divided levels also increases. Therefore, as shown in  FIG. 7 , it is preferred to define three levels of UE speed, which can achieve efficient allocation of the channel quality information transmission mode and can reduce the complexity of the UE and the overhead of the speed information fed back to the node B. However, in order to reduce the overhead fed back or to achieve efficient scheduling, it is possible to use less than three levels or more than three speed status levels.  
      Reference numeral  711  denotes an LSS-USS threshold condition which draws a boundary between the LSS  701  and the USS  702 , and uses THRESHOLD_USS_LSS as its condition parameter. Reference numeral  712  denotes an HSS-USS threshold condition which draws a boundary between the HSS  703  and the USS  702 , and uses THRESHOLD_HSS_USS as its condition parameter. When a measured mobility of the UE satisfies the LSS-USS threshold condition  711 , the speed status of the UE is determined as the LSS  701 . When the measured mobility of the UE satisfies the HSS-USS threshold condition  712 , the speed status of the UE is determined as the HSS  703 . When the measured mobility of the UE does not satisfy the LSS-USS threshold condition  711  or the HSS-USS threshold condition  712 , the speed status of the UE is determined as the USS  702 . The mobility of the UE may be measured through the following three methods.  
      The first method for determining the mobility of the UE is to use the number of cells through which the UE has passed during a predetermined time interval (which will be referred to as “algorithm 0” hereinafter). In this method, each of the parameters THRESHOLD_USS_LSS and THRESHOLD_HSS_USS include a timer and the number of cells passed through. For example, the parameters THRESHOLD_USS_LSS and THRESHOLD_HSS_USS may be constructed as follows: 
      THRESHOLD_USS_LSS: timer T 1 , the number N 1  of cells passed through     THRESHOLD_HSS_USS: timer T 2 , the number N 2  of cells passed through    

      The UE determines the speed status as the LSS when the number of cells through which the UE has passed during T 1  is smaller than N 1 , and determines the speed status as the HSS when the number of cells through which the UE has passed during T 2  is larger than N 2 . When neither of the two conditions are satisfied, the UE determines the speed status as the USS. T 1  and T 2  may have different values or the same value, and N 2  may usually be larger than N 1 .  
      The second method for determining the mobility of the UE is to use a fluctuation of an average value of the signal intensity of the N sub-bands or the downlink pilot channel measured during a predetermined time interval (which will be referred to as “algorithm 1” hereinafter). In this method, each of the parameters THRESHOLD_USS_LSS and THRESHOLD_HSS_USS include a timer and a standard deviation. For example, the parameters THRESHOLD_USS_LSS and THRESHOLD_HSS_USS may be constructed as follows: 
      THRESHOLD_USS_LSS: timer T 3 , a standard deviation V 1  of signal intensities     THRESHOLD_HSS_USS: timer T 4 , a standard deviation V 2  of signal intensities    

      The UE determines the speed status as the LSS when the standard deviation of the signal intensities for the N sub-bands or the downlink pilot channel measured by the UE during T 3  is smaller than V 1 , and determines the speed status as the HSS when the standard deviation of the signal intensities for the N sub-bands or the downlink pilot channel measured by the UE during T 4  is larger than V 2 . When neither of the two conditions are satisfied, the UE determines the speed status as the USS. The fact that the standard deviation of the signal intensities measured for the N sub-bands or the downlink pilot channel is large implies that the channel status rapidly changes, thereby causing intensive variation of the measured signal intensity with respect to the average value of the signal intensities. In contrast, the fact that the standard deviation of the signal intensities measured for the N sub-bands or the downlink pilot channel is small implies that the channel status is relatively stable, resulting in a small variation of the measured signal intensity with respect to the average value of the signal intensities. T 3  and T 4  may have different values or the same value, and V 2  is usually larger than V 1 .  
      The third method for determining the mobility of the UE is to use an average speed actually measured during a predetermined time interval by a UE which can receive a Global Positioning System (GPS) signal or is equipped with a separate speed measurement module (which will be referred to as “algorithm 2” hereinafter). In this method, each of the parameters THRESHOLD_USS_LSS and THRESHOLD_HSS_USS include a timer and an average numerical speed. For example, the parameters THRESHOLD_USS_LSS and THRESHOLD_HSS_USS may be constructed as follows: 
      THRESHOLD_USS_LSS: timer T 5 , an average numerical speed S 1      THRESHOLD_HSS_USS: timer T 6 , an average numerical speed S 2     

      The UE determines the speed status as the LSS when an average numerical speed (for example, 15 Km/h) measured during T 5  is smaller than S 1 , and determines the speed status as the HSS when an average numerical speed (for example, 68 Km/h) measured during T 6  is larger than S 2 . When neither of the two conditions are satisfied, the UE determines the speed status as the USS. T 5  and T 6  may have different values or the same value, and S 2  may usually be larger than S 1 .  
      When the speed status has been changed as a result of determination based on THRESHOLD_USS_LSS and THRESHOLD_HSS_USS, the UE reports the changed speed status to the node B, and the node B determines an available channel quality information transmission mode based on the reported speed status and reports the determined channel quality information transmission mode to the UE.  
       FIG. 8  is a message flowchart which illustrates a process for transmitting channel quality information for a speed status of the UE according to a first exemplary embodiment of the present invention. Reference numeral  801  denotes a UE (the speed status of the UE  801  is changing from the USS to the HSS), reference numeral  802  denotes a serving node B for the UE  801 , and reference numeral  803  denotes a target node B controlling a target cell to which the UE will handover from a serving cell controlled by the serving node B  802 .  
      In step  811 , the serving node B  802  transmits parameters used for use in the determination of the speed status of the UE  801  to the UE  801  through system information broadcasted within the cell. The transmitted parameters include THRESHOLD_USS_LSS and THRESHOLD_HSS_USS. The THRESHOLD_USS_LSS and THRESHOLD_HSS_USS include different values depending on the algorithm for determination of the speed status of the UE. Examples which may be included in the system information for the three types of speed status determination algorithms are as follows.  
                                                  Algorithm 0 (using the number of cells passed through)           - THRESHOLD_USS_LSS           &gt; Timer T1             &gt; N1 (the number of cells passed through)             - THRESHOLD_HSS_USS           &gt; Timer T2             &gt; N2           Algorithm 1 (using variation of signal intensities)           - THRESHOLD_USS_LSS           &gt; Timer T3             &gt; V1 (standard variation of signal intensities)             - THRESHOLD_HSS_USS           &gt; Timer T4             &gt; V2           Algorithm 2 (using actual average speed)           - THRESHOLD_USS_LSS           &gt; Timer T5             &gt; S1 [Km/h]             - THRESHOLD_HSS_USS           &gt; Timer T6             &gt; S2 [Km/h]                      
 
      Multiple values according to the three types of speed status determination algorithms may be included in the system information, and the UE selects one of the speed status determination algorithms according to the capability of the UE. For example, a UE capable of receiving a GPS signal selects algorithm 2, while a UE incapable of receiving a GPS signal selects algorithm 0 or 1. According to another exemplary embodiment of the present invention, the serving node B  802  transmits information including one or more speed status determination algorithms to a specific UE according to the capability of the UE.  
      In step  820 , the UE  801  requests a service from the serving node B  802  in order to start to receive the service. If the UE  801  requests the service without transmitting information indicating the speed status of the UE  801  and the serving node B  802  does not recognize the speed status of the UE  801 , the serving node B  802  considers the speed status of the UE  801  as the USS (step  821 ). This is because it is possible to minimize an impact due to possible erroneous determination about the speed status of the UE by considering the speed status as the USS rather than the HSS or the LSS. When the speed status has been erroneously determined as the HSS even though it is not the HSS, it is impossible to set a modulation method or a coding rate to be used in a DRCH when the DRCH is allocated and to perform initial power control. When the speed status has been erroneously determined as the LSS, even though it is not the LSS, the UE may unnecessarily transmit channel quality information for each of the K sub-bands.  
      When the UE requests the service in step  820 , the UE  801  can report the speed status of the UE  801  itself to the serving node B  802  in step  820 . This can be done if the UE  801  is already performing an operation for determination of the speed status while either receiving or not receiving another service different from the service the UE requested. Then, in step  821 , the serving node B  802  exactly sets the speed status of the UE  801  in accordance with the report from the UE  801 .  
      After the speed status of the UE  801  is set as the USS, the serving node B  802  allocates resources/channels for the requested service in step  822 . In step  822 , because the serving node B does not know the speed status of the UE  801  and has not received a report for channel quality information about each sub-band, the serving node B  802  allocates the DRCH instead of the sub-band. Further, in step  822 , the serving node B  802  reserves resources of a CQI channel for receiving channel quality information from the UE  801  and reports the reserved resources to the UE  801 . At this time, because the speed status of the UE  801  has been considered as the USS in step  821 , the serving node B  802  allocates CQI channel resources only enough for feedback of an average value of channel quality information of all the N sub-bands. As a result, the information about the allocated DRCH and CQI channel indicates the channel quality information transmission mode allowed for the UE  801 . That is, the UE  801  recognizes the allowed channel quality information transmission mode based on the quantity of the resources of the CQI channel allocated in step  822 .  
      In steps  831  to  833 , the UE  801  transmits a channel quality information report message including the average channel quality value for the N sub-bands, that is, a CQI REPORT [AVERAGE], to the serving node B  802  by using the resources of the allocated CQI channel. The CQI REPORT [AVERAGE] is repeatedly transmitted at a predetermined CQI REPORT [AVERAGE] period  832 . The CQI REPORT [AVERAGE] period  832  is either provided together with the resource/channel information of step  822  to the UE  801  or set as a fixed value.  
      In step  841 , the UE  801  continuously measures the mobility of the UE  801  by using the parameters acquired in step  811 , and recognizes that the UE  801  is in the HSS. Then, in step  842 , the UE  801  transmits indication information or an indication message HSS_IND to the serving node B  802 , which reports that the current speed status of the UE  801  is the HSS. The HSS_IND is included in and transmitted by a specific message or the CQI REPORT [AVERAGE]. In order to insert the HSS_IND into the CQI REPORT [AVERAGE], the CQI REPORT [AVERAGE] has bits predefined in order to indicate the HSS_IND. In step  843 , the serving node B  802  transmits an ACK message of layer  2  or layer  3  to the UE  801  in response to the HSS_IND.  
      After receiving the ACK message in step  843 , the UE  801  does not perform the CQI report in step  851 . At this time, no CQI report implies that the UE does not feed back an average value of channel quality of the N sub-bands as well as the channel quality information of each of the K sub-bands. After transmitting the ACK in step  843 , the serving node B  801  can use the resource of the CQI channel, which was allocated for the UE  801  in step  822 , for another purpose in step  852 . For example, the resource may be allocated to a data transmission channel of the UE  801  or to another UE. This is because the UE  801  is in the HSS and does not transmit any channel quality information and it is thus inefficient to reserve resources of a CQI channel for periodic transmission of channel quality information by the UE  801 .  
      In step  861 , the UE  801  moves from the serving cell controlled by the serving node B  802  to the target cell to begin a handover procedure. The handover procedure may be based on the UE  801  or the network, and a detailed description thereof will be omitted because it has no relation to the core of an exemplary embodiment of the present invention. After the handover procedure is started, the serving node B  802  reports the current speed state of the UE  801  to the target node B  803  which controls the target cell in step  862 . At this time, the current speed state of the UE  801  and information for use in the determination of the channel quality information transmission mode such as the class of the UE  801  may be reported. Specifically, in step  862 , the serving node B  802  transmits HSS_IND to the target node B  803 , which reports that the current speed state of the UE  801  is the HSS.  
      In step  863 , the target node B  803  does not reserve resources for transmission of the channel quality information for the UE  801  in the HSS. Then, in step  864 , the handover procedure is completed, and the movement of the UE  801  to the target cell controlled by the target node B  803  is completed. Because the UE  801  is in the HSS, the UE  801  does not transmit the channel quality information to the target node B  803 .  
      While the UE  801  is connecting with the target node B  803 , the UE  801  recognizes that its speed state has been changed from the HSS to the USS (step  871 ). The speed status determination algorithm may be selected from the three exemplary algorithms described above. In step  872 , the UE  801  transmits indication information or an indication message reporting the changed speed status (USS), that is, USS_IND, to the target node B  803 . The USS_IND is included in and transmitted by a specific message or another message such as the CQI REPORT [AVERAGE]. In step  873 , the target node B  803  transmits an ACK message of layer  2  or layer  3  to the UE  801  in response to the USS_IND. The ACK message includes CQI_CH which indicates information about resources of the CQI channel allocated to the UE  801  for transmission of the channel quality information. Because the UE  801  is in the USS, the CQI_CH indicates resources for the CQI REPORT [AVERAGE], and it is unnecessary to reserve resources for transmission of channel quality information of each of the K sub-bands. As a result, the CQI_CH indicates the channel quality information transmission mode allowed for the UE  801 .  
      In steps  881  and  882 , the UE  801  transmits CQI REPORT [AVERAGE], which indicates the average channel quality value for the N sub-bands by the resources according to the CQI_LCH, to the target node B  803  at a predetermined CQI REPORT [AVERAGE] period. The CQI REPORT [AVERAGE] period is either indicated by the CQI_CH or set as a fixed value.  
       FIGS. 9A and 9B  illustrate a message flowchart of a process for transmission of channel quality information according to the second exemplary embodiment of the present invention, wherein reference numeral  901  denotes a UE (the speed status of the UE  901  is changing from the USS to the LSS), reference numeral  902  denotes a serving node B for the UE  901 , and reference numeral  903  denotes a target node B controlling a target cell to which the UE will handover from a serving cell controlled by the serving node B  902 .  
      In step  911 , the serving node B  902  transmits parameters used for use in the determination of the speed status of the UE  901  to the UE  901  through system information broadcasted within the cell. The transmitted parameters include THRESHOLD_USS_LSS and THRESHOLD_HSS_USS. In step  920 , the UE  901  requests a service from the serving node B  902  to start to receive the service. If the UE  901  requests the service without transmitting information indicating the speed status of the UE  901  and the serving node B  902  does not recognize the speed status of the UE  901 , the serving node B  902  considers the speed status of the UE  901  as the USS (step  921 ).  
      When the UE requests the service in step  920 , if the UE  901  is already performing an operation for determination of the speed status while either receiving or not receiving another service different from the service the UE requested, the UE  901  can report the speed status of the UE  901  itself to the serving node B  902  in step  920 . Then, in step  921 , the serving node B  902  exactly sets the speed status of the UE  901  in accordance with the report from the UE  901 .  
      After the speed status of the UE  901  is set as the USS, the serving node B  902  allocates resources/channels for the requested service in step  922 . In step  922 , because the serving node B does not know the speed status of the UE  901  and has not received a report for channel quality information about each sub-band, the serving node B  902  allocates the DRCH instead of the sub-band. Further, in step  922 , the serving node B  902  reserves resources of a CQI channel for receiving channel quality information from the UE  901  and reports the reserved resources to the UE  901 . According to an exemplary implementation, once the speed status of the UE  901  had been considered to be the USS in step  921 , the serving node B  902  allocates CQI channel resources only enough for feedback of an average value of channel quality information of all the N sub-bands. The information about the resources of the CQI channel indicates the channel quality information transmission mode allowed for the UE  901 .  
      In steps  931  to  933 , the UE  901  transmits a channel quality information report message including the average channel quality value for the N sub-bands, that is, a CQI REPORT [AVERAGE], to the serving node B  902  at a predetermined CQI REPORT [AVERAGE] period  832  by using the resources of the allocated CQI channel.  
      In step  941 , the UE  901  continuously measures the mobility of the UE  901  by using the parameters acquired in step  911 , and recognizes that the UE  901  is in the LSS. Then, in step  942 , the UE  901  transmits indication information or an indication message HSS_IND to the serving node B  902 , which reports that the current speed status of the UE  901  is the LSS. The LSS_IND is included in and transmitted by a specific message or the CQI REPORT [AVERAGE]. To insert the LSS_IND into the CQI REPORT [AVERAGE], the CQI REPORT [AVERAGE] has bits predefined to indicate the LSS_IND. In step  943 , the serving node B  902  transmits an ACK message of layer  2  or layer  3  to the UE  901  in response to the LSS_IND.  
      The ACK message includes CQI_CH which indicates information about resources of the CQI channel allocated to the UE  901  for transmission of the channel quality information. If the transmission of the channel quality information transmission mode for each of the K sub-bands is not limited by other factors, such as a class of the UE, a service type requested by the UE, a requested QoS, and downlink/uplink load, except for the speed of the UE, it is possible to feed back the channel quality information of each of the K sub-bands as well as the average channel quality value for the N sub-bands in the USS. When the serving node B  902  makes a determination to feedback the channel quality information of each of the K sub-bands as well as the average channel quality value for the N sub-bands as described above, the CQI_CH includes information about resources of the CQI channel required for the transmission of multiple pieces of channel quality information. As a result, the CQI_CH indicates a channel quality information transmission mode allowed for the UE  801 .  
      In the process shown in  FIGS. 9A and 9B , the channel quality information of each sub-band is expressed as “CQI REPORT [AMC_BAND_SPECIFIC].” Further, the CQI_CH includes period information for transmission of the CQI REPORT [AMC_BAND_SPECIFIC]. If the CHI_CH in step  943  includes information indicating resources and periods of the CQI channel for the CQI REPORT [AMC_BAND_SPECIFIC], the transmission period of the CQI REPORT [AMC_BAND_SPECIFIC] thereafter is changed based on period information indicated by the ACK message.  
      In steps  951  and  957 , the UE  901  periodically transmits the average channel quality value for the N sub-bands, that is CQI REPORT [AVERAGE], to the serving node B  902  at the CQI REPORT [AVERAGE] period  961 . Further, if the UE  901  has been assigned resources for transmission of the channel quality information of each sub-band through the CQI_CH, the UE  901  transmits the channel quality information of each sub-band, that is, CQI REPORT [AMC_BAND_SPECIFIC], to the serving node B  902  at the CQI REPORT [AMC_BAND_SPECIFIC] period  962  in steps  952 ,  955 , and  956 . Although the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC ] are transmitted at different periods  961  and  962  in the process shown in  FIGS. 9A and 9B , it is possible to transmit one message including both the average channel quality value for the N AMC sub-bands and the channel quality information of each sub-band at the same period.  
      In step  953 , the serving node B  902  determines whether to allocate a sub-band by referring to the class of the UE and the QoS of the service that the UE  901  requested according to the CQI REPORT [AMC_BAND_SPECIFIC] of step  952 . If the serving node B  902  determines to allocate at least one sub-band, the serving node B  902  reports the allocated sub-band or sub-bands to the UE  901  by using a resource re-allocation message (step  954 ).  
      In step  971 , the UE  901  moves from the serving cell controlled by the serving node B  902  to the target cell, so that a handover procedure is started. After the handover procedure is started, the serving node B  902  reports the current speed state of the UE  901  to the target node B  903  which controls the target cell (step  972 ). At this time, the current speed state of the UE  901  and information for use in the determination of the channel quality information transmission mode such as the class of the UE  901  may be reported. Specifically, in step  972 , the serving node B  902  transmits LSS_IND to the target node B  903 , which reports that the current speed state of the UE  901  is the LSS.  
      In step  973 , as long as the transmission of the channel quality information transmission mode for each of the K sub-bands is not limited by other factors that determine the channel quality information transmission mode, the target node B  903  reserves resources of the CQI channel for transmission of the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC] for the UE  901 . In step  974 , the handover procedure is completed, and the movement of the UE  901  to the target cell controlled by the target node B  903  is completed. Thereafter, if the CQI REPORT [AMC_BAND_SPECIFIC] of the UE  901  is reported to the target node B  903 , the target node B  903  may allocate at least one sub-band for the UE  901  by referring to the CQI REPORT [AMC_BAND_SPECIFIC] in step  973 .  
      The target node B  903  allocates resources of the CQI channel similar to that of the serving node B  902  for transmitting the channel quality information of the UE  901  in the LSS, and receives the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC] from the UE  901  through the allocated resources. If the target node B  903  cannot allocate the resources of the same CQI channel as that of the serving node B  902 , that is, if the resources of the CQI channel allocated by the serving node B  902  are already being used by the target node B  903 , the target node B  903  allocates resources of a new CQI channel for receiving a report of the channel quality information from the UE  901 , and reports the newly allocated resources to the UE  901 . Then, the UE  901  transmits an average channel quality value for the N sub-bands and the channel quality information of each of the K sub-bands to the target node B  903  by using the new resources.  
      While the UE  901  is connecting with the target node B  903 , the UE  901  recognizes that its speed state has been changed from the LSS to the USS (step  981 ). The speed status determination algorithm may be selected from the three exemplary algorithms described above. In step  982 , the UE  901  transmits indication information or an indication message reporting the changed speed status (USS), that is, USS_IND, to the target node B  903 . The USS_IND is included in and transmitted by a specific message or another message such as the CQI REPORT [AVERAGE]. In step  983 , the target node B  903  transmits an ACK message of layer  2  or layer  3  to the UE  901  in response to the USS_IND. The ACK message includes CQI_CH which indicates information about resources of the CQI channel allocated to the UE  901  for transmission of the channel quality information. Because the UE  901  is in the USS, the CQI_CH indicates resources for the CQI REPORT [AVERAGE], which may be different from resources for the previously used CQI REPORT [AVERAGE]. It is unnecessary to reserve resources for transmission of channel quality information of each of the K sub-bands.  
      In steps  984  and  986 , the UE  901  transmits the CQI REPORT [AVERAGE], which indicates the average channel quality value for the N sub-bands by the resources according to the CQI_CH, to the target node B  903  at a predetermined CQI REPORT [AVERAGE] period  985 . The CQI REPORT [AVERAGE] period  985  is indicated by the CQI_CH.  
       FIG. 10  is a flowchart illustrating an operation of a node B for determining a channel quality information transmission mode according to an exemplary embodiment of the present invention.  
      Referring to  FIG. 10 , a node B receives an uplink message or information from a UE in step  1001 , and determines if the received information or message includes information indicating the speed status of the UE in step  1002 . If the received information or message does not include indication information, the node B determines if the received information or message requests service or resource/channel in step  1003 . If the received information or message requests service or resource/channel, the node B determines that the initial speed status of the UE is the USS and only the CQI REPORT [AVERAGE] is available for the channel quality information of the UE, and proceeds to step  1022 .  
      In step  1022 , the node B determines that the UE will use the USS transmission mode for transmitting the CQI REPORT [AVERAGE], and proceeds to step  1031 . In step  1031 , the node B determines if the channel quality information will be transmitted according to the channel quality information transmission mode determined for the UE. Meanwhile, in step  1022 , the node B can determine a final channel quality information transmission mode based on other factors for determination of the channel quality information transmission mode, such as UE class, the type of the service requested by the UE, requested QoS, and downlink/uplink load, among others. If the node B determines that the channel quality information will be transmitted in step  1031 , the node B reserves resources of a CQI channel for transmission of the CQI REPORT [AVERAGE] and allocates the reserved resources to the UE. In contrast, if the node B determines that the channel quality information will not be transmitted in step  1031 , the node B does not reserve or allocate resources for a CQI channel of the UE in step  1042 . Meanwhile, if the information or message received in step  1003  does not request service or resource/channel, the node B properly processes the received information or message in step  1004 .  
      If the information or message received in step  1002  includes the information indicating the speed status of the UE, the node B determines if the information indicates the LSS in step  1011 . If the information indicates the LSS, the node B determines to use the LSS transmission mode for transmitting both the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC] for the UE and then proceeds to step  1031 . The determination in step  1021  is based on the other factors for determination of the channel quality information transmission mode. In step  1021 , it is possible to determine whether to transmit both the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC], or to transmit one of them, or to transmit neither of them.  
      In step  1031 , the node B determines if the channel quality information will be transmitted from the UE. If the node B determines in step  1031  that the channel quality information will be transmitted from the UE, the node B reserves resources of a CQI channel for at least one of the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC] according to the channel quality information transmission mode determined in step  1021  and allocates the reserved resources of the CQI channel to the UE in step  1041 . In contrast, if the node B determines in step  1031  to use neither of the CQI REPORT [AVERAGE] and the CQI REPORT [AMC_BAND_SPECIFIC], the node B does not reserve or allocate resources for the CQI channel of the UE in step  1042 .  
      If a determination is made in step  1011  that the information does not indicate the LSS, the node B determines in step  1012  if the information indicates the USS. If the information indicates the USS, the node B determines that only the CQI REPORT [AVERAGE] is available for the channel quality information of the UE, and proceeds to step  1022 .  
      If a determination is made in step  1012  that the information does not indicate the USS, the node B determines in step  1013  whether the information indicates the HSS. If the speed status information indicates the HSS, the node B determines that channel quality information for the UE is unnecessary and proceeds to step  1042  in which the node B does not reserve or allocate resources for the CQI channel of the UE. If it is determined in step  1013  that the speed status information does not indicate the HSS, the node B proceeds to step  1014  in which the node B decides the process as an error.  
       FIGS. 11A and 11B  illustrate a flowchart of an operation of a UE for determining the speed status of the UE according to the first exemplary embodiment of the present invention.  
      Referring to  FIG. 11A , the UE requests a service or resources/channels for the service in step  1101 . Then, in step  1102 , the UE determines if the UE currently possesses available speed status information. For example, the UE may be performing an operation for determination of the speed status because it is already receiving another service instead of the service which the UE wants to request or may keep on performing the operation for determination of the speed status before requesting the service. If the UE currently possesses the speed status information, the UE proceeds to step  1111  in which the UE transmits a service (or resource/channel) request information message including the speed status information to the node B, and then proceeds to step  1121 . By contrast, if the UE determines in step  1102  that the UE currently does not possess available speed status information, the UE proceeds to step  1112  in which the UE transmits a service (or resource/channel) request message including no speed status information to the node B, and then sets the initial speed status to the USS in step  1113 .  
      Although not shown in  FIG. 11A , as a modification of steps  1112  and  1113 , the UE may first set the initial speed status to the USS, and may then transmit a service (or resource/channel) request information message comprising the initial speed status set to the USS to the node B. As described above, the UE sets the initial speed status to the USS if the UE currently possesses no available speed status information when the UE requests a service or resources/channels for the service.  
      After step  1113 , the UE starts timers T 1  and T 2  provided by system information. The timers T 1  and T 2  and the number N 1  and N 2  of cells passed through are as described above. When the time interval of the timer T 1  expires in step  1121 , the UE determines whether the number of cells through which the UE has passed during the time interval of the timer T 1  is smaller than N 1  in step  1131 . If the number of cells passed through is smaller than N 1 , the UE sets the speed status to the LSS in step  1141 . In step  1151 , the UE determines whether the set speed status is equal to the previous speed status. If the set speed status is different from the previous speed status, the UE reports to the node B that the speed status of the UE has been changed to the LSS, and proceeds to step  1171 . If the previous speed status is the LSS, the UE does not perform step  1161  and proceeds to step  1171 . In step  1171 , the UE initializes the number of cells through which the UE has passed during the time interval of the timer T 1 , restarts the timer T 1 , and returns to step  1121 .  
      Meanwhile, if a determination is made in step  1131  that the number of cells through which the UE has passed during the time interval of the timer T 1  is not smaller than N 1 , the UE determines if the current speed status is the HSS in step  1132 . If the UE is not in the HSS, the UE sets the speed status to the USS in step  1142  and determines in step  1152  whether the setup speed status is equal to the previous speed status. If the previous speed status is not the USS, the UE reports to the node B in step  1162  that the speed status of the UE has been changed to the USS, and then proceeds to step  1171 . If it is determined in step  1152  that the previous speed status is the USS, the UE does not perform step  1162  and proceeds to step  1171 .  
      Meanwhile, if it is determined in step  1121  that the time interval of the timer T 1  has not expired, the UE determines in step  1122  of  FIG. 11B  if the time interval of the timer T 2  has expired. If the time interval of the timer T 2  has expired, the UE determines in step  1133  if the number of cells through which the UE has passed during the time interval of the timer T 2  is larger than N 2 . If the number of cells passed through is larger than N 2 , the UE sets the speed status to the HSS in step  1143 . In step  1153 , the UE determines if the setup speed status is equal to the previous speed status. If the previous speed status is not the HSS, the UE reports to the node B in step  1163  that the speed status has been changed to the HSS, and proceeds to step  1172 . If the previous speed status is the HSS, the UE initializes the number of cells through which the UE has passed during the time interval of the timer T 2 , restarts the timer T 2 , and returns to step  1121 .  
      Meanwhile, if it is determined in step  1133  that the number of cells passed through is not larger than N 2 , the UE determines in step  1134  if the current speed status is the LSS. If the UE is not in the LSS, the UE sets the speed status of the UE to the USS in step  1144 , and determines in step  1154  if the setup speed status is equal to the previous speed status. If the previous speed status is not the USS, the UE reports to the node B in step  1164  that the speed status has been changed to the USS, and proceeds to step  1172 . If it is determined in step  1154  that the previous speed status is the USS, the UE does not perform step  1164  and proceeds to step  1172 .  
       FIGS. 12A and 12B  illustrates a flowchart of an operation of a UE for determining the speed status of the UE according to the second exemplary embodiment of the present invention.  
      Referring to  FIG. 12A , the UE determines whether to request a service or resources/channels for the service in step  1201 . Then, in step  1202 , the UE determines if the UE currently possesses available speed status information. For example, the UE may be performing an operation for determination of the speed status because it is already receiving another service instead of the service that the UE wants to request or may keep on performing the operation to determine the speed status before requesting the service. If the UE currently possesses the speed status information, the UE proceeds to step  1211 , in which the UE transmits a service (or resource/channel) request information message including the speed status information to the node B, and then proceeds to step  1221 . If the UE determines in step  1202  that the UE currently does not possess available speed status information, the UE proceeds to step  1212  in which the UE transmits a service (or resource/channel) request information message including no speed status information to the node B, and then sets the initial speed status to the USS in step  1213 .  
      To modify steps  1212  and  1213 , the UE may first set the initial speed status to the USS, and may then transmit a service (or resource/channel) request information message comprising the initial speed status set to the USS to the node B. As described above, the UE sets the initial speed status to the USS if the UE currently possesses no available speed status information when the UE requests a service or resources/channels for the service.  
      After step  1213 , the UE starts timers T 3  and T 4  provided by system information. The timers T 3  and T 4  and the signal intensity standard variations V 1  and V 2  as described above are used in the exemplary embodiment of the present invention. When the time interval of the timer T 3  expires in step  1221 , the UE determines whether the standard variation of measured signal intensities for the pilot channel or N sub-bands periodically measured during the time interval of the timer T 3  is smaller than V 1  in step  1231 . If the standard variation is smaller than V 1 , the UE sets the speed status to the LSS in step  1241 . In step  1251 , the UE determines whether the previous speed status is the LSS. If the previous speed status is not the LSS, the UE reports to the node B in step  1261  that the speed status of the UE has been changed to the LSS, and proceeds to step  1271 . If the previous speed status is the LSS, the UE does not perform step  1261  and proceeds to step  1271 . In step  1271 , the UE initializes the standard variation measured during the time interval of the timer T 3 , restarts the timer T 3 , and returns to step  1221 .  
      If a determination is made in step  1231  that the standard variation is not smaller than V 1 , the UE determines whether the current speed status is the HSS in step  1232 . If the UE is not in the HSS, the UE sets the speed status to the USS in step  1242  and determines in step  1252  if the previous speed status is the USS. If the previous speed status is not the USS, the UE reports to the node B in step  1262  that the speed status of the UE has been changed to the USS, and then proceeds to step  1271 . If it is determined in step  1252  that the previous speed status is the USS, the UE does not perform step  1262  and proceeds to step  1271 .  
      In step  1221 , if a determination is made that the time interval of the timer T 3  has not expired, the UE determines in step  1222  of  FIG. 12B  if the time interval of the timer T 4  has expired. If the time interval of the timer T 4  has expired, the UE determines in step  1233  if the standard variation of measured signal intensities for the pilot channel or N AMC sub-bands periodically measured during the time interval of the timer T 4  is larger than V 2 . If the standard variation is larger than V 2 , the UE sets the speed status to the HSS in step  1243 . In step  1253 , the UE determines whether the previous speed status is the HSS. If the previous speed status is not the HSS, the UE reports to the node B in step  1263  that the speed status has been changed to the HSS, and proceeds to step  1272 . If the previous speed status is the HSS, the UE does not perform step  1263  and proceeds to step  1272 . In step  1272 , the UE initializes the standard variation measured during the time interval of the timer T 4 , restarts the timer T 4 , and returns to step  1221 .  
      If a determination is made in step  1233  that the standard variation measured during the time interval of the timer T 4  is not larger than V 2 , the UE determines in step  1234  if the current speed status is the LSS. If the UE is not in the LSS, the UE sets the speed status of the UE to the USS in step  1244 , and determines in step  1254  if the previous speed status is the USS. If the previous speed status is not the USS, the UE reports to the node B in step  1264  that the speed status has been changed to the USS, and proceeds to step  1272 . If it is determined in step  1254  that the previous speed status is the USS, the UE does not perform step  1264  and proceeds to step  1272 .  
       FIGS. 13A and 13B  illustrate a flowchart of an operation of a UE for determining the speed status of the UE according to the third exemplary embodiment of the present invention.  
      Referring to  FIG. 13A , the UE determines whether to request a service or resources/channels for the service in step  1301 . Then, in step  1302 , the UE determines if the UE currently possesses available speed status information. For example, the UE may be performing an operation to determine the speed status because it is already receiving another service instead of the service that the UE wants to request or may keep on performing the operation to determine the speed status before requesting the service. If the UE currently possesses the speed status information, the UE proceeds to step  1311  in which the UE transmits a service (or resource/channel) request information message including the speed status information to the node B, and then proceeds to step  1321 . In contrast, if the UE determines in step  1302  that the UE currently does not possess available speed status information, the UE proceeds to step  1312  in which the UE transmits a service (or resource/channel) request information message including no speed status information to the node B, and then sets the initial speed status to the USS in step  1313 .  
      To modify the steps  1312  and  1313 , the UE may first set the initial speed status to the USS, and may then transmit to the node B a service (or resource/channel) request information message comprising the initial speed status set to the USS. As described above, the UE sets the initial speed status to the USS if the UE currently possesses no available speed status information when the UE requests a service or resources/channels for the service.  
      After step  1313 , the UE starts timers T 5  and T 6  provided by system information. The timers T 5  and T 6  and the numerical average speeds S 1  and S 2  as described above are used in the exemplary embodiment of the present invention. When the time interval of the timer T 5  expires in step  1321 , the UE verifies in step  1331  that the numerical average speed measured during the time interval of the timer T 5  is smaller than S 1 . If the average speed is smaller than S 1 , the UE sets the speed status to the LSS in step  1341 . In step  1351 , the UE determines whether the previous speed status is the LSS. If the previous speed status is not the LSS, the UE reports to the node B in step  1361  that the speed status of the UE has been changed to the LSS, and proceeds to step  1371 . If the previous speed status is the LSS, the UE does not perform step  1361  and proceeds to step  1371 . In step  1371 , the UE initializes the average speed measured during the time interval of the timer T 5 , restarts the timer T 5 , and returns to step  1321 .  
      Meanwhile, if it is determined in step  1331  that the average speed is not smaller than S 1 , the UE determines in step  1332  if the current speed status is the HSS. If the UE is not in the HSS, the UE sets the speed status to the USS in step  1342  and determines in step  1352  if the previous speed status is the USS. If the previous speed status is not the USS, the UE reports to the node B in step  1362  that the speed status of the UE has been changed to the USS, and then proceeds to step  1371 . If it is determined in step  1352  that the previous speed status is the USS, the UE does not perform step  1362  and proceeds to step  1371 .  
      Meanwhile, if a determination is made in step  1321  that the time interval of the timer T 5  has not expired, the UE determines in step  1322  of  FIG. 13B  if the time interval of the timer T 6  has expired. If the time interval of the timer T 6  has expired, the UE determines in step  1333  if the average speed measured during the time interval of the timer T 6  is larger than S 2 . If the average speed is larger than S 2 , the UE sets the speed status to the HSS in step  1343 . In step  1353 , the UE determines if the previous speed status is the HSS. If the previous speed status is not the HSS, the UE reports to the node B in step  1363  that the speed status has been changed to the HSS, and proceeds to step  1372 . If the previous speed status is the HSS, the UE does not perform step  1363  and proceeds to step  1372 . In step  1372 , the UE initializes the average speed measured during the time interval of the timer T 6 , restarts the timer T 6 , and then returns to step  1321 .  
      If a determination is made in step  1333  that the average speed measured during the time interval of the timer T 6  is not larger than S 2 , the UE determines in step  1334  if the current speed status is the LSS. If the UE is not in the LSS, the UE sets the speed status of the UE to the USS in step  1344 , and determines in step  1354  if the previous speed status is the USS. If the previous speed status is not the USS, the UE reports to the node B in step  1364  that the speed status has been changed to the USS, and proceeds to step  1372 . If it is determined in step  1354  that the previous speed status is the USS, the UE does not perform step  1364  and proceeds to step  1372 .  
      Exemplary embodiments of the present invention have been described above in relation to an example of the orthogonal frequency division multiple access system. However, the present invention may also be applied to the use of multiple center carrier frequencies, that is, the multi-carrier DS-CDMA scheme.  
      According to an exemplary embodiment of the present invention as described above, a transmission mode of channel quality information is selected based on three speed status levels of a UE or is not performed, so that the uplink or downlink load may be minimized and the system capability may be maximized. Further, when the UE moves, information necessary to determine the transmission mode of the channel quality information is transmitted to a node B controlling a target cell, so that the present invention can minimize the uplink or downlink load and can maximize the system capability.  
      While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.