Patent Publication Number: US-2005143082-A1

Title: Apparatus for scanning a mobile communication channel and method therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 0072668/2003, filed on Oct. 17, 2003, the contents of which are hereby incorporated by reference herein in their entirety.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a mobile communication system, and more particularly to, an apparatus for scanning a mobile communication channel, such as an intelligent Wideband Code Division Multiple Access (WCDMA) channel, allowing a mobile terminal to scan an optimized channel in a mobile communication network and a method therefore.  
      2. Description of the Related Art  
      A number of countries have adopted mobile communication systems, such as Wideband Code Division Multiple Access (WCDMA) network, for multimedia data transmission. As compared with other mobile communication systems, WCDMA network provides a high quality image service and a high data rate.  
      A mobile terminal, within a WCDMA network, performs a call or uses a data service through a channel (or frequency) allocated by a base station of a corresponding region. Manufacturers of mobile terminals use diverse methods to increase scanning efficiency for allocating channels. One method for increasing scanning efficiency includes scanning a specified fixed frequency band or an entire allocated frequency band within the WCDMA network. However, channels using different frequency bands, or other mobile communication provider networks are not scanned.  
      During peak traffic times, it may be desirable to handover signals to adjacent channels such as a channel in an unallocated frequency band. The handover to the unallocated frequency band (unscanned band) would introduce a communication delay (while the system determines channel availability). This delay may result in reduced quality of service to a user or a base station.  
     SUMMARY OF THE INVENTION  
      The present invention provides an apparatus and a method for scanning communication channels, such as an intelligent Wideband Code Division Multiple Access (WCDMA) channels, for determining availability for receiving and transmitting communication signals. A mobile terminal, for example, using the method and/or system disclosed, scans an optimized channel in a WCDMA network, which results in increased communication efficiency.  
      In one aspect, the communication channels are scanned according to priority established by an occupation number of the channel. The occupation number refers to the number of signals utilizing the channel. In another aspect, the communication channels are scanned according to priority established by a frequency ranking of selected channel.  
      In yet another aspect, an apparatus scans an intelligent WCDMA channel, including a baseband unit, a table unit, a control unit, and a radio frequency unit. The baseband unit processes baseband signals transmitted or received by a mobile terminal. The table unit provides a table of all channels allocated to a WCDMA system, and records and stores occupation numbers of each channel. The control unit scans the channel having a highest occupation number stored as data in the table unit, and selects a communication channel according to priority. The control unit selects the radio frequency unit for transmitting or receiving communication signals through the channel.  
      In another aspect, a method for scanning an intelligent WCDMA channel includes: selecting a frequency group having highest priority, scanning sequentially channels which composes the frequency group according to priority, deciding whether and when an channel that is available exists in the frequency group, and performing communication through the channel.  
      In another aspect, the table unit forms the frequency group by arranging the allocated channels into 5 MHz intervals, accumulating and storing the occupation numbers of each channel, and storing an updated priority of the frequency group.  
      In another aspect, the control unit receives the data from the table unit, selects the frequency group having priority that is the highest, and scans the channels of the selected frequency group according to the priority. The control unit confirms an occupation state of the scanned channel, occupies, registers the channel with, for example, a base station for use when available, and transmits and/or receives communication signals through the channel upon receiving a data communication request, for example, by a user.  
      In yet another aspect, priority is determined by accumulating and storing an occupation number for each of the channels. The priority of a frequency group is stored according to the occupation number. The occupation numbers are accumulated for each channel. When the accumulation of occupation numbers reaches a predetermined upper limit value, the occupation numbers are reduced at a predetermined ratio and the priority of the channels is updated.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.  
      It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
      Features, elements, and aspects of the invention that are referenced by the same numerals in different figures represent the same, equivalent, or similar features, elements, or aspects in accordance with one or more embodiments. In the drawings:  
       FIG. 1  is a structure view illustrating an apparatus for scanning an intelligent WCDMA channel in accordance with the present invention.  
       FIG. 2  is a view illustrating one example of a table created by the apparatus for scanning the intelligent WCDMA channel in accordance with the present invention.  
       FIG. 3  is a view illustrating another example of the table created by the apparatus for scanning the intelligent WCDMA channel in accordance with the present invention.  
       FIG. 4  is a flowchart showing sequential steps of a method for scanning an intelligent WCDMA channel in accordance with the present invention.  
       FIG. 5  is a flowchart showing sequential steps of a method for setting priority of channels in accordance with the present invention.  
       FIG. 6  is a block diagram illustrating a mobile communications device of an embodiment of the present invention.  
       FIG. 7  is a block diagram illustrating a UTRAN according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      References are made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. An apparatus for scanning an intelligent WCDMA channel and a method therefor in accordance with the preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.  
       FIG. 1  is a structure view illustrating the apparatus for scanning the intelligent WCDMA channel. The apparatus for scanning an intelligent WCDMA channel which includes a baseband unit  100 , a table unit  120 , a control unit  110 , and a radio frequency unit  130 .  
      The baseband unit  100  processes baseband signals transmitted or received by a mobile terminal. The baseband signals are, for example, voice, characters, symbols, or image signals.  
      The table unit  120  provides a table of channels allocated to a WCDMA system. The channels are communication channels for transmitting and receiving signals. An occupation number is assigned to each channel. The occupation number is the total number of signals occupying a channel. The table unit  120  records and stores the occupation numbers of each channel. The table unit  120  arranges in 5 MHz intervals the allocated channels to form a frequency group. The occupation number for each channel is accumulated and stored by the table unit  120 . The table unit  120  stores priority that signals are assigned for the frequency group. A highest occupation number, for example, is assigned to a channel that is the least occupied by signals. The least occupied channel, in this example, has the highest priority to receive and/or to transmit signals.  
      The control unit  110  scans for a channel having the highest occupation number in the table unit  120 . The control unit  110  receives the data from the table unit  120 , selects a frequency group having the highest priority, scans the channels of the selected frequency group according to priority, and confirms an operational state (such as available or not available). If the scanned channel is available, the channel is selected (registered). The radio frequency unit  130  transmits or receives signals through the selected channel.  
      The accumulated occupation number is increased for the scanned channel and the data is updated in the table unit  120 . If the occupation number of the channel reaches a predetermined upper limit value, the control unit  110  reduces the accumulated occupation number of the channel stored in the table unit  120  by a predetermined ratio, and updates the priority.  
      If the occupation numbers of three channels are 49, 25 and 10, for example, and the upper limit value is 50, the first channel is re-occupied so that its occupation number can reach 50; the control unit  110  reduces the accumulated occupation numbers of the channels.  
      Other methods can be used to reduce the occupation numbers of the channels. For example, the occupation numbers of the channels can be reduced by ‘1’ or divided by ‘5’. When it is presumed that the occupation numbers of the channels are reduced by ‘10’, the occupation number of the third channel becomes ‘0’. Accordingly, the third channel is not scanned, which increases a scanning speed.  
       FIG. 2  is a view illustrating one example of a table created by the table unit.  
      As shown in  FIG. 2 , X denotes each channel, and numbers over X denote priority or frequency ranking for selecting channels. In addition, columns of each channel represent frequency groups, and the uppermost numbers 1, 2 and 3 represent priority in which the frequency groups are selected.  
      ‘8’ is shown on the second row of the first column in which priority of the frequency group is ‘2’. Thus, the priority or frequency ranking of the corresponding channel is ‘8’. In the same manner, the priority or frequency ranking of the channel of the fourth row of the first column is ‘2’, of the sixth row is ‘14’, of the eighth row is ‘7’, and of the eleventh row is ‘6’.  
      In one example, the channel having the smallest number is the channel having the highest priority or frequency ranking, and the channel having the large number is the channel having the low priority or frequency ranking. Therefore, the channel whose priority or frequency ranking is ‘2’ is the channel having the highest priority or frequency ranking, and the channel whose priority or frequency ranking is ‘14’ is the channel having the lowest priority or frequency ranking. That is, the priority or frequency ranking of the frequency group of priority 2 is 2→4→6→4→7→4→8→4→14.  
      In another example, priority or frequency ranking of the second channel of the sixth column in which priority of the frequency group is ‘1’ is ‘3’, of the fourth channel is ‘9’, of the fifth channel is ‘1’, of the seventh channel is ‘12’, of the ninth channel is ‘4’, and of the eleventh channel is ‘13’. In summary, the priority or frequency ranking is 1→3→4→9→12→13.  
      Priority or frequency ranking of the third, seventh, tenth and eleventh channels of the eleventh column in which priority of frequency group is ‘3’ is ‘15’, ‘5’, ‘10’ and ‘11’, respectively. The priority or frequency ranking becomes 5→10→11→15.  
      If one frequency group is selected from the table, channels are scanned according to priority or frequency ranking of the frequency group.  
      For example, when the frequency group of priority 2 is selected, the channel whose priority or frequency ranking of ‘2’ is scanned first and availability of the scanned channel is confirmed. If the channel is available, the channel is occupied so that communication signals can be transmitted or received through the channel.  
      If not available, the channel of priority ‘6’ is scanned. The ‘6’ channel is scanned for availability. If ‘6’ channel is available, it is occupied so that communication signals can be transmitted or received through the channel.  
      If the channel is unavailable, the channels, in this example, are sequentially scanned; namely, channel corresponding to ranking ‘7’, then if fully occupied then to ranking ‘8’, then if still fully occupied, then to channel ranking ‘14’.  
      If the channels of the frequency group of priority 2 are not available, then channels of the frequency group corresponding to the second highest priority are scanned using a similar methodology as discussed above.  
       FIG. 3  is a view illustrating another example of the table created by the table unit.  
      As illustrated in  FIG. 3 , O denotes offset values of each channel recorded on the table unit, and F denotes frequencies in which the corresponding channels are selected.  
      In general, the radio frequency band allocated to the WCDMA system ranges from 2110 MHz to 2170 MHz. An interval between the frequency bands allocated to each channel is set 200 KHz for reduce channel interferences. In this example, the channel frequencies are 2112.4 MHz, 2112.6 MHz, 2112.8 MHz, . . . , 2167.4 MHz and 2167.6 MHz which resulting in 277 possible channels.  
      Universal Terrestrial Radio Access (UTRA) Absolute Radio Frequency Channel Number (UARFCN) is assigned to each frequency band. The UARFCN is obtained by multiplying each channel frequency by ‘5’ resulting in values ranges from ‘10562’ (obtained by multiplying channel frequency ‘2112.4’ by ‘5’) to ‘10838’ (obtained by multiplying channel frequency ‘2167.6’ by ‘5’).  
      The offset values represent offsets starting from UARFCN 10562. If the offset value is ‘5’, the UARFCN is ‘10567’ obtained by adding the offset value ‘5’ to ‘10562’. If the offset value is ‘30’, the UARFCN is ‘10592’ obtained by adding ‘30’ to ‘10562’. If the offset value is ‘80’, the UARFCN is ‘10562+80’, namely ‘10642’, and the corresponding frequency is ‘010642/5’, namely 2124.4 MHz. In this example, the table unit utilizes the offset values, but alternatively may also use the UARFCN or frequencies.  
      Values of the frequencies are updated until the values reach the upper value limit. In case channels are not selected by using the stored channel information, the frequencies are used to decide priority of the channel scanning process.  
      Priority of the groups is decided by selecting the channel having the highest frequency, namely the highest priority in each group, and comparing the selected channels. In Group 1, the channel having O of 105 has the highest frequency, 50. In Group 2, the channel having O of 75 has the highest frequency, 48. In Group 3, the channel having O of 85 has the highest frequency, 44.  
      When priority of the channels having the highest frequencies in each group is decided, Group 1 has the highest priority and Group 3 has the lowest priority. Accordingly, the priority is decided as Group 1→ Group 2→ Group 3.  
      After the priority of the groups is decided, channels of the group having the high priority are scanned first. In this example, Group 1 has the highest priority, the channel having the highest frequency in Group 1 is scanned first. If the available channel exists, the channel is occupied and used for communication. However, if after all the channels having the highest frequency to the lowest frequency in Group 1 all have been scanned, the available channel does not exist, channels of the group having the second highest priority are scanned. The channels allocated to the system are scanned according to priority until the available channel is scanned.  
      Therefore, the channels can be rapidly efficiently scanned even if channel information is not stored, and the optimized frequencies can be scanned in each region and each mobile communication provider.  
       FIG. 4  is a flowchart showing sequential steps of a method for scanning an intelligent WCDMA channel in accordance with the present invention. When the mobile terminal starts communication (S 400 ), the mobile terminal (control unit of the mobile terminal) selects the frequency group having the highest priority by searching the data of the table unit (S 410 ). The mobile terminal sequentially scans the channels of the selected frequency group according to priority (S 420 ). During the scanning process, the mobile terminal checks whether the communication-available channel exists (S 430 ).  
      If the communication-available channel does not exist, the mobile terminal selects the frequency group having the second highest priority, and repeats the above procedure (S 420  to S 430 ) (S 440 ). If the communication-available channel exists, the mobile terminal occupies the corresponding channel by registering the channel in the base station (S 450 ). After occupying the channel, the mobile terminal accumulates the occupation number of the channel, stores the accumulated number as data (S 460 ), and uses the communication service through the channel (S 470 ). A method for setting priority of channels will be explained with reference to  FIG. 5  below.  
       FIG. 5  is a flowchart showing sequential steps of the method for setting priority of the channels. When the mobile terminal firstly occupies the channel for communication (S 500 ), the mobile terminal (control unit of the mobile terminal) accumulates the occupation number of the channel, and stores the accumulated number in the table unit as data (S 510 ). The mobile terminal updates priority of each frequency group according to the occupation number and stores the priority in the table unit as data (S 520 ). Thereafter, the mobile terminal decides whether the accumulated occupation number reaches an upper limit value (S 530 ).  
      If the accumulated occupation number reaches the upper limit value, the mobile terminal reduces the accumulated occupation numbers of the channels by a predetermined ratio, and updates the priority (S 540 ). As discussed earlier, the apparatus for scanning the intelligent WCDMA channel and the method thereof rapidly efficiently scan and occupy the channel in consideration of priority of the frequency groups and the channels in each region or each mobile communication provider.  
      In addition, the apparatus for scanning the intelligent WCDMA channel and the method thereof, reduce load of the system and improve reliability of the service, by scanning and occupying the optimized channel by updating priority of the used channels.  
      Moreover, the apparatus for scanning the intelligent WCDMA channel and the method thereof may improve quality and speed of the communication service by rapidly scanning the channels.  
      Referring to  FIG. 6 , a block diagram of a mobile communication device  600  of the present invention such as a mobile phone for performing the methods of the present invention. The mobile communication device  600  includes a processing unit  610  such as a microprocessor or digital signal processor, an RF module  635 , a power management module  606 , an antenna  640 , a battery  655 , a display  615 , a keypad  620 , a storage unit  630  such as flash memory, ROM or SRAM, a speaker  645  and a microphone  650 .  
      A user enters instructional information, such as a telephone number, for example, by pushing the buttons of a keypad  620  or by voice activation using the microphone  650 . The processing unit  610  receives and processes the instructional information to perform the appropriate function, such as to dial the telephone number. Operational data may be retrieved from the storage unit  630  to perform the function. Furthermore, the processing unit  610  may display the instructional and operational information on the display  615  for the user&#39;s reference and convenience.  
      The processing unit  610  issues instructional information to the RF module  635 , to initiate communication, for example, transmit radio signals comprising voice communication data. The RF module  635  comprises a receiver and a transmitter to receive and transmit radio signals. The antenna  640  facilitates the transmission and reception of radio signals. Upon receive radio signals, the RF module  635  may forward and convert the signals to baseband frequency for processing by the processing unit  610 . The processed signals would be transformed into audible or readable information outputted via the speaker  645 , for example.  
      The processing unit  610  is adapted to perform the methods as illustrated above in the discussions related to  FIGS. 1 and 2 . As an example, the processing unit  610  is adapted to selecting a frequency group wherein availability of the frequency group to receive or transmit signals is stored as an occupation number; sequentially scanning channels composing the frequency group according to the priority; deciding whether a channel that is available exists within the frequency group; performing communication through the channel when available. Other features, as described above in  FIGS. 1 and 2 , may be incorporated into the processing unit  610 .  
      The processing unit  610  stores the messages received from and messages transmitted to other users in the storage unit  630 , receive a conditional request for message input by the user, process the conditional request to read message data corresponding to the conditional request from the storage unit, and output the message data to the display unit  615 . The storage unit  630  is adapted to store message data of the messages both received and transmitted.  
       FIG. 7  illustrates a block diagram of a UTRAN  700  according to the preferred embodiment of the present invention. The UTRAN  700  includes one or more radio network sub-systems (RNS)  725 . Each RNS  725  includes a radio network controller (RNC)  723  and a plurality of Node-Bs (base stations)  721  managed by the RNC. The RNC  723  handles the assignment and management of radio resources and operates as an access point with respect to the core network. Furthermore, the RNC  723  is adapted to perform the methods of the present invention.  
      The Node-Bs  721  receive information sent by the physical layer of the terminal through an uplink, and transmit data to the terminal through a downlink. The Node-Bs  721  operate as access points, or as a transmitter and receiver, of the UTRAN  700  for the terminal. It will be apparent to one skilled in the art that the mobile communication device  600  (of  FIG. 6 ) may be readily implemented using, for example, the processing unit  610  (of  FIG. 6 ) or other data or digital processing device, either alone or in combination with external support logic.  
      By utilizing the present invention, the user of a mobile communication device may scan channels in a mobile communication system based on priority which determines eligibility of a channel to receive or to transmit a communication signal, as described above in  FIGS. 1 and 2 . For example, the controller may selecting a frequency group wherein availability of the frequency group to receive or transmit signals is stored as an occupation number; sequentially scanning channels composing the frequency group according to the priority; deciding whether a channel that is available exists within the frequency group; and performing communication through the channel when available. It will be apparent to one skilled in the art that the preferred embodiments of the present invention can be readily implemented using, for example, the processing unit  610  (of  FIG. 6 ) or other data or digital processing device, either alone or in combination with external support logic.  
      Although the present invention is described in the context of mobile communication, the present invention may also be used in any wireless communication systems using mobile devices, such as PDAs and laptop computers equipped with wireless communication capabilities. Moreover, the use of certain terms to describe the present invention should not limit the scope of the present invention to certain type of wireless communication system, such as UMTS. The present invention is also applicable to other wireless communication systems using different air interfaces and/or physical layers, for example, TDMA, CDMA, FDMA, WCDMA, etc.  
      The preferred embodiments may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware logic (e.g., an integrated circuit chip, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium (e.g., magnetic storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.).  
      Code in the computer readable medium is accessed and executed by a processor. The code in which preferred embodiments are implemented may further be accessible through a transmission media or from a file server over a network. In such cases, the article of manufacture in which the code is implemented may comprise a transmission media, such as a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope of the present invention, and that the article of manufacture may comprise any information bearing medium known in the art.  
      The logic implementation shown in the figures described specific operations as occurring in a particular order. In alternative implementations, certain of the logic operations may be performed in a different order, modified or removed and still implement preferred embodiments of the present invention. Moreover, steps may be added to the above described logic and still conform to implementations of the invention.  
      The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structure described herein as performing the recited function and not only structural equivalents but also equivalent structures.  
      As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly as defined in the appended claims. Therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.