PATENT DOCUMENT

Publication Number: US-9686740-B2
Application Number: US-201414536371-A
Country: US
Kind Code: B2

Title: Systems and methods for intelligent frequency selection in carrier aggregation enabled networks

Abstract:
Systems and methods that enhance radio link performance in a multi-carrier environment. A method may be performed by a UE that includes scanning a plurality of carrier components for a primary cell, determining a first bandwidth of the primary cell, scanning for a secondary cell, determining a second bandwidth of the secondary cell, determining a maximum aggregated bandwidth by combining the first bandwidth and the second bandwidth and when the maximum aggregated bandwidth exceeds a bandwidth capability of the UE, performing a cell selection procedure to select one of the primary cell or the secondary cell based on a higher of the first bandwidth and the second bandwidth.

Claims:
What is claimed is: 
     
       1. A method, comprising:
 at a user equipment (“UE”):
 scanning a plurality of carrier components for a primary cell; 
 determining a first bandwidth of the primary cell; 
 scanning for a secondary cell; 
 determining a second bandwidth of the secondary cell; 
 
 determining a maximum aggregated bandwidth by combining the first bandwidth and the second bandwidth; and
 when the maximum aggregated bandwidth exceeds a bandwidth capability of the UE, performing a cell selection procedure to select one of the primary cell or the secondary cell based on a higher of the first bandwidth and the second bandwidth. 
 
 
     
     
       2. The method of  claim 1 , wherein the UE is configured to operate in a carrier aggregation mode and wherein, in the carrier aggregation mode the UE receives signals on a first operating band of the primary cell and a second operating band of the secondary cell. 
     
     
       3. The method of  claim 2 , wherein the UE disables the carrier aggregation mode when the maximum aggregated bandwidth exceeds the bandwidth capability of the UE. 
     
     
       4. The method of  claim 2 , wherein the carrier aggregation mode is a Long Term Evolution (“LTE”) carrier aggregation. 
     
     
       5. The method of  claim 1 , further comprising:
 determining a first operating band of the primary cell, wherein the scanning for the secondary cell is performed after the first operating band of the primary cell is identified as one of a plurality of predetermined operating bands. 
 
     
     
       6. The method of  claim 5 , wherein the plurality of predetermined operating bands are operating bands that, when aggregated with further operating bands, have an aggregated bandwidth that potentially exceeds the bandwidth capability of the UE. 
     
     
       7. The method of  claim 5 , further comprising:
 determining a second operating band of the secondary cell, wherein the determining the maximum aggregated bandwidth is performed after a combination of the first operating band and the second operating band is identified as one of a plurality of predetermined operating band combinations. 
 
     
     
       8. The method of  claim 7 , wherein the plurality of predetermined operating band combinations are operating band combinations that have an aggregated bandwidth that potentially exceeds the bandwidth capability of the UE. 
     
     
       9. The method of  claim 1 , wherein the determining the first bandwidth includes:
 decoding a management information block (“MIB”) for the primary cell. 
 
     
     
       10. The method of  claim 1 , further comprising:
 when the maximum aggregated bandwidth does not exceed the bandwidth capability of the UE, performing a cell selection algorithm, wherein parameters for the cell selection algorithm is different from the cell selection procedure. 
 
     
     
       11. The method of  claim 1 , further comprising:
 determining radio conditions of the primary cell and the secondary cell, wherein the performing a cell selection procedure is further based on the radio conditions. 
 
     
     
       12. The method of  claim 1 , further comprising:
 performing a background scan after the cell selection procedure to identify a further cell having a higher bandwidth than the one of the primary cell or the secondary cell; and 
 performing a further cell selection procedure to select the further cell. 
 
     
     
       13. The method of  claim 1 , wherein the secondary cell is one of an overlay cell or an underlay cell. 
     
     
       14. A method, comprising:
 at a user equipment (“UE”):
 attaching to a primary cell within a network; 
 sending an advertisement message indicating that the UE does not support operating band combinations of the primary cell; 
 determining a first bandwidth of the primary cell; 
 scanning for a secondary cell within the network that meets a predetermined criteria; 
 when the secondary cell meets the predetermined criteria:
 determining a second bandwidth for the secondary cell, and 
 determining a maximum aggregated bandwidth by combining the first bandwidth and the second bandwidth; and 
 
 when the maximum aggregated bandwidth exceeds a bandwidth capability of the UE:
 determining one of the primary cell or the secondary cell that has a higher of the first bandwidth and the second bandwidth, and 
 storing information indicating the one of the primary cell or the secondary cell that has a higher of the first bandwidth and the second bandwidth. 
 
 
 
     
     
       15. The method of  claim 14 , further comprising:
 receiving information from the primary cell, the information comprising neighbor measurements of frequencies of secondary cells. 
 
     
     
       16. The method of  claim 14 , further comprising:
 performing a cell selection procedure to select the secondary cell when the information indicates the secondary cell has the higher bandwidth. 
 
     
     
       17. The method of  claim 14 , further comprising:
 when the UE is intended to attach to the primary cell, attaching to the secondary cell when the information indicates the secondary cell has the higher bandwidth. 
 
     
     
       18. The method of  claim 14 , wherein the network is a Long Term Evolution (“LTE”) network, the UE is a carrier aggregation enabled device and the primary and secondary cells are evolved Node B′s (“ENBs”) of the LTE network. 
     
     
       19. A integrated circuit comprising:
 circuitry to scan a plurality of carrier components for a primary cell; 
 circuitry to determine a first bandwidth of the primary cell; 
 circuitry to scan for a secondary cell; 
 circuitry to determine a second bandwidth of the secondary cell; 
 circuitry to determine a maximum aggregated bandwidth by combining the first bandwidth and the second bandwidth; and 
 when the maximum aggregated bandwidth exceeds a bandwidth capability of a UE, circuitry to perform a cell selection procedure to select one of the primary cell or the secondary cell based on a higher of the first bandwidth and the second bandwidth. 
 
     
     
       20. The integrated circuit of  claim 19 , wherein the integrated circuit is configured to operate in a carrier aggregation mode and wherein, in the carrier aggregation mode the integrated circuit receives signals on a first operating band of the primary cell and a second operating band of the secondary cell.

Description:
PRIORITY CLAIM/INCORPORATION BY REFERENCE 
     This application claims priority to U.S. Provisional Application 61/901,327 entitled “Systems and Methods for Intelligent Frequency Selection in Carrier Aggregation Enabled Networks,” filed on Nov. 7, 2013, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Long-term evolution (“LTE”) is a wireless communication standard used for high-speed data for mobile devices and data terminals. LTE-Advanced is a major enhancement to the LTE standard. Within the LTE-Advanced standard, carrier aggregation is used to increase the bandwidth, and thereby increase the bitrates. Carrier aggregation was introduced in the 3rd Generation Partnership Project (“3GPP”) Release 10 (LTE-Advanced standard) and has been carried through to later Releases to provide wider than 20 MHz transmission bandwidth to a single device (e.g., user equipment or “UE”) while maintaining the backward compatibility with legacy UEs. Specifically, carrier aggregation may be defined as the aggregation of two or more component carriers to support wider transmission bandwidths. 
     Carrier aggregation configuration may be defined as a combination of carrier aggregation operating bands, each supporting a carrier aggregation bandwidth class by a UE. The bandwidth class may be defined by the aggregated transmission bandwidth configuration and maximum number of component carriers supported by a UE. For intra-band contiguous carrier aggregation, a carrier configuration may be a single operating band supporting a carrier aggregation bandwidth class. For each carrier aggregation configuration, requirements may be specified for all bandwidth combinations contained within a bandwidth combination set, as indicated by the radio access capabilities of the UE. Accordingly, a UE may indicate support of several bandwidth combination sets for each band combination.  FIG. 1  shows an exemplary table  100  including the requirements for inter-band aggregation as defined for the carrier aggregation configurations and bandwidth combination sets. 
     Under the current LTE standards, each aggregated carrier is referred to as a component carrier, and each component carrier can have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz and a maximum of five component carriers can be aggregated. As illustrated in  FIG. 2 , two exemplary component carriers may each have a bandwidth of 10 MHz to combine for a total bandwidth of 20 MHz. With carrier aggregation features enabled, the LTE-Advanced standard device supporting 20 MHz carrier aggregation may achieve downlink (“DL”) throughput of 100 Mbps. 
     It is possible for a UE utilizing carrier aggregation configuration to support an aggregate maximum bandwidth greater than the capabilities of the device. In other words, a UE limited to a certain bandwidth threshold may have component carriers exceeding that limitation through carrier aggregation. Accordingly, there may be scenarios in which the UE is allocated resources to a carrier components not necessarily having the highest available bandwidth within the UE&#39;s capabilities. 
     SUMMARY 
     Described herein are systems and methods to enhance radio link performance in a multi-carrier environment. A method may be performed by a UE that includes scanning a plurality of carrier components for a primary cell, determining a first bandwidth of the primary cell, scanning for a secondary cell, determining a second bandwidth of the secondary cell, determining a maximum aggregated bandwidth by combining the first bandwidth and the second bandwidth and when the maximum aggregated bandwidth exceeds a bandwidth capability of the UE, performing a cell selection procedure to select one of the primary cell or the secondary cell based on a higher of the first bandwidth and the second bandwidth. 
     Further described herein is another method that may be performed by a UE that includes attaching to a primary cell within a network, sending an advertisement message indicating that the UE does not support operating band combinations of the primary cell, determining a first bandwidth of the primary cell, and scanning for a secondary cell within the network that meets a predetermined criteria. When the secondary cell meets the predetermined criteria, the method further includes determining a second bandwidth for the secondary cell, and determining a maximum aggregated bandwidth by combining the first bandwidth and the second bandwidth. When the maximum aggregated bandwidth exceeds a bandwidth capability of the UE, the method further includes determining one of the primary cell or the secondary cell that has a higher of the first bandwidth and the second bandwidth, and storing information indicating the one of the primary cell or the secondary cell that has a higher of the first bandwidth and the second bandwidth. 
     Further described herein is a method that may be performed by a network component such as a network server that includes determining which of a primary cell and secondary cell within a carrier aggregation pair of a network has a higher priority based on bandwidth capabilities for each of the primary cell and the secondary cell and configuring the primary cell and the secondary cell of the carrier aggregation pair such that the higher bandwidth cell in the pair is designated as a higher priority cell. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  (discussed above) shows a table listing carrier aggregation configurations and bandwidth combination sets. 
         FIG. 2  (discussed above) shows an example of carrier aggregation including two component carriers each having a bandwidth of 10 MHz for a total bandwidth of 20 MHz. 
         FIG. 3  shows an exemplary arrangement including a UE, a PCell and two SCells. 
         FIG. 4  shows an exemplary UE for intelligent frequency selection in carrier aggregation enabled networks. 
         FIG. 5  shows an exemplary method for intelligent frequency selection in carrier aggregation enabled networks. 
         FIG. 6  shows a further exemplary method for intelligent frequency selection in carrier aggregation enabled networks. 
         FIG. 7  shows a further exemplary method for intelligent frequency selection in carrier aggregation enabled networks. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments show systems and methods for intelligent frequency selection in carrier aggregation enabled networks. More specifically, the exemplary embodiments described herein may allow for the selection of a frequency based on a bandwidth combination used by a UE and thus, optimize throughput and performance of the UE. 
     When carrier aggregation is used, there may be a number of serving cells for each of the component carriers. The coverage of the serving cells may differ due to both component carrier frequencies and power planning, which is useful for heterogeneous network planning. A radio resource control (“RRC”) connection is handled by one cell, namely the primary serving cell (“PCell”), served by the primary component carrier (“PCC”) for uplink (“UL”) and downlink (“DL”). 
     The other component carriers may be referred to as secondary component carriers (“SCC”) for UL and DL, serving the secondary serving cells (“SCells”). The SCCs are added and removed as required, while the PCC is changed at handover. Those skilled in the art will understand that the PCell and SCells are logical constructs allowing for the addition of SCells as needed. The PCell is the main cell that is used for all RRC signaling and control procedures, while the SCell is considered an augmentation to the PCell. 
       FIG. 3  shows an exemplary arrangement  300  including a UE  340 , a PCell  310  and two SCells  320  and  330 . The PCell  310  and the SCells  320  and  330  are further connected to a cellular core network  350 . The cellular core network  350  may include various components and logical structures that are used to implement the cellular network (e.g., a Mobile Management Entity (MME), a serving gateway (SG), a PDN Gateway (PGW), etc.). The PCell  310 , the SCells  320  and  330  and the cellular core network  350  are generally components controlled by the cellular network provider (e.g., Verizon, AT&amp;T, Sprint, T-Mobile, etc.). This skilled in the art will understand that a cellular network may have thousands of cells that are distributed over a service area of the cellular network and the inclusion of three cells in  FIG. 3  is only exemplary. 
     In this example, it may be considered that the UE  340  is currently connected to the PCell  310  and the SCell  320 . The SCells  320  and  330  are shown in phantom because, as described above, these SCells may be added and removed as required. Thus, while the arrangement  300  shows the SCell  320  connected to the UE  340 , it may be that at a later time it is determined that SCell  320  is no longer needed, leaving only PCell  310  being connected to the UE  340 . Such a determination may be made based on the throughput requirements that are needed for UL or DL for the UE  340 . In another example, it may be considered that the UE  340  has a higher UL or DL throughput requirement and therefore, an SCell connection needs to be added. In this case, the SCell  330  may be connected to the UE  340 , resulting in PCell  310  and SCell  330  being connected to the UE  340 . It should be noted that while the exemplary embodiments are generally described as the UE  340  being connected to a PCell  310  and one of either SCell  320  or  330 , it may be possible for the UE to be connected to multiple SCells at the same time, e.g., connected to SCells  320  and  330  simultaneously. Thus, it should be understood that the exemplary embodiments are not limited to a single SCell connection. As will be described in greater detail below, the systems and methods for intelligent frequency selection in carrier aggregation enabled networks may be used to select the higher bandwidth cell as the PCell. 
     According to an exemplary embodiment described herein, a carrier may deploy a carrier aggregation configuration using two component carriers. Furthermore, the exemplary two component carrier configuration may utilize bandwidth combination supporting an aggregate maximum bandwidth greater than a threshold value for a bandwidth supported by the UE. According to one embodiment, a chipset limitation on the UE may dictate the threshold value for a maximum aggregate bandwidth for the UE. For instance, the exemplary UE  340  may be limited to support a threshold bandwidth of 20 MHz. The two CC carrier aggregation configuration may support an aggregate maximum bandwidth of 25 MHz (e.g., a 15 MHz CC and a 10 MHz CC). 
     In addition to the performance capabilities of the UE (e.g., the chipset limitations), a plurality of carrier configurations may pose as a potential problem for the UE. Referring back to  FIG. 1 , the table  100  includes the maximum aggregated bandwidths for each of the carrier configurations listed. Using the exemplary UE  340  discussed above (e.g., having a chipset limitation of 20 MHz), certain carrier aggregation configurations would be unusable by this UE. Specifically, the unusable configurations may include any configuration in which the maximum aggregated bandwidth is greater than the 20 MHz limitation of the UE  340 . 
     Referring back to  FIG. 3 , it may be considered that the PCell  310  is a component carrier of 10 MHz, the SCell  320  is a component carrier of 10 MHz and the SCell  330  is a component carrier of 15 MHz. Thus, the combination of the PCell  310  and the SCell  320  results in a carrier aggregated bandwidth of 20 MHz and the combination of the PCell  310  and the SCell  330  results in a carrier aggregated bandwidth of 25 MHz. If, as described above, the capabilities of the UE  340  are limited to a threshold bandwidth of 20 MHz, then it would not be possible for the UE  340  to utilize the aggregate bandwidth of the two component carriers for the combination of the PCell  310  and the SCell  330 . Instead, the UE  340  may only use either one component carrier (e.g., any one of the PCell  310 , SCell  320  or SCell  330 ) or the aggregation of the PCell  310  and the SCell  320  to operate within its limitations. It should be understood that if the UE  340  is going to use the component carriers of either the SCell  320  or  330  as a single component carrier, these component carriers will actually be switched to be a PCell (e.g., via a handover procedure) because the UE  340  cannot be connected to an SCell without a corresponding PCell to handle the RRC and other requirements. 
     If the UE  340  is configured by the cellular core network  350  to use the PCell  310  having 10 MHz bandwidth, then the UE  340  will achieve only a modest throughput (e.g., 50 Mbps). However, selecting the component carrier of the SCell  330  having the 15 MHz carrier allocation as a single component carrier would be more appropriate from a performance and throughput perspective. 
       FIG. 4  shows an exemplary UE  340  for intelligent frequency selection in carrier aggregation enabled networks according to exemplary embodiments described herein. The UE  340  may represent any electronic device that is configured to perform wireless functionalities. For example, the UE  340  may be a portable device such as a phone, a smartphone, a tablet, a phablet, a laptop, etc. In another example, the UE  340  may be a stationary device such as a desktop terminal. The UE  340  may include an antenna  405  connected to a transceiver  420 , which is connected to a baseband processor  430 , which is further connected to an applications processor  410 . The UE  340  may further include a display  440 , an I/O device  450 , a memory arrangement  460  that are accessible by the baseband processor  430  or the applications processor  410 . Those skilled in the art will understand that the UE  340  may also include additional components  470 , for example, a Bluetooth/WiFi transceiver, further input devices (e.g., a keypad, a touchscreen, etc.), a battery, etc. 
     The transceiver  420  and the baseband processor  430  may be used to perform operations such as, but not limited to, scanning the network for specific radio frequency bands, exchanging information with one or more mobile switching centers, etc. It should be noted that the exemplary embodiments are described as being performed by the transceiver  420  and the baseband processor  430 . However, either of these components may perform the described functionalities without the other component. In addition, other components (e.g., the application processor  410 ) may also perform some or all of the functionalities described herein. The application processor  410 , the transceiver  420  and the baseband processor  430  may be, for example, general purpose processors, an application specific integrated circuit (ASIC), another type of integrated circuit and these processors may execute software programs or firmware. 
     According to one exemplary embodiment, specific carrier aggregation band combinations supported by the UE  340  may be a cause for concern based on the limitations of the UE  340 . For instance, referring to the Table  100  of  FIG. 1 , it may be considered that the following carrier aggregation configurations and band combinations may be deemed problematic: CA_ 1 A- 18 A (Band (B) 1 +B 18 ); CA_ 3 A- 5 A (B 3 +B 5 ); CA_ 3 A- 8 A (B 3 +B 8 ) and CA_ 4 A- 13 A (B 4 +B 13 ). Those skilled in the art will understand that each of the band combinations described above are only exemplary and are merely used as an example of band combinations that may be deemed problematic. Each carrier (e.g., Verizon, AT&amp;T, T-Mobile, etc.) may have their own problematic bands based on how the carrier has defined the particular band and carrier aggregation combinations. 
       FIG. 5  shows an exemplary method  500  for intelligent frequency selection in carrier aggregation enabled networks based on system selection criteria. The exemplary method  500  will be described with reference to the exemplary arrangement  300  of  FIG. 3  and the exemplary UE  340  of  FIG. 4 . It is noted that the UE  340  may perform the entirety of method  500 . It is also noted that UE  340  is considered to be a carrier aggregation capable device. 
     In step  505 , the UE  340  that is capable of utilizing a plurality of carrier components (e.g., a carrier aggregation enabled device) may scan for a primary cell and determine a first operating band of the primary cell in an area (e.g., B 1 , B 2 , B 3 , etc.). For example, the transceiver  420  in combination with the baseband processor  430  of the UE  340  may scan for the PCell  310  and determine the operating band of the PCell  310 . 
     In step  510 , the UE  340  may determine if the operating band of the PCell  310  is a problematic band. In the example described above, it was considered that the operating bands B 1 , B 3 , B 4 , B 5 , B 8 , B 13  and B 18  may have problematic combinations. Thus, using the above-described example, if the operating band of PCell  310  was one of these bands, the UE  340  would consider the band to be a problematic band. As described above, the reason the band may be considered to be problematic is that it is a band that is capable of being aggregated with another band to result in a combined carrier aggregation bandwidth that exceeds the capabilities of the UE  340 . It should be noted that the UE  340  may store the information that is shown in table  100  of  FIG. 1  in, for example, the memory  460  of the UE  340 . This will allow the UE  340  to determine if the operating band of the PCell  310  is a problematic band. It should be noted that it is not required that table  100  be stored, but rather just an indication of the potentially problematic bands. 
     If it is determined in step  510  that the operating band of the PCell  310  is not problematic, then the method  500  may end because the UE  340  may use all available carrier aggregation combinations using the PCell  310  and no further steps of the method  500  need to be performed. The UE  340  may perform the normal cell selection algorithm and if carrier aggregation is enabled, use any SCells as instructed by the core network. 
     If the determined operating band of the PCell  310  is a band that may have a problematic combination, the method  500  will continue to step  515  where the UE  340  will scan for an underlay or overlay secondary cell and determine a second operating band of the secondary cell in the area. Thus, if the UE  340  determined that the operating band of the PCell  310  was one of the problematic bands identified in the above example, the UE  340  will scan for the underlay or overlay secondary cell (e.g., SCells  320  and  340 ) and determine the operating band(s) of the secondary cell(s). 
     In step  520 , the UE  340  may determine whether the combination of the primary and secondary cells is problematic based on the combination of the first and second bands. For example, it may be determined in step  505  that PCell  310  had an operating band of B 1 , a possibly problematic band based on the above example, and it further may be determined in step  515  that SCell  320  had an operating band of B 18 . In step  520 , the UE  340  will determine that the band combination of the PCell  310  and SCell  320  (B 1 +B 18 ) is a potentially problematic combination. In another example, it may be determined in step  515  that SCell  330  had an operating band of B 21 . In step  520 , the UE  340  will determine that the band combination of the PCell  310  and SCell  330  (B 1 +B 21 ) is not a potentially problematic combination. If the band combination is not potentially problematic, the method  500  may end because, similar to the negative outcome of step  510 , all available carrier aggregation combinations of the PCell  310  and SCell  330  may be used by the UE  340  and no further steps of the method  500  need to be performed. 
     However, if the result of step  520 , is a potentially problematic combination, the UE  340 , in step  525 , may decode management information blocks (“MIB”) for each carrier aggregation bandwidth combination and determine which combinations are configured to each of the plurality carrier components. It should be noted that the above-identified problematic band combinations are not definitely problems. Rather, the combinations are potential problems because they may exceed the capabilities of the UE  340 . However, the mere identifying of the combination does not guarantee a problem will exist. Further information about the combination is needed to make this determination. 
     Thus, in step  525  the MIBs are decoded for the combination to determine certain information about the combination. One exemplary piece of information that may be included in the MIBs is the maximum aggregated bandwidth for the combination. In step  530 , the UE  340  determines this maximum aggregated bandwidth for the combination. 
     In step  535 , the UE determines if the maximum aggregated bandwidth exceeds a threshold. The threshold is based on the capabilities of the UE  340 . For example, it was considered above that the maximum bandwidth capability of the UE  340  was 20 MHz. If this example is considered, then the threshold would be set at 20 MHz. If the maximum aggregated bandwidth for the band combination is less than or equal to the threshold, the method continues to step  540  where the normal cell selection algorithm is used (e.g., in LTE networks, the normal cell selection algorithm is based on the S-criterion). In other words, the potentially problematic combination of the PCell  310  and SCell  320  operating bands is not problematic for the UE  340  because the maximum aggregated bandwidth of the combination does not exceed the operating characteristics of the UE  340 . To provide a specific example, the maximum operating characteristics of the UE  340  may be 25 MHz and the PCell  310  operating band may have a bandwidth of 10 MHz and the SCell  320  operating band may have a bandwidth of 15 MHz, meaning that the maximum aggregated bandwidth of the combination is 25 MHz, within the operating characteristics of the UE  340 . 
     However, in step  535 , the UE  340  may determine that the maximum aggregated bandwidth of the band combination exceeds the threshold value. If this is the case, the UE  340  cannot perform carrier aggregation using the cells because the identified cells exceed the bandwidth capabilities of the UE  340 . Thus, as described above, the UE  340  will select only one of the available cells as the primary cell. The method  500  proceeds to step  545  where the UE  340  may select one of the primary and secondary cells based on the highest bandwidth between the first and second band. To provide a specific example, the PCell  310  operating band may have a bandwidth of 10 MHz and the SCell  320  operating band may have a bandwidth of 15 MHz, meaning that the maximum aggregated bandwidth of the combination is 25 MHz just as in the above example. However, in this example, the maximum operating characteristic of the UE  340  is 20 MHz, meaning that the maximum aggregated bandwidth of the band combination exceeds the operating characteristics of the UE  340 . The UE  340  in step  535  would determine this and the UE would continue to step  540  where the UE  340  would select the SCell  320  as the cell having the highest available bandwidth (e.g., 15 MHz). However, this does not mean that the UE  340  will automatically perform a cell selection procedure to use the SCell  320  as the primary cell. The method will continue to perform further evaluations of the cells before the cell selection procedure is performed. 
     In step  550 , the UE  340  may determine the radio conditions at each of the primary and secondary cells and may select one of the primary and secondary cells based on the determined radio conditions. For instance, if the RSRP/RSRQ difference (RSRPx−RSRPy&lt;=x dbm or RSRQx−RSRQy&lt;=y db) between the primary and secondary cells is within a certain threshold limit then the UE  340  may choose the cell with the higher bandwidth carrier. That is, while the UE  340  in step  545  will choose the carrier with the higher bandwidth as the primary cell, if the UE in step  550  determines that the higher bandwidth carrier does not meet certain signal quality standards, the UE  340  may select the lower bandwidth carrier. The method  500  will then continue to step  555  where the UE  340  will perform a cell selection procedure based on the selection as made in steps  545  and  550 . 
     To continue with the example above, the UE  340  in step  545  would select the SCell  320  as the primary cell because it has the higher bandwidth (e.g., 15 MHz). However, if the UE  340  performing step  550  determines that the radio conditions of SCell  320  do not meet certain requirements, the UE  340  may select the PCell  310  as the primary cell and perform a cell selection procedure in step  555  to connect to the PCell  310  as the primary cell, even though the PCell  310  has a lower throughput than the SCell  320 . On the other hand, if the SCell  320  radio conditions are satisfactory as determined in step  550 , the UE  340  will perform a cell selection procedure to select the SCell  320  as the primary cell. As described above, when the cell selection procedure is performed to make the SCell  320 , the primary cell, the SCell  320  is no longer an SCell, but is rather a PCell. 
     The method  500  may continue to step  560  where the UE  340  may periodically perform a background scan to determine the availability of higher bandwidth carriers. If higher bandwidth carriers are available following the background scan, and if the carrier aggregation combination is not possible for the UE  340  based on device capabilities, then in step  565  the UE  340  may use a suitability criterion to move to one of the higher bandwidth carriers. It should be understood that the determination of whether carrier aggregation combinations are possible with the higher bandwidth carrier may be performed in the same manner as described above in steps  505 - 535  for the higher bandwidth carrier and the currently used carrier. In addition, the suitability criterion may also be similar to the determination of the radio conditions as performed in step  550  to determine if the UE  340  should perform a cell selection procedure with the cell having the higher available bandwidth carrier. 
       FIG. 6  shows a further exemplary method  600  for intelligent frequency selection in carrier aggregation enabled networks based on measurement data of the network. For instance, the exemplary method  600  may utilize measurements from an SCell while in RRC_Connected state. The exemplary method  600  will be described with reference to the exemplary arrangement  300  of  FIG. 3  and the exemplary UE  340  of  FIG. 4 . The method  600  is performed when the UE  340  attaches to a cell for the first time. Unlike the method  500  described above that may be performed entirely by the UE  340 , the method  600  may include operations performed by the cellular core network  350  and/or one or more of the cells  310 - 330 . 
     In step  610 , the UE  340  may attach to a network and camp on a cell within the network. As described above, it is considered that this is the first time that the UE  340  has attached to this cell of the network. In this example, it may be considered that the UE  340  has camped on the PCell  310 . As part of this step  610 , the UE  340  being camped on the PCell  310  will know the bandwidth of the PCell  310 . This known bandwidth will be used in further steps of the method. 
     In step  620 , the UE  340  may advertise in a message (e.g., the “UE_CAPABILITY_INFO message”) that the UE  340  does not support the band/bandwidth combinations with which the camped cell is configured. This does not necessarily mean that the UE  340  does not support the combinations, it is merely a default that is communicated to the cell (e.g., PCell  310 ) because the UE  340  may not support the combination. Thus, based on this message, the cellular core network  350  will not initially activate carrier aggregation for the UE  340 . The remainder of the method  600  will determine whether carrier aggregation will be activated for the UE  340  attached to the PCell  310  and if not, which carrier the UE  340  should use in a single carrier situation. 
     In step  630 , the cell (e.g., PCell  310 ) to which the UE  340  is attached may then configure the UE  340  with neighbor measurements for frequencies of secondary cell(s) (e.g., SCells  320  and  330 ). Those skilled in the art will understand that enhanced node Bs (“eNBs”) of an LTE network communicate with neighbor cells and may have this information that may then be provided to the UE  340 . 
     In step  640 , the UE  340  may scan for any overlay/underlay cells within the network that meet a predetermined criteria, such as belonging to one of the problematic carrier aggregation pairs. For example, if it is assumed that the problematic pairs are the same as the examples described above (e.g., (B 1 +B 18 ); (B 3 +B 5 ); (B 3 +B 8 ) and (B 4 +B 13 ), the UE  340  will scan the secondary cells for these bands. That is, the UE  340  does not need to scan for all bands of the secondary cells, but rather just the bands that may be problematic. 
     In step  650 , the UE  340  may determine that there exists a secondary cell that matches the predetermined criteria, e.g., the secondary cell may be operating on one of bands B 1 , B 3 , B 4 , B 5 , B 8 , B 13  or B 18 . If this is the case, the UE  340  may then decode the MIB for the secondary cell to find its configured bandwidth. 
     In step  660 , the UE  340  may determine the maximum aggregated bandwidth of primary cell (PCell  310 ) and the identified problematic secondary cell. As described above, since the UE  340  is camped on the PCell  310 , the UE  340  knows the bandwidth of the PCell  310 . The decoding of the MIB for the secondary cell in step  650  provides the UE  340  with the bandwidth of the secondary cell. The UE  340  may then add these two bandwidths together to determine the maximum aggregated bandwidth of the potential band combination of the PCell  310  and the identified problematic secondary cell. This step  660  may also include a comparison of the maximum aggregated bandwidth to a threshold value. This portion of step  660  is similar to the comparison described for step  545  of the method  500 . For example, the threshold is the bandwidth capability of the UE  340 . If the maximum aggregated bandwidth exceeds the bandwidth capability, this means the above-identified problem (i.e., the carrier aggregation bandwidth exceeds the capabilities of the UE) has been encountered. Thus, the UE  340  should not be operated in a carrier aggregation state. However, the UE  340  should still select the one of the primary and secondary cells that has the highest bandwidth. That is, the UE  340  will identify that either the primary cell (e.g., PCell  310 ) or the problematic secondary cell has a higher bandwidth and the UE  340  will select this cell as the primary cell. 
     In step  670 , the UE  340  may store this configuration for this network operator and then any further RRC connections may be attempted via the cell having the larger bandwidth. In other words, the UE  340  may then use gapless inter-frequency measurements using a secondary RF unit and the pre-configured knowledge of deployed carrier aggregation band combinations to decide if this was truly a candidate secondary cell that it could not use due to limited carrier aggregation bandwidth combination support. The UE  340  may use this information in conjunction with measurement results to trigger a cell switch in connected state. 
     For example, as described above, the UE  340  was camped on the PCell  310  and it may be considered that the problematic secondary cell was SCell  320 . If it was determined in step  660  that the maximum aggregated bandwidth exceeded the threshold, and the SCell  320  had a higher bandwidth than the PCell  310 , this may cause the UE  340  to select the SCell  320  as the primary cell, rather than the PCell  310 . The measurements results described above may be similar to the determination of the radio conditions as performed in step  550  of method  500 . As described above, there may be instances when the higher bandwidth cell may not be selected because of the measurement results. 
     Alternatively, the UE  340  may use this information if the UE  340  is not mobile to camp on the secondary cell instead the next time the UE  340  creates an RRC Connection. For example, the next time the UE  340  is attempting to camp on the PCell  310 , the UE  340 , using the stored information, may know that the SCell  320  has a higher bandwidth capability and therefore, instead of camping on the PCell  310 , the UE  340  will camp on the SCell  320 . Again, when camping on the SCell  320 , the SCell  320  will not be a secondary cell but will be a primary cell. 
       FIG. 7  shows a further exemplary method  700  for intelligent frequency selection in carrier aggregation enabled networks based on priority levels of the carrier aggregation cells. The exemplary method  700  will be described with reference to the exemplary arrangement  300  of  FIG. 3  and the exemplary UE  340  of  FIG. 4 . 
     In step  710 , the network provider may determine which of a primary cell and secondary cell within a carrier aggregation pair has a higher priority based on bandwidth capabilities. For example, the network provider that operates cellular core network  350 , the PCell  310 , and the SCells  320  and  330  may determine the operating bands of each of these cells  310 - 330 . The network provider may also know the carrier aggregation combinations of the cells  310 - 330  and which of the cells has a higher bandwidth. For example, the network provider may know that PCell  310  operates on band B 1  and has a bandwidth of 10 MHz and SCell  320  operates on band B 18  and has a bandwidth of 15 MHz. The network provider may also know that there is a carrier aggregation combination PCell  310  (B 1 ) and SCell  320  (B 18 ). Thus, the network provider will know that SCell  320  has a higher bandwidth capability than the PCell  310 . This information may be stored in the cellular core network  350 . For example, the cellular core network  350  may also include network servers or network databases that may store this information. 
     In step  720 , the network operator may configure the carrier aggregation cells in such a way that the higher bandwidth cell in the pair has the higher priority. To carry on the example started above, the network provider will configure the SCell  320  to have the higher priority based on its higher bandwidth. 
     In step  730 , the UE  340  in an idle camped state may select the higher priority bandwidth cell to camp on and use as the primary cell. That is, the network configuration will indicate to the UE  340  that when the choice for camping is between the PCell  30  and the SCell  320 , the UE  340  will camp on the SCell  320  because it is the higher bandwidth cell. 
     The exemplary embodiments are described with reference to the LTE-Advanced carrier aggregation scheme that has certain characteristics. For example, in frequency-division duplexing (“FDD”), the characteristics include that the number of aggregated carriers may be different in DL and uplink (“UL”), typically, the number of UL component carriers is equal to or lower than the number of DL component carriers. In addition, the individual component carriers may also be of different bandwidths. Alternatively, when time division duplexing (“TDD”) is used, the number of component carriers and the bandwidth of each component carrier are the same for DL and UL. However, those skilled in the art will understand that the exemplary embodiments may be applied to any carrier aggregation scheme including those having different characteristics from the LTE-Advanced scheme. 
     Those skilled in the art will understand that the above-described exemplary embodiments may be implemented in any suitable software or hardware configuration or combination thereof. An exemplary hardware platform for implementing the exemplary embodiments may include, for example, an Intel x86 based platform with compatible operating system, a Mac platform, MAC OS, iOS, Android OS, etc. In a further example, the exemplary embodiments of the above described method may be embodied as a program containing lines of code stored on a non-transitory computer readable storage medium that, when compiled, may be executed on a processor or microprocessor. 
     It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Metadata:
Filing Date: 20141107
Publication Date: 20170620
Grant Date: 20170620
Priority Date: 20131107
Inventors: VALLATH SREEVALSAN
BHATTACHARJEE DEEPANKAR
DAMJI NAVID
MUCKE CHRISTIAN W.
RIVERA-BARRETO RAFAEL L.
TABET TARIK
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W48/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W48/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W48/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W48/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W48/18", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L5/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/001", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 53370182