Abstract:
Systems and methods for network entry management are provided. The system includes a base station and a mobile station. The base station broadcasts synchronization channels (SCH) on multiple carriers, where the SCH may be hierarchical synchronization channel composed of primary synchronization channel (P-SCH) and secondary synchronization channel (S-SCH) which are used for timing, frequency synchronization, cell identification, etc. The carriers include at least a first carrier including at least one P-SCH and do not include a S-SCH. The mobile station scans the first carrier, and checks whether a P-SCH is broadcasted on the first carrier. If a P-SCH is broadcasted on the first carrier, the mobile station checks whether an S-SCH is broadcasted on the first carrier. If no S-SCH is broadcasted on the first carrier, the mobile station scans for a second carrier broadcasted by the base station.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/235,480 filed Aug. 20, 2009, the entirety of which is incorporated by reference herein 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The disclosure relates generally to systems and methods for network entry management, and, more particularly to systems and methods for network entry management that provide a hierarchical synchronization channel design for a multi-carrier system to reduce network entry latency. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, mobile stations, such as mobile devices having wireless communication capabilities have become more and more popular. Due to increased convenience and functions of the mobile devices, these devices have become basic necessities of life. 
         [0006]    In a multi-carrier system, when a mobile station powers on, it will scan various carriers based on known channel rasters. In 3GPP 36.101 v9.0.0, the center raster is 100 kHz for all bands. A mobile station may scan synchronization channels on every 100 kHz in each band to discover if there is a 3GPP system. When a band  1  ranges from 2110 MHz to 2170 MHz, a mobile station will scan from 3GPP systems on the carriers 2110 MHz, 2110.1 MHz, 2110.2 MHz, . . . , 2169.9 MHz. Multi-carrier systems may be composed of fully configured carriers and partially configured/extension carriers. The fully configured carriers can operate standalone. The partially configured/extension carriers can not operate standalone, and can not be used for network entry. Currently, hierarchical synchronization channels (SCH) have been adopted by some orthogonal frequency division modulation (OFDM) systems, such as IEEE 802.16m and 3GPP LTE. Hierarchical SCH is composed of a primary synchronization channel (P-SCH) and secondary a synchronization channel (S-SCH). The P-SCH and S-SCH may be time division multiplexed. The P-SCH is used for timing acquisition and frequency synchronization, and is used for symbol boundary detection. The S-SCH may carry a cell identity (cell ID) or partial cell ID information, e.g. Physical ID in a 3GPP LTE. The S-SCH may be used for channel estimation. 
         [0007]    Generally, a frame structure may include two P-SCHs and two S-SCHs, and a broadcasting channel (BCH) follows either the P-SCH or S-SCH. The BCH can carry system information, such as a bandwidth, identity, frame configurations, location of control channels, and other system information. The SCH is generally used as an identity for a station to lock onto the system. When a system adopts the hierarchical SCH, a mobile station may detect the P-SCH to synchronize system timing and center frequency, and then the mobile station will detect the S-SCH to acquire complete cell IDs. After, a mobile station can retrieve system information via the BCH. It is understood that, a mobile station will leave the carrier and scan for another carrier if the mobile station can not detect the P-SCH, S-SCH or BCH. It is noted that, a mobile station will scan every carrier within each band to try to lock onto the system. If no related information or mechanism can be provided in the hierarchical SCH, network entry latency will be serious. 
         [0008]    IEEE C802.16m — 08 — 1093 proposes a method to reduce network entry latency. It applies different P-SCHs to the fully configured carrier and the partially configured carrier. Therefore, a mobile station can detect the P-SCH to verify if a current carrier is the fully configured carrier. If the current carrier is a partially configured carrier, a mobile station will skip the carrier to scan for another carrier, such that network entry latency can be reduced. However, in IEEE C802.16m — 08 — 1093, the number of P-SCHs has increased. If only three sequences are set for the P-SCHs, it will cause at least a 33% detection complexity overhead. The structure also wastes resources for the S-SCH. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Systems and methods for network entry management are provided. 
         [0010]    An embodiment of a system for network entry management includes a base station and a mobile station. The base station broadcasts on multiple carriers. The carriers include at least a first carrier including at least one P-SCH and does not include an S-SCH, wherein the P-SCH may be used for timing acquisition and frequency synchronization, and the S-SCH may be used for cell identification. The mobile station scans the first carrier, and checks whether a P-SCH is broadcasted on the first carrier. If a P-SCH is broadcasted on the first carrier, the mobile station checks whether an S-SCH is broadcasted on the first carrier. If no S-SCH is broadcasted on the first carrier, the mobile station scans a second carrier broadcasted by the base station. 
         [0011]    An embodiment of a system for network entry management at least includes a base station. The base station broadcasts on multiple carriers. The carriers are classified into fully configured carriers and partially configured carriers. The fully configured carrier includes at least one P-SCH and at least one S-SCH, and the partially configured carrier includes at least one P-SCH, and does not include the S-SCH. The P-SCH may be used for timing acquisition and frequency synchronization, and the S-SCH may be used for cell identification. 
         [0012]    An embodiment of a system for network entry management at least includes a mobile station. The mobile station scans a first carrier within multiple carriers, and checks whether a P-SCH is broadcasted on the first carrier. If a P-SCH is broadcasted on the first carrier, the mobile station retrieves recommended information in the P-SCH, selects a second carrier within the carriers based on the recommended information, and scans for the second carrier. 
         [0013]    In an embodiment of a method for network entry management, multiple carriers are broadcasted by a base station, wherein the carriers include at least a first carrier including at least one P-SCH, and does not include an S-SCH, and the P-SCH may be used for timing acquisition and frequency synchronization, and the S-SCH may be used for a cell identification. The first carrier is scanned by a mobile station, and it is checked whether a P-SCH is broadcasted on the first carrier. If a P-SCH is broadcasted on the first carrier, it is checked whether an S-SCH is broadcasted on the first carrier. If no S-SCH is broadcasted on the first carrier, a second carrier broadcasted by the base station is scanned by the mobile station. 
         [0014]    In an embodiment of a method for network entry management for use in a base station, multiple carriers are broadcasted, wherein the carriers are classified into fully configured carriers and partially configured carriers. The fully configured carrier includes at least one P-SCH and at least one S-SCH, and the partially configured carrier includes at least one P-SCH, and does not include the S-SCH. The P-SCH may be used for timing acquisition and frequency synchronization, and the S-SCH may be used for cell identification. 
         [0015]    In an embodiment of a method for network entry management for use in a mobile station, a first carrier within multiple carriers is scanned. It is checked whether a P-SCH is broadcasted on the first carrier. If a P-SCH is broadcasted on the first carrier, it is checked whether an S-SCH is broadcasted on the first carrier. If no S-SCH is broadcasted on the first carrier, recommended information in the P-SCH is retrieved, a second carrier within the carriers is selected based on the recommended information, and the second carrier is scanned. 
         [0016]    In some embodiments, the recommended information may be a channel space or a coarse raster, or a carrier configuration. The carrier configuration indicates whether a band including the first carrier has a fully configured carrier, and the fully configured carrier is in a higher frequency, or the fully configured carrier is in a lower frequency. 
         [0017]    Methods for network entry management may take the form of a program code embodied in a tangible media. When the program code is loaded into and executed by a machine, the machine becomes an apparatus for practicing the disclosed method. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention will become more fully understood by referring to the following detailed description with reference to the accompanying drawings, wherein: 
           [0019]      FIG. 1  is a schematic diagram illustrating an embodiment of a system for network entry management of the invention; 
           [0020]      FIG. 2  is a schematic diagram illustrating an embodiment of a base station of the invention; 
           [0021]      FIG. 3  is a schematic diagram illustrating an embodiment of a mobile station of the invention; 
           [0022]      FIG. 4  is a schematic diagram illustrating an embodiment of a frame structure of a fully configured carrier of the invention; 
           [0023]      FIG. 5A  is a schematic diagram illustrating an embodiment of a frame structure of a partially configured carrier of the invention; 
           [0024]      FIG. 5B  is a schematic diagram illustrating another embodiment of a frame structure of a partially configured carrier of the invention; 
           [0025]      FIG. 5C  is a schematic diagram illustrating another embodiment of a frame structure of a partially configured carrier of the invention; 
           [0026]      FIG. 6  is a flowchart of an embodiment of a method for network entry management for a base station of the invention; 
           [0027]      FIG. 7  is a flowchart of an embodiment of a method for network entry management for a mobile station of the invention; and 
           [0028]      FIG. 8  is a flowchart of another embodiment of a method for network entry management for a mobile station of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Systems and methods for network entry management are provided. 
         [0030]      FIG. 1  is a schematic diagram illustrating an embodiment of a system for network entry management of the invention. 
         [0031]    The system for network entry management  100  comprises a base station  110  and a plurality of mobile stations ( 132 ,  134  and  136 ).  FIG. 2  is a schematic diagram illustrating an embodiment of a base station of the invention. The base station  110  may be an electronic device implemented with a multi-carrier system. It is understood that, the basic protocols, concept and related terminologies of the multi-carrier system are well known in the art, and omitted here. The base station  110  comprises a transceiver unit  112  and a processing unit  114 . The processing unit  114  can enable the transceiver unit  112  to broadcast multiple carriers  120  comprising fully configured carriers and partially configured carriers. It is understood that, the partially configured carrier may have different names, such as an extension carrier, in various systems. In the present application, the partially configured carrier is used for explanation, and the present invention is not limited thereto. Details of fully configured carriers and partially configured carriers will be discussed later. 
         [0032]      FIG. 3  is a schematic diagram illustrating an embodiment of a mobile station of the invention. The mobile station  300  may be an electronic device having wireless communications capability. The mobile station  300  comprises a transceiver unit  310  and a processing unit  320 . The processing unit  320  can scan carriers via the transceiver unit  310 , perform related analysis with the carriers, and accordingly lock onto a network provided by the base station  110 . Related details will be discussed further in the following paragraphs. 
         [0033]    As described, the system is a multi-carrier system with fully configured carriers and partially configured carriers. The fully configured carriers can operate standalone. The partially configured/extension carriers can not operate standalone, and can not be used for network entry. In the present invention, the hierarchical SCH composed of P-SCH, S-SCH, and BCH can be used for carrier configuration in the multi-carrier system. The P-SCH may be used for timing acquisition and frequency synchronization, and may be used for symbol boundary detection. The S-SCH may carry cell identity (cell ID) or partial cell ID information, e.g. Physical ID in 3GPP LTE. The S-SCH may be used for channel estimation. The BCH can carry system information, such as bandwidth, identity, frame configurations, location of control channels, and others. 
         [0034]    In the present invention, the frame structure of the fully configured carrier comprises at least one P-SCH and at least one S-SCH.  FIG. 4  is a schematic diagram illustrating an embodiment of a frame structure of a fully configured carrier of the invention. In the embodiment of  FIG. 4 , the fully configured carrier  400  is composed of S-SCHs ( 402  and  406 ) and P-SCHs ( 404  and  408 ). It is understood that, the fully configured carrier  400  in  FIG. 4  is similar to that in conventional arts. A mobile station can detect both synchronization channels (P-SCH and S-SCH) in the fully configured carrier  400  and enter the network provided by the system. 
         [0035]    In the present invention, the frame structure of the partially configured carrier comprises at least one P-SCH, and has no S-SCH.  FIG. 5A  is a schematic diagram illustrating an embodiment of a frame structure of a partially configured carrier of the invention. As shown in  FIG. 5A , the partially configured carrier  500  is composed of P-SCHs ( 502  and  504 ). Since the S-SCH is removed from the partially configured carrier  500 , a mobile station cannot detect the S-SCH through the carrier, and will ignore the carrier. To save radio resources for data transmission, in some embodiments, the system can transmit data at the position for S-SCH in the partially configured carrier since no S-SCH should be transmitted in the partially configured carrier. Further, in some embodiments, if several P-SCHs are within a frame, the amount of P-SCHs can also be adjusted to save radio resources for data transmission. For example, the P-SCH  502  in the partially configured carrier  500  of  FIG. 5A  can be removed, as shown in  FIG. 5B . For example, the P-SCH  504  in the partially configured carrier  500  of  FIG. 5A  can be removed, as shown in  FIG. 5C . Similarly, the position of the removed P-SCH can be used to transmit data. 
         [0036]    It is understood that, in some embodiments, the P-SCH may have 2 times time domain repeated characteristic, and the P-SCH may use a Zadoff Chu code or generalized chirp like code. In some embodiments, the P-SCH can be applied in frequency domain interleave preambles, and an FDM/CDM based synchronization channel. It is understood that, in some embodiments, the P-SCH may use MIMO schemes, such as cyclic delay diversity and/or cluster-based phase rotation. It is understood that, in some embodiments, the S-SCH may have 3 times time domain repeated characteristics or 5 times time domain repeated characteristics. Similarly, the S-SCH may use a Zadoff Chu code or generalized chirp like code. In some embodiments, the S-SCH may use the MIMO scheme, such as cyclic delay diversity, or the FSTD MIMO scheme. 
         [0037]    It is noted that, in some embodiments, the P-SCH in the partially configured carrier may comprise recommended information. The recommended information may be a channel space, a coarse raster, or a carrier configuration. In the channel space, for example, when three sequences are used for the P-SCH in the partially configured carrier, one sequence can be set as a first channel space, another sequence can be set as a second channel space, and the other sequence can be set as a third channel space. In an example of 3GPP LTE, one sequence can be set as a 1.4 MHz channel space, another sequence can be set as a 3 MHz channel space, and the other sequence can be set as a 5 MHz/10 MHz/20 MHz channel space. A mobile station can select and scan for another carrier based on the referent channel space to largely avoid redundant carrier scan. It is noted that, in the LTE case, the channel space can be further restricted to be used in the current band or adjacent carriers. In a coarse raster, for example, when three sequences are used for the P-SCH in the partially configured carrier, one sequence can be set as a small bandwidth scanning step, another sequence can be set as a medium bandwidth scanning step, and the other sequence can be set as a large bandwidth scanning step. For example, one sequence can be set as a 1.4 MHz coarse raster, another sequence can be set as a 3 MHz coarse raster, and the other sequence can be set as a 5 MHz coarse raster. In some embodiments, the center frequency can be defined to be allocated between +XHz and −XHz to the scanned frequency. In a carrier configuration, for example, when three sequences are used for the P-SCH in the partially configured carrier, one sequence can be set to indicate that no fully configured carrier is in a band, another sequence can be set to indicate that the fully configured carrier is in a higher frequency, and the other sequence can be set to indicate that the fully configured carrier is in a lower frequency. In some embodiments, the P-SCH in the partially configured carrier may indicate that a carrier currently being scanned is a partially configured carrier. The mobile station can select and scan for another carrier based on the recommended information retrieved from the P-SCH in the partially configured carrier. Related details will be discussed later. 
         [0038]      FIG. 6  is a flowchart of an embodiment of a method for network entry management for a base station of the invention. 
         [0039]    In step S 602 , the base station broadcasts at least one fully configured carrier. As described, the fully configured carrier comprises at least one P-SCH and at least one S-SCH. It is noted that, in some embodiment, the base station will also broadcast system information, such as bandwidth, identity, frame configurations, location of control channels, and others in a BCH. In step S 604 , the base station broadcasts at least one partially configured carrier. Similarly, the partially configured carrier comprises at least one P-SCH, and has no S-SCH. Further, in some embodiment, the base station can further embed recommended information and/or an indication into the P-SCH in the partially configured carrier. Similarly, the recommended information may be a channel space, a coarse raster, or a carrier configuration, and the indication may indicate that a carrier is currently being scanned is a partially configured carrier. 
         [0040]      FIG. 7  is a flowchart of an embodiment of a method for network entry management for a mobile station of the invention. In the embodiment, the partially configured carrier comprises at least one P-SCH, and has no S-SCH. 
         [0041]    In step S 702 , the mobile station scans for a carrier within the carriers broadcasted by a base station. In step S 704 , it is determined whether a P-SCH is within the carrier. If no P-SCH is broadcasted on the carrier (No in step S 704 ), in step S 706 , the mobile station scans for another carrier, and the procedure goes to step S 704 . If at least one P-SCH is broadcasted on the carrier (Yes in step S 704 ), in step S 708 , the mobile station acquires information from the P-SCH to synchronize system timing and center frequency. In step S 710 , it is determined whether an S-SCH is within the carrier. If no S-SCH is broadcasted on the carrier (No in step S 710 ), in step S 706 , the mobile station scans for another carrier, and the procedure goes to step S 704 . It is understood that, as described, since the S-SCH is removed from the partially configured carrier broadcasted by the base station, the mobile station cannot detect the S-SCH through the carrier, and will ignore the carrier. If at least one S-SCH is broadcasted on the carrier (Yes in step S 710 ), in step S 712 , the mobile station acquires a cell identity from the S-SCH. Then, in step S 714 , the mobile station detects the BCH from the carrier, and retrieves system information, such as bandwidth, identity, frame configurations, location of control channels, and others from the BCH, and in step S 716 , accordingly enters a network provided by the base station implementing the multi-carrier system. 
         [0042]      FIG. 8  is a flowchart of another embodiment of a method for network entry management for a mobile station of the invention. In the embodiment, the partially configured carrier comprises at least one P-SCH, and has no S-SCH, and the mobile station can select and scan for another carrier based on recommended information recorded in the P-SCH in the partially configured carrier. 
         [0043]    In step S 802 , the mobile station scans for a carrier within the carriers broadcasted by a base station. In step S 804 , it is determined whether a P-SCH is within the carrier. If no P-SCH is broadcasted on the carrier (No in step S 804 ), in step S 806 , the mobile station scans for another carrier, and the procedure goes to step S 804 . If at least one P-SCH is broadcasted on the carrier (Yes in step S 804 ), in step S 808 , the mobile station acquires information from the P-SCH to synchronize system timing and center frequency. In step S 810 , it is determined whether an S-SCH is broadcasted on the carrier. If no S-SCH is broadcasted on the carrier (No in step S 810 ), in step S 812 , the mobile station acquires recommended information from the P-SCH in the partially configured carrier, and in step S 814 , selects and scans another carrier based on the retrieved recommended information, and the procedure goes to step S 804 . Similarly, the recommended information may be a channel space, a coarse raster, or a carrier configuration. If at least one S-SCH is broadcasted on the carrier (Yes in step S 810 ), in step S 816 , the mobile station acquires a cell identity from the S-SCH. Then, in step S 818 , the mobile station detects the BCH from the carrier, and retrieves system information, such as bandwidth, identity, frame configurations, location of control channels, and others from the BCH, and in step S 820 , accordingly enters a network provided by the base station implementing the multi-carrier system. 
         [0044]    As described, the P-SCH in the partially configured carrier may have an indication to indicate whether the carrier is a partially configured carrier. In some embodiments, once the indication in the P-SCH in a carrier is detected by the mobile station, the mobile station will leave the carrier and scan another carrier. It is understood that, in some embodiments, the mobile station scans another carrier based on the recommended information. 
         [0045]    Therefore, the systems and methods for network entry management can provide a hierarchical synchronization channel design for a multi-carrier system to reduce network entry latency and save radio resources. 
         [0046]    Methods for network entry management, or certain aspects or portions thereof, may take the form of a program code (i.e., executable instructions) embodied in tangible media, such as floppy diskettes, CD-ROMS, hard drives, or any other machine-readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine thereby becomes an apparatus for practicing the methods. The methods may also be embodied in the form of a program code transmitted over some transmission medium, such as electrical wiring or cabling, through fiber optics, or via any other form of transmission, wherein, when the program code is received and loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the disclosed methods. When implemented on a general-purpose processor, the program code combines with the processor to provide a unique apparatus that operates analogously to application specific logic circuits. 
         [0047]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the present invention shall be defined and protected by the following claims and their equivalents.