Abstract:
Apparatus having corresponding methods and computer-readable media comprise: a wireless receiver configured to scan for a beacon in one or more of a first plurality of predetermined wireless channels, wherein each of the first plurality of predetermined wireless channels has the same carrier frequency in a plurality of different geographical regions; and a controller configured to identify, based on a beacon scanned by the wireless receiver in one or more of the first plurality of predetermined wireless channels, a first geographical region of the plurality of different geographical regions, wherein the controller is further configured to select a second plurality of wireless channels associated with the first geographical region, wherein the wireless receiver is further configured to scan for a beacon in one or more of the second plurality of wireless channels selected by the controller.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This claims the benefit of U.S. Provisional Patent Application Ser. No. 61/610,911, filed on Mar. 14, 2012, entitled “CHANNELIZATION FOR SENSOR NETWORKS,” the disclosure thereof incorporated by reference herein in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally to the field of wireless communication networks. More particularly, the present disclosure relates to access to such networks. 
     BACKGROUND 
     Rapid developments in the use of wireless network communications technology have necessitated the development of additional frequency bands. Such developments include technologies commonly referred to as the Internet-of-Things (IoT), Machine-to-Machine (M2M) communication, and the like, and will support sensor devices such as wireless smart meters and the like. In response, the IEEE 802.11ah standardization task group is developing a global Wireless LAN (WLAN) standard that will allow wireless access using carrier frequencies below 1 GHz in the ISM (Industrial, Scientific, and Medical) band. 
     One challenge with such networks results from the fragmented nature of the allocated spectrum below 1 GHz, with different countries using different portions of the band. For example, available bands below 1 GHz for use in China, the European Union, and the United States do not overlap. Such fragmentation, if not addressed, could lead to reduced deployment. 
     SUMMARY 
     In general, in one aspect, an embodiment features an apparatus comprising: a wireless receiver configured to scan for a beacon in one or more of a first plurality of predetermined wireless channels, wherein each of the first plurality of predetermined wireless channels has the same carrier frequency in a plurality of different geographical regions; and a controller configured to identify, based on a beacon scanned by the wireless receiver in one or more of the first plurality of predetermined wireless channels, a first geographical region of the plurality of different geographical regions, wherein the controller is further configured to select a second plurality of wireless channels associated with the first geographical region, wherein the wireless receiver is further configured to scan for a beacon in one or more of the second plurality of wireless channels selected by the controller. 
     Embodiments of the apparatus can include one or more of the following features. Some embodiments comprise a wireless transceiver, wherein the wireless transceiver comprises the wireless receiver, and a wireless transmitter, wherein the wireless transceiver is configured to communicate in one of the second plurality of wireless channels. Some embodiments comprise one or more integrated circuits comprising the apparatus. Some embodiments comprise a wireless communication device comprising the one or more integrated circuits; and a sensor configured to collect sensor data, wherein the wireless transmitter is further configured to transmit the sensor data in the one of the second plurality of wireless channels. Some embodiments comprise a wireless access point comprising: the one or more integrated circuits, wherein the controller is further configured to i) determine whether any of the first plurality of predetermined wireless channels are available, ii) establish a wireless network in one of the first plurality of predetermined wireless channels responsive to determining that no wireless network exists in the one of the first plurality of predetermined wireless channels, iii) determine whether any of the second plurality of wireless channels are available responsive to determining that none of the first plurality of predetermined wireless channels are available, and iv) establish a wireless network in one of the second plurality of wireless channels responsive to determining that no wireless network exists in the one of the second plurality of wireless channels. In some embodiments, the apparatus is compliant with all or part of IEEE standard 802.11ah, including draft and approved amendments. In some embodiments, the controller is further configured to identify the first geographical region based on a geographical region element ID contained in the beacon scanned by the wireless receiver in one or more of the first plurality of predetermined wireless channels. In some embodiments, the first plurality of predetermined wireless channels have carrier frequencies at 921 MHz, 922 MHz, and 923 MHz. In some embodiments, the second plurality of wireless channels have carrier frequencies at 920.5 MHz, 921.5 MHz, and 922.5 MHz. 
     In general, in one aspect, an embodiment features a method comprising: scanning for a beacon in one or more of a first plurality of predetermined wireless channels, wherein each of the first plurality of predetermined wireless channels has the same carrier frequency in a plurality of different geographical regions; based on a beacon scanned in one or more of the first plurality of predetermined wireless channels, identifying a first geographical region of the plurality of different geographical regions; selecting a second plurality of wireless channels associated with the first geographical region; and scanning for a beacon in one or more of the second plurality of wireless channels. 
     Embodiments of the method can include one or more of the following features. Some embodiments comprise communicating in one of the second plurality of wireless channels. Some embodiments comprise collecting sensor data; and transmitting the sensor data in the one of the second plurality of wireless channels. Some embodiments comprise determining whether any of the first plurality of predetermined wireless channels are available; establishing a wireless network in one of the first plurality of predetermined wireless channels responsive to determining that no wireless network exists in the one of the first plurality of predetermined wireless channels; determining whether any of the second plurality of wireless channels are available responsive to determining that none of the first plurality of predetermined wireless channels are available; and establishing a wireless network in one of the second plurality of wireless channels responsive to determining that no wireless network exists in the one of the second plurality of wireless channels. In some embodiments, the method is compliant with all or part of IEEE standard 802.11ah, including draft and approved amendments. In some embodiments, identifying the first geographical region comprises: identifying the first geographical region based on a geographical region element ID contained in the beacon scanned in one or more of the first plurality of predetermined wireless channels. 
     In general, in one aspect, an embodiment features computer-readable media embodying instructions executable by a computer to perform functions comprising: scanning for a beacon in one or more of a first plurality of predetermined wireless channels, wherein each of the first plurality of predetermined wireless channels has the same carrier frequency in a plurality of different geographical regions; based on a beacon scanned in one or more of the first plurality of predetermined wireless channels, identifying a first geographical region of the plurality of different geographical regions; selecting a second plurality of wireless channels associated with the first geographical region; and scanning for a beacon in one or more of the second plurality of wireless channels. 
     Embodiments of the computer-readable media can include one or more of the following features. In some embodiments, the functions further comprise: communicating in one of the second plurality of wireless channels. In some embodiments, the functions further comprise: collecting sensor data; and transmitting the sensor data in the one of the second plurality of wireless channels. In some embodiments, the functions further comprise: determining whether any of the first plurality of predetermined wireless channels are available; establishing a wireless network in one of the first plurality of predetermined wireless channels responsive to determining that no wireless network exists in the one of the first plurality of predetermined wireless channels; determining whether any of the second plurality of wireless channels are available responsive to determining that none of the first plurality of predetermined wireless channels are available; and establishing a wireless network in one of the second plurality of wireless channels responsive to determining that no wireless network exists in the one of the second plurality of wireless channels. In some embodiments, the computer-readable media is compliant with all or part of IEEE standard 802.11ah, including draft and approved amendments. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates the availability of the IEEE 802.11ah spectrum by geographical region. 
         FIG. 2  shows a wireless network access system for a station according to some embodiments. 
         FIG. 3  shows a process for the wireless network access system of  FIG. 2  according to some embodiments. 
         FIG. 4  shows a wireless network access system for an access point according to some embodiments. 
         FIG. 5  shows a process for the wireless network access system  400  of  FIG. 4  according to some embodiments. 
     
    
    
     The leading digit(s) of each reference numeral used in this specification indicates the number of the drawing in which the reference numeral first appears. 
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure enable the use of common channels in fragmented frequency bands for access to wireless networks. While these embodiments are described herein in terms of IEEE 802.11ah networks, this description is also applicable to other sorts of wireless networks—e.g., IEEE 802.11af networks, and so on. 
       FIG. 1  illustrates the availability of the IEEE 802.11ah spectrum by geographical region. Referring to  FIG. 1 , the 8 MHz band spanning 779-787 MHz is allocated to China, the 5.6 MHz band spanning 863-868.6 MHz is assigned to the European Union (EU), the 26 MHz band spanning 902-928 MHz is assigned to the United States (US), the 6.5 MHz band spanning 917-923.5 MHz is assigned to the Republic of Korea, and the 13.8 MHz band spanning 915.9-929.7 MHz is assigned to Japan, while Singapore has been assigned two bands: the 3 MHz band spanning 866-869 MHz and the 5 MHz band spanning 920-925 MHz. 
     In  FIG. 1  it can be seen that there is considerable overlap in the frequency bands assigned to certain geographical regions. For example, the bands assigned to the United States, Korea, Singapore and Japan have significant or complete overlap. According to some embodiments, common channels are assigned across these overlapping bands. 
     In one embodiment, channels are assigned to Korea, Japan, the United States (US) and Singapore as shown in Table 1. Of course, other assignment plans may be used instead. For example, while the bandwidth of each channel in Table 1 is 1 MHz, the IEEE 802.11ah standard permits channel bandwidths of 1, 2, 4, 8 and 16 MHz. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Carrier 
                   
               
               
                   
                   
                 Bandwidth 
                 Frequencies 
                 No. of 
               
               
                 Region 
                 Band (MHz) 
                 (MHz) 
                 (MHz) 
                 Channels 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Korea 
                 917.5-923.5 
                 6 
                 918, 919, 920, 
                 6 
               
               
                   
                   
                   
                 921, 922, 923 
                   
               
               
                 Japan 
                 915.9-929.7 
                 13.8 
                 917, 918, 919, 
                 12 
               
               
                   
                   
                   
                 920, 921, 922, 
                   
               
               
                   
                   
                   
                 923, 924, 925, 
                   
               
               
                   
                   
                   
                 926, 927, 928 
                   
               
               
                 US 
                 902-928 
                 26 
                 903, . . . , 921, 
                 25 
               
               
                   
                   
                   
                 922, 923, . . . , 
                   
               
               
                   
                   
                   
                 927 
                   
               
               
                 Singapore 
                 920-925 
                 5 
                 921, 922, 923, 
                 4 
               
               
                   
                   
                   
                 924 
               
               
                   
               
             
          
         
       
     
     The channel assignment of Table 1 allows for the assignment of three common channels having respective carrier frequencies of 921, 922 and 923 MHz across the United States, Korea, Singapore and Japan. These common carrier frequencies are shown in bold in Table 1. This channelization allows for the maximum of 6 channels in Korea, but reduces the effective number of channels to 12, 25 and 4 for Japan, United States and Singapore, respectively. 
     In another embodiment, channels are assigned to Korea, Japan, the United States and Singapore as shown in Table 2. Of course, other assignment plans may be used instead. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Carrier 
                   
               
               
                   
                   
                 Bandwidth 
                 Frequencies 
                 No. of 
               
               
                 Region 
                 Band (MHz) 
                 (MHz) 
                 (MHz) 
                 Channels 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Korea 
                 917.5-923.5 
                 6 
                 918.5, 919.5, 
                 5 
               
               
                   
                   
                   
                 920.5, 921.5, 
                   
               
               
                   
                   
                   
                 922.5 
                   
               
               
                 Japan 
                 915.9-929.7 
                 13.8 
                 916.5, 917.5, 
                 12 
               
               
                   
                   
                   
                 918.5, 919.5, 
                   
               
               
                   
                   
                   
                 920.5, 921.5, 
                   
               
               
                   
                   
                   
                 922.5, 923.5, 
                   
               
               
                   
                   
                   
                 924.5, 925.5, 
                   
               
               
                   
                   
                   
                 926.5, 927.5 
                   
               
               
                 US 
                 902-928 
                 26 
                 902.5, . . . , 
                 26 
               
               
                   
                   
                   
                 920.5, 921.5, 
                   
               
               
                   
                   
                   
                 922.5, . . . , 
                   
               
               
                   
                   
                   
                 927.5 
                   
               
               
                 Singapore 
                 920-925 
                 5 
                 920.5, 921.5, 
                 5 
               
               
                   
                   
                   
                 922.5, 923.5, 
                   
               
               
                   
                   
                   
                 924.5 
               
               
                   
               
             
          
         
       
     
     The channel assignment of Table 2 allows for the assignment of three common channels having respective carrier frequencies of 920.5, 921.5 and 922.5 MHz across the United States, Korea, Singapore and Japan. These common carrier frequencies are shown in bold in Table 2. This channelization allows for the maximum number of channels in Japan, United States and Singapore, but reduces the effective number of channels in Korea to 5. 
     The use of common channels as described herein permits two-step channel access procedures, as described in detail below. In some embodiments, a station desiring channel access first scans for beacons in common channels. If the station finds a beacon, it can identify its geographic region based on the beacon. After identifying the geographic region, the station can then scan all of the channels used in that geographic region. Before describing this process in detail, an example wireless network access system is described. 
       FIG. 2  shows a wireless network access system  200  for a station according to some embodiments. Although in the described embodiments the elements of the wireless network access system  200  are presented in one arrangement, other embodiments may feature other arrangements. For example, elements of the wireless network access system  200  can be implemented in hardware, software, or combinations thereof. 
     Referring to  FIG. 2 , the wireless network access system  200  includes a wireless sensor device  202 , an access point (AP)  204  transmitting beacons  224  in a common channel, and an access point (AP)  206  transmitting beacons  226  in a regional channel (that is, a channel that is not common to multiple geographic regions). In the example of  FIG. 2 , the wireless network access system  200  is located in the United States, the access point  204  transmits in the 922 MHz channel of Table 1, and the access point  206  transmits in the 910 MHz channel of Table 1. 
     The wireless sensor device  202  includes a sensor  208  and a station (STA)  210 . The station (STA)  210  includes a wireless transceiver  212  and a controller  214 . The wireless transceiver  212  includes a wireless transmitter  216  and a wireless receiver  218 . The sensor  208  provides sensor data  220  to the wireless transceiver  212  for transmission by the wireless transmitter  216  under the control of the controller  214 . The sensor  208  can be any sort of sensor. In the present example, the sensor  208  is a thermometer, and the sensor data  220  is temperature data. The controller  214  can be implemented in any manner, for example as a microcontroller, processor, state machine, and the like. The wireless transceiver  212  and the controller  214  can be implemented as one or more integrated circuits. In some embodiments, all or part of the wireless network access system  200  is compliant with all or part of IEEE standard 802.11 ah, including draft and approved amendments. 
       FIG. 3  shows a process  300  for the wireless network access system  200  of  FIG. 2  according to some embodiments. Although in the described embodiments the elements of process  300  are presented in one arrangement, other embodiments may feature other arrangements. For example, in various embodiments, some or all of the elements of process  300  can be executed in a different order, concurrently, and the like. Also some elements of process  300  may not be performed, and may not be executed immediately after each other. In addition, some or all of the elements of process  300  can be performed automatically, that is, without human intervention. 
     Referring to  FIG. 3 , at  302 , the wireless receiver  218  scans for beacons in common channels, that is, in predetermined wireless channels that have the same carrier frequency in a plurality of different geographical regions. In the present example, the common channels are 921, 922 and 923 MHz, each of which has the same carrier frequency in the United States, Korea, Singapore and Japan. At  304 , the wireless receiver  218  receives the beacon  224  transmitted by the access point  204  in a common channel. In the present example, the beacon  224  is transmitted by the access point  204  in the 922 MHz channel. 
     At  306 , the controller  214  decides whether to connect with the access point  204  on the 922 MHz channel. This decision can be based on any criteria. If the controller  214  decides to connect with the access point  204  on the 922 MHz channel, then at  308 , the wireless transceiver  212  establishes a wireless network connection with the access point  204  on the 922 MHz channel, and then, at  310 , transmits the sensor data  220  over the 922 MHz channel. 
     On the other hand, if the controller  214  decides not to connect with the access point  204  on the 922 MHz channel, then at  312 , the controller  214  identifies the geographical region in which the access point  204  is located based on the beacon  224  received from the access point  204 . In the present example, the geographical region is the United States. In some embodiments, the controller  214  identifies the geographical region based on a geographical region element ID contained in the beacon  224  received from the access point  204 . Then at  314 , the controller  214  selects the regional channels associated with the identified geographical region. In the present example, referring to Table 1, the wireless channels are the 22 channels in the 903-920 MHz and 924-927 MHz bands. Then at  316 , the wireless receiver  218  scans for beacons in the selected regional channels. 
     At  318 , the wireless receiver  218  receives the beacon  226  transmitted by the access point  206  in a regional channel. In the present example, the beacon  226  is transmitted by the access point  206  in the 910 MHz channel. Then at  320 , the wireless transceiver  212  establishes a wireless network connection with the access point  206  on the 910 MHz channel, and then, at  322 , transmits the sensor data  220  over the 910 MHz connection. 
     Two-step wireless network establishment procedures can also be employed by access points and the like, as described in detail below. In some embodiments, an access point desiring to establish a wireless network such as a basic service set (BSS) first scans for beacons in common channels. If the access point finds a common channel having no beacons, the access point can establish a wireless network in that common channel. But if beacons are found in all of the common channels scanned, the access point can identify its geographic region based on one or more of the beacons. After identifying the geographic region, the access point can then scan all of the channels used in that geographic region. Before describing this process in detail, an example wireless network access system is described. 
       FIG. 4  shows a wireless network access system  400  for an access point according to some embodiments. Although in the described embodiments the elements of the wireless network access system  400  are presented in one arrangement, other embodiments may feature other arrangements. For example, elements of the wireless network access system  400  can be implemented in hardware, software, or combinations thereof. 
     Referring to  FIG. 4 , the wireless network access system  400  includes a wireless sensor device  402  operating in a regional channel, three access points (AP)  404 A,  404 B, and  404 C transmitting respective beacons  424 A,  424 B, and  424 C in three respective common channels, and an access point (AP)  406  desiring to establish a wireless network. In the example of  FIG. 4 , referring to Table 1, the wireless network access system  400  is located in the United States, the access points  404 A,  404 B, and  404 C are transmitting respective beacons  424 A,  424 B, and  424 C in the 921, 922, and 923 MHz channels, respectively, and the wireless sensor device  402  is configured to operate in the 910 MHz channel. The wireless sensor device  402  can be implemented in a manner similar to that of the wireless sensor device  202  of  FIG. 2 . 
     The access point  406  includes a wireless transceiver  412  and a controller  414 . The wireless transceiver  412  includes a wireless transmitter  416  and a wireless receiver  418 . The controller  414  can be implemented in any manner, for example as a microcontroller, processor, state machine, and the like. The wireless transceiver  412  and the controller  414  can be implemented as one or more integrated circuits. In some embodiments, all or part of the wireless network access system  400  is compliant with all or part of IEEE standard 802.11ah, including draft and approved amendments. 
       FIG. 5  shows a process  500  for the wireless network access system  400  of  FIG. 4  according to some embodiments. Although in the described embodiments the elements of process  500  are presented in one arrangement, other embodiments may feature other arrangements. For example, in various embodiments, some or all of the elements of process  500  can be executed in a different order, concurrently, and the like. Also some elements of process  500  may not be performed, and may not be executed immediately after each other. In addition, some or all of the elements of process  500  can be performed automatically, that is, without human intervention. 
     Referring to  FIG. 5 , at  502 , the wireless receiver  418  scans for beacons in common channels, that is, in predetermined wireless channels that have the same carrier frequency in a plurality of different geographical regions. In the present example, the common channels are 921, 922 and 923 MHz, each of which has the same carrier frequency in the United States, Korea, Singapore and Japan. At  504 , the wireless receiver  418  receives the beacons  424 A,  424 B, and  424 C transmitted by the access points  404 A,  404 B, and  404 C, respectively. 
     At  506 , the controller  414  determines whether any of the scanned common channels are available. That is, the controller  414  determines whether wireless networks exist in the common channels. If any of the common channels are available, then at  508 , the access point  406  can establish a wireless network in an available common channel. At  522 , the access point  406  can communicate with stations over the wireless network. 
     On the other hand, if none of the common channels are available, then at  512 , the controller  414  identifies the geographical region in which one or more of the access points  404  are located based on one or more of the beacons  424  received from the access points  404 . In some embodiments, the controller  414  identifies the geographical region based on a geographical region element ID contained in a beacon  424  received from an access point  404 . Then at  514 , the controller  414  selects the regional channels associated with the identified geographical region. Then at  516 , the wireless receiver  418  scans for beacons in the selected regional channels. 
     In the present example, none of the scanned common channels are available because each of the scanned common channels is in use by one of the access points  404 . Also in the present example, the geographical region is the United States, and, referring to Table 1, the wireless channels are the 22 channels in the 903-920 MHz and 924-927 MHz bands. 
     At  518 , the controller  414  determines whether any of the scanned regional channels are available. That is, the controller  414  determines whether wireless networks exist in the regional channels. If none of the regional channels are available, then the process can terminate or resume at  502  or at  516 . But if any of the regional channels are available, then at  520 , the access point  406  can establish a wireless network in one of the available regional channels. At  522 , the access point  406  can communicate with stations over the wireless network. 
     In the present example, the controller  414  determines that the 910 MHz channel is available, and establishes a wireless network in that channel. Then the wireless transceiver  412  receives sensor data  220  from the wireless sensor device  402  over the 910 MHz connection, for example as described above. 
     Various embodiments of the present disclosure can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof. Embodiments of the present disclosure can be implemented in a computer program product tangibly embodied in a computer-readable storage device for execution by a programmable processor. The described processes can be performed by a programmable processor executing a program of instructions to perform functions by operating on input data and generating output. Embodiments of the present disclosure can be implemented in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, processors receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer includes one or more mass storage devices for storing data files. Such devices include magnetic disks, such as internal hard disks and removable disks, magneto-optical disks; optical disks, and solid-state disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). As used herein, the term “module” may refer to any of the above implementations. 
     A number of implementations have been described. Nevertheless, various modifications may be made without departing from the scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.