Patent Publication Number: US-11026125-B2

Title: Spectrum sharing with switching of tier levels between networks and/or devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/693,132, filed on Aug. 31, 2017 and issued on Aug. 13, 2019 as U.S. Pat. No. 10,383,006, which is incorporated hereto in its entirety. 
    
    
     BACKGROUND 
     Various types of wireless networks that utilize channels in frequency spectrum that is shared with other networks have been proposed. The sharing of frequency spectrum allows a wireless network to increase system bandwidth efficiency when channels in the shared frequency spectrum are available for use by the wireless network. In various configurations of these networks, the shared frequency spectrum may be spectrum in unlicensed frequency bands or spectrum in licensed or allocated frequency bands that are shared between licensed networks, for example, on a prioritization basis. The prioritization may be implemented on a tier level basis, in which different levels of priority for use of the frequency spectrum are assigned to different networks. These networks may include networks configured for use with different market segments. For example, the networks that share frequency spectrum may each be configured for Department of Defense (DOD) users, police department users, or cellular users. The networks may also be configured for the same market segment. For example, the networks that share frequency spectrum may each be configured as a corporate network. 
     An example of networks utilizing shared frequency spectrum is illustrated by a Dynamic Spectrum Access (DSA) system that includes multiple base stations/networks that operate independent of one another to share an allocated frequency spectrum. A DSA system typically includes an incumbent frequency spectrum user that has highest priority for spectrum access. A DSA system is typically configured so that the base stations/networks within the DSA system use channels in a frequency spectrum that is shared with other base stations/networks of the DSA system. The sharing of the frequency spectrum in the DSA system may be done under the coordination of a controller that manages a channel assignment database. Various groups in the wireless industry are currently working to standardize operating rules for DSA systems that have multiple tier levels of priority for spectrum access. In these systems, each base station/network in the DSA system may be assigned one of the multiple tier levels of priority. A DSA database system enabling multiple tier levels of priority is commonly known as a spectrum access system (SAS). 
     SUMMARY 
     In an implementation, a device includes a processor and a memory in communication with the processor. The memory includes executable instructions that, when executed by the processor, cause the processor to control the device to perform functions of connecting a remote device to a network via a first channel associated with a first tier level; determining that a tier level switch condition is met; sending, to a controller of the network, a request for tier level switch from the first tier level to a second tier level; receiving, from the controller of the network, an authorization for switching from the first tier level to the second tier level; and connecting the remote device to the network via a second channel associated with the second tier level. 
     In another implementation, a method for operating a device includes connecting a remote device to a network via a first channel associated with a first tier level; determining that a tier level switch condition is met; sending, to a controller of the network, a request for tier level switch from the first tier level to a second tier level; receiving, from the controller of the network, an authorization for switching from the first tier level to the second tier level; and connecting the remote device to the network via a second channel associated with the second tier level. 
     In another implementation, a non-transitory computer readable medium containing instructions which, when executed by a processor, cause a device to perform functions of connecting a remote device to a network via a first channel associated with a first tier level; determining that a tier level switch condition is met; sending, to a controller of the network, a request for tier level switch from the first tier level to a second tier level; receiving, from the controller of the network, an authorization for switching from the first tier level to the second tier level; and connecting the remote device to the network via a second channel associated with the second tier level. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example spectrum access system including networks having devices configured to operate according to an implementation; 
         FIGS. 2A-2C  are diagrams illustrating portions of example controllers in a spectrum access system; 
         FIGS. 3A-3C  illustrate operations performed during a tier switch between a first network and a second network in a spectrum access system; 
         FIG. 4  is a flow diagram illustrating operations performed by an example network controller when switching network tier levels in a spectrum access system; 
         FIG. 5A  is a flow diagram illustrating operations performed by an example spectrum access system controller when switching tier levels to utilize available spectrum in a spectrum access system; 
         FIG. 5B  is a flow diagram illustrating operations performed by an example network controller when switching tier levels to utilize available spectrum in a spectrum access system; 
         FIG. 6A  is a diagram illustrating an example network having devices configured to switch between spectrum access system tier levels within the network; 
         FIG. 6B  is a flow diagram illustrating operations performed by an example network controller when switching devices between spectrum access system tier levels within a network; 
         FIG. 7  is a simplified block diagram showing an example network controller; and, 
         FIG. 8  is a simplified block diagram showing an example spectrum access system controller. 
     
    
    
     DETAILED DESCRIPTION 
     The system, method and apparatus will now be described by use of example embodiments. The example embodiments are presented in this disclosure for illustrative purposes, and not intended to be restrictive or limiting on the scope of the disclosure or the claims presented herein. 
     The methods, systems, and apparatus of the embodiments provide tier level switching between or within networks/devices in a spectrum access system (SAS) in which the networks/devices are assigned tier levels that indicate priority for spectrum access. An SAS of this type may be a multi-tier level system, for example, a 3-tier level priority system that includes spectrum users (networks and/or devices) that are each assigned one of three priority levels for use of channels within the shared spectrum. As used in this disclosure, the term channel means a portion or a band of frequency spectrum within which a network/device may transmit and/or receive signals. For example, a channel assignment to a network/device may comprise the assignment of one or more portions or bands of frequency spectrum within which the network/device may transmit and receive signals. The network/device may transmit and receive using any technology on frequency channels within the one or more portions or bands of frequency spectrum. In some implementations, the channel assignment may include channel numbers defined by a particular wireless standard. 
     The three priority levels of a SAS 3-tier level system may include a tier-1 level that includes incumbent spectrum users, a tier-2 level that includes spectrum users who are each licensed to use a certain portion of spectrum, and a tier-3 level that includes spectrum users who are general allowed access (GAA) users. In the 3-tier level system, when a tier-1 level user is active on a channel x, proximity tier-2 level and tier-3 level users cannot use the same channel x. In the absence of an active tier-1 level user on a channel x, a tier-2 level user can use the channel x. In the case where a tier-2 level user is using channel x, a tier-3 level user cannot use channel x. A tier-3 level user can only use channel x if there are no active tier-1 level or tier-2 level users on channel x. 
     Spectrum access management in a 3-tier level SAS is accomplished by using a SAS controller to manage an SAS channel assignment database. In a 3-tier level SAS, since tier-1 level devices are the incumbents and have highest priority in the spectrum for which they are incumbent, a tier-1 level user does not need to request a channel assignment from the controller of the SAS channel assignment database. The tier-1 level users may use the spectrum for which they are incumbent based on their own decisions, independently of the controller. Tier-1 level users may or may not inform (register with) the controller of the SAS channel assignment database to inform the SAS controller of the channels being used by the tier-1 level users. Whether or not a tier-1 level user informs the controller of its channel use depends on the system configuration. For example, if a tier-1 level user is a department of defense (DOD) or Military related entity, the tier-1 level user may not want to inform the controller of its channel usage for security reasons. In other cases, a spectrum access system operator may have agreements with tier-1 level users that the tier-1 level users will register their channel usage with the controller. In these cases, the registration of channel usage by tier-1 level users may allow the SAS controller to more efficiently manage channel assignments to tier-2 level and tier-3 level users. 
     In a 3-tier level SAS, tier-2 level and tier-3 level users send database queries to request channel assignments from the SAS controller in order to use spectrum in the SAS. The database queries allow the SAS controller to register the tier-2 level and tier-3 level users in an SAS database in order to manage and coordinate the spectrum usage according to a set of rules that avoids channel conflicts and interference. 
     Implementations of this disclosure provide technical advantages in systems such as a multi-tier level SAS by allowing the networks or devices operating in the multi-tier level SAS to switch tier levels. In an implementation, the switching of tier levels may be a swap of tier levels between a network/device and another network/device. In this case, the tier level of a network/device is switched or swapped with the tier level of another network/device and each network device operates at the tier level of the other network/device after the tier switch. In another implementation, the switching of tier levels may be a switching of tier levels used by a single network or a single device without any swap occurring with another network or device. In this case, the tier level of a network or device may be switched to another tier level for operation in the SAS. 
     In one example, an implementation provides advantages in a SAS by allowing a first network having low priority tier level to temporarily switch tier levels with a second network having a high priority tier level. The tier level switch may take place during a time period when the channel quality and/or bandwidth provided to the first network at the low priority level is degraded and the second network is not fully utilizing, or doesn&#39;t require, the channel quality and/or bandwidth available to the second network at the high priority level. In this case, the tier switch allows the first network to utilize the higher channel quality and/or bandwidth available at the high priority level when the higher channel quality and/or bandwidth are not needed by the second network. 
     In another example, an implementation provides advantages by allowing a network to self-initiate the switching of tier levels at which the network operates based on channel quality and/or bandwidth in the network and a cost function that indicates a cost of switching tier levels. The cost may be additional charges incurred by the network to operate at a higher tier level. When channel quality and/or bandwidth need improvement and the cost function indicates the cost is acceptable, the network may inform the spectrum access system that the network is switching tier levels and initiate operation at the higher tier level. The tier switch allows the network to utilize the higher channel quality and/or bandwidth available at the higher priority level. In this case, the tier switch may allow a network to operate in a spectrum access system while trading off the lower cost of operating at a low tier level with the higher cost of operating at the higher tier level for better quality service. 
     In a further example, another implementation provides advantages by allowing a first network operating at the first tier level and having available spectrum at the first tier level that is not being utilized to share the available spectrum with one or more second networks. In this example, a network controller in the first network having the available spectrum may provide information on the available spectrum to a SAS controller of a spectrum access system. The SAS controller may then broadcast the information to one or more second networks of the spectrum access system and coordinate a tier switch between the first network and a selected network of the one or more second networks. The tier switch allows the selected network to utilize the excess spectrum of the first network at the first tier level. The coordination of the tier switch by the network controller may involve determining that the selected network meets a condition of use included in the information provided by the first network. In an example, the conditions of use may include a cost condition and the coordination of the tier switch may include determining that the selected network of the one or more second networks meets the cost condition. In an example, the selected network may meet the cost condition by responding to the controller with a highest proposed payment or bid to be credited to the first network for use of the first tier level spectrum as compared to proposed payments received from other networks. In another example, the selected network may meet the cost condition by agreeing to a set payment of a cost set out in the cost condition. The payment may be credited an account associated with the first network by the SAS controller. 
     The implementations have applicability to systems such as Wi-Fi systems or long term evolution-unlicensed (LTE-U) systems, systems utilizing frequency spectrum in the television white space (TVWS), dynamic spectrum access (DSA) systems, and any other systems in which frequency spectrum is shared based on assignment of tier levels for priority of access to spectrum. 
       FIG. 1  shows a spectrum access system  100  that includes three networks. Network A includes devices  114 ,  116 ,  118 , and  120 , and network A controller  103 . Network B includes devices  122 ,  124 ,  126 , and  128 , and network B controller  102 . Network C includes devices  132  and  134 , and network C controller  106  that includes high power access point  130 . Devices  122  and  126  may be base stations configured as cellular base stations and devices  124  and  128  may be mobile handsets or similar devices operating in a cellular network comprising network B. Devices  114  and  118  may be base stations configured as wireless access nodes (functioning as base stations or access points) for a private/public service network comprising network A, and devices  116  and  120  may be tablet computers or similar devices operating in the private/public service network A. Device  132  may be a base station configured as a Wi-Fi access point of a business/organizational local area network (LAN) comprising network C, and device  134  may be a laptop computer or similar device operating in the LAN network.  FIG. 1  also shows system  101  that includes network X controller  108 , base station  110  and mobile handset  112 . System  101  may be located remotely from networks A, B, and C and may be a spectrum access system that is different from, and independent of, spectrum access system  100 . Network A controller  103 , network B controller  102 , and network C controller  106  are each shown communicating with a SAS controller  104  of spectrum access system  100 . SAS controller  104  includes a spectrum access system (SAS) database. While devices  116 ,  120 ,  124 ,  128 , and  134  are shown as particular types of mobile devices, in other implementations each of these devices may be configured as any other type of wireless device, such as a mobile phone, a laptop, a tablet device, a gaming/media device, a personal computer, or any other type of wireless device. Also, while devices  114 ,  118 ,  122 ,  126 , and  132  are shown as particular types of base stations, in other implementations each of these devices may be implemented as any other type of base station, access point, transmitter station, or other type of apparatus/device that provides a communications interface between a network and a wireless device. 
     Networks A, B, and C of spectrum access system  100  may each be assigned to a tier level of 3 available tier levels of spectrum access system  100 . In an implementation, devices (nodes)  114  and  118  of network A may be assigned to tier-1 level (highest priority), devices (base stations)  122  and  126  of network B may be assigned to tier-2 level (medium priority), and device (access point)  132  of network C may be assigned to tier-3 level (lowest priority). Tier-1 users/networks may be in the category of high priority users such as radar systems and Department of Defense (DoD) users. Tier-2 users/networks may be in the category of intermediate priority users such as police departments, fire departments, or licensed cellular systems. Tier-3 users/networks may be in the category of other users with general allowed access. For example, tier-3 users may be local access networks (LANs) of businesses or other organizations. 
     In the 3-tier spectrum access system  100 , when a tier-1 user (network or base station) is active on a channel x, proximity tier-2 and tier-3 users cannot use the same channel x. In the absence of an active tier-1 user on a channel x, a tier-2 user can use the channel x. In this case, a tier-3 channel cannot use channel x. A tier-3 user can only use channel x if there are no active tier-1 and tier-2 users on channel x. The overall management of spectrum access system  100  according to these rules is performed by SAS controller  104 . 
     In an implementation of spectrum access system  100 , each of the tier-2 level and tier-3 level network controllers may send queries for channel assignment on behalf of the devices in their network and allocate the assigned channels to the individual devices in the network. For example, network B controller  102  may send a query to SAS controller  104  for channel assignments for network B. When SAS controller  104  responds with channel assignments based on network B having a tier-2 level priority and the location of network B, network B controller may then allocate the channels assigned to network B to the individual base stations  122  and  126 . Network C controller  106  may send a query to SAS controller  104  for channel assignments for network C. When SAS controller  104  responds with channel assignments based on network C having a tier-3 level priority and the location of network C, network C controller may then allocate the channels assigned to network C to the access point  132 . 
     In another implementation of  FIG. 1 , each of the tier-2 level base stations  122  and  126  of network B may be implemented to send a query for a channel assignment to SAS controller  104  through network B controller  102 . SAS controller  104  responds to the query by sending a channel assignment of one or more channels directly to each base station  122  and  126  based on Network B having tier-2 level priority and the locations of base stations  122  and  126 . Also, tier-3 level access point  132  of network C may send a query for a channel assignment to SAS controller  104  through high power access point  130  and network C controller  106 . SAS controller  104  responds to the query by sending a channel assignment of one or more channels directly to access point  132  based on network C having tier-3 level priority and on the location of access point  132 . 
     Access nodes  114  and  118  of network A are tier-1 level devices that have a highest priority for use of designated spectrum that is within the spectrum usable in spectrum access system  100 . Access nodes  114  and  118  may use the designated spectrum for communication with tablet computing devices  116  and  120  without permission or assignment from SAS controller  104 . In the implementation of  FIG. 1 , access nodes  114  and  118  may send information through network A controller  103  to SAS controller  104  that informs SAS controller  104  of channels that are being used in network A. SAS controller  104  may then use the information received from nodes  114  and  118  when assigning channels to tier-2 and tier-3 level devices in network B and network C. 
       FIGS. 2A-2C  are diagrams illustrating portions of example controllers in a shared frequency spectrum system.  FIG. 2A  shows functional portions of network C controller  106  of  FIG. 1 . Network C controller  106  may include processor  220 , access point interface  216 , network interface  219 , channel/network parameter monitor  222 , channel assignment manager  218 , and tier switch timer  224 . Access point interface  216  may include high power access point/transceiver  130  that allows network C controller  106  to communicate with access point  132  over a wireless interface.  FIG. 2B  shows functional portions of network B controller  102  of  FIG. 1 . Network B controller  102  may include processor  206 , base station interface  202 , network interface  208 , channel/network parameter monitor  210 , channel assignment manager  204 , and tier switch timer  212 .  FIG. 2C  shows functional portions of SAS controller  104  of  FIG. 1 . SAS controller  104  may include processor  234 , network interface  228 , channel assignment database  230 , network subscription database  236 , network tier database  232 , and tier switch manager/database  226 . The operations of the portions of network A controller  103 , network B controller  102 , and SAS controller  104  in various implementations of  FIG. 1  may be explained in relation to the flow diagrams of  FIGS. 3A-3C ,  FIG. 4 , and  FIGS. 5A-5B . 
       FIGS. 3A-3C  illustrate example operations performed during a tier switch between a first network and a second network in a spectrum access system.  FIGS. 3A-3C  show an implementation of spectrum access system  100  in which network C controller  106  and a network B controller  102  communicate with SAS controller  104  of spectrum access system  100  to perform a tier level switch between network C and network B. 
       FIG. 3A  illustrates example operations performed by network C controller  106  as network C controller  106  interacts with SAS controller  104  in spectrum access system  100  during a tier level switch between network C and network B. 
     The process begins at  302  where network C controller  106  initiates operation at the tier-3 level in spectrum access system  100 . To initiate operation at the tier-3 level, processor  220  of network C controller  106  may send a database query to SAS controller  104  requesting a channel assignment as a tier-3 level network. Processor  220  of network C controller  106  may control channel assignment manager  218  to configure the database query and send the database query through network interface  219  over link  214  to SAS controller  104 . Network C controller  106  then receives a query response from SAS controller  104  at network interface  219  on link  214  that includes a channel assignment identifying channels that SAS controller  104  has assigned to network C as a tier-3 level network. Channel assignment manager  218  processes the channel assignment and stores the identity of the assigned channels in a channel assignment database. Processor  220  then controls channel assignment manager  218  to communicate with access point  132  through access point interface  216  to allocate channels to access point  132 . 
     At  304 , access point  132  operates on one or more of the channels assigned to network C as a tier-3 level device. In the example of  FIG. 3A , at least one uplink channel and at least one downlink channel may be assigned by network C controller  106  for communications between access point  132  and device  134 . During the operation of network C, access point  132  and/or device  134  monitor channel parameters on the assigned channels on which access point  132  and device  134  communicate with one another. In monitoring the channel parameters, access point  132  may sample a signal on at least one channel from device  134  on the uplink and device  134  may sample a signal on at least one channel from access point  132  on the downlink. During the monitoring, access point  132  may generate N parameter samples (S 1  . . . S N ) for each at least one channel on the uplink, and device  134  may generates N parameter samples (S 1 , SN) for each at least one channel on the downlink. The samples may be normally uniform samples and the number of samples may be fixed. Access point  132  and/or device  134  may send the series of N parameter samples for the at least one channel to network C controller  106  at selected times. Network C controller  106  receives the N parameter samples at access point interface  216  on link  237  and the N parameter samples are provided to channel/network parameter monitor  222 . In an implementation, the N parameter samples may comprise power level measurements of interference on the assigned channels. In other implementations, the N parameter samples may comprise any other type of measurements on the selected channel such as bit error rate/packet error rate, channel throughput, or other quality of services (QoS) related parameters. 
     At  306 , as network C operates as a tier-3 level network, network C controller  106  determines if a tier switch is needed. The determination at  306  may be performed, for example, periodically. In an implementation, processor  220  may control channel/network parameter monitor  222  to determine a metric n using the N samples (S 1 , . . . S N ) that were received from access point  132  and/or device  134  by channel/network parameter monitor  222  during the channel monitoring time period. The metric n may comprise a power measurement determined from the N samples that indicates a level of interference as measured by access point  132  or device  134  on the uplink or downlink, respectively. The metric for the selected channel may be determined from the samples as the value n, where n is represented by: 
     
       
         
           
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     To determine if a tier switch is needed processor  220  may determine if n&gt;n threshold  for the selected channel, where n threshold  is set at a threshold level of interference that triggers a tier switch. In other implementations, the metric used to determine if a tier switch is needed may comprise any other type of metric that may be associated with quality of service in network C, such as bit error rate/packet error rate, channel throughput, network throughput or other quality of services (QoS) related parameters. 
     If, at  306 , it is determined that a tier switch is not needed the process moves back to  304  and network C controller  106  continues to operate network C as a tier-3 network. If, at  306 , is it determined that a tier switch is needed the process moves to  308 . 
     At  308 , network C controller  106  generates a tier switch request. The tier switch request may include information associated with a desired tier level into which network C requests to switch. The tier switch request may also include information associated with an amount of spectrum or range of frequencies that is to be included in the tier switch, and a time period for which the tier switch is requested to last. Processor  220  may generate the tier switch request and initiate sending of the tier switch request to SAS controller  104  over link  214  through network interface  219 . 
     At  310 , network C controller  106  receives a response to the tier switch request from SAS controller  104 . Processor  220  may receive the response to the tier switch request from SAS controller  104  at network interface  219  over link  214 . The response to the tier switch request may include an indication that SAS controller  104  is able to perform the tier switch. 
     At  312 , processor  220  determines if the response to the tier request confirms that the tier switch is to take place. If the response to the tier switch request indicates that SAS controller  104  accepts the tier switch request, the tier switch is confirmed and the process moves to  314 . Alternatively, at  312 , if the response to the tier switch request indicates SAS controller  104  rejects the tier switch request, the tier switch is not confirmed and the process moves back to  304 . At  304 , network C controller  106  continues to operate network C as a tier-3 network. 
     At  314 , network C controller  106  initiates tier-2 level operation. Processor  220  of network C controller  106  may send a database query to SAS controller  104  requesting a channel assignment as a tier-2 network. Processor  220  of network C controller  106  may control channel assignment manager  218  to configure the database query and send the database query through network interface  219  over link  214  to SAS controller  104 . Network C controller  106  then receives a query response at network interface  219  on link  214  that includes a channel assignment identifying at least one channel that SAS controller  104  has assigned to network C as a tier-2 level network. Channel assignment manager  218  processes the channel assignment and stores the identity of the assigned channels in a channel assignment database. Processor  220  then controls channel assignment manager  218  to communicate with access point  132  to allocate channels for use by access point  132 . At  314 , processor  220  may also set tier switch timer  224  to run for the time period of the tier switch. 
     At  316 , access point  132  then operates on one or more of the channels assigned to network C as a tier-2 level device in the tier switch. At  322 , as network C operates as a tier-2 network, network C controller monitors tier switch timer  224  to determine if the tier switch time period is expired. If the tier switch timer  224  is not expired, processor  220  continues to control network C controller to operate as a tier-2 network at  316 . If the tier switch timer  224  is expired, the process moves to  302  where processor  220  terminates operation at the tier-2 level and initiates operation at the tier-3 level for network C in spectrum access system  100 . 
       FIG. 3B  illustrates example operation performed by network B controller  102  as network B controller  102  interacts with SAS controller  104  in spectrum access system  100  as a tier level switch between network C and network B is performed. In an implementation, the process of  FIG. 3B  may be performed concurrently with the performance of the process of  FIG. 3A  by network C controller  106 . 
     The process begins at  330  where network B controller  102  initiates operation at the tier-2 level in spectrum access system  100 . To initiate operation at the tier-2 level, processor  206  of network controller  102  may initiate the sending of a database query to SAS controller  104  requesting a channel assignment as a tier-2 network. Processor  206  of network B controller  102  may control channel assignment manager  204  to configure the database query and send the database query through network interface  208  over link  214  to SAS controller  104 . Network B controller  102  then receives a query response at network interface  208  on link  214  that includes a channel assignment identifying channels that SAS controller  104  has assigned to network B as a tier-2 level network. Channel assignment manager  204  processes the channel assignment and stores the identity of the assigned channels in a channel assignment database. Processor  206  then controls channel assignment manager  204  to communicate with base stations  122  and  126  to allocate channels for use by base stations  122  and  126 . 
     At  332 , base stations  122  and  126  operate on one or more of the channels assigned to network B as tier-2 level devices. 
     At  334 , as network B operates as a tier-2 network, network B controller  102  determines if a tier switch query has been received from SAS controller  104 . The determination at  334  may be performed by processor  206  monitoring communications received at network interface  208  on link  214  from SAS controller  104 . If a tier switch query has not been received, the process returns to  332  and network B continues operation as a tier-2 network. If a tier switch query has been received the process moves to  336 . 
     At  336 , network B controller  102  initiates sending of a response to the tier switch query to SAS controller  104 . In the example of  FIG. 3B , the response may comprise an acceptance indicating to SAS controller  104  that network B controller  102  is able to accept the tier switch. Processor  206  may determine that network B is able to accept the tier switch based on information in the tier switch query that indicates the tier level and the amount of spectrum or range of frequencies that the network requesting the tier switch has requested, and the time period for which the tier switch is requested to last. Information provided by channel/network parameter monitor  210  may be considered in conjunction with the information in the tier switch query when making the determination. For example, processor  206  may determine that network B has spectrum which is unused and available in a large enough amount to allow it to accept the tier switch request. As part of determining if it may accept the tier switch, processing  206  may also determine that interference conditions in network B on tier-2 and/or tier-3 channels are at a low level and Network B devices could operate on tier-3 channels without degradation. In one implementation, channel/network parameter monitor  210  may monitor a parameter x during tier-2 operation in a process similar to the monitoring performed by network C controller  106  when the parameter n is determined at operations  304  and  306  of  FIG. 3A . The monitoring of the parameter x may be performed on tier-3 and/or tier-2 channel frequencies. When interference conditions as indicated by the parameter x in network B are good and network B has available spectrum, network B may accept the tier switch. 
     At  338 , network B controller  102  determines if a confirmation to the response comprising the acceptance of the tier switch is received from SAS controller  104 . If a confirmation is not received, the process returns to  332  and network B continues to operate as a tier-2 network. If a confirmation is received, the process moves to  342 . 
     At  342 , network B controller  102  initiates operation as a tier-3 network. The initiation of operation network B as a tier-3 network at  342  may be performed similar to the initiation of the operation as a tier-2 network at  330  with the exception that network B controller  102  sends a database query to SAS controller  104  as a tier-3 network and network B is assigned channels as a tier-3 network. At  342 , processor  206  may also set tier switch timer  212  to run for the time period of the tier switch. At  346 , base stations  122  and  126  operate on one or more of the channels assigned to network B as a tier-3 level network. 
     At  348 , as network B operates as a tier-3 network, network B controller  102  determines if the tier switch time period has expired. Processor  206  determines if the tier switch period has expired by monitoring tier switch timer  212 . If the tier switch period is not expired, processor  206  continues to control network B controller to operate as a tier-3 network at  346 . If the tier switch period is expired, the process moves to  330  where processor  206  terminates operation at the tier-3 level and initiates operation at the tier-2 level in spectrum access system  100 . 
       FIG. 3C  illustrates example operation performed by SAS controller  104  as SAS controller  104  interacts with network B controller  102  and network C controller  106  in spectrum access system  100  as a tier level switch between network C and network B is performed. In an implementation, the process of  FIG. 3C  may be performed concurrently with the performance of the processes of  FIG. 3A  and  FIG. 3B  by network C controller  106  and network B controller  102 , respectively. 
     The process of  FIG. 3C  begins at  349  where SAS controller assigns channels to network B as a tier-2 level network and to network C as a tier-3 level network. During operation at  349 , processor  234  may receive database queries from network B controller  102  and network C controller  106  at network interface  228  over link  214 . Processor  234  may then interact with network tier database  232  and channel assignment database  230  to assign channels from channel assignment database  230  to network B and network C. The channel assignments will be based on network C being assigned tier-3 level and network B being assigned tier-2 level in network tier database  232 . The channel assignments may be stored in channel assignment database  230 . Processor  214  then initiates the sending of the channel assignments to network B controller  102  and network C controller  106  over link  214  through network interface  228 . 
     At  350 , as network C and network B operate as tier-3 and tier-2 level networks, respectively. SAS controller  104  receives a tier switch request from network C controller  106  at network interface  228  on link  214 . Processor  234  receives the tier switch request and interacts with tier switch manager/database  226  to initiate processing of the tier switch request. The tier switch request may include information associated with a desired tier level into which network C requests to switch. The tier switch request may also include information associated with an amount of spectrum or range of frequencies that is to be included in the tier switch, and a time period for which the tier switch is requested. 
     At  352 , SAS controller  104  determines a potential tier switch that may be performed. Processor  234  may determine that network B is a candidate for a tier switch with network C based on the information in the tier switch request and information from tier switch manager/database  226 . The information in tier switch manager/database  226  may include tier switch information that is associated with other networks in SAS system  100 . For example, the information in tier switch manager/database  226  may include information that indicates that network B will accept tier switches with other networks. The information in tier switch manager/database  226  may also include information on what tier levels and spectrum/frequency ranges network B will switch to or from, and other information such as particular time periods during which network B will accept tier switches. 
     At  354 , SAS controller  104  sends a tier switch query to network B controller  102 . Processor  234  initiates the sending of the tier switch query through network interface  228  over link  214 . The tier switch query may include the information associated with a desired tier level into which network C requests to switch. The tier switch query may also include the information associated with an amount of spectrum or range of frequencies that is to be included in the tier switch, and the time period for which the tier switch is requested. 
     At  356 , SAS controller  104  receives a response from network B controller  102 . Processor  234  receives the response from network interface  228  and, at  358 , determines whether the response indicates that network B controller  102  has accepted the tier switch with network C. If the tier switch has been accepted the process moves to  359 . If the tier switch has not been accepted the process ends. 
     At  359 , SAS controller  104  initiates the tier switch between network C and network B. Processor  234  initiates the sending of a response to the tier switch request to network C controller  106  indicating that the tier switch is confirmed through network interface  228  over link  214 . The response sent to network C controller may include confirmation of the desired tier level that network C requested. The response may also include confirmation of the amount of spectrum or range of frequencies that is to be included in the tier switch, and the time period for which the tier switch is requested. Processor  234  also may initiate the sending of a response to the tier switch acceptance received from network B controller  102  at  356  to confirm the tier switch through network interface  228  over link  214 . 
     At  360 , the tier switch is implemented as SAS controller  104  assigns channels to network B as a tier-3 level network and to network C as a tier-3 level network. In order to implement the operation of  360 , processor  234  may interact with network tier database  232  and channel assignment database  230  to create temporary assignments of network C to the tier-2 level and network B to the tier-3 level. Then, during operation at  360 , processor  234  may receive database queries from network B controller  102  and network C controller  106  at network interface  228  over link  214  and assign channels from channel assignment database  230  to network B and network C. The channel assignments will be based on network C being assigned tier-2 level and network B being assigned tier-3 level in network tier database  232 . Processor  234  then initiates the sending of the channel assignments to network B controller  102  and network C controller  106  over link  214  through network interface  228 . The channel assignments used at  360  may be stored in network tier database and channel assignment database  230  as temporary assignments that are valid for the time period of the tier switch. 
     At  362 , as SAS controller  104  assigns channels to network B as a tier-3 level network and to network C as a tier-3 level network, SAS controller  104  determines if the tier switch time period is expired. Processor  234  may monitor a timer to perform the operation of  362 . If the tier switch time period is not expired, processor  234  controls SAS controller  104  to continue to assign channels to network B as a tier-3 level network and to network C as a tier-3 level network. If the tier switch period is expired, the process moves to  364 . 
     At  364 , SAS controller  104  terminates the tier switch between network B and network C. Processor  234  may interact with network tier database  232  to change the temporary assignment of tier-2 to network C back to an assignment of tier-3 to network C, and change the temporary assignment of tier-3 to network B back to an assignment of tier-2 to network B. the process then moves to  349  where SAS controller assigns channels to network B as a tier-2 level network and to network C as a tier-3 level network. 
     In other examples of the process shown in  FIGS. 3A-3C , the tier switching may take place between networks operating at any of the tier levels of spectrum access system  100 . For example, depending on the situation, a network may request a tier switch to a lower priority level, for example from tier-2 level to tier-3 level. In another example, a first network operating at tier-2 or tier-3 level may request a tier switch with a second network operating at tier-1 level. In this case, the first network would operate as a tier-1 level network in tier-1 level spectrum after the tier switch and would not need to receive channel assignments from the SAS controller, while the second network would operate as a tier-2 or tier-3 level network and need to receive channel assignments during the period of the tier switch. 
     In other implementations, a network may switch the tier level that it operates in by self-initiating a tier switch. In this case, the network may not switch tier levels with another network, but switch its own tier level independently of the tier levels that other networks in the spectrum access system use. The switching of tier levels may incur a cost or credit to the network depending on the tier level switched into. For example, if the network switches to a higher priority tier level, a cost may be incurred by the network and, if the network switches to a lower priority tier level, a credit may be given to the network. In an implementation, SAS controller  104  may include functions for maintaining accounting for tier switches of networks within spectrum access system  100  in network subscription database  236 . 
       FIG. 4  is a flow diagram illustrating operations performed by an example network controller when switching network tier levels in a spectrum access system.  FIG. 4  may be explained using network C controller  106  of  FIGS. 1 and 2A  as the controller of  FIG. 4 . 
     The process begins at  402  where network C controller  106  initiates operation at the tier-3 level in spectrum access system  100 . To initiate operation at the tier-3 level, processor  220  of network C controller  106  may send a database query to SAS controller  104  requesting a channel assignment as a tier-3 network. Processor  220  of network C controller  106  may control channel assignment manager  218  to configure the database query and send the database query through network interface  219  over link  214  to SAS controller  104 . Network C controller  106  then receives a query response at network interface  219  on link  214  that includes a channel assignment identifying at least one channel that SAS controller  104  has assigned to network C as a tier-3 level network. Channel assignment manager  218  processes the channel assignment and stores the identity of the assigned channels in a channel assignment database. Processor  220  then controls channel assignment manager  218  to communicate with access point  132  through access point interface  216  to allocate channels to access point  132 . 
     At  404 , access point  132  operates on one or more of the channels assigned to network C as a tier-3 level network. In the example of  FIG. 4 , at least one uplink channel and at least one downlink channel may be assigned by network C controller  106  for communications between access point  132  and device  134 . 
     At  406 , during the operation of network C, access point  132  and/or device  134  monitor channel parameters on the assigned channels on which access point  132  and device  134  communicate with one another. In monitoring the channel parameters, access point  132  may sample a signal on at least one channel from device  134  on the uplink, and device  134  may sample a signal on at least one channel from access point  132  on the downlink. During the monitoring, access point  132  may generate N parameter samples (S 1  . . . SN) for each at least one channel on the uplink, and device  134  may generates N parameter samples (S 1  . . . SN) for each at least channel on the downlink. The samples may be normally uniform samples and the number of samples may be fixed. Access point  132  and/or device  134  may send the series of N parameter samples for the at least one channel to network C controller at selected times. Network C controller  106  receives the N parameter samples at access point interface  216  on link  237  and the N parameter samples are provided to channel/network parameter monitor  222 . In an implementation, the N parameter samples may comprise power level measurements of interference on the assigned channels. In other implementations, the N parameter samples may comprise any other type of measurements such as bit error rate/packet error rate, channel throughput, or other quality of services (QoS) related parameters. In further implementations, the N parameter samples may comprise network parameters such as throughput measurements. 
     At  408 , as network C operates as a tier-3 network, network C controller  106  determines if a tier switch is needed. The determination at  408  may be performed, for example, periodically. Processor  220  controls channel/network parameter monitor  222  to determine a metric n using the N samples (S 1 , . . . SN) for the selected channel that were received by channel/network parameter monitor  222  during the channel monitoring time period. In an implementation, the metric n may comprise a power measurement determined from the N samples that indicates a level of interference on the selected channel as measured by access point  132  or device  134  on the uplink or downlink, respectively. The metric for the selected channel may be determined from the samples as a value n, where n is represented by 
     
       
         
           
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     To determine if a tier switch is needed processor  220  may determine if n&gt;n threshold  for the selected channel, where n threshold  is set at a threshold level of interference. 
     In other implementations, the metric used to determine if a tier switch is needed may comprise any other type of metric that may be associated with quality of service in network C, such as bit error rate/packet error rate, channel throughput, network throughput or other quality of services (QoS) related parameters. 
     If, at  408 , it is determined that a tier switch is not needed the process moves back to  404  and  406  where network C controller  106  continues to operate network C as a tier-3 level network. Network C controller  106  will also continue to monitor parameters on the assigned channels. If, at  408 , is it determined that a tier switch is needed the process moves to  410 . 
     At  410 , processor  220  analyzes the tier switch in view of factors including the value of n, network/device requirements, and a cost function. In the operation of  410 , processor  220  analyzes whether the benefits of making a switch from the tier-3 level to the tier-2 level outweigh the cost as defined by the cost function. The cost function may be a function provided by the spectrum access network and stored network C controller  106 . For example, SAS controller  104  may send an updated cost function to network controllers in spectrum access system periodically. SAS controller  104  may also send an updated cost function to the network controllers as conditions change in spectrum access system  100 . The cost function may define a cost to the operators and/or users of network C that will be incurred if a tier switch to the tier-2 level is made based on conditions of the tier switch. For example, the cost function may define the cost of a tier switch to tier-2 based on a time of time of day that the tier switch takes place and the duration of the tier switch. Processor  220  may also include information/data on various thresholds defined for network C when determining whether a tier switch should be performed. For example, a higher level of cost for a tier switch may be accepted for higher levels of interference as indicated by the value of the parameter n. In another example, a higher level of cost for a tier switch may be accepted for a given level of interference, as indicated by the parameter n, when higher than normal quality level transmissions, for example high quality video transmissions, are required in network C. 
     At  412 , processor  220  determines if the tier switch is confirmed based on the analysis of operation  410 . If the analysis determines that the cost of the tier switch is not acceptable, the process moves back to  404  where network C continues to operate as a tier-3 network. If the analysis determines that the cost of the tier switch is acceptable, the tier switch is confirmed and the process moves to  414 . 
     At  414 , network C controller  106  sends an indication of the tier switch of network C to tier-2 to SAS controller  104 . The indication may include a database query requesting channel assignments for network C as a tier-2 network. Processor  220  of network C controller  102  may control channel assignment manager  204  to configure the database query and send the database query through network interface  219  over link  214  to SAS controller  104 . 
     At  416 , SAS controller  104  assigns channels to network C as a tier-2 level network. In order to implement the operation of  416 , processor  234  of SAS controller  104  may interact with network tier database  232  and channel assignment database  230  to create a temporary assignment of network C to the tier-2 level. During operation at  360 , processor  234  may receive database query from network C controller  106  at network interface  228  over link  214  and assign channels from channel assignment database  230  to network C. The channel assignments will be based on network C being assigned tier-2 in network tier database  232 . Processor  214  then initiates the sending of the channel assignments to network C controller  106  over link  214  through network interface  228 . The channel assignments may be stored in network tier database  232  and channel assignment database  230  as temporary assignments that are valid for the time period of the tier switch. 
     At  418 , Network C controller  106  receives a response to the indication of the tier switch at network interface  219  on link  214 . The response includes a channel assignment identifying at least one channel that SAS controller  104  has assigned to network C as a tier-2 level network. Channel assignment manager  218  processes the channel assignment and stores the identity of the assigned channels in a channel assignment database. Processor  220  then controls channel assignment manager  218  to communicate with access point  132  through access point interface  216  over link  237  to allocate channels for use by access point  132 . 
     At  420 , access point  132  then operates on one or more of the channels assigned to network C as a tier-2 level device in the tier switch. As network C operates as a tier-2 network, processor  220  of network C controller  106  may monitor switch timer  212  to determine if the tier switch period has expired. When the tier switch period expires, the process moves back to  402  where network C controller  106  terminates operation at the tier-2 level and initiates operation of network C at the tier-3 level in spectrum access system  100 . 
       FIGS. 5A and 5B  illustrate operations of a process in which tier switching may be performed to allow spectrum of a spectrum access system to be utilized when the spectrum would be otherwise unutilized and/or unavailable for use.  FIGS. 5A and 5B  show an implementation of spectrum access system  100  in which network B controller  102  and network C controller  106  communicate with SAS controller  104  of spectrum access system  100  to perform a tier switch for network C that allows network C to utilize spectrum that is unutilized in network B. 
       FIG. 5A  is a flow diagram illustrating operations performed by an example system controller when switching tier levels to utilize available spectrum in a spectrum access system.  FIG. 5A  may be explained using SAS controller  104  and network B controller  102  of  FIGS. 1 and 2A  as the network B controller and SAS controller, respectively, of  FIG. 5A . 
     The process begins at  502  where network B controller  102  determines that network B has excess spectrum available at the tier-2 level and sends an indication of the availability to SAS controller  104 . For example, network B controller  102  may determine that network B has been assigned tier-2 level channels that are not being utilized by network B devices and send an indication of this to SAS controller  104 . The determination at  502  may be made on a time period basis. For example, the determination at  502  may be a determination that the spectrum is underutilized during a certain time of day. Processor  206  may make the determination by monitoring the use of channels assigned to network B by SAS controller  104  and stored in channel assignment database. When the number of unused channels as indicated by channel assignment manager  204  is above a designated amount, the spectrum comprising the channel may be considered underutilized. For example, processor  206  may determine that the number of unused channels indicated by channel assignment manager  204  is above the designated amount each day between the times of 1 am and 4 am. In this case, processor  206  may make a determination that it has excess spectrum tier-2 level available between 1 am and 4 pm each day and send an indication of this availability to SAS controller  104  through network interface  208  over link  214 . In other examples, the determination may also be made on a current basis, where the determination is a determination that spectrum is presently being underutilized. This determination may include a determination that the underutilization has continued for the duration of a certain time period and is likely to continue. In this case, processor  206  may make a determination that it has excess spectrum tier-2 level that is presently available and will be available for some time period into the future, and send an indication of this availability to SAS controller  104  through network interface  208  over link  214 . The indication of availability sent to SAS controller  104  at  502  may also include conditions of use. For example, the conditions of use may include a cost condition indicating that network B will grant the tier switch to a network responding with a highest bid for the available spectrum. In this case network B will switch the available spectrum with the network responding with a highest proposed payment or bid to be credited to network B for use of the tier-2 level spectrum as compared to proposed payments received from other networks. In another example, the selected network may meet the cost condition by agreeing to payment of a set cost that is indicated in the cost condition. Upon a switch being made, the payment may be credited by the SAS controller  104  to an account associated with the network B. The conditions of use may also define the time period during which the available spectrum may be used and information on the frequency band and/or channels comprising the spectrum. 
     At  504 , SAS controller  104  receives the indication of tier-2 excess spectrum availability and conditions of use from network B controller  102 . Processor  234  may receive the indication of tier-2 level spectrum availability and conditions of use though network interface  228  over link  214 . Processor  234  of SAS controller  104  may process the indication of the available spectrum and conditions of use of the spectrum along with information in network subscription database  236  to determine one or more other networks of spectrum access system  100  that may utilize the available spectrum. For example, the information in network subscription database used in the determination may include information as to whether particular networks at particular tier levels should receive indications of available spectrum at the tier-2 level. 
     At  506 , SAS controller  104  broadcasts an indication of the available tier-2 level spectrum and conditions of use of the spectrum to the one or more other networks in spectrum access system  100  as determined at  504 . Processor  234  may initiate the broadcast of the indication of the available tier-2 level spectrum and conditions of use of the spectrum though network interface  228  on link  214  to the controllers of the one or more other networks. For example, the controllers of the one or more other networks may include network C controller  106  and the controllers of other networks of spectrum access system  100  not shown in  FIG. 1 . 
     At  508 , SAS controller  104  receives requests for the available tier-2 level spectrum and responses to conditions of use from the one or more other networks. Processor  234  may receive the requests for the available tier-2 level spectrum and responses to conditions of use over link  214  at network interface  228 . 
     At  510 , SAS controller  104  processes the requests for the available tier-2 level spectrum and responses to the conditions of use. In an implementation in which the conditions of use include the payment of a set cost, processor  234  may process the requests for the available tier-2 level spectrum and responses to the conditions of use by determining the networks associated with the responses indicating that the conditions of use are acceptable. If only one network is associated with a response indicating that the conditions of use are acceptable, that network is chosen for the tier switch. If more than one network is associated with a response indicating that the conditions of use are acceptable, processor  234  may chose a network for the tier switch based on a priority. For example, network subscription database  236  may store a priority for each network of spectrum access system  100  that defines each network&#39;s priority relative to other networks for access to available excess spectrum. In an implementation in which the conditions of use include offering the highest bid for the available spectrum, a network that offers the highest bid for use of the spectrum as compared to other networks to which the available spectrum is presented is chosen for the tier switch. If no requests for the available tier-2 level spectrum are received at  508  the broadcast may be repeated. Also, in an implementation in which the conditions of use include offering the highest bid/payment of use for the available spectrum and two or more networks have offered the same highest bid, the broadcast may be repeated to those two or more networks in order that the networks may send another bid/payment. 
     At  512 , SAS controller  104  assigns the available tier-2 spectrum for network B to the network chosen in  510 . In order to implement the operation of  512 , processor  234  of SAS controller  104  may interact with network tier database  232  and channel assignment database  230  to create a temporary assignment of network C to the tier-2 level for the available spectrum and a temporary block of network B from use of the spectrum in the tier-2 level. Processor  214  then initiates the sending of the channel assignments to network C controller  106  over link  214  through network interface  228 . The channel assignments used at  512  may be stored in network tier database and channel assignment database  230  as temporary assignments that are valid for the time period of the tier switch. Based on what the cost conditions were, processor  234  may also initiate a credit to an account associated with network B, and a corresponding debit to an account associated with network C, in network subscription database  236 . 
       FIG. 5B  is a flow diagram illustrating operations performed by an example network controller when switching tier levels to utilize available spectrum in a spectrum access system.  FIG. 5B  may be explained using SAS controller  104  and network C controller  106  of  FIGS. 1 and 2A  as the network C controller and SAS controller, respectively, of  FIG. 5B .  FIG. 5B  shows how a network C controller would communicate with an SAS controller performing the process of  FIG. 5A . 
     The process begins at  520  where network C controller  106  receives an indication of the available tier-2 level spectrum and conditions of use of the spectrum broadcast by SAS controller  104 . Processor  220  may receive the indication of the available tier-2 level spectrum and conditions of use of the spectrum at network interface  219 , and at  522 , process the received indication and conditions of use. Processor  220  may process the indication of the available tier-2 spectrum and the conditions of use using a cost/benefits analysis to determine if network C may benefit from use of the available tier-2 spectrum subject to the conditions of use. For example, Processor  220  may determine that network C may benefit from having additional bandwidth during the time periods defined in the condition of use based on information stored in channel/network parameter monitor  222 . Processor  220  may also determine that that cost indicated in the conditions of use is bearable given the extent of the need for additional bandwidth during those time periods defined in the conditions of use. In an implementation in which the conditions of use include offering the highest bid for the available spectrum, processor  220  may determine a bid offer based on the need during that time period. In the example of  FIG. 5B , processor  220  may determine that network C may benefit from use of the available spectrum subject to the conditions of use and the process moves to  524 . In an alternative scenario, if processor  220  had determined that network would not benefit from use of the additional spectrum subject to the conditions of use, processor  220  may end the process at  522 . 
     At  524 , network C controller  106  initiates the sending of a request for the tier-2 level spectrum and a response to the conditions of use to SAS controller  104 . Processor  220  initiates the sending of the request on link  214  from network interface  219 . The response to the condition of use may include an indication of acceptance of the conditions of use, for example acceptance of a set cost or a bid for use of the tier-2 level spectrum. Network C controller  106  may be one of a number of network controllers in spectrum access system  100  that have received the indication of the available tier-2 spectrum and the conditions of use, and are responding in a similar manner. 
     At  526 , network C controller  106  determines if a request for the tier-2 level spectrum and a response to the conditions of use have been accepted by SAS controller  104 . Processor  220  may receive a response to the request for the tier-2 level spectrum at network interface  219  on link  214  from SAS controller  104  that indicates whether SAS controller  104  has accepted the request of network C controller  106  for the available spectrum. If it determined that SAS controller  104  does not accept the request, the process ends. If it is determined that SAS controller accepts the request, the process moves to  528 . 
     At  528 , Network C controller  106  receives tier-2 channel assignments in the available tier-2 level spectrum from SAS controller  104 . Processor  220  receives the channel assignments at network interface  219  on link  214  identifying at least one channel that SAS controller  104  has assigned to network C as a tier-2 level network. Channel assignment manager  218  processes the channel assignment and stores the identity of the assigned channels in a channel assignment database. Processor  220  then controls channel assignment manager  218  to communicate with access point  132  to allocate channels for use by access point  132 . 
     The timing of when operation  528  takes place depends on the time periods defined in the conditions of use. For example, if the conditions for use defined a particular time period of the day or week, network C controller  106  would receive tier-2 channel assignments for use at that time period. 
     At  530 , access point  132  then operates on one or more of the channels assigned at  528  to network C as a tier-2 level device in the spectrum switched to network C from another network. As network C operates as a tier-2 network, processor  220  of network C controller  106  may monitor a timer to determine if the time period for the tier switch according to the conditions of use has expired. When the tier switch time period expires, the process moves back to  402  where network C controller  106  terminates operation at the tier-2 level and initiates operation at the tier-3 level in spectrum access system  100 . 
       FIG. 6A  is a diagram illustrating an example network having devices configured to switch between tier levels within the network in a spectrum access system.  FIG. 6A  shows network  800  that includes network controller  602 , access points  604 ,  606 ,  608 ,  610 , and  612 , and devices  614 ,  616 ,  618 ,  620 ,  622 ,  624 , and  626 . Network  800  may be business/organizational local area network (LAN) and access points  604 - 612  may be access points that operate according to one or more Wi-Fi standards. Devices  614 - 626  may be any type of device that has capability to communicate with one or more of access points  604 - 612  using channels implemented according to the appropriate W-Fi standard. Network  600  may be one network that is part of a larger spectrum access system that includes SAS controller  628 . 
     In the implementation of  FIG. 6A , SAS controller  628  may assign at least a first tier level and/or a second tier level of priority to networks, including network  800 , operating in the spectrum access system. Network controller  602  may assign either the first and/or the second tier level to each of the access points  604 - 612  operating in network  600 . 
     For example, network controller  602  may receive an assignment of at least one first channel from the SAS controller  628  and assign the at least one first channel to access points  604  and  606  based on access points  604  and  606  being assigned the first tier level by network controller  602 . Network controller  602  may also receive an assignment of at least one second channel from SAS controller  628  and assign the at least one second channel to access points  608 ,  610 , and  612  based on access points  608 ,  610 , and  612  being assigned the second tier level by network controller  602 . In an implementation, the priority of the second tier level may be higher than the priority of the first tier level within the spectrum access system. For example, the first and second tier levels may be the tier-3 and tier-2 levels, respectively, of a 3-tier spectrum access system controlled by SAS control  628 . 
     During operation of network  600 , network controller  602  may determine that a tier switch between access points  604  and  606  and access points  610  and  612  is to take place, i.e., is triggered. Network controller  602  may initiate the tier switch by assigning access points  604  and  606  to the second tier level and access points  610  and  612  to the first tier level, and assign the at least one second channel to access point  604  and  605  and the at least one first channel to access points  610  and  612 . In one example scenario, the controller may determine that the tier switch between access points  604  and  606  and access points  610  and  612  is to take place by determining that the at least one first channel used by access points  604  and  606  is degraded and that, based on some network criteria, access points  604  and  606  should be given better quality channels than access points  610  and  612 . 
       FIG. 6B  is a flow diagram illustrating operations performed by an example network controller when switching device tier levels within a network of a spectrum access system.  FIG. 6B  may be explained with reference to  FIG. 6A  using the example described above with SAS controller  628  being the controller of a 3-tier level spectrum access system that includes network  600  under its management. 
     The process begins at  630  where network controller  602  receives tier-2 level and tier-3 level channel assignments from SAS controller  628 . The channels assignments may be received in response to one or more database queries sent to SAS controller  628  by network controller  602 . The tier-2 level and tier-3 level channel assignments may assign a set of channels at the tier-2 level and a set of channels at the tier-3 level for use by network  600 . 
     At  632 , network controller  602  configures groups of access points within network  600  into tier-2 level and tier-3 level access point groups. Controller  600  may configure the groups based on the relative priority of communications carried by each of the access points  604 - 612 . For example, controller  600  may determine access points  604  and  606  currently carry lower priority communications and configure access points  604  and  606  as a tier-3 level access point group. Controller  600  may also determine that access points  608 ,  610 , and  612  currently carry higher priority communications and configure access point  608 ,  610 , and  612  as a tier-2 level access point group. In an example scenario of this, access points  608 ,  610 , and  612  may be installed in an executive meeting room where important meetings often take place, while access points  604  and  606  are installed in a secondary meeting room. Access points  608 ,  610 , and  612  therefore merit a higher priority tier level. 
     At  634 , network controller  602  assigns tier-2 channels to the tier-2 access point group comprising access points  608 ,  610 , and  612  and tier-3 channels to the tier-3 access point group comprising access points  604  and  606 . 
     At  636 , during operation of network  600 , network controller  602  monitors channel parameters and the traffic usage/load of access points  604 - 612 . For example, network controller  602  may monitor interference levels, bit error rates, or other parameters related to channel quality of each of the channels used by the individual access points  604 - 612 . Network controller  602  may receive results of measurements performed at devices  614 - 624  and access point  604 - 612  to perform the monitoring. Network controller  602  may also monitor throughput and traffic usage/load demands on each of the access points  604 - 612  during operation of network  600 . 
     At  638 , network controller  602  determines if a tier switch is triggered in network  600 . If network controller  602  determines that a tier switch is not triggered, the process returns to  636  where controller  602  continues to monitor channel parameters and the traffic usage/load of access points  604 - 612 . If network controller  602  determines that a tier switch is triggered, the process moves to  640 . 
     The determination at  638  of whether a tier switch is triggered may be based on information from the monitoring performed at  434 . For example, network controller  602  may determine that channel quality of the tier-3 channels assigned to the tier-3 access point group comprising access points  604  and  606  has degraded to below an acceptable level while the traffic usage/load demands of access points  604  and  606  have increased. At the same time controller  602  may determine that the traffic usage/load demands on the tier-2 channels assigned to the tier-2 access point group comprising access points  608 ,  610 , and  612  have decreased and the tier-2 channels are underutilized. Based on the relative situations of each of the access points, network controller may determine that a tier switch should occur between the tier-3 access point group comprising access points  604  and  606  and the tier-2 access point group comprising access points  608 ,  610 , and  612 . In other words, the tier levels of the access point groups should be switched so that access points  604  and  606  may utilize the higher priority tier-2 level channels that are currently underutilized and assigned to access points  608 ,  610 , and  612 . 
     At  640 , controller  602  reconfigures the tier-2 and tier-3 access point groups based on the monitoring results by reconfiguring access points  604  and  606  as a tier-2 level access point group and reconfiguring access points  608 ,  610 , and  612  as a tier-2 level access point group. The process then moves back to  634 . At  634 , network controller  602  assigns tier-2 channels to the tier-2 access point group comprising access points  604  and  606  and tier-3 channels to the tier-3 access point group comprising access points  608 ,  610 , and  612 . 
     The tier switching achieved by the example process of  FIG. 6B  may be implemented using any type of access point group. For example, the access points may each be treated separately by treating each access point as an access point group with one member, and the tier switching may be performed between individual access points rather than groups of access points. Also, the tier switching may include moving individual access point between access point groups to switch the tier level of individual access points, rather than switching the tier levels of the all the access points of an access point group. 
       FIG. 7  is a simplified block diagram showing an example network controller  700  that may be implemented in a network in a spectrum access system. Network controller  700  represents an example implementation of network B controller  102  that was described in relation to  FIGS. 1, 2B, and 3B . Network controller  700  may also represent an example implementation of network C controller  106  that was described in relation to  FIGS. 1, 2A, and 3A . 
     Network controller  700  includes processor  704 , network interface  714 , interface to base stations/access points  702 , and memory/storage  706 . Memory/storage  706  includes code and program/instructions for channel assignment manager programs  708 , channel/network parameter monitoring programs  710 , and tier switch timing programs  712 . Network controller  700  may connect though network interface  714  to a backend network that provides a connection to an SAS controller of a spectrum access system. Network interface  714  may be any type of interface, wireless or otherwise, to a backend network, for example the interne. Interface to base stations/access points  702  may be any type of interface, wireless or otherwise, that allows network controller  700  to communicate with base stations and/or access points such as base stations  122  and  126 , and access point  132  of  FIG. 1A . 
     Processor  704  may comprise one or more processors, or other control circuitry or any combination of processors and control circuitry that provide overall control of network controller  700  according to the disclosed embodiments. Memory  706  may be implemented as any type of as any type of computer readable storage media, including non-volatile and volatile memory. 
     In an implementation, execution of channel assignment manager programs  708 , channel/network parameter monitoring programs  710 , and tier switch timer  712  causes processor  704  to implement operations that cause network controller  700  to operate according to the operations described for network controllers  102  and  106  in relation to the implementations described in this disclosure. 
       FIG. 8  is a simplified block diagram showing an SAS controller  800  that may be implemented in a spectrum access system. SAS controller  800  represents an example implementation of SAS controller  104  that was described in relation to  FIGS. 1, 3C, 5A and 6B . Base station  800  includes processor  804 , network interface  802 , and memory/storage  806  that includes code and program/instructions for network channel assignment programs  808 , channel assignment database  810 , device tier/subscription database  812 , and tier switch manager/database programs  814 . SAS controller may connect to one or more network controllers, such as network controllers  102  and  105  of  FIG. 1 , through network interface  802 . Network interface  802  may be any type of interface, wireless or otherwise, to a network, for example the internet. Processor  804  may comprise one or more processors, or other control circuitry or any combination of processors and control circuitry that provide overall control of SAS controller  800  according to the disclosed embodiments. Memory  806  may be implemented as any type of as any type of computer readable storage media, including non-volatile and volatile memory. 
     In an implementation, execution of network channel assignment programs  808  and tier switch manager/database programs  814 , in conjunction with channel assignment database  810  and device tier/subscription database  812 , causes processor  804  to implement operations that cause SAS controller  800  to operate according to the operations described for SAS controller  104  in relation to the implementations of this disclosure. 
     The example embodiments disclosed herein may be described in the general context of processor-executable code or instructions stored on memory that may comprise one or more computer readable storage media (e.g., tangible non-transitory computer-readable storage media such as memory  706  or  806 ). As should be readily understood, the terms “computer-readable storage media” or “non-transitory computer-readable media” include the media for storing of data, code and program instructions, such as memory  706  or  806 , and do not include portions of the media for storing transitory propagated or modulated data communication multi-carrier signals. 
     While the functionality disclosed herein has been described by illustrative example using descriptions of the various components and devices of embodiments by referring to functional blocks and processors or processing units, controllers, and memory including instructions and code, the functions and processes of the embodiments may be implemented and performed using any type of processor, circuit, circuitry or combinations of processors and/or circuitry and code. This may include, at least in part, one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system-on-a-chip systems (SOCs), complex programmable logic devices (CPLDs), etc. Use of the term processor or processing unit in this disclosure is mean to include all such implementations. 
     The disclosed implementations include a controller for controlling a first and a second network in a spectrum access system having a plurality of tier levels for spectrum access. The controller comprised one or more processors and memory in communication with the one or more processors. The memory comprises code that, when executed, causes the one or more processors to control the controller to assign one or more first channels to a first network based on the first network being assigned a first tier level of the plurality of tier levels, determine that a tier switch is to take place between the first network and a second network assigned a second tier level of the plurality of tier levels, initiate the tier switch between the first network and the second network, and, assign, in response to the determination that the tier switch is to take place, one or more second channels to the second network based on the second network being assigned the first tier level. The controller may further assign, in response to the determination that the tier switch is to take place, one or more third channels to the first network based on the first network being assigned the second tier level. The code may further cause the controller to receive a tier switch request from the first network and determine that the tier switch is to take place based on the tier switch request. The code may further causes the controller to receive a tier switch request from the first network, send a tier switch query to the second network based on the tier switch request, receive a response from the second network, and, determine that the tier switch is to take place based on the response from the second network. The controller may determine that the tier switch is to take place between the first network and the second network for the duration of a tier switch period, and assigns the one or more second channels to the second network for the duration of the tier switch period. The second tier level may be a tier-1 level of a three tier spectrum access system or the second tier level may be a tier-2 level of a three tier spectrum access system. 
     The disclosed implementations also include a controller for a network in a spectrum access system having a plurality of tier levels for spectrum access priority. The controller comprises one or more processors and memory in communication with the one or more processors. The memory comprises code that, when executed, causes the one or more processors to control the controller to receive an assignment of at least one first channel based on the network being assigned a first tier level of the plurality of tier levels by the spectrum access system, monitor a parameter of the network, determine that a switch to a second tier level of the plurality of tier levels is to take place based at least on the parameter, send an indication to the spectrum access system that the network is switching to the second tier level of the plurality of tier levels, and, initiate operation of the network on at least one second channel based on the network being assigned the second tier level of the plurality of tier levels by the spectrum access system. The controller may determine that the switch to the second tier level of the plurality of tier levels is to take place based at least on the parameter and a cost function. The controller determines that the tier switch to the second tier level is to take place for the duration of a time period, and control the network to operate on the at least one second channel based on the network having the second tier level during duration of the time period. The parameter may include a parameter on a selected channel of the at least one first channel. 
     The disclosed implementations also include a controller for controlling devices in a network within a spectrum access system having at least a first tier level and a second tier level of priority for spectrum access. The controller comprises one or more processors and memory in communication with the one or more processors. The memory comprises code that, when executed, causes the one or more processors to control the controller to receive an assignment of at least first channel from the spectrum access system and assign the at least one first channel to at least one first device based on the at least one first device being assigned the first tier level in the network, assign at least one second channel to at least one second device based on the at least one second device being assigned the second tier level in the network, determine that a tier switch between the at least one first device and the at least one second device is to take place, initiate a tier switch between the at least one first device and at least one second device, and, assign the at least one second channel to the at least one first device and the at least one first channel to the at least one second device. The controller may further receive an assignment of the at least one second channel from the spectrum access system. The second tier level may be a highest priority level of the spectrum access system. The priority of the first tier level may be lower than the priority of the second tier level, and the controller may determines that a tier switch between the at least one first device and the at least one second device is to take place by determining that the quality of the at least one first channel is degraded. 
     The disclosed implementations further include a controller for controlling a plurality of networks in a spectrum access system having at least first and second tier levels for spectrum access. The controller comprises one or more processors and memory in communication with the one or more processors. The memory comprises code that, when executed, causes the one or more processors to control the controller to receive information on first tier level spectrum available for use by one or more second networks from a first network, wherein the first network is operating at the first tier level, send the information on the first tier level spectrum to the one or more second networks, receive at least one response from the one or more second networks, process the at least one response, and, assign one or more channels of the first tier level spectrum to a selected network of the one or more second networks based on the at least one response. The information on the first tier level spectrum may include conditions of use for the first tier level spectrum. The conditions of use may include a cost condition and the at least one response may indicate that the selected network of the one or more second networks accepts the cost condition. The conditions of use may include responding with a highest proposed payment, and the at least one response may indicate that the selected network of the one or more second networks has responded with the highest proposed payment. The conditions of use may include a time period during which the first tier level spectrum is available. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example embodiments, implementations, and forms of implementing the claims and these example configurations and arrangements may be changed significantly without departing from the scope of the present disclosure. Moreover, although the example embodiments have been illustrated with reference to particular elements and operations that facilitate the processes, these elements, and operations may be combined with or, be replaced by, any suitable devices, components, architecture or process that achieves the intended functionality of the embodiment. Numerous other changes, substitutions, variations, alterations, and modifications may be ascertained to one skilled in the art and it is intended that the present disclosure encompass all such changes, substitutions, variations, alterations, and modifications as falling within the scope of the appended claims.