Abstract:
A method of allocating resources in a first wireless system, wherein the first wireless system shares a frequency spectrum with a second wireless system, is described. The method comprises detecting a level of interference to the second wireless system caused by the first wireless system on a first frequency within the spectrum; determining if transmission on the first frequency should be restricted based on the level of interference; and restricting transmissions in the first system on the first frequency if it was determined that transmission on the first frequency should be restricted while allowing normal use of the remaining portions of the frequency spectrum to continue in the first system. A system for allocating resources in a first wireless system, wherein the first wireless system shares a frequency spectrum with a second wireless system, is also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 62/132,669, filed Mar. 13, 2015, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to spectrum sharing and interference management between wireless systems. 
       BACKGROUND 
       [0003]    The proliferation of smartphones and other wireless devices has led to the ever-increasing demand for wireless spectrum. In an effort to ameliorate this problem, the U.S. Federal Communications Commission (“FCC”) has opened up the 3550-3700 MHz band (“3.5 GHz band”), which has traditionally been reserved for military use, for shared-spectrum use. Shared-spectrum use has also been contemplated for the 1695-1710 MHz, 175-51780 MHz, and 2155-2180 MHz bands (collectively, the “AWS-3” bands) during a transitional period when federal incumbent systems relocate out of the bands. When spectrum is shared, some mechanism must be adopted to ensure users of the same spectrum do not interfere with each other and users with higher priorities are guaranteed access to the spectrum in a situation of a conflict. 
         [0004]    Using the 3.5 GHz band as an example, to protect existing users of the band, a three-tiered model has been adopted by the FCC, as illustrated in  FIG. 1 . As shown in the figure, incumbent access (IA) users, shown as federal and non-federal incumbent systems, are positioned at the top tier and have the highest priority. One or more Spectrum Access Systems (“SASs”) may facilitate spectrum sharing between the incumbent users and public users, such as commercial cellular operators, emergency vehicles, police, etc. Among the public users, some may obtain higher priority under a Priority Access License (“PAL”), while others may operate under General Authorized Access (“GAA”), i.e., without a license, but with the lowest priority. A spectrum access system (“SAS”) may facilitate the three-tiered model by ensuring that devices in a lower-priority access tier do not interfere with those in a higher-priority tier. The SAS may accomplish this by monitoring interference and dynamically assigning frequency bands to devices operating in the shared spectrum. It will be understood that a “frequency” may be a frequency band, a frequency channel, or a channel, and vice versa. 
         [0005]    The public use devices, i.e., the PAL and GAA devices, may each operate or run a communications system and communicate with end user devices, such as smartphones or other portable devices carried by end users, via any suitable wireless communication technologies or standard protocols, such as Long Term Evolution (LTE), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile Communications (GSM), etc. The SAS coordinates and manages spectrum sharing among the incumbents, the PAL systems, and the GAA systems, by assigning spectrum to the PAL and GAA devices as requested for use by the respective systems, while at the same time ensuring that the PAL and GAA devices and systems do not interfere with the incumbents, that the GAA systems do not interfere with the incumbents and the PAL systems, and that the PAL users do not interfere with each other. 
         [0006]    When the systems are in close proximity with one another, functions of the SAS alone may be insufficient to avoid harmful interference. Assistance from the individual systems may be necessary to ensure interference stays at a permissible level. 
       SUMMARY 
       [0007]    The present disclosure is directed to systems and methods for spectrum sharing and interference management between wireless systems. 
         [0008]    Consistent with at least one disclosed embodiment, a method is disclosed for allocating resources in a first wireless system, wherein the first wireless system shares a frequency spectrum with a second wireless system. In one embodiment this may be accomplished by detecting a level of interference to the second wireless system caused by the first wireless system on a first frequency within the spectrum; determining if transmission on all or a portion of the first frequency should be restricted based on the level of interference; and restricting transmissions in the first system on the first frequency if it was determined that transmission on all or a portion of the first frequency should be restricted while allowing normal use of the remaining portions of the frequency spectrum to continue in the first system. 
         [0009]    Consistent with at least one disclosed embodiment, a wireless communications system is disclosed for allocating resources in a first wireless system. In one embodiment this may be accomplished with a first wireless system that shares a frequency spectrum with a second wireless system; at least one sensor configured to detect a level of interference to the second wireless system caused by the first wireless system on a first frequency within the spectrum; and at least one processor configured to receive the level of interference, determine if transmission on all or a portion of the first frequency should be restricted based on the level of interference, and generate at least one instruction for the first system to restrict transmissions therein on the first frequency if it was determined that transmission on the first frequency should be restricted while allowing use of the remaining portions of the frequency spectrum to continue in the first system, 
         [0010]    Consistent with at least one disclosed embodiment, a wireless communications device is disclosed for allocating resources in a first wireless system. In one embodiment this may be accomplished with at least one receiver configured to receive from a sensor a level of interference caused by a first wireless system on a first frequency within a frequency spectrum to a second wireless system, wherein the first wireless system shares the spectrum with the second wireless system; at least one processor configured to receive the level of interference, determine if transmission on the first frequency should be restricted based on the level of interference, and generate at least one instruction for the first system to restrict transmissions therein on the first frequency if it was determined that transmission on the first frequency should be restricted while allowing use of the remaining portions of the frequency spectrum to continue in the first system; and at least one transmitter configured to transmit the instruction to the first wireless system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated in and constitute part of this specification, and together with the description, illustrate and serve to explain various embodiments. 
           [0012]      FIG. 1  illustrates a three-tiered model adopted by the FCC for a shared-spectrum system; 
           [0013]      FIG. 2  illustrates an exemplary shared-spectrum system for implementing methods and systems consistent with the present disclosure; 
           [0014]      FIG. 3  illustrates an exemplary architecture of an LTE system; 
           [0015]      FIG. 4  illustrates an exemplary time-frequency resource grid structure for uplink communications in accordance with an embodiment of the present disclosure; 
           [0016]      FIG. 5  illustrates an exemplary use restriction of a portion of otherwise available bandwidth, in accordance with an embodiment of the present disclosure; and 
           [0017]      FIG. 6  is a flow diagram illustrating an exemplary method for allocating resources in a shared-spectrum system, in accordance with an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several illustrative embodiments are described herein, modifications, adaptations and other implementations are possible. For example, substitutions, additions or modifications may be made to the components illustrated in the drawings, and the illustrative methods described herein may be modified by substituting, reordering, removing, or adding steps to the disclosed methods. Accordingly, the following detailed description is not limited to the disclosed embodiments and examples. Instead, the proper scope is defined by the appended claims. 
         [0019]    LTE has been widely deployed in the U.S. In a shared-spectrum system, such as the three-tiered model adopted by FCC for the 3.5 GHz band, many PAL and GAA users will likely choose LTE as their wireless communication standard and their LTE systems will coexist with non-LTE systems. LTE employs orthogonal frequency division multiplexing (OFDM) technology, where the frequency band is divided into a number of smaller orthogonal frequency bands called subcarriers. The subcarriers may be grouped into Physical Radio Resource Blocks (PRBs), each containing 12 subcarriers over seven OFDM symbols. Seven OFDM symbols may comprise a 0.5 millisecond slot. End user devices can be assigned the subcarriers according to a scheduling algorithm in the system. The term “frequency” as used in this disclosure may refer to frequency band, a singular frequency, a subcarrier, or a group of subcarriers. 
         [0020]    Consistent with embodiments of the present invention, an LTE system coexisting with other system(s) in a shared-spectrum network allocates spectrum, subcarriers, or spectrum resources to its end users such that the LTE system does not utilize the spectrum used by another system in close proximity, so as to reduce interference to the other system if the other system has a higher priority. This “blanking” or “notching” of otherwise allocable spectrum may be permanent or dynamic. Blanking may be used, for example, in an LTE system on PAL so that the system would avoid using a portion of its spectrum if that portion is used by a nearby incumbent user, and in an LTE system on GAA so that the system would avoid using a portion of its spectrum if that portion is used by nearby incumbent users or PAL users. 
         [0021]    Descriptions of embodiments are provided below using the example of an LTE system and the three-tiered model adopted by the FCC, but are not limited to such. 
         [0022]      FIG. 2  illustrates an exemplary shared-spectrum system  200  consistent with the present disclosure. System  200  includes a network  202  to which all devices of the system connect, one or more LTE systems  206 , non-LTE incumbent systems (“incumbents”)  208 , one or more SASs  210 , and/or other non-LTE, non-incumbent systems  212 . Network  202  may comprise any suitable network such as the Internet, a wide area network, or any other network that permits exchange of information between various components of the system. LTE system  206  may comprise, for example, cellular network base stations, emergency vehicles, or any other system that does not have incumbent status. In the three-tiered model shown in  FIG. 1 , LTE system  206  may be operating on PALs or as GAAs. In the example of the 3.5 GHz band, non-LTE incumbents  208  may comprise systems used by branches of armed forces, for example, U.S. Department of Defense air surveillance radar systems, or devices used by other government operators. Non-LTE, non-incumbent systems  212  may comprise, for example, Wi-Fi networks or other telecommunication networks using Wideband Code Division Multiple Access (WCDMA), Global System for Mobile Communication (GSM), or any other suitable technology. SAS  210  coordinates and manages spectrum sharing among non-LTE incumbents  208 , LTE system  206 , and non-LTE, non-incumbent systems  212  by assigning spectrum to LTE system  206  as requested, while at the same time ensuring that the LTE system  206  and non-LTE, non-incumbent systems  212  do not interfere with non-LTE incumbents  208 . SAS  210  may facilitate spectrum sharing by notifying LTE system  206  and non-LTE, non-incumbent systems  212  what frequencies they may operate on, when they should vacate certain frequencies, or what power level they may transmit at. All of the LTE system  206 , incumbent non-LTE systems  208 , SASs  210 , and non-LTE, non-incumbent systems  212  may include necessary components to facilitate wireless communication among them. Such components may include antennas, transmitters, receivers, and/or transceivers. They may also include processors for processing and generating signals. 
         [0023]    LTE system  206  may communicate with end user devices, or user equipment (“UE”), such as smartphones or other portable devices carried by end users.  FIG. 3  illustrates an exemplary architecture of LTE system  206  by reference to an exemplary LTE system  300 . LIE system  300  may include end user devices or UE  310  ( 310   a,    310   b,    310   c ), an Evolved Universal Terrestrial Radio Access Network (E-UTRAN)  304 , and an evolved packet core (EPC)  306 . E-UTRAN  304  may include one or more base stations  302  ( 302   a,    302   b ), also referred to as eNode B or eNB, which control radio communications of UE  310  within their respective cells. EPC  306  communicates between E-UTRAN  304  and external packet data networks  308  ( 308   a,    308   b,  etc.) Each eNB  302  may include a Resource Scheduler  316  that assigns frequency resources to UE  310 . One flavor of the LTE standards is the so-called frequency division duplexing (FDD), where different frequency bands are assigned for communications from UE to eNB (uplink) and communications from eNB to UE (downlink). LTE standards also provide for use of the same frequency band on both the uplink and downlink but at alternating times, a scheme referred to as time division duplexing (TDD). 
         [0024]    Using FDD LTE as an example,  FIG. 4  shows a type-1 time-frequency resource grid structure  400  for normal LTE FDD uplink communications, where the horizontal axis indicates time and the vertical axis indicates frequency, Type-2 time-frequency resource grid structure, not shown, may be used for normal LTE TDD uplink communications. In the exemplary type-1 resource grid structure shown in  FIG. 4 , the frequency band is divided into a number of 15 kHz orthogonal narrower frequency bands or subcarriers  402 . A time frame  404  of ten milliseconds is also defined for uplink transmissions. Each time frame  404  may be divided into time slots  406  that are each 0.5 milliseconds. Two slots  406  make up a 1-millisecond subframe  408 , Each time slot  406  is further divided into seven symbol units  410 . 
         [0025]    Resources in the form of subcarriers and symbol units are assigned for UE  310  to transmit to base stations  302  on the uplink. The smallest assignable block of resources, referred to as the physical radio block (PRB), labeled in the figure as  412 , comprises, for example, 12 subcarriers with a total of 180 kHz bandwidth spanning over one time slot  406  or seven symbol units  410 . Thus, a 10 MHz frequency band containing a 1 MHz guard band has 9 MHz bandwidth divided into 50 (=9 MHz/180 kHz) PRBs in parallel. Different UEs  310  may transmit over different PRBs across the frequency band at the same time, and one UE  310  may transmit on multiple PRBs consecutive in frequency. Resource scheduler  316  is responsible for allocating PRBs to UE  310  within the corresponding cell based on need and availability. The uppermost and lowermost portions, or the edges, of the band are generally designated as Physical Uplink Control Channels (PUCCHs)  414 . Other portions of the band may be designated as Physical Uplink Shared Channels (PUSCHs)  416 . PUCCHs  414  are used to carry uplink control information, and PUSCHs  416  are used for transmitting UE data. 
         [0026]    Consistent with embodiments of the present disclosure, when operations of LTE system  206  cause harmful interference to a non-LTE incumbent system  208  or a higher priority system, either because they are in close physical proximity or for any other reason, it may be necessary for the LTE system to restrict, eliminate, notch, or blank interfering signals.  FIG. 5  illustrates an example where use of a portion of the otherwise available bandwidth is restricted so resource scheduler  316  does not assign PRBs within the portion of the bandwidth to UE  310  in the uplink. As shown in  FIG. 5 , PRBs  502 ,  504 ,  506 , and  508  in the edge portions of the frequency band are allocated for PUCCH transmission. Resource scheduler  316  assigns a minimum of 2 PRBs to a piece of UE for PUSCH transmission. For example, PRBs  510  and  512  are allocated to user  1  and PRBs  514  and  516  are allocated to user  2 . A certain frequency within the PUSCH region of the frequency band may be used by higher-priority systems (such as incumbent systems  208 ). To avoid harmful interference, resource scheduler  316  may restrict the use of PRBs via blocking or blanking or notching so that UE on LTE system  206  does not transmit on those PRBs at or around the certain frequency. In one aspect, resource scheduler  316  may block the use of a PRB such that no UE may transmit on the PRB. Alternatively, resource scheduler  316  may instruct UE  310  to reduce transmission power to below a harmful level. In one aspect, resource scheduler  316  may issue instructions based on information received from SAS  210  to achieve the blocking, blanking, notching, or reduced transmission power. In another aspect, SAS  210  may provide instructions to resource scheduler  316  to block the use of a PRB. It will be appreciated by those skilled in the art that the blocked spectrum resource may be any smallest group of subcarriers or a frequency-time segment used by the wireless system for scheduling and is not limited to PRBs in an LTE system. Such smallest allocable spectrum resource may be generally referred to as a “scheduling unit.” 
         [0027]    In one aspect, the blocking or blanking or notching may be permanent, so that LTE system  206  never uses those PRBs in the neighborhood of the frequency used by the higher priority system and resource scheduler  316  never assigns such PRBs to UE  310 . In another aspect, resource scheduler  316  dynamically restricts use of the PRBs within the potentially interfering portion of the frequency band. In the example shown in  FIG. 5 , resource scheduler  316  blocks a region  518  over a subframe and a plurality of PRBs and may unblock the use of the PRBs in a subsequent subframe. Resource scheduler  316  may continue to assign other portions of the bandwidth to UE  310  for normal use. 
         [0028]    In one aspect, resource scheduler  316  communicates with SAS  210  to determine if any portion of the uplink frequency band is used by a higher priority system such as an incumbent user and if transmissions from UE  310  in the cell cause significant interference to the higher-priority system, to receive instructions as to how to use an uplink frequency, or to confirm that use of an uplink frequency is permitted. In that regard, system  200  may further include one or more sensors (not shown) that sense spectrum usage and report the sensed information to SAS  210  to facilitate detection of frequency use by various systems. The sensors may comprise any device suitable for detecting wireless transmissions and determining spectrum usage, such as antennas, radars, etc. The sensors may be distributed over the area covered by the network, either installed within systems  206 ,  208 ,  212 , or separately from those devices. The sensors may be mobile or in fixed locations. Alternatively, end user devices may also sense the environment and report measurements to the systems  206 ,  208 , and/or  212 , which may then report the information to SAS  210 . Existing sensors, such as those for sensing and detecting incumbent users, may also gather and forward frequency use information to SAS  210 . 
         [0029]    Information gathered from the sensors may identify devices or systems, the relative priority (i.e., incumbent vs. PAL vs. GAA), frequency ranges used by the systems, the time period of such use, transmission power, and/or a tolerance level for interference. SAS  210  communicates such information to LTE system  206 , and LTE system  206  determines whether and when to restrict use of certain PRBs that might cause harmful interference to a system with a higher priority of use than LTE system  206 . Resource scheduler  316  may simply decide to permanently block the use of all PRBs within the entire frequency spectrum used by a higher-priority system. But that may be inefficient. Interference varies across the frequency spectrum and maybe only a small portion of the spectrum is more susceptible to harmful interference, in which case only the use of PRBs within the small portion need to be blocked or restricted. SAS  210  or LTE system  206  may calculate the level of interference and determine that potential interference is harmful if it exceeds a certain threshold level generated from empirical data or provided by SAS  210 . Alternatively, or in addition, the higher-priority system&#39;s use of the spectrum may be temporary, in which case the use of PRBs that might cause harmful interference only needs to be blocked or restricted for a limited period of time. Resource scheduler  316  may also employ other criteria in deciding whether and when restricting or blocking the use of PRBs should take place, such as the absolute priority level of the incumbent system that might be harmed by the interference. For example, if LTE system  206  is a GAA system, resource scheduler  316  may give incumbent systems  208  a higher level of deference than PAL users, such that a lower threshold will be used for blocking or restricting use of PRBs that might cause harmful interference to incumbent users than to PAL users. 
         [0030]    Determination of the level of possible interference and/or whether blocking or restricting the use of PRBs is necessary may be performed by either a SAS  210 , or a component within the LTE system  206  based on the information received from the SAS  210 . SAS  210  generally has access to much more frequency use data, and can perform necessary computation on a server or in the cloud, and provide the computation results to LTE system  206 . SAS  210  can also provide sufficient frequency use data to LTE system  206  such that a component thereof (such as a processor within eNB  302 ) can perform the computation. 
         [0031]    Proper operation of LTE system  206  requires PUCCH assignment at all times. Therefore, resource scheduler cannot block PUCCHs  502 . In the event transmissions on the PRBs for PUCCH cause harmful interference to a higher-priority system, resource scheduler  316  may allocate a different set of PRBs for PUCCH and restrict or block the use of the PRBs originally assigned for PUCCH. This may be called an “over-provisioned PUCCH.” 
         [0032]    Consistent with embodiments of the present disclosure, resource scheduler  316  may include necessary hardware and/or software that interacts with SAS  210  to gather frequency use or interference data and determines, based on the gathered information, whether certain subcarriers within a time frame should be blanked. The scheduling of PRBs according to the above-described blocking/blanking/notching scheme may be easily implemented as a software update in resource scheduler  316 . 
         [0033]      FIG. 6  is a flow diagram illustrating an exemplary method  600  consistent with embodiments of the present disclosure. At Step  602 , frequency use data is gathered for the frequency band used by LTE system  206  and particular frequency or frequencies are identified if they are used by another system (such as non-LTE incumbent system  208 ) with a higher priority than LTE system  206  in the shared-spectrum system. The gathering of the data at Step  602  may be performed by SAS  210  in coordination with other devices or components in the system, as described above. 
         [0034]    At Step  604 , the level of potential interference on a particular frequency from LTE system  206  to the other system is detected. This detection may be performed by LTE system  206  (such as resource scheduler  316 ) based on frequency use data provided by SAS  210 , or by SAS  210 , or by both. 
         [0035]    At Step  606 , a determination is made as to whether transmissions on the particular frequency should be reduced. The determination may be made by the SAS  210 , or LTE system  206  (such as resource scheduler  316 ) based on information received from SAS  210 . The determination may comprise determining whether the interference level exceeds a threshold. If so, transmissions on the particular frequency or corresponding PRBs may be reduced (Step  608 ). In one aspect, transmission power from UE on the cell must be reduced to a permissible level or lower. Alternatively, resource scheduler  316  may simply block transmissions on the particular frequency or corresponding PRBs completely. 
         [0036]    As discussed above and as shown in  FIG. 6 , method  600  may repeat the determination of whether transmissions on a frequency or corresponding PRBs should be blocked or reduced to achieve a dynamic and efficient PRB schedule in LTE system  206 . 
         [0037]    Although the above descriptions use LTE as an example, it should be apparent to one skilled in the art that the system and method consistent with the present disclosure may be implemented with any multi-carrier system or the like that allows division of the frequency spectrum into subcarriers, or smaller frequency bands, and assigns spectrum on the basis of the subcarriers or smaller frequency bands. The scheduling granularity in LTE systems is at the PRB level. This method can be generalized to other radio technologies with different scheduling units, such as individual or a group of subcarriers or frequency bands over any suitable time periods. 
         [0038]    The systems and methods described above may be implemented by any hardware, software, or a combination of hardware and software having the above-described functions. The software code, either in its entirety or a part thereof, may be stored in a computer readable memory. 
         [0039]    While several implementations have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be implemented in many other specific forms without departing from the scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented. 
         [0040]    Also, techniques, systems, subsystems, and methods described and illustrated in the various implementations as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein, 
         [0041]    While the above detailed description has shown, described, and pointed out the fundamental novel features of the disclosure as applied to various implementations, it will be understood that various omissions and substitutions and changes in the form and details of the system illustrated may be made by those skilled in the art, without departing from the intent of the disclosure.