Patent Publication Number: US-9420606-B2

Title: Full duplex operation in a wireless communication network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of provisional patent application No. 62/017,182, filed in the United States Patent and Trademark Office on Jun. 25, 2014, the entire content of which is incorporated herein by reference as if fully set forth below and for all applicable purposes. 
    
    
     TECHNICAL FIELD 
     Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to scheduling algorithms for wireless communication systems that combine full duplex nodes and half duplex nodes. 
     BACKGROUND 
     Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. In many networks, resources are allocated for bi-directional communication utilizing either time division duplexing (TDD) or frequency division duplexing (FDD). In either TDD or FDD, communication utilizing a single frequency channel is only possible in one direction at any given instant of time. Thus, TDD and FDD networks implement full duplex functionality by either utilizing multiple frequency channels, as in the case of FDD, or by dividing the two directions of communication according to allocated time slots, as in the case of TDD. 
     Recently, with technological improvements to interference cancellation techniques, true radio level full duplex communication is feasible, where bi-directional communication between devices occurs utilizing a single frequency channel, and at the same time. As the demand for mobile broadband access continues to increase, research and development continue to advance wireless communication technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience. 
     BRIEF SUMMARY OF SOME EXAMPLES 
     The following presents a simplified summary of one or more aspects of the present disclosure, in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the disclosure, and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in a simplified form as a prelude to the more detailed description that is presented later. 
     Some aspects of the present disclosure provide for methods, apparatus, and computer software for communicating within a wireless communication network including a scheduling entity, configured for full duplex communication, and user equipment (UE), configured for half duplex communication. In some examples, one or more UEs may be configured for limited (quasi-) full duplex communication. Some aspects relate to scheduling the UEs, including determining whether co-scheduling of the UEs to share a time-frequency resource is suitable based on one or more factors such as an inter-device path loss. 
     In one aspect, the disclosure provides a network node configured for wireless communication, including at least one processor, a computer-readable medium communicatively coupled to the at least one processor, and a transceiver communicatively coupled to the at least one processor. Here, the at least one processor may be configured to utilize the transceiver to communicate with a first device and a second device, by utilizing half duplex communication with each of the first device and the second device, to determine an inter-device path loss between a first device and a second device, and to co-schedule the first device and the second device to utilize a first time-frequency resource if an inter-device path loss between the first device and the second device is greater than a threshold. 
     Another aspect of the disclosure provides a method of wireless communication operable at a network node. Here, the method includes communicating with a first device and a second device, by utilizing half duplex communication with each of the first device and the second device, determining an inter-device path loss between a first device and a second device, and co-scheduling the first device and the second device to utilize a first time-frequency resource if an inter-device path loss between the first device and the second device is greater than a threshold. 
     Another aspect of the disclosure provides a UE configured for wireless communication, including at least one processor, a computer-readable medium communicatively coupled to the at least one processor, and a transceiver communicatively coupled to the at least one processor. Here, the at least one processor may be configured to utilize the transceiver to communicate with a network node utilizing half duplex communication, to utilize the transceiver to receive an interference discovery signal from an interfering UE, to utilize the transceiver to transmit an interference report to the network node corresponding to a strength of the received interference discovery signal, and to utilize the transceiver to receive a resource allocation from the network node, wherein the resource allocation is co-scheduled with the interfering UE only if a path loss, corresponding to the strength of the received interference discovery signal, is greater than a threshold. 
     Another aspect of the disclosure provides a method of wireless communication operable at a UE. Here, the method includes communicating with a network node utilizing half duplex communication, receiving an interference discovery signal from an interfering UE, transmitting an interference report to the network node corresponding to a strength of the received interference discovery signal, and receiving a resource allocation from the network node, wherein the resource allocation is co-scheduled with the interfering UE only if a path loss, corresponding to the strength of the received interference discovery signal, is greater than a threshold. 
     These and other aspects of the invention will become more fully understood upon a review of the detailed description, which follows. Other aspects, features, and embodiments of the present invention will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments of the present invention in conjunction with the accompanying figures. While features of the present invention may be discussed relative to certain embodiments and figures below, all embodiments of the present invention can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments of the invention discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments it should be understood that such exemplary embodiments can be implemented in various devices, systems, and methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of a hardware implementation for a scheduling entity employing a processing system according to some embodiments. 
         FIG. 2  is a block diagram illustrating an example of a hardware implementation for a user equipment (UE) employing a processing system according to some embodiments. 
         FIG. 3  is a block diagram illustrating an example of a wireless communication network including a full duplex scheduling entity and half duplex UEs according to some embodiments. 
         FIG. 4  is a flow chart illustrating a process for determining whether to co-schedule a pair of UEs in a time-frequency resource according to some embodiments. 
         FIG. 5  is a block diagram illustrating an example of a wireless communication network including a full duplex scheduling entity and half duplex UEs with interference discovery and interference report signaling, according to some embodiments. 
         FIG. 6  is a flow chart illustrating a process for interference discovery and co-scheduling UEs according to some embodiments. 
         FIG. 7  is a flow chart illustrating another process for interference discovery and co-scheduling UEs according to some embodiments. 
         FIG. 8  is a flow chart illustrating a process for utilizing an inter-UE distance to determine an inter-UE path loss and co-scheduling UEs according to some embodiments. 
         FIG. 9  is a schematic illustration showing the use of radial coordinates to determine an inter-UE distance according to some embodiments. 
         FIG. 10  is a block diagram illustrating an example of a wireless communication network including a full duplex base station and half duplex UEs with additional detail of signal parameters according to some embodiments. 
         FIG. 11  is a flow chart illustrating a process for determining whether to implement quasi-full duplex communication at a scheduling entity according to feasibility conditions, according to some embodiments. 
         FIG. 12  is a block diagram illustrating an example of a wireless communication network including a full duplex base station and a limited full duplex UE according to some embodiments. 
         FIG. 13  is a flow chart illustrating a process of controlling a quasi-full duplex UE according to some embodiments. 
         FIG. 14  is a block diagram illustrating an example of a wireless communication network including a full duplex base station and a limited full duplex UE with additional detail of generalized signal parameters according to some embodiments. 
         FIG. 15  is a block diagram illustrating an example of a wireless communication network including a full duplex base station and half duplex UEs with additional detail of generalized signal parameters according to some embodiments. 
         FIG. 16  is a block diagram illustrating an example of a wireless communication network including an intermediate relay node operating in full duplex mode between a plurality of anchor base stations and a plurality of terminal UEs, in accordance with some embodiments. 
         FIG. 17  is a block diagram illustrating an example of a wireless communication network including a relay node receiving downlink data from an anchor base station and transmitting the downlink data to a UE in accordance with some embodiments. 
         FIG. 18  is a block diagram illustrating an example of a wireless communication network including a relay node receiving uplink data from a UE and transmitting the uplink data to an anchor base station in accordance with some embodiments. 
         FIG. 19  is a block diagram illustrating an example of a wireless communication network including a relay node transmitting downlink data to a first UE and receiving uplink data from a second UE in accordance with some embodiments. 
         FIG. 20  is a block diagram illustrating an example of a wireless communication network including a relay node receiving downlink data from a first base station and transmitting uplink data to a second base station in accordance with some embodiments. 
         FIG. 21  is a block diagram illustrating an example of a wireless communication network including a relay node transmitting and receiving data to/from a full duplex base station in accordance with some embodiments. 
         FIG. 22  is a block diagram illustrating an example of a wireless communication network including a relay node transmitting and receiving data to/from a full duplex UE in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
       FIG. 1  is a block diagram illustrating an example of a hardware implementation for an apparatus  100  employing a processing system  114 . In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system  114  that includes one or more processors  104 . For example, the apparatus  100  may be a scheduling entity, network node, base station (BS), or relay, as illustrated in any of  FIGS. 3, 5, 9, 10, 12, 14, 15, 16, 17, 18, 19, 20, 21 , and/or  22 . Examples of processors  104  include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. That is, the processor  104 , as utilized in an apparatus  100 , may be used to implement any one or more of the processes described below. 
     In this example, the processing system  114  may be implemented with a bus architecture, represented generally by the bus  102 . The bus  102  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  114  and the overall design constraints. The bus  102  links together various circuits including one or more processors (represented generally by the processor  104 ), a memory  105 , and computer-readable media (represented generally by the computer-readable medium  106 ). The bus  102  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface  108  provides an interface between the bus  102  and a transceiver  110 . The transceiver  110  provides a means for communicating with various other apparatus over a transmission medium. In various examples, the transceiver  110  may include one or more antennas, and in multi-antenna examples, may be enabled to determine an angle from which a received signal arrives. The transceiver  110  may include various sub-components configured to enable wireless communication, including but not limited to one or more power amplifiers, a transmitter, a receiver, filters, oscillators, etc. Depending upon the nature of the apparatus, a user interface  112  (e.g., keypad, display, speaker, microphone, joystick) may also be provided. 
     The processor  104  is responsible for managing the bus  102  and general processing, including the execution of software stored on the computer-readable medium  106 . The software, when executed by the processor  104 , causes the processing system  114  to perform the various functions described below for any particular apparatus. The computer-readable medium  106  may also be used for storing data that is manipulated by the processor  104  when executing software. 
     One or more processors  104  in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium  106 . The computer-readable medium  106  may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium  106  may reside in the processing system  114 , external to the processing system  114 , or distributed across multiple entities including the processing system  114 . The computer-readable medium  106  may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system. 
     In various aspects of the disclosure, the processor  104  may include a half duplex communication circuit  141 , which may function in coordination with half duplex communication software  161 . Here, the half duplex communication circuit  141  and/or software  161  may utilize the transceiver  110  to enable communication with one or more devices (e.g., UEs  200 , described further below) utilizing half duplex communication techniques, such as time division duplexing (TDD) and/or frequency division duplexing (FDD). 
     The processor  104  may further include a full duplex communication circuit  142 , which may function in coordination with full duplex communication software  162 . Here, the full duplex communication circuit  141  and/or software  161  may enable full duplex communication with one or more devices (e.g., UEs  200 ) utilizing a single frequency channel. In some examples, the full duplex communication circuit  141  may function in coordination with the interference cancellation circuit  143 . 
     That is, the processor  104  may further include an interference cancellation circuit  143 , which may function in coordination with interference cancellation software  163 . Here, the interference cancellation circuit  143  and/or software  163  may be configured to enable automatic interference cancellation at the transceiver  110 , which may function to cancel intra-device interference (e.g., self-interference). The interference cancellation circuit  143  and/or software  163  may utilize any suitable interference cancellation algorithm or technique, including but not limited to antenna/RF isolation, transmit signal reconstruction and cancellation (e.g., using a digital baseband signal and/or transceiver output signal, channel response estimation, transceiver non-linearity modeling etc.), power amplifier noise cancellation, etc. In some examples, the interference cancellation circuit  143  and/or software  163  may further function to cancel inter-device interference. That is, interference with one or more other transmitting devices. The interference cancellation circuit  143  and/or software  163  may include any suitable filter or equalizer configured for interference cancellation. 
     The processor  104  may further include a path loss discovery and determination circuit  144 , which may function in coordination with path loss discovery and determination software  164 . Here, the path loss discovery and determination circuit  144  and/or software  164  may enable determination of an inter-device path loss between pairs of devices (e.g., UEs  200 ) in accordance with one or more factors or parameters such as the distance between the respective devices; may enable determination and storing of a path loss value  151  between a single device (e.g., a UE  200 ) and the network node/scheduling entity  100 ; and, in some examples, may enable determination of the distance between a pair of UEs utilizing one or more algorithms as described in detail herein below, and accordingly, determination of a path loss between the UEs based on the determined distance. Further, the path loss discovery and determination circuit  144  and/or software  164  may compare a determined inter-device path loss with a path loss threshold  152  to make various determinations, e.g., whether to co-schedule pairs of UEs to share time-frequency resources. 
     The processor  104  may further include a resource allocation and scheduling circuit  145 , which may function in coordination with resource allocation and scheduling software  165 . Here, the resource allocation and scheduling circuit  154  and/or software  165  may allocate resources for one or more devices (e.g., UEs  200 ) to utilize for communication with the network node/scheduling entity  100 , and/or for communication between UEs (e.g., for interference discovery signals); it may select a resource for allocation utilizing any suitable resource selection scheme, including but not limited to random selection, or selection corresponding to an identifier unique to the respective devices; it may schedule time-frequency resources for one or more devices (e.g., UEs  200 ) to utilize; and it may determine whether to co-schedule two or more devices (e.g., UEs  200 ) to utilize the same time-frequency resource based on one or more factors or parameters, such as if their inter-device path loss is greater than a path loss threshold  151 , based on a path loss between the respective devices and the network node/scheduling entity  100 , and/or based on a data rate and/or data type  153  utilized by the respective devices. Further, the resource allocation and scheduling circuit  145  and/or software  165  may function in coordination with the transceiver  110 , to transmit resource allocation signals to devices (e.g., UEs  200 ). 
     The processor  104  may further include an optional backhaul communication circuit  146 , which may function in coordination with an optional backhaul communication software  166 . Here, the backhaul communication circuit  146  and/or software  166  may enable communication with an upstream node utilizing any suitable wired or wireless backhaul communication interface. The backhaul communication circuit  146  and/or software  166  are optional, and may generally be included in examples wherein the network node/scheduling entity  100  is a relay node, described in further detail below. 
       FIG. 2  is a block diagram illustrating an example of a hardware implementation for an apparatus  200  employing a processing system  214 . In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system  214  that includes one or more processors  204 . For example, the apparatus  200  may be a user equipment (UE) as illustrated in any of  FIGS. 3, 5, 9, 10, 12, 14, 15, 16, 17, 18, 19, 20, 21 , and/or  22 . The apparatus  200  has many components the same as or similar to those described above in relation to  FIG. 1 . For example, a bus  202 , a bus interface  208 , a transceiver  210 , and a user interface  212 , are substantially the same as those described above in relation to  FIG. 1 . Furthermore, processor  204 , the memory  205 , and the computer-readable medium  206  have many similarities to those so-named components described above in relation to  FIG. 1 , except for the differences described herein below. 
     That is, in various aspects of the disclosure, the processor  204  may include a half duplex communication circuit  241 , which may function in coordination with half duplex software  261 . Here, the half duplex communication circuit  241  and/or software  261  may utilize the transceiver  210  to enable communication with one or more devices utilizing half duplex communication techniques, such as time division duplexing (TDD) and/or frequency division duplexing (FDD). 
     The processor  204  may further include a full duplex communication circuit  242 , which may function in coordination with full duplex communication software  262 . Here, the full duplex communication circuit  242  and/or software  262  may function in coordination with the interference cancellation circuit  243  and/or software  262 , described below, to enable full duplex communication with one or more devices utilizing a single frequency channel. Accordingly, the full duplex communication circuit  242  and/or software  262  may enable full duplex communication, for example, if a configured transmit power is less than a transmit power threshold  253 . In some examples, the full duplex communication circuit  242  and/or software  262  may be optional, and some UEs may lack such full duplex communication capabilities. 
     The processor  204  may further include an interference cancellation circuit  243 , which may function in coordination with interference cancellation software  263 . Here, the interference cancellation circuit  243  and/or software  263  may enable interference cancellation (e.g., automatic interference cancellation), e.g., functioning to cancel intra-device interference (e.g., self interference) and/or functioning to cancel inter-device interference. Further the interference cancellation circuit  243  and/or software  263  may include any suitable filter or equalizer configured for interference cancellation. 
     The processor  204  may further include an interference determination and report generation circuit  244 , which may function in coordination with interference determination and report generation software  264 . Here, the interference determination and report generation circuit  244  and/or software  264  may enable determination of an interference level corresponding to an interfering device (e.g., by determining a strength of a received interference discovery signal from the interfering device), and may accordingly generate and transmits (e.g., utilizing the transceiver  210 ) an interference report to the network node/scheduling entity  100 , based on the determined interference level. Further, the interference determination and report generation circuit  244  and/or software  264  may calculate and store a path loss value  251 , which may be included in the transmitted report. 
     The processor  204  may further include a target SNR determination circuit  245 , which may function in coordination with target SNR determination software  265 . Here, the target SNR determination circuit  245  and/or software  265  may enable a determination of a signal-to-noise ratio (SNR), and/or a signal-to-interference-and-noise ratio (SINR), and may compare the determined SNR/SINR to a target SNR/SINR for the purpose of enabling full duplex communication based on the SNR/SINR. 
     INTRODUCTION 
     In wireless communication systems, communication devices can exhibit full duplex or half duplex functionality. With half duplex operation, communication is only possible in one direction at a time on a particular channel, generally being time-divided between segments in one direction or the other direction. This is frequently referred to as time division duplexing (TDD). With full duplex operation, simultaneous communication to and from a device is possible. 
     In currently deployed systems, full duplex functionality is generally enabled by utilizing frequency division duplexing (FDD), wherein one frequency band is used for communication in one direction, and another frequency band is used for communication in the other direction. In these deployments, although the communication may be full duplex in time, it remains half duplex in the frequency domain, since communication remains only in one direction on each channel. 
     A communication node that is truly full duplex at the radio level utilizes the same frequency channel to transmit and receive signals simultaneously in time. In the description that follows, the term full duplex is used to refer to radio level full duplex operation on the same frequency channel at the same time. Furthermore, in the disclosure that follows, both time and frequency division duplexing systems (TDD and FDD) are regarded as radio level half duplex systems. 
     Recently, due in part to improvements in active interference cancellation technology, radio level full duplex functionality, wherein full duplex communication may be achieved utilizing a single frequency channel, is possible with high reliability. In such a system, it may be the case where some wireless nodes (e.g., a base station, eNodeB, access point, scheduling entity, etc.) may be configured with full duplex radios for true radio level full duplex functionality, whereas some other nodes (e.g., wireless devices, UEs, subordinate entities, etc.) may be configured only with half duplex radios for half duplex functionality at the radio level. Furthermore, some radios in such a system may have partial and/or conditional full duplex capabilities, e.g., wherein they utilize only half duplex functionality unless certain conditions are satisfied. 
       FIG. 3  is a simplified block diagram illustrating an exemplary wireless communication network with a base station  302  capable of full duplex functionality in communication with two UEs  304  and  306  that are only capable of half duplex communication. In the illustration, the base station  302  is illustrated transmitting a downlink signal to a first UE  304 , and at the same time, receiving an uplink signal from a second UE  306 . 
     In such a network, where full duplex nodes communicate with half duplex nodes, interference between the half duplex nodes can become problematic. For example, as illustrated in the scenario in  FIG. 3 , the first UE  304  and the second UE  306  are co-scheduled, such that the first UE  304  is allocated a particular resource to utilize for receiving downlink signals, and the second UE  306  is allocated that same particular resource to utilize for transmitting uplink signals. In this case, co-scheduling the UEs can cause the transmission from the second UE  306  to produce cross-device interference that affects the receiving performance of the first UE  304 . In such a wireless communication system, a scheduling entity  308  at the base station  302  (e.g., a scheduler at the medium access control or MAC layer) or any other suitable scheduling node would benefit from taking suitable precautions to mitigate such cross-UE interference when the base station  302  or other scheduling node is operating in full duplex mode. For example, such cross-device interference may be reduced when a path loss between the UEs is large. Accordingly, various aspects of the present disclosure explore methods by which a base station may choose UEs to be co-scheduled based, for example, on a path loss between the respective UEs. Further aspects of the disclosure consider data rates to assign to the transmitter and receiver links at the base station when co-scheduling such UEs. 
     Therefore, in one or more aspects of the disclosure, a wireless communication network may be configured to choose a pair of UEs with a sufficiently large inter-UE path loss, so that a scheduling node or base station may transmit to one UE and receive from the other UE utilizing the same time-frequency resource, while reducing or avoiding cross-device interference between the respective UEs. In various aspects of the disclosure, several methods or algorithms to determine the inter-UE path loss are presented. The base station or scheduling node may further choose the UEs such that their path loss to the base station is small enough to sustain the required link SINR, and/or may determine the data rate or data type (traffic vs. control) to use for each of the two links, so that the SINR targets may be met by both links of the full duplex configuration. 
       FIG. 4  is a flow chart illustrating an exemplary process  400  for determining whether to co-schedule a given pair of UEs in accordance with one or more aspects of the present disclosure. In some examples, the process  400  may be carried out by a network node such as a scheduling entity  100  and/or a processing system  114  as described above and illustrated in  FIG. 1 . In some examples the process  400  may be carried out by any suitable means for implementing the described functions. 
     At block  402 , the scheduling entity  100  may communicate with a first device (e.g., a UE  200 ) and a second device (e.g., a UE  200 ) by utilizing half duplex communication with each of the first device and the second device. Here, the scheduling entity  100  may determine an inter-device path loss between the first device and the second device, utilizing any suitable inter-device path loss discovery algorithm, method, or technique. Several such inter-device path loss algorithms are described below. If the discovered inter-UE path loss is high (e.g., being greater than some suitable path loss threshold), then the process may proceed to block  404 . Here, the scheduling entity  100  may co-schedule the first device and the second device to utilize the same time-frequency resource. On the other hand, if the discovered inter-UE path loss is low (e.g., not being greater than the path loss threshold), then the process may proceed to block  406 . Here, the scheduling entity  100  may not co-schedule the first device and the second device to utilize the same time-frequency resource. 
     Discovery of Inter-UE Path Loss 
     In accordance with one or more aspects of the disclosure, a network node, base station, or other scheduling entity (hereafter referred to as a scheduling entity) may be enabled to discover an inter-UE path loss. Here, a path loss may be an attenuation of a signal from transmission to receipt. That is, due to one or more factors or conditions, the power or energy of a signal when it is received at a receiving device may be less than the power or energy of the signal when it is transmitted from a transmitting device. This change is generally referred to as a path loss. In various embodiments, any one or more of a number of techniques, methods, or algorithms may be utilized for discovery of inter-UE or inter-device path loss. By taking the path loss into account, two or more co-scheduled UEs (e.g., at least one UE scheduled for transmission and at least one other UE scheduled for reception utilizing the same time-frequency resource) may cause a suitably low amount of cross-device interference such that their simultaneous scheduling is possible. For example, the inter-UE path loss may be correlated with the distance between the respective UEs, e.g., being proportional to the fourth power of the distance between the UEs. Further, the inter-UE path loss may be affected by other potentially random phenomena, such as shadowing. In general, if two UEs are close to one another, then the cross-device interference may be high; but if the two UEs are far enough apart from one another, then the cross-device interference may be suitably low. 
     In one example, with reference to  FIG. 5 , in order to discover the inter-UE path loss at least one of the UEs (e.g., the second UE  306 ) may transmit a pilot signal, a reference signal, or any other suitable interference discovery signal  510 , while another UE (e.g., the first UE  304 ) may detect and/or measure the strength of the received interference discovery signal  510 . In some aspects, the first UE  304  may transmit an interference report  512  including one or more factors such as a signal strength of the received interference discovery signal  510  back to the base station or scheduling entity  302 . Here, the scheduling entity  302  may already have knowledge of the transmit power of the transmitted interference discovery signal  510 , e.g., because the transmit power is dictated by the scheduling entity  302 , or the transmit power is reported to the scheduling entity  302  by the transmitting UE  306 . Therefore, the path loss between the first UE  304  and the second UE  306  may be determined by the scheduling entity  302 , by determining the difference between the received signal strength reported by the receiving UE  304  and the actual transmit power utilized by the transmitting UE  306 . Accordingly, in some examples, if the determined path loss, and/or the value of the receive power reported by the UE  304 , is too low (e.g., below a suitable path loss threshold) or too high (e.g., above a suitable path loss threshold), then the corresponding pair of UEs may be eliminated as candidates for co-scheduled full duplex operation at the scheduling entity  302 . That is, in various aspects of the disclosure, the scheduling entity  302  may determine whether to co-schedule a given pair of UEs, corresponding to a particular time-frequency resource, in accordance with the determined or discovered inter-UE path loss between that given pair of UEs. 
     Resource Allocation for Interference Discovery 
     In some examples, such as (but not limited to) large networks where many UEs are served by a base station or other scheduling entity, certain resources may be dedicated specifically for cross-device interference discovery. For example, in an aspect of the disclosure, a subset (e.g., half) of the UEs in the network may be configured to send pilot/discovery signals at a given discovery time-slot, while the remaining UEs may be instructed to look for these signals, and to report the strength of each discovery signal that is detected, to the base station. Here, each transmitting UE may be assigned a unique signal resource (e.g., a unique time-frequency allocation) on which to send its discovery signal/pilot/reference signal with specified transmit power. 
     In a further aspect of the disclosure, the subset of UEs scheduled to transmit pilot/discovery signals may be changed (e.g., randomly) over subsequent discovery time slot(s), e.g., until the path loss between each pair of proximate UEs can be determined 
     As an alternative to random selection of UEs that transmit on a given interference discovery slot, in another aspect of the disclosure, each UE may be assigned a unique tag, which may be based on an identifier  252  stored at the UE, such as its MAC ID and/or its radio network temporary identifier (RNTI). Here, as one example, a UE  306  may transmit its interference discovery signal  510  during an i-th discovery time slot if the i-th bit of its unique tag is ‘1’, and may listen for interference discovery signals from other UEs if the i-th bit of its unique tag is zero. 
     After transmitting and receiving interference discovery signals, each UE may report the source and strength of each pilot/discovery signal it received during the corresponding discovery time slots. Accordingly, the base station or scheduling entity may avoid pairing UEs whose mutual path loss is determined to be too low. In this way, the various UEs in the network can be enabled to withstand cross-UE interference during full duplex data transfer at the scheduling entity. 
       FIG. 6  is a flow chart illustrating an exemplary process  600  for allocating resources for inter-device interference discovery in accordance with some aspects of the present disclosure. In some examples, the process  600  may be carried out by a network node such as a scheduling entity  100  and/or a processing system  114  as described above and illustrated in  FIG. 1 . In some examples the process  600  may be carried out by any suitable means for implementing the described functions. 
     At block  602 , a scheduling entity  100  may select a subset of devices (e.g., UEs  200 ) from among a plurality of devices, to transmit interference discovery signals. In some examples, the subset may be half of the devices connected to the scheduling entity  100 . Further, in some examples, the subset may be randomly selected from among the devices connected to the scheduling entity  100 , or in other examples, may be selected based on other suitable criteria such as a device tag or identifier. At block  604 , the scheduling entity  100  may allocate a time-frequency resource for selected subset of devices to utilize for the transmission of interference discovery signals. Accordingly, the selected devices may utilize the allocated resource and may discover inter-device interference between pairs of devices. Further, one or more devices (e.g., the non-selected subset of devices), which receives the interference discovery signals, may transmit suitable interference reports back to the scheduling entity. 
     At block  606 , the scheduling entity  100  may receive the interference report from the one or more devices (e.g., the non-selected subset of devices), and at block  608 , the scheduling entity  100  may determine the inter-device path loss. Here, for example, the inter-device path loss may be based on a difference between the strength of a transmitted interference discovery signal (which may be known to the scheduling entity  100 ), and a strength reported in the interference report. 
     At block  610 , the scheduling entity  100  may determine whether sufficient inter-device path losses have been determined. That is, decisionmaking as to whether time-frequency resources may be co-scheduled to two or more UEs may be improved when larger numbers of inter-UE path loss combinations among the connected UEs are available. If sufficient inter-device path losses have not yet been determined, the process may return, e.g., to block  602  and further interference discovery may be implemented. On the other hand, if sufficient inter-device path losses have been determined by the scheduling entity  100 , then the process may proceed to block  612 , wherein the scheduling entity  100  may schedule time-frequency resources for half-duplex devices. Here, the scheduling entity  100  may co-schedule pairs of devices if the inter-device path loss between that pair of devices is low (e.g., being less than a suitable path loss threshold). 
     Measuring RF Signals for Discovering Inter-UE Path Loss 
     Referring once again to  FIG. 5 , according to another aspect of the disclosure, to discover inter-device path loss, the scheduling entity  302  may be configured to schedule multiple UEs for data/control transmission, or any suitable interference discovery signal  510 , on separate time-frequency resources. Here, UEs that are not scheduled for interference discovery signal  510  transmission utilizing a particular time-frequency resource may be instructed to measure the energy received in each time-frequency resource, and to transmit an interference report  512  corresponding to this measurement. In this way, based on the particular time-frequency resource being reported on, the scheduling entity  302  may know the identity of the UE that transmitted an interference discovery signal  510  using that resource. Furthermore, based on the identity of the reporting UE and the reported signal strength of a given time-frequency resource, the scheduling entity  302  may determine the path loss between a corresponding pair of UEs. That is, the scheduling entity  302  may determine the inter-UE path loss between a pair of UEs by determining a difference between a known strength of a transmitted interference discovery signal  510 , transmitted utilizing a predetermined time-frequency resource that identifies the transmitting UE, and a report strength of the received interference discovery signal  510 . Here, the identity of the reporting UE may be determined based on any suitable information, e.g., contained in the interference report  512  transmitted by the reporting UE. 
     In a related example, to better facilitate the determination of cross-device interference across all UEs in the network, the scheduling entity  302  may change (e.g., randomly change) the subset of UEs transmitting data/control over sequential time slots or other suitable time durations. Accordingly, as described above, over time the path loss between any pair of UEs may be determined by the scheduling entity  302 . 
     In yet another example, rather than relying on the scheduling entity  302  to use the time-frequency location of the interference discovery signals  510  to identify the UE that transmits the signal, the transmitting UEs may actively tag their respective interference discovery signals  510  with their own identity (e.g., a MAC ID/RNTI/UE-Id/UE-signature). In various examples, such tagging may involve the inclusion of the MAC ID or other suitable identifier as part of a packet header within the interference discovery signal  510 . In another example, such tagging may involve using a UE-specific sequence to scramble at least part of the interference discovery signal  510 . Here, the receiving UE may include the same, or corresponding information in its interference report  512 , so that the scheduling entity  302  knows the identity of the UE that transmitted the interference discovery signal  510 . 
       FIG. 7  is a flow chart illustrating an exemplary process  700  for allocating resources for inter-device interference discovery in accordance with some aspects of the present disclosure. In some examples, the process  700  may be carried out by a network node such as a scheduling entity  100  and/or a processing system  114  as described above and illustrated in  FIG. 1 . In some examples the process  700  may be carried out by any suitable means for implementing the described functions. 
     At block  702 , a network node such as a scheduling entity  100  may select a subset of devices (e.g., UEs  200 ) to transmit interference discovery signals, and at block  704 , the scheduling entity  100  may allocate time-frequency resources for the selected subset of devices to utilize to transmit interference discovery signals. 
     At block  706 , the scheduling entity  100  may instruct one or more devices (e.g., the non-selected subset of UEs) to measure energy according to selected time-frequency resources (e.g., each time-frequency resource), and to transmit an interference report based on their respective measurements. Accordingly, the devices may transmit their interference reports back to the scheduling entity. Then, at block  708 , the scheduling entity  100  may determine an inter-device path loss, based on a difference between a strength of a transmitted interference discovery signal (which may be known to the scheduling entity  100 ), and the strength reported in the interference report. 
     Using Geographic Information to Infer Path Loss 
     In accordance with some aspects of the disclosure, a determination of the path loss between a pair of UEs may be made indirectly, or may be inferred, based on a determination of the distance between the respective UEs. Accordingly, the geographic distance between the UEs may be used to determine if the inter-UE path loss is high enough for full duplex co-scheduling. As a simple example, if the geographic distance between two UEs is sufficiently large (e.g., greater than a predetermined threshold), then their path loss may be considered guaranteed to be high enough for co-scheduling. On the other hand, if the geographic distance between two UEs is relatively small (e.g., less than the threshold), then their path loss may or may not be high enough. In this case, in some aspects of the disclosure, an explicit path loss estimation, as described above (e.g., utilizing interference discovery) may be used to determine inter-UE path losses. 
     Various approaches may be utilized within the scope of the present disclosure to determine the distance between a pair of UEs. As one example, each UE (e.g., the pair of UEs) may provide a scheduling entity  302  with its respective global positioning satellite (GPS) coordinates. Accordingly, the distance between the two can be directly calculated. In another example, one or both UEs in a pair may be in fixed locations, which may be recorded in a database. Such stationary UEs are frequently found as sensors, alarm systems, meters, or other static machine-type communication devices. With stationary UEs, a database lookup from the base station may be used instead of real-time GPS information, to determine the location of the respective stationary UE or UEs. Accordingly, as above, the distance between the two can be directly calculated. Here, if the distance between the two UEs is large enough then the UEs may be co-scheduled to utilize a time-frequency resource for full duplex communication. 
     In yet another example, crowd-sourcing of data may be used to infer RF isolation (i.e., whether a sufficiently large inter-UE path loss exists) between a pair of UEs of interest, based on their geographic location. For instance, if two (or more) other UEs at locations close to a given pair of UEs have previously reported a large path loss between them (e.g., through RF measurements or discovery, as described above), then the given pair of UEs may also be considered to be eligible for co-scheduling. 
       FIG. 8  is a flow chart illustrating an exemplary process  800  for utilizing geographic information to infer the inter-device interference between devices in accordance with some aspects of the present disclosure. In some examples, the process  800  may be carried out by a network node such as a scheduling entity  100  and/or a processing system  114  as described above and illustrated in  FIG. 1 . In some examples the process  800  may be carried out by any suitable means for implementing the described functions. 
     At block  802 , a device (e.g., a scheduling entity  100 ) may determine the distance between a pair of wireless devices (e.g., a pair of UEs  200 ) utilizing any suitable means, some of which are described above. At block  804 , the scheduling entity  100  may determine whether the distance between the UEs is greater than a suitable distance threshold. If the distance between the UEs is great enough, then it may be inferred that the inter-device interference is great enough for co-scheduling. Accordingly, the process may proceed to block  806 , wherein the scheduling entity  100  may so-schedule the pair of UEs to share a time-frequency resource. 
     On the other hand, if the distance between the UEs is not great enough (e.g., not greater than the distance threshold), then the process may proceed to block  808  wherein the scheduling entity may utilize any other suitable means, technique, or algorithm to explicitly determine a path loss between the UEs. For example, any one or more of the interference discovery algorithms described above may be utilized, e.g., implementing suitable signaling between the respective UEs, to discover their inter-device path loss. 
     At block  810 , the scheduling entity  100  may determine if the determined inter-device path loss is large (e.g., greater than a path loss threshold). If the inter-device path loss is large, then the process may proceed to block  812  and the scheduling entity  100  may co-schedule the pair of UEs to share a time-frequency resource. On the other hand, if the inter-device path loss is small (e.g., not greater than the path loss threshold), then the process may proceed to block  814  wherein the scheduling entity  100  may not co-schedule the pair of UEs to share the time-frequency resource. 
     Using Polar Coordinates to Find Geographic Information 
     Based on uplink transmissions, a scheduling entity  302  may determine the approximate distance between itself and a UE. For example, the scheduling entity  302  may estimate a round trip delay (RTD). RTD estimation is used in existing systems to provide uplink timing corrections to the UE, so details of the performance or determination of the RTD estimation are not described in detail in the present disclosure. In essence, a timer at the scheduling entity determines the time from transmission of a signal to the UE, until a response is received from the UE, corresponding to a round trip. Furthermore, a scheduling entity  302  with multiple receive antennas (e.g., see transceiver  110 / 210  in  FIGS. 1 / 2 ) may be enabled to estimate the angle of arrival of the signals from a given UE, based on multiple observations of the signal received on the uplink. In some examples, multiple observations may be used to filter out any effect of small-scale fading and noise. Based on the range of two UEs, and their differential angle of arrival, the scheduling entity  302  may calculate a lower bound of the distance between the two UEs. 
     For example,  FIG. 9  is a schematic illustration of a wireless communication network including a scheduling entity  302 , a first UE  304 , and a second UE  306 , as viewed from overhead (e.g., a bird&#39;s-eye view). For example, if the UEs  304  and  306  are estimated to be at distance r 1  and r 2  from the scheduling entity  302 , and their angles of arrival θ 1  and θ 2  differ by at least θ diff , then a triangle rule may be used to obtain a lower bound for the distance d between the two UEs according to the following equation:
 
   d   ≧sqrt( r   1   2   +r   2   2 −2 r   1   r   2  cos θ diff )
 
     That is, according to the inequality given above, it may be determined that the distance between a given pair of UEs  304  and  306  is greater than or equal to a predetermined threshold, and accordingly, inferred that the path loss between the respective UEs is great enough for co-scheduling of time-frequency resources. In some examples, for a given angular separation θ diff , the scheduling entity  302  may set a threshold on the distances r 1  and r 2 . That is, if both r 1  and r 2  exceed a certain threshold, the UEs  304  and  306  may be considered to be far enough apart for full duplex co-scheduling. As an alternative, the scheduling entity  302  may use an estimate of its own path loss to the two UEs as a proxy for its own distance from the UEs. 
     Accordingly, in various aspects of the disclosure, by determining geographic information of a pair of UEs, the path loss between those UEs can be inferred, and accordingly, co-scheduling of those UEs can be planned based on whether inter-UE interference would be problematic. 
     Recap of Full Duplex MAC and Path Loss Determination 
     As described above, the choice of co-scheduled UEs for full duplex operation (at a scheduling entity) may utilize knowledge of the path loss between the scheduling entity and the two UEs, as well as the path loss between the two UEs to be co-scheduled. As mentioned before, the inter-UE-path loss (i.e., the RF proximity) between a pair of UEs may be determined explicitly using UE-to-UE discovery signals (or other data/control signals). Furthermore, UE-to-scheduling entity pilot/sounding/reference signals may be reused for UE-to-UE path loss discovery as well. In other aspects of the disclosure, specialized discovery signals and/or mechanisms may be employed, which could also be leveraged for other purposes such as proximity/service discovery, direct communication between UEs, etc. 
     The path loss between the scheduling entity  302  and a given UE may be measured using any of the techniques currently used in cellular systems, including but not limited to downlink RSRP measurements and reporting by the UEs, RACH/sounding reference signal transmissions by the UE and measurements at the scheduling entity, etc. 
     A lack of geographic proximity, as determined by any suitable positioning/ranging technique, such as GPS, may also be used to infer that the path loss between two UEs is large enough for full duplex co-scheduling. In some examples, the RF proximity may be determined explicitly only among those UE pairs for which geographic proximity estimates do not necessarily imply a large path loss. 
     SINR Analysis 
     As briefly discussed above, a full duplex-capable scheduling entity  302  may be configured with a degree of self-interference suppression. Suppose, for the discussion that follows, that a given scheduling entity  302  is capable of suppressing X dB worth of self-interference at its receiver. The value of X may be determined by the complexity and effectiveness of the selected set of self-interference suppression measures taken at a particular scheduling entity  302 . In various aspects of the disclosure, self-interference suppression may be realized at a scheduling entity  302  through any of various suitable means. As one example, a scheduling entity  302  may utilize one or more of antenna/RF isolation, transmit signal reconstruction and cancellation (e.g., using a digital baseband signal and/or transceiver output signal, channel response estimation, transceiver non-linearity modeling etc.), power amplifier noise cancellation, etc. 
       FIG. 10  is a block diagram illustrating the same network as discussed above and illustrated in  FIG. 3 , but in  FIG. 10 , additional information such as values corresponding to the transmit power values and path losses are shown. In  FIG. 10 :
         P tx,1  represents the transmitted power from the scheduling entity  302 ;   P tx,2  represents the transmitted power from UE 2 ,  306 ;   P rx,1  represents the received power at UE 1 ,  304 , corresponding to the transmission from the scheduling entity  302 ;   I 2  represents self-interference at the scheduling entity  302 ;   I 12  represents the cross-device interference power received at UE 1 ,  304 , corresponding to the transmission from UE 2 ,  306 ;   PL 1  represents the path loss corresponding to a transmission from the scheduling entity  302  to UE 1 ,  304 ;   PL 2  represents the path loss corresponding to a transmission from UE 2 ,  306 , to the scheduling entity  302 ;   PL 12  represents the path loss corresponding to a transmission from UE 2 ,  306 , to UE 1 ,  304 ;   SINR 1  represents the SINR detected at UE 1 ,  304 ;   SINR 2  represents the SINR detected at the scheduling entity  302 ;   X represents the magnitude of interference suppression at the scheduling entity  302 ; and   N 0  represents noise.       

     In an aspect of the present disclosure, a signal-to-interference and noise ratio (SINR) that may be achieved at the two receivers (i.e., UE 1 ,  304  and the scheduling entity  302 ) may be calculated as shown. In these calculations, the V operator denotes the linear addition of dB values. That is: 
     
       
         
           
             
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     In an aspect of the disclosure, the SINR at each receiver (i.e., UE 1 ,  304  and the scheduling entity  302 ) may be required to satisfy a minimum requirement:
 
SINR 1 ≧SINR 1,min  and SINR 2 ≧SINR 2,min .
 
     The minimum value of the scheduling entity  302  transmit power may be given by:
 
SINR 1   =P   tx,1   −PL   1 −( N   0   V ( P   tx,2   −PL   12 ))=SINR 1,min .
 
 P   tx,1 =SINR 1,min   +PL   1 +( N   0   V ( P   tx,2   −PL   12 )).  (1)
 
     With this choice of P tx,1 , the parameters of the second link may be required to satisfy the inequality:
 
 P   tx,2,max   ≧P   tx,2 ≧SINR 2,min   +PL   2 +( N   0   V (SINR 1,min   +PL   1 +( N   0   V ( P   tx,2   −PL   12 ))− X )).  (2)
 
     In the above inequality, P tx,2,max  denotes the peak transmit power capability of the device UE 2 ,  306 . If the two co-scheduled UEs  304  and  306  are sufficiently far apart, so as to ensure that P tx,2 −PL 12 &lt;N 0 , or equivalently,
 
 PL   12   &gt;P   tx,2   −N   0 ,  (2.5)
 
then it is sufficient for P tx,2,max  to satisfy the inequality:
 
 P   tx,2,max   ≧P   tx,2 ≧SINR 2,min   +PL   2 +( N   0   V (SINR 1,min   +PL   1   +N   0 +3.011− X )).  (3)
 
     To summarize, a MAC/scheduler at the full duplex scheduling entity  302  may choose the two co-scheduled UEs so as to comply with certain feasibility conditions, particularly as described in inequalities (2.5) and (3). Clearly, by these equations and inequalities, a larger value of X (which corresponds to a better self-interference cancellation capability at the scheduling entity  302 ) reduces the right-hand side, and eases the transmit power requirement on UE 2 ,  306 . For a fixed value of X (which may be determined by hardware capabilities of the scheduling entity  302 ), the right-hand side of the inequalities may be decreased by increasing either PL 1 , PL 2 , SINR 1,min  or SINR 2,min . 
     Full Duplex MAC Principles 
     Modification of the above parameters can be utilized to control desired features of such a full duplex system. For example, reducing PL 1  amounts to transmitting to a UE (e.g., UE 1 ,  304 ) that is closer to the scheduling entity  302 , so that the scheduling entity  302  transmit power may be reduced, thereby reducing self-interference at its own receiver. Reducing PL 2  amounts to receiving from a UE (e.g., UE 2 ,  306 ) that is closer to the scheduling entity  302 , so that the strength of the desired signal at the scheduling entity  302  receiver is high, which provides better immunity to self-interference. Reducing SINR 1  amounts to serving low-rate data or control signals such as ACK/CQI/Grant (rather than high-rate data) to a UE (e.g., UE 1 ,  304 ) during full duplex operation. Reducing SINR 2  amounts to receiving low-rate user data or control signals such as ACK/CQI/REQ (rather than high-rate user data) from a UE (e.g., UE 2 ,  306 ) during full duplex operation. Furthermore, using a full duplex capability to maintain “always-on” control channels can enable low latency data transfer for interactive/delay-sensitive applications. 
     Each of the above involves a degree of compromise that goes along with operation in a full duplex mode. For example, the lower the value of X, the higher the degree of compromise that the scheduler (e.g., at the MAC layer at the scheduling entity  302 ) may to resort to during full duplex operation. In some aspects of the disclosure, the scheduling entity  302  may fall back to half duplex operation while serving UEs at a cell edge (e.g., high PL), or serving high-rate data (e.g., high SINR) in either direction. 
     Exact Analysis 
     The description given above relies in part on the approximation (x V y)≦max(x, y)+3.022. In the description that follows, the exact set of conditions are described under which full duplex operation is possible. That is, based on the SINR analysis, the minimum transmit power at the scheduling entity  302  and UE 2 ,  306  may satisfy the following:
 
SINR 1,min   +PL   1 +( N   0   V ( P   tx,2   −PL   12 ))≦ P   tx,1   ≦P   tx,1,max   (1′)
 
SINR 2,min   +PL   2 +( N   0   V ( P   tx,2   −X ))≦ P   tx,2   ≦P   tx,2,max   (2′)
 
     The above two equations may be solved simultaneously, provided the following conditions are satisfied:
 
 D≡X+PL   12 −(SINR 1,min +SINR 2,min   +PL   1   +PL   2 )&gt;0;
 
SINR 1,min   +PL   1   +N   0 +(0 V (SINR 2,min   +PL   2   −PL   12 ))−10 log 10 (1−10 −D/10 )≦ P   tx,1,max ; and
 
SINR 2,min   +PL   2   +N   0 +(0 V (SINR 1,min   +PL   1   −X ))−10 log 10 (1−10 −D/10 )≦ P   tx,2,max .
 
     The left-hand side of the last two inequalities are in fact the minimum required transmit power (P tx,1 , P tx,2 ) at the two nodes. 
     As before, feasibility conditions for co-scheduling are facilitated by reducing one or more of SINR 1,min , SINR 2,min , PL 1 , or PL 2 , or by increasing one or more of PL 12  or X. The scheduler (e.g., the MAC at the scheduling entity  302 ) may increase/decrease the path loss through user selection, and may decrease the minimum SINR requirement through data rate/type/format (i.e., data vs. control) selection. 
     Improving the Effective Value of Self-Interference Factor X, or the Cross Interference Path Loss PL 12    
     In some aspects of the disclosure, co-scheduling of UEs may include not only utilizing the same time-frequency resource, but more broadly, a quasi-full duplex mode may be utilized, wherein co-scheduled UEs may utilize different frequency channels or sub-bands, within the same band. 
     Suppose the feasibility conditions for co-scheduling (as described above) are violated for a given choice of UEs to pair (e.g., UE 1 ,  304  and UE 2 ,  306 ) and a given choice of target SINRs (SINR 1,min  and SINR 2,min ). In this case, full duplex operation on the same channel is still possible, but it may be worth considering to schedule the two links on different channels in the same band. That is, one or more aspects of the present disclosure may utilize a quasi-full duplex operation, where the transmit and receive links at a given node reside on different channels (or sub-bands) on the same band. In this case, certain adjacent channel leakage ratio (ACLR) requirements at the transmitter and adjacent channel suppression (ACS) requirements at the receiver can boost the effective value of X at the scheduling entity  302 , and the effective value of PL 12  at UE 1 ,  304 . Furthermore, the feasibility conditions may be met with these improved values of X and PL 12 . In this case, in some aspects of the disclosure, the MAC at the scheduling entity  302  may choose to co-schedule the UEs in a quasi-full duplex mode. 
     To summarize, the scheduler (e.g., a MAC entity at the scheduling entity  302 ) may make a choice of co-scheduled UEs and data-rate/type for each link. To this end, the base station may first determine if the feasibility conditions for full duplex operation are met. If so, the two links may be scheduled in full duplex mode. Otherwise, the MAC at the scheduling entity may determine if the feasibility conditions for quasi-full duplex operation are met. If so, the two links may be scheduled in quasi-full duplex mode. Otherwise, the two links may be scheduled in different time-slots or bands (i.e., half duplex). 
     Upon determining two or more feasible configurations, possibly involving multiple UE pairs and data-rate configurations, the scheduling entity  302  may determine a utility metric associated with each feasible configuration, and choose the configuration with the best utility metric. 
       FIG. 11  is a flow chart illustrating an exemplary process  1100  for co-scheduling devices based on certain feasibility conditions in accordance with one or more aspects of the present disclosure. In some examples, the process  1100  may be carried out by a network node such as a scheduling entity  100  and/or a processing system  114  as described above and illustrated in  FIG. 1 . In some examples the process  1100  may be carried out by any suitable means for implementing the described functions. 
     At block  1102 , a first device (e.g., a scheduling entity  100 ) may select a pair of wireless devices (e.g., UEs  200 ) for potential co-scheduling, and at block  1104 , the scheduling entity  100  may determine whether one or more primary feasibility conditions are met. These feasibility conditions for co-scheduling are described throughout the present disclosure, and include, for example, a geographic distance between UEs or an explicit inter-device interference value between UEs. If the primary feasibility conditions are satisfied, then the process may proceed to block  1106 , wherein the scheduling entity  100  may co-schedule the selected pair of UEs to utilize the same time-frequency resource. On the other hand, if the primary feasibility conditions are not satisfied, then the process may proceed to block  1108  wherein the scheduling entity  100  may determine whether one or more secondary feasibility conditions are met. These feasibility conditions for co-scheduling are described throughout the present disclosure, and include, for example, a geographic distance between UEs or an inter-device interference value between UEs. As one simple example, the primary feasibility conditions at block  1104  may correspond to first threshold values, and the secondary feasibility conditions at block  1108  may be second threshold values, with more inter-device interference tolerance than the first threshold values. If the secondary feasibility conditions are satisfied, then the process may proceed to block  1110 , wherein the scheduling entity  100  may implement a quasi-full duplex option, wherein the selected pair of UEs are co-scheduled to utilize different frequency channels within the same band. Here, if even the secondary feasibility conditions are not satisfied, then the process may proceed to block  1112  wherein the scheduling entity  100  may determine not to co-schedule the selected pair of UEs. 
     Limited Full Duplex Capability at a UE 
     In the description above, while the scheduling entity  302  has been described as being capable of full duplex communication, the UEs  304  and  306  have been assumed only to be capable of half duplex communication. However, in other aspects of the disclosure, one or more UEs in the wireless communication system may be capable of supporting full duplex operation, at least to a limited extent. For example,  FIG. 12  is a block diagram illustrating a scheduling entity  302  configured for full duplex communication, and a UE  1204 , configured for limited full duplex communication. In an aspect of the disclosure, the UE  1204  may be capable of full duplex communication when there exists a small value for the self-inference-cancellation factor X. 
     That is, in some aspects of the disclosure, one or more UEs such as the UE  1204  may support full duplex operation, e.g., as long as their transmit power is low (e.g., below a suitable threshold). For example, at a lower transmit power, the UE  1204  may be able to bypass its power amplifier, thereby reducing or eliminating the need to compensate for distortions and noise introduced by the power amplifier. 
     Here, if a full duplex scheduling entity  302  serves a UE  1204  with such limited full duplex capability, the same UE  1204  may be scheduled in both directions (i.e., downlink and uplink) at the same time. In this case, the UE  1204  may transmit at the lowest possible power that yields the target SINR at the scheduling entity  302  receiver. Further, the scheduling entity  302  may transmit at a power high enough to ensure that the UE  1204  receiver achieves the desired SINR, despite any partial leakage from its own transmission. 
     If the transmit power at the scheduling entity  302  exceeds its capability, the scheduling entity  302  may switch to a lower transmission rate, which reduces the required SINR. The scheduling entity may choose the highest possible data rate for which the target SINR may be met without exceeding its transmit power capabilities. 
     Alternatively, the scheduling entity  302  may select a lower data rate at which to receive data from the UE  1204 , which results in a lower transmit power from the UE  1204 . This, in turn, translates to lower self-interference at the UE  1204 . 
       FIG. 12  illustrates the following parameters in a network with a UE  1204  capable of limited full duplex functionality. In the illustration:
         P tx,1  corresponds to the power of the signal transmitted from the scheduling entity  302 .   P tx,2  corresponds to the power of the signal transmitted from the UE  1204 .   PL corresponds to the path loss between the scheduling entity  302  and the UE  1204 .   P rx,1  corresponds to the power received at the scheduling entity  302 . Here, P rx,1 =P tx,2 −PL.   P rx,2  corresponds to the power received at the UE  1204 . Here, P rx,2 =P tx,1 −PL.   X 1  represents the self-interference cancellation capability at the scheduling entity  302 .   X 2  represents the self-interference cancellation capability at the UE  1204 .   I 2  corresponds to the self-interference at the scheduling entity  302 , taking account of its self-interference cancellation capability. That is, I 2 =P tx,1 −X 1 .   I 1  corresponds to the self-interference at the UE  1204 , taking account of its self-interference cancellation capability. That is, I 1 =P tx,2 −X 2 .   SINR 1  corresponds to the SINR at the UE  1204 .   SINR 2  corresponds to the SINR at the scheduling entity  302 .       

     Here, SINR 1 =P tx,1 −PL−(N 0 V(P tx,2 −X 2 )); and SINR 2 =P tx,2 −PL−(N 0 V(P tx,1 −X 1 )). In an aspect of the disclosure, full duplex capabilities at the UE  1204  may be enabled under certain conditions relating to one or both of SINR 1  and/or SINR 2 , e.g., whether one or both are at or above given threshold values. For example, full duplex may be enabled when SINR 1 ≧SINR 1,min ; and when SINR 2 ≧SINR 2,min . 
     Feasibility Conditions for Full Duplex Operation with a Single UE 
     Based on the SINR analysis, the minimum transmit power at the scheduling entity  302  and the UE  1204  (with reference to  FIG. 12 ) may satisfy the following equations:
 
 P   tx,1 =SINR 1,min   +PL +( N   0   V ( P   tx,2   −X   2 ))≦ P   tx,1,max   (1″)
 
 P   tx,2 =SINR 2,min   +PL +( N   0   V ( P   tx,1   −X   1 ))≦ P   tx,2,max   (2″)
 
     The above two equations may be solved simultaneously, provided that:
 
 D≡X   1   +X   2 −(SINR 1,min +SINR 2,min +2 PL )&gt;0;
 
SINR 1,min   +PL+N   0 +(0 V (SINR 2,min   +PL−X   2 )−10 log 10 (1−10 −D/10 )≦ P   tx,1,max ; and
 
SINR 2,min   +PL+N   0 +(0 V (SINR 1,min   +PL−X   1 )−10 log 10 (1−10 −D/10 )≦ P   tx,2,max .
 
     The left-hand side of the last two inequalities above is in fact the minimum transmit power at the two nodes. Feasibility conditions for enabling limited full duplex functionality at the UE  1204  are facilitated by reducing one or more of SINR 1,min , SINR 2,min , or PL, or by increasing one or more of X 1  or X 2 . The scheduling entity  302  may increase or decrease the path loss PL through user selection, and may decrease the minimum SINR requirement through data rate/type/format (i.e., data vs. control) selection. 
     Here, if the self-interference rejection capability at the UE  1204  (X 2 ) is much smaller than that at the scheduling entity  302  (X 1 ), then for similar link SINRs, the required transmit power at the scheduling entity  302  (P tx,1 ) is beneficially much smaller than that at the UE  1204  (P tx,2 ). 
     In a further aspect of the disclosure, the scheduling entity  302  may also increase the effective values of X 1  and/or X 2  by choosing to operate in quasi-full duplex mode, wherein the two links assigned to different channels/sub-channels on the same band. 
       FIG. 13  is a flow chart illustrating an exemplary process  1300  for determining whether to enable full duplex operation at a UE in accordance with one or more aspects of the present disclosure. In some examples, the process  1300  may be carried out by a network node such as a scheduling entity  100  and/or a processing system  114  as described above and illustrated in  FIG. 1 . In some examples the process  1300  may be carried out by any suitable means for implementing the described functions. 
     At block  1302 , a device (e.g., a scheduling entity  100 ) may communicate with a first wireless device (e.g., a UE  200 ), and at block  1304  the scheduling entity  100  may determine whether a transmit power of the first UE  200  is undesirably low (e.g., being below a suitable transmit power threshold). If the transmit power is not below the transmit power threshold, then the process may proceed to block  1306  wherein the scheduling entity  100  may configure the first UE  200  for half duplex functionality. On the other hand, if the transmit power of the UE  200  is less than the transmit power threshold, then the process may proceed to block  1308 , wherein the scheduling entity  100  may enable full duplex functionality at the UE  100 . Further, at block  1310 , the scheduling entity  100  may configure the transmit power of the full duplex-enabled UE  100  to the lowest possible transmit power that yields a suitable target SINR. 
     Extension to More Generalized Self Interference Cancellation Model 
       FIG. 14  is a block diagram illustrating an exemplary wireless communication system similar to the system illustrated in  FIG. 12 , wherein a UE  1404  is configured for limited full duplex functionality. However, in  FIG. 14 , the transmission characteristics illustrate a generalized model for self-interference cancellation. That is, as illustrated:
         P tx,1  corresponds to the power of the signal transmitted from the scheduling entity  302 .   P tx,2  corresponds to the power of the signal transmitted from the UE  1404 .   PL 1 =PL 2 =PL corresponds to the path loss between the scheduling entity  302  and the UE  1404 .   P rx,1  corresponds to the power received at the scheduling entity  302 . Here, P rx,1 =P tx,2 −PL 2 .   P rx,2  corresponds to the power received at the UE  1404 . Here, P rx,2 =P tx,1 −PL 1 .   X 1  represents the self-interference cancellation capability at the scheduling entity  302 .   X 2  represents the self-interference cancellation capability at the UE  1404 .   The uncancelled self-interference power may be given by, for example, I=(1/X)·P λ . In the dB domain, this may be written as I=λP−X.   λ 1  and λ 2  represent the relationship between the transmission power P and the residual interference power I. In general, for many full duplex radio implementations, 0&lt;λ&lt;1, although this is not necessarily the case. In the previous examples and analysis, it was assumed that λ was equal to 1, in which case the residual interference I would be X dB less than the transmit power P. In an example where λ were equal to 0.5, then if the transmit power P were increased by 1 dB, then the residual interference power I would increase only by 0.5 dB.   I 1  corresponds to the self-interference at the scheduling entity  302 , taking account of its self-interference cancellation capability. Here, a generalized model of the self-interference power may be represented by the equation I 1 =λ 1 P tx,1 −X 1 .   I 1  corresponds to the self-interference at the UE  1404 , taking account of its self-interference cancellation capability. Here, a generalized model of the self-interference power may be represented by the equation I 1 =λ 2 P tx,2 −X 2 .   SINR 1  corresponds to the SINR at the UE  1404 .   SINR 2  corresponds to the SINR at the scheduling entity  302 .       

     Here, SINR 1 =P tx,1 −PL−(N 0 V(λ 2 P tx,2 −X 2 )); and SINR 2 =P tx,2 −PL−(N 0 V(λ 1 P tx,1 −X 1 )). In an aspect of the disclosure, full duplex capabilities at the UE  1404  may be enabled under certain feasibility conditions relating to one or both of SINR 1  and/or SINR 2 , e.g., whether one or both are at or above given threshold values. For example, full duplex may be enabled when SINR 1 ≧SINR 1,min ; and when SINR 2 ≧SINR 2,min . 
     Feasibility Conditions for Full Duplex Operation with a Single UE, with Generalized Self-Interference Model 
     Based on the SINR analysis of the transmitted signals, the minimum transmit power at the scheduling entity  302  and the UE  1404  might benefit from satisfying the following inequalities:
 
SINR 1,min   +PL   1 +( N   0   V (λ 2   P   tx,2   −X   2 ))≦ P   tx,1   ≦P   tx,1,max ; and  (1′″)
 
SINR 2,min   +PL   2 +( N   0   V (λ 1   P   tx,1   −X   1 ))≦ P   tx,2   ≦P   tx,2,max ,  (2′″)
 
where PL 1 =PL 2 =PL.
 
     In the above disclosure, prior to generalizing, the case where λ 1 =λ 2 =1 has already been addressed. Therefore, it suffices to consider λ 1 ≦1, λ 2 ≦1, and λ 1 λ 2 &lt;1. In these cases, a feasible power allocation may exist as long as:
 
 P   tx,1,max   −PL   1 −( N   0   V (λ 2 (SINR 2,min   +PL   2 +( N   0   V (λ 1   P   tx,1,max   −X   1 )))− X   2 ))≧SINR 1,min .
 
 P   tx,2,max   −PL   2 −( N   0   V (λ 1 (SINR 1,min   +PL   1 +( N   0   V (λ 2   P   tx,2,max   −X   2 )))− X   1 ))≧SINR 2,min .
 
     Another way to express the above may be to generate feasibility functions. For example, by subtracting SINR 1,min  from both sides, a first feasibility function f 1 ( ) may be obtained:
 
 P   tx,1,max   −PL   1 −( N   0   V (λ 2 (SINR 2,min   +PL   2 +( N   0   V (λ 1   P   tx,1,max   −X   1 )))− X   2 ))−SINR 1,min ≧0.
 
     Here, f 1 ( )=P tx,1,max −PL 1 −(N 0 V(λ 2 (SINR 2,min +PL 2 +(N 0 V(λ 1 P tx,1,max −X 1 )))−X 2 ))−SINR 1,min , and the feasibility condition may be satisfied if f 1 ( )≧0. 
     Similarly, a second feasibility function f 2 ( ) may be obtained as follows:
 
 P   tx,2,max   −PL   2 −( N   0   V (λ 1 (SINR 1,min   +PL   1 +( N   0   V (λ 2   P   tx,2,max   −X   2 )))− X   1 )) SINR 2,min ≧0.
 
     Here, f 2 ( )=P tx,2,max −PL 2 −(N 0 V(λ 1 (SINR 1,min +PL 1 +(N 0 V(λ 2 P tx,2,max −X 2 )))−X 1 )) SINR 2,min , and the feasibility condition may be satisfied if f 2 ( )≧0. 
     As expected, the left-hand side of the above inequalities may be increased by decreasing PL 1 (=PL 2 =PL) and/or SINR 1,min /SINR 2,min , or by increasing X 1  or X 2 . In other words, feasibility conditions may be facilitated by reducing one or more of SINR 1,min , SINR 2,min , PL 1 (=PL 2 =PL), or by increasing one or more of X 1  or X 2 . This implies that the qualitative behavior of the scheduling entity  302  is the same as that in the original interference model. That is, the scheduling entity  302  may reduce path loss(es) through judicious user selection, or may decrease the target SINR(s) through judicious selection of data rate or data type (e.g., traffic vs. control). 
     Full Duplex Capability Reporting 
     In a further aspect of the disclosure, in order to facilitate the full duplex operation between a scheduling entity  302  and a UE  1404 , the UE  1404  may declare (e.g., by transmitting a corresponding information element) one or more interference cancellation capability parameters  254 , such as its self-interference cancellation factor (λ 2 , X 2 ), to the scheduling entity  302 . In some examples, this declaration may be part of the UE category reporting, or in another example, this declaration may be a separate capability attribute. 
     Furthermore, because the value of (λ 2 , X 2 ) may further depend on the power amplifier state at the UE  1404  (e.g., ON or OFF), the UE  1404  may declare a list/array/table of interference cancellation capability parameters (λ 2 , X 2 ), e.g., one (pair of) value(s) per power amplifier state. In addition, in some examples, the UE  1404  may report its power amplifier state or path loss on a regular basis, so that the scheduling entity  302  may determine the extent of interference cancellation that may be performed by the UE  1404  in a given state/configuration. 
     Revisiting a Full Duplex Base Station Serving Two Half Duplex UEs, with Extended/Generalized Model for Self-Interference Cancellation at the Base Station 
       FIG. 15  is a block diagram of a wireless communication network including two half duplex UEs UE 1 ,  1504  and UE 2 ,  1506 , wherein the illustrated communication parameters correspond to the extended or generalized model for self-interference cancellation at the full duplex scheduling entity  302 . In this illustration:
         P tx,1  represents the transmitted power from the scheduling entity  302 ;   P tx,2  represents the transmitted power from UE 2 ,  1506 ;   P rx,1  represents the received power at UE 1 ,  1504 , corresponding to the transmission from the scheduling entity  302 ;   I 2 =λP tx,1 −X represents self-interference at the scheduling entity  302 ;   I 12 =P tx,2 −PL 12  represents the cross-device interference power received at UE 1 ,  1504 , corresponding to the transmission from UE 2 ,  1506 ;   PL 1  represents the path loss corresponding to a transmission from the scheduling entity  302  to UE 1 ,  1504 ;   PL 2  represents the path loss corresponding to a transmission from UE 2 ,  1506 , to the scheduling entity  302 ;   PL 12  represents the path loss corresponding to a transmission from UE 2 ,  1506 , to UE 1 ,  1504 ;   SINR 1  represents the SINR detected at UE 1 ,  1504 ;   SINR 2  represents the SINR detected at the scheduling entity  302 ;   X represents the magnitude of interference suppression at the scheduling entity  302 ; and   N 0  represents noise.       

     The analysis of this scenario may be considered a special case of the analysis presented above, in relation to  FIG. 14 , for the single full duplex UE case. However, here,
 
λ 1 =λ, λ 2 =1, X 1 =X, X 2 =PL 12 .
 
     Furthermore, in this illustration, the path losses PL 1  and PL 2  may be different from one another. This results in the following. The above disclosure has addressed the case where λ=1. Accordingly, it should suffice to consider λ&lt;1. In this case, a feasible power allocation exists as long as:
 
 P   tx,1,max   −PL   1 −( N   0   V (SINR 2,min   +PL   2 +( N   0   V (λ P   tx,1,max   −X ))− PL   12 ))≧SINR 1,min ; and
 
 P   tx,2,max   −PL   2 −( N   0   V (λ(SINR 1,min   +PL   1 +( N   0   V (λ 2   P   tx,2,max   −PL   12 )))− X ))≧SINR 2,min .
 
     As in the single-UE scenario, described above in connection with  FIG. 14 , the generalized model illustrated in  FIG. 15  leads to the qualitative behavior of the scheduling entity  302  as that in the original interference model. That is, the scheduling entity  302  may reduce path loss(es) through judicious user selection, or decrease the target SINR(s) through judicious selection of data rate or data type (traffic vs. control). 
     Extension to Multi-Hop Networks 
     Above, the disclosure has basically been limited to the discussion of a radio level full duplex capable scheduling entity  302  (e.g., a base station) transmitting to a first UE and receiving from a second UE at the same time, on the same frequency channel/band. However, the present disclosure is broadly not limited thereto. That is, referring now to  FIG. 16 , in some aspects of the disclosure the concepts described herein may be generalized to apply to a multi-hop/mesh system, where the full duplex node is an intermediate node  1604  in a multi-hop/relay network that receives data from an upstream node and transmits data to a downstream node. Here, the upstream node may be a base station  1602 / 1603 , a UE, or even another relay node. Similarly, the downstream node may be a UE  1606 / 1610 , or another relay node. In some examples, the intermediate node (e.g., the relay  1604 ) may have connectivity not only with multiple downstream nodes (e.g., a plurality of UEs), but also with multiple upstream nodes (e.g., a plurality of anchor base stations). 
     In one particular example, the relay node  1604  may carry downlink data from an upstream node such as the anchor base station  1602 , to a downstream node such as the UE  1606 . In another example, the same relay node  1604  may carry uplink data from a downstream node such as UE  1606 , to an upstream node such as the anchor base-station  1602 . In these examples, the relay node  1604  may have a radio level full duplex capability, but the other upstream/downstream nodes may or may not have such full duplex capabilities. In other words, the anchor base-station(s) and UE(s) may be half duplex, full duplex, or limited full duplex, as described above. 
     In various aspects of the disclosure, the relay node  1604  may engage in full duplex operation in any of several different ways, with several examples being illustrated in  FIGS. 17, 18, 19, 20, 21, and 22 . 
     For example,  FIG. 17  illustrates a wireless communication system wherein a relay node  1704  may simultaneously (and on the same frequency channel/band) receive downlink data from an anchor base station  1702  and transmit downlink data to a UE  1706 . 
       FIG. 18  illustrates a wireless communication system according to another example, wherein a relay node  1804  may simultaneously (and on the same frequency channel/band) receive uplink data from a UE  1806  and transmit uplink data to an anchor base station  1802 . 
       FIG. 19  illustrates a wireless communication system according to still another example, wherein a relay node  1904  may simultaneously (and on the same frequency channel/band) transmit downlink data to UE  1910  and receive uplink data from another UE  1906 . 
       FIG. 20  illustrates a wireless communication system according to still another example, wherein a relay node  2004  may simultaneously (and on the same frequency channel/band) receive downlink data (destined for some UE) from an anchor base station  2002  and transmit uplink data (originating from some other UE) to another anchor base station  2003 . 
       FIG. 21  illustrates a wireless communication system according to still another example, wherein a relay node  2104  may simultaneously (and on the same frequency channel/band) transmit and receive data to/from the same anchor base station  2102 , provided the anchor base station also has a radio level full duplex capability. 
       FIG. 22  illustrates a wireless communication system according to yet another example, wherein a relay node  2204  may simultaneously (and on the same frequency channel/band) transmit and receive data to/from the same UE  2210 , provided the UE also has a radio level full duplex capability. 
     In summary, the two co-scheduled links in the full duplex operation may be associated with any suitable number of nodes (e.g., one or more) on the downstream, and any suitable number of nodes (e.g., one or more) on the upstream. If an upstream/downstream node also has a full duplex capability, then the two co-scheduled links may be associated with the same upstream/downstream node. 
     In all these cases, the relay node  1604  may operate in full duplex mode on the access hops (i.e., the radio link between the relay node  1604  and the terminal UE  1606 ), or on the backhaul hops (i.e., the radio link between the relay node  1604  and its anchor base station  1602 ) or across an access hop and a backhaul hop if the associated path losses, SINR targets, and self-interference cancellation parameters satisfy the feasibility conditions described in the previous sections. Otherwise, as described in the examples above, the relay node  1604  may use time or frequency division duplexing to operate on the two links. The considerations regarding user selection, SINR target selection (through selection of the appropriate data rate or data type, i.e., user traffic vs. control signaling such as CQI/ACK/REQ) that may be used to facilitate the feasibility conditions for full duplex operation, may carry over almost verbatim to this case of relay operation. 
     In a further aspect of the disclosure, the same type of feasibility conditions and considerations for full duplex operation described above may apply to more general multi-hop/mesh systems with full duplex capabilities at any number of intermediate nodes, even though the distinction between backhaul hop vs. anchor hop, as well as the distinction between anchor base station and terminal UE, may be blurred in these mesh-based communication systems. In particular, an intermediate node with a radio level full duplex capability may co-schedule an upstream node and downstream node, so as to transmit data/control to one of them and receive data/control from the other simultaneously, as long as the associated path losses, self-interference cancellation/rejection parameters (λ and X), and link SINR targets satisfy the feasibility conditions. As before, the scheduling entity (which may be hosted on the intermediate node, or another controlling node, such as an anchor base station) may vary the path loss parameters through appropriate selection of the upstream/downstream node(s), while the SINR targets may be changed through an appropriate selection of data rate and/or data type (e.g., traffic vs. control). If the feasibility conditions for co-channel full duplex conditions can not be met, the scheduling entity may consider quasi-duplex operation (on different channels/subchannels in the same frequency band), or fall back to half duplex operation as needed. 
     CONCLUSION 
     As described above, one or more aspects of the disclosure provide for a wireless communication system wherein a full duplex node (e.g., a scheduling entity) may wirelessly communicate with one or more other nodes or devices. Here, the full duplex node may determine the path loss {PL k } between itself and the devices it communicates with. The path loss {PL k } may be determined in any suitable fashion, many of which are described above. 
     In some examples, the full duplex node may determine, directly and/or indirectly, the inter-device path loss {PL i,j } between pairs of devices with which it communicates. The inter-device path loss {PL i,j } may be determined in any suitable fashion, many of which are described above. 
     The full duplex node may determine certain target SINR values for multiple links between itself and one or more of the devices it communicates with. Furthermore, the full duplex node may determine one or more feasibility functions f n ( ) involving the path loss between itself and a pair of devices, the path loss between that pair of devices, as well as target SINR values for multiple links involving the full duplex node and the pair of devices. In some cases, the two devices may be one and the same. In this case, self-interference cancellation parameters of the device take the place of inter-device path loss. 
     In some examples, if all the feasibility functions have a positive value, the pair of devices may be selected for full duplex co-scheduling. In some aspects of the disclosure, each feasibility function f n ( ) may be a non-increasing or decreasing function of the path losses, and target SINR. 
     In some aspects of the disclosure, the path loss terms that go into the feasibility functions may be changed by considering different pairs of UEs for full duplex co-scheduling. In still further aspects, the target SINR of the links in question may be changed by considering different modulation and coding schemes (MCS), or traffic types (e.g., user data vs. control/signaling). 
     In a still further aspect of the disclosure, a pair of UEs that are not compatible for full duplex scheduling may be considered for quasi full duplex scheduling, on different/neighboring channels/subchannels in the same band. 
     As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to any suitable telecommunication systems, network architectures and communication standards. By way of example, various aspects may be applied to UMTS systems such as W-CDMA, TD-SCDMA, and TD-CDMA. Various aspects may also be applied to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems, including those described by yet-to-be defined wide area network standards. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system. 
     Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another—even if they do not directly physically touch each other. For instance, a first die may be coupled to a second die in a package even though the first die is never directly physically in contact with the second die. The terms “circuit” and “circuitry” are used broadly, and intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, enable the performance of the functions described in the present disclosure, without limitation as to the type of electronic circuits, as well as software implementations of information and instructions that, when executed by a processor, enable the performance of the functions described in the present disclosure. 
     One or more of the components, steps, features and/or functions illustrated in  FIGS. 1-22  may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated in  FIGS. 1, 2, 3, 5, 9, 10, 12, 14, 15, 16, 17, 18, 19, 20, 21 , and/or  22  may be configured to perform one or more of the methods, features, or steps described herein and illustrated in  FIGS. 4, 6, 7, 8, 11 , and/or  13 . The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware. 
     It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”