Patent Publication Number: US-2017353964-A1

Title: Apparatus and method for reducing interference in a wireless communication system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. patent application Ser. No. 14/137,340 filed Dec. 20, 2013, pending, to be issued as U.S. Pat. No. 9,750,034 on Aug. 29, 2017, the entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates generally to communication systems. The present disclosure relates more particularly to a mechanism for adjusting characteristics of a communication device based on the signal strength of received radio frequency signals. 
     Wireless broadband networks have become very popular for data communication. Such networks may be set up relatively inexpensively and quickly. Such networks may provide local communication among network client devices through an access point which controls communication in the network. Instead, or in addition, such networks may provide communication access to remote networks including the Internet. 
     The Institute of Electrical and Electronics Engineers (IEEE) has promulgated several data communication standards which have subsequently been adopted by industry. One example of a family of such standards is commonly referred to IEEE 802.11. IEEE 802.11 includes several protocols including IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n and IEEE 802.11ac. 802.11 networks and devices are commonly referred to as WiFi devices. The 802.11 protocols define devices and operations that may communicate in a network, including messaging and timing. According to the protocols, an access point or base station controls data communication including timing of communication between the access point and respective stations or client devices in a service area around the access point. Client devices operate according to the same protocol to communicate with the access point. Messaging is defined by the protocol. 
     To improve the utility of these networks, manufacturers have been expanding the range of communication and thus the size of the service area. Initially, WiFi communication was limited to line of sight or a few tens of meters between transmitter and receiver. More recently, networks are being developed with a service area radius or node size of 5 to 15 km. 
     Increasing the scale of networks in this manner has met with commercial success. This success has created opportunities for additional features in systems and methods for communication as well as opportunities for improving performance and efficiency. 
     BRIEF SUMMARY 
     This disclosure relates to a synchronized WiFi network such as a network according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11n standard. The network includes a plurality of access points (APs). Each AP provides wireless communication service to stations (STAs) in the vicinity of the AP. In the new network, the cell coverage may be  5  miles in diameter, compared to conventional 802.11n. 
     In some scenarios the service or coverage area of a plurality of access points may overlap. Furthermore, the access points may communicate with their respective stations via the same range of frequency. In these situations, an access point may receive radio signals transmitted by stations that are in communication with the access point as well as from stations that are in communication with another access point. In such a scenario, an access point may implement schemes to minimize the reception of radio signals from stations that are in communication with another access. 
     In some scenarios, a station may be located in an area where the service areas of two or more access points overlap. The station may be in communication with one of the access points but may receive radio frequency signals from other access points. To minimize the reception of radio frequency signals from the other access points, the station may adjust its hardware characteristics based on the signal strength of the radio frequency signals received from the access points. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary communication system; 
         FIG. 2  is a representative diagram of example TDD frames; 
         FIG. 3  is a timing diagram of TDD frames that may be communicated in the communication system of  FIG. 1   
         FIG. 4  is a block diagram of a representative access point and representative client device; 
         FIG. 5  is a timing diagram of TDD frames that may be communicated in the communication system of  FIG. 1 ; 
         FIG. 6  is another timing diagram illustrating communication of TDD frames by wireless devices of communication system of  FIG. 1 ; and 
         FIG. 7  is a flow diagram of an example method that may be implemented at an access point; 
         FIG. 8  is a flow diagram of another example method that may be implemented at an access point; 
         FIG. 9  is a flow diagram of an example method that may be implemented at a station; 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     Radio devices described herein respond to receiving radio signals at different power levels from multiple sources by adjusting their receiver characteristics to improve the reception of radio signals from some of the multiple sources. In some embodiments, the receiver characteristics are adjusted based on the power level of the received radio signals and the identity of the multiple sources. 
       FIG. 1  is a block diagram of an example communication system  100  that includes wireless devices that implement a combination of methods described herein to mitigate the effect of radio frequency interference produced by other wireless devices operating in the vicinity of the wireless devices at the same range of frequencies. The communication system  100  is intended to be exemplary only for purposes of illustrating the concepts described herein. 
     In this exemplary embodiment, the communication system  100  includes a first access point  102 , a second access point  104 , a third access point  106  and a fourth access point  108 . Each respective access point provides radio communication to a service area indicated by the dashed areas surrounding the respective access point. In the illustrated embodiment, each respective access point  102 ,  104 ,  106 ,  108  operates according to the Institute of Electrical and Electronic Engineers (IEEE) standard 802.11n, commonly referred to as WiFi. In other embodiments, one or more of the access points  102 ,  104 ,  106 ,  108  operates according to another wireless standard such as WiMAX or another of the family of 802.11 standards. The devices and techniques described herein may be extended to standards and protocols other than IEEE 802.11n. 
     In the example of  FIG. 1 , each respective access point operates as a base station for radio devices within a cell or service area surrounding the access point. In this example, the access point  102  provides radio communication service to one or more station near the access point. As used herein, radio communication generally refers to the communication of data by the transmission and reception of radio frequency signals representative of the data. Each station (STA) communicates with the access point using a radio communication protocol such as IEEE 802.11n. The radio communication protocol defines frequency allocation, timing, frame structure and other characteristics of the transmission and reception of information between radio devices including the access point and the radio devices. In one embodiment, the radio communication protocol implemented at access points  102 ,  104 ,  106  and  108  is configured to allocate the same range of operating frequencies to access points  102 ,  104 ,  106  and  108 . 
     In the example of  FIG. 1 , the access point  102  is in radio communication with five radio devices, including a first station  102 - 2 , a second station  102 - 2 , a third station  102 - 3 , and a fourth station  102 - 4  and a fifth station  102 - 5 . In this example, the first station  102 - 1  is designated STA  1 , the second station  102 - 2  is designated STA  2 , the third station  102 - 3  is designated STA  3 , the fourth station  102 - 4  is designated STA  4  and the fifth station  102 - 5  is designated STA  5 . The first station  102 - 1 , second station  102 - 2 , third station  102 - 3 , fourth station  102 - 4  and fifth station  102 - 5  may be considered clients of the access point  102  and may be referred to as wireless client devices. An access point such as access point  102  and its corresponding wireless client devices may be referred to as a wireless network. While  FIG. 1  shows five stations in radio communication with the access point  102 , this is intended to be exemplary only. Any number of stations may communicate with the access point  102 . Also, the stations illustrated in  FIG. 1  may selectively leave the wireless network and re-enter the network and other stations may enter the wireless network as well. The stations may be mobile and may move in and out of the service area served by the access point  102 . 
     Each of first station  102 - 2 , second station  102 - 2 , third station  102 - 3 , fourth station  102 - 4  and fifth station  102 - 5  may include a radio communication circuit in combination with any other suitable device or equipment. Exemplary devices that may include a radio circuit and form a station or wireless client device include a mobile phone, a smart phone, a personal digital assistant (PDA), a laptop computer, a tablet computer, a personal computer and any other data processing device. A radio circuit provides data communication between the data processing device and the access point  102 . The radio circuit may be a module or component or group of components and may be a permanent part of the station or may be removable or detachable from the station. 
     The access point  102  may, in turn, provide data communication between respective stations among the first station  102 - 2 , second station  102 - 2 , third station  102 - 3 , fourth station  102 - 4  and a fifth station  102 - 5 , or between a respective station and another network  110 . The arrangement of access point  102  and stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  is referred to a point to multi-point (PMP) arrangement or scheme. The network  110  may be any network or combination of networks and may include directly or indirectly the Internet or networks in communication with the Internet. 
     In the example of  FIG. 1 , each of the access points  102 ,  104 ,  106 ,  108  is in communication with the network  110 . In one embodiment, the operation and configuration of access point  102 ,  104 ,  106  and  108  may be controlled by network controller  124 . In other embodiments, each of the access points  102 ,  104 ,  106 ,  108  may operate independently with no interaction with adjacent networks and with no overall control or supervision of individual access points. Second access point  104  is in data communication with a STA  120 , embodied as a PDA, and stations  104 - 1  and  104 - 2 . The third access point  106  is in data communication with a STA  122 , embodied as a mobile phone and stations  106 - 1 ,  106 - 2  and  106 - 3 . Access point  104  and STA  120 , and stations  104 - 1  and  104 - 2  comprise a second wireless network and access point  106  and stations  106 - 1 ,  106 - 2 ,  106 - 3  and STA  122  constitute a third wireless network. 
     In some scenarios, the service area surrounding one access point may overlap the service areas of one or more other access points. The service area of an access point may be defined by factors such as the configuration and coverage of antennas which communicate radio signals with radios in the service area, the transmit signal strength of each respective radio, and objects in the service area that may cause signal degradation and interference. When service areas overlap, one access point may receive transmissions from one or more of the other access points. Access points with overlapping service areas may be referred to as neighboring access points, for example, access point  102  and  106  of  FIG. 1 . A station in the overlapping service area may receive transmissions from its access point and the neighboring access point. For example, station  102 - 1  may receive radio frequency signals transmitted by access point  102  and access point  106 . 
     In the example of  FIG. 1 , the access point  102  and the stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  may receive and transmit data via a radio frequency communication channel in accordance with a time division duplexing (TDD) scheme. A radio frequency communication channel is a defined frequency or band of frequencies that may be shared by multiple radio devices at designated times. In a TTD scheme, wireless devices are scheduled to transmit and receive data via a shared radio frequency channel at pre-assigned points in time. For example, station  102 - 1  may be scheduled to transmit data at time T 1  and receive data at time T 4 , station  102 - 2  may be scheduled to transmit data at time T 2  and receive data at time T 5  and so on. By scheduling each of the wireless devices to transmit and receive data at different points in time, the radio frequency channel may be shared in an orderly fashion. In one example, an access point such as the access point  102  includes a module referred to as a scheduler which determines scheduling and designation of times for communication by respective radios. 
     In the PMP arrangement of  FIG. 1 , a TTD scheme may comprise data communications from access point  102  to stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  for a period of time and data communication from one or more of the stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  to the access point  102  for a subsequent period of time. Data communicated by access point  102  to stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  is referred to as downlink data. Downlink data is communicated in logical structures called downlink frames and the time period or duration of a downlink frame is referred to as downlink frame period. In this embodiment, the transmission window discussed above may correspond to the downlink frame. Data communicated from the stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  to the access point  102  is referred to as uplink data. Uplink data is communicated in logical structures called uplink frames and the time period or duration of a downlink frame is referred to as downlink frame period. Generally, the start of downlink data coincides with or is aligned with the start of a downlink frame and the start of uplink data coincides with or is aligned with the start of an uplink data frame. 
     Communication between access point  102  and stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  is accomplished via alternating downlink frames and uplink frames. A downlink frame and an uplink frame together constitute a TDD frame. The time duration of the TDD frame is referred to as a TDD frame duration or period. Wireless networks comprising access points  104 ,  106  and  108  and the respective stations in data communication with access points  104 ,  106  and  108  may also operate in accordance with the TDD scheme. 
       FIG. 2  is a timing diagram illustrating operation of the communication system  100  of  FIG. 1  in accordance with a TDD scheme.  FIG. 2  illustrates a sequence  200  of time division duplex (TDD) frames for wireless communication in a communication system using a network protocol such as 802.11. In particular, the sequence  200  of frames has application in extended range networks such as 802.11n networks having a service area diameter greater than a few tens of meters. The sequence  200  may correspond to data communication between an access point and one or more stations in radio communication with the access point. 
     The sequence  200  of frames includes a first frame  202 , a second frame  204  and a third frame  206 . In  FIG. 2 , time is on the horizontal axis. The first frame  202  includes a downlink frame  208  followed in time by an uplink frame  210 . Similarly, the second frame  204  includes a downlink frame  212  followed in time by an uplink frame  214  and the third frame  206  includes a downlink frame  216  followed in time by an uplink frame  218 . A subsequent downlink frame  220  indicates a following frame. Each respective downlink frame  208 ,  212 ,  216 ,  220  defines a time period when an access point such as the access point  102  ( FIG. 1 ) transmits to stations or client devices in the service area of the access point. Each respective uplink frame  210 ,  214 ,  218  defines a time period when stations or client devices in the service area transmit to the access point. The composition and timing of each downlink or uplink is defined by the network protocol. Each downlink frame and its corresponding uplink frame is separated by transmit to receive gap (TTRG) period  222 . Each uplink frame from one frame is separated from the downlink frame of the next frame by receive to transmit gap (RTTG) period  224 . 
     The period of a TDD frame  204  for example, comprises a sum of the period of downlink frame  212 , the period of uplink frame  216 , TTRG period  222  and RTTG period  224 . The duty cycle of a frame is defined as the ratio of the period of downlink frame to the period of the frame. The ratio of the period or duration of the downlink frame  208 , for example, to the period of TDD frame  202 , for example, is referred to as the duty cycle. The period of the downlink frame and the period of uplink frame may be appropriately configured based on the particular application. 
     Returning to  FIG. 1 , in a communication system  100  that comprises several wireless networks with overlapping service areas and which operate via radio frequency channels with the same range of frequencies, an access point of a wireless network may synchronize its timing with other wireless networks of the same technology or other technologies operating in the same frequency ranges. To synchronize access points such as access points  102 ,  104 ,  106  and  108 , the wireless networks must operate in a time division duplex mode in which all access points transmit at the same time for a fixed duration, then switch to a receive mode for a fixed duration. This is done according to the sequence  200  of TDD frames of  FIG. 2 . During the downlink frames  208 ,  212 ,  216 ,  220 , all access points  102 ,  104 ,  106 ,  108  transmit in synchrony. During the uplink frames, all access points  102 ,  104 ,  106 ,  108  receive in synchrony. 
     To achieve the discussed synchronous operation, in some embodiments, access points  102 ,  104 ,  106  and  108  may be configured to receive global position satellite (GPS) signals from GPS satellites  128 ,  130  and  132 . Based on the GPS signals, access points  102 ,  104 ,  106  and  108  may generate synchronization events. In an embodiment, transmission of downlink frames by access points and transmission of uplink frames by stations may be configured to occur in response to the generated synchronization events. Because the synchronization events generated by the access points  102 ,  104 ,  106  and  108  are based on the same GPS signals, transmission of downlink frames and uplink frames occur in near synchrony. With reference to  FIG. 2 , in the context of a TDD scheme, access points may schedule the transmission of TDD frames  202 ,  206  and  208  in response to receiving a synchronization event corresponding to time  226 . 
     However, synchronized operation using the same range of frequencies allows a station such as station  102 - 2  to receive radio frequency signals from its access point  102  and neighboring access point  106 . The received radio frequency signals are representative of the downlink data communicated in downlink frames transmitted by access points  102  and  106 . An access point similarly receives radio frequency signals transmitted by stations in its vicinity. For example, access point  102  may receive uplink data not only from its client wireless devices  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  but also from one or more stations  104 - 1 ,  104 - 2 ,  120 ,  106 - 1 ,  106 - 2 ,  106 - 3  and  122  (neighboring stations). 
       FIG. 3  depicts a detailed view of three TDD frames  300 ,  320  and  340  that may be communicated via the same radio frequency communication channel. TDD frame  300  comprises downlink frame  302  and uplink frame  304 . Downlink frame  302  comprises broadcast data slot  310 , and downlink data portions or slots  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4  and  302 - 5 . Uplink frame  304  comprises uplink data portions or slots  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4  and  302 - 5 . Downlink frame  322  of TDD frame  320  comprises broadcast data  330  and downlink data slot  322 - 1 ,  322 - 2 ,  322 - 3  and  322 - 4 . Uplink frame  342  of TDD frame  340  comprises uplink data slots  342 - 1 ,  342 - 2  and  342 - 3 . 
     An access point may communicate information in broadcast data slot  310  that wireless client devices in the wireless network utilize to determine the position of their respective downlink data slots in downlink frame  302  and uplink data slots in uplink frame  304 . The position information may be represented as a time offset from start  301  of TDD frame  300 , in an embodiment. The position information may be referred to as a schedule. The schedule may specify for example when during the corresponding uplink frame a station should communicate data to the access point and the time apportioned to each station. As an example, the schedule may specify the uplink ( 304 - 1 ,  304 - 2 ,  304 - 3 ,  304 - 4  and  304 - 5 ) and downlink slot times ( 302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4  and  302 - 5 ) assigned to stations in radio communication with the access point. The slot times may be represented as time offsets from the synchronization events. 
     The downlink frame  302  may correspond to a downlink frame transmitted by access point  102  and the uplink frame  304  may correspond to uplink data transmitted by stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5 . Access point  102  communicates data to station  102 - 2  in downlink data slot  302 - 1 . Similarly, downlink data slots  302 - 2 ,  302 - 3 ,  302 - 4  and  302 - 5  may correspond to data communicated by access point  102  to stations  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5 , respectively. 
     Downlink frame  322  may correspond to a downlink frame transmitted by access point  106 . Access point  106  may communicate data to stations  106 - 1 ,  106 - 2 ,  106 - 3  and  122  in downlink data slots  322 - 1 ,  322 - 2 ,  322 - 3  and  322 - 4 , respectively, in accordance with the schedule communicated via broadcast data  330 . Because the operation of access point  102  and  106  is synchronized, downlink link frame  302  and  322  are transmitted substantially simultaneously by access points  102  and  106 , respectively. Uplink frame  340  may correspond to uplink data transmitted by stations  104 - 1 ,  104 - 2  and  120  in uplink data slots  342 - 1 ,  342 - 2  and  342 - 3 , respectively. 
     One consequence of synchronized operation of different wireless networks via the same radio frequency communication channel is that a station located in the overlapping service areas of two access points may receive downlink frames transmitted from both of the access points nearly simultaneously. For example, a station such as  102 - 2  receives radio frequency signals from its access point  102  and neighboring access point  106 . The received radio frequency signals are representative of the downlink data communicated in downlink frames transmitted by access points  102  and  106 . Station  102 - 2  will receive radio frequency signals representative of downlink data slot  302 - 1  of downlink frame  302  and downlink data slot  322 - 1  of downlink frame  322 . 
     Generally, the signal strength of radio frequency signals decreases with increasing distances from the source of the radio frequency signals. With reference to  FIG. 1 , because the distance XXX between station  102 - 2  and access point  102  is less than the distance YYY between station  102 - 2  and access point  106 , the signal strength of radio frequency signals received by station  102 - 2  (receive signal strength) from access point  102  is greater than the receive signal strength of radio frequency signals transmitted by station  106 . 
     In an exemplary embodiment, station  102 - 2  measures the receive signal strength of radio frequency signals transmitted by both access points  102  and  106  and configures its hardware characteristics to disregard radio frequency signals having receive signal strengths less than or equal to the signal strength of radio frequency signals received from access point  106 . Thus, in an exemplary embodiment, station  102 - 2  may receive radio frequency signals representative of downlink data slot  302 - 2  and not receive radio frequency signals representative of downlink data slot  322 - 2 . 
     An access point similarly receives radio frequency signals corresponding to uplink data transmitted by stations in its vicinity. The receive signal strength of the radio frequency signals transmitted by the stations and measured by the access point may be different, in part because the stations are at different distances from the access point. 
     With reference to  FIG. 3 , access point  102  may receive uplink frames  304  and  344 . As previously stated, uplink frame  304  may correspond to uplink data transmitted by wireless client devices of the access point  102 , including stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5 . Specifically, uplink data slots  304 - 1 ,  304 - 2 ,  304 - 3 ,  304 - 3 ,  304 - 4  and  304 - 5  includes uplink data transmitted by station  102 - 2 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5 , respectively. Uplink frame  344  may correspond to uplink data transmitted by stations  104 - 1 ,  104 - 2  and  120 . The access point  102  receives radio frequency signals from each of the stations at different signal strengths. 
     In an exemplary embodiment discussed in detail later, access point  102  may group its wireless client devices, stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  based on the receive signal strength of their respective radio signals. The access point  102  may compute a threshold based on the receive signal strength of radio frequency signals corresponding to uplink data in uplink slots  344 - 1 ,  344 - 2  and  344 - 3 . 
     Wireless client devices with a receive signal strength above the threshold may be assigned to a first group and stations with a receive signal strength below the threshold may be assigned to a second group. Group assignments of the client devices may be made by the access point or any other suitable network component. Access point  102  may instruct stations in the first group to transmit uplink data during a first uplink frame of a first TDD frame and stations in the second group to transmit uplink data during a second uplink frame of a second TDD frame. Access point  102  may communicate the instructions via information in the broadcast data slot of the first downlink frame of the first TDD frame and the second downlink frame, in an embodiment. Access point  102  may adjust its hardware characteristics during the first uplink frame and the second uplink frame to minimize the reception of radio signals corresponding to uplink data in uplink data slots  344 - 1 ,  344 - 2  and  344 - 3 , in this embodiment. 
       FIG. 4  is a block diagram of a representative access point  402  and representative client device  404 . The access point  402  may be representative of one of the access points  102 ,  104 ,  106 ,  108  of  FIG. 1 . Similarly, the client device  404  may be representative of one of the stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5  in  FIG. 1 . However, the embodiments shown are intended to be exemplary only. 
     The access point  402  includes a host processor  406 , a network interface  408 , a global positioning system (GPS) circuit  410 , a timing circuit  412 , a scheduler  414  and an antenna  416 . In other embodiments, the access point  402  may include more or fewer or alternative elements relative to those shown in  FIG. 4 . 
     The host processor  406  controls operation of the access point  402 . The host processor may include one or more circuits, modules, interfaces or code for implementing control functions. For example, the host processor  406  may include a microprocessor and memory. The memory may store data and instructions for controlling the microprocessor and other components of the access point  402 . The microprocessor in turn may operate in response to the stored data and instructions to control operation of the access point. 
     The network interface  408  controls data communication between the access point  402  and other devices, including the client device  404 . The network interface  408  controls wireless communication using the antenna  416 . In this regard, the network interface  408  may implement one or more radio circuits to transmit and receive radio communications by means of the antenna  416 . The network interface  408  implements a physical layer (PHY)  418  in accordance with the Open Systems Interconnection (OSI) model of computer networking and a transmitter and receiver circuit (TX/RX)  420 . In some embodiments the network interface  408  may be implemented in a single commercial semiconductor device or chipset. Examples of such chipsets include Avastar 88W8764 and Atheros AR9002U UB94. 
     The transmitter portion of TX/RX  420  is adapted to transmit a radio signal representation of the downlink frame of a TDD frame. The transmitter portion of TX/RX  320  may apply the appropriate modulation and coding schemes (MCS) as specified by the 802.11 standard to the downlink frame before transmission. The transmitter portion may also include mixers, frequency synthesizers, digital to analog convertors, power amplifier etc. 
     The receiver portion of TX/RX  320  is configured to receive radio signal representations of uplink frames of TDD frames. The receiver decodes the radio signals to recover the uplink data. The receiver includes amplifiers, automatic gain control circuits, IF amplifiers, demodulators etc. The receiver may also measure characteristics of the received radio signals including the receive power or signal strength, the signal to noise ratio (SNR) of a received radio signal and the carrier interference to noise ratio (CINR). The receive signal strength is frequently referred to as the receive signal strength intensity (RSSI). Further, the network interface  408  implements a media access control layer (MAC)  322  in accordance with the OSI model. The MAC  422  may control the operation of the PHY  418  including configuring the appropriate MCS. 
     In an exemplary embodiment, hardware characteristics of receiver portion of TX/RX  420  may be adjusted based on the RSSI of radio frequency signals received from stations. In this embodiment, adjusting the hardware characteristics may include decreasing the sensitivity of the receiver portion of TX/RX  420 . Sensitivity is generally defined as the lowest receive signal strength at which the receiver can detect a radio frequency signal and demodulate data represented by the radio frequency signal. Demodulation is the process of extracting the original information-bearing signal from a modulated radio frequency signal. 
     By dynamically adjusting (increasing or decreasing) the sensitivity of a receiver, receiver portion of TX/RX  420 , for example, access point  402  may control which transmissions received from neighboring stations are demodulated based on the respective signal strengths (RSSI)of received radio frequency transmissions. For example if the RSSI of a radio frequency signal transmitted by a station and as measured at receiver portion of TX/RX  420  is −100 dBm and if the sensitivity of receiver portion of TX/RX  420  is decreased to −90 dBm, the receiver portion of TX/RX  420  may be prevented from detecting and demodulating the radio frequency signal. Conversely, if the sensitivity of receiver portion of TX/RX  420  increased to −105 dBm, receiver portion of TX/RX  420  may detect and demodulate the radio frequency signal. Thus, by decreasing the sensitivity, access point  402  may prevent low RSSI radio frequency signals, such as those transmitted by stations not part of the wireless network of access point  402  from being demodulated. 
     In one embodiment, the network interface  408  implements the IEEE 802.11n protocol, including the 802.11n PHY and MAC layers. The network interface  308  may also or instead implement other data communication protocols for both wireless and wire line communication. For example, the network interface  408  may control communication to other wire line network elements such as network  110  of  FIG. 1 . In this regard, the network interface may implement protocols such as Ethernet or internet protocol (IP) for communication with other network elements. 
     The network interface  408  may include data processing circuits such as one or more processors, circuits, interfaces, modules and memory for implementing network control and communication. Moreover, the network interface  408  may include analog circuitry such as amplifiers, oscillators and filters for data communication with the antenna  416 . 
     The antenna  416  may be any suitable device or combination of devices for transmission and reception of signals. In one example, the antenna  416  is a multiple-input, multiple-output (MIMO) antenna array for data communication. In one particular embodiment, the antenna  416  is configured for communication according to the IEEE 802.11 protocol at frequencies such as 2.4 GHz and 3.7 GHz and 5 GHz. Also, the antenna  416  may include multiple structures for communication of other signals such as GSM signals. 
     The GPS circuit  410  receives GPS signals or other location determination signals such as GLONASS signals. In response to the received location determination signals, the GPS circuit  410  determines geographic location of the access point  402 . Also, in response to the received location determination signals, the GPS circuit  410  determines the current time with high precision. The GPS circuit  410  may communicate data about the geographic location of the access point and about the current time to other components of the access point  402 , such as the timing circuit  412 . The GPS circuit  410  may also generate the previously discussed synchronization event used to synchronize the transmission of TDD frames of access points  102 ,  104 ,  106  and  108 . 
     The timing circuit  412  controls timing of the access point  302 . The timing circuit  412  may receive current time data and other timing information from the GPS circuit  410 . In turn, the timing circuit  412  conveys timing information to other components of the access point  402 . The timing information may include data defining the current time, clocking signals, alarm signals and other information. The access point  402  may include suitable means for data communication among its components such as data and control buses by which information such as timing information may be communicated. 
     The scheduler  414  operates to control timing of transmissions from the access point  402 . The scheduler performs functions such as sorting of frames, deciding what frames may be aggregated and timing frame transmissions. 
     As discussed in the preceding paragraphs, the receiver portion of TX/RX  320  may measure the signal strength of the received radio signals that correspond to uplink data transmitted by neighboring stations. For example, scheduler  414  of access point  102  ( FIG. 1 ) may cause receiver TX/RX  320  to measure and report the RSSI of received radio frequency signals, in one embodiment. With reference to  FIG. 3 , in this embodiment scheduler  414  may cause the receiver portion of TX/RX  320  to measure and report the RSSI of radio signals corresponding to uplink data received during uplink data slots  304 - 1 ,  304 - 2 ,  304 - 3 ,  304 - 4 , and  304 - 5  of uplink frame  304  transmitted by wireless client devices associated with the access point  102 , stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5 , respectively. Scheduler  414  may cause the receiver portion of TX/RX  320  to measure and report the RSSI of radio signals corresponding to uplink data received during uplink data slots  344 - 1 ,  344 - 2  and  344 - 3  of uplink frame  344  transmitted by access point  104 &#39;s wireless client devices, stations  104 - 1 ,  104 - 2 , and  120 , respectively. 
     In an embodiment, scheduler  414  may determine a threshold based on the RSSI of radio signals corresponding to uplink frame  344 . The threshold may correspond to an average of the RSSI of the radio signals corresponding to uplink frame  344 , in an embodiment. 
     Scheduler  414  may compare the RSSI of radio signals received during each of the uplink data slots of uplink frame  304  with the threshold. Scheduler  414  may group wireless client devices of access point  102  based on the comparison of the RSSI of their respective radio frequency signals with the threshold. As an example, radio frequency signals from wireless client devices with RSSI values that exceed the threshold by 20 dB may constitute a first group and radio frequency signals from wireless client devices with RSSI values that are below the threshold may constitute a second group. 
     Scheduler  414  generates and transmits a communication schedule (broadcast data  310 ) during the downlink frame of each TDD frame. In an embodiment, the communication schedule transmitted during a first TDD frame may instruct stations in the first group to transmit uplink data during the uplink frame of the first TDD frame. Scheduler  414  may configure the hardware characteristics of receiver TX/RX  320  based on the determined threshold during the uplink frame of the first TDD frame. For example, scheduler  414  may decrease the sensitivity of the receiver TX/RX  320  for the period corresponding to the first uplink frame period. In an embodiment, adjusting the sensitivity of the receiver TX/RX  320  comprising adjusting automatic gain control (AGC) registers in the receiver TX/RX  320 . In an embodiment, RSSI levels determined during a previous uplink frame period may be used to determine an AGC level that will be used to configure receiver TX/RX  320  during the first uplink frame period when data from stations instructed to transmit data during the first uplink frame period is received. Separately, a different AGC level will be determined that will be used to configure receiver section of TX/RX  320  during the second uplink frame period when data from stations instructed to transmit data during the second uplink frame period is received. Thus, the AGC registers of receiver TX/RX  320  is dynamically configured for each uplink frame period. 
     The communication schedule includes respective data for each respective station served by the AP. The respective data includes data identifying the intended recipient station (station identifier) and data defining the communication timing or other schedule information for that intended recipient station. The station identifier may correspond to a unique identifier of the station, media access control (MAC) address for example. The communication timing for a station may correspond to a time offset from a predefined point in time,  226  of  FIG. 2  for example. The respective data for each respective station may be placed in respective time slots of the downlink frame, or communicated in any other suitable manner. The respective data for a respective station may also include a transmit power level. The respective station may transmit data at the specified time offset and at the specified transmit power level during uplink frame  210 , for example. 
     In another embodiment, scheduler  414  may utilize data stored in table  450  to group its wireless client devices based on the RSSI of their respective radio frequency signals. Table  450  may be stored in the memory (not shown) of host  406 , in accordance with one embodiment. By way of example and without limitation, table  450  comprises entries  450 - 1 ,  450 - 2  and  450 - 3 . In this embodiment, wireless client devices with RSSI values less than −50 dBm and greater than or equal to −60 dBm are assigned to group I. Similarly wireless client devices with RSSI values less than −60 dBm and greater than or equal to −70 dBm are assigned to group II, and so on. 
     Scheduler  414  may instruct wireless client devices associated with group  1  to transmit uplink data during a first uplink frame. Scheduler  414  may configure or change receiver of TX/RX  320  for the duration corresponding to the first uplink frame with one or more receiver configuration parameters (REF  1 ) stored in table  450  and associated with group  1 . Receiver configuration parameters may include receiver chipset settings, automatic gain control setting, etc. Changing the receiver configuration parameters may have the effect of decreasing or increasing the sensitivity of receiver of TX/RX  320 . Similarly, scheduler  414  may instruct wireless client devices associated with group  2  to transmit uplink data during a second uplink frame and configure receiver TX/RX  320  with configuration parameters corresponding to REF  2 , and so on. 
     Subsequently, upon the occurrence or detection of a change in communication environment, the scheduler may change or update or reconfigure the receiver according to settings appropriate for the changed condition. 
     In another embodiment, access point  102  may include a second table  452 . As previously discussed, scheduler  414  may determine a threshold based on the RSSI of radio signals corresponding to uplink data received from stations that are not wireless client devices of access point  102  (uplink frame  344 ). In this embodiment, table  450  may be utilized to group wireless client devices when the threshold is within a first range of threshold values and table  452  may be utilized to group wireless client devices when the threshold is within a second range of threshold values. 
     The scheduler  414  may include any suitable combination of circuits, processors, interfaces, memory or code for performing the necessary functions. In the example of  FIG. 3 , the scheduler  414  is a separate component of the access point  402 . In some embodiments, however, the scheduler  414  may be implemented by other components such as the network interface  408  or the host processor  406 . 
     The client device  404  includes a host processor  424 , a network interface  426 , an antenna  428  and a timing circuit  436 . In other embodiments, the client device  404  may include other components providing other functionality. For example, in embodiments where the client device  404  is a mobile phone, the client device  404  includes a call processor circuit, a user interface and possibly other components such as a camera and accelerometers. In embodiments where the client device  404  is a portable computer, the client device  404  may include a keyboard, a display and a hard disk drive or other mass storage. In some embodiments, the client device  404  may be a module within a host device such as the portable computer or mobile phone. 
     The host processor  424  controls operation of the client device  404 . The host processor  424  may include one or more circuits, modules, interfaces or code for implementing control functions. For example, the host processor  424  may include a microprocessor and memory. The memory may store data and instructions for controlling the microprocessor. The microprocessor in turn may operate in response to the stored data and instructions to control operation of the client device  404 . 
     The network interface  426  controls data communication between the client device  404  and other devices, including the access point  402 . The network interface  426  controls wireless communication using the antenna  428 . In this regard, the network interface  426  may implement one or more radio circuits to transmit and receive radio communications by means of the antenna  428 . In the illustrated embodiment, the network interface  426  implements a physical layer (PHY)  430  as well as a transmitter and receiver circuit (TX/RX)  432 . Further, the network interface  326  implements a media access control layer (MAC)  434  in accordance with the OSI model. The network interface  426  forms a radio circuit for radio communication with a remote access point or other radio device. 
     The transmitter and receiver circuit (TX/RX)  432  is configured to synchronize its operation to a downlink frame received from an access point. The receiver portion of TX/RX  432  is configured to receive radio frequency signals representative of downlink data transmitted by access points. The receiver portion of TX/RX  432  (receiver) decodes the radio signals to recover the downlink data. In a typical embodiment, receiver includes amplifiers, automatic gain control circuits, IF amplifiers, demodulators and other conventional signal processing components. The receiver may also measure characteristics of the received radio signals including the receive power or signal strength, the signal to noise ratio (SNR) of a received radio signal and the carrier interference and noise ratio (CINR). Any suitable circuit or component for measuring such characteristics may be used for this purpose. The measurement may be expressed as a signal level such as a voltage or a current or as a data value or as a power level in decibels. 
     In one embodiment, the network interface  426  implements the IEEE 802.11n protocol, including the 802.11n PHY layer  330  and MAC layer  434 . In this regard, the client device  404  forms or is a part of an 802.11 station or STA. The network interface  426  may also or instead implement other data communication protocols for both wireless and wire line communication. For example, the network interface  326  may control communication to other components of the client device  304 . 
     The network interface  426  may include data processing circuits such as one or more processors, circuits, interfaces, modules and memory for implementing network control and communication. Moreover, the network interface  426  may include analog circuitry such as amplifiers, oscillators and filters for communication with the antenna  428 . 
     The antenna  428  may be any suitable device or combination of devices for transmission and reception of signals. In one example, the antenna  428  is a multiple-input, multiple-output (MI MO) antenna array for data communication. In one particular embodiment, the antenna  428  is configured for communication according to the IEEE 802.11 protocol at frequencies such as 2.4 GHz and 3.7 GHz and 5 GHz. Also, the antenna  428  may include multiple structures for communication of other signals such as GSM signals. 
     The timing circuit  436  maintains timing and synchronization information for the client device  404 . In one example, the client device receives timing or synchronization information periodically from the access point  402 . This information may come in the form of a beacon signal transmitted by the access point  402 . By synchronizing the timing information transmitted in the beacons to the periodic synchronization event, the local times of the stations may be synchronized to the periodic synchronization event. The stations may accordingly schedule the start of their respective portions of uplink frames at appropriate times during the uplink frame. 
     In operation, the access point  402  and client device  404  are in selective wireless data communication. The access point  402  operates as a base station and provides data communication in a service area adjacent to the access point  402  to client devices or stations such as the client device  404 . Data communication is conducted according to a protocol such as IEEE 802.11. The access point  402  operates as a host or server to client devices such as the client device  404  in the service area and establishes a communication network for the stations in the service area. 
       FIG. 5  is a timing diagram  500  of an example scenario where an access point such as access point  102  ( FIG. 1 ) groups wireless client devices based on the RSSI of their respective radio frequency signals and adjusts characteristics based on the RSSI of the wireless client devices assigned to the group. In some scenarios, an access point may also receive radio frequency signals from neighboring wireless devices that are not clients and decode the radio frequency signals to identify the non-client neighboring stations. Generally, a non-client neighboring station corresponds to a wireless device which is not in communication with the access point and which transmits radio frequency signals that may be decoded by the access point. The radio frequency signals received by the access point from the non-client neighboring station are interference signals. For example, with reference to  FIG. 1 , radio frequency signals received by access point  102  from stations  104 - 1 ,  104 - 2  and access point  106  for example constitute interference radio frequency signals. In these scenarios, the access point may detect the RSSI of these radio frequency transmissions and based on the detected RSSI and the identity of the non-client neighboring stations, the access point may adjust the characteristics of its receiver to prevent the access point from decoding and synchronizing to the radio frequency signals received from these non-client neighboring stations. 
     The vertical axis of the timing diagram corresponds to the receive signal strength of received radio frequency signals as detected by the receiver of access point  102 . Uplink frame  502  comprises uplink data slots  502 - 1 ,  502 - 2 ,  502 - 3 ,  502 - 4  and  502 - 5 . The vertical height of the uplink data slots corresponds to the relative RSSI of radio frequency signals. The horizontal width of the slot corresponds to the uplink data slot period assigned by scheduler  414 . In this example, uplink frame  516  comprises uplink data transmitted by stations  104 - 1 ,  104 - 2  and  120 . The stations  104 - 1 ,  104 - 2  and  120  are neighboring wireless devices that are not clients of access point  102 . 
     Uplink data slots  502 - 1 ,  502 - 2 ,  502 - 3 ,  502 - 4  and  502 - 5  may correspond to data transmitted by stations  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4  and  102 - 5 , respectively. Level  510  corresponds to the noise floor level. The noise floor level sets the lowest received signal power level, RSSI for example, that can be decoded by the receiver, TX/RX  320  for example. The lowest received signal power level that can be decoded by a receiver may also be referred to as the minimum discernible signal level. The RSSI of the received radio frequency signals are measured with reference to this noise floor level. The noise floor level can be changed (moved up or down) by adjusting the AGC settings in receiver TX/RX  320 , in an embodiment. As the noise floor level is raised by adjusting software programmable hardware settings in the receiver, TX/RX  320  for example, interfering radio frequency signals like those received from neighboring wireless devices having RSSI signal levels below the noise floor will not be decoded by the receiver. Radio frequency signals with RSSI below the noise floor level  510  may not be detected. 
     Because uplink frame  516  is above the noise floor level  510 , in some scenarios access point  102  may receive and decode uplink frame  516 , although uplink frame  516  does not include any data from stations in communication with access point  102 . With reference to  FIG. 5 , by elevating the noise floor above the signal level of uplink frame  516 , reception of uplink frame  516  by the access point  102  may be prevented. One consequence of elevating the noise floor level above the signal level of uplink frame  516  is that access point  102  will not attempt to synchronize to and decode uplink frame  516  and will instead decode uplink frames that include data transmitted by stations that are in actual communication with access point  102 . 
     Ranges  508 - 1 ,  508 - 2  and  508 - 3  correspond to different ranges of RSSI values. For example, range  508 - 1  may correspond to minimum and maximum RSSI values for entry  450 - 1  (group  1 ) of table  450 . Range  508 - 2  corresponds to minimum and maximum RSSI values for entry  450 - 2  (group  2 ) of table  450 . Range  508 - 3  corresponds to minimum and maximum RSSI values for entry  450 - 3  (group  3 ) of table  450 . 
     Based on the RSSI of the radio frequency signals and data from the decoded radio frequency signals, scheduler  414  may identify stations  102 - 1 ,  102 - 3  and  103 - 5  as belonging to a first group. Accordingly, access point  102  may schedule stations  102 - 1 ,  102 - 3  and  102 - 5  to transmit uplink data during uplink frame  504 . In one embodiment, a scheduler of an access point such as scheduler  414  ( FIG. 4 ) may adjust receiver characteristics to elevate the noise floor level  510  to new first noise floor level  512 . Because the amplitude of the uplink frame  516  is below the new first noise floor level  512 , uplink frame will not be decoded. 
     In one embodiment, a scheduler of an access point such as scheduler  414  ( FIG. 4 ) assigns stations  102 - 2  and  102 - 4  to transmit uplink data during uplink frame  506 . During the time period corresponding to uplink frame  506 , scheduler  414  may adjust the noise floor  510  to a second new noise floor level  514 . 
     In some scenarios, elevating the noise floor level has the effect of decreasing the signal to noise ratio (SNR) of the received radio frequency signals. For example,  518  corresponds to the SNR of radio signals received from station  102 - 5  before elevation of the noise floor and  516  corresponds to the SNR of radio signals received from station  102 - 5  after elevation of the noise floor to  512 . 
     MAC  422  ( FIG. 4 ) determines the SNR for each uplink frame slot from the RSSI of the radio frequency signal received during the uplink time slot and the noise floor level. Generally, MAC  422  ( FIG. 4 ) selects a modulation and coding scheme (MCS) that is used to encode radio frequency signals transmitted to a station based on the SNR of the radio frequency signals received from the station. The MCS may be varied as channel quality varies to maintain the best data throughput for current circumstances. The MCS determines the rate at which data may be communicated via a radio frequency communication channel. Higher modulation schemes are associated with increased data throughput. However, higher modulation schemes require higher SNR values. Because elevating the noise floor results in lower SNR, stations assigned to a group where the noise floor is elevated may encounter decreased data throughput. Decreased data throughout is reflected by a decreased data rate. The decreased data rate is caused by the change in MCS that results when the noise floor is elevated. As an example, the modulation scheme may be changed from 256 QAM to 64 QAM when the noise floor is elevated. As a result, the data rate may change from a data rate of 4 Megabits/sec (Mbps) to 1 Mbps. 
     In an embodiment, to account for the decreased data throughput, scheduler  414  may increase the uplink and downlink slot periods assigned to the stations to maintain their respective data throughput. Allowing a station to receive and transmit for a longer period of time at a lower data rate allows enables maintenance of the guaranteed data throughput rates. 
     In other embodiments, a station whose data throughput is adversely affected by changing channel quality may be assigned to TDD frames more frequently. For example, with reference to  FIG. 5 , if stations assigned to group  2  encounter data throughput degradation because of shifting the noise floor to second new noise floor level  516 , scheduler  414  may schedule the stations  102 - 2  and  102 - 4  to TDD frames more frequently. 
     The timing diagram  600  of  FIG. 6  illustrates a scenario where client device  404  receives a first downlink frame  602  and a second downlink frame  604 . Client device  404  may correspond to station  102 - 2  of  FIG. 1 . Downlink frame  602  may correspond to a downlink frame transmitted by access point  102  and downlink frame  604  may correspond to a downlink frame transmitted by access point  106 . The vertical axis of the timing diagram corresponds to the receive signal strength of received radio frequency signals as detected by the receiver portion of TX/RX  432  (receiver). The horizontal axis corresponds to time. The receiver of TX/RX  432  measures the receive signal strength  606  and  608  for radio frequency signals corresponding to downlink frame  602  and downlink frame  604 , respectively. Based on the receive signal strength  608 , station  102 - 2  may determine a new noise floor level  614  which is elevated from the original noise floor level  612 . Characteristics of receiver of TX/RX  432  may be adjusted to elevate the noise floor to the new noise floor level  614  from the original noise floor level  612 . During a subsequent downlink frame  616 , station  102 - 2  may receive downlink data  610  with the new receiver settings. 
       FIG. 7  is a flow diagram of an example method  700  that may be implemented at access point  402 . Method  700  may be implemented using machine executable instructions that host  406  may execute to perform grouping to stations based on the RSSI of received radio frequency signals. 
     At block  710 , access point  402  may receive uplink data transmitted by its wireless client devices during an uplink data frame. The uplink data from the wireless client devices may be received over the course of several uplink data frames. In some scenarios, the wireless client devices may have be previously grouped. In these scenarios, uplink data from each group may be received during respective uplink data frames. 
     At block  720 , for each station scheduler  414  of access point  402  may receive one or more signal characteristics such as RSSI values for radio frequency signals corresponding to data received from the station. The RSSI values may be computed by receiver TX/RX  420 . 
     At block  730 , scheduler  414  may retrieve data stored in table  450  of  FIG. 4 . As previously explained, the data stored in table  450  may correspond to a set of entries where each entry is associated with a group identifier, a minimum and a maximum RSSI value. If the RSSI values for a station lie between the minimum and maximum RSSI value of an entry, scheduler  414  may associate the station with the group associated with the entry. Scheduler  414  may assign each group to a corresponding uplink frame. As previously discussed, the group assignment may be communicated to the stations in the broadcast frame  310  ( FIG. 3 ). As previously discussed, stations assigned to a group transmit during their assigned uplink frame. In another embodiment, scheduler  414  may group stations dynamically based on their RSSI values. 
       FIG. 8  is a flow diagram of an example method  800  that may be implemented in access point  102 , for example, to perform dynamic allocation of stations to uplink frames, in an embodiment. 
     At block  810 , access point  402  may receive uplink data transmitted by its wireless client devices during an uplink data frame,  210  for  FIG. 2 , for example. The uplink data from the wireless client devices may be received over the course of several uplink data frames. In some scenarios, the wireless client devices may have be previously grouped. In these scenarios, uplink data from each group may be received during respective uplink data frames. 
     At block  820 , for each station, scheduler  414  of access point  402  may receive one or more signal characteristics such as RSSI values for radio frequency signals corresponding to data received from each of the stations at block  810 . The RSSI values may be computed by receiver TX/RX  420 . In an embodiment, the respective data received from each station may include the power level at which the respective data was transmitted by the respective station. The difference between the computed RSSI for the radio frequency received from a station and the power level determined from the decoded data may be used to determine the channel characteristics or attenuation. 
     At block  830 , a threshold RSSI level may be calculated based on the respective RSSI signal strength computed from respective received radio frequency signals from the stations associated with the access point and from neighboring stations not associated with the access point. An example method of calculating the threshold may include computing an average (mean) based on the computed RSSI signal strengths. The average may correspond to the threshold. In another example, at block  830 , more than one threshold may be determined. For example, standard deviation (SD) values may be calculated. The −1 SD value, the mean and the +1 SD value may correspond to a first threshold, second threshold and third threshold, respectively, in this embodiment. Other mathematical methods of calculating the threshold may be used. Also, at block  830 , in an embodiment, table  450  and  452  of  FIG. 4  may be generated and populated with the calculated threshold value(s). In one embodiment, receiver settings may be determined corresponding to the threshold(s). 
     In another embodiment, the threshold may correspond to average RSSI signal strengths of radio frequency signal transmissions received from neighboring stations not associated with the access point. In yet another embodiment, at block  830 , the threshold may be adjusted to normalize the distribution of stations above and below the threshold. 
     At block  840 , the stations may be grouped based on their respective computed RSSI signal strengths. As an example, in the scenario where a single threshold such as the mean is utilized. Stations with computed RSSI signal strengths below the mean may be assigned to a first group (first uplink frame) and stations with computed RSSI signal strengths above the mean may be assigned to a second group (second uplink frame). In one embodiment, receiver settings may be determined that are applied to the receiver during the first uplink frame and the second uplink frame. 
     At block  840 , as previously discussed, the group assignment may be communicated to the stations in the broadcast frame  310  ( FIG. 3 ). As previously discussed, stations assigned to a group transmit during their assigned uplink frame. The method  800  may be periodically executed to account for changing channel characteristics, in an embodiment. In another embodiment, the method may be executed whenever a new station establishes communication with the access point. 
       FIG. 9  is a flow diagram of an example method  900  that may adjust the receiver characteristics of a station,  102 - 1  for example, to improve the reception of radio signals from access point  102  that the station  102 - 1  is in communication with and to reduce the reception of radio signals from neighboring access point  106 , for example. By way of example and without limitation the method  900  is implemented at a station. The method  900  may also be implemented in an access point such as access point  102 . 
     At block  910 , receiver (TX/RX  432  of  FIG. 4 ) of station  102  for example may receive radio frequency signals corresponding to one or more downlink data frames. A downlink data frame may be received from access point  102  and access point  106 , for example during the same downlink frame period in an embodiment. 
     At block  920 , the received radio frequency signals may be decoded and demodulating. The decoded data may be analyzed to determine the identity of the access points or stations that transmitted the respective downlink data frames. For example, at block  920  based on the determined respective identity of the wireless devices that transmitted the respective radio frequency signals, station  102 - 1  may conclude that the first downlink frame was received from access point  102  and the second downlink data frame was received from access point  106 . As was discussed in  FIG. 1 , station  102 - 1  is communicatively coupled to access point  102 . Therefore, the downlink data frame from access point  102  may include information for station  102 - 1 . The downlink data frame from access point  106  comprises interference for station  102 - 1 . 
     At block  920 , respective RSSI signal levels may be determined for the radio frequency signals corresponding to the downlink data frames received from access points  102  and  106 . 
     At block  930 , receiver characteristics for receiver of TX/RX  432  may be adjusted based on the determined RSSI signal levels. As previously discussed, the noise floor level of receiver of TX/RX  432  may be elevated above the RSSI level of the radio frequency signals corresponding to the downlink data frames received from access points  106  during the start of a subsequent downlink data frame, in an embodiment As a result the downlink data frame from access point  106  will not be received or the RSSI level for the radio frequency signals corresponding to downlink data frame from  106  will be caused to be sufficiently attenuated so that it will not be decoded. This reduces the interference effects of downlink data frame from access point  106 . 
     The preceding method may be implemented in a point to point (PTP), ad-hoc or back haul scheme. In a PTP scheme, two stations,  102 - 1  and  102 - 2  for example, are configured to establish a communication channel exclusively between the two stations. In other embodiments, methods described herein may be implemented in the network controller  124  of  FIG. 1 . In these embodiments, the access points may communicate RSSI measurements to the network controller  124  and network controller may generate the above described grouping scheme and communicate the grouping scheme to the access points to implement. In this embodiment, the network controller  124  may utilize the committed data rates that the network provider is contractually obligated to provide to the stations in determining the grouping scheme. Thus, for example, the network controller  124  may appropriately cause, for example, the noise floor to be elevated at an access point, to prevent an excessive reduction/degradation in data throughput. 
     Each of the methods described herein may be encoded in a computer-readable storage medium (e.g., a computer memory), programmed within a device (e.g., one or more circuits or processors), or may be processed by a controller or a computer. If the processes are performed by software, the software may reside in a local or distributed memory resident to or interfaced to a storage device, a communication interface, or non-volatile or volatile memory in communication with a transmitter. The memory may include an ordered listing of executable instructions for implementing logic. Logic or any system element described may be implemented through optic circuitry, digital circuitry, through source code, through analog circuitry, or through an analog source, such as through an electrical, audio, or video signal. The software may be embodied in any computer-readable or signal-bearing medium, for use by, or in connection with an instruction executable system, apparatus, or device. Such a system may include a computer-based system, a processor-containing system, or another system that may selectively fetch instructions from an instruction executable system, apparatus, or device that may also execute instructions. 
     A “computer-readable storage medium,” “machine-readable medium,” “propagated-signal” medium, and/or “signal-bearing medium” may comprise a medium (e.g., a non-transitory medium) that stores, communicates, propagates, or transports software or data for use by or in connection with an instruction executable system, apparatus, or device. The machine-readable medium may selectively be, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. A non-exhaustive list of examples of a machine-readable medium would include: an electrical connection having one or more wires, a portable magnetic or optical disk, a volatile memory, such as a Random Access Memory (RAM), a Read-Only Memory (ROM), an Erasable Programmable Read-Only Memory (EPROM or Flash memory), or an optical fiber. A machine-readable medium may also include a tangible medium, as the software may be electronically stored as an image or in another format (e.g., through an optical scan), then compiled, and/or interpreted or otherwise processed. The processed medium may then be stored in a computer and/or machine memory.