Abstract:
A method, according to various aspects of the present invention, for improving a data throughput between the wireless cell and the client. A wireless cell performs the method. The method includes in any practical order (1) determining a primary direction of data flow between the wireless cell and the client, wherein if the primary direction of data flow is from the wireless cell to the client, denominating the wireless cell as a transmitting device and the client as a receiving device, otherwise, denominating the client as a transmitting device and the wireless cell as a receiving device; (2) the receiving device detecting a factor that reduces data throughput for each one channel of the plurality of channels; and (3) assigning one channel of the plurality of channels to the transmitting device and the receiving device responsive to detecting thereby improving data throughput.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation and claims the benefit under 35 U.S.C. §120 of U.S. application Ser. No. 11/420,605 filed May 26, 2006 now U.S. Pat. No. 7,400,860, which is a continuation-in-part of U.S. application Ser. No. 10/869,201 filed Jun. 15, 2004 now U.S. Pat. No. 7,302,278, herein incorporated by reference, and a continuation-in-part of U.S. application Ser. No. 10/880,387 filed Jun. 29, 2004 now U.S. Pat. No. 7,359,675, herein incorporated by reference. U.S. application Ser. No. 11/420,605 also claims the benefit under of provisional Application No. 60/692,490 filed Jun. 21, 2005, herein incorporated by reference, and provisional Application No. 60/743,897 filed Mar. 29, 2006, herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to wireless communications, and more particularly, to apparatus and methods configured to increase data throughput for wireless cells, wireless clients, and wireless networks. 
     2. Description of Related Art 
     Many systems incorporate communication protocols, minimally interfering channels, and directional antennas to improve communication between wireless cells and wireless clients. Wireless devices may benefit from detecting and using primary direction of data flow to select at least one of an antennas and a channel to improve data throughput. 
     BRIEF SUMMARY OF THE INVENTION 
     A method, according to various aspects of the present invention, for improving a data throughput between the wireless cell and the client. A wireless cell performs the method. The method includes in any practical order (1) determining a primary direction of data flow between the wireless cell and the client, wherein if the primary direction of data flow is from the wireless cell to the client, denominating the wireless cell as a transmitting device and the client as a receiving device, otherwise, denominating the client as a transmitting device and the wireless cell as a receiving device; (2) the receiving device detecting a factor that reduces data throughput for each one channel of the plurality of channels; and (3) assigning one channel of the plurality of channels to the transmitting device and the receiving device responsive to detecting thereby improving data throughput. 
     Another method, according to various aspects of the present invention, for improving a data throughput between the wireless cell and the client. A wireless cell performs the method. The method includes in any practical order (1) determining a primary direction of data flow between the wireless cell and the client, wherein: the wireless cell comprises a first plurality of antennas and a plurality of channels, the client comprises a second plurality of antennas and the plurality of channels, and if the primary direction of data flow is from the wireless cell to the client, denominating the wireless cell as a transmitting device and the client as a receiving device, otherwise, denominating the client as a transmitting device and the wireless cell as a receiving device; (2) the receiving device detecting a factor that reduces data throughput through each one of the plurality of antennas of the receiving device and for each one of the channels; (3) responsive to detecting, selecting one of the plurality of antennas of the receiving device for communicating with the transmitting device thereby improving the data throughput; and (4) responsive to detecting, assigning one channel of the plurality of channels to the transmitting device and the receiving device thereby improving the data throughput. 
     Another method, according to various aspects of the present invention, for detecting a receiving device. A wireless cell performs the method. The method includes in any practical order (1) detecting a primary direction of data flow between the wireless cell and the client; and (2) responsive to detecting, if the primary direction of data flow is from the wireless cell to the client denominating the wireless cell as a transmitting device and the client as a receiving device, otherwise denominating the client as a transmitting device and the wireless cell as a receiving device. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Embodiments of the present invention will now be further described with reference to the drawing, wherein like designations denote like elements, and: 
         FIG. 1  is a diagram of a wireless cell having an omni-directional antenna, a client having an omni-directional antenna, a noise source, and a primary direction of data flow from client to wireless cell in accordance with one embodiment of the present invention; 
         FIG. 2  is a diagram of a wireless cell having an omni-directional antenna, a client having an omni-directional antenna, a noise source, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 3  is a diagram of a wireless cell having an omni-directional antenna, a client having an omni-directional antenna, and two noise sources in accordance with one embodiment of the present invention; 
         FIG. 4  is a diagram of a wireless cell having an omni-directional antenna, a client having a directional antenna, a noise source, and a primary direction of data flow from client to wireless cell in accordance with one embodiment of the present invention; 
         FIG. 5  is a diagram of a wireless cell having an omni-directional antenna, a client having a directional antenna, a noise source, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 6  is a diagram of a wireless cell having an omni-directional antenna, a client having a plurality of directional antennas, a noise source, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 7  is a diagram of a wireless cell having an omni-directional antenna, a client having a directional antenna, two noise sources, and a primary direction of data flow from client to wireless cell in accordance with one embodiment of the present invention; 
         FIG. 8  is a diagram of a wireless cell having an omni-directional antenna, a client having a directional antenna, two noise sources, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 9  is a diagram of a wireless cell having a directional antenna, a client having a directional antenna, two noise sources, and a primary direction of data flow from client to wireless cell in accordance with one embodiment of the present invention; 
         FIG. 10  is a diagram of a wireless cell having a directional antenna, a client having a directional antenna, two noise sources, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 11  is a diagram of a wireless cell having a plurality of directional antennas, a client having a plurality of directional antennas, two noise sources, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 12  is a diagram of a wireless cell having a directional antenna, a client having a directional antenna, three noise sources, and a primary direction of data flow from client to wireless cell in accordance with one embodiment of the present invention; 
         FIG. 13  is a diagram of a wireless cell having a directional antenna, a client having a directional antenna, three noise sources, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention; 
         FIG. 14  is a diagram of a wireless cell having an omni-directional antenna, a client having an omni-directional antenna, three noise sources, and a primary direction of data flow from client to wireless cell in accordance with one embodiment of the present invention; 
         FIG. 15  is a diagram of a wireless cell having an omni-directional antenna, a client having an omni-directional antenna, three noise sources, and a primary direction of data flow from wireless cell to client in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The detailed description of exemplary embodiments of the invention herein makes reference to the accompanying drawings, which show the exemplary embodiments by way of illustration and its best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical and mechanical changes may be made without departing from the spirit and scope of the invention. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not limited to the order presented. 
     For the sake of brevity, conventional aspects may not be described in detail herein. Furthermore, the component positions shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. As will be appreciated by one of ordinary skill in the art, the present invention may be embodied as a customization of an existing system, an add-on product, a stand alone system, and/or a distributed system. Accordingly, the present invention may take the form of an entirely hardware embodiment, or an embodiment combining aspects of both software and hardware. 
     Generally, the invention comprises wireless cells, wireless clients, and methods for improving data throughput. Regarding data throughput, as used herein, the term “throughput” is the number of bits transmitted and/or received per second. Throughput may generally be categorized into two classes, namely total throughput and usable data throughput. Total throughput includes all bits transmitted and/or received per time period between two devices. Total throughput includes, for example, overhead required by the communication protocol, retransmitted data, and data. As used herein, the term “usable data throughput” means the actual data transmitted and/or received per time period. Usable data throughput excludes, for example, bits dedicated to overhead, error corrections bits, and retransmitted data. Usable data throughput is also referred to herein as “data throughput.” Data throughput may also be described in terms of, for example, minimum, maximum, and average data throughput. As used herein, the term “average data throughput” is the number of data bits transmitted and/or received divided by the period of time of transmission and/or reception. As used herein, the term “maximum data throughput” is the maximum number of data bits per time period measured during transmission and/or reception. As used herein, the term “minimum data throughput” is the minimum number of data bits per time period measured during transmission and/or reception. Data throughput may be express as the number of bits per second. Data throughput is influenced by factors such as, for example, the presence of noise, receive error, multipath signals, and other factors that may require communicating devices to decrease their rate of transmission, and to retransmit data. Data throughput may be increased, for example, by decreasing the influence of noise on reception, decreasing the need to retransmit, increasing the transmission and/or reception rates, increasing available transmission and/or reception bandwidth, channel assignments, directional antennas, bandwidth management, bandwidth prioritization, client load balancing, primary direction of data flow, client priority, application priority, attenuating incoming signals, and protocol selection. 
     Regarding using the direction of data flow as a method to improve throughput, as used herein, the term “primary direction of data flow” is the direction of transmission of a majority of data between two devices. For example, referring to  FIG. 2 , suppose that client  18  is running a video application and receives the video data from wireless cell  10 . The majority of the data that flows between wireless cell  10  and client  18  flows from wireless cell  10  to client  18 , thus, the primary direction of data flow is from wireless cell  10  to client  18 . Client  18  may transmit retransmission requests or status information, but in a typical video application, client  18  receives more data from wireless cell  10  than it transmits to wireless cell  10 . 
     In particular, in one embodiment of the invention, a wireless cell and/or client detects noise sources, detects the channels used by the noise sources, determines the primary direction of data flow, and selects a channel for communication between the wireless cell and client that reduces noise source interference with the primary direction of data flow. In an exemplary embodiment, the selected channel minimizes noise source interference with the primary direction of data flow even though interference with the non-primary direction of data flow may not be minimized. 
     Some of the examples and embodiments associated with the primary direction of data flow, show omni-directional antennas, directional antennas, specific directional antenna orientations, distances between noise sources and receiving devices, directions of primary data flow, signal strengths, and channel assignments. The examples and embodiments are given by way of explanation and not by way of limitation. Antennas of any type or having any desirable characteristics may be used, for example, gain, angle of coverage, number of active elements, and level of attenuation of signals from behind the antenna. The antennas may be oriented in any manner. Physical sectors may overlap or be non-overlapping. Any number of antennas may be used with either wireless cells or clients. The antennas of any wireless device may be use simultaneously or individually. The criteria for selecting which antenna or antennas are used may utilize any metric such as, for example, signal-to-noise ratio, noise source signal strength, data throughput, error rate, transmission activity level, and retransmission rate. Each wireless cell and/or client may have any number of radios and/or other electronic elements to utilize the antennas. The primary direction of data flow may be from any wireless device to any other wireless device, for example, wireless cell to client, client to wireless cell, wireless cell to wireless cell, client to client, client to multiple wireless cells, and wireless cell to multiple clients. The primary direction of data flow may be substantially static or change dynamically. The channel used for communication may change independently or coincidental to a change in an operational factor such as, for example, a change in the primary direction of data flow, change of channel usage by noise sources, change of position of a noise source, and movement of a client. The transmit signal strengths of the various wireless devices and/or noise sources may be uniform or vary. Any channel may be assigned to any wireless device and/or antenna. For example, wireless cells and clients may be assigned the same channel as a noise source, different minimally interfering channels may be assigned to the different antennas of a single wireless device, channels may be assigned to be different from a noise source, and channel assignments may be static or changed dynamically. 
     Data throughput may be improved by detecting and using the primary direction of data flow. In one embodiment, referring to  FIG. 1 , wireless cell  10  and client  18  have omni-directional antennas that form physical sectors  12  and  74  respectively. Assume that the majority of the communications between client  18  and wireless cell  10  comprises transmissions from client  18  to wireless cell  10 . In such operating circumstances, the primary direction of data flow is from client  18  to wireless cell  10  as depicted by arrow  72 . Assume also that noise source  60  transmits information on the same channel as client  18  and wireless cell  10 , for example, on channel C 1 . Any type of a device may operate as a noise source, for example, a wireless cell, a client, a cell phone, and any wireless device that transmits in the frequency band of interest. Transmissions from noise source  60 , represented by arrows  76 , may reach both client  18  and wireless cell  10 , thus transmissions from noise source  60  may interfere with transmissions from client  18  as received by wireless cell  10 . When the primary direction of data flow is reversed, referring arrow  72  in  FIG. 2 , transmissions from noise source  60  may still reach both client  18  and wireless cell  10 , thus transmissions from noise source  60  may interfere with transmissions from wireless cell  10  as received by client  18 . 
     Environmental conditions and the distance from the noise source to the receiving device combined with the primary direction of data flow may improve data throughput even when both the client  18  and the wireless cell  10  use omni-directional antennas. For example, referring to  FIG. 3 , wireless cell  10  and client  18  are positioned in a room surrounded by wall  78 . Noise source  60  is positioned outside of the room while noise source  62  is inside the room. For this embodiment, assume both noise source  60  and  62  transmit on the same channel as wireless cell  10  and client  18 . Also assume that client  18  and noise source  62  are positioned a distance  80 , as shown in  FIG. 3 , from wireless cell  10  and noise source  60  is positioned a distance  80  from client  18 . When the primary direction of data flow is from client  18  to wireless cell  10 , as indicated by arrow  72 , signals from client  18  and noise source  62  travel a distance  80  before reaching wireless cell  10 ; whereas, signals from noise source  60  travel a distance of twice distance  80  before reaching wireless cell  10 . Further assume that client  18  and noise sources  60  and  62  transmit at the same power levels and with approximately the same level of transmission activity. Estimating the signal-to-noise ratio (“SNR”) for the signal from client  18  to the noise of noise source  60  and noise source  62  separately provides insight in to how the primary direction of data flow may be used to improve data throughput. The equations below are simplified estimates of the SNR for each noise source acting independently. Calculating the SNR with respect to multiple noise sources operating simultaneously on the same channel requires complex equations. The equations of this application simplify the calculation by analyzing the SNR of a desired signal against the signal of a single noise source as though the other noise sources provide no additional interference. 
     In an exemplary embodiment, referring to  FIG. 3 , where the primary direction of data flow is from client  18  to wireless cell  10 , the SNR of the signal from client  18  to the noise of noise source  62  may be estimated by noticing that signals transmitted from client  18  and noise source  62  travel a distance of distance  80  before reaching wireless cell  10 . For the distances traveled, the SNR of the signal from client  18  to the noise from noise source  62  as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     Distance 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                   
                     Distance 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 1 
                 ) 
               
             
             ≈ 
             
               0 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     A resulting SNR of 0 dB means that wireless cell  10  may perceive signals from client  18  and noise from noise source  62  equally. In estimating the SNR of the signal from client  18  to the noise of noise source  60 , signals from noise source  60  travel a distance of two times distance  80  before reaching wireless cell  10 . For the distances traveled by signals between client  18 , noise source  60 , and wireless cell  10 , the SNR of the signal from client  18  to the noise from noise source  60  as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         2 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 4 
                 ) 
               
             
             ≈ 
             
               6 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The term “D 80 ” is shorthand for the distance  80 . A resulting SNR of 6 dB means that wireless cell  10  may more readily perceive signals from client  18  than noise from noise source  60 . Absent any other factors, noise source  60  interferes with transmissions from client  18  less than noise source  62  when the primary direction of data flow is from client  18  to wireless cell  10 . Environmental factors, such as wall  78  may also play a role in the interference due to a noise source for a given primary direction of data flow. Signals transmitted through a plaster wall may lose about 5 dB of signal strength. Noise transmitted by noise source  60  passes through wall  78  before reaching wireless cell  10 . The decrease in the signal strength of the signals from noise source  60  results in a SNR of the signal from client  18  to the noise from noise source  60  as perceived and/or received by wireless cell  10  of approximately 11 dB. Because noise source  62  is in the room with wireless cell  10 , its signals do not pass through wall  78  before reaching wireless cell  10 , thus the SNR of the signals of client  18  to the noise of noise source  62  is not improved by the presence of wall  78 . When the primary direction of data flow is from client  18  to wireless cell  10 , wall  78  may improve data throughput by weakening the interference caused by noise source  60 . When the primary direction of data flow is from wireless cell  10  to client  18 , wall  78  still provides a benefit, but the amount of the benefit is decreased because the receiving device, client  18 , is closer to noise source  60  than when the primary direction of data flow was from client  18  to wireless cell  10 . 
     Based on the estimates of the above equations, for the embodiment show in  FIG. 3 , wireless cell  10  and/or client  18  may take any action to improve data throughput. For example, switching wireless cell  10 , client  18  and noise source  60  to a channel different from the channel used by noise source  62  may improve data throughput because the strongest source of interference, noise source  62 , would be reduced. Another action may be to switch wireless cell  10  and client  18  switching to a channel that is different from the channels used by both noise sources  60  and  62 . Another possible action depends on the level of transmission activity of noise source  62 . In a situation where noise source  62  transmits intermittently and significantly less than noise source  60 , data throughput may be improved by switching wireless cell  10 , client  18 , and noise source  62  to the same channel while noise source  60  uses a different channel. while interference from noise source  62  may be stronger than interference from noise source  60  for the primary direction of data flow, interference from noise source  62  occurs less frequently than interference from noise source  60 . The action taken to improve data throughput may also be affected by the transmit strength of each noise source. The SNR estimation equations presume that each noise source transmits with equal strength; however, equal signal strength is not a requirement. Wireless cell  10  and client  18  may use a channel, taking in to account the primary direction of data flow, that carries a weaker interference signal strength. 
     In a variation of the embodiment of  FIG. 3 , the primary direction of data flow is from wireless cell  10  to client  18  (not shown in  FIG. 3 ) and the SNR of the signals from wireless cell  10  to the noise from noise sources  60  as received by client  18 , neglecting any loss through wall  78 , may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 1 
                 ) 
               
             
             ≈ 
             
               0 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     Accounting for the loss through wall  78  may improve the SNR with respect to noise source  60 . The SNR of the wireless cell  10  signals to the noise of noise source  62  only as perceived by client  18  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         2 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 4 
                 ) 
               
             
             ≈ 
             
               6 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     Based on the estimates of the above two equations, changing the primary direction of data flow changed the amount of possible interference from the noise sources. Wireless cell  10  and/or client  18  may improve data throughput by taking similar actions to those taken above. For example, switching wireless cell  10 , client  18  and noise source  62  to a channel different from the channel used by noise source  60 . Switching wireless cell  10 , client  18 , and noise source  62  to a channel different from noise source  60  when noise source  60  transmits intermittently. 
     Data throughput may be improved by equipping clients with at least one directional antenna and positioning the antenna physical sectors according to the primary direction of data flow. In an exemplary embodiment, referring to  FIG. 4 , client  18  has one directional antenna that forms physical sector  74 . Wireless cell  10  has an omni-directional antenna that forms physical sector  12 . In this embodiment, client  18  is positioned to point its directional antenna towards wireless cell  10  and away from noise source  60 . Assume that noise source  60  transmits information on the same channel as client  18  and wireless cell  10 , for example, on channel C 1 . Assume also that the primary direction of data flow is from client  18  to wireless cell  10  as indicated by arrow  72 . Even though client  18  has a directional antenna because wireless cell  10  has an omni-directional antenna and the primary direction of data flow is into wireless cell  10 , transmissions from noise source  60  may interfere, to some degree, with transmissions from client  18 . 
     Reversing the primary direction of data flow, referring to arrow  72  in  FIG. 5 , may improve data throughput because of the positioning of the directional antenna. Noise source  60  transmits towards client  18  from behind the directional antenna. Directional antennas attenuate signals transmitted from a direction other than the direction in which the antenna is oriented. In this embodiment, the directional antenna of client  18  receives transmissions from wireless cell  10 , as depicted by arrow  72 ; whereas, signals from noise source  60 , depicted as arrows  76 , are attenuated. Thus, client  18  perceives signals from the direction of wireless cell  10  as being stronger than the signals from the direction of noise source  60 . Data throughput may improve, in this embodiment, referring to  FIG. 5 , when the primary direction of data flow is from wireless cell  10  to client  18  because the signal-to-noise ratio of the signal, arrow  72 , to the noise, arrows  76 , is higher as received by client  18  than when the primary direction of data flow is from the client  18  to the wireless cell  10 , as shown in  FIG. 4 . The orientation of the directional antenna of client  18 , as shown in  FIG. 5 , combined with the primary direction of data flow from the wireless cell  10  to client  18 , referring to line  72 , may provide an improvement in data throughput even when noise source  60 , client  18 , and wireless cell  10  all use the same channel. 
     In another embodiment, client  18  has multiple directional antennas with physical sectors that may overlap. For example, referring to  FIG. 6 , client  18  has six directional antennas forming physical sectors  74 ,  78 ,  80 ,  82 ,  84 , and  86  that overlap to form virtual sectors. Each antenna is oriented in a different direction. Multiple directional antennas enable client  18  to use the antenna and/or antennas that provide the best data throughput for a given primary direction of data flow. The antenna or antennas used by client  18  may be selected in any manner using any criteria, for example, signal-to-noise ratio, data throughput, error rate, and signal strength. In the embodiment shown in  FIG. 6 , the antenna that forms physical sector  74  may deliver higher data throughput than the other antennas because it is oriented more directly towards wireless cell  10  and more opposed to noise source  60 . 
     In an embodiment that utilizes directional antennas, referring to  FIG. 7 , client  18  uses a single directional antenna that forms physical sector  74  which is oriented in the direction of wireless cell  10  and noise source  62 . Noise source  60  is positioned outside of the room formed by wall  78  while noise source  62  is inside the room. As performed above, the SNR for each noise sources with respect to the primary direction of data flow may be estimated. In the case of the SNR of the signal from client  18  to the noise of noise source  62 , signals transmitted from client  18  and noise source  62  travel a distance of distance  80  before reaching wireless cell  10 . For the distances traveled by signals, the SNR of the signal from client  18  to the noise from noise source  62  as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 1 
                 ) 
               
             
             ≈ 
             
               0 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     In the case of the SNR of the signal from client  18  to the noise of noise source  60 , signals transmitted from client  18  travel a distance of distance  80  before reaching wireless cell  10 , while the signals from noise source  60  travel a distance of two times distance  80  before reaching wireless cell  10 . For the distances traveled, the SNR of the signal from client  18  to the noise from noise source  60  only as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         2 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 4 
                 ) 
               
             
             ≈ 
             
               6 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     Wall  78  may also improve the SNR of noise source  60 , but not the SNR of noise source  60 . For the resulting SNR values, data throughput may be improved by taking action to first reduce the interference from noise source  62 . Next, data throughput may be additionally improved by reducing the interference from noise source  60 . Such actions may include, for example, switching wireless cell  10 , client  18 , and noise source  60  to a channel that is different from noise source  62 ; switching wireless cell  10  and client  18  to a channel that is different from both noise sources  60  and  62 ; and switching wireless cell  10  and client  18  to a channel used by the noise source whose level of transmission activity lowest. 
     Reversing the primary direction of flow of data may change the method of achieving improved data throughput. In an exemplary embodiment, referring to  FIG. 8 , the primary directional of data flow, arrow  72 , is from wireless cell  10  to client  18 . Noise source  62  transmits signals, arrow  82 , which are received by client  18  because the directional antenna used by client  18  is oriented in the direction of noise source  62 . Noise source  60  transmits signals, arrows  76 , in the direction of client  18 , but they are attenuated by the directional antenna. Wall  78  may both attenuate and reflect signals, for example, transmitted signal  76  may pass through wall  78 , travel across the room, reflect off the inner surface of wall  78  and travel towards client  18  in the direction where client  18  may receive signal  76 . As performed above, the SNR may be estimated for each noise source. In the case of the SNR of the signal from wireless cell  10  to the noise of noise source  62 , signals transmitted from wireless cell  10  travel a distance of distance  80  and signals from noise source  62  travel a distance of twice distance  80  before reaching client  18 . For the distances traveled by signals, the SNR of the signal from wireless cell  10  to the noise from noise source  62  only as received by client  18  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         2 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 4 
                 ) 
               
             
             ≈ 
             
               6 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     In the case of the SNR of the signal from wireless cell  10  to the noise of noise source  60 , signals transmitted from wireless cell  10  travel a distance of distance  80  before reaching client  18 . Ignoring signals from noise source  60  that are attenuated behind the directional antenna of client  18 , signals from noise source  60  travel a distance of five times distance  80  before reaching client  18 . For the distances traveled, the SNR of the signal from wireless cell  10  to the noise from noise source  60  only as received by client  18  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         5 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 25 
                 ) 
               
             
             ≈ 
             
               14 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The SNR ratio of wireless cell  10  to noise source  60  may improve by accounting for wall  78 . For the embodiment of  FIG. 8 , the directional antenna combined with the primary direction of data flow from wireless cell  10  to client  18  improved SNR over the embodiment of  FIG. 7  without further action; however, SNR may improve even further by taking action to reduce the interference first from noise source  62  then from noise source  60  as previously described. 
     The analysis of the effects of the primary direction of data flow on an embodiment where wireless cell  10  is equipped with at least one directional antenna and client  18  with an omni-directional antenna is similar to the analysis where wireless cell  10  has an omni-directional antenna and client  18  at least one directional antenna as analyzed above. In general, orienting a directional antenna away from a noise source and towards the primary direction of data flow tends to improve SNR and data throughput. Assigning a channel to wireless cell  10  and client  18  that is different from the channel used by the nearest noise source while taking into account the primary direction of data flow may further improve data throughput. 
     Equipping both client  18  and wireless cell  10  with at least one directional antenna may improve data throughput for various directions of primary data flow. In one embodiment, referring to  FIG. 9 , wireless cell  10  has one directional antenna that forms physical sector  66 . The directional antenna of wireless cell  10  is oriented towards client  18  and away from noise source  62 . Client  18  has one directional antenna that forms physical sector  74  that is oriented towards wireless cell  10  and away from noise source  60 . Arrow  72  indicates the primary direction of data flow and transmissions from noise sources  60  and  62  are represented by arrows  76  and  82  respectively. Transmissions from noise source  60  enter the directional antenna of wireless cell  10  and interfere to some degree with transmissions from client  18  to wireless cell  10 . Transmissions from noise source  62  approach the directional antenna of wireless cell  10  from behind and are attenuated. Switching client  18  and wireless cell  10  to work on a channel that is different from the channel used by noise source  60  may reduce interference of transmissions from noise source  60  with wireless cell  10  reception of data from client  18 , thereby increasing throughput. Reversing the direction of primary data flow, referring to  FIG. 10 , simply changes which noise source may interfere with reception at client  18 . Transmissions from noise source  62  may interfere with the reception of data by client  18  from wireless cell  10 . Transmissions from noise source  60  approach the directional antenna of client  18  from behind and are attenuated. Changing the channel used by wireless cell  10  and client  18  to be different from the channel used by noise source  62  may reduce interference from noise source  62  with client  18  reception of data from wireless cell  10 , thereby increasing data throughput. Wireless cell  10  and/or client  18  may have multiple directional antennas as shown in the embodiments of  FIGS. 6 and 11 . Wireless cell  10  and/or client  18  may use any method to select an antenna and/or antennas for communication. 
     Environmental conditions and the distance of the noise source from the receiving device combined with the primary direction of data flow may improve data throughput when wireless cell  10  and client  18  use directional antennas. In one embodiment, referring to  FIG. 12 , wireless cell  10  and client  18  are positioned in a room surrounded formed by wall  78 . Client  18  uses a single directional antenna that forms physical sector  74  which is oriented in the direction of wireless cell  10 , noise source  62 , and noise source  64 . Wireless cell  10  uses a single directional antenna that forms physical sector  66  which is oriented in the direction of client  18  and noise source  60 . Noise sources  60  and  64  are positioned outside of the room while noise source  62  is inside the room. Client  18  and noise source  62  are positioned a distance  80  from wireless cell  10 , noise source  60  is positioned a distance  80  from client  18 , and noise source  64  a distance  80  from noise source  62 . The primary direction of data flow, indicated by arrow  72 , is from client  18  to wireless cell  10 . Signals from client  18  travel a distance  80  before being received by the directional antenna of wireless cell  10 . Signals from noise source  62 ,  60 , and  64  travel three, two, and four times distance  80 , lines  82 ,  76 , and  90 , respectively, before being received by the directional antenna of wireless cell  10 . In the case of the SNR of the signal from client  18  to the noise of noise source  60 , signals transmitted from client  18  travel a distance of distance  80  before reaching wireless cell  10 . However, signals from noise source  60  travel a distance of two times distance  80 , referring to line  76 , before reaching wireless cell  10 . For the distances traveled, the SNR of the signal from client  18  to the noise from noise source  60  as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         2 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 4 
                 ) 
               
             
             ≈ 
             
               6 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The SNR ratio of client  18  to noise source  60  may improve by accounting for attenuation through wall  78 . In the case of the SNR of the signal from client  18  to the noise of noise source  62 , signals transmitted from noise source  62 , referring to line  82 , cross the room, reflect from the inner portion of wall  78  and enter the directional antenna of wireless cell  10 . Signals from noise source  62  travel a distance of three times distance  80  before reaching wireless cell  10 . Assume that the reflection from the inner surface of wall  78  is lossless. For the distances traveled, the SNR of the signal from client  18  to the noise from noise source  62  as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         3 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 9 
                 ) 
               
             
             ≈ 
             
               9.5 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The SNR ratio of client  18  to noise source  62  does not pass through wall  78  and does not benefit from the attenuation of the noise source as it passes through the wall. In the case of the SNR of the signal from client  18  to the noise of noise source  64 , signals transmitted from noise source  64 , referring to line  90 , travel a distance of four times distance  80  before reaching wireless cell  10 . For the distances, the SNR of the signal from client  18  to the noise from noise source  64  as received by wireless cell  10  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     wirelesscell 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   10 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         4 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 16 
                 ) 
               
             
             ≈ 
             
               12 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The SNR ratio of client  18  to noise source  64  may improve by accounting for attenuation through wall  78 . Based on the estimates of the above three equations, for the embodiment shown in  FIG. 12 , wireless cell  10  and/or client  18  may improve data throughput by taking any action that may reduce interference first from noise source  60 , next from noise source  62 , and then by noise source  64 . For example, wireless cell  10  and client  18  may reduce interference from the two nearest noise sources, accounting for the primary direction of data flow, by switching to a channel that is from the channels used by noise sources  60  and  62  even though it may be the same channel used by noise source  64 . 
     Reversing the primary direction of flow of data may change the method of achieving improved data throughput. In another embodiment, referring to  FIG. 13 , the primary directional of data flow, arrow  72 , is from wireless cell  10  to client  18 . Following the methods of analysis presented above, only the equations that estimate the SNR are given. The SNR of the signal from wireless  10  to the noise of noise source  62  as received by client  18  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         2 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 4 
                 ) 
               
             
             ≈ 
             
               6 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The SNR of the signal from wireless  10  to the noise of noise source  64  as received by client  18  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         3 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 9 
                 ) 
               
             
             ≈ 
             
               9.5 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     The SNR of the signal from wireless  10  to the noise of noise source  60  as received by client  18  may be estimated as: 
     
       
         
           
             
               SNR 
               ⁡ 
               
                 ( 
                 
                   
                     @ 
                     client 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               
                 log 
                 ( 
                 
                   
                     
                       ( 
                       
                         5 
                         * 
                         D 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         80 
                       
                       ) 
                     
                     2 
                   
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       80 
                       2 
                     
                   
                 
                 ) 
               
             
             ≈ 
             
               10 
               ⁢ 
               
                   
               
               ⁢ 
               log 
               ⁢ 
               
                   
               
               ⁢ 
               
                 ( 
                 25 
                 ) 
               
             
             ≈ 
             
               14 
               ⁢ 
               
                   
               
               ⁢ 
               dB 
             
           
         
       
     
     Based on the estimates of the above three equations, for the embodiment shown in  FIG. 13 , wireless cell  10  and/or client  18  may improve data throughput by taking any action that will reduce interference first from noise source  62 , next from noise source  64 , and followed by noise source  60 . 
     In another embodiment, referring to  FIG. 14 , wireless cell  10  and client  18  have omni-directional antennas. Wireless cell  10  is an I.E.E.E. 802.11a/b/g compliant access point. Client  18  is an I.E.E.E. 802.11a/b/g compliant client, for example, a mobile computer. Noise sources  60 ,  62 , and  64  each use a different 802.11a/b/g minimally interfering channel, for example, channel  1 , channel  6 , and channel  11  respectively. Because wireless cell  10  and client  18  have omni-directional antennas both receive noise signals from each noise source  60 - 64 . Highest throughput may be achieved when wireless cell  10  and client  18  communicate using the channel with the least amount of interference and/or highest SNR for the primary direction of data flow. In this embodiment, the primary direction of data flow is from client  18  to wireless cell  10 . Noise source  60  lies farther from wireless cell  10  than noise sources  62  and  64 , thus data throughput may be increased when wireless cell  10  and client  18  communicate using the channel  1  as opposed to channels  6  or  11 . Changing the direction of data flow changes the channel that may provide the highest data throughput. Referring the  FIG. 15 , wireless cell  10  communicates with client  18  with a primary data flow from wireless cell  10  to client  18 . Noise sources  60 ,  62 , and  64  are assigned channel  1 , channel  6 , and channel  11  respectively. Noise sources  62  and  64  are equidistance from client  18  and both are farther away from client  18  than noise source  60 , thus for the primary direction of data flow, data throughput may be increased when wireless cell  10  and client  18  use either channel  6  or  11 . Using directional antennas for the embodiments of  FIGS. 14 and 15  may also improve SNR and data throughput, but may require different channel assignments. Directional antennas may alter which noise source provides the most interference for a given primary direction of data flow. Channel assignments may also be made in systems using directional antennas to reduce the interference from the nearest noise sources with respect to the primary direction of data flow. Channel assignments and/or primary direction of data flow are not required to be static. When the primary direction of data flow changes, channel assignments may also change to a configuration that provides an improved SNR and/or data throughput for the new primary direction of data flow. Detecting environmental effects and system operation such as, for example, the primary direction of data flow, interference from noise sources, SNR, channels of noise sources, data throughput and signal strengths may be accomplished in any manner. 
     Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the exemplary embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described exemplary embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein 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.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, no element described herein is required for the practice of the invention unless expressly described as “essential” or “critical.”