Abstract:
Systems and methods for improving data throughput in an interference-rich wireless environment are described herein. Some illustrative embodiments include a method including receiving a modulated radio frequency (RF) signal including a message packet, identifying a preamble of the message packet generating a correlated preamble by combining the message packet preamble with a correlation sequence corresponding to an expected preamble, determining a characteristic of a correlated signal representing the correlated preamble, comparing the determined characteristic of the correlated signal to a first threshold value, and discarding the message packet if the determined characteristic of the correlated signal is below the first threshold value.

Description:
BACKGROUND 
       [0001]    The proliferation of wireless communication devices (e.g., WiFi enabled computers and cellular telephones) has brought with it a corresponding growth in the amount of interference that such devices create for each. This growth in sources of interference, when coupled with an increase in the quality and sensitivity of wireless receivers, can result in a decrease in the performance of a wireless communication device. The decrease in performance is due to the fact that the device is being bombarded with messages which must be identified as destined for the device and processed, or identified as messages not destined for the device and discarded. The process of discriminating between messages takes time and processing resources. As a result, the device may fail to identify and process a message destined for the device while determining that another message is not destined for the device, may discard a message destine for the device when a message from a closer, stronger sources is received, or may delay transmitting a packet from the device while determining whether a message is destined for the device. The time spent by a device processing messages that are not destined for the device can be significant in interference-rich wireless environments, where large numbers of devices and access points may be operating simultaneously. 
       SUMMARY 
       [0002]    Systems and methods for improving data throughput in an interference-rich wireless environment are described herein. Some illustrative embodiments include a method including receiving a modulated radio frequency (RF) signal including a message packet, identifying a preamble of the message packet generating a correlated preamble by combining the message packet preamble with a correlation sequence corresponding to an expected preamble, determining a characteristic of a correlated signal representing the correlated preamble, comparing the determined characteristic of the correlated signal to a first threshold value, and discarding the message packet if the determined characteristic of the correlated signal is below the first threshold value. 
         [0003]    Other illustrative embodiments include a wireless communication system that includes a receiver configured to receive a radio frequency (RF) signal including a message packet (the message packet including a preamble), a correlator coupled to the receiver and configured to combine the received preamble with a correlation sequence associated with an expected preamble, and an amplifier coupled to the correlator that generates a sample signal (the voltage of which is proportional to the power of a correlator signal output by the correlator). The message packet is not processed further by the wireless communication system if the sample voltage is below a first threshold value. 
         [0004]    Yet further illustrative embodiments include a computer-readable medium comprising software that causes a processor to receive a modulated radio frequency (RF) signal comprising a message packet, identify a preamble of the message packet, generate a correlated preamble by combining the message packet preamble with a correlation sequence corresponding to an expected preamble, determine a characteristic of a correlated signal representing the correlated preamble, compare the determined characteristic of the correlated signal to a first threshold value, and discard the message packet if the determined characteristic of the correlated signal is below the first threshold value. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    For a detailed description of illustrative embodiments of the invention, reference will now be made to the accompanying drawings in which: 
           [0006]      FIG. 1  shows a laptop computer communicating with one of two of wireless access points, in accordance with at least some illustrative embodiments; 
           [0007]      FIG. 2  shows an example of the structure of a wireless message, in accordance with at least some illustrative embodiments; 
           [0008]      FIG. 3A  shows an example of a system configuration, suitable for use as a the laptop computer of  FIG. 1 , in accordance with at least some illustrative embodiments; 
           [0009]      FIG. 3B  shows a block diagram of the system configuration of  3 A, in accordance with at least some illustrative embodiments; 
           [0010]      FIG. 4A  shows a block diagram of the receiver of the wireless transceiver of  FIG. 3B , in accordance with at least some illustrative embodiments; 
           [0011]      FIG. 4B  shows a block diagram of a preamble filter that identifies a preamble with a characteristic that is within a range of threshold values, in accordance with at least some illustrative embodiments; 
           [0012]      FIG. 4C  shows a block diagram of a preamble filter that identifies a preamble that is above a threshold value, in accordance with at least some illustrative embodiments; 
           [0013]      FIG. 5  shows a method for filtering a wireless message packet, in accordance with at least some illustrative embodiments; and 
           [0014]      FIG. 6  shows a method for determining threshold values based upon a preamble power level, in accordance with at least some illustrative embodiments. 
       
    
    
     NOTATION AND NOMENCLATURE 
       [0015]    Certain terms are used throughout the following discussion and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including but not limited to . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. Additionally, the term “system” refers to a collection of two or more hardware and/or software components and may be used to refer to an electronic device, such as a wireless communication device, a portion of a wireless communication device, a combination of wireless communication devices, etc. Further, the term “software” includes any executable code capable of running on a processor, regardless of the media used to store the software. Thus, code stored in non-volatile memory, and sometimes referred to as “embedded firmware,” is included within the definition of software 
       DETAILED DESCRIPTION 
       [0016]    The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims, unless otherwise specified. The discussion of any embodiment is meant only to be illustrative of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. 
         [0017]      FIG. 1  shows a laptop computer  100  that wirelessly receives message packets from wireless access points  110  and  120 , in accordance with at least some illustrative embodiments. Wireless access points  110  and  120  each respectively couple to network A ( 112 ) and network B ( 122 ), providing wireless access to each network. While laptop computer  100  may only be communicating with one of these networks (e.g., network A via wireless access point  110 ), laptop computer  100  still continues to receive message packets transmitted by the other wireless access point (e.g., wireless access point  120 ). This is due to the fact that laptop computer  100  is within the communication range limits of both wireless access points (shown by dashed lines  114  and  124  around each access point). 
         [0018]      FIG. 2  shows an example of a wireless message packet  200  received by laptop computer  100 , in accordance with at least some illustrative embodiments. Message packet  200  includes a preamble  210  (used by laptop computer  100  to identify the beginning of a new message packet), a header  220  (used by laptop computer  100  to identify the format of data within the message packet), and message packet data  230 . Preamble  210  includes a synchronization field  212  (used to synchronize wireless receiving circuits within laptop computer  100  to the incoming message packet) and a start frame delimiter (SFD) field  214 , which marks the beginning of a frame defined by header  220  and data  230 . When encoded according to a known wireless communication protocol (e.g., IEEE 802.11b), the format of the preamble, as well as other constraints such as the encoding scheme, spreading sequence, modulation type, center frequency and bandwidth of the wireless message packet are all known in advance. 
         [0019]    By searching for a received message packet with a particular preamble transmitted according to particular constraints, other wireless message packets with non-conforming preambles can be discarded or ignored by laptop computer  100  without having to process the entire message packet. However, if messages are being received by laptop computer  100  from multiple sources (e.g., wireless access points  110  and  120  of  FIG. 1 ), and both are operating using the same preamble transmitted using the same constraints (e.g., the same protocol and channel as defined under the IEEE 802.11b specification), other characteristics may be identified and used by laptop computer  100  to distinguish between preambles (e.g., the power of a signal associated with the preamble of a received message packet), and to thus allow message packets not destined for laptop computer  100  to be ignored or discarded without having to decode and process the rest of the wireless message packet. 
         [0020]      FIGS. 3A and 3B  show an illustrative system configuration  300  suitable for implementing laptop computer  100  of  FIG. 1 . As shown in  FIG. 3A , the illustrative system configuration  300  includes a display  304  and an input device (e.g., a keyboard)  306 . The system configuration  300 , as shown in  FIG. 3B , further includes processing logic  330  (e.g., a microprocessor), non-volatile storage  332 , and volatile storage  334 . Non-volatile storage  332  includes a computer-readable medium such as a flash random access memory (flash RAM), a read-only memory (ROM), a hard disk drive, a floppy disk (e.g., floppy  370 ), a compact disk read-only memory (CD-ROM, e.g., CD-ROM  360 ), as well as combinations of some and/or all such medium. Volatile storage  334  includes a computer-readable medium such as random access memory (RAM). 
         [0021]    The computer-readable media of both non-volatile storage  332  and volatile storage  334  include, for example, software that is executed by processing logic  330  and provides laptop computer  100  with at least some of the functionality described herein. The system configuration  300  also includes a wireless network interface (Wireless Net I/F)  326  that enables the system configuration  300  to transmit information to, and receive information from, a local area network (LAN) and/or a wide area network (WAN) (e.g., networks A and B of  FIG. 1 ). Wireless network interface  326  includes wireless transceiver  400  (described in more detail below) which couples to RF antenna  340 , and transceiver interface (Xcvr I/F)  328  which couples to wireless network interface  326  and bus  320 . A graphics interface (Graphics I/F)  322  couples to the display  304 . A user interacts with the processing system via an input device such as keyboard  306  and/or pointing device (Pointing Dev)  336  (e.g., a mouse), which both couple to a peripheral interface (Peripheral I/F)  324 . The display  304 , keyboard  306  and pointing device  336  together may operate as a user interface. 
         [0022]    System configuration  300  may be a bus-based computer, with the bus  320  interconnecting the various elements shown in  FIG. 3B . The peripheral interface  324  accepts signals from the keyboard  306  and other input devices such as pointing device  336 , and transforms the signals into a form suitable for communication on bus  320 . The graphics interface  322  may include a video card or other suitable display interface that accepts information from the bus  320  and transforms it into a form suitable for the display  304 . Similarly, transceiver interface  328  accepts signals from wireless transceiver  400  and transforms them into a form suitable for communication on bus  320 , and further accepts information from bus  320  and transforms it into a form suitable for wireless transceiver  400 . 
         [0023]    Processing logic  330  gathers information from other system elements, including input data from the peripheral interface  324 , and program instructions and other data from non-volatile storage  332  or volatile storage  334 , or from other systems (e.g., a server used to store and distribute copies of executable code) coupled to a local area network or a wide area network via the wireless network interface  326 . Processing logic  330  executes the program instructions and processes the data accordingly. The program instructions may further configure processing logic  330  to send data to other system elements, such as information presented to the user via the graphics interface  322  and display  304 . The wireless network interface  326  enables processing logic  330  to communicate with other systems via a network. Volatile storage  334  may serve as a low-latency temporary store of information for processing logic  330 , and non-volatile storage  332  may serve as a long-term (but higher latency) store of information. 
         [0024]    Processing logic  330 , and hence the system configuration  300  as a whole, operates in accordance with one or more programs stored on non-volatile storage  332  or received via wireless network interface  326 . Processing logic  330  may copy portions of the programs into volatile storage  334  for faster access, and may switch between programs or carry out additional programs in response to user actuation of the input devices. The additional programs may be retrieved or received from other locations via wireless network interface  326 . One or more of these programs executes on system configuration  300 , causing the configuration to perform at least some of the functions of laptop computer  100  as disclosed herein. 
         [0025]      FIG. 4A  shows a receiver within a wireless transceiver  400 , constructed in accordance with at least some illustrative embodiments. Wireless transceiver  400  comprises correlator  402 , which couples to antenna  430 , and from which correlator  402  receives the RF signal that includes the received message packet. Correlator  402  detects the sync field of a message preamble, identifies the incoming signal as representing a message packet preamble and synchronizes the correlator with the incoming signal. Correlator  402  then combines a correlation sequence with the preamble of the incoming message. The correlation sequence corresponds to an expected preamble and when combined with the received signal, which is distributed over the full bandwidth of the transmission channel (e.g., as implemented in spread spectrum transmissions of an IEEE 802.11b signal, or in an ultra wide band (UWB) signal), produces only those portions of the signal that include encoded segments of the message packet. The resulting signal output by the correlator, if the signal and correlation sequence match, is the recreated, original, narrow-band signal representing the message packet, a process sometimes referred to as “de-spreading.” Many such correlators are well known in the art (e.g., see Timothy M. Schmidl and Donald C. Cox,  Robust Frequency Timing Synchronization for OFDM , 45 IEEE Transactions on Communications no. 12, 1613-1621 (December 1997)), and all such correlators are within the scope of the present disclosure. See also U.S. Pat. No. 5,732,113, entitled “Timing and Frequency Synchronization of OFDM signals,” and issued Mar. 24, 1998 to Schmidl et al., hereby incorporated by reference. 
         [0026]    The output node of correlator  402  couples to the input nodes of both demodulator  404  and preamble filter  450 . Demodulator  404  couples to decoder  406  and produces the demodulate Q/I baseband signals. The signal output by decoder  406  is the original, digital data frame, which is forwarded for further processing (e.g., by software executing on processing logic  330  of  FIG. 3B ). Although the demodulator, decoder and descrambler shown are those used for extracting a baseband signal encoded using a spread spectrum signal modulated using differential quadrature phase shift keying (DQPSK), those of ordinary skill in the art will recognize that other types of encoding, decoding, modulating and demodulating a wireless signal may be used together with the methods and systems described herein, and all such types of encoding, decoding, modulating and demodulating are within the scope of the present disclosure. 
         [0027]    Preamble filter  450  also receives the signal output by correlator  402 .  FIG. 4B  shows an example of preamble filter  450 , constructed in accordance with at least some illustrative embodiments. Switch S 1 , which couples to both the output node of correlator  402  and the input node of amplifier  452 , controls when the correlator output is provided to the input of preamble filter  450 . The closure of switch S 1  is timed to couple the output of correlator  402  to the input of amplifier  452  during the period of time in which a preamble is being received. Switch S 2 -A couples to both the input node of amplifier  452  and ground. The output node of amplifier  452  couples to resistor R 1 , which in turn couples to switch S 2 -B (also coupled to ground), capacitor C 1  (also coupled to ground), the negative input node of comparator  458 , and the positive input node of comparator  460 . When switches S 2 -A and S 2 -B are closed, the circuit is initialized by forcing the input node to amplifier  452 , the negative input node of comparator  458  and the positive input node of comparator  460  to ground. 
         [0028]    When switch S 1  is closed and switches S 2 -A and S 2 -B are both open, the circuit formed by amplifier  452 , resistor R 1  and capacitor C 1  acts as an integrator, and the voltage that develops across capacitor C 1  is proportional to the overall AC power of the received, de-spread preamble. The resulting sampled voltage is compared with a reference voltage generated by upper voltage reference source (Upper V-Ref)  454  using comparator  458 , and also compared with a reference voltage generated by lower voltage reference source (Lower V-Ref)  456  using comparator  460 . In at least some illustrative embodiments, both reference voltage sources are programmable and may be configured, for example, by processing logic  330  of  FIG. 3B . The values used may be based, for example, on values provided by a user of the system, or on values derived from sampled signal values accumulated over time by a system incorporating preamble filter  450 . The output nodes of comparators  458  and  460  couple to the input nodes of AND gate  462 , which provides the Process Message packet signal, indicative of a sampled correlator output signal that is within a power range that corresponds to the voltage range defined by the two reference voltages. 
         [0029]    Although simplified hardware integrator and comparator circuits are shown in the illustrative embodiment of  FIG. 4B , those of ordinary skill in the art will recognize that many other techniques using a variety of hardware designs, software designs and combinations of hardware and software designs may be used to determine and characterize the relative power level of samples of the signal output by a correlator (e.g., see Timothy M. Schmidl and Donald C. Cox,  Robust Frequency Timing Synchronization for OFDM , 45 IEEE Transactions on Communications no. 12, 1613-1621, 1615 (December 1997) (equation 7, used to describe the received energy of a symbol), and all such techniques and designs are within the scope of the present disclosure. Also, although the embodiments described show wireless network interface  326  incorporated within system configuration  300  of  FIG. 3B , wireless interface  326  itself may include a system configuration similar to system configuration  300 , for example, in the form of a system on a chip (SoC). Such an SoC may include the elements shown in  FIG. 3B  (except for wireless  326 ) wherein, for example, software executing on the processing logic allows such an embodiment of wireless network interface  326  to implement the functionality of wireless transceiver  400  in software. 
         [0030]    Continuing to refer to  FIGS. 1 ,  4 A and  4 B, if the output signal from correlator  402  produces a sample voltage across capacitor C 1  that is below the upper reference voltage, but is also above the lower reference voltage, the corresponding received preamble is considered to be a preamble of interest and Process Message Packet signal  463  is asserted. The assertion of the Process Message Packet signal  463  causes the message packet associated with the sampled preamble (represented by Message Packet signal  461 ) to be processed further by laptop computer  100 . If, however, the output signal from correlator  402  produces a sample voltage across capacitor C 1  that is either above the upper reference voltage or below the lower reference voltage, one of the two comparators will cause the output of AND gate  462  to de-assert Process Message Packet signal  463 . The de-assertion of Process Message packet signal  363  causes the message packet associated with the sampled preamble to be ignored and/or discarded, and thus not processed by other logic within laptop computer  100  (e.g., by processing logic  330  of  FIG. 3B ). 
         [0031]    By characterizing the power profile of the preamble of a message packet (e.g., by using multiple samples, integrated over time, of a voltage across components of a known value), wireless transceiver  400  is able to discriminate between message packets transmitted from different sources that otherwise might not be distinguishable based only on the data content and/or format of the preamble. Referring again to the illustrative embodiment of  FIGS. 1 ,  4 A and  4 B, for example, if both wireless access points  110  and  120  are transmitting message packets using the same protocol and transmission frequency (i.e., the same channel), laptop computer  100  will receive packets from both wireless access points. The overall magnitude of the signal received from wireless access point  110  will be higher than the signal received from wireless access point  120 , due to the fact that laptop computer  100  is significantly closer to wireless access point  110 . 
         [0032]    In order to receive and process message packets transmitted by wireless access point  120 , while ignoring and/or discarding message packets from wireless access point  110 , laptop computer  100  is configured such that the upper reference voltage is higher than a sample voltage produced by a correlator output signal corresponding to a preamble of a message packet originating from wireless access point  120 . The lower reference voltage is configured to be lower than a sample voltage produced by a message packet received from wireless access point  120 . At the same time, the values selected for both the upper and lower reference voltages are both lower than the sample voltage produced by a preamble from a message packet transmitted by wireless access point  110 . Thus, when a message packet from wireless access point  120  is received by transceiver  400  of  FIG. 4A , the resulting voltage produced across capacitor C 1  of  FIG. 4B  will be between the values of both reference voltages, producing an indication that the packet needs to be processed further by laptop computer  100 . By contrast, when transceiver  400  of  FIG. 4A  receives a message packet from wireless access point  110 , the voltage produced across capacitor C 1  by the correlator output signal is higher than the upper reference voltage. This causes the de-assertion of Process Message Packet signal  463 , which is an indication that the received message packet should not be processed further by laptop computer  100 . 
         [0033]    The description above illustrate an example of a scenario wherein laptop computer  100  is further away from the wireless access point coupled to the network with which laptop computer  100  was communicating. In an alternative scenario, laptop computer  100  communicates with network A via wireless access point  110 , which is closer to laptop computer  100  than wireless access point  120 . In such a situation, the preamble characterization may be simplified to a single threshold comparison, rather than two comparisons defining a range.  FIG. 4C  shows a simplified version of the preamble filter  400  of  FIG. 4B , in accordance with at least some illustrative embodiments. The filter operates in a manner similar to that described above for preamble filter  400  of  FIG. 4B , except that there is only one comparison with a single reference voltage (generated by lower voltage reference source  456 ). 
         [0034]    A voltage across capacitor C 1  is above the value of the lower voltage reference results in an indication to process the message packet is signaled by comparator  460 . Thus, laptop  100  of  FIG. 1  can be configured to accept message packets from wireless access point  110  while rejecting and/or ignoring message packets from wireless access point  120 . This configuration is achieved by setting the value of lower voltage reference such that message packets originating from wireless access point  110  will produce a sample voltage across capacitor C 1  above the lower reference voltage (and thus will be processed), while message packets originating from wireless access point  120  will produce a sample voltage across capacitor C 1  below the lower reference voltage (and thus will be ignored and/or discarded). 
         [0035]    By characterizing the output of the correlator as described above, a laptop computer incorporating a preamble filter as described in the present disclosure can significantly reduce the number of message packets processed that are not destined for the laptop computer as compared to a laptop computer without such a preamble filter. By reducing the number of processed message packets, a laptop computer that includes the described preamble filter is less likely to miss a message packet destined for the laptop while processing a message packet not destined for the laptop, less likely to abandon processing a message packet destined for the laptop if a message packet from a closer source that is not destined for the laptop is received, and less likely to delay transmission of its own packets as a result of being busy processing message packets not destined for the laptop. 
         [0036]      FIG. 5  shows a method  500  for filtering a wireless message packet, in accordance with at least some illustrative embodiments. After identifying the preamble of a received message packet (block  502 ), and if filtering based upon a minimum correlation threshold value is enabled (block  504 ), the received preamble is combined with a correlation sequence corresponding to an expected preamble (block  506 ), generating a correlated preamble signal. If filtering based upon a minimum correlation threshold value is not enabled (block  504 ), the received message packet is forwarded for processing (block  514 ), ending the method (block  518 ). If the power of the correlated preamble signal (e.g., the AC power of the signal) generated in block  506  is below the minimum correlation threshold value (block  508 ), the received message packet is discarded/ignored (block  516 ), ending the method (block  518 ). 
         [0037]    If the sampled voltage of the correlated preamble signal (which is proportional to the power of the signal) is above the minimum correlation threshold value (block  508 ), if filtering based upon a maximum correlation threshold value is enabled (block  510 ), and if the sampled voltage of the correlated preamble signal is not greater than the maximum threshold value (block  512 ), the message packet is considered to be within the power tolerance associated with packets destined for the system receiving the message packet. The received message packet is forwarded for processing (block  514 ), ending the method (block  518 ). If filtering based upon a maximum threshold is not enabled (block  510 ) the message packet is forwarded for processing (block  514 ) since the power of the correlated preamble signal has already been identified as exceeding the minimum threshold value, and the method ends (block  518 ). If the sampled voltage of the correlated preamble signal is greater than the maximum threshold value (block  512 ), the message packet is discarded/ignored (block  516 ), ending the method (block  518 ). 
         [0038]      FIG. 6  shows a method  600  for determining correlation threshold values, in accordance with at least some illustrative embodiments. After a message packet is identified as destined for the system receiving the message packet (block  602 ), a power level (e.g., an AC power level) associated with a signal representing the correlated preamble of the received message packet is determined (block  604 ). A voltage level is derived from the determined power level, associated with the preamble of the received message, and the derived voltage level is used to determine and set a minimum correlation threshold value, and filtering of message packet preambles based upon the lower correlation threshold value is enabled (block  606 ). In at least some illustrative embodiments the minimum correlation threshold value is determined by subtracting a fixed value from the derived voltage level. Similarly, the derived voltage level is also used to determine and set a maximum correlation threshold value, and filtering of message packet preambles based upon the maximum correlation threshold value is enabled (block  608 ), completing the method (block  610 ). In at least some illustrative embodiments the upper correlation threshold value is determined by adding a fixed value to the derived voltage level. 
         [0039]    The method  600  may be used to set minimum and maximum threshold levels at different times during the operation of a system performing the method, and in response to various changes in operating conditions. Thus, for example, the threshold levels may be set upon initially establishing communication with a wireless access point, at some point after initially establishing communication with a wireless access point (allowing time to statistically characterize multiple received preambles of packets received from the wireless access point of interest), or after detecting a change in the characteristics of a received signal (e.g., an increase or decrease in the power level of a correlated preamble of interest due to a relocation of the system performing the method). Further, responses to changes in the power of a correlated preamble may include, for example, disabling minimum/maximum threshold filtering, progressively shifting the thresholds (e.g., decreasing the minimum and/or increasing the maximum) until a lost signal is re-acquired), or a combination of shifting and disabling (e.g., shifting twice and then temporarily disabling filtering if the signal is not re-acquired after the second shift). Also, in at least some illustrative embodiments only one threshold value may be used (e.g., only a minimum threshold value), while in other illustrative embodiments more than two thresholds may be used (e.g., four thresholds defining two correlated preamble power ranges). Many other criteria for determining when to set the thresholds, techniques for selectively changing the threshold values, and numbers and combinations of threshold values will become apparent to those of ordinary skill in the art, and all such setting criteria, changing techniques, numbers of thresholds and combinations of thresholds are within the scope of the present disclosure. 
         [0040]    The above disclosure is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, although the embodiments described in the present disclosure include wireless communication devices used within the context of wireless data networks, other illustrative embodiments may include peer-to-peer wireless communication devices (e.g., Bluetooth-enabled devices). Also, although the embodiments of the present disclosure are described within the context of a laptop computer, other illustrative embodiments include other types of personal computers, as well as other types of wireless communication devices such as cellular telephones, WiFi enabled personal digital assistants (PDAs), and wireless peripheral devices (e.g., wireless keyboards, mice, and headphones). Further, although the illustrative embodiments described herein identify message packets of interest using the power of the correlated signal as the characteristic that is compared against one or more threshold values, other characteristics may be used in a similar manner, and all such characteristics are within the scope of the present disclosure. Additionally, although the preamble filter of the illustrative embodiments described herein are shown as implemented in hardware, other illustrative embodiments may include a preamble filter implemented at least in part in software, either by the processing logic shown in the illustrative embodiments described herein, or by separate processing logic. It is intended that the following claims be interpreted to embrace all such variations and modifications.