KR101005708B1 - Dynamic noise floors in a wireless device - Google Patents

Abstract

Wireless devices configured to support wireless networking protocols utilize signal processing techniques that can mitigate the effects of jammer signals. For example, if the measurement power associated with a digital sample of a received wireless signal is greater than a threshold, the wireless device may determine whether the wireless signal corresponds to a wireless networking packet to be demodulated. If the wireless signal does not correspond to a wireless networking packet to be demodulated, the wireless device may adjust the threshold such that the power associated with the digital sample is less than the threshold. In other words, if the signal is a jammer signal, the wireless device can up-regulate its noise floor such that subsequent reception of the same jammer signal does not trigger demodulation twice.

Description

DYNAMIC NOISE FLOORS IN A WIRELESS DEVICE

The present invention relates to wireless communications, and more particularly to wireless networking.

Wireless networking allows wireless devices to share information and resources via wireless communication. Examples of wireless devices used in wireless networks include laptop or desktop computers, personal digital assistants (PDAs), mobile phones, terminal terminals, data collection devices, consumer electronics, and other portable and non-portables. Wireless computing devices. Many devices that support wireless networking standards can also support other communication standards, such as those commonly used for voice communications.

A set of standards developed to facilitate wireless networking are described in the IEEE 802.11 standards. The original IEEE 802.11 standard provides wireless data transfer rates of 1-2 megabits per second (Mbps) in the 2.4 -2.483 gigahertz (GHz) frequency band (hereafter 2.4 GHz band). However, many extensions to the original IEEE 802.11 standard have been developed to increase wireless data transmission rates.

The IEEE 802.11b standard (802.11 wireless fidelity or 802.11 Wi-Fi in some cases) provides 11 Mbps transmission with fallback to 5.5, 2.0 and 1.0 Mbps within the 2.4 GHz band. The IEEE 802.11g standard is another extension of the IEEE 802.11 standard. The IEEE 802.11g standard uses Orthogonal Frequency Division Multiplexing (OFDM) in the 2.4 GHz frequency band to provide data transmission up to 54 Mbps. The IEEE 802.11g standard also provides backward capability with 802.11b networks. The IEEE 802.11a standard is an extension of the IEEE 802.11 standard that uses OFDM in the 5 GHz frequency band to provide data transmission up to 54 Mbps. Other wireless networking protocols include "Bluetooth protocols" developed by the Bluetooth Special Interest Group. Additional extensions to IEEE 802.11 as well as other WLAN standards will emerge in the future.

One attempt at wireless networking involves the processing of "jammer signals". Jammer signals generally refer to noise signals received by a wireless device that do not correspond to data packets supported by the device. Jammer signals are signals transmitted from other devices operating in accordance with protocols not supported by the wireless device, or signals emitted from microwave ovens, or wireless telephones or any other device emitting electromagnetic radiation. Can be caused by them. In many wireless networking standards, operating frequencies are not regulated, so the presence of jammer signals at operating frequencies is likewise not regulated.

In general, the present invention describes techniques that can mitigate the effects of jammer signals received by a wireless device. Jammer signals generally refer to noise signals received by a wireless device that do not correspond to data packets supported by the device. By reducing the likelihood that the same jammer signal is demodulated by the wireless device at many different times, the performance of the wireless device can be improved. The techniques described herein may be used in wireless networking protocols such as one or more IEEE 802.11 protocols or the like.

In one embodiment, the present invention includes receiving a wireless signal and determining whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with the wireless signal is greater than a threshold. To provide. The method further includes adjusting the threshold so that power associated with the wireless signal is less than a threshold if the wireless signal does not correspond to a wireless networking packet to be demodulated. In other words, when the signal is a jammer signal, the wireless device adjusts its noise floor so that subsequent reception of the same jammer signal does not trigger another demodulation.

Various embodiments may be implemented in software, hardware, firmware, or various combinations thereof. Additional details of various embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

1 is a block diagram illustrating a wireless communication system in which wireless devices may implement one or more techniques described herein.

2 is a block diagram of the example wireless device shown in FIG. 1.

3 is a block diagram of an example power detector that implements dynamic thresholds that are adjusted when jammer signals are present.

4 and 5 are flow diagrams illustrating signal processing techniques that can mitigate the effects of jammer signals in a wireless networking environment.

The present invention describes a wireless device configured to perform certain signal processing tasks associated with wireless networking. More specifically, a wireless device configured to support a wireless networking protocol can use signal processing techniques that can mitigate the effects of jammer signals. Jammer signals refer to noise signals received by a wireless device that do not correspond to data packets supported by the wireless networking protocol. Jammer signals are signals transmitted from other devices operating in accordance with protocols not supported by the wireless device, or signals emitted from microwave ovens, cordless phones or any other device emitting electromagnetic radiation. Can be caused by

For example, if the measurement power associated with the digital sample of the received wireless signal is greater than the threshold, the wireless device can determine whether the wireless signal corresponds to a wireless networking packet to be demodulated. If the wireless signal does not correspond to a wireless networking packet to be demodulated, the wireless device adjusts the threshold such that the power associated with the digital sample is less than the threshold. In other words, if the signal is a jammer signal, the wireless device adjusts its noise floor upward so that successive receptions of the same jammer signal do not trigger demodulation twice.

Once the jammer signal is no longer present, the noise floor can be readjusted to reflect this fact, ie the threshold (s) can be reset. In some embodiments, adjustments to the noise floor may occur with each signal processing cycle, i.e., with each digital sample of the signal. Furthermore, the adjustments can only occur if processing is occurring in certain discrete gain states of the wireless device, for example gain states other than the first gain state with maximum sensitivity. In this way, the performance of the wireless device operating in accordance with the wireless networking protocol can be improved.

1 is a block diagram illustrating a wireless communication system 2 that includes a number of wireless devices 10A-10C collectively referred to as wireless devices 10. The wireless devices 10 can be any portable computing device configured to support wireless networking. Each device may be a personal digital assistant based on a similar operating system environment for, for example, a desktop or portable computer, Palm ^TM , Windows CE, or small portable devices operating in a Windows ^TM , Macintosh ^TM , Unix, or Linux environment. PDAs) or other wireless devices such as mobile wireless telephones, interactive televisions, wireless data terminals, wireless data collection devices, Internet kiosks, home network-equipment devices, wireless servers, and the like.

The wireless devices 10 communicate with each other in the wireless communication system 2 via wireless signals 8A-8D (hereafter wireless signals 8). In particular, the wireless devices 10 can communicate according to a wireless protocol such as, for example, the protocol defined by the wireless networking standard, which is one of the standards in a set of IEEE 802.11 standards. Wireless signals 8 may be transmitted and received between wireless access points 11A and 11B and respective wireless devices 10. The access points 11 may have wired connections with a network 14, such as a LAN, a wide area network, or a global network such as the Internet.

In addition to supporting wireless networking standards, one or more wireless devices 10 in system 2 may also be configured to support one or more voice communication standards. For example, one or more base stations 4 may be voiced such as code division multiple access (CDMA) techniques, frequency division multiple access (FDMA) techniques, time division multiple access (TDMA) techniques, various combined techniques, and the like. Communication technologies may communicate voice data 9 to the wireless device 10A.

As described in more detail below, the wireless devices 10 can be configured to dynamically adjust the noise floors to improve signal reception when jammer signals are present. In particular, power detectors may implement dynamic thresholds for wireless signal detection. For example, if the measurement power associated with the digital sample of the wireless signal is greater than the threshold, the wireless devices 10 enable demodulation components and, for example, peak detection search for the signal. By performing, it can be determined whether the wireless signal corresponds to a wireless networking packet to be demodulated. If the wireless signal does not correspond to a wireless networking packet to be demodulated, the wireless devices 10 can adjust the threshold such that the power associated with the sample of the wireless signal is less than the threshold. In this way, the performance of wireless devices 10 operating in accordance with one or more wireless networking protocols may be improved. In particular, the same jammer signal should not allow demodulation components to be enabled after the threshold is adjusted because the adjusted threshold may compensate for the presence of the jammer signal. In other words, at the dynamic power detection threshold, the wireless device 10 can selectively avoid demodulation of jammer signals, resulting in power savings and reduced computational overhead.

In the following embodiment, many details will be provided in the situation where the wireless device 10 operates in accordance with discrete gain states. Implementation of the abnormal gain states can improve and / or simplify the wireless devices 10 by avoiding the need for analog closed-loop automatic gain control. In one example, the gain state selection process includes processing a received signal in accordance with the first gain state, detecting whether the gain state is too large, reducing the gain state if possible, and whether the reduced gain state is too large. It may involve steps such as detecting, possibly reducing the gain state again. Thus, the gain state selection process may include a series of stepwise decreases (or increases) for each gain state until an appropriate gain state is selected. Dynamic adjustments to the noise floor may only occur in some of the gain states. In either case, the gain state selection process can be performed within the time allotted by the wireless networking standards, and noise floor adjustments, ie adjustments to the threshold (s), to mitigate the problems associated with jammer signals. May occur.

2 is a block diagram illustrating one embodiment of a wireless device 10E. The wireless device 10E includes a receiver 22 connected to a (modulator / demodulator) modem 26. The receiver 22 generally performs signal processing of the received analog signal, while the modem 26 generally performs signal processing of digital values generated from the baseband analog signal. Modem 26 refers to a structure or set of structures that performs modulation, demodulation, or both. In particular, modem 26 may form a digital control unit and may be implemented with one or more dedicated processors, DSP execution software, or the like. The A / D converter 40 is shown to form part of the modem 26, but may alternatively be formed as part of the receiver 22 or as a separate component.

Wireless signals are received by the receiver 22 via the antenna 18. As shown, receiver 22 may include a gain state unit 32 that stores a selected gain state for processing the received signal. The gain state unit 32 may be programmed and commanded as the default to the highest gain state, for example, to ensure that the lowest power signals can be detected and processed. Modem 26 identifies the case where the gain state is too large, and in that case, sends one or more commands to gain state unit 32 to cause gain state unit 32 to reduce the gain state. In general, the selected gain state individually defines one or more amplifiers 33, mixers 34, or other components within receiver 22. Implementation of discrete gain states can simplify and improve the wireless device 10E by avoiding the need for continuous analog closed-loop automatic gain control.

The amplifier 33 scales the received RF signal according to the current gain state and provides the scaled signal to the mixer 34. Mixer 34 receives the RF signal from amplifier 33 and downmixes the signal to baseband (sometimes referred to as a downconversion process). For demodulation used in IEEE 802.11b wireless networks, for example, mixer 34 generates baseband signals for the I- and Q-components of the RF signal, as is known. The I-component is referred to as the in-phase component of the complex waveform, while the Q-component is referred to as the quadrature-phase component of the complex waveform. In both cases, mixer 34 delivers the baseband signal for each I- or Q-component of the complex waveform to coarse DC rejection unit 36.

For example, mixer 34 may implement a frequency synthesizer that uses a local oscillator (LO) of wireless device 10E as a timing reference. Thus, mixer 34 may remove the RF carrier component of the received RF signal to generate baseband signals associated with the received wireless networking packet. If desired, the receiver 22 may include additional components, such as various filters and the like.

The coarse DC removal unit 36 stores values indicating the estimated DC offset associated with the received baseband signal. For this reason, coarse DC cancellation unit 36 can quickly remove DC from the baseband signal associated with the received packet within the time constraints imposed on wireless networking standards. In particular, the coarse DC removal unit 36 can store the DC offset values associated with each gain state. In such a case, the coarse DC removal unit 36 may select an appropriate DC offset value according to the current gain state identified by the gain state unit 32 to remove an appropriate amount of DC from the analog baseband signal. .

After the coarse DC removal unit 36 removes the DC offset in the baseband signals, the baseband signals can be sent to the modem 26 for demodulation. For example, baseband signals may be transmitted from receiver 22 to modem 26 via analog transmission line 31. Receiver 22 and modem 26 may also be coupled together by serial bus 29. Thus, receiver 22 and modem 26 may each include serial bus interfaces 37 and 39 to facilitate data transfer over serial bus 29.

Upon receiving the I-baseband signal and the Q-baseband signal, the modem 26 converts the signals into a digital representation (referred to as a digital baseband signal). In particular, although a larger or smaller A / D converter can be used to generate a digital baseband signal in the form of larger or smaller samples, the analog-to-digital (A / D) converter 40 receives the received analog. Sample the baseband signal and generate a corresponding digital baseband signal in the form of 10-bit digital samples. In other words, the A / D converter 40 may have any desired dynamic range. In some cases, A / D converter 40 delivers the samples to gain control unit 47 and precision DC rejection unit 42. In other embodiments, A / D converter 40 may be a unit that forms part of receiver 22 or is separate from receiver 22 and modem 26.

The gain control unit 47 may perform gain state selection based on the output of the A / D converter 40. The gain control unit 47 can receive digital samples directly from the A / D converter 40 and can select a gain state based on the digital samples. Alternatively, the gain control unit 47 may receive digital values from a digital filter (not shown) that filters the output of the A / D converter 40, in particular for gain state selection purposes. In either case, the output of the A / D converter 40 (direct output or digitally filtered output) can be used by the gain control unit 47 to select the gain state. Alternatively, power detector 44 may be used to define a gain state and may transmit a control signal to gain state unit 32.

In the example shown, if the (direct or filtered) output of A / D converter 40 is above the upper gain state threshold, gain control unit 47 stores gain value stored in gain state unit 32. Other gain states can be selected to reduce the noise, thus reducing the gains of amplifier 33 and / or mixer 34. Similarly, if the output of A / D converter 40 is below the lower gain state threshold, gain control unit 47 may select another gain state to increase the gains stored in gain state unit 32. . Adjustments to the gain states can be transferred from the gain control unit 47 to the gain state unit 32 via the serial bus 29.

In one example, the upper gain state threshold used by gain control unit 37 may correspond to a saturation point of A / D converter 40. In such a case, gain state switching causing a reduction in gain in amplifier 33 and / or mixer 34 may occur when A / D converter 40 is at or near the saturation point. In other cases, the upper gain state threshold may be selected to correspond to a point below the saturation point of the A / D converter 40 that may further help the wireless device 10E process jammer signals.

Precision DC rejection unit 42 also receives the output of A / D converter 40 and executes a DC rejection loop to remove residual DC from the digital baseband signal. In addition, the precision DC cancellation unit 42 is configured to remove the residual DC offset associated with the baseband signal in the current gain state, and to receive the coarse DC removal unit 36 after received packets have been processed in the gain state. A coarse DC estimator may be included to update the coarse DC removal unit 36 via the serial bus 29 to have a more appropriate DC removed by it. After removing residual DC from the digital baseband signal, precision DC removal unit 42 may pass the digital baseband signals to power detector 44 and digital voltage gain amplifier (DVGA) 46.

The power detector 44 may include a plurality of power detection modules each performing power detection according to different algorithms. In particular, the high power detection module may perform power detection according to the first algorithm to quickly identify whether a high power signal is present, and the low power module may detect power according to the second algorithm to identify whether a low power signal is present. Can be performed.

When the power detector 44 detects a signal, the detector may enable demodulation components such as the DVGA 46 and the demodulation unit 48 so that wireless networking packets can occur. In other words, demodulation components such as DVGA 46 and demodulation unit 48 are designed for power conservation until power detector 44 detects a signal that may be a wireless networking packet supported by wireless device 10E. Can be disabled.

The power detector 44 may implement one or more dynamic thresholds that are automatically adjusted when jammer signals are present. In particular, after enabling the DVGA 46 and the demodulation unit 48, if the peak detection search for the signal fails, the power detector 44 may assume that the signal is not a wireless networking packet requiring demodulation. have. If the demodulation components of the modem 26 determine that the signal is not a wireless networking packet, the thresholds of the power detector 44 may be automatically adjusted up so that successive signals at the same power level are not called for the demodulation components. have. In this case, the signal may be a jammer signal. Accordingly, power detector 44 may adjust the thresholds of the detector such that the same jammer signal does not cause additional demodulation cycles when the jammer signal is being received continuously. This demodulation avoidance of jammer signals can conserve power and also cause the wireless device to respond to wireless packets at a higher power level than jammer, which is consistent after the wireless device continuously determines that the signal is not a wireless packet. It does not reset.

As mentioned, similar techniques may be implemented when a single detection module is implemented, but the power detector 44 may implement low power and high power detection modules. The low power detection module may be a slower and more precise detection module than the high power detection module. Additional precision of the low power detection module may improve power detection, particularly for low power signals, to better ensure that packets received at low power are not lost by the wireless device 10E.

In some embodiments, control signals adjusting gain state unit 32 operate in accordance with power detector 44, rather than gain state unit 47 directly receiving the output from A / D converter 40. May be transmitted from a specific gain control unit. In such a case, the use of dual power detectors allows faster high power detectors to quickly detect power levels causing gain state changes, while slower low power detectors gain when the signal is detected only by the low power detector. This may be more accurate because no state reductions are needed. Also, in this case, multiple thresholds may be used by the high power detector, for example to call one threshold value, and a gain state change to invoke gain state changes, but in the current gain state a high power signal. Another threshold may be used that indicates the presence of.

In some implementations, the wireless device 10E can integrate multiple antennas. In this case, the antenna may also be selected to improve signal reception using the output of the power detector 44 or the gain control unit 47. For example, different antennas may be selected depending on the power level of the received signal as indicated by the output of A / D converter 40 or the output of power detector 44. In some cases, other antennas may be selected depending on whether the high power detection module or low power detection module in power detector 44 issues a power detection indicator. In other cases, other antennas may be selected based on the applicable gain state.

When enabled by the power detector 44, the DVGA 46 can be used to scale the digital baseband signal by amplifying or attenuating digital samples. In particular, DVGA 46 may perform the remaining gain adjustments on the digital baseband signal. After scaling the digital baseband signal, DVGA 46 passes the scaled digital baseband signal to demodulation unit 48 for demodulation. Demodulation unit 48 may perform a peak detection search to identify whether the signal is a wireless networking packet supported by wireless device 10E, and to ensure that the signal has sufficient strength to enable efficient demodulation. Can be. For example, in an IEEE 802.11 situation, peak detection may include correlating an incoming data stream to a known Barker sequence, and comparing the correlation result to a predefined threshold. If peak detection fails, demodulation unit 48 may be disabled, and the thresholds within power detector 44 are adjusted according to the previous signal strength of the jammer signal. On the other hand, when peak detection indicates that the signal is a wireless networking packet with sufficient strength, demodulation unit 48 proceeds to demodulate the packet, and thresholds within power detector 44 may be reset following such demodulation. have.

3 is a more detailed block diagram of an exemplary implementation of power detector 44. As shown, power detector 44 executes a number of power detection modules 50, 60. In the example shown, the present invention is not limited thereto, but two power detection modules are implemented. In other words, for some wireless networking standards, such as those not yet developed, additional power detection modules may be useful. In addition, the single power detection module may also execute the step of dynamically adjusting the thresholds as described herein.

In the illustrated example of FIG. 3, the power detector 44 includes a high power detection module 50 and a low power detection module 60. I-baseband samples and Q-baseband samples are received from the precision DC cancellation unit 42 at inputs 51, 52, 61 and 62, for example according to the 802.11b standard. In one implementation, only a subset of the least significant bits (LSBs) may be received by the low power detection module 60 at inputs 61 and 62. Low power signals will have zero values for the most significant bits. Thus, by providing only some of the least significant bits at the inputs 61 and 62, the components of the low power detection module 60 can be simplified.

In high power detection module 50, power estimator 54 uses I technique at inputs 51 and 52 using one technique such as, for example, the sum of the magnitudes of the I-baseband component and the Q-baseband component. Estimate the power contained in the baseband component and the Q-baseband component. The sum is provided to a fast integrator 56 capable of executing an infinite impulse response (IRR), for example with a tap weight value of 0.75. The fast integrator 56 integrates over a smaller efficient window than the slow integrator 66 in the low power detection module 50. However, the actual speed of the integrators may vary from implementation to implementation.

For example, fast integrator 56 may integrate baseband samples over a sliding effective window of eight samples, or more or less samples, by varying the tap weight value as needed. By integrating over a relatively small window, fast integrator 56 can generate power estimates very quickly. Fewer samples reduce accuracy, but more samples increase the integration time. For example, the integration time of two samples received at a rate of 22 MHz is approximately 0.09 ms, the integration time of four samples received at a rate of 22 MHz is 0.18 ms, and the integration of eight samples received at a rate of 22 MHz The time may be 0.36 ms and is similar below.

The low power detection module 60 operates in parallel with the high power detection module 50 to detect low power signals. The low power detection module 60 may operate slower with higher accuracy than the high power detector 50. Thus, the low power detection module 60 may integrate over a much larger effective window than the high power detection module 60 when calculating power estimates, thus the term slow integrator 56. However, it should be noted that the terms slow integrator 66 and fast integrator 56 are relative terms describing the size of the sliding window of the integrators relative to each other. The actual speed of the integration can be very different for different implementations.

In the low power detection module 60, the power estimator 64 may use other techniques than the high power detection module 50, such as, for example, the sum of squares of the I-baseband components and the Q-baseband components. Estimate the power included in the I-baseband component and the Q-baseband component at inputs 61 and 62. However, in some cases, the same summation technique can be used for different power detection modules that integrate across different sliding windows. In the example shown, the sum of squares is provided to the slow integrator 66, which may implement an infinite impulse response (IIR) filter having a tap weight value of, for example, 0.9921875 or 0.984375. The slow integrator 66 integrates over a larger integration time, ie, a larger effective window, than the fast integrator 56 in the high power detection module 50. However, as mentioned above, the actual speed of the integrators may vary depending on the implementation.

For example, the slow integrator 66 may integrate baseband samples over a window of 128 samples, 256 samples, or less or larger amounts of samples by varying tap weights as needed. By integrating over a relatively large effective window, the slow integrator 60 can generate very accurate power estimates. For example, the integration time of 64 samples received at a rate of 22 MHz may be approximately 2.9 ms, the integration time of 128 samples received at a rate of 22 MHz may be 5.8 ms and 256 received at a rate of 22 MHz The integration time of the two samples may be 11.6 ms and the integration time of the 512 samples received at a rate of 22 MHz may be 23.3 ms, which is similar below.

Logic may be coupled to the first and second power detection modules to ensure that no second power indicator is generated when the first power indicator is generated. For example, timer unit 67 may be added to low power detection module 60 to ensure that low power indicators are not generated prior to high power indicators. An AND gate 70 with an inverting input entering from the output of the high threshold comparison unit 58 may be used to ensure that no low power indicator is produced when a high power indicator is generated. In other words, the timer unit 67 may add a delay that causes the power detection module 60 to verify that the high threshold comparison unit 58 does not produce a high power indicator. The AND gate 70 then determines that the low power threshold comparison unit 68 exceeds the programmed lower limit threshold, and the high power threshold comparison unit 58 has programmed the average estimated power. Only when it is determined that the upper threshold is not exceeded, a low power indicator is generated. Thus, if a high power indicator is generated, no low power indicator will be generated. In addition, if power detector 44 is used to effect gain state changes, high power detector 50 may include a number of threshold comparison units, for example to determine if gain state changes occur. One unit using the state threshold and another unit using different thresholds to determine if the signal is present in the current gain state can be used.

The power estimates of the respective digital samples sent to the integrators 56, 66 are each thresholded by the high threshold comparison unit 58 and the low threshold comparison unit 68 to determine whether a signal to be demodulated exists. Can be compared to values. However, as mentioned above, in some cases jammer signals may cause the received power to exceed one of the thresholds. For this reason, each of the high power detection module 50 and the low power detection module has a threshold value for dynamically adjusting or controlling the threshold values used by the comparison units 58 and 68 for the purpose of identifying the packets to be demodulated. Units 59 and 69 can be executed.

Threshold units 59, 69 receive average power measurements from integrators 56, 66, and generate an upper and lower threshold for average power estimates. In one implementation, the individual values of the received samples are used by threshold units 59 and 69 until four samples are received and integrated by integrators 56 and 66, and then the average power is four Defined by threshold units 59 and 69 for the sliding window of the sample. Thereafter, when integrators 56, 66 receive eight samples, threshold units 59, 69 may define an average power using a sliding window of eight samples. In this case, the upper and lower thresholds may also change so that the thresholds are closer to the mean value when more samples are available. In other words, if one sample is used to define thresholds, threshold units 59 and 69 may define thresholds as being +/− X of the sample. If four samples are available and used to define thresholds, threshold units 59 and 69 can define thresholds as being +/− Y of the mean, where Y is less than X. Similarly, if eight samples are available and used to define thresholds, threshold units 59 and 69 can define thresholds as +/- Z of the mean, where Z is less than Y. In the low power detector 60, a much larger number of samples can be used to define the mean values, because a larger number of samples are available.

In either case, by adjusting the thresholds based on the power of the received signals, the same jammer signal should not cause demodulation at multiple times. If the wireless packet is identified and demodulated, the thresholds can be reset. However, if the jammer signal causes demodulation to start a peak detection search, for example, then the thresholds will remain valid and will be adjusted by the strength of the jammer signal. Thus, the likelihood that the same jammer will cause different demodulations can be significantly reduced because the first occurrence of jammers will cause the threshold to increase. Furthermore, if the threshold is adjusted because of the presence of the jammer signal, the wireless networking packet will still be received and demodulated if it has sufficient power above the jammer signal.

If the power of the received signal sample falls below the lower threshold, the thresholds can be reset, e.g., any jammer signal that was present when the power of the received power sample dropped below the lower thresholds. This is because they are unlikely to exist anymore. Thus, resetting the thresholds when the power of the received signal sample drops below the lower threshold may improve responsiveness to the disappearance of jammer signals. For example, resetting the thresholds even allows a relatively low power 802.11b packet to be received and demodulated between successive generations of relatively high power Bluetooth packets, the Bluetooth packets being sent to a device that supports 802.11b. May be jammer signals.

4 is a flow diagram illustrating a signal processing technique that may be executed by one or more wireless devices 10 (see FIG. 1), such as wireless device 10E (see FIG. 2). The technique is a relatively complex state machine that controls and coordinates the logic circuits of the modem 26, the various block components of the modem 26 as shown in FIG. 2, or the performance of the modem 36. It can be executed substantially by a state machine.

As shown in FIG. 4, the wireless device 10E is initialized in gain state 1 (10), which may define the highest gains, that is, the best sensitivity. The gain state unit 32 stores the gain state and provides gain control signals to the mixer 34 and the coarse DC rejection unit 36 consistent with the current gain state. The wireless device 10E then performs DC settling 102 within the time constraints imposed by the wireless networking protocol. In particular, the coarse DC removal unit 36 may select an appropriate DC offset value in accordance with the current gain state identified by the gain state unit 32 to remove the appropriate amount of DC from the baseband signal. The precision DC rejection unit 42 also receives the output of the A / D converter 40 and executes a DC rejection loop to remove the remaining DC from the digital baseband signal. In addition, precision DC cancellation unit 42 may remove the remaining DC offset associated with the baseband signal in the current gain state, such that the successively received packets processed in that gain state are inaccurate DC removal unit 36. The coarse DC removal unit 36 can be updated via the serial bus 29 to have a more appropriate DC than removed by. After removing the remaining DC from the digital baseband signal, precision DC removal unit 42 may pass the digital baseband signals to power detector 44 and digital voltage gain amplifier (DVGA) 46.

The power detector 44 integrates in gain state 1 103 and powers as described herein to determine 104 whether a wireless networking signal has been received, for example by comparing digital samples with thresholds. Perform detection. If the power of the sample is greater than the threshold, there is a signal (“yes” branch of 104). If no gain state change is incurred at this point (the “no” branch of 106), then the power detector 44 may cause demodulation components such as DVGA 46 and demodulation unit 48 to peak for signal 107. Allow detection. If peak detection is successful (“yes” branch of 107) indicating that a wireless networking packet has been received, demodulation unit 48 demodulates signal 105, and wireless device 10E returns gain state 1 101. Return to. If peak detection fails at that point (“no” branch of 107), the wireless device 10E continues to integrate in gain state 1 103. In the example embodiment of FIG. 4, adjustments to thresholds may be avoided in gain state 1 because gain state 1 represents the most sensitive gain state. However, in other embodiments, adjustment to thresholds may also occur in gain state 1, as described in more detail below with reference to gain state 2 and gain state 3.

During the integration in gain state 1 103 and signal detection 104, if wireless device 10E determines that a gain state change is needed (“yes” branch of 106), the wireless device is in gain state 108. To change. In particular, the wireless device 10E may change from gain state 1 with the highest gains to gain state 2 with reduced gains compared to gain state 1. To make these gain state determinations, the wireless device 10E uses a gain state based on the output of the A / D converter 40, for example, reducing the gain when the A / D converter 40 is saturated. The gain state control unit 47 may execute to make decisions. Alternatively, gain state determinations may be made by a gain state unit operating in accordance with power detector 44 rather than gain state unit 47 directly receiving an output to A / D converter 40. In this case, the use of dual power detectors allows the faster high power detector 50 to quickly detect power levels that will result in gain state changes, while the slower low power detector 60 may signal the lower power detector 60. It may be more accurate because gain state reductions will not be needed if detected only by. Also in this case, the multiple threshold units have a high power detector 50, for example one which results in gain state changes and the other one which does not cause a gain state change but indicates the presence of a high power signal in the current gain state. It can be used by.

Following the gain state change 108, the wireless device 10E again performs DC settling (109). In particular, the coarse DC removal unit 36 selects an appropriate DC offset value according to the new gain state, and the precision DC removal unit 42 executes a DC removal loop to remove the remaining DC from the digital baseband signal. In addition, the precision DC removal unit 42 removes the residual DC offset associated with the baseband signal in the new gain state and updates the coarse DC removal unit 36.

The power detector 44 performs power detection as described herein to determine 111 whether the wireless networking signal has been received by comparing digital samples, eg, with thresholds. If the power of the sample is greater than the threshold, then there is a signal (“yes” branch of 111). If a signal is present (“yes” branch of 111) and no gain state change is caused (“no” branch of 112), then the power detector 44 is such as DVGA 46 and demodulator unit 48. Demodulation components enable peak detection 114. If peak detection is successful (“yes” branch of 114) to indicate that a wireless networking packet has been received, demodulation unit 48 demodulates signal 105, and wireless device 10E returns gain state 1 (101). Return to). If peak detection at that point fails (the “no” branch of 114), then full demodulation of the signal is not performed. In other words, demodulation beyond the peak detection search is performed only if the peak detection is successful, i.e., the signal is not a jammer signal (" yes " branch of 114).

If peak detection fails and indicates that the detected signal is a jammer signal (“no” branch of 114), noise thresholds are updated 115 in the power detector 44. By updating the noise thresholds, the wireless device 10E can operate more efficiently. In particular, if the thresholds in power detector 44 are adjusted such that the power associated with the wireless signal is less than the threshold, the same jammer signal will prevent demodulation components from being enabled. As mentioned, this results in reduced power conservation and computational overhead in the wireless device 10E.

If the signal is not detected in the current gain state 110 (the “no” branch of 111) and the power level of the digital sample of the signal falls below the lower threshold (“yes” branch of 113), then wireless The device reinitializes to gain state 1 and the process begins again. In this case, the jammer signal that was present may disappear or expire. Thus, returning the wireless device to the maximum sensitivity state of the gain state value 101 in response to a digital sample of the signal falling below the lower threshold (" yes " branch of 113) may result in responsiveness to removal of jammer signals. Can provide.

If the wireless device detects a signal (111), but determines that another gain state change is required (“yes” branch of 112), then the process of blocks 108-115 is in gain state 3, possibly in a gain state. 4 and so on. However, an implementation with three possible gain states may be sufficient for wireless networking applications.

Importantly, following detection of the jammer signal, the thresholds are updated 115 (“no” branch of 114). Thus, because the threshold will be set so that the jammer signal does not go above the threshold, the same jammer signal will not allow demodulation components to be enabled. The power detector 44 can define dynamic upper and lower thresholds, which define how much power is required to enable demodulation components, and the lower threshold Defines when the wireless device 10E should be reset to gain state 1. Resetting the wireless device 10E when the power of the received signal sample drops below the lower threshold may improve responsiveness to the disappearance of jammer signals, even with relatively low power 802.11b packets being continuous and Received and demodulated between occurrences of relatively high power Bluetooth packets, which will be jammer signals for devices that support only 802.11b.

FIG. 5 is another flow diagram illustrating a signal processing technique that may be executed by one or more wireless devices 10 (see FIG. 1), such as wireless device 10E (see FIG. 2). In particular, FIG. 5 illustrates techniques for adjusting thresholds in the power detector to improve signal processing in the presence of jammer signals. In some embodiments, the technique of FIG. 5 may be implemented in a wireless device following the selection of the desired gain state for processing the received signal.

As shown in FIG. 5, the power detector 44 measures 201 the power of the received signal, such as measuring the power of one or more samples of the signal. The power detector 44 also determines 202 the average power of the received signal, such as by integrating over the sliding window of samples. In some cases, the average power may be chosen to correspond to the power of a single sample until a selected number of samples is available to calculate the average. The power detector 44 then selects the thresholds based on the average power during the previous cycle (203). For example, threshold units 59, 69 of power detection modules 50, 60 may receive average power measurements from integrators 56, 66, and an upper and lower limit for average power estimates. Generate a threshold. As mentioned, the individual values of the received samples can be used as averages, for example, until a number of samples, four samples, have been received and integrated by the integrators 56, 66. After four samples have been received, the average power may be defined by threshold units 59, 69 for the sliding window of four samples. In addition, when integrators 56 and 66 receive eight samples, threshold units 59 and 69 can define an average power using a sliding window of eight samples, which is similar below.

In addition, the upper and lower thresholds may change so that the thresholds are closer to the mean when more samples are available. In other words, if one sample is used to define thresholds, threshold units 59 and 69 may define the threshold as being +/- X of the sample. When four samples are available and used to define thresholds, threshold units 59 and 69 may define thresholds as being +/− X of the mean, where Y is less than X. Likewise, when eight samples are available and used to define thresholds, threshold units 59 and 69 can define thresholds as being +/- Z of the mean, where Z is less than Y. .

If the current digital sample is stronger than the current upper threshold (" Yes " branch of 204), then the power detector 44 is supported by the wireless networking packet to which the signal is to be demodulated, i.e., the protocol of the wireless device 10E. Enable demodulation components 205 to determine if they are packets. To determine whether the signal is a wireless networking packet to be demodulated, demodulation unit 48 performs a peak detection search algorithm on the signal as known (206). For example, the process of performing a peak detection search includes applying a correlation function to the signal to determine if the signal has a sufficient signal strength and follows a waveform that conforms to the protocol to be used. In this way, peak detection 206 may be used to determine whether the received signal corresponds to a packet to be demodulated. If so (“yes” branch of 207), the wireless device demodulates packet 208. Following demodulation 208 of the packet, the thresholds of power detector 44 may be reset 209 to the noise floor such that the wireless device has maximum sensitivity.

If the current digital sample is not stronger than the current upper threshold (“no” branch of 204) and is not weaker than the current lower threshold (“no” branch of 210), steps 201-203. ) Is repeated for the next sample. In this way, the thresholds are continuously adjusted for the average power of the received samples. The average power of the previous cycle is used to define the threshold for the next cycle.

Also, following enabling 205 of demodulation components, if peak detection fails at step 206 indicating that the signal does not correspond to a wireless networking packet to be demodulated (“No” branch of 207), The process of steps 201-203 is repeated for the next sample. In this case, the received signal that resulted in the enabling of the demodulation components was a jammer signal. Importantly, during the next cycle, the same jammer signal may not be stronger than the current upper limit threshold since the thresholds are defined based on the average power of the previous cycle (“No” branch of 204). Since the jammer signal was present during the previous cycle, the signal strength will increase the average signal strength, thereby increasing the thresholds for subsequent cycles, and the samples corresponding to the same jammer signal are present thresholds in subsequent cycles. We do not become stronger than (204). Thus, the same jammer signal will not cause the auxiliary components to be enabled 205 in subsequent cycles. Thus, this processing technique may improve signal processing in the presence of jammer signals, which typically occur in the unregulated frequency bands associated with wireless networking protocols.

If the current sample is weaker than the current lower threshold (" yes " branch of 210), the thresholds are reset 209 before repeating the process. In this case, if the jammer signal was present but disappeared, resetting the thresholds 209 causes the wireless device 10E to respond to these cases. When the power of the received signal sample falls below the lower threshold (“yes” branch of 210), resetting the thresholds 209 may, for example, between occurrences of consecutive relatively high power Bluetooth packets. Allows relatively low power 802.11b packets to be received and demodulated, where the Bluetooth packets may be jammer signals for a device that supports only 802.11b.

Various techniques for processing wireless packets have been described as being implemented in hardware. Exemplary hardware implementations of modem 26 or similar control units include implementations in a DSP, application specific semiconductor (ASIC), field programmable gate array (FPGA), programmable logic device, specially designed hardware components, or any combination thereof. It may include. In addition, one or more of the techniques described herein may be implemented in part or in whole in software. In such a case, the computer readable medium may store computer readable instructions, such as program code, that may be executed by a processor or a DSP to perform one or more of the techniques described above. For example, computer readable media includes random access memory (RAM), read-only memory (ROM), nonvolatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, and the like. can do. In addition, various other modifications may occur without departing from the spirit and scope of the invention. Accordingly, these and other embodiments are within the scope of the following claims.

Claims (36)

Receiving a wireless signal; Determining whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with the wireless signal is greater than a threshold; And Adjusting the threshold so that the power associated with the wireless signal is less than the threshold if the wireless signal does not correspond to a wireless networking packet to be demodulated. The method of claim 1, Determining whether the wireless signal corresponds to a wireless networking packet to be demodulated determines whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with a digital sample of the wireless signal is greater than the threshold. Comprising the steps of; Adjusting the threshold comprises adjusting the threshold such that power associated with a digital sample of the wireless signal is less than the threshold if the wireless signal does not correspond to a wireless networking packet to be demodulated. The method of claim 2, Adjusting the threshold further includes determining whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with another digital sample of the wireless signal is greater than the adjusted threshold. Way. The method of claim 1, If the wireless signal corresponds to a wireless networking packet to be demodulated, further comprising demodulating the wireless signal. The method of claim 4, wherein Resetting the threshold following demodulation of the wireless signal; And Receiving another wireless signal. The method of claim 1, Adjusting the threshold comprises adjusting the threshold when the wireless signal is a jammer signal. The method of claim 1, And continuously adjusting the threshold in relation to the average power associated with the received wireless signal. The method of claim 1, The threshold is an upper threshold, and the method includes: And continuously adjusting the upper and lower thresholds in relation to the average power associated with the digital samples of the received signal. The method of claim 8, Resetting the upper threshold and the lower threshold when the measured power associated with the digital sample of the wireless signal is less than the adjusted lower threshold. The method of claim 1, Determining whether the wireless signal corresponds to a wireless networking packet to be demodulated includes processing the wireless signal in one of a plurality of gain states and performing a peak detection algorithm on the wireless signal. Including, the method. The method of claim 10, Processing the wireless signal in one of the plurality of gain states comprises adjusting from a first gain state to a second gain state. The method of claim 11, Processing the wireless signal in one of the plurality of gain states further comprises adjusting from the second gain state to a third gain state. Receiving a wireless signal; Processing the wireless signal in one of a plurality of gain states; Measuring an average power level associated with a plurality of digital samples of the wireless signal; Defining an upper limit threshold and a lower limit threshold in relation to the average power level; Determining whether the wireless signal is a wireless networking packet to be demodulated when the power level associated with one sample exceeds the upper threshold; And Adjusting the upper threshold so that the power associated with the one sample is less than the upper threshold if the wireless signal does not correspond to a wireless networking packet to be demodulated. The method of claim 13, Resetting the upper threshold and the lower threshold when the power level associated with the one sample is less than the lower threshold. The method of claim 14, And continuing to define an upper threshold and a lower threshold for an average power level associated with a sliding window of digital samples of the wireless signal. As a wireless device, A receiver for receiving a wireless signal; And Determine whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with the wireless signal is greater than a threshold, and associated with the wireless signal if the wireless signal does not correspond to a wireless networking packet to be demodulated. And a control unit for adjusting the threshold such that power is less than the threshold. The method of claim 16, The wireless device further comprises an analog-to-digital converter for converting the wireless signal into digital samples, The control unit determines whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with the digital sample of the wireless signal is greater than the threshold, and corresponds to the wireless networking packet to be demodulated. Otherwise adjust the threshold such that power associated with a digital sample of the wireless signal is less than the threshold. The method of claim 17, The control unit determines whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with another digital sample of the wireless signal is greater than the adjusted threshold. The method of claim 16, The control unit demodulates the wireless signal when the wireless signal corresponds to a wireless networking packet to be demodulated. The method of claim 19, And the control unit resets the threshold following demodulation of the wireless signal. The method of claim 16, And the control unit continues to adjust the threshold in relation to the average power associated with the received wireless signal. The method of claim 16, The threshold is an upper threshold, and the control unit continuously adjusts the upper and lower thresholds in relation to the average power associated with the digital samples of the received wireless signal. The method of claim 22, And the control unit resets the upper limit threshold and the lower limit threshold when the measured power associated with the digital sample of the radio signal is less than the adjusted lower limit threshold. The method of claim 16, And the control unit determines whether the radio signal corresponds to a radio networking packet to be demodulated by processing the radio signal in one of a plurality of gain states and performing a peak detection algorithm on the radio signal. The method of claim 24, And the control unit processes the wireless signal in one of a plurality of gain states by adjusting from a first gain state to a second gain state. As a wireless device, A receiver for receiving a wireless signal and processing the wireless signal in one of a plurality of gain states; An analog-to-digital converter for converting the wireless signal into digital samples; And Measure an average power level associated with multiple digital samples of the wireless signal, define an upper and lower threshold in relation to the average power level, and the power level associated with one sample exceeds the upper threshold Determine whether the wireless signal is a wireless networking packet to be demodulated, and if the wireless signal does not correspond to a wireless networking packet to be demodulated, the upper threshold such that the power associated with the one sample is less than the upper threshold; And a modem to adjust the value. The method of claim 26, The modem resets the upper threshold and the lower threshold when the power level associated with one sample is less than the lower threshold. The method of claim 26, The modem continues to define the upper and lower thresholds for an average power level associated with a sliding window of digital samples of the wireless signal. As a modem, A power detector for measuring an average power level associated with a plurality of digital samples of a wireless signal and defining an upper threshold value and a lower threshold value in relation to the average power level; And Determines whether the wireless signal is a wireless networking packet to be demodulated when the power level associated with one sample exceeds the upper threshold, and if the wireless signal does not correspond to the wireless networking packet to be demodulated, And a demodulation unit for adjusting the upper threshold so that an associated power is less than the upper threshold, and for demodulating the radio signal when the radio signal is a radio networking packet to be demodulated. 30. The method of claim 29, And the power detector comprises a plurality of power detection modules. 30. The method of claim 29, The modem resets the upper threshold and the lower threshold when the power level associated with the one sample is less than the lower threshold. 30. The method of claim 29, Wherein the modem continues to define an upper and lower threshold for an average power level associated with a sliding window of digital samples of the wireless signal. A computer readable medium comprising program code, the program code causing the wireless device when executed at the wireless device: Determine whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with a received wireless signal is greater than a threshold; And If the wireless signal does not correspond to a wireless networking packet to be demodulated, causing the threshold to be adjusted such that power associated with the wireless signal is less than the threshold. The method of claim 33, wherein The program code causes the wireless device to execute when: Determine whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with the digital sample of the wireless signal is greater than a threshold; And If the wireless signal does not correspond to a wireless networking packet to be demodulated, causing the threshold to be adjusted such that power associated with a digital sample of the wireless signal is less than the threshold. Means for determining whether the wireless signal corresponds to a wireless networking packet to be demodulated when the measured power associated with a received wireless signal is greater than a threshold; And Means for adjusting the threshold such that the power associated with the wireless signal is less than a threshold if the wireless signal does not correspond to a wireless networking packet to be demodulated. 36. The method of claim 35, And means for receiving the wireless signal.

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