Address filtering in a receiver radio frequency front end

Abstract

A radio frequency (RF) front end receives one or more symbols of a first frame transmitted by a transmitter. The RF front end determines that the one or more received symbols are related to one or more address symbols, where each of the one or more address symbols is a time domain signal of a subcarrier transmitted by the transmitter. The RF front end provides the one or more received symbols to a baseband system based on the relation. The baseband system recovers bits of a second frame within the first frame based on the one or more received symbols.

Description

Technical Field

[0001] This disclosure generally relates to address filtering in the receiver radio frequency (RF) front end, and more specifically, to filtering frame addresses in the receiver RF front end. Background Technology

[0002] A wireless system operating according to the IEEE 802.11 standard family of standards includes a transmitter and a receiver. The transmitter transmits frames to the receiver via an air interface. The receiver has a radio frequency (RF) front-end and a baseband system for recovering the bits of the frame provided to the host. The host parses the bits of the frame to determine one or more source frame addresses, which identify the source host that transmitted the frame and the destination host that will receive the frame. If some or all of the source and destination frame addresses do not match predetermined addresses, the host will not process the frame and the frame will be discarded. Summary of the Invention

[0003] In one embodiment, a method is disclosed. The method includes: receiving one or more symbols of a first frame transmitted by a transmitter from a receiver's radio frequency (RF) front end; determining, by the RF front end, that the one or more received symbols are associated with one or more address symbols, wherein each of the one or more address symbols is a time-domain signal of a subcarrier transmitted by the transmitter to cause the receiver to receive a frame address; and providing the one or more received symbols to a baseband system based on the association, wherein the baseband system recovers bits of a second frame within the first frame based on the one or more received symbols. In one embodiment, a plurality of orthogonal subcarriers define the one or more address symbols and the one or more received symbols associated by the RF front end. In another embodiment, the method further includes: receiving, from the baseband system, the one or more address symbols associated with the one or more received symbols. In another embodiment, a host provides an indication of the frame address, and the baseband system generates the one or more address symbols provided to the RF front end to be associated with the one or more received symbols. In another embodiment, providing the one or more received symbols by the RF front end includes: waking the baseband system from a sleep state based on providing the one or more received symbols to the baseband system. In an embodiment, the method further includes: measuring time after receiving a preamble symbol of the one or more symbols; and wherein associating the one or more received symbols with one or more address symbols by the RF front end includes determining, based on the time, that the received symbol is the same as the address symbol. In an embodiment, determining that the one or more received symbols are associated with one or more address symbols includes: associating in-phase and quadrature-phase (IQ) samples of the time-domain signal of the address symbol, wherein the I samples are orthogonal to the Q samples. In an embodiment, the method further includes: the baseband system demodulating the IQ samples of the one or more received symbols to recover the bits of the second frame. In an embodiment, the method further includes: sending an indication to wake up the host; and providing the second frame to the host, wherein the host is unsure whether to discard the second frame.

[0004] In another embodiment, a radio frequency (RF) front-end for a receiver is disclosed. The RF front-end includes: a tuner implemented via a circuit system, configured to receive one or more symbols of a first frame transmitted by a transmitter; a correlator implemented via a circuit system, configured to determine a correlation between the received symbols and one or more address symbols, wherein each of the one or more address symbols is a time-domain signal of a subcarrier transmitted by the transmitter; and a detector implemented via a circuit system, configured to: determine that the correlation exceeds a threshold level; and cause the RF front-end to provide the one or more received symbols to a baseband system based on the correlation, wherein the baseband system recovers bits of a second frame within the first frame based on the one or more received symbols. In an embodiment, the frame address is either a source frame address or a destination frame address of the second frame. In an embodiment, the RF front-end further includes: a correlation symbol memory implemented via a circuit system, configured to store the one or more address symbols associated with the one or more received symbols, the one or more address symbols being received from the baseband system. In one embodiment, the first frame is associated with a Layer 1 frame of the Open Systems Interconnection (OSI) model, and the second frame is associated with a Layer 2 frame of the OSI model. In another embodiment, one or more address symbols associated with the one or more received symbols define the frame address and one or more fixed data other than the frame address. In yet another embodiment, the detector is further implemented via circuitry and configured to wake the baseband system from a sleep state based on the correlation exceeding the threshold level.

[0005] In yet another embodiment, a radio frequency (RF) front-end for a receiver is disclosed. The RF front-end includes: a tuner implemented via circuitry, configured to receive one or more symbols of a first frame transmitted by a transmitter; wherein the first frame is associated with a layer 1 frame of the Open Systems Interconnection (OSI) model; an analog-to-digital converter implemented via circuitry, configured to output in-phase and quadrature-phase (IQ) samples of one or more received symbols; a correlated symbol memory implemented via circuitry, configured to store IQ samples of one or more address symbols, wherein each of the one or more address symbols is a time-domain signal of a subcarrier transmitted by the transmitter; a correlator implemented via circuitry, configured to determine a correlation between the IQ samples of the one or more received symbols and the IQ samples of the one or more address symbols; and a detector implemented via circuitry, configured to: determine that the one or more received symbols are correlated with the address symbols; and cause the RF front-end to provide the one or more symbols to a baseband system to recover bits of a second frame within the first frame, wherein the second frame is associated with a layer 2 frame of the OSI model. In one embodiment, the one or more address symbols associated with the one or more received symbols define the source frame address or destination frame address of the second frame. In another embodiment, the detector is further implemented via circuitry and configured to wake the baseband system from a sleep state based on the determination that the one or more received symbols are associated with the address symbol. In another embodiment, the one or more received symbols and the address symbol are each 6 bytes modulated based on a 1 / 2 QPSK format. In yet another embodiment, the detector is further implemented via circuitry and configured to measure time after receiving the preamble symbol of the one or more symbols; and to determine the received symbol as the address symbol based on the time. Attached Figure Description

[0006] Figure 1 This is an example block diagram of a wireless system having a radio frequency (RF) front end arranged to perform address filtering according to an embodiment of the present invention.

[0007] Figure 2 Various examples of correlations performed by a correlator between received symbols and address symbols associated with a WiFi frame are shown according to embodiments of the present invention.

[0008] Figure 3 This is an example block diagram of a wireless system arranged to facilitate address updates associated with address filtering, according to an embodiment of the present invention.

[0009] Figure 4This is an example flowchart of a function associated with address filtering performed by an RF front end according to an embodiment of the present invention.

[0010] Figure 5 This is an example block diagram of an RF front-end that performs address filtering according to an embodiment of the present invention.

[0011] The drawings are for illustrative purposes only, but it should be understood that the embodiments are not limited to the arrangements and methods shown in the drawings. Detailed Implementation

[0012] The following description includes an example system, method, technique, and procedure flow associated with address filtering in the receiver's radio frequency (RF) front end for reducing frames dropped by the host. Address filtering begins with the RF front end receiving baseband signals of an RF modulated carrier and recovered subcarriers. In this example, a group of subcarriers defines the received Orthogonal Frequency Division Multiplexing (OFDM) symbols. The RF front end samples the baseband signals of the subcarriers to generate in-phase and quadrature-phase (IQ) samples of the received symbols. The RF front end determines whether a frame defined by the received symbols has a specific source frame address, destination frame address, or a combination thereof; this is called address filtering. This determination is based on the correlation between the IQ samples of the received symbols and the IQ samples of stored symbols representing a specific frame address. If the correlation exceeds a threshold, the frame defined by the received symbols has a specific source frame address and / or destination frame address. The RF front end wakes up the baseband system and provides the IQ samples of the received symbols to the baseband system, which in turn provides the bits of the frame to the host for processing. If the correlation does not exceed a threshold, the RF front end will not provide IQ samples of the received symbols to the baseband system and will not wake up the baseband system. Address filtering is performed by the RF front end, eliminating the need for the host to decide whether to discard a frame. Unless the host provides additional conformance checks and / or additional address filtering, the RF front end has determined that the frame is correlated. Furthermore, the baseband system remains in sleep or low-power state to conserve power and reserve resources associated with processing frames, unless the frame is correlated. To avoid obfuscation, well-known instructions, protocols, structures, and technologies are not shown in detail.

[0013] Example System

[0014] Figure 1This is an example block diagram of a wireless system 100 having a radio frequency (RF) front end arranged to perform address filtering. In this example, the wireless system 100 may operate according to a wireless standard such as WiFi based on the IEEE 802.11 standard family and includes a transmitter 106 for transmitting frames 102 and a receiver 108 for receiving frames 102. In this example, the receiver 108 may be further coupled to a host 110, which may be a computer system, a multi-media access point, a cellular phone, a (portable) gaming console, a personal digital assistant (PDA), a smartphone, an Internet of Things (IoT) device, or any other type of device that benefits from access to a wireless network infrastructure. The transmitter 106 may be implemented using, for example, analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, processing circuitry, or combinations thereof, wherein the processing circuitry is arranged to execute code stored in memory, and when the code is executed by the processing circuitry, the disclosed functions of the transmitter are performed. Receiver 108 may be implemented using, for example, analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, processing circuitry, or combinations thereof, wherein the processing circuitry is arranged to execute code stored in memory, and when the code is executed by the processing circuitry, the disclosed functions of the receiver are performed. Host 110 may be implemented using, for example, analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, processing circuitry, or combinations thereof, wherein the processing circuitry is arranged to execute code stored in memory, and when the code is executed by the processing circuitry, the disclosed functions of the host are performed.

[0015] Frame 102 may have multiple fields. These fields may be associated with layers of the Open Systems Interconnection (OSI) model, which standardizes communication functions between transmitter 106 and receiver 108. Frame 102 may be a Physical Layer (L1) frame with a preamble field 112 and a payload field 114. The preamble field 112 may include one or more bits to facilitate synchronization between transmitter 106 and receiver 108 and channel estimation between them via air interface 104. The payload field 114 may include one or more bits and has a header 118 and data 120. In this example, the header 118 and data 120 of the payload field 114 define a Data Link Layer (L2) frame. The header 118 may indicate the source frame address of data 120 in frame 116, the destination frame address of data 120 in frame 116, or a combination thereof. The source frame address can identify the source of data 120, such as the host transmitting frame 102, and the destination frame address can identify the host that will receive frame 102. The header 118 may also include error checking bits, such as cyclic redundancy check (CRC) bits and other bits. Frame 102 may include other fields and other information that are also associated with other layers of the OSI model.

[0016] Transmitter 106 can perform various signal processing steps to transmit one or more bits of frame 102 to receiver 108. For payload 114, signal processing may include encoding groups of N > 1 bits in payload 114 by encoder 162, where N = 8 in this example. In this example, one or more bits may be encoded by scrambling the bits of the frame's bit groups or by interleaving the bits, in a manner that allows receiver 108 to decode the bit groups by descrambling the encoded bits or deinterleaving the encoded bits to recover the one or more bits before encoding. For example, both transmitter 106 and receiver 108 may have pseudo-random number generators that are started with the same random number seed. Scrambling or interleaving may be based on the output from the pseudo-random number generator. Because receiver 108 can generate the same output from its pseudo-random number generator, receiver 108 is able to perform the corresponding descrambling or deinterleaving to recover the bits before encoding. For preamble 112, signal processing may include grouping N > 1 bits of the preamble but not encoding those bits.

[0017] Signal processing may further include a subcarrier mapper 164 that maps each of the M bits in a group of N bits to a corresponding modulation constellation point in a constellation diagram, where in this example M < N and M = 2. The modulation constellation point defines a unique subcarrier for each possible combination of M > 1 bits, resulting in modulation of the M bits of the subcarrier. In this example, the modulation may be based on one of binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), or quadrature modulation (QAM), and the subcarriers may be sine waves orthogonal to each other according to orthogonal frequency division multiplexing (OFDM). For example, each subcarrier in the constellation diagram may be spaced 312.5 kHz apart. The subcarrier mapper 164 may output a complex number defining the corresponding constellation point to which the M bits are mapped, and in this example, the complex number represents the magnitude and phase of the subcarrier in the frequency domain. The subcarrier mapper 164 may output a vector of complex numbers associated with each of the M bits in a group of N bits. X The transmitter 106 can then apply an inverse Fourier transform (IFFT) 166 to one or more complex numbers. The IFFT 166 can output the baseband signal of the subcarriers. The baseband signal can have time-varying in-phase and quadrature components (orthogonal to each other). The OFDM symbol can be a time-domain signal of subcarriers comprising groups of N bits. In some examples, depending on the modulation format, the OFDM symbol can be defined by 48 subcarriers representing frame 102, ranging from N=24 bits to N=216 bits. Alternatively, a frame can be transmitted in the form of one or more OFDM symbols.

[0018] Transmitter 106 transmits an analog representation of the baseband signal mixed with a radio frequency (RF) carrier via a subcarrier to generate a modulated RF carrier. In this example, the RF carrier may have a carrier frequency, and the transmission antenna 132 can transmit the modulated RF carrier to the receiver 108 via the air interface 104. Transmitter 106 can mix (multiply) the baseband signal with the RF carrier using an RF mixer 168. In this example, the RF carrier may consist of in-phase RF carriers and quadrature RF carriers that are 90° out of phase with each other. Mixer 168 can mix the in-phase component of the baseband signal with the in-phase RF carrier. Additionally, transmitter 106 can mix the quadrature component of the baseband signal with the quadrature phase RF carrier. Transmitter 106 can then add the mixed signals and transmit the modulated RF carrier. To facilitate this transmission, transmitter 106 may have one or more mixers and one or more local oscillators. The local oscillators can generate the RF carrier, and the mixers can mix the baseband signal onto the carrier. In the example, the local oscillator oscillates at frequencies ranging from, for example, 5.8 GHz to 10 GHz.

[0019] Receiver 108 may be configured with a radio frequency (RF) front-end 122 and a baseband system 124 to receive frame 102 transmitted by transmitter 106 via air interface 104. RF front-end 122 may include a tuner 126 and an analog-to-digital converter (ADC) 128. Tuner 126 is coupled to receive antenna 130 to receive and mix an RF carrier with an RF modulated carrier to recover the baseband signal of the subcarrier. Tuner 126 may have one or more local oscillators and mixers to perform this mixing. For example, the RF front-end may have a local oscillator that generates the RF carrier. The modulated RF carrier is mixed with an in-phase RF carrier to generate an in-phase signal. Additionally, the modulated RF carrier is mixed with a quadrature RF carrier to generate a quadrature-phase signal. The in-phase and quadrature signals may define the baseband signal of the subcarrier. Analog-to-digital converter (ADC) 128 may sample the in-phase and quadrature-phase signals to generate IQ samples of the received symbol. I-samples can correspond to samples of in-phase signals, and Q-samples can correspond to samples of quadrature-phase signals, with I-samples and Q-samples being orthogonal. The I-Q samples received over time can define one or more received symbols.

[0020] The RF front end may have a acquisition frame 134 for detecting whether a received symbol is associated with the preamble of a frame. A buffer 140 of the acquisition frame 134 may store the received symbols; in some examples, the buffer 140 may be in the form of a first-in-first-out (FIFO) buffer. Then, a correlator 136 may determine a correlation based on the received symbols, and a detector 138 may provide an indication of whether the received symbol is associated with the preamble of a frame.

[0021] In one example, buffer 140 can provide received symbols to correlator 136, and correlator 136 can perform autocorrelation on the received symbols. Autocorrelation is the correlation between data and a delayed copy of the data as a function of delay. Correlator 136 may include a complex multiplier and an accumulator to perform autocorrelation. Correlator 136 can perform correlation based on depth, which can be the number of IQ samples of the received symbols that are correlated simultaneously. For example, with a depth of 16, the correlator can correlate 16 IQ samples of the received symbols simultaneously. As another example, with a depth of 64 bytes, correlator 136 can correlate 64 IQ samples of the received symbols simultaneously. As yet another example, the depth of the correlator can be configurable to correlate a variable number of IQ samples of the received symbols simultaneously. Detector 138 can receive the correlation result and determine whether the correlation result exceeds a threshold amount. Preamble field 112 of frame 102 may have a bit pattern converted to an IQ sample pattern. If the correlation result exceeds the threshold amount, the received symbol may be associated with the preamble. The controller 144 in the RF front-end 122 can establish one or more of frequency, time synchronization, or channel estimation with the transmitter 106 based on the preamble to facilitate the reception of additional symbols associated with the payload field 114 of frame 102. If the correlation does not exceed a threshold amount, the received symbols may not be associated with the preamble.

[0022] In another example, correlator 136 can perform cross-correlation between the received symbol and the preamble symbol indicating the preamble. Cross-correlation is a measure of the similarity between two sequences as a sequence function. The preamble symbol can be derived from the signal processing performed by transmitter 106 to transmit the symbol of preamble 112. In this example, signal processing may include one or more of modulation of the subcarrier through the preamble bits in the preamble field 112, IFFT, and ADC sampling to form IQ samples of the preamble symbol. In this example, acquisition frame 134 may further have a correlated symbol memory 142 storing the IQ samples of the preamble symbol. Correlator 136 may include a complex multiplier and an accumulator to perform correlation (e.g., cross-correlation) between the IQ samples of the preamble symbol and the IQ samples of the received symbol. In this example, the cross-correlation function may be expressed as:

[0023]

[0024] Here, "x" and "y" are the inputs to the cross-correlation function. "y" can be a vector of IQ samples from one or more received symbols, and "x" can be a vector of IQ samples from one or more preamble symbols. In this context, IQ samples are represented as complex numbers, where I is the real component and Q is the complex component, "x" and "y" are vectors of complex numbers, and * indicates the conjugate operation. Higher z indicates better correlation, while lower z indicates worse correlation. In the example, "i" defines the index in the output vector of the cross-correlation value z.

[0025] Detector 138 can receive correlation results and determine whether the correlation results exceed a threshold amount. If the correlation results exceed the threshold amount, the received symbol is associated with a preamble. The controller in RF front-end 122 can establish one or more of frequency and time synchronization or channel estimation with transmitter 106 based on the preamble to facilitate the reception of additional symbols associated with payload field 114 of frame 102. If the correlation results do not exceed the threshold amount, the received symbol is not associated with the preamble, and preamble detection continues.

[0026] The various embodiments described herein involve RF front-end 122 performing address filtering to determine whether a received symbol specifies a particular source frame address and / or destination frame address of an L2 frame. Host 110 can process payloads with specific source frame addresses, destination frame addresses—i.e., L2 frames, or combinations thereof (“correlated frames”). If the received symbol specifies a particular source frame address and / or destination frame address of an L2 frame, an IQ sample of the received symbol is provided to baseband system 124 to recover the bits of the frame subsequently provided to host 110. If the received symbol does not have a specific source frame address and / or destination frame address, an IQ sample is not provided to baseband system 124 to recover the bits of the frame. In this example, host 110 does not need to decide whether to discard frames that do not have a specific source frame address or destination frame because the RF front-end has determined the frame to be correlated. Additionally, the baseband system remains in sleep or low-power state to conserve power, and the host and baseband system conserve resources associated with processing uncorrelated frames.

[0027] The correlated symbol memory 142 can store IQ samples of one or more address symbols defining a specific frame address, such as a source frame address, a destination frame address, or a combination thereof. If symbols for a specific frame address in frame 102 are to be transmitted, the IQ samples of the address symbols can be derived from signal processing performed by transmitter 106. In this example, the signal processing may include one or more of the following: encoding a group of N bits associated with an address in frame 102; mapping each of the M bits of the N bits to a corresponding modulation constellation point in a constellation diagram; and performing an IFFT to output a baseband signal for a subcarrier. The in-phase and quadrature components of the baseband signal each comprise digital samples, collectively referred to as IQ samples, and one or more IQ samples of the M-bit group can define a corresponding address symbol associated with a modulation format used by transmitter 132. Correlator 136 can receive address symbols from correlated symbol memory 142, and buffer 140 can provide the received symbols to correlator 136. Correlator 136 can perform the correlation in a manner similar to that used for preamble symbols, but now performs the correlation using IQ samples of one or more address symbols and one or more received symbols. In the correlation equation above, "y" can be one or more IQ samples of received symbols, and "x" can be one or more IQ samples of address symbols.

[0028] The detector 138 performing address filtering can receive the correlation result and determine whether the correlation result exceeds a threshold amount. In one example, the correlator 136 can be the same correlator used for detecting the preamble. In other examples, the RF front end 122 can have another correlator for performing this correlation. If the correlation result between the IQ sample of the received symbol and the IQ sample of the address symbol does not exceed the threshold amount, the baseband system 124, which will otherwise process the IQ sample of the received symbol, does not need to process the IQ sample of the received symbol. Frame 102 does not have an L2 frame associated with a specific source frame address and / or destination frame address. The RF front end 108 may not provide an indication to the baseband system 124 to wake the baseband system 124 from a sleep or low-power state to a wake-up state or a higher-power state. The baseband system 124 may remain in sleep or conserve processing resources. If the correlation result between the IQ sample of the received symbol and the IQ sample of the address symbol exceeds the threshold amount, the baseband system 124 may process the IQ sample of the received symbol. Frame 102 has an L2 frame associated with a specific source frame address and / or destination frame address. RF front-end 108 can provide indication to baseband system 124 to wake up baseband system 124 from a low-power or sleep state to a wake-up state or a higher-power state, thereby processing the received symbols. In this example, controller 144 of RF front-end 122 can provide indication to controller 148 of baseband system 124 to wake up baseband system 124.

[0029] In some examples, detector 138 may further cross-check the correlation with the timer value of timer 152 before providing an indication to wake up baseband system 124. After receiving a symbol of the preamble, the received symbol associated with the source frame address and / or destination frame address of frame 102 may be located at a fixed time offset. Acquisition frame 134 may start timer 152 upon receiving a symbol associated with the preamble and measure the time offset indicated by the timer value after receiving a symbol associated with the address of frame 102. If the timer value of timer 152 matches the fixed time offset and the correlation between the received symbol and the address symbol at that time exceeds a threshold amount, RF front-end 108 may provide an indication to wake up baseband system 124. Otherwise, RF front-end 108 may not provide an indication to wake up baseband system 124. In this respect, a timer value matching the fixed offset time provides additional confirmation of the symbol-defined source address and / or destination address of frame 102.

[0030] Baseband system 124 can wake up based on an instruction provided by RF front-end 108 to perform additional processing. Baseband system 124 can receive IQ samples of received symbols. Baseband system 124 may be configured with demodulator 154, decoder 156, and error checking 158. For each received symbol, demodulator 154 can perform a Fourier transform of the corresponding IQ sample and map the identified subcarriers to coded bits based on the constellation diagram used by transmitter 106. Decoder 156 can descramble or deinterleave the coded bits corresponding to the scrambling or interleaving performed by transmitter 106, and error checking 158 can perform a cyclic redundancy check (CRC) on the decoded bits based on the CRC bits in the CRC field of frame 102. If the decoded bits are error-free, the bits associated with one or more symbols can define an L2 frame. In this example, baseband system 124 may provide an instruction to wake host 110 from a low-power or sleep state and process the L2 frame. In this example, the Media Access Control (MAC) layer 160 of host 110 can process L2 frames. MAC layer 160 controls how devices in the network gain access to the media and the right to transmit data. Because RF front-end 122 determines that the L2 frame is a relevant frame to be processed by host 102 (i.e., having a specific source frame address and / or destination frame address), host 110 does not need to determine whether the L2 frame from baseband system 124 is a relevant frame. Furthermore, host 110 does not need to decide whether to discard the L2 frame because the RF front-end has determined it to be a relevant frame. In this respect, host 110 saves power and conserves resources associated with processing the frame.

[0031] RF front-end 122 uses address symbols stored in correlation symbol memory 142 to perform address filtering. If the correlation indicator detects a frame address, detector 138 causes baseband system 124 to process the IQ samples of the received symbol; otherwise, detector 138 does not cause baseband system 124 to process the received symbol. RF front-end 122 may perform alternative processing. For example, if the correlation indicator detects a frame address, detector 138 does not provide IQ samples of the received symbol to baseband system 124. If the correlation indicator does not detect a frame address, detector 138 provides IQ samples of the received symbol to baseband system 124. Other variations are also possible.

[0032] In some examples, the received symbols may also be associated with symbols representing data in other fields of frame 102. For example, symbols associated with the Logical Link Control (LLC) layer of the OSI model or symbols associated with the Networking layer of the OSI model may be associated with the received symbols. The associated symbol memory 142 may store IQ samples of symbols representing fixed bits of a frame associated with one or more of these layers, which are derived from signal processing performed by the transmitter 106 if the transmitter 106 is to transmit fixed bits in the layer. Thus, these symbols represent fixed bits in the layer and a smaller number of variable bits associated with the layer, and the transmitter 106 may use a modulation format that produces symbols associated with a smaller number of bytes. For example, 1 / 2 BPSK subcarrier modulation may be used to define symbols with a granularity of 3 bytes per symbol, such that the symbols define several bytes of data with more fixed bits according to the fixed bits of the layer. In this example, "1 / 2" may indicate a coding rate in which one redundant bit is added for each individual bit. Detector 138 may wake up baseband system 124 based on this correlation in addition to the correlation with the address symbols described above, or may wake up baseband system 124 instead of the correlation with the address symbols described above.

[0033] Figure 2 Various examples of correlation between received symbols and address symbols associated with WiFi frame 200 are shown. In the examples, WiFi frame 200 can be the payload 114 of frame 102 and define fields associated with the data link layer. WiFi frame 200 can be a data link layer (L2) frame. In the examples, correlator 136 can perform the correlation. Example WiFi frame 200 can have multiple fields, including four bytes of fixed header information 202, six bytes of MAC destination address 204, six bytes of MAC source address 206, 14 bytes of fixed header information 208, and data (not shown). Fixed header information 202, 208 can be known bits of a specific source address and destination address in WiFi frame 200. WiFi frame 200 can be transmitted in the form of one or more symbols, and the modulation format can define the size of the symbol.

[0034] In the first example 210, if the modulation format is 1 / 2QAM16, the transmitter 106 can transmit 12 bytes of symbols, and the source and destination addresses can be transmitted together as a single symbol. The correlated symbol memory 142 can store address symbols 214 indicating specific source and destination addresses of the WiFi frame 200. In some examples, the source address can identify the host, and the destination address can include fixed bytes (ff:ff:ff:ff:ff:ff). When the receiver 108 is associated with a vehicle network, the fixed bytes can indicate a safety message (e.g., accident, traffic jam) broadcast by one vehicle to other vehicles in the area. The correlator 136 can correlate the address symbols with one or more corresponding symbols in the received array. The detector 138 can compare the correlations to a threshold, and if all correlations exceed the threshold, the frame 200 has specific source and destination addresses. Other variations are also possible.

[0035] In the second example 218, if the modulation format is 3 / 4QAM64, the transmitter 106 can transmit 27 bytes of symbols, and the source and destination addresses can be transmitted as a single symbol. The address symbol 220 transmitted by the transmitter 106 may include 15 bytes of fixed information and 12 bytes associated with the source and destination addresses. The frame symbol memory can store the address symbol 220 indicating the symbols transmitted by the transmitter for a specific source and destination address of the WiFi frame 200. The correlator 136 can then correlate the address symbol with the corresponding received symbol. The detector 138 can compare the correlation result with a threshold to determine whether the frame has a specific source and destination address.

[0036] In the third example 222, the transmitter 106 may transmit symbols that only define an address byte without defining any other fixed information. If the modulation format is 1 / 2 QPSK, the transmitter 106 may transmit symbols of 6 bytes, and the source address and destination address may be transmitted in the form of 2 symbols. The first address symbol 224 may have 6 bytes of the destination address of the WiFi frame 200, and the second address symbol 226 may have 6 bytes of the source address of the WiFi frame 200. The frame symbol memory may store address symbols indicating the symbols transmitted by the transmitter for the specific source and destination addresses of the WiFi frame 200. Then, the correlator 136 may correlate the address symbols with the corresponding received symbols depending on the depth of the correlator. For example, if the depth of the correlator is 2 symbols, the correlator 136 may correlate 2 consecutive received symbols with the address symbols. The result of the correlation may be compared with a threshold to determine whether the frame has a specific source and destination address. As another example, if the depth of the correlator is 1 symbol, the correlator 136 may correlate each of the address symbols with the corresponding received symbol. The detector 138 may compare the result of the correlation with a threshold to determine whether the frame 200 has a specific source and destination address.

[0037] In the example, the host 110 may process L2 frames having specific source frame addresses and destination frame addresses that vary over time. In this regard, it may be necessary to update the address symbols associated with the received symbols to detect the L2 frames processed by the host 110.

[0038] Figure 3 An example block diagram 300 of a wireless system 100 arranged to facilitate the update of addresses associated with address filtering. The transmitter 104, the receiver 108, and the host 110 may perform functions in a manner similar to that described with respect to Figure 1 and will not be described again for the sake of brevity. In the example, the baseband system 124 is further shown to have an encoder 302, a mapper 304, and an inverse Fourier transform (IFFT) 322. The encoder 302 may be arranged to encode a group of N bits of the frame in a manner similar to the way the transmitter 106 encodes a group of N bits of the frame 102. The mapper 304 may be arranged to map each M bits of the N bits to a corresponding modulation constellation point in the constellation diagram, where M < N. Each constellation point may be associated with a subcarrier and represent a complex number. Steps 306 - 314 are example operations associated with the update of addresses associated with address filtering.

[0039] In step 306, host 110 provides an indication of the frame address associated with the L2 frame to be processed by host 110 to baseband system 124, such as the source frame address and / or destination frame address. The indication of the frame address utilized by host 110 can be used to facilitate the updating of IQ samples of the address symbols associated with address filtering. In this example, controller 316 of host 110 can provide the indication of the frame address to controller 148 of baseband system 124. Controller 148 of baseband system 124 can then provide the indication of the frame address to encoder 302.

[0040] In step 308, the encoder 302 of the baseband system 124 receives an indication of the source frame address and / or the destination frame address. The indication can be one or more bits. The encoder 302 can be arranged to encode the group of M bits by scrambling or interleaving in a manner similar to how the transmitter 106 encodes the bits of frame 102 using the source frame address and / or the destination frame address. In this example, the encoder 302 can encode the bits of the source frame address and / or the destination frame address using other fixed bits in frame 102.

[0041] In step 310, mapper 304 receives each group of M encoded bits from encoder 302. Mapper 304 can map each of the N bits in each group of M bits to a corresponding modulation constellation point in the constellation diagram. Each constellation point can be associated with a subcarrier. Each modulation constellation point can be represented by the magnitude and phase of the subcarrier using complex numbers, and the constellation diagram can be the same as the constellation diagram used by transmitter 106 to transmit frame 102. In this example, N bits are modulated on the subcarrier based on the mapping.

[0042] In step 312, the inverse Fourier transform (IFFT) 322 receives the indication of the complex number associated with each group of M bits and generates the baseband signal of the subcarrier. The baseband signal may have time-varying in-phase and quadrature components (orthogonal to each other). The in-phase and quadrature components each comprise digital samples, collectively referred to as IQ samples, and one or more IQ samples of the group of M bits may define a corresponding address symbol associated with the modulation format used by the transmitter 132. This process is repeated to generate a corresponding address symbol associated with each group of M bits.

[0043] In step 314, baseband system 124 provides IQ samples of one or more address symbols to RF front-end 122. In this example, RF front-end 122 stores one or more address symbols in correlated symbol memory 142 as updated address symbols to facilitate the correlation of the received symbol with the updated address symbol. Then, when receiver 102 receives a symbol, correlator 136 can then correlate the updated address symbol with the received symbol, and detector 138 can detect whether frame 102 has a frame address represented by the updated address symbol. In some examples, baseband system 124 may also provide an indication of the time offset between the preamble symbol and the address symbol. Detector 138 can use the time offset to further identify whether the received symbol is associated with the address symbol.

[0044] Example Operation

[0045] Figure 4 This is an example flowchart of function 400 associated with address filtering performed by the RF front end. The RF front end 122 can determine whether a received frame has a specific source frame address or destination frame address, and then, based on this determination, instruct the baseband system 124 to process IQ samples of the received symbols. The function can be performed by one or more of the RF front end 122, the baseband system 124, or the host 110, or can be implemented in one or more of the following: analog circuitry, mixed-signal circuitry, memory circuitry, logic circuitry, processing circuitry, or a combination thereof, wherein the processing circuitry is arranged to execute code stored in memory, and the disclosed function is performed when the code is executed by the processing circuitry.

[0046] In step 402, the RF front end receives a physical layer (L1) frame defined by one or more received symbols. The L1 frame may include fields of the physical layer. In this example, the RF front end receives a modulated RF carrier defining the L1 frame and mixes the RF modulated carrier with the RF carrier to recover the baseband signal of the subcarrier, and then samples the baseband signal of the subcarrier to output in-phase and quadrature-phase (IQ) samples of the received symbols.

[0047] In step 404, the received symbol is correlated with a preamble symbol representing the preamble of the L1 frame, the preamble being derived from signal processing performed by transmitter 106 to transmit frame 102. Correlator 136 can detect whether the IQ samples of the received symbol are correlated with the IQ samples of the preamble symbol. Correlator 136 can receive the IQ samples of the received symbol as input. Correlator 136 can also receive the IQ samples of the preamble symbol as input.

[0048] In step 406, it is determined whether the correlation at 404 exceeds a threshold. If the correlation exceeds the threshold, detector 138 detects the preamble of frame 116, and processing continues to 408. Otherwise, no frame is detected, and processing returns to 402.

[0049] In step 408, the received symbol is associated with an address symbol. The address may represent a specific frame address derived from signal processing performed by transmitter 106 to transmit a specific frame address, such as a source frame address, a destination frame address, or a combination thereof. Correlator 136 may detect whether the IQ samples of the received symbol are associated with the IQ samples of one or more address symbols defining a specific frame address, such as a source frame address, a destination frame address, or a combination associated with address filtering. Correlator 136 may receive the IQ samples of one or more received symbols and the IQ samples of one or more address symbols as input.

[0050] In step 410, it is determined whether the correlation at 408 exceeds a threshold. If the correlation exceeds the threshold, detector 138 detects a specific source frame address and / or destination frame address in the frame, and processing continues to 412 due to the correlated frame. Otherwise, the frame is not correlated and processing returns to 402. In some examples, detector 138 may further cross-check the correlation with the timer value of timer 152. When a preamble symbol is detected, detector 138 may start timer 152. If the timer reaches its timer value and the correlation at 408 meets the threshold, detector 138 may determine that the received symbol is associated with an address symbol.

[0051] In step 412, an instruction is provided to the baseband system 124 to process the IQ samples of the received symbols. Additionally, the instruction may wake the baseband system 124 from a sleep state.

[0052] In step 414, baseband system 124 receives IQ samples of the received symbols and performs further processing on the IQ samples of the received symbols based on the indication. Baseband system 124 may have demodulator 154, decoder 156, and error checking 158 to recover the bits of the L2 frame to be provided to host 110.

[0053] In step 416, the baseband system provides an L2 frame to host 110. The L2 frame can be the payload of an L1 frame associated with the data link layer. In this example, the baseband system can also wake host 110 from a sleep state. The L2 frame may include fields associated with the data link layer.

[0054] In step 418, host 110 can process the L2 frame. In this example, processing may involve host 110's Media Access Layer (MAC) receiving and processing the frame. By performing the disclosed address filtering in the RF front end 122, host processor 110 may not need to detect whether the L2 frame is a relevant frame to be processed, unless in some examples the host provides additional conformance checks and / or additional address filtering. Host processing resources are reserved for processing the relevant L2 frame, and host 110 may not need to discard the L2 frame because the received L2 frame has a specific source frame address or destination frame address.

[0055] Example device

[0056] Figure 5 Example block diagram 500 of an RF front-end 122 performing functions associated with address filtering. The RF front-end 122 may have a controller 144 (potentially including a microcontroller, multiprocessor, multicore, multinode, and / or implementing multiple threads, etc.) and a memory 504 such as system memory (e.g., one or more of cache, SRAM, DRAM, zero-capacitance RAM, dual-transistor RAM, eDRAM, EDO RAM, DDRRAM, EEPROM, NRAM, RRAM, SONOS, PRAM, etc.), or any one or more other possible implementations of non-transitory machine-readable media. The memory 504 may store computer code, program instructions, computer instructions, program code associated with correlators 136 and detectors 138, shown as correlator module 506 and detector module 508. Additionally, the memory 504 may be partitioned into a correlation symbol memory 142 and a buffer 140. The RF front-end 122 may also have a tuner 126 including one or more of a mixer and oscillator for mixing RF modulated carriers with RF carriers, and an ADC 128 for generating IQ samples of received symbols. Interface 510 facilitates providing received IQ samples of received symbols to baseband system 124 and provides an indication to wake up baseband system 124. Timer 152 facilitates determining whether a received symbol is associated with a source frame address or a destination frame address. Processing circuitry system 502, memory 504, interface 510, ADC 128, and timer 152 may be communicatively coupled together via interconnect 512, such as a bus (e.g., PCI, ISA, PCI-Express).

[0057] Some embodiments have been described in detail above, and various modifications are also possible. The disclosed subject matter, including the functional operations described herein, can be implemented in electronic circuit systems, computer hardware, firmware, software, or combinations thereof, such as in the structural components and their structural equivalents disclosed herein: potentially including programs (e.g., program code encoded in a non-transitory computer-readable medium, which may be a memory device, storage device, machine-readable storage substrate or other entity, machine-readable medium, or a combination thereof) operable to cause one or more data processing devices, such as a processor, to perform the described operations.

[0058] Although this specification contains numerous details, these details should not be construed as limiting the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in this specification in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually in multiple embodiments or in any suitable sub-combination. Furthermore, although features may be described above as functioning in certain combinations and even initially claimed in this manner, in some cases, one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve sub-combinations or variations of sub-combinations.

[0059] Similarly, although operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring such operations to be performed in the specific order shown or in sequential order, or to perform all the illustrated operations to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system components in the embodiments described above should not be construed as requiring such separation in all embodiments.

[0060] Unless explicitly stated otherwise, the phrase “at least one of” following a list with the conjunction “and” should not be considered an exclusive list and should not be interpreted as a list of categories with one item from each category. A sentence stating “at least one of A, B, and C” may contain only one of the listed items, an integer multiple of the listed items, and one or more of the listed items and other unlisted items.

[0061] Other embodiments are within the scope of the appended claims.

Claims

1. A method, characterized in that, include: The receiver receives one or more symbols of the first frame transmitted by the transmitter via its radio frequency (RF) front end. The RF front end determines that one or more received symbols are associated with one or more address symbols, wherein each of the one or more address symbols is transmitted by the transmitter to enable the receiver to receive the time-domain signal of a subcarrier of a frame address; as well as The RF front end provides one or more received symbols to the baseband system based on the correlation, wherein the baseband system recovers the bits of the second frame within the first frame based on the one or more received symbols.

2. The method according to claim 1, characterized in that, The RF front end determines that the associated one or more address symbols and the one or more received symbols are defined by a plurality of orthogonal subcarriers.

3. The method according to claim 1, characterized in that, In addition, including: Receive one or more address symbols associated with one or more received symbols from the baseband system.

4. The method according to claim 1, characterized in that, In addition, including: Measuring time after receiving the preamble symbol of the one or more symbols; and wherein associating the one or more received symbols with one or more address symbols by the RF front end includes determining, based on the time, that the received symbol is the same as the address symbol.

5. The method according to claim 1, characterized in that, Determining that the one or more received symbols are associated with one or more address symbols includes: associating in-phase and quadrature-phase IQ samples of the time-domain signal of the address symbol, wherein the I samples are orthogonal to the Q samples.

6. A radio frequency (RF) front-end for a receiver, characterized in that, The RF front end includes: A tuner implemented through a circuit system, the tuner being configured to receive one or more symbols of a first frame transmitted by a transmitter; A correlator implemented via a circuit system is configured to determine a correlation between a received symbol and one or more address symbols, each of which is a time-domain signal of a subcarrier transmitted by the transmitter; and A detector implemented by a circuit system is configured to: determine that the correlation exceeds a threshold level; and cause the RF front end to provide one or more received symbols to a baseband system based on the correlation, wherein the baseband system recovers bits of a second frame within the first frame based on the one or more received symbols.

7. The RF front-end according to claim 6, characterized in that, In addition, including: A correlated symbol memory implemented by a circuit system, the correlated symbol memory being configured to store one or more address symbols associated with the one or more received symbols, the one or more address symbols being received from the baseband system.

8. A radio frequency (RF) front end for a receiver, characterized in that, The RF front end includes: A tuner implemented via a circuit system, the tuner being configured to receive one or more symbols of a first frame transmitted by a transmitter; wherein the first frame is associated with a layer 1 frame of the Open Systems Interconnection (OSI) model. An analog-to-digital converter implemented by a circuit system, the analog-to-digital converter being configured to output one or more in-phase and quadrature-phase IQ samples of the received symbols; A correlated symbol memory implemented by a circuit system is configured to store IQ samples of one or more address symbols, wherein each of the one or more address symbols is a time-domain signal of a subcarrier transmitted by the transmitter. A correlator implemented by a circuit system is configured to determine the correlation between IQ samples of the one or more received symbols and IQ samples of the one or more address symbols; A detector implemented by a circuit system is configured to: determine that the one or more received symbols are associated with the address symbol; and cause the RF front end to provide the one or more symbols to the baseband system to recover bits of a second frame within the first frame, wherein the second frame is associated with a layer 2 frame of the OSI model.

9. The system according to claim 8, characterized in that, The detector is further implemented via a circuit system and is configured to wake the baseband system from a dormant state based on the determination that one or more received symbols are associated with the address symbol.

10. The system according to claim 8, characterized in that, The detector is further implemented via a circuit system and is configured to measure time after receiving the preamble symbol of the one or more symbols; and to determine the received symbol as the address symbol based on the time.

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