Digital radio receiver

Abstract

A method of operating a digital radio receiver (2) is provided. The method comprises: a) receiving an incoming radio signal comprising an incoming symbol sequence (102); b) selecting a portion of the incoming symbol sequence (102); c) determining a first error between the selected portion of the incoming symbol sequence (102) and a first predetermined symbol sequence (11) using a difference metric; d) determining a set of second errors between the selected portion of the incoming symbol sequence (102) and a corresponding set of second predetermined symbol sequences (13) using the difference metric, each second predetermined symbol sequence being formed by prefixing a different length portion of a predetermined preamble symbol sequence (104) to the start of the first predetermined symbol sequence (11); e) determining a minimum error from the first error and the set of second errors. If the first error is not the minimum error, a different portion of the incoming symbol sequence (102) is selected and steps c) to e) are repeated. If the first error is the minimum error, a subsequent portion of the incoming symbol sequence (102) is decoded to produce a data payload.

Description

Technical Field

[0001] This invention relates to a digital radio receiver and a method of operating a digital radio receiver. Background Technology

[0002] In packet-based radio communication, data is transmitted in blocks or packets, which typically include a header and a payload. The header usually identifies the intended destination of the packet, while the payload contains the actual data to be transmitted.

[0003] In many packet-based radio protocols, the header of each packet begins with a preamble, which consists of a sequence of symbols known to the receiver (e.g., 1s or 0s) designed to allow the receiver to synchronize with the transmitter (i.e., to determine and correct for frequency or timing offsets). The preamble typically consists of symbols in a simple repeating pattern (e.g., "01010101").

[0004] Data packets following a preamble typically include an address portion (e.g., identifying the specific device the packet is addressed to). For example, the physical layer of the Bluetooth (RTM) standard uses packets that include a preamble followed by an access address portion, which identifies the specific Bluetooth connection associated with the incoming signal. Once the receiver has synchronized with the incoming signal using the preamble, it compares the address portion with the expected bit sequence corresponding to its unique address. If the addresses match, the receiver continues to acquire data from the payload portion. The receiver can also use the address portion to identify where the payload portion of a packet begins (a process known as frame synchronization).

[0005] Radio communications are often affected by noise or interference, making it impossible to correctly receive individual bits of a received packet. Therefore, some packet-based radio communication protocols utilize error-correcting coding schemes, where some or all of the data bits of a packet are encoded into multiple symbols to increase resilience to bit errors (while sacrificing the bit rate or baud rate of a given symbol). For example, the Bluetooth LE coding physical layer uses a forward error-correcting coding scheme, which encodes a single data bit using up to eight symbols, allowing for correct data recovery even if many detected symbols are erroneous (e.g., due to noise). Thus, the use of such coding schemes can increase the effective range of a radio transmitter because the transmitted data remains recoverable even when the signal-to-noise ratio of the radio signal is below typically tolerable levels.

[0006] To recover the encoded data, the receiver uses techniques such as Viterbi decoding to decode the received symbol sequence. However, during frame synchronization, a large number of candidate bit sequences may need to be examined before finding the sequence corresponding to the expected address portion. To avoid having to decode every possible symbol sequence during frame synchronization, a difference metric (such as Hamming distance) is typically used to simply determine the error between the original symbol sequence and the expected encoded address portion, and when the error is below a preset threshold, the symbol sequence is assumed to correspond to the encoded address.

[0007] However, setting this threshold too low risks reducing the noise tolerance of the radio connection (i.e., reducing its range), while setting it too high risks confusing unrelated symbol sequences with the intended address, leading to incorrect frame synchronization and decoding errors. This can result in higher power consumption than required and may cause delays in successfully receiving other packets for the receiver. Summary of the Invention

[0008] According to a first aspect of the present invention, a method for operating a digital radio receiver is provided, comprising:

[0009] a) Receiving incoming radio signals including a sequence of incoming symbols;

[0010] b) Select a portion of the input symbol sequence;

[0011] c) Use a difference measure to determine a first error between a selected portion of the incoming symbol sequence and a first predetermined symbol sequence;

[0012] d) Using a difference metric, determine a set of second errors between selected portions of the incoming symbol sequence and the corresponding set of second predetermined symbol sequences, each second predetermined symbol sequence being formed by prepending a portion of a predetermined leader symbol sequence of varying length to the beginning of the first predetermined symbol sequence; and

[0013] e) Determine the minimum error from the set of the first error and the second error;

[0014] If the first error is not the minimum error, select a different portion of the input symbol sequence and repeat steps c) through e).

[0015] If the first error is the minimum error, then the subsequent part of the incoming symbol sequence is decoded to produce the data payload.

[0016] According to a second aspect of the invention, a digital radio receiver is provided, arranged as follows:

[0017] a) Receiving incoming radio signals including a sequence of incoming symbols;

[0018] b) Select a portion of the input symbol sequence;

[0019] c) Use a difference measure to determine a first error between a selected portion of the incoming symbol sequence and a first predetermined symbol sequence;

[0020] d) Using a difference metric, determine a set of second errors between selected portions of the incoming symbol sequence and the corresponding set of second predetermined symbol sequences, each second predetermined symbol sequence being formed by prepending a portion of a predetermined leader symbol sequence of varying length to the beginning of the first predetermined symbol sequence; and

[0021] e) Determine the minimum error from the set of the first error and the second error;

[0022] Wherein, if the first error is not the minimum error, the radio receiver is arranged to select different portions of the incoming symbol sequence and repeat steps c) to e); and

[0023] If the first error is the minimum error, the radio receiver is configured to decode the subsequent part of the incoming symbol sequence to produce the data payload.

[0024] Therefore, those skilled in the art will recognize that the present invention can generate data payload more reliably because the likelihood of the receiver erroneously attempting to decode a portion of the incoming symbol sequence other than the portion corresponding to the data payload is reduced, i.e., the likelihood of incorrect (e.g., premature) frame synchronization is reduced. By comparing selected portions of the incoming symbol sequence not only with a first predetermined symbol sequence (e.g., encoded access addresses) but also with a set of second predetermined symbol sequences (e.g., corresponding to encoded access addresses with some preambles placed at the beginning), and only continuing to decode subsequent portions when the first error is minimal, the receiver can more confidently ensure that selected portions of the symbol sequence actually correspond to the first predetermined symbol sequence (i.e., increasing the likelihood of correct frame synchronization), rather than erroneously mistaking the end of the preamble as part of the predetermined symbol sequence. The applicant has recognized that this can be a common source of synchronization errors.

[0025] The aforementioned method improves communication reliability and reduces energy consumption because the receiver is less likely to waste time attempting to decode portions of the incoming symbol sequence that do not correspond to the data payload. For example, if the selected portion of the incoming symbol sequence is actually one symbol early (i.e., it includes the last symbol of the leading symbol followed by all symbols of the first predetermined symbol sequence except the last symbol, with any transmission errors), the corresponding second predetermined symbol sequence is likely to be more similar to the selected portion than the first predetermined symbol sequence, such that the corresponding second error will be less than the first error (i.e., the first error will not be the minimum). In this case, the selected portion can be discarded without any decoding attempts on subsequent portions, and a new portion (e.g., a portion starting one symbol later, which in this case is the correct portion) can be selected. This avoids premature (one symbol) frame synchronization.

[0026] In some implementations, the incoming symbol sequence comprises an encoded bit sequence (e.g., where one bit in the bit sequence is represented by several symbols in the symbol sequence). The incoming symbol sequence may include a bit sequence encoded using an error-correcting coding scheme—such as a convolutional coding scheme like FEC coding and / or a mode mapping scheme (e.g., where a "0" symbol is mapped to "0011" and a "1" symbol is mapped to "1100"). Different portions of the bit sequence may be encoded using different coding schemes (or may not be encoded at all). For example, the incoming symbol sequence may include packets according to the Bluetooth LE coding standard, comprising a header portion encoded using an S=8 coding scheme and a payload portion encoded using an S=8 or S=2 coding scheme. The receiver may remove the mode mapping from the incoming symbol sequence before selecting the portion to be compared with a predetermined symbol sequence.

[0027] In some implementations, the first predetermined symbol sequence corresponds to an address, such as an access address identifying a digital radio receiver and / or a specific radio communication link (e.g., a specific bit sequence identifying a specific Bluetooth connection). The first predetermined symbol sequence may include an encoded version of the address, such as using multiple symbols to represent each bit of the address. The first predetermined symbol sequence may include an address encoded using an error correction coding scheme—e.g., a convolutional coding scheme such as FEC coding and / or a pattern mapping scheme (e.g., where one bit is represented as a symbol of a fixed pattern). For example, the first predetermined symbol sequence may include a 16-bit or 32-bit address encoded according to an S=2 coding scheme (i.e., two symbols per bit, producing a sequence of 32 or 64 symbols). In some implementations, the first predetermined symbol sequence may include a 16-bit or 32-bit address encoded according to an S=8 coding scheme (i.e., eight symbols per bit, producing a sequence of 256 symbols), such as a Bluetooth LE-coded access address, which is encoded using an FEC coding scheme with two symbols per bit and a P=4 pattern mapper.

[0028] In some implementations, if the incoming symbol sequence contains packets for a digital radio receiver, it includes a preamble followed by a coded address portion that corresponds to (and may be equivalent to) a first predetermined symbol sequence if the transmission error is low. The applicant has recognized that, in this case, for some coded addresses, a portion of the incoming symbol sequence that begins one or several symbols earlier than the address portion may be very similar to the coded address portion (e.g., within a similar Hamming distance to what is expected due to transmission errors). For example, for a 16-bit address encoded according to the FEC S=2 coding scheme, there may be 228 potentially problematic addresses. Therefore, simply applying a preset frame synchronization threshold to the error between a selected portion of the incoming symbol sequence and the first predetermined symbol sequence may lead to false alarms, resulting in an early frame synchronization error. However, as in embodiments of the present invention, by also considering the error between the selected portion and the symbol sequence consisting of the end portion of the preamble concatenated with the start portion of the first predetermined symbol sequence, the receiver is less likely to generate false alarms and can avoid early frame synchronization.

[0029] Dissimilarity measures may include Hamming distance (i.e., the number of distinct positions between two symbol sequences). Hamming distance is an easily computed dissimilarity measure that provides a sufficiently accurate and reliable indication of the similarity or dissimilarity between two symbol sequences. A digital radio receiver may include one or more Hamming distance calculators arranged to calculate a first and / or second error. In some implementations, other dissimilarity measures, such as Euclidean distance, may be used.

[0030] In some implementations, the method further includes checking that selected portions of the incoming symbol sequence correspond to a first predetermined symbol sequence (e.g., coded address checking). This additional testing can help prevent a digital radio receiver from attempting to decode portions of the incoming bit sequence that do not actually carry a data payload for the receiver (e.g., this only happens by chance, resulting in a first error being the minimum error). Checking that selected portions of the incoming symbol sequence correspond to the first predetermined symbol sequence may include comparing the first error to a threshold if the first error is the minimum error, and only decoding subsequent portions if the first error is below the threshold.

[0031] However, as mentioned above, if the threshold is set too high, using the preset threshold for coded address checking may produce false alarms, while if the threshold is set too low, it will unnecessarily reduce the radio connectivity range. Therefore, in some embodiments, additionally or alternatively, the method includes:

[0032] Determine the most likely encoded address corresponding to the selected portion of the incoming symbol sequence;

[0033] Determine the fitting error between the most likely encoded address and a selected portion of the incoming symbol sequence; and

[0034] If the first error is the minimum error, then the deviation between the first error and the fitting error is determined, and subsequent parts are decoded only if the deviation is equal to or less than the deviation threshold.

[0035] In such an implementation, the most likely encoded address is the encoded address that most likely corresponds to the selected portion of the incoming symbol sequence (i.e., the encoded address most similar to the selected portion). If the fitting error between the most likely encoded address and the selected portion is equal to or similar to the first error between the first predetermined symbol sequence and the selected portion, then the selected portion is very likely to indeed correspond to the first predetermined symbol sequence (e.g., the encoded address identifying the receiver).

[0036] This method is less likely to generate false alarms because even if the first error happens to be the minimum error and small (e.g., below a preset threshold), subsequent portions are only decoded if the deviation indicates that a selected portion of the incoming symbol sequence closely matches a first predetermined symbol sequence. In other words, if the error between the incoming symbol sequence and its most similar coded address is equal to or close to the error between the incoming symbol sequence and the first predetermined symbol sequence (e.g., a predetermined coded address), it is assumed that the most similar coded address is indeed the first predetermined symbol sequence, and it is not actually necessary to compare the two (which would require additional logic and processing). Furthermore, even if the underlying coded addresses match, some techniques used to determine the most likely coded address (e.g., when the technique encounters a decision where two branches have equal probabilities) have a non-zero probability of producing the most likely coded address that does not match the first predetermined symbol sequence. However, the applicant has recognized that in this case, the most likely coded address found may still have a fitting error of the incoming symbol sequence that is the same as or similar to the first error between the incoming symbol sequence and the first predetermined symbol sequence. Therefore, avoiding direct comparisons also prevents the unintentional discarding of radio signals for the receiver.

[0037] The fitting error can be determined using a difference metric (such as Hamming distance). This can be the same difference metric used to determine the first and second errors.

[0038] In some implementations, the most likely encoded address includes a maximum likelihood sequence detection (MLSD) solution. The most likely encoded address may include one of a predetermined plurality of possible addresses (e.g., a plurality of addresses specified according to a part of a communication standard such as Bluetooth LE, and / or a plurality of addresses including a specific bit structure). In some implementations, determining the solution for the most likely encoded address includes using a Viterbi decoding method. In some implementations, the bias threshold is equal to zero.

[0039] Digital radio receivers can be arranged to determine the set of first and second errors in parallel (e.g., simultaneously using multiple Hamming distance calculators, all arranged to determine the corresponding errors in the first and second errors).

[0040] The set of second errors may include a single second error between a selected portion of the incoming symbol sequence and a second predetermined symbol sequence formed by prepending a portion of a predetermined leading symbol sequence to the beginning of the first predetermined symbol sequence. For example, in some such embodiments, the second predetermined symbol sequence includes a first predetermined symbol sequence prepended with the last symbol of the predetermined leading symbol sequence. In such embodiments, the second predetermined symbol sequence may include a truncated version of the first predetermined symbol sequence (e.g., omitting the last symbol) to ensure that it has the same length as the untruncated first predetermined symbol sequence.

[0041] In some implementations, the set of second errors includes multiple errors between selected portions of the incoming symbol sequence and corresponding multiple second predetermined symbol sequences formed by prepending different portions of a predetermined leading symbol sequence to the starting portion of the first predetermined symbol sequence (e.g., truncating the ending portion).

[0042] In some such implementations, multiple second predetermined symbol sequences may include successively longer final portions (e.g., the last one, two, three, four, etc. symbols) of a predetermined preamble sequence concatenated (i.e., preceding) the beginning portion of the first predetermined symbol sequence. Therefore, in such implementations, the receiver checks whether a selected portion of the incoming symbol sequence corresponds to the first predetermined symbol sequence, or whether the selected portion is one, two, three, four, etc., symbols earlier. As explained above, premature frame synchronization to a portion of the incoming symbol sequence containing the last few symbols of the preamble can be a common cause of decoding errors.

[0043] In some implementations, the plurality of second predetermined symbol sequences includes four or more second predetermined symbol sequences, and in some implementations, the plurality of second predetermined symbol sequences may include up to sixteen or more second predetermined symbol sequences.

[0044] The incoming radio signal may include a carrier signal modulated by a digital signal corresponding to the incoming symbol sequence. The incoming radio signal may include any suitable type of modulation, but in some implementations, the radio signal is modulated according to a frequency modulation scheme such as Gaussian Frequency Shift Keying (GFSK). The incoming radio signal may include Bluetooth. TM Radio signals.

[0045] A receiver typically demodulates an incoming radio signal to generate an incoming symbol sequence. The receiver can synchronize with the frequency of the incoming radio signal, for example, by detecting the timing and / or frequency of the preamble portion included in the incoming symbol sequence.

[0046] In some implementations, the receiver employs hard-decision demodulation to generate the incoming symbol sequence, where the incoming symbol sequence comprises a sequence of binary values ​​(i.e., a sequence of 0s and 1s). For example, the receiver can compare the properties of the incoming radio signal (e.g., frequency or amplitude) to a fixed threshold to determine whether it includes a 0 or a 1 symbol at any given moment. For instance, if the radio signal is modulated using a frequency-shift keying (FSK) scheme such that binary "0" is represented by a frequency of 100 MHz and binary "1" by a frequency of 101 MHz, then all time periods with frequencies above 100.5 MHz can be classified as "1" symbols, and time periods with frequencies below 100.5 MHz can be classified as "0" symbols. In implementations where the receiver uses hard-decision demodulation, the difference metric can include Hamming distance.

[0047] In some alternative implementations, the receiver employs soft-decision demodulation to generate an incoming symbol sequence, such as a sequence of symbols having two or more possible binary values ​​indicating the confidence or likelihood that the symbol represents a particular binary state. In such implementations, the incoming symbol sequence may include a sequence of symbols having continuous values ​​between 0 and 1, or having one of a plurality of discrete values ​​between 0 and 1. The receiver can determine the value of a symbol by measuring properties of the incoming radio signal, such as the frequency or amplitude within the time period corresponding to the symbol. For example, if the radio signal is modulated using a frequency-shift keying (FSK) scheme that represents binary “0” at a frequency of 100 MHz and binary “1” at a frequency of 101 MHz, the symbols can be classified using a linear mapping from the interval between 100 MHz and 101 MHz to the interval between 0 and 1 (e.g., a time period with a frequency of 100.6 MHz is classified as a “0.6” symbol, which could indicate that the binary state “1” has a 60% confidence level). Using soft-decision demodulation can produce more accurate results because information is not lost during the demodulation stage, but it may require intensive computation. In implementations where the receiver uses soft-decision demodulation, the difference metric may include Euclidean distance.

[0048] The receiver may store the incoming symbol sequence. For example, the receiver may include a buffer arranged to store the incoming symbol sequence. The receiver may include a shift register that stores selected portions of the incoming symbol sequence in the shift register while calculating the first and second errors.

[0049] Using the deviation between the first error and the fitting error to check the encoded address, as described above, is an independent invention. Therefore, according to another aspect of the invention, a method for checking the encoded address is provided, comprising:

[0050] a) Receiving incoming radio signals including a sequence of incoming symbols;

[0051] b) Select a portion of the input symbol sequence;

[0052] c) Determine the first error between the selected portion of the incoming symbol sequence and the first predetermined symbol sequence;

[0053] d) Determine the most likely encoded address corresponding to the selected portion of the incoming symbol sequence;

[0054] e) Determine the fitting error between the selected portion of the incoming symbol sequence and the most likely encoded address;

[0055] e) Determine the deviation between the first error and the fitting error and compare the deviation with a deviation threshold;

[0056] If the deviation is greater than the deviation threshold, select a different portion of the input symbol sequence and repeat steps c) through e).

[0057] If the deviation is less than or equal to the deviation threshold, the subsequent part of the incoming symbol sequence is decoded to produce the data payload.

[0058] The present invention extends to a digital radio receiver, which is arranged as follows:

[0059] a) Receiving incoming radio signals including a sequence of incoming symbols;

[0060] b) Select a portion of the input symbol sequence;

[0061] c) Determine the first error between the selected portion of the incoming symbol sequence and the first predetermined symbol sequence;

[0062] d) Determine the most likely encoded address corresponding to the selected portion of the incoming symbol sequence;

[0063] e) Determine the fitting error between the selected portion of the incoming symbol sequence and the most likely encoded address;

[0064] e) Determine the deviation between the first error and the fitting error and compare the deviation with a deviation threshold;

[0065] If the deviation is greater than the deviation threshold, select a different portion of the input symbol sequence and repeat steps c) through e).

[0066] If the deviation is less than or equal to the deviation threshold, the subsequent part of the incoming symbol sequence is decoded to produce the data payload.

[0067] In some implementations, the most likely encoded address includes the maximum likelihood sequence detection (MLSD) solution. In some implementations, determining the most likely encoded address involves using a Viterbi decoding method. In some implementations, the bias threshold can be equal to zero.

[0068] Dissimilarity measures can include Hamming distance.

[0069] The incoming symbol sequence may include, for example, data packets according to the Bluetooth LE encoding standard. The incoming symbol sequence may include an encoded bit sequence.

[0070] Features of any aspect or embodiment described herein may be applied, where appropriate, to any other aspect or embodiment described herein. Where different embodiments are referred to, it should be understood that they are not necessarily different but may overlap. It will be appreciated that all relevant preferred features of the methods and apparatus according to the first and second aspects above may also be applied to other aspects of the invention. Attached Figure Description

[0071] Now, one or more non-limiting examples will be described by way of example only, with reference to the accompanying drawings, wherein:

[0072] Figure 1 This is a schematic diagram of a digital radio receiver according to an embodiment of the present invention;

[0073] Figure 2 The structure of Bluetooth LE encoded packets is shown;

[0074] Figure 3 This illustrates the operation according to an embodiment of the present invention. Figure 1 A flowchart of a method for using a digital radio receiver;

[0075] Figure 4 This illustrates operation according to another embodiment of the invention. Figure 1 A flowchart of a method for using a digital radio receiver; and

[0076] Figure 5 This is a schematic diagram of the part of a digital radio receiver used to perform coded address checks. Detailed Implementation

[0077] Figure 1 A digital radio receiver 2 is shown, which includes an antenna 4, an RF module 6 (e.g., including one or more baluns, amplifiers, mixers, oscillators, filters, ADCs, demodulators, or buffers), a shift register 8, a first Hamming distance calculator 10, a set 12 of second Hamming distance calculators, and a comparison circuit section 14.

[0078] Figure 3The diagram illustrates a flowchart of the operation of the digital radio receiver 2. In step 202, the digital radio receiver 2 receives a modulated radio signal (e.g., a GFSK modulated radio signal) via antenna 4, which includes a sequence of digital incoming symbols. In step 204, the RF module 6 filters, amplifies, and demodulates the radio signal to generate the incoming symbol sequence.

[0079] The incoming symbol sequence contains data packets, such as Bluetooth Low Energy (LE) encoded packets. Figure 2 The structure of the LE-encoded packet is shown. Packet 102 includes a preamble portion 104, followed by an access address portion 106.

[0080] The preamble 104 includes ten repeating 8-symbol patterns “00111100” (i.e., pattern “01”, to which a P=4 pattern mapping is applied). As part of step 202, the RF module 6 detects the repeating pattern and uses it to synchronize the frequency of the receiver 2 with the incoming radio signal (e.g., to correct for frequency offsets caused by the Doppler effect).

[0081] Access address portion 106 includes a 32-bit access address encoded using an S=8 forward error correction (FEC) coding scheme (including a P=4 mode mapping), generating eight symbols per data bit and producing 256 symbols in total. Following access address portion 106 is a 16-symbol (i.e., 2-bit) encoding indicator portion 108, which indicates the encoding scheme applied to the subsequent payload portion 110 (which contains the actual data of interest carried by packet 102). In the case of LE-coded packet 102, the encoding scheme used for payload portion 110 is an S=2 or S=8 FEC coding scheme. A 24-symbol (3-bit) termination portion 112 follows the encoding indicator 108 and precedes payload portion 110.

[0082] To ensure that data packet 102 is directed to receiver 2, receiver 2 must check that access address portion 106 corresponds to a predetermined access address associated with receiver 2 (e.g., associated with a specific Bluetooth connection in which receiver 2 is part). Identifying the position of access address portion 106 in the incoming symbol sequence also helps with frame synchronization (i.e., identifying where payload portion 110 begins in the symbol sequence).

[0083] In step 206, receiver 2 selects a portion of the incoming symbol sequence and loads it into shift register 8. In this example, receiver 2 removes the P=4 pattern mapping on the incoming symbol sequence before loading the selected portion into shift register 8, but this is not required. In step 208, the first Hamming distance calculator 8 calculates the first Hamming distance between the selected portion in shift register 8 and the encoded access address 11 generated by encoding the predetermined access address using the same FEC encoding scheme as the access address portion 106 (although there is no P=4 pattern mapping in this example). Figure 1 In the diagram, the encoded address 11 is shown as 16 symbols long (A0-A1). 15 However, this is merely illustrative; encoded addresses can be up to 256 symbols long (e.g., in the case of Bluetooth LE encoded packets), or even longer in other implementations.

[0084] In step 210 (which can occur simultaneously with step 208), the set of second Hamming distance calculators 12 determines the set of second Hamming distances between selected portions of the incoming symbol sequence and the corresponding set 13 of second predetermined symbol sequences. Each second predetermined symbol sequence 13 is formed by prepending a different number of the last symbols of the leading portion 104 to the beginning of the encoded address 11, with the same number of the last symbols of the encoded address 11 truncated to maintain the length of the second predetermined symbol sequence 13 as the same as the length of the encoded address 11 (i.e., at...). Figure 1 (Shown as 16 symbols).

[0085] As described above, the incoming symbol sequence decoded from the radio signal contains data packets (e.g., LE-coded packets). However, even if a repeated preamble is detected (e.g., as part of an initial synchronization step), receiver 2 does not know the exact location where address portion 106 or payload portion 110 begins (i.e., which symbol in the incoming symbol sequence), and therefore does not know how to decode the incoming symbol sequence to reproduce the data contained therein. Furthermore, due to noise and interference, the incoming symbol sequence may not perfectly match the symbol sequence forming the data packets. By determining the set of a first Hamming distance between a selected portion of the incoming symbol sequence and the coded address 11, and a second Hamming distance between a selected portion of the incoming symbol sequence and a second predetermined symbol sequence 13, receiver 2 determines the closeness of the match between the selected portion of the incoming sequence symbols and the expected address, and the closeness of the match when the expected address has a specific number of symbols from the preamble added to the start point (prefix).

[0086] In step 212, receiver 2 determines the minimum Hamming distance (i.e., the minimum error) between the first and second Hamming distances. If the first Hamming distance is the minimum error, receiver 2 infers that the selected portion is likely the address portion 106 of data packet 102. This means that the position of address portion 106 in the incoming symbol sequence has been found (i.e., frame synchronization has been completed), and address portion 106 matches the access address associated with receiver 2 (although in some examples additional tests may be applied to confirm this). Then, in step 216, the receiver proceeds accordingly to decode the payload portion 110 of the packet.

[0087] However, if the first error is not the minimum error in step 214 (i.e., if one of the sets of second Hamming distances is the minimum error), the receiver determines that the location of address portion 106 has not been correctly found because it is more likely to be one or more symbols early, and returns to step 206, where a new portion of the symbol sequence is selected (e.g., starting one symbol later). This avoids premature frame synchronization.

[0088] As described above, in some examples, additional tests can be applied to check whether address portion 106 matches the access address associated with receiver 2 (encoded address check). For example, a first error can be compared to a preset threshold, and receiver 2 can continue decoding only if the first error is below that threshold. However, in some examples... Figure 4 Another method for operating the digital radio receiver 2 is shown, in which a different encoded address checking method is used. This method includes... Figure 2 All the steps of the method shown are not described in detail here, but the method also includes additional steps 252-258 before the payload is decoded. Figure 5 This describes the part of digital radio receiver 2 used to perform coded address checks. Figure 5 This part of the receiver 2 shown includes a shift register 8, a first Hamming distance calculator 10, an MLSD solver 512, and a comparison circuit section 514.

[0089] In this embodiment, in step 252 (following step 214), the MSLD solver 512 uses the maximum likelihood sequence detection (MLSD) technique to determine the most likely encoded address corresponding to a selected portion of the incoming symbol sequence. The most likely encoded address (“MLSD solution”) is the encoded address most likely to correspond to the selected portion of the incoming symbol sequence. If the data packets included in the incoming symbol sequence are for receiver 2, the most likely encoded address is likely to match the encoded address 11 associated with receiver 2.

[0090] In step 254, the MSLD solver 512 determines the MSLD Hamming distance (i.e., a measure of how well the MSLD solution fits the selected portion of the input symbol sequence) between the MSLD solution and the selected portion.

[0091] In step 256, the comparison circuit section 514 determines the deviation between the MSLD Hamming distance and the first Hamming distance calculated in step 208. If the deviation is low (e.g., equal to zero), the MSLD solution is likely to match the encoded address 11, confirming that the selected portion of the incoming symbol sequence is indeed the address portion 106 of the data packet and matches the access address associated with receiver 2. Therefore, in step 258, the comparison circuit section 514 compares the deviation with a predetermined threshold (e.g., zero). If the deviation is less than or equal to the threshold, receiver 2 continues decoding the payload portion in step 216. If it is greater than the threshold, the receiver returns to step 206 to select a new portion of the incoming symbol sequence.

[0092] This implementation also reduces the probability of erroneous frame synchronization and thus improves receiver performance, since it is not actually necessary to compare the MSLD decryption with the encoded address 11 (which would require additional logic and processing work).

[0093] Although the invention has been described in detail with reference to only a limited number of embodiments, it should be readily understood that the invention is not limited to these disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not previously described but commensurate with the scope of the invention. Furthermore, while various embodiments of the invention have been described, it should be understood that aspects of the invention may include only some of the described embodiments. Therefore, the invention should not be considered limited to the foregoing description, but only to the scope of the appended claims.

Claims

1. A method of operating a digital radio receiver, comprising: a) Receive incoming radio signals including a sequence of incoming symbols; b) Select a portion of the incoming symbol sequence; c) Use a difference metric to determine a first error between a selected portion of the incoming symbol sequence and a first predetermined symbol sequence; d) Use the difference metric to determine a set of second errors between the selected portion of the incoming symbol sequence and a set of corresponding second predetermined symbol sequences, each of the second predetermined symbol sequences being formed by prepending a different length portion of a predetermined leader symbol sequence to the beginning of the first predetermined symbol sequence; as well as e) Determine the minimum error from the set of the first error and the second error; If the first error is not the minimum error, then select a different portion of the input symbol sequence and repeat steps c) to e); as well as If the first error is the minimum error, then the subsequent part of the incoming symbol sequence is decoded to generate a data payload.

2. The method according to claim 1, wherein, The incoming symbol sequence contains a sequence of encoded bits encoded using an error-correcting coding scheme.

3. The method according to claim 1 or 2, wherein, The first predetermined symbol sequence corresponds to an access address that identifies the digital radio receiver and / or a specific radio communication link.

4. The method according to claim 1 or 2, wherein, The difference metric includes Hamming distance.

5. The method according to claim 1 or 2, further comprising: Check that the selected portion of the incoming symbol sequence corresponds to the first predetermined symbol sequence.

6. The method according to claim 5, wherein, Checking that the selected portion of the incoming symbol sequence corresponds to the first predetermined symbol sequence includes: if the first error is the minimum error, comparing the first error with a threshold, and decoding the subsequent portion only if the first error is below the threshold.

7. The method according to claim 1 or 2, further comprising: Determine the most likely encoded address corresponding to the selected portion of the incoming symbol sequence; Determine the fitting error between the most likely encoded address and the selected portion of the incoming symbol sequence; and If the first error is the minimum error, then the deviation between the first error and the fitting error is determined, and the subsequent part is decoded only if the deviation is equal to or less than the deviation threshold.

8. The method according to claim 7, wherein, The fitting error includes the Hamming distance.

9. The method according to claim 7, wherein, The most likely encoded address includes the maximum likelihood sequence detection (MLSD) solution.

10. The method according to claim 1 or 2, comprising: The sets of the first error and the second error are determined in parallel.

11. The method according to claim 1 or 2, wherein, The set of second errors includes multiple errors between the selected portion of the incoming symbol sequence and a plurality of corresponding second predetermined symbol sequences, each of which is formed by prepending a different portion of a predetermined leading symbol sequence to the starting portion of the first predetermined symbol sequence.

12. The method according to claim 11, wherein, The plurality of second predetermined symbol sequences include successively longer endpoint portions of the predetermined leading symbol sequence that are concatenated to the starting portion of the first predetermined symbol sequence.

13. The method according to claim 1 or 2, wherein, The incoming radio signal is modulated according to a frequency modulation scheme.

14. The method of claim 13, comprising: The incoming symbol sequence is generated using soft-decision demodulation.

15. A digital radio receiver, arranged as follows: a) Receive incoming radio signals including a sequence of incoming symbols; b) Select a portion of the incoming symbol sequence; c) Use a difference metric to determine a first error between a selected portion of the incoming symbol sequence and a first predetermined symbol sequence; d) Use the difference metric to determine a set of second errors between the selected portion of the incoming symbol sequence and a set of corresponding second predetermined symbol sequences, each of the second predetermined symbol sequences being formed by prepending a different length portion of a predetermined leader symbol sequence to the beginning of the first predetermined symbol sequence; as well as e) Determine the minimum error from the set of the first error and the second error; in, If the first error is not the minimum error, the radio receiver is arranged to select different portions of the incoming symbol sequence and repeat steps c) to e). as well as If the first error is the minimum error, the radio receiver is configured to decode the subsequent portion of the incoming symbol sequence to produce a data payload.

16. The digital radio receiver of claim 15, comprising: One or more Hamming distance calculators are configured to calculate the first error and / or the second error.

17. The digital radio receiver of claim 15 or 16, comprising: The shift register stores the selected portion of the input symbol sequence when calculating the first error and the second error.

18. A method for checking an encoded address, comprising: a) Receive incoming radio signals including a sequence of incoming symbols; b) Select a portion of the incoming symbol sequence; c) Determine a first error between a selected portion of the input symbol sequence and a first predetermined symbol sequence; d) Determine the most likely encoded address corresponding to the selected portion of the incoming symbol sequence; e) Determine the fitting error between the selected portion of the incoming symbol sequence and the most likely encoded address; e) Determine the deviation between the first error and the fitting error and compare the deviation with a deviation threshold; If the deviation is greater than the deviation threshold, then select different portions of the input symbol sequence and repeat steps c) to e); and If the deviation is less than or equal to the deviation threshold, the subsequent part of the incoming symbol sequence is decoded to generate a data payload.

19. A digital radio receiver, arranged as follows: a) Receive incoming radio signals including a sequence of incoming symbols; b) Select a portion of the incoming symbol sequence; c) Determine a first error between a selected portion of the input symbol sequence and a first predetermined symbol sequence; d) Determine the most likely encoded address corresponding to the selected portion of the incoming symbol sequence; e) Determine the fitting error between the selected portion of the incoming symbol sequence and the most likely encoded address; e) Determine the deviation between the first error and the fitting error and compare the deviation with a deviation threshold; If the deviation is greater than the deviation threshold, then select different portions of the input symbol sequence and repeat steps c) to e); and If the deviation is less than or equal to the deviation threshold, the subsequent part of the incoming symbol sequence is decoded to generate a data payload.

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