Efficient physical layer preamble format

[0068] figure 1 It is a block diagram of an example wireless communication system 10 in which devices such as the transmitting device 12 and the receiving device 14 can transmit and receive data packets through the shared wireless communication channel 16. In one embodiment, devices 12 and 14 may communicate according to a communication protocol that uses an effective PHY preamble format detailed below. Each of the devices 12 and 14 may be, for example, a mobile station or a non-mobile station, which is equipped with one or more sets of antennas 20-24 and 30-34, respectively. in spite of figure 1 The wireless communication system 10 shown in includes two devices 12, 14, each with three antennas, but the wireless communication system 10 can of course include any number of devices, each equipped with the same or a different number of antennas (such as , 1, 2, 3, 4 antennas, etc.).

[0069] And, it will be noted that although figure 1 The wireless communication system 10 shown in FIG. 1 includes a transmitting device 12 and a receiving device 14, but the devices in the wireless communication system 10 can generally operate in multiple modes (e.g., transmitting mode and receiving mode). Thus, in some embodiments, antennas 20-24 and 30-34 can support both transmission and reception. Alternatively or additionally, a given device may include independent transmitting antennas and independent receiving antennas. It will also be understood that because each of the devices 12 and 14 may have a single antenna or multiple antennas, the wireless communication system 10 may be a multiple input multiple output (MIMO) system, multiple input single output (MISO) system, single input multiple output ( SIMO) system or single input single output (SISO) system.

[0070] figure 2 The relevant parts of the architecture of the transmitting device 12 and the receiving device 14 are shown. The transmitting device 12 can generally convert the sequence of information bits into an appropriate signal for passing through a wireless channel (for example, figure 1 Channel 16) for transmission. More specifically, the transmitting device 12 may include: an encoder 52 (for example, a convolutional encoder) to encode information bits; an expander 54 to convert each encoded bit into a chip sequence; and a modulator 56 to convert The coded chips are converted into data symbols, which are mapped and converted into signals suitable for transmission via one or more transmit antennas 20-24. Generally, the modulator 56 can implement any desired modulation technique based on one or more of the following: phase shift keying, binary phase shift keying (BPSK), π/2BPSK (wherein, for each symbol or chip, the modulation rotates π/2, which reduces the maximum phase shift between adjacent symbols/chips from 180° to 90°), quadrature phase shift keying (QPSK), π/2QPSK, frequency modulation, amplitude modulation, quadrature amplitude Modulation (QAM), π/2QAM, switch keying, minimum shift keying, Gaussian minimum shift keying, double alternating mark inversion (DAMI), etc. In some embodiments, the modulator 56 may include: a bit-to-symbol mapper 70, which maps the encoded bits to symbols; and a symbol-to-stream mapper 72, which maps the symbols into multiple parallel streams. If only one transmit antenna is used, the symbol-to-stream mapper 72 may be omitted. Information is transmitted in data units such as packets. This data unit usually includes a PHY preamble and a PHY payload. To generate the PHY preamble, the PHY preamble controller 74 receives control parameters through the control input 76 and sends commands to the expander 54 and optionally the modulator 56, which will be described in detail below. The transmitting device 50 may include various additional modules, which are not included for clarity and conciseness. figure 2 Shown in. For example, the transmitting device 50 may include an interleaver that interleaves the coded bits to mitigate burst errors. The transmitting device 50 may also include a radio frequency (RF) front end for performing up-conversion, various filters, power amplifiers, and the like.

[0071] The receiving device 14 may include: a pre-processor for space-time processing, an equalizer 90 coupled with one or more receiving antennas 30-34, a PHY preamble processor 92, a demodulator 94, and a decoder 96. The unit 90 may include an equalizer. It will be understood that the receiving device 1 may also include other components, such as filters, analog-to-digital converters, etc., which are removed for clarity and conciseness. figure 2 Omitted in. The preamble processor 92 may cooperate with the demodulator 94 to process the received signal.

[0072] In some embodiments, devices 12 and 14 can communicate using effectively formatted PHY preambles, which include the short duration PHY preambles specified by the IEEE 802.15.3c draft D0.0 standard. The information included. In some embodiments, the devices 12 and 14 communicate information through the PHY preamble (eg, PHY communication mode, piconet id, etc.). In addition, devices 12 and 14 may use a common preamble in different operating modes (e.g., SC mode and OFDM mode).

[0073] In order to better explain the technology of effective PHY preamble formatting, first refer to image 3 with Figure 4 Discuss the prior art format for the SC and OFDM PHY preamble in the IEEE 802.15.3c draft D0.0 standard, as well as several related concepts related to wireless communication. image 3 It is a block diagram of SC mode packet 120. SC mode packet 120 includes: SC PHY preamble 122, which has SYNC field 124, SFD field 126, and CES field 128; frame header 130; and payload with frame check sequence (FCS) 132 . As mentioned above, the receiver usually uses PHY preamble for AGC setting, antenna diversity selection or phase array setting, timing acquisition, coarse frequency offset estimation, packet and frame synchronization, and channel estimation. The SYNC field 132 of the PHY preamble 122 has n cycles, and the time of each cycle is T. During this period, the positive or negative polarity is used to transmit the 128-chip preamble sequence (or "code") s 128，m. Generally, the transmission time of the preamble sequence can be T. In some embodiments, the transmission length of the preamble sequence may be less than T.

[0074] Depending on the modulation scheme, one, two, four, or other numbers of data bits or chips can be mapped into a single symbol. For example, BPSK modulation maps each binary number to one of two symbols, while QPSK maps each pair of binary numbers to one of four symbols or constellation points. For example, {0, 0} bit tuples can be mapped to the first constellation point, {0, 1} bit tuples can be mapped to the second constellation point, {1, 0} bit tuples can be mapped to the third constellation point, The {1, 1} bit group can be mapped to the fourth constellation point. Thus, QPSK defines four symbols, and each symbol can correspond to a specific combination of two binary digits. Other modulation schemes, such as 8-QAM, 16-QAM, 32-QAM, 64-QAM, etc., can also be used.

[0075] According to the IEEE 802.15.3c draft D0.0 standard, the π/2 binary phase shift keying (BPSK) scheme is used to modulate the sequence s 128，m. In the π/2BPSK scheme, each chip is mapped to one of two symbols separated by 180°, and the modulation scheme rotates each chip by π/2 counterclockwise. For example, the first chip in the sequence can be mapped to one of -1 or +1, and the next chip in the sequence is mapped to one of +j or -j. Sequence+s 128，m And -s 128，m Can be regarded as the two's complement of each other. And, with the sequence +s 128，m And -s 128，m The corresponding modulated signals will have a phase shift of 180° with respect to each other.

[0076] Refer again image 3 , At symbol s 128，m Where the subscript m is multiple available sequences s 128，m One of the indexes. In particular, three sequences s are specified for SC mode 128，1 , -S 128，2 , S 128，3 , Each sequence corresponds to the corresponding piconet id. Once selected, the same extended sequence will be applied in each period of the fields SYNC 124 and SFD 126, such as image 3 Shown.

[0077] The term "cover code" as used herein indicates how to amplify a series of leader sequences to form a longer sequence. For example, for the sequence [+a, -a, +a, -a], where a is the preamble, the cover code can be expressed as [+1, -1, +1, -1], where -1 can indicate the Is the twos complement of code a, or the modulated signal corresponding to code-a is phase-shifted by 180° with respect to the modulated signal corresponding to code+a. In this example [+a, -a, +a, -a], the coverage code can be expressed differently, such as [1, 0, 1, 0], where 0 indicates the use of -a. In some embodiments, a longer sequence can be formed by spreading the cover code by one or more preamble sequences. For example, the cover code [+1, -1, +1, -1] (or [1, 0, 1, 0]) can be extended by using the preamble (or extended) code a to generate the sequence [+a, -a, +a, -a]. Similarly, the coverage code [+1, -1, -1, +1] (or [1, 0, 0, 1]) can be performed by using the preamble (or extended) code a and the preamble (or extended) code b. Expand to generate the sequence [+a, -b, -a, +a]. In other words, +a can be generated by extending +1 with a, -b can be generated by extending -1 with b, and so on. Refer again image 3 , The coverage code of the SYNC field 124 can be expressed as [+1, +1,...+1]. The cover code of the SFD field 126 is a sequence of length 4. It can vary according to the specific preamble to be transmitted (for example, one of two different lengths for CES field 128, and one of four different header expansion factors), but it is always -1 (or some other indicator) , Such as 0, to indicate that the code s will be used 128，m )Start.

[0078] Continue to refer image 3 , CES field 128 includes 256-chip complementary Golay sequence a 256，m And b 256，m. In order to reduce the effect of inter-symbol interference (ISI), sequence a 256，m And b 256，m The previous is the corresponding cyclic prefix (a pre, m And b pre, m , A copy of the last 128 chips of the corresponding sequence), followed by the corresponding suffix (a pos, m And b pos, m , A copy of the first 128 chips of the corresponding sequence).

[0079] Figure 4 It is a block diagram of an OFDM mode packet 150. The packet 150 includes: an OFDMPHY preamble 152 with a SYNC field 154, an SFD field 156 and a CES field 158; a frame header 160; and a payload with a frame check sequence (FCS) 162. During each period of the SYNC field 154, s is transmitted 512. Each sequence s 512 Corresponds to the coverage code [c 1 , C 2 , C 3 , C 4 ]Amplified four 128-chip leader sequence a 128. Similarly, the SFD field 156 is the sequence f 512 , Which corresponds to the four sequences a 128 , But according to the coverage code [d 1 , D 2 , D 3 , D 4 ] Was amplified. CES field 158 includes 512 chip sequence u 512 And v 512 And the corresponding prefix (u pre And v pre ). The entire packet 150 is modulated by OFDM.

[0080] Such as image 3 with Figure 4 It can be seen that different preamble formats are used for SC mode packets and OFDM mode packets. Moreover, the preambles in the SC mode and the OFDM mode are modulated in different ways. This application discloses an effective PHY preamble format and an implementation of a technique for formatting and processing such a PHY preamble, which allows the use of a common preamble format for SC mode packets and OFDM mode packets. In addition, in some embodiments, an effective PHY preamble format allows the device to detect the boundary between and/or the preamble field based on signal correlation (eg, detect the beginning of the CES field) without relying on the overlay code. Moreover, in some embodiments, if desired, the SFD field can be completely omitted in the PHY preamble. In some embodiments, the effective PHY preamble of the present disclosure includes a short training field (STF) generally associated with synchronization information, and a subsequent long training field (LTF) generally associated with channel estimation information. In addition, in some embodiments, effective PHY preamble formatting allows a specific preamble sequence to perform multiple functions, thereby reducing the total length of the PHY preamble. For example, the preamble sequence can serve as both the cyclic prefix and the field delimiter of the CES symbol. In some embodiments, the valid PHY preamble may use CES sequence ordering to signal additional information.

[0081] Refer again figure 2 The PHY preamble controller 74 of the transmitter 12 generally controls the generation of the PHY preamble. Similarly, the PHY preamble processor 92 of the receiver 14 analyzes the PHY preamble to, for example, identify field positions and/or field boundaries in the PHY preamble, decode the information encoded in the PHY preamble, and so on. PHY preamble controller 74 will be in reference Figure 5 Detailed, reference hereafter Image 6 Discuss PHY preamble processor 92.

[0082] reference Figure 5 The PHY preamble controller 74 can receive various input parameters through the control input 76. In one embodiment, the input parameters may include: PHY mode selector 190, used to indicate, for example, one of various SC and OFDM communication modes; Piconet identifier selector 192, used to receive piconet information; Header rate identifier 194. Used to receive, for example, an indication of a rate (for example, SC (normal) rate, or SC low rate general mode rate); channel estimation parameter 196, etc. In some embodiments, the control input 76 may be coupled to a processor such as a PHY processor, other components serving higher layers of the communication protocol, and the like. The PHY preamble controller 74 may include an STF formatter 200 and an LTF formatter 202, each of which may be implemented using hardware, a processor that executes machine-readable instructions, or a combination thereof. Each of the formatters 200 and 202 is communicatively coupled to at least one of the signal generator 204 and the overlay code generator 206. in spite of Figure 5 The connection between the formatters 200-202 and the input signals 190-196 is not depicted in the diagram, but the formatters 200-202 may respond to at least some signals of the control input 76.

[0083] The signal generator 204 generally receives the cover code and when to use the chip sequence a or the chip sequence b from the STF formatter 200, the LTF formatter 202, and the cover code generator 206 to generate an indication of the signal. Chip sequences a and b are complementary sequences. In some embodiments, the signal generator 204 may include a memory device 212, such as RAM, ROM, or another type of memory, to store complementary sequences a and b. In other embodiments, the signal generator 204 may include a and b generators. In one embodiment, the signal generator 204 includes a binary selector 210 for selecting one of the complementary sequences a and b for preamble signal generation. The two complementary sequences a and b have relevant properties suitable for detection at the receiving device. For example, complementary extended sequences a and b can be selected such that the sum of the corresponding out-of-phase aperiodic autocorrelation coefficients of sequences a and b is zero. In some embodiments, the complementary sequences a and b have zero or almost zero periodic autocorrelation. On the other hand, the sequences a and b may have aperiodic cross-correlation with a narrow main lobe or low-level side lobes, or aperiodic auto-correlation with a narrow main lobe and low-level side lobes. In certain of these embodiments, sequences a and b are complementary Golay sequences. Although sequences a and b of various lengths can be used, in some embodiments, sequences a and b are each 128 chips in length.

[0084] As is known, the complementary Golay sequence can be effectively defined by the weight vector W and the delay vector D. When the weight vector W and the delay vector D are applied to an appropriate generator, it produces a pair of complementary sequences. In one embodiment, the weights and delay vectors associated with sequences a and b are given as:

[0085] W=[1 1 -1 1 -1 1 -1] (1) and

[0086] D=[1 2 4 8 16 32 64]. (2)

[0087] Vectors W and D generate a pair of 128-chip Golay sequences

[0088] a=D12E2121D121DEDE2ED1DED1D121DED; (3)

[0089] b=1D12E2121D121DED1D12E212E2EDE212, (4)

[0090] It is represented here in hexadecimal notation.

[0091] In another embodiment, the delay vector D is given as:

[0092] D=[64 16 32 1 8 2 4]. (5)

[0093] Use D and the vector W given by (1) to generate a 128-chip Golay sequence

[0094] a=0C950C95A63F59C00C95F36AA63FA63F; (6)

[0095] b=039A039AA93056CF039AFC65A930A930. (7)

[0096] In yet another embodiment, the vector W given by (1) is used with the following delay vector:

[0097] D=[64 32 16 8 4 2 1] (8)

[0098] To generate

[0099] a=4847B747484748B84847B747B7B8B747; (9)

[0100] b=1D12E2121D121DED1D12E212E2EDE212. (10)

[0101] Continue to refer Figure 5 The coverage code generator 206 may include a memory device 220, such as RAM, ROM, or another type of memory, to store the coverage code group. Similarly, the coverage code generator 206 may include a memory device 222, such as RAM, ROM, or another type of memory, to store u/v sequences. The coverage code generator 206 may also include one or more other memory devices to store all or part of the STF field, all or part of the LTF field, or other sequences of both the STF field and the LTF field. In response to commands from the STF formatter 200 and the LTF formatter 202, the coverage code generator 206 may generate a coverage code for a specific PHY preamble.

[0102] As will be understood from the above, the PHY preamble controller 74 may control the signal generator 204 to use only a pair of sequences a and b to generate the PHY preamble. However, generally, in addition to the sequences a and b, the PHY preamble controller 74 can also control the signal generator 204 to use other sequences x and y to generate a specific part of the same PHY preamble. In addition, the signal generator 204 may include a cyclic shifter 230 for generating sequences a'and b'by cyclically shifting the sequences a and b in response to specific commands from the formatters 200 and 202.

[0103] Reference now Image 6 The PHY preamble processor 92 may include: a/b correlator 250, which has an input 252 and two outputs Xa and Xb coupled to the coverage code detector 254; u/v correlator 258; STL/LTF boundary detector 260 ; Channel estimator 262; and PHY preamble decoder 264. In some embodiments, the channel estimator 262 may be a component independent of the PHY processor 92. The PHY preamble decoder 264 can provide several output signals, including, for example, a PHY mode identifier 270, a piconet identifier 272, and a header rate identifier 274.

[0104] Generally, since a correlator (such as the a/b correlator 250) correlates the received signal with the sequence s, when the sequence s overlaps the corresponding sequence in the preamble field, a peak will appear. When there is no signal or the signal-to-noise ratio level is poor, there is no peak or only a small peak may appear. One technique used to measure peaks in correlated signals is to generate peak-to-average measurements of correlated signals. With particular reference to the a/b correlator 250, the signal received through the input 252 can be cross-correlated with the sequence a, with the sequence b, or autocorrelated with itself. If desired, the a/b correlator 250 may perform two or all three of these operations. The a/b correlator 250 can output related signals for use by other components of the PHY preamble processor 92. Optionally, the a/b correlator 250 may include detection logic to determine when sequence a is detected and when sequence b is detected in the received signal. The a/b correlator 250 may output an indication of detection of sequence a and sequence b. Thus, the outputs Xa and Xb can be related signals, or a and b detection signals.

[0105] Next, the coverage code detector 254 may determine the coverage codes associated with the detected a and b sequences. The cover code detector 254 may provide the detected cover code to the PHY preamble decoder 264, and optionally the detected a and b sequences, for further processing. For example, if a signal corresponding to [+a, -b, -a, +b] is received, the coverage code detector 254 may send the coverage code [+1, -1, -1, + to the PHY preamble decoder 264 1], or optionally send the sequence [+a, -b, -a, +b].

[0106] The STF/LTF boundary detector 260 may monitor the output of the a/b correlator 250 to detect a pattern representing the boundary between the PHY preamble fields. For example, the STF/LTF boundary detector 260 may detect a transition from a repetitive sequence a, a, ..., a to b to generate a signal indicating the boundary between the STF and LTF fields. It will be noted that the STF/LTF boundary detector 260 can simply detect the transition from a to -b, from b to a, from a'to b', and so on. More generally, a detector such as STF/LTF boundary detector 260 can detect a change from a first sequence (e.g., a) to a second sequence that is complementary to the first sequence (e.g., b). It will also be noted that the STF/LTF boundary detector 260 can detect multiple transitions in the preamble, and thereby generate multiple signals, which may indicate different transitions in the preamble. For example, the STF/LTF boundary detector 260 may generate a first signal in response to a transition from a to b, and a second signal in response to a transition from b to a. In some embodiments, the PHY preamble processor 92 may interpret the first transition as a transition from SYNC to SFD and the second transition as a transition from SFD to CES.

[0107] Continue to refer Image 6 The u/v correlator 258 can detect the symbol pattern that defines the CES symbol (for example, u and v or u'and v'), and the length can be 2, 4, or 8 times larger than the individual a and b sequences. The symbols u and v (or u'and v') may include 2, 4, 8 individual a and b sequences amplified by the overlay code. To this end, in some embodiments, the u/v correlator 258 may receive coverage code information from the coverage code generator 254. In some embodiments, the function of the u/v correlator 258 may be distributed among the PHY preamble decoder 264, the overlay code generator 254, and the like. When detecting the symbol patterns u and v, the u/v correlator 258 may provide the channel estimator 262 with a signal indicating the presence of u and v in the received signal for further processing. Optionally, the u/v correlator 258 may also provide the PHY preamble decoder 264 with a signal indicating the presence of u and v in the received signal.

[0108] Based on the output from the overlay code detector 254, the STF/LTF boundary detector 260, and possibly other components (for example, the a/b correlator 250), the PHY preamble decoder 264 can determine the various operating parameters conveyed in the PHY preamble. In particular, the PHY preamble decoder 264 can determine whether the PHY preamble specifies SC or OFDM mode, regular or low SC, determine the header rate, determine the piconet ID, and so on.

[0109] As an illustration, Figure 7 The cross-correlation output that the a/b correlator 250 can generate in response to an example signal received through the input 252 is depicted. In particular, the graph 310 corresponds to the cross-correlation with a (XCORR A), the graph 312 corresponds to the cross-correlation with b (XCORRB), and the graph 314 corresponds to the autocorrelation (AUTO-CORR). The multiple peaks 318 in the graph 310 correspond to the positions of the sequence a in the received signal. Similarly, the positions of the multiple peaks 320 in the graph 320 correspond to the positions of the sequence b in the received signal. The vertical line 324 generally corresponds to the STF/LTF boundary. On the left side of the STF/LTF boundary (which corresponds to the time before the occurrence of the STF/LTF boundary), in XCORR A, there are multiple peaks appearing at the interval corresponding to the length a, while in XCORR B there is no peak. This pattern can be used to detect STF/LTF boundaries, for example. Alternatively, by detecting, for example, the falling edge of the autocorrelation "plateau" 322, graph 314 may be used to detect the STF/LTF boundary.

[0110] Thus, by analyzing patterns in one or more of XCORR A, XCORR B, and AUTO-CORR, the STF/LTF detector 260 can detect the transition between the a and b sequences. Similarly, for example, other components of the PHY preamble processor 92 may use one or more correlation outputs from the a/b correlator 250 to further process the received signal, for example to determine a coverage code.

[0111] Various example PHY preamble formats will now be described. Such a preamble can be, for example, Figure 5 System generated. Similarly, such a preamble can be Image 6 System to deal with. Figure 8 This is an illustration of an example of the PHY preamble format 350. Generally, the PHY preamble 350 can precede the frame header and payload (similar to the above reference Figure 4 The discussed frame header 160 and payload 162), or can be used in combination with any other desired format data unit. The PHY preamble 350 includes an STF field 352 and an LTF field 354. The STF field 352 may include several repetitions of the same sequence a, including the last instance 356. In some embodiments, the STF field 352 can implement the SYNC field 124 of the PHY preamble of the prior art (see image 3 ) And/or SYNC field 154 (see Figure 4 ), that is, the receiving device 14 can use the repeating sequence in the STF field 352 to detect the start of transmission, synchronize the clock, and so on.

[0112] Similarly, in at least some embodiments of the effective PHY preamble format 350, the LTF field 354 may implement the CES field 128 or 158 of the prior art PHY preamble (see image 3 with Figure 4 ) Function. For example, the LTF field 354 may include a pair (or a longer sequence) of complementary CES symbols (u, v), and in some embodiments, the corresponding cyclic prefix and/or cyclic suffix. As described above, the CES symbol may include multiple individual a and b sequences amplified by the overlay code. In some cases, CES symbols can have corresponding complementary sequences. For example, if the sequences a and b are complementary Golay sequences, then [a b] and [a-b] are also complementary Golay sequences, and [b a] and [b-a] are complementary Golay sequences. You can also recursively apply this rule to pairs of [a b] and [a-b], [b a] and [b-a] to form longer sequences. The term "complementary CES symbol" as used herein means a pair of CES symbols that are complementary sequences (for example, complementary Golay sequences).

[0113] Generally, for Golay sequences, it should also be noted that if a and b define a pair of complementary Golay sequences, then a and -b also define a pair of complementary Golay sequences. In addition, equal cyclic shifts of complementary Golay sequences a and b produce a pair of complementary Golay sequences a'and b'. Moreover, a pair of complementary Golay sequences a" and b" can be generated by shifting each of the sequences a and b by an unequal number of positions.

[0114] in Figure 8 In the example shown, before the CES symbol 360(u) is a cyclic prefix 362, which is a copy of the last part of the CES symbol u. For clarity purposes, Figure 8 As with other illustrations in the present disclosure, arrows pointing from a part of the CES symbol to the corresponding copy outside the CES symbol are used to depict the prefix and suffix relationship. Consider a specific example. The CES symbol 360 may be a Golay sequence of 512 chips, and the cyclic prefix 362 may be a copy of the last 128 chips of the CES symbol 360. Generally, the CES symbol 360 may be followed by a cyclic suffix of the CES symbol 360, another CES symbol, a cyclic prefix of another CES symbol, and so on. In addition, it will be noted that the LTF field 354 may include multiple repetitions of the CES symbol pattern. At least some of these embodiments will be detailed below.

[0115] As described above, the CES symbol u includes complementary sequences a (also used in the STF field 352) and b amplified by the cover code. Thus, the last part 356 of STF 352 is the same as the first part of LTF 354 (which is in Figure 8 In the embodiment, it is the complementary sequence corresponding to the cyclic prefix of the CES symbol 354). In at least some embodiments, sequences a and b are complementary Golay sequences. It will be noted that the boundary between the STF field 352 and the LTF field 354 corresponds to the end of the last part 356 of the STF 352 and the beginning of the cyclic prefix 362. Thus, the a/b correlator 250 and the STF/LTF boundary detector 260 can determine the STF by cross-correlating the received signal with one or both of the sequences a and b, and/or generating autocorrelation of the received signal. The end of field 352 and the start of LTF field 354.

[0116] Picture 9 Is in line with the above reference Figure 8 An illustration of a specific example of the PHY preamble of the effective format discussed. For the sake of brevity, the STF and LTF fields will be referred to simply as "STF" and "LTF" hereinafter. The PHY preamble 370 includes: a series of sequences a, which are repeatedly transmitted with the same polarity (+1) until the end of the STF; and LTF, which has at least one period, including a pair of complementary CES symbols u and v, each The length of is twice the sequence a, and the corresponding cyclic prefix and suffix of u and v. Of course, LTF can include any suitable number of cycles. However, for simplification purposes, Figure 8 And the LTF in the subsequent figures will only show one cycle. It will be noted that the cyclic prefix +b of the CES symbol u is associated with the extended sequence b, which is complementary to the extended sequence a used in conjunction with the last part of the STF. Thus, the cyclic prefix +b can serve as both to reduce or eliminate ISI, and to delimit the boundary between STF and LTF. The PHY preamble 370 effectively eliminates the SFD field (see image 3 with Figure 4 ) And compare image 3 with Figure 4 The preamble of the prior art is shorter. Also, the PHY preamble 370 can be used as a common preamble for both SC and OFDM communication modes.

[0117] Picture 10 Is in line with the above reference Figure 8 An illustration of another specific example of the PHY preamble of the effective format discussed. The LTF of the PHY preamble 380 includes Picture 9 The symbols u and v are the same as the CES symbols u and v. However, the LTF in the PHY preamble 380 omits the cyclic suffixes of the CES symbols u and v. Picture 10 The format shown in is particularly useful for frequency domain channel estimation. The PHY preamble 380 can also be used for SC communication, although the receiver may experience some ISI in the estimated channel due to the lack of a suffix. versus Picture 9 The format is similar. The receiver can detect the STF/LTF boundary based on the difference between the correlation output between the last symbol of the STF and the first symbol of the LTF.

[0118] Picture 11 It is an illustration of an example of PHY preamble. The LTF of the PHY preamble 390 includes at least one period during which the complementary CES symbols u'=[b a] and v'=[b -a] are transmitted. The CES symbol u'is transmitted immediately after the last period of the STF (i.e., there is no cyclic prefix for u'). However, because the sequence a transmitted in the last period of the STF is the same as the last part of the CES symbol u', the last sequence of the STF beneficially serves as the cyclic prefix of u'(and the complement of the first part b of the CES symbol u') . In this way, and Picture 9 Compared to the example format of Picture 11 The format in further reduces the length of the PHY preamble.

[0119] Picture 12 This is an illustration of another example of the PHY preamble 400. The PHY preamble 400 includes: a series of sequences a, which are repeatedly transmitted until the end of the STF; and LTF, which has a pair of complementary CES symbols u=[ab ab] and v=[ a ba b], and the corresponding cyclic prefix and suffix. Generally, the length of u and v symbols can be expressed as:

[0120] The length of u = the length of v = n times the length of a = the length of n x a (11) where n is a positive integer equal to or greater than 2. Preferably, n is a multiple of 2. in Picture 12 In the example, n is 4. In this example, the PHY preamble 410 corresponds to the PHY preamble 370 (see Picture 9 ) Has a very similar structure, because the cyclic prefix -b of the CES symbol u is associated with the extended sequence b, which is complementary to the extended sequence a used as the last period of the field STF.

[0121] Figure 13 It is an illustration of another example of the PHY preamble 410. The LTF of the PHY preamble 410 includes CES symbols u and v, which are the same as Picture 12 The symbols u and v are the same. However, the LTF in the PHY preamble 410 omits the cyclic suffixes of the CES symbols u and v. Figure 13 The format shown in can be used for frequency domain channel estimation in OFDM or SC, for example, although in SC mode the receiver may experience some ISI in the estimated channel. versus Picture 12 The format is similar, the receiver can detect the STF/LTF boundary based on the difference of the correlation output between the last symbol of the STF and the first symbol of the LTF.

[0122] Picture 14 It is an illustration of another example of the PHY preamble 420. The CES symbol u'of the PHY preamble 420 is transmitted immediately after the last period of the STF. However, because the sequence a transmitted in the last period of the STF is the same as the last part of the CES symbol u', the last sequence of the STF beneficially serves as the cyclic prefix of u'(and the complement of the first part of the CES symbol u'-b. ). In this way, and Picture 12 Compared to the example preamble format 400 Picture 14 The format shown further reduces the length of the PHY preamble.

[0123] From Figure 9-14 In the discussion, it will be understood that a common PHY preamble can be defined for use in SC and OFDM communication modes; for example, complementary spreading sequences such as Golay sequences can be used to signal STF/LTF boundaries; sometimes channel quality can be estimated This is a relatively small cost, and the prefix is ​​omitted; by selecting the first CES symbol, the final sequence of the CES symbol is the same as the sequence transmitted in the last period of the STF, which can further shorten the PHY. It will also be noted that in general, CES symbols of any desired length can be used.

[0124] Figure 15 It is an illustration of another example of the PHY preamble 420. In the PHY preamble 430, the LTF includes two CES symbols u=[-b a b a] and v=[-b -a -b a]. The CES symbol v is followed by its cyclic suffix -b. Similar to the example discussed above, STF includes a series of repeated sequences a. in Figure 15 In the specific implementation manner, the last period of the STF is the same as the last period of the first CES symbol u. The first symbol of the CES symbol u is -b, which is complementary to the spreading sequence a in the last period of the STF. Thus, the last period of STF serves as a delimiter between STF and LTF, and serves as a cyclic prefix for the CES symbol u. Moreover, the last period of the CES symbol u is the same as the last period of the symbol v, thereby providing the additional function of the cyclic prefix of the CES symbol v. As will be understood from the foregoing, although the CES symbol v immediately follows the CES symbol u, and the CES symbol u in turn follows the STF, each of the CES symbols u and v has both a prefix and a suffix. Therefore, the PHY preamble 430 is a highly efficient format, which can provide sufficient information for both SC and OFDM communication modes.

[0125] Figure 16 It is an illustration of another example of the PHY preamble 440. The PHY preamble 440 includes CES symbols u'and v'. In this example, the CES symbol u'is preceded by the cyclic prefix b transmitted at the beginning of the LTF. versus Figure 15 Compared with the PHY preamble 440 of the PHY preamble 440, each of the symbol sequence of u'is transmitted in such a way that the complementary sequence (for example, a or b) of the sequence used in combination with the corresponding symbol of u is used, and the same is applied to the sequence Cover code of (for example, -a in u'corresponds to -b in u, b in u'corresponds to a in u, etc.). The CES symbols u'and v'have the same relationship. In other words, u'and v'are constructed by "inverting" each corresponding spread sequence in each cycle of u and v. Because the STF in the preamble 430 and 440 are the same, b is transmitted at the beginning of the LTF to provide the STF/LTF delimiter and the cyclic prefix of u'. Similar to at least some examples discussed above, the PHY preamble 440 can be used for both SC and OFDM modes of operation.

[0126] Figure 17 It is an illustration of another example of the PHY preamble 450. The STF includes a relatively short field in which the sequence b is repeatedly transmitted after the repeated transmission of a in the earlier part of the STF. In a sense, the repetition of b (in this example, two cycles) acts as an explicit frame delimiter ("FD"), thereby signaling the frame timing in a reliable manner. LTF includes CES symbols u'and v', where the last part of u'matches the sequence and cover code in FD. Therefore, the last period of FD not only signals the end of STF, but also provides a cyclic prefix of u'. If desired, the number of cycles in the FD can be increased (ie, there can be 3 or more b sequences). reference Figure 16 , Will also note that Figure 16 The PHY preamble 440 shown in can be considered to include an FD of length 1. Thus, the boundary between STF and LTF in the preamble 440 can be interpreted as the beginning of the symbol u'.

[0127] Figure 18 It is an illustration of another example of the PHY preamble 460. In the example preamble 460, the CES symbols u and v are adjacent, and u is transmitted immediately at the beginning of the LTF. Similar to the reference above Figure 15 In the case of discussion, the last period of STF and u provides additional functions for the corresponding prefixes of u and v. Figure 19 It is an illustration of another example of the PHY preamble 470. The format of the PHY preamble 470 is similar to the format of the PHY preamble 460, except that the last cycle of the LTF (the suffix of v) is omitted. As mentioned above, with a certain potential cost of channel estimation quality, this format can be used in both SC and OFDM modes.

[0128] Picture 20 It is an illustration of another example of the PHY preamble 480. The PHY preamble 480 includes the FD at the end of the STF. In this example, the FD includes two cycles during which sequence b is transmitted. Of course, FDs with other lengths (for example, one cycle, or three or more cycles) can also be used. The last sequence b of FD serves as a prefix of u, and the last sequence b of u serves as a prefix of v. Figure 21 It is an illustration of another example of the PHY preamble 490. The PHY preamble 490 omits the last cycle of the LTF, and the PHY preamble 480 uses it to transmit the cyclic suffix of v. Figure 22 with Figure 23 It is an illustration of other examples of PHY preambles 500, 510. Each of the preambles 500, 510 includes the cyclic prefix of the first CES symbol in the first cycle of the LTF, and the cyclic prefix at the beginning of the LTF is also a sequence complementary to the sequence used in the last cycle of the STF, and therefore acts as a reliable STF/LTF delimiter. Moreover, the last b sequence in u serves as the prefix of v. It will also be noted that the corresponding Figure 22 with Figure 23 The PHY preamble 500 and 510 are similar, except that the cyclic suffix of v is omitted in the PHY preamble 510.

[0129] Will notice, Figure 15-Figure 23 Various embodiments are shown in which the four-period CES symbols u and v are effectively used to eliminate at least some of the following: cyclic prefix, cyclic suffix, and (in at least some embodiments) explicit SFD fields. In addition, in Figure 15-Figure 23 It shows that the second CES symbol can be transmitted immediately after the first CES symbol while still eliminating ISI (ie, because the cyclic prefix of v is provided by u). Moreover, in some embodiments, the first CES symbol may be transmitted at the very beginning of the LTF (ie, following the STF without an intermediate period), where the last sequence of the STF provides the cyclic prefix for the first CES symbol.

[0130] Next, Figure 24 A technique is shown by which the selection of a and b sequences in STF and LTF indicates different transmission modes (for example, SC mode or OFDM mode). The PHY preambles 520 and 530 have the same format, except that the sequences a and b are exchanged. In particular, the PHY preamble 520 corresponds to similar Figure 15 In the format shown, the extended sequence a is used in STF, and the PHY preamble 530 has the same format as the PHY preamble 520, except that the sequences a and b are exchanged. The PHY preamble 520 may be used for SC communication, and the PHY preamble 530 may be used for OFDM communication. Of course, the opposite association between the preambles 520 and 530 and the PHY mode can be used instead. In one aspect, Figure 24 Shows a common preamble format, which can be used in both SC and OFDM communications, and enables receiving devices (e.g., figure 1 The receiving device 14) can determine whether the packet is transmitted through SC or OFDM by analyzing the preamble. For example, STF with a sequence may indicate SC mode, and STF with b sequence may indicate OFDM mode.

[0131] Figure 25 Shows signaling SC/OFDM selection but relies on the above reference Figure 16 Discussion of the PHY preamble format technology. More specifically, the PHY preambles 540 and 550 have: LTF, which includes a cyclic prefix for u'at the beginning of the LTF; u'; v'immediately following u'; and a cyclic suffix of v. The preamble 540 and 550 are the same, except that the sequences a and b are exchanged. The STF with the a sequence can indicate the SC mode, and the STF with the b sequence can indicate the OFDM mode. The sequence a in the STF indicates the SC operation mode, and the extended sequence b in the STF indicates the OFDM mode (or vice versa). in spite of Figure 24 with Figure 25 The discussion is about coding parameters used to indicate the SC mode relative to the OFDM mode, but the same technique can be used to indicate other modes or parameters.

[0132] Figure 26 A technique is shown by which the selection of the a and b sequences in the STF indicates different transmission modes (for example, SC mode or OFDM mode). Thus, the LTFs in the PHY preamble 560 and 570 are basically the same, but the STF in the PHY preamble 560 (which may correspond to the SC) uses sequence a, and the STF in the PHY preamble 570 uses b (which may correspond to OFDM). Therefore, the receiving device (for example, the receiving device 14) can detect the STF/LTF boundary in the OFDM mode only after the first period of LTF. If desired, the PHY preamble 570 can be considered as having an LTF starting with the first period of the first CES symbol, and where the cyclic prefix of the first CES symbol is the last period of the STF. The STF with the a sequence can indicate the SC mode, and the STF with the b sequence can indicate the OFDM mode.

[0133] Figure 27 Use something like Picture 20 The PHY preamble 480 is the preamble format, and the exchange of sequences a and b is applied to SC mode or OFDM mode. Figure 27 The technology is similar to Figure 25 The technology only uses a different u’. Figure 28 Another technique is shown, whereby the selection of a and b sequences in STF indicates different transmission modes (for example, SC mode or OFDM mode). Figure 28 Similar to Figure 26 Technology, just using a different u’.

[0134] As yet another method, the PHY mode selection (or the selection of other operating parameters of the PHY layer or possibly other layers) may be signaled as follows: an explicit SFD field is included between the STF and LTF fields, and various parameters of the SFD are changed. Figure 29 This is an example PHY preamble format 620, in which by applying specific complementary sequences a, b (for example, complementary Golay codes) in the SFD, or through various combinations of these technologies, the PHY mode or parameters can be indicated by the coverage code in the SFD . For example, LTF may use complementary sequences a'and b', and the last period of SFD may use a sequence complementary to that of the first period of LTF. Meanwhile, STF can use another sequence such as a. Thus, the PHY preamble 620 can use more than one pair of complementary sequences. Generally speaking, in all periods except the last period of the SFD, any appropriate sequence can be used in the STF, as long as the boundary between the SFD and the LTF is clearly signaled through a pair of complementary sequences. Therefore, the STF can use one or both of the sequences a and b used in the LTF, one or both of the sequences a'and b'corresponding to the corresponding sequences a and b that have been cyclically shifted, or independent of a And b (that is, different from, or not derived from, sequence a or b) one or more other sequences (e.g., c, d, etc.).

[0135] Figure 30 An example technique using SFD to indicate two or more physical PHY modes is shown. For convenience, Figure 30 The frame delimiter field (FD) is shown as the last part of the STF in each PHY preamble 630 and 640. In order to signal between SC and OFDM without changing u'and v', pattern [b b] can be used for SC, and another pattern [-bb] can be used for OFDM. It will be noted that in each of these two cases, the last period of the FD is a sequence complementary to the sequence used in the first period of the LTF, thereby signaling the STF/LTF boundary. Generally, the FD sequence used as the last part of the STF can include any number of periods, and different cover codes can be used to signal the selection of SC or OFDM. As another example, Figure 31 PHY preambles 650 and 660 are shown, which use another CES symbol u’ but are otherwise different from Figure 30 The preamble is the same.

[0136] Next, Figure 32 It shows a method of indicating operating parameters such as SC/OFDM selection by changing the relevant sequence of the CES symbols in the LTF. Such as Figure 32 As shown, the PHY preamble 670 includes a CES symbol u, which is transmitted immediately before another CES symbol v. On the other hand, the PHY preamble 680 includes the CES symbol v, which immediately precedes the CES symbol u. In this embodiment, the STF of the PHY preamble 670 and 680 are the same. Thus, except for the ordering of the CES symbols in the LTF, the PHY preambles 670 and 680 are the same. In addition, u and v in this specific example are selected to provide a cyclic prefix and suffix in the corresponding first and last parts of other CES symbols. In particular, each of the u and v symbols includes -b in the first period, and includes a in the last period. Thus, the first part (period) of u or v can serve as a cyclic suffix of other CES symbols u or v, and the last part of u or v can serve as a cyclic prefix of other CES symbols u or v. In other embodiments, the symbols u and v that do not have this attribute can be used. Therefore, the PHY preamble that changes the order between u and v to signal the PHY mode or other parameters can include the cyclic prefix/suffix Additional period.

[0137] Figure 33 Another example of PHY preambles 690 and 700 is shown, where the ordering of u and v CES symbols indicates SC mode or OFDM mode. However, it will be noted that the leading 690 and 700 omit the cyclic suffix of u and therefore cannot provide Figure 33 The same example of ISI protection.

[0138] It will also be noted that in at least some embodiments, it may be desirable to indicate other information in the PHY preamble. For example, indicating the piconet ID may allow a receiving device associated with a specific piconet to process the data frame of the piconet, and ignore, for example, data frames in other piconets. To this end, multiple pairs of Golay complementary sequences a i , B i (Or other appropriate sequence), and for a specific pair of STF, LTF, or both (a i , B i The selection of) can signal the piconet identification. For example, for a 1 , B 1 Can indicate piconet ID 1, right a 2 , B 2 Can indicate piconet ID 2, etc.

[0139] Additionally or alternatively, the coverage code in the STF may signal the piconet identification. If desired, in this case, a single pair of Golay complementary sequences a, b can be used for all piconets. For example, coverage code c 1 =(1 1 1 1) can indicate piconet ID 1, coverage code c 2 =(1 -11 -1) can indicate piconet ID 2, and so on.

[0140] Moreover, the combination of a/b selection and the overlay code in the STF can effectively signal the PHY mode, header rate, piconet identification, and other operating parameters, and may also signal multiple parameters at the same time. For example, the four-period covering codes (1 1 1 1), (1 -1, 1, -1), (-1, 1, -1, 1), (1, j, -1, -j) and (1 Each of, -j, -1, j) can signal a specific unique selection of piconet identification, SC or OFDM mode, header rate, etc. In the PSK modulation scheme, for example, each cover code defines a set of phase offsets. By selectively applying each of these cover codes to sequence a or b, the transmitting device can transmit even more parameters to the receiving device.

[0141] Figure 34 A simple example of applying a cover code of length 4 to the STF along with the specific selection of a or b sequence to signal between SC regular, SC low-rate general mode or OFDM is shown. The STF format 710 uses the sequence a together with the cover code (1, 1, 1, 1) to define the STF sequence pattern [a, a, a, a]. The STF format 720 uses the same sequence a together with the cover code (-1, 1, -1, 1) to define the STF sequence pattern [-a, a, -a, a]. Finally, the STF format 730 uses the sequence b together with the cover code (1, 1, 1, 1) to define the STF sequence pattern [b, b, b, b]. Although any association between formats 710-730 and operating parameters is possible, Figure 34 The example shown in maps the format 710 as a tuple {SC, regular header rate}, the format 720 as a tuple {SC, low header rate}, and the format 730 as OFDM. Of course, this technology can also be applied to signal the piconet identifier, the combination of the piconet identifier and SC/OFDM, or other PHY layer parameters.

[0142] reference Figure 35 , The combination of a/b selection in STF and a specific SFD format can also signal a single operating parameter of the PHY layer. In this example, the PHY preambles 750 and 760 may share the same STF, but their corresponding SFD fields may be different. For example, the SFD field can be of different lengths, or can use different coverage codes or different sequences, and so on. Meanwhile, the PHY preamble 770 used in OFDM uses a different spreading sequence in each period of the STF. The receiving device may first choose between SC and OFDM by correlating the STF field with a and b. If the STF field is related to a, it further processes the subsequent SFD field to determine whether the PHY preamble is related to the regular or low header rate Joint.

[0143] Figure 36 Shows with Figure 35 The similar method shown in, only indicates the header rate in the PHY preamble 780, 790, and 800 through the extended sequence in the STF. At the same time, the SC/OFDM selection is indicated through the SFD field. Similar to the example discussed above, the SFD field can be extended using a specific sequence, transmitted by using different coverage codes, changed in length, or changed in other ways to distinguish between various operating modes.

[0144] Reference now Figure 37 The combination of the cover code in STF and the change in SFD can similarly be used to indicate parameters such as PHY mode. In the PHY preambles 810, 820, and 830, the same sequence a is used to extend the STF, but the coverage code in at least one PHY mode in the STF is different. For the two remaining modes with the same coverage code in the STF, the change in the SFD can provide further differentiation.

[0145] In addition, Figure 38 The techniques shown in PHY preambles 840, 850, 860 depend on the ordering of u and v in LTF, and on the selection of spreading codes a and b in STF. Thus, the combination of the use of sequence a in STF and the ordering {u, v} can signal a PHY mode/rate configuration (for example, SC normal). On the other hand, the use of the same sequence and the different ordering of u and v can signal the second PHY mode/rate configuration (e.g., OFDM), for example. Finally, the use of the extended sequence b in the STF can signal the third PHY mode/rate configuration (eg, SC low rate). It will also be noted that for the SC low-rate universal mode, the LTF length can be shorter than the LTF length of the PHY preamble used in the SC routine (such as Figure 39 Shown in).

[0146] Refer again Image 6 A preamble processor such as the preamble processor 92 can generally use the received signal to detect the data frame, detect the start of the LTF field, and determine the PHY parameters by analyzing the PHY preamble using the techniques described above. For example, the STF/LTF boundary detector 260 may detect the start of the LTF boundary based on detecting changes from multiple a-sequences to b-sequences or from multiple b-sequences to a-sequences. The PHY preamble decoder 264 can determine PHY parameters such as modulation mode, piconet ID, header rate, etc. based on one or more of the following: 1) Determine whether a sequence or b sequence is used in STF; 2) Determine u in LTF And v or the sequence of u'and v'; and 3) determine the coverage code in STF, LTF and/or SFD.

[0147] Next, Figure 40 An example of the generator 900 is shown. The generator 900 responds to the pulse signal [1 0 0...], using a weight vector W of length 7 such as (1) and such as (2), (5) or ( 8) The delay vector D of length 7 is used to generate a pair of complementary Golay sequences a and b. Such as Figure 40 As shown, the generator 900 may include an input 902, delay elements 904-910, adders/subtractors 920-934, and multipliers 936-942. For example, each value in the weight vector W given by (1) is mapped to one of the inputs of the corresponding multiplier 936-942. For the weight vector given by (1), the multiplier 936 is assigned W 1 = 1, assign W to the multiplier 938 2 = 1, assign W to multiplier 940 6 = 1, assign W to the multiplier 942 7 = -1, etc. As an example, the delay elements 904-910 are assigned the value of the delay vector D given by (2): the delay element 904 is assigned D 1 = 1, assign D to delay element 906 2 = 2, etc. Such as Figure 40 As shown, the elements of the generator 900 are interconnected to generate the Golay sequences a and b given by (3) and (4) in response to the vectors D and W considered in this example. Similarly, the generator 900 generates the Golay sequence given by (6) and (7) in response to the weight vector W given by (1) and the delay vector D given by (5). Although the transmitting device 12 may include a generator 900, storing the desired vectors D and W in a memory unit, and applying the vectors D and W to the generator 900 to generate sequences a and b, it is conceivable that the transmitting device 12 is preferably Two or more pairs of sequences a and b are stored in the memory for faster application in expanding bits and/or generating PHY preambles.

[0148] On the other hand, the receiving device 14 can implement Image 6 Shown and in Figure 41 The correlator 250 is shown in more detail in. The correlator 250 generally has a structure similar to that of the generator 900. However, in order to generate the correlation output between the complementary Golay sequences a and b (determined by the vectors D and W), the correlator 250 "inverts" the adder and subtractor of the generator 900 (ie, replaces the adder with a subtractor) , Replace the subtractor with an adder), and multiply the output of the delay element assigned to D7 by -1. Generally, other designs of correlator 250 are possible. However, it will be understood that Figure 41 The example architecture shown in implements the correlator as a filter with an impulse response, which can be expressed as the inverse of the chip ordering in sequences a and b, or a rev And b rev.

[0149] In addition, Figure 41 The a/b correlator 250 shown in can effectively interact with the u/v correlator 258 (see Image 6 ) Collaborative use. Figure 42 An embodiment of the u/v correlator 258 is shown, which detects u/v correlation for u=[-b a b a] and v=[-b -a -b a]. In this example, a delay element 950 with a delay of 128 is connected to the b-related output 952 (see Figure 7 In the diagram 312, the cross-correlation output between b and the input signal (an example of XCORR B)), the subtractor 956 is connected to the a-correlation output 954, and so on. Delay elements 958 and 960 and several additional adders and subtractors provide u/v correlation. Of course, if the sequences a and b whose length is not 128 chips are used, the factors in the delay elements 950, 958, and 960 can be adjusted. The u/v correlator 258 can generate cross-correlation outputs 962 and 964, which correspond to the cross-correlations between the received signal and the sequences u and v, respectively.

[0150] It will be noted that the u/v correlator 258 effectively uses the correlation output generated by the a/b correlator 250, and only a few additional components are required to correlate the sequences u and v. It will also be understood that u/v correlators for other sequences u and v can be similarly constructed. As an example, Figure 43 The u/v correlator 970 shown in FIG. 5 generates a cross-correlation output between the received signal and the sequence u=[ba -ba] and v=[-b -a -ba]. versus Figure 42 Similar to the example shown in, the u/v generator 970 effectively uses the output of the a/b correlator 250.

[0151] As described above, compared with the prior art PHY preamble, the specific CES symbols u and v in the LTF allow the PHY preamble to use less cycles to effectively transmit PHY level parameters. The following example shows another technique for developing effective u and v sequences for use in LTF. If the repetition of sequence a is used to transmit STF, then let:

[0152] u 1 =[c 1 b c 2 a c 3 b c 4 a) (12)

[0153] And make

[0154] v 1 =[c 5 b c 6 a c 7 b c 8 a], (13)

[0155] Where c 1 To c 8 Each of is +1 or -1. In order to make u 1 And v 1 More effective, use

[0156] c 4 = C 8 (14)

[0157] And preferably,

[0158] c 1 = C 5 (15)

[0159] Remaining symbol c 2 , C 3 , C 5 And c 7 Should be chosen so that u 1 And v 1 Complementary. It will be noted that in at least some of the embodiments discussed above, other sequences u and v may be used. However, if conditions (14) and (15) are met, the LTF can be made shorter, at least because the adjacent sequences u and v provide each other with a cyclic prefix and/or suffix. In addition, the complementary sequence u 1 And v 1 Can be effectively combined with another pair of complementary sequence u 2 And v 2 Used in combination, so that the transmitting device can be used to {u 1 , V 1 } Or {u 2 , V 2 } To construct the PHY preamble, and the selection of one of these two pairs of sequences can transmit one or more operating parameters (for example, SC or OFDM communication mode, header rate, etc.) to the receiving device. If the STF has multiple repetitions of sequence a unconditionally, the second pair of CES symbols can be similar to {u 1 , V 1 } To qualify:

[0160] u 2 =[d 1 b d 2 a d 3 b d 4 a) (16)

[0161] v 2 =[d 5 b d 6 a d 7 b d 8 a], (17)

[0162] Where d 1 To d 8 Each of is +1 or -1, where preferably

[0163] d 4 =d 8 (18)

[0164] And also preferably

[0165] d 1 =d 5 (19)

[0166] In order to enable the receiving device in {u 1 , V 1 } And {u 2 , V 2 } To distinguish between, sequence c 1 c 2...c 8 And d 1 d 2...d 8 Should not be the same.

[0167] In another embodiment, a repetition of either a or b is used to transmit STF. Then a pair of sequences can be defined according to (12)-(14) (u 1 , V 1 }, and {u 2 , V 2 } Can then be limited to:

[0168] u 2 =[d 1 a d 2 b d 3 a d 4 b] (20)

[0169] v 2 =[d 5 a d 6 b d 7 a d 8 b], (21)

[0170] Where d 1 -d 8 Each of is +1 or -1; wherein preferably, conditions (18) and (19) are also satisfied; and the remaining symbols d 2 , D 3 , D 5 And d 7 Make u 2 , V 2 Complementary. In at least some cases that fit this approach, u 2 Can start from u 1 Export, and v 2 Can be from v 1 Export. Alternatively, u 2 Can be from v 1 Export, and v 2 Can start from u 1 Export.

[0171] Consider some specific examples, {u 1 , V 1 } Can be defined according to (12) and (13), and {u 2 , V 2 } Can be limited to:

[0172] u 2 =m[c 2 a c 3 b c 4 a c 1 b] (22)

[0173] v 2 =m[c 6 a c 7 b c 8 a c 5 b], (23)

[0174] Where m is +1 or -1.

[0175] As another example, where {u 1 , V 1 } Is still provided by (12) and (13), {u 2 , V 2 } Can be limited to:

[0176] v 2 =m[c 2 a c 3 b c 4 a c 1 b] (24)

[0177] u 2 =m[c 6 a c 7 b c 8 a c 5 b], (25)

[0178] Where m is +1 or -1. It will be noted that this restriction corresponds to the u provided by (22) and (23) 2 And v 2 The "exchange" limit.

[0179] As yet another example, where {u 1 , V 1 } Meets (12) and (13), and where m is +1 or -1, {u 2 , V 2 } Can be given as

[0180] u 2 =m [c 4 a c 1 b c 2 a c 3 b], (26)

[0181] v 2 =m [c 8 a c 5 b c 6 a c 7 b], (27)

[0182] or

[0183] v 2 =m[c 4 a c 1 b c 2 a c 3 b], (28)

[0184] u 2 =m[c 8 a c 5 b c 6 a c 7 b], (29)

[0185] or

[0186] u 2 =m[c 2 a c 3 b c 4 a c 1 b], (30)

[0187] v 2 =m[c 8 a c 5 b c 6 a c 7 b], (31)

[0188] or

[0189] v 2 =m[c 2 a c 3 b c 4 a c 1 b], (32)

[0190] u 2 =m[c 8 a c 5 b c 6 a c 7 b], (33)

[0191] or

[0192] u 2 =m[c 4 a c 1 b c 2 a c 3 b], (34)

[0193] v 2 =m[c 6 a c 7 b c 8 a c 5 b], (35)

[0194] or

[0195] v 2 =m[c 4 a c 1 b c 2 a c 3 b], (36)

[0196] u 2 =m[c 6 a c 7 b c 8 a c 5 b], (37)

[0197] As described above, the use of STF patterns, SFD patterns, CES symbols, a/b sequences, etc., and various combinations of these parameters can beneficially serve as an indication of one of the PHY layer parameters associated with the data frame. Moreover, the transition between patterns can also be used to transmit PHY layer parameters or other data to the receiving device. For example, the a-to-a transition between the last period of SFD and the first period in CES may indicate SC, the a-to-b transition may indicate OFDM, and so on.

[0198] Generally, for the above discussion, it will be understood that the terms "transmitting device" and "receiving device" only represent the operating state of physical devices, and it is not intended that these devices are always limited to only receiving or transmitting in the corresponding communication network. For example, at certain points during operation, figure 1 The device 12 in can operate as a receiver, and the device 14 can operate as a transmitter.

[0199] At least some of the blocks, operations, and techniques described above can be implemented using hardware, a processor that executes firmware instructions, a processor that executes software instructions, or any combination thereof. When implemented by a processor that executes software or firmware instructions, the software or firmware instructions can be stored in any computer-readable memory, such as on a magnetic disk, optical disk or other storage medium, or stored in RAM or ROM or flash memory, processing , Hard disk drive, optical disk drive, tape drive, etc. Likewise, the software or firmware instructions can be delivered to the user or system by any known or desired delivery method, such as including on a computer-readable disk or other transferable computer storage mechanism, or through a communication medium. Communication media usually embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transmission mechanism. The term "modulated data signal" means a signal whose one or more characteristics are set or changed in such a way that information is encoded into the signal. By way of example and not limitation, communication media includes wired media, such as a wired network or direct wired connection; and wireless networks, such as acoustic, radio frequency, infrared, or other wireless media. Thus, it is possible to deliver software or firmware instructions to users or systems through communication channels such as telephone lines, DSL lines, cable television lines, optical fiber lines, wireless communication channels, and the Internet (which are regarded as the same as those provided through a transportable storage medium). Such software is the same or interchangeable). The software or firmware instructions may include machine-readable instructions, which when executed by the processor, cause the processor to perform various actions.

[0200] When implemented by hardware, the hardware may include one or more of the following: discrete components, integrated circuits, application specific integrated circuits (ASIC), and so on.

[0201] Although detailed descriptions of various different embodiments have been described above, it should be understood that the scope of this patent is defined by the appended claims. The detailed description should be understood as merely exemplary, and does not describe all feasible implementation manners, because it would be unrealistic or even impossible to describe all feasible implementation manners. Using current technology or technology developed after the filing date of the present disclosure, various alternative embodiments can be implemented, which will still fall within the scope of the claims.