MX2008005742A - Apparatus and method for sensing an atsc signal in low signal-to-noise ratio - Google Patents

Abstract

A Wireless Regional Area Network (WRAN) receiver comprises a transceiver for communicating with a wireless network over one of a number of channels, and an Advanced Television Systems Committee (ATSC) signal detector for use in forming a supported channel list comprising those ones of the number of channels upon which an ATSC signal was not detected, wherein the ATSC signal detector includes a filter matched to a PN511 sequence of an ATSC signal for filtering a received signal on one of the number of channels for providing a filtered signal for use in determining if the received signal is an ATSC signal. The ATSC signal detector can be a coherent or a non-coherent ATSC signal detector.

Description

APPARATUS AND METHOD FOR DETECTING AN ATSC SIGNAL (ADVANCED TELEVISION SYSTEMS COMMITTEE) IN A LOW NOISE SIGNAL RELATION Field of the Invention The present invention relates in general to communication systems and more particularly to wireless systems, for example, terrestrial, cellular broadcast, wireless fidelity (WI-FI), satellite, etc.

BACKGROUND OF THE INVENTION A wireless regional area network (WRAN) system is being studied in the IEEE 80222 standard group. The WRAN system is intended to make use of unused broadcast television (TV) channels in the spectrum. TV, on a non-interference basis, to address, as a primary objective to rural and remote areas and low-population markets with similar levels of operation to transmission access technologies that work in urban and suburban areas. The WRAN system may also have the ability to scale to serve in denser population areas where the spectrum is available. Since one objective of the WRAN system is not to interfere with TV transmissions, an important procedure is to detect it in a robust manner and Exactly the legal TV signals that exist in the area, offered by the WRAN (the WRAN area) In the United States, the TV spectrum currently It comprises ATSC (Advanced Television Systems Committee) transmission signals that co-exist with NTSC (National Television Systems Committee) transmission signals. ATSC transmission signals are also called digital TV (DTV) signals. Currently, NTSC transmission is will abandon in 2009, and at that time, the TV spectrum will only include ATSC transmission signals. As noted above, one objective of the WRAN system is not to interfere with the TV signals that exist in a particular WRAN area, it is important in a WRAN system have the ability to detect ATSC transmissions A known method to detect the ATSC signal is to look for a small pilot signal that is part of the ATSC signal Such a detector is simple and includes a phase-locked circuit with a very broadband filter narrow to extract the ATSC pilot signal In a WRAN system, this method provides an easy way to verify the transmission channel is currently in use simply by reviewing whether the ATSC detector provides an extracted ATSC pilot signal. Unfortunately, this method is not accurate, especially in an environment of a very low signal-to-noise (SNR) ratio. In fact, the false detection of a signal ATSC can occur when there is a miscellaneous signal present in the band that has a spectral component in the position of the pilot carrier Brief Description of the Invention It has been observed that by increasing the accuracy to detect ATSC transmission signals in environments with very low signal-to-noise ratio (SNR), the segment synchronization symbols and the field synchronization symbols embedded within An ATSC DTV signal is used to improve the probability of detection, while the probability of false alarm is reduced. In particular, and in accordance with the principles of the invention, an apparatus comprises a transceiver to communicate with the wireless network over one of a number of channels and an Advanced Television Systems Committee (ATSC) signal detector to be used in forming a supported channel list, which comprises those of the number of channels over which the ATSC signal was not detected, where the ATSC signal detector includes a matched filter with a PN511 sequence of an ATSC signal to filter the received signal into one of a number of c analogs to provide a filtered signal to be used in determining whether the received signal is an ATSC signal In an illustrative embodiment of the invention, the receiver is a receiver of the wireless regional area network (WRAN) and wherein the ATSC signal detector is A coherent ATSC signal detector In another illustrative embodiment of the invention, the receiver is a receiver of the wireless regional area network (WRAN) and where the ATSC signal detector is a non-coherent ATSC signal detector In view of the above and as will be evident from reading the detailed description , other modalities and features are possible and may fall within the principles of the invention Brief Description of the Drawings Figure 1 shows Table One, which lists the television channels (TV) Figures 2 and 3 show Tables Two and Three , which lists the frequency shifts under different conditions for a received ATSC signal. Figure 4 shows an illustrative WRAN system in accordance with the principles of the invention. Figure 5 shows an illustrative receiver for use in the WRAN system of Figure 4, of In accordance with the principles of the invention Figure 6 shows an illustrative flow diagram for use in the WRAN system of Figure 4 Figures 7 and 8 stran the tuner 305 and the tracking circuit 315 of the carrier of Figure 5 Figures 9 and 10 show a format for an ATSC DTV signal, and Figures 11 to 21 show various embodiments of the ATSC signal detectors in accordance with the principles of the invention Detailed Description of the Invention Other than the inventive concept, the elements shown in the Figures are well known and will not be described in detail. Also, familiarity with television transmission, receivers, networks and video coding is assumed and not they are described in detail here For example, different from the inventive concept, familiarity is assumed with the current recommendations and proposals for TV standards, such as NTSC (National Television Systems Committee), PAL (Phase Alteration Lines), SECAM (Sequential Couleur Avec) Memoire) and ATSC (Advanced Television Systems Committee) Other information on ATSC transmission signals can be found in the following ATSC standards Digital Television Standard (A / 53), Revision C, including Amendment No. 1 and Errata No. 1, Doc A / 53C, and Recommended Practice Guide to the Use of the ATSC Digital Television Standard (A / 54) In the same way, different from the inventive concept, s e assume transmission concepts such as vestigial eight-level sideband (8-VSB), Quadrature Amplitude Modulation (QAM), orthogonal frequency division multiplexing (OFDM) or coded (COFDM), and receiver components such as the main radio-frequency (RF) end, or the receiving section, such as the low-noise block, the tuners, and demodulators, correlators, leak integrators, or leakage squares. Similarly, different from the inventive concept, the formatting and coding methods (such as the standards of Movmg Pictures Experts Group (MPEG-2) systems (ISO / IEC 13818-1) for generating transport bit streams are well known and will not be described here in detail. Note that the inventive concept can be implemented with the use of conventional programming techniques, which, as such, will not be described here. Finally, the equal numbers in the Figures represent sim elements. illa A TV spectrum for the United States, as is known in the art, is shown in Table One of Figure 1, which provides a list of TV channels in very high frequency (VHF) and ultra high frequency bands ( UHF) For each TV channel, the corresponding lower edge of the assigned frequency band is shown. For example, TV channel 2 starts at 54 MHz (million hertz), TV channel 37 starts at 608 MHz and the channel 68 of TV starts at 794 MHz, etc. As is known in the art, each TV channel or band occupies 6 MHz of the bandwidth. As such, TV channel 2 covers the frequency spectrum (or interval) of 54 MHz. at 60 MHz, TV channel 37 spans the band from 608 MHz to 614 MHz and TV channel 68 spans the band from 794 MHz to 800 MHz As mentioned above, a WRAN system makes use of television transmission channels (TV) not used in the TV spectrum With respect to this, the WRAN system carries out a "channel detection" p To determine which of these TV channels is really active (or "operational") in the WRAN area in order to determine that portion of the TV spectrum that is actually available for use by the WRAN system. In addition to the TV spectrum shown in Figure 1, a particular ATSC DTV signal in a particular channel can also be affected by the NTSC signals, or even by other ATSC signals, which are co-located (ie on the same channel) or adjacent to the ATSC signal (for example, in the next higher or lower channel) This is illustrated in Table Two, of Figure 2, in the context of an ATSC pilot signal as it is affected by different interference conditions. For example, the first row 71 of the Table Two provides the offset of the lower edge in Hz of an ATSC pilot signal, when there is no co-located or adjacent interference of another NTSC or ATSC signal This corresponds to the ATSC pilot signal as defined in the ATSC standards before scrolls, ie, the pilot signal is presented at 30944059 KHz (thousands of Hertz) over the lower edge of the particular channel (Again, Table One, of Figure 1 provides the value of the lower edge in MHz for each channel) However , reference is now made to the row labeled 72 of Table Two, which provides for the displacement of the lower edge of an ATSC pilot signal, where an NTSC signal is co-located. In such a situation, an ATSC receiver will receive a pilot signal. ATSC that is 338065 KHz on the lower edge In the context of NTSC and ATSC transmissions, from Table Two, it can be seen that the total number of possible displacements is 14 However, once the NTSC transmission is discontinued, the The total number of possible displacements decreases to two, with a tolerance of 10 Hz, which is illustrated in Table Three of Figure 3 Because it is important that the detection of any channel is accurate, it has been observed that the inc The accuracy of any reference of time or carrier frequency in a receiver, improves the operation of signal detection, or channel detection, techniques (whether these techniques are coherent or non-coherent). In particular and in accordance with the present invention, a receiver comprises a tuner for tuning to one of a number of channels, a transmit signal detector coupled to the tuner for detecting whether there is a transmission signal in at least one of the channels, wherein the tuner is calibrates as a function of the received transmission signal An illustrative embodiment of the invention is described in the context of using an existing ATSC channel as a reference An illustrative wireless regional area network (WRAN) system 200 incorporating the principles of the invention is shown in Figure 4 The 200 WRAN system serves as a geographic area (the WRAN area) (not shown in the F Figure 4) In general terms, the WRAN system comprises at least one base station (BS) 205, which communicates with one or more user stations (CPE) 250 The latter can be stationary or mobile The CPE 250 is a system processor based and includes one or more processors and associated memory, as represented by processor 290 and memory 295, shown in the form of dotted boxes in Figure 4 In this context, computer programs, or software, they are stored in the memory 295 to be executed by the processor 290 The latter is representative of one or more stored program control processors and these do not have to be dedicated to the function of the transmitter, for example, the processor 290 can also control other functions of the CPE 250 The memory 295 is representative of any storage device, for example, a random access memory (RAM), a read-only memory (ROM), etc., can be internal and / or external to CPE 250, and is volatile and / or non-volatile, as needed The physical layer of communication between BS 205 and CPE 250, through antennas 210 and 255, illustratively, is based on OFDM , for example, OFDMA through transceiver 285 and is represented by arrows 211 To enter a WRAN network, CPE 250 can first "associate" with BS 210 During this association, CPE 250 transmits information, through transceiver 285 , with the capacity of the CPE 250 to BS 205 through a control channel (not shown) The reported capacity includes, for example, the maximum and minimum transmission power, and a list of supported channel for transmission and In this regard, the CPE 250 performs a "channel detection" in accordance with the principles of the invention, in order to determine the TV channels that are not active in the WRAN area. The resulting list of available channels. which is used in WRAN communications, then sent to BS 205 An illustrative portion of a receiver 300 for use in CPE 250 is shown in Figure 5 Only that portion of receiver 300 relevant to the inventive concept is shown. Receiver 300 comprises a tuner 305, a carrier tracking circuit (CTL) 315, an ATSC signal detector 320 and a controller 325 The latter is representative of one or more stored program control processors, eg, a microprocessor (such as processor 290), and these do not have to be dedicated to the inventive concept, for example, the controller 325 can also control other functions of the receiver 300. In addition, the receiver 300 includes a memory (such as the memory 295), for example, a random access memory ( RAM), a read-only memory (ROM), etc., and may be part of or may be separated from the controller 325 For simplicity, some elements are not shown in Figure 5, such as an automatic gain control element (AGC). ), an analog to digital converter (ADC) when the processing is in the digital domain, and additional filtering Different to the inventive concept, these elements will be evident to the experienced people in the digital domain. With respect to this, the embodiments described herein can be implemented in the analog or digital domain. In addition, those skilled in the art will recognize that certain processing can involve complex signal paths, as necessary. Before describing the inventive concept, the operation General of the receiver 300 is as follows An input signal 304 (for example, received through the antenna 255 of Figure 4) is applied with the tuner 305 The input signal 304 represents a digital VSB modulated signal according to the above mentioned "Digital Television Standard ATSC" and transmitted in one of the channels shown in Table One of Figure 1 Tuner 305 is tuned to different channels by controller 325 through a bidirectional signal path 326 to select channels of Particular TVs and provides the signal 306 converted into a downlink centered to an IF (intermediate frequency) spec The signal 306 is applied on the CTL 315, which processes the signal 306 to remove any frequency shift (such as between the local oscillator (LO) of the transmitter and the LO of the receiver) and to demodulate the VSB signal ATSC received in descending to the baseband from an intermediate frequency (IF) or near the baseband frequency, (for example, see United States Advanced Television Systems Committee, "Guide to the use of the ATSC Digital Television Standard," Document A / 54, October 4, 1995), and U.S. Patent No. 6,233,295, issued May 15, 2001 to Wang, entitled "Segment Sync Recovery Network for an HDTV Receiver") CTL 315 provides signal 316 to detector 320 ATSC signal, which processes the signal 316 (described below) to determine whether the signal 316 is an ATSC signal The ATSC signal detector 320 provides the resulting information for the controller 325 through the path 321 With reference Referring now to Figure 6, there is shown an illustrative flow chart for use in a receiver 300 in accordance with the principles of the invention. In particular, the detection of the presence of ATSC DTV signals in the VHF and UHF TV bands at levels of signal below those required to demodulate a signal that can be improved by having an accurate carrier and time-shift information. Illustratively, the stability and known frequency allocation of the DTV channels themselves are used to provide this information As specified in the aforementioned ATSC A / 54A ATSC Recommended Practice, carrier frequencies are specified to be at least 1 KHz (thousands of hertz), and narrower tolerances are recommended for good practice. this, in step 260, the controller 325 first scans the known TV channels, such as those illustrated in Table One of Figure 1, for an AT signal Easily identifiable, existing SC In particular, the controller 325 controls the tuner 305 to select each of the TV channels The resulting signals (if any) are processed by the ATSC signal detector 320 (described below) and the results are provided to the controller 325 through the path 321 Preferably, the controller 325 searches for the strongest ATSC signal transmitted at that time in the WRAN area. However, the controller 325 may stop at the first detected ATSC signal. With brief reference to FIG. 7, a block diagram of a tuner 305 is shown. The tuner 305 comprises the amplifier 355, the multiplier 600, the filter 365, a division element between n 370, the voltage controlled oscillator 385 (VCO), the phase detector 375, the circuit filter 390, an element 380 of division between m and local oscillator 395 (LO) Different from the inventive concept, the elements of tuner 305 are well known and will not be described in more detail In general, the following relationship is maintained between the signals provided by LO 395 and VCO 385 nf ((J md) where Fref is the reference frequency provided by the LO 395, F co is the frequency provided by the VCO 385, n is the value of the divisor represented by the division element 370 between n and m is the value of the divisor represented by the division element 380 between m Equation (1) is rewritten as F F r. < l = n- nF m »p (2) From equation (2) it can be seen that FVco can be adjusted in different ATSC DTV bands with the appropriate values of n, as adjusted by controller 325 (step 260 of Figure 6) through path 326 however , as mentioned before, the receiver 300 includes the CTL 315, which removes any frequency shift, Flection There are two frequency shifts The first is the error caused by the frequency differences between LO 395 and the frequency reference of the transmitter. second is the error caused by the value used for Fpaso, since the actual frequency, Frf, provided by LO 395 is only approximately known within a given tolerance of the local oscillator. As such, FdeSpyz includes both the error from the value of nFpaSo of the selected channel and the error caused by the frequency differences in the local frequency reference and the frequency reference of the transmission Referring now to Figure 8, an illustrative block diagram of the CTL 315 is shown. The CTL 315 comprises the multiplier 405, a phase detector 410, a cycle filter 415, a numerically controlled oscillator 420 (NCO), and a Table 425 of Sen / Cos Different to the inventive concept, the CTL 315 elements are well known and will not be described here. The NCO 420 determines the Fdesp? Azam? Ent as is known in the art and these frequency shifts are removed from the signal received through Table 425 of Sen / Cos and multiplier 405. Continuing with step 270 of Figure 6, once an existing ATSC signal is found, controller 325 calibrates receiver 300 by determining at least one characteristic of frequency (time) related from the detected ATSC signal In particular, the general operation of the receiver 300 of Figure 5 can be represented by the following equation F = nF + F r.? (3) where Fc represents the frequency of the pilot signal of the detected ATSC signal With respect to the value for FdeSpray in equation (3), the controller 325 determines this value simply by having access to the associated data in NCO 420 , through a bidirectional path 327 However, although this value for n was already determined by controller 325 for the selected ATSC channel, the actual value of "To move is unknown, however, equation (3) is rewritten as F -F. '.r F ".i (4) Although this solution seems straightforward, it can be renamed that the value for Fc is not determined uniquely as suggested by Table One of Figure 1 Rather, the ATSC DTV signal detected may be affected by other NTSC or ATSC signals as shown in Table Two of Figure 2 and Table Three of Figure 3 When there are NTSC and ATSC transmissions in the WRAN region, then the 14 possible offsets should be taken into account, as shown in Table Two of Figure 2 However, when there are no NTSC transmissions in the WRAN region, then only two offsets should be taken into account, as shown in Table Three of Figure 3 For simplicity, it is assumed that there are no NTSC transmissions and only Table Three is used in this example As such, with the use of the values in Table One and Table Three (for example, stored in the aforementioned memory), controller 325 performs two calculations to determine mine different values for Fpaso F ° > - F F.p (4a) F (1) -F / • \ .'- '(4b) where Fc () represents the lower band edge of Table One for the selected ATSC channel plus the offset of the lower band edge of the first row of the Table Three, and Fc () represents the lower band edge of Table One for the selected ATSC channel plus the lower band edge offset of the second row of Table Three. As a result, controller 325 determines two possible values for Fpaso to be used. at receiver 300 Thus, in step 270, controller 325 determines the tuning parameters to be used in calibrating receiver 300 Finally, in step 275, controller 325 scans the TV spectrum to determine the list of supported channel , which comprises one or more TV channels that are not used and as such, are available to support WRAN communications for each channel that is selected by controller 325 (for example, from the list in Table One) , the observations with respect to equations (3), (4), (4a) and (4b) still apply In other words, for each selected channel, the displacements shown in Table Three must be taken into account Since there are two displacements shown in Table Three and there are two possible values for Fpaso are determined in step 270 (equations (4a) and (4b)), four scans are carried out (When the displacements listed in the Table were used) Two, there will be 142 scans or 196 scans. For example, in the first scan, controller 325 sets tuner 305 through path 326 in different values for n for each of the ATSC channels Controller 325 determines the values for n and n Fdespiazam? Ento from where value for Fpaso is equal to the value determined for F () step and the value for Fc is equal to the lower band edge of Table One for the selected ATSC channel plus the lower band edge offset of the first row of the Table Three However, for the second scan, while the value for Fpaso remains the same, for the value determined for F (1) step, the value for Fc is now changed to be equal for the lower band edge of Table One for the selected ATSC channel plus the lower band edge offset from the second row of Table Three The third and fourth scans are similar except that the value for Fpass is now set equal to the value determined for F (2) step During each of these scans, as the tuner 305 is tuned to provide a selected channel, the ATSC signal detector 320 processes the received signals to determine when an ATSC signal is present in the channel. to the currently selected data or information, for the presence of an ATSC signal is provided to the controller 325 through the path 321 From this information, the controller 325 constructs the list of supported channel In this way, the stability and the assignment The known frequency of the DTV channels themselves are used to calibrate the receiver 300 in order to improve the detection of the low ATSC DTV SNR signals. As such, in step 275, the receiver 300 has the ability to scan the ATSC signals. which can be present even in a very low SNR environment, due to the exact frequency information (Fdesp? azam? ent and the different values for Fpaso), determined in step 270. The objective sensitivity is to detect the ATSC signals with a force of signal of -116dBm (decibels relative to the energy level of one mi watt) This is more than 30 dB (decibels) below the visibility threshold (ToV) It should be noted, that according to the For example, the ATSC signal detected in step 260 may be excluded from the scans carried out in the same way. It may be necessary to re-calibrate periodically. step 275 In addition, any re-caching can be carried out immediately by tuning in to the ATSC signal identified from step 260 without having to perform step 260 again. Also, once an ATSC signal is detected in step 275 , the associated band can be excluded from any subsequent scanning As noted above, the receiver 300 includes an ATSC signal detector 320 In accordance with the principles of the invention, an ATSC signal detector 320 takes advantage of the ATSC DTV signal format. DTV data are modulated with the use of 8-VSB (vestigial sideband). In particular, for a receiver operating in low SNR environments, the symbols of Segment synchronization and field synchronization symbols embedded within an ATSC DTV signal are used by the receiver to improve the probability of accurately detecting the presence of an ATSC DTV signal, which reduces the likelihood of false alarm in an ATSC DTV signal In addition to the eight-level digital data stream, a four-symbol (binary) two-level data segment synchronization is inserted at the start of each data segment. One segment of ATSC data is shown in Figure 9. ATSC data consists of 832 symbols, four symbols for data segment synchronization and 828 data symbols The data segment synchronization pattern is a binary 1001 pattern, as can be seen from Figure 9 The multiple data segments (313 segments) comprise the ATSC data field, which comprises a total of 260,416 symbols (832x313) The first data segment in a data field os is called field synchronization segment The structure of the field synchronization segment is shown in Figure 10, where each symbol represents a data bit (two levels) In the field synchronization segment, a 511-bit pseudo-aleatopa sequence (PN511) immediately follows the data segment synchronization After the PN511 sequence, there are three 63-bit identical pseudo-random sequences (PN63) concatenated together, with the second PN63 sequence inverted each other data field In view of the foregoing, one modality of the ATSC signal detector 320 is shown in Figure 11 In this embodiment, a ATSC signal detector 320 comprises an equalized filter 505 which coincides with the aforementioned PN511 sequence to identify the presence of the PN511 sequence. Another variation is shown in Figure 12. In this Figure, the matched filter output is accumulated multiple times to decide whether there is an important peak This improves the probability of detection and reduces the probability of false alarm A disadvantage of this modality of Figure 12 is that requier e a large memory Another measure is shown in Figure 13 In this measurement, the peak value is detected (520), together with its position within a field (510, 515) of data It should be noted that the remitted signal also increases the address counter (ie, "jumps the address") to store the results in different locations of the RAM 525 As such, the results are stored in multiple data fields in the RAM 525 When the peak positions are the same for a certain percentage of the data fields, then it is decided that a DTV signal is present in the DTV channel. Another method to detect the presence of an ATSC DTV signal is to use the data segment synchronization since the data segment synchronization repeats each segment of data. data, usually used for time recovery This method of time recovery is noted in "Recommended Practice Guide to the Use of the ATSC Digital Television Standard (A / 54) However, A data segment synchronization can also be used to detect the presence of a DTV signal with the use of the time recovery circuit. When the time recovery circuit provides a time closure indication, it ensures the presence of the DTV signal with high accounting This method will work well even when the initial local symbol clock is not close to the transmitter symbol clock, as long as the clock offset is within the activation interval of the time recovery circuit. However, it should be noted that since the useful range was low at 0 dB SNR, it is necessary to have an improvement of additional 15 dB to reach the target detection of -116 dBm Another measure that can be used to detect an ATSC signal is to process the segment synchronizations independent of the recovery mechanism of time employed This is illustrated in Figure 14, which shows a synchronization detector of coherent segment using infinite impulse response (MR) filter 550 comprising a leak integrator (where the a symbol is a predefined constant) The use of a MR filter constructs the peak of time for detection, reinforcing the information that occurs with a repetition period of a segment This assumes that the carrier displacement and the time offset are small Different to the coherent methods described above for detecting the ATSC signal, non-coherent measures can be used, ie, it is not necessary the downward conversion to the baseband through the use of the pilot carrier This is advantageous, since robust extraction of the pilot can be problematic in low SNR environments A non-coherent segment synchronization detector, illustrative is shown in the Figure 15, which shows the delay line structure The input signal is multiplied by the conjugate version, delayed by itself a (570, 575) The result is applied to a filter to match the data segment synchronization (the 580 filter matched data segment synchronization) The conjugation ensures that any displacement of the carrier does not affect the amplitude after the matched filter Alternatively, an integrating and pulling measure can be taken After the matched filter 580, the magnitude (585) of the signal is taken (or more easily, the square magnitude is taken as I2 + Q2), where I and Q are in phase and the quadrature components, respectively, of the signal outside the matched filter). This magnitude value (586) can be examined directly to see if there is an important peak indicating the presence of a DTV signal. Alternatively, as indicated in Figure 15, the signal 586 can be further refined when processed with the 550 MR filter, in order to improve the robustness of the calculation over multiple segments. An alternative modality is shown in Figure 16 In this embodiment, the integration (580) takes performed consistently (ie, maintaining the phase information), after which the magnitude (585) of the signal is taken. Similar to the modalities described above that operate in the baseband, other non-coherent modalities ta They may also use the longer PN511 sequences found within the field synchronization. However, it should be noted that certain modifications will have to be made to adapt the frequency offset. For example, when the PN511 sequence is to be used as an indicator of the ATSC signal, there may be several correlators used simultaneously to detect its presence The case where the frequency shift is such that the carrier undergoes a complete cycle or rotation during the PN511 sequence should be considered in such a case, the output of the correlator matched However, when the PN511 sequence is broken into N parts, each part will have an appreciable energy, since the carrier will only rotate by 1 / N cycles during each part. Therefore, the measure of the non-coherent correlator can be used when breaking the long correlator in smaller counts, and approach each sub-sequence with a non-coherent correlator, such as that shown in Figure 17 In this Figure, the sequence to be correlated is broken into N sub-sequences, numbered from 0 to N-1 input are delayed such that the outputs of the correlator are combined (590) to produce a usable non-coherent combination. Another illustrative mode of an ATSC signal detector is shown in Figure 18 in order to reduce the complexity of the signal detector. ATSC, an ATSC signal detector of Figure 18 uses an equalized filter (710) that matches the PN63 sequence. The output signal of the matched filter 710 is applied to the delay line 715. In the embodiment of Figure 18, it is used a measure of coherent combination Since the average PN63 is inverted in each other data field synchronization, two outputs y1 and y2 are generated through the adders 720 and 725, 5 corresponding to these two cases of no data field timing As can be seen from Figure 18, the processing path for the output y1 includes multipliers to invert the average PN63 before the combination through the summer 720. It should be noted that the modality of Figure 18 leads to out peak detection When I0 an important peak appears in y1 or in y2, then it is assumed that an ATSC DTV signal is present An alternative mode of an ATSC signal detector that matches the PN63 sequence is shown in Figure 19 This mode is similar to that shown in Figure 18, except that the signal The output I5 of the matched filter 710 is first applied to the element 730, which computes the square magnitude of the signal. This is an example of a non-coherent combination measurement. As shown in Figure 18, the modality of Figure 19 leads to out peak detection The adder 735 combines the different elements of the delay line 715 for 0 provides the output signal y3 When an important peak appears in y3, then it is assumed that an ATSC DTV signal is present It should be noted that when the carrier displacement is relatively large, the measure of the non-coherent combination of Figure 19 may be more appropriate than the coherent combination Also, it should be noted that the element 730 can simply determine the magnitude of the signal Also, the additional variations are shown in Figures 20 and 21 In these illustrative embodiments, PN511 and PN63 sequences are used together for ATSC signal detection With reference p At the same time as the embodiment shown in Figure 20, the signals y1 and y2 are generated as described above with respect to the embodiment of Figure 18, to detect a PN63 sequence. In addition, the output of the matched filter 505 (which matches the sequence PN511) is applied to the delay line 770, which stores data on the time interval for the three PN63 sequences. The modality of Figure 20 carries out the peak detection When an important peak appears in z1 or in z2, (provided through the adders 760 and 765, respectively), then it is assumed that an ATSC DTV signal is present. Referring now to Figure 21, the embodiment of Figure 21 also combines the detection of the PN511 sequence with the detection of the sequence PN63, as shown in Figure 19 In this embodiment, the matched filter 505 output signal is first applied to element 780, which computes the square magnitude of the signal This is an example of another combination measure Non-coherent ion As in Figure 20, the modality of Figure 21 performs peak detection. Adder 785 combines the different elements of delay line 770 with the output signal y3 to provide the output signal z3. an important peak appears in z3, it is assumed that an ATSC DTV signal is present Also, it should be noted that the element 780 can simply determine the magnitude of the signal Other variations are possible for the above For example, the matched filters PN63 and PN511 can be in cascade, in order to make use of its inherent delay line structure to reduce the amount of additional delay line needed In another modality, three equalized PN63 filters can be employed better than a single PN63 equalized filter plus lines This can be done with or without the use of a PN511 matched filter. As described above, the performance of the transmit signal detector is improved to the first calibrate the tuner with a received transmission signal before scanning the spectrum for other transmission signals In this way, in the context of a WRAN system, it is possible to detect the presence of ATSC DTV signals in environments with a low signal to noise ratio, with high accounting It should be noted that although the receiver of Figure 5 is described in the context of the CPE 250 of Figure 4, the invention is not limited and also applies for example to the receiver of a BS 205 that can carry out channel detection In addition, although the receiver of Figure 5 is described in the context of a WRAN system, the invention is not limited and applies to any receiver that performs channel detection. Also, it should be noted that although It is preferable to use the aforementioned ATSC signal detectors, together with the calibrated tuner mentioned above, the use of the calibrated tuner mentioned above is not required. In view of the foregoing, only the principles of the invention are illustrated and therefore, those skilled in the art will be able to contemplate various alternative arrangements that although not explicitly described here, they incorporate the principles of the invention and are within the scope and spirit of the same. For example, although illustrated within the context of separate functional elements, these functional elements can be incorporated into one or more integrated circuits ( IC) Similarly, although they are shown as a separate processor, any or all of the elements can be implemented in a stored program-controlled processor, for example, a digital signal processor, which executes the associated software, for example, corresponding to one or more of the steps shown for example, in Figure 6 In addition, the Principles of the invention can be applied in other types of communication systems, for example, such, Wireless-Fidelity (WI-FI), cellular, etc. Certainly, the inventive concept can also be applied in stationary or mobile receivers. therefore, it should be understood that vain modifications may be made in the illustrative embodiments and that other arrangements may be contemplated without departing from the spirit and scope of the present invention, as defined in the appended claims.

Claims (1)

1. CLAIMS 1 An apparatus characterized in that it comprises a transceiver for communicating with a wireless network over one of a number of channels, and a signal detector for use in forming a list of supported channel comprising those of the number of channels over which a channel was not detected. operational signal, wherein the signal detector includes a matched filter with a pseudo-random sequence number to filter a received signal on one of the channels to provide the filtered signal to be used in determining whether the received signal is an operational signal. apparatus according to claim 1, characterized in that the sequence of pseudo-aletoto number is a sequence PN511 of a signal of Advanced Television Systems Committee (ATSC) 3 The apparatus according to claim 2, characterized in that it also comprises an integrator to integrate the filtered signal over a period of time to provide an integrated signal for us In addition, it determines whether the received signal is an ATSC signal 4. The apparatus according to claim 2, characterized in that it further comprises a peak detector for detecting a peak of the filtered signal, and a memory for storing the peak positions over a period of time. time, and a processor to determine that the received signal is an ATSC signal when a percentage of the stored peak positions are the same. The apparatus according to claim 2, characterized in that it further comprises a processor coupled with the signal detector to form a list of supported channel comprising those of the number of channels over which an ATSC signal was not detected, wherein the processor transmits the channel list supported on the wireless network through the transceiver 6. The apparatus according to claim 2, characterized in that the matched filter comprises a number of correlators, each correlator c further relates the received signal to a different portion of the PN511 sequence. The apparatus according to claim 6, characterized in that it further comprises a combiner for combining the magnitudes of the correlator output signals from each of the number of correlators to provide a signal output for use in determining whether the received signal is an ATSC signal 8 The apparatus according to claim 2, characterized in that the signal detector also uses a PN63 sequence of an ATSC signal to determine whether the received signal is an ATSC signal. The apparatus according to claim 1, characterized in that the wireless network is a wireless regional area network (WRAN) 10 The apparatus according to claim 1, characterized in that the signal detector is coherent 11 The apparatus according to claim 2, characterized in that the signal detector is non-coherent A method for use in a wireless network receiver, the method is characterized in that it comprises tuning to one of a number of channels to recover the received signal, and processing the received signal with a signal detector to be used in forming a channel list. supported comprising those of the number of channels over which an operational signal was not detected, wherein the processing step includes filtering the received signal with a matched filter with a pseudo-random sequence to provide the filtered signal to be used when determining if the received signal is an operational signal 13 The method according to claim 12, characterized in that the pseudo-random sequence number is a PN511 sequence of a signal from Advanced Television Systems Committee (ATSC) 14 The method according to claim 13, characterized in that the processing step also comprises integrating the signal filtr over a period of time to provide an integrated signal to be used in determining whether the received signal is an ATSC signal 15 The method according to claim 13, characterized in that the processing step also comprises detecting a peak of the filtered signal, and storing the peak positions over a period of time, and determining that the received signal is an ATSC signal when a percentage of the stored peak positions are the same. The method according to claim 13, characterized in that it further comprises transmitting the supported channel list 17 The method according to claim 13, characterized in that the processing step also comprises correlating the received signal with different portions of the PN511 sequence to provide the output signals of the respective correlator, and combine the magnitudes of the output signals of the correlator to provide an output signal to be used in determining whether the received signal is an ATSC signal. The method according to claim 13, characterized in that the Filtration step also in The filter according to claim 12, characterized in that the wireless network receiver the wireless network is a wireless regional area network (WRAN), the filtered signal received with a filter matched with a PN63 sequence of an ATSC signal.