• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention relates to a synchronization method for an uplink channel in point-to-multipoint communication using OFDM modulation. The method of the present invention comprises: first, performing frequency and time synchronization with respect to the downlink channel (from head end equipment 1 to user equipment 2) using synchronization sequence 3; Then, based on the estimation, the sampling frequency of the user equipment is corrected, and the frequency synchronization of the uplink channel is performed without correction of the headend equipment. The user equipment determines the moment 9 of transmitting the OFDM symbol 7 to the headend equipment such that the headend equipment receives the OFDM symbol 7 at a given moment. Access the upstream channel by contacting the user equipment. The present invention can be used for bidirectional communication in which data is transmitted through a telecommunication network.
    公开号:KR20030097896A
    申请号:KR10-2003-7015230
    申请日:2002-05-21
    公开日:2003-12-31
    发明作者:호르게비센떼 블라스꼬클라레뜨；후안카를로스 리베이로인수아；후안미구엘 가비예로마틴；살바도르 이란조몰리네로
    申请人:디세노 데 시스테마스 엔 실리시오, 에스.에이.；
    IPC主号:
    专利说明:

    SYNCHRONISATION METHOD FOR THE UPLINK CHANNEL IN A POINT-TO-MULTIPOINT COMMUNICATION WITH OFDM MODULATION}
    [6] Although various methods are known in the prior art for synchronizing communications on the uplink channel for transmissions from multi-user equipment using OFDM modulation, in order to prevent false indication of synchronization in point-to-multipoint systems where the transmission means is a telecommunications network. No high security level was required.
    [7] BACKGROUND OF THE INVENTION Telecommunication networks are well known as transmission media which are difficult due to the fact that the channel response changes over time by generating voltage peak and impedance changes on the line by connecting and disconnecting other devices on the network.
    [8] Among the known synchronization methods, it is important to mention the method described in US Pat. No. 5,537,113, which relates to a time synchronization method using one synchronization symbol having two identical halves, wherein the method proposed in the present invention for performing synchronization is Since fewer samples are used, and impulse noise, which is very common in telecommunications networks, affects synchronization even more because of the fact that by definition there is an incidental noise that affects a small number of samples, Likewise, the method described in U. S. Patent No. 5732113 is more affected than the solution proposed in the present invention, and therefore, a method using only one synchronization symbol in a transmission system using a telecommunication network is not preferable.
    [9] Also, the use of one synchronization symbol implies a greater variation in the calculation or estimation of the synchronization due to the use of a smaller number of samples to perform the synchronization.
    [10] P. Moose published the concept of using two identical symbols in "Technology for Orthogonal Frequency Division Multiple Frequency Offset Correction. IEEE Trans. On Comm., Vol. 42, pp 2908-2914, October 1994". As shown, these symbols have never been considered or used to perform time synchronization, and instead Moose used them to estimate errors in the analog conversion frequency.
    [11] In addition, as described above, the frequency synchronization in the uplink channel is performed starting from the frequency synchronization in the downlink channel, and as shown in Spanish Patent Application No. 200101154, an arc tangent for correcting an error in an analog conversion frequency. Correlation frequency synchronization is known in the art, such as in US Pat. No. 5,72113 or in the papers of Moose; In the case of the present invention, frequency synchronization is performed by estimating the sampling frequency error in the analog / digital converter in each one of the user receivers.
    [1] The present invention relates to a telecommunications sector, in particular a telecommunications sector that can be applied to bidirectional communication between a headend and a plurality of users to perform synchronization in an uplink channel, which is a link between a user and a headend. A telecommunications network is used as the communication means for providing.
    [2] It is an object of the present invention to avoid the generation of false indications of synchronization in the upstream channel, by avoiding problems due to frequency selectivity and high noise levels inherent in the transmission of data over a telecommunication network in general. To provide a new time and frequency synchronization method with high stability for the uplink channel in a telecommunication network.
    [3] According to the method according to the invention, starting from a signal received in a downlink channel defined as communication from the headend equipment to the user equipment, a plurality of user transmitters perform frequency synchronization by synchronizing to a frequency used by the headend receiver and Thus, the headend equipment does not need to make any corrections in frequency.
    [4] In addition, the method according to the present invention is adapted to modify the instant of transmission of an OFDM symbol by the user equipment for the purpose of estimating the moment at which the user equipment should transmit the OFDM symbol so that the headend equipment receives the OFDM symbol at a given moment. Corresponding time synchronization, so that the headend equipment does not have to make corrections in time.
    [5] As described in the present invention, the synchronization in the uplink channel is based on the synchronization performed in the downlink channel, and as described herein, the synchronization in the uplink channel may be applied to the downlink channel as described in Spanish Patent Application No. 200102254. It is desirable to be based on the synchronization method.
    [32] 1 is a schematic diagram illustrating a time synchronization acquisition step configured by an open loop for transmission by user equipment in an uplink channel;
    [33] 2 is a diagram for explaining transmission of an OFDM symbol in an uplink channel following a time synchronization acquisition step;
    [34] 3 is a time diagram of a time synchronization tracking step performed by a closed loop;
    [35] 4 is a diagram showing an example of allocation of a query slot for determining what a user wants to transmit;
    [36] 5 is a diagram showing a possible example of a filter used to detect a POLLING symbol.
    [12] In order to perform frequency and time synchronization in an uplink channel for multiple users in a point-to-multipoint transmission system by OFDM modulation using a telecommunication network as a transmission means, the present invention provides an estimation performed in frequency synchronization in a downlink channel. Beginning with the frequency synchronization by correcting sampling frequencies at the plurality of user equipments. The method also includes performing pre-compensation in the user equipment in order to take into account the rotation received by the plurality of carriers when transmitting in the uplink channel calculated based on the estimation of the rotation received by the carrier in the downlink channel. These two features are due to the fact that the synchronization is done at the user equipment, so that upon reception at the upstream channel, the headend equipment can perform frequency synchronization on the upstream channel without performing correction.
    [13] The method also includes time synchronization that estimates the moment when the user equipment transmits the OFDM symbol to the headend equipment such that the headend equipment receives the OFDM symbol at a given moment, so that time synchronization is received on the uplink channel. At the time the headend does not make a correction, but is performed from the signal received on the downlink channel.
    [14] In addition, the present invention is directed to the user equipment by the headend equipment by the assignment slot (time and / or frequency fragments), so that when the user wants to transmit a petition to access the uplink channel The equipment is responsive to the headend equipment, and in order to transmit without collision, the headend distributes the bandwidth among the users in the upstream channel and transmits the allocated bandwidth to the user equipment.
    [15] Since time synchronization is performed by the user equipment transmitting the OFDM symbol at the moment estimated from the signal received in the downlink channel, the headend receives the OFDM symbol at a given moment or in at least a time window with a few samples, whereby It prevents the occurrence of interference by not windowing the user signal correctly.
    [16] As a result, the headend equipment never precedes or delays the receive window; Rather, the headend equipment is maintained at some fixed moment and the user equipment is adjusted.
    [17] Since the same oscillator is used to generate transmit and receive sample frequencies for both the headend equipment and the user equipment, frequency synchronization in the uplink channel is performed from frequency synchronization in the downlink channel.
    [18] Pre-compensation for the rotation performed at the user equipment is done by the rotor starting with a rotation estimate on each one of the carriers in the signal received via the down channel at the user equipment, each user equipment having a transmitter as well as a rotor device used in the receiver. Edo has a rotor device, and both have similar functions. Therefore, the rotor in the transmitter of the user equipment will work in the same way as described in Spanish Patent Application No. 200102254.
    [19] Precompensation for rotation is due to the fact that the rotation performed in the transmission according to the invention precompensates for the rotation caused by the transmission of data through the electrical distribution network, thus preventing the signal from reaching the headend equipment if there is no frequency error. Allow.
    [20] In addition, the present invention provides that when the headend equipment requires a synchronization sequence, time synchronization includes the generation and transmission of one or more synchronization sequences from the user equipment to the headend equipment, wherein the synchronization sequence consists of two identical synchronization symbols. It features. The synchronization sequence is detected at the headend by maximizing maximum likelihood criteria (priorly known techniques), so that time synchronization is performed from the calculation of the maximum correlation of sequence samples transmitted by a plurality of users. The maximum is determined as the midpoint of the flat region of the correlation peak, and the number of samples is a cyclic prefix (i.e. a prefix introduced conventionally to prevent intersymbol interference without ISI). Is the same as the number of samples, all of which are identical except for one difference that occurs in the downlink channel, the difference being a slot assignment message (SAM) followed by a slot assignment or conventional headend equipment Due to the fact that a previous request was made by allocating a resource to an user on an uplink channel transmitted to the user equipment , Head-end equipment, so that synchronization sequence substantially recognize the moment that reaches from a specific user equipment, the synchronization sequence is transmitted in a slot assigned to the user.
    [21] The time synchronization method in the uplink channel includes an acquisition stage, and as described above, estimating the transmission moment of OFDM symbols in a plurality of user equipments such that OFDM symbols are received by the headend equipment at a predetermined moment. Tracking stage.
    [22] The time synchronization obtaining step is defined as an open loop in which the user equipment estimates the arrival moment of the OFDM symbol received in the downlink channel, and estimates the start of transmission for each OFDM symbol starting from the time synchronization performed in the downlink channel; The user equipment compensates for the delay introduced by the filters in its receiver and transmitter, as well as the average error defined by the cyclic prefix, and estimates that the moment the symbol starts on the electricity line is nearly the same in the up and down directions. At the moment, the OFDM symbol is transmitted.
    [23] The time synchronization tracking step precedes the transmission of the OFDM symbol 7 by the user equipment in order to receive the OFDM symbol at the headend exactly at the expected moment by the received signal transmitted by the headend equipment. Or a closed loop estimating the number of samples that should be delayed; Therefore, the headend equipment transmits the information in the downlink channel to the user equipment by calculation performed as a parameter of the SAM message, from which the user equipment performs the preceding or delay in the transmission of the OFDM symbol.
    [24] In time synchronization, the open loop continues with the estimation performed by the closed loop by compensating for the delay introduced by the channel, to achieve accurate synchronization.
    [25] If the headend equipment wants to recognize that the user is involved in transmission through the uplink channel, allocate an interrogation slot to the user equipment, and a predetermined symbol (inquiry to the inquiry) Send a POLLING symbol indicating a response.
    [26] The query slot is divided into smaller fragments of one or more symbols to query multiple user equipments at the same time, the headend allocates fragments to one or more user equipments to be queried by the SAM, and the user to transmit is not the entire slot. Use this fragment to answer a query.
    [27] When the user equipment is not synchronized correctly in time and responds to two separate fragments, in each fragment, the user transmits only one POLLING symbol so that there is no overlap of the POLLING symbol in response to the user's query. When this occupies more than one symbol, the rest of the fragments are left silent.
    [28] The detection of the POLLING symbol, which is a response to the query request, is performed by the correlation of the received signal with the POLLING symbol previously stored in the headend equipment. In order to perform this function, it is also preferable to use a matched filter.
    [29] If it is necessary to transmit on the uplink channel, since the POLLING symbol has X equal parts, it is also possible to use a finite response matched filter with N / X products and delay in detection, where N is assigned to the query slot. The number of samples in the POLLING symbol transmitted by the user in the fragment.
    [30] Therefore, the headend equipment knows what the user equipment wants to transmit by means of the POLLING symbol, so request the synchronization sequence by the SAM as needed.
    [31] The following drawings are provided to aid the understanding of the present invention, and are described with reference to a series of drawings, which are components of the present specification, but do not limit the purpose of the present invention.
    [37] EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on the drawing mentioned above.
    [38] As described above, the present invention can be applied to bidirectional communication via a telecommunication network between the headend 1 and the plurality of users 2, and is orthogonal frequency division multiplexing, such as the method described in Spanish Patent Application No. 20003024. It is an object of the present invention to provide a method for enabling synchronization on an uplink channel in a point-to-multipoint system using OFDM) modulation.
    [39] As can be seen in the above technical phenomena, the headend equipment comprises an analog-to-digital converter connected to some analog component (separator and filter) which causes the signal to be introduced into the telecommunications network and the signal to the other user equipment 2. By transmitting a, the receiver acquires a signal from the telecommunication network by means of a separator and an analog filter, providing this signal to the analog-to-digital converter, so that all of this causes the communication to occur in the downlink channel.
    [40] Similarly, the receiver of the headend equipment includes an analog-to-digital converter and the transmitter of the user equipment includes a digital-to-analog converter to allow communication in the up channel.
    [41] In one embodiment of the invention, there is an error in the sampling frequency between the headend receiver and the user transmitter because the difference between the oscillators in their transducers and the sampling frequency used for these equipment do not exactly match.
    [42] Errors in the sampling frequency cause the constellation of each carrier to rotate per symbol during modulation. In addition, errors in the sampling frequency cause attenuation and noise in the system; Therefore, it is necessary to correct this error by synchronization on the upstream channel so that the sampling frequency of the headend receiver and the sampling frequency of the transmitter of the user equipment coincide.
    [43] In addition, the headend receiver may receive different information from another user on any carrier related to the uplink channel; Therefore, there is a problem in that it is necessary to perform conversion on the entire spectrum in the received signal.
    [44] In addition, the headend receiver must be aware of the moment when the user equipment transmits the OFDM symbol, and because it cannot accurately detect the signal transmitted by the user equipment, it must perform time synchronization to prevent the occurrence of interference.
    [45] Sampling frequency synchronization is performed at the transmitter of the user equipment from frequency synchronization in the downlink channel.
    [46] Therefore, as described in Spanish Patent Application No. 200101154, frequency synchronization at the user's transmitter is performed from a reference transmitted by a downlink channel that synchronizes the user receiver.
    [47] The frequency used by the headend equipment to transmit on the downlink channel is the same as the sampling frequency (or multiples or divisor thereof) used to receive on the uplink channel, and therefore the frequency used on the downlink channel is used to receive on the uplink channel. It has the same error with respect to the nominal frequency that is used. Therefore, when the user receives the synchronization information in the downlink channel and performs frequency synchronization, it simultaneously synchronizes the frequency in the uplink channel, and consequently, takes some additional steps for frequency synchronization of the multi-user equipment when transmitting from the uplink channel to the headend. There is no need to add more.
    [48] As described in Spanish Patent Application No. 200101154, in the down channel, if frequency error correction is performed by a VCXO (voltage controlled crystal oscillator), frequency correction is then performed on the user, and at the same time, Since frequency correction is also performed at the time of transmission, frequency correction is simultaneously performed on both channels. On the other hand, as described in Spanish Patent Application No. 200101154, if frequency error correction in the downlink channel is performed by a resampler, the error is pre-compensated for transmission and the signal received by the headend equipment is a frequency error. To ensure that it does not have, it is necessary to use a similar resampler in the same transmission for the user equipment.
    [49] In addition, to correct the carrier rotation problem in the upstream channel, it is necessary to use a rotor in the headend equipment, and for each user in the system, a fuse memory is proposed and a signal received by the upstream channel is used. This is a significant difficulty since it handles capacity and multiple users transmit simultaneously on the uplink channel.
    [50] To compensate for this difficulty, the method of the present invention performs precompensation of rotation upon transmission by each one of the users, and each user equipment is not only used in its receiver as described in Spanish Patent Application No. 200101154, but also in the transmitter. It includes a rotor in the.
    [51] The rotor of the transmitter of the user equipment estimates the amount by which the carrier should be rotated in the upstream channel, starting from the amount rotated by the constellation in each one of the carriers for the signal received from the downlink channel.
    [52] Therefore, since the rotation generated during transmission over the telecommunications network is pre-compensated, the signal reaches the headend equipment if there is no rotation in the carrier.
    [53] The operation of the rotor of the transmitter of the user equipment uses the same concept as that used to operate the rotor upon reception, which is used for synchronization in the downlink channel, and is described in Spanish Patent Application No. 200101154 as described above.
    [54] Time synchronization in the uplink channel includes an aspect of estimating the moment at which user equipment transmits an OFDM symbol to the headend equipment such that the headend equipment receives the OFDM symbol at a given moment, i. never precedes or delays a reception window; Rather, the user precedes or delays the start of the transmission of the OFDM symbol so that the OFDM symbol arrives exactly at the receive window of the headend equipment, and performs adjustment in that transmission window.
    [55] In order to perform this function, time synchronization in the uplink channel is performed by an acquisition step and a tracking step.
    [56] The time synchronization acquisition step is performed in an open loop and consists in extracting information of time synchronizations performed in the downlink channel to perform time synchronization in the uplink channel. In order to prevent intersymbol interference, this is not limited to the system, since the propagation time by the telecommunication network is very small for the frequency used compared to the period of the cyclic prefix added to the OFDM symbol.
    [57] Upon receipt of the synchronization signal transmitted by the headend in the downlink channel, each transmitter of the user equipment estimates the start of an OFDM symbol. The error in this estimation is negative by the system design, i.e., presumes that the start of the symbol is before its actual position (previously before the OFDM symbol) so that the start of the symbol is always included in the cyclic prefix; This prevents intersymbol interference due to bad estimation. The mean error in the estimation in the presence of distributed channels is half the length of the cyclic prefix. In a distributed channel in the case of a telecommunications network, the error is somewhat less since the beginning of the cyclic prefix is affected by intersymbol interference.
    [58] Each user equipment inserts an OFDM symbol to be transmitted in the uplink channel, starting from the moment it is assumed to be the start of the symbol in the downlink channel. In this regard, for example, as described in the above-described Spanish Patent Application No. 200101154, the receiver of the user equipment estimates the moment of arrival of the symbol for the downlink channel, the reception filter in the downlink channel, and the transmission filter in the uplink channel. Compensating for the delay by, and the average error committed as described above is half the length of the cyclic prefix. By this way, from the point of view of the user equipment, the symbol in the down channel and the symbol in the up channel start at the same moment in the channel. Other transient relationships between symbols in the upstream and downlink channels may be selected without being limited to the method described herein. The temporary difference between the symbol transmitted in the downlink channel and the symbol received by the uplink channel corresponds to the round trip travel delay introduced by the downlink and uplink channels in terms of headend.
    [59] 1 shows an acquisition step performed by an open loop known as blind acquisition, where the start 4 of the synchronization sequence symbol 3 transmitted in the downlink channel serves as a temporary reference for the user equipment 2. And indicated by reference numeral 5.
    [60] In FIG. 1, reference numeral 6 denotes the remaining symbols (data, equalization, etc.) transmitted on the downlink channel.
    [61] FIG. 2 schematically shows the moment 8 when the OFDM symbol 7 is transmitted in the uplink channel, that is, the moment 8 calculated as the arrival of the OFDM symbol 7 in the downlink channel in accordance with the synchronization of this channel. Starting at 9), the transmission 9 on the uplink channel is estimated, where the committed error is always negative and represented by the difference between 8 and 9.
    [62] Once the blind acquisition has been performed, since the blind acquisition from synchronization in the downlink channel provides a temporary reference in transmission in the uplink channel, since the tracking phase is initiated by a closed loop, this blind acquisition may not be sufficiently precise. The headend equipment may not be able to identify the received signal because, as described above, it always windowes the received signal at a fixed moment.
    [63] Even if the blind acquisition is done correctly, due to the round trip delay in the channel estimated by time synchronization in the closed loop, one unknown value remains in view of the headend equipment.
    [64] Because of this, time synchronization is performed in a closed loop, so that the number of samples that the user must precede or delay the transmission to ensure that windowing is optimized for the headend equipment is determined by the signal received by the headend from the user equipment. Is calculated through.
    [65] This feedback information is transmitted in the downlink channel to the associated user equipment as a parameter of the SAM message.
    [66] This process starts with the synchronization in the downlink channel, where the headend transmits the synchronization sequence 28 and the blind acquisition 12 is performed in the manner described above, at which point the user equipment transmits the data and synchronization sequence. If this sequence is requested by the headend after receiving the SAM message 11 sent by the headend, one or more slots may be selected, as indicated by some frequency and time, i. It is expressed in a time scheme, which allows it to be used. Starting from the synchronization sequence sent from the user equipment, the headend calculates 14 the number of samples that must be advanced or delayed for optimal windowing. The headend detects the moment of arrival of the OFDM symbol from the user and calculates the difference between this moment and the exact moment that must arrive. This difference in the number of samples is the criterion to be transmitted to the associated user equipment so that the moment the symbol is transmitted can be corrected.
    [67] According to this, the headend transmits a SAM message 15 indicating the preceding or delay that the user equipment should include in the transmission of the OFDM symbol 7 on the uplink channel. Reference numeral 16 denotes the detection of this information transmitted by the headend, where the user equipment performs the above-described correction and transmits the OFDM symbol 7 at the corrected moment, and also with reference numeral 18. As indicated, the synchronization sequence 17 is included such that the OFDM symbol arrives at the headend at the moment windowing is performed.
    [68] The acquiring step is performed continuously each time a synchronization sequence is detected in the downlink channel, and the instant of transmission is corrected by the open loop algorithm as described above. Due to the fact that there may be some error between the headend and the user equipment in the sampling frequency, the windowing changes slowly, and before the transmission is preceded or delayed so that the receiver does not window correctly, it is obtained by the acquisition step described above. Need to be corrected.
    [69] In the method described above, identification of the user equipment to be transmitted at a given moment is a challenge that must be solved by the headend.
    [70] To this end, when the user wants to transmit on the upstream channel, the downlink channel is noted, and the headend 1 is used by the information contained in the SAM message 26 for one or more slots for inquiry. Wait for something to show up. In the example shown in Fig. 4, a query slot is assigned to each one of the three user equipments 2 shown, and it may or may not be transmitted. An inquiry slot 19 divided into a plurality of fragments 27 (each fragment is assigned to one of the inquired users) is allocated, and each user to be transmitted has an inquiry slot 19 as long as it wants to access an uplink channel. Respond to this slot by sending a predetermined symbol, known as the POLLING symbol 20, to indicate a response to the query to the fragment 27 assigned by. When a plurality of equipment is queried from the same group in the same portion of the slot 19, the request by the user equipment may collide, and therefore may be undertaken to resolve contention or be affected. Allow the user to resend the access request later.
    [71] The query slot 19 is divided into fragments 27 larger than or equal to the size of the POLLING symbol 20, and overlapping the POLLING symbol 20 in response to a plurality of users' inquiries responsive to the plurality of fragments 27. Leave the rest of the fragments silent to prevent. Thus, since the user equipment is already time synchronized by blind acquisition, the probability of interference is reduced, i.e. in the form of a partial optimization, and some POLLING symbols 20 can be overlapped, which can be avoided by introducing silence 21. Can be.
    [72] To detect the POLLING symbol 20, the headend equipment uses a special device that includes a filter in the form of a POLLING symbol as shown in FIG. 5. This filter includes a continuous delay 22 through which the response received in the query slot 19 passes.
    [73] These delays 22 are determined by the sample interval, that is, the interval of the sampling frequency used to sample the signal.
    [74] The output of the delay 32 is due to the fact that it is multiplied by a filter coefficient (C i), the head-end to recognize the symbol is the same as the form of the POLLING symbol (20). These coefficients are the conjugate complex numbers of the samples that make up the POLLING symbol, so when the headend receives the POLLING symbol 20, it multiplies it by its multiplier 23, adds them by the adder 24, and the maximum value. Will be reached, and therefore can detect the arrival of a POLLING symbol, which is used at the headend to indicate the arrival of a response to the query message.
    [75] Due to the fact that N is relatively large, the number of products required is also large, but the present invention does not require N multipliers 23 and delayers 22 since the POLLING symbol 20 having X equal parts is transmitted. No, all N / X is required, so that the number of operations can be reduced. When the POLLING symbol arrives, the maximum is detected and X maximums appear. In summary, the detection of the POLLING symbol is performed by the correlation of the received signal with the POLLING symbol previously stored in the headend equipment, and detected by the matched filter as described above.
    [76] By module 25, when the module detects all X peaks with approximately the same power level, a signal is generated that indicates the detection of the POLLING symbol and occupies N / X samples.
    [77] Once it is detected that one or more users wish to transmit, the headend equipment communicates by means of a SAM message 26, the user may have access to an uplink channel and available slots (time and / or frequency intervals) and As used in the processing example described in Spanish Patent Application No. 200100916, these SAM messages are transmitted periodically on the downlink channel and, if necessary, the transmission of the synchronization sequence after the blind acquisition 12 as described above. You may ask.
    权利要求:
    Claims (13)
    [1" claim-type="Currently amended] Means for adding and extracting the cyclic prefix 10 from the OFDM symbol 7 to prevent inter-symbol interference (ISI), and by transmitting the synchronization sequence 3 from the headend equipment 1 to the user equipment ( A method of synchronizing communications with respect to multi-user equipment and head-end equipment by uplink and OFDM modulation, which can be performed in a downlink channel, which is communication with 2), and which can be applied to bidirectional communication through a telecommunication network,
    Frequency synchronization by correction of sampling frequencies at the plurality of user equipments (2) starting from the estimation performed in the frequency synchronization in the downlink channel;
    In the user equipment 2, a plurality of carriers are generated starting from the estimation of the rotation the carrier receives in the downlink channel so that the headend equipment 1 does not need to perform correction upon reception in the uplink channel. Precompensation for rotations transmitted in the uplink channel;
    Time synchronization by the user equipment (2) and the headend equipment (1) by estimating the moment at which the OFDM symbol (7) is transmitted to the headend so that the headend can receive the OFDM symbol at a given moment; And
    Inquiring the user by assignment by the headend of the time and / or frequency interval in the upstream channel, the user to the fragment 27 for the inquiry of the user equipment 2 in response to the headend 1. The upstream channel is distributed between the petitions received by the headend equipment 1 so that the user equipment can transmit without collision only if the query for the divided slot 19 and the user equipment wants to access the upstream channel. And a query made from transmitting the distributed to the user equipment (2). A method for synchronizing communications with respect to multi-user equipment and head-end equipment by uplink and OFDM modulation.
    [2" claim-type="Currently amended] The method of claim 1,
    Using the same oscillator so that the frequency error in the uplink channel is proportional to the frequency error in the downlink channel, and the frequency synchronization in the uplink channel is performed simultaneously with the frequency synchronization in the downlink channel. A method of synchronizing communications with respect to multi-user equipment and head-end equipment by uplink, OFDM modulation, comprising generating sampling transmission and reception frequencies in both user equipment.
    [3" claim-type="Currently amended] The method of claim 2,
    Pre-compensation of rotation performed in the user equipment is performed downward in the user equipment by a rotor included in the transmitter so that the headend equipment does not need to perform rotation correction of signals received from a plurality of user equipment. A method of synchronizing communications with respect to multi-user equipment and head-end equipment by means of uplink, OFDM modulation, characterized in that it is achieved from an estimate performed on each one of the carriers of the signal received on the channel.
    [4" claim-type="Currently amended] The method of claim 1,
    The synchronization includes generating and transmitting one or more synchronization sequences from user equipment (2) to headend equipment (1) when the headend equipment requires a synchronization sequence; Since the synchronization sequence consists of two identical synchronization symbols and the synchronization sequence is detected at the headend by maximizing the maximum possible range, time synchronization is performed from the calculation of the maximum correlation of sequence samples transmitted by a plurality of users and This maximum is determined as the midpoint of the flat region of the correlation peak, and the number of samples is the same as the number of samples of the cyclic prefix 10 with no intersymbol interference. A method of synchronizing communications between equipment and headend equipment.
    [5" claim-type="Currently amended] The method of claim 4, wherein
    The time synchronization comprises an acquisition and tracking step in which the moment of transmission of the OFDM symbol 7 in the plurality of user equipments 2 is modified starting from the estimation in which the symbol is received by the headend equipment at a given moment. A method for synchronizing communications with respect to multi-user equipment and head-end equipment by uplink and OFDM modulation.
    [6" claim-type="Currently amended] The method of claim 5,
    The time synchronization obtaining step is performed by the user equipment 2 estimating the arrival moment 9 of the OFDM symbol 7 received in the downlink channel, starting from the time synchronization performed in the downlink channel. Is determined by an open loop that estimates 12 the start of transmission 8 for < RTI ID = 0.0 > The user equipment compensates for the delay introduced by the filters in its receiver and transmitter, as well as the average error defined by the cyclic prefix 10, and transmits the OFDM symbol 7 at an estimated moment 9 after the compensation. A method of synchronizing communications with respect to multi-user equipment and headend equipment by up-channel and OFDM modulation.
    [7" claim-type="Currently amended] The method according to claim 5 or 6,
    The time synchronization tracking step is performed by the headend equipment 14 by the received signal 13 transmitted in the time synchronization acquisition step by the user equipment 2 so as to accurately receive an OFDM symbol at an expected moment. Determined by the user equipment as a closed loop for estimating the number of samples that must precede or delay transmission of the OFDM symbol 7; Therefore, the headend equipment transmits 15 this number of samples to the user equipment in the downlink channel as a parameter of the SAM message 26 that the headend transmits to the user equipment. (16) performs the preceding or delay in the transmission of an OFDM symbol, and subsequently performs an open loop of time synchronization, so that the estimation performed by the closed loop compensates for the delay introduced by the channel. A method of synchronizing communications for multi-user equipment and head-end equipment by uplink and OFDM modulation.
    [8" claim-type="Currently amended] The method of claim 1,
    The headend equipment refers to a plurality of user equipments when it wishes to transmit the synchronization sequence 3, and in order to perform proper synchronization with respect to the user equipments, slots are allowed by SAM messages transmitted on the downlink channel, and thus Communication of the multi-user equipment and the head-end equipment by uplink and OFDM modulation, characterized in that detection of the synchronization sequence 3 is performed for the user in the uplink channel only by the user being instructed to transmit the synchronization sequence. How to sync.
    [9" claim-type="Currently amended] The method of claim 1,
    The headend equipment allocates the query slot 19 divided into the fragments 27 to the user equipment by sending a SAM message 26 to the plurality of user equipments 2, and if necessary, the user equipment Uplink, OFDM modulation, characterized in that for transmitting information and transmitting a POLLING symbol 20 in the assigned fragment 27, so that the headend equipment determines to optimize the uplink distribution algorithm between the user equipment. Synchronization method for multi-user equipment and head-end equipment by means of synchronization.
    [10" claim-type="Currently amended] The method of claim 9,
    The query slot 19 is divided into smaller fragments that are equal to or larger than the size of the POLLING symbol 20 to query multiple user equipments at the same time, so that the headend is one or more user equipments to query by the SAM message. A user who wants to assign a fragment to and transmit a response to the query by the POLLING symbol 20 in the assigned fragment. The method for synchronizing communication with respect to multi-user equipment and head-end equipment by uplink and OFDM modulation. .
    [11" claim-type="Currently amended] The method of claim 10,
    In each fragment, the user is one, so that when the user equipment is not correctly synchronized in time and responds to two separate fragments, there is no overlap of the POLLING symbol 20 in response to the user's inquiry. Synchronization of communication with respect to multi-user equipment and headend equipment by up-channel, OFDM modulation, characterized in that it transmits only the POLLING symbol 20 of the device, and sets the remaining fragments to silence 21 when it occupies one or more symbols. Way.
    [12" claim-type="Currently amended] The method according to claim 1 or 11, wherein
    The detection of the POLLING symbol 20 is performed by a matching filter for performing detection, by correlation of the received signal and the POLLING symbol pre-stored in the headend equipment. Synchronization method for multi-user equipment and head-end equipment by means of synchronization.
    [13" claim-type="Currently amended] The method of claim 12,
    If it is necessary to transmit on the uplink channel, since the POLLING symbol 20 has X equal parts, a finite response matching filter having N / X products 23 and delays 22 is used, where N is The number of samples in the POLLING symbol 20 transmitted by the user in the fragment allocated by the query slot 19, characterized in that synchronization of communication with respect to multi-user equipment and head-end equipment by uplink, OFDM modulation Way.
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    同族专利:
    公开号 | 公开日
    JP2004533769A|2004-11-04|
    IL158619D0|2004-05-12|
    CN1511382A|2004-07-07|
    ES2188372B1|2004-11-16|
    CN1274095C|2006-09-06|
    EA200301170A1|2004-08-26|
    WO2002095977A1|2002-11-28|
    CA2448152A1|2002-11-28|
    MXPA03010657A|2004-03-02|
    EP1396945A1|2004-03-10|
    KR100685685B1|2007-02-23|
    EA005608B1|2005-04-28|
    BR0210050A|2004-08-17|
    AU2002304583B2|2007-12-13|
    ES2188372A1|2003-06-16|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2001-05-23|Priority to ESP200101179
    2001-05-23|Priority to ES200101179A
    2002-05-21|Application filed by 디세노 데 시스테마스 엔 실리시오, 에스.에이.
    2002-05-21|Priority to PCT/ES2002/000239
    2003-12-31|Publication of KR20030097896A
    2007-02-23|Application granted
    2007-02-23|Publication of KR100685685B1
    优先权:
    申请号 | 申请日 | 专利标题
    ESP200101179|2001-05-23|
    ES200101179A|ES2188372B1|2001-05-23|2001-05-23|Procedure for the synchronization of the communication through ofdm modulation of multiple user equipment with a headphone equipment .|
    PCT/ES2002/000239|WO2002095977A1|2001-05-23|2002-05-21|Synchronisation method for the uplink channel in a point-to-multipoint communication with ofdm modulation|
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