Method for achieving downlink synchronization of a user equipment with a 5g cellular network, and associated user equipment

Abstract

The invention relates to a method (100) for achieving downlink synchronization of a user equipment with a 5G cellular network, comprising: - a reception step (105); - a first frequency-synchronization and time-synchronization step (110), comprising first estimates of a frequency difference (DF1) and time difference (DT1) between the transmitted signal and the received signal (S) and determination of a first component (N_PSS) of the cell number (N_cell) through autocorrelation and intercorrelation; and - a second frequency-synchronization and time-synchronization step (120), comprising second estimates of the frequency difference (DF2) and time difference (DT2) through autocorrelation and intercorrelation, taking into account the first component (N_PSS). The second estimates are more accurate than the first estimates.

Description

[0001] DESCRIPTION

[0002] TITLE: Downlink synchronization method of a user device to a 5G cellular network and associated user device

[0003] The present invention relates to a downlink synchronization method of a user device to a 5G cellular network.

[0004] It also relates to user equipment configured to implement such a process.

[0005] The article "Synchronization Procedure in 5G NR Systems" (A. Omri, M. Shaqfeh, A. Ali and H. Alnuweiri, in IEEE Access, vol. 7, pp. 41286-41295, 2019) is a reference concerning the downlink synchronization procedure of a user device to a 5G cellular network following the 3GPP (3rd Generation Partnership Project) consortium's 5G standard. This article describes, in particular, the sequence of operations to be performed by a user device to retrieve the cell identity of a base station and to decode the physical broadcast channel.

[0006] We also know from document EP 0665665 B1 an algorithm allowing a modem to synchronize with a digital data transmitter while being robust to interference thanks to spatial or space-time processing.

[0007] However, applying the processing method proposed in document EP 0665665 B1 to the synchronization procedure of user equipment to the 5G cellular network would require a very large number of correlations for each of the primary synchronization sequences, secondary synchronization sequences, and demodulation reference symbols of the physical broadcast channel potentially transmitted by the base station. This is not feasible for user equipment within a reasonable timeframe for the application. Therefore, the downlink synchronization methods to a 5G network currently implemented by user equipment are not robust to interference.

[0008] The aim of the invention is therefore to offer a downlink synchronization method from a user device to a 5G cellular network that is more robust to interference.

[0009] To this end, the invention relates to a downlink synchronization method of a user device to a 5G cellular network, comprising:

[0010] - a stage of receiving a signal emitted by a base station, the emitted signal comprising at least one synchronization signal block belonging to a burst of synchronization signal blocks emitted by the base station and identified within the burst by a block index, the base station belonging to a cell characterized by a cell number, the cell number being a function of a first component on which a primary synchronization sequence of the synchronization block depends and a second component on which a secondary synchronization sequence of the synchronization block depends, the synchronization block further comprising data from a physical broadcast channel;

[0011] - a first frequency and time synchronization step, during which a first estimate of a frequency difference between the signal emitted by the base station and a signal received by the user equipment during the reception step, a first estimate of a time difference between the signal emitted by the base station and the received signal and a determination of the first component of the cell number are carried out by autocorrelation of a first portion of received signal and cross-correlation of the first portion of received signal with a first set of reference sequences, the first portion of received signal comprising at least one of the primary synchronization sequences of the received signal and the first set of reference sequences comprising a reference signal for each of the primary synchronization sequences to be tested;and - a second frequency and time synchronization step, during which a second frequency gap estimate and a second time gap estimate are made by autocorrelation of a second portion of the received signal and cross-correlation of the second portion of the received signal with a second set of reference sequences after correction of the second portion of the received signal using the first estimates of the frequency and time gaps, the primary synchronization sequence being fixed, the second estimates being made taking into account the first component determined during the first time and frequency synchronization step, the second estimates of the frequency gap and the time gap being more accurate than the first estimates of the frequency gap and the time gap respectively.;

[0012] Thanks to the invention, the number of correlations to be performed is significantly reduced by dividing the process into two successive steps of increasing precision. In particular, the first synchronization step provides information about the signal that allows the search field to be narrowed during the second synchronization step. Thus, the process can be implemented with the computing capabilities of user equipment in a time frame consistent with the application, and allows the user equipment to synchronize with a 5G network base station even in the presence of interference. According to other advantageous aspects of the invention, the synchronization process comprises one or more of the following features, taken individually or in any technically feasible combination:

[0013] - the second frequency and time synchronization step includes a filtering substep, during which the second corrected received signal portion is filtered, so as to limit the second received signal portion to the primary and secondary synchronization sequences;

[0014] - the received signal is a multi-channel signal and the process includes a recombination and demodulation step, during which:

[0015] • a third portion of the received signal is corrected using the second estimates of the frequency and time deviations, the third portion of the received signal including at least one synchronization block;

[0016] • a spatial or spatio-temporal filter is calculated by autocorrelation of the third portion of the corrected received signal and cross-correlation of the third portion of the corrected received signal with a reference signal, belonging to the second set of reference sequences and having been retained during the second step of frequency and time synchronization;

[0017] • the third corrected received signal portion is recombined into a single-channel received signal portion using the spatial or spatio-temporal filter; and • the single-channel received signal portion is demodulated, providing received orthogonal frequency division symbols;

[0018] - the process further includes a secondary synchronization sequence estimation step, during which a determination of the second component of the cell number is carried out by correlation of the received orthogonal frequency distribution symbols or of the multi-channel received signal portion with a third set of reference sequences, the third set of reference sequences comprising secondary synchronization sequences to be tested, the primary synchronization sequence being fixed;

[0019] - the second portion of the received signal includes at least the secondary synchronization sequence of the received signal and the second set of reference sequences includes a reference signal for each of the secondary synchronization sequences to be tested, and the second frequency and time synchronization step further includes the determination of a value for the second component of the cell number; - the method further includes a step of determining the cell number as a function of the first and second components;

[0020] - the process further includes a step of determining the block index by correlation of at least a part of the received orthogonal frequency distribution symbols with a set of reference symbols, corresponding to the block indices to be tested;

[0021] - the process further includes an equalization and demodulation step of the physical broadcast channel, during which:

[0022] • the physical broadcast channel is estimated from the received orthogonal frequency division symbols, knowing the block index within the burst and the cell number;

[0023] • a single-channel frequency equalization of the orthogonal frequency distribution symbols is performed using the estimated physical diffusion channel, providing equalized symbols from the physical diffusion channel; and

[0024] • the equalized symbols of the physical broadcast channel are demodulated, providing the logarithm of a likelihood ratio for each bit of a codeword, corresponding to the master information block contained in the physical broadcast channel data;

[0025] - the process further includes an equalization and demodulation step of the physical broadcast channel, during which:

[0026] • the multi-way physical diffusion channel and a spatial autocorrelation of noise and interference is estimated from a fourth portion of the received signal, corrected using second estimates of frequency and time gaps, knowing the block index within the burst and the cell number, the fourth portion of the received signal including at least one synchronization block;

[0027] • Frequency equalization of the fourth portion of the received signal is performed by a minimum root mean square error-interference rejection combination equalizer, known as MMSE-IRC type, providing equalized symbols of the physical broadcast channel; and • the equalized symbols of the physical broadcast channel are demodulated, providing the logarithm of a likelihood ratio for each bit of a codeword, corresponding to the master information block contained in the data of the physical broadcast channel; - the method further includes a recombination and decoding step of the data of the physical broadcast channel during which the master information block is decoded from the logarithms of the likelihood ratios of the codeword, providing parameters to complete the synchronization of the user equipment 3 to the 5G cellular network.

[0028] The invention also relates to user equipment intended to be connected to a 5G cellular network configured to implement a synchronization process as defined above.

[0029] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0030] [Fig. 1] Figure 1 is a schematic diagram of an initial access procedure of a user device to a base station according to the 5G standard of the 3GPP consortium;

[0031] [Fig. 2] Figure 2 is a diagram of a synchronization block emitted by a base station according to the 5G standard of the 3GPP consortium;

[0032] [Fig. 3] Figure 3 is a block diagram of a synchronization method according to the invention;

[0033] [Fig. 4] Figure 4 is a block diagram of a first frequency and time synchronization step of the synchronization process according to the invention;

[0034] [Fig. 5] Figure 5 is a block diagram of a second frequency and time synchronization step of the synchronization process according to a first implementation of the invention;

[0035] [Fig. 6] Figure 6 is a block diagram of a second frequency and time synchronization step of the synchronization process according to a second implementation of the invention;

[0036] [Fig. 7] Figure 7 is a block diagram of a recombination and demodulation step of the synchronization process according to the invention;

[0037] [Fig. 8] Figure 8 is a block diagram of a primary synchronization sequence estimation step of the synchronization process according to the first implementation of the invention;

[0038] [Fig. 9] Figure 9 is a block diagram of a step in determining the block index of the synchronization process according to the invention;

[0039] [Fig. 10] Figure 10 is a block diagram of an equalization and demodulation step of the synchronization process according to a first example of the invention; [Fig. 11] Figure 11 is a block diagram of an equalization and demodulation step of the synchronization process according to a second example of the invention.

[0040] In Figure 1, a user device 3 is intended to connect to a cellular radio communication network according to standard 5 ème Generation - New Radio (5G-NR - New Radio) from the 3GPP (3rd Generation Partnership Project) consortium. This includes, for example, a commercial civilian network or another network inspired by this standard.

[0041] The network comprises base stations 1, one of which is shown in Figure 1. Each base station 1 belongs to a cell, which is an area of ​​space covered by one or more base stations 1, and characterized by a cell number N_cell. The cell number N_cell is a function of a first component N_PSS and a second component N_SSS.

[0042] Base station 1 periodically transmits bursts of SSB synchronization blocks. A burst of SSB blocks comprises one or more SSB synchronization blocks. The individual SSB synchronization blocks within a burst of SSB blocks can be transmitted in separate directions as directional beams, or in the same direction using a respective omnidirectional antenna. The bursts of SSB blocks are broadcast to user equipment via a physical broadcast channel.

[0043] Each SSB synchronization block is identified within the burst that contains it by a block index i_SSB. According to version 18 of the 3GPP standard, an SSB synchronization block, shown in Figure 2, occupies 4 orthogonal frequency-division multiplexing (OFDM) modulation symbols in time, represented on the x-axis of Figure 2, and occupies 240 subcarriers, represented on the y-axis of Figure 2. An SSB synchronization block comprises a primary PSS synchronization sequence, a secondary SSS synchronization sequence, a DM RS demodulation reference sequence for the physical broadcast channel, and PBCH physical broadcast channel data. The PBCH physical broadcast channel data allows the transmission of a 32-bit block of information through 432 quadrature phase-modulated symbols (QPSK modulation) encoded with a polar code.The PBCH physical broadcast channel data contains the message of a 24-bit BCH logical broadcast channel and 8 bits of information about the cell's timing configuration and SSB synchronization blocks. Within the BCH logical broadcast channel, 23 bits correspond to the Master Information Block (M / B), which provides information about the cell's OFDM grid configuration (frequency resolution, system frame number, etc.), a cell saturation level (celIBarred; this indicator signals if the cell can no longer accept a user), and other information necessary for the user equipment to synchronize with the cell, track system information blocks (SI B), and initiate a connection request. These concepts are detailed in the 3GPP 5G NR standard technical specifications, TS38.331.

[0044] The PSS primary synchronization sequence depends on the first component N_PSS of the cell number N_cell. In the mathematical expressions that follow, the first component N_PSS is denoted N^\. The PSS primary synchronization sequence is an m-sequence defined by:

[0045]

[0046] Or:

[0047] mod 127 with n = 0,...,126, and

[0048]

[0049] x PSS (j) is a binary sequence obtained by a shift register with linear feedback, where:

[0050] o PSS (i mod 2, and

[0051] o

[0052]

[0053] 1.0.1.

[0054]

[0055] The PSS primary synchronization sequences occupy symbol 0 of an SSB synchronization block, and they are allocated to subcarriers k = 56 + n for n = 0,...,126, relative to the start of an SSB synchronization block. There are three possible PSS primary synchronization sequences.

[0056] The secondary synchronization sequence SSS depends on the second component N_SSS of the cell number N_cell. In the mathematical expressions that follow, the second component N_SSS is denoted N$. The secondary synchronization sequence SSS is a product of two m-sequences, defined by:

[0057]

[0058] Or:

[0059] N

[0060] m o = 1N I W

[0061] (n + 15P + 5N®) mod 127

[0062] 112

[0063] m1= (n + vp^mod 112^ od 127 with n = 0,...,126.

[0064] binary sequences xsss o (i) and x sss l (i) are obtained by linear feedback shift registers, with:

[0065]

[0066] mod 2,

[0067] ss,o(6:0) = [0.0, 0.0, 0.0.1],

[0068] x sss,i - + 7) = (x sss>1 (i + 1) + x ss s,i(i)) mod 2,

[0069] Xsss, 1(6: 0) = [0,0, 0,0, 0,0,1]. Secondary synchronization sequences (SSS) occupy symbol 2 of an SSB synchronization block; they are allocated to subcarriers k = 56 + n for n = 0,...,126, relative to the beginning of the SSB synchronization block. There are 1008 possible secondary synchronization sequences (SSS), but 336 for a given primary synchronization sequence (PSS).

[0070] The DMRS demodulation reference sequence includes quadrature phased kung fu (QPSK) modulation symbols, defined by:

[0071]

[0072] where c(n) = (%! (n + N) c ) + x2(n + ÎV c ))mod 2, with:

[0073] ON c = 1600,

[0074] o )mod 2,

[0075] o

[0076]

[0077] + 2) + x2(n + 1) + x2( n )) mo d 2, o %i (0) = 1,

[0078] o x1(n) = 0, pourn = 1,...,30.

[0079] The register x2(n) is initialized such that c init = £ =0%2(02', et in the case of the canal

[0080]

[0081] ï SSB is a parameter that depends on the burst configuration 5 and the block index l_SSB and N B 11is the cell number N_cell. The DMRS demodulation reference sequence occupies 60 subcarriers on symbols 1 and 3 of the SSB synchronization block, with subcarrier indices k = 0 + v,...,236 + v, and 24 subcarriers on symbol 2, with k = 0 + v,...,44 + v, 192 + v,...,236 + v, and v = N B 11 mod 4. The sequence r DMRS (m) is associated with these resources in ascending order of subcarrier indices first, and then of symbols. We denote N SSB the number of possibilities for the DMRS demodulation reference sequence for a given PSS-SSS sequence pair.

[0082] Thus, there are 3*336*N SSB , or 1008 / V ÇÇB Possible configurations of the SSB synchronization block.

[0083] The data for the PBCH physical broadcast channel comprises a Master Information Block (MIB) and is scrambled with a sequence dependent on the block index l_SSB. Symbols 1 and 3 of the SSB synchronization block each contain 240 subcarriers allocated for the physical broadcast channel (including the DMRS demodulation reference sequence), and symbol 2 contains 96 subcarriers (including the DMRS demodulation reference sequence). The PBCH physical broadcast channel data is associated with all these resources except those already occupied by the DMRS demodulation reference sequence.

[0084] The number of SSB synchronization blocks in a 5-bit burst is limited to 4 for carrier frequencies up to 3 GHz, 8 for 3-6 GHz, and 64 for frequencies above 6 GHz. The periodicity of this transmission can range from 5 ms to 160 ms. The 5-bit burst is always limited to a 5 ms window in the first or second half of a 10 ms radio frame. The arrangement of SSB synchronization blocks in a 5-bit burst depends on the subcarrier spacing and the carrier frequency.

[0085] An initial network access procedure for user equipment 3 is shown in Figure 1. This access procedure occurs in two stages. First, a downlink synchronization allows user equipment 3 to synchronize with broadcast signals from base station 1. These broadcast signals include bursts of SSB synchronization signal blocks. Once synchronized, user equipment 3 can listen for system information, including a random access channel resource configuration. Second, an uplink synchronization, via random access channel 7, among other channels, and including a message exchange, allows base station 1 to acquire more information about user equipment 3 in order to allocate resources to it.According to this access procedure, the connection 11 between base station 1 and user equipment 3 is established.

[0086] The present invention relates to the processing carried out by the user equipment 3 during the downlink synchronization phase, the objective of which is to decode the master information block Ml B.

[0087] To do this, user equipment 3 includes a downlink synchronization unit 48.

[0088] The downlink synchronization unit 48 includes a receive module 58 and a time and frequency synchronization module 60. Preferably, the downlink synchronization unit 48 further includes an OFDM recombination and demodulation module 62, a secondary synchronization sequence estimation module 64, a cell number determination module 66, a block index determination module 68, an equalization and demodulation module 70 and a recombination and decoding module 72.

[0089] The receiving module 58 is configured to receive a signal emitted by base station 1.

[0090] The time and frequency synchronization module 60 is configured to perform a first and second estimation of the frequency and time differences between the signal emitted by the base station and a signal received S by the user equipment 3, as well as to estimate the first component N_PSS of the cell number N_cell.

[0091] The recombination and demodulation module 62 is configured to recombine the received multi-channel signal S into a single-channel signal and to demodulate OFDM signals.

[0092] Secondary synchronization sequence estimation module 64 is configured to determine the second component N_SSS of the cell number N_cell.

[0093] The cell number determination module 66 is configured to determine the cell number N_cell based on the first component N_PSS and the second component N_SSS.

[0094] The block index determination module 68 is configured to determine the i_SSB block index of the SSB synchronization block within burst 5.

[0095] The equalization and demodulation module 70 is configured to estimate the physical broadcast channel and to demodulate equalized symbols obtained using the estimated physical broadcast channel.

[0096] The recombination and decoding module 72 is configured to decode the master information block Ml B.

[0097] The details of the operations performed by each of the modules of reception 58, synchronization 60, recombination and OFDM demodulation 62, secondary sequence estimation 64, cell number determination 66, block index determination 68, equalization and demodulation 70 and recombination and decoding 72 are described later in the description, in particular in the description of the steps of the downlink synchronization process according to the invention.

[0098] In the example in Figure 1, the downlink synchronization unit 48 includes an information processing unit 50 formed for example of a memory 52 and a processor 54 associated with the memory 52.

[0099] In the example of Figure 1, the receive module 58, the synchronization module 60, the recombination and demodulation module 62, the estimation module 64, the cell number determination module 66, the block index determination module 68, the equalization and demodulation module 70, and the recombination and decoding module 72 are each implemented as software, or a software block, executable by the processor 54. The memory 52 of the downlink synchronization unit 48 is then capable of storing receive software, time and frequency synchronization software, OFDM recombination and demodulation software, secondary synchronization sequence estimation software, cell number determination software, block index determination software, equalization and demodulation software, and recombination and decoding software. The processor 54 is then capable of running each of the aforementioned software programs.

[0100] In an alternative not shown, the receiving module 58, the synchronizing module 60, the OFDM recombination and demodulation module 62, the secondary sequence estimation module 64, the cell number determination module 66, the block index determination module 68, the equalization and demodulation module 70, and the recombination and decoding module 72 are each implemented as a programmable logic component, such as an FPGA (Field Programmable Gate Array), or as a dedicated integrated circuit, such as an ASIC (Application Specific Integrated Circuit).

[0101] When the downlink synchronization unit 48 is implemented as one or more software programs, i.e., as a computer program, it is also capable of being stored on a computer-readable medium (not shown). A computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. Examples of such a readable medium include an optical disc, a magneto-optical disc, ROM, RAM, any type of non-volatile memory (e.g., EPROM, EEPROM, FLASH, NVRAM), a magnetic card, or an optical card. A computer program containing software instructions is then stored on this readable medium.

[0102] When the downlink synchronization unit 48 further comprises one or more receiving antennas 56, configured to receive at least partially the signal transmitted by the base station 1. We denote N RX The number of antenna(s) is 56.

[0103] Prior to the initial access, user equipment 3 considers, for example, that a burst of 5 SSB synchronization blocks is emitted every 20 ms.

[0104] A method 100 enabling user equipment 3 to synchronize downlink to the network, implemented by the downlink synchronization unit 48, is shown in Figure 3 and described in the following description.

[0105] The process 100 includes a reception step 105, a first time and frequency synchronization step 110 and a second time and frequency synchronization step 120. Advantageously, it further includes an OFDM recombination and demodulation step 130, a cell number determination step 150, a physical broadcast channel equalization and demodulation step 170 and a physical broadcast channel recombination and decoding step 180.

[0106] The invention is expressed in two preferred implementations and two preferred embodiments, which are described in detail below. Each preferred embodiment can be implemented with either of the two preferred implementations. According to the second implementation of the invention, the method 100 includes, in addition to the first implementation, a secondary synchronization sequence estimation step 140. In Figure 3, the dashed lines correspond to the steps and links that are present only in one of the implementations or only in one of the embodiments of the invention.

[0107] The reception stage 105 is implemented by the receiving module 58. During this reception stage 105, the antenna(s) 56 receive at least partially the signal transmitted by the base station 1. The received signal S is the signal received by the receiving antenna(s) 56. The received signal S corresponds to the transmitted signal modified by the physical broadcast channel and by the presence of interference.

[0108] The received signal S comprises a useful part, called the useful signal, and an interfering part, called the interfering signal.

[0109] The received signal S, through a multipath propagation channel, in the presence of interference, noise and time and frequency deviations with the signal emitted s(t) by base station 1, is written in baseband:

[0110]

[0111] with:

[0112] n r = 1,..., N RX an index of antenna 56 of the receiver,

[0113] At the time lag,

[0114] Af the frequency shift,

[0115] gains from the path lengths of the useful signal channel,

[0116]

[0117] [

[0118] 1 T S Î I

[0119] ' L}

[0120] J the channel travel times of the useful signal,

[0121] neither

[0122] gains from the channel paths of the interfering signal,

[0123]

[0124] delays in channel paths of the interfering signal,

[0125]

[0126] N L the maximum number of paths of the channels of the useful and interfering signals, j(t) the interfering signal,

[0127] w ( “ r) (t) an additive Gaussian noise.

[0128] After correcting the time and frequency offsets, the signal r( “ r) (t + At)e _j27rA ' ft can be filtered to limit interference and noise in the SSB signal band, then the OFDM signals can be demodulated, after which we find an equivalent model in the frequency domain, with a single input and multiple outputs:

[0129]

[0130] Or:

[0131] ■ s,k,i e i,k,i are vectors N RX x 1 multi-channel receiver, respectively for the useful signal and the interfering signal,

[0132] has k l is the symbol at k iime OFDM symbol and / ' ème ,

[0133] - k,i is un additive Gaussian noise with zero mean and covariance matrix. It is assumed that the interference i k i behaves in frequency like noise with zero mean and variance 0 and with a spatial signature R lk t

[0134]

[0135] and on the occupied subcarriers the useful signal satisfies E. We can assume without

[0136]

[0137] loss of generality that the useful signal can have an average power a s 2 k which varies with k and l, depending on the power allocation policy for emissions.

[0138] We set M k i =

[0139]

[0140] to group the interference and noise terms, which have a spatial covariance matrix R M = O^, I NRX + Ri,k,i- The process 100 allows user equipment 3 to synchronize in downlink to the network even in the presence of significant interference, i.e. when Oi l Os > 1.

[0141] The first frequency and time synchronization step 110, shown more precisely in Figure 4, is implemented by the synchronization module 60. This step consists of providing an initial estimate of the frequency offset DF1 and an initial estimate of the time offset DT1 between the signal transmitted by base station 1 and the received signal S, as well as determining the first component N_PSS of the cell number N_cell. This first synchronization step is performed considering only the primary synchronization sequence PSS of the SSB synchronization block.Indeed, since there are only 3 possible PSS sequences, and the PSS sequence is identical on each SSB block of burst 5, using an interference-robust correlation synchronization algorithm on the PSS sequence only is less computationally expensive than using the same interference-robust synchronization algorithm on all possible PSS sequence - SSS sequence pairs.

[0142] Prior to step 110, a coarse synchronization time horizon 15 and coarse Doppler boxes 19 are fixed. The coarse synchronization time horizon 15 consists of

[0143]

[0144] samples. The coarse Doppler boxes 19 have a resolution Af r and there are N DThese parameters are called "coarse" in contrast to a fine synchronization time horizon 21 shorter than the coarse synchronization time horizon 19 and fine Doppler boxes 23 finer than the coarse Doppler boxes 19, used during the second frequency and time synchronization step 120. Similarly, a burst configuration hypothesis 17 is chosen prior to step 110.

[0145] Optionally, step 110 includes a substep 111 of subsampling the received signal S to the rate of the PSS sequence. This reduces the complexity of step 110 and is possible because the signal bandwidth of the PSS sequence is smaller than the signal bandwidth of the SSB block.

[0146] We then consider a first portion of the received signal, which we denote r n The first portion of the received signal corresponds to the received signal S, denoted

[0147]

[0148] sampled at an F rate e at least equal to the bandwidth of the PSS sequence signal. Thus, the first portion of the received signal includes at least the primary PSS synchronization sequence of the received signal S. Due to the frequency offset of the received signal S relative to the signal transmitted by base station 1, the PSS sequence is probably not carrier-centered, but resampling allows the out-of-band signal to be folded back onto the bandwidth corresponding to F. e - In the case of spatial synchronization, we have:

[0149]

[0150] which is a vector of size N RX x 1.

[0151] In the case of spatio-temporal synchronization, we have an extended vector:

[0152]

[0153] which is a vector of size N RX L ST x 1 where L ST is a spatio-temporal horizon length and i stis a spatiotemporal spacing step. The case of spatial processing is deduced from the spatiotemporal case by taking a spatiotemporal horizon length L ST = 1.

[0154] Step 110 includes a substep 112 for estimating a primary autocorrelation matrix of the first portion of the received signal, expressed as:

[0155]

[0156] on the coarse synchronization time horizon 15, where N ref is the length of the synchronization sequence in number of samples.

[0157] The primary autocorrelation matrix is ​​then inverted in a substep 113 of autocorrelation matrix inversion.

[0158] For each possible PSS sequence, therefore for each value of the first component N_PSS, denoted N^\ possible, we denote d a generated reference signal

[0159]

[0160] based on hypothesis 17 of burst configuration 5. We note d n (N^,\e reference signal sampled at the same rate as r n This yields a first set of reference sequences, including the reference signal for each of the PSS primary synchronization sequences to be tested.

[0161] Step 110 includes a substep 114 for estimating primary cross-correlation vectors of the first portion of the received signal with the first set of reference sequences. The primary cross-correlation vectors are written as:

[0162]

[0163] where k =

[0164]

[0165] an index associated with the coarse Doppler boxes 19.

[0166] Then, in substep 115 of the criterion calculation, a primary synchronization criterion is calculated from the inverted primary correlation matrix and the primary cross-correlation vectors. The primary synchronization criterion is expressed as:

[0167]

[0168] During substep 116 of the optimum search, an optimum of the primary synchronization criterion is sought for the N D coarse Doppler cases 19, the N sync e samples of the coarse synchronization time horizon 15 and the three possible PSS sequences.

[0169] In the case of a spatial synchronization criterion, one can simply search for the maximum, and it is possible to use a minimum threshold to reject weak peaks of the primary synchronization criterion, in order to target a certain probability of false alarm. In the spatiotemporal case, it may be preferable to work on the detection of a rising edge on a sliding window, for example, of the order of size of the cyclic prefix.

[0170] Knowledge of the coarse Doppler box 19 optimizing the primary synchronization criterion provides the first estimate of the frequency shift DF1, knowledge of the sample of the time horizon of coarse synchronization 15 optimizing the primary synchronization criterion provides the first estimate of the frequency shift DF1, and knowledge of the PSS sequence optimizing the primary synchronization criterion provides the first component N_PSS of the cell number N_cell.

[0171] According to hypothesis 17 regarding the configuration of burst 5, and knowing a priori the directivity of the beams emitted by base station 1, it is sometimes possible to use the PSS sequence of several SSB blocks to perform these correlations. In this case, the accuracy of the time offset estimation DT1 and the frequency offset estimation DF1 is significantly improved, but at the cost of introducing ambiguities in the frequency of the primary synchronization criterion. These ambiguities can nevertheless be managed by knowing a priori the positions of the PSS sequences during substep 116, the optimum search.

[0172] The second frequency and time synchronization step 120 is also implemented by the synchronization module 60. Alternatively, the second synchronization step 120 is implemented by a separate, unshown synchronization module distinct from the synchronization module 60. This step aims to provide a second estimate of the frequency offset DF2 and a second estimate of the time offset DT2. These second estimates of the frequency offset DF2 and the time offset DT2 are more accurate than the first estimates of the frequency offset DF1 and the time offset DT1, respectively. In other words, the first estimates of the frequency offset DF1 and DT1 are coarse estimates, while the second estimates of the frequency offset DF2 and the time offset DT2 are fine estimates.

[0173] The second frequency-time synchronization step 120 is similar to the first frequency-time synchronization step 110, except that it involves a second portion of the received signal and a second set of reference sequences, with the primary PSS synchronization sequence being fixed. The second step 120 also involves a shorter fine synchronization time horizon 21 than the coarse synchronization time horizon 19, and finer Doppler cells 23 than the coarse Doppler cells 19. In particular, the fine Doppler cells 23 result from a finer frequency segmentation than the coarse Doppler cells 19. The amount of calculation required in steps 110 and 120 is thus reduced compared to a solution that would require performing correlations from the outset on each PSS-SSS sequence pair, on the fine synchronization time horizon 21, and on the fine Doppler cells 23.

[0174] The second synchronization step 120 is divided into a first variant corresponding to the first implementation of the invention, and respectively a second variant corresponding to the second implementation, the second synchronization step 120 being then noted 120A according to the first variant, and respectively 120B according to the second variant.

[0175] According to the first variant corresponding to the first implementation of the invention, the second synchronization step 120A is shown in Figure 5. It includes a substep 121A for compensating the frequency synchronization error, consisting of correcting the second portion of the received signal using the first estimate of the frequency deviation DF1, and a substep 122A for compensating the time synchronization error, consisting of correcting the second portion of the received signal using the first estimate of the time deviation DT1.

[0176] The second portion of the received signal thus corrected is advantageously filtered during a filtering sub-step 123A, in order to limit the band of the received signal to that of the primary PSS and secondary SSS sequences, and to reject out-of-band noise and interference.

[0177] A secondary autocorrelation matrix is ​​calculated during a substep 124A, corresponding to the autocorrelation of the second portion of the received signal corrected and filtered over the fine synchronization time horizon 21.

[0178] The secondary autocorrelation matrix is ​​then inverted in a 125A autocorrelation matrix inversion substep.

[0179] In parallel, step 120A includes a substep 126A for estimating secondary cross-correlation vectors, by correlating the second portion of the received signal with the second set of reference sequences, the first PSS synchronization sequence being fixed by estimating the first N_PSS component determined in the first synchronization step 110. The estimation of secondary cross-correlation vectors is carried out on the fine Doppler squares 23.

[0180] Similar to the criterion calculation substep 115 and optimum search substep 116 of step 110, step 120A includes a secondary synchronization criterion calculation substep 127A and an optimum search substep 128A on each of the fine Doppler squares 23 and samples of the fine synchronization time horizon 21, providing the second estimates of the frequency offset DF2 and the time offset DT2.

[0181] According to the second variant corresponding to the second implementation of the invention, the second synchronization step 120B shown in Figure 6 comprises substeps 121B to 128B analogous to substeps 121A to 128A of the first implementation of the invention. Only the differences compared to this implementation are described below.

[0182] According to the second implementation of the invention, the second portion of the received signal comprises at least one of the secondary synchronization sequences (SSS) of the received signal, and the second set of reference sequences used in the secondary cross-correlation vector estimation substep 126B comprises a reference signal for each of the secondary synchronization sequences (SSS) to be tested 25, the primary synchronization sequence (PSS) being fixed. In the worst case, there are 336 SSS sequences to be tested 25. However, if the user equipment 3 has prior knowledge of the possible values ​​for the cell identity N_cell, the number of SSS sequences to be tested 25 is less than 336.

[0183] The substep of optimum search 128B is further performed on each of the SSS sequences to be tested 25 and knowledge of the SSS sequence optimizing the secondary synchronization criterion provides the second component N_SSS of the cell number N_cell.

[0184] The computational workload in step 120 is greater in the second implementation than in the first implementation of the invention. This is because, in step 120A of the first implementation, the number of PSS-SSS sequence pairs tested is less than the number of PSS-SSS sequence pairs tested in step 120B of the second implementation, which includes all SSS sequences that could potentially be present in the transmitted signal. This step eliminates the uncertainty regarding the SSS sequence actually present in the transmitted signal. For this reason, the first implementation is chosen when the user equipment 3 has limited computing power, preventing the implementation of the second implementation within a reasonable timeframe for the application in question.

[0185] The recombination and demodulation step 130 is implemented by the recombination and demodulation module 62. The received signal S is generally a multi-channel signal. The recombination and demodulation step 130 then aims to recombine the received multi-channel signal S into a received single-channel signal by means of a spatial or spatio-temporal filter, in order to facilitate the estimation of the other unknown parameters of the SSB synchronization block, and to demodulate the received signal S, which is modulated by orthogonal frequency division, known as OFDM modulation, according to the 5G standard of the 3GPP consortium.

[0186] The recombination and demodulation step 130 is performed on a third portion of the received signal, comprising at least one SSB synchronization block. The third portion of the received signal is corrected using the second frequency deviation estimate DF2 in a substep 131 and using the second time deviation estimate DT2 in a substep 132, before being filtered in a substep 133.

[0187] The recombination and demodulation step 130 then includes a substep 134 of estimating a tertiary autocorrelation matrix of the third portion of the received signal corrected and filtered, and a substep 135 of estimating tertiary autocorrelation vectors between the third portion of the received signal corrected and filtered and the reference signal of the second set of reference sequences retained during the optimum search substep 128A or 128B of the second time and frequency synchronization step 120. In other words, the cross-correlation is calculated between the third portion of the received signal corrected and filtered and the reference signal of the second set of reference sequences which optimized the secondary synchronization criterion during the second time and frequency synchronization step 120.The substeps of estimating a tertiary autocorrelation matrix 134 and estimating tertiary autocorrelation vectors 135 allow us to obtain correlation parameters over the entire third portion of the received signal, therefore over the entire band of the SSB synchronization block.

[0188] The tertiary autocorrelation matrix R xx and the tertiary autocorrelation vectors r̂ xd are then used in a substep 136 of calculating a spatially or spatio-temporally adapted filter w = R̂ xx -1 r̂ xd .

[0189] Then, during a substep 137 of spatiotemporal filtering and demodulation, the third corrected portion of the received signal is recombined into a single-channel received signal portion, using the spatially or spatiotemporally matched filter. In particular, the single-channel received signal is written as r̃ n = w H r nDuring this same substep 137 of spatiotemporal filtering and demodulation, the received single-channel signal portion is demodulated, yielding received orthogonal frequency division symbols (SYM_OFDM). More precisely, demodulation consists of obtaining resource elements

[0190]

[0191] ~ s,k,i a k,i + j, où is a subcarrier index in OFDM modulation and, l is a symbol index in OFDM modulation,

[0192]

[0193] k ( is the equivalent physical diffusion channel after recombination, and

[0194]

[0195] is the residual noise and interference after recombination. In cases where spatial or spatiotemporal filtering succeeds in rejecting all significant interference paths, wj (It essentially has only a noise component, but otherwise, it will continue to have a strong interference component. This step assumes that over the duration of an SSB block, the signal correlation properties evolve slowly enough to maintain the same behavior on the OFDM modulation symbols of the SSB block, which should be largely verified after the second frequency synchronization.

[0196] In the first implementation of the invention, the secondary synchronization sequence estimation step 140, implemented by the secondary sequence estimation module 64, makes it possible to determine the second component N_SSS of the cell number N_cell, which was not determined during the second time and frequency synchronization step 120.

[0197] This secondary synchronization sequence estimation step 140, shown in Figure 8, includes a substep 141 of correlating the received orthogonal frequency division symbols SYM_OFDM or the multi-channel received signal portion with a third set of reference sequences. This third set of reference sequences comprises the secondary synchronization sequences SSS to be tested 25 and is generated based on the burst configuration hypothesis 17 5, with the primary synchronization sequence PSS being fixed. A tertiary correlation criterion is calculated, defined by:

[0198]

[0199] Or:

[0200] li is the index of the DMRS demodulation sequence symbols corresponding to the N SSB possibilities considered in configuration hypothesis 17

[0201] fixed to the value detected during

[0202]

[0203] the first step 110,

[0204] varies with the SSS sequences to be tested 25.

[0205] The secondary synchronization sequence estimation step 140 further includes a substep for finding the maximum of the tertiary correlation criterion 142 on each of the secondary synchronization sequences (SSS) to be tested 25, the primary synchronization sequence (PSS) being fixed. Knowledge of the secondary synchronization sequence (SSS) that maximizes the correlation criterion provides the second component N_SSS of the cell number N_cell.

[0206] Knowing the first component N_PSS and the second component N_SSS of the cell number, the cell number determination step 150, implemented by the cell number determination module 66, allows the cell number N_cell to be determined based on the first component N_PSS and the second component N_SSS by applying the function linking the cell number N_cell to the first component N_PSS and the second component N_SSS. According to the 3GPP consortium's 5G standard, this function is written as N ID cell = 3N ID (1) + N ID (2)

[0207] The block index determination step 160, shown in Figure 9, is implemented by the block index determination module 68. The objective is to find the block index i_SSB of the SSB synchronization block within burst 5.

[0208] To this end, the block index determination step 160 includes a substep 161 that correlates at least some of the received orthogonal frequency division symbols SYM_OFDM, corresponding to the DMRS demodulation reference symbols, with a set of reference symbols corresponding to the block indices i_SSB to be tested. More precisely, v = N is calculated ID cell mod 4 is used to retrieve indices of the OFDM subcarriers and symbols to which the DMRS is allocated. A quaternary correlation criterion C is defined. DMRS (i SSB ) depending on the block index l_SSS. The value of the cell number N_cell is fixed to the previously determined value. The expression of the quaternary correlation criterion depends on the number of SSB synchronization blocks considered in the synchronization process. For example, if only one SSB synchronization block is considered, then the quaternary correlation criterion is expressed as:

[0209]

[0210] The quaternary correlation criterion is evaluated for each value of the block index l_SSB to be tested, and the value optimizing the quaternary correlation criterion provides the block index l_SSB of the received signal S under consideration.

[0211] The equalization and demodulation step of the physical broadcast channel 170 is implemented by the equalization and demodulation module 70. It consists of providing likelihood ratios for each bit of the master MIB information block.

[0212] According to the first example of the invention, the equalization and demodulation step 170A, shown in Figure 10, performs an estimation of the physical broadcast channel from the received orthogonal frequency distribution symbols SYM_OFDM.

[0213] In particular, the equalization and demodulation step 170A includes a substep 171 A of estimating the equivalent single-way physical diffusion channel 27 and the variance of the noise and residual interference 29. This estimation is carried out from the received orthogonal frequency distribution symbols SYM_OFDM, knowing the block index i_SSB within the burst and the cell number N_cell.

[0214] For example, substep 171A performs a least-squares channel estimation on the DMRS demodulation reference sequences and the SSS sequences, and then performs a two-dimensional interpolation of this estimation over all k subcarriers and l symbols covering the data bandwidth of the PBCH physical broadcast channel. Alternatively, denoising methods could be used, by calculating the time impulse response h ni, where n is a time-sample index, by applying an inverse Fourier transform to each symbol l, and truncating the impulse response to minimize the noise contribution. The variance of the equivalent noise 27 can also be estimated on these truncated samples, as well as on the subcarriers not carrying data. The frequency equalizer is then calculated after frequency conversion. The frequency equalizer thus estimated is then used in a single-channel frequency equalization substep 172A of the orthogonal frequency distribution symbols SYM_OFDM, providing equalized symbols of the physical diffusion channel 31 and a post-equalization equivalent noise variance 33. The equalized symbols of the physical diffusion channel 31 are symbols using quadrature phase modulation, known as QPSK modulation.

[0215] The equalized symbols of the physical broadcast channel 31 are then demodulated in a 173A substep of QPSK demodulation, providing the logarithm of an LLR likelihood ratio, called the log-LLR likelihood ratio, for each of the 864 bits of a codeword corresponding to the master information block Ml B.

[0216] According to the second example of the invention, the equalization and demodulation step of the physical broadcast channel 170B, shown in Figure 11, performs the estimation of the physical broadcast channel from the received multi-channel signal S. More specifically, the processing is carried out on a fourth portion of the received signal S, comprising at least one SSB synchronization block.

[0217] The equalization and demodulation stage 170B includes a substage 171B for frequency gap correction from the second frequency gap estimate DF2, a substage 172B for time gap correction from the second time gap estimate DT2 and a filtering substage 173B.

[0218] The fourth portion of the received signal, thus corrected and filtered, is then jointly processed by spatial or spatio-temporal filtering and equalized, all in the frequency domain.

[0219] The multi-way equivalent physical diffusion channel estimation substep 174B performs an estimation of a noise and interference covariance matrix 60 and an estimation of the single-way equivalent physical diffusion channel 37 by a minimum root mean square error-interference rejection combination equalizer, known as MMSE-IRC type.

[0220] If we assume that the noise and interference covariance matrix remains constant across all subcarriers, then spatial interference mitigation is preferable. Conversely, if we assume that the noise and interference covariance matrix changes with the subcarriers, then spatiotemporal interference mitigation is preferable. For the spatiotemporal case, since the number of symbols in the PBCH physical broadcast channel data is insufficient to accurately estimate the noise and interference covariance matrix for each subcarrier, the 240 subcarriers carrying the PBCH physical broadcast channel data are advantageously divided into groups of

[0221]

[0222] subcarrier groups are used to estimate a noise and interference covariance matrix for each group. The equalization and demodulation step 170B then includes a frequency equalization substep 176B of the fourth portion of the received signal using the estimated MMSE-IRC equalizer, providing equalized symbols of the physical broadcast channel 31 and a post-equalization equivalent noise variance 33. Spatial or spatiotemporal filtering is performed concurrently with frequency equalization during substep 176B.

[0223] The equalized symbols of the physical broadcast channel 31 are then demodulated in a 173B substep of QPSK demodulation, providing the logarithm of an LLR likelihood ratio, called the log-LLR likelihood ratio, for each of the 864 bits of the codeword corresponding to the master information block Ml B.

[0224] In configurations where the number of SSB synchronization blocks in burst 5 is less than 64 (particularly for carrier frequencies below 6 GHz), the PBCH physical broadcast channel data on the different SSB blocks is identical. In this case, several SSB blocks are advantageously equalized and demodulated, and their log-likelihood ratios (LLRs) are combined, which allows for a more refined decoding of the master information block M1 B.

[0225] In both examples of the invention, the recombination and decoding step of the physical broadcast channel 180 is implemented by the recombination and decoding module 72. During this substep 180, the master information block (MIB) is decoded from the log-likelihood ratios (LLRs), providing a transmitted frame index, a subcarrier offset of the SSB synchronization block relative to the rest of a resource grid (i.e., the set of subcarriers I and symbols k), information about physical control channels, and information about physical data channels. These parameters complete the synchronization of the user equipment 3 to the network.

[0226] The recombination and decoding step of the physical broadcast channel 180 is the final step in the downlink synchronization process of user equipment 3.

[0227] Any feature described above for an implementation, example or variant can also be implemented for the implementations, examples and variants described above, as far as technically possible.

Claims

DEMANDS 1. A method (100) for downlink synchronization of a user device (3) to a 5G cellular network, comprising: - a step (105) of receiving a signal emitted by a base station (1), the emitted signal comprising at least one synchronization signal block (SSB) belonging to a burst (5) of synchronization signal blocks (SSB) emitted by the base station (1) and identified within the burst (5) by a block index (i_SSB), the base station (1) belonging to a cell characterized by a cell number (N_cell), the cell number being a function of a first component (N_PSS) on which depends a primary synchronization sequence (PSS) of the synchronization block (SSB) and a second component (N_SSS) on which depends a secondary synchronization sequence (SSS) of the synchronization block (SSB), the synchronization block (SSB) further comprising data from a physical broadcast channel (PBCH); characterized in that the process (100) further comprises: - a first frequency and time synchronization step (110), during which a first estimation of a frequency gap (DF1) between the signal emitted by the base station and a signal received (S) by the user equipment (3) during the reception step (105), a first estimation of a time gap (DT1) between the signal emitted by the base station (1) and the received signal (S) and a determination of the first component (N_PSS) of the cell number (N_cell) are carried out by autocorrelation of a first portion of received signal and cross-correlation of the first portion of received signal with a first set of reference sequences, the first portion of received signal comprising at least one of the primary synchronization sequences (PSS) of the received signal (S) and the first set of reference sequences comprising a reference signal for each of the primary synchronization sequences (PSS) to be tested;and - a second step (120, 120A, 120B) of frequency and time synchronization, during which a second estimate of the frequency gap (DF2) and a second estimate of the time gap (DT2) are made by autocorrelation of a second portion of the received signal and cross-correlation of the second portion of the received signal with a second set of reference sequences after correction of the second portion of the received signal using the first estimates of the frequency gap (DF1) and time gap (DT1), the primary synchronization sequence (PSS) being fixed, the second estimates being made taking into account the first component (N_PSS) determined during the first step (110) of time and frequency synchronization; the second estimates of the frequency deviation (DF2) and the time deviation (DT2) being more accurate than the first estimates of the frequency deviation (DF1) and the time deviation (DT1) respectively.

2. Method (100) according to claim 1, wherein the second frequency and time synchronization step (120, 120A, 120B) comprises a filtering substep (123A, 123B), during which the corrected second received signal portion is filtered, so as to limit the second received signal portion to the primary (PSS) and secondary (SSS) synchronization sequences.

3. A method (100) according to claim 1 or 2, wherein the received signal (S) is a multichannel signal and wherein the method (100) comprises a recombination and demodulation step (130), during which: - a third portion of the received signal is corrected using the second estimates of the frequency (DF2) and time (DT2) deviations, the third portion of the received signal including at least one synchronization block (SSB); - a spatial or spatio-temporal filter is calculated by autocorrelation of the third portion of the corrected received signal and cross-correlation of the third portion of the corrected received signal with a reference signal, belonging to the second set of reference sequences and having been retained during the second step (120) of frequency and time synchronization; - the third corrected portion of the received signal is recombined into a single-channel received signal portion using the spatial or spatiotemporal filter; and - the single-channel received signal portion is demodulated, providing received orthogonal frequency distribution symbols (SYM_OFDM).

4. Method (100) according to claim 3, further comprising a step (140) of secondary synchronization sequence estimation, during which a determination of the second component (N_SSS) of the cell number (N_cell) is carried out by correlation of the received orthogonal frequency division symbols (SYM_OFDM) or of the multi-channel received signal portion with a third set of reference sequences, the third set of reference sequences comprising secondary synchronization sequences (SSS) to be tested, the primary synchronization sequence (PSS) being fixed.

5. Method (100) according to any one of claims 1 to 3, wherein the second received signal portion comprises at least the secondary synchronization sequence (SSS) of the received signal (S) and the second set of reference sequences comprises a reference signal for each of the secondary synchronization sequences (SSS) to be tested, and wherein the second frequency-time synchronization step (120, 120B) further comprises the determination of a value of the second component (N_SSS) of the cell number (N_cell).

6. Method (100) according to any one of claims 4 or 5, further comprising a step (150) of determining the cell number (N_cell) as a function of the first component (N_PSS) and the second component (N_SSS).

7. Method (100) according to claims 3 and 6, further comprising a step (160) of determining the block index (i_SSB) by correlation of at least a part of the received orthogonal frequency distribution symbols (SYM_OFDM) with a set of reference symbols, corresponding to the block indices (i_SSB) to be tested.

8. A method (100) according to claim 7, further comprising a step (170A) of equalizing and demodulating the physical broadcast channel, during which: - the physical broadcast channel is estimated from the received orthogonal frequency division symbols (SYM_OFDM), knowing the block index (i_SSB) within the burst (5) and the cell number (N_cell); - a single-channel frequency equalization of the orthogonal frequency distribution symbols (SYM_OFDM) is performed using the estimated physical diffusion channel, providing equalized symbols of the physical diffusion channel (31); and - the equalized symbols of the physical broadcast channel (31) are demodulated, providing the logarithm of a likelihood ratio (LLR) for each bit of a codeword, corresponding to the master information block (Ml B) contained in the physical broadcast channel data (PBCH).

9. A method (100) according to claim 7, further comprising a step (170B) of equalizing and demodulating the physical broadcast channel, during which: - the multi-way physical diffusion channel and a spatial autocorrelation of noise and interference are estimated from a fourth portion of the received signal (S), corrected using the second estimates of the frequency (DF2) and time (DT2) deviations, knowing the block index (i_SSB) within the burst (5) and the cell number (N_cell), the fourth portion of received signal (S) comprising at least one synchronization block (SSB); - Frequency equalization of the fourth portion of the received signal is performed by a minimum root mean square error-interference rejection combination equalizer, known as MMSE-IRC type, providing equalized symbols of the physical broadcast channel; and - the equalized symbols of the physical broadcast channel are demodulated, providing the logarithm of a likelihood ratio (LLR) for each bit of a codeword, corresponding to the master information block (Ml B) contained in the physical broadcast channel (PBCH) data.

10. Method (100) according to claim 8 or 9, further comprising a step (180) of recombination and decoding of the physical broadcast channel (PBCH) data during which the master information block (Ml B) is decoded from the logarithms of the likelihood ratios (LLR) of the codeword, providing parameters to complete the synchronization of the user equipment (3) to the 5G cellular network.

11. User equipment (3) intended to be connected to a 5G cellular network, characterized in that it is configured to implement a method (100) according to one of the preceding claims.

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