WO2021038264A1

WO2021038264A1 - Method for connecting a user equipment to a mobile telecommunication system, user equipment and base station

Info

Publication number: WO2021038264A1
Application number: PCT/IB2019/000976
Authority: WO
Inventors: Hao Lin
Original assignee: Orope France Sarl
Priority date: 2019-08-26
Filing date: 2019-08-26
Publication date: 2021-03-04

Abstract

The user equipment performs the steps of detecting a synchronization signal block in a first slot transmitted by a base station; determining an index of said synchronization signal block from a basic system information included in the synchronization signal block; determining from said synchronization signal block index a slot index of a second slot containing a control signal carrying a location information for a data signal including a remaining system information, said location information defining an area for said data signal within a resource grid representing the second slot in time domain and in frequency domain; and reading the remaining system information in the data signal of the second slot, according to said location information, in order to continue connecting to the network. In addition, the user equipment receives a presence information, transmitted by the base station, related to the presence or not of at least one synchronization signal block in the second slot, at a known position in the resource grid representing said second slot. If the presence information indicates the presence of at least one synchronization signal block in the second slot, the user equipment reads the resources of said area for the data signal in the second slot resource grid, excluding the resources that correspond to the at least one synchronization signal block which presence is given by the presence information.

Description

Title: Method for connecting a user equipment to a mobile telecommunication system, user equipment and base station

TECHNICAL FIELD

[0001] The present disclosure relates to the field of telecommunication, an in particular to a method for connecting a user equipment to a mobile telecommunication system, a user equipment and a base station.

[0002] The telecommunication system is for example a 5G (fifth generation) network using the 5G NR (New Radio) as radio access technology (RAT) defined by 3GPP. The present disclosure is applicable to 5G NR-U (NR in unlicensed spectrum), but also to 5G NR (NR in licensed spectrum).

BACKGROUND

[0003] When a user equipment wants to connect to a mobile telecommunication system, the first step the user equipment has to do is to connect to a base station of the access network. To do so, the user equipment must be able to synchronize with the access network. According to 3GPP 5G NR standards, the way the user equipment does the synchronization with the network relies on a SSB (for Synchronization Signal Block), also called SS block or SS/PBCH block. A SSB contains a synchronization signal and a MIB (for Master Information Block) that is a basic system information. The base station transmits a plurality of SS blocks in a plurality of slots, each slot containing a maximum of two SSBs (in other words, either two SSBs, or one SSB, or no SSB). Each SS block has an index for ordering. Figure 1 shows an example of six SSB, having respective indices from SSB#0 to SSB#5, transmitted in three consecutive slots, having respective indices from slot#0 to slot#2. On figure 1, each slot transmitted from the base station contains two SSBs. The MIB included in one SS block contains the index of said SS block. The SSBs are located at two known (fixed) SSB candidate positions in the slots. The SSB candidate (possible) positions in a slot are given by 3GPP 5G NR standards.

[0004] In order to carry out the synchronization, the user equipment has to first detect one SSB. The detected SSB may depend on the user equipment location in a cell covered by the base station, where different SSB indices correspond to different directions for example.

[0005] Once the user equipment has detected one SSB index, the user equipment starts to perform the synchronization process. For that purpose, the user equipment reads the MIB in the detected SSB and obtains the SSB index.

[0006] After the first step of detecting one SSB, reading the MIB in the detected SSB and extracting the SSB index from the MIB, the user equipment proceeds with a second step of obtaining a remaining system information (RMSI) to complete the system information, in addition to the basic system information contained in the MIB. Indeed, the user equipment needs to know the remaining system information (RMSI) in order to be able to continue the connection to the network.

[0007] The remaining system information (RMSI) is given in a data signal, more precisely PDSCH defined by 3GPP standards. In order to acquire the RMSI-PDSCH (data signal PDSCH including RMSI), the user equipment has to determine where this data signal RMSI-PDSCH is located. The RMSI- PDSCH location information, indicating where to find the data signal PDSCH containing the RMSI, is transmitted by the base station in a control signal that is carried in a TypeO-PDCCH channel defined by 3GPP standards.

[0008] After detecting one SSB and its index “i” in a first slot, the user equipment determines a frame index and a slot index, related to a second slot in which the user equipment receives the control signal carried in TypeO- PDCCH and providing the location information for the RMSI-PDSCH, using rules specified by the 3GPP standards such as:

- frame index derivation given by the first equation below L(o-2" + Li-Mj)/iV '-"Jmod2 = 0

- and slot index derivation given by the second equation below

[0009] The second slot including the control signal, or “TypeO-PDCCH slot”, may be different from or the same as the first slot including the SSB detected by the user equipment.

[0010] The second slot (TypeO-PDCCH slot in the example) contains the control signal carried in TypeO-PDCCH and also a scheduled data signal PDSCH including the remaining system information. The control signal carried in TypeO-PDCCH indicates the location of this data signal PDSCH within the TypeO-PDCCH slot.

[0011] Each slot can be represented by a resource grid in time domain and in frequency domain. Additionally, as previously indicated, the slot, for example the TypeO-PDCCH slot, may contain one BB block, or two SS blocks, or no block.

TECHNICAL PROBLEM

[0012] In the 3GPP 5G NR standards, it is defined that, while a user equipment is receiving TypeO-PDCCH, the user assumes that the scheduled RMSI-PDSCH of the TypeO-PDCCH slot does not overlap with any of the SSB present in the TypeO-PDCCH slot. Moreover, since the resource allocation type in frequency domain is only localized allocation, the only possible RMSI-PDSCH allocation is either on one side of the SSB in frequency domain on the resource grid representing the slot, as shown in figure 2, or between two SSBs in time domain on the resource grid representing the slot, as shown in figure 3. In other words, the standard allows that the data channel PDSCH, including RMSI and one SSB or two SSBs, are mixed in the same slot in only two ways. In a first way, the RMSI- PDSCH and the SSB are separately allocated in the frequency domain (figure 2). In a second way, the RMSI-PDSCH and the SSB are separately allocated in the time domain (figure 3). In such a configuration of the slot (TypeO- PDCCH slot in the example), many resources of the slot are unoccupied. The unoccupied resources are represented by blank elements in the resource grids of figures 2 and 3.

[0013] In addition, the initial bandwidth allocated when the user equipment starts connecting to the access network may be limited. For example, an initial BWP (for Bandwidth Part) for NR-U is limited to 20 Mhz. [0014] It results from the above that the available resource for the data signal including the remaining system information (RMSI-PDSCH) is also limited. Consequently, the robustness of the transmission of the data signal (RMSI- PDSCH) is reduced.

[0015] An option to optimize the resource for the data signal including the remaining system information (RMSI-PDSCH) may be to take advantage of all the available (unoccupied) resources within the slot. However, such a solution results in an unavoidable resource collision between the data signal (RMSI-PDSCH) and actual transmitted SSB within the slot.

[0016] The present disclosure aims to improve the situation. In particular, a purpose is to improve the robustness of the transmission of the remaining system information within the downlink data signal, from the base station to the user equipment. When the resources for transmitting the remaining system information (RMSI-PDSCH in the example) are increased, the robustness of the transmission is improved and the quality of reception is better.

SUMMARY

[0017] An object of the present disclosure is a method for connecting a user equipment to a mobile telecommunication system, comprising the following steps, performed by the user equipment: - detecting a synchronization signal block in a first slot transmitted by a base station;

- determining an index of said synchronization signal block from a basic system information included in the synchronization signal block; - determining from said synchronization signal block index a slot index of a second slot containing a control signal carrying a location information for a data signal including a remaining system information, said location information defining an area for said data signal within a resource grid representing the second slot in time domain and in frequency domain; - reading the remaining system information in the data signal of the second slot, according to said location information, in order to continue connecting to the network; characterized in that

- the method comprises a further step, performed by the user equipment, of receiving a presence information, transmitted by the base station, related to the presence or not of at least one synchronization signal block in the second slot, at a known position in the resource grid representing said second slot, and the presence information indicating the presence of at least one synchronization signal block in the second slot, in the step of reading the remaining system information, the user equipment reads the resources of said area for the data signal in the resource grid representing the second slot, excluding the resources of said area for the data signal that correspond to the at least one synchronization signal block which presence is given by the presence information.

[0018] The data signal including the remaining system information is for example carried in a PDSCH channel defined by the 3GPP standards. [0019] The control signal including the location information for the data signal containing the remaining system information is for example carried in TypeO- PDCCH defined by 3GPP standards.

[0020] In the present disclosure, the base station can use more resources within the second slot (for example the TypeO-PDCCH slot) to carry the data signal containing the remaining system information. In order to avoid any resource collision between the data signal containing the remaining system information (RMSI-PDSCH in the example) and actually transmitted synchronization signal block(s) (SSB(s)) within the second slot (TypeO- PDCCH slot in the example), a SSB presence information is transmitted from the base station to the user equipment. The user equipment performs a rate matching on the basis of the received SSB presence information. It means that the user equipment reads the resources allocated for the data signal containing the remaining system information (RMSI-PDSCH in the example) within the second slot (TypeO-PDCCH slot in the example), as defined by the information location given by the control signal (carried in TypeO-PDCCH in the example), and skips (or ignores, or excludes) the resources used by the SSB(s) present in the second slot (TypeO-PDCCH slot in the example), using the SSB presence information. The SSB(s) are located at known (fixed) SSB candidate positions in the resource grid representing the second slot in time domain and in frequency domain. Actually, the allocated resources (allocated for RMSI-PDSCH in the example) in the second slot (TypeO-PDCCH slot in the example), as defined by the location information given by the control signal (carried in TypeO-PDCCH in the example), extend over an area of the second slot resource grid, that includes at least partially the SSB(s) present in the second slot resource grid. Therefore, in the allocated resources (allocated for RMSI-PDSCH in the example), the user equipment has to skip (or ignore, or exclude) the resources that are reserved for SSB transmission, according to the SSB presence information. This SSB presence information allows the user equipment to know whether SSB(s) are actually transmitted in the second slot at the known (fixed) SSB candidate position(s). [0021] In a first example embodiment, the presence information is read in said control signal.

[0022] Advantageously, in case that the second slot containing the control signal is also the first slot containing the synchronization signal block detected by the user equipment, the user equipment only determines whether another synchronization signal block is present or not in the slot from the presence information.

[0023] Advantageously, in the above example,

- in case that the slot only contains the synchronization signal block detected by the user equipment, the user equipment only excludes the resources that correspond to the detected synchronization signal block, in the step of reading the remaining system information, and

- in case that the slot contains the synchronization signal block detected by the user equipment and another synchronization signal block which presence is given by the presence information, the user equipment excludes the resources that correspond to both the detected synchronization signal block and the other synchronization signal block.

[0024] Advantageously, in case that the second slot containing the control signal is also the first slot containing the synchronization signal block detected by the user equipment, the presence information is read from one bit.

[0025] In case that the second slot containing the control signal is different from the first slot containing the synchronization signal block detected by the user equipment, the user equipment determines the presence or not of each of two possible synchronization signal blocks at two known positions in the second slot resource grid from the presence information.

[0026] In the above example, the presence information is read in two bits, related respectively to the two possible synchronization signal blocks. [0027] Advantageously, the presence information is read in a downlink control information carried in the control signal.

[0028] Advantageously, the control signal is carried in TypeO-PDCCH defined by 3GPP standards. [0029] In a second example embodiment, the presence information is read in the basic system information included in the synchronization signal block detected by the user equipment.

[0030] Advantageously, the presence information is read in a MIB, for master block information, defined by 3GPP standards, included in the synchronization signal block detected by the user equipment.

[0031] Advantageously, the second slot being likely to contain either two, or one, or no synchronization signal block at two known candidate positions in the resource grid representing said second slot, the presence information is read from N bits, the precision of the presence information depending on the number N of bits.

[0032] Advantageously, the presence information is read from bits inserted into the MIB information in replacement to existing bits defined by 3GPP standards.

[0033] A second aspect of the present disclosure concerns a user equipment comprising a module for connecting to a mobile telecommunication system, configured to control the execution of the steps above defined.

[0034] A third aspect of the present disclosure concerns a method for connecting a user equipment to a mobile telecommunication system, comprising the following steps, performed by a base station: - transmitting to the user equipment a synchronization signal block in a first slot, said synchronization signal block including an index of said synchronization signal block and a basic system information;

- transmitting to the user equipment a control signal and a data signal including a remaining system information, in a second slot, said control signal containing a location information defining an area for said data signal including the remaining system information within a resource grid representing the second slot in time domain and in frequency domain; characterised in that - the method comprises a further step, performed by the base station, of transmitting a presence information related to the presence or not of at least one synchronization signal block in the second slot, at a known position in the resource grid representing said second slot.

[0035] In a first example embodiment, the base station adds the presence information in said control signal.

[0036] Advantageously, in case that the second slot containing the control signal is also the first slot containing the synchronization signal block detected by the user equipment, the presence information only indicates whether another synchronization signal block is present or not in the slot. [0037] Advantageously, in the above example, the presence information is indicated in one bit.

[0038] Advantageously, in case that the second slot containing the control signal is different from the first slot containing the synchronization signal block detected by the user equipment, the presence information indicates the presence or not of each of two possible synchronization signal blocks at two known candidate positions in the resource grid.

[0039] Advantageously, in the above example, the presence information is indicated in two bits, related respectively to the two possible synchronization signal blocks. [0040] Advantageously, the presence information is added by the base station in a downlink control information (DCI) carried in the control signal.

[0041] Advantageously, the presence information is added by the base station in the control signal carried in TypeO-PDCCH defined by 3GPP standards. [0042] In a second example embodiment, the base station adds the presence information in the basic system information included in the synchronization signal block detected by the user equipment.

[0043] Advantageously, the presence information is added by the base station in a MIB, for master block information, defined by 3GPP standards, included in the synchronization signal block to be detected by the user equipment.

[0044] Advantageously, the second slot being likely to contain either two, or one or no synchronization signal block at two known candidate positions in the resource grid representing said second slot, the presence information is indicated in N bits, the precision of the presence information depending on the number N of bits.

[0045] Advantageously, the presence information is indicated in bits inserted into the MIB in replacement to existing bits defined by 3GPP standards.

[0046] A fourth aspect of the present disclosure concerns a base station in a mobile telecommunication network, comprising a module for connecting a user equipment to the mobile telecommunication system, configured to control the execution of the steps above defined, performed by the base station.

[0047] A fifth aspect of the present disclosure concerns a computer readable medium comprising program instructions for causing a user equipment to perform the steps of the method performed by the user equipment, as previously defined.

[0048] A sixth aspect of the present disclosure concerns a computer readable medium comprising program instructions for causing a base station to perform the steps of the method performed by the base station, as previously defined. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Other features, purposes and advantages of the present disclosure will become more explicit by means of reading the detailed statement of the non-restrictive embodiments made with reference to the accompanying drawings. [0050] Fig. 1 shows a schematic representation of three consecutive slots transmitted from a base station, each slot including two synchronization signal blocks, as defined by the 5G NR standard;

[0051] Fig. 2 and Fig. 3 show schematic representations of two respective resource grids each representing a slot including two synchronization signal blocks and a data signal carrying a remaining system information, according to a first and a second configuration respectively, as defined by the 5G NR standard;

[0052] Fig. 4 represents a flowchart of a method for connecting a user equipment to a mobile telecommunication system, according to an example embodiment;

[0053] Fig. 5 to Fig. 14 show schematic representations of resource grids each representing a slot including either two, or one, or no synchronization signal block, and a data signal carrying a remaining system information, according to different example embodiments of the present disclosure; [0054] Fig. 15 is a table of a MIB information, defined by 3GGP 5G standards.

DETAILED DESCRIPTION

[0055] The present disclosure relates to a method for connecting a user equipment to a mobile telecommunication system, or mobile network.

[0056] The mobile telecommunication system is for example a 5G mobile network comprising a 5G NR access network. [0057] When a user equipment wants to access to the mobile network, it first detects one synchronization signal block SSB (also called “SS block” or “SS/PBCH block”) among a plurality of SSBs, having respective SSB indices, in a first slot transmitted from a base station of the access network, and finds out the SSB index of the detected SSB. Then, the user equipment reads out a MIB (for Master Information Block) information, that includes basic system information, in the detected SSB, in order to derive a frame and slot index for a second slot including a control signal carried in TypeO-PDCCH and perform a TypeO-PDCCH monitoring operation. The user equipment uses the following formula, given by the 3GPP 5G NR standards, to find the frame index L(o - 2" + L? - Af jy^V^r" Jmod 2 where, i stands for the SSB index, M is a variable given by MIB whose values are (1/2, 1,2) and O is an offset shift also given by MIB. If the above formula with the detected SSB index equals to 0, it means the TypeO-PDCCH is sent in every even frame index. If the formula equals to 1, the TypeO-PDCCH is sent in every odd frame index.

[0058] After the frame index determination, the user equipment determines the slot index of the second slot, namely the TypeO-PDCCH slot in the present example embodiment. To this end, the user equipment uses the following formula given by the 5G NR standard to obtain the slot index:

[0059] After finding the TypeO-PDCCH slot, the user equipment determines a location information of a data signal containing a remaining system information, from the control signal in TypeO-PDCCH. The data channel including RMSI is named RMSI-PDSCH. For example, the location information indicates that the possible symbols (in time domain) to be scheduled for RMSI-PDSCH are from the third or fourth symbol up to the last symbol of the TypeO-PDCCH slot. Then the user equipment reads the RMSI- PDSCH in the TypeO-PDCCH slot according to the location information given by TypeO-PDCCH. [0060] In addition, the user equipment receives a SSB presence information, transmitted by the base station, related to the presence or not of at least one synchronization signal block in the second slot (or TypeO-PDCCH slot), at a known (fixed) candidate position in a resource grid representing said second slot. The SSB presence information is read by the user equipment either in TypeO-PDCCH, for example in a downlink control information (DCI) of TypeO- PDCCH, or in the detected SSB, for example in the MIB of the detected SSB.

[0061] Then, in order to read the remaining system information in the TypeO- PDCCH slot, the user equipment reads the resources of the symbols allocated to RMSI-PDSCH (from the third or fourth symbol up to the last symbol of the TypeO-PDCCH slot in the given example), as indicated by the location information, excluding (or skipping, or ignoring) the resources that correspond to the at least one synchronization signal block which presence is given by the SSB presence information. [0062] The term “resource” designate an element (one square) in the resource grid representing a slot in time domain and in frequency domain.

[0063] The term “symbol” designates an OFDM symbol. One slot includes a plurality of symbols, for example 14 symbols. One symbol corresponds to one column in each of the resource grids represented in figures 2, 3 and 5-14. [0064] Figure 4 represents a flowchart of the method for connecting the user equipment to the mobile telecommunication system, according to a second example embodiment.

[0065] The method comprises a step S1 of transmitting a plurality of synchronization signal blocks (SSBs) having respective SSB indices, in a plurality of slots, from the base station. Each synchronization signal block includes an index of said synchronization signal block and a basic system information, such as a MIB information (for Master Information Block). Each slot transmitted by the base station may comprise either one SSB, or two SSBs or no SSB. [0066] Then, in a step S2, the user equipment detects one synchronization signal block (SSB) in a slot transmitted by the base station. This slot is here called “first slot”.

[0067] In a following step S3, the user equipment determines the index of the detected synchronization signal block from the basic system information, or MIB, included in the detected synchronization signal block.

[0068] Then, in a step S4, the user equipment determines, from said synchronization signal block index, a slot index of a second slot containing a control signal carrying a location information for a data signal including a remaining system information (RMSI). For example, the control signal is carried in TypeO-PDCCH and the data signal is in PDSCH and carries the remaining system information (RMSI), as defined by 3GPP standards. The second slot is also called the “TypeO-PDCCH slot” in the given example. Said second slot is transmitted from the base station to the user equipment and includes the control signal (for example in TypeO-PDCCH), the data signal containing the remaining system information (for example RMSI-PDSCH) and possibly one or two synchronization signal blocks at two fixed (known) SSB candidate positions.

[0069] The location information for the RMSI data signal defines an area A for said data signal within a resource grid representing the second slot (TypeO- PDCCH slot) in time domain and in frequency domain. This area A includes at least partially the two SSB candidate positions in the second slot, where two SSBs are likely to be present. These two SSB candidate positions are fixed by the 3GPP standards and known by the user equipment. For example, this area A for the RMSI data signal may extend over the entire range of the second slot resource grid in the frequency domain and from the third or fourth symbol to the last symbol of the second slot resource grid in the time domain.

[0070] In a step S5, the user equipment acquires the control signal (carried in Type 0-PDCCH in the example) in the second slot (TypeO-PDCCH in the example) and reads the location information of the RSMI data signal (RMSI- PDSCH in the example) in the second slot.

[0071] In a step S6, the user equipment receives a SSB presence information, transmitted from the base station. The SSB presence information indicates the presence or not of at least one synchronization signal block in the second slot (TypeO-PDCCH slot in the example), at known (fixed) candidate positions in the resource grid representing said second slot. As will be explained later, this step S6 may be performed either when the user equipment reads the control signal (in TypeO-PDCCH in the example), or when the user reads the detected SSB (in the first slot).

[0072] After acquisition of the control signal (in TypeO-PDCCH in the example) and reception of the SSB presence information, the user equipment performs a step S7 of reading the remaining system information in the data signal (RSMI-PDSCH in the example) of the second slot (TypeO-PDCCH slot in the example), according to the location information for the RSMI data signal (RMSI-PDSCH in the example) read in step S5, in order to continue connecting to the network.

[0073] If the presence information acquired in step S6 indicates the presence of at least one synchronization signal block in the second slot (TypeO-PDCCH slot in the example), in step S7 of reading the remaining system information, the user equipment reads the resources within the area A for the RMSI data signal in the resource grid representing the second slot, excluding (or ignoring) autonomously those of the area A resources that correspond to the at least one synchronization signal block which presence is given by the presence information.

[0074] In a third example embodiment, the SSB presence information is transmitted from the base station and received by the user equipment in the control signal (in TypeO-PDCCH for example). More precisely, the SSB presence information is for example in a downlink control information (DCI) carried in the control signal (TypeO-PDCCH), as in the second example embodiment.

[0075] In this third example embodiment, the second slot (TypeO-PDCCH slot) containing the control signal (carried in TypeO-PDCCH) is also the first slot containing the synchronization signal block detected by the user equipment. In that case, the presence information transmitted from the base station only indicates whether another synchronization signal block is present or not in the slot. Thus, the user equipment only determines whether another synchronization signal block is present or not in the slot from the presence information.

[0076] If the slot only contains the synchronization signal block detected by the user equipment, the user equipment only excludes (or ignores) the resources that correspond to the detected synchronization signal block, in the step S7 of reading the remaining system information.

[0077] If the slot contains the synchronization signal block detected by the user equipment and another synchronization signal block which presence is given by the presence information, the user equipment excludes (or ignores) the resources that correspond to both the detected synchronization signal block and the other synchronization signal block

[0078] In the third example embodiment, the presence information is avantageously indicated in one bit by the base station. So, the user equipment reads one bit to determine the SSB presence information. This indication bit indicates whether another synchronization signal block (other than the one detected by the user equipment) is present or not in the slot.

[0079] Figure 5 illustrates a first example wherein one bit indicates that only one SSB is actually transmitted in the TypeO-PDCCH slot and the data signal containing the remaining system information (RMSI-PDSCH) starts from the third symbol up to the last symbol in the time domain and uses the entire bandwidth in the frequency domain, in the resource grid representing the TypeO-PDCCH slot. [0080] Figure 6 illustrates a second example wherein one bit indicates that only one SSB is actually transmitted in the slot and the data signal (PDSCH) starts from the fourth symbol up to the last symbol in the time domain and uses the entire bandwidth in the frequency domain, in the resource grid representing the TypeO-PDCCH slot.

[0081] Figure 7 illustrates a third example wherein one bit indicates that two SSBs are actually transmitted in the slot and the data signal (PDSCFI) starts from the third symbol in the time domain and uses the entire bandwidth in the frequency domain.

[0082] Figure 8 illustrates a fourth example wherein one bit indicates that two SSBs are actually transmitted in the slot and the data signal (RMSI-PDSCFI) starts from the fourth symbol up to the last symbol in the time domain in the time domain and uses the entire bandwidth in the frequency domain , in the resource grid representing the TypeO-PDCCFI slot.

[0083] Figures 9 and 10 illustrate a fifth and sixth example, that are variants of the first and second example, wherein the detected SSB are located at the second SSB position in the slot.

[0084] In a fourth example embodiment, the SSB presence information is transmitted from the base station and received by the user equipment in the control signal (TypeO-PDCCFI for example). More precisely, the SSB presence information is for example in a downlink control information (DCI) carried in the control signal (TypeO-PDCCFI), as in the second example embodiment. In addition, in the fourth example embodiment, the second slot (TypeO-PDCCFI slot) containing the control signal is different from the first slot containing the synchronization signal block detected by the user equipment.

[0085] In that case, the presence information transmitted by the base station indicates the presence or not of each of two synchronization signal blocks at the two known SSB candidate positions in the second slot resource grid. So, the user equipment determines the presence or not of each of two possible synchronization signal blocks at two known candidate positions in the second slot resource grid, from the presence information.

[0086] The presence information is indicated in two bits by the base station. These two bits relates respectively to the two possible synchronization signal blocks, for example.

[0087] Figure 11 illustrates a seventh example wherein two bits indicate that only one SSB is actually transmitted in the second slot and located at the first SSB position and the data signal (RMSI-PDSCH) starts from the third symbol up to the last symbol in the time domain and uses the entire bandwidth in the frequency domain, in the resource grid representing the TypeO-PDCCH slot.

[0088] Figure 12 illustrates an eighth example wherein two bits indicate that only one SSB is actually transmitted in the slot and located at the second SSB position and the data signal (RMSI-PDSCFI) starts from the fourth symbol up to the last symbol in the time domain in the time domain and uses the entire bandwidth in the frequency domain, in the resource grid representing the TypeO-PDCCFI slot.

[0089] Figure 13 illustrates a ninth example wherein two bits indicate that two SSBs are actually transmitted in the second slot and the data signal (RMSI- PDSCFI) starts from the third symbol up to the last symbol in the time domain in the time domain and uses the entire bandwidth in the frequency domain, in the resource grid representing the TypeO-PDCCFI slot.

[0090] Figure 14 illustrates a tenth example wherein two bits indicate that no SSB are actually transmitted in the second slot and the data signal (RMSI- PDSCFI) starts from the third symbol up to the last symbol in the time domain in the time domain and uses the entire bandwidth in the frequency domain, in the resource grid representing the TypeO-PDCCFI slot.

[0091] In a fifth embodiment, the presence information is included in the basic system information included in the synchronization signal block detected by the user equipment. So, the user equipment reads the presence information in the basic system information within the detected SSB. More precisely, the presence information is for example included in the MIB of the detected SSB.

[0092] The presence information is indicated in N bits in the basic system information. [0093] In a first example, N is equal to 1. The presence information is indicated by one bit indicating if all known synchronization signal block positions of the second slot (TypeO-PDCCH slot) are occupied or if there is no synchronization signal block in the second slot (TypeO-PDCCH slot).

[0094] In a second example, N is equal to 2. The presence information is indicated by two bits, each bit indicating for example the presence or not of one of the two possible synchronization signal blocks.

[0095] In a third example, N is equal to 4. The presence information is indicated by four bits. In that case, the base station can give very precise information about the presence or not of the SSBs in each of the SSB candidate positions among two consecutive TypeO-PDCCH slots.

[0096] In a sixth embodiment, the presence information is included in the basic system information, for example the MIB, included in the synchronization signal block detected by the user equipment. In this embodiment, the SSB presence information is indicated by the base station using bits that are inserted into the MIB information of the detected SSB, in replacement to existing bits defined by 3GPP standards. For example, the bit indicating the SSB presence information replace some bits of the second column of the table shown on figure 15.

[0097] The present disclosure also concerns : - a user equipment comprising a module for connecting to a mobile telecommunication system, for example to a 5G network comprising a 5G NR access network, configured to control the execution of those of the steps described in the present description that are performed by the user equipment; - a base station comprising a module for connecting to a mobile telecommunication system, for example to a 5G network comprising a 5G NR access network, configured to control the execution of those of the steps described in the present description that are performed by the base station; - a computer readable medium comprising program instructions for causing a user equipment to perform the steps of the method performed by the user equipment, as previously described;

- a computer readable medium comprising program instructions for causing a base station to perform the steps of the method performed by the base station, as previously described.

[0098] In the above description, the mobile telecommunication system is a 5G mobile network comprising a 5G NR access network. The present example embodiment is applicable to NR in unlicensed spectrum (NR-U) and also to NR in licensed spectrum (NR). The present disclosure can be applied to other mobile networks, in particular to mobile network of any further generation cellular network technology (6G, etc.).

[0099] List of abbreviations in the description and drawings:

Claims

1. A method for connecting a user equipment to a mobile telecommunication system, comprising the following steps, performed by the user equipment:

- detecting (S2) a synchronization signal block in a first slot transmitted by a base station;

- determining (S3) an index of said synchronization signal block from a basic system information included in the synchronization signal block; - determining (S4) from said synchronization signal block index a slot index of a second slot containing a control signal carrying a location information for a data signal including a remaining system information, said location information defining an area for said data signal within a resource grid representing the second slot in time domain and in frequency domain; - reading (S5) the remaining system information in the data signal of the second slot, according to said location information, in order to continue connecting to the network; characterized in that

- the method comprises a further step, performed by the user equipment, of receiving (S6) a presence information, transmitted by the base station, related to the presence or not of at least one synchronization signal block in the second slot, at a known position in the resource grid representing said second slot, and

- the presence information indicating the presence of at least one synchronization signal block in the second slot, in the step (S7) of reading the remaining system information, the user equipment reads the resources of said area for the data signal in the resource grid representing the second slot, excluding the resources of said area for the data signal that correspond to the at least one synchronization signal block which presence is given by the presence information.

2. The method according to claim 1, characterized in that the presence information is read in said control signal.

3. The method according to any of claims 1 and 2, characterized in that, in case that the second slot containing the control signal is also the first slot containing the synchronization signal block detected by the user equipment, the user equipment only determines whether another synchronization signal block is present or not in the slot from the presence information.

4. The method according to claim 3, characterized in that

5. The method according to any of claims 2 to 4, characterized in that the presence information is read from one bit.

6. The method according to any of claims 1 and 2, characterized in that, in case that the second slot containing the control signal is different from the first slot containing the synchronization signal block detected by the user equipment, the user equipment determines the presence or not of each of two synchronization signal blocks at two known positions in the resource grid of the second slot, from the presence information.

7. The method according to claim 6, characterized in that the presence information is read in two bits, related respectively to the two possible synchronization signal blocks.

8. The method according to the preceding claim, characterized in that the presence information is read in a downlink control information carried in the control signal.

9. The method according to any of claims 1 to 6, characterized in that the control signal is carried in TypeO-PDCCH defined by 3GPP standards.

10. The method according to claim 1, characterized in that the presence information is read in the basic system information included in the synchronization signal block detected by the user equipment.

11. The method according to claim 10, characterized in that the presence information is read in a MIB information, for master block information, defined by 3GPP standards, included in the synchronization signal block detected by the user equipment.

12. The method according to claim 10 or 11, characterized in that, the second slot being likely to contain either two, or one, or no synchronization signal block at two known candidate positions in the resource grid representing said second slot, the presence information is read from N bits, the precision of the presence information depending on the number N of bits.

13. The method according to claim 11 , characterized in that, the presence information is read from bits inserted into the MIB information in replacement to existing bits defined by 3GPP standards.

14. A user equipment comprising a module for connecting to a mobile telecommunication system, configured to control the execution of the steps defined in claims 1 to 13.

15. A method for connecting a user equipment to a mobile telecommunication system, comprising the following steps, performed by a base station: - transmitting to the user equipment a synchronization signal block in a first slot, said synchronization signal block including an index of said synchronization signal block and a basic system information;

16. A base station in a mobile telecommunication network, comprising a module for connecting a user equipment to the mobile telecommunication system, configured to control the execution of the steps defined in claim 15.

17. A computer readable medium comprising program instructions for causing a user equipment to perform the steps of a method according to any of claims 1 to 13.

18. A computer readable medium comprising program instructions for causing a base station to perform the steps of a method according to claim 15.