Patent Description:
In order to connect to a network, a terminal device needs to acquire network synchronization information and obtain essential system information. Synchronization signals (SSs) are used for adjusting the frequency of the terminal device relative to the network, and for finding proper timing of the received signal from the network.

In the New Radio (NR) system, a procedure for synchronization and access may involve several signals as follows:.

A synchronization signal block (SSB) as proposed for the NR system may comprise the above signals NR-PSS, NR-SSS, NR-PBCH and related DMRS. <FIG> shows an illustration of the SSB in which the NR-PBCH is a part of the SSB. In the illustration, two OFDM symbols are reserved for NR-PBCH transmission. The NR-PSS and NR-SSS are defined to be <NUM> subcarriers wide whereas the NR-PBCH is defined to be <NUM> subcarriers wide.

A number of SS blocks that are typically close in time constitute an SS burst set. The SS burst set may repeated periodically, e.g. every <NUM> in default. The terminal device can, by using the SS blocks in the SS burst set, determine downlink timing and frequency offset, and acquire some fundamental system information from the NR-PBCH. It has been agreed that an NR UE in idle mode can expect an SS burst set transmitted once per <NUM>, and the NR UE in connected mode can expect the SS burst sets once per <NUM>. Hence, once the NR UE has obtained downlink synchronization, it knows in which slots to expect the SS block transmissions. The location of the SS block in a SS burst set needs to be provided to the NR UE to derive the subframe level synchronization.

Document <CIT> discloses a device and method for transmitting or receiving the system information. The system information transmitting device comprises a processor for transmitting the system information on a broadcast channel, and the system information comprises multi-carrier information relating to a multi-carrier operation.

Document <CIT> discloses a method of performing a downlink machine type communication from a base station to a MTC (machine type communication) terminal which includes, at the base station, transmitting at least one of a system information - the system information excluding a Master Information Block (MIB) -, a control information and data to the MTC terminal using a system bandwidth having a predetermined size. The base station performs frequency hopping using a frequency hopping pattern in a unit of narrow band on the at least one of the system information - the system information excluding a Master Information Block (MIB) -, the control information and the data to transmit to the MTC terminal, and the narrow band is less than the system bandwidth.

Document <CIT> discloses a communication method and system for converging a <NUM>-Generation (<NUM>) communication system for supporting higher data rates beyond a <NUM>-Generation (<NUM>) system with a technology for Internet of Things (loT). A method of a base station (BS) for transmitting a master information block (MIB) in a wireless communication network is provided. The method includes identifying first resources reserved for transmission of a first reference signal (RS) for a first communication using a first frequency bandwidth, identifying second resources reserved for transmission of a second RS for a second communication using a second frequency bandwidth, wherein the second frequency bandwidth is narrower than the first frequency bandwidth, determining third resources for a broadcast channel of the second communication based on the first resources and the second resources, and transmitting the MIB using the third resources via the broadcast channel.

It is therefore an object of embodiments of the present disclosure to provide a method for synchronization in a wireless system which can indicate the location of the SS block in the SS burst set as well as additional system information.

According to a first aspect of the present disclosure, there is provided a method performed in a base station for synchronization in a wireless system. The method comprises transmitting a Synchronization Signal Block, SSB, comprising a physical broadcast channel, PBCH, including one or more bits, wherein the SSB is one of a set of candidate SSBs within a half frame and a total number of the candidate SSBs within the half frame is L, wherein in response to a frequency of the wireless system being within a frequency range up to a predefined frequency, the one or more bits indicate additional system information and wherein in response to the frequency of the wireless system being above the predefined frequency, the one or more bits indicate a location of a slot group containing the SSB among the set of candidate SSBs within the half frame.

According to a second aspect of the present disclosure, there is provided a base station in a wireless system. The base station comprises a processor and a memory. The memory contains instructions which, when executed by the processor, cause the base station to perform the method of the first aspect.

According to a third aspect of the present disclosure, there is provided a method performed in a terminal device for synchronization in a wireless system. The method comprises receiving a Synchronization Signal Block, SSB, comprising a physical broadcast channel, PBCH, including one or more bits from a base station, wherein the SSB is one of a set of candidate SSBs within a half frame and a total number of the candidate SSBs within the half frame is L, wherein in response to a frequency of the wireless system being within a frequency range up to a predefined frequency, the one or more bits indicate additional system information and wherein in response to the frequency of the wireless system being above the predefined frequency, the one or more bits indicate a location of a slot group containing the received SSB among the set of candidate SSBs within the half frame.

According to a fourth aspect of the present disclosure, there is provided a terminal device in a wireless system. The terminal device comprises a processor and a memory. The memory contains instructions which, when executed by the processor, cause the terminal device to perform the method of the third aspect.

According to a fifth aspect of the present disclosure, there is provided a computer readable storage medium having a computer program stored thereon. The computer program is executable by a base station to cause the base station to carry out the method of the first aspect; or the computer program is executable by a terminal device to cause the terminal device to carry out the method of the third aspect.

Whenever in the following disclosure any of the above-stated aspects (corresponding to the independent claims) is disclosed as "optional" (e.g., due to usage of conjunctive terms, such as "can", "may", "should", etc.), it is nevertheless to be read as "mandatory".

It is an advantage that the method for synchronization can indicate the locations of the SS blocks as well as the additional system information in the PBCH, especially in the NR-PBCH, thereby greatly reducing network detection of a terminal device.

Hereinabove and in the following, "examples" pertain to principles underlying the claimed subject-matter and/or being useful for understanding the claimed subject-matter, while "embodiments" pertain to the claimed subject-matter within the claim scope. Through the more detailed description of some embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein the same reference generally refers to the same components in the embodiments of the present disclosure.

Whenever in this description an "embodiment" is described, reference is to be made to the above figure list to determine whether this is to be read as "embodiment" or "example".

Some preferable embodiments will be described in more detail with reference to the accompanying drawings, in which the preferable embodiments of the present disclosure have been illustrated. However, the present disclosure can be implemented in various manners, and thus should not be construed to be limited to the embodiments disclosed herein. On the contrary, those embodiments are provided for the thorough and complete understanding of the present disclosure, and completely conveying the scope of the present disclosure to those skilled in the art.

Currently in 3GPP, it has been agreed that the transmission of the SS blocks within the SS burst set is confined to a <NUM> window regardless of a periodicity of the SS burst set. Within this <NUM> window, the number of locations of possible candidate SS blocks is L. Therefore the maximum number of the SS blocks within the SS burst set L is different for different frequency ranges. For a frequency range up to <NUM> (i.e. ≤<NUM>), L is <NUM>. For a frequency range from <NUM> to <NUM> (i.e. <NUM> < the frequency ≤ <NUM>), L is <NUM>. For a frequency range from <NUM> to <NUM> (i.e. <NUM> < the frequency ≤ <NUM>), L is <NUM>. Note that it is assumed that the minimum number of the SS blocks within each SS burst set is one to define performance requirements. The SS burst set is as shown in <FIG>. The blocks with a gray scale represents the slots for transmitting the SS blocks. "<NUM>", "<NUM>", "<NUM>" and "<NUM>" as shown in <FIG> refer to the subcarrier spacing.

Further it has been agreed that some bits of a SS block time index which indicates the locations of the SS blocks are carried by changing the DMRS sequence within each <NUM> period. Scrambling sequence of the PBCH may or may not carry a part of timing information. The remaining bits of the SS block time index may be carried explicitly in the NR-PBCH payload. Therefore, it has been agreed to deliver the SS block time index by the NR-PBCH transmission using an implicit approach by the DMRS sequence and explicit bits in the NR-PBCH payload.

There are following problems to indicate the SS block time index by this way:.

In summary, the number of the explicit bits for the higher frequency range would be larger than that for the lower frequency range.

In view of the above problems, a new method for synchronization in a wireless system is proposed. <FIG> shows a diagram illustrating the method for synchronization according to some embodiments of the present disclosure. In some embodiments of the present disclosure, the method may be performed by a network device in the wireless system. The wireless system may be for example the NR system, and the network device may be a base station, e.g. gNodeB, in the NR system.

As shown in <FIG>, at block <NUM>, the network device may include at least one bit in the PBCH, particularly the NR-PBCH in the NR system. One or more bits of the at least one bit may indicate a location of a slot group comprising at least one SS block in a SS burst set and/or additional system information. In particular, the network device transmits the PBCH including the one or more bits to a terminal device. The one or more bits indicate the additional system information if a frequency of the wireless system is within a frequency range up to a predefined frequency, e.g. <NUM>. Otherwise, if the frequency is above the predefined frequency, the one or more bits indicate the location of the slot group comprising the at least one SS block in the synchronization signal burst set including the slot group.

In some embodiments, one or more bits of the at least one bit may indicate a location of the at least one SS block within the slot group. In such embodiments, the one or more bits may be carried by different downlink pilot signal sequences, e.g. the DMRS sequences.

As described above, the SS burst set may comprise multiple SS blocks. For the frequency range up to <NUM>, the SS burst set may comprise <NUM> SS blocks. For the frequency range from <NUM> to <NUM>, the SS burst set may comprise <NUM> SS blocks. For the frequency range from <NUM> to <NUM>, the SS burst set may comprise <NUM> SS blocks. In some embodiments, it is assumed that a slot group comprises continuous four slots for the frequency range from <NUM> and comprises continuous <NUM> slots for the frequency range up to <NUM>, and that each slot may contain at most two SS blocks, for example. Therefore, for the frequency range up to <NUM>, the SS burst set may comprise one slot group, and each slot of the one slot group comprises <NUM> SS blocks, so the SS burst set comprises <NUM> SS blocks (i.e. L=<NUM>). For the frequency range from <NUM> to <NUM>, the SS burst set may comprise one slot group and each slot of the slot group may comprise <NUM> SS blocks, so the SS burst set comprises <NUM> SS blocks (i.e. L=<NUM>). For the frequency range from <NUM> to <NUM>, the SS burst set may comprise eight slot groups, and each of the eight slot groups may comprise <NUM> SS blocks, so the SS burst set comprises <NUM> SS blocks (i.e. L=<NUM>). A person skilled in the art will appreciate that the slot group may be consisted of any other number of slots.

Next an example in which the method for synchronization is implemented for all frequency ranges will be described in detail. This example is applied in the NR system. In this example, the NR-PBCH may include <NUM> bits indicative of the locations of the SS blocks in the SS burst set. Three bits of the <NUM> bits may be used to indicate the location of the slot group in the SS burst set and/or additional system information, and may be included in a payload of the NR-PBCH. In the following, the bits in the payload of the NR-PBCH may be also referred to as "explicit bits". The other <NUM> bits may be used to indicate the locations of the SS blocks within the slot group, and may be carried by the DMRS sequences. Referring to <FIG>, three explicit bits s(<NUM>), s(<NUM>), s(<NUM>) to indicate the location of the slot group and/or the additional system information are attached with MIB (Master Information Block) from higher layer and L1 payload to constitute the payload of the NR-PBCH.

In the case of the frequency range less than <NUM>, the maximum number of the SS blocks in the SS burst set is eight. So the locations of the SS blocks may be indicated by using the DMRS sequence only. The remaining <NUM> explicit bits may be used to indicate the additional system information, which will be described later.

In the case of the frequency range higher than <NUM>, the maximum number of the SS blocks in the SS burst set is <NUM>. All the six bits are used to indicate the locations of the SS blocks. In this case, the three explicit bits in the payload of the NR-PBCH may indicate the locations of the eight slot groups, and the three bits carried by the different DMRS sequences may implicitly indicate the locations of the eight SS blocks within the slot group, as shown in <FIG>.

Although the example in which the bits carried by the DMRS sequences are <NUM> bits and the explicit bits in the payload of the NR-PBCH are <NUM> bits has been described above, a person skilled in the art will appreciate that the bits carried by the DMRS sequences may be <NUM> bits and the explicit bits in the payload of the NR-PBCH may be <NUM> bits.

In addition, a person skilled in the art will also appreciate that the number of bits in the NR-PBCH may be more than <NUM> bits. In this case, the bits other than those indicative of the locations of the SS blocks may indicate the additional system information.

In some embodiments, the bits carried by the DMRS sequences may indicate the location of a slot group comprising at least one SS block in a SS burst set, and the explicit bits in the payload of the NR-PBCH may indicate the location of the SS block within the slot group and/or the additional system information.

In some embodiments, the additional system information may comprise a frame number offset of a coexisting system relative to the wireless system. In the case that the wireless system is the NR system, the coexisting system may be the LTE system. In the two systems, the frame durations are defined as <NUM>, and may have different frame number as illustrated in <FIG>. In <FIG>, the frame number in the LTE system is denoted by <MAT>, and the frame number in the NR system in the same time duration is denoted by <MAT>. Since almost all the data transmissions, especially the system information, are based on the frame number, the exact frame number will make much more sense for a terminal device such as NR user equipment. Thus, the frame number offset between the two systems, i.e. <MAT> may be indicated by the explicit bits. Dependent on the number of the explicit bits, the frame number offset is within a range, such as <NUM> frames for three explicit bits, and more frames for more explicit bits.

In some embodiments, the additional system information may comprise system information of a neighbor cell in the coexisting system. Such the system information may comprise an identifier of the neighbor cell, e.g. a target cell.

In the LTE system, there are <NUM> unique physical-layer cell identities. The physical-layer cell identities may be grouped into <NUM> unique physical-layer cell-identity groups, each group containing three unique identities. The grouping is such that each physical-layer cell identity is a part of one and only one physical-layer cell-identity group. Thus a physical-layer cell identity may be uniquely defined by <MAT>, wherein the number <MAT>is in the range of <NUM> to <NUM>, representing the physical-layer cell-identity group, and the number <MAT> is in the range of <NUM> to <NUM>, representing the physical-layer identity within the physical-layer cell-identity group.

In this case, the three explicit bits can be used to indicate presence of one or more neighbor cells of the coexisting LTE system, with the physical-layer identity <NUM>, <NUM> or <NUM> within the physical-layer cell-identity group in the neighborhood (coverage area) of the current serving cell as shown in Table <NUM>.

In some embodiments, the additional system information may comprise configuration information of the SS burst set of a neighbor cell in the wireless system. For example, such the configuration information may comprise the number of the synchronization signal blocks actually transmitted in the neighbor cell and periodicity of the synchronization signal burst set.

In the case of the frequency range less than <NUM>, the maximum number L of the SS blocks is <NUM> or <NUM>, and the candidate locations for the actual SS block(s) transmission need to be pre-defined as a set to avoid arbitrary allocation. For example, the locations may be defined as the continuous N (N≤L) blocks in the SS burst set, such that there are only <NUM>, <NUM> and <NUM> (for the frequency range higher than <NUM>) bits needed for all the three frequency ranges.

Therefore three explicit bits may be defined as below to indicate the number of actual transmitted SS blocks for one NR neighbor cell (if existed) with maximum number of actual transmitted SS blocks among all the neighbor NR cell(s) or the number of actual transmitted SS blocks of a neighbor cell as the target cell:.

In some embodiments, the additional system information may comprise an indication related to synchronization information in the wireless system. In addition, a person skilled in the art will appreciate that the additional system information may be any combination of the above described system information.

It can be seen from the above description that the method for synchronization according to the above embodiments can indicate the locations of the SS blocks as well as the additional system information in the NR-PBCH. Moreover the same number of the explicit bits may be used for all the frequency ranges for the wireless system, especially the NR system. The explicit bits can be used to indicate the additional system information, other than indicating the part of the locations.

<FIG> is a schematic block diagram of the network device <NUM> according to some embodiments of the present disclosure. The network device <NUM> may be a base station in the wireless system, e.g. gNodeB in the NR system. As shown in <FIG>, the network device <NUM> may comprise a processor <NUM> and a memory <NUM>. The memory <NUM> may contain instructions executable by the processor <NUM>. The network device <NUM> is operative to include at least one bit in a PBCH, one or more bits of the at least one bit indicating a location of a slot group comprising at least one synchronization signal block in a synchronization signal burst set and/or additional system information. In particular, the network device <NUM> is operative to transmit the PBCH including the one or more bits. The one or more bits indicate the additional system information if a frequency of the wireless system is within a frequency range up to a predefined frequency, e.g. <NUM>. Otherwise if the frequency of the wireless system is above the predefined frequency, the one or more bits indicate the location of the slot group comprising the at least one SS block in the SS burst set including the slot group.

The processor <NUM> may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architectures, as non-limiting examples. The memory <NUM> may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

In some embodiments, the network device <NUM> may further comprise a transceiver <NUM> operative to transmit signals to and receive signals from a wireless terminal, and a network interface <NUM> operative to communicate signals with backend network elements.

According to some embodiments of the present disclosure, a network device <NUM> for synchronization is provided. As shown in <FIG>, the network device <NUM> may be a base station, e.g. gNodeB, in the NR system. The network device may comprise a transmitting module <NUM> operable to include at least one bit in a physical broadcast channel (PBCH), one or more bits of the at least one bit indicating a location of a slot group comprising at least one synchronization signal block in a synchronization signal burst set and/or additional system information.

It should be noted that <FIG> merely illustrates various functional modules in the network device <NUM>, and a person skilled in the art can implement these functional modules in practice using any suitable software and hardware. Thus the embodiments herein are generally not limited to the shown structure of the network device <NUM> and functional modules.

In some embodiments of the present disclosure, there is also provided a computer readable storage medium having a computer program stored thereon. The computer program is executable by a device to cause the device to carry out the above method for synchronization.

According to some embodiments of the present disclosure, a method performed in a terminal device for synchronization in a wireless system is further provided. As shown in <FIG>, at block <NUM>, at least one bit in a PBCH is received from a network device. One or more bits of the at least one bit indicates a location of a slot group comprising at least one synchronization signal block in a synchronization signal burst set and/or additional system information. In particular, the terminal device receives the PBCH including the one or more bits from a base station. The one or more bits indicate additional system information if a frequency of the wireless system is within a frequency range up to a predefined frequency e.g. <NUM>. Otherwise, if the frequency of the wireless system is above the predefined frequency, the one or more bits indicate the location of the slot group comprising the at least one SS block in the SS burst set including the slot group. Then at block <NUM>, the location of the slot group in the synchronization signal burst set and/ or the additional system information are obtained from the at least one bit.

In some embodiments, one or more bits of the at least one bit indicate a location of the at least one synchronization signal block within the slot group. In the method, the location of the at least one synchronization signal block within the slot group are obtained from the one or more bits.

In some embodiments, the wireless system is a NR system.

According to some embodiments of the disclosure, a terminal device <NUM> in a wireless system is further provided. As shown in <FIG>, the terminal device <NUM> comprises a processor <NUM>, and a memory <NUM>. The memory <NUM> contains instructions executable by the processor <NUM>, whereby the terminal device is operative to perform the method for synchronization as described with regard to <FIG>. The terminal device <NUM> may be a radio device, such as a mobile phone, a wearable device, a tablet, etc., a vehicle with radio communication functionality, or any other type of electronic device with radio communication functionality.

For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto.

It should thus be appreciated that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure.

Claim 1:
A method in a base station (<NUM>) for synchronization in a wireless system comprising:
transmitting a Synchronization Signal Block, SSB, comprising a physical broadcast channel, PBCH, including one or more bits, wherein the SSB is one of a set of candidate SSBs within a half frame and a total number of the candidate SSBs within the half frame is L;
wherein in response to a frequency of the wireless system being within a frequency range up to a predefined frequency, the one or more bits indicate additional system information; and
wherein in response to the frequency of the wireless system being above the predefined frequency, the one or more bits indicate a location of a slot group containing the SSB among the set of candidate SSBs within the half frame.