CN117546592A - Method and apparatus for random access in a wireless communication system - Google Patents

Abstract

The present disclosure relates to 5G or 6G communication systems for supporting higher data transmission rates than 4G systems such as LTE. More particularly, a method and apparatus are disclosed that relate to generating and detecting a random access preamble signal for random access in ultra-high band wireless communications. A terminal according to embodiments disclosed herein includes: a transmitting and receiving unit, and a control unit, wherein the control unit is configured to: generating a preamble signal; transmitting the preamble signal to a base station; and receiving a random access response including Timing Advance (TA) information from the base station in response to the transmission of the preamble signal, wherein the preamble signal may include a first signal portion associated with the first sequence and a second signal portion associated with the guard time and the second sequence.

Description

Method and apparatus for random access in a wireless communication system

Technical Field

The present disclosure relates to a PRACH preamble structure having a symbol of a relatively short length compared to a maximum round trip time in a cell in ultra-high frequency band wireless communication, and a method and apparatus for random access.

Background

A review of the generation of mobile communications shows that the development mainly involves techniques for human-directed services, such as voice-based services, multimedia services and data services. It is expected that exponentially growing connection means will connect to the communication network after commercialization of the 5G communication system. Examples of things connected to the network may include vehicles, robots, drones, home appliances, displays, smart sensors connected to various infrastructure, construction machinery, and factory equipment. Mobile devices are expected to evolve in a variety of form factors, such as augmented reality glasses, virtual reality headphones, and hologram devices. In order to provide various services by connecting billions of devices and things in the 6G age, efforts have been made to develop improved 6G communication systems. For these reasons, 6G communication systems are referred to as super 5G systems.

It is expected that a 6G communication system to be implemented in about 2030 will have a maximum transmission rate of too (1,000 giga) level bps and a radio delay of 100 musec, and thus will be 50 times faster than a 5G communication system and have a radio delay of 1/10 thereof.

To achieve such high data transmission rates and ultra-low latency, it has been considered to implement 6G communication systems in the terahertz frequency band (e.g., the 95GHz to 3THz frequency band). It is expected that a technique of securing a signal transmission distance (i.e., coverage) will become more critical since path loss and atmospheric absorption in the terahertz band are more serious than those in the millimeter wave band introduced in 5G. As a main technique for securing coverage, it is necessary to develop multi-antenna transmission techniques including Radio Frequency (RF) elements, antennas, new waveforms having better coverage than OFDM, beamforming and massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas. In addition, new technologies such as metamaterial-based lenses and antennas, orbital Angular Momentum (OAM), and reconfigurable smart surfaces (RIS) have been discussed for improving coverage of terahertz band signals.

Furthermore, in order to improve frequency efficiency and system networks, the following techniques for 6G communication systems have been developed: full duplex technology for implementing uplink (UE transmission) and downlink (node B transmission) to use the same frequency resources simultaneously at the same time; network technology for utilizing satellites, high Altitude Platform Stations (HAPS), etc. in an integrated manner; network structure innovation techniques for supporting mobile node bs and the like and for implementing network operation optimization, automation, and the like; dynamic spectrum sharing techniques for collision avoidance by prediction based on spectrum usage; AI-based communication techniques for implementing system optimization by using Artificial Intelligence (AI) from a technology design step and internalizing end-to-end AI support functions; and next generation distributed computing techniques for implementing services with complexity exceeding the limits of UE computing capabilities by using ultra-high performance communication and computing resources (mobile edge computing (MEC), cloud, etc.). In addition, attempts have been continuously made to further enhance connectivity between devices, further optimize networks, push software implementations of network entities, and increase the openness of wireless communications by designing new protocols to be used in 6G communication systems, developing mechanisms for implementing hardware-based secure environments and secure usage data, and developing techniques for privacy maintenance methods.

Such research and development of 6G communication systems is expected to enable the next super-connection experience in new dimensions through super-connectivity of connections between covered things and connections between humans and things of the 6G communication system. In particular, services such as true immersion XR, high fidelity mobile holograms, and digital replicas are contemplated to be provided through 6G communication systems. In addition, with the enhancement of safety and reliability, services such as teleoperation, industrial automation and emergency response will be provided through the 6G communication system, and thus, these services will be applied to various fields including industrial, medical, automotive and home appliance fields.

Meanwhile, the terminal may perform a random access procedure with the base station to match uplink synchronization to communicate with the base station. For example, the terminal may transmit a random access preamble generated in a predetermined sequence to the base station, and the base station may measure a Round Trip Delay (RTD) with the terminal through the random access preamble, then determine a Timing Advance (TA) value for adjusting a transmission time of an uplink signal of the terminal based on the measured RTD, and may transmit the determined TA value to the terminal through a random access response.

At this time, the Physical Random Access Channel (PRACH) in the existing LTE or NR is designed to be suitable for an environment in which the symbol length of a signal is much larger than the maximum RTD of a cell. However, wireless communication systems of ultra-high frequency bands such as terahertz (THz) and sub-THz frequency bands can use waveforms having very short symbol lengths because they use a large subcarrier spacing due to effects such as extreme phase noise. In this case, there is a limit in applying the PRACH preamble sequence according to the existing LTE or NR method.

Disclosure of Invention

[ problem ]

Accordingly, it is an aspect of the present disclosure to provide a method for generating and detecting a preamble sequence that can be applied to a communication system of an ultra-high frequency band having a symbol of a relatively short length compared to a maximum RTD of a cell.

[ solution to the problem ]

In order to solve the above problems, a terminal of a communication system according to an embodiment of the present disclosure may include a transceiver and a controller, wherein the controller is configured to: generating a preamble signal; transmitting the preamble signal to a base station; and receiving a random access response from the base station in response to the transmission of the preamble signal, the random access response including Timing Advance (TA) information, and wherein the preamble signal includes a first signal portion associated with the first sequence, a guard time, and a second signal portion associated with the second sequence.

According to an embodiment, the timing advance may be determined based on a Round Trip Delay (RTD) measured from the preamble signal, and the RTD may be determined based on a first delay time determined from the first signal portion and a second delay time determined from the second signal portion.

According to an embodiment, the first delay time is determined based on a cyclic correlation between the first correlation signal and a signal received in a first window based on the length of the first signal portion, and the second delay time is determined based on a cyclic correlation between the second correlation signal and a signal received in one or more second windows based on the first delay time.

According to an embodiment, the controller may be further configured to obtain a root index set related to the first sequence and a root index set related to the second sequence, generate the first sequence based on a root index randomly selected from the root index set related to the first sequence, and generate the second sequence based on a root index randomly selected from the root index set related to the second sequence.

According to an embodiment, the first signal portion may include a first Cyclic Prefix (CP) and one or more symbols including a first sequence, and the second signal portion may include a second CP and one symbol including a second sequence.

According to an embodiment, the length of the guard time may be determined according to the length of the first signal portion.

According to an embodiment, the length of the guard time may have a pre-configured length.

According to an embodiment, the first sequence and the second sequence may be generated based on the same root index and have different cyclic shifts.

According to an embodiment, the length of the first signal portion may be determined based on a maximum Round Trip Delay (RTD) or delay spread of the cell.

A base station of a communication system according to embodiments of the present disclosure may include a transceiver and a controller, wherein the controller is configured to: receiving a preamble signal from a terminal; and transmitting a random access response including Timing Advance (TA) information to the terminal in response to receipt of the preamble signal, and wherein the preamble signal includes a first signal portion associated with the first sequence, a guard time, and a second signal portion associated with the second sequence.

A method performed by a terminal of a communication system according to an embodiment of the present disclosure may include: generating a preamble signal; transmitting the preamble signal to a base station; and receiving a random access response from the base station in response to the transmission of the preamble signal, the random access response including Timing Advance (TA) information, wherein the preamble signal includes a first signal portion associated with the first sequence, a guard time, and a second signal portion associated with the second sequence.

A method performed by a base station of a communication system according to an embodiment of the present disclosure may include: receiving a preamble signal from a terminal; and

a random access response including Timing Advance (TA) information is transmitted to the terminal in response to receipt of a preamble signal, wherein the preamble signal includes a first signal portion associated with a first sequence, a guard time, and a second signal portion associated with a second sequence.

[ beneficial effects ]

According to the embodiments of the present disclosure, a terminal may generate a preamble signal in a system to which a relatively short symbol length compared to a maximum RTD of a cell in a ultra-high frequency band is applied, the preamble signal including a first signal part, a guard time, and a second signal part, and a base station may receive the preamble signal and perform a preamble detection operation and RTD calculation of the signal even in a case where the symbol length is shorter than the maximum RTD of the signal, thereby having an effect of being able to perform a random access operation in the ultra-high frequency band system.

Drawings

Fig. 1 shows a basic structure of a time-frequency domain in LTE;

fig. 2 shows a downlink control channel of LTE;

fig. 3 shows transmission resources of a downlink control channel in 5G;

Fig. 4 shows an example of the configuration of the control area in 5G;

fig. 5 shows an example of a configuration of a downlink RB structure in 5G;

fig. 6A is a flowchart illustrating the operation of a base station transmitting and receiving PRACH preamble signals;

fig. 6B is a flowchart illustrating an operation of a UE transmitting and receiving PRACH preamble signals;

fig. 7A illustrates a basic structure of a PRACH preamble signal according to an embodiment of the present disclosure;

fig. 7B is a flowchart illustrating an operation of a terminal to generate a PRACH preamble signal according to an embodiment of the present disclosure;

fig. 8 illustrates a method of transmitting root index values of SEQ1 and SEQ2 and resource information through a Physical Broadcast Channel (PBCH) according to an embodiment of the present disclosure;

fig. 9 illustrates a method of transmitting root index values of SEQ1 and SEQ2 and resource information through a Master Information Block (MIB) according to an embodiment of the present disclosure;

fig. 10 illustrates a method of transmitting root index values of SEQ1 and SEQ2 and resource information through a System Information Block (SIB) according to an embodiment of the present disclosure;

fig. 11A and 11B illustrate the basic principle according to an embodiment of the present disclosure, in which a base station receives a preamble transmitted by a terminal in order to estimate an RTD of a signal;

fig. 12 illustrates a structure of a preamble generated by a terminal according to a first embodiment of the present disclosure;

Fig. 13 illustrates a detection window for detecting a preamble signal by a base station according to a first embodiment of the present disclosure;

fig. 14 shows an example of a preamble reception operation of a base station according to the first embodiment of the present disclosure;

fig. 15 illustrates a structure of a preamble generated by a terminal according to a second embodiment of the present disclosure;

fig. 16 illustrates a detection window for detecting a preamble signal by a base station according to a second embodiment of the present disclosure;

fig. 17 shows an example of a preamble reception operation of a base station according to a second embodiment of the present disclosure;

fig. 18 is a block diagram showing an internal structure of a base station according to an embodiment of the present disclosure;

fig. 19 is a block diagram showing an internal structure of a terminal according to an embodiment of the present disclosure; and is also provided with

Fig. 20 shows simulation results obtained by evaluating the reception performance of a preamble signal according to the first embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description of the present disclosure, a detailed description of known functions or configurations incorporated herein will be omitted when it may be determined that the description may make the subject matter of the present disclosure unnecessarily unclear. The terms to be described below are terms defined in consideration of functions in the present disclosure, and may be different according to users, intention of users, or custom. Accordingly, the definition of terms should be determined based on the contents throughout the specification.

The advantages and features of the present disclosure, as well as the manner of attaining them, will become apparent by reference to embodiments described in detail below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments set forth below, but may be embodied in various forms. The following examples are provided solely to fully disclose the present disclosure and to inform those of ordinary skill in the art of the scope of the present disclosure and the present disclosure is limited only by the scope of the appended claims. The same or similar reference numbers will be used throughout the specification to refer to the same or similar elements.

Wireless communication systems are evolving into broadband wireless communication systems to provide high-speed and high-quality packet data services as well as typical voice-based services using communication standards such as high-speed packet access (HSPA) of 3GPP, LTE { long term evolution or evolved universal terrestrial radio access (E-UTRA) }, LTE-advanced (LTE-a), LTE-Pro, high-speed packet data (HRPD) of 3GPP2, ultra Mobile Broadband (UMB), IEEE 802.16E, and the like.

As a typical example of a broadband wireless communication system, an LTE system employs an Orthogonal Frequency Division Multiplexing (OFDM) scheme in a Downlink (DL) and a single carrier frequency division multiple access (SC-FDMA) scheme in an Uplink (UL). The uplink indicates a radio link through which a User Equipment (UE) (or a Mobile Station (MS)) transmits data or control signals to a Base Station (BS) (eNode B), and the downlink indicates a radio link through which the base station transmits data or control signals to the UE. The above multiple access scheme separates data or control information of respective users by allocating and operating time-frequency resources to transmit the data or control information of each user so as to avoid overlapping each other (i.e., to establish orthogonality).

Since a 5G communication system, which is a post LTE communication system, has to freely reflect various requirements of users, service providers, and the like, services satisfying the various requirements have to be supported. Services considered in 5G communication systems include enhanced mobile broadband (emmbb) communication, mass machine type communication (mctc), ultra Reliable Low Latency Communication (URLLC), and the like.

The eMBB is intended to provide higher data rates than supported by existing LTE, LTE-A or LTE-Pro. For example, in a 5G communication system, for a single base station, an eMBB must provide a peak data rate of 20Gbps in the downlink and 10Gbps in the uplink. Furthermore, the 5G communication system must provide the UE with an increased user perceived data rate as well as a maximum data rate. To meet such requirements, there is a need for improvements in transmit/receive techniques including further enhanced multiple-input multiple-output (MIMO) transmit techniques. Furthermore, the data rate required for the 5G communication system may be obtained using a frequency bandwidth exceeding 20MHz in a frequency band of 3 to 6GHz or higher, instead of transmitting signals using a transmission bandwidth up to 20MHz in a 2GHz frequency band used in LTE.

Further, in 5G communication systems, mctc is considered to support application services such as internet of things (IoT). mctc has requirements such as supporting the connection of a large number of UEs within a cell, enhancing the coverage of UEs, increasing battery time, reducing the cost of UEs, etc., in order to effectively provide the internet of things. Since the internet of things provides communication functions while providing various sensors and various devices, it must support a large number of UEs (e.g., 1,000,000 UEs/km 2) in a cell. Furthermore, a UE supporting mctc may need to be more widely covered than other services provided by a 5G communication system, because the UE is likely to be located in a shadow area, such as a basement of a building, that is not covered by a cell due to the nature of the service. UEs supporting mctc must be configured to be inexpensive and require very long battery life times, such as 10 years to 15 years, because it is difficult to replace the battery of the UE frequently.

Finally, URLLC, which is a cellular-based mission critical wireless communication service, may be used for remote control of robots or machines, industrial automation, unmanned aerial vehicles, remote healthcare, emergency alerts, etc. Therefore, URLLC must provide communication with ultra low latency and ultra high reliability. For example, services supporting URLLC should meet an air interface delay of less than 0.5ms and also require packet error rates of 10-5 or less. Thus, for services supporting URLLC, 5G systems must provide shorter Transmission Time Intervals (TTIs) than other traffic, and designs for allocating a large amount of resources within the frequency band may be required in order to ensure the reliability of the communication link.

Three 5G services (i.e., emmbb, URLLC, and mctc) may be multiplexed and transmitted in a single system. Different transmission/reception techniques and transmission/reception parameters may be used between the figures in order to meet different requirements of the respective services.

Hereinafter, the framework structure of LTE and LTE-a systems will be described in more detail with reference to the accompanying drawings.

Fig. 1 illustrates a basic structure of a time-frequency domain, which is a radio resource domain in which data or control channels are transmitted in an LTE system.

In fig. 1, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The smallest transmitting unit in the time domain is An OFDM symbol. Aggregation N _symb A 101OFDM symbol to constitute one slot 102 and two slots are aggregated to constitute one subframe 103. The length of the slot is 0.5ms and the length of the subframe is 1.0ms. In addition, the radio frame 104 is a time domain unit configured by 10 subframes. The smallest transmitting unit in the frequency domain is a subcarrier, and the bandwidth of the entire system transmission bandwidth is made up of a total of N _BW 105 subcarrier configurations. The basic unit of resources in the time-frequency domain is a Resource Element (RE) 106, and may be represented by an OFDM symbol index and a subcarrier index. A resource block (RB or Physical Resource Block (PRB)) 107 is defined as N in the time domain _symb Successive OFDM symbols 101 and N in the frequency domain _RB Successive subcarriers 108. Thus, one RB 108 is composed of N _symb ×N _RB The REs 106 are configured. In general, the smallest transmission unit of data is an RB unit. In the LTE system, N _symb =7 and N _RB =12, and N _BW And N _RB Proportional to the bandwidth of the system transmit band.

Next, downlink Control Information (DCI) in LTE and LTE-a systems will be described in detail.

In the LTE system, scheduling information for downlink data or uplink data is transmitted from a base station to a terminal through DCI.

The DCI defines several formats and applies a DCI format determined according to

Whether scheduling information for uplink data or scheduling information for downlink data,

whether or not it is compact DCI with control information of smaller size

Whether spatial multiplexing using multiple antennas is applied

Whether DCI is used for power control.

For example, DCI format 1 as scheduling control information for downlink data is configured to include at least the following pieces of control information.

-resource allocation type 0/1 flag: the resource allocation method is notified whether it is type 0 or type 1.

Type 0 is to allocate resources in units of Resource Block Groups (RBGs) by applying a bitmap method. In the LTE system, the basic scheduling unit is a Resource Block (RB) represented by time and frequency domain resources, and the RBG is configured by a plurality of RBs to be a basic scheduling unit in the type 0 method.

Type 1 allows for allocation of a particular RB within an RBG.

-resource block allocation: the RBs allocated for data transmission are notified. The resources to be expressed are determined according to the system bandwidth and the resource allocation method.

-Modulation and Coding Scheme (MCS): the modulation scheme used for data transmission and the size of a transport block as data to be transmitted are notified.

-HARQ process number: the HARQ process number is notified.

-a new data indicator: whether HARQ initial transmission or retransmission is notified.

Redundancy version: the redundancy version of HARQ is notified.

-Transmit Power Control (TPC) commands for the Physical Uplink Control Channel (PUCCH): transmit power control commands of PUCCH as an uplink control channel are notified.

The DCI is transmitted through a Physical Downlink Control Channel (PDCCH) as a downlink control channel via a channel coding and modulation procedure.

A Cyclic Redundancy Check (CRC) is added to the DCI message payload and is scrambled by a Radio Network Temporary Identifier (RNTI) corresponding to an identity of the terminal.

Different RNTIs are used depending on the purpose of the DCI message (e.g., UE-specific data transmission, power control commands, or random access response). The RNTI is not explicitly transmitted but is included in the CRC calculation process and transmitted. After receiving the DCI message transmitted on the PDCCH, the terminal may identify the CRC by using the assigned RNTI, and when the CRC identification result is correct, it may be identified that the corresponding message has been transmitted to the terminal.

Fig. 2 shows a PDCCH 201 as a physical downlink channel of LTE through which DCI is transmitted.

Referring to fig. 2, a pdcch 201 is time-multiplexed with a PDSCH 202 as a data transmission channel and transmitted through the entire system bandwidth. The region of PDCCH 201 is expressed as the number of OFDM symbols, which is indicated to the UE using a Control Format Indicator (CFI) transmitted through a Physical Control Format Indicator Channel (PCFICH).

By allocating the PDCCH 201 to the OFDM symbol existing in the front portion of the subframe, the UE can decode the downlink scheduling assignment as quickly as possible. Accordingly, a downlink shared channel (DL-SCH) decoding delay, i.e., an overall downlink transmission delay, may be reduced. A single PDCCH delivers a single DCI message, and multiple UEs may be scheduled simultaneously in downlink and uplink, and thus transmission of multiple PDCCHs may be performed simultaneously in each cell.

A cell-specific reference signal (CRS) 203 is used as a reference signal for decoding PDCCH 201. CRS203 is transmitted over the entire frequency band for each subframe, and the scrambling and resource mapping for each cell Identification (ID) may be different.

CRS203 is a reference signal that is commonly used by all UEs and thus may not be possible to use UE-specific beamforming. Accordingly, the multi-antenna transmission scheme of the PDCCH for LTE may be limited to an open-loop transmit diversity scheme. The UE is implicitly informed of the port number of the CRS by decoding a Physical Broadcast Channel (PBCH).

The resource allocation of the PDCCH 201 is performed in units of Control Channel Elements (CCEs), and a single CCE includes 9 Resource Element Groups (REGs), that is, 36 Resource Elements (REs) in total. The number of CCEs required for a particular PDCCH 201 may be 1, 2, 4, or 8, which is determined based on the channel coding rate of the DCI message payload.

As described above, the link adaptation of PDCCH 201 is achieved using a different number of CCEs. The UE needs to detect the signal without knowing the information associated with PDCCH 201. In LTE, a search space is defined for blind decoding that indicates a set of CCEs.

The search space includes multiple sets according to each CCE Aggregation Level (AL), which is not explicitly signaled but implicitly defined by a number of subframes and a function associated with the UE identity.

In each subframe, the UE decodes PDCCH 201 with respect to all possible resource candidates that may be generated from CCEs in the configured search space and processes information declared valid for the corresponding UE via CRC identification.

The search space may be classified into a UE-specific search space and a common search space. A group of UEs or all UEs may search a common search space of the PDCCH 201 in order to receive cell common control information, such as paging messages or dynamic scheduling related to system information. For example, scheduling allocation information (including cell operator information, etc.) of DL-SCH for transmission of System Information Block (SIB) -1 may be received by searching a common search space of PDCCH 201.

In LTE, the entire PDCCH region is configured as a set of CCEs in a logical region, and there is a search space that includes the set of CCEs. The search space may be classified into a common search space and a UE-specific search space, and the search space for the LTE PDCCH may be defined as follows:

According to the above definition of the search space for the PDCCH, the UE-specific search space is not explicitly signaled, but is implicitly defined by the number of subframes and a function associated with the UE identity.

In other words, the fact that the UE-specific search space varies according to the number of subframes indicates that the UE-specific search space may vary with time. Through the above, the problem that a specific UE cannot use the search space due to other UEs among the UEs (blocking problem) can be overcome.

The UE may not be scheduled in a subframe because all CCEs searched for by the UE are currently used by other scheduled UEs within the same subframe. However, since the search space varies with time, this problem does not occur in subsequent subframes. For example, although UE-specific search spaces for ue#1 and ue#2 partially overlap in a particular subframe, overlapping may be expected to be different in subsequent subframes because UE-specific search spaces for each subframe are different.

According to the above definition of the search space for the PDCCH, the common search space is defined as a pre-agreed set of CCEs, since a predetermined set of UEs or all UEs need to receive the PDCCH. In other words, the common search space does not change according to UE identity, the number of subframes, etc.

Although there is a common search space for transmitting various system messages, the common search space may be used for transmitting control information of individual UEs. With the above, the common search space may be used as a solution to the phenomenon that UEs cannot be scheduled due to lack of available resources in the UE-specific search space.

The search space is a set of candidate control channels including CCEs that the UE should attempt decoding at a given aggregation level. There are various aggregation levels to bundle one, two, four and eight CCEs into a single bundle, and thus the UE has multiple search spaces.

In LTE PDCCH, the number of PDCCH candidates to be monitored in the search space by the UE and defined based on the aggregation level is defined in the table below.

[ Table 1]

According to [ Table 1], in case of a UE-specific search space, aggregation levels {1,2,4,8} are supported, and in this case {6,6,2,2} PDCCH candidates exist, respectively. In the case of the common search space 302, aggregation levels {4,8} are supported, and in this case {4,2} PDCCH candidates exist, respectively.

The common search space only supports aggregation levels {4,8} in order to improve coverage characteristics, as system messages typically need to reach the cell edge.

The DCI transmitted in the common search space is defined only for a specific DCI format corresponding to the purpose of power control of a UE group or a system message, etc., such as 0/1A/3/3A/1C.

In the common search space, DCI formats involving spatial multiplexing are not supported.

The downlink DCI format that should be decoded in the UE-specific search space may be changed according to a transmission mode configured for the corresponding UE. The transmission mode is configured via RRC signaling and thus the number of subframes is not accurately defined in association with whether the corresponding configuration is valid for the corresponding UE. Thus, the UE may always perform decoding with respect to DCI format 1A regardless of the transmission mode in order to operate in a manner that does not lose transmission.

In the above description, a method of transmitting or receiving a downlink control channel and downlink control information and search spaces in conventional LTE and LTE-a have been described.

Hereinafter, a downlink control channel in the 5G communication system currently in question will be described in detail with reference to the accompanying drawings.

Fig. 3 shows an example of a basic unit of time and frequency resources for a downlink control channel configuration that can be used in 5G. According to fig. 3, a basic unit (REG) of time and frequency resources configured for a control channel includes one OFDM symbol 301 on a time axis and 12 subcarriers 302 (i.e., 1 RB) on a frequency axis.

By assuming that 1 OFDM symbol 301 is a basic time axis unit when configuring a basic unit of a control channel, a data channel and a control channel can be time-multiplexed within a single subframe.

By placing the control channel before the data channel, the processing time perceived by the user can be reduced and, therefore, the latency requirements can be easily met.

The basic frequency axis unit of the control channel is configured to 1 RB 302, and thus, frequency multiplexing between the control channel and the data channel can be effectively performed.

The control channel region may be configured to various sizes by concatenating REGs 303 shown in fig. 3. For example, when CCEs 304 are basic units for allocating downlink control channels in 5G, 1 CCE 304 may include a plurality of REGs 303.

Description will be provided with reference to REG 303 of fig. 3.

When REGs 303 include 12 REs and 1 CCE 304 includes 6 REGs 303, this indicates that 1 CCE 304 includes 72 REs.

If a downlink control region is configured, the corresponding region may include a plurality of CCEs 304, and a particular downlink control channel may be transmitted through a plurality of CCEs 304 mapped to a single CCE or control region, depending on an Aggregation Level (AL).

CCEs 304 in the control region may be distinguished by numbers, and these numbers may be allocated according to a logical mapping scheme.

Basic unit of the downlink control channel of fig. 3

(i.e., REG 303) may include both REs to which DCI is mapped and regions to which demodulation reference signals (DMRS) 305, which are reference signals for decoding DCI, are mapped.

As shown in fig. 3, DMRS 305 may be transmitted in 6 REs within 1 REG 303. For reference, the DMRS303 is transmitted using the same precoding as the control signal mapped to the REG 303, and thus, the UE can decode the control information without information associated with precoding applied by the base station.

Fig. 4 shows an example of a control region (control resource set (core)) in which a downlink control channel is transmitted in a 5G wireless communication system. Fig. 4 shows an example in which two control regions (control region #1 401 and control region #2 402) are configured within a system bandwidth 410 on a frequency axis and 1 slot 420 on a time axis (for example, the example of fig. 4 assumes that 1 slot includes 7 OFDM symbols). The control region 401 or 402 may be configured based on a particular sub-band 403 within the overall system bandwidth 410 on the frequency axis. On the time axis, the control region may be configured based on one or more OFDM symbols, which may be defined as a control region length (control resource set duration 404). In the example of fig. 4, the control area #1 401 is configured based on a control area length of 2 symbols, and the control area #2 is configured based on a control area length of 1 symbol.

As described above, the control region in the 5G system may be configured via higher layer signaling (e.g., system information, master Information Block (MIB), RRC signaling) of the base station to the UE.

The UE is configured with information associated with the location of the control region, the subbands, the resource allocation of the control region, the control region length, etc. For example, the following information may be included.

[ Table 2 ]

In addition to the above configuration information, various information required to transmit a downlink control channel may be configured for the UE.

Next, downlink Control Information (DCI) in 5G will be described in detail.

In a 5G system, scheduling information associated with uplink data (physical uplink shared channel (PUSCH)) or downlink data (physical downlink shared channel (PDSCH)) may be transmitted from a base station to a UE via DCI.

The UE may monitor DCI formats for backoff and DCI formats for non-backoff associated with PUSCH or PDSCH.

The fallback DCI format may be implemented as a fixed field between the base station and the UE, and the non-fallback DCI format may include a configurable field.

The backoff DCI for scheduling PUSCH may include information shown below.

[ Table 3 ]

The non-fallback DCI scheduling PUSCH may include information shown below.

[ Table 4 ]

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The fallback DCI of the scheduled PDSCH may include information shown below.

[ Table 5-1 ]

The non-fallback DCI of the scheduled PDSCH may include information shown below.

[ Table 5-2 ]

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The DCI may be transmitted via a Physical Downlink Control Channel (PDCCH) after a channel coding and modulation procedure.

A Cyclic Redundancy Check (CRC) is added to the payload of the DCI message and the CRC may be scrambled by a Radio Network Temporary Identifier (RNTI) corresponding to the UE identity.

Depending on the purpose of the DCI message (e.g., UE-specific data transmission, power control commands, random access response, etc.), different RNTIs may be used. The RNTI is not explicitly transmitted but is transmitted by being included in the CRC calculation process.

If the UE receives the DCI message transmitted on the PDCCH, the UE may identify the CRC by using the allocated RNTI. If the CRC recognition result is correct, the UE may recognize that the corresponding message is transmitted to the UE.

For example, DCI scheduling PDSCH associated with System Information (SI) may be scrambled by SI-RNTI.

DCI scheduling a PDSCH associated with a Random Access Response (RAR) message may be scrambled by the RA-RNTI.

The DCI scheduling the PDSCH associated with the paging message may be scrambled by the P-RNTI.

The DCI reporting a Slot Format Indicator (SFI) may be scrambled by an SFI-RNTI.

The DCI reporting the Transmit Power Control (TPC) may be scrambled by a TPC-RNTI.

The DCI scheduling the UE-specific PDSCH or PUSCH may be scrambled by a cell RNTI (C-RNTI).

If a data channel (i.e., PUSCH or PDSCH) is scheduled for a specific UE via PDCCH, data may be transmitted or received with the DMRS within a correspondingly scheduled resource region.

Fig. 5 shows the following case: a specific UE uses 14 OFDM symbols in the downlink as a single slot (or subframe), the PDCCH is configured to transmit in the first two OFDM symbols, and the DMRS is configured to transmit in the third symbol.

In the case of fig. 5, in a specific RB in which the PDSCH is scheduled, the PDSCH is transmitted by mapping data to REs through which the DMRS is not transmitted in the third symbol and REs from the fourth symbol to the last symbol.

The subcarrier spacing af expressed in fig. 5 is 15kHz in the case of the LTE/LTE-a system, and one of {15, 30, 60, 120, 240, 480} kHz may be used in the case of the 5G system.

As described above, the base station needs to transmit a reference signal in order to measure the downlink channel state in the cellular system. In the case of a long term evolution advanced (LTE-a) system of 3GPP, a UE may measure a channel state between a base station and the UE by using CRS or CSI-RS transmitted by the base station.

The channel state may need to be measured in consideration of various factors, and the amount of interference in the downlink may be included among these factors.

The amount of interference in the downlink may include an interference signal, thermal noise, etc. generated by antennas belonging to neighboring base stations, and is important when the UE determines a channel state in the downlink.

For example, in the case that a base station having a single transmit antenna transmits to a UE having a single receive antenna, the UE needs to determine Es/Io by determining energy per symbol that can be received in downlink and an amount of interference that may be simultaneously received for a duration of receiving a corresponding symbol based on a reference signal received from the base station.

The determined Ex/Io may be converted to a data rate or a value corresponding thereto, may be transmitted to the base station in the form of a Channel Quality Indicator (CQI), and may be used when the base station determines a data rate to be used for transmission to the UE.

In the case of the LTE-a system, the UE feeds back information associated with a channel state of the downlink to the base station, and thus, the base station can perform downlink scheduling using the information. That is, the UE measures a reference signal transmitted by the base station in the downlink and feeds back information extracted from the measured reference signal to the base station in a form defined in the LTE/LTE-a standard. As described above, the information fed back by the UE in LTE/LTE-a is referred to as channel state information, and the channel state information may include the following three pieces of information:

Rank Indicator (RI): indicating the number of spatial layers that the UE can receive in the current channel state.

Precoding Matrix Indicator (PMI): an indicator associated with a precoding matrix preferred by the UE in the current channel state.

Channel Quality Indicator (CQI): indicating the maximum data rate that the UE can receive in the current channel state.

The CQI may be replaced with a signal to interference plus noise ratio (SINR), maximum error correction code rate and modulation method, data efficiency per frequency, etc., which may be used in a manner similar to the maximum data rate.

RI, PMI and CQI have meanings related to each other. For example, the precoding matrix supported in LTE/LTE-a may be defined differently for each rank. Therefore, the PMI value X when RI is 1 and the PMI value X when RI is 2 may be interpreted as different. In addition, the UE determines CQI under the assumption that PMI and X reported to the base station by the UE are applied in the base station. That is, reporting ri_ X, PMI _y and cqi_z to the base station by the UE may correspond to reporting that the UE can perform reception at a data rate corresponding to cqi_z when the rank is ri_x and the PMI is pmi_y. As described above, the UE calculates CQI under the assumption of a transmission scheme to be performed with respect to the base station, and thus, the UE can obtain the best performance when the UE actually performs transmission using the corresponding transmission scheme.

In LTE/LTE-a, RI, PMI, and CQI, which are channel state information fed back by the UE, may be periodically or aperiodically fed back. In case that the base station desires to aperiodically obtain channel state information of a specific UE, the base station may configure aperiodic feedback (or aperiodic channel state information report) to be performed using an aperiodic feedback indicator (or channel state information request field or channel state information request information) included in Downlink Control Information (DCI) for the UE. In addition, when the UE receives an indicator configured to perform aperiodic feedback in the nth subframe, the UE may perform uplink transmission by including aperiodic feedback information (or channel state information) in data transmission in the (n+k) th subframe. Here, k is a parameter defined in the 3GPP LTE release 11 standard, which is 4 in Frequency Division Duplexing (FDD) and may be defined as shown in table 6 in case of Time Division Duplexing (TDD).

TABLE 6 value of k for number of subframes n per TDD UL/DL configuration

In case of aperiodic feedback being configured, the feedback information (or channel state information) may include RI, PMI, and CQI, and according to the feedback configuration (or channel state report configuration), RI and PMI may not be fed back.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, although embodiments of the present disclosure will be described with reference to an LTE or LTE-a system as an example, embodiments of the present disclosure may be applied to other communication systems having similar technical contexts or similar channel types. For example, fifth generation mobile communication technology (5G, new Radio (NR)) or sixth generation mobile technology developed after LTE-a may be included. In addition, embodiments of the present disclosure may be modified by those skilled in the art and may be applied to other communication systems without departing from the scope of the present disclosure.

The Physical Random Access Channel (PRACH) in existing LTE or NR is designed to be suitable for an environment in which the symbol length of a signal is much larger than the maximum Round Trip Delay (RTD) of a cell. The base station may perform differentiation of each terminal and estimation of preamble signal delay by using a preamble sequence received via the PRACH. On the other hand, a wireless communication system using an ultra-high frequency band such as a terahertz (THz) or a sub-THz band may use a waveform having a very large subcarrier spacing (i.e., a very small symbol length) due to extreme phase noise. Therefore, PRACH preamble sequence designs of existing LTE or NR methods in a mobile communication system that simply extend ultra-high frequency bands may have limitations in terms of use.

Accordingly, the present disclosure proposes a new PRACH preamble signal design suitable for ultra-high frequency bands (including THz and sub-THz frequency domains) and a technique for transmitting and receiving the preamble signal. This includes a method for generating and transmitting a PRACH preamble sequence for random access by a terminal, a method for receiving the PRACH preamble sequence by a base station in order to estimate an RTD of a signal for Timing Advance (TA) feedback, and a method for detecting an ID of a preamble generated by the terminal. The proposed technique enables a base station to estimate RTD of a preamble signal while distinguishing each terminal even in an environment where the symbol length of the preamble signal is very short compared to the maximum RTD of a cell.

Fig. 6A is a flowchart showing a basic operation of a base station to receive a PRACH preamble signal.

Referring to fig. 6A, a base station according to an embodiment of the present disclosure may transmit a synchronization signal to a plurality of UEs (operation 601). Here, the synchronization signals may include, for example, a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), and a Physical Broadcast Channel (PBCH).

In addition, the base station may receive a random access preamble signal from the UE through PRACH resources (operation 602). When receiving the random access preamble signal as described, the base station may identify an Identifier (ID) of the UE based on the random access preamble signal and determine a Timing Advance (TA) value for the UE through an estimation of a Round Trip Delay (RTD) between the base station and the UE (operation 603).

In addition, the base station may transmit a random access response including the thus determined TA value to the identified UE (operation 604).

Fig. 6B is a flowchart illustrating a basic operation of a UE transmitting a PRACH preamble signal.

Referring to fig. 6B, after receiving a synchronization signal transmitted by a base station (operation 605), a UE may adjust downlink synchronization accordingly and transmit a random access preamble to the base station through PRACH resources (operation 606).

Thereafter, when receiving a random access response from the base station in response to transmitting the random access preamble (operation 607), the UE may apply a TA value included in the random access response based on an uplink grant included in the random access response to transmit a message for access to the base station.

Fig. 7A shows a basic structure of a PRACH preamble signal transmitted by a UE.

Referring to fig. 7a, the prach preamble signal 700 may include: a first signal portion 701 having a total length T ₁ And is formed from K identical OFDM symbols and length T _CP1 Is composed of Cyclic Prefix (CP); total length T _GT Is a guard time 702 of (2); and a second signal portion 703 having a total length T ₂ And consists of one OFDM symbol and CP. In each symbol, a sequence of lengths L (indicated by reference numerals 704 and 705) may be arranged.

First, in the case of the first signal portion, the length of the sum of the length of the previous (K-1) symbols of the first signal portion and the length of the CP (i.e., the length T _CP1 +(K-1)·T _sym ) Is typically configured to be equal to or greater than the value of the maximum RTD of the cell, or is configured to be equal to or greater than the sum of the maximum RTD of the cell and the maximum delay spread of the cell.

Here, T _sym Can indicate the length of OFDM symbolAnd T is _sym The relationship with the subcarrier spacing deltaf of the system can generally be defined byAnd (3) representing. In addition, each OFDM symbol is composed of L discrete-time samples, where L may represent the size of an IDFT used to generate the OFDM symbol or the length of a sequence to be generated.

In other words, the value of the subcarrier spacing or T of the system is given _sym In the case of the values of (a) the length of the first signal portion (i.e., the value of K and T _CP1 Is determined by the target maximum RTD value (i.e., target maximum distance). Here, the length T of the first signal part ₁ The maximum distance corresponding to the maximum measurable RTD corresponding thereto may have a relationship shown in the following mathematical expression.

In the above mathematical expression, c represents the speed of light (3 x 10≡8 m/s).

Here, the CP of the first signal portion may use a signal obtained by copying a latter part of one of K identical symbols of the first signal portion. In addition, the length T of the CP of the first signal portion _CP1 Can be configured to 0 and T by considering the maximum RTD of the cell _sym And a signal obtained by copying a latter part of each symbol of the first signal part may be used. Here, a sequence of length L among K symbols arranged in the first signal portion 701 is referred to as SEQ1, and may be composed of s1[0 ]]、s1[1]、……、s1[L-1]And (3) representing.

Next, for the second signal portion 703, the CP length T may be configured by considering the delay spread value of the cell _CP2 . For example T _CP2 May be configured to be equal to or greater than the value of the delay spread value of the cell. Here, the sequence of length L arranged in the symbols comprised in the second signal part is referred to as SEQ2 and may be made of s2[0 ]]、s2[1]、……、s2[L-1]Representation of。

Fig. 7B illustrates UE operation generating PRACH preamble signals according to the present disclosure.

Referring to fig. 7B, in the present disclosure, a UE may receive a synchronization signal from a base station (operation 710), and the UE may obtain sequence information in a corresponding cell based on the synchronization signal and then generate a sequence (SEQ 1) of length L by using the sequence information (operation 711). The method of obtaining sequence information in the present disclosure will be described later by fig. 9 to 11. Subsequently, the UE may generate a first signal portion based on the generated SEQ1 (operation 712). In addition, the UE may generate a sequence (SEQ 2) of length L based on the obtained sequence information in the corresponding cell (operation 713). Subsequently, the UE may generate a second signal portion based on the generated SEQ2 (operation 714). Thereafter, the UE may transmit the generated PRACH preamble signal to the base station (operation 715).

In addition, SEQ1 and SEQ2 generated by the UE may be sequences having good cyclic correlation characteristics so that the base station can easily detect the preamble and estimate the RTD.

Fig. 8-10 relate to various embodiments in which a UE acquires sequence information for generating SEQ1 and SEQ2 according to embodiments of the present disclosure.

First, in embodiments of the present disclosure, for example, a Zadoff-Chu (ZC) sequence of length L may be used for SEQ1 and SEQ2 of length L. At this time, the UE may generate a ZC sequence by using the sequence information. Here, the sequence information may be cell-specifically determined as, for example, a root index value, and UEs within the cell may generate ZC sequences by using different root index values. The UE may obtain the root index set I for generating SEQ1 from the base station ₁ And root index set I for generating SEQ2 can be obtained from the base station ₂ . The UE may select from the obtained group I ₁ And I ₂ The root index used to generate SEQ1 and SEQ2 is randomly selected and may be used to identify the UE ID by the base station. In an embodiment, the UE may obtain a set of time/frequency resources from the base station for transmitting the preamble signal. The UE may randomly select resources from a set of time/frequency resources for transmitting the preamble signal to transmit by using the selected resources And transmitting the preamble signal.

In an embodiment, the UE may receive such sequence information (e.g., cell-specific root index) and resource information via a Physical Broadcast Channel (PBCH) of a synchronization signal transmitted by the base station, as shown in fig. 8.

In another embodiment, the UE may receive the sequence information (information about the root index) and the resource information through a Master Information Block (MIB) as shown in fig. 9 or through a System Information Block (SIB) as shown in fig. 10.

Meanwhile, fig. 11A and 11B illustrate a basic principle in an embodiment of the present disclosure, in which a base station receives a preamble transmitted by a UE in order to estimate an RTD value of a signal, i.e., T _RTD Is a value of (2).

Referring to fig. 11A, a preamble signal transmitted by a UE is received by a base station with a delay equal to T from a start symbol of a PRACH slot of the base station _RTD . As previously described, in a communication system to which the present disclosure is applicable, T _RTD May have a value greater than the symbol length and may therefore be expressed as follows. In the following mathematical expression, k _sym Is an integer equal to or greater than 0 and may be referred to as a symbol level delay. In addition, t _r Is a real number greater than or equal to 0 and may be referred to as a residual delay. However, the remaining delay or symbol level delay is commanded only as an example of explanation and does not limit the scope of the present disclosure, and it should be noted that the remaining delay or symbol level delay may also be generalized and referred to as any name that may be interpreted as having the same technical meaning, e.g., a first delay time or a second delay time.

T _RTD ＝k _sym ·T _sym +t _r

For reference, the above mathematical expression expresses the delay value as a real number in absolute time, and may also express the delay value as a sample unit in discrete time domain as follows.

N _RTD ＝k _sym ·N _sym +n _r

Here, the parameters of the above two equations may have the following relationship.

Here, L may represent the size of IDFT used to generate the OFDM-based signal, or the length of a sequence to be generated.

Referring to FIG. 11B, a method for calculating T in accordance with an embodiment of the present disclosure is described _RTD The method of the values of (2) is as follows.

First, the base station may receive a PRACH preamble signal from the UE (operation 1101). Thereafter, the base station may perform a two-stage estimation operation to estimate T of the signal from the received preamble signal _RTD Values. In a first estimation operation, the base station may estimate the remaining delay, i.e., t _r In (operation 1102), and in a second stage estimation operation, the base station may estimate a symbol level delay, i.e., k _sym Is a value of (operation 1103). Finally, the base station may follow formula T _RTD ＝k _sym ·T _sym +t _r By using t estimated in the above two-stage estimation process _r Value sum k _sym Values to derive T _RTD A value (operation 1104).

To derive RTD values using the two-stage estimation operation, the base station may generate a first correlation signal used in the first-stage estimation operation and a second correlation signal used in the second-stage estimation operation. In an embodiment, the first correlation signal to be generated may be a signal generated by the root index set I ₁ The ZC sequence consisting of root indexes in (a) and the second correlation signal can be a set I of root indexes ₂ A ZC sequence consisting of root indexes of (a).

Next, based on the preamble structure proposed by the present disclosure shown in fig. 7 and the RTD estimation operation of the base station shown in fig. 11A and 11B, specific embodiments of the structure of the preamble signal transmitted by the UE to the base station, the preamble signal reception operation of the base station using the structure of each preamble signal and the RTD value estimation operation according thereto will be described below.

< first embodiment >

Fig. 12 shows a structure of a preamble generated by a UE according to the first embodiment.

Referring to fig. 12, in a first embodiment of the present disclosure, a PRACH preamble signal 1200 may include: a first signal portion 1201 having a total length T ₁ And is formed from K identical OFDM symbols and length T _CP1 Is composed of Cyclic Prefix (CP); total length T _GT Protection time 1202 of (2); and a second signal portion 1203 having a total length T ₂ And consists of one OFDM symbol and CP. In each symbol configuring the first signal portion 1201, a sequence of lengths L (indicated by reference numeral 1204) may be arranged. A sequence SEQ2 having a length L may be arranged in each symbol configuring the second signal portion 1202 (indicated by reference numeral 1205). In the case of the first signal portion, the sum of the length of the previous (K-1) symbols of the first signal portion and the length of the CP (i.e., length T _CP1 +(K-1)·T _sym ) May be configured to be equal to or greater than the value of the maximum RTD of the cell, or to be equal to or greater than the value of the sum of the maximum RTD of the cell and the maximum delay spread of the cell. Here, the CP of the first signal portion may use a signal obtained by copying a latter part of one of K identical symbols of the first signal portion. In addition, the length T of the CP of the first signal portion _CP1 Can be configured to 0 and T by considering the maximum RTD of the cell _sym And a signal obtained by copying a latter part of each symbol of the first signal part may be used. Here, a sequence of length L arranged in K symbols included in the first signal portion 1201 is referred to as SEQ1, and may be formed of s1[0 ]]、s1[1]、……、s1[L-1]And (3) representing. Next, in the case of the second signal portion 1203, the CP length T may be configured by considering the delay spread value of the cell _CP2 . For example T _CP2 May be configured to be equal to or greater than the value of the delay spread value of the cell. Here, the sequence of length L arranged in the symbols comprised in the second signal part is referred to as SEQ2 and may be made of s2[0 ]]、s2[1]、……、s2[L-1]And (3) representing.

In a first embodiment of the present disclosure, a guard time between the first signal portion and the second signal portion The length may be T _GT ＝(K-2)·T _sym +(T _sym -T _CP2 ) (indicated by reference numeral 1202). In fig. 12, an example of a case (indicated by reference numeral 1206) in which k=4 and k=10 is shown, but this is for illustrative purposes only and does not limit the scope of the present disclosure. That is, K may be configured as a random value, e.g., based on the maximum RTD value of the cell, the sum of the length of the previous (K-1) symbols of the first signal portion and the length of the CP of the first signal portion (i.e., length T _CP1 +(K-1)·T _sym ) May be determined to be equal to or greater than the maximum RTD of the cell. In an embodiment, to reduce the time resource overhead, the value of K may be determined as the smallest integer value satisfying the above condition. However, the method of determining the K value in the present disclosure is not limited thereto.

Fig. 13 shows a detection window for detecting a preamble signal by a base station according to a first embodiment of the present disclosure.

Referring to fig. 13, a base station according to a first embodiment of the present disclosure may configure a detection window 1 (W1) 1301 and a detection window 2 (W2) 1302 for detecting a preamble signal transmitted from a UE. Here, W1 may be a minimum interval for detecting a preamble signal in a first stage estimation operation of a base station to estimate whether a UE is attempting random access and a remaining delay value of a received signal. The length of W1 may be configured to be, for example, the length T of one symbol length _sym As shown in fig. 13, and the starting position of W1 may be configured to be spaced apart from the starting point of the PRACH slot in which the PRACH preamble is received by, for example, a length T _W1 ＝(K-1)·T _sym +T _CP1 Is a position of (c). Here, T _W1 ＝(K-1)·T _sym +T _CP1 The length of (c) may generally correspond to, for example, a value, such as the maximum RTD value of the cell, that is,values. Further, the detection window 2 (W2) 1302 may be an interval for estimating a symbol-level delay value of the received preamble signal in the second-stage estimation operation of the base station. The length of W2 may be configured as (K+1). T _sym For example, as shown in the figure14, and the starting position of W2 may be configured, for example, to be spaced apart by a length (K-1). T from the position where the detection window 1 ends _sym Or spaced apart from the starting point of the PRACH slot in which the PRACH preamble is received by T _W2 ＝T _CP1 +(2K-1)·T _sym Is a position of (c).

Fig. 14 shows an example of a preamble reception operation of a base station according to the first embodiment of the present disclosure.

Referring to fig. 14, a residual delay estimation operation by the first stage estimation performed in W1 and a symbol-level delay estimation operation by the second stage estimation performed in W2 according to the first embodiment will be described. For convenience of explanation, fig. 14 shows a case where a preamble signal having a structure corresponding to k=4 is generated and the preamble is received by the base station at a specific value of RTD as an example.

Referring to the example of fig. 14, in the first embodiment, when the base station receives a preamble signal from the UE, the base station may perform first stage estimation as described below. The base station may perform cyclic correlation between the signal received in the configured W1 and the first correlation signal generated as described above, and detect a peak in the magnitude of a resultant value obtained by performing the cyclic correlation. The base station may estimate whether the UE attempts random access, the root index of SEQ1 generated by the UE, and the remaining delay value of the preamble signal by the root index of the first correlation signal in which the peak is detected and the position of the detected peak in the first correlation signal. At this time, the cyclic correlation performed by the base station may be expressed in the time domain by the following equation.

Here, y [ n ]]Representing the signal received by the base station in W1,representing the first correlation signal (i ₁ ∈I ₁ ) And->Representing the result value of the loop correlation. The peak value may be defined as being +.>Is detected when the magnitude of the (c) or the square value of the magnitude is greater than a certain threshold value beta. The base station can detect the peak value i in the first correlation signal ₁ To determine that the UE has passed the index corresponding to i ₁ SEQ1 is generated and used to identify the UE ID. In addition, the position at which the peak is detected may suggest +. >The value of l with a peak. Further, for example, in the case where the cyclic correlation value of the ZC sequence included in the first signal portion is configured to be zero, the base station according to the first embodiment estimates the estimated value of the remaining delay defined above as +.>Or n _r =l. Here, Δf refers to a subcarrier spacing of the system. In addition, the above-described cyclic correlation may also be performed in the frequency domain, as shown in the following equation.

Here the number of the elements is the number,the DFT operations herein may also be performed via a low complexity IFFT.

Next, referring to the example of fig. 14, after performing the above first stage estimation, the base station may perform second stage estimation as described below. By referring to the remaining delay value of the received preamble signal estimated in the first phase estimation, the base station may be configured to generate a second correlation signal according to the starting point of W2 so as to perform K sub-windows (SW) of the second phase estimation. Here, eachThe SW's may have a length of one symbol, i.e., T _sym Is a length of (c). Specifically, the positions of the first SWs (SW 1) may be configured to be spaced apart from the start point of W2 by an offset corresponding to the remaining delay value estimated in the first stage estimation, and the positions of the remaining (K-1) SWs may be configured to be sequentially spaced apart by one symbol with reference to the first SWs. The base station can perform correlation in each of the K configured SWs using the second correlation signal generated above, and generate a correlation result value c on each SW ₁ ，c ₂ ，…，c _K . Here, c ₁ ，c ₂ ，…，c _K Can be calculated asOr (b)Here, y _k [n]Represents the signal received on the kth SW, and +.>Representing the second correlation signal (i ₂ ∈I ₂ ). In addition, the base station according to the first embodiment may be based on c ₁ ，c ₂ ，...，c _K The value of the detected peak in the values of (c) to perform the estimation of the symbol-level delay defined above. Specifically, at value c ₁ ，c ₂ ，...，c _K In the case where each of them is equal to or greater than a certain threshold β, the base station may determine that a peak has been detected. The base station may detect the peak i in the second correlation signal ₂ To determine that the UE has passed the index corresponding to i ₂ SEQ2 is generated and used to identify the UE ID. In addition, at c _k In the event that a peak is detected, the base station may determine the estimated value of the symbol-level delay defined above as k _sym = (k-1). For reference, the example shown in FIG. 14 shows that at c ₃ Where a peak is detected and an estimate of the symbol level delay is determined to be k _sym Case=2.

Finally, according to the first embodimentThe base station may estimate the remaining delay t by using the residual delay t estimated in the first stage estimation _r Or n _r Value and symbol level delay k estimated in the second stage estimation _sym Value to derive T as the final RTD value of the received preamble signal _RTD ＝k _sym ·T _sym +t _r Or N as the final RTD value in the sample cell _RTD ＝k _sym ·N _sym +n _r 。

Fig. 20 shows simulation results obtained by evaluating the reception performance (omission rate (MD) probability) of a preamble signal according to the first embodiment.

In this simulation, the following ultra-high band cases have been configured in various channel model environments (AWGN, tapped Delay Line (TDL) model C (non-line of sight), TDL model D (line of sight)). The carrier frequency is 140GHz, the subcarrier spacing is 3.2MHz, the sequence length L is 139, and the sequence root index value is configured as i ₁ ＝i ₂ =1, and k=1, t _CP1 ＝P，T _CP2 =21 ns. For reference, the maximum distance corresponding to the maximum RTD in this simulated environment is given as 421.875 meters. In addition, the β threshold has been configured to be 0.001. According to the simulation results, the preamble of the structure proposed by the present disclosure has MD probability values that generally satisfy the performance of the reception demand. It should be noted that the environment or configuration used in the simulation of fig. 20 is for illustrative purposes only and is not intended to limit the applicable environment or configuration of the present disclosure.

< second embodiment >

Fig. 15 shows a structure of a preamble generated by a UE according to a second embodiment.

Referring to fig. 15, in a second embodiment of the present disclosure, a PRACH preamble signal 1500 may include: a first signal portion 1501 having a total length T ₁ And is formed from K identical OFDM symbols and length T _CP1 Is composed of Cyclic Prefix (CP); total length T _GT Is a guard time 1502 of (2); and a second signal portion 1503 having a total length T ₂ And consists of one OFDM symbol and CP. In each symbol configuring the first signal portion 1501, a symbol having a length L may be arrangedSequence SEQ1 (indicated by reference numeral 1504). A sequence SEQ2 having a length L may be arranged in each symbol configuring the second signal portion 1502 (indicated by reference numeral 1505). In the case of the first signal portion, the sum of the length of the previous (K-1) symbols of the first signal portion and the length of the CP (i.e., length T _CP1 +(K-1)·T _sym ) May be configured to be equal to or greater than the value of the maximum RTD of the cell, or to be equal to or greater than the value of the sum of the maximum RTD of the cell and the maximum delay spread of the cell. Here, the CP of the first signal portion may use a signal obtained by copying a latter part of one of K identical symbols of the first signal portion. In addition, the length T of the CP of the first signal portion _CP1 Can be configured to 0 and T by considering the maximum RTD of the cell _sym And a signal obtained by copying a latter part of each symbol of the first signal part may be used. Here, a sequence of length L among K symbols arranged in the first signal portion 1501 is referred to as SEQ1, and may be formed of s1[0 ] ]、s1[1]、……、s1[L-1]And (3) representing. Next, in the case of the second signal part 1503, the CP length T may be configured by considering the delay spread value of the cell _CP2 . For example T _CP2 May be configured to be equal to or greater than the value of the delay spread value of the cell. Here, the sequence of length L arranged in the symbols comprised in the second signal part is referred to as SEQ2 and may be made of s2[0 ]]、s2[1]、……、s2[L-1]And (3) representing.

In a second embodiment of the present disclosure, the length of the guard time between the first signal portion and the second signal portion may be T _GT ＝T _sym -T _CP2 (indicated by reference numeral 1502). In other words, unlike the first embodiment, the preamble structure of the second embodiment is characterized by a guard time of a constant length even when the value of K is changed, and thus may have less time resource overhead than the first embodiment. In fig. 15, an example of a case (indicated by reference numeral 1506) in which k=4 and k=10 is shown, but this is for illustrative purposes only and does not limit the scope of the present disclosure. That is, K may be configured as a random value, e.g., according toThe maximum RTD value of the cell, the sum of the length of the previous (K-1) symbols of the first signal portion and the length of the CP of the first signal portion (i.e., length T _CP1 +(K-1)·T _sym ) May be determined to be equal to or greater than the maximum RTD of the cell. In an embodiment, to reduce the time resource overhead, the value of K may be determined as the smallest integer value satisfying the above condition. However, the method of determining the K value in the present disclosure is not limited thereto.

Further, in the second embodiment of the present disclosure, the sequences of the length L included in the first preference portion and the second signal portion may be sequences having different cyclic shifts of ZC sequences generated with the same root index. This is for eliminating ambiguity between the first signal portion and the second portion that may be caused by a guard time shorter than that in the preamble structure of the first embodiment in the second stage estimation described later with reference to fig. 17.

Fig. 16 shows a detection window for detecting a preamble signal at a base station according to a second embodiment.

Referring to fig. 16, a base station according to a second embodiment of the present disclosure may configure a detection window 1 (W1) 1601 and a detection window 2 (W2) 1602 for detecting a preamble signal transmitted from a UE. Here, W1 may be a minimum interval for detecting a preamble signal in a first stage estimation operation of a base station to estimate whether a UE is attempting random access and a remaining delay value of a received signal. The length of W1 may be configured to be, for example, the length T of one symbol length _sym As shown in fig. 16, and the starting position of W1 may be configured to be spaced apart from the starting point of the PRACH slot in which the PRACH preamble is received by a length T, for example _W1 ＝(K-1)·T _sym +T _CP1 Is a position of (c). Here, T _W1 ＝(K-1)·T _sym +T _CP1 The length of (c) may generally correspond to, for example, a value, such as the maximum RTD value of the cell, that is,values. In addition, the detection window 2 (W2) 1602 may be a symbol level for estimating the received preamble signal in a second stage estimation operation of the base stationInterval of delay values. The length of W2 may be configured as (K+1). T _sym For example, as shown in fig. 17, and the starting position of W2 may be configured to be spaced apart from the position where the detection window 1 ends by a length T, for example _sym Or spaced apart from the starting point of the PRACH slot in which the PRACH preamble is received by T _W2 ＝T _CP1 +(K+1)·T _sym Is a position of (c).

Fig. 17 shows an example of a preamble receiving operation of the base station according to the second embodiment. Referring to fig. 17, a residual delay estimation operation by the first stage estimation performed in W1 and a symbol-level delay estimation operation by the second stage estimation performed in W2 according to the second embodiment will be described. For convenience of explanation, fig. 17 shows a case where a preamble signal having a structure corresponding to k=4 is generated and the preamble is received by the base station at a specific value of RTD as an example.

Referring to the example of fig. 17, in the second embodiment, when the base station receives a preamble signal from the UE, the base station may perform first stage estimation as described below. The base station may perform cyclic correlation between the signal received in the configured W1 and the first correlation signal generated as described above, and detect a peak in the magnitude of a resultant value obtained by performing the cyclic correlation. The base station may estimate whether the UE attempts random access, the root index of SEQ1 generated by the UE, and the remaining delay value of the preamble signal by the root index of the first correlation signal in which the peak is detected and the position of the detected peak in the first correlation signal. At this time, the cyclic correlation performed by the base station may be expressed in the time domain by the following equation.

Here, y [ n ]]Representing the signal received by the base station in W1,representing the first correlation signal (i ₁ ∈I ₁ ) And->Representing the result value of the loop correlation. Here, the peak value may be defined as being +.>Is detected when the magnitude of the (c) or the square value of the magnitude is greater than a certain threshold value beta. The base station can detect the peak value i in the first correlation signal ₁ To determine that the UE has passed the index corresponding to i ₁ SEQ1 is generated and used to identify the UE ID. In addition, the position at which the peak is detected may suggest +. >The value of l with a peak. Further, for example, in the case where the cyclic correlation value of the ZC sequence included in the first signal portion is configured to be zero, the base station according to the first embodiment estimates the estimated value of the remaining delay defined above as +.>Or n _r =l. Here, Δf refers to a subcarrier spacing of the system. In addition, the above-described cyclic correlation may also be performed in the frequency domain, as shown in the following equation.

Here the number of the elements is the number,the DFT operations herein may also be performed via a low complexity IFFT.

Next, referring to the example of fig. 17, after performing the above first stage estimation, the base station may perform second stage estimation as described below. The base station may be configured to generate a second correlation signal according to the starting point of W2 by referring to the remaining delay value of the received preamble signal estimated in the first phase estimation so as to perform the first phase estimationK sub-windows (SW) of the two-stage estimation. Here, each SW may have a length of one symbol, i.e., T _sym Is a length of (c). Specifically, the positions of the first SWs (SW 1) may be configured to be spaced apart from the start point of W2 by an offset corresponding to the remaining delay value estimated in the first stage estimation, and the positions of the remaining (K-1) SWs may be configured to be sequentially spaced apart by one symbol with reference to the first SWs. The base station may perform correlation within each of the configured K SW's by using the second correlation signal generated above, and generate a correlation result value c on each SW ₁ ，c ₂ ，...，c _K . Here, c ₁ ，c ₂ ，...，c _K Can be calculated asOr (b)Here, y _k [n]Represents the signal received on the kth SW, and +.>Representing the second correlation signal. In addition, the base station according to the second embodiment may be based on c ₁ ，c ₂ ，...，c _K The value of the detected peak in the values of (c) to perform the estimation of the symbol-level delay defined above. Specifically, at value c ₁ ，c ₂ ，...，c _K In the case where each of them is equal to or greater than a certain threshold β, the base station may determine that a peak has been detected. If at c _k Where a peak is detected, the base station may determine an estimate of the symbol-level delay defined above as k _sym = (k-1). In addition, the base station can detect the peak value i in the second related signal ₂ To determine that the UE has passed the index corresponding to i ₂ SEQ2 is generated and used to identify the UE ID. For reference, the example shown in FIG. 17 shows that at c ₃ Where a peak is detected and is determined to be k _sym Case=2.

Finally, according to the second embodimentBy using the residual delay t estimated in the first stage estimation _r Or n _r Value and symbol level delay k estimated in the second stage estimation _sym Value to derive T as the final RTD value of the received preamble signal _RTD ＝k _sym ·T _sym +t _r Or T as the final RTD value in the sample cell _RTD ＝k _sym ·T _sym +n _r 。

Fig. 18 is a block diagram illustrating a structure of a base station according to an embodiment of the present disclosure.

Referring to fig. 18, a base station may include a base station receiver 1802, a base station transmitter 1803, and a base station processor 1801. The base station receiver 1802 and the base station transmitter 1803 may be referred to as transceivers. The base station receiver 1802, base station transmitter 1803, and base station processor 1801 may operate according to the communication methods of the base stations described above. However, the elements of the base station are not limited to the above examples. For example, a base station may include more or fewer elements (e.g., memory, etc.) than those described above. In addition, the base station receiver 1802, the base station transmitter 1803, and the base station processor 1801 may be implemented in the form of a single chip.

The base station receiver 1802 and the base station transmitter 1803 (or transceivers) may transmit signals to and receive signals from the UE. Here, the signal may include control information and data. To this end, the transceiver may include an RF transmitter for up-converting and amplifying the frequency of the transmitted signal and an RF receiver for low noise amplifying the received signal and down-converting the frequency. However, this is merely an exemplary embodiment of a transceiver, and the elements of a transceiver are not limited to RF transmitters and RF receivers.

In addition, the transceiver may receive signals through a radio channel, output signals to the base station processor 1801, and transmit signals output from the base station processor 1801 through the radio channel.

The memory (not shown) may store programs and data required for the operation of the base station. In addition, the memory may store control information or data included in a signal obtained from the base station. The memory may include storage media such as ROM, RAM, hard disk, CD-ROM, and DVD or a combination of storage media.

The base station processor 1801 may control a series of processes so that the base station operates according to the above-described embodiments of the present disclosure. The base station processor 1801 may be implemented as a controller or one or more processors.

Fig. 19 is a block diagram illustrating a structure of a UE according to an embodiment of the present disclosure.

Referring to fig. 19, a UE may include a UE receiver 1902, a UE transmitter 1903, and a UE processor 1901. The UE receiver 1902 and the UE transmitter 1903 may be referred to as transceivers. The UE receiver 1902, the UE transmitter 1903, and the UE processor 1901 may operate according to the UE communication methods described above. However, elements of the UE are not limited to the above examples. For example, the UE may include more or fewer elements (e.g., memory, etc.) than those described above. Further, the UE receiver 1902, the UE transmitter 1903, and the UE processor 1901 may be implemented in the form of a single chip.

The UE receiver 1902 and the UE transmitter 1903 (or transceiver) may transmit signals to and receive signals from a base station. Here, the signal may include control information and data. To this end, the transceiver may include an RF transmitter for up-converting and amplifying the frequency of the transmitted signal and an RF receiver for low noise amplifying the received signal and down-converting the frequency. However, this is merely an exemplary embodiment of a transceiver, and the elements of a transceiver are not limited to RF transmitters and RF receivers.

In addition, the transceiver may receive signals through a wireless channel, output the signals to the UE processor 1901, and transmit the signals output from the UE processor 1901 through the wireless channel.

The memory (not shown) may store programs and data required for the operation of the UE. In addition, the memory may store control information or data included in a signal obtained from the UE. The memory may include storage media such as ROM, RAM, hard disk, CD-ROM, and DVD or a combination of storage media.

The UE processor 1901 may control a series of processes so that the UE may operate according to the above-described embodiments of the present disclosure. The UE processor 1901 may be implemented as a controller or one or more processors.

In the above detailed embodiments of the present disclosure, elements included in the present disclosure are expressed in singular or plural according to the presented detailed embodiments. However, for convenience of description, a singular form or a plural form is appropriately selected for the presented case, and the present disclosure is not limited to the elements expressed in the singular or the plural. Accordingly, an element expressed in a plurality of numbers may include a single element, or an element expressed in a singular may include a plurality of elements.

Although particular embodiments have been described in the detailed description of the disclosure, various modifications and changes can be made thereto without departing from the scope of the disclosure. Accordingly, the scope of the disclosure should not be defined as limited to the embodiments but should be defined by the appended claims and equivalents thereof.

Claims (15)

1. A terminal of a communication system, the terminal comprising:

a transceiver; and

the controller is used for controlling the operation of the controller,

wherein the controller is configured to:

generating a preamble signal;

transmitting the preamble signal to a base station; and

receiving a random access response from the base station in response to the transmission of the preamble signal, the random access response including timing advance, TA, information, and

Wherein the preamble signal comprises a first signal portion associated with a first sequence, a guard time, and a second signal portion associated with a second sequence.

2. The terminal of claim 1, wherein the timing advance is determined based on a round trip delay RTD measured from the preamble signal,

wherein the RTD is determined based on a first delay time determined from the first signal portion and a second delay time determined from the second signal portion,

wherein the first delay time is determined based on a cyclic correlation between a first correlation signal and a signal received in a first window based on the length of the first signal portion, an

Wherein the second delay time is determined based on a cyclic correlation between a second correlation signal and signals received in one or more second windows based on the first delay time.

3. The terminal of claim 1, wherein the controller is further configured to: obtaining a root index set associated with the first sequence and a root index set associated with the second sequence,

wherein the first sequence is generated based on a root index randomly selected from the set of root indices associated with the first sequence, and

Wherein the second sequence is generated based on a root index randomly selected from the set of root indices associated with the second sequence.

4. The terminal of claim 1, wherein the first signal portion comprises a first cyclic prefix CP and one or more symbols comprising the first sequence, and

wherein the second signal portion comprises a second CP and one symbol comprising the second sequence.

5. The terminal of claim 1, wherein the length of the guard time is determined according to a pre-configured length or a length of the first signal portion.

6. The terminal of claim 1, wherein the first sequence and the second sequence are generated based on a same root index and have different cyclic shifts.

7. The terminal of claim 1, wherein the length of the first signal portion is determined based on a maximum round trip delay, RTD, or delay spread of a cell.

8. A base station of a communication system, the base station comprising:

a transceiver; and

the controller is used for controlling the operation of the controller,

wherein the controller is configured to:

receiving a preamble signal from a terminal; and

transmitting a random access response including timing advance, TA, information to the terminal in response to the receiving of the preamble signal, and

Wherein the preamble signal comprises a first signal portion associated with a first sequence, a guard time, and a second signal portion associated with a second sequence.

9. The base station of claim 8, wherein the timing advance is determined based on a round trip delay RTD measured from the preamble signal,

wherein the RTD is determined based on a first delay time determined from the first signal portion and a second delay time determined from the second signal portion,

wherein the first delay time is determined based on a cyclic correlation between a first correlation signal and a signal received in a first window based on the length of the first signal portion, an

Wherein the second delay time is determined based on a cyclic correlation between a second correlation signal and signals received in one or more second windows based on the first delay time.

10. The base station of claim 8, wherein the controller is further configured to: obtaining a root index set associated with the first sequence and a root index set associated with the second sequence,

wherein the first sequence is generated based on a root index randomly selected from the set of root indices associated with the first sequence, and

Wherein the second sequence is generated based on a root index randomly selected from the set of root indices associated with the second sequence.

11. The base station of claim 8, wherein the first signal portion comprises a first cyclic prefix CP and one or more symbols comprising the first sequence, and

wherein the second signal portion comprises a second CP and one symbol comprising the second sequence.

12. The base station of claim 8, wherein the length of the guard time is determined based on a pre-configured length or a length of the first signal portion.

13. The base station of claim 8, wherein the first and second sequences are generated based on a same root index and have different cyclic shifts, an

Wherein the length of the first signal portion is determined based on a maximum round trip delay, RTD, or delay spread of the cell.

14. A method performed by a terminal of a communication system, the method comprising:

generating a preamble signal;

transmitting the preamble signal to a base station; and

receiving a random access response from the base station in response to the transmission of the preamble signal, the random access response including timing advance, TA, information, and

Wherein the preamble signal comprises a first signal portion associated with a first sequence, a guard time, and a second signal portion associated with a second sequence.

15. A method performed by a base station of a communication system, the method comprising:

receiving a preamble signal from a terminal; and

transmitting a random access response including timing advance, TA, information to the terminal in response to the receiving of the preamble signal, and

wherein the preamble signal comprises a first signal portion associated with a first sequence, a guard time, and a second signal portion associated with a second sequence.