KR20230007224A - Random access control method, and base station - Google Patents

Abstract

Embodiments of the present invention may provide a random access control method and a base station. Specifically, a random access control method and base station, which can increase resource use efficiency by allocating a preamble resource according to service quality and priority, can be provided. Especially, the embodiments may provide the random access control method and the base station which can solve the congestion for large-scale activation since the base station estimates the number of active terminals based on the number of idle preambles to allocate a preamble resource according to service quality and priority and adjust a transmission probability.

Description

Random access control method and base station {RANDOM ACCESS CONTROL METHOD, AND BASE STATION}

The present embodiments relate to a random access control method and a base station.

Recently, the Internet has evolved from a human-centered connection network in which humans generate and consume information to an Internet of Things (IoT) network in which information is exchanged between distributed components such as objects and processed. In order to implement IoT, technical elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, sensor networks for connection between objects and machine to machine , M2M), and MTC (Machine Type Communication) technologies are being studied. In particular, various attempts are being made to apply the 5G communication system to the IoT network. In addition, as the demand from the mobile Internet and Internet of Things increases, the increase in mobile traffic will increase almost 1000 times by 2020 compared to 2010 (4G era), and the number of user equipment connections will exceed 17 billion. can be expected to Such a large-scale connection can cause many problems due to various characteristics of periodicity, delay importance, and quality of service (QoS) requirements, as well as tremendous scalability.

A random access procedure (RAP) is the first step for most devices to connect to a base station, and may be an important method for establishing a connection with a base station. In particular, major transformations may be required in random access procedures for cellular IoT as the amount of connected devices far exceeds human-centric connectivity in legacy networks. In addition, the random access procedure may support a wireless access method in a medium access control layer for the Internet of Things. However, while the random access procedure restricts access according to the access class of IoT devices, it does not support preamble resource allocation according to the quality of service (QoS) of the access group. there is.

Therefore, there is a need for a random access control method and apparatus capable of improving resource use efficiency by allocating preamble resources according to service quality and priority of IoT devices.

Against this background, the present embodiments are to provide a random access control method and a base station capable of improving resource use efficiency by allocating preamble resources according to service quality and priority.

In one aspect, the present embodiments are a method for a base station to control random access communication of a terminal, including a group generation step of generating a plurality of non-overlapping preamble groups to divide usable preambles according to priority information, time slots estimating the number of active terminals corresponding to each preamble group based on the number of idle preambles for each preamble group; and calculating the service rate for each terminal based on the estimated number of active terminals in each time slot. It is possible to provide a random access method including a preamble allocation step of setting weights for priority information and dynamically allocating the number of preambles for a preamble group using the weights.

In another aspect, the present embodiments generate a plurality of non-overlapping preamble groups to divide usable preambles according to priority information in a base station controlling random access communication, and the number of idle preambles per time slot The number of active terminals corresponding to each preamble group is estimated based on, a service rate for each terminal is calculated based on the estimated number of active terminals in each time slot, and weights for priority information are set. A control unit for dynamically allocating the number of preambles for a preamble group using , a transmitter for transmitting the transmission probability calculated by the number of preambles to at least one or more terminals, and a receiver for receiving a random access preamble from the terminal. It is possible to provide a random access method that does.

According to the present embodiments, it is possible to provide a random access control method and a base station capable of improving resource use efficiency by allocating preamble resources according to service quality and priority.

1 is a diagram schematically illustrating the structure of an NR wireless communication system to which this embodiment can be applied.
2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.
3 is a diagram for explaining a resource grid supported by a radio access technology to which this embodiment can be applied.
4 is a diagram for explaining a bandwidth part supported by a radio access technology to which this embodiment can be applied.
5 is a diagram exemplarily illustrating a synchronization signal block in a radio access technology to which this embodiment can be applied.
6 is a diagram for explaining a random access procedure in a radio access technology to which this embodiment can be applied.
7 is a diagram for explaining CORESET.
8 is a diagram for explaining an operation of a base station according to the present embodiment.
9 is a diagram for explaining the configuration of a base station according to the present embodiment.
10 is a diagram for explaining a system model according to the present embodiment.
11 is a diagram for explaining a network scenario according to the present embodiment.
12 is a diagram for explaining a first algorithm for preamble allocation according to this embodiment.
13 is a diagram for explaining a second algorithm for preamble allocation according to the present embodiment.
14 is a diagram for explaining a third algorithm for preamble allocation according to this embodiment.
15 is a diagram for explaining an average access delay with respect to a service rate for each terminal according to the present embodiment.
16 is a diagram for explaining the performance of the first algorithm according to the present embodiment.
17 is a diagram for explaining the performance of the second algorithm according to the present embodiment.
18 is a diagram for explaining the performance of the third algorithm according to this embodiment.

DETAILED DESCRIPTION Some embodiments of the present disclosure are described in detail below with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present embodiments, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present technical idea, the detailed description may be omitted. When "comprises", "has", "consists of", etc. mentioned in this specification is used, other parts may be added unless "only" is used. In the case where a component is expressed in the singular, it may include the case of including the plural unless otherwise explicitly stated.

Also, terms such as first, second, A, B, (a), and (b) may be used in describing the components of the present disclosure. These terms are only used to distinguish the component from other components, and the nature, sequence, order, or number of the corresponding component is not limited by the term.

In the description of the positional relationship of components, when it is described that two or more components are "connected", "coupled" or "connected", the two or more components are directly "connected", "coupled" or "connected". "It may be, but it will be understood that two or more components and other components may be further "interposed" and "connected", "coupled" or "connected". Here, other components may be included in one or more of two or more components that are “connected”, “coupled” or “connected” to each other.

In the description of the temporal flow relationship related to components, operation methods, production methods, etc., for example, "after", "continued to", "after", "before", etc. Alternatively, when a flow sequence relationship is described, it may also include non-continuous cases unless “immediately” or “directly” is used.

On the other hand, when a numerical value or corresponding information (eg, level, etc.) for a component is mentioned, even if there is no separate explicit description, the numerical value or its corresponding information is not indicated by various factors (eg, process factors, internal or external shocks, noise, etc.) may be interpreted as including an error range that may occur.

A wireless communication system in the present specification refers to a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The present embodiments disclosed below may be applied to wireless communication systems using various wireless access technologies. For example, the present embodiments include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and singlecarrier frequency division multiple access (SC-FDMA). Alternatively, it may be applied to various radio access technologies such as non-orthogonal multiple access (NOMA). In addition, wireless access technology may mean not only a specific access technology, but also a communication technology for each generation established by various communication consultative organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA may be implemented as a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced datarates for GSM evolution (EDGE). OFDMA may be implemented with a wireless technology such as institute of electrical and electronic engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e, and provides backward compatibility with a system based on IEEE 802.16e. UTRA is part of the universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) that uses evolved-UMTSterrestrial radio access (E-UTRA). Adopt FDMA. As such, the present embodiments may be applied to currently disclosed or commercialized radio access technologies, and may also be applied to radio access technologies currently under development or to be developed in the future.

Meanwhile, a terminal in the present specification is a comprehensive concept meaning a device including a wireless communication module that communicates with a base station in a wireless communication system, and includes WCDMA, LTE (Long Term Evolution), NR (New Radio), HSPA, and IMT. -Including UE (User Equipment) in 2020 (5G or New Radio), MS (Mobile Station), UT (User Terminal), SS (Subscriber Station), wireless device in GSM, etc. concept should be interpreted. In addition, the terminal may be a user portable device such as a smart phone depending on the type of use, or may mean a vehicle or a device including a wireless communication module in the vehicle in the V2X communication system. In addition, in the case of a machine type communication system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module to perform machine type communication.

A base station or cell in this specification refers to an end that communicates with a terminal in terms of a network, and includes Node-B (Node-B), eNB (evolved Node-B), gNB (gNode-B), LPN (Low Power Node), Sector, site, various types of antennas, base transceiver system (BTS), access point, point (e.g. transmission point, reception point, transmission/reception point), relay node ), mega cell, macro cell, micro cell, pico cell, femto cell, remote radio head (RRH), radio unit (RU), and small cell. Also, a cell may mean including a bandwidth part (BWP) in the frequency domain. For example, the serving cell may mean the activation BWP of the terminal.

Since there is a base station controlling one or more cells in the various cells listed above, the base station can be interpreted in two meanings. 1) In relation to the radio area, it may be a device itself that provides a mega cell, macro cell, micro cell, pico cell, femto cell, or small cell, or 2) it may indicate the radio area itself. In 1), all devices providing a predetermined radio area are controlled by the same entity or all devices interacting to form a radio area cooperatively are directed to the base station. A point, transmission/reception point, transmission point, reception point, etc., according to a configuration method of a radio area, becomes an embodiment of a base station. In 2), the radio area itself in which signals are received or transmitted may be indicated to the base station from the viewpoint of the user terminal or the neighboring base station.

In this specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission/reception point or a coverage of a signal transmitted from a transmission/reception point (transmission point or transmission/reception point), and the transmission/reception point itself. can

Uplink (UL, or uplink) means a method of transmitting and receiving data from a terminal to a base station, and downlink (DL, or downlink) means a method of transmitting and receiving data from a base station to a terminal do. Downlink may mean communication or a communication path from multiple transmission/reception points to a terminal, and uplink may mean communication or communication path from a terminal to multiple transmission/reception points. In this case, in the downlink, the transmitter may be a part of a multi-transmission/reception point, and the receiver may be a part of a terminal. Also, in uplink, a transmitter may be a part of a terminal, and a receiver may be a part of a multi-transmission/reception point.

In uplink and downlink, control information is transmitted and received through control channels such as a physical downlink control channel (PDCCH) and a physical uplink control channel (PUCCH), and a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH). It configures the same data channel to transmit and receive data. Hereinafter, a situation in which signals are transmitted and received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH may be expressed as 'transmitting and receiving PUCCH, PUSCH, PDCCH, and PDSCH'.

For clarity of explanation, 3GPP LTE/LTE-A/NR (New RAT) communication system is mainly described in the following technical idea, but the technical features are not limited to the corresponding communication system.

3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next-generation wireless access technology after research on 4G (4th-Generation) communication technology. Specifically, 3GPP develops a new NR communication technology separate from LTE-A pro and 4G communication technology, which has improved LTE-Advanced technology to meet the requirements of ITU-R as a 5G communication technology. Both LTE-A pro and NR refer to 5G communication technology. Hereinafter, 5G communication technology will be described focusing on NR when a specific communication technology is not specified.

Operating scenarios in NR defined various operating scenarios by adding consideration to satellites, automobiles, and new verticals in the existing 4G LTE scenarios. It is deployed in the range to support mMTC (Massive Machine Communication) scenarios that require low data rates and asynchronous access, and URLLC (Ultra Reliability and Low Latency) scenarios that require high responsiveness and reliability and can support high-speed mobility. .

In order to satisfy this scenario, NR discloses a wireless communication system to which a new waveform and frame structure technology, low latency technology, mmWave support technology, and forward compatible technology are applied. In particular, the NR system proposes various technical changes in terms of flexibility in order to provide forward compatibility. The main technical features of NR are described below with reference to the drawings.

<NR System General>

1 is a diagram schematically showing the structure of an NR system to which this embodiment can be applied.

Referring to FIG. 1, the NR system is divided into 5GC (5G Core Network) and NR-RAN parts, and NG-RAN controls the user plane (SDAP / PDCP / RLC / MAC / PHY) and UE (User Equipment) It consists of gNBs and ng-eNBs providing plane (RRC) protocol termination. The gNB mutual or gNB and ng-eNB are interconnected through the Xn interface. gNB and ng-eNB are each connected to 5GC through NG interface. 5GC may include an Access and Mobility Management Function (AMF) in charge of a control plane such as terminal access and mobility control functions, and a User Plane Function (UPF) in charge of a control function for user data. NR includes support for both frequency bands below 6 GHz (FR1, Frequency Range 1) and above 6 GHz frequency band (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to a terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to a terminal. The base station described in this specification should be understood as encompassing gNB and ng-eNB, and may be used to refer to gNB or ng-eNB separately as needed.

<NR wave form, numerology and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with multiple input multiple output (MIMO) and has the advantage of using a low-complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, latency, coverage, etc. are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through a frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing radio resources based on a plurality of different numerologies has been proposed.

Specifically, the NR transmission numerology is determined based on the sub-carrier spacing and cyclic prefix (CP), and as shown in Table 1 below, the μ value is used as an exponent of 2 based on 15 kHz, changed adversely.

μ subcarrier spacing Cyclic prefix Supported for data Supported for synch 0 15 Normal Yes Yes One 30 Normal Yes Yes 2 60 Normal, Extended Yes No 3 120 Normal Yes Yes 4 240 Normal No Yes

As shown in Table 1 above, the numerology of NR can be classified into five types according to the subcarrier spacing. This is different from the fact that the subcarrier interval of LTE, which is one of 4G communication technologies, is fixed at 15 kHz. Specifically, in NR, subcarrier intervals used for data transmission are 15, 30, 60, and 120 kHz, and subcarrier intervals used for synchronization signal transmission are 15, 30, 120, and 240 kHz. In addition, the extended CP is applied only to the 60 kHz subcarrier spacing. Meanwhile, a frame structure in NR is defined as a frame having a length of 10 ms composed of 10 subframes having the same length of 1 ms. One frame may be divided into half frames of 5 ms, and each half frame includes 5 subframes. In the case of a 15 kHz subcarrier spacing, one subframe consists of one slot, and each slot consists of 14 OFDM symbols.

2 is a diagram for explaining a frame structure in an NR system to which this embodiment can be applied.

Referring to FIG. 2, a slot is fixedly composed of 14 OFDM symbols in the case of a normal CP, but the length of the slot in the time domain may vary according to the subcarrier interval. For example, in the case of a numerology having a 15 kHz subcarrier interval, a slot is 1 ms long and has the same length as a subframe. In contrast, in the case of numerology having a 30 kHz subcarrier interval, a slot is composed of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5 ms. That is, subframes and frames are defined with a fixed time length, and slots are defined by the number of symbols, and the time length may vary according to subcarrier intervals.

Meanwhile, NR defines a basic unit of scheduling as a slot, and introduces a mini-slot (or sub-slot or non-slot based schedule) to reduce transmission delay in a radio section. When a wide subcarrier interval is used, the length of one slot is shortened in inverse proportion to a transmission delay in a radio section. Mini-slots (or sub-slots) are for efficient support of URLLC scenarios and can be scheduled in units of 2, 4, or 7 symbols.

Also, unlike LTE, NR defines uplink and downlink resource allocation at the symbol level within one slot. In order to reduce HARQ delay, a slot structure capable of directly transmitting HARQ ACK/NACK within a transmission slot has been defined, and this slot structure is named and described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported through a combination of various slots. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols of a slot are set to uplink, and a slot structure in which downlink symbols and uplink symbols are combined are supported. NR also supports that data transmissions are distributed and scheduled over one or more slots. Therefore, the base station can inform the terminal whether the slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI). The base station may indicate the slot format by indicating the index of the table configured through UE-specific RRC signaling using SFI, dynamically indicating through DCI (Downlink Control Information), or static or static through RRC. It can also be given quasi-statically.

<NR physical resources>

Regarding physical resources in NR, antenna ports, resource grids, resource elements, resource blocks, bandwidth parts, etc. are considered do.

An antenna port is defined such that the channel on which a symbol on an antenna port is carried can be inferred from the channel on which other symbols on the same antenna port are carried. Two antenna ports are quasi co-located or QC/QCL (quasi co-located or quasi co-location). Here, the wide range characteristics include one or more of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram for explaining a resource grid supported by a radio access technology to which this embodiment can be applied.

Referring to FIG. 3 , since NR supports a plurality of numerologies in the same carrier, a resource grid may exist according to each numerology. Also, resource grids may exist according to antenna ports, subcarrier intervals, and transmission directions.

A resource block consists of 12 subcarriers and is defined only in the frequency domain. Also, a resource element is composed of one OFDM symbol and one subcarrier. Accordingly, as shown in FIG. 3, the size of one resource block may vary according to the subcarrier interval. In addition, in NR, “Point A”, which serves as a common reference point for the resource block grid, and common resource blocks and virtual resource blocks are defined.

4 is a diagram for explaining a bandwidth part supported by a radio access technology to which this embodiment can be applied.

In NR, unlike LTE where the carrier bandwidth is fixed at 20Mhz, the maximum carrier bandwidth is set from 50Mhz to 400Mhz for each subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in NR, as shown in FIG. 4, a bandwidth part (BWP) can be designated and used by a UE within a carrier bandwidth. In addition, the bandwidth part is associated with one numerology, is composed of a subset of consecutive common resource blocks, and can be dynamically activated according to time. Up to four bandwidth parts each of uplink and downlink are configured in the terminal, and data is transmitted and received using the active bandwidth part at a given time.

In the case of paired spectrum, the uplink and downlink bandwidth parts are set independently, and in the case of unpaired spectrum, to prevent unnecessary frequency re-tuning between downlink and uplink operations. For this purpose, the bandwidth parts of downlink and uplink are paired to share a center frequency.

<NR initial connection>

In NR, a UE accesses a base station and performs a cell search and random access procedure to perform communication.

Cell search is a procedure in which a UE synchronizes with a cell of a corresponding base station using a synchronization signal block (SSB) transmitted by the base station, acquires a physical layer cell ID, and obtains system information.

5 is a diagram exemplarily illustrating a synchronization signal block in a radio access technology to which this embodiment can be applied.

Referring to FIG. 5, the SSB consists of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) occupying 1 symbol and 127 subcarriers, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

The UE receives the SSB by monitoring the SSB in the time and frequency domains.

SSB can be transmitted up to 64 times in 5 ms. A plurality of SSBs are transmitted in different transmission beams within 5 ms, and the UE performs detection assuming that SSBs are transmitted every 20 ms period based on one specific beam used for transmission. The number of beams usable for SSB transmission within 5ms may increase as the frequency band increases. For example, up to 4 SSB beams can be transmitted below 3 GHz, SSBs can be transmitted using up to 8 different beams in a frequency band of 3 to 6 GHz, and up to 64 different beams in a frequency band of 6 GHz or higher.

Two SSBs are included in one slot, and the start symbol and the number of repetitions within the slot are determined according to the subcarrier interval as follows.

On the other hand, SSB is not transmitted at the center frequency of the carrier bandwidth, unlike SS of conventional LTE. That is, the SSB can be transmitted even in a place other than the center of the system band, and a plurality of SSBs can be transmitted in the frequency domain when wideband operation is supported. Accordingly, the UE monitors the SSB using a synchronization raster that is a candidate frequency location for monitoring the SSB. The carrier raster and synchronization raster, which are the center frequency location information of the channel for initial access, are newly defined in NR, and the synchronization raster has a wider frequency interval than the carrier raster, so it can support fast SSB search of the terminal. can

The UE may acquire the MIB through the PBCH of the SSB. MIB (Master Information Block) includes minimum information for the terminal to receive the remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, the PBCH includes information about the position of the first DM-RS symbol in the time domain, information for monitoring SIB1 by the UE (eg, SIB1 numerology information, information related to SIB1 CORESET, search space information, PDCCH related parameter information, etc.), offset information between the common resource block and the SSB (the location of the absolute SSB within the carrier is transmitted through SIB1), and the like. Here, the SIB1 numerology information is equally applied to some messages used in the random access procedure for accessing the base station after the UE completes the cell search procedure. For example, the numerical information of SIB1 may be applied to at least one of messages 1 to 4 for a random access procedure.

The aforementioned RMSI may mean System Information Block 1 (SIB1), and SIB1 is periodically (eg, 160 ms) broadcast in a cell. SIB1 includes information necessary for the terminal to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the terminal to receive SIB1, it needs to receive numerology information used for SIB1 transmission and CORESET (Control Resource Set) information used for SIB1 scheduling through the PBCH. The UE checks scheduling information for SIB1 using the SI-RNTI in CORESET, and acquires SIB1 on PDSCH according to the scheduling information. The remaining SIBs except for SIB1 may be transmitted periodically or may be transmitted according to the request of the terminal.

6 is a diagram for explaining a random access procedure in a radio access technology to which this embodiment can be applied.

Referring to FIG. 6, when cell search is completed, the terminal transmits a random access preamble for random access to the base station. The random access preamble is transmitted through PRACH. Specifically, the random access preamble is transmitted to the base station through a PRACH composed of contiguous radio resources in a periodically repeated specific slot. In general, when a UE initially accesses a cell, a contention-based random access procedure is performed, and when random access is performed for beam failure recovery (BFR), a non-contention-based random access procedure is performed.

The terminal receives a random access response to the transmitted random access preamble. The random access response may include a random access preamble identifier (ID), UL Grant (uplink radio resource), temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier), and TAC (Time Alignment Command). Since one random access response may include random access response information for one or more terminals, the random access preamble identifier may be included to indicate to which terminal the included UL Grant, temporary C-RNTI, and TAC are valid. The random access preamble identifier may be an identifier for the random access preamble received by the base station. The TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, a random access-radio network temporary identifier (RA-RNTI).

Upon receiving a valid random access response, the terminal processes information included in the random access response and performs scheduled transmission to the base station. For example, the UE applies TAC and stores the temporary C-RNTI. In addition, data stored in the buffer of the terminal or newly generated data is transmitted to the base station using the UL grant. In this case, information capable of identifying the terminal must be included.

Finally, the terminal receives a downlink message for contention resolution.

<NR CORESET>

The downlink control channel in NR is transmitted in a CORESET (Control Resource Set) having a length of 1 to 3 symbols, and transmits up/down scheduling information, SFI (Slot Format Index), TPC (Transmit Power Control) information, etc. .

In this way, NR introduced the CORESET concept to secure system flexibility. CORESET (Control Resource Set) means time-frequency resources for downlink control signals. The UE may decode the control channel candidate using one or more search spaces in the CORESET time-frequency resource. A Quasi CoLocation (QCL) assumption for each CORESET is set, which is used for the purpose of notifying the characteristics of the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are characteristics assumed by the conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7 , a CORESET may exist in various forms within a carrier bandwidth within one slot, and a CORESET may consist of up to three OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of 6 resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration to allow additional configuration and system information to be received from the network. After establishing a connection with the base station, the terminal may receive and configure one or more CORESET information through RRC signaling.

In this specification, a frequency, frame, subframe, resource, resource block, region, band, subband, control channel, data channel, synchronization signal, various reference signals, various signals, or various messages related to NR (New Radio) can be interpreted in various meanings used in the past or currently used or in the future.

8 is a diagram for explaining an operation of a base station according to the present embodiment.

Referring to FIG. 8 , a method for controlling random access communication by a base station according to the present embodiment may include a group generating step of generating a plurality of non-overlapping preamble groups (S810). For example, a base station controlling random access communication may dynamically divide usable random access preambles by generating a plurality of non-overlapping preamble groups. In addition, the UE may be classified into different priority information according to requirements, and the UE may start a random access procedure by selecting a random access preamble. Accordingly, terminals having different priority information may be provided with different chances of succeeding in a random access procedure (RAP).

A method for controlling random access communication by a base station according to an embodiment may include a step of estimating the number of active terminals corresponding to each preamble group (S820). For example, a base station controlling random access communication may estimate the number of active terminals corresponding to each preamble group based on the number of idle preambles for each time slot. For example, a base station controlling random access communication calculates a probability that a preamble is in an idle state for an active terminal by using Bayesian estimation in each time slot, and at the end of the time slot, a posteriori for the active terminal is calculated. distribution can be estimated. In addition, the base station controlling random access communication may calculate a change in the number of active terminals by subtracting the number of active terminals estimated in the previous time slot from the average of the posterior distribution updated for each time slot. In addition, the base station may update the number of active terminals for each time slot based on the calculated amount of change.

For another example, a base station controlling random access communication may calculate an access class barring (ACB) factor maximizing throughput for priority information based on the average number of successful preambles. And, the base station controlling random access communication can estimate the number of active terminals for priority information using the ACB factor. Specifically, the base station controlling random access communication calculates the maximum value of the average number of successful preambles using the ACB factor, and calculates the maximum value of the average number of successful preambles to the number of active terminals according to the priority information. A service rate for each terminal may be calculated. Here, the average number of successful preambles may be calculated by calculating a probability that transmission of a specific preamble succeeds for the number of active terminals having specific priority information. Also, the ACB factor may be updated according to the change in the estimated number of active terminals and allocated preambles for each time slot.

For another example, the base station controlling random access communication may change the number of active terminals using a boosting factor when the estimated number of active terminals increases in consecutive time slots. A boosting factor may be used to reflect the addition of a new active terminal. Specifically, when the number of active terminals increases in consecutive time slots, the base station controlling random access communication may multiply the number of active terminals by a boosting factor and add the number to the existing number of active terminals. On the other hand, if the number of active terminals does not increase, the boosting factor may be set to 0 to maintain the number of existing active terminals.

A method for controlling random access communication by a base station according to an embodiment may include a preamble allocation step of dynamically allocating the number of preambles based on the estimated number of active terminals in each time slot (S830). For example, a base station controlling random access communication may set a weight for priority information by calculating a service rate for each terminal based on the estimated number of active terminals in each time slot. And, the base station controlling the random access communication may dynamically allocate the number of preambles to the preamble group using the set weight. For example, a base station controlling random access communication may allocate a limited total number of preambles to each preamble group linearly proportional to the number of active terminals and their weights. For another example, the base station controlling random access communication may calculate the number of reference preambles for maintaining the service rate for each terminal, and sequentially allocate the number of preambles from a preamble group having higher priority information based on the number of reference preambles. there is. However, if the number of remaining preambles is less than the reference number of preambles, the number of remaining preambles may be allocated in proportion to the number of active terminals and weights. Here, the reference number of preambles may be calculated using the minimum service rate per terminal for priority information required to satisfy a specific delay condition and the number of active terminals.

9 is a diagram for explaining the configuration of a base station according to the present embodiment.

Referring to FIG. 9 , a base station 1000 controlling random access communication according to the present embodiment may include a controller 910, a receiver 920, and a transmitter 930.

For example, the controller 910 may generate a plurality of non-overlapping preamble groups. For example, the control unit 910 may generate a plurality of non-overlapping preamble groups according to priority information in order to dynamically divide usable random access preambles. Accordingly, it is possible to provide success opportunities of different random access procedures (RAPs) for terminals having different priority information.

For example, the controller 910 may estimate the number of active terminals corresponding to each preamble group based on the number of idle preambles for each time slot. For example, the controller 910 calculates the probability that the preamble is in an idle state for an active terminal using Bayesian estimation in each time slot, and estimates a posterior distribution for the active terminal at the end of the time slot. can do. In addition, the controller 910 may calculate the amount of change in the number of active terminals by subtracting the number of active terminals estimated in the previous time slot from the average of the posterior distribution updated for each time slot. Also, the controller 910 may update the number of active terminals for each time slot based on the calculated amount of change.

For another example, the control unit 910 may estimate the number of active terminals for priority information by calculating an Access Class Barring (ACB) factor that maximizes throughput for priority information based on the average number of successful preambles. there is. Specifically, the controller 910 calculates the maximum value of the average number of successful preambles using the ACB factor, and uses the ratio of the maximum average value of the number of successful preambles to the number of active terminals to provide service for each terminal according to the priority information. rate can be calculated. Here, the average number of successful preambles may be calculated by calculating a probability that transmission of a specific preamble succeeds for the number of active terminals having specific priority information. Also, the ACB factor may be updated according to the change in the estimated number of active terminals and allocated preambles for each time slot.

For another example, when the estimated number of active terminals increases in consecutive time slots, the controller 910 may change the number of active terminals using a boosting factor. A boosting factor may be used to reflect the addition of a new active terminal. Specifically, when the number of active terminals increases in consecutive time slots, the controller 910 may multiply the number of active terminals by a boosting factor and add the number to the number of existing active terminals. On the other hand, if the number of active terminals does not increase, the boosting factor may be set to 0 to maintain the number of existing active terminals.

For example, the controller 910 may dynamically allocate the number of preambles based on the estimated number of active terminals in each time slot. For example, the controller 910 may set a weight for priority information by calculating a service rate for each terminal based on the number of active terminals estimated in each time slot. And, the control unit 910 can dynamically allocate the number of preambles to the preamble group using the set weight. Specifically, the control unit 910 may allocate the limited total number of preambles to each preamble group linearly proportional to the number of active terminals and their weights. Alternatively, the control unit 910 may calculate the number of reference preambles for maintaining the service rate for each terminal, and sequentially allocate the number of preambles from a preamble group having higher priority information based on the number of reference preambles. However, if the number of remaining preambles is less than the reference number of preambles, the number of remaining preambles may be allocated in proportion to the number of active terminals and weights. Here, the reference number of preambles may be calculated using the minimum service rate per terminal for priority information required to satisfy a specific delay condition and the number of active terminals.

For example, the receiving unit 920 may receive a random access preamble selected from the terminal. Also, the receiving unit 920 may receive a third message that is a connection establishment message from the terminal.

For example, the transmitter 930 may transmit the transmission probability calculated by the number of preambles to at least one or more terminals. For example, the transmission probability may be calculated based on the number of random access preambles allocated to the preamble group and the number of active terminals to perform random access communication. In addition, the transmitter 930 may transmit a random access response (RAR) message including an identifier of the random access preamble received from the terminal to the corresponding terminal. Here, the random access response message may include a timing command and an uplink resource. Also, the transmitter 930 may transmit a fourth message, which is a contention resolution message, to a terminal that has successfully transmitted the decoded third message. Here, the third message may be an RRC Connection Request Message transmitted for RRC connection establishment, and the fourth message may be a Connection Resolution Message.

In addition to this, the control unit 1020 controls the overall operation of the base station 1000 according to the operation of dividing the random access preamble and calculating the transmission probability by using a preset algorithm necessary for performing the present disclosure described above. can In addition, the receiving unit 920 and the transmitting unit 930 may be used to transmit/receive signals, messages, or data necessary for performing the above-described present disclosure to and from the terminal.

Hereinafter, a detailed operation in which a base station dynamically divides a random access preamble and calculates a transmission probability using a preset algorithm to control random access communication of a terminal will be described in detail with reference to the drawings. In addition, hereinafter, an access point (AP) may mean the aforementioned base station, and a machine type communication (MTC) device may mean the aforementioned terminal. However, this is an example for explanation, and the MTC device is not limited thereto as long as it is a device to which a random access method can be applied and wireless communication is possible.

10 is a diagram for explaining a system model according to the present embodiment.

Referring to FIG. 10, a system model in which a large-scale terminal connection is made according to the present embodiment can be described. For example, the system model may generalize priority information indexed by parameter i. In addition, the MTC device included in the system model can accommodate various services and application programs according to various requirements and priority information. Among them, some devices require immediate data transmission, while others may tolerate delay in data transmission. However, all devices may attempt a random access procedure through a limited number of preambles. Accordingly, a device requiring urgent data transmission may be classified as high priority information, and a device that allows periodic data transmission or delay may be classified as low priority information.

For example, the priority information may mean increasing as the value of parameter i decreases. That is, priority information indexed as 1 for parameter i may have a higher priority than priority information indexed as 2 for parameter i. As shown in FIG. 10, a UE having arbitrary priority information may be located in an arbitrary position in a cell. The number of active terminals with priority information i can be expressed as n _i for i = 1, 2, ..., N. Here, the active terminal may mean a device waiting for packet transmission. Such an active terminal may perform communication with the base station 1000 to realize cellular IoT.

이 될 수 있다. 여기서, M은 셀에서 경쟁 기반 랜덤 액세스 절차를 위해 사용 가능한 전체 프리앰블 수를 의미할 수 있다. M은 고정된 값이고, M_i 와 n_i는 시간에 따라 변경되는 값일 수 있다. 각 시간 슬롯은 5ms마다 주기적으로 나타날 수 있는 RACH(Random Access Channel)을 의미할 수 있다. 구체적인 예를 들면, LTE 와 5G-New Radio(NR)는 사용 가능한 전체 프리앰블 수는 64개로 제한될 수 있다. 일반적으로 기지국은 64개 중 일부 프리앰블을 경합 없는 랜덤 액세스 절차를 위해 사용할 수 있다. 3GPP 표준에서는 54개의 프리앰블이 경쟁 기반 랜덤 액세스 절차에 사용될 수 있다. For example, the system model may allocate a limited number of preambles in each time slot t according to priority information. For example, the system model allocates the number of preambles M _i for priority information i in each time slot t,

This can be. Here, M may mean the total number of preambles usable for a contention-based random access procedure in a cell. M is a fixed value, and M _i and n _i may be values that change over time. Each time slot may mean a Random Access Channel (RACH) that may periodically appear every 5 ms. For a specific example, LTE and 5G-New Radio (NR) may limit the total number of usable preambles to 64. In general, a base station may use some of the 64 preambles for a contention-free random access procedure. In the 3GPP standard, 54 preambles can be used for contention-based random access procedures.

For example, a system model may be modeled using various mathematical distributions for an activation operation of a terminal. For example, a system model may be modeled using a Poisson distribution for active terminals as a traffic model. The Poisson distribution is probably the most general method, as it can be characterized simply using the average arrival rate and has the property of having no memory. In addition, the system model may be modeled using a beta distribution and a uniform distribution as traffic models in addition to the Poisson distribution. In particular, the beta distribution can reflect bursts of new arrivals in a concentrated short period of time, making it suitable for large-scale system models. According to the 3GPP report, the beta distribution can model extreme scenarios where a large number of terminals attempt to access the network in a highly synchronized manner. For example, active terminals may be assumed to follow an exclusive distribution in order to consider large-scale connection activation in a short period of time. Equation 1 can express active terminals following an exclusive distribution with parameters α = 3 and β = 4.

이고, T_A는 활성화 기간을 의미할 수 있다. where B(α,β) is the beta function

, and T _A may mean an activation period.

11 is a diagram for explaining a network scenario according to the present embodiment.

Referring to FIG. 11 , the network scenario according to the present embodiment may be a structure in which a plurality of terminals send packets to a base station at the center of the network. At this time, the number of terminals to transmit packets may be changed in real time for each quality of service (Qos) or priority information. Accordingly, the UE can transmit the allocated preamble with the allocated transmission probability according to an algorithm to be described later. That is, FIG. 11 may be an example of a phenomenon in which the number of terminals is different according to each priority information and the allocated preamble is different accordingly. For example, the base station may divide available contention-based random access preambles into a plurality of non-overlapping preamble groups. In addition, the base station may provide different random access procedure success opportunities to terminals having different priority information based on the divided preamble groups. As a result, the UE can start the random access procedure by selecting a preamble only from preambles allocated to the mapped preamble group. For example, a terminal corresponding to high priority information may be a device having high delay sensitivity, such as a medical application or a disaster management application. On the other hand, a terminal corresponding to low-priority information may be a delay-tolerant device such as a smart sensor application. For another example, if the number of terminals corresponding to the high priority information is large, the throughput of the random access procedure may be low and the average delay may be high even though the number of preambles allocated to the priority information is larger. On the other hand, if the number of allocated preambles is too large when the number of terminals corresponding to high priority information is small, unnecessary congestion may occur in low priority information according to the limited total number of preambles. Accordingly, estimating the number of active terminals corresponding to each priority information by the base station according to the present embodiment may be an important method to improve the performance of the random access procedure by alleviating severe congestion.

12 is a diagram for explaining a first algorithm for preamble allocation according to this embodiment.

Referring to FIG. 12, a procedure for dynamically controlling the number of preambles by the first algorithm according to the present embodiment can be described. For example, the base station may dynamically control the number of preambles according to priority information using the first algorithm. For example, the base station may dynamically allocate the number of preambles by estimating the number of active terminals corresponding to each priority information changed over time using the first algorithm using Bayesian estimation.

For example, the base station may estimate the number of active terminals corresponding to each priority information. And, the base station may allocate the number of preambles for priority information based on the estimated number of active terminals in all time slots. For example, the base station can estimate the a posteriori distribution for the active terminal at the end of each time slot through the a priori distribution in the previous time slot t-1 and the distribution in the current time slot t using Bayesian estimation. Then, the posterior distribution can be applied to the next time slot t+1 as an updated prior distribution. Accordingly, the estimated number of active terminals may be continuously updated over time using recursive Bayesian estimation. Specifically, the distribution of active terminals may be approximated by applying a Poisson distribution to the probability of the number of active terminals in each time slot. The Poisson distribution can simplify the estimation process by using only the mean to determine the distribution. A Poisson distribution with an average probability v of the number n _i of active terminals corresponding to priority information i can be expressed as Equation 2.

And, n _i of the next time slot can be estimated by updating v for each time slot. Also, the binomial distribution can be another way of approximating the estimated distribution. However, in the case of a large scale, such as a large-scale connected system, it can converge to the Poisson distribution.

For another example, the base station may estimate the mean of the posterior distribution based on the number of idle preambles per time slot. An active UE may randomly select a preamble from preamble M _i mapped to priority information i. Accordingly, the probability that the active terminal selects the preamble may be 1/M _i . In addition, the probability that preamble I is in an idle state for an active terminal corresponding to priority information i can be expressed as Equation 3.

Here, P _e (I│M _i ) may mean a probability that preamble I among preambles M _i is not selected by active UE n _i . P(M _i -I) may mean a probability that at least one preamble among the remaining M _i -I is not selected. In addition, the joint probability of observing I idle preambles when there are n _i active terminals can be expressed as Equation 4.

As a result, the unconditional idle preamble probability for n _i can be expressed as Equation 5 by summing P(I,ni) for all possible n _i .

Also, when there are I idle preambles, the posterior distribution for ni active UEs can be expressed as Equation 6.

And, the mean of the posterior distribution can be expressed as Equation 7.

The mean E[n _i │M _i ] of the posterior distribution may be updated for each slot. In addition, the amount of change in the number of active terminals is calculated as the difference from the mean of the posterior distribution to the number v of active terminals estimated in the previous time slot, and can be expressed as Equation 8.

For example, the base station may classify priority information by calculating a service rate for each terminal based on the estimated number of active terminals. That is, high priority information may be accompanied by a high service rate for each terminal. For example, if there are n _i active terminals in priority information i, it can be assumed that the number of preambles allocated to the priority information is M _i . Then, the success probability of the k-th preamble can be expressed as Equation 9.

In addition, the corresponding joint probability can be expressed as Equation 10.

Here, the distribution of active terminals may be a Poisson distribution (φ _ni (v)) with an average v. Therefore, the success probability of the kth preamble can be expressed as Equation 11.

As a result, the throughput can be the average of the number of successful preambles in each time slot and can be expressed as Equation (12).

The service rate for each terminal can be expressed as in Equation 13 using the throughput.

를 설정할 수 있다. 즉, i 번째 우선 순위 정보의 단말 별 서비스율은 가중치

에 비례할 수 있다. 이는 수학식 14와 같이 표현할 수 있다. Accordingly, when the base station calculates the service rate for each terminal for each priority information, it can compare it with the priority information. Since high priority information has a high service rate per UE, the base station assigns a weight to the i-th priority information.

can be set. That is, the service rate for each terminal of the i-th priority information is

can be proportional to This can be expressed as in Equation 14.

으로 표현할 수 있다. 여기서,

는 우선 순위 정보에 대한 가중치로 실제 조건에 따라 설정되며, 변수 x는 비례 계수일 수 있다. Also, Equation 4 is

can be expressed as here,

Is a weight for the priority information and is set according to actual conditions, and the variable x may be a proportional coefficient.

Accordingly, the base station can calculate the number of preambles allocated for the i-th priority information. This can be expressed as in Equation 15.

Here, x is a proportionality coefficient and may be a value that satisfies Equation 16.

That is, the base station can control the number of preambles allocated to the priority information i by estimating the number of active terminals related to the priority information.

For example, it may be initially set so that all preambles usable in the first algorithm are uniformly distributed over all priority information. Also, the average number of active terminals may be initially set to be the same as the number of preambles allocated to the priority information. However, the initial setting may not affect the overall result of the first algorithm.

And, in the first algorithm, the number of active terminals may be updated based on the current number of idle preambles associated with each priority information. The number of active terminals may be changed by reflecting the addition and removal of terminals capable of successfully performing random access.

And, in the first algorithm, an increase in active terminals may be processed using a boosting factor ηi for the i-th priority information. If the number of active terminals is increased in successive time slots, the number of active terminals may be changed using a boosting factor.

And, in the first algorithm, the preamble distribution may be recalculated based on the updated number of active terminals. However, since it is practically difficult to re-allocate the preamble for each time slot, the period during which the preamble is re-allocated can be controlled by the parameter T _update .

And, in the first algorithm, the number of active terminals may be further updated by subtracting the average number of active terminals that have performed successful random access.

13 is a diagram for explaining a second algorithm for preamble allocation according to the present embodiment.

Referring to FIG. 13, a procedure for dynamically controlling the number of preambles by the second algorithm according to the present embodiment can be described. For example, the base station may dynamically control some active preamble numbers according to an access class barring (ACB) mechanism using the second algorithm. For example, the base station may restrict the terminal from attempting a random access procedure through an ACB mechanism. Then, the terminal may retry the random access procedure after waiting. Therefore, the ACB mechanism may be suitable for congestion control when the number of terminals is large. Specifically, in the ACB mechanism, an active terminal may generate a random number (q) between 0 and 1 and compare it with an ACB factor (p). If the ACB factor p is greater than the random number q, the terminal can select a random access preamble and proceed with the remaining random access procedures. On the other hand, if the ACB factor (p) is smaller than the random number (q), the random access procedure in the current time slot is blocked and can be tried again in the next time slot. Therefore, the base station can limit the number of terminals for the limited number of preambles by appropriately selecting the ACB factor (p). That is, the base station can independently allocate the ACB factor (p) to each priority information. In addition, the base station may estimate the number of active terminals and allocate the number of preambles for priority information considering the optimally controlled ACB factor (p).

For example, the base station may estimate the number of active terminals using an ACB factor for each priority information. For example, when the priority information i indicates the ACB factor p, the base station may express the probability that I idle preambles are observed in n _i active terminals as shown in Equation 17.

In addition, Equation 17 can be expressed as Equation 18 by applying the Bayesian rule.

When the estimated distribution of n _i follows the Poisson distribution with mean v, the mean of the posterior distribution can be expressed as Equation 19.

Here, Ep[n _i │I] may mean an estimated average of the number of active terminals of priority information i. In addition, the probability that n _i active terminals having priority information i can successfully transmit the k th preamble can be expressed as Equation 20.

And, the unconditional success probability of the k-th preamble for n _i can be expressed as Equation 21.

In addition, the base station can calculate the average of the number of successful preambles that can effectively represent the throughput for priority information i. The average number of successful preambles can be expressed as Equation 22.

The base station may calculate an ACB factor (p*) that maximizes throughput for priority information i. The ACB factor (p*) can be expressed as in Equation 23.

For example, the base station may estimate the number of active terminals for the priority information using the ACB factor. For example, the base station may calculate the average number of active terminals for priority information as shown in Equation 24 using the ACB factor (p*).

The average number of active terminals may be updated for each time slot based on the number of idle preambles and the number of allocated preambles. In particular, the difference value from the average active terminal estimated in the previous time slot can be expressed as Equation 25.

In addition, the maximum throughput can be expressed as in Equation 26 by applying the ACB factor (p*).

Accordingly, the base station can calculate the service rate for each terminal for the i-th priority information. The service rate for each terminal can be expressed as Equation 27.

In addition, the service rate for each terminal can be expressed as in Equation 28 by applying a weight corresponding to the priority information.

Accordingly, the number of preambles allocated to priority information i can be expressed as Equation 29.

In the contention-based random access procedure, the total number of preambles may be M. At this time, the total number of preambles M can be expressed as Equation 30 by M _i .

Here, the variable x can be expressed as in Equation 31.

The number of preambles for each priority information can be expressed as Equation 32.

That is, the base station may allocate the limited total number of preambles to each preamble group in linear proportion to the number of active terminals and their weights.

For a specific example, the base station may dynamically control the number of preambles for different priority information through an access class barring (ACB) mechanism through the second algorithm. The performance of the second algorithm may differ from that of the first algorithm.

A method of estimating the average number of active terminals in the second algorithm may be different from that of the first algorithm. That is, there is a difference in that the average number of active terminals in the second algorithm is updated through a simple algebraic calculation.

On the other hand, in the second algorithm, an increase in active terminals may be processed using a boosting factor ηi for the i-th priority information. This may be similar to the first algorithm.

And, in the second algorithm, preambles for different priority information can be reallocated by Equation 32. Also, in the second algorithm, the number of active terminals may be further updated by subtracting the average number of active terminals that have performed successful random access.

Finally, in the second algorithm, the ACB factor (p) can be updated as the number of preambles and active terminals changes in every time slot.

14 is a diagram for explaining a third algorithm for preamble allocation according to this embodiment.

Referring to FIG. 14, a procedure for dynamically controlling the number of preambles by the third algorithm according to the present embodiment can be described. For example, the base station may dynamically control the number of preambles according to a specific delay condition using the third algorithm. For example, the base station may allocate the number of preambles according to the minimum limiting condition for the service rate of each terminal. For example, UEs may have different delay tolerances. The limiting condition for this delay is important even in priority information, but it may be impossible to consider it independently due to limited resources. Accordingly, the base station may set the weight by reflecting the correlation between priority information and quality of service (QoS) through the third algorithm. The first and second algorithms set weights on priority information to calculate the service rate for each terminal, but the third algorithm may set weights by reflecting the correlation between priorities. On the other hand, the third algorithm may set a minimum limiting condition for the service rate of each terminal in order to satisfy a specific delay condition in each priority information. Specifically, s _i (i = 1, ..., N) may mean a minimum service rate for each terminal for priority information required to satisfy a specific delay condition. In the second algorithm, the number of preambles may be calculated as M _i =s _i v _i e in order to maintain a minimum service rate per UE. And in the third algorithm, the preamble may be allocated using the calculated number of preambles. That is, the base station allocates preambles sequentially from the highest priority information, but if the number of remaining preambles does not satisfy the minimum limiting condition, it can allocate preambles in proportion to the remaining priority information.

15 is a diagram for explaining an average access delay with respect to a service rate for each terminal according to the present embodiment.

로 주어지면, 프리앰블 수는 각각의 Si에 대해

를 사용하여 산출될 수 있다. 그리고, 각 단말은 M_i 개의 프리앰블 중 하나를 전송할 수 있다. Referring to FIG. 15 , simulation results to which the first and second algorithms according to the present embodiment are applied can be described. For example, the simulation result can be confirmed as an average access delay performance for service rates for each terminal. For example, according to the result of the simulation 1510 to which the first algorithm is applied, the higher the service rate for each terminal, the lower the average access delay performance. Also, the average delay may be similar even in the number of different terminals. Specifically, in the simulation 1510 to which the first algorithm is applied, the service rate for each terminal of the ith priority information is

Given that, the number of preambles is for each Si

can be calculated using And, each terminal can transmit one of M _i preambles.

로 주어지면, 프리앰블 수는

일 수 있다. 또한, ACB 인자는

로 설정될 수 있다. For another example, according to the result of the simulation 1520 to which the second algorithm is applied, the average delay may appear almost the same even in the number of different terminals. Specifically, in the simulation 1520 to which the second algorithm is applied, the service rate for each terminal is

Given that, the number of preambles is

can be Also, the ACB factor is

can be set to

Average delay curves in the simulation 1510 to which the first algorithm is applied and the simulation 1520 to which the second algorithm is applied may appear almost overlapped regardless of the presence or absence of the ACB mechanism. When the service rates for each terminal are 0.3, 0.5, and 0.7, the respective average access rates may be 3.3, 2.1, and 1.7. This is because the service rate for each terminal corresponds to each terminal. Accordingly, the service rate for each terminal may be appropriately calculated according to a given average delay performance by applying the results of the simulation 1510 to which the first algorithm is applied and the simulation 1520 to which the second algorithm is applied.

16 is a diagram for explaining the performance of the first algorithm according to the present embodiment.

Referring to FIG. 16 , simulation results applied to scenarios in which the first algorithm according to the present embodiment includes various priority information can be described. For example, the simulation result may be expressed as throughput performance for each priority information according to the first algorithm. At this time, it can be assumed that a new active terminal is added in a Poisson pattern in each priority information. Also, the total simulation time may be set to 105 time slots, T _update may be set to 1, and the total number of preambles may be set to 54. The weight for the priority information is set to r ₁ :r ₂ :r ₃ :r ₄ =4:3:2:1, and may be the reach rate of the corresponding terminal [4λ,3λ,2λ,1λ]. Here, λ can be regarded as a normalized reach rate. Specifically, simulation results show that the throughput of all algorithms is 0 as a result of severe congestion as λ is larger. As long as the number of active terminals is accurate, the throughput to which the first algorithm is applied can be moved to the maximum limit at the point corresponding to 93% of the throughput of the ideal algorithm (λ = 1.45).

17 is a diagram for explaining the performance of the second algorithm according to the present embodiment.

Referring to FIG. 17, simulation results to which the second algorithm according to the present embodiment is applied can be explained. As an Access Class Barring (ACB) mechanism is applied, the performance of the second algorithm may be significantly different from that of the first algorithm. Some number of active preambles can be dynamically controlled. For example, the simulation result may be expressed as throughput performance for each priority information according to the second algorithm. At this time, it can be confirmed that the throughput is stably maintained even after the saturation point. This may be because the ACB mechanism performs a congestion control function.

18 is a diagram for explaining the performance of the third algorithm according to this embodiment.

Referring to FIG. 18, simulation results to which the third algorithm according to the present embodiment is applied can be described. For example, the third algorithm may be an algorithm designed to maintain a service rate for each terminal in higher priority information. For example, the simulation result may be expressed as throughput performance for each priority information according to the third algorithm. At this time, the simulation may set service rates for each terminal to 0.7, 0.5, and 0.3 for priority information 1, 2, and 3, respectively. In addition, the simulation result to which the third algorithm is applied may show a throughput similar to that of the simulation result to which the second algorithm is applied.

As described above, according to the present disclosure, a random access control method and a base station can be provided. In particular, it is possible to provide a random access control method and a base station capable of improving resource use efficiency by allocating preamble resources according to service quality and priority. Specifically, the base station estimates the number of active terminals based on the number of idle preambles, allocates preamble resources according to service quality and priority, and adjusts transmission probability, thereby solving congestion for large-scale activation, and a random access control method and base station can provide.

The above-described embodiments may be supported by standard documents disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, which are wireless access systems. That is, among the present embodiments, steps, configurations, and parts not described to clearly reveal the present technical idea may be supported by the above-mentioned standard documents. In addition, all terms disclosed in this specification may be explained by the standard documents disclosed above.

The present embodiments described above may be implemented through various means. For example, the present embodiments may be implemented by hardware, firmware, software, or a combination thereof.

In the case of hardware implementation, the method according to the present embodiments includes one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, or microprocessors.

In the case of implementation by firmware or software, the method according to the present embodiments may be implemented in the form of a device, procedure, or function that performs the functions or operations described above. The software codes may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor and exchange data with the processor by various means known in the art.

Also, the terms "system", "processor", "controller", "component", "module", "interface", "model", or "unit" as described above generally refer to computer-related entities hardware, hardware and software. can mean a combination of, software or running software. For example, but is not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, a thread of execution, a program, and/or a computer. For example, a component can be both an application running on a controller or processor and a controller or processor. One or more components may reside within a process and/or thread of execution, and components may reside on one device (eg, system, computing device, etc.) or may be distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the technical idea. In addition, since the present embodiments are not intended to limit the technical idea of the present disclosure, but to explain, the scope of the present technical idea is not limited by these embodiments. The scope of protection of the present disclosure should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of the present disclosure.

Claims (16)

A method for controlling random access communication by a base station,
a group creation step of generating a plurality of non-overlapping preamble groups to divide usable preambles according to priority information;
estimating the number of active terminals corresponding to each preamble group based on the number of idle preambles for each time slot; and
A service rate for each UE is calculated based on the number of active UEs estimated in each time slot, weights for the priority information are set, and the number of preambles for a preamble group is dynamically determined using the weights. Random access method comprising a; preamble allocation step of allocating to. According to claim 1,
The step of estimating the number of terminals,
A random access method characterized by calculating a probability that a preamble is in an idle state for an active terminal using Bayesian estimation in each time slot, and estimating a posterior distribution for the active terminal at the end of the time slot. . According to claim 2,
The step of estimating the number of terminals,
Calculating a change in the number of active terminals by subtracting the number of active terminals estimated in a previous time slot from the average of the posterior distribution updated for each time slot, and updating the number of active terminals based on the change amount random access method. According to claim 1,
The step of estimating the number of terminals,
Based on the average of the number of successful preambles, an Access Class Barring (ACB) factor maximizing throughput for the priority information is calculated, and the number of active terminals for the priority information is estimated using the ACB factor. Random access method with. According to claim 4,
The average number of successful preambles is
A random access method characterized in that the calculation is made by calculating the probability that transmission of a specific preamble succeeds for the number of active terminals having specific priority information. According to claim 1,
In the step of estimating the number of terminals,
and changing the number of active terminals using a boosting factor when the estimated number of active terminals increases in consecutive time slots. According to claim 1,
The preamble allocation step,
A random access method characterized in that allocating a limited total number of preambles to each preamble group in linear proportion to the number of active terminals and the weight. According to claim 1,
The preamble allocation step,
calculating the number of reference preambles for maintaining the service rate for each terminal, and sequentially allocating the number of preambles from the preamble group having the highest priority information based on the number of reference preambles;
and allocating the remaining number of preambles in proportion to the number of active terminals and the weight when the number of remaining preambles is less than the reference number of preambles. In a base station controlling random access communication,
A plurality of non-overlapping preamble groups are generated to divide usable preambles according to priority information, and the number of active terminals corresponding to each preamble group is estimated based on the number of idle preambles for each time slot, A service rate for each UE is calculated based on the number of active UEs estimated in each time slot, weights for the priority information are set, and the number of preambles for a preamble group is dynamically determined using the weights. A control unit that allocates to;
a transmitter for transmitting the transmission probability calculated by the number of preambles to at least one or more terminals; and
A base station comprising a receiver for receiving a random access preamble from the terminal. According to claim 9,
The control unit,
A base station characterized by calculating a probability that a preamble is in an idle state for an active terminal using Bayesian estimation in each time slot, and estimating a posterior distribution for an active terminal at the end of the time slot. According to claim 10,
The control unit,
A change in the number of active terminals is calculated by subtracting the number of active terminals estimated in a previous time slot from the average of the posterior distribution updated for each time slot, and the number of active terminals is updated based on the variation. base station to. According to claim 9,
The control unit,
Based on the average of the number of successful preambles, an Access Class Barring (ACB) factor maximizing throughput for the priority information is calculated, and the number of active terminals for the priority information is estimated using the ACB factor. base station to. According to claim 12,
The average number of successful preambles is
The base station characterized in that the calculation is calculated by calculating the probability that transmission of a specific preamble succeeds for the number of active terminals having specific priority information. According to claim 9,
The control unit,
When the estimated number of active terminals increases in consecutive time slots, the base station changes the number of active terminals using a boosting factor. According to claim 9,
The control unit,
A base station characterized in that allocating a limited total number of preambles to each preamble group in linear proportion to the number of active terminals and the weight. According to claim 9,
The control unit,
The number of reference preambles for maintaining the service rate for each terminal is calculated, and based on the number of reference preambles, the number of preambles is sequentially allocated from the preamble group having the higher priority information, and the number of remaining preambles is greater than the number of reference preambles. If less, the base station allocates the remaining number of preambles in proportion to the number of active terminals and the weight.

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