KR20220150571A - Method for controlling random access and apparatuses thereof - Google Patents

Abstract

Embodiments of the present invention can provide a method for controlling random access and an apparatus thereof. More particularly, embodiments of the present invention can provide a splitting algorithm-based random access control method with high transmission efficiency while using transmission probability. Specifically, the present invention may provide a splitting algorithm-based random access control method which minimizes a collision resolution period and maximizes system efficiency by classifying a collision state based on a degree to which a base station recognizes the number of collision packets and calculating a transmission probability through each algorithm, and an apparatus thereof.

Description

Random access control method and apparatus thereof

The present embodiments relate to a random access control method and apparatus thereof.

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. Accordingly, various attempts are being made to apply the 5G communication system to the IoT network. For example, technologies such as a sensor network, machine to machine (M2M), and machine type communication (MTC) are being implemented by various techniques.

Also, in a cellular mobile communication system, a random access system is used for a terminal to access a base station. For example, in a long term evolution (LTE) system, a UE is assigned a cell-radio network temporary identifier (C-RNTI), which is a unique identifier of the UE, to obtain uplink synchronization. random access for However, if a plurality of terminals perform random access at the same time, the random access success rate of the terminals decreases due to collisions that may occur during random access, and thus the terminals may not be able to access the base station.

Specifically, among existing splitting algorithms applied to random access, the algorithm known as First-Come First-Serve (FCFS), which shows the best performance, can transmit packets from an average of 0.487 users per slot, but the packet arrival time of users is They should not overlap and be clearly distinguishable. However, in a communication system, a single system clock is commonly used, and in a situation where the resolution of the clock is limited, there is a problem in that the arrival times of users' packets are not clearly distinguished.

Therefore, there is a need for a random access control method and apparatus capable of effectively performing a random access operation in a simpler manner.

Against this background, the present embodiments are to provide a splitting algorithm-based random access control method and apparatus having high transmission efficiency while using transmission probability.

In one aspect, the present embodiments are a method for a base station to control random access communication of a terminal, including a packet receiving step of receiving at least one packet from a plurality of terminals, a collision in which the state of a slot in the same slot is a packet collision ( Collision state, a collision state classification step of classifying collision states based on information on the number of users obtained by the base station, and a transmission probability calculation step of calculating the transmission probability of the next slot using a preset algorithm for each classified collision state. and a transmission probability transmitting step of transmitting the transmission probability to the terminal.

In another aspect, the present embodiments are a method for performing random access communication by a terminal, including a packet transmission step of transmitting packets to a base station in each slot, and when the state of the same slot is determined to be a collision state, the base station obtains a user A transmission probability receiving step of receiving a transmission probability of the next slot calculated using a preset algorithm for each collision state classified based on number information from the base station, and transmitting a packet of the next slot to the base station based on the transmission probability It is possible to provide a random access method comprising the step of transmitting a packet to.

In another aspect, the present embodiments are a base station for controlling random access communication of a terminal, a receiver for receiving at least one packet from a plurality of terminals, and a slot state in the same slot is a collision state in which packets collide If it is determined as , a control unit that classifies collision states based on the information on the number of users obtained by the base station and calculates a transmission probability of the next slot using a preset algorithm for each classified collision state, and a transmission unit that transmits the transmission probability to the terminal. A base station including a base station may be provided.

According to the present embodiments, it is possible to provide a splitting algorithm-based random access control method and apparatus having high transmission efficiency while using transmission probability.

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 a terminal operation according to the present embodiment.
10 is a diagram for explaining the configuration of a base station according to this embodiment.
11 is a diagram for explaining a first collision state according to the present embodiment.
12 is a diagram exemplarily illustrating transmission probability and collision resolution period versus the number of collision users in a first collision state according to the present embodiment.
13 is a diagram for explaining a first algorithm applied to a first collision state according to the present embodiment.
14 is a diagram for explaining a second collision state according to the present embodiment.
15 is a diagram exemplarily illustrating the number of collision resolution periods and the number of successful transmissions versus the number of collision users in the second collision state according to the present embodiment.
16 is a diagram for explaining a second algorithm applied to a second collision state according to the present embodiment.
17 is a diagram for explaining a third collision state according to the present embodiment.
18 is a diagram illustratively showing the number of conflicting users versus the conflict resolution period and the number of successful transmissions in the third conflict state according to the present embodiment.
19 is a diagram for explaining a third algorithm applied to a third collision state according to the present 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 in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio) It should be interpreted as a concept that includes not only User Equipment (UE), but also Mobile Station (MS), User Terminal (UT), Subscriber Station (SS), and wireless device in GSM. 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 concept of CORESET to secure the flexibility of the system. A control resource set (CORESET) means a time-frequency resource for a downlink control signal. 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 a base station to control random access communication of a terminal may include a packet receiving step of receiving at least one packet from a plurality of terminals (S810). For example, a base station controlling random access communication of a terminal may receive at least one or more packets from a plurality of terminals in a random slot. For example, when a plurality of packets are received in the same slot, the base station may fail to receive the plurality of packets due to collision between packets. On the other hand, the base station can successfully receive the packet when one packet is received in the same slot.

The method for the base station to control the random access communication of the terminal may include a collision state classification step of classifying the collision state based on the number of users information when packets collide in the same slot (S820). For example, when the base station controlling the random access communication of the terminal determines that the state of the slot in the same slot is a collision state in which packets collide, the base station may classify the collision state based on information on the number of users obtained by the base station. . For example, if the slot state corresponds to a collision state, the base station may classify the collision state into one of a first collision state, a second collision state, and a third collision state based on user number information. Specifically, when a packet collision occurs, the base station may classify the collision state according to whether or not the number of packets colliding in the physical layer is known. For another example, the base station may classify a collision state in which the number of collided packets, which is the number of collided users, is accurately known as the first collision state. Alternatively, the base station may classify a collision state in which the number of collided packets, which is the number of collided users, is unknown as a second collision state. Alternatively, the base station may classify a collision state in which only partial information about the collision is known as a third collision state. That is, the base station may classify a collision state in which only the number of colliding users in which a collision occurs is 2 or 3 or more, into a third collision state.

The method for the base station to control the random access communication of the terminal may include a transmission probability calculation step of calculating the transmission probability of the next slot using a preset algorithm for each classified collision state (S830). For example, a base station controlling random access communication of a terminal may calculate an arrival rate using each algorithm according to a classified collision state and update a backlog size to calculate a transmission probability. . Here, the backlog size may be a user distribution calculated based on a Poisson distribution. For example, in a method for estimating the number of colliding users, the base station may preset an algorithm so that a variable is changed according to a collision state. For another example, the base station determines which state of the idle state, success state, and collision state corresponds to the state of the same slot corresponding to the embedded point, and according to the state You can preset an algorithm that calculates the arrival rate and updates the backlog size.

For example, when the collision state of the packet is classified as the first collision state, the base station may use the first algorithm for transmitting the packet using the CRPW during the collision resolution period. For example, when the base station is classified as the first collision state, the base station performs the first collision using at least one of an arrival rate, a weight, a backlog size, a collision resolution procedure (CRP), and the number of collision users. The transmission probability can be calculated by an algorithm. For another example, the first algorithm transmits with a random transmission probability in the first slot based on the number of collision users, and transmits with a transmission probability in the second slot based on the first number of users transmitted in the first slot and the collision resolution period. can be calculated. Here, the first slot is temporally continuous with the second slot, and the second slot may correspond to a next time slot after the first slot.

For example, in the case of the first collision state, the base station may perform CRPW in the slot by making the slot state a collision resolution period as a collision occurs in the slot. Specifically, whenever a collision occurs, since the base station knows the number k of colliding users, it can store it and transmit a transmission probability q _k corresponding to k for each slot. Then, the user can generate a random number between 0 and 1 and transmit the packet if this number is smaller than q _k . On the other hand, if the number is not less than q _k , you can create a counter to zero it and not send it. In addition, the user may increase the counter by one when a collision occurs in each slot and decrease the counter by one when the base station gives a signal to decrease the counter. The user transmits a packet using a transmission probability of q _k only when the counter becomes 0. Therefore, the base station can calculate the optimized transmission probability q _k that minimizes the length of the collision resolution period and maximizes system efficiency. In addition, since the base station knows the number of users waiting for the next transmission as the user successfully transmits, the base station can calculate and provide a signal for decreasing the counter and a transmission probability q _k corresponding to the number of waiting users.

As another example, when the collision state of the packet is classified as the second collision state, the base station may use the second algorithm for transmitting the packet using CRPO during the collision resolution period. For example, if the base station is classified as the second collision state, the base station may calculate the transmission probability with a second algorithm using at least one of an arrival rate, a weight, a backlog size, a collision resolution period, and the number of successful transmissions. For another example, the second algorithm may transmit with a random transmission probability in the first slot, and calculate the transmission probability of the second slot according to the number of first users transmitted in the first slot and the transmission result of the first slot. have.

For example, in the case of the second collision state, the base station may perform CRPO in the corresponding slot by making the slot state a collision resolution period as a collision occurs in the slot. Specifically, the base station may allow the user to transmit with a transmission probability of 0.5 from the first slot in which the collision resolution period starts until the next slot succeeds or a collision occurs. In this case, if the transmission result of the user who has transmitted in the slot is successful, the base station may allow the user who failed to transmit to transmit with a transmission probability of 1 in the next slot. On the other hand, if the transmission result is a collision, it may be provided to wait without transmitting until the collision resolution period ends, and transmit with a transmission probability p ⁺ when the collision resolution period ends.

As another example, when the collision state of the packet is classified as the third collision state, the base station may use the third algorithm for transmitting the packet using CRPP during the collision resolution period. For example, when the number of colliding users corresponds to 2, the base station may calculate the transmission probability using a third algorithm using at least one of an arrival rate, a weight, a backlog size, a collision resolution period, and a specific constant. And, if the number of collision users is 3 or more, the base station may calculate the transmission probability using a third algorithm using at least one of the arrival rate, the weight, the backlog size, the collision resolution period, and the number of successful transmissions.

For example, in the case of the third collision state, the base station may perform CRPP in the corresponding slot by making the slot state a collision resolution period as a collision occurs in the slot. Specifically, the base station can distinguish between a collision state in which two packets are transmitted and collided in the same slot and a collision state in which three or more packets are transmitted and collided. Accordingly, the base station may divide the collision resolution period into a collision resolution period 1 and a collision resolution period 2 according to the collision state. First of all, the collision resolution period 1 is when a collision occurs due to transmission of two packets, the user transmits with a transmission probability of 0.5, and the collision resolution period 1 may end when the transmission of the two users ends. Then, the base station may provide the transmission probability p ^★ calculated through the third algorithm in the slot where the collision resolution period 1 ends so that other users can use the transmission probability p ^★ . Next, in the collision resolution period 2, when three or more packets are transmitted and the number of packets is k, the user may transmit a packet with a transmission probability of 0.5 in the first slot where the collision resolution period 2 starts. In addition, when there are two packets to be transmitted in the first slot, k-2 packets may be waited until the two transmissions are completed, and then transmitted with a transmission probability of 1 after the transmission is completed. At this time, if the transmission result is successful, the collision resolution period 2 ends, and if the transmission result is a collision, transmission may be repeated with a transmission probability of 0.5. In addition, if there are two or more packets transmitted in the first slot, the remaining untransmitted packets wait until the collision resolution period 2 ends, and when the collision resolution period 2 ends, the user moves to the next slot with a transmission probability p ^★ can transmit That is, when two or more packets transmitted in the first slot are transmitted in the next slot, the base station may perform CRPP by repeating transmission as if the first slot of the collision resolution period 2 starts. Details of the collision state and algorithm will be described later with reference to FIGS. 11 to 19 .

The method for the base station to control the random access communication of the terminal may include a transmission probability transmission step of transmitting the transmission probability to the terminal (S840). For example, the base station controlling the random access communication of the terminal may transmit the transmission probability in a slot in which the state of the slot is not a collision resolution period (CRP) or in a slot in which the collision resolution period ends. In addition, the base station may estimate the number of users for each slot, take this into consideration, and transmit the calculated transmission probability in a direction that minimizes the occurrence of a collision resolution period.

9 is a diagram for explaining a terminal operation according to the present embodiment.

Referring to FIG. 9 , a method for performing random access communication by a terminal may include a packet transmission step of transmitting packets to a base station in each slot (S810). For example, a terminal performing random access communication may transmit a packet by randomly selecting up to one slot in one frame. However, when a plurality of packets are received in the same slot, packet transmission may fail due to collision between packets. On the other hand, if one packet is received in the same slot, packet transmission may be successful.

A method for performing random access communication by a terminal may include a transmission probability reception step of receiving transmission probability of a next slot from a base station (S820). The received transmission probability may be calculated as described above. For example, a terminal performing random access communication may receive a transmission probability calculated in a direction that minimizes occurrence of a collision resolution period from a base station. For example, the terminal may receive from the base station a transmission probability of the next slot calculated using a preset algorithm for each collision state classified based on information on the number of users from the base station. In addition, the terminal may calculate the arrival rate using each algorithm according to the classified collision state, update the backlog size, and receive the calculated transmission probability. Here, the backlog size may be a user distribution calculated based on a Poisson distribution. As a specific example, when the collision state of the packet is the first collision state, the terminal may receive the transmission probability calculated by the first algorithm using the CRPW during the collision resolution period. Alternatively, when the collision state of the packet is the second collision state, the terminal may receive the transmission probability calculated by the second algorithm using CRPO during the collision resolution period. Alternatively, when the collision state of the packet is the third collision state, the terminal may receive the transmission probability calculated by the third algorithm using CRPP during the collision resolution period.

A method for performing random access communication by the terminal may include a packet transmission step of transmitting a packet of the next slot based on the transmission probability to the base station (S830). For example, a terminal performing random access communication may transmit a packet of a next slot with a transmission probability received from a base station.

10 is a diagram for explaining the configuration of a base station according to this embodiment.

Referring to FIG. 10 , a base station 1000 controlling random access communication of a terminal according to the present embodiment may include a receiving unit 1010, a control unit 1020, and a transmitting unit 1030.

For example, the receiving unit 1010 may receive at least one or more packets from a plurality of terminals.

If the controller 1020 determines that the state of the slot is a collision state in which packets collide in the same slot, the controller 1020 may classify the collision state based on information on the number of users obtained by the base station. For example, if the slot state corresponds to a collision state, the controller 1020 classifies the collision state into one of a first collision state, a second collision state, and a third collision state based on the number of users information. can Here, the first conflicting state is a conflicting state in which the number of conflicting users is known, the second conflicting state is a conflicting state in which the number of colliding users is unknown, and the third conflicting state is only when the number of conflicting users is 2 or 3 or more. may be a known conflict state.

In addition, the controller 1020 may calculate the transmission probability of the next slot using a preset algorithm for each classified collision state. For example, the control unit 1020 may calculate an arrival rate using an algorithm according to the classified collision state, and may calculate a transmission probability by updating a backlog size. Here, the backlog size may be a user distribution calculated based on a Poisson distribution. As a specific example, the algorithm determines whether the state of the same slot corresponding to each embedded point corresponds to an idle state, a success state, and a collision state, and determines which state corresponds to the state. It can be set as an algorithm that calculates the arrival rate and updates the backlog size.

For another example, if the collision state is classified as the first collision state, the controller 1020 may calculate the transmission probability of the next slot using a first algorithm. For example, if the collision state is classified as the first collision state, the control unit 1020 calculates the transmission probability using at least one of the arrival rate, weight, backlog size, collision resolution period, and the number of collision users. algorithm can be used. In addition, the first algorithm transmits with a random transmission probability in the first slot based on the number of collision users, and calculates the transmission probability of the second slot based on the number of first users transmitted in the first slot and the collision resolution period. can

For another example, if the collision state is classified as the second collision state, the controller 1020 may calculate the transmission probability of the next slot using the second algorithm. For example, when the collision state is classified as the second collision state, the control unit 1020 calculates the transmission probability using at least one of the arrival rate, weight, backlog size, collision resolution period, and number of successful transmissions. algorithm can be used. In addition, the second algorithm may transmit with a random transmission probability in the first slot, and calculate the transmission probability of the second slot according to the number of first users transmitted in the first slot and the transmission result of the first slot.

For another example, if the collision state is classified as the third collision state, the controller 1020 may calculate the transmission probability of the next slot using the third algorithm. For example, if the conflict state is classified as the third conflict state, and the number of conflicting users corresponds to 2, the control unit 1020 uses at least one of the arrival rate, weight, backlog size, conflict resolution period, and a specific constant. A third algorithm for calculating transmission probability may be used. In addition, if the number of collision users is 3 or more, the controller 1020 may use a third algorithm for calculating the transmission probability using at least one of the arrival rate, weight, backlog size, collision resolution period, and number of successful transmissions.

The transmitter 1030 may transmit the calculated transmission probability to the terminal.

In addition to this, the control unit 1020 controls the operation of classifying collision states based on the information on the number of users necessary to perform the present disclosure described above and calculating the transmission probability by using a preset algorithm for each classified collision state. Operations of the base station 1000 may be controlled.

In addition, the receiving unit 1010 and the transmitting unit 1030 may be used to transmit and receive signals, messages, and data necessary for performing the above-described present disclosure to and from the terminal.

Hereinafter, a specific operation of calculating a transmission probability using a preset algorithm for each classified collision state in order for the base station to control random access communication of the terminal will be described in more detail with reference to the drawings. Also, hereinafter, an access point (AP) may mean the aforementioned base station, and a user may mean the aforementioned terminal. However, as an example for explanation, the access point (AP) 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.

In a wireless communication system, an access point (AP) is located at the center of a cell, and time may be divided into slots having the same length as a slot corresponding to one packet transmission. Packets transmitted by each terminal to the access point may be randomly received. Accordingly, the size of the backlog, which is the number of active users of the system, may change over time due to the randomly received packets of the terminal. This can make designing a random access protocol difficult. Active users transmit packets with a specific transmission probability broadcast by the access point, and consequently the number of packets arriving at the access point may vary over time.

For example, if the access point receives one packet, the packet can be successfully decoded. On the other hand, if several packets are received simultaneously in one slot, collision may occur. At this time, the access point may start retransmission in a collision resolution procedure (CRP) for retransmitting only users involved in the collision using a preset algorithm. Details will be described later with reference to FIGS. 13 to 19 . However, in this specification, it is assumed that a normal slot is defined as a slot without a collision resolution period, and that the access point can provide feedback information. The feedback information may be information about a success state, an idle state, a conflict state, and the start and end of a conflict resolution period provided at the end of each slot.

11 is a diagram for explaining a first collision state according to the present embodiment.

Referring to FIG. 11, according to the present embodiment, the first collision state may be a collision state in which the number of collision users in which collision occurs is known when packets collide in the same slot. For example, when a collision occurs in the same slot, the access point may classify it as a first collision state if information on the number of collided users can be obtained. At this time, CRPW(k) may be defined as the starting time of the collision resolution period (CRP) in which the number of conflicting users is k. In addition, the period of CRPW(k) can be defined as T _k =E[t _k ] when t _k (k≥2).

According to an example, only one packet to be successfully received by the access point may be transmitted in slot 2 and slot 5. Also, in slot 7, as two packets collide, CRPW(2), which lasts for three slots (t ₂ =3), may start. Also, in slot 13, CRPW(3) starts as three packets collide, and the duration may be t ₃ =7. Also, if packets 5 and 6 collide again in slot 14 within the collision resolution period, CRPW(2) can be restarted and resolved in slot 18. At this time, the conflict resolution period may be divided into level 1 starting from slot 13 and level 2 starting from slot 15.

Here, the embedded point may mean each idle slot, each success slot, and the last slot of each level 1. However, embedded points do not include idle slots and success slots generated within the conflict resolution period.

A random access method for minimizing an average collision resolution period of CRPW(k) for each k and a method for controlling transmission probabilities of backlogged users in each normal slot will be described later with reference to FIGS. 12 and 13 .

12 is a diagram exemplarily illustrating transmission probability and collision resolution period versus the number of collision users in a first collision state according to the present embodiment.

Referring to FIG. 12 , a random access method corresponding to CRPW(k) may be applied to the first collision state according to the present embodiment. For example, when the number of collision users is k, CRPW(k) may transmit a packet with a transmission probability q _k in a first slot that is a first slot within a collision resolution period. The access point knows k, but does not know which users are involved in the collision. Also, the first number of users is the number of users transmitted in the first slot and may be defined as j.

For example, if the first number of users is 0 or k, CRPW(k) may start from the second slot, that is, the second slot. Alternatively, if the first number of users is 1 and transmission is successful, the remaining (k-1) users may start CRPW(k-1) in the second slot. At this time, if the transmission probability (q1) is set to 1, CRPW(1) can occupy at least one slot. Alternatively, if the first number of users is 2 ≤ j ≤ k-1, CRPW(j) may start at the next slot. When CRPW(j) is complete, the remaining (k-j) users can start CRPW(k-j) in the resulting slot.

For another example, the access point may terminate CRPW(k) when all k colliding users are transmitted successfully. Since the access point knows k in the first collision state, it can optimally control the transmission probability q _k . Accordingly, the access point can minimize T _k , which is an average period of the collision resolution period CRP(k). In this case, q _k may be different for each k.

또는

일 수 있다. CRPW(2)는 제 2 슬롯에서 다시 시작될 수 있다. 이 때, 평균 충돌 해결 기간은 1+T₂ 일 수 있다. 또는, CRPW(2)는 제 1 슬롯에서 제 1 사용자 수 j가 1 일 수 있다. 그러면 전송 확률은

일 수 있다. 1 개의 사용자가 전송을 성공하면 남은 1 개의 사용자는 제 2 슬롯에서 전송 확률 q₁은 1로 전송될 수 있다. 이 때, 평균 충돌 해결 기간은 1+T₁=2 일 수 있다. For example, when the number of colliding users is 2 (k=2), the first number of users j in the first slot of CRPW(2) may be 0 or 2. Then the transmission probability is

or

can be CRPW 2 may be restarted in the second slot. In this case, the average conflict resolution period may be 1+T ₂ . Alternatively, in the CRPW(2), the first user number j may be 1 in the first slot. Then the transmission probability is

can be If one user succeeds in transmission, the remaining one user may be transmitted with a transmission probability q ₁ of 1 in the second slot. In this case, the average conflict resolution period may be 1+T ₁ =2.

T ₂ can be expressed as Equations 1 and 2.

Here, if q ₂ ∈ [0, 1], in the case of CRPW(2), q ₂ =0.5 and T ₂ =3.

As another specific example, when the number of conflicting users is 3 or more (k≥3), the average conflict resolution period may be divided into the first number of users j in the first slot of CRPW(k).

또는

일 수 있다. 그리고, CRPW(k)는 제 2 슬롯에서 다시 시작될 수 있다. 이 때, 평균 충돌 해결 기간은 1+T_k일 수 있다. 또는, 제 1 사용자 수 j가 1인 경우, 전송 확률은

일 수 있다. 그리고, CRPW(k-1)는 제 2 슬롯에서 다시 시작될 수 있다. 이 때, 평균 충돌 해결 기간은 1+T_k-1일 수 있다. 또는, 제 1 사용자 수 j가 2 ≤ j ≤ k-1인 경우, 전송 확률은

일 수 있다. 그리고, CRPW(k-j)는 제 2 슬롯에서 다시 시작될 수 있다. 이 때, 평균 충돌 해결 기간은 1+T_j+T_k-j일 수 있다. When the first user number j is 0 or 2, the transmission probability is

or

can be And, CRPW(k) may be started again in the second slot. In this case, the average conflict resolution period may be 1+T _k . Alternatively, if the first number j of users is 1, the transmission probability is

can be And, CRPW(k-1) may be started again in the second slot. In this case, the average conflict resolution period may be 1+T _k-1 . Alternatively, when the first number j of users is 2 ≤ j ≤ k-1, the transmission probability is

can be And, CRPW(kj) may be started again in the second slot. In this case, the average conflict resolution period may be 1+T _j +T _kj .

T _k can be expressed as Equations 3 and 4.

12 may indicate an optimal transmission probability and a minimum collision resolution period that vary according to the number of colliding users in the first collision state. That is, it can be seen that the conflict resolution period increases linearly as the number of conflicting users increases.

For example, a normal slot may have n backlog users and transmit packets with a transmission probability p. Then, according to the Renewal Theory, the expected service rate can be defined as in Equation 5.

Therefore, the optimal transmission probability q can be calculated through Equation 5 using Equation 5. The transmission probability q can maximize the service speed. This may provide an effect of maximizing system throughput and minimizing access delay by maximizing the average number of packets provided per slot.

13 is a diagram for explaining a first algorithm applied to a first collision state according to the present embodiment.

Referring to FIG. 13, a procedure for controlling the transmission probability in the first collision state by the first algorithm according to the present embodiment can be described. For example, the first algorithm may calculate an arrival rate and update a backlog size. For example, the arrival rate can be calculated by applying a weight θ to the previous arrival rate. Specifically, the arrival rate may be calculated by lines 3, 6 and 11 of the first algorithm. At this time, the weight θ may be set to 0.99, but is not limited thereto.

As another example, the backlog size can be updated using vx ^* and λE, the number of new users. Specifically, the backlog size can be updated by lines 4, 7 and 12 of the first algorithm. Also, the transmission probability p ^* can be calculated by line 14 of the first algorithm. Accordingly, when a collision occurs, the base station makes the slot state a collision resolution period, informs the users, and performs CRPW in the corresponding slot, as in line 8 of the first algorithm.

As another example, the first algorithm may apply Bayes' rule to estimate the backlog size of each slot. The backlog size can be estimated as a distribution by Bayes' rule instead of a constant. Accordingly, each slot may recursively update the distribution of the backlog size. Also, the backlog size of each slot may be a user distribution calculated based on a Poisson distribution.

Here, the distribution of the backlog size n may be a Poisson distribution having an average v, and can be expressed as in Equation 6.

And, the average v can be updated recursively to estimate the backlog size at each slot.

For example, the service rate may be calculated using Equation 5 based on the backlog size n. At this time, if the distribution of the backlog size n is Φ _v (n), the average service speed can be expressed as Equation 7.

일 수 있다. pv는 도 12에서 산출된 전송 확률과 충돌 해결 기간을 이용하여 산출할 수 있다. here,

can be pv can be calculated using the transmission probability and the collision resolution period calculated in FIG. 12 .

In addition, the transmission probability p ^* can be expressed as in Equation 8.

Here, x ^* may mean the average number of users transmitting in a normal slot and may be x ^* =1.8842. The maximum service rate can be expressed as in Equation 9.

For another example, when m out of n users are transmitted in a normal slot, the transmission probability p can be expressed as Equation 10.

In addition, when Φ _n (v) is an a priori distribution, m unconditional transmission probabilities can be expressed as in Equation 11.

If m users are simultaneously transmitted in one slot according to Bayes' rule, the transmission probability can be expressed as in Equation 12.

Here, it may be a posterior distribution of backlog size n. Also, the average may be updated by Equation 13.

The updated average can be expressed as in Equation 14 when the transmission probability p ^* calculated by Equation 8 is applied.

Here, x ^* may be 1.8842, and this value may be the average of the a priori distribution of the next slot. m=0 and m=1 may mean an idle slot and a successful slot, and m greater than 2 (m>2) may mean a conflict resolution period. Therefore, the average after the contention resolution period can be estimated by subtracting m since m users can be successfully transmitted within the contention resolution period. That is, the average backlog size can be updated by vx ^* for all values of m.

14 is a diagram for explaining a second collision state according to the present embodiment.

Referring to FIG. 14, according to the present embodiment, the second collision state may be a collision state in which the number of collision users in which collision occurs is unknown when packets collide in the same slot. That is, the second collision state may be a collision state in which the access point knows that at least two users transmitted data according to the occurrence of a collision, but does not know the number of collision users.

For example, when a collision occurs in the same slot, the access point may classify the access point into a second collision state if collided user number information cannot be obtained. At this time, CRPO(k) may be defined as the time when the collision resolution period (CRP) starts due to the k number of conflicting users while there is no information on the number of conflicting users. In addition, CRPO (k) may differ from CRPW (k) when t _k (k≥2).

For example, the access point cannot control the transmission probability according to K because it does not know the number of collision users k. Therefore, the access point can transmit packets with a constant probability q regardless of the number k of colliding users. Also, l _k may be a collision resolution period of CRPO(k), and s _k may be the number of successful transmissions within CRPO(k). Here, it can be defined as L _k =E[l _k ] and S _k =E[s _k ].

14, packets 5, 6 and 7 are involved in a collision in slot 12, while packets 5 and 6 are successfully transmitted from their CRPO(3) and packet 7 leaves CRPO(k). You can check. For example, if a packet is successfully transmitted within CRPO(k), the remaining (k-1) users may transmit packets with transmission probability 1 in the resulting slot. Through this, it is possible to check whether the current k is 1. Also, CRPO(k) may be terminated when transmission succeeds twice in a row.

15 is a diagram exemplarily illustrating the number of collision resolution periods and the number of successful transmissions versus the number of collision users in the second collision state according to the present embodiment.

Referring to FIG. 15 , a random access method corresponding to CRPO(k) may be applied to the second collision state according to the present embodiment. For example, when the access point does not know the number of collision users, k collision users may transmit packets with transmission probability q in the first slot. Here, the transmission probability q may be set to 0.5, but is not limited thereto. Also, the first number of users is the number of users transmitted in the first slot and may be defined as j.

For example, if the first number of users is 0 or k, CRPO(k) may start from the second slot, that is, the second slot. Alternatively, if the first number of users is 1 and transmission is successful, the remaining (k-1) users may transmit with a transmission probability of 1 in the second slot. At this time, if the transmission result of the second slot is successful, CRPO(k) may end, but if the transmission result is failure, CRPO(k-1) may start in the third slot. Alternatively, if the first number of users is j≧2, a new collision occurs, and the j number of users may start CRPO(j) in the second slot. Then, the remaining (k-j) users may wait until the current conflict resolution period ends or wait in normal slots to start a new random access.

For another example, the access point may terminate CRPO(k) when two consecutive successful transmissions occur.

또는

이면, CRPO(2)는 제 2 슬롯에서 다시 시작될 수 있다. 이 때, 평균 충돌 해결 기간은 1+L₂ 일 수 있다. 또는, CRPO(2)는 제 1 슬롯에서 제 1 사용자 수 j가 1 일 수 있다. 그리고 전송 확률이

이면, 1개의 사용자는 전송을 성공하고 나머지 1개의 사용자는 제 2 슬롯에서 전송 확률 1로 전송할 수 있다. 이 때, 평균 충돌 해결 기간은 1+1=2 일 수 있다. As another example, when the number of colliding users is 2 (k=2), in CRPO(2), the first user number j in the first slot may be 0 or 2. and the transmission probability

or

, then CRPO(2) can be started again in the second slot. In this case, the average conflict resolution period may be 1+L ₂ . Alternatively, in CRPO(2), the first number of users j may be 1 in the first slot. and the transmission probability

, one user can transmit successfully and the other user can transmit with a transmission probability of 1 in the second slot. In this case, the average conflict resolution period may be 1+1=2.

L ₂ can be expressed as Equations 15 and 16.

이면, CRPO(k)는 제 2 슬롯에서 시작될 수 있다. 이 때, 평균 충돌 해결 기간은 1+L_k 일 수 있고, 평균적으로 성공한 전송 횟수는 S_k일 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 1일 수 있다. 그리고 전송 확률이

이면, 나머지(k-1) 사용자는 제 2 슬롯에서 전송 확률 1로 전송할 수 있다. 구체적으로 k-1≥2 이면, 제 2 슬롯은 충돌이 발생하고, 나머지(k-1) 사용자는 제 3 슬롯에서 CRPO(k-1)를 시작할 수 있다. 이 때, 평균 충돌 해결 기간은 1+1+L_k-1 일 수 있고, 평균적으로 성공한 전송 횟수는 1+S_k-1일 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 2 이상(j≥2)일 수 있다. 그리고 전송 확률이

이면, j개의 사용자는 제 2 슬롯에서 CRPO(j)를 시작할 수 있다. 나머지(k-j) 사용자는 현재 충돌 해결 기간이 끝날 때까지 대기할 수 있다. 이 때, 평균 충돌 해결 기간은 1+L_j 일 수 있고, 평균적으로 성공한 전송 횟수는 S_j일 수 있다. As another example, when the number of colliding users is 3 or more (k≥3), CRPO(k) may be 0 for the first number of users j in the first slot. and transmission probability

, CRPO(k) may start in the second slot. In this case, the average collision resolution period may be 1+L _k , and the average number of successful transmissions may be S _k . Alternatively, the first user number j may be 1 in the first slot. and the transmission probability

, the remaining (k-1) users can transmit with a transmission probability of 1 in the second slot. Specifically, if k−1≥2, a collision occurs in the second slot, and the remaining (k−1) users may start CRPO (k−1) in the third slot. In this case, the average collision resolution period may be 1+1+L _k-1 , and the average number of successful transmissions may be 1+S _k-1 . Alternatively, the first number of users j in the first slot may be 2 or more (j≥2). and the transmission probability

, then j users can start CRPO(j) in the second slot. The remaining (kj) users may wait until the current conflict resolution period ends. In this case, the average collision resolution period may be 1+L _j , and the average number of successful transmissions may be S _j .

Accordingly, L _k and S _k can be expressed as in Equation 17, and based on Equation 17, L _k and S _k can be expressed as in Equation 18.

15 may show a collision resolution period (L _k ) and the number of successful transmissions (S _k ) that vary according to the number of colliding users when the transmission probability q is 0.5 in the second collision state. That is, while the collision resolution period gradually increases as the number of colliding users increases, the number of successful transmissions may converge to 2.5 except when the number of colliding users is 2.

For example, a normal slot may have n backlog users and transmit packets with a transmission probability p. Then, according to the Renewal Theory, the expected service rate can be defined as in Equation 19.

Here, since the collision resolution period (L _k ) and the number of successful transmissions (S _k ) are already known, the optimal transmission probability p can be calculated by knowing the backlog size n.

16 is a diagram for explaining a second algorithm applied to a second collision state according to the present embodiment.

Referring to FIG. 16, a procedure for controlling the transmission probability in the second collision state by the second algorithm according to the present embodiment can be described.

For example, the second algorithm may calculate an arrival rate and update a backlog size. For example, the arrival rate can be calculated by applying a weight θ to the previous arrival rate. Specifically, the arrival rate may be calculated by lines 3, 6 and 13 of the second algorithm. As another example, the backlog size can be updated using the number of successful transfers s observed in CRPO. Specifically, the backlog size can be updated by lines 4, 7 and 14 of the second algorithm. Also, the transmission probability can be calculated by line 16 of the second algorithm.

As another example, if the distribution of backlog size n is Ф _v (n), the average service speed can be expressed as Equation 20.

For example, pv can be calculated using the collision resolution period (L _k ) calculated in FIG. 15 and the number of successful transmissions (S _k ). In addition, the transmission probability p ⁺ can be expressed as Equation 21.

Here, x ⁺ may mean the average number of users transmitting in a normal slot and may be x ⁺ =1.2663. The maximum service rate can be expressed as Equation 22.

As another example, the second algorithm may apply Bayes' rule to estimate the backlog size of each slot. Also, the backlog size of each slot may be a Poisson distribution with mean v. For example, if the transmission probability is P and m (0 or 1) users are simultaneously transmitted in one slot, the mean of the posterior distribution can be expressed as Equations 23 and 24.

Here, x ⁺ may be 1.2663, and this value may be the average of the a priori distribution of the next slot. m=0 and m=1 may mean an idle slot and a success slot. For example, if m is 1 (m=1), 1 can be subtracted from the updated average since one user has been successfully transmitted. Thus, the updated average may be vx ⁺ . For another example, if m is 2 or more (m>2), a collision occurs and the access point cannot recognize the value of m. Therefore, the backlog size cannot be estimated using m, and the probability of collision when the backlog size is n can be expressed as Equation 25.

In addition, the unconditional probability that a collision will occur can be expressed as Equation 26.

And, the conditional probability that a collision will occur can be expressed as Equation 27 by applying the Bayesian rule.

In addition, if the Poisson distribution is approximated by the mean, it can be expressed as Equation 28.

Here, when the optimal transmission probability p is applied, it can be expressed as Equation 29.

Here, when the transmission probability q in the first slot is 0.5, c ⁺ may be 1.2514. Therefore, the average backlog size can be updated by v+c ⁺ when a collision occurs.

17 is a diagram for explaining a third collision state according to the present embodiment.

Referring to FIG. 17, according to the present embodiment, the third collision state may be a collision state in which only the number of colliding users is 2 or 3 or more when packets collide in the same slot. Specifically, the access point may obtain the value k when the number k of collision users is 2 (k=2). On the other hand, if the number k of collision users is 3 or more (k ≥ 3), the access point knows that at least 3 users have transmitted, but does not know the value of k. That is, the third collision state may be a collision state in which the access point recognizes whether a collision has occurred between two users.

For example, CRPP(k) may be defined as the time at which the collision resolution period (CRP) starts due to k colliding users while k is unknown when the number k of colliding users is 3 or more (k≥3). However, if the number k of colliding users is 2, the access point can start CRPW(2) because it knows the number k of colliding users. CRPW(2) may correspond to slot 4 of FIG. 17 .

For example, the access point cannot control the transmission probability according to k because it does not know the number of collision users k. Therefore, the access point can transmit a packet with a constant probability r regardless of the number k of collision users. Here, the transmission probability r may be set to 0.5, but is not limited thereto. Also, d _k may be a collision resolution period of CRPP(k), and z _k may be the number of successful transmissions within the collision resolution period. Here, it can be defined as D _k =E[d _k ] and Z _k =E[z _k ].

Referring to FIG. 17, while 4 packets collide in slot 9, only packets 5, 6 and 7 can be successfully transmitted in CRPP(4). For example, in CRPP(4), Z ₄ may be 3 and D _k may be 7. Also, when k is 2, Z ₂ may be 2 and D ₂ may be 3, similarly to CRPW(2).

18 is a diagram illustratively showing the number of conflicting users versus the conflict resolution period and the number of successful transmissions in the third conflict state according to the present embodiment.

Referring to FIG. 18, a random access method corresponding to CRPP(k) may be applied to the third collision state according to the present embodiment. For example, when the access point does not know the number of collision users, k collision users may transmit packets with transmission probability r in the first slot. Here, the first user number is the number of users transmitted in the first slot and may be defined as j.

For example, if the first number of users is 0, the slot may be in an idle state, and k users may start CRPP(k) in the second slot, that is, the second slot. Alternatively, if the first number of users is 1 and transmission is successful, the remaining (k-1) users may start CRPP (k-1) in the second slot. Alternatively, if the first number of users is 2, a new collision between the two users may start CRPW(2). At this time, after the CRPW ends, the remaining (k-2) users can transmit with a transmission probability of 1. If k-2 is 1, the transmission result is success, whereas if k-2 is not 1, collision may occur. However, in this slot, CRPP may be terminated regardless of the transmission result. Alternatively, if the first number of users is j≧3, j users may start CRPP(j). Then, the remaining (k-j) users may wait until the current conflict resolution period ends or wait in normal slots to start a new random access.

For another example, the access point may terminate CRPP(k) in a slot where CRPO ends or in a slot next to the point where CRPW(2) ends.

또는

이면, CRPP(3)는 제 2 슬롯에서 시작할 수 있다. 이 때, 평균 충돌 해결 기간은 1+D₃일 수 있고, CRPP에서 성공한 전송 횟수는 Z₃일 수 있다. 여기서 1은 이미 점유된 제 1 슬롯을 의미할 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 1 일 수 있다. 그리고 전송 확률이

이면, 1개의 사용자는 전송을 성공하고 나머지 2개의 사용자는 제 2 슬롯에서 CRPO(2)를 시작할 수 있다. 다만, 액세스 포인트는 제 2 슬롯에서 CRPO에 관련된 사용자가 2개 이상임은 알지만 정확한 사용자 수는 알 수 없다. 이 때, 평균 충돌 해결 기간은 1+L₂=3 일 수 있고, 성공한 전송 횟수는 1+S₂=3일 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 2 일 수 있다. 그리고 전송 확률이

이면, 2개의 사용자는 제 2 슬롯에서 CRPW(2)를 시작할 수 있다. 여기서 CRPW(2)가 종료되면, 나머지(k-j=1) 사용자는 확률 1로 전송하여 성공할 수 있다. 이 때, 평균 충돌 해결 기간은 1+T₂+1=4 일 수 있고, 성공한 전송 횟수는 1+2=3일 수 있다. 여기서 마지막 1은 나머지 사용자의 전송을 의미할 수 있다. As another example, when the number of colliding users is 3 (k=3), in CRPP(3), the first user number j in the first slot may be 0 or 3. and the transmission probability

or

, CRPP(3) may start in the second slot. In this case, the average collision resolution period may be 1+D ₃ , and the number of successful transmissions in CRPP may be Z ₃ . Here, 1 may mean a first slot already occupied. Alternatively, the first user number j may be 1 in the first slot. and the transmission probability

, one user succeeds in transmission and the other two users can start CRPO(2) in the second slot. However, the access point knows that there are two or more users related to CRPO in the second slot, but cannot know the exact number of users. In this case, the average collision resolution period may be 1+L ₂ =3, and the number of successful transmissions may be 1+S ₂ =3. Alternatively, the first user number j may be 2 in the first slot. and the transmission probability

, then the two users can start CRPW(2) in the second slot. Here, when CRPW(2) ends, the remaining (kj=1) users can transmit with probability 1 and succeed. In this case, the average collision resolution period may be 1+T ₂ +1=4, and the number of successful transmissions may be 1+2=3. Here, the last 1 may mean transmission of the remaining users.

Accordingly, D ₃ and Z ₃ may be expressed as in Equation 30 or as in Equation 31 based on Equation 30.

또는

이면, CRPP(k)는 제 2 슬롯에서 시작할 수 있다. 이 때, 평균 충돌 해결 기간은 1+D_k일 수 있고, CRPP에서 성공한 전송 횟수는 1+Z_k일 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 1일 수 있다. 그리고 전송 확률이

이면, 1개의 사용자는 전송을 성공하고, 나머지(k-1) 사용자는 제 2 슬롯에서 CRPO(k-1)을 시작할 수 있다. 다만, 액세스 포인트는 제 2 슬롯에서 CRPO에 관련된 사용자가 2개 이상임은 알지만 정확한 사용자 수는 알 수 없다. 이 때, 평균 충돌 해결 기간은 1+L_k-1일 수 있고, CRPP에서 성공한 전송 횟수는 1+Z_k-1일 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 2일 수 있다. 그리고 전송 확률이

이면, 2개의 사용자는 제 2 슬롯에서 CRPW(2)을 시작할 수 있다. 그리고 CRPW가 종료되면, 나머지(k-j) 사용자는 전송 확률 1로 전송하여 충돌 해결 기간을 종료할 수 있다. 이 때, 평균 충돌 해결 기간은 1+T₂일 수 있고, CRPP에서 성공한 전송 횟수는 2 일 수 있다. 또는, 제 1 슬롯에서 제 1 사용자 수 j가 3 이상(j≥3)일 수 있다. 그리고 전송 확률이

이면, j개의 사용자는 제 2 슬롯에서 CRPP(j)을 시작할 수 있고 나머지(k-j) 사용자는 충돌 해결 기간을 떠날 수 있다. 이 때, 평균 충돌 해결 기간은 D_j일 수 있고, CRPP에서 성공한 전송 횟수는 1+Z_j일 수 있다. As another example, when the number of colliding users is 4 or more (k≥4), the first user number j in the first slot may be 0 or k. and the transmission probability

or

, CRPP(k) may start in the second slot. In this case, the average collision resolution period may be 1+D _k , and the number of successful transmissions in CRPP may be 1+Z _k . Alternatively, the first user number j may be 1 in the first slot. and the transmission probability

If , one user succeeds in transmission, and the remaining (k-1) users can start CRPO (k-1) in the second slot. However, the access point knows that there are two or more users related to CRPO in the second slot, but cannot know the exact number of users. In this case, the average collision resolution period may be 1+L _k-1 , and the number of successful transmissions in CRPP may be 1+Z _k-1 . Alternatively, the first number of users j may be 2 in the first slot. and the transmission probability

, the two users can start CRPW(2) in the second slot. When the CRPW is terminated, the remaining (kj) users may transmit with a transmission probability of 1 to end the collision resolution period. In this case, the average collision resolution period may be 1+T ₂ , and the number of successful transmissions in CRPP may be 2. Alternatively, the first number of users j in the first slot may be 3 or more (j≥3). and the transmission probability

, then j users can start CRPP(j) in the second slot and the remaining (kj) users can leave the conflict resolution period. In this case, the average collision resolution period may be D _j , and the number of successful transmissions in CRPP may be 1+Z _j .

Accordingly, D _k and Z _k may be expressed as in Equation 32, or may be expressed as in Equation 33 based on Equation 32.

17 may show the collision resolution period (D _k ) and the number of successful transmissions (Z _k ) that vary according to the number of colliding users when the transmission probability r is 0.5 in the third collision state. That is, while the collision resolution period gradually increases as the number of colliding users increases, the number of successful transmissions may converge to 2.71 except for cases where the number of colliding users is 2 and 3.

For example, a normal slot may have n backlog users and transmit packets with a transmission probability p. Then, according to the Renewal Theory, the expected service rate can be defined as in Equation 34.

Here, since the collision resolution period (D _k ) and the number of successful transmissions (Z _k ) are already known, the optimal transmission probability p can be calculated if the backlog size n is known.

19 is a diagram for explaining a third algorithm applied to a third collision state according to the present embodiment.

Referring to FIG. 19, a procedure for controlling the transmission probability in the third collision state by the third algorithm according to the present embodiment can be described.

For example, the third algorithm may calculate an arrival rate and update a backlog size. For example, the arrival rate can be calculated by applying a weight θ to the previous arrival rate. Specifically, the arrival rate may be calculated by lines 3, 6, 11 and 13 of the third algorithm. As another example, the backlog size can be updated using the number of successful transfers s observed in CRPP. Specifically, the backlog size can be updated by lines 4, 7, 12 and 19 of the third algorithm. Also, the transmission probability can be calculated by line 21 of the third algorithm. However, the third algorithm differs from the second algorithm in that the access point knows the number of colliding users 2, which is the starting criterion for CRPW(2).

As another example, if the distribution of the backlog size n is Ф _v (n), the average service speed can be expressed as Equation 35.

For example, pv can be calculated using the collision resolution period (D _k ) calculated in FIG. 18 and the number of successful transmissions (Z _k ). In addition, the transmission probability p ^★ can be expressed as Equation 36.

Here, x ^★ may mean the average number of users transmitting in a normal slot and may be x ^★ =1.3877. The maximum service rate can be expressed as in Equation 37.

As another example, the third algorithm may apply Bayes' rule to estimate the backlog size of each slot. Also, the backlog size of each slot may be a Poisson distribution with mean v. For example, if the transmission probability is P and m (0 or 1) users are simultaneously transmitted in one slot, the mean of the posterior distribution can be expressed as Equations 38 and 39.

Here, x ^★ may be 1.3877, and this value may be the average of the a priori distribution of the next slot. m=0 and m=1 may mean an idle slot and a success slot. As a specific example, if m=1 and m=2, then m can be subtracted from the updated average since m number of users have been transmitted successfully. Thus, the updated mean may be vx ^★ .

For another example, if m is greater than or equal to 3 (m>3), the access point cannot recognize the value of m. Therefore, the backlog size cannot be estimated using m, and the probability of collision when the backlog size is n can be expressed as Equation 40.

In addition, the unconditional probability that a collision will occur can be expressed as Equation 41.

And, the conditional probability that a collision will occur can be expressed as Equation 42 by applying the Bayesian rule.

In addition, if the Poisson distribution is approximated by the mean, it can be expressed as Equation 43.

Here, when the optimal transmission probability p is applied, it can be expressed as Equation 44.

Here, when the transmission probability r in the first slot is 0.5, c ^★ may be 2.0397. Therefore, the average backlog size can be updated by v+c ^★ when a collision occurs.

As a result, the random access method according to the present embodiment is longer than the method using the existing First-Come First-Serve (FCFS) algorithm based on the average period required for successful random access and the number of successful random accesses per slot. It can provide better performance.

As described above, according to the present disclosure, a random access control method and apparatus can be provided. In particular, it is possible to provide a splitting algorithm-based random access control method having high transmission efficiency while using transmission probability. Specifically, splitting algorithm-based random access that minimizes the collision resolution period and maximizes system efficiency by classifying the collision state based on the degree to which the base station recognizes the number of collided packets and calculating the transmission probability through each algorithm. A control method and its device can be provided.

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 can 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 (15)

A method for a base station to control random access communication of a terminal,
A packet reception step of receiving at least one or more packets from a plurality of terminals;
a collision state classifying step of classifying the collision state based on information on the number of users acquired by the base station when the state of the slot in the same slot is determined to be a collision state in which packets collide;
a transmission probability calculation step of calculating a transmission probability of a next slot using a preset algorithm for each of the classified collision states; and
A random access method comprising a transmission probability transmission step of transmitting the transmission probability to the terminal. According to claim 1,
In the collision state classification step,
If the slot state corresponds to the collision state, classify the collision state into one of a first collision state, a second collision state, and a third collision state based on the number of users information,
The first conflicting state is a conflicting state in which the number of conflicting users is known, the second conflicting state is a conflicting state in which the number of conflicting users is unknown, and the third conflicting state is a conflicting state in which the number of conflicting users is 2 or A random access method characterized in that it is a collision state in which only 3 or more are known. According to claim 1,
The transmission probability calculation step,
In the classified collision state, an arrival rate is calculated using the algorithm called EK, and the transmission probability is calculated by updating a backlog size, but the backlog size is Poisson distribution Random access method characterized in that the user distribution calculated based on. According to claim 3,
The algorithm is
Determine which state of the same slot corresponding to each embedded point corresponds to an idle state, a success state, and a collision state, and calculate the arrival rate according to the state Random access method characterized in that for updating the backlog size. According to claim 2,
The transmission probability calculation step,
When the collision state is classified as the first collision state, the algorithm calculates the transmission probability using at least one of an arrival rate, a weight, a backlog size, a collision resolution procedure (CRP), and the number of collision users. Random access method, characterized in that the first algorithm to do. According to claim 5,
The first algorithm,
Transmission is performed with a random transmission probability in a first slot based on the number of collision users, and transmission probability in a second slot is calculated based on the number of first users transmitted in the first slot and the collision resolution period. random access method. According to claim 2,
The transmission probability calculation step,
When the collision state is classified as the second collision state, the algorithm is a second algorithm for calculating the transmission probability using at least one of an arrival rate, a weight, a backlog size, a collision resolution period, and the number of successful transmissions. Random access method with. According to claim 7,
The second algorithm,
Random access method characterized by transmitting with a random transmission probability in a first slot, and calculating a transmission probability of a second slot according to the number of first users transmitted in the first slot and a transmission result of the first slot. According to claim 2,
The transmission probability calculation step,
When the collision state is classified as the third collision state, the algorithm calculates the transmission probability using at least one of an arrival rate, a weight, a backlog size, a collision resolution period, and a specific constant when the number of collision users corresponds to 2 Random, characterized in that a third algorithm for calculating the transmission probability using at least one of the arrival rate, the weight, the backlog size, the collision resolution period, and the number of successful transmissions when the number of collision users is 3 or more. access method. A method for performing random access communication by a terminal,
A packet transmission step of transmitting packets to the base station in each slot;
If the state of the same slot is determined to be a collision state, a transmission probability receiving step of receiving, from the base station, a transmission probability of the next slot calculated using a preset algorithm for each collision state classified based on the number of users information obtained by the base station. ; and
and a packet transmission step of transmitting a packet of the next slot to the base station based on the transmission probability. According to claim 10,
The collision state is
It is classified into one of a first conflict state, a second conflict state, and a third conflict state based on the number of users information,
The first conflicting state is a conflicting state in which the number of conflicting users is known, the second conflicting state is a conflicting state in which the number of conflicting users is unknown, and the third conflicting state is a conflicting state in which the number of conflicting users is 2 or A random access method characterized in that it is a collision state in which only 3 or more are known. According to claim 10,
The transmission probability is,
According to the classified collision state, the arrival rate is calculated using the algorithm and the transmission probability is calculated by updating the backlog size, wherein the backlog size is a user distribution calculated based on a Poisson distribution. Way. In the base station for controlling random access communication to the terminal,
a receiving unit for receiving at least one or more packets from a plurality of terminals;
In the same slot, if the state of the slot is determined to be a collision state in which packets collide, the base station classifies the collision state based on information on the number of users obtained, and uses a preset algorithm for each classified collision state in the next slot. A control unit for calculating the transmission probability of; And
A base station including a transmitter for transmitting the transmission probability to the terminal. According to claim 13,
The control unit,
If the slot state corresponds to a collision state, the collision state is classified into one of a first collision state, a second collision state, and a third collision state based on the number of users information,
The first conflicting state is a conflicting state in which the number of conflicting users is known, the second conflicting state is a conflicting state in which the number of conflicting users is unknown, and the third conflicting state is a conflicting state in which the number of conflicting users is 2 or A base station characterized in that it is a collision state that only knows that it is 3 or more. According to claim 13,
The control unit,
The base station, characterized in that the arrival rate is calculated using the algorithm according to the classified collision state and the transmission probability is calculated by updating a backlog size, wherein the backlog size is a user distribution calculated based on a Poisson distribution.

Images