KR-102964585-B1 - Base station and method for improving paging reception success rate of 5G standalone small cell and mobile communication system

KR102964585B1KR 102964585 B1KR102964585 B1KR 102964585B1KR-102964585-B1

Abstract

A base station and a method for improving the success rate of paging reception by suppressing paging interference between adjacent cells by distributing the paging transmission timing for each cell in a mobile communication system in Time Division Duplexing (TDD) mode are disclosed. A base station using TDD mode according to one aspect includes: a control unit that extracts downlink slots from a wireless frame, determines slots capable of paging transmission among the extracted downlink slots by referring to a common search space, and determines a paging opportunity slot among the slots capable of paging transmission using a predetermined number of paging modules and identification information of each cell; and a transmitter unit that transmits a paging message through the paging opportunity slot for each cell.

Inventors

권영대
장재선

Assignees

주식회사 케이티

Dates

Publication Date: 20260512
Application Date: 20210930

Claims (11)

In a base station using TDD (Time Division Duplexing) mode, A control unit that extracts downlink slots from a wireless frame, determines slots capable of paging transmission among the extracted downlink slots by referring to a control resource set and a common search space, and determines paging opportunity slots among the slots capable of paging transmission using a previously determined number of paging modules and identification information of each cell; and A base station including a transmitter that transmits a paging message through the paging opportunity slot for each cell.
In paragraph 1, The above control unit is, A base station characterized by determining the slots capable of paging transmission by excluding slots corresponding to other types of common search spaces that share resources with the common search space for paging transmission among the downlink slots.
In paragraph 1, The above control unit is, A base station characterized by extracting a downlink slot and a flexible slot having a downlink symbol capable of paging transmission from a wireless frame into the downlink slots.
In paragraph 1, The above control unit is, A base station characterized by determining the slot in the order corresponding to the value obtained by adding 1 to the result of modular operation of the identification information of each cell with the paging modular number as the paging opportunity slot of each cell.
In paragraph 1, The above control unit is, A base station characterized by not transmitting a signal in an area corresponding to the paging common search space in each cell, in a slot that is capable of paging transmission but is not a paging opportunity slot.
As a method for transmitting paging messages in a base station using TDD (Time Division Duplexing) mode, Step of extracting downlink slots from a wireless frame; A step of determining the slots capable of paging transmission among the extracted downlink slots by referring to the control resource set and the common search space; A step of determining a paging opportunity slot among the slots capable of paging transmission using the previously determined number of paging modules and identification information of each cell; and A method comprising the step of transmitting a paging message through the paging opportunity slot for each cell.
In paragraph 6, The step of determining the slots capable of the above-mentioned paging transfer is: A method characterized by determining the slots capable of paging transmission by excluding from the downlink slots the slots corresponding to another type of common search space that shares resources with the common search space for paging transmission.
In paragraph 6, The above extraction step is, A method characterized by extracting a downlink slot and a flexible slot having a downlink symbol capable of paging transmission from a wireless frame into the downlink slots.
In paragraph 6, The step of determining the above paging opportunity slot is, A method characterized by determining the slot in the order corresponding to the result of performing a modular operation on the identification information of each cell with the paging modular number plus 1 as the paging opportunity slot of each cell.
In paragraph 6, A method characterized by further including the step of not transmitting a signal in an area corresponding to a paging common search space in each cell, in a slot that is capable of paging transmission but is not a paging opportunity slot.
A computer program that executes a method according to any one of paragraphs 6 through 10 through a computer system, and is stored on a computer-readable recording medium.

Description

Base station and method for improving paging reception success rate of 5G standalone small cell and mobile communication system The present invention relates to paging transmission in a 5G standalone base station, and more specifically, to a base station and a method for improving the paging reception success rate by suppressing paging interference between adjacent cells. In a mobile communication system, when a mobile terminal, or User Equipment (UE), has no data to transmit or receive, the UE can be transitioned to an idle state to reduce battery consumption. When data to be transmitted to an idle UE or an incoming call is received, the core system (e.g., MME/AMF) sends an S1AP/NG-AP paging message to the base station. The base station then sends an RRC paging message at the paging occasion (PO) determined by the UE's unique identification information (UE-ID). During every paging cycle, the idle UE checks for paging reception at the paging occasion (PO) determined by the UE-ID. The UE performs location registration when initially registering a location or when entering a new Tracking Area Code (TAC) area, and through this process, registers its changed location with the core system. The core system allows the UE to register a location and provides it with the S-TMSI uniquely available within the area, and the Tracking Area List (TAL) information, which is a list of TACs or TACs for which the S-TMSI is valid. A UE in an idle state does not report a change in location (e.g., Tracking Area Update (TAU)) to a subscriber location management device (e.g., VLR such as MME/AMF) when moving between base stations with the same TAC or between base stations with TACs belonging to the TAL. Therefore, when a UE is in an idle state, the cell the UE last connected to may differ from the cell where the UE is actually located; thus, paging is always transmitted in TAC units or TAL units. Generally, when designing a TAC, dozens of cells are grouped together and assigned to the same TAC. Consequently, if paging messages are transmitted in TAC units, they are sent simultaneously to dozens of cells, and if they are transmitted in TAL units, they are sent simultaneously to hundreds of cells, which increases the signaling load and can reduce the success rate of paging reception due to inter-cell interference. Figure 1 is a diagram showing an LTE base station and a 5G base station. As shown on the left side of Figure 1, an LTE base station consists of a Digital Unit (DU) and a Radio Unit (RU). It uses a configuration where the RU, which processes RF signals, and the antenna, which transmits the RF signals generated by the RU, are separated. In many cases, the signal from the same RU is split into three (or two) using a 3 (or 2) way splitter to radiate the same signal from three (or two) antennas. On the other hand, as shown on the right side of Figure 1, a 5G base station uses integrated equipment with an antenna built into the Remote Unit (RU) to support Massive MIMO, and feedline splitting using a splitter is not possible. Therefore, in the case of LTE, signals from a single RU are often split into three and transmitted through three antennas to configure one site as one RU (=cell), whereas in the case of 5G, three RUs/antennas are deployed at a single site, increasing the number of cells by two to three times compared to LTE and thus increasing the number of cells per unit area. In addition, while LTE systems using Frequency Division Duplexing (FDD) only require frequency synchronization between base stations and do not need to maintain timing synchronization due to the nature of FDD, 5G systems using Time Division Duplexing (TDD) require not only frequency synchronization but also timing synchronization between base stations to prevent quality degradation caused by UL/DL co-existence issues. Consequently, in the case of TDD 5G base stations, the number of cells with matching transmission timings increases, leading to increased inter-cell interference. In particular, regarding the transmission of paging messages, when a paging message is sent to a single UE, multiple cells with the same TAC/TAL that have matching transmission timings simultaneously transmit the paging message, resulting in a large amount of inter-cell interference signals and a decrease in the paging reception success rate. Therefore, in 5G, where the number of interfering cells is higher than in LTE, the reduced paging reception success rate may make normal 5G Stand-Alone (SA) service impossible or necessitate operating with a very small 5G SA coverage area. Figure 1 is a diagram showing an LTE base station and a 5G base station. FIG. 2 is a diagram showing the configuration of a base station according to one embodiment of the present invention. FIG. 3 is a diagram showing slots of cells according to one embodiment of the present invention. FIG. 4 is a flowchart illustrating a method for determining a slot capable of paging transmission in a base station acco