RU2780218C1 - Method for sending data using two 5g new radio base stations - Google Patents

Abstract

FIELD: communication technology.

SUBSTANCE: invention relates to the field of communication. The method for sending data using two 5G New Radio base stations operating in the low-frequency and high-frequency bands includes receiving packets for transmission to the PDCP level of the low-frequency base station (MgNB), buffering at the PDCP level and estimating the maximum storage time of each packet on the low-frequency base station (MgNB), taking into account the data transfer rate, queue length and restrictions on the time of package delivery, sending duplicate packages via a high-frequency base station (SgNB) to the user, receiving confirmations to the high-frequency base station (SgNB) about packet delivery and notifying the PDCP level at the low-frequency base station (MgNB), removing already delivered packets from the waiting queue at the low-frequency base station (MgNB), when the timer expires for the time of packet storage at the PDPC level at the low-frequency base station (MgNB), the packet it is sent to the user via a low-frequency base station (MgNB).

EFFECT: providing the possibility of data delivery in the 5G New Radio network, using a dual user connection via high-frequency and low-frequency channels, with the implementation of restrictions on the time of data delivery and minimal consumption of channel resources of the low-frequency channel.

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Description

Technical field

The present invention relates to 5G wireless communication systems in which data transmission to user devices can be carried out using two frequency channels: low frequency (carrier frequency <7 GHz) and high frequency (>24 GHz).

State of the art

Currently, virtual and augmented reality applications are actively developing, in which a high-resolution video stream is transmitted from a remote server to a user device connected to a network using wireless data transmission technologies. On the data network side, these applications need to provide both high bandwidth and low latency in order to meet the specified user quality of service requirements (for example, a high delay in the delivery of video frames leads to image distortion on the user's side, which can lead to such unpleasant sensations in the latter, such as dizziness, disorientation and nausea).

One way to achieve high data rates and low latency in a wireless network is to use fifth-generation 5G New Radio technology. New Radio technology provides for the simultaneous use of two frequency bands: the traditional low-frequency band (carrier frequency up to 7 GHz) and the millimeter wave range (carrier frequency from 24 GHz). Wider frequency channels are available in the millimeter wave range, which theoretically makes it possible to achieve high data transfer rates (more than 1 Gb / s per user), which are necessary for servicing virtual and augmented reality applications. However, the use of high frequencies has several disadvantages. The appearance of obstacles or an increase in the distance between the device and the base station entails significant fluctuations in signal strength, which can lead to a significant decrease in throughput or even the inability to transmit data. This is especially critical in the case of real-time traffic, since a sharp decrease in the bandwidth of the high-frequency channel will lead to the inability to meet the restriction on the data delivery time and distortion of the video image on the user.

To improve the reliability of data transmission in New Radio (NR) technology, it is possible to operate the device in Dual Connectivity mode, in which the user device is connected simultaneously to two base stations: to a base station operating in the traditional low-frequency range, and to base station operating in the millimeter wave. These two base stations are referred to as the main (Master Next Generation Node B, MgNB) and secondary (Secondary Next Generation Node B, SgNB). As a rule, a low-frequency base station is assigned to the main one, and a high-frequency base station is assigned to the secondary one in order to ensure a continuous connection of the user to the network.

To improve the reliability of data delivery and ensure minimal delay in the case of using two frequency channels, an approach is used that consists in duplicating packets at the PDCP (Packet Data Convergence Protocol) level and then sending them through both base stations. On the user device, if necessary, remove duplicates and reorder packages. A significant disadvantage of this approach is the high consumption of channel resources at the base station operating in the low frequency range. This should be avoided because a large number of devices are connected to a low-frequency base station as it provides a much larger coverage area and higher received signal strength. Connecting to a high-frequency base station, in turn, is considered as an additional opportunity to increase the data transfer rate. Creating a high load when transmitting high-definition video streams through a low-frequency base station can lead to a significant decrease in the quality of service of a large number of other user devices connected to this base station.

An analogue of this technical solution is Discarding a Duplicate Packet of an RLC Entity in Response to an Acknowledgment (US2020344723A1, publ. 10/29/2020). The disadvantage of this analog is the high consumption of channel resources of the base station using the low frequency range, due to the need to transmit packets using the low frequency range until confirmation of data delivery using the high frequency range is received.

Another analogue of this technical solution is PDCP and flow control for a divided unidirectional channel (RU2658586 C2, publ. 06/22/2018). The disadvantage of this analogue is also the high use of channel resources of the base station using the low-frequency range, since the data is sent immediately through both base stations.

One possible solution to the problem described above is to develop a new way of sending data in Dual Connectivity mode, first sending packets through a high frequency base station and buffering these packets at a low frequency base station. In this case, data is sent through the low frequency base station only when it cannot be successfully delivered in a predetermined time through the high frequency base station.

Disclosure of invention

The technical result of this technical solution is to ensure the delivery of data in the 5G New Radio network using a dual user connection through high-frequency and low-frequency channels, with the restriction on the data delivery time and minimal consumption of low-frequency channel channel resources.

The claimed technical result is achieved by means of a method for sending data using two 5G New Radio base stations operating in the low-frequency and high-frequency ranges, comprising the following steps: receiving packets for transmission to the PDCP level of a low-frequency base station (MgNB); buffering at the PDCP level and estimation of the maximum storage time of each packet at a low-frequency base station (MgNB), taking into account the data transfer rate, queue length and packet delivery time limit; sending duplicate packets through the high frequency base station (SgNB) to the user, receiving acknowledgments to the high frequency base station (SgNB) about the delivery of the packets and notifying the PDCP layer at the low frequency base station (MgNB); removal of already delivered packets from the waiting queue at the low frequency base station (MgNB); when the timer expires while the packet is stored at the PDPC layer at the low frequency base station (MgNB), the packet is sent to the user via the low frequency base station (MgNB).

In a private embodiment, the maximum packet storage time is recalculated every time the queue length changes, as well as the data transfer rate changes at the MgNB low-frequency base station.

In another embodiment, the low frequency base station is an LTE base station connected to the New Radio high frequency base station in Multi-Radio Dual Connectivity.

Brief description of the drawings

Figure 1 - architecture of the New Radio network with a dual connection of the user device.

Figure 2 - Protocol stack of New Radio base stations in dual connection mode.

Figure 3 is a flowchart of the proposed method describing packet processing at base stations.

Implementation of the invention

Figure 1 shows a diagram of a New Radio (NR) network, where the user device (130) is connected to two base stations: the main one (Master Next Generation Node B, MgNB), operating in the low frequency band (for example, 3500 MHz @ 100 MHz) (121 ) , and a secondary (Secondary Next Generation NodeB, SgNB) operating in the high frequency range (eg 25 GHz @ 400 MHz) (122 ). The base stations are connected to the SMF (111) , AMF (112) , UPF (113) functions and other functions included in the NR network core (5GC) (102) . With the help of the UPF function (113) , communication is carried out with a public access network, which includes a remote server that generates a user data stream (101) . Upper layer control data (such as RRC) is transmitted via the MgNB. User data is transmitted over the MgNB and/or SgNB and between these base stations using the Xn (123) interface.

Figure 2 shows the protocol stack used on the MgNB and SgNB to transfer user data in the downlink. We will consider a network configuration in which user data, i.e. IP packets arrive on the SDAP protocol at the MgNB base station(211)by MCG (Master Cell Group, Russian: master base station group) split bearer (Russian: split virtual connection)(200), At the PDCP level(212) depending on the implemented data sending procedure, which is not specified by the standard, the packets can be: (a) transmitted to the RLC protocol at the MgNB base station(213)and, thus, further transmitted over a low-frequency channel, (b) transmitted over the interface Xn(230)to the RLC protocol of the secondary base station SgNB(221), and, accordingly, be transmitted over a high-frequency channel, (c) are duplicated and transmitted to both RLC protocols(213)and(221). MAC level(222) performs media access and radio resource scheduling for user data transmission, and notifies the RLC protocol of successful data delivery. All the protocols indicated in the diagram are communicated by bidirectional interfaces, i.e. support feedback.

Figure 3 shows a block diagram of the proposed procedure for processing and sending packets using a dual connection with limited packet buffering time and minimal use of low frequency channel resources. For simplicity, consider the procedure for processing a single packet.

First, consider the actions from the MgNB base station. The PDCP protocol at the MgNB base station receives a packet from the upper SDAP layer (310). The PDCP protocol compresses and encrypts the packet and adds a header containing the sequence number (English: sequence number, seqNo) of this packet (311) to it. The packet with the header added to it will be referred to as the PDCP PDU (Protocol Data Unit). The PDCP protocol at the MgNB base station sends a duplicate of this PDCP PDU to the SgNB base station on the Xn (312) interface.

определено максимальное время отправки

, при котором данный пакет (а также последующие за ним) будут доставлены по соединению MgNB-UE за заданное время

. Ограничение

задается протоколами вышележащих уровней при при установке виртуального соединения MCG split bearer. The MgNB base station maintains a QUEUE1 queue in which PDCP PDUs are ordered by arrival time (ie, by their sequence numbers). For each package

the maximum sending time is defined

, at which this packet (as well as subsequent ones) will be delivered over the MgNB-UE connection in a given time

. Limitation

is set by higher layer protocols when establishing a virtual MCG split bearer connection.

=

, где

- текущее время,

- размер PDCP PDU,

- оценка скорости передачи данных по соединению MgNB-UE, которая может быть получена из оценки качества канала по соединению MgNB-UE и объема доступных частотных ресурсов. Для других пакетов новое время отправки пересчитывается следующим образом:

. Следует отметить, что при таком подходе времена отправки

пакетов в очереди QUEUE1 будут отсортированы от меньшего к большему. When a new PDCP PDU arrives, it is added to the tail of the QUEUE1 queue (313) , and the sending times of all packets are recalculated (because adding a new packet increases the delivery time of packets stored in QUEUE1) (314) . The calculation of packet sending times starts from the tail of the queue. For a newly arrived packet, the maximum sending time

=

, where

- current time,

- PDCP PDU size,

- an estimate of the data rate over the MgNB-UE connection, which can be obtained from an estimate of the channel quality over the MgNB-UE connection and the amount of available frequency resources. For other packages, the new dispatch time is recalculated as follows:

. It should be noted that with this approach, the sending times

packets in queue QUEUE1 will be sorted from smallest to largest.

If an acknowledgment of successful delivery of the PDCP PDU with the given PDCP sequence number (315) is received from the SgNB, the packet does not need to be sent on the low frequency wireless channel and is removed from the QUEUE1 queue (316) . In one of the implementations of this procedure, when removing packets from QUEUE1, it is possible to optionally restart the procedure for recalculating the sending times of the remaining packets (314).

с условием непринятия подтверждения его успешной доставки по низкочастотному беспроводному каналу (317) выполняется его отправка на уровень RLC MgNB (318), пакет удаляется из очереди QUEUE1 (316).When it's time to send the head packet

with the condition of not accepting confirmation of its successful delivery over the low-frequency wireless channel (317) , it is sent to the RLC MgNB level (318) , the packet is removed from the QUEUE1 queue (316) .

Next, we describe the actions on the part of SgNB. The SgNB RLC protocol receives the PDCP PDU from the MgNB and adds it to the tail of the RLC queue (321) . The MAC layer (Medium Access Control, Russian: medium access control) of the SgNB base station periodically accesses the wireless channel and, if there is data to transmit, generates a MAC PDU into which the PDCP PDUs stored in the queue on the RLC (322) are placed. The RLC protocol creates a MAP1 table where, when a MAC PDU is sent, the association of the MAC PDU with the PDCP PDU sequence numbers contained in the sent MAC PDU (323) is stored. After sending the MAC PDU (324) , it is necessary to wait for confirmation of successful receipt of this MAC PDU by the MAC layer of the user device. To do this, the MAC layer uses the HARQ (Hybrid Automatic Repeat reQuest) protocol. The receiver, upon receipt of the MAC PDU and its successful decoding, sends back an acknowledgment of its receipt (HARQ-ACK). The sender (SgNB), upon receipt of this acknowledgment (325) , may match this acknowledgment with a MAC PDU. The MAC layer notifies the RLC protocol of the successful delivery of the MAC PDU (326) . The RLC protocol uses the MAP1 table to determine the corresponding sequence numbers of the PDCP PDUs (327) that were delivered in this MAC PDU, and sends information about successfully delivered PDCP PDUs to the MgNB PDCP protocol (328) .

It is possible that the PDCP PDU successfully reached the user via the SgNB, but the acknowledgment of receipt did not reach the MgNB before the PDCP PDU queue timer expired. In such a case, both base stations will send the same PDU to the user. However, algorithms for removing duplicates and permuting packets operating at the PDCP level of the user device will avoid duplicates at the application level and deliver data in the correct order.

Example

Let the remote server sent 10 packets to the user, and each of them reached the SDAP protocol at the MgNB base station. We will assume that these packets arrive first after the user device connects to the base stations, and their PDCP sequence numbers start from 0. When setting the MGC split bearer, the higher protocols set the target packet delivery time to 10 ms. The estimate of the data transfer rate on the low-frequency wireless channel for the period of transmission of this data is 50 Mbps and varies slightly.

на протокол PDCP базовой станции MgNB последовательно поступают 10 пакетов (310). Ограничение на время доставки пакетов

составляет 10 мс. После сжатия и добавления заголовков (311) размер каждого пакета равен 1500 байт. Каждый пакет отправляется на передачу через базовую станцию SgNB по интерфейсу Xn (312). Пакеты, начиная с порядкового номера 0 и далее в порядке его возрастания, добавляются в очередь QUEUE1 (313). Для каждого пакета подсчитываются максимальные времена доставки

(314), которые, с учетом размера PDCP PDU, целевого времени доставки и оценки скорости передачи данных, равны 7,6 мс, 7,84 мс, 8,08 мс, ..., 9,76 мс (от первого к последнему элементу QUEUE1). Let at the moment

10 packets (310) are sequentially received on the PDCP protocol of the MgNB base station. Packet delivery time limit

is 10 ms. After compression and adding headers (311), the size of each packet is 1500 bytes. Each packet is sent for transmission through the SgNB base station on the Xn (312) interface. Packets, starting at sequence number 0 and moving forward in ascending order, are added to queue QUEUE1 (313) . For each package, the maximum delivery times are calculated

(314) , which, given the PDCP PDU size, target delivery time, and data rate estimate, are 7.6 ms, 7.84 ms, 8.08 ms, ..., 9.76 ms (from first to last element QUEUE1).

Let the PDCP MgNB protocol receive confirmation of successful delivery of packets over the SgNB-UE connection with PDCP sequence numbers from 0 to 7 (315) sent by the RLC SgNB protocol (328) at a time of 5 ms. Then these packets are removed from the queue QUEUE1 (316) , and the sending times of the remaining packets - with numbers 8 and 9 - are recalculated (314) . The new send times for packets 8 and 9 are 9.52 and 9.76 ms, respectively. As of 9.52 ms, packet number 8 has not been acknowledged and is timed out (317) . Then this packet is sent to be sent via a low-frequency wireless channel (318) and removed from the queue (316) , the time for sending packet number 9 remains equal to 9.76 ms (314) . Let the confirmation of delivery of packets 8 and 9 arrive at time 9.7 ms (315) . Then packet 9 is removed from the queue QUEUE1 (316) , the queue becomes empty.

The data was successfully delivered to the recipient, and only one packet was sent for transmission over a low-frequency wireless channel, while using the known approach of duplicated packet sending, each packet would be sent over a low-frequency channel, which results in a significant reduction in the consumption of channel resources of a low-frequency wireless channel. channel.

Claims (3)

1. A method for sending data using two 5G New Radio base stations operating in the low-frequency and high-frequency ranges, comprising the following steps: receiving packets for transmission to the PDCP level of the low-frequency base station (MgNB); buffering at the PDCP level and estimation of the maximum storage time of each packet at a low-frequency base station (MgNB), taking into account the data transfer rate, queue length and packet delivery time limit; sending duplicate packets through a high frequency base station (SgNB) to the user; receiving confirmations to the high frequency base station (SgNB) about the delivery of packets and notification of the PDCP layer at the low frequency base station (MgNB); removal of already delivered packets from the waiting queue at the low frequency base station (MgNB); when the timer for the duration of the packet storage at the PDPC layer at the low frequency base station (MgNB) expires, the packet is sent to the user through the low frequency base station (MgNB). 2. The method according to claim 1, characterized in that the maximum packet storage time is recalculated each time the queue length changes, as well as the data transfer rate at the low-frequency base station (MgNB). 3. The method according to claim 1, characterized in that the role of the low-frequency base station is an LTE base station associated with the high-frequency New Radio base station according to the Multi-Radio Dual Connectivity principle.

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