WO2024144622A1

WO2024144622A1 - A coordinated data transmission system and method in an unlicensed radio-frequency spectrum

Info

Publication number: WO2024144622A1
Application number: PCT/TR2023/051454
Authority: WO
Inventors: Ali ARSAL; Huseyin Arslan
Original assignee: Ulak Haberlesme Anonim Sirketi
Priority date: 2022-12-30
Filing date: 2023-12-04
Publication date: 2024-07-04

Abstract

The invention is a system (100) comprising a plurality of transmission points (120), which is developed for providing cellular communication services on unlicensed radio-frequency channels to a plurality of user equipments (UE) via the said transmission points (129). Accordingly, it is characterized in that it comprises at least one central control unit (110) connected with the transmission points (120) to control the transmission points (120); that the said central control unit (110) is configured to enable the said transmission points (120) to transmit in synchronization with a reference clock, according to a channel status map including information on the suitability of the unlicensed radio-frequency channel assigned thereto by the central control unit (110) for sending data.

Description

A COORDINATED DATA TRANSMISSION SYSTEM AND METHOD IN AN UNLICENSED RADIO-FREQUENCY SPECTRUM

TECHNICAL FIELD

The invention relates to a system comprising a plurality of transmission points, which is developed for providing cellular communication services on unlicensed radio-frequency channels to a plurality of user equipments via the said transmission points.

PRIOR ART

Due to the insufficient amount of licensed spectrum, the use of unlicensed spectrum at 5-6 Ghz for cellular communication services is essential to meet sustainable growth requirements. The surplus of unlicensed bands available for use enables high data rates comparable to those in the millimeter wave bands. Devices using the 6 Ghz band can reach these rates without the problems encountered in millimeter wave bands (high propagation losses, susceptibility to blockage, etc.).

In order to access the unlicensed channel, wireless nodes first measure the suitability of the channel. For this, the listen before talk (LBT) procedure is used. Before communicating, the wireless node determines whether the band on which it intends to communicate is in use. In the present art, Wi-Fi and 5G NR-U radio access technologies (RAT) operate in unlicensed spectrum. Regarding the Wi-Fi technology proposed by the IEEE 802.11 standardization group, the LBT procedure is implemented by the CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) mechanism. 5G NR-U is another radio access technology proposed by the 3GPP standardization group that has another variant of the LBT procedure used by wireless nodes to access the unlicensed channel.

Application No. US2022124801 describes a system that transmits data when the unlicensed spectrum is suitable by applying an LBT procedure in the unlicensed spectrum in a variable size contention window (CW) and during periods when a predetermined counter is full. SUMMARY OF THE INVENTION

The present invention relates to a system and method for using unlicensed spectrum for cellular communications in order to introduce new advantages to the relevant technical field.

It is an object of the invention to set forth a system for providing cellular communication services to user equipments using unlicensed spectrum.

Another object of the invention is to enable more efficient use of unlicensed spectrum for cellular communications.

Another object of the invention is to provide cellular communication coverage in unlicensed spectrum for geographical areas with increased data transfer rate and efficiency.

Another object of the invention is to provide a system and method that eliminates the hidden node and exposed node problems.

In order to achieve all of the aforementioned objects and those that will be apparent from the detailed description below, the present invention is a system comprising a plurality of transmission points, which is developed for providing cellular communication services on unlicensed radio-frequency channels to a plurality of user equipments via the said transmission points. Accordingly, its novelty is that it comprises at least one central control unit connected with the transmission points to control the transmission points; that the said control unit is configured to enable the said transmission points to transmit in synchronization with a reference clock, according to a channel status map including information on the suitability of the unlicensed radio-frequency channel assigned thereto by the said central control unit for sending data. Thus, it is ensured that the transmission points provide cellular communication services in a coordinated manner in the unlicensed spectrum.

A possible embodiment of the invention is characterized in that the central control unit is configured to enable the transmission points to send a reservation signal to the suitable channels selected for transmission. Another possible embodiment of the invention is characterized in that the transmission points are divided into clusters according to their geographical location; that the central control unit is configured such that the transmission points in the same cluster transmit on the same frequency band, and that the central control unit is also configured such that geographically neighboring clusters transmit on different frequency bands. This reduces the amount of interference between clusters.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 shows a representative view of the system.

Fig. 2 shows a view of the transmission points in a possible embodiment of the system with the beam direction and frequencies to which they are assigned.

Fig. 3 shows a representative view of a possible embodiment of the invention with joint transmission.

Fig. 4 shows a representative view of how the invention obtains the channel quality signal.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the subject matter of the invention is described only by way of examples for a better understanding of the subject matter, without any limiting effect.

When describing the embodiments of the invention, reference is made to the Third Generation Partnership Project (3GPP) system. The present application uses acronyms, terms and technologies defined in accordance with the Third Generation Partnership Project (3GPP) technology standards, including the following standards and definitions. The 3GPP technical specifications (TS) and technical reports (TR) are hereby incorporated by reference in their entirety and define the relevant terms and the following architectural reference models.

Abbreviations: 3GPP: 3rd Generation Partnership Project

CCA: Clear Channel Assessment

AP: Access Point

CW: Contention Window

UE: User Equipment

LBT: Listen Before Talk

C-RAN: Cloud Radio Access Network

RF: Radio-frequency

Referring to Fig. 1 , the subject of the invention is a system (100) for providing cellular communication services in unlicensed radio-frequency (RF) spectrum. The system (100) comprises a central control unit (110) and transmission points (120) controlled by the said central control unit (110). The central control unit (110) controls the data transmission of the transmission points (110) to the user equipments (UE) in the unlicensed radio wave spectrum according to the channel suitability map so as to operate in synchronization with a reference clock according to a channel suitability map.

The said transmission points (120) are known in the art as TP. The transmission points (120) may include a plurality of receiving and transmitting antennas for transmitting downlink signals to the user equipments (UE) or receiving uplink signals from the user equipments (UE), and other components well known in the art but not described herein that enable these antennas to perform these operations.

The said central control unit (110) may comprise processing units such as a microprocessor, CPU, GPU, etc. or suitable combinations thereof. The said central control unit (110) may comprise memories or suitable combinations of these memories, enabling data to be stored temporarily or permanently.

The central control unit (110) selects the frequency bands on which the transmission points (120) will perform transmission and communication. A communication line (111 ) is provided between the central control unit (110) and the transmission points (120). The said communication line (111 ) may comprise a fiber optic line.

Referring to Fig. 2, the central control unit (110) divides the transmission points (120) into clusters according to their geographical proximity. In this way, a coverage area is provided to enable cellular communication for user equipments (UE) in unlicensed spectrum in a region. The central control unit (110) assigns the same frequency band to the same clusters (C). Clusters (C) that are geographically close to each other also transmit on different frequency bands. The transmission points (120) can communicate based on the beam direction. The transmission points (120) can include a plurality of antennas to send and receive data based on the beam direction accordingly. In a possible embodiment of the invention, the central control unit (110) assigns a different beam direction to each transmission point (120). With CCA based on the beam direction, hidden node and exposed node problems are prevented.

A channel suitability map can be generated with the channel measurements performed by the transmission points (120) or sensors in synchronization with the reference clock. The channel suitability map may include the channel information for which these measurements were taken, the beam orientation of the channel, the location of the transmission point (120) which took the measurement and the time when the measurement was taken.

In a possible embodiment of the invention, the central control unit (110) may enable a reservation signal to be sent to at least some of the channels determined to be suitable. The channels referred to herein can be the suitable channels selected to provide data transmission with the user equipments (UE). This prevents the channel from being used by an external access point (D). The external access point (D) referred to herein indicates any access point (AP) that communicates on the unlicensed RF channel and causes interference on the channels used by the transmission points (120) in the system. The external access point (D) can for example be a Wi-Fi access point (AP). The term suitability referred to herein means that there is no data transmission on the channel, that the channel is clear.

The central control unit (110) ensures data transmission on the channels to which a reservation signal has been sent.

Data transmission can be performed by one of the following methods: Coordinated Beamforming (CB), Dynamic Point Selection (DPS) and Joint Transmission (JP). In a possible embodiment of the invention, transmission is performed by the coordinated beamforming method. In this method, the transmission points (120) of an interference source are muted, which are assigned to the channel assigned to a user and are not appointed to transmit to the user. In this embodiment of the invention, the transmission points (120) in the clusters (C) have channel and beam directions that can cause interference within themselves and between the neighboring clusters (C).

In a possible embodiment of the invention, the central control unit (110) provides data transmission by the dynamic point selection method. In this method, a plurality of transmission points (120) are controlled by the central control unit (110) so as to transmit data alternately to the user equipment (UE).

Referring to Fig. 3, in a possible embodiment of the invention in which the central control unit (110) transmits data by the joint transmission method, at least one first transmission point (120a) and at least one second transmission point (120b) are provided. The central control unit (110) enables the first transmission point (120a) and the second transmission point (120b) to transmit in coordination to the single user equipment (UE).

The central control unit (110) calculates a scheduling metric for a plurality of user equipments (UE) connected by a group of transmission points. It is ensured that the data of users with high scheduling metric are transmitted with priority. This metric varies according to both data transmission capabilities and user priorities. The formula for calculating the said scheduling metric is given below.

In this equation,

denotes the selected user, ^(0 denotes the bit rate that the selected user can receive from the TP / transmission point (120) at time t, ⁰

< ¹ denotes the priority level of the selected user;

denotes the average bit rate received by the selected user from the TP / transmission point (120) until time t; and N denotes the number of TPs operating in coordination. Referring to Fig. 4, in a possible embodiment of the invention, the available bandwidth of the suitable channel selected for data transmission to the user equipment (UE) is determined prior to the data transmission via joint transmission. For this purpose, the central control unit (110) enables the transmission points (120) connected with the user equipment (UE), to which the data will be transmitted, to send a reference signal to this user equipment (UE). The user equipment (UE) calculates the received signal strength indicator (RSSI) for each reference signal it receives. The user equipment sends a channel quality signal including the calculated RSSI to the transmission points (120).

The channel quality signal referred to herein may include the RSSI value converted into a channel quality indicator (CQI) value known in the art and also a quality of service class identifier (QCI). The calculation of QCI and CQI values is not described in more detail here as it is well known in the art.

The central control unit (110) obtains the received channel quality signal as input. The central control unit (110) then schedules the transfer of data from the transmission points (120) to the user equipments (UE) using a scheduling algorithm according to the received channel quality signal. The said scheduling algorithm can be one of the maximum SINR (Signal to interference plus noise ratio) algorithm, Round Robin (RR) algorithm, and Proportional Fairness (PF) algorithm. After the scheduling is completed, the number of source blocks corresponding to the bandwidth allocated to the user; modulation and code scheme; and transmission strength information are determined. The central control unit then ensures transmission with the determined source blocks, at the determined transmission strength, and with the determined modulation and code scheme.

The aforementioned channel suitability map can be obtained, for example, as follows: The transmission points (120) or sensors (121) measure on the unlicensed RF channel to which they are assigned by the central control unit (110) in synchronization with a reference clock. The central control unit (110) can generate a channel suitability map according to the synchronized measurements from the transmission points and/or sensor units (110). The sensor units (121) may comprise antennas for receiving signals and electronic components well known in the art for transforming the signals received by these antennas to control channel suitability. The said sensor units (121) measure whether the channel to which they are assigned is clear or not. The sensor unit (121 ) can perform the CCA step of the LBT protocol. The transmission points (120) also communicate with the LBT protocol and perform the CCA step of the LBT protocol. When elements such as an external access point (D) (other AP) cause interference since they use Wi-Fi or similar protocols, the channel is occupied and this occupancy is detected by the sensor units (121 ). The central control unit (110) is configured to generate a channel status map for controlling the transmission of the transmission points (120) on the suitable unlicensed radio-frequency channel according to the measurements received synchronously from the sensor units (121) and the transmission points (120). The transmission points (120) are configured to transmit data based on beam direction. The sensor units (121 ) are also configured to measure based on the beam direction. The central control unit (110) assigns different beam directions to the transmission points (120) and sensor units (121). The central control unit (110) enables the sensor units (121) to start measuring at the same time in synchronization with the said reference clock. Measurements continue over a contention window (CW).

The scope of protection of the invention is set out in the appended claims and shall in no way be limited to what is described in this detailed description for illustrative purposes. Indeed, it is clear that a person skilled in the art can come up with similar embodiments in light of the foregoing description without departing from the main theme of the invention.

REFERENCE NUMBERS IN THE DRAWING

100 System

110 Central control unit 111 Communication line

120 Transmission point

120a First transmission point

120b Second transmission point

121 Sensor unit C Cluster

C1 First cluster

C2 Second cluster

C3 Third cluster

UE User equipment D External access point

B Beam

Claims

1. A system (100) comprising a plurality of transmission points (120), which is developed for providing cellular communication services on unlicensed radiofrequency channels to a plurality of user equipments (UE) via the said transmission points (129), characterized in that it comprises at least one central control unit (110) connected with the transmission points (120) to control the transmission points (120); that the said central control unit (110) is configured to enable the said transmission points (120) to transmit in synchronization with a reference clock, according to a channel status map including information on the suitability of the unlicensed radio-frequency channel assigned thereto by the central control unit (110) for sending data.

2. A system (100) according to claim 1 , characterized in that the central control unit (110) is configured to enable the transmission points (120) to send a reservation signal to the suitable channels selected for transmission.

3. A system (100) according to claim 1 , characterized in that the transmission points (120) are divided into clusters (C) according to their geographical location; that the central control unit (110) is configured such that the transmission points (120) in the same cluster (C) transmit on the same frequency band, and that the central control unit (110) is also configured such that the geographically neighboring clusters (C) transmit on different frequency bands.

4. A system (100) according to claim 1 , characterized in that it comprises a communication line (111) between the central control unit (110) and the transmission points (120).

5. A system (100) according to claim 4, characterized in that the said communication line (111 ) is a fiber optic line.

6. A system (100) according to claim 1 , characterized in that the transmission points (120) comprise a plurality of antennas suitable for communication based on beam direction.

7. A system (100) according to claim 6, characterized in that the control unit (110) is configured to assign a different beam direction to each transmission point (120).

8.

9. A system (100) according to claim 1 , characterized in that the data transmission is performed by one of the following methods: Coordinated Beamforming (CB), Dynamic Point Selection (DPS) and Joint Transmission (JP).

10. A system (100) according to claim 1 , characterized in that the control unit (110) is configured to mute, during said transmission, the transmission points (120) assigned to a user and not appointed to transmit to the user, which are detected as sources of interference.

11.

12. A system (100) according to claim 1 , characterized in that the control unit (110) is configured to enable the plurality of transmission points (120) to alternately transmit data to the user equipment (UE).

13. A system (100) according to claim 1 , characterized in that the control unit (110) is configured to enable the plurality of transmission points (120) to transmit data to the user equipment (UE) in a coordinated manner.

14. A system (100) according to claim 1 , characterized in that the control unit (110) is configured to calculate a scheduling metric for a plurality of user equipments (UE) connected by a group of transmission points; to ensure that the data is transmitted with priority to the user equipments (UE) with high scheduling metric.

15. A system (100) according to claim 1 , characterized in that the control unit (110) is configured to calculate the said scheduling metric according to the channel between the user equipment (UE) and the transmission points (120) and to a user priority value.

16. A method performed by a system (100) comprising a plurality of transmission points (120), which is developed for providing cellular communication services on unlicensed radio-frequency channels to a plurality of user equipments (UE) via the said transmission points (129), characterized in that it comprises the step of enabling, by the at least one central control unit (110) connected with the transmission points (120) for controlling the transmission points (120), the said transmission points (120) to transmit in synchronization with a reference clock, according to a channel status map including information on the suitability of the unlicensed radio-frequency channel assigned thereto by the central control unit (110) for sending data.

17. A method according to claim 14, characterized in that it comprises step of enabling, by the central control unit (110), the transmission points (120) to send a reservation signal to the suitable channels selected for transmission.