A user location information-assisted millimeter wave access and tracking process considering reflected beams

Abstract

The present invention proposes a millimeter wave access and tracking process based on user location. Specifically, the macro gNB side maintains a "position-beamforming path record table". During initial access, the gNB selects the optimal beam for the user for initial access by looking up the table to avoid exhaustive beam scanning. If there is no corresponding record in the table, the user measures the quality of each signal in the beam scanning path set (all direct and reflected paths from TRP to the user) and feeds it back to the macro station side. The macro station selects the beam with the largest SINR value to serve the user, and adds the optimal beam information of the location to the "position-beamforming path record table". The user periodically detects the SINR quality of the service beam and sets two thresholds. If the service beam quality is good, there is no need to report the location information. If the service beam quality is lower than the first threshold, combined with the record table on the base station side, it decides whether to switch or use the reflected beam for service to avoid unnecessary ping-pong switching.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a study of a millimeter wave access and tracking process based on user location in a fifth generation mobile communication system (the 5th generation, referred to as 5G for short). Background Art

[0002] The rapid development of mobile Internet and smart terminals has brought about an explosive growth in mobile data services, and data traffic has shown an exponential growth. These changes have triggered discussions in the industry about the fifth generation (5G) mobile communications. Future networks will face huge challenges, including greater capacity and lower latency. Millimeter wave (mmWave) communication is one of the key technologies of the fifth generation of mobile communications, which can effectively increase the capacity of the link by utilizing the huge bandwidth of the millimeter wave range. The first severe challenge in achieving millimeter wave communication is path loss. In order to compensate for the severe path loss of millimeter wave transmission, millimeter wave base stations usually use large-scale antenna arrays for narrow beam transmission, which can effectively concentrate the transmission energy in a certain area or direction. However, the directional transmission of millimeter waves is very sensitive to blocking and may even cause connection interruptions, which also brings new challenges to the establishment and maintenance of millimeter wave links.

[0003] Initial Access refers to the process of establishing an initial connection between a user and the core network, which is a key prerequisite for any subsequent communication. How to perform initial access connection in mmWave networks is one of the main challenges of initial access design, mainly for the following reasons: First, mmWave links usually require highly directional beams to achieve sufficient signal-to-interference-and-noise ratio (SINR), but UE and TRP do not know the direction of the transmit and receive beams during the initial access process. Therefore, UE and TRP must search for each other's transmit and receive beam directions in a larger beam space. Secondly, since mmWave communications are achieved using highly directional beams, mmWave links are easily blocked or beams are misaligned due to user movement, which places higher requirements on the robustness of processes such as initial access, beam tracking, mobility management, and switching.

[0004] Studies have long shown that millimeter waves have good reflection properties and the reflected beam power is much greater than the noise level. Recent experimental studies have found that if the size of the obstacle is appropriate, the reflected beam receiving power of the indirect link is very close to the direct free space receiving power at the same link distance, proving the feasibility of using reflected beams to serve users.

[0005] Existing millimeter wave beam access methods: The traditional exhaustive beam scanning method uses uniform planar array (UPA) on both the base station side and the user side. Compared with the use of uniform linear array (ULA), the beam alignment and beam tracking scanning overhead will be greater; the beam scanning method assisted by user location information determines the beam scanning direction (i.e., the direction pointing to the user location) according to the user location, narrowing the scanning range, but missing the reflected beam with good link quality. At the same time, the direct link is easily blocked by obstacles, which may cause a large number of ping-pong switches.

[0006] In view of the high overhead of traditional beam scanning in the above scheme, and the frequent switching caused by the beam scanning method assisted by user location information cannot give full play to the coverage potential of the reflected beam, it is necessary to design a millimeter wave access and tracking process based on user location that takes the reflected beam into consideration. Summary of the invention

[0007] The present invention takes into account the frequent switching problems caused by the existing millimeter wave access and tracking processes, and gives full play to the coverage potential of the reflected beam. In particular, in the millimeter wave dense urban area scenario, there are abundant reflected beam components. A millimeter wave access process based on user location and reflected beam is proposed to improve the shortcomings of the existing beam access method assisted by user location information. When the service beam quality is lower than the second threshold during the user's initial beam access or tracking process, the gNB can query the "position-beamforming path record table" according to the user's location information, and select the optimal beamforming path for initial beam access, avoiding complex and detailed beam scanning. When the direct beam quality of the service station does not meet the service requirements and the reflected beam quality meets the service requirements, the reflected beam can be used for service, thereby avoiding frequent user switching. The macro station gNB controls multiple TRPs within the coverage area and is responsible for the scheduling of user service sites and the selection of direct beams and reflected beams.

[0008] The millimeter wave access and tracking process based on user position and reflected beam of the present invention is described as follows:

[0009] Step 200: The user associates with the macro gNB. The UE listens to the system message to obtain the PRACH channel configuration of the macro gNB, achieves downlink synchronization with the macro, and sends a Preamble code, i.e., a random access preamble code, to the gNB, and reports its location information to the macro.

[0010] Step 210: After receiving the user's Preamble, the macro gNB sends a random access response signal, namely a random access response (RAR), to the UE, so that the UE can synchronize uplink with the macro gNB. At the same time, the macro gNB searches the "position-beamforming path record table" according to the user's position. The "position-beamforming path record table" records some discrete location points in the macro base station coverage area, the optimal service TRP when the user is at this location, the optimal service beam pair configuration information, and whether the service beam is a reflection beam. If the current user's location has been recorded, go to step 220; if the current user's location has not been recorded, go to step 230. The current user's location has been recorded means that there is a recorded location point in the table whose distance from the user's current location is less than the distance threshold d.

[0011] In step 220, the macro gNB obtains the optimal service TRP and beam pair configuration information based on the table lookup result. The macro gNB sends the user information and beam pair configuration information to the optimal service TRP, and at the same time sends the optimal service TRP information and beam pair configuration information to the user. The optimal service TRP and the user receive the indication information from the macro gNB and use the optimal beam pair configuration information to complete the mutual association, and then enter the beam tracking process, that is, step 240.

[0012] Step 230: If there is no information corresponding to the current user location in the current "position-beamforming path record table", the macro gNB determines the beam scanning path set according to the location information of the user and all TRPs in the coverage area. The beam scanning path set refers to the direct beam path and reflected beam path from all TRPs to the user. The macro gNB notifies the user side of all beam labels and information in the beam scanning path set, and notifies the small stations in the beam scanning path set to scan the beams in the set. The user receives the downlink reference signals of different beams of each small station, measures the reference signal SINR and feeds it back to the base station side. The UE i and TRP j The signal-to-interference-noise ratio is expressed as

[0013]

[0014] In the above formula (1), the beamforming gain from the transmitter to the receiver is: Among them, H i,j TRP i and UE j The channel matrix between is the beamforming matrix at the receiving end, is the beamforming matrix at the transmitting end, W is the beam width, N 0The macro gNB selects the service beam with the largest SINR value from the measurement information feedback sent by the user to provide service to the user, and adds the optimal beam information of the position to the "position-beamforming path record table", notifies the user side and the TRP side to complete the association, and then enters the beam tracking process, that is, step 240.

[0015] Step 240: The user periodically detects the SINR quality of the serving beam pair, given two SINR limits η 1 and η 2 (η 2 <η 1 ), when the serving beam pair SINR is greater than the first threshold η 1 (i.e. SINR>η 1 ), there is no need to report the location information to the macro station, and the process returns to step 240; when the service beam pair SINR is greater than the second threshold η 2 and is less than the first threshold η 1 (i.e. η 2 <SINR<η 1 ) When the user reports his position to the macro base station, the macro base station searches the "position-beamforming path record table" according to the user's current position. If the table contains relevant information about the current position, the macro base station checks whether the current service TRP is the optimal service TRP. If so, it sends the optimal beam configuration information to the serving small base station according to the information in the table, and notifies the small base station to make beam adjustments. If not, the macro gNB further checks whether the current service beam is a direct beam. If so, it is considered that the beam performance degradation may be caused by obstruction of obstacles, and the small base station is notified to activate the reflected beam and measure the reflected beam quality. If the reflected beam SINR is greater than the first threshold η 1 , then the reflected beam is used as the service beam, if the reflected beam SINR is less than the first threshold η 1 , it is considered that the user has moved away from the TRP that provides the beam pair connection, and the gNB sends the optimal service TRP and the optimal beam configuration information to the current service TRP. If the current service beam is a reflection beam, it is also considered that the user has moved away from the TRP that provides the beam pair connection, and the gNB sends the optimal service TRP and the optimal beam configuration information to the current service TRP. If there is no relevant information about the current position in the table, the gNB sends an initial access indication message to the current service TRP, and returns to step 200; when the service beam pair SINR is less than the second threshold η 2 (i.e. SINR<η 2 ), the current service beam cannot meet the link performance requirements, and the user sends a low link performance signal to the service station to proceed to the next step.

[0016] In step 250, the service TRP performs the following operations according to the information sent by the macro station: if the service station receives the initial access indication information from the macro station, it notifies the user to perform initial beam access; if the service station receives the optimal beam configuration information from the macro station, it adjusts the beam direction according to the configuration information and returns to step 200; if the current service TRP receives the new optimal service TRP and beam pair configuration information, it notifies the new optimal service TRP and the user to switch TRP at the same time.

[0017] Beneficial Effects

[0018] The present invention considers the frequent switching problem caused by the existing millimeter wave access and tracking process, gives full play to the coverage potential of the reflected beam, especially in the millimeter wave dense urban area scenario, there are abundant reflected beam components, and proposes a millimeter wave access process based on user location and reflected beam to improve the shortcomings of the existing beam access method assisted by user location information. The macro gNB maintains a "position-beamforming path record table", which records some discrete location points in the coverage area of ​​the macro base station, the optimal service TRP when the user is at this location, the optimal service beam pair configuration information, and whether the service beam is a reflected beam. When the user initially accesses the beam, the gNB can query the "position-beamforming path record table" according to the user's location information and select the optimal beamforming path for initial beam access to avoid complex and detailed beam scanning. If there is no corresponding record in the table, the macro gNB determines the beam scanning path set according to the location information of the user and all TRPs in the coverage area. The beam scanning path set refers to the direct beam path and reflected beam path from all TRPs to the user. The scanning range of the path set is also much smaller than the traditional beam scanning. At the same time, the reflected path is included in the beam scanning range, which reasonably increases the beam candidate set, so that the service beam selected by the user has better performance. The small station in the beam scanning path set scans the beams in the set. The user measures the downlink reference signals of different beams of each small station and feeds them back to the base station side. The macro gNB selects the service beam with the largest SINR value from the measurement information feedback sent by the user to provide services to the user, and adds the optimal beam information of the location to the "position-beamforming path record table". When the direct beam quality of the service base station does not meet the service requirements but the reflected beam quality meets the service requirements, the reflected beam can be used for service, thereby avoiding frequent switching of users.

[0019] Compared with the traditional exhaustive beam scanning access method, the beam scanning delay and signaling overhead of the scheme proposed in the present invention are smaller. Compared with the existing user location information-assisted beam access method, the present invention takes into account the reflection direction when determining the beamforming path set, appropriately increases the complexity while giving full play to the coverage potential of the reflected beam, thereby improving the link performance of the service beam pair and reducing the ping-pong switching caused by temporary obstruction of buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a scenario of a millimeter wave access and tracking process assisted by user location information of a reflected beam in the present invention;

[0021] Figure 2 It is the "position-beamforming path record table" maintained by the macro gNB side.

[0022] Figure 3 is a flowchart of the user location information-assisted millimeter wave initial access considering the reflected beam of the present invention;

[0023] Figure 4 is a flow chart of millimeter wave tracking assisted by user position information considering reflected beams of the present invention;

[0024] Figure 5 It is a flowchart of the algorithm implementation of the present invention; DETAILED DESCRIPTION

[0025] System architecture or scenario of application of the present invention

[0026] The access and tracking method of the present invention is mainly applied to millimeter wave cellular networks, such as Figure 1 As shown, the macro gNB maintains a "position-beamforming path record table", which records some discrete location points in the coverage area of ​​the macro base station, the optimal service TRP when the user is at this location, the optimal service beam pair configuration information, and whether the service beam is a reflection beam.

[0027] Users can establish associations with nearby TRPs through millimeter wave direct beams or reflected beams. The gNB covers multiple TRPs within the control range and is responsible for user beam switching and site scheduling decisions. In order to avoid frequent ping-pong switching, when the direct beam does not meet the service requirements, it measures whether the reflected beam meets the service requirements. If so, no site switching occurs, but the reflected beam is used instead for service.

[0028] When the user initially accesses the beam, the gNB can query the "position-beamforming path record table" according to the user's location information and select the optimal beamforming path for initial beam access to avoid complex and detailed beam scanning. If there is no corresponding record in the table, the macro gNB determines the beam scanning path set based on the location information of the user and all TRPs in the coverage area. The beam scanning path set refers to the direct beam path and reflected beam path from all TRPs to the user. The small base station in the beam scanning path set scans the beams in the set. The user measures the downlink reference signals of different beams of each small base station and feeds them back to the base station side. The macro gNB selects the service beam with the largest SINR value from the measurement information feedback sent by the user to provide services to the user, and adds the optimal beam information of the location to the "position-beamforming path record table".

[0029] Implementation steps of user location information-assisted millimeter wave access and tracking process considering reflected beams

[0030] The user location information-assisted millimeter wave access and tracking process considering the reflected beam mainly consists of two parts: the initial beam access process and the beam tracking process. The macro gNB establishes a "position-beamforming path record table" and updates and maintains it during subsequent use. The "position-beamforming path record table" records some discrete location points in the macro base station coverage area, the optimal service TRP when the user is at this location, the optimal service beam pair configuration information, and whether the service beam is a reflected beam, such as Figure 2 shown.

[0031] 1) Initial beam access process

[0032] Figure 3 The figure shows the initial beam access process of the user. The user is associated with the macro gNB. The UE listens to the system message to obtain the PRACH channel configuration of the macro gNB, achieves downlink synchronization with the macro, and sends a Preamble code to the gNB, i.e., a random access preamble, and reports its location information to the macro.

[0033] After receiving the user's Preamble, the macro gNB sends a random access response signal, namely a random access response (RAR), to the UE, so that the UE can synchronize with the macro gNB uplink. At the same time, the macro gNB searches the "position-beamforming path record table" according to the user's position. If the distance between the recorded position in the table and the user's position is less than the distance threshold d, it is considered that the user's position has been recorded, and the user's position is replaced by the position point closest to the user in the table; if the distance between all the recorded position points in the table and the user is greater than the threshold d, it is considered that the user's position has not been recorded. If the current user's position has been recorded, the macro gNB obtains the optimal service TRP and beam pair configuration information based on the table query result. The macro gNB sends the user information and beam pair configuration information to the optimal service TRP, and sends the optimal service TRP information and beam pair configuration information to the user at the same time. The optimal service TRP and the indication information received by the user from the macro gNB are associated with each other using the optimal beam pair configuration information. If the current user's location has not been recorded, the macro gNB determines the beam scanning path set based on the location information of the user and all TRPs in the coverage area. The beam scanning path set refers to the direct beam path and reflected beam path from all TRPs to the user. The macro gNB notifies the user side of all beam labels and information in the beam scanning path set, and at the same time notifies the small stations in the beam scanning path set to scan the beams in the set. The user receives the downlink reference signals of different beams of each small station. The macro gNB selects the service beam with the largest SINR value from the measurement information feedback sent by the user to provide services to the user, and at the same time adds the optimal beam information of the location to the "position-beamforming path record table", notifying the user side and the TRP side to complete the association.

[0034] 2) Beam tracking process

[0035] Figure 4 The user periodically detects the SINR quality of the serving beam pair, given two SINR limits η 1 and η 2 (η 2 <η 1 ), when the serving beam pair SINR is greater than the first threshold η 1 (i.e. SINR>η 1 ), there is no need to report the location information to the macro station, and periodic detection continues. When the SINR of the serving beam pair is greater than the second threshold η 2 and is less than the first threshold η 1 (i.e. η 2 <SINR<η 1) When the user reports his position to the macro base station, the macro base station searches the "position-beamforming path record table" according to the user's current position. If the table contains relevant information about the current position, the macro base station checks whether the current service TRP is the optimal service TRP. If so, it sends the optimal beam configuration information to the serving small base station according to the information in the table, and notifies the small base station to make beam adjustments. If not, the macro gNB further checks whether the current service beam is a direct beam. If so, it is considered that the beam performance degradation may be caused by obstruction of obstacles, and the small base station is notified to activate the reflected beam and measure the reflected beam quality. If the reflected beam SINR is greater than the first threshold η 1 , then the reflected beam is used as the service beam, if the reflected beam SINR is less than the first threshold η 1 , it is considered that the user has moved away from the TRP that provides the beam pair connection, and the gNB sends the optimal service TRP and the optimal beam configuration information to the current service TRP. If the current service beam is a reflection beam, it is also considered that the user has moved away from the TRP that provides the beam pair connection, and the gNB sends the optimal service TRP and the optimal beam configuration information to the current service TRP. If there is no relevant information about the current location in the table, the gNB sends the initial access indication information to the current service TRP to perform the initial beam access process. When the service beam pair SINR is less than the second threshold η 2 (i.e. SINR<η 2 ), that is, the current service beam cannot meet the link performance requirements, the user sends a link performance too low signal to the service station, and the service TRP performs the following operations according to the information sent by the macro station: if the service station receives the initial access indication information from the macro station, it notifies the user to perform initial beam access; if the current service TRP receives the new optimal service TRP and beam pair configuration information, it notifies the new optimal service TRP and the user to switch TRP at the same time.

[0036] Technical effects of the implementation of the solution of the present invention

[0037] The present invention considers the frequent switching problem caused by the existing millimeter wave access and tracking process, gives full play to the coverage potential of the reflected beam, especially in the millimeter wave dense urban scene, there are abundant reflected beam components, and proposes a millimeter wave access process based on user location and reflected beam, which improves the shortcomings of the existing beam access method assisted by user location information. The macro gNB maintains the "position-beamforming path record table". When the user initially accesses the beam, the gNB can query the "position-beamforming path record table" according to the user's location information, select the optimal beamforming path for initial beam access, and avoid complex and detailed beam scanning. If there is no corresponding record in the table, the macro gNB determines the beam scanning path set according to the location information of the user and all TRPs in the coverage area. The beam scanning path set refers to the direct beam path and reflected beam path from all TRPs to the user. The scanning range of the path set is also much smaller than the traditional beam scanning. At the same time, the reflected path is included in the beam scanning range, which reasonably increases the beam candidate set, so that the service beam selected by the user has better performance. The small base station in the beam scanning path set scans the beams in the set. The user measures the downlink reference signals of different beams of each small base station and feeds them back to the base station side. The macro gNB selects the service beam with the largest SINR value from the measurement information feedback sent by the user to provide services to the user, and adds the optimal beam information of the position to the "position-beamforming path record table". When the direct beam quality of the service small base station does not meet the service requirements but the reflected beam quality meets the service requirements, the reflected beam can be used for service, thereby avoiding frequent user switching.

[0038] Compared with the traditional exhaustive beam scanning access method, the beam scanning delay and signaling overhead of the scheme proposed in the present invention are smaller. Compared with the existing user location information-assisted beam access method, the present invention takes into account the reflection direction when determining the beamforming path set, appropriately increases the complexity while giving full play to the coverage potential of the reflected beam, thereby improving the link performance of the service beam pair and reducing the ping-pong switching caused by temporary obstruction of buildings.

Claims

1. A millimeter wave access and tracking method based on user location, It is characterized in that The macro gNB maintains a "position-beamforming path record table", which records some discrete location points in the coverage area of ​​the macro base station, the optimal service TRP when the user is at this location, the optimal service beam pair configuration information, and whether the service beam is a reflection beam; when the user initially accesses the beam, the gNB can query the "position-beamforming path record table" according to the user's location information, select the optimal beamforming path for initial beam access, and avoid complex and detailed beam scanning. If there is no corresponding record in the table, the macro gNB determines the beam scanning path set according to the location information of the user and all TRPs in the coverage area. The beam scanning path set refers to all TRPs. The direct beam path and reflected beam path from RP to the user, the beams in the scan set of the small station in the beam scanning path set, the user measures the downlink reference signal of different beams of each small station and feeds it back to the base station side, the macro gNB selects the service beam with the largest SINR value from the measurement information feedback sent by the user to provide service to the user, and adds the optimal beam information of the position to the "position-beamforming path record table"; when the direct beam quality of the service small station does not meet the service requirements but the reflected beam quality meets the service requirements, the reflected beam can be used for service, thereby avoiding frequent switching of users between TRPs; the user periodically detects the SINR quality of the service beam, given two SINR limits η 1 and η 2 ; When the service beam pair SINR is greater than the first threshold η 1 When the service beam pair SINR is greater than the second threshold η, stop reporting the location information; when the service beam pair SINR is greater than the second threshold η 2 and is less than the first threshold η 1 When the user reports his position to the macro base station, the macro base station searches the "position-beamforming path record table" according to the user's current position. If the table contains relevant information about the current position, the macro base station checks whether the current service TRP is the optimal service TRP. If so, it sends the optimal beam configuration information to the serving small base station according to the information in the table, and notifies the small base station to make beam adjustments. If not, the macro gNB further checks whether the current service beam is a direct beam. If so, it is considered that the beam performance degradation is caused by obstacles, and the small base station is notified to activate the reflected beam and measure the reflected beam quality. If the reflected beam SINR is greater than the first threshold η 1 , then the reflected beam is used as the service beam, if the reflected beam SINR is less than the first threshold η 1 , the user is considered to be far away from the TRP that provides the beam pair connection, and the user will enter the handover preparation state. If the current service beam is a reflection beam, the user is also considered to be far away from the TRP that provides the beam pair connection, and the user enters the handover preparation state. If there is no relevant information about the current location in the table, the gNB sends an initial access indication message to the current service TRP; when the service beam pair SINR is less than the second threshold η 2 When the user sends a link performance low signal to the service base station, the service TRP notifies the user to switch or initially access based on the information sent by the macro base station.

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