WO2019029080A1 - INTERFERENCE MITIGATION FOR AERIAL VEHICLES IN WIRELESS COMMUNICATIONS - Google Patents

INTERFERENCE MITIGATION FOR AERIAL VEHICLES IN WIRELESS COMMUNICATIONS Download PDF

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Publication number
WO2019029080A1
WO2019029080A1 PCT/CN2017/116337 CN2017116337W WO2019029080A1 WO 2019029080 A1 WO2019029080 A1 WO 2019029080A1 CN 2017116337 W CN2017116337 W CN 2017116337W WO 2019029080 A1 WO2019029080 A1 WO 2019029080A1
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Prior art keywords
aerial
cells
interference
aerial device
network
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PCT/CN2017/116337
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English (en)
French (fr)
Inventor
Ioannis Xirouchakis
Guillaume Vivier
Caroline Jactat
Sebastian Wagner
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Jrd Communication (Shenzhen) Ltd
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Priority to CN201780091637.8A priority Critical patent/CN110710134B/zh
Publication of WO2019029080A1 publication Critical patent/WO2019029080A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/02—Arrangements for optimising operational condition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C39/00—Aircraft not otherwise provided for
    • B64C39/02—Aircraft not otherwise provided for characterised by special use
    • B64C39/024—Aircraft not otherwise provided for characterised by special use of the remote controlled vehicle type, i.e. RPV
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/18502—Airborne stations
    • H04B7/18504—Aircraft used as relay or high altitude atmospheric platform
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • Embodiments of the present invention generally relate to wireless communication systems and in particular to devices and methods for enabling a wireless communication device, such as a User Equipment (UE) or mobile device to access a Radio Access Technology (RAT) or Radio Access Network (RAN) , particularly but
  • a wireless communication device such as a User Equipment (UE) or mobile device to access a Radio Access Technology (RAT) or Radio Access Network (RAN) , particularly but
  • UE User Equipment
  • RAT Radio Access Technology
  • RAN Radio Access Network
  • Wireless communication systems such as the third-generation (3G) of mobile telephone standards and technology are well known.
  • 3G standards and technology have been developed by the Third Generation Partnership Project (3GPP) .
  • 3GPP Third Generation Partnership Project
  • the 3 rd generation of wireless communications has generally been developed to support macro-cell mobile phone communications.
  • Communication systems and networks have developed towards a broadband and mobile system.
  • LTE Long Term Evolution
  • E-UTRAN Evolved Universal Mobile Telecommunication System Territorial Radio Access Network
  • 5G or NR new radio
  • One current area of interest is the study of aerial vehicles, often referred to as drones, within an LTE network or equivalent.
  • An objective of the study is to investigate the ability for aerial vehicles for LTE to be served using LTE network deployments with Base Station antennas targeting terrestrial coverage, supporting Release 14 functionality (i.e. including active antennas and FD-MIMO.
  • the focus includes investigations to determine at which level aerial devices could re-use the existing LTE networks, and, if necessary, what enhancements can be introduced to the LTE standards to allow co-existence with terrestrial or ground devices.
  • Figure 1 shows a typical network setup for terrestrial and aerial devices.
  • the common coverage area of inter-cells is significantly increased for aerial devices compared to terrestrial UEs.
  • some potential issues are highlighted and addressed, mainly with respect to the expected interference aerial devices would introduce to the LTE networks.
  • aerial devices such as drones, are expected to fly above base station (BS) antenna heights, thus having an increased line-of-sight (LOS) probability which then results to decrease experienced path-loss (PL) , as shown in Figure 1.
  • BS base station
  • LOS line-of-sight
  • PL path-loss
  • interference to a specific UE is caused by Up Link (UL) signals of inter-users.
  • Aerial vehicles have a stronger UL interference contribution to inter-cells which serve ground and aerial UEs.
  • An aerial UE causes UL interference to inter-cells, i.e. neighboring cells using the same carrier frequency as the serving cell of the drone. Therefore, the UL signal of UEs using that cell is interfered with by the drone.
  • a UE served by an inter-cell related to an aerial UE would experience increased UL interference compared to the case where the aerial UE were a ground UE.
  • Interference increase is also observed for aerial UEs, although not as severely as for ground UE because aerial devices are more dominant due to the increased Line of Sight (LOS) probability.
  • the DL and UL signal quality degradations depicted in Figure 2 and Figure 3 represent the two problems that the present invention is seeking to addressing and aiming to improve.
  • the comparison of Figure2 and Figure, 3 shows the channel quality difference between the UL and the DL, where the UL is 5 dB better on average. This might lead to situations where, if no interference mitigation technique is used, an aerial device might be able to synchronize to a cell but not complete its attachment as it will be unable to receive DL information (Msg2, etc. ) . Thus, any intended interference mitigation technique might have to be activated as early as the Random Access Channel (RACH) procedure.
  • RACH Random Access Channel
  • an aerial device may be obligated to inform the system that it is an aerial device.
  • the eNB can take necessary actions to guarantee that the AV device will not affect the system performance. In some cases, this might be translated to connection limitation or even connection refusal.
  • the network should be able to detect and refuse connection of any aerial device that has not or falsely reported that it is an aerial.
  • the two main metrics for evaluating the DL and UL performance of a user k are the DL signal-to-interference-plus-noise ratio (SINR) and UL SINR respectively:
  • SINR DL signal-to-interference-plus-noise ratio
  • UL SINR UL SINR
  • the uplink SINR is given by the equation 2 below:
  • N is the total number of cells in a network and K the total number of active users within the network.
  • P tx is the transmit power
  • G tx and G rx are the antenna gains of the transmitter and receiver respectively
  • PL is the path-loss between the transmitter and receiver
  • SF is the shadow fading factor
  • Interference management has been an active topic in communications systems and a variety of methods has already been defined.
  • LTE also has several standardized methods for handling different types of interference. Some of them are already being proposed for re-use in the case of aerial devices.
  • the proposed interference mitigation techniques include the following approaches:
  • Inter-Cell Interference Coordination (ICIC) and enhanced ICIC (eICIC) ;
  • any of the methods that have already been standardized were introduced assuming solely terrestrial UEs within the LTE network.
  • the elevation of the aerial devices completely changes the LTE network planning, and these techniques might require varying degrees of adjustments and/or enhancements to be efficiently applied to the aerial vehicles, while maintaining the existing performance of terrestrial UEs.
  • ICIC was originally introduced in LTE, as a method for interference coordination between cells for users at the cell edge.
  • the main concept is that neighboring cells are coordinated to transmit at different power levels for different parts of the frequency spectrum.
  • this method enables a desired frequency reuse factor of one, it requires cells to transmit with less power in a large part of their bandwidth which degrades the overall network performance. Additionally, interference is handled only at cells edges. As a result, this concept cannot be applied for example in heterogeneous networks (HetNets) where a pico-cell can be located in the heart of a macro eNB.
  • HetNets heterogeneous networks
  • ABS Almost Blank Subframes
  • a macro cell is must obey a set of predefined network configurations.
  • control and data information channels are muted (for example, Physical Downlink Shared Channel (PDSCH) , Physical Dedicated Control Channel (PDCCH) , Physical Hybrid ARQ Indicator Channel (PHICH) , Physical Control Format Indicator Channel (PCFICH) ) , see right part of Figure 4
  • PDSCH Physical Downlink Shared Channel
  • PDCCH Physical Dedicated Control Channel
  • PHICH Physical Hybrid ARQ Indicator Channel
  • PCFICH Physical Control Format Indicator Channel
  • CRE Cell Range Extension
  • ICIC ICIC
  • eICIC network assisted information of interfering cells
  • Uplink power control is a procedure where the network can control the transmit power of each UE based on some physical layer parameters in order to make sure that the UL receiver power is within a desired range. This can be done per uplink physical channel, as each of them can follow a different formula, depending on the receive requirements of each channel. For example, equation 4 below shows the corresponding power control formula of PUSCH
  • P PUSCH (i) is the PUSCH transmit power in subframe i
  • M PUSCH (i) are the number of assigned physical resource blocks in that UE in subframe i.
  • P 0_PUSCH is the nominal PUSCH power
  • a (j) is a weight factor
  • PL is the estimated path-loss
  • ⁇ TF (i) is a factor that accounts different modulation and coding the given subframe i
  • f (i) is the closed-loop power correction applied from the network.
  • Other physical channels have similar power expressions depending on each channel’s reliability requirements.
  • the final transmit power of the UE is a function of several physical layer parameter (power class, path-loss, assigned resources, modulation and coding) , but can also be controlled by the network by transmit power control (TPC) commands sent in the uplink grants.
  • TPC transmit power control
  • Beamforming is generally an antenna method for focusing the power of an antenna transmission towards a specific direction, but also receiving a transmission with higher receive power from a specific direction, and having “holes” in the direction of the interferers.
  • beamforming has some other properties like beam-width, i.e. how wide is the receive/transmit beam lobe. These properties are usually characterized by the antenna 3D pattern, or alternatively the azimuth and elevation plane patterns, as shown in Figure. 5.
  • Figure5 shows the3D and 2D antenna patterns of a typical 3-sector cellular base station antenna.
  • a common use of beamforming is for network planning and cell sectorization. Each sector is designed to cover a specific angle width.
  • eNB antennas are designed to have a 120° beam-width such that three sectors are able to cover all 360° of the azimuth plain.
  • the purpose of the sectorization is to allow sectors of the same eNB to interfere less with each other. By doing this, the network can re-use the same frequency band for all sectors (frequency re-use factor of one) .
  • Beam-steering is a technique where the antenna broadside of a beam is steered towards a specific direction instead of pointing to a fixed direction all the time.
  • CoMP is an eNB cooperative technique to improve the throughput performance of UEs, especially the ones located in the cell edge.
  • UE at the cell edge is usually visible by two or more cells.
  • CoMP has three “flavors” : Joint Transmission (JT) ; Coordinated Scheduling and Beamforming (CS/CB) ; and Dynamic Point Selection (DPS) .
  • JT CoMP Joint Transmission
  • CS/CB Coordinated Scheduling and Beamforming
  • DPS Dynamic Point Selection
  • JT CoMP the DL signal can be transmitted from two or more cells, instead of one cell, thereby significantly improving the DL SINR.
  • CS/CB data to a single UE is transmitted from one eNB.
  • the scheduling decisions as well as any beams are coordinated to control the interference that may be generated.
  • DPS CoMP the UE selects the best DL signal from the available CoMP cells. Joint Processing (JP) and DPS methods are depicted in Figure 7.
  • CoMP has two “flavors” : Joint Reception (JR) and Coordinated Scheduling (CS) .
  • JR CoMP Joint Reception
  • CS Coordinated Scheduling
  • the UE can transmit towards multiple cells and improve the UL SINR by signal combining at the network level.
  • the CS CoMP scheme operates by coordinating the scheduling decisions amongst the eNBs to minimize interference.
  • CoMP can also be thought of as an interference mitigation technique as inter-cells act as additional serving cells instead of interferers.
  • CoMP is a complex technique as it not only requires control, but potentially also data exchange between different nodes.
  • a method for mitigating interference in communications between a plurality of wireless communications devices wherein at least a first wireless communications device is moving within a Radio Access Network comprising: identifying the first moving wireless device to be an aerial device based on one or a combination of an Interference Coordination method; a beam forming and steering process and one or more of a collection of criteria indicating a location of the first moving device.
  • the network performance method comprises at least one of increasing the power of a predetermined part of a signal in the communication; decreasing the power of interfering signals; decreasing a number of interfering cells in the vicinity of the aerial device.
  • the method further comprises using at least one of joint transmission; muting one or more interfering cells coordinated scheduling; beamforming and dynamic point selection to achieve the interference coordination method.
  • the method further comprising: when an aerial device enters a cell in a network determining a quality metric based on a channel quality of the aerial device; determining a number of serving cell to be used for a first function based on a predicted position of the aerial device; determining a number of muted cells to be used for a second function based on the predicted position of the aerial device; coordinating the control and data requirements of the aerial device based on using one of the determined number of first or second serving cells.
  • the aerial device is capable of beam forming and steering process to enable the antenna to be steered to a predetermined serving cell.
  • the method further comprising activating beam forming such that a metric is improved; acquiring the serving cell; and adjusting to a line of sight of the beam such that interference in the communication is reduced.
  • the aerial device includes a plurality of antennae and the method relies on the aerial device to select the antenna which experiences the lowest level of interference in the communication.
  • the collection of criteria comprises one or more of: an angle of arrival estimation; an angle spread; estimation; a positioning estimation; a estimation of the velocity of the aerial device; a path loss estimation; scheme for reporting intra frequency cells; a MIMO measurement; an aerial vehicle indicator; and explicit signalling.
  • the Radio Access Network is a New Radio/5G network.
  • the aerial device is a drone.
  • a base station adapted to perform the method of another aspect of the present invention.
  • a UE adapted to perform the method of another aspect of the present invention.
  • a non-transitory computer readable medium having computer readable instructions stored thereon for execution by a processor to perform the method of another aspect of the present invention.
  • the non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory.
  • Figure 1 is a simplified diagram showing a network setup for terrestrial and aerial devices, according to the prior art.
  • Figure 2 is a graph showing Downlink Signal-to-Noise-Ratio Cumulative Distribution Function (DL SINR CDF) of ground and aerial UEs with and without the presence of aerial devices, according to the prior art.
  • DL SINR CDF Downlink Signal-to-Noise-Ratio Cumulative Distribution Function
  • Figure 3 is a graph showing Uplink Signal-to-Noise-Ratio Cumulative Distribution Function (UL SINR CDF) of ground and aerial UEs with and without the presence of aerial devices, according to the prior art.
  • UL SINR CDF Uplink Signal-to-Noise-Ratio Cumulative Distribution Function
  • Figure 4 is a simplified diagram showing ICIC and eICIC subframes, according to the prior art.
  • Figure 5 is a simplified diagram showing the 3D and 2D antenna patterns of a typical 3-sector cellular base station antenna, according to the prior art.
  • Figure 6 is a simplified diagram showing an example of 3-sector horizontal, and 2-sector vertical network sectorization, according to the prior art.
  • Figure 7 is a graph showing JP and DPS downlink CoMP, according to the prior art.
  • Figure 8 is a simplified diagram showing an X2 communication of a scenario inter-cell interference coordination with two joint-transmission cells and two muted cells using ABS, according to an embodiment of the present invention.
  • Figure 9 is a graph DL SINR CDF of aerial UEs with different combination of JP CoMP and eICIC/ABS, according to an embodiment of the present invention.
  • Figure 10 is a simplified diagram showing a sequence chart of the proposed hybrid IC method, according to an embodiment of the present invention.
  • Figure 11 is a simplified diagram showing Aerial vehicle interference venerability to inter-cell interference when using omni-directional antennas, according to an embodiment of the present invention.
  • Figure 12 is a simplified diagram showing aerial vehicle inter-cell interference suppression when using beamforming, according to an embodiment of the present invention
  • Figure 13 is a graph showing two DL SINR CDF of aerial UEs with agnostic beamforming, according to an embodiment of the present invention.
  • Figure 14 is a graph showing UL SINR CDF of aerial UEs with agnostic beamforming in the presence of omni-directional ground UEs, according to an embodiment of the present invention.
  • Figure 15 is a graph showing UL SINR CDF of omni-directional ground UEs in the presence of aerial UEs with agnostic beamforming, according to an embodiment of the present invention.
  • Figure 16 is a simplified diagram showing aerial vehicle inter-cell interference suppression when using LOS gnostic beamforming, according to an embodiment of the present invention.
  • Figure 17 is a graph showing DL SINR CDF of aerial UEs with agnostic beamforming, according to an embodiment of the present invention.
  • Figure 18 is a graph showing UL SINR CDF of aerial UEs with gnostic beamforming in the presence of omni-directional ground UEs, according to an embodiment of the present invention.
  • Figure 19 is a graph showing UL SINR CDF of omni-directional ground UEs in the presence of aerial UEs with gnostic beamforming, according to an embodiment of the present invention.
  • Figure 20 is a simplified diagram showing line-of-Sight azimuth and zenith angles between the serving cell and the aerial, according to an embodiment of the present invention.
  • the invention relates to methods for mitigating the uplink and downlink interference that aerial vehicles (AV) may introduce and experience inside a network, which comprises for example one or more LTE base stations (eNB) , and terrestrial and aerial user equipment (UE) .
  • AV aerial vehicles
  • eNB LTE base stations
  • UE terrestrial and aerial user equipment
  • the methods can also be used in future 5G/NR base stations (gNBs) and in other base stations which function in a similar way and/or experience similar problems and issues.
  • gNBs 5G/NR base stations
  • the invention presents methods to handle the identified interference issues of aerial devices.
  • the methods can be used solely or combined to reduce the interference effects.
  • the following methods are presented.
  • a hybrid interference mitigation method which inherits properties from Joint Transmission CoMP and eICIC using Almost Blank Subframes (ABS) .
  • the first solution proposes increasing the number of serving cells by using a similar method to DL JP CoMP. This may increase the power of the useful information signal and decrease the power of the interference signal.
  • the second solution proposes decreasing the number of interfering cells by using a similar method to eICIC and the use of ABS. This may decrease the power of the interference signal.
  • the corresponding DL SINRs for JP CoMP, eICIC/ABS and JP CoMP+eICIC/ABS can be respectively equations 5, 6 and 7 below:
  • M is the total number of cells used for JP CoMP
  • L is the total number of cells applying eICIC/ABS.
  • the eNB would have available Reference Symbol Received Power (RSRP) and Reference Symbol Received Quality (RSRQ) reports of an aerial UE for a number of intra-frequency interfering cells. Thus, it can decide which cells are the most dominant interferers and which are least dominant. The most dominant interferers are chosen for CoMP and least dominant for ABS in order to maximize the DL SINR gain. Alternatively, due to the increased LOS probability, the eNB can obtain a reliable estimate of an aerial device’s position. Then, the eNB can sort the interferers by interfering power based on the aerial device’s position and the knowledge of the network layout.
  • RSRP Reference Symbol Received Power
  • RSRQ Reference Symbol Received Quality
  • the serving cell reported RSRQ can decide on the number of needed CoMP and ABS cells in order to establish a reliable DL connection.
  • An eNB shall be able to ignore a specific cell to be used in this method if there is the possibility that the aerial device is outside the cover range of that cell.
  • the eNB After deciding on the number of JP CoMP cells M and eICIC/ABS cells L, the eNB can signal them showing its intention to serve an aerial device. The eNB may then send the needed scheduling control information (scheduled subframes, frequency resources, etc. ) , similar to those sent to the aerial device, to allow coordination between the M+L cells.
  • the DL packets of the aerial device For CoMP cells, the DL packets of the aerial device have to be additionally retrieved from the network.
  • a new hybrid network message can be introduced which can be shared with cells for undertaking either CoMP and/or eICIC. This procedure shall be able to adapt to the movement of the aerial device. As it moves, the aerial device may experience different receive signal powers from different cells. A cell can be added to the list of interferers, removed, or changed from CoMP to eICIC, and the opposite.
  • a high level description of the procedure for an eNB to apply the proposed hybrid CoMP/eICIC interference mitigation technique for aerial vehicles follows.
  • an aerial vehicle attaches to an LTE cell (through RACH)
  • a decision is made as to whether a DL interference mitigation technique is required. If yes, the available channel quality of an aerial device towards its intra-frequency cells is sorted relative to others.
  • the aerial device Based on the aerial device’s channel quality towards the serving cell, and the estimated position of the aerial device: the total number of intra-frequency cells M and their cell identities to be used for JP CoMP for the aerial; and the total number of intra-frequency cells L and their cell identities to be used for eICIC/ABS for the aerial are determined.
  • the required control and data information is coordinated and shared with the network so that during a set of scheduled DL TTIs, the aerial device receives the same PDSCH data from M intra-frequency cells, while L intra-frequency cells are muted by using ABS.
  • Figure8 shows the X2 interface between interference-coordinated eNBs using the hybrid JT-CoMP+eICIC/ABS method.
  • An X2-interface is the interface that allows communication between neighboring cells.
  • two cells are transmitting PDSCH to the aerial device (serving cells #0 and #1) and two cells transmit ABS (muted cells#0 and #1) .
  • the original serving cell of the aerial device needs to communicate a similar control signal to each of the coordinated cells, indicating to each one if it is a JT or an ABS cell.
  • Cells that are indicated as JT additional require the PDSCH data content intended to the aerial to be communicated over the X2 interface.
  • the control information sent over X2 to all the coordinated cells needs to include all the required scheduling information (TTI, frequency allocation information, etc. ) of the aerial device so that the eNBs are aware when and which resources to reserve for the service of the aerial device.
  • the data information sent to JT cells needs to be the exact PDSCH information that the original serving cell intends to transmit to the aerial device.
  • Figure9 shows the network performance of aerial devices for different combinations of JP CoMP and eICIC/ABS, which exploit the proposed hybrid interference mitigation method.
  • the figure can provide the SINR gains for the different techniques and their combination, and different number of cells used for CoMP and/or eICIC.
  • Figure 10 shows a sequence chart of the proposed hybrid IC method.
  • the eNB receives an AV indication from an attached UE along with its measurement reports.
  • the measurement reports contain RSRP/RSRQ measurements of intra (same) and inter (different) frequency cells that the UE might re-select or hand-over to. They are a measure of the power and quality of neighboring cells.
  • intra-frequency RSRP/RSRQ reports can be used as a metrics for defining how much interference is experienced by that UE.
  • the eNB decides on the number and identities of the JT and ABS cells.
  • the eNB informs the cells on its intention to perform aerial interference coordination and receives the replies from those cells.
  • the eNB Upon reception of a DL packet for the aerial device, the eNB sends the required scheduling/control information to the coordinated cells.
  • the eNB additionally uses the X2-interface to send the aerial device DL packets.
  • the broadside is the direction of maximum signal transmission and reception of an antenna. It is often used as the reference direction where azimuth and zenith angles are measured.
  • the antennas of the UE are generally assumed to be omni-directional, i.e. the antenna gain is independent of the direction of the signal, i.e. For ground UEs, this is generally required because the serving cell signal can be received from any angle due to the scattering-rich terrestrial environment.
  • the signal from the serving and inter-cells is very likely to arrive from the respective LOSs.
  • the use of omni-directional antennas allows interfering cells to pollute the serving cell’s DL signal to the aerial devices, and the aerial devices to pollute the UL signals to other (ground and aerial) UEs of the network, as shown in Figure 11.
  • the use of directional antennas can be extremely useful to suppress the interference to a large number of inter-cells.
  • the interference suppression is dependent on the used beam-width and the direction of the broadside.
  • the UE If the UE is agnostic (not aware) of the direction of the serving cell, it can point in a fixed direction e.g. towards the direction of travel (DoT) for the azimuth angle ⁇ and a zenith angle ⁇ which depends e.g. from the inter-site-distance (ISD) of the network, assuming that this is available to the UE. By doing this, the UE suppresses a number of inter-cell interferers as the LOS signals arriving at the UE away from the broadside will be attenuated as depicted in Figure12.
  • DoT direction of travel
  • ISD inter-site-distance
  • a downside of agnostic beamforming method is that the UE might point its beam away from the serving cell which would reduce the receive power of the serving cell signal and the UL and DL performance of the aerial device. Thus, if the beam is too narrow, it has the effect of degrading the DL signal quality as the reception of the serving cell’s signal is negatively impacted.
  • Figure 13 to 15 show that there are only a few benefits in using agnostic beamforming.
  • the signal of the aerials is improved by very little and for just small range of beam-width.
  • Figure 13 shows 2 DL SINR CDF of aerial UEs with agnostic beamforming (DoT tracking) .
  • ⁇ 3dB and are the zenith and azimuth 3dB beam-width, respectively.
  • Figure 14 shows the UL SINR CDF of aerial UEs with agnostic beamforming (DoT tracking) in the presence of omni-directional ground UEs.
  • Figure 15 shows the UL SINR CDF of omni-directional ground UEs in the presence of aerial UEs with agnostic beamforming (DoT tracking) .
  • the performance of ground UEs is benefited by the use of aerial agnostic beamforming, however, the performance of the aerial UEs is heavily degraded and may not achieve the high data rate requirements of the aerial device UL.
  • the aerial device In the situation where the aerial device is gnostic (aware) of the direction of the serving cell, by either estimating it itself and/or by receiving it from the eNB, the aerial device can beam-steer the broadside towards the serving cell and maximize its DL receive power.
  • the DL SINR improvement is dependent on the beam-width as shown in Figure 17.
  • the beam-width of the aerial devices has little effect on their UL SINR, as is shown in Figure 18.
  • the aerial device now causes less UL interference, which is again a function of the used beam-width as shown in Figure 19.
  • this direction can be communicated to the aerial device via the serving cell sending estimates of the LOS Azimuth angle of Arrival (AoA) and the Zenith angle of Arrival (ZoA) , which can be relative to a predefined coordination system, see Figure 20, which shows the LOS azimuth and zenith angles between the serving cell and the aerial device.
  • the UE can then point towards that direction to improve the DL and UL SINR and reduce interference.
  • either the beam-steering towards the serving cell can be carried out by the UE based on its velocity and direction of travel (DoT) , or the AoA/ZoA can be signalled periodically from the eNB.
  • DoT velocity and direction of travel
  • any interference mitigation technique may have to be activated as early as the RACH procedure.
  • AoA/ZoA may be difficult to be communicated through the initial attachment steps (Msg2, Msg4) .
  • the UE can perform synchronization via, for example, PSS/SSS processing and attachment via RACH as follows. Firstly, agnostic beamforming is activated to obtain an initial improvement on a metric such as the SINR. Secondly, the beam is steered or rotated until a serving cell is acquired. Next, the altitude is reduced until interference of any intra-cells is less severe. This could occur in the initial stage of the aerial devices’flight.
  • the eNB When attached, the eNB can assist the UE to find the LOS direction and further improve the UL and DL communication with the serving cell, and reduce the UL interference it causes to other UEs.
  • the aerial vehicle shall communicate its beamforming capabilities, for example, its beam-width, beam-steering and beam-tracking capabilities.
  • the AV can communicate the 3dB beam-width and maximum attenuation in both the vertical and horizontal planes.
  • the following list describes a high-level procedure and message exchange between the aerial vehicle and the eNB to enable the proposed functionalities to take place.
  • the UE activates beamforming and performs cell acquisition. The UE might have to steer its beam until it is able to successfully receive DL signals from the serving cell.
  • the UE Upon connection, such as via RACH completion, and during Radio Resource Control (RRC) connection, the UE informs the eNB about its beamforming capabilities through the RRC UE capability information message.
  • This may comprise the following beamforming properties such as AV-BeamformingEnabled is the aerial vehicle beamforming indicator;
  • ⁇ AV-H-Beamwidth is the 3 dB beam-width in the horizontal direction
  • ⁇ AV-V-Beamwidth is the 3 dB beam-width in the vertical direction
  • ⁇ AV-max-H-BeamAttenuation is the maximum antenna attenuation in the horizontal direction
  • ⁇ AV-max-V-BeamAttenuation is the maximum antenna attenuation in the vertical direction
  • ⁇ AV-BeamSteeringEnabled is the aerial vehicle beam-steering capability indicator
  • ⁇ AV-BeamTrackingEnabled is the aerial vehicle beam-tracking indicator.
  • the eNB can estimate and communicate the AoA/ZoA angles to the UE through signaling.
  • the eNB can periodically estimate and communicate the AoA/ZoA angles to the UE through signaling so that the UE corrects its beam direction.
  • the eNB can use the UEs beam-forming reported capabilities to estimate the level of UL interference the aerial is causing and determine if adaptation to its UL power transmission is needed and at which level.
  • a simpler embodiment of beam-steering at the AV side may be to consider that the aerial vehicle embeds by default several sectorized antenna. To illustrate, it is assume that a drone quadcopter (with four legs) will have one antenna per leg, which may further reduce the probability of having the antenna hidden during a flight event (yaw or roll or pitch with high angle) . The AV could then select the antenna that provides the best SINR and conduct regular measurement on the other to anticipate handover when and if needed.
  • This approach can be achieved by at least one of the following. Relying on AV (UE) decision only, with no network implication and extending the existing LTE feature of antenna selection to support more antennas and aerial case
  • the network may need to be able to detect any aerial devices that have not properly reported that they are aerial devices, in order to protect the network’s performance degradation of any unhandled interference introduced by non-reported aerial devices.
  • This may require eNBs to be able to efficiently detect if a UE is an aerial vehicle and act accordingly.
  • the eNB could use one or more methods for the aerial vehicle detection.
  • the eNB could estimate the ZoA and based on the outcome can set a ZoA limit after which the UE device is considered to be an aerial device. This can be dependent on, for example, the eNB antenna height, the local environment, the max/average building height, and other similar parameters. However, the ZoA criteria to refuse connection may be standardized so that all eNBs follow the same criteria for rejecting aerial devices.
  • Angle spread (AS) estimation is not an efficient standalone method for aerial vehicle detection because ground UEs can also experience low AS when e.g. in LOS.
  • AS estimation can be an ideal complementary method to other aerial device detection methods because aerial devices have higher LOS probability which results to very narrow angle spreads.
  • AS estimation can act as a sanity check, e.g. if the estimated AS is low then the eNB can be sure the UE is an aerial device. If the AS is high then the eNB can re-estimate the ZoA and AS before making a decision for connection refusal.
  • the angle spread range in which a UE cannot be considered an aerial device may be standardized.
  • At least three timing measurements from geographically dispersed eNBs with good geometry may be needed to solve for two coordinates (x, y) of the UE.
  • This method is designed with the assumption that UEs are moving within the terrestrial plane. For aerial devices this assumption may not always be true.
  • OTDOA OTDOA to be used as a 3D positioning method
  • the eNB may be required to handle this geometry problem in 3 dimensions.
  • GPS Global Positioning Systems
  • Velocity estimation can provide additional information in order for an eNB to differentiate an aerial device from an outdoor stationary UE in elevated areas (e.g. antenna technician) , since aerial devices are expected to be moving in a higher velocity.
  • Velocity estimation can be derived by a time derivative of available parameters such as AoA, ZoA (through AoZ/ZoA estimation) or x, y, z (through positioning) .
  • Doppler shift estimation could be another method for velocity estimation, (e.g. based on rotation of the reference signals.
  • Path-loss estimation can provide additional information in order for an eNB to differentiate an aerial device from an indoor UE which is located within a high building. Indoor UEs are expected to have a higher path-loss value due to penetration losses.
  • the eNB can additionally process the RSRP/RSRQ reports for the intra-frequency cells that a UE makes and then use this to decide if the reported values are too high for a ground UE. This information may be combined with other criteria to decide if a UE is actually an aerial device.
  • the network may also exploit the 3D MIMO feature 3GPP has introduced and from this determine which elevation angle provides the best communication path with the UE and use this information for the decision to mark a UE as an aerial device or not.
  • eNBs that have detected the presence of an aerial vehicle which has not indicated as being an aerial vehicle shall be able to communicate this information over the X2-interface to neighboring cells. These cells might be potential serving cells of the aerial device when a hand-over occurs. Thus, this information may be shared between potential serving cells of the aerial device so that any necessary interference mitigation actions take place.
  • Every AV should declare themselves as being an aerial device. This can be done by in a number of different ways. For example, by extending an existing UE capability to indicate an aerial vehicle or by introducing a new UE capability, such as the following:
  • the network can set and broadcast (e.g. in the System Information Block (SIB) ) an altitude threshold above which a UE shall be considered an aerial.
  • SIB System Information Block
  • the altitude threshold can be dependent on at least the following criteria: eNB antenna height; network environment (macro-cell, micro-cell, etc. ) ; and other environment properties (average building height, street width, etc. )
  • the UE By knowing its altitude, when the UE exceeds this threshold, it can inform the eNB via signaling that it is now flying above that threshold. It can also indicate the opposite, i.e. when it is no longer flying above that threshold.
  • two indications can be introduced. A first which informs of its capability of flying above the terrestrial environment and another which informs that the aerial is actually flying above the altitude threshold.
  • any of the devices or apparatus that form part of the network may include at least a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the method of any aspect of the present invention. Further options and choices are described below.
  • the signal processing functionality of the embodiments of the invention especially the gNB and the UE may be achieved using computing systems or architectures known to those who are skilled in the relevant art.
  • Computing systems such as, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc. ) , mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment can be used.
  • the computing system can include one or more processors which can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control module.
  • the computing system can also include a main memory, such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by a processor. Such a main memory also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor.
  • the computing system may likewise include a read only memory (ROM) or other static storage device for storing static information and instructions for a processor.
  • ROM read only memory
  • the computing system may also include an information storage system which may include, for example, a media drive and a removable storage interface.
  • the media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW) , or other removable or fixed media drive.
  • Storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive.
  • the storage media may include a computer-readable storage medium having particular computer software or data stored therein.
  • an information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system.
  • Such components may include, for example, a removable storage unit and an interface , such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to computing system.
  • the computing system can also include a communications interface.
  • a communications interface can be used to allow software and data to be transferred between a computing system and external devices.
  • Examples of communications interfaces can include a modem, a network interface (such as an Ethernet or other NIC card) , a communications port (such as for example, a universal serial bus (USB) port) , a PCMCIA slot and card, etc.
  • Software and data transferred via a communications interface are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by a communications interface medium.
  • computer program product may be used generally to refer to tangible media such as, for example, a memory, storage device, or storage unit.
  • These and other forms of computer-readable media may store one or more instructions for use by the processor comprising the computer system to cause the processor to perform specified operations.
  • Such instructions generally referred to as ‘computer program code’ (which may be grouped in the form of computer programs or other groupings) , when executed, enable the computing system to perform functions of embodiments of the present invention.
  • the code may directly cause a processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.
  • the non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory
  • the software may be stored in a computer-readable medium and loaded into computing system using, for example, removable storage drive.
  • a control module in this example, software instructions or executable computer program code
  • the processor in the computer system when executed by the processor in the computer system, causes a processor to perform the functions of the invention as described herein.
  • inventive concept can be applied to any circuit for performing signal processing functionality within a network element. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a microcontroller of a digital signal processor (DSP) , or application-specific integrated circuit (ASIC) and/or any other sub-system element.
  • DSP digital signal processor
  • ASIC application-specific integrated circuit
  • aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these.
  • the invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors or configurable module components such as FPGA devices.
  • the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

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