A method of beam selection for localization and communication in MIMO networks

Abstract

The invention is related to a beam selection method for localization and communication in MIMO networks based on the time of arrivals, signal power strength, and angle to reduce the system latency with providing high accuracy.

Description

[0001] A METHOD OF BEAM SELECTION FOR LOCALIZATION AND COMMUNICATION IN MIMO NETWORKS

[0002] Technical Field

[0003] The invention is related to a beam selection method for localization and communication in MIMO networks.

[0004] Prior Art

[0005] In wireless networks, the localization process relies on parameters such as time of arrival, angle of arrival, and signal power level. Achieving higher accuracy in localization is particularly evident when operating at higher frequencies. With the adoption of the mmWave spectrum in the 5G standard for communication, beamforming techniques become instrumental in facilitating communication on this spectrum. While beam selection methods based on signal power level have been extensively explored in the literature for communication, these methods may not perform optimally for localization, especially in non- line-of-sight (NLOS) channels.

[0006] Unlike communication scenarios where signal power is a critical factor, it may not be the most crucial parameter for effective localization. Conventional beam selection methods relying solely on signal power level may not be suitable for localization purposes, particularly in NLOS channels. To illustrate, consider a scenario where there are two beam options in an NLOS channel. The first beam exhibits a higher signal power level at the receiver compared to the second beam, making it the preferred choice for communication. However, this doesn't necessarily make it the best beam for localization. The accuracy of localization, involving parameters such as time of arrival and angle of arrival, is influenced by factors beyond signal power.

[0007] The primary challenge at hand is determining how to select beams specifically for localization, taking into account parameters like angle of arrival and time of arrival. This problem addresses the need for a nuanced approach to beam selection, recognizing that the optimal beam for communication may not align with the requirements for accurate localization, especially in complex NLOS channel scenarios. Beam management is one of the main technical innovations for 5G MEMO systems and beyond. It is a set of PHY and MAC layers procedures to establish and retain an optimal beam pair for good connectivity [1], It comprises various aspects and components, as defined in the IEEE 802. Had standard [2,3,4]: beam sweep and measurement, beam determination, beam reporting, beam recovery, and beam switching. In general, the beam management mechanism for beamforming-based initial accessing, beamforming training in active states, and the corresponding flexible frame structure designs is presented in [5], where the base station sweeps the beams for a possible connection, while the user side receives the beams and calculates the frequency-time resource of the beams that exceed the receiver signal quality to obtain the symbol, subframe, timing beam sequences, and its corresponding receiver beamforming weights. After that, the user decodes the selected beam ID and feeds it back to the BS via uplink transmitter beamforming.

[0008] In non-coordinated networks, many algorithms are developed in the literature to reduce the latency time introduced by the beam management procedures discussed before. Unlike the conventional exhaustive beam sweeping standardized to scan the space to find the best alignment between the nodes in the beam management process which takes up a few seconds, [6] develops a learning algorithm namely the hierarchical beam alignment algorithm in the multipath channel to identify the optimal beam. [7] presents an Agile-Link platform to find the correct alignment of the beams between a transmitter and a receiver without the need of scanning the whole space by hashing the beam directions using carefully chosen hash functions and then tracking how the energy changes across different hash functions, while [8] present a framework for fast beam alignment with low-resolution phase shifters. This framework uses an efficient set of antenna weight vectors to acquire channel measurements and allows faster beam alignment. [9] presents a location-aided beam alignment as a potential approach for fast link establishment that is resilient to mobility and estimation processing imperfection with a reduced complexity overhead. This is done based on a probabilistic location information setting for both nodes BS and UE where the pre-selection decision is recast to decentralized coordination between the BS and UE. Although this method reduces the complexity overhead at both nodes, it still keeps large processing to be done at the UE side where the feedback is still necessary for completing the connection. In

[0010] , group-based reporting which is a reduced level of beam-based reporting is introduced to minimize the feedback overhead in the system. Unlike conventional beam-based reporting, the reporting table in group-based reporting includes the RSRP for the representative beam and the differential RSRP value for each additional beam in the group only which reduce the transmission cycle. The representative beam refers to either the beam that has the maximum measurement value compared to the other beams in the group or an average of the beams in the group.

[0009] The beam selection for communication is done based on the signal power level or RSRP. For localization, if the direction of the receiver is known, the beam is conventionally selected on the known direction. The beam selection based on the signal power level is also done for localization similar to communication. This approach is only suitable for the localization methods with the signal power level. However, it is not good for the localization with the parameters of angle of arrival and time of arrival. Therefore, IEEE 802. Hay uses a first path beamforming training method for a better localization accuracy [11,12], Note that the localization in new wireless standards such as 5G is mainly done based on the with the parameters of angle of arrival and time of arrival.

[0010] As a result, all of the problem mentioned above has made it necessary to provide a novelty in the related field.

[0011] Objects of the Invention

[0012] The main object of the present invention is to enhance the precision of localization and facilitate swift beam searching and alignment with minimal complexity in communication processes. This dual-purpose innovation seeks to improve accuracy in determining the location while concurrently optimizing the efficiency of beam alignment, ensuring a faster and less complex communication system.

[0013] Another object of the invention is to achieve a more precise determination of the device's location, especially in scenarios involving asynchronous transmission between the transmitter and receiver. This capability is particularly valuable in applications where pinpoint accuracy is essential.

[0014] Another object of the invention is to addresses the need for expeditious beam searching and alignment in communication scenarios. This not only contributes to faster communication processes but also enhances the overall efficiency of the network. Description of the Figures of the Invention

[0015] The figures and related descriptions necessary for the subject matter of the invention to be understood better are given below.

[0016] Figure 1. A schematic view of the system.

[0017] Figure 2. A magnitude-delay graphic of channel impulse response for a single beam transmission.

[0018] Figure 3. A flow chart of the present method for selecting beams.

[0019] Figure 4a. A schematic view shows of the system with two beams transmission; omnidirectional and wide beams for wide beam selection.

[0020] Figure 4b. A graphical representation of the SBB burst sets of the an omnidirectional and a wide signal in time domain.

[0021] Figure 4c. Multiple magnitude-delay graphic of channel impulse response for omnidirectional and wide beams.

[0022] Figure 5. A schematic view shows that the transmitter transmits a wide and narrow signal to the receiver for narrow beam selection.

[0023] Figure 5a. Channel impulse response for wide and narrow beams.

[0024] Figure 6. A flow chart of the present method for beam selection.

[0025] Figure 7. A flow chart of the present method for beam searching.

[0026] Reference Numbers

[0027] The parts and components are given in the figures are referenced for the subject matter of the invention to be understood better.

[0028] 101. Transmitter

[0029] 102. Transmit beam

[0030] 103. Receive beam

[0031] 104. Receiver

[0032] 201. Multipath components

[0033] 401. Transmit wide beam

[0034] 402. Omnidirectional beam 403. SSB burst set for omnidirectional beam

[0035] 404. SSB burst set for wide beam

[0036] 405. Time of arrival of the omnidirectional beam

[0037] 406. Time of arrival of the wide beam

[0038] 501. Narrow beam

[0039] 502. Time of arrival for the transmit narrow beam

[0040] Detailed Description of the Invention

[0041] The invention is related to a beam selection method for localization and communication in MIMO networks.

[0042] The system model for the invention is described in Figure 1. The system model comprises multiple-input multiple-output (MIMO) transmitter (Tx) (101), transmit beam (102), receive beam (103), and MIMO receiver (Rx) (104) for mmWave channel. The total number of beams and the beam indices of the transmitter and receiver are denoted by (N, M) and (n, ni), respectively. In this system model, the wireless channel between the transmitter (101) and receiver (104) is different for each beam pair selection (^^-^m) where and SK I W. > . Therefore, the path losses and multipath components for the beam pair of ( are different. In conventional communication systems, beam selection is done based on the received signal strength indicator (RSSI) value. The base station transmits a reference signal from each beam serially in the time domain at the transmitter. Then, the receiver measures the signal strength for each beam within a certain period of time. Then, the receiver reports the signal strength measurement results to the transmitter. Thus, the signal is transmitted from the beam pair that provides the best signal quality.

[0043] The channel impulse response of a wireless channel is represented in Figure 2. The figure comprises resolvable multipath components (201). The x-axis and y-axis represent the delays and magnitudes of resolvable multipath components (201). As seen from the figure, the multipath components reach to receiver (104) with different delay and signal strength. For the communication, the receiver (104) needs to estimate all multipath components (201) for the channel equalization. On the other hand, for localization in wireless network, the first multipath component (?: ) is considered to estimate the time of arrival of the signal at the receiver (104). Also, the first multipath (^) component denotes the time of arrival of the shortest path that the transmitted signal passes through. The shortest path between the transmitter (101) and receiver (104) is normally direct path from the transmitter to receiver, and this provides a good accuracy in localization considering time of arrival and angle of arrival parameters. If this is case, the channel has line-of sight (LOS) path. However, this is not always the case especially for mmWave channel. Therefore, due to the blockages, the multipath components come from the non-LOS (NLOS) paths. In this scenario, the receiver (104) does not receive a signal from the direct path, and this decrease the accuracy in localization considering time of arrival and angle of arrival parameters. If the receiver (104) has angular resolution and multipaths come from different angles, the angles of the multipaths can be estimated at the receiver.

[0044] The flow chart of the invention is given in Figure 3. Firstly, the system model has the N transmit and M receive beams. For each beam pair the channel has different time of arrivals, angle of arrivals, and signal strengths where these parameters are denoted by f°rthe £-th multipath component (201) on the beam pair of respectively. At the receiver (104), the parameters are obtained for each k value where s (301). Since mmWave channel with narrow beamforming has flat fading channel (one-tap channel), and the first multipath component is generally most powerful and first-time arrival to the receiver, the k index can be taken as 1 and it can be dropped as . If the receiver has omnidirectional reception, these can be also denoted as and ^..Here, these parameters represent the time of arrival, angle of arrival, and signal power of the first multipath components on the beam pair of (%»%»), respectively. At the receiver, a power threshold value is needed to detect legitimate multipath components. If the signal power of a multipath component is lower than this threshold, it is considered as noise. Otherwise, it is taken as legitimate multipath at the receiver. Then, the receiver (104) finds the beam pair that gives the minimum time of arrival. This can be obtained as where TRis the reference time for the beginning of the transmission between the transmitter and receiver This is feasible in a synchronous transmission; however, in practice, providing a synchronous transmission is costly and complex process. However, this only select the beam with first path coming to the receiver. Since the power of signal affects the accuracy of the time of arrival estimation or the beam may serve for both localization and communication jointly, then beam pair selection should be done based on jointly first time of arrivals and signal power as where is the required signal power to satisfy requirements of localization and / or communication services (302). For instance, if the signal power of a beam pair is smaller than the power and it has minimum time of arrival, then the signal power on the next beam is measured where it has second minimum time of arrival. This continues until is met. Therefore, this provides the beam pair that gives the minimum time of arrival along with meeting the requirements . Next, the receiver (104) needs to report the detected beam index (S') to the transmitter (303). Lastly, transmitter (101) sends reference signal for localization or data signal for communication on the SSB burst set for wide beam (404).

[0045] The invention selects the beam pair based on the time of arrivals. However, this requires a reference time of arrival at the receiver (104), and beam search causes high computational complexity and latency in the system. The reference time of arrival is needed if they are not perfectly time synchronized. Actually, this is valid in practice that the transmitter and receiver have clock errors due to imperfect time synchronization. To provide a reference time of arrival and low complexity for beam selection, a two-step method is proposed. First step is described in Figure 4, second step is described in Figure 5, and the flow chart of whole method is given in Figure 6. Figure 4 comprises MIMO transmitter (101), transmit wide beam (401), transmitter omnidirectional beam (402), MIMO receiver (104), synchronization signal block (SSB) for a wide beam within one SSB burst set for omnidirectional beam (403), SSB for an omnidirectional beam within one SSB burst set for omnidirectional beam (403), time of arrival of the omnidirectional beam (405), and time of arrival of the wide beam (406). Figure 5 comprises MIMO transmitter (101), a transmit narrow beam within the selected wide beam (501), transmit wide beam (401), receive beam (103), MIMO receiver (104), time of arrival of the wide beam (406), and time of arrival for the transmit narrow beam within the selected wide beam (502).

[0046] In the first step, the transmitter (104) generates the wide beam (401) and omnidirectional beam (402), which omnidirectional beam (402) is always wider than wide beam (401), simultaneously (601) over same time resources, and the receiver receives the signals with an omnidirectional reception. It is assumed that the receiver can separate these two beams due to the use of orthogonal resource allocation (i.e., orthogonal code or orthogonal frequency allocation). For two simultaneous beam transmission in the time domain, at least two radiofrequency (RF) chains are needed at the transmitter (101). The omnidirectional transmission passes through all possible path to reach the receiver (104); therefore, the minimum first time of arrival is obtained from the omnidirectional beam as The first time of arrival of wide and narrow beams cannot be smaller than if sufficient power is used for omnidirectional beam. Because omnidirectional beam requires more power compared to narrow beam, which is always narrower than omnidirectional beam, for a reliable transmission. With this assumption, delay value is used as reference delay to evaluate first time of arrival of wide beams at the receiver. The first of time arrival of wide beams (401) are denoted by where and M® is the total number of transmit wide beams (401). The SSB signals for omnidirectional beam (403) within the one SSB burst set are transmitted serially in the time domain as seen from Figure 4. The SSB burst set for wide beam (404) is transmitted by overlapping with SSB signals for omnidirectional beam (403) within the one SSB burst set in the time domain. Therefore, for the SSB time slot of each wide beam ssss., the time of arrival of the omnidirectional beam (405) and time of arrival of the wide beam (406) are estimated. Then, the wide beam selection is done at the receiver as

[0047] If there is a required signal power for a beam, the wide beam selection can be done as where M.;i. is the measured signal power at the receiver on the ss^-th wide beam (602). Then, the receiver (104) reports the selected wide beam index to the transmitter (101).

[0048] In the second step, the transmitter (101) generates the wide beam (401) and the narrower beam (501) simultaneously where M - s-^Mt and Ms is the total number of transmit narrow beams within a transmit wide beam (603). Like in first step, the SSB signals for narrow beams (501) within the one SSB burst set are transmitted serially in the time, and the SSB signal for wide beam (401) is transmitted by overlapping with SSB signals of narrow beams (501) within the one SSB burst set in the time domain. Here, the receiver (104) also generates M receive narrow beams (103) to receive the transmitted signal. In this case, the signal of the wide beam is received by omnidirectional receive beam with a delay for its first of arrival (406). On the other hand, the first of arrivals (502) are denoted by where the beam pair of has different first of arrivals (502) at the receiver (104).

[0049] The beam pair selection is done at the receiver as

[0050] If there are a required signal power for a beam, the beam pair selection can be done as is the measured signal power at the receiver for the beam pair Then, the receiver (104) reports the selected narrow beam index to the transmitter (101).

[0051] The invention provides a beam selection mechanism by utilizing the first time of arrivals of the beams along with signal power requirement. After the beams are selected, conventional procedures for communication and localization are applied to the received signal (605). Here, the invention increases the accuracy of localization parameters and fast beam selection with low complexity for communication due to utilizing the difference of the time of arrivals of the wide and narrow beams. In conventional beam training methods, each beam is searched and the beam with best RSSI is chosen. Therefore, this creates a latency and causes high computational complexity. With the invention, the beam selection for communication can be done in a faster and low complex way. For this, the method is provided in Figure 7. Firstly, the transmitter (101) transmits a wide and narrow beam simultaneously as in Figure 5. The receiver (104) finds first time of arrivals of for wide and narrow beams, respectively. Here, the wide beam transmission can be an omnidirectional or sectorized transmission, and the wide transmit beam is determined before this method. Also, the first multipath is generally the most powerful path between the transmitter (101) and receiver (104). This is accurate especially for LOS channels. Therefore, the receiver (104) obtains the absolute value of the difference of the first time of arrivals as (702). Assume that there is a positive threshold value as to evaluate the transmit narrow beam (B^w) search continues. The receiver (104) may feedback this result, and transmitter (101) select the beam index for beam training according to this result. Conventionally, the transmitter sends the transmit beams in an order as However, if is known at the transmitter, the transmit beam index can be ordered in a better way. For instance, if the beam is transmitted and is large, the transmitter chooses the beam index as instead However, if there is no feedback signaling for then transmitter (104) sends the transmit beams in an interleaved order as These examples are provided how can be used for beam ordering for beam index selection. By using this absolute difference, a different beam ordering method can be developed. the transmit narrow beam (^sj search is terminated at the receiver (704). Then, the receiver reports the transmit beam while Therefore, all transmit narrow beams are not searched, and if a beam satisfies the equation of while the beam search for beam training is terminated. In this way, a fast beam selection for communication is achieved. The receiver in the invention can know when the beam search needs to be terminated especially for LOS channel.

[0052] This method can be used for wireless sensing and communication networks with MIMO technology can utilize this invention to provide better beam searching, beam alignment, and higher localization accuracy with low signaling overhead compared to the existing beam searching approaches. However, standards like 3GPP -based cellular and IEEE 802.11 based Wi-Fi networks, or any wireless network are particularly relevant to the invention. Furthermore, the described method in this invention can be implemented on any device, system or network capable of supporting any of the aforementioned standards, for instance: Long Term Evolution (LTE), LTE-advanced, AMPS, 5G New Radio (NR), or other known signals that are used to communicate and sense within a wireless network.

[0053] REFERENCES

[0054] [1] Understanding 5G Beam Management, white paper, 2021, MathWorks.

[0055] [2] Giordani, M., Polese, M., Roy, A., Castor, D. and Zorzi, M., 2018. A tutorial on beam management for 3GPP NR at mmWave frequencies. IEEE Communications Surveys & Tutorials, 21(1), pp.173-196.

[0056] [3] 3GPP, Beam Failure Detection and Beam Recovery Actions, document Tdoc RAN1#88- Bis, Rl-1705893, Ericsson, Spokane, WA, USA, Apr. 2017.

[0057] [4] NR and NG-RAN Overall Description — Release 15, 3GPP Standard TS 38.300, 2018.

[0058] [5] Zhang et al., “Beamforming sweeping and training in a flexible frame structure for new radio,” Jul. 25, 2019, US Patent 0229789A1.

[0059] [6] Wu, W., Cheng, N., Zhang, N., Yang, P., Zhuang, W. and Shen, X., 2019. Fast mmwave beam alignment via correlated bandit learning. IEEE Transactions on Wireless Communications, 18(12), pp.5894-5908.

[0060] [7] Abari, O., Hassanieh, H., Rodriguez, M. and Katabi, D., 2016, November. Millimeter wave communications: From point-to-point links to agile network connections. In Proceedings of the 15th ACM Workshop on Hot Topics in Networks (pp. 169-175).

[0061] [8] Myers, N.J., Mezghani, A. and Heath, R.W., 2019. FALP: Fast beam alignment in mmWave systems with low-resolution phase shifters. IEEE Transactions on Communications, 67(12), pp.8739-8753.

[0062] [9] Maschietti, F., Gesbert, D., de Kerret, P. and Wymeersch, H., 2017, December. Robust location-aided beam alignment in millimeter wave massive MIMO. In GLOBECOM 2017- 2017 IEEE global communications conference (pp. 1-6). IEEE.

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[0010] Xi et al., “Group-based beam management,” Sep. 8, 2022, US Patent 0286192A1.

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[0012] Kasher, A. et al., “ First path BF text,” IEEE 802.11 -17 / 1436r 1 , 2017.

Claims

CLAIMS1. A computer implemented beam pair selection method for wireless localization in multiple-input and multiple-output (MIMO) systems having a transmitter (101) and a receiver (104) with antenna arrays having that is capable to transmit / receive at least pair of beams, characterized byDetermining required signal power threshold to satisfy requirements of localization services of the system,Receiving and detecting the time of arrival, received signal power, and angle of each beam pair at a given channel path,Comparing each signal power of pair of beams from the lowest time of arrivals to the highest time of arrivals with the required signal power threshold, until determine the first pair of beams of which signal power is higher than the required signal power threshold wherein the time of arrival is signal travel time from the transmitter to the receiver.

2. A method according to Claim 1, characterized byTransmitting wide beams (401) and omnidirectional beam (402) simultaneously from the transmitter (101) to the receiver (104) and determining the first arrival of the omnidirectional beam (402) to the receiver as the reference time of arrival at the receiver,Comparing each signal power of wide beams from the lowest value that difference between time of arrivals of the wide beams (401) and the omnidirectional beam (402) to the highest value with the required signal power threshold, until determine the first wide beam of which signal power is higher than the required signal power threshold, wherein the time of arrival is signal travel time from the transmitter to the receiver, Transmitting the wide beams (401) and a narrower beam (501) simultaneously from the transmitter (101) to the receiver (104) and generating receive beams to receive the transmitted signal by the receiver (104),Determining arrival time of the wide beam which is received receive beam and arrival time of the pair of beams,determine the pair of beams has lowest time difference between its arrival time and arrival time of the value that difference between time of arrivals of the narrower beams (501) and the wide beam (402)Comparing each signal power of the pair of beams from the lowest time of arrivals to the highest time of arrivals with the required signal power threshold, until determine the first pair beam of which signal power is higher than the required signal power threshold, wherein the time of arrival is signal travel time from the transmitter to the receiver.

3. A method according to Claim 2, wherein receive beam is directional beam or omnidirectional beam.

4. A method according to Claim 2, characterized by wide beams and omnidirectional beam is transmitted as SSB burst set are transmitted serially in the time where SSB burst set of omnidirectional beam overlaps SSB burst set of the wide beams.

5. A method according to Claim 2 or 4, characterized by the wide beams and a narrower beam is transmitted as SSB burst set are transmitted serially in the time where SSB burst set of wide beam overlaps SSB burst set of the narrower beams.

6. A computer implemented wireless communication method in multiple-input and multiple-output (MIMO) systems having a multiple antenna transmitter (101) and a multiple antenna receiver (104) with multiplepath channels having pair of beams characterized by use of a pair of beams selected according to any of Claim 1-5.

7. A computer implemented localization method in multiple-input and multiple-output (MIMO) systems having a transmitter and a receiver with multipath channel having pair of beams characterized by use of a pair of beams selected according to any of Claim 1-5.

8. A data processing device comprising means for carrying out the steps of the method of Claim 6 or 7.

9. A computer program comprising instructions which, when the program is executed by a data processing device, cause the data processing device to carry out the steps of the method of Claim 6 or 7.

10. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of Claim 6 or 7.

11. A computer implemented beam pair selection method for communication in multipleinput and multiple-output (MIMO) systems having a transmitter (101) and a receiver (104) with antenna arrays having that is capable to transmit / receive at least pair of beams, characterized byTransmitting wide beams (401) and narrower beams (501) simultaneously, Determining required signal power threshold to satisfy requirements of communication services of the system,Receiving and detecting the time of arrival, received signal power, and angle of each beam pair at a given channel path,Comparing absolute value of difference between time of arrivals of wide beams (401) and narrower beams (501) with predetermined threshold, until determine the first pair of beams of which the absolute value is lower than the predetermined threshold wherein the time of arrival is signal travel time from the transmitter to the receiver, wherein if the threshold is larger than value of difference between time of arrivals of wide beams (401) and narrower beams (501) and the receiver (104) feedback this result to transmitter (101), the transmitter (110) chooses the index of the next beam as ^Tx,N-nnwhere N number of total transmitter (101) and nnis the index of the compared beam and if the threshold is larger than value of difference between time of arrivals of wide beams (401) and narrower beams (501) and the receiver (104) doesn’t feedback this result to transmitter (101), transmitter (110) chooses the index of the next beam in an interleaved order as where x is an integer between 0 and —and Nnis the index of the compared beam.

12. A computer implemented communication method in multiple-input and multipleoutput (MIMO) systems having a multiple antenna transmitter and a multiple antennareceiver with multiplepath channels having pair of beams characterized by use of a pair of beams selected according to any of Claim 11.

13. A data processing device comprising means for carrying out the steps of the method of Claim 12.

14. A computer program comprising instructions which, when the program is executed by a data processing device, cause the data processing device to carry out the steps of the method of Claim 12.

15. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of Claim 12.

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