WO2021121255A1

WO2021121255A1 - Access procedure associated with beamformed broadcast signals

Info

Publication number: WO2021121255A1
Application number: PCT/CN2020/136742
Authority: WO
Inventors: Salah Eddine HAJRI; Mohamad Assaad
Original assignee: Tcl Communication Limited; Centralesupelec
Priority date: 2019-12-17
Filing date: 2020-12-16
Publication date: 2021-06-24
Also published as: CN114902715A; CN114902715B

Abstract

In an embodiment, a method for enabling a wireless communication device to access services provided by a Radio Access Network, the method performed by a base station and comprising: obtaining a set of different beam patterns, each of which is constituted of multiple beams; and irradiating the multiple beams of each beam pattern to broadcast synchronization signals for an access procedure. In an embodiment, the beam patterns are scheduled according to beam pattern scheduling policy.

Description

ACCESS PROCEDURE ASSOCIATED WITH BEAMFORMED BROADCAST SIGNALS

1. Field of the Disclosure

Embodiments of the present invention generally relate to wireless communication systems, and more particularly to wireless networks supporting beamformed broadcast signals for enabling a wireless communication device, such as a user equipment (UE) , to access a radio access technology (RAT) or radio access network (RAN) .

2. Description of the Related Art

This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

Wireless communication networks have become critical in today’s societies. Such networks are required to provide communication capabilities to an array of applications that keeps on widening, evolving from the need to interconnect people, to include also the requirements to interconnecting and controlling machines, objects, and devices.

The fifth-generation (5G) provides a common connectivity platform to a wide range of communication types with heterogeneous requirements, playing a much larger role than previous wireless network generations. 5G will lower the cost of mobile broadband services available today on 3G and 4G networks, while considerably enhancing performance and enabling new services, such as Internet of Things (IoT) and mission-critical control through ultra-reliable communication.

5G networks take the criterion of spectrum efficiency to a whole new level, gaining the most out of the whole available frequency range and even including previously unutilized frequencies. 5G exploits licensed, shared, and unlicensed spectrum in all bands, ranging from low bands under 1 GHz, to mid bands between 1 GHz and 6 GHz to millimeter waves.

While previous generation networks operated mainly under the threshold of 3 GHz, 5G considerably expands the exploited spectrum range which will usher in the age of extremely high data rates and capacity. Operating in such high frequency comes with its toll of challenges. Indeed, the signal propagation conditions such as penetration, attenuation and refraction become very challenging in high frequency. Consequently, a proper adaptation of the network procedures is needed.

In order to combat such problems, 5G NR will employ beamforming as a mean to efficiently direct the radiated energy in the spatial space. By applying beamforming, coverage can be extended as transmitted energies can be concentrated on specific targets. Nevertheless, the angular range in which signals are received, with high enough power, is narrowed. The latter impact is particularly problematic for Synchronization Signals (SS) and Physical Broadcast Channel (PBCH) transmission as these signals need to reach all devices within the coverage area.

In order to address this problem, 5G employs beam sweeping in the initial access procedure for mmWave. Beam sweeping transmission refers to the transmission of the cell-specific signals by the base station while switching beam direction in a sequential manner in order to cover the whole cell. However, the beam sweeping suffers from latency because it takes time to scan the whole angular space.

Related arts are provided below:

1-RANDOM ACCESS AND GRANT-FREE ACCESS

In cellular networks, the access to the network is usually done by letting the devices contending over random access channel (RACH) to be connected. The data transmission can then be done over granted resources. This method is clearly not suitable for massive MTC and therefore new schemes have been developed by 3GPP with the introduction of narrow-band cellular IoT (NB-CIoT) [1] . However, there is still overhead signaling for synchronization, listening for ACK per messages, etc. Grant-free communications for short-packets have been proposed and investigated recently in several works. In [2, 3] , asynchronous ALOHA has been studied which has the advantage of reduced required complexity at the transmitter side. Successive interference cancellation (SIC) -based receivers for asynchronous ALOHA systems have been investigated in [2, 4] . Non-orthogonal multiple access (NOMA) has been investigated in several works [5-7] and [19-28] . For example, non-orthogonal multiple access schemes, such as Interleave-Grid Multiple Access (IGMA) [19] and Interleave Division Multiple Access (IDMA) [20] are available in the literature. In these schemes, different data streams are discriminated using device specific signatures and sophisticated receivers such as SIC, PIC, MP and ML. Uplink NOMA schemes were investigated by 3GPP in its 5G standardization effort [25-26] . Different NOMA schemes were proposed, relying on various receivers and user specific signatures. Power domain NOMA, for example, rely on differentiating users in the power domain and employs a SIC receiver [21] . IGMA [19] uses a combination of user specific interleaves and sparse mapping patterns in order to distinguish their signals. IGMA employs an ESE or a MAP algorithm at the receiver. IDMA [24] also employs an ESE receiver in addition to an Interleave based signature. Other proposed schemes include, among others, RSMA [22] , MUSA [23] , PDMA [25] and NCMA [26] . Grant free solutions based on NOMA were also discussed in [27-28] . Furthermore, Grant-free solutions with the use of massive MIMO at the receiver have been investigated in [8, 9] . However, the performance of the proposed solutions decreases as the traffic load, and thus, the amount of interference increases. In this case, the contention among the grant-free devices should be carefully addressed in order to control the interference level in the network and hence ensure correct packet reception. Such contention control may not be possible with pure grant-free access schemes.

2-INITIAL ACCESS USING BEAM SWEEPING

On the other hand, in order to address the initial access problem, 5G employs beam sweeping in mmWave, e.g. [10-18] . In the current specifications, the DL cell-specific signals are arranged in a periodically transmitted structure called SS burst sets, consisting of a finite number of SS bursts. Each SS burst contains a finite number of SS blocks that include the necessary signals, such as SS and PBCH. The SS blocks are defined as units for beam-sweeping in multi-beam operation since different beams are applied to different SS/PBCH blocks. Beam sweeping suffers however from several issues that should be addressed:

● Beam sweeping latency.

● Scheduling.

● Identification of the frame and subframe boundaries.

● Cell edge coverage

The beam sweeping latency is of particular interest. The latter is defined by the covered dimension during each transmission occasion. The widths of beams and the design of the beam sweeping procedure involve a trade-off between cell coverage performance and initial access latency. If the access of users at the cell edge is to be guaranteed, narrow single beams need to be used, at each occasion. Nevertheless, such approach will lead to high latency to have initial access.

The references mentioned above are listed below:

[1] 3GPP TS 45.820, “Cellular system support for ultra-low complexity and low throughput internet of things (ciot) , ” Tech. Rep., (Rel. 13) .

[2] R.D. Gaudenzi et al., “Asynchronous contention resolution diversity ALOHA: Making CRDSA truly asynchronous, ” IEEE Trans. Wireless Commun., vol. 13, no. 11, pp. 6193–6206, Nov 2014.

[3] Z. Li et al., “2D time-frequency interference modelling using stochastic geometry for performance evaluation in low-power wide-area networks, ” arXiv preprint arXiv: 1606.04791, 2016.

[4] F. Clazzer et al., “Exploiting combination techniques in random ac-cess MAC protocols: Enhanced contention resolution ALOHA, ” arXiv preprint arXiv: 1602.07636, 2016.

[5] Y. Du, C. Cheng, B. Dong, Z. Chen, X. Wang, J. Fang, and S. Li, “Block-sparsity-based multiuser detection for uplink grant-free NOMA, ” IEEE Trans. Wireless Commu., to appear in 2018.

[6] M. Shirvanimoghaddam, M. Condoluci, M. Dohler, and S. J. Johnson, “On the fundamental limits of random non-orthogonal multiple access in cellular massive IoT, ” IEEE J. Sel. Topics Signal Process., vol. 35, no. 10, pp. 2238–2252, Oct. 2017.

[7] J. Choi, “NOMA based random access with multichannel ALOHA, ” IEEE J. Sel. Areas Commun., vol. PP, no. 99, pp. 1–1, 2017.

[8] L. Liu and W. Yu, “Massive connectivity with massive MIMO -Part I: Device activity detection and channel estimation, ” IEEE Trans. on Signal Process., vol. 66, no. 11, pp. 2933–2946, Jun. 2018.

[9] --, “Massive connectivity with massive MIMO -Part II: Achievable rate characterization, ” IEEE Trans. Signal Process., vol. 66, no. 11, pp. 2947–2959, Jun. 2018.

[10] Samsung Electronics Co Ltd, “Method and apparatus for adjusting a beam sweeping pattern in wireless communication system” , US 20160323075 A1, 2016

[11] ASUSTek Computer Inc. Peitou, Taipei-City 112 (TW) , “METHOD AND APPARATUS FOR UE BEAMFORMING AND BEAM SWEEPING IN A WIRELESS COMMUNICATION SYSTEM” , EP 3 261 176 A2, 2017.

[12] Qualcomm Inc, “Wireless communication system with base station beam sweeping” , US 6,782,277 B1, 2004

[13] Qualcomm Inc, “Interleaved beam sweeping for synchronization and random access procedures” , US20170289932A1, 2017.

[14] Telefonaktiebolaget LM Ericsson AB, “Graph-Based Determination of Initial Synchronization Beam Scanning” , US20170250739A1, 2017.

[15] LG Electronics Inc, “Random access procedure with beam sweeping” , US20180084585A1, 2018.

[16] ASUSTeK, “Synchronization in NR considering beam sweeping” , R1-1709051 Hangzhou, P. R. China, 15 ^th -19 ^th May 2017

[17] Ericsson, “Response-driven paging to reduce beam sweeping overhead in NR” , R2-1710446, Prague, Czech Republic, 9 ^th –13 ^th October, 2017

[18] ETSI TR 138 912 V14.1.0, “5G; Study on new radio access technology” (3GPP TR 38.912 version 14.1.0 Release 14) , (2017-10)

[19] Samsung, “Non-orthogonal multiple access candidate for NR, ” R1-163992, 3GPP TSG RAN WG1 Meeting #85, Nanjing, China, May 2016.

[20] Nokia, Alcatel-Lucent Shanghai Bell, “Performance of Interleave Division Multiple Access (IDMA) in combination with OFDM family waveforms, ” R1-165021, 3GPP TSG RAN WG1 Meeting #85, Nanjing, China, May 2016.

[21] NTT DOCOMO, “Initial views and evaluation results on non-orthogonal multiple access for NR uplink” , R1-163111, 3GPP TSG RAN WG1Meeting #84bis, Busan, Korea 11th -15th April 2016.

[22] Qualcomm Incorporated, “Candidate NR Multiple Access Schemes” , R1-163510, 3GPP TSG-RAN WG1 #84 bis, Busan, Korea 11th -15th April 2016

[23] ZTE, “Discussion on multiple access for new radio interface” , R1-162226, 3GPP TSG-RAN WG1 #84 bis, Busan, Korea 11th -15th April 2016

[24] Nokia, Alcatel-Lucent Shanghai Bell, “Performance of Interleave Division Multiple Access (IDMA) in combination with OFDM family waveforms, ” R1-165021, 3GPP TSG RAN WG1 Meeting #85, Nanjing, China, May 2016.

[25] CATT, “Candidate Solution for New Multiple Access” , R1-163383, 3GPP TSG-RAN WG1 #84 bis, Busan, Korea 11th -15th April 2016

[26] LG Electronics, “Considerations on DL/UL multiple access for NR” , 3GPP TSG-RAN WG1 #84bis, Busan, Korea 11th -15th April 2016

[27] ZTE, “Contention-based non-orthogonal multiple access for UL mMTC” , R1-164269, 3GPP TSG RAN WG1 Meeting #85, Nanjing, China, 23 ^rd -27 ^th May, 2016

[28] ZTE, “Grant-based and grant-free multiple access for mMTC” , R1-164268, 3GPP TSG RAN WG1 Meeting #85, Nanjing, China, 23 ^rd -27 ^th May 2016

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description of the Embodiments. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is intended to be used as an aid in determining the scope of the claimed subject matter.

There is provided a method for enabling a wireless communication device to access services provided by a Radio Access Network, the method performed by a base station and comprising: obtaining a set of different beam patterns, each of which is constituted of multiple beams; and irradiating the multiple beams of each beam pattern to transmit beamformed broadcast signals for an access procedure.

The multiple beams of each beam pattern are irradiated simultaneously.

The multiple beams of each beam pattern are utilized to transmit beamformed broadcast signals having a same synchronization signal block (SSB) .

The set of beam patterns is constructed by: maximizing distance between the multiple beams in each beam pattern; and providing a maximum coverage of spatial space by a combination of different beam patterns.

The set of beam patterns is constructed based on Grassmannian subspace packing.

Each beam pattern is based on a discrete Fourier transform (DFT) codebook.

The method further comprises irradiating the beams with the beam patterns according to a beam pattern scheduling policy.

The method further comprises determining the beam pattern scheduling policy by determining a scheduling policy for the set of beam patterns to maximize an average of throughput.

Determining the beam pattern scheduling policy comprises estimating the average of throughput by taking a scheduling frequency of each beam pattern in the set of beam patterns as an input.

The method further comprises irradiating narrow high-power beams for cell edge coverage in addition to the beams in the set of beam patterns.

The method further comprises determining the beam pattern scheduling policy by determining a scheduling policy for the set of beam patterns to maximize a number of packets successfully decoded by the base station.

Determining the beam pattern scheduling policy comprises estimating the number of packets successfully decoded by the base station, by taking a scheduling frequency of each beam pattern in the set of beam patterns as an input.

There is provided a base station, comprising a processor, a storage unit and a communication interface, wherein the processor, the storage unit and the communication interface are configured to perform the methods described herein.

There is provided a non-transitory computer readable medium having computer readable instructions stored thereon for execution by a processor to perform the methods described herein.

There is provided a random access (RA) method, implemented between a base station and a user equipment, the method performed by the base station and comprising: irradiating multiple beams of a beam pattern in a set of different beam patterns to transmit beamformed broadcast signals by the base station; and receiving by the base station a RA preamble and data transmission in response to the beamformed broadcast signals.

The multiple beams of each beam pattern are irradiated simultaneously.

There is provided a method for enabling a wireless communication device to access services provided by a Radio Access Network, the method performed by a user equipment and comprising: receiving beamformed broadcast signals broadcasted using one of irradiated multiple beams of a beam pattern in a set of different beam patterns.

The method further comprises sending a RA preamble and starting transmission of data from the user equipment to the base station, upon receiving the beamformed broadcast signals.

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.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present disclosure or related art, the following figures will be described in the embodiments are briefly introduced. It is obvious that the drawings are merely some embodiments of the present disclosure, a person having ordinary skill in this field can obtain other figures according to these figures without paying the premise.

FIG. 1 is a diagram illustrating a telecommunication network according to some embodiments.

FIG. 2 is a diagram illustrating beam pattern examples according to some embodiments.

FIG. 3 is a diagram illustrating a random-access procedure between gNB and UE according to some embodiments.

FIG. 4 is a diagram illustrating a comparison between conventional grant free scheme and proposed scheme.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present disclosure are merely for describing the purpose of the certain embodiment, but not to limit the invention.

Referring now to FIG. 1, an example of part of a telecommunication system operating in accordance with at least some embodiments herein is illustrated schematically. The telecommunication system comprises a base station (BS) 100 and a user equipment (UE) 700. The telecommunication network may comprise multiple BSs 1100 and multiple UEs.

Normally, when the UE 700 wants to access a radio access network, the UE 700 may establish a reliable communication link between the UE 700 and the BS 1100 by initiating a random-access (RA) procedure. In certain cases, BS may command the UE using DL resources to initiate an UL RA procedure.

Examples of the telecommunication that may be used in certain embodiments of the described apparatus, methods and systems may be at least one communication network or combination thereof including, but not limited to, communications networks based on wireless, cellular or satellite technologies such as mobile networks, Global System for Mobile Communications (GSM) , GPRS networks, Wideband Code Division Multiple Access (W-CDMA) , CDMA2000 or Long Term Evolution (LTE) /LTE Advanced networks or any 2nd, 3rd, 4th or 5th Generation and beyond type communication networks and the like.

The UE 700 may be an automotive part with wireless communication capability mounted in a vehicle, a wearable device with wireless communication capability, a mobile terminal, or a wireless terminal, a mobile phone, a computer such as e.g. a laptop, a Personal Digital Assistants PDAs or a tablet computer, sometimes referred to as a surf plate, with wireless capability, or any other radio network units capable to communicate over a radio link in a wireless communications network. Please note that the term UE 700 used in this document also covers other wireless devices such as device-to-device (D2D) devices, Machine to machine (M2M) devices, even though they do not have any user. The wearable device, which is also referred to as wearable communication device, or electronic wearable portable device. The term wearable device refers to electronic technologies or computers that are incorporated into items of clothing and accessories, which can be worn on the body of a user to collect data. Generally, the wearable device has some form of communications capability and will allow a server and the wearer access to collect the data.

The base station (BS) 1100 is operable in a Radio Access Network (RAN) and serving a cell. The base station 1100 may be, e.g. a Radio Base Station (RBS) , which sometimes may be referred to as e.g. “gNB” , “eNB” , “eNodeB” , “NodeB” , “B node” , gNodeB or BTS (Base Transceiver Station) , depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or Pico base station, based on transmission power and thereby also cell size.

In this disclosure, two problems are considered in some embodiments. The first one is the access procedure for machine-type communications (MTCs) and the second one is the initial access procedure. A new scheme is provided that can be used for both problems. It is worth mentioning that for the initial access problem, it does not rely on beam sweeping which suffers from latency and does not take into account the traffic characteristics. In more detail, new beamforming patterns switching based random access is developed, which can work for any frequency band. The proposed scheme is particularly useful for grant-free access for massive MTC. In fact, beamformed broadcast signals can be leveraged as a tool to manage grant-free access since leveraging the beamformed broadcast signals can reduce collisions and consequently enhances the performance of grant-free access.

As stated before, the proposed method can also be for initial access procedure. The major criterions to be considered when designing the beam based initial access procedure are the following:

● Access latency.

● Scheduling.

● Identification of the frame and subframe boundaries.

● Cell edge coverage.

The proposed initial access procedure which is based on beamformed broadcast signals keeps the communication between the gNB and the devices to a minimum and enables to control the resulting levels of interference in a dense deployment scenario. Based on optimized multi-beam patterns, the transmission of the covered devices is controlled in an open loop manner.

Based on all above, the main contributions in this invention are as follows:

● First, the base station constructs different optimized beam patterns that are based on Grassmannian subspace packing, for example. Each pattern is constituted of multiple beams. The aggregation of the different beam patterns provides a maximum coverage of the angular space which is needed to guarantee complete cell coverage. The latter results in:

a) Reduced random access or initial access latency.

b) Optimized resulting performance (rate or density of MTC)

● Second, the base station is allowed to learn the optimal beam transmission strategy so that it can adapt to user repartition and their respective traffic patterns. During the learning process, the gNB uses the constructed optimized beam patterns in addition to a set of narrow beams for cell edge coverage. The results of the latter are as follows:

a) Beam pattern transmission periodicity is optimized as a function of the resulting traffic.

b) Beam transmission latency can further be reduced since the base station will prioritize the direction from which a majority of the traffic is received.

c) Cell edge coverage is maintained with minimal impact on grant-free or initial access latency.

● Third, once a user or MTC device selects a beam direction, it notifies the gNB then starts transmission directly. This protocol reduces the control information exchange between the network and devices. Such procedure is very well adapted to the requirement of high connection density for massive MTCs (mMTCs) as it manages efficiently the interference in the context of grant-free access using the proposed advanced beamforming patterns definition and switching method.

The existing arts do not consider beamforming-based grant-free access and are only based on nonorthogonal multiple access (NOMA) , which suffers from high receiver complexity and complex interference management. The beamforming-based solutions are more efficient to handle the interference in wireless networks as the transmitted data can be in almost orthogonal subspaces, which reduces the experienced interference in the network.

BEAM PATTERNS GENERATION:

As previously stated, the present invention advocates multiple beams to be used as an access grant for the covered users. This enables to limit the initial access delay and to cover the whole angular space. At each access occasion, the subsequently active users will have their signals concentrated in almost-orthogonal subspaces resulting in reduced interference.

Since multiple beams can be used simultaneously, multi-user interference can be problematic. Indeed, if the spatial separation between the beams is not high enough, active users that are aligned with different beams will have relatively interfering channels which engenders considerable levels of mutual interference. Consequently, the design of the beam patterns is crucial for the success of the proposed access approach. Practically speaking, the main goals of the beam patterns design should be as follows:

● The distance between the beams in each pattern should be maximized in order to reduce the resulting multi-user interference.

● The combination of the totality of beam patterns should provide a maximum coverage of the angular (spatial) space.

The latter criterions relate the present problem of beam pattern generation to Grassmannian subspace packing. Grassmannian subspace packing is the problem of finding a set of N K-dimensional subspaces in G (M, K) that maximize the minimum distance between any pair of subspaces in the set. In the considered setting, in order to meet the desired criterions for the initial access procedure, the transmitted beams should be constructed so that interference is efficiently mitigated. In addition, the final selected beam patterns should provide a maximum coverage of the entire angular space.

The beam construction procedure goes as follows

i. Initialize:

T= The total number of candidate patterns

N= The number of Slots to cover the entire angular space

M= the total signal dimension

K= the dimension covered in each slot

Beam Codebook B: Different beam designs can be considered. We take as example a DFT codebook where each beam is given by

The latter constitutes a basis of the channel covariance matrix for Uniform Linear Antenna Arrays (ULAs) .

ii. Generate C>T different patterns of dimension K, the set of patterns Δ= [δ _j, j=1, …, C] . Each pattern is a DFT column of a combination of multiple DFT columns.

iii. Select T patterns in Δ δ _(j) , j=1, …, T verifying

δ _(j) =argmax d _i, min (δ _i) , δ _i∈ Δ \δ _(j-1)

where d is the distance with pattern δ _i

iv. Select N beam patterns that are a solution to the following combinatorial optimization problem:

Where θ _m, m=1, …, M is the set of different beams. x _j=1 if pattern j is selected and 0 otherwise. y _m=1 if dimension m is covered and 0 otherwise

The latter procedure provides N beam patterns that maximize the coverage of the angular space since the objective function maximizes the number of covered dimensions. The second constraint ensures that the number of selected patterns is less or equal to N while the first constraint ensures the consistency of the problem (the dimension m is selected through y _m implies that at least one beam containing this dimension is selected) . An example of beam patterns for ULAs is shown in FIG. 2.

DYNAMIC BEAM BASED INITIAL ACCESS: LEANING A BEAMFORMING POLICY

After deriving the optimized beam patterns, thanks to Grassmannian subspace packing and maximum coverage optimization, an optimized control signal beamforming procedure is provided. The invention further aims at addressing the trade-off between latency, coverage and frame structure. Consequently, on top of the optimized beam patterns, narrow high-power beams are included in order to cover users at the cell edge. The use of such beams will be restrained so that latency is reduced. The basic principle of the present idea is to allow the gNB to learn the best policy of control signal beamforming in order to achieve the best average long-term throughput.

Formally, the beam transmission optimization can be formulated as a restless multi-armed bandit problem. In this case, each gNB will learn the best beam pattern to use at each SS transmission occasion in order to maximize the long-term average achievable throughput.

The goal is to derive a beam pattern scheduling policy γ= (γ ₁, γ ₂, …) that maximizes the following:

Where

The latter optimization enables the beam based initial access procedure to adapt to the traffic patterns of the covered devices. Indeed, the base station is enabled to learn the beam patterns that result in high data throughput when transmitted. This means that the network will adapt its beam patterns transmission to the actual traffic patterns of the devices which result in a more efficient random-access procedure as more priority is given to the beams that engender higher response from active devices with larger data load to transmit.

Users at the cell edge are also covered. Nevertheless, this is not achieved at the expense of latency. Indeed, as the gNB learns the best policy of beam based initial access, the narrow high-power beams will be transmitted during a limited number of slots.

This adaptation of the beam based initial access procedure is different from traditional traffic-agnostic approaches. Indeed, while covering the entire, or at least a maximum of, the angular space is still highly important, it can be critical to prioritize specific beam patterns in order to assure some stability in the network

SIMPLIFIED RANDOM ACCESS FOR MTC:

The optimized beam based initial access approach in the present invention is particularly adapted to the random-access procedure of MTC devices and the nature of their traffic. Indeed, as MTC assumes high connection density as one of its major KPIs, reducing the control information exchange in the initial access procedure of such devices will be beneficial. Nevertheless, an uncontrolled grant-free access can result in high levels of interference in addition to higher error rates. As the proposed beam based approach enables to identify the main direction of arrivals (DoAs) of the future transmitted data, the implicated beam patterns can be used in decoding the signal of subsequently active devices.

Where

The utility function can be for example the amount of successfully decoded packets (which is for MTC with given packet size directly related to the number of served MTCs) . Other functions related to interference can be used as well. The latter optimization enables the beam based grant-free access procedure to adapt to the traffic patterns (activity and density) of the covered MTC devices. In fact, the state of the system that depends on the number of active devices that transmitted at a given time is an input of the aforementioned learning problem that adapts to the activity and density of the devices. The gNB is therefore enabled to learn the beam patterns that result in high amount of successfully received packets.

FIG. 3 depicts an initial access procedure. The gNB irradiates multiple beams of a beam pattern to broadcast beamformed synchronization signals such as primary synchronization signals (PSS) and secondary synchronization signals (SSS) . The beam pattern is one of an optimized set of beam patterns as described above. The beam patterns may be scheduled according to the aforesaid beam pattern scheduling policy to adapt to the actual traffic patterns of the devices or covered devices. Once a UE or MTC device selects a beam direction, the UE sending a random-access preamble to notify the gNB and starts transmission of data to the gNB directly. This protocol reduces the control information exchange between the UE and gNB.

SIMULATION RESULTS:

The results of numerical simulations showcasing the gains that the proposed invention can provide are provided. The performance of the proposed access procedure is compared to a conventional grant-free approach. It is assumed that a gNB at the center of a cell with radius 100 m and the gNB is equipped with 64 antenna elements. Various number of users per cell is considered, with randomly generated activation probabilities. Note that the activation patterns of the MS are independent. The gNB uses 60 different beam patterns of maximum rank 6 that are generated according to Grassmaninan subspace packing.

FIG. 4 shows a comparison of performance in terms of average spectral efficiency. The figure shows a clear improvement in the achievable performance which is the result of the reduced interference. Indeed, in the proposed invention, the gNB controls the activation of the MSs through beamformed SS which limits the number of active MSs at each slot. In an interference limited regime, the proposed invention provides considerable improvement in the achievable performance without resorting to complex grant-based scheduling.

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.

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.

In alternative embodiments, 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. Such 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.

In this document, the terms ‘computer program product’ , ‘computer-readable medium’ and the like 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. Note that 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

In an embodiment where the elements are implemented using software, 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) , when executed by the processor in the computer system, causes a processor to perform the functions of the invention as described herein.

Furthermore, the 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.

It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to a single processing logic. However, the inventive concept may equally be implemented by way of a plurality of different functional units and processors to provide the signal processing functionality. Thus, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

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. Thus, 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.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘comprising’ does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to ‘a’ , ‘an’ , ‘first’ , ‘second’ , etc. do not preclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘comprising’ or “including” does not exclude the presence of other elements.

Claims

A method for enabling a wireless communication device to access services provided by a Radio Access Network, the method performed by a base station and comprising:

obtaining a set of different beam patterns, each of which is constituted of multiple beams; and

irradiating the multiple beams of each beam pattern to transmit beamformed broadcast signals for an access procedure.
The method according to claim 1, wherein the multiple beams of each beam pattern are irradiated simultaneously.
The method according to claim 1, wherein the multiple beams of each beam pattern are utilized to transmit beamformed broadcast signals having a same synchronization signal block (SSB) .
The method according to claim 1, wherein the set of beam patterns is constructed by:

maximizing distance between the multiple beams in each beam pattern; and

providing a maximum coverage of spatial space by a combination of different beam patterns.
The method according to claim 4, wherein the set of beam patterns is constructed based on Grassmannian subspace packing.
The method according to claim 4, wherein each beam pattern is based on a discrete Fourier transform (DFT) codebook.
The method according to claim 1, further comprising:

irradiating the beams with the beam patterns according to a beam pattern scheduling policy.
The method according to claim 7, further comprising:

determining the beam pattern scheduling policy by determining a scheduling policy for the set of beam patterns to maximize an average of throughput.
The method according to claim 8, wherein determining the beam pattern scheduling policy comprises:

estimating the average of throughput by taking a scheduling frequency of each beam pattern in the set of beam patterns as an input.
The method according to claim 7, further comprising:

irradiating narrow high-power beams for cell edge coverage in addition to the beams in the set of beam patterns.
The method according to claim 7, further comprising:

determining the beam pattern scheduling policy by determining a scheduling policy for the set of beam patterns to maximize a number of packets successfully decoded by the base station.
The method according to claim 11, wherein determining the beam pattern scheduling policy comprises:

estimating the number of packets successfully decoded by the base station, by taking a scheduling frequency of each beam pattern in the set of beam patterns as an input.
A base station, comprising a processor, a storage unit and a communication interface, wherein the processor, the storage unit and the communication interface are configured to perform the method as claimed in any of claims 1 to 12.
A non-transitory computer readable medium having computer readable instructions stored thereon for execution by a processor to perform the method as claimed in any of claims 1 to 12.
A random access (RA) method, implemented between a base station and a user equipment, the method performed by the base station and comprising:

irradiating multiple beams of a beam pattern in a set of different beam patterns to transmit beamformed broadcast signals by the base station; and

receiving by the base station a RA preamble and data transmission in response to the beamformed broadcast signals.
The method according to claim 15, wherein the multiple beams of each beam pattern are irradiated simultaneously.
The method according to claim 15, wherein the multiple beams of each beam pattern are utilized to transmit beamformed broadcast signals having a same synchronization signal block (SSB) .
The method according to claim 15, further comprising:

irradiating narrow high-power beams for cell edge coverage in addition to the beams in the set of beam patterns.
A method for enabling a wireless communication device to access services provided by a Radio Access Network, the method performed by a user equipment and comprising:

receiving beamformed broadcast signals broadcasted using one of irradiated multiple beams of a beam pattern in a set of different beam patterns.
The method according to claim 19, further comprising:

upon receiving the beamformed broadcast signals, sending a RA preamble and starting transmission of data from the user equipment to the base station.