CN114902715A - Access procedure related to beamformed broadcast signals - Google Patents
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- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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Abstract
In one embodiment, there is provided a method for enabling a wireless communication device to access a service provided by a radio access network, the method being performed by a base station and comprising: obtaining a set of different beam patterns, each beam pattern being formed by a plurality of beams; and transmitting a plurality of beams of each beam pattern to transmit a beamformed broadcast signal for the access procedure. In one embodiment, the beam patterns are scheduled according to a beam pattern scheduling policy in one embodiment.
Description
Technical Field
Embodiments of the present invention relate generally to wireless communication systems, and more particularly, to a wireless Network supporting beamformed broadcast signals to enable wireless communication devices, such as User Equipment (UE), to Access a Radio Access Technology (RAT) or a Radio Access Network (RAN).
Background
This section introduces some details that help to better understand the present application. Accordingly, what is described in this section is to be read in this manner and is not to be construed as an admission that it is prior art, or that it is not prior art.
Wireless communication networks are becoming of considerable importance in today's society. Such networks need to provide communication capabilities for an ever expanding array of applications that have evolved from meeting the needs of people to interconnect to also include the need to interconnect and control machines, objects and devices.
Fifth generation (5G) technology provides a common connectivity platform for various types of communication with heterogeneous requirements, and plays a much more important role than previous generations of wireless networks. 5G will reduce the cost of mobile broadband services currently available on 3G and 4G networks while significantly improving performance and supporting new services such as Internet of Things (IoT) and mission critical control through ultra-reliable communications. The 5G network raises the spectral efficiency standard to a completely new level, making full use of the entire available frequency range, even including frequencies not previously used. The 5G uses licensed, shared and unlicensed spectrum in all bands, from low bands below 1GHz to intermediate bands between 1GHz and 6GHz to millimeter waves.
While previous generations of networks operate primarily at the 3GHz threshold, 5G greatly expands the spectrum range that has been developed, which will lead to the era of extremely high data rates and capacity. Operating at such high frequencies presents many challenges. In fact, signal propagation scenarios such as penetration, attenuation, and refraction become very challenging at high frequencies. Therefore, appropriate adjustment of the network program is required.
To solve such problems, the 5G NR will employ beamforming as a means of efficiently guiding radiated energy in space. By applying beamforming techniques, the coverage can be extended, as the transmitted energy can be concentrated on a particular target. However, the angular range in which signals with sufficiently high power are received is narrowed. The ensuing impact is particularly problematic for the transmission of Synchronization Signals (SS) and Physical Broadcast Channels (PBCH), since these signals need to reach all devices in the coverage area. To solve this problem, 5G employs beam scanning (beam scanning) in the initial access procedure of the millimeter wave. The beam scanning transmission refers to that a base station switches beam directions in sequence to cover the whole cell while transmitting a signal specific to the cell. However, beam scanning is delayed because it takes time to scan the entire angular space.
The related art provides the following:
1-random access and unlicensed access
In cellular networks, access to the network is typically accomplished by having devices contend on a Random Access Channel (RACH) to reach a connection. The data transfer may then be completed on the granted resources. This approach is obviously not applicable to massive Machine Type Communication (MTC), so 3GPP has developed a new scheme to introduce narrowband-cellular internet of things (NB-CIoT) [1 ]. However, there is still overhead signaling for synchronization, listening for Acknowledgement (ACK) of each message, etc. Unlicensed communication of short packets has been proposed and studied in several recent works. In the documents [2,3], studies have been made on asynchronous ALOHA techniques, which have the advantage of reducing the complexity required at the transmitting end. Successive Interference Cancellation (SIC) based receivers for asynchronous ALOHA systems have been studied in literature [2,4 ]. Non-orthogonal multiple access (NOMA) technology has been studied in several works [5-7] and [19-28 ]. For example, non-orthogonal Multiple Access schemes such as an interlace-Grid Multiple Access (IGMA) technique [19] and an Interlace Division Multiple Access (IDMA) technique [20] exist in the literature. In these schemes, different data streams are distinguished with device-specific signatures and complex receivers (e.g., SIC, PIC, MP, and ML). The 3GPP has studied the uplink NOMA scheme in its 5G standardization work [25-26 ]. Different NOMA schemes are proposed which rely on various receivers and user-specific signatures. For example, power domain NOMA techniques rely on distinguishing users in the power domain and employing SIC receivers [21 ]. IGMA [19] uses a combination of user-specific interleaving and sparse mapping patterns to distinguish their signals. IGMA employs an ESE or MAP algorithm at the receiving end. In addition to the interlace-based signature, IDMA [24] employs an ESE receiver. Other proposed protocols include RSMA [22], MUSA [23], PDMA [25], and NCMA [26], among others. NoMA-based unlicensed solutions are also discussed in documents [27-28 ]. Furthermore, an unlicensed solution using massive MIMO at the receiver is studied in documents [8,9 ]. However, the performance of the proposed solution decreases with traffic load, so the amount of interference increases. In this case, contention between unlicensed devices should be carefully resolved to control the degree of interference in the network to ensure correct reception of data packets. A purely unlicensed access scheme may not have such contention control.
2-initial Access Using Beam scanning
On the other hand, to solve the problem of initial access, 5G employs beam scanning on millimeter waves, e.g., [10-18 ]. In the current specification, cell-specific DL signals are arranged in a periodically transmitted structure called SS burst sets (SS burst sets), which are composed of a limited number of SS bursts. Each SS burst contains a limited number of SS blocks, which include necessary signals, e.g., SS and PBCH. These SS blocks are defined as multiple beam scanning elements in multi-beam operation, since different beams apply to different SS/PBCH blocks. However, beam scanning presents several problems that should be solved:
delay of beam scanning
Scheduling
Identification of frame and subframe boundaries
Cell edge coverage
Beam scanning delay is of particular interest. This is defined by the coverage dimension at each transmission opportunity. The width of the beam and the design of the beam scanning procedure involve a trade-off between cell coverage performance and initial access delay. If access is to be guaranteed for users at the cell edge, a narrow single beam is required for each occasion. However, this approach will result in high delay for the initial access.
The references mentioned above are as follows:
[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 MACprotocols: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”,R1-1709051Hangzhou,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 912V14.1.0,“5G；Study on new radio access technology”(3GPP TR 38.912version 14.1.0Release 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#84bis,Busan,Korea 11th-15th April 2016
[23]ZTE,“Discussion on multiple access for new radio interface”,R1-162226,3GPP TSG-RAN WG1#84bis,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#84bis,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
disclosure of Invention
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it 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 a service provided by a radio access network, the method being performed by a base station and comprising: obtaining a set of different beam patterns, each beam pattern being formed by a plurality of beams; and transmitting a plurality of beams of each beam pattern to transmit a beamformed broadcast signal for the access procedure.
The transmissions are made simultaneously in a plurality of beams of each beam pattern.
The multiple beams of each beam pattern are used to transmit a beamformed broadcast signal having the same Synchronization Signal Block (SSB).
The set of beam patterns is formed by: maximizing the distance between the plurality of beams in each beam pattern; and by combining different beam patterns to provide maximum spatial coverage.
The set of beam patterns is constructed based on grassmann subspace packing.
Each beam pattern is based on a Discrete Fourier Transform (DFT) codebook.
The method further comprises the following steps: transmitting a beam of the plurality of beam patterns according to a beam pattern scheduling policy.
The method further comprises the following steps: determining the beam pattern scheduling policy by determining a scheduling policy for the set of beam patterns that maximizes an average throughput.
Determining the beam pattern scheduling policy comprises: the average throughput is estimated by taking as input the scheduled frequency of each beam pattern in the set of beam patterns.
The method further comprises the following steps: in addition to the beams in the set of beam patterns, high power narrow beams for cell edge coverage are transmitted.
The method further comprises the following steps: the beam pattern scheduling policy is determined by determining a scheduling policy for the set of beam patterns that maximizes the number of data packets successfully decoded by the base station.
Determining the beam pattern scheduling policy comprises: the number of data packets successfully decoded by the base station is estimated by taking as input the scheduling frequency of each beam pattern in the set of beam patterns.
There is provided a base station comprising a processor, a memory unit and a communication interface, wherein the processor unit, the memory unit and the communication interface are configured to perform the method described herein.
A non-transitory computer readable medium is provided 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 being performed by the base station and comprising: transmitting with a plurality of beams of one beam pattern of a set of different beam patterns to transmit a beamformed broadcast signal emitted by the base station; and the base station receiving an RA preamble and a data transmission in response to the beamformed broadcast signal.
The transmissions are made simultaneously in a plurality of beams of each beam pattern.
The multiple beams of each beam pattern are used to transmit a beamformed broadcast signal having the same Synchronization Signal Block (SSB).
The method further comprises the following steps: in addition to the beams in the set of beam patterns, high power narrow beams for cell edge coverage are transmitted.
A method for enabling a wireless communication device to access a service provided by a radio access network, the method being performed by a user equipment and comprising: a beamformed broadcast signal is received that is broadcast using one of a plurality of transmitted beams of one of a set of different beam patterns.
The method further comprises the following steps: upon receiving the beamformed broadcast signal, transmitting an RA preamble and beginning data transmission from the user equipment to the base station.
The non-transitory computer readable medium may include at least one of the group consisting of: hard disk, CD-ROM, optical storage devices, magnetic storage devices, read-only memory, programmable read-only memory, erasable programmable read-only memory, EPROM, electrically erasable programmable read-only memory, and flash memory.
Drawings
In order to more clearly illustrate the embodiments of the present application or the related art, the following drawings will be described in the embodiments and briefly introduced as follows. It is obvious that these drawings represent only some embodiments of the application and that other drawings can be derived by those skilled in the art from these drawings without presetting them.
Fig. 1 shows a schematic diagram of a telecommunications network according to some embodiments.
Fig. 2 shows a schematic diagram of an example of a beam pattern according to some embodiments.
Fig. 3 shows a schematic diagram of a random access procedure between a gNB and a UE, according to some embodiments.
Fig. 4 shows a schematic diagram of a comparison between the proposed scheme of the present application and a conventional unlicensed scheme.
Detailed Description
The embodiments of the present application will be described in detail with reference to the accompanying drawings, wherein the embodiments are described in detail with reference to the accompanying drawings. In particular, the terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Reference is now made to fig. 1, which schematically illustrates an example of a portion of a telecommunications system operating in accordance with at least some embodiments herein. The telecommunication system includes a Base Station (BS) 100 and a User Equipment (UE) 700. The telecommunication network may include a plurality of BSs 1100 and a plurality of UEs.
Generally, when UE 700 wants to access a radio access network, UE 700 may establish a reliable communication link between UE 700 and BS 1100 by initiating a random-access (RA) procedure. In some cases, the BS may use the DL resources to command the UE to initiate the UL RA procedure.
Examples of telecommunications that may be used in certain embodiments of the described apparatus, methods and systems may be, but are not limited to, a communication network based on wireless, cellular or satellite technology, such as a mobile network, a global system for mobile communications (GSM), a GPRS network, a wideband code division multiple access (W-CDMA), CDMA2000 or Long Term Evolution (LTE)/LTE advanced network, or any second, third, fourth or fifth generation and beyond type of communication network, or the like, or a combination thereof.
The UE 700 may be an automotive part with wireless communication capability installed in a vehicle, a wearable device with wireless communication capability, a mobile terminal or wireless terminal, a mobile phone, a computer such as a laptop, a personal digital assistant PDA or a tablet computer (sometimes also referred to as a web pad, with wireless capability), etc., any other radio network unit capable of communicating over a radio link in a wireless communication network. Note that the term "UE 700" as used herein also encompasses other wireless devices, such as device-to-device (D2D) devices and machine-to-machine (M2M) devices, even if they do not have any users. Wearable devices are also known as wearable communication devices or wearable electronic portable devices. The term "wearable device" refers to electronic technology or computers incorporated into clothing and accessories that can be worn on the body of a user to collect data. Typically, wearable devices have some form of communication capability and allow access or access by the server and the wearer to collect data.
A Base Station (BS)1100 may operate in a Radio Access Network (RAN) and serve a cell. Base Station 1100 may be, for example, a Radio Base Station (RBS), which depending on the technology and terminology used may sometimes be referred to as, for example, "gNB", "eNB", "eNodeB", "NodeB", "B node", gbnodeb or Base Transceiver Station (BTS). The base stations may be divided into different categories, e.g. based on transmission power, and therefore also based on cell size, macro eNodeB, home eNodeB or Pico base station.
In the present application, some embodiments consider two issues. The first problem relates to the access procedure for Machine Type Communication (MTC) and the second problem relates to the initial access procedure. A new solution is provided here which can be used for both problems. It is worth mentioning that for the initial access problem it does not rely on beam scanning with delays, nor does it take into account the traffic properties. In more detail, a new random access based on beamforming pattern switching has been developed, which can be applied to any frequency band. The proposed scheme is particularly useful for unlicensed access for massive MTC. In fact, the beamformed broadcast signals may be used as a tool to manage unlicensed access, as the use of beamformed broadcast signals may reduce collisions, thereby improving the performance of unlicensed access.
As mentioned before, the proposed method can also be used for initial access procedures. The main criteria to be considered when designing the beam-based initial access procedure are as follows:
access delay
Scheduling
Identification of frame and subframe boundaries
Cell edge coverage
The proposed initial access procedure based on beamformed broadcast signals keeps the communication between the gNB and the devices to a minimum and is able to control the extent of interference that occurs thereby in a densely deployed scenario. The transmission of the devices under coverage is controlled in an open-loop manner based on the optimized multi-beam pattern.
In summary, the main contributions of the present invention are as follows:
first, the base station constructs a different optimized beam pattern based on, for example, Grassmannian (Grassmannian) subspace packing. Each pattern is formed by a plurality of beams. The aggregation of the different beam patterns provides the maximum coverage of the angular space, which is required to ensure complete cell coverage. So that:
a) random access or initial access delay reduction
b) The performance (rate or density of MTC) is optimized
Secondly, the base station is allowed to learn the optimal beam transmission strategy so that it can adapt to user repartitioning and their respective traffic patterns. In the learning process, the gbb uses the constructed optimized beam pattern, as well as a set of narrow beams for cell-edge coverage. Thus, the following results were obtained:
a) the transmission period of the beam pattern is optimized according to the occurring traffic
b) The beam transmission delay can be further reduced because the base station will prioritize the direction in which most of the traffic is received
c) Cell edge coverage is maintained while minimizing the impact on unlicensed or initial access delays.
Third, once the user or MTC device selects the beam direction, it informs the gNB and then starts the transmission directly. This protocol reduces the exchange of control information between the network and the device. This procedure is well suited for the requirement of high connection density for massive mtc (mtc), because it manages interference efficiently without authorized access using the proposed advanced beamforming pattern definition and handover method.
The prior art does not consider the unlicensed access based on beamforming, but only based on non-orthogonal multiple access (NOMA), which has the problems of high receiver complexity and complex interference management. Beamforming-based solutions may more efficiently handle interference in wireless networks because the transmitted data may be in nearly orthogonal subspaces, thereby reducing the interference encountered in the network.
Beam pattern generation:
as mentioned before, the present invention advocates the use of multiple beams for access authorization for users under signal coverage. This may constrain the initial access delay and cover the entire angular space. At each access occasion, for subsequently active users, their signals will be concentrated in nearly orthogonal subspaces, thereby reducing interference.
Multi-user interference can be problematic since multiple beams can be used simultaneously. In practice, if the spatial separation between beams is not large enough, active users aligned with different beams will have channels that interfere with each other, which can produce considerable mutual interference. The design of the beam pattern is therefore crucial for the success of the proposed access scheme. In practice, the main goal of beam pattern design should be as follows:
the distance between the beams of each pattern should be maximized to reduce the multi-user interference that may be generated
The combination of the beam pattern ensemble should provide maximum coverage in angle (space)
These criteria are to associate the current beam pattern generation problem with Grassmannian subspace packing (Grassmannian subspace packing). Grassmann subspace packing is the problem of finding a set of N K-dimensional subspaces in G (M, K) that maximizes the minimum distance between any pair of subspaces in the set. In the configuration considered, in order for the initial access procedure to be able to meet expectations, the transmit beam should be constructed appropriately in order to effectively mitigate interference. In addition, the final selected beam pattern should provide the greatest coverage throughout the angular space.
The beam construction process is as follows:
i. initialization:
ii.formation of C>T different patterns of dimension K, the set of patterns Delta [ Delta ] j ,j＝1,…,C]. Each pattern is a DFT column of a combination of a plurality of DFT columns.
At Δ δ iii (j) J is 1, …, T pattern is selected from T, and:
δ (j) ＝argmaxd i，min (δ i )，δ i ∈Δ\δ (j-1)
wherein d is the sum pattern delta i The distance of (c).
Selecting N beam patterns, which is a solution to the combinatorial optimization problem:
wherein theta is m M is 1, …, M is the set of different beams. If pattern j is selected, x j Otherwise, it is 0. If dimension m is covered, then y m 1, otherwise 0.
This process provides N beam patterns, maximizing the coverage of the angular space, since the objective function maximizes the number of coverage dimensions. The second constraint ensures that the number of selected patterns is less than or equal to N, while the first constraint ensures that the problem is consistent (the dimension m being selected by ym means that at least one beam is selected that includes this dimension). An example of a beam pattern for a ULA is shown in fig. 2.
Initial access based on dynamic beams: learning beamforming strategies
Thanks to the manger subspace filling and maximum coverage optimization, an optimized control signal beamforming procedure is provided herein after deriving the optimized beam pattern. The present invention further focuses on achieving a trade-off between delay, coverage and frame structure. Thus, in addition to the optimized beam pattern, high power narrow beams are included to cover users at the cell edge. The use of such beams will be limited, reducing the delay. The rationale for this concept is to let the gNB learn the best strategy to control signal beamforming to achieve the best long term average throughput.
In the form, beam transmission optimization can be expressed as a more than one dobby slot machine problem. In this case, each gNB will learn the best beam pattern to use at each SS transmission opportunity to maximize the long term average throughput achievable.
The goal is to derive a beam pattern scheduling strategy γ ═ (γ) 1 ,γ 2 …) which maximizes the following equation:
wherein:
| β | the optimized set of beam patterns |
| U i (t),i＝1,…,|β| | Control action at time t |
| N i (t),i＝1,…,|β| | Up to sub-framet, number of uses of beam pattern of index i |
| X i (N i (t)) | State of the System (e.g., queue, traffic load, etc.) at subframe t |
| R i (X i (N i (t)),U i (t)) | Throughput achieved at subframe t |
| t | Index of subframe with SS signal |
| α | |
| Z(t) | Up to subframe t, set of states |
This optimization enables beam-based initial access procedures to be adapted to the traffic pattern of the covered device. In fact, the base station is able to learn the beam pattern that results in high data throughput when data is transmitted. This means that the network will adapt its beam pattern transmission to the actual traffic pattern of the device, resulting in a more efficient random access procedure, since a higher response beam precedence is given to active devices that have a larger data load to transmit.
This also covers users at the cell edge. However, this is not achieved at the cost of delay. In fact, when the gNB learns the best strategy based on initial access of the beam, high power narrow beams may be transmitted in a limited number of time slots.
This adaptation of the beam-based initial access procedure is different from the traditional traffic-independent approach. Indeed, although covering the whole or at least a large part of the angular space, the angular space is still very important, and it may be crucial to prioritize the use of a particular beam pattern in order to ensure a certain degree of stability of the network.
Simplified random access for MTC:
the initial access method based on the optimized beam is particularly suitable for the random access procedures of the MTC equipment and the service properties of the random access procedures. Indeed, since MTC considers high connection density as one of its main KPIs, it would be beneficial to reduce the exchange of control information in the initial access procedure of such devices. However, uncontrolled unlicensed access, in addition to a higher error rate, may also result in a high degree of interference. Since the proposed beam-based method is able to identify the main direction of arrival (DoA) of data to be transmitted in the future, the implied beam pattern can be used to decode the signals of subsequently active devices.
The goal is to derive a beam pattern scheduling strategy γ ═ y (γ) 1 ,γ 2 …) which maximizes the following equation:
wherein:
the utility function may be, for example, the amount of successfully decoded packets (for MTC with a given packet size, directly related to the number of MTC served). Other interference related functions may also be used. This optimization enables beam-based initial access procedures to adapt to the traffic pattern (activity and density) of the MTC devices being covered. In fact, the state of the system, which depends on the number of active devices transmitting at a given time, is one input to the above-mentioned learning problem, which adapts to the activity and density of the devices. Thus, the gNB is able to learn a beam pattern that allows a large number of data packets to be successfully received.
Fig. 3 shows the initial access procedure. The gNB transmits multiple beams of one beam pattern to broadcast beamformed synchronization signals, such as Primary Synchronization Signals (PSS) and Secondary Synchronization Signals (SSS). This beam pattern is one of a set of optimized beam patterns as described above. These beam patterns may be scheduled according to the beam pattern scheduling policies mentioned above to adapt to the actual traffic pattern of the device or devices being covered. Once the UE or MTC device selects one beam direction, the UE may send a random access preamble to inform the gNB and directly start sending data to the gNB. This protocol reduces the exchange of control information between the UE and the gNB.
Simulation results are as follows:
numerical simulation results of the benefits that can be achieved by the proposed invention are provided herein. The performance of the proposed access procedure is compared to the traditional unlicensed approach. It is assumed here that the gNB is located in the center of a cell of radius 100m, which is equipped with 64 antenna elements. The activation probabilities are randomly generated considering that each cell has a different number of users. Note that the activation patterns of the MS are independent. The gNB uses 60 different beam patterns of maximum rank 6(rank 6), which are generated from the grassmann subspace packing.
Fig. 4 shows a comparison of the performance in terms of average spectral efficiency. This figure shows a significant improvement in achievable performance as a result of the reduced interference. Indeed, in the proposed invention, the gNB controls the activation of the MSs through the beamforming SS, which limits the number of active MSs per slot. In interference limited architectures, the proposed invention provides a considerable improvement in achievable performance without resorting to complex grant-based scheduling schemes.
The signal processing functions of embodiments of the present invention, and in particular the gNB and UE, may be implemented using computing systems or architectures known to those skilled in the relevant art. Computing systems such as desktop, laptop or notebook computers, hand-held computing devices (PDAs, cell phones, palmtops, etc.), mainframes, servers, clients, or any other type of special or general purpose computing device as may be desired or appropriate for a given application or environment may be used. The computing system may include one or more processors, which may be implemented using a general or special purpose processing engine such as, for example, a microprocessor, microcontroller or other control module.
The computing system may also include a main memory, such as a Random Access Memory (RAM) or other dynamic memory, for storing information and instructions to be executed by the processor. Such main memory may also be used for storing temporary variables or other intermediate information to be executed by the processor during execution of instructions. The computing system may similarly include a Read Only Memory (ROM) or other static storage device for storing static information and instructions for the processor.
The computing system may also include an information storage system that 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 Disk (CD) or Digital Video Drive (DVD), a read or write drive (R or RW), or other removable or fixed media drive. The storage medium 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 a media drive. The storage media may include a computer-readable storage medium having stored therein particular computer software or data.
In alternative embodiments, the 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, removable storage units and interfaces, such as program cartridges and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to the computing system.
The computing system may also include a communication interface. Such communication interfaces may be used to allow software and data to be transferred between the computing system and external devices. Examples of a communication interface may include a modem, a network interface (such as an ethernet or other NIC card), a communication port (such as a Universal Serial Bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via the communications interface are in the form of signals which may be electrical, electromagnetic and optical or other signals capable of being received by the 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 memory, storage devices, or storage units. These and other forms of computer-readable media may store one or more instructions for use by a processor, including a 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 the 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 include at least one of the group consisting of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memories, programmable read-only memories, erasable programmable read-only memories, EPROMs, electrically erasable programmable read-only memories, and flash memories.
In embodiments where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into a computing system using, for example, a removable storage drive. The control module (in this example, software instructions or executable computer program code), when executed by a processor in a computer system, causes the processor to perform the functions of the invention as described herein.
Furthermore, the concepts of the present invention may be applied to any circuit for performing signal processing functions within a network element. It is further envisioned that, for example, a semiconductor manufacturer may utilize the concepts of the present invention in designing a stand-alone device and/or any other subsystem element of a microcontroller such as an Application Specific Integrated Circuit (ASIC) or a Digital Signal Processor (DSP).
It will be appreciated that for clarity purposes, the above description has described embodiments of the invention with reference to a single processing logic. The inventive concept may, however, equally be implemented by means of a plurality of different functional units and processors to provide the signal processing functions. Hence, 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 as configurable modular 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 invention is limited only by the accompanying claims. Furthermore, 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 e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may possibly advantageously be 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. Furthermore, 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 invention is limited only by the accompanying claims. Furthermore, 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.
Claims (20)
1. A method for enabling a wireless communication device to access a service provided by a radio access network, the method being performed by a base station and comprising:
obtaining a set of different beam patterns, each beam pattern being formed by a plurality of beams; and
a plurality of beams of each beam pattern are transmitted to transmit a beamformed broadcast signal for an access procedure.
2. The method of claim 1, wherein: the transmissions are made simultaneously in a plurality of beams of each beam pattern.
3. The method of claim 1, wherein: the multiple beams of each beam pattern are used to transmit a beamformed broadcast signal having the same Synchronization Signal Block (SSB).
4. The method of claim 1, wherein the set of beam patterns is formed by:
maximizing the distance between the plurality of beams in each beam pattern; and
maximum spatial coverage is provided by combining different beam patterns.
5. The method of claim 4, wherein: the set of beam patterns is constructed based on grassmann subspace packing.
6. The method of claim 4, wherein: each beam pattern is based on a Discrete Fourier Transform (DFT) codebook.
7. The method of claim 1, further comprising:
transmitting a beam of the plurality of beam patterns according to a beam pattern scheduling policy.
8. The method of claim 7, further comprising:
determining the beam pattern scheduling policy by determining a scheduling policy for the set of beam patterns that maximizes an average throughput.
9. The method of claim 8, wherein determining the beam pattern scheduling policy comprises:
the average throughput is estimated by taking as input the scheduled frequency of each beam pattern in the set of beam patterns.
10. The method of claim 7, further comprising:
in addition to the beams in the set of beam patterns, high power narrow beams for cell edge coverage are transmitted.
11. The method of claim 7, further comprising:
the beam pattern scheduling policy is determined by determining a scheduling policy for the set of beam patterns that maximizes the number of data packets successfully decoded by the base station.
12. The method of claim 11, wherein determining the beam pattern scheduling policy comprises:
the number of data packets successfully decoded by the base station is estimated by taking as input the scheduling frequency of each beam pattern in the set of beam patterns.
13. A base station comprising a processor, a memory unit, and a communication interface, wherein the processor unit, the memory unit, and the communication interface are configured to perform the method of any one of claims 1 to 21.
14. A non-transitory computer readable medium having stored thereon computer readable instructions for execution by a processor to perform the method of any of claims 1 to 12.
15. A Random Access (RA) method implemented between a base station and a user equipment, the method performed by the base station and comprising:
transmitting with a plurality of beams of one beam pattern of a set of different beam patterns to transmit a beamformed broadcast signal emitted by the base station; and
the base station receives an RA preamble and a data transmission in response to the beamformed broadcast signal.
16. The method of claim 15, wherein: the transmissions are made simultaneously in a plurality of beams of each beam pattern.
17. The method of claim 15, wherein: the multiple beams of each beam pattern are used to transmit a beamformed broadcast signal having the same Synchronization Signal Block (SSB).
18. The method of claim 15, further comprising:
in addition to the beams in the set of beam patterns, high power narrow beams for cell edge coverage are transmitted.
19. A method for enabling a wireless communication device to access a service provided by a radio access network, the method being performed by a user equipment and comprising:
a beamformed broadcast signal is received that is broadcast using one of a plurality of illuminated beams of one of a set of different beam patterns.
20. The method of claim 19, further comprising:
upon receiving the beamformed broadcast signal, transmitting an RA preamble and beginning data transmission from the user equipment to the base station.
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