EP4014662A1

EP4014662A1 - Interferrence detection for random access false alarm reduction

Info

Publication number: EP4014662A1
Application number: EP19784125.7A
Authority: EP
Inventors: Talha KHAN; Olof Liberg; Yi-Pin Eric Wang; Yutai SUI
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2019-08-16
Filing date: 2019-08-16
Publication date: 2022-06-22
Also published as: WO2021033009A1

Abstract

Systems and methods are disclosed herein for random access interference detection and mitigation. Embodiments of a method performed by a base station and corresponding embodiments of a base station are disclosed. In some embodiments, a method performed by a base station in a cellular communications system comprises detecting interference on at least a portion of a random access resource for a respective cell based on either or both of: (a) one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in at least a portion of the random access resource and (b) frequency hopping patterns used by one or more other cells for single-tone frequency hopping random access preambles. The method further comprises performing one or more actions to mitigate the detected interference. In this manner, false alarm reduction can be reduced.

Description

INTERFERRENCE DETECTION FOR RANDOM ACCESS FALSE ALARM REDUCTION

Technical Field

[0001] The present disclosure relates to interference detection for random access false alarm reduction.

Background

[0002] In Release 13, the Third Generation Partnership Project (3GPP) developed Narrowband Internet of Things (NB-IoT). This New Radio (NR) access technology provides connectivity to services and applications demanding qualities such as reliable indoor coverage and high capacity in combination with low device complexity and optimized power consumption.

[0003] A NB-IoT User Equipment (UE) establishes connection to an enhanced or evolved Node B (eNB) using the Narrowband Physical Random Access Channel (NPRACH). Unfortunately, the reliability of the NPRACH is compromised in the presence of inter-cell interference. This may increase the False Alarm Rate (FAR) as well as the misdetection rate on NPRACH.

Release 13 NB-IoT NPRACH

[0004] In NB-IoT, the Random Access (RA) procedure provides the means of synchronization to the uplink frame structure. A UE initiates the RA procedure after synchronizing to the downlink frame structure. In the first step of the RA procedure, a UE transmits a preamble. In the second step, the eNB detects the preamble Time of Arrival (TA) and signals the TA value to the UE. The UE will thereafter use the TA value to align its transmission to the uplink frame structure.

[0005] Regarding the Frequency Division Duplexing (FDD) NPRACH waveform, according to 3GPP Technical Specification (TS) 36.211 section 10.1.6.1, "the physical layer random access preamble is based on single-subcarrier frequency hopping symbol groups." An NPRACH symbol group consists of a Cyclic Prefix (CP) and a sequence of five identical symbols. The NPRACH preamble consists of four symbol groups transmitted without gaps transmitted N_rI_v ^RACH times. In other words, together four symbols groups are referred to as an NPRACH frequency hopping symbol group, which is also referred to herein as an NPRACH preamble repetition unit. The NPRACH preamble consists of N_rep ^RACH repetitions of this NPRACH preamble repetition unit. Each symbol corresponds to an unmodulated sinus wave of frequency 3.75 kilohertz (kHz) and periodicity 8192T_S =266 microseconds (ps), where T_s equals 1/(15000x2048) seconds (s). The NPRACH preamble is transmitted over a 3.75 kHz channel. Two CP lengths are supported, i.e. 66 ps (Format 0) and 266 ps (Format 1). For the 266 ps choice, the CP is identical to a symbol. Figure 1 illustrates a RA symbol group of length 1.4 milliseconds (ms) or 1.6 ms, depending on the choice of the CP length.

[0006] The NB-IoT FDD minimum system bandwidth of 180 kHz is divided into 48 subcarriers, or tones, each 3.75 kHz wide. For a single FDD NPRACH transmission, the symbol group of Figure 1 frequency hops four times across at most seven subcarriers as shown in Figure 2, which illustrates an NPRACH frequency hopping symbol group. This physical signal, also called an NPRACH preamble repetition unit, is uniquely defined by the first subcarrier in the frequency hopping pattern, i.e. the starting subcarrier. In total, forty-eight (48) orthogonal preambles can be defined, one for each available starting subcarrier.

[0007] To support higher levels of coverage, a Coverage Enhancement (CE) level may be associated with up to 128 repetitions of the NPRACH preamble repetition unit. A pseudo-random frequency hop is used between the NPRACH preamble repetition units, as illustrated in Figure 3. The pseudo-random frequency hop is bounded so that the NPRACH preamble transmission never spans more than 12 x 3.75 = 45 kHz. Also, the direction of the large 22.5 kHz frequency hop within each repetition is restricted to secure that the NPRACH preamble transmission never spans more than 12 x 3.75 = 45 kHz. In this example, both the first and second NPRACH preamble repetition units use the same hopping direction when making the large 22.5 kHz hop.

NPRACH CE Level Selection

[0008] The NB-IoT radio interface has been designed to support three separate NPRACH radio resources, where each NPRACH radio resource (also referred to herein as an "NPRACH resource" or more generally as a "random access resource") is associated with an NPRACH coverage range (i.e., with a CE level) and a set of NPRACH preamble repetitions. Thus, as used herein, an NPRACH radio resource, NPRACH resource, or RA resource is the time and frequency resources configured for uplink RA.

[0009] Figure 4 illustrates a typical NPRACH configuration. The left most NPRACH resource is intended for UEs in good radio conditions (CE level 0), where the NPRACH preamble is sent a single time. The system may configure two additional NPRACH resources to be used by UEs in extended (CE level 1) and extreme coverage (CE level 2). Each NPRACH resource is associated with a respective CE level. A CE level is furthermore associated with a set of repetitions used for the NPRACH preamble transmission. The number of repetitions increases if the coverage intended to be supported by the NPRACH resource is extended.

[0010] To select an NPRACH resource, the UE measures the downlink received power and, based on this measurement and a set of broadcasted signal level thresholds, selects the NPRACH resource to use for its system access, i.e., the number of times the NPRACH preamble repetition unit should be repeated.

[0011] Assuming that the eNB transmits twelve (12) NB-IoT subcarriers with 43 decibel-milliwatts (dBm), the power per 15 kHz subcarrier is approximately 32 dBm. If CE level 1 (CE1) starts at a coupling loss of 144 dB and CE level 2 (CE2) starts at a coupling loss of 154 dB, then the NRSRP thresholds (PcE,Th.2, PcE h.i) may be associated with NRSRP levels of 32 - 144 = -112 dBm and 32 - 154 = -122 dBm as illustrated in Figure 5.

NPRACH Power Control

[0012] When a UE accesses the system using the CE level 0 (CEO), the UE must use power control and meet a received power level target at the eNB, taking its estimated pathloss into account. For CE1 and CE2, the UE uses repetitions in combination with its maximum configurable power. The received power level at the eNB is then determined by the UE maximum power and the coupling loss associated with the UE, which should be within the bounds defined by the CE level thresholds depicted in Figure 5. NPRACH Reliability

[0013] The reliability of NPRACH is typically quantified in terms of FAR and Misdetection Rate (MDR). In the context of NPRACH, a brief description of the two metrics is as follows.

• False Alarm: False alarm is the event when no valid NPRACH preamble is transmitted but the NPRACH receiver incorrectly detects a preamble. This could be triggered by inter-cell interference or noise.

• Misdetection: Misdetection occurs when a valid preamble is transmitted but the NPRACH receiver either fails to detect an NPRACH preamble or accurately estimate its TA. This could be triggered by noise or interference.

[0014] An NPRACH detector typically processes the received signal to calculate a detection metric which is compared against a detection threshold. The detection threshold may introduce a tradeoff between FAR and MDR. If the detection threshold is too large, the eNB may not be able to detect a weak signal from a valid UE, which leads to a higher MDR. If the detection threshold is too small, noise and/or interference signal may trigger a false alarm despite the absence of a valid NPRACH preamble from a UE in the target cell. In the absence of interference, this tradeoff may not be obvious as it is possible to achieve an acceptable MDR (e.g., < 1%) and an acceptable FAR (e.g., < 0.1%). Amid interference, however, this problem is exacerbated since both FAR and MDR may exceed the acceptable operating ranges.

[0015] Interference including inter-cell interference can considerably degrade NPRACH detector performance. It can increase the FAR or increase the MDR. Therefore, a smart NPRACH receiver with the ability to detect, identify, and reduce interference is desirable.

Summary

[0016] Systems and methods are disclosed herein for random access interference detection and mitigation. Embodiments of a method performed by a base station and corresponding embodiments of a base station are disclosed. In some embodiments, a method performed by a base station in a cellular communications system comprises detecting interference on at least a portion of a random access resource for a respective cell based on either or both of: (a) one or more expected signal characteristics of a single- tone frequency hopping random access preamble received in at least a portion of the random access resource and (b) frequency hopping patterns used by one or more other cells for single-tone frequency hopping random access preambles. The method further comprises performing one or more actions to mitigate the detected interference. In this manner, false alarm reduction can be reduced.

[0017] In some embodiments, detecting interference on the at least a portion of the random access resource for the respective cell comprises detecting interference on the at least a portion of the random access resource for the respective cell based on the one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in at least a portion of the random access resource. The one or more expected signal characteristics comprise an expected energy pattern. Further, in some embodiments, detecting interference on at least a portion of the random access resource for the respective cell based on the one or more expected signal characteristics of a single^¬ tone frequency hopping random access preamble received in the random access resource comprises determining received energy for a received signal on one or more resources that correspond to a portion of a particular random access preamble for the respective cell and determining that the received energy is greater than a threshold energy level. In some embodiments, the portion of the particular random access preamble for the respective cell is a symbol group of the particular random access preamble for the respective cell. In some other embodiments, the portion of the particular random access preamble for the respective cell is a symbol within a symbol group of the particular random access preamble for the respective cell, two or more symbols within a symbol group of the particular random access preamble for the respective cell, two or more symbol groups of the particular random access preamble for the respective cell, a repetition unit of the particular random access preamble for the respective cell, or two or more repetition units of the particular random access preamble for the respective cell.

[0018] In some embodiments, the threshold energy level is the sum of an energy metric and a rejection threshold, wherein the energy metric corresponds to an expected energy level and the rejection threshold is a configurable parameter. In some embodiments, the energy metric is an average received energy across resources within the random access resource that correspond to a plurality of portions of the particular random access preamble for the respective cell. In some embodiments, each portion of the plurality of portions of the particular random access preamble for the respective cell is a symbol within a symbol group of the particular random access preamble for the respective cell, two or more symbols within a symbol group of the particular random access preamble for the respective cell, a random access symbol group of the particular random access preamble for the respective cell, two or more symbol groups of the particular random access preamble for the respective cell, a repetition unit of the particular random access preamble for the respective cell, or two or more repetition units of the particular random access preamble for the respective cell.

[0019] In some other embodiments, the energy metric is a weighted or running average of received energy per random access preamble portion for at least a subset of previously received single-tone frequency hopping random access preambles received within a predefined or configurable time window. In some embodiments, the random access preamble portion is a symbol within a symbol group, two or more symbols within a symbol group, a random access symbol group, two or more symbol groups, a preamble repetition unit, or two or more preamble repetition units.

[0020] In some other embodiments, the energy metric is a function of a coverage enhancement level of the random access resource.

[0021] In some embodiments, performing the one or more actions to mitigate the detected interference comprises discarding at least the portion of the particular random access preamble for the respective cell for which the received energy is greater than the threshold energy level. In some embodiments, discarding at least the portion of the particular random access preamble for the respective cell comprises discarding at least the portion of the particular random access preamble for the respective cell from a random access preamble detection metric calculation for time-of-arrival estimation.

[0022] In some embodiments, detecting interference on at least a portion of the random access resource for the respective cell comprises detecting interference on at least a portion of the random access resource for the respective cell based on the one or more expected signal characteristics of a random access preamble received in at least a portion of the random access resource, the one or more expected signal characteristics comprising one or more expected covariance or correlation properties. In some embodiments, detecting interference on the random access resource for the respective cell based on the one or more expected signal characteristics of a random access preamble received in the random access resource comprises determining a covariance or correlation metric for a received signal on a set of resources within the random access resource that correspond to a particular random access preamble for the respective cell and determining that the determined covariance or correlation metric differs from an expected covariance or correlation metric. In some embodiments, determining the covariance or correlation metric comprises determining a covariance or correlation of two or more samples of the received signal that are received via two or more respective antennas of the base station. In some other embodiments, determining the covariance or correlation metric comprises determining a covariance or correlation of two or more portions of the received signal that are received via one or more antennas of the base station during two or more respective time windows.

[0023] In some embodiments, detecting interference on at least a portion of the random access resource for the respective cell comprises detecting random access preambles from the one or more other cells based on the frequency hopping patterns used by the one or more other cells. In some embodiments, performing the one or more actions to mitigate the detected interference comprises identifying the one or more other cells for which random access preambles are detected and performing one or more actions to mitigate the interference from the one or more identified cells. In some embodiments, the method further comprises receiving, from a network node, one or more cell identities of one or more respective neighbor cells of the respective cell, wherein detecting random access preambles from the one or more other cells based on the frequency hopping patterns used by the one or more other cells comprises attempting to detect random access preambles of the one or more neighbor cells.

[0024] In some embodiments, the method further comprises determining a false alarm rate for random access preamble detection and determining that the false alarm rate is greater than a predefined or preconfigured threshold. Further, detecting interference on at least a portion of the random access resource for the respective cell comprises detecting interference on at least a portion of the random access resource for the respective cell upon determining that the false alarm rate is greater than the predefined or preconfigured threshold.

[0025] In some embodiments, a base station for a cellular communications system is adapted to detect interference on at least a portion of a random access resource for a respective cell based on either or both of: (a) one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in at least a portion of the random access resource and (b) frequency hopping patterns used by one or more other cells for single-tone frequency hopping random access preambles. The base station is further adapted to perform one or more actions to mitigate the detected interference. [0026] In some embodiments, the base station comprises processing circuitry configured to cause the base station to detect interference on the random access resource for the respective cell and perform the one or more actions to mitigate the detected interference.

Brief Description of the Drawings

[0027] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0028] Figure 1 illustrates a Random Access (RA) symbol group of length 1.4 milliseconds (ms) or 1.6 ms, depending on the choice of the Cyclic Prefix (CP) length; [0029] Figure 2 illustrates a Narrowband Internet of Things (NB-IoT) Narrowband Physical Random Access Channel (NPRACFI) frequency hopping symbol group where a symbol group is 1.6 ms long;

[0030] Figure 3 illustrates a RA NPRACFI preamble repetition unit repeated once;

[0031] Figure 4 illustrates a typical NPRACFI configuration with three resources for Coverage Enhancement (CE) level 0 (CEO), CE level 1 (CE1), and CE level 2 (CE2);

[0032] Figure 5 illustrates example NPRACFI thresholds;

[0033] Figure 6 illustrates one example of a cellular communications system in which embodiments of the present disclosure may be implemented;

[0034] Figure 7 is a flow chart that illustrates the operation of a base station, and more specifically an NPRACFI receiver at the base station, to perform NPRACFI preamble detection with interference mitigation in accordance with some embodiments of the present disclosure;

[0035] Figure 8 is a flow chart that illustrates the operation of the base station to perform signal-energy based interference detection and mitigation of NPRACH interference in accordance with a first embodiment;

[0036] Figure 9A is a flow chart that illustrates the operation of the base station to perform covariance based interference detection and mitigation of NPRACFI interference in accordance with a second embodiment;

[0037] Figure 9B is a flow chart that illustrates the operation of the base station to perform correlation based interference detection and mitigation of NPRACFI interference in accordance with a second embodiment;

[0038] Figure 10 is a flow chart that illustrates the operation of the base station to perform network-assisted NPRACFI interference detection and identification in accordance with a third embodiment;

[0039] Figure 11 is a flow chart that illustrates the operation of the base station to perform False Alarm Rate (FAR)-triggered NPRACFI interference detection in accordance with a fourth embodiment;

[0040] Figure 12 is a schematic block diagram of a radio access node according to some embodiments of the present disclosure;

[0041] Figure 13 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node of Figure 12 according to some embodiments of the present disclosure;

[0042] Figure 14 is a schematic block diagram of the radio access node of Figure 12 according to some other embodiments of the present disclosure;

[0043] Figure 15 is a schematic block diagram of a User Equipment device (UE) according to some embodiments of the present disclosure;

[0044] Figure 16 is a schematic block diagram of the UE of Figure 15 according to some other embodiments of the present disclosure;

[0045] Figure 17 illustrates a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments of the present disclosure; [0046] Figure 18 is a generalized block diagram of a host computer communicating via a base station with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure;

[0047] Figure 19 is a flowchart illustrating a method implemented in a communication system in accordance with one embodiment of the present disclosure;

[0048] Figure 20 is a flowchart illustrating a method implemented in a communication system in accordance with one embodiment of the present disclosure;

[0049] Figure 21 is a flowchart illustrating a method implemented in a communication system in accordance with one embodiment on the present disclosure; and [0050] Figure 22 is a flowchart illustrating a method implemented in a communication system in accordance with one embodiment of the present disclosure.

[0051] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure. [0052] Radio Node: As used herein, a "radio node" is either a radio access node or a wireless device.

[0053] Radio Access Node: As used herein, a "radio access node" or "radio network node" is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), and a relay node.

[0054] Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing a Access and Mobility Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

[0055] Wireless Device: As used herein, a "wireless device" is any type of device that has access to (i.e., is served by) a cellular communications network by wirelessly transmitting and/or receiving signals to a radio access node(s). Some examples of a wireless device include, but are not limited to, a User Equipment device (UE) in a 3GPP network and a Machine Type Communication (MTC) device.

[0056] Network Node: As used herein, a "network node" is any node that is either part of the RAN or the core network of a cellular communications network/system.

[0057] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0058] Note that, in the description herein, reference may be made to the term "cell"; however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0059] Systems and methods are disclosed herein for reducing the False Alarm Rate (FAR) at a Narrowband Physical Random Access Channel (NPRACH) receiver (also referred to herein as an NPRACH detector) amid interference such as, e.g., inter-cell interference.

In some embodiments, the received signal energy pattern is used to detect and discard the portion(s) of the received signal impacted by interference. In some other embodiments, the special structure in the NPRACH preamble frequency hopping patterns is leveraged to detect interference and identify the interfering cells. [0060] It should be noted that while the embodiments described herein focus on NPRACH and the NPRACH preamble, the embodiments described herein are not limited thereto. For example, the embodiments described herein can be applied for other types of single-subcarrier (i.e., single-tone) frequency hopping Random Access (RA) preambles. [0061] Certain embodiments of the present disclosure provide advantages over conventional solutions. For example:

• Certain embodiments do not rely on prior knowledge about the interference signal or interfering source. They attempt to detect the presence of interference by processing the received signal.

• Certain embodiments are compatible with existing 3GPP standards and only require a modification to the eNB receiver algorithm.

• Certain embodiments are also viable in the interference-free scenario where the received signal is mainly corrupted by noise.

• Certain embodiments, for false alarm reduction, do not seem to worsen the Misdetection Rate (MDR).

• Certain embodiments are dynamic in the sense they can be activated or deactivated based on FAR estimation.

[0062] In this regard, Figure 6 illustrates one example of a cellular communications system 600 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 600 is cellular communications system 600 that supports 3GPP Narrowband Internet of Things (NB-IoT) or similar radio access technology that utilizes a single-tone frequency hopping RA preamble. In this example, the RAN includes base stations 602-1 and 602-2, which are sometimes referred to as eNBs, controlling corresponding (macro) cells 604-1 and 604-2. The base stations 602-1 and 602-2 are generally referred to herein collectively as base stations 602 and individually as base station 602. Likewise, the (macro) cells 604-1 and 604-2 are generally referred to herein collectively as (macro) cells 604 and individually as (macro) cell 604. The RAN may also include a number of low power nodes 606-1 through 606-4 controlling corresponding small cells 608-1 through 608-4. The low power nodes 606-1 through 606-4 can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells 608-1 through 608-4 may alternatively be provided by the base stations 602. The low power nodes 606-1 through 606-4 are generally referred to herein collectively as low power nodes 606 and individually as low power node 606. Likewise, the small cells 608-1 through 608-4 are generally referred to herein collectively as small cells 608 and individually as small cell 608. The cellular communications system 600 also includes a core network 610. The base stations 602 (and optionally the low power nodes 606) are connected to the core network 610.

[0063] The base stations 602 and the low power nodes 606 provide service to wireless devices 612-1 through 612-5 in the corresponding cells 604 and 608. The wireless devices 612-1 through 612-5 are generally referred to herein collectively as wireless devices 612 and individually as wireless device 612. The wireless devices 612 are also sometimes referred to herein as UEs.

[0064] In the embodiments described herein, at least some of the base stations 602 and/or low power nodes 606 support NB-IoT.

[0065] Now, the discussion turns to a description of some particular embodiments of the present disclosure. The embodiments described below are described at the granularity of one NPRACH symbol group. It should be noted that similar concepts are also applicable at other granularity levels such as a symbol, an NPRACH preamble repetition unit, a group containing multiple symbols or symbol groups or preamble repetition units, etc.

[0066] Figure 7 is a flow chart that illustrates the operation of a base station 602, and more specifically an NPRACH receiver at the base station 602, to perform NPRACH preamble detection with interference mitigation in accordance with some embodiments of the present disclosure. Note that dashed lines represent optional steps. As illustrated, the base station 602 (optionally) makes a decision to activate NPRACH interference detection and mitigation (step 700). For example, if the FAR or estimated FAR of the base station 602 is above a predefined or configurable threshold level, the base station 602 makes the decision to activate NPRACH interference detection and mitigation. Note that, in some other embodiments, NPRACH interference detection and mitigation may always be active, in which case step 700 is not performed.

[0067] The base station 602 performs NPRACH preamble detection with interference detection and mitigation (step 702). More specifically, the base station 602 detects NPRACH interference (step 702A). As used herein, NPRACH interference is interference (e.g., inter-cell interference) within an NPRACH resource in which the base station 602 attempts to detect NPRACH preamble transmissions. A number of embodiments are described below which provide example procedures by which the base station 602 can detect NPRACH interference. In general, the base station 602 detects NPRACH interference on at least a portion of an NPRACH resource based on either or both of: (a) one or more expected signal characteristics (e.g., expected signal energy and/or expected covariance or correlation, e.g., across multiple receive antennas or multiple time windows) of an NPRACH preamble received in at least a portion of a particular NPRACH resource for which interference detection is being performed and (b) NPRACH frequency hopping patterns used by one or more other cells. Once the interference is detected, the base station 602 performs one or more actions to mitigate the interference (step 702B). Examples of the actions that may be taken are described below.

[0068] In a first embodiment, the base station 602, and more specifically an NPRACH receiver at the base station 602, performs signal energy-based interference detection and mitigation of NPRACH interference. More specifically, the average received power for a valid NPRACH preamble transmission received at the base station 602 should be limited by the power control target in Coverage Enhancement (CE) Level 0 (CEO) and the coupling loss thresholds associated with CE Level 1 and CE Level 2 (CE2) (see, e.g., Figure 5). An interfering NPRACH preamble transmission (e.g., an NPRACH preamble transmission from a neighboring cell) does not follow this restriction, which allows the base station 602 to detect the presence of the interfering NPRACH preamble transmission.

[0069] Figure 8 is a flow chart that illustrates the operation of the base station 602 to perform signal energy-based interference detection and mitigation of NPRACH interference in accordance with the first embodiment. Optional steps are represented with dashed lines. Note that steps 800 and 802 of Figure 8 correspond to step 702A of Figure 7, and step 804 of Figure 8 corresponds to step 702B of Figure 7. As illustrated, the base station 602 determines (e.g., measures) a received energy for an NPRACH symbol group for a particular NPRACH preamble (step 800). In other words, the base station 602 determines a received energy for a signal received on one or more time-frequency resources (e.g., resource elements) that correspond to the symbols of the NPRACH symbol group for the particular NPRACH preamble. The base station 602 compares the received energy for the NPRACH symbol group to an energy threshold (step 802). In this example, the energy threshold is a value denoted "energy metric + R_T" decibels (dB). Examples of how the energy metric and R_T can be determined or configured are described below.

[0070] If the received energy is greater than the energy threshold (e.g., if the received energy is greater than "energy metric" by at least R_T dB) (step 802, YES), the base station 602 discards the NPRACH symbol group, e.g., from an NPRACH detection metric calculation for Time of Arrival (TA) estimation (step 804). In other words, the received signal that corresponds to this NPRACH symbol group is not taken into account by the base station 602 when calculating an NPRACH detection metric for TA estimation. In this manner, the effect of the interference is mitigated. However, if the received energy is not greater than the energy threshold (e.g., if the received energy is not greater than "energy metric" by at least R_T dB) (step 802, NO), the base station 602 does not discard the NPRACH symbol group, e.g., from an NPRACH detection metric calculation for TA estimation (step 806). In other words, the received signal that corresponds to this NPRACH symbol group is taken into account by the base station 602 when calculating an NPRACH detection metric for TA estimation.

[0071] The process then returns to step 800 and is repeated for the next NPRACH symbol group. Again, note that while this example uses a granularity of an NPRACH symbol group, the present disclosure is not limited thereto. Other granularities may be used.

[0072] The energy metric used in the process of Figure 8 may be defined or derived as a function of the received signal energy in each CE level. In one embodiment, the energy metric is set to the average symbol group energy of the received NPRACH preamble. In other words, for each NPRACH symbol group of the particular NPRACH preamble, the base station 602 measures the received energy on the resources that correspond to the symbols in that NPRACH symbol group. The base station 602 then computes an average of these received energy measurements, which is then used as the energy metric.

[0073] In another embodiment, the energy metric is a weighted or running average of the NPRACH symbol group energy of the NPRACH preambles previously received by the base station 602 (NPRACH preambles that the base station 602 previously attempted to detect) in a configurable time window. In yet another embodiment, the energy metric is a weighted or running average of the symbol group energy of a subset of the NPRACH preambles previously received by the base station 602 (NPRACH preambles that the base station 602 previously attempted to detect). For example, this subset may exclude the received preambles resulting in successful detection attempts. In a further embodiment, the energy metric is made dependent on the CE1 and CE2 Reference Signal Received Power (RSRP) thresholds, and the CEO power control target (see, e.g., Figure 5).

[0074] The rejection threshold (R_T) is a configurable parameter where R_T >0 dB. If the rejection threshold is set too high, the base station 602 (i.e., the NPRACH receiver at the base station 602) will likely detect interfered symbol groups only when the interference power is sufficiently high. The symbol groups corrupted by relatively weaker interference signals will go undetected, thus increasing the FAR. As R_T ® ¥, the proposed solution becomes ineffective, i.e. the receiver is reduced to a legacy receiver. Conversely, if the rejection threshold is set too low, the receiver may incorrectly discard interference-free symbol groups, which may impact the MDR. In other words, the rejection threshold should allow for received energy variation due to fading.

[0075] Example. A base station 602 scans for valid RA attempts on the configured NPRACH resources within the cell. Ideally, in the absence of a valid NPRACH transmission on a resource, the base station 602 should not detect any preamble. That is, the detection metric for the received signal should be less than the detection threshold. However, inter^¬ cell interference or receiver noise may incorrectly increase the detection metric beyond the detection threshold, triggering a false alarm. When there is bursty interference, the entire received signal may not be impacted by it. By detecting and discarding the symbol groups impacted by interference by means of signal energy-based interference detection and removal, it is possible to avoid a misleading increase in the detection metric, which helps reduce the FAR.

[0076] In a second embodiment, a covariance metric or a correlation metric is utilized for NPRACH interference detection. More specifically, in one embodiment, the base station 602 evaluates a covariance metric or a correlation metric to detect interference. In case of a multi-antenna receiver, the covariance metric can be calculated over a received NPRACH preamble across multiple antenna branches. In case of a single antenna receiver, the covariance metric or the correlation metric can be calculated over received NPRACH symbols or symbol groups consecutive in time.

[0077] Figure 9A is a flow chart that illustrates the operation of the base station 602 to perform covariance based interference detection and mitigation of NPRACH interference in accordance with the second embodiment. Optional steps are represented with dashed lines. Note that steps 900A and 902A of Figure 9A correspond to step 702A of Figure 7, and step 904A of Figure 9A corresponds to step 702B of Figure 7. As illustrated, the base station 602 determines a covariance metric for detecting NPRACH interference (step 900A). As discussed above, in some embodiments, the base station 602 has multiple receive antennas, and the covariance metric is a metric that represents the covariance between two or more receive signals via two or more respective receive antennas on time-frequency resources that correspond to a particular NPRACH preamble that the base station 602 is attempting to detect. The covariance metric may be represented, e.g., in a matrix form or other form for tracking determined covariance values. By evaluating and inspecting the covariance metric (e.g., here, the receive antenna covariance matrix), the presence of interference can be detected. This is because the covariance matrix in the presence of interference can be different from that in the presence of receiver noise only. In some other embodiments, a single receive antenna of the base station 602 is used, and the covariance metric is a metric that represents the covariance between two or more portions of a receive signal that is received via the single antenna on time-frequency resources that correspond to a particular NPRACH preamble that the base station 602 is attempting to detect. The two or more portions of the receive signal may be, e.g., two or more portions received on resources that correspond to two or more portions of the particular NPRACH preamble (e.g., two or more NPRACH preamble repetitions).

[0078] The base station 602 determines whether NPRACH interference is present based on the covariance metric (step 902A). For example, the base station 602 may compare the covariance metric to one or more expected covariance metrics (e.g., a set of expected covariance metrics). If the covariance metric differs from the one or more expected covariance metrics (e.g., if the covariance metric differs from the one or more expected covariance metrics by more than a predefined or preconfigured threshold amount or degree), the base station 602 determines that NPRACH interference is present. In other words, the covariance may be expressed as a covariance matrix consisting of entries. The covariance matrix may be the covariance metric. Interference may change the covariance matrix characteristics. So, the presence of interference can be detected based on the covariance matrix. For example, without interference, white noise across two receive antennas may yield a diagonal covariance matrix. However, due to interference, the signal plus noise on the antennas may be correlated and the resulting covariance matrix will be no longer diagonal. Of course, to determine this, post-processing of the covariance matrix or one or more entries of the covariance matrix (where post-processing could be as simple as comparing the entries of the covariance matrix with corresponding threshold values or corresponding sets of values, or performing some matrix operations) can be performed. Upon determining that NPRACH interference is present (step 902A, YES), the base station 602 performs one or more actions to mitigate the interference (step 904A). For example, the base station 602 may configure separate, non-overlapping NPRACH resources in one or more neighbor cells.

[0079] Figure 9B is a flow chart that illustrates the operation of the base station 602 to perform correlation based interference detection and mitigation of NPRACH interference in accordance with the second embodiment. Optional steps are represented with dashed lines. Note that steps 900B and 902B of Figure 9B correspond to step 702A of Figure 7, and step 904B of Figure 9B corresponds to step 702B of Figure 7. As illustrated, the base station 602 determines a correlation metric for detecting NPRACH interference (step 900B). As discussed above, in some embodiments, the base station 602 has multiple receive antennas, and the correlation metric is a metric that represents the correlation between two or more receive signals via two or more respective receive antennas on time-frequency resources that correspond to a particular NPRACH preamble that the base station 602 is attempting to detect. By evaluating and inspecting the correlation metric, the presence of interference can be detected. In some other embodiments, a single receive antenna of the base station 602 is used, and the correlation metric is a metric that represents the correlation between two or more portions of a receive signal that is received via the single antenna on time-frequency resources that correspond to a particular NPRACH preamble that the base station 602 is attempting to detect. The two or more portions of the receive signal may be, e.g., two or more portions received on resources that correspond to two or more portions of the particular NPRACH preamble (e.g., two or more NPRACH preamble repetitions).

[0080] In this regard, an interfering signal may, unlike Gaussian noise, display a correlation in time or in space. Two consecutive transmissions from the same interfering source are similar, i.e. correlated. Two or more receive antenna branches will pick up the same interfering signal which is correlated, while the thermal noise generated in the receive branches are Gaussian. This correlation can be detected, and the presence of an interfering signal can be identified, or distinguished from thermal Gaussian noise. At the same time, it is likely that an interferer does not display the same type of correlation as will be displayed by a real NPRACH preamble transmission. This is due to the special structure of the NPRACH preamble. This may also allow interference to be distinguished from a NPRACH preamble reception.

[0081] The base station 602 determines whether NPRACH interference is present based on the correlation metric (step 902B). For example, the base station 602 may compare the correlation metric to one or more expected correlation metrics (e.g., a set of one or more expected correlation metrics). If the correlation metric differs from the one or more expected correlation metrics (e.g., if the correlation metric differs from the one or more expected correlation metrics by more than a predefined or preconfigured threshold amount or degree), the base station 602 determines that NPRACH interference is present. Upon determining that NPRACH interference is present (step 902B, YES), the base station 602 performs one or more actions to mitigate the interference (step 904B). For example, the base station 602 may configure separate, non-overlapping NPRACH resources in one or more neighbor cells.

[0082] Example. In the presence of persistent interference, the entire NPRACH received signal may be impacted by interference. In this scenario, the solution proposed in the first embodiment may not be helpful due to lack of disparity in signal energy across the symbol groups. In the extreme case, none of the interfered symbol groups will be discarded as the individual energy for each symbol group will be close to the energy metric (e.g., mean symbol group energy). This means that the false alarm may not be avoided. [0083] In a third embodiment, the base station 602 performs network-assisted NPRACH interference detection and identification. More specifically, the base station 602 leverages the special structure in the NPRACH frequency hopping patterns to detect interference and identify the interfering cells. That is, it attempts to detect preambles in the frequency hopping patterns used by other (neighboring) cells.

[0084] Figure 10 is a flow chart that illustrates the operation of the base station 602 to perform network-assisted NPRACH interference detection and identification in accordance with the third embodiment. Optional steps are represented with dashed lines. Note that steps 1002 and 1004 of Figure 10 correspond to step 702A of Figure 7, and step 1006 of Figure 10 corresponds to step 702B of Figure 7. As illustrated, the base station 602 optionally receives, from a network node, cell Identifiers (IDs) (e.g., Physical Cell IDs (PCIDs)) of one or more neighboring cells of the cell served by the base station 602 and for which NPRACH detection is being performed (step 1000). This information may be beneficial in order to reduce the search space. In other words, rather than attempting to detect all other possible NPRACH preambles from all other cells in step 1002 below, the base station 602 may attempt to detect NPRACH preambles from only the one or more neighbor cells indicated in step 1000.

[0085] The base station 602 detects NPRACH preambles from one or more other cells (e.g., one or more neighboring cells) (step 1002). In other words, in addition to attempting to detect NPRACH preambles from the particular cell served by the base station 602 (and for which interference detection and mitigation is being performed), the base station 602 also attempts to detect NPRACH preambles from other cells, which is interference, using the known frequency hopping patterns of NPRACH preambles in the other cells.

[0086] The base station 602 identifies the interfering cell(s) based on the detected NPRACH preambles (step 1004), and performs one or more actions to mitigate the interference (step 1006). These one or more actions may include, e.g., reconfiguring the NPRACH resources in the interfering or victim cells.

[0087] Example. A basic NPRACH frequency resource spans 45 kilohertz (kHz) and consists of 12 subcarriers spaced 3.75 kHz apart. A UE randomly chooses any of the 12 subcarriers to transmit its preamble. Each preamble corresponds to a different frequency hopping pattern consisting of deterministic hops within a preamble repetition unit and pseudo-random hops (determined by the PCID) between successive preamble repetition units.

• Without repetitions, there are 12 unique frequency hopping patterns (i.e., 12 unique NPRACH preambles) in a cell. These preambles are identical for all cells.

• With 2 repetitions, there are 12 unique NPRACH preambles in a cell. However, the frequency hopping patterns are typically different across cells due to the (PCID- dependent) pseudorandom hop between repetitions. There could be up to 144 non^¬ identical frequency hopping patterns in total. Note that only 12 of those patterns are valid hopping patterns for a given cell.

• The total number of possible frequency hopping patterns increases with the number of NPRACH repetitions.

Thus, an eNB receiver can process the received signal to detect which of the 144 patterns are present. In one embodiment, the network uses this information to identify the potentially interfering cells. The network uses this information to reduce inter-cell interference for example by reconfiguring the NPRACH resources in the interfering or victim cells.

[0088] In a fourth embodiment, the base station 602 performs FAR-triggered NPRACH interference detection. More specifically, in some embodiments, the base station 602 uses a conventional NPRACH detector (e.g., an NPRACH detector as described above in the background) when the NPRACH FAR is low (e.g., below a threshold). However, a high NPRACH FAR triggers the NPRACH detector to employ an advanced NPRACH detecting procedure, e.g., one that uses NPRACH interference detection and mitigation in accordance with any of the embodiments described above. An NPRRACH false alarm will result in the base station 602 sending a Random Access Response (RAR) message to the UE 612 and expecting the UE 612 to reply with an uplink message known as Message3. Thus, an NPRACH FAR can be estimated by tracking the percentage of RAR without a corresponding correctly received Message3.

[0089] With this embodiment, the base station 602 can conserve its computational budget when the interference level is low enough to not to cause degradation in NPRACH FAR. The base station 602 computational budget often has strong implications on capacity. Therefore, it is advantageous to conserve such computational resources when the operating conditions do not call for an advanced, but more complex, NPRACH detecting procedure.

[0090] Figure 11 is a flow chart that illustrates the operation of the base station 602 to perform FAR-triggered NPRACFI interference detection in accordance with the fourth embodiment. Optional steps are represented with dashed lines. Note that steps 1100 and 1102 of Figure 11 correspond to step 700 of Figure 7, and step 1104 of Figure 11 corresponds to steps 702A and 702B of Figure 7. As illustrated, the base station 602 determines an NPRACFI FAR (e.g., an actual FAR or an estimated FAR) (step 1100). The base station 602 compares the determined FAR to a predefined or configured FAR threshold (step 1102). If the determined FAR exceeds the FAR threshold (step 1100, YES), the base station 602 performs NPRACFI interference detection and mitigation, e.g., in accordance with any of the embodiments described above (step 1104). Otherwise, the base station 602 refrains from performing NPRACFI interference detection and mitigation (step 1106).

[0091] Figure 12 is a schematic block diagram of a radio access node 1200 according to some embodiments of the present disclosure. The radio access node 1200 may be, for example, a base station 602 or 606. As illustrated, the radio access node 1200 includes a control system 1202 that includes one or more processors 1204 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 1206, and a network interface 1208. The one or more processors 1204 are also referred to herein as processing circuitry. In addition, the radio access node 1200 includes one or more radio units 1210 that each includes one or more transmitters 1212 and one or more receivers 1214 coupled to one or more antennas 1216. The radio units 1210 may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) 1210 is external to the control system 1202 and connected to the control system 1202 via, e.g., a wired connection (e.g., an optical cable). Flowever, in some other embodiments, the radio unit(s) 1210 and potentially the antenna(s) 1216 are integrated together with the control system 1202. The one or more processors 1204 operate to provide one or more functions of a radio access node 1200 as described herein (e.g., one or more functions of the base station 602 such as, e.g.,

NPRACFI interference detection and mitigation as described above, e.g., with respect to Figures 7 through 11). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 1206 and executed by the one or more processors 1204.

[0092] Figure 13 is a schematic block diagram that illustrates a virtualized embodiment of the radio access node 1200 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures. As used herein, a "virtualized" radio access node is an implementation of the radio access node 1200 in which at least a portion of the functionality of the radio access node 1200 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the radio access node 1200 includes the control system 1202 that includes the one or more processors 1204 (e.g., CPUs, ASICs, FPGAs, and/or the like), the memory 1206, and the network interface 1208 and the one or more radio units 1210 that each includes the one or more transmitters 1212 and the one or more receivers 1214 coupled to the one or more antennas 1216, as described above. The control system 1202 is connected to the radio unit(s) 1210 via, for example, an optical cable or the like. The control system 1202 is connected to one or more processing nodes 1300 coupled to or included as part of a network(s) 1302 via the network interface 1208. Each processing node 1300 includes one or more processors 1304 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1306, and a network interface 1308.

[0093] In this example, functions 1310 of the radio access node 1200 described herein (e.g., one or more functions of the base station 602 such as, e.g., NPRACFI interference detection and mitigation as described above, e.g., with respect to Figures 7 through 11) are implemented at the one or more processing nodes 1300 or distributed across the control system 1202 and the one or more processing nodes 1300 in any desired manner.

In some particular embodiments, some or all of the functions 1310 of the radio access node 1200 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 1300. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 1300 and the control system 1202 is used in order to carry out at least some of the desired functions 1310. Notably, in some embodiments, the control system 1202 may not be included, in which case the radio unit(s) 1210 communicate directly with the processing node(s) 1300 via an appropriate network interface(s).

[0094] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of radio access node 1200 or a node (e.g., a processing node 1300) implementing one or more of the functions 1310 of the radio access node 1200 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0095] Figure 14 is a schematic block diagram of the radio access node 1200 according to some other embodiments of the present disclosure. The radio access node 1200 includes one or more modules 1400, each of which is implemented in software. The module(s) 1400 provide the functionality of the radio access node 1200 described herein (e.g., one or more functions of the base station 602 such as, e.g., NPRACH interference detection and mitigation as described above, e.g., with respect to Figures 7 through 11). This discussion is equally applicable to the processing node 1300 of Figure 13 where the modules 1400 may be implemented at one of the processing nodes 1300 or distributed across multiple processing nodes 1300 and/or distributed across the processing node(s) 1300 and the control system 1202.

[0096] Figure 15 is a schematic block diagram of a UE 1500 according to some embodiments of the present disclosure. As illustrated, the UE 1500 includes one or more processors 1502 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1504, and one or more transceivers 1506 each including one or more transmitters 1508 and one or more receivers 1510 coupled to one or more antennas 1512. The transceiver(s) 1506 includes radio-front end circuitry connected to the antenna(s) 1512 that is configured to condition signals communicated between the antenna(s) 1512 and the processor(s) 1502, as will be appreciated by on of ordinary skill in the art. The processors 1502 are also referred to herein as processing circuitry. The transceivers 1506 are also referred to herein as radio circuitry. In some embodiments, the functionality of the UE 1500 described above may be fully or partially implemented in software that is, e.g., stored in the memory 1504 and executed by the processor(s) 1502. Note that the UE 1500 may include additional components not illustrated in Figure 15 such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the UE 1500 and/or allowing output of information from the UE 1500), a power supply (e.g., a battery and associated power circuitry), etc.

[0097] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the UE 1500 according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0098] Figure 16 is a schematic block diagram of the UE 1500 according to some other embodiments of the present disclosure. The UE 1500 includes one or more modules 1600, each of which is implemented in software. The module(s) 1600 provide the functionality of the UE 1500 described herein.

[0099] With reference to Figure 17, in accordance with an embodiment, a communication system includes a telecommunication network 1700, such as a 3GPP-type cellular network, which comprises an access network 1702, such as a RAN, and a core network 1704. The access network 1702 comprises a plurality of base stations 1706A, 1706B, 1706C, such as Node Bs, eNBs, gNBs, or other types of wireless Access Points (APs), each defining a corresponding coverage area 1708A, 1708B, 1708C. Each base station 1706A, 1706B, 1706C is connectable to the core network 1704 over a wired or wireless connection 1710. A first UE 1712 located in coverage area 1708C is configured to wirelessly connect to, or be paged by, the corresponding base station 1706C. A second UE 1714 in coverage area 1708A is wirelessly connectable to the corresponding base station 1706A. While a plurality of UEs 1712, 1714 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 1706.

[0100] The telecommunication network 1700 is itself connected to a host computer 1716, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server, or as processing resources in a server farm. The host computer 1716 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections 1718 and 1720 between the telecommunication network 1700 and the host computer 1716 may extend directly from the core network 1704 to the host computer 1716 or may go via an optional intermediate network 1722. The intermediate network 1722 may be one of, or a combination of more than one of, a public, private, or hosted network; the intermediate network 1722, if any, may be a backbone network or the Internet; in particular, the intermediate network 1722 may comprise two or more sub-networks (not shown).

[0101] The communication system of Figure 17 as a whole enables connectivity between the connected UEs 1712, 1714 and the host computer 1716. The connectivity may be described as an Over-the-Top (OTT) connection 1724. The host computer 1716 and the connected UEs 1712, 1714 are configured to communicate data and/or signaling via the OTT connection 1724, using the access network 1702, the core network 1704, any intermediate network 1722, and possible further infrastructure (not shown) as intermediaries. The OTT connection 1724 may be transparent in the sense that the participating communication devices through which the OTT connection 1724 passes are unaware of routing of uplink and downlink communications. For example, the base station 1706 may not or need not be informed about the past routing of an incoming downlink communication with data originating from the host computer 1716 to be forwarded (e.g., handed over) to a connected UE 1712. Similarly, the base station 1706 need not be aware of the future routing of an outgoing uplink communication originating from the UE 1712 towards the host computer 1716.

[0102] Example implementations, in accordance with an embodiment, of the UE, base station, and host computer discussed in the preceding paragraphs will now be described with reference to Figure 18. In a communication system 1800, a host computer 1802 comprises hardware 1804 including a communication interface 1806 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 1800. The host computer 1802 further comprises processing circuitry 1808, which may have storage and/or processing capabilities. In particular, the processing circuitry 1808 may comprise one or more programmable processors, ASICs, FPGAs, or combinations of these (not shown) adapted to execute instructions. The host computer 1802 further comprises software 1810, which is stored in or accessible by the host computer 1802 and executable by the processing circuitry 1808. The software 1810 includes a host application 1812. The host application 1812 may be operable to provide a service to a remote user, such as a UE 1814 connecting via an OTT connection 1816 terminating at the UE 1814 and the host computer 1802. In providing the service to the remote user, the host application 1812 may provide user data which is transmitted using the OTT connection 1816.

[0103] The communication system 1800 further includes a base station 1818 provided in a telecommunication system and comprising hardware 1820 enabling it to communicate with the host computer 1802 and with the UE 1814. The hardware 1820 may include a communication interface 1822 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 1800, as well as a radio interface 1824 for setting up and maintaining at least a wireless connection 1826 with the UE 1814 located in a coverage area (not shown in Figure 18) served by the base station 1818. The communication interface 1822 may be configured to facilitate a connection 1828 to the host computer 1802. The connection 1828 may be direct or it may pass through a core network (not shown in Figure 18) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 1820 of the base station 1818 further includes processing circuitry 1830, which may comprise one or more programmable processors, ASICs, FPGAs, or combinations of these (not shown) adapted to execute instructions. The base station 1818 further has software 1832 stored internally or accessible via an external connection.

[0104] The communication system 1800 further includes the UE 1814 already referred to. The UE's 1814 hardware 1834 may include a radio interface 1836 configured to set up and maintain a wireless connection 1826 with a base station serving a coverage area in which the UE 1814 is currently located. The hardware 1834 of the UE 1814 further includes processing circuitry 1838, which may comprise one or more programmable processors, ASICs, FPGAs, or combinations of these (not shown) adapted to execute instructions. The UE 1814 further comprises software 1840, which is stored in or accessible by the UE 1814 and executable by the processing circuitry 1838. The software 1840 includes a client application 1842. The client application 1842 may be operable to provide a service to a human or non-human user via the UE 1814, with the support of the host computer 1802. In the host computer 1802, the executing host application 1812 may communicate with the executing client application 1842 via the OTT connection 1816 terminating at the UE 1814 and the host computer 1802. In providing the service to the user, the client application 1842 may receive request data from the host application 1812 and provide user data in response to the request data. The OTT connection 1816 may transfer both the request data and the user data. The client application 1842 may interact with the user to generate the user data that it provides.

[0105] It is noted that the host computer 1802, the base station 1818, and the UE 1814 illustrated in Figure 18 may be similar or identical to the host computer 1716, one of the base stations 1706A, 1706B, 1706C, and one of the UEs 1712, 1714 of Figure 17, respectively. This is to say, the inner workings of these entities may be as shown in Figure 18 and independently, the surrounding network topology may be that of Figure 17.

[0106] In Figure 18, the OTT connection 1816 has been drawn abstractly to illustrate the communication between the host computer 1802 and the UE 1814 via the base station 1818 without explicit reference to any intermediary devices and the precise routing of messages via these devices. The network infrastructure may determine the routing, which may be configured to hide from the UE 1814 or from the service provider operating the host computer 1802, or both. While the OTT connection 1816 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

[0107] The wireless connection 1826 between the UE 1814 and the base station 1818 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 1814 using the OTT connection 1816, in which the wireless connection 1826 forms the last segment.

[0108] A measurement procedure may be provided for the purpose of monitoring data rate, latency, and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1816 between the host computer 1802 and the UE 1814, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 1816 may be implemented in the software 1810 and the hardware 1804 of the host computer 1802 or in the software 1840 and the hardware 1834 of the UE 1814, or both. In some embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 1816 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which the software 1810, 1840 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1816 may include message format, retransmission settings, preferred routing, etc.; the reconfiguring need not affect the base station 1818, and it may be unknown or imperceptible to the base station 1818. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer's 1802 measurements of throughput, propagation times, latency, and the like. The measurements may be implemented in that the software 1810 and 1840 causes messages to be transmitted, in particular empty or 'dummy' messages, using the OTT connection 1816 while it monitors propagation times, errors, etc.

[0109] Figure 19 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station, and a UE which may be those described with reference to Figures 17 and 18. For simplicity of the present disclosure, only drawing references to Figure 19 will be included in this section. In step 1900, the host computer provides user data. In sub-step 1902 (which may be optional) of step 1900, the host computer provides the user data by executing a host application. In step 1904, the host computer initiates a transmission carrying the user data to the UE. In step 1906 (which may be optional), the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1908 (which may also be optional), the UE executes a client application associated with the host application executed by the host computer.

[0110] Figure 20 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station, and a UE which may be those described with reference to Figures 17 and 18. For simplicity of the present disclosure, only drawing references to Figure 20 will be included in this section. In step 2000 of the method, the host computer provides user data. In an optional sub-step (not shown) the host computer provides the user data by executing a host application. In step 2002, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In step 2004 (which may be optional), the UE receives the user data carried in the transmission.

[0111] Figure 21 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station, and a UE which may be those described with reference to Figures 17 and 18. For simplicity of the present disclosure, only drawing references to Figure 21 will be included in this section. In step 2100 (which may be optional), the UE receives input data provided by the host computer. Additionally or alternatively, in step 2102, the UE provides user data. In sub-step 2104 (which may be optional) of step 2100, the UE provides the user data by executing a client application. In sub-step 2106 (which may be optional) of step 2102, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in sub-step 2108 (which may be optional), transmission of the user data to the host computer. In step 2110 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

[0112] Figure 22 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station, and a UE which may be those described with reference to Figures 17 and 18. For simplicity of the present disclosure, only drawing references to Figure 22 will be included in this section. In step 2200 (which may be optional), in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In step 2202 (which may be optional), the base station initiates transmission of the received user data to the host computer. In step 2204 (which may be optional), the host computer receives the user data carried in the transmission initiated by the base station.

[0113] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure. [0114] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). [0115] At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

• ps Microsecond

• 3GPP Third Generation Partnership Project

• 5G Fifth Generation

• AMF Access and Mobility Function

• AP Access Point

• ASIC Application Specific Integrated Circuit

• AUSF Authentication Server Function

• CE Coverage Enhancement

• CEO Coverage Enhancement Level 0

• CE1 Coverage Enhancement Level 1

• CE2 Coverage Enhancement Level 2

• CP Cyclic Prefix

• CPU Central Processing Unit

• dB Decibel

• dBm Decibel-Milliwatt

• DSP Digital Signal Processor

• eNB Enhanced or Evolved Node B

• FAR False Alarm Rate

• FDD Frequency Division Duplexing

• FPGA Field Programmable Gate Array

• gNB New Radio Base Station

• HSS Home Subscriber Server

• ID Identifier

• kHz Kilohertz

• LTE Long Term Evolution

• MDR Misdetection Rate

• MME Mobility Management Entity ms Millisecond

MTC Machine Type Communication

NB-IoT Narrowband Internet of Things

NEF Network Exposure Function

NF Network Function

NPRACH Narrowband Physical Random Access Channel

NR New Radio

NRF Network Function Repository Function

NSSF Network Slice Selection Function

OTT Over-the-Top

PCF Policy Control Function

PCID Physical Cell Identifier

P-GW Packet Data Network Gateway

RA Random Access

RAM Random Access Memory

RAN Radio Access Network

RAR Random Access Response

ROM Read Only Memory

RRH Remote Radio Head

RSRP Reference Signal Received Power s Second

SCEF Service Capability Exposure Function

SMF Session Management Function

TA Time of Arrival

TS Technical Specification

UDM Unified Data Management

UE User Equipment

UPF User Plane Function

[0116] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

Claims What is claimed is:

1. A method performed by a base station in a cellular communications system, comprising: detecting (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) interference on at least a portion of a random access resource for a respective cell based on either or both of: (a) one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in at least a portion of the random access resource and (b) frequency hopping patterns used by one or more other cells for single-tone frequency hopping random access preambles; and performing (702B; 804; 904A; 904B; 1004-1006; 1104) one or more actions to mitigate the detected interference.

2. The method of claim 1 wherein detecting (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) interference on the at least a portion of the random access resource for the respective cell comprises detecting (702A; 800-802; 1104) interference on the at least a portion of the random access resource for the respective cell based the one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in at least a portion of the random access resource, the one or more expected signal characteristics comprising an expected energy pattern.

3. The method of claim 2 wherein detecting (702A; 800-802; 1104) interference on at least a portion of the random access resource for the respective cell based on the one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in the random access resource comprises: determining (800) received energy for a received signal on one or more resources that correspond to a portion of a particular random access preamble for the respective cell; and determining (802) that the received energy is greater than a threshold energy level.

4. The method of claim 3 wherein the portion of the particular random access preamble for the respective cell is a symbol group of the particular random access preamble for the respective cell.

5. The method of claim 3 wherein the portion of the particular random access preamble for the respective cell is: a symbol within a symbol group of the particular random access preamble for the respective cell; two or more symbols within a symbol group of the particular random access preamble for the respective cell; two or more symbol groups of the particular random access preamble for the respective cell; a repetition unit of the particular random access preamble for the respective cell; or two or more repetition units of the particular random access preamble for the respective cell.

6. The method of any one of claims 3 to 5 wherein the threshold energy level is the sum of an energy metric and a rejection threshold, wherein the energy metric corresponds to an expected energy level and the rejection threshold is a configurable parameter.

7. The method of claim 6 wherein the energy metric is an average received energy across resources within the random access resource that correspond to a plurality of portions of the particular random access preamble for the respective cell.

8. The method of claim 7 wherein each portion of the plurality of portions of the particular random access preamble for the respective cell is: a symbol within a symbol group of the particular random access preamble for the respective cell; two or more symbols within a symbol group of the particular random access preamble for the respective cell; a symbol group of the particular random access preamble for the respective cell; two or more symbol groups of the particular random access preamble for the respective cell; a repetition unit of the particular random access preamble for the respective cell; or two or more repetition units of the particular random access preamble for the respective cell.

9. The method of claim 6 wherein the energy metric is a weighted or running average of received energy per random access preamble portion for at least a subset of previously received single-tone frequency hopping random access preambles received within a predefined or configurable time window.

10. The method of claim 9 wherein the random access preamble portion is: a symbol within a symbol group; two or more symbols within a symbol group; a symbol group; two or more symbol groups; a preamble repetition unit; or two or more preamble repetition units.

11. The method of claim 6 wherein the energy metric is a function of a coverage enhancement level of the random access resource.

12. The method of any one of claims 3 to 11 wherein performing (702B; 804; 904A; 904B; 1004-1006; 1104) the one or more actions to mitigate the detected interference comprises discarding (804) at least the portion of the particular random access preamble for the respective cell for which the received energy is greater than the threshold energy level.

13. The method of claim 12 wherein discarding (804) at least the portion of the particular random access preamble for the respective cell comprises discarding (804) at least the portion of the particular random access preamble for the respective cell from a random access preamble detection metric calculation for time of arrival estimation.

14. The method of claim 1 wherein detecting (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) the interference on the at least a portion of the random access resource for the respective cell comprises detecting (702A; 900A-902A; 1104) interference on at least a portion of the random access resource for the respective cell based on the one or more expected signal characteristics of a random access preamble received in at least a portion of the random access resource, the one or more expected signal characteristics comprising one or more expected covariance or correlation properties.

15. The method of claim 14 wherein detecting (702A; 900A-902A; 900B-902B; 1104) interference on the random access resource for the respective cell based on the one or more expected signal characteristics of a random access preamble received in the random access resource comprises: determining (900A; 900B) a covariance or correlation metric for a received signal on a set of resources within the random access resource that correspond to a particular random access preamble for the respective cell; and determining (902A) that the determined covariance or correlation metric differs from an expected covariance or correlation metric.

16. The method of claim 15 wherein determining (900A) the covariance or correlation metric comprises determining a covariance or correlation of two or more samples of the received signal that are received via two or more respective antennas of the base station.

17. The method of claim 15 wherein determining (900A) the covariance or correlation metric comprises determining a covariance or correlation of two or more portions of the received signal that are received via one or more antennas of the base station during two or more respective time windows.

18. The method of claim 1 wherein detecting (702A; 800-802; 900A-902A;

900B-902B; 1002; 1104) interference on at least a portion of the random access resource for the respective cell comprises detecting (702A; 1002; 1104) random access preambles from the one or more other cells based on the frequency hopping patterns used by the one or more other cells.

19. The method of claim 18 wherein performing (702B; 804; 904A; 904B; 1004-1006; 1104) the one or more actions to mitigate the detected interference comprises: identifying (1004) the one or more other cells for which random access preambles are detected; and performing (1006) one or more actions to mitigate the interference from the one or more identified cells.

20. The method of claim 18 or 19 further comprising: receiving (1000), from a network node, one or more cell identities of one or more respective neighbor cells of the respective cell; wherein detecting (702A; 1002; 1104) random access preambles from the one or more other cells based on the frequency hopping patterns used by the one or more other cells comprises attempting to detect random access preambles of the one or more respective neighbor cells.

21. The method of any one of claims 1 to 20 further comprising: determining (1100) a false alarm rate for random access preamble detection; and determining (1102) that the false alarm rate is greater than a predefined or preconfigured threshold; wherein detecting (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) interference on at least a portion of the random access resource for the respective cell comprises detecting (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) interference on at least a portion of the random access resource for the respective cell upon determining (1102) that the false alarm rate is greater than the predefined or preconfigured threshold.

22. A base station for a cellular communications system, the base station adapted to: detect (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) interference on at least a portion of a random access resource for a respective cell based on either or both of: (a) one or more expected signal characteristics of a single-tone frequency hopping random access preamble received in at least a portion of the random access resource and (b) frequency hopping patterns used by one or more other cells for single-tone frequency hopping random access preambles; and perform (702B; 804; 904A; 904B; 1004-1006; 1104) one or more actions to mitigate the detected interference.

23. The base station of claim 22 wherein the base station is further adapted to perform the method of any one of claims 2 to 21.

24. The base station of claim 22 or 23 comprising: processing circuitry configured to cause the base station to: detect (702A; 800-802; 900A-902A; 900B-902B; 1002; 1104) interference on the random access resource for the respective cell; and perform (702B; 804; 904A; 904B; 1004-1006; 1104) the one or more actions to mitigate the detected interference.