WO2021089109A1

WO2021089109A1 - Automatic gain control for advanced antenna systems

Info

Publication number: WO2021089109A1
Application number: PCT/EP2019/080100
Authority: WO
Inventors: Peter Jakobsson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2019-11-04
Filing date: 2019-11-04
Publication date: 2021-05-14

Abstract

A method is disclosed of operating automatic gain control (AGC) for an advanced antenna system (AAS) receiver. The AAS receiver comprises two or more receiver paths, and each receiver path comprises a respective AGC controller. The method comprises causing, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval. The selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period. Corresponding apparatus, AAS receiver, communication device, and computer program product are also disclosed.

Description

AUTOMATIC GAIN CONTROL FOR ADVANCED ANTENNA SYSTEMS

TECHNICAL FIELD

The present disclosure relates generally to the field of wireless communication. More particularly, it relates to automatic gain control (AGC) for an advanced antenna system (AAS) receiver.

BACKGROUND

Advanced antenna system (AAS) typically apply a multi-antenna arrangement having a plurality of antennas (or antenna elements). As is well known, AAS may be used for improving system capacity and/or coverage, e.g., by using beam forming communication.

Typical AAS receiver implementations employ a plurality of receiver paths (e.g., one per antenna or antenna element). Also typically, each receiver path applies a respective automatic gain control (AGC). As is well known, AGC may generally be used to scale (e.g., using an amplifier) the received signal such that its amplitude falls within a suitable range for receiver processing.

There is a need for approaches to AGC that are particularly applicable for AAS receivers.

US 8,090,061 B1 describes AGC control for MIMO systems, wherein an AGC control unit coordinates AGC gain changes between individual receive chains. This approach may, in some scenarios, be insufficient for enabling a target performance.

Hence, there is a need for additional or alternative approaches to AGC for AAS receivers. Preferably, such approaches enables improvements in system performance (e.g., increased throughput, increased capacity, increased coverage, reduced latency, etc.).

SUMMARY

It should be emphasized that the term "comprises/comprising" (replaceable by "includes/including") when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It is an object of some embodiments to solve or mitigate, alleviate, or eliminate at least some of the above or other disadvantages.

A first aspect is a method of operating automatic gain control (AGC) for an advanced antenna system (AAS) receiver, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller.

The method comprises causing, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval.

The selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period.

In some embodiments, the AAS receiver is an orthogonal frequency division multiplex (OFDM) receiver and the time period is a cyclic prefix (CP) time interval.

In some embodiments, the one or more second receiver paths comprises all receiver paths - other than the first receiver path - of the AAS receiver, or only some receiver paths - other than the first receiver path - of the AAS receiver.

In some embodiments, the respective AGC controllers of the second receiver paths are caused to apply the corresponding gain reduction during a same selected time interval.

In some embodiments, a receiver path, whose respective AGC controller autonomously performs a gain reduction before the selected time interval, is excluded from the one or more second receiver paths.

In some embodiments, the respective AGC controller of one or more selected receiver paths is configured with an AGC power threshold value for gain reduction which is lower than a default AGC power threshold value for gain reduction. A second aspect is a method of operating automatic gain control (AGC) for an advanced antenna system (AAS) receiver configured to receive an orthogonal frequency division multiplex (OFDM) signal, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller.

The method comprises causing, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval, wherein the selected time interval is within a cyclic prefix (CP) time interval of the OFDM signal.

A third aspect is a computer program product comprising a non-transitory computer readable medium, having thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit and configured to cause execution of the method according to any of the first and second aspects when the computer program is run by the data processing unit.

A fourth aspect is an apparatus for operating automatic gain control (AGC) of an advanced antenna system (AAS) receiver, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller.

The apparatus comprises controlling circuitry configured to, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, cause the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval.

A fifth aspect is an apparatus for operating automatic gain control (AGC) for an advanced antenna system (AAS) receiver configured to receive an orthogonal frequency division multiplex (OFDM) signal, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller.

The apparatus comprises controlling circuitry configured to, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, cause the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval, wherein the selected time interval is within a cyclic prefix (CP) time interval of the OFDM signal.

A sixth aspect is an advanced antenna system (AAS) receiver comprising the apparatus of any of the fourth and fifth aspects and two or more receiver paths, wherein each receiver path comprises a respective AGC controller, and wherein each receiver path is connectable to one or more respective antenna elements of a multi-antenna arrangement.

In some embodiments, the AAS receiver further comprises the multi-antenna arrangement.

A seventh aspect is a communication device comprising the apparatus of any of the fourth and fifth aspects and/or the AAS receiver of the sixth aspect.

In some embodiments, the communication device is a radio access network node (such as a base station) or a radio communication terminal (such as a user equipment).

In some embodiments, any of the above aspects may additionally have features identical with or corresponding to any of the various features as explained above for any of the other aspects.

An advantage of some embodiments is that approaches to AGC are provided for AAS receivers.

Another advantage of some embodiments is that system performance may be improved (e.g., increased throughput, increased capacity, increased coverage, reduced latency, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

Figure 1 is a flowchart illustrating example method steps according to some embodiments;

Figure 2 is a schematic drawing illustrating example AGC operation according to some embodiments; Figure 3 is a schematic block diagram illustrating an example arrangement according to some embodiments;

Figure 4 is a schematic block diagram illustrating an example arrangement according to some embodiments;

Figure 5 is a flowchart illustrating example method steps according to some embodiments; and

Figure 6 is a schematic drawing illustrating an example computer readable medium according to some embodiments.

DETAILED DESCRIPTION

As already mentioned above, it should be emphasized that the term "comprises/comprising" (replaceable by "includes/including") when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure will be described and exemplified more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the embodiments set forth herein.

In the following, embodiments will be described where approaches to automatic gain control (AGC) are provided that are particularly applicable for advanced antenna system (AAS) receivers. According to some embodiments, the approaches to AGC applies coordination of gain reduction among two or more of the receiver paths (e.g., first and second receiver paths) of an AAS receiver. Furthermore, the approaches of some embodiment coordinate the gain reduction to occur where it interferes as little as possible with ongoing information reception.

Figure 1 illustrates an example method 100 according to some embodiments. The method 100 is a method of operating AGC for an AAS receiver, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller. Typically, each receiver path is connectable (e.g., connected) to one or more respective antenna (or antenna element) of a multi-antenna arrangement.

The method 500 may, for example, be performed by the controller 310 of Figure 3 or the AGC controllers 431, 432, 433 of Figure 4.

As illustrated by step 150, the method comprises causing, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path (Y-path out of step 120), the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval.

Generally, the first receiver path is one of the two or more receiver paths of the AAS receiver. For example, the first receiver path is a receiver path that detects a need for gain reduction earlier that the second receiver paths of the AAS receiver.

Also generally, the one or more second receiver paths are one or more of the two or more receiver paths - other than the first receiver path - of the AAS receiver. In some embodiments, the one or more second receiver paths comprises all receiver paths - other than the first receiver path - of the AAS receiver. In some embodiments, the one or more second receiver paths comprises only some receiver paths - other than the first receiver path

- of the AAS receiver.

The latter case may, for example, be particularly suitable when the receiver paths are grouped into two or more groups, in which case the second receiver paths may comprise - or consist of

- some or all receiver paths which are in the same group as the first receiver path.

For example, receiver path grouping may be defined as each group comprising - or consisting of- receiver paths implemented on a same hardware chip (e.g., application specific integrated circuit - ASIC, system on chip - SoC, or system in package - SiP). Alternatively or additionally, receiver path grouping may be defined as each group comprising - or consisting of - receiver paths connectable (e.g., connected) to a same group of antennas or antenna elements of the multi-antenna arrangement. For example, a group of antennas or antenna elements may be defined as each group comprising - or consisting of - antennas or antenna elements of a same antenna panel, or of a same antenna panel partition. A possible advantage with applying gain reduction coordination within, but not between, receiver path groups is that performance improvement due to gain reduction coordination may be provided at a low cost (e.g., in terms of power consumption and/or signaling overhead); e.g., since it typically requires less power and/or signaling to coordinate within a hardware chip than between hardware chips.

A possible advantage with applying gain reduction coordination within, but not between, receiver path groups is that gain reduction coordination is only used when it has the potential to provide performance improvements; e.g., since gain reduction coordination between antenna panels or antenna panel partitions typically does not improve the performance when different antenna panels or antenna panel partitions are used to receive signals from different transmitters.

The selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period. Generally, when a "time period" is referred to herein it is meant to refer to the time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period if nothing else is explicitly stated.

Typically, the respective AGC controllers of the second receiver paths are caused to apply the corresponding gain reduction during a same selected time interval.

The selected time interval may have the same size as the time period, or may be of shorter duration than the time period. For example, the selected time interval may comprise the mid time of the time period; e.g., the selected time interval may be centered within the time period, or may be shifted to be biased towards the early parts of the time period.

For example, when the AAS receiver is configured to receive an orthogonal frequency division multiplex (OFDM) signal, the time period may be the cyclic prefix (CP) time interval.

Another example of the time period includes a time period wherein there is no signal for reception (e.g., a guard interval, a non-scheduled interval, etc.).

In some embodiments, the time period may be defined as a time period which does not comprise any information that is necessary for the AAS receiver to be able to process the received signal appropriately. Put differently, the time period may be defined as a time period which is destitute of data for information reception.

Typically, each (or some) of the receiver paths are configured to perform autonomous gain reduction in addition to the coordinated gain reduction. Autonomous gain reduction may be seen as a process with is local to the particular receiver path; i.e., AGC based on (only) the received signal of the particular receiver path and causing gain reduction for (only) the particular receiver path.

When a receiver path performs autonomous gain reduction before the selected time interval (and after the first receiver path indicating gain reduction), it may be excluded from the one or more second receiver paths, or may be caused to apply a smaller gain reduction than the other ones of the second receiver paths. This approach has the possible benefit of avoiding excessive gain reduction.

For example, a receiver path which performs an autonomous gain reduction which is larger than, or equal to, the gain reduction indicated by the first receiver path may be excluded from the one or more second receiver paths, and a receiver path which performs an autonomous gain reduction which is smaller than the gain reduction indicated by the first receiver path may be caused to apply a gain reduction which equals the gain reduction indicated by the first receiver path minus the performed autonomous gain reduction.

In some embodiments, the respective AGC controller of one or more selected receiver paths is configured with an AGC power threshold value for gain reduction which is lower than a default AGC power threshold value for gain reduction (typically applied by non-selected receiver paths).

Such a selected receiver path may be referred to as "pilot" path and is often the first receiver path due to the lower AGC power threshold value. Having pilot path(s) may typically increase the probability that all second receiver paths get to perform their needed gain reduction within the time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period (since they are less likely to perform an autonomous gain reduction before the time period during which gain reduction is less harmful). The one or more selected receiver paths may be a single receiver path (e.g., associated with an antenna or antenna element centrally located within the multi-antenna arrangement or within the group of antennas or antenna elements), some receiver paths (e.g., associated with respective antennas or antenna elements uniformly distributed within the multi-antenna arrangement or within the group of antennas or antenna elements), or all receiver paths.

The AGC power threshold value of the selected receiver paths may, for example, be defined in terms of a power offset from the default AGC power threshold value. The AGC power threshold value of the selected receiver paths may be static, or may be dynamically adjustable (e.g., based on a target probability of gain reduction with the time period, antenna correlation, physical communication scenario, communication channel properties, etc.). A static threshold value may be set by factory calibration according to some embodiments. A dynamically adjustable threshold value may be controlled based on machine learning according to some embodiments.

Thus, one or more selected paths may be configured with a lowered AGC threshold value, as illustrated in Figure 1 by optional step 110.

Step 120 illustrates monitoring for gain reduction indication for the first path. As mentioned before, the first receiver path may be the receiver path that earliest detects a need for gain reduction. This condition may, for example, be applied within a received signal entity (e.g., within a duration of time between two consecutive time periods).

In some embodiments, the first receiver path is statically defined as a particular receiver path (e.g., when the particular receiver path has an AGC power threshold value for gain reduction which is substantially lower than the default AGC power threshold value for gain reduction).

In some embodiments, the first receiver path is dynamically variable (e.g., depending on which receiver path first detects a need for gain reduction within a received signal entity).

The monitoring of step 120 continues when there is no gain reduction indication (N-path out of step 120). When a gain reduction indication is detected - for a first receiver path - (Y-path out of step 120), the method comprises causing the respective AGC controller of the second receiver path(s) to apply a corresponding gain reduction during a selected time interval, as elaborated on above and illustrated by step 150. Typically, step 150 comprises sending a control signal to the respective AGC controller of the second receiver path(s) to cause the gain reduction. The signal may, for example, be indicative of the size of the gain reduction and/or of the selected time interval.

Also typically, the first receiver path may perform the gain reduction as soon as it detects a need for it (this may be compared to an autonomous gain reduction and typically takes place before the selected time interval). In some embodiments, the first receiver path may perform the gain reduction together with the second receiver paths during the selected time interval.

When the gain reduction indication is detected (Y-path out of step 120) and before performing step 150, the method may further comprise selecting the time interval as illustrated by optional step 130 and/or determining the one or more second receiver path(s) as illustrated by optional step 140.

For example, step 130 may comprise acquiring information regarding an upcoming non- scheduled time interval.

Step 140 may, for example, comprise determining the second receiver path(s) based on any of the approaches elaborated on above. In some embodiments, step 140 comprises excluding receiver path(s), whose respective AGC controller autonomously performs a gain reduction before the selected time interval, as illustrated by optional sub-step 145.

Figure 2 schematically illustrates example AGC operation according to some embodiments. The time line of Figure 2 comprises OFDM symbols 201, 202 and corresponding CP 211, 212.

Part (a) illustrates the analog gain 220 for the first receiver path and part (b) illustrates the total gain 230 for the first receiver path. When the first receiver path detects a need for gain reduction, the gain reduction is performed directly as illustrated at 225.

The reduction 225 in the analog gain causes disturbance (e.g., a transient) in the total gain as is illustrated at 235. Since this disturbance is in the time interval for the OFDM symbol 201 during which a fast Fourier transform (FFT) 271 is applied by the receiver, the disturbance negatively affects the reception of this symbol.

Part (c) illustrates the analog gain 240 for the one of the second receiver path(s) and part (d) illustrates the total gain 250 for this second receiver path. When the first receiver path detects a need for gain reduction, the second receiver path is caused to apply a corresponding gain reduction as illustrated at 245. The gain reduction of the second receiver path is delayed in relation to the detection of the need for gain reduction by the first receiver path, as illustrated by 200.

The reduction 245 in the analog gain causes disturbance (e.g., a transient) in the total gain as is illustrated at 255. Due to the delay 200, the disturbance 255 due to the gain reduction 245 of the second receiver path is within a time period (here, a CP) 212 during which gain reduction is less harmful to information reception than gain reduction applied during another time period (e.g., 201, 202). Thus, this disturbance is not in a time interval of an OFDM symbol during which a fast Fourier transform (FFT) 281, 282 is applied by the receiver, and the disturbance does not affect the reception as negatively as it would if it occurred during another time period (e.g., 201, 202).

Figure 3 schematically illustrates an example arrangement (e.g., an apparatus) according to some embodiments. The arrangement is for AGC operation in an AAS receiver 300. The AAS receiver 300 may be comprised in a communication device (e.g., a radio access network node, such as a base station, or a radio communication terminal, such as a user equipment, UE).

The arrangement of Figure 3 may, for example, be configured to perform one or more method steps as described in connection to Figure 1 or Figure 5.

The AAS receiver 300 comprises two or more receiver paths (RXP) 321, 322, 323 and other signal processing circuitry - schematically represented in Figure 3 by a processor (PROC) 390 - configured to process the outputs from the receiver paths. Each receiver path comprises a respective AGC controller 331, 332, 333 and is connectable (e.g., connected) to respective antennas 341, 342, 343 of a multi-antenna arrangement.

The arrangement of Figure 3 comprises a controller (CNTR; e.g., controlling circuitry or a control module) 310.

The controller 310 is configured to, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, cause the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval (compare with step 150 of Figure 1). The selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period.

The controller 310 may be configured to acquire information regarding the first receiver path indicating gain reduction for the first receiver path via signaling over connections 339. Alternatively or additionally, the controller 310 may be configured to cause the respective AGC controllers of the one or more second receiver paths to apply the corresponding gain reduction during the selected time interval via signaling over connections 339.

In some embodiments, the controller 310 is further configured to cause configuration (e.g., via signaling over connections 339) of the respective AGC controller of one or more selected receiver paths with an AGC power threshold value for gain reduction which is lower than a default AGC power threshold value for gain reduction (compare with step 110 of Figure 1).

To this end, the controller 310 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) a configurer (CONF; e.g., configuring circuitry or a configuration module) 311. The configurer may be configured to configure the respective AGC controller of the selected receiver path(s) with the AGC power threshold value for gain reduction.

In some embodiments, the controller 310 may be further configured to cause selection of the time interval (compare with step 130 of Figure 1).

To this end, the controller 310 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) a selector (SEL; e.g., selecting circuitry or a selection module) 312. The selector may be configured to select the time interval.

In some embodiments, the controller 310 may be further configured to cause determination of the second receiver path(s) (compare with step 140 of Figure 1).

To this end, the controller 310 may comprise, or be otherwise associated with (e.g., connectable, or connected, to) a determiner (DET; e.g., determining circuitry or a determination module) 313. The determiner may be configured to determine the second receiver path(s).

Figure 4 schematically illustrates an example arrangement (e.g., an apparatus) according to some embodiments. The arrangement is for AGC operation in an AAS receiver 400. The AAS receiver 400 may be comprised in a communication device (e.g., a radio access network node, such as a base station, or a radio communication terminal, such as a user equipment, UE).

The arrangement of Figure 4 may, for example, be configured to perform one or more method steps as described in connection to Figure 1 or Figure 5. Alternatively or additionally, the arrangement of Figure 4 may be seen as a variant of the arrangement 300 of Figure 3. It should be noted that features mentioned and/or explained in connection to Figure 3 may be equally applicable to the arrangement of Figure 4, and vice versa.

The AAS receiver 400 comprises two or more receiver paths 421, 422, 423 and other signal processing circuitry - schematically represented in Figure 4 by a processor (PROC) 490 - configured to process the outputs from the receiver paths. The processor 490 may, for example, be implemented by a digital signal processor (DSP). Each receiver path comprises a respective AGC controller 431, 432, 433 and is connectable (e.g., connected) to respective antennas 441, 442, 443 of a multi-antenna arrangement.

Each receiver path also comprises a low noise amplifier (LNA) 451, 461, 471 configured to receive and amplify the antenna signals, a down-converter 453, 463, 473 configured to down- convert the received signal, and first and second variable gain amplifiers 452, 454, 462, 464, 472, 474 configured to scale the received signal before and after down-conversion based on control instructions from the AGC controller 431, 432, 433.

Each receiver path further comprises a filter 455, 465, 475 configured to pass relevant parts of the down-converted received signal, an analog-to-digital converter (ADC) 456, 466, 476 configured to convert the filtered down-converted received signal to the digital domain, a digital decimator (DEC) 457, 467, 477 configured to decimate the digital received signal, and a digital channel filter 458, 468, 478 configured to further filter the decimated signal before passing it to the processor 490.

The arrangement of Figure 4 does not comprise a centralized controller such as the controller 310 of Figure 3. Instead, the AGC controllers 431, 432, 433 - circularly interconnected as shown by 439 - together comprises controlling circuitry which is configured to, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, cause the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval (compare with step 150 of Figure 1).

Each AGC controller 431, 432, 433 may be configured to receive information regarding the first receiver path indicating gain reduction for the first receiver path, and to relay such information to the next receiver path, via signaling over the circular connection 439. Alternatively or additionally, each AGC controller 431, 432, 433 may be configured to cause the respective AGC controller of the next receiver path to apply the corresponding gain reduction via signaling over the circular connection 439.

In some embodiments, one or more of the respective AGC controllers 431, 432, 433 may be configured with an AGC power threshold value for gain reduction which is lower than a default AGC power threshold value for gain reduction (compare with step 110 of Figure 1).

The arrangement of Figure 4 further comprises a timer (TIM; e.g., timing circuitry or a timer module) 480 configured to select the time interval (compare with step 130 of Figure 1). The timer may be configured to cause the application of the corresponding gain reduction to be performed during the selected time interval via signaling (e.g., a strobe signal) over the trigger connection 481.

Figure 5 illustrates an example method 500 according to some embodiments. The method 500 is a method of operating AGC for an AAS receiver, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller. Typically, each receiver path is connectable (e.g., connected) to one or more respective antenna (or antenna element) of a multi-antenna arrangement.

As illustrated by step 570 (compare with step 150 of Figure 1), the method comprises causing, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path (Y-path out of step 550), the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval. The method 500 may, for example, be seen as a variant of the method 100 of Figure 1. It should be noted that features mentioned and/or explained in connection to Figure 1 may be equally applicable to the method of Figure 5, and vice versa.

The method 500 may, for example, be performed by the controller 310 of Figure 3 or by each of the AGC controllers 431, 432, 433 of Figure 4.

Any of the receiver paths 1, 2, ..., N can indicate (e.g., via connection 339 of Figure 3 or connection 439 of Figure 4) that they have detected a need for gain reduction (represented by 511, 512, 513 in Figure 5).

When at least one of the receiver paths indicate gain reduction (resulting in "true" at the output of OR-step 530; compare with step 120 of Figure 1, and with 439 of Figure 4) and the selected time interval - e.g., CP time window - is reached (represented by 520 in Figure 5; compare with step 130 of Figure 1), the AND-step 540 will output "true". Then (Y-path out of step 550), the other receiver paths are caused to apply a corresponding gain reduction as illustrated by 570. For example, when the method 500 is performed by an AGC controller of the arrangement 400 of Figure 4, step 570 may comprise applying the corresponding gain reduction in the receiver path of the AGC controller and relaying the gain reduction indication (represented by 511, 512, 513 in Figure 5) to the next AGC controller.

When none of the receiver paths indicate gain reduction (resulting in "false" at the output of OR-step 530) and/or the selected time interval is not reached, the AND-step 540 will output "false".

Then (N-path out of step 550), autonomous/local gain reduction may be performed if needed as illustrated by the Y-path out of optional step 580 (if not needed, N-path out of step 580, the method may return to 550 for continued monitoring of gain reduction indications). This may be particularly applicable when the method 500 is performed by an AGC controller of the arrangement 400 of Figure 4. Then, step 570 may also comprise sending a gain reduction indication (represented by 511, 512, 513 in Figure 5) to the next AGC controller.

Alternatively, the N-path out of step 550 may directly return to 550 for continued monitoring of gain reduction indications. This may be particularly applicable when the method 500 is performed by the controller 310 of Figure 3. Some embodiments may be particularly relevant for fifth generation (5G) cellular systems, where one technique to improve system performance is to use AAS.

In typical AAS, an array of antennas controlled via phase (or time delay) enables beamforming of transmitted and/or received radio frequency (RF) signals. This can be used to improve system performance (e.g., increase reliability, lower latency, increase capacity, increase coverage, etc.) for a cellular system.

Exemplifying a radio access network node by a base transceiver station (BTS) and a radio communication terminal by a user equipment (UE), the path loss in the communication link between UE and BTS will vary, e.g., depending on the distance between the UE and the BTS. Typically, this is mitigated by the up-link power control loop, wherein the BTS measures the power of the received signal and instructs the UE to adapt its transmitted power when needed.

However, power control loop is typically only applicable within the network of each operator. Therefore, a BTS of one operator may be blocked by signals from UE:s using another operator; "uncoordinated UE:s". When a BTS gets blocked by signals from one or several "uncoordinated UE:s", it needs to reduce the gain in the receiver to avoid compression.

Conventionally, each receiver path of an AAS receiver has its individual AGC control and gain reduction generally causes disturbance which may be harmful to signal reception (e.g., in terms of decreased signal-to-noise ratio, SNR, increased bit error probability, BER, more retransmissions which yields increased latency, etc.) as explained in connection to Figure 2, parts (a)-(b). Even if an AGC control unit coordinates AGC gain changes between individual receive chains in similarity to US 8,090,061 Bl, the disturbance may be harmful to signal reception.

Therefore, it is proposed that the respective AGC controllers of the receiver paths apply the coordinated gain reduction during a selected time interval, wherein the selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period

For an OFDM-based system there are at least two scenarios that could lead to triggering of a gain change (AGC state update), such as a gain reduction. One such scenario (case A) relates to a single strong interfering UE that is close to the BTS starting to transmit at high power.

Another such scenario (case B) relates to the total power of a plurality of transmitting UE:s adding up so that the peak amplitude exceeds the dynamic range of the receiver radio. In case B, the AGC state toggling for each antenna conventionally depends on how the combined signal from the plurality of UE:s appears at the corresponding antenna. The momentary signal energy at each antenna may vary quickly over time, and the peak amplitude of the combined signal typically changes slowly over time (e.g., as a function of the number of active UE:s in the plurality and/or the pathloss to the BTS). Case B may be especially cumbersome for high bandwidth (e.g., multi-band scenarios). This may, for example, be due to that there are more potentially blocking UE:s so that even low power emissions from each UE adds up to a high power as seen by the BTS.

Approaches according to some embodiments improve system performance for case B, without negative impact for case A.

Generally, when an arrangement is referred to herein, it is to be understood as a physical product; e.g., an apparatus. The physical product may comprise one or more parts, such as controlling circuitry in the form of one or more controllers, one or more processors, or the like.

The described embodiments and their equivalents may be realized in software or hardware or a combination thereof. The embodiments may be performed by general purpose circuitry. Examples of general purpose circuitry include digital signal processors (DSP), central processing units (CPU), co-processor units, field programmable gate arrays (FPGA) and other programmable hardware. Alternatively or additionally, the embodiments may be performed by specialized circuitry, such as application specific integrated circuits (ASIC). The general purpose circuitry and/or the specialized circuitry may, for example, be associated with or comprised in an apparatus such as communication device (e.g., a radio access network node, such as a base station, or a radio communication terminal, such as a user equipment).

Embodiments may appear within an electronic apparatus (such as a communication device) comprising arrangements, circuitry, and/or logic according to any of the embodiments described herein. Alternatively or additionally, an electronic apparatus (such as a communication device) may be configured to perform methods according to any of the embodiments described herein.

According to some embodiments, a computer program product comprises a computer readable medium such as, for example a universal serial bus (USB) memory, a plug-in card, an embedded drive or a read only memory (ROM). Figure 6 illustrates an example computer readable medium in the form of a compact disc (CD) ROM 600. The computer readable medium has stored thereon a computer program comprising program instructions. The computer program is loadable into a data processor (PROC; e.g., data processing circuitry or a data processing unit) 620, which may, for example, be comprised in a communication device 610. When loaded into the data processor, the computer program may be stored in a memory (MEM) 630 associated with or comprised in the data processor. According to some embodiments, the computer program may, when loaded into and run by the data processor, cause execution of method steps according to, for example, any of the methods illustrated in Figures 1 and 5 or otherwise described herein.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used.

Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims.

For example, the method embodiments described herein discloses example methods through steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims. Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence. Thus, the steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means intended as limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. Furthermore, functional blocks described herein as being implemented as two or more units may be merged into fewer (e.g. a single) unit.

Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever suitable. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa.

Hence, it should be understood that the details of the described embodiments are merely examples brought forward for illustrative purposes, and that all variations that fall within the scope of the claims are intended to be embraced therein.

Claims

1. A method of operating automatic gain control, AGC, for an advanced antenna system, AAS, receiver, wherein the AAS receiver comprises two or more receiver paths, and wherein each receiver path comprises a respective AGC controller, the method comprising: causing (150), responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path (120), the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval, wherein the selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period.

2. The method of claim 1, wherein the AAS receiver is an orthogonal frequency division multiplex, OFDM, receiver and the time period is a cyclic prefix, CP, time interval.

3. The method of any of claims 1 through 2, wherein the one or more second receiver paths comprises all receiver paths - other than the first receiver path - of the AAS receiver, or only some receiver paths - other than the first receiver path - of the AAS receiver.

4. The method of any of claims 1 through 3, wherein the respective AGC controllers of the second receiver paths are caused to apply the corresponding gain reduction during a same selected time interval.

5. The method of any of claims 1 through 4, wherein a receiver path, whose respective AGC controller autonomously performs a gain reduction before the selected time interval, is excluded (145) from the one or more second receiver paths.

6. The method of any of claims 1 through 5, wherein the respective AGC controller of one or more selected receiver paths is configured (110) with an AGC power threshold value for gain reduction which is lower than a default AGC power threshold value for gain reduction.

7. A computer program product comprising a non-transitory computer readable medium

(600), having thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to any of claims 1 through 6 when the computer program is run by the data processing unit.

8. An apparatus for operating automatic gain control, AGC, of an advanced antenna system,

AAS, receiver (300), wherein the AAS receiver comprises two or more receiver paths (321, 322, 323), and wherein each receiver path comprises a respective AGC controller (331, 332, 333), the apparatus comprising controlling circuitry (310) configured to, responsive to the respective AGC controller of a first receiver path indicating gain reduction for the first receiver path, cause the respective AGC controllers of one or more second receiver paths to apply a corresponding gain reduction during a selected time interval, wherein the selected time interval is within a time period during which gain reduction is less harmful to information reception than gain reduction applied during another time period.

9. The apparatus of claim 8, wherein the AAS receiver is an orthogonal frequency division multiplex, OFDM, receiver and the time period is a cyclic prefix, CP, time interval.

10. The apparatus of any of claims 8 through 9, wherein the one or more second receiver paths comprises all receiver paths - other than the first receiver path - of the AAS receiver, or only some receiver paths - other than the first receiver path - of the AAS receiver.

11. The apparatus of any of claims 8 through 10, wherein the controlling circuitry is configured to cause the respective AGC controllers of the second receiver paths to apply the corresponding gain reduction during a same selected time interval.

12. The apparatus of any of claims 8 through 11, wherein the controlling circuitry is further configured to cause exclusion of a particular receiver path from the one or more second receiver paths responsive to the respective AGC controller of the particular receiver path autonomously performing a gain reduction before the selected time interval.

13. The apparatus of any of claims 8 through 12, wherein the respective AGC controller of one or more selected receiver paths is configurable with an AGC power threshold value for gain reduction which is lower than a default AGC power threshold value for gain reduction.

14. An advanced antenna system, AAS, receiver (300) comprising the apparatus of any of claims 8 through 13 and two or more receiver paths (321, 322, 323), wherein each receiver path comprises a respective AGC controller (331, 332, 333), and wherein each receiver path is connectable to one or more respective antenna elements (341, 342, 343) of a multi-antenna arrangement.

15. The AAS receiver of claim 14, further comprising the multi-antenna arrangement.

16. A communication device comprising the apparatus of any of claims 8 through 13 and/or the AAS receiver of any of claims 14 through 15.

17. The communication device of claim 16, wherein the communication device is a radio access network node, such as a base station, or a radio communication terminal, such as a user equipment.