Selectivity constraints in beamforming transmission scheduling

Abstract

A radio base station RBS (10) of a wireless communication network indicates to a wireless device (14, 18, 20) where in the time domain and / or frequency domain to perform radio quality measurements. If the RBS (10) determines that one or more wireless devices (14, 18, 20) (including those that are idle) are at risk of performing degraded quality measurements, it suppresses scheduling beamformed downlink data in the time / frequency region where the wireless device (14, 18, 20) performs quality measurements when a reference signal (e.g., a cell-specific reference signal or CRS) is broadcast. This avoids RSRQ degradation due to beamforming gain and allows existing legacy functions that rely on RSRQ to continue to operate as originally planned. The restriction applies only to beamformed data - the transmission of non-beamformed data in the relevant bandwidth is already taken into account when using RSRQ measurements.

Description

Technical Field

[0001] The present invention relates generally to wireless communication networks, and more particularly to systems and methods for mitigating interference to existing channel quality measurements by selectively limiting the use of beamforming. Background Art

[0002] Wireless communication networks provide voice and data communications between a network of fixed nodes and a large number of mobile wireless devices (e.g., mobile phones, smartphones, laptops and tablets, wearable devices, vehicles, etc.) At a very high level, wireless communication networks standardized by the Third Generation Partnership Project (3GPP) can be said to consist of wireless devices (often referred to as user equipment or UE), a radio access network (RAN), and a core network (CN), e.g. Figure 1 . UE is a wireless device (which may be mobile) used by a user to access the network wirelessly. RAN includes radio base stations (RBSs, also called eNBs or gNBs), which are responsible for providing radio communications with wireless devices and connecting the wireless devices to the core network. As is well known in the art, a radio frequency (RF) carrier is modulated with information and sent from the RBS to the wireless device (downlink transmission) and vice versa (uplink transmission). CN includes several types of core network functions, which are responsible for various tasks, such as handling the mobility of wireless devices, interconnection with data networks, packet routing and forwarding, authentication and billing, and other functions.

[0003] Wireless communication networks continue to grow in terms of technical complexity, system capacity, data rates, bandwidth, supported services, etc. To accommodate both more users and a wider range of types of devices that may benefit from wireless communication, the technical standards governing the operation of wireless communication networks continue to evolve. The fourth generation of network standards (4G, known as Long Term Evolution or LTE) has been deployed, and the fifth generation (5G, also known as New Radio or NR) is under development.

[0004] 5G is not yet fully defined but is at an advanced draft stage within the 3rd Generation Partnership Project (3GPP), the technical standards body. 5G wireless access will be achieved through a combination of LTE evolution on existing spectrum and new radio access technology targeting primarily new spectrum. The target spectrum range for the NR air interface is from below 1 GHz to 100 GHz, and initial deployment is expected to be in bands not used by LTE.

[0005] One of the advanced features of NR is the extensive use of beamforming between the RBS and wireless devices for both control signaling and user data. Beamforming is the process of sending and receiving signals in a relatively tightly focused RF carrier beam directly aimed at a target receiver or transmitter. Beamforming can be achieved by combining signals from different individual elements of an antenna array in such a way that signals going to or coming from certain angles interfere constructively (i.e., increase signal power), while signals going to or coming from other angles interfere destructively (i.e., signal cancellation). Beamforming (also known as highly directional transmission / reception) is different from omnidirectional transmission / reception, in which the radio signal power is roughly equal to / from all angles. In fact, the improvement in signal strength compared to the omnidirectional case is called beamforming gain.

[0006] In LTE (and other legacy systems), a cell-specific reference signal (CRS) is broadcast throughout the coverage area of ​​a cell to help nearby wireless devices detect a radio base station (RBS). CRS is broadcast using a single RF carrier beam that is beamformed to cover the entire coverage area of ​​the cell—i.e., an omnidirectional beam if the RBS is near the center of the coverage area. Therefore, the CRS carrier beam has a relatively low beamforming gain. Wireless devices use CRS to perform radio quality measurements.

[0007] Some radio quality measurements are reported to the RBS to facilitate mobility and load balancing decisions. Specifically, in LTE, Reference Signal Received Quality (RSRQ) is an important radio signal measurement metric that is used by many mobility and load balancing functions in the LTE RAN system.

[0008] As mentioned above, narrower and more directional RF beams have significantly higher beamforming gain than wider beams that cover the entire cell. Deployed systems (e.g., LTE) typically use fewer, wider beams for common control signals (including CRS), and narrower beams for more dedicated signaling (including data payloads for wireless devices).

[0009] The 3GPP standard defines a transmission mode (TM), which defines the degree of beamforming for a particular transmission. For example, in TM3, the beamforming gain of CRS and data is the same, while in TM8, the beamforming gain of data is several times higher than the beamforming gain of CRS.

[0010] The Reference Signal Received Power (RSRP) is defined as the linear average of the power contributions (in Watts) of the resource elements carrying the CRS within the considered measurement frequency bandwidth. For RSRP determination, CRS R0 shall be used according to 3GPP Technical Standard (TS) 36.211. If the wireless device can reliably detect that R1 is available, it can use R1 in addition to R0 to determine RSRP. The reference point for RSRP measurement shall be the antenna connector of the wireless device.

[0011] Reference Signal Received Quality (RSRQ) is defined as the ratio N × RSRP / (E-UTRA carrier RSSI), where N is the number of resource blocks of the E-UTRA carrier RSSI measurement bandwidth (where RSSI is the received signal strength indicator). The measurements of the numerator and denominator shall be made on the same set of resource blocks. RSRP and RSRQ are defined in 3GPP TS 36.214 v12.0.0 (2014-09).

[0012] The E-UTRA carrier received signal strength indicator (RSSI) consists of the linear average of the total received power (in Watts) observed by the UE over N resource blocks from all sources (including co-channel serving and non-serving cells, adjacent channel interference, thermal noise, etc.) in the measurement bandwidth, only in the OFDM symbols containing the reference symbol for antenna port 0. If higher layer signaling indicates that certain subframes are used to perform RSRQ measurements, the RSSI is measured over all OFDM symbols in the indicated subframes. The reference point for RSRQ should be the antenna connector of the wireless device. If the wireless device uses receiver diversity, the reported RSRQ value should not be lower than the corresponding RSRP of any of the individual diversity branches.

[0013] RSRQ is intended to represent downlink signal quality. However, since the denominator (RSSI) includes power from all sources, RSRQ is affected not only by other cell interference, external interference, and thermal noise (which all degrade signal quality), but also by the traffic load on the serving cell (which does not degrade signal quality). In non-beamforming systems, RSRQ values ​​above -11dB to -13dB are typically dominated by the own cell load, but may also be affected by interference from other cells or external sources, with no indication of which is dominant. Below these levels, interference or thermal noise becomes increasingly dominant, and RSRQ drops rapidly as the serving cell RSRP decreases.

[0014] The radio quality measurements currently in use were developed at a time when beamformed data transmissions were rare, and they were not designed to take into account. Currently, when beamformed data is sent in the downlink, the quality measurements performed by the wireless device can fluctuate and degrade dramatically. This can have a detrimental impact on the legacy functionality in the RBS that relies on these quality measurements.

[0015] As mentioned above, the denominator of RSRQ (RSSI) includes power from all sources. When beamforming with high gain is applied to data transmission, the data portion of the RSSI will increase in proportion to the applied beamforming gain for data transmissions reaching the measurement wireless device (even if the data is not intended for the measurement wireless device, but for nearby wireless devices). This will further reduce the measured RSRQ value. Even in good radio conditions (low noise and low interference), the measured RSRQ value will drop below the reportable range defined by 3GPP.

[0016] The background section of this document is provided to place the embodiments of the present invention in a technical and operational context to help those skilled in the art understand their scope and utility. The methods described in the background section may be considered, but these methods are not necessarily methods that have been previously conceived or considered. Unless explicitly stated, any statement herein is not considered to be prior art by virtue of being included in the background section. Summary of the invention

[0017] A brief summary of the disclosure is presented below to provide a basic understanding to those skilled in the art. This summary is not an extensive overview of the disclosure and is not intended to identify key / important elements in embodiments of the present invention or to delineate the scope of the present invention. The sole purpose of this summary is to present some of the concepts disclosed herein in a simplified form as a preface to a more detailed description presented later.

[0018] According to one or more embodiments described and claimed herein, a radio base station (RBS) of a wireless communication network can indicate to a wireless device where in the frequency domain to perform radio quality measurements. If the RBS determines that one or more wireless devices (including those that are idle) are at risk of performing degraded quality measurements, it will suppress scheduling beamformed downlink data in the frequency region where the wireless device performs quality measurements when broadcasting a reference signal (e.g., a cell-specific reference signal or CRS). This avoids RSRQ degradation due to beamforming gain and allows existing legacy functions that rely on RSRQ to continue to operate as planned. The restriction is only for beamformed data - the transmission of non-beamformed data in the relevant bandwidth is already taken into account when using RSRQ measurements. Although the scheduling restrictions imposed are small, in one embodiment, they are further minimized by applying the restrictions only under low traffic load conditions. In another embodiment, the wireless device is instructed to perform measurements only during specific time slots, and the beamforming scheduling restrictions are applied only then.

[0019] One embodiment is directed to a method of sending a signal to one or more wireless devices in a cell of a wireless communication network. A time and frequency range is determined at which the wireless device is to perform radio quality measurements. A reference signal is broadcast during a determined time within the determined frequency range to facilitate the wireless device to perform radio quality measurements. A radio base station selectively suppresses downlink transmissions scheduled beamforming during the determined time within the determined frequency range.

[0020] Another embodiment relates to a radio base station operable in a cell of a wireless communication network. The radio base station includes a transceiver and a processing circuit operatively connected to the transceiver. The processing circuit is characterized by being adapted to perform the following operations: determining a time and frequency range at which a wireless device is to perform radio quality measurements; broadcasting a reference signal during a determined time within the determined frequency range to facilitate the wireless device to perform radio quality measurements; and, selectively suppressing downlink transmissions of scheduled beamforming during the determined time within the determined frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the present invention are shown. However, the present invention should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure will be comprehensive and complete, and fully convey the scope of the present invention to those skilled in the art. Throughout the text, similar reference numerals represent similar elements.

[0022] Figure 1 is a block diagram of a wireless communication network.

[0023] Figure 2is a diagram of beamformed transmissions in a cell of a wireless communication network.

[0024] Figure 3 is a flow chart of a method of transmitting a signal to one or more wireless devices in a cell.

[0025] Figure 4 is a block diagram of a radio base station.

[0026] Figure 5 is a diagram of hardware modules in a processing circuit in a radio base station.

[0027] Figure 6 is a diagram of software executed by processing circuitry in a radio base station. DETAILED DESCRIPTION

[0028] For the purpose of simplicity and illustration, the present invention is described primarily by reference to exemplary embodiments of the present invention. In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that the present invention can be practiced without limiting these specific details. In this specification, well-known methods and structures are not described in detail to avoid unnecessarily obscuring the present invention.

[0029] Figure 2 A radio base station 10 operable in a wireless communication network, such as a 4G 3GPP LTE network implementing an active antenna system (AAS), is depicted. The radio base station 10 provides wireless communication services to a plurality of wireless devices 14, 18, 20 (also referred to as user equipment (UE)) within a geographical range of a service area or cell 12. In order to facilitate the evaluation of the air interface by the wireless devices 14, 18, 20, the radio base station 10 broadcasts a cell-specific reference signal (CRS) throughout the cell 12. Due to the location of the radio base station 10 near the center of the cell 12, the CRS is broadcast using an RF carrier in an omni-directional beam (not shown) that covers substantially all directions of the cell equally. Therefore, the CRS carrier beam has a very low beamforming gain. The wireless devices 14, 18, 20 use the CRS to perform radio quality measurements, such as reference signal reception quality (RSRQ). However, it is noted that the location of the radio base station 10 relative to the cell 12 is a limitation of embodiments of the present invention. For example, the radio base station 10 may provide coverage for the cell 12 from the cell edge, or may broadcast the CRS into a sector (e.g., 120 degrees azimuth of the cell). In these cases, the CRS carrier beam may not be omnidirectional. However, its beamforming gain is typically lower than the beamforming gain of a highly directional data transmission (i.e., tightly focused, with high beamforming gain) to the wireless device.

[0030] Figure 2 The radio base station 10 is also depicted transmitting data to the wireless device 14 via an RF carrier in a beamformed wave 16. Although tightly focused and directed at the (estimated) location of the intended recipient wireless device 14, the beamformed wave 16 is actually received by the wireless devices 18 and 20 as well.

[0031] As mentioned above, RSRQ is defined as the ratio:

[0032]

[0033] in

[0034] RSRP is the received signal reference power;

[0035] RSSI is the received signal strength indicator; and

[0036] N is the number of resource blocks of the E-UTRA carrier RSSI measurement bandwidth.

[0037] The denominator RSSI of this ratio is the total received power, which includes interference from other cells, external interference and thermal noise (all of which degrade signal quality) and the received traffic load in the serving cell 12 (which does not degrade signal quality). During data transmission on the beamformed wave 16, not only the wireless device 14, but also the wireless devices 18 and 20 will measure a high RSSI and therefore result in a low RSRQ due to the high beamforming gain even if the channel conditions are good and the actual received signal quality is very good. In some cases, the wireless devices 14, 18, 20 may report an RSRQ that is so low, caused by the high beamforming gain of the downlink RF beam 16, that the radio base station 10 forms an incorrect assessment of the overall channel quality. This in turn may cause the radio base station 10 to take suboptimal actions, such as a handover error (missing a handover or failing to initiate a handover that should have occurred). Idle UE cell reselection may also be negatively affected.

[0038] According to an embodiment of the present invention, in order to avoid harmful effects on the radio quality measurements of the wireless devices 14, 18, 20, the radio base station 10 first determines the time and frequency range in which the wireless device 14 will perform the radio quality measurements. For example, the radio base station 10 may instruct the wireless device 14 to perform the radio quality measurements during at least one of the specified time and the specified frequency range. An example of a specified time in which the wireless device 14 performs the radio quality measurements is during a subframe when a broadcast message or a synchronization signal is transmitted. An example of a specified frequency range in which the wireless device 14 should perform the radio quality measurements is within the six center physical resource blocks (PRBs) of the carrier.

[0039] After determining the time and frequency range in which the wireless device will perform radio quality measurements, the radio base station 10 broadcasts a reference signal (e.g., CRS) within the determined frequency range during the determined time period to facilitate the wireless device to perform radio quality measurements. During this determined time period and within the determined frequency range, the radio base station 10 selectively suppresses scheduling beamformed downlink transmissions - that is, downlink transmissions with a beamforming gain greater than the CRS broadcast. However, during the determined time period and within the determined frequency range, the radio base station 10 may continue to schedule non-beamformed downlink transmissions to one or more wireless devices 14, 18, 20 - that is, downlink transmissions with a beamforming gain comparable to the CRS broadcast. Conventional radio quality measurements (e.g., RSRQ) typically already take into account own-cell, non-beamformed downlink transmissions, and such transmissions will not excessively degrade the RSRQ measurement.

[0040] By refraining from scheduling beamformed downlink transmissions when one or more wireless devices 14, 18, 20 may be making radio quality measurements, the radio base station 10 ensures that legacy functions (e.g., those functions that rely on or at least accept RSRQ or other radio quality indicators as input) will continue to operate as expected. That is, the radio base station 10 minimizes the deleterious effects or distortions caused by high beamforming gain (for which the RSRQ indicator is not designed). The radio base station 10 can continue to utilize radio resources in other ways to send non-beamformed downlink data.

[0041] It is expected that the overall scheduling constraints imposed by this selective suppression of scheduled beamforming for downlink transmissions will be small. Therefore, the impact on the maximum system throughput will also be small.

[0042] However, in one embodiment, the application of scheduling restrictions is of a more dynamic nature, in situations where this assumption of minimal impact may not apply. When the traffic load in the cell 12 (e.g., measured as PRB utilization) is low, the radio base station 10 applies beamformed transmission scheduling restrictions. When one or more wireless devices 14, 18, 20 present in the cell 12 report that the transmission buffer is full and request all available resources, the scheduling restrictions are disabled. During this temporary deactivation of scheduling restrictions - i.e., during the time period when beamformed transmissions can be scheduled without restriction - any impact on the maximum throughput is avoided. When the cell 12 returns to a low traffic state again, the radio base station 10 applies scheduling restrictions again, suppressing scheduled beamformed transmissions during the time and frequency range when the wireless devices 14, 18, 20 are performing radio quality measurements.

[0043] In another embodiment, the time during which beamformed transmissions are suppressed is minimized (while minimizing any impact on throughput) by instructing the wireless devices 14, 18, 20 to perform measurements during specific time slots during which beamforming is already limited for other reasons. For example, functionality in various versions of the wireless communication network operating protocol restricts the radio base station 10 to schedule beamformed data in the six center PRBs during certain time slots to avoid conflicts with other signals that periodically occupy those time / frequency resources. For example, it is limited to scheduling transmission mode 7 (TM7, defining beamforming on antenna port 5, defined in 3GPP Release 8) or TM8 (defining dual-layer beamforming on antenna ports 7 and 8, defined in 3GPP Release 9) in the center PRBs in subframe 0; TM8 is also suppressed at other times. Examples of signaling that appears in these PRBs (to avoid interference from beamformed transmissions) include the physical broadcast channel (PBCH); primary and secondary synchronization signals (PSS / SSS); and demodulation reference signals (DMRS).

[0044] In another embodiment, the radio base station 10 transmits CRS on all PRBs, but may instruct one or more wireless devices 14, 18, 20 to perform radio quality measurements only in the six center PRBs. In this embodiment, the radio base station 10 may transmit beamformed data in all frequencies except the six center PRBs without adversely affecting the radio quality measurements of the associated wireless devices 14, 18, 20. As is known in the art, the radio base station 10 may instruct the wireless devices 14, 18, 20 by including the measurement information in system information (SI), which is broadcast in the cell 12 or alternatively to each wireless device 14, 18, 20 via radio resource control (RRC) signaling of measurement configuration information.

[0045] In another embodiment, the radio base station 10 exploits existing restrictions in various versions of the wireless communication network operating protocols that require the wireless devices 14, 18, 20 to perform radio quality measurements only during certain time slots, e.g., for inter-cell interference coordination (ICIC). The parameters used (e.g., measSubframePatternPCell) are defined in 3GPP TS 36-311. The radio base station 10 may avoid sending beamformed data to the wireless devices 14, 18, 20 during these time slots. The radio base station 10 may freely schedule beamformed transmissions in other time slots without risk of adversely affecting the radio quality measurements.

[0046] Embodiments of the present invention are only needed when the network operating functions performed by the radio base station 10 utilize radio quality measurements reported by the wireless devices 14, 18, 20. Therefore, before scheduling beamformed downlink transmissions, the radio base station 10 should check whether any such operating functions are enabled. If not enabled, the impact of beamforming gain on, for example, RSRQ is insignificant and scheduling restrictions do not need to be applied. However, if one or more such operating functions are enabled, the radio base station 10 utilizes one or more embodiments described herein to selectively suppress scheduling beamformed downlink transmissions in the following frequency ranges and during the following times, in which frequency ranges and during which it is determined that the wireless devices will perform radio quality measurements.

[0047] Figure 3 The steps of a method 100 of transmitting a signal to one or more wireless devices 14, 18, 20 in a cell 12 of a wireless communication network, performed by a radio base station 10 operable in the cell 12, are depicted. A time and frequency range is determined in which the wireless device is to perform radio quality measurements (block 102). A reference signal is broadcast during a determined time within the determined frequency range to facilitate the wireless device to perform radio quality measurements (block 104). The radio base station 10 selectively suppresses downlink transmissions for scheduled beamforming within the determined frequency range during the determined time (block 106).

[0048] Figure 4 A radio base station 10 operable in a wireless communication network is depicted. As known to those skilled in the art, the radio base station 10 is a network node that provides wireless communication services to one or more wireless devices 14, 18, 20 (also referred to as user equipment (UE)) in a geographical area (referred to as a cell or sector) 12. The radio base station 10 in LTE is referred to as an e-NodeB or eNB, and in NR is referred to as a gNB; however, the present invention is not limited to LTE or NR. The radio base station 10 includes: communication circuitry 22 operable to exchange data with other network nodes; processing circuitry 24; memory 26; and radio circuitry, such as a transceiver 28, one or more antennas 30, etc., to enable wireless communications to the one or more wireless devices 14, 18, 20 over an air interface. As known to those skilled in the art, and as Figure 4As shown by the continuous line in the antenna feed line of the antenna, the antenna 30 can be physically separated from the radio base station 10, such as mounted on a tower, building, etc. Although the memory 26 is described as being separate from the processing circuit 24, it will be understood by those skilled in the art that the processing circuit 24 includes internal memory, such as a cache memory or a register file. It will be additionally understood by those skilled in the art that virtualization technology allows some functions nominally performed by the processing circuit 24 to be actually performed by other hardware that may be located remotely (e.g., in the so-called "cloud").

[0049] According to an embodiment of the invention, the memory 26 is operable to store, and the processing circuitry 24 is operable to execute, the software 32 which, when executed, is operable to cause the base station 10 to perform the method 100 described herein.

[0050] The processing circuitry 24 may include any one or more sequential state machines operable to execute machine instructions stored as a machine-readable computer program in the memory 26, such as, for example, one or more hardware-implemented state machines (e.g., implemented in discrete logic, an FPGA, an ASIC, etc.); programmable logic together with appropriate firmware; one or more stored program, general-purpose processors (e.g., a microprocessor or a digital signal processor (DSP)); or any combination of the above.

[0051] The memory 26 may include any non-transitory machine-readable medium known or developable in the art, including but not limited to magnetic media (e.g., floppy disks, hard drives, etc.), optical media (e.g., CD-ROMs, DVD-ROMs, etc.), solid-state media (e.g., SRAM, DRAM, DDRAM, ROM, PROM, EPROM, flash memory, solid-state disks, etc.), and the like.

[0052] The radio circuitry may include one or more transceivers 28 for communicating with one or more other transceivers via a radio access network (RAN) according to one or more communication protocols known in the art or that may be developed (e.g., IEEE 802.xx, CDMA, WCDMA, GSM, UTRAN, LTE, NR, LTE-M, NB-IoT, WiMax, etc.). The transceiver 28 implements transmitter and receiver functions (e.g., frequency allocation, etc.) suitable for a radio access network link. The transmitter and receiver functions may share circuit components and / or software, or may alternatively be implemented separately.

[0053] The communication circuit 22 may include a receiver and transmitter interface for communicating with one or more other nodes over a communication network according to one or more communication protocols known in the art or that may be developed (e.g., Ethernet, TCP / IP, SONET, ATM, SIP, etc.). The communication circuit 22 implements receiver and transmitter functions appropriate to the communication network link (e.g., optical, electrical, etc.). The transmitter and receiver functions may share circuit components and / or software, or may alternatively be implemented separately.

[0054] Figure 5 An example processing circuit 24 is shown, for example, Figure 4 The processing circuit 24 may include one or more physical units. Specifically, the processing circuit 24 may include: a time and frequency range determination unit 34; a reference signal broadcast unit 36; and a beamforming transmission scheduling suppression unit 38. The time and frequency range determination unit 34 is configured to determine the time and frequency range in which the wireless device will perform radio quality measurements. The reference signal broadcast unit 36 ​​is configured to broadcast a reference signal during a determined time within the determined frequency range to facilitate the wireless device to perform radio quality measurements. The beamforming transmission scheduling suppression unit 38 is configured to selectively suppress downlink transmissions scheduled for beamforming during a determined time within the determined frequency range.

[0055] Figure 6 Example software 32 is shown, for example, Figure 4 The software 32 may include one or more software modules. Specifically, the software 32 may include: a time and frequency range determination unit 40; a reference signal broadcast unit 42; and a beamforming transmission scheduling suppression unit 44. The time and frequency range determination unit 40 is configured to determine the time and frequency range in which the wireless device will perform radio quality measurements. The reference signal broadcast unit 42 is configured to broadcast a reference signal during a determined time within the determined frequency range to facilitate the wireless device to perform radio quality measurements. The beamforming transmission scheduling suppression unit 44 is configured to selectively suppress downlink transmissions scheduled for beamforming during a determined time within the determined frequency range.

[0056] Embodiments of the present invention present a number of advantages over the prior art. By avoiding sending beamformed data when one or more wireless devices 14, 18, 20 may be performing radio quality measurements, existing legacy functionality that relies on, for example, RSRQ can continue to operate as intended. "Reserved" radio resources can still be used for non-beamformed data. Non-beamformed data will affect the RSRQ measurement even though it does not affect signal quality - this is the same behavior in a conventional non-beamforming system and is therefore taken into account. Many embodiments propose alternatives that minimize any impact on system throughput.

[0057] Of course, without departing from the essential characteristics of the present invention, the present invention may be implemented in other ways than those specifically set forth herein. The embodiments presented are considered in all respects to be illustrative rather than restrictive, and all changes falling within the meaning and equivalent scope of the appended claims are intended to be included therein.

Claims

1. A method (100) for transmitting a signal to one or more wireless devices (14, 18, 20) in a cell (12) of a wireless communication network, the method (100) being characterized by: determining (102) a time and frequency range at which a first wireless device of the one or more wireless devices (14, 18, 20) is to perform radio quality measurements; broadcasting (104) a reference signal during the determined time within the determined frequency range using a single RF carrier beam to facilitate the one or more wireless devices (14, 18, 20) performing radio quality measurements, the single RF carrier beam being beamformed to cover an entire coverage area of ​​the cell; and selectively refraining (106) from scheduling a beamformed downlink transmission to any of the one or more wireless devices (14, 18, 20) during the determined time within the determined frequency range, the beamformed downlink transmission having a beamforming gain greater than a reference signal broadcast, wherein Selectively inhibits: suppressing downlink transmission of the scheduled beamforming only when the traffic load in the cell is below a first predetermined threshold, and Scheduling restrictions are disabled and beamformed downlink transmissions are scheduled during the determined time within the determined frequency range if the one or more wireless devices (14, 18, 20) request air interface resources for beamformed downlink transmissions exceeding a second predetermined threshold.

2. The method (100) according to claim 1, wherein: The time at which the first wireless device is to perform radio quality measurements is any time.

3. The method (100) according to claim 1, wherein: The radio quality measurement is a reference signal reception quality measurement.

4. The method (100) of claim 1, further comprising: Non-beamformed downlink transmissions are scheduled to the one or more wireless devices (14, 18, 20) within the determined frequency range during the determined time.

5. The method (100) of claim 1, further comprising: Prior to the step of determining (102), determining whether any enabled operating functions use radio quality measurements reported by the one or more wireless devices (14, 18, 20); and If not, the inhibiting (106) step is omitted.

6. The method (100) of claim 1, wherein: Determining (102) a time and a frequency range at which the one or more wireless devices (14, 18, 20) are to perform radio quality measurements includes instructing the one or more wireless devices (14, 18, 20) to perform radio quality measurements during a specified time and a specified frequency range.

7. The method (100) of claim 1, wherein: Instructing the one or more wireless devices (14, 18, 20) to perform radio quality measurements during a specified time and a specified frequency range includes instructing the one or more wireless devices (14, 18, 20) by one of the following ways: broadcasting system information, or sending radio resource control measurement configuration information to the one or more wireless devices (14, 18, 20).

8. The method (100) of claim 1, wherein: Instructing the one or more wireless devices (14, 18, 20) to perform radio quality measurements includes instructing the one or more wireless devices (14, 18, 20) to perform radio quality measurements in a plurality of center physical resource blocks of a carrier and during a subframe in which one of a broadcast message and a synchronization signal is transmitted.

9. The method (100) of claim 1, wherein: Instructing the one or more wireless devices (14, 18, 20) to perform radio quality measurements includes: instructing the one or more wireless devices (14, 18, 20) to perform radio quality measurements during subframes in which the one or more wireless devices (14, 18, 20) otherwise need to perform measurements, and wherein selectively suppressing (106) downlink transmissions with scheduled beamforming includes: suppressing downlink transmissions with scheduled beamforming during these subframes.

10. A radio base station (10) operable in a cell (12) of a wireless communication network, comprising: transceiver (28); as well as Processing circuitry (24) operatively connected to the transceiver (28) for performing the method according to any one of claims 1 to 9.

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