Patent Description:
Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system). A wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

Wireless communication systems may operate in millimeter wave (mmW) frequency ranges, (e.g., <NUM>, <NUM>, <NUM>, etc.). Wireless communications at these frequencies may be associated with increased signal attenuation (e.g., path loss), which may be influenced by various factors, such as temperature, barometric pressure, diffraction, etc. As a result, signal processing techniques, such as beamforming, may be used to coherently combine energy and overcome the path losses at these frequencies. Due to the increased amount of path loss in mmW communication systems, transmissions from the base station and/or the UE may be beamformed.

Wireless communications between two wireless nodes, (e.g., between a base station and a UE), may use beams or beam-formed signals for transmission and/or reception. A base station may transmit beamformed synchronization signals on downlink (DL) synchronization beams. A UE may receive a synchronization signal on one or more of the DL synchronization beams, and thus be enabled to initiate a RACH procedure with the base station. In some instances, the UE may send a message to the base station as part of the RACH procedure, and the base station may assume that the uplink (UL) beam on which the RACH message is received is representative of a DL beam which the base station should use in communicating with the UE. In other words, the base station assumes DL-UL correspondence. However, correspondence between the DL channel and UL channel may be missing, for various reasons. Thus, the base station assumption may be incorrect, meaning that the DL beam selected by the base station may not be the most appropriate beam for communications with the UE.

<CIT> discloses a method for performing random access in which the UE selects between several DL beams and selects the UL beam to information found in a SIB or MIB.

<CIT> discloses a mmWave system, in which the UE performs random access using the UL beam according to information in the selected DL beam.

The described techniques relate to improved methods, systems, devices, or apparatuses that support RACH conveyance of DL beam information for various DL-UL correspondence states. Generally, the described techniques provide for a base station to transmit DL signals to a UE. The DL signals may be transmitted on DL beam(s). The UE may use the DL beam from the DL beam(s) that can be used for communicating with the base station, (e.g., DL communications). The UE may select a resource and/or a random access channel (RACH) waveform for transmission of a RACH message, (e.g., RACH msg1, to the base station). In some aspects, the UE may select the resource and/or the RACH waveform based on the DL beam. The UE may transmit the RACH message to the base station on the selected resource and/or the RACH waveform. The base station may receive the RACH message on the resource and/or the RACH waveform and identify the DL beam selected by the UE based on the resource and/or the RACH waveform. The base station may use the selected DL beam for subsequent communications with the UE.

The invention is defined by a method according to independent claim <NUM>, or <NUM>, or by a device according to independent claims <NUM> or <NUM>.

Free space path loss may increase with carrier frequency. Transmission in millimeter wave (mmW) systems may also be impacted from additional non-line-of-sight losses, (e.g., diffraction loss, penetration loss, oxygen absorption loss, foliage loss, etc.). During initial access, the base station and the user equipment (UE) may attempt to overcome these high path losses to discover or detect each other. Aspects of the present disclosure provide for improved initial access in a mmW system.

Aspects of the disclosure are initially described in the context of a wireless communications system. Generally, the described techniques provide for a UE to convey an indication to a base station of a selected downlink (DL) beam by selecting a corresponding resource and/or random access channel (RACH) waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message. For example, the base station may transmit DL signal(s) on DL beam(s). The UE may select a DL beam from the DL signal(s) that can be used for DL communications,( e.g., from the base station to the UE). The UE may select a resource and/or a waveform (e.g., a RACH waveform or a scheduling request waveform) for transmission of the RACH message/scheduling request message/beam recovery or beam tracking message to the base station, where the selection is based on the selected DL beam. The UE may then transmit the RACH message/scheduling request message/beam recovery or beam tracking message to the base station using the selected resource and/or RACH waveform. The base station receives the RACH message/scheduling request message/beam recovery or beam tracking message on the selected resource and/or RACH waveform and uses the resource and/or RACH waveform to identify the selected DL beam. In one non-limiting example, the UE may select a resource (e.g., channel) that corresponds to the timing feature of the DL signal(s) (e.g., symbol). The base station may then use the selected DL beam for communications from the base station to the UE, (e.g., for subsequent DL communications). In some aspects, a resource may refer to a time resource, a frequency resource, a time-frequency resource, and the like.

Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. In some aspects, the term correspondence may refer to reciprocity.

<FIG> illustrates an example of a wireless communications system <NUM> in accordance with various aspects of the present disclosure. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be an LTE (or LTE-Advanced) network.

Each base station <NUM> may provide communication coverage for a respective geographic coverage area <NUM>. Communication links <NUM> shown in wireless communications system <NUM> may include UL transmissions from a UE <NUM> to a base station <NUM>, or DL transmissions, from a base station <NUM> to a UE <NUM>. A UE <NUM> may also be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE <NUM> may also be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, an appliance, an automobile, or the like.

During an initial access procedure, also referred to as a RACH procedure, UE <NUM> may transmit a RACH preamble to a base station <NUM>. This may be known as RACH message <NUM>. For example, the RACH preamble may be randomly selected from a set of <NUM> predetermined sequences. This may enable the base station <NUM> to distinguish between multiple UEs <NUM> trying to access the system simultaneously. The base station <NUM> may respond with a random access response (RAR), or RACH message <NUM>, that provides an UL resource grant, a timing advance and a temporary cell radio network temporary identity (C-RNTI). The UE <NUM> may then transmit an radio resource control (RRC) connection request, or RACH message <NUM>, along with a temporary mobile subscriber identity (TMSI) (if the UE <NUM> has previously been connected to the same wireless network) or a random identifier. The radio resource control (RRC) connection request may also indicate the reason the UE <NUM> is connecting to the network (e.g., emergency, signaling, data exchange, etc.). The base station <NUM> may respond to the connection request with a contention resolution message, or RACH message <NUM>, addressed to the UE <NUM>, which may provide a new C-RNTI. If the UE <NUM> receives a contention resolution message with the correct identification, the UE <NUM> may proceed with RRC setup. If the UE <NUM> does not receive a contention resolution message(e.g., if there is a conflict with another UE <NUM>) the UE <NUM> may repeat the RACH process by transmitting a new RACH preamble.

Wireless communication system <NUM> may operate in an ultra-high frequency (UHF) frequency region using frequency bands from <NUM> to <NUM> (<NUM>), although in some cases WLAN networks may use frequencies as high as <NUM>. This region may also be known as the decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may propagate mainly by line of sight, and may be blocked by buildings and environmental features. However, the waves may penetrate walls sufficiently to provide service to UEs <NUM> located indoors. Transmission of UHF waves is characterized by smaller antennas and shorter range (e.g., less than <NUM>) compared to transmission using the smaller frequencies (and longer waves) of the high frequency (HF) or very high frequency (VHF) portion of the spectrum. In some cases, wireless communication system <NUM> may also utilize extremely high frequency (EHF) portions of the spectrum (e.g., from <NUM> to <NUM>). This region may also be known as the millimeter band, since the wavelengths range from approximately one millimeter to one centimeter in length. Thus, EHF antennas may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within a UE <NUM> (e.g., for directional beamforming). However, EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than UHF transmissions.

Specifically, wireless communication system <NUM> may operate in mmW frequency ranges, (e.g., <NUM>, <NUM>, <NUM>, etc.). Wireless communication at these frequencies may be associated with increased signal attenuation (e.g., path loss), which may be influenced by various factors, such as temperature, barometric pressure, diffraction, etc. As a result, signal processing techniques such as beamforming (i.e., directional transmission) may be used to coherently combine signal energy and overcome the path loss in specific beam directions. In some cases, a device, such as a UE <NUM>, may select a beam direction for communicating with a network by selecting the strongest beam from among a number of signals transmitted by a base station <NUM>. In one example, the signals may be DL synchronization signals (e.g., primary or secondary synchronization signals) or DL reference signals (e.g., channel state information reference signals (CSI-RS)) transmitted from the base station <NUM> during discovery. The discovery procedure may be cell-specific, for example, may be directed in incremental directions around the coverage area <NUM> of the base station <NUM>. The discovery procedure may be used, at least in certain aspects, to identify and select beam(s) to be used for beamformed transmissions between the base station <NUM> and a UE <NUM>.

In some cases, base station antennas may be located within one or more antenna arrays. One or more base station antennas or antenna arrays may be collocated at an antenna assembly, such as an antenna tower. A base station <NUM> may multiple use antennas or antenna arrays to conduct beamforming operations for directional communications with a UE <NUM>.

Wireless communication system <NUM> may be or include a multicarrier mmW wireless communication system. Broadly, aspects of wireless communication system <NUM> may include a UE <NUM> and a base station <NUM> configured to support RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. For example, the base station <NUM> may transmit DL signal(s) on DL beam(s). The UE <NUM> may select a DL beam from the DL signal(s) that can be used for DL communications, (e.g., from the base station <NUM> to the UE <NUM>). The UE <NUM> may select a resource and/or a RACH waveform for transmission of the RACH message to the base station <NUM>, where the selection is based on the selected DL beam. The UE <NUM> may then transmit the RACH message to the base station <NUM> using the selected resource and/or RACH waveform. The base station <NUM> receives the RACH message on the selected resource and/or RACH waveform and uses the resource and/or RACH waveform to identify the selected DL beam. In one non-limiting example, the UE <NUM> may select a resource (e.g., channel) that corresponds to the timing feature of the DL synchronization signal(s) (e.g., symbol). The base station <NUM> may then use the selected DL beam for communications from the base station <NUM> to the UE <NUM>, (e.g., for subsequent DL communications).

<FIG> illustrates an example of a process flow <NUM> for RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. Process flow <NUM> may implement aspects of wireless communication system <NUM> of <FIG>. Process flow <NUM> may include a UE <NUM>-a and a base station <NUM>-a, which may be examples of the corresponding devices of <FIG>. Base station <NUM>-a may be a mmW base station and a serving base station for UE <NUM>-a.

According to the invention (see also step <NUM>), base station <NUM>-a transmits an indication of correspondence associated with DL beams at the base station side. In some aspects, the base station <NUM>-a may explicitly indicate correspondence to UE <NUM>-a. For example, a bit may be dedicated to conveying the correspondence indication. In other aspects, base station <NUM>-a may implicitly indicate correspondence. For example, UE <NUM>-a may deduce that correspondence is present or absent at base station <NUM>-a from a mapping of DL beams to the RACH resources or waveform. In one example, if the DL beams and the RACH resources are configured using time division duplexing (TDD), then this may indicate that the base station <NUM>-a may have correspondence.

In some cases, base station <NUM>-a may include the indication of correspondence in a master information block (MIB) (e.g., bits reserved for indicating correspondence) or a system information block (SIB) (e.g., bits reserved for indicating correspondence) transmitted to UE <NUM>-a. In some examples, the base station may transmit the MIB over a physical broadcast channel (PBCH), and the base station may transmit the SIB over an extended PBCH. In some examples, the indication may be based on a preamble format where one preamble format may convey an indication of no correspondence, a second preamble format may convey an indication of partial correspondence, and a third preamble format may convey and indication of full correspondence. Based on the indication of correspondence, UE <NUM>-a may determine whether there is full correspondence, no correspondence, or partial correspondence (e.g., with uncertainty region <NUM>*N+<NUM>, where N represents a number of subarrays at UE <NUM>-a or with uncertainty <NUM>*M+<NUM>, where M represents a number of beams transmitted by base station <NUM>-a). If UE <NUM>-a determines that correspondence is absent, UE <NUM>-a may select a UL beam (e.g., for communication with base station <NUM>-a) that is different from the DL beam used by base station <NUM>-a.

Additionally or alternatively, at <NUM>, UE <NUM>-a may transmit an indication of correspondence associated with UL beams at the UE side. For example, UE <NUM>-a may transmit a nature of correspondence between one or more receive DL synchronization beams at the UE and one or more transmit uplink (UL) beams at the UE, the indication of correspondence in a RACH message (e.g., RACH msg <NUM> or RACH msg <NUM>) or over a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). Base station <NUM>-a may receive the indication of correspondence at the UE side and, based on the indication, base station <NUM>-a may determine to map beams used to transmit channel state information reference signals (CSI-RSs) to beams used to transmit sounding reference signals (SRSs) or vice versa. Additionally, base station <NUM>-a may determine to map beams used in DL beam training to beams used in UL beam training or vice versa based on the indication.

At <NUM>, base station <NUM>-a may transmit (and UE <NUM>-<NUM> may receive) a DL synchronization signal to UE <NUM>-a. The DL synchronization signal may be a beamformed signal transmitted from base station <NUM>-a on DL synchronization beam(s). The DL synchronization signal may be associated with an index and/or a symbol of a subframe. The DL synchronization signal may be associated with a transmit power condition.

In some aspects, base station <NUM>-a transmits a plurality of DL synchronization signals during a synchronization subframe. Each DL synchronization signal may be transmitted in a symbol of the synchronization subframe, (e.g., DL synchronization signal <NUM> may be transmitted during symbol <NUM>, Dl synchronization signal <NUM> may be transmitted during symbol <NUM>, etc.).

According to the invention (see also <NUM>), UE <NUM>-a identifies a selected DL beam of the DL synchronization beams to use for communications from base station <NUM>-a to UE <NUM>-a based on (not according to the invention) a signal strength or (according to the invention) a signal quality (or both) of the DL synchronization signal, (e.g., high received signal strength and/or low interference level). In some aspects, UE <NUM>-a may identify the selected DL beam by identifying a transmit power condition of the DL synchronization signal on the DL synchronization beams, (e.g., a transmit power above a threshold level).

At <NUM>, UE <NUM>-a may select a resource and/or RACH waveform for transmission of the RACH message to base station <NUM>-a. The resource and/or RACH waveform may be selected based, at least in certain aspects, on the selected DL beam, (e.g., based on the index of the selected DL beam, based on the symbol of a subframe of the DL synchronization signal of the selected DL beam, etc.). The resource and/or RACH waveform may be associated with tone(s) in a component carrier and/or associated with a component carrier.

According to the invention (see <NUM>), UE <NUM>-a transmits a RACH message to base station <NUM>-a. The RACH message may be transmitted on the selected RACH resource and/or RACH waveform. The RACH message is transmitted during an entire duration of a corresponding random access subframe, according to the invention during each symbol of the random access subframe. In some aspects, the RACH message may be transmitted during an entire duration of a corresponding random access slot, subframe, occasion, burst, burst set, and the like. Generally, these terms may refer to a time duration where the gNB sweeps some or all of its receive beams to receive RACH message(s). In some aspects, UE <NUM>-a may select a RACH waveform for transmission of the RACH message. The RACH waveform may be selected based on the selected DL beam and may include a RACH preamble, a cyclic shift, etc. In some aspects, UE <NUM>-a may transmit the RACH message on a plurality of UL beams.

At <NUM>, base station <NUM>-a may identify the selected DL beam. Base station <NUM>-a may identify the selected DL beam based on the resource and/or RACH waveform used for the RACH message transmission. In some aspects, base station <NUM>-a may identify the selected DL beam by associating the resource and/or RACH waveform with an index of the selected DL beam. In some aspects, base station <NUM>-a may identify the selected DL beam by associating the resource and/or RACH waveform with a symbol of a subframe of the DL synchronization signal of the selected DL beam.

In some aspects, base station <NUM>-a may identify the selected DL beam based on the RACH waveform of the RACH message. For example, base station <NUM>-a may identify the selected DL beam based on the RACH preamble of the RACH message, a cyclic shift of the RACH message, etc..

At <NUM>, base station <NUM>-a may transmit subsequent messages to UE <NUM>-a using the selected DL beam. In some cases, the selected DL beam is a preferred DL beam. Moreover, in some aspects base station <NUM>-a may use the RACH message received from UE <NUM>-a to determine a selected UL beam for communications from UE <NUM>-a to base station <NUM>-a. For example, base station <NUM>-a may measure a quality of the RACH message that is received on a plurality of UL beams and determine the selected UL beam based on the measured quality. Measuring the quality of the RACH message may include measuring a reference signal received power (RSRP), a received signal strength indicator (RSSI), a reference signal received quality (RSRQ), a signal to noise ratio (SNR), a signal to interference noise ratio (SINR), etc..

In some cases, UE <NUM>-a may measure an RSRP of a received signal transmitted on a synchronization signal block (e.g., where a combination of one or more synchronization signals are transmitted together in a certain direction) to identify the best signal. In cases where UE <NUM>-a is unable to determine a strongest port associated with a certain symbol, UE <NUM>-a may indicate or convey a best SS block index or the preferred DL beam to base station <NUM>-a using different spreading codes (e.g., orthogonal cover codes (OCCs)). In some examples, base station <NUM>-a may transmit one or more additional reference signals (e.g., a beam reference signal (BRS), a mobility reference signal (MRS), etc.) inside symbols used for synchronization signals <NUM>, and UE <NUM>-a may identify a best transmission port (e.g., best downlink transmission beam ID). As a result, UE <NUM>-a may feed back the best downlink transmission beam ID by using different spreading codes.

If base station <NUM>-a does not have beam correspondence, base station <NUM>-a may request UE <NUM>-a transmit RACH in all symbols of the RACH slot. Base station <NUM>-a may then find the best uplink reception beam based on the quality of received RACH signals. In some examples, when base station <NUM>-a does not have transmit/reception beam correspondence, base station <NUM>-a may configure an association between a downlink signal or downlink channel and a subset of RACH resources and/or a subset of preamble indices (e.g., RACH preamble indices), which may be used to determine a downlink transmission beam (e.g., for sending Msg2). Based on a downlink measurement of received signals and the corresponding association, UE <NUM>-a may select the subset of RACH resources and/or the subset of RACH preamble indices. In such cases, a preamble index may comprise a preamble sequence index and an OCC index, such as in cases when OCC is supported. In some examples, a subset of preambles may be indicated by OCC indices.

In some aspects, correspondence may be absent between the DL synchronization beams from base station <NUM>-a and UL beams from UE <NUM>-a. Thus, in some examples the selected DL beam may be different from the selected UL beam. Aspects of the present disclosure may support partial or no beam correspondence between the DL transmission beams and the UL receive beams. In the case of partial correspondence, the RACH message transmitted at <NUM> may be transmitted over a transmission time with a center symbol corresponding to the best, (e.g., strongest received signal strength), DL synchronization beam or with a center symbol corresponding to the symbol associated with the best DL synchronization beam. Similarly, UE <NUM>-a may determine the RACH preamble of the RACH message at <NUM> based on the best DL synchronization beam, and UE <NUM>-a may determine the subcarrier region used for the transmission of the RACH message at <NUM> based on the best DL synchronization beam. This may apply to frequency division duplexing (FDD) system where full beam correspondence may not be present between the DL and UL. The amount of partial beam correspondence may vary from one scenario to the next. In some examples, the absent correspondence may be associated with different channel propagation characteristics for the DL and the UL beams, (e.g., different transmit power levels, different angle of departure and/or arrival, etc.).

In some cases, correspondence may be present at the base station <NUM>-a. In this case, the base station <NUM>-a may transmit different DL synchronization signals at different times, and the base station105-a may receive the corresponding RACH resources simultaneously from UE <NUM>-a through a digital receiver sub-system, which may not suffer from analog beam constraints. In this case, a base station <NUM>-a may request that the UE <NUM>-a map DL synchronization signals to the RACH resources or waveforms. The base station <NUM>-a may then analyze each receive beam path with a RACH detector.

Aspects of the present disclosure may also support beam correspondence between the DL transmission beams and the UL receive beams. In the case that correspondence is present, the RACH message transmitted at <NUM> may be transmitted over a transmission time that corresponds to the best DL synchronization beam or the symbol corresponding to the best DL synchronization beam.

<FIG> illustrates an example of a system <NUM> for wireless communications that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. System <NUM> may be an example of aspects of wireless communication system <NUM> of <FIG>. System <NUM> may be a mmW wireless communication system. System <NUM> may include a UE <NUM>-b and a base station <NUM>-b, which may be examples of the corresponding devices of <FIG> and <FIG>. Broadly, system <NUM> illustrates aspects of a discovery procedure where UE <NUM>-b discovers base station <NUM>-b based on DL synchronization signals transmitted on DL synchronization beams.

In some examples, base station <NUM>-b may be a mmW base station that transmits beamformed transmissions on an active beam to UE <NUM>-b. The transmissions from base stations <NUM>-b may be beamformed or directional transmissions that are directed towards UE <NUM>-b.

For example, base station <NUM>-b may transmit DL synchronization signal on DL synchronization beams <NUM>. Base station <NUM>-b may transmit DL synchronization signals (e.g., for random access) in a beamformed manner and swept through the angular coverage region (e.g., in azimuth and/or elevation). Each DL synchronization beam <NUM> may be transmitted in a beam sweeping operation in different directions so as to cover the coverage area of base station <NUM>-b. For example, DL synchronization beam <NUM>-a may be transmitted in a first direction, DL synchronization beam <NUM>-b may be transmitted in a second direction, DL synchronization beam <NUM>-c may be transmitted in a third direction, and DL synchronization beam <NUM>-d may be transmitted in a fourth direction. Although system <NUM> shows four DL synchronization beams <NUM>, it is to be understood that fewer and/or more DL synchronization beams <NUM> may be transmitted. Moreover, the DL synchronization beams <NUM> may be transmitted at differing beam widths, at different elevation angles, etc. In some aspects, DL synchronization beams <NUM> may be associated with a beam index, for example, an indicator identifying the beam.

In some aspects, DL synchronization beams <NUM> may also be transmitted during different symbol periods of a synchronization subframe. For example, DL synchronization beam <NUM>-a may be transmitted during a first symbol period (e.g., symbol <NUM>), DL synchronization beam <NUM>-b may be transmitted during a second symbol period (e.g., symbol <NUM>), DL synchronization beam <NUM>-c may be transmitted during a third symbol period (e.g., symbol <NUM>), and DL synchronization beam <NUM>-d may be transmitted during a fourth symbol period (e.g., symbol <NUM>). Additional DL synchronization beams <NUM> may be transmitted during other symbol periods of the synchronization subframe.

Generally, performing the beam sweeping operation supports base station <NUM>-b determining which direction UE <NUM>-b is located (e.g., after receiving response messages from UE <NUM>-b). This supports transmission of RACH message <NUM> from base station <NUM>-b. Moreover, the beam sweeping operation improves communications when correspondence does not hold between DL and UL channels, UE <NUM>-b may select the frequency region and/or the waveform configuration (e.g., resource and/or RACH waveform) for transmitting the random access signal (e.g., RACH message, RACH msg1, or RACH msg3) based on the index of the best or preferred DL synchronization signal on the DL synchronization beam <NUM>. In some cases, UE <NUM>-a may convey the best or preferred DL beam using an index or identification in a RACH msg1. During the random access period, base station <NUM>-a may find the suitable UL beam by receiving the random access signal in a sweeping manner. Base station <NUM>-b may identify the UE <NUM>-a selected DL beam from the resource and/or RACH waveform used (e.g., the used frequency region and/or waveform configuration) that contains the RACH message (e.g., RACH msg1 or RACH msg3) of the random access signal.

Thus, UEs within the coverage area of base station <NUM>-b may receive the DL synchronization signals on DL synchronization beams <NUM>. The UE <NUM>-b may identify which DL synchronization signal is best, (e.g., strongest received signal strength, best channel quality, etc.), and identify this as the selected DL beam. UE <NUM>-b may then select a resource and/or RACH waveform to use for transmission of the RACH message based on the selected DL beam, for example the preferred DL beam. In one example, the resource and/or RACH waveform used for the transmission of the RACH message may correspond to the symbol of the selected DL beam. In another example, the RACH message may include an identification or index of the preferred DL beam.

As one non-limiting example, there may be <NUM> different DL beams available. Thus, UE <NUM>-b may use four bits to convey the DL beam information to base station <NUM>-b. There may be four subcarrier regions (e.g., resources) and four different RACH waveforms available for use by UE <NUM>-b. Accordingly, UE <NUM>-b may transmit the four bits by selecting one out of four different RACH waveforms and one out of four subcarriers. Thus, UE <NUM>-b may select a combination of the resource and the RACH waveform to transmit the RACH message to base station <NUM>-b.

Thus, in certain aspects system <NUM> may support UE <NUM>-b selecting a combination of a RACH waveform and/or the resource used for its RACH message transmission based on one or more combinations of the index of a DL synchronization beam or a symbol of the DL synchronization subframe. UE <NUM>-b may transmit random access signal (e.g., RACH message, RACH msg1 or RACH msg3) during the entire duration of the random access subframe and/or during a portion of the random access subframe.

In some aspects, base station <NUM>-b may determine the selected DL beam of UE <NUM>-b from the used frequency region and/or RACH waveform that contains the message <NUM> of random access signal. Base station <NUM>-b may determine the best UL receive beam by measuring the quality of the received signal at different uplink receiver beams. The signal quality may denote one or more combinations of RSRP, RSSI, RSRQ, SNR, SINR, etc..

In some aspects, UE <NUM>-b may select the best DL synchronization signal and the frequency region of RACH and/or RACH waveform based on the index of the best DL synchronization signal. UE <NUM>-b may select a DL synchronization beam <NUM> that satisfies a transmit power condition. UE <NUM>-b may select a RACH preamble and cyclic shift partially based on the index of a DL synchronization beam <NUM>.

The absence of correspondence may indicate that the best DL beam and the best UL beam are not same.

In some aspects, UE <NUM>-b may select a combination of RACH and the resource used for its transmission based on a symbol of the DL synchronization subframe if the base station <NUM>-b transmits multiple beams using multiple antenna ports in each symbol of the synchronization subframe. In some aspects, the resource may denote the tones in a component carrier and/or a component carrier.

Although the example described with reference to <FIG> is directed to transmitting RACH message in a RACH subframe, this example is also applicable to transmitting a scheduling request message, beam recovery message, or beam tracking message in a RACH subframe. In some cases, UE <NUM> may find that the best synchronization beam was transmitted during a specific symbol, and UE <NUM> may transmit a scheduling request message, beam recovery message, or beam tracking message in a frequency region that corresponds to the specific symbol. The frequency region may be in a different resource (or resource block) in a RACH subframe. That is, a first portion of the resources in a RACH subframe may be allocated for RACH message transmissions, a second portion of the resources in a RACH subframe may be allocated for scheduling request message transmissions, and a third portion of the resources in a RACH subframe may be allocated for beam recovery or beam tracking message transmissions.

UE <NUM>-b may receive an indication of the subcarrier region for a scheduling request message transmission or a beam recovery or beam tracking message transmission through RRC signaling. In some cases, there may be eight (<NUM>) possible subcarrier regions. UE <NUM>-b may also receive the desired cyclic shift for the scheduling request message transmission or the beam recovery or beam tracking message transmission through RRC signaling. In some examples, UE <NUM>-b may use twelve (<NUM>) different cyclic shifts to generate a sequence for the scheduling request message transmission or the beam recovery or beam tracking message transmission. The number of available cyclic shifts for the scheduling request message transmission or the beam recovery or beam tracking message transmission may be greater than the number of available cyclic shifts for a RACH message transmission, since a timing error may be corrected before UE <NUM>-b transmits the scheduling request message transmission or the beam recovery or beam tracking message. Further, the transmission of the scheduling request message transmission or the beam recovery or beam tracking message may span two (<NUM>) symbols which may provide additional degrees of freedom (e.g., <NUM> degrees of freedom in each symbol pair).

<FIG> illustrate examples of a beam-subframe mapping configuration <NUM> for RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. Configuration <NUM> may implement aspects of wireless communication system <NUM>, process flow <NUM> and/or system <NUM> if <FIG>. In some aspects, aspects of configuration <NUM> may be implemented by a base station <NUM> and/or a UE <NUM>, as is described with reference to <FIG>.

With reference to <FIG>, beam-subframe mapping configuration <NUM> may include a plurality of DL synchronization signals transmitted on DL synchronization beams <NUM>. A base station <NUM> may transmit DL synchronization signals (e.g., for random access) in a beamformed manner and swept through the angular coverage region (e.g., in azimuth and/or elevation). Each DL synchronization beam <NUM> may be transmitted in a beam sweeping operation in different directions to cover the coverage area of base station <NUM>. For example, DL synchronization beam <NUM>-a may be transmitted in a first direction, DL synchronization beam <NUM>-b may be transmitted in a second direction, and so on. In some aspects, DL synchronization beams <NUM> may be associated with a beam index, for example, an indicator identifying the beam.

In some aspects, DL synchronization beams <NUM> may also be transmitted during different symbol periods of a synchronization subframe <NUM>. The synchronization subframe <NUM> may be associated with a time feature along the horizontal axis (e.g., symbols) and with a frequency feature along the vertical axis (e.g., frequencies or tones). For example, DL synchronization beam <NUM>-a may be transmitted during a first symbol period (e.g., symbol <NUM>), DL synchronization beam <NUM>-b may be transmitted during a second symbol period (e.g., symbol <NUM>), and so on until DL synchronization beam <NUM>-h is transmitted during an eighth symbol period (e.g., symbol <NUM>).

In some aspects, each DL synchronization signal transmitted on a DL synchronization beam <NUM> may be transmitted on some or all of the frequencies during the symbol. For example, DL synchronization beam <NUM>-a may be transmitted on frequency or tones <NUM>-<NUM> during symbol <NUM>, DL synchronization beam <NUM>-b may be transmitted on frequency or tones <NUM>-<NUM> during symbol <NUM>, and so on.

Thus, base station <NUM> may sweep DL synchronization beams <NUM> in eight directions during eight symbols of the synchronization subframe <NUM>.

With reference to <FIG>, UEs <NUM> within the coverage area of base station <NUM> may receive the DL synchronization signals on DL synchronization beams <NUM>. The UE <NUM> may identify which DL synchronization signal is best, (e.g., strongest received signal strength, best channel quality, etc.), and identify this as the selected DL beam. In the example <FIG>, the UE <NUM> has identified DL synchronization signal transmitted on DL synchronization beam <NUM>-b as the selected DL beam. As indicated, DL synchronization beam <NUM>-b was transmitted during the second symbol.

In some aspects, UE <NUM> may then select a resource to use for transmission of the RACH message based on the selected DL beam and during the RACH subframe <NUM>. In one example, the resource used for the transmission of the RACH message may correspond to the symbol of the selected DL beam. Thus, UE <NUM> may select the second resource <NUM> (e.g., frequency or tone <NUM>) as the resource for transmission of the RACH message. That is, UE <NUM> may select to the second resource <NUM> to convey an indication of the DL synchronization beam transmitted during the second symbol as being the selected DL beam. As discussed above, UE <NUM> may also select a RACH waveform to transmit the RACH message.

Thus, UE <NUM> may find that the best synchronization beam was transmitted during the second symbol. UE <NUM> may transmit a RACH message in the second frequency region for all time slots (e.g., during all symbols of the RACH subframe <NUM>). Base station <NUM> may find the best DL transmit beam from the used frequency region (e.g., second resource <NUM>) of the random access signal (e.g., RACH message). In some examples, the RACH message transmission time units may be greater than the synchronization subframe time units due to DL-UL power differences, for example.

In some aspects, base station <NUM> may sweep the same eight directions during the same eight symbols during the RACH subframe <NUM>. For example, base station <NUM> may configure one or more antenna arrays to receive the RACH message according to the same sweeping patter used to transmit the DL synchronization signal on the DL synchronization beams <NUM> during the RACH subframe <NUM>.

The example described above with reference to <FIG> may apply to cases when there is no correspondence at the base station <NUM> for the selected DL beam. Additionally, the example may apply to cases when there is no correspondence at both base station <NUM> and UE <NUM>. In such cases, UE <NUM> may identify a method to transmit using the selected DL beam based on a link gain associated with transmissions from UE <NUM>. In some cases, UE <NUM> may determine its link gain based on synchronization signals received from base station <NUM>. If UE <NUM> has a sufficient link gain to satisfy a link budget, UE <NUM> may transmit the RACH message in a single RACH subframe. However, if UE <NUM> does not have sufficient link gain to satisfy a link budget, UE <NUM> may transmit the RACH message in multiple RACH subframes.

Although the example described with reference to <FIG> is directed to transmitting RACH message in RACH subframe <NUM>, this example is also applicable to transmitting a scheduling request message, beam recovery message, or beam tracking message in RACH subframe <NUM>. In some cases, UE <NUM> may find that the best synchronization beam was transmitted during the second symbol, and UE <NUM> may transmit a scheduling request message, beam recovery message, or beam tracking message in a second frequency region for all time slots. The second frequency region may be in a different resource (or resource block) in RACH subframe <NUM>. That is, a first portion of the resources in RACH subframe <NUM> may be allocated for RACH message transmissions, a second portion of the resources in RACH subframe <NUM> may be allocated for scheduling request message transmissions, and a third portion of the resources in RACH subframe <NUM> may be allocated for beam recovery or beam tracking message transmissions.

<FIG> illustrate an example of a beam-subframe mapping configuration <NUM> for RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. Configuration <NUM> may implement aspects of wireless communication system <NUM>, process flow <NUM> and/or system <NUM> of <FIG>. In some aspects, aspects of configuration <NUM> may be implemented by a base station <NUM> and/or a UE <NUM>, as is described with reference to <FIG>.

With reference to <FIG>, beam-subframe mapping configuration <NUM> may include a plurality of DL synchronization signals transmitted on DL synchronization beams <NUM>. A base station <NUM> may transmit DL synchronization signals (e.g., for random access) in a beamformed manner and swept through the angular coverage region (e.g., in azimuth and/or elevation). Each DL synchronization beam <NUM> may be transmitted in a beam sweeping operation in different direction so as to cover the coverage area of base station <NUM>. For example, DL synchronization beam <NUM>-a may be transmitted in a first direction, DL synchronization beam <NUM>-b may be transmitted in a second direction, and so on. In some aspects, DL synchronization beams <NUM> may be associated with a beam index, for example, an indicator identifying the beam.

In some aspects, DL synchronization beams <NUM> may also be transmitted during different symbol periods of a synchronization subframe <NUM>. The synchronization subframe <NUM> may be associated with a time feature along the horizontal axis (e.g., symbols) and with a frequency feature along the vertical axis (e.g., frequencies or tones). In the example <FIG>, base station <NUM> may be configured with four antenna arrays where base station <NUM> sweeps four directions in each symbol. For example, antenna ports <NUM>-<NUM> may be grouped into subgroup <NUM> and used to transmit DL synchronization beams <NUM>-a through <NUM>-d during the first symbol (e.g., symbol <NUM>) of the synchronization subframe <NUM>. Also, antenna ports <NUM>-<NUM> may be grouped into subgroup <NUM> and used to transmit DL synchronization beams <NUM>-e through <NUM>-h during the second symbol (e.g., symbol <NUM>) of the synchronization subframe <NUM>. Thus, base station <NUM> may sweep eight directions during two symbols of the synchronization subframe <NUM>.

In some aspects, each DL synchronization signal transmitted on a DL synchronization beam <NUM> may be transmitted on some or all of the frequencies during the symbol. For example, DL synchronization beam <NUM>-a may be transmitted on any of frequency or tones <NUM>-<NUM> during symbol <NUM>, DL synchronization beam <NUM>-b may be transmitted on any of frequency or tones <NUM>-<NUM> during symbol <NUM>, and so on. In some aspects, the DL synchronization beams <NUM> transmitted during a symbol may not be transmitted on overlapping frequencies.

With reference to <FIG>, UEs <NUM> within the coverage area of base station <NUM> may receive the DL synchronization signals on DL synchronization beams <NUM>. The UE <NUM> may identify which DL synchronization signal is best, (e.g., strongest received signal strength, best channel quality, etc.), and identify this as the selected DL beam. In the example <FIG>, the UE <NUM> has identified DL synchronization signal transmitted on DL synchronization beam <NUM>-a as the selected DL beam. As indicated, DL synchronization beam <NUM>-a was transmitted during the first symbol (e.g., during symbol <NUM>).

In some aspects, UE <NUM> may then select a resource to use for transmission of the RACH message based on the selected DL beam and during the RACH subframe <NUM>. In one example, the resource used for the transmission of the RACH message may correspond to the symbol of the selected DL beam. Thus, UE <NUM> may select the first resource <NUM> (e.g., frequency or tone <NUM>) as the resource for transmission of the RACH message. That is, UE <NUM> may select to the first resource <NUM> to convey an indication of the DL synchronization beam transmitted during the first symbol as being the selected DL beam.

Thus, UE <NUM> may find that the best synchronization beam was transmitted during the first symbol. UE <NUM> may transmit a RACH message in the first frequency region for all time slots (e.g., during all symbols of the RACH subframe <NUM>). Base station <NUM> may find the best UL received beam by measuring the quality of the received signal during different time slots (e.g., during different symbols). In some aspects, base station <NUM> may find the best course DL beam from the used frequency region (e.g., first resource <NUM>) of the random access signal (e.g., RACH message).

In some aspects, base station <NUM> may sweep the same eight directions during the same eight symbols during the RACH subframe <NUM>. For example, base station <NUM> may configure one or more antenna arrays to receive the RACH message according to the same sweeping patter used to transmit the DL synchronization signal on the DL synchronization beams <NUM> during the synchronization subframe <NUM>.

With reference to <FIG>, beam-subframe mapping configuration <NUM> may include a plurality of DL synchronization signals transmitted on DL synchronization beams <NUM>. A base station <NUM> may transmit DL synchronization signals (e.g., for random access) in a beamformed manner and swept through the angular coverage region (e.g., in azimuth and/or elevation). Each DL synchronization beam <NUM> may be transmitted in a beam sweeping operation in different directions to cover the coverage area of base station <NUM>. For example, DL synchronization beam <NUM>-a may be transmitted in a first direction, DL synchronization beam <NUM>-b may be transmitted in a second direction, and so on. In some aspects, DL synchronization beams <NUM> may be associated with a beam index, (e.g., an indicator identifying the beam).

In some aspects, DL synchronization beam <NUM>-b may have full correspondence at base station <NUM> and UE <NUM>. That is, the DL synchronization beam <NUM>-b may be used for transmission and reception at both base station <NUM> and UE <NUM>. Thus, UE <NUM> may select the DL synchronization beam <NUM>-b to transmit a RACH message to base station <NUM>. In some cases, UE <NUM> may randomly select the subcarrier region for transmission of the RACH message to provide diversity in the presence of multiple UEs. In the example <FIG>, the UE <NUM> has selected subcarrier <NUM> for the transmission of the RACH message.

In other aspects, DL synchronization beam <NUM>-b may have full correspondence at base station <NUM> and no correspondence at UE <NUM>. That is, the DL synchronization beam <NUM>-b may be used for transmission and reception at base station <NUM>, but a transmission from UE <NUM> on DL synchronization beam <NUM>-b may be noisy. In such cases, UE <NUM> may identify a method to transmit using the selected DL beam based on a link gain associated with transmissions from UE <NUM>. In some cases, UE <NUM> may determine its link gain based on synchronization signals received from base station <NUM>. If UE <NUM> has a sufficient link gain to satisfy a link budget, UE <NUM> may transmit the RACH message in a single RACH subframe. However, if UE <NUM> does not have sufficient link gain to satisfy a link budget, UE <NUM> may transmit the RACH message in multiple RACH subframes.

Although the example described with reference to <FIG> is directed to transmitting RACH message in RACH subframe <NUM>, this example is also applicable to transmitting a scheduling request message, beam recovery message, or beam tracking message in RACH subframe <NUM>. In some cases, UE <NUM> may find that the best synchronization beam was transmitted during the second symbol, and UE <NUM> may transmit a scheduling request message, beam recovery message, or beam tracking message in a second frequency region for all time slots. The second frequency region may be in a different resource (or resource block) in the second symbol. That is, a first portion of the resources in RACH subframe <NUM> may be allocated for RACH message transmissions, a second portion of the resources in RACH subframe <NUM> may be allocated for scheduling request message transmissions, and/or a third portion of the resources in RACH subframe <NUM> may be allocated for beam recovery or beam tracking message transmissions.

In some aspects, DL synchronization beam <NUM>-b may have partial correspondence at base station <NUM> and UE <NUM>. That is, the DL synchronization beam <NUM>-b may be used for transmission and reception at both base station <NUM> and UE <NUM> with little noise. However, it may be desirable for UE <NUM> to identify a better beam (e.g., stronger signal strength) for uplink transmission. Thus, UE <NUM> may transmit the RACH message on the symbol of the selected DL beam and symbols of adjacent DL beams (e.g., DL synchronization beams <NUM>-a and <NUM>-c). In order to receive the uplink transmission, base station <NUM> may sweep a portion of the eight directions during symbols <NUM>, <NUM>, and <NUM> in the RACH subframe <NUM>.

UE <NUM> may then select a resource to use for transmission of the RACH message based on the selected DL beam and during the RACH subframe <NUM>. In one example, the resource used for the transmission of the RACH message may correspond to the symbol of the selected DL beam. Thus, UE <NUM> may select the second resource <NUM> (e.g., frequency or tone <NUM>) as the resource for transmission of the RACH message. That is, UE <NUM> may select the second resource <NUM> to convey an indication of the DL synchronization beam transmitted during the second symbol as being the selected DL beam. As discussed above, UE <NUM> may also select a RACH waveform to transmit the RACH message.

Thus, UE <NUM> may find that the best synchronization beam was transmitted during the second symbol. UE <NUM> may transmit a RACH message in the second frequency region for a portion of the time slots (e.g., during a portion of the symbols of the RACH subframe <NUM>). Base station <NUM> may find the best DL transmit beam from the used frequency region (e.g., second resource <NUM>) of the random access signal (e.g., RACH message). In some examples, the RACH message transmission time units may be greater than the synchronization subframe time units due to DL-UL power differences, for example.

Although the example described with reference to <FIG> is directed to transmitting RACH message in RACH subframe <NUM>, this example is also applicable to transmitting a scheduling request message, beam recovery message, or beam tracking message in RACH subframe <NUM>. In some cases, UE <NUM> may find that the best synchronization beam was transmitted during the second symbol, and UE <NUM> may transmit a scheduling request message, beam recovery message, or beam tracking message in a second frequency region for a portion of the symbols. The second frequency region may be in a different resource (or resource block) in RACH subframe <NUM>. That is, a first portion of the resources in RACH subframe <NUM> may be allocated for RACH message transmissions, a second portion of the resources in RACH subframe <NUM> may be allocated for scheduling request message transmissions, and/or a third portion of the resources in RACH subframe <NUM> may be allocated for beam recovery or beam tracking message transmissions.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a UE <NUM> as described with reference to <FIG>. Wireless device <NUM> may include receiver <NUM>, UE synchronization manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

Receiver <NUM> may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to RACH conveyance of DL synchronization beam information for various DL-UL correspondence states, etc.). Information may be passed on to other components of the device. The receiver <NUM> may be an example of aspects of the transceiver <NUM> described with reference to <FIG>.

UE synchronization manager <NUM> may be an example of aspects of the UE synchronization manager <NUM> described with reference to <FIG>. UE synchronization manager <NUM> may receive a DL synchronization signal from a base station on one or more DL synchronization beams, and identify a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE.

Transmitter <NUM> may also transmit the RACH message/scheduling request message/beam recovery or beam tracking message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the selected DL beam. In some cases, transmitting the RACH message/scheduling request message/beam recovery or beam tracking message includes: transmitting the RACH message/scheduling request message/beam recovery or beam tracking message during an entire duration of a corresponding random access subframe.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a wireless device <NUM> or a UE <NUM> as described with reference to <FIG> and <FIG>. Wireless device <NUM> may include receiver <NUM>, UE synchronization manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

UE synchronization manager <NUM> may be an example of aspects of the UE synchronization manager <NUM> described with reference to <FIG>. UE synchronization manager <NUM> may also include synchronization signal component <NUM>, beam selection component <NUM>, and resource selection component <NUM>.

Synchronization signal component <NUM> may receive a DL synchronization signal from a base station on one or more DL synchronization beams. In some cases, a correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station. In some cases, the one or more DL synchronization beams are within a single symbol of a synchronization subframe, where selecting the resource and/or RACH waveform for transmission of the RACH message/scheduling request message/beam recovery or beam tracking message includes: selecting the resource and/or RACH waveform based on the symbol of the selected DL beam.

Beam selection component <NUM> may identify a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE. In some cases, identifying the selected DL beam includes: identifying the DL beam based on the DL synchronization signal on the one or more DL synchronization beams meeting a transmit power condition. In some cases, the selected DL beam from the base station is different from a selected UL beam from the UE. In some cases, a base station may identify a preferred UL beam based on the quality of a received RACH message. The base station may also transmit one or more subsequent messages to the UE conveying an indication of the preferred UL beam.

Resource selection component <NUM> may select a resource and/or RACH waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message to the base station, the resource and/or RACH waveform being selected based on the selected DL beam. In some cases, selecting the resource and/or RACH waveform includes: selecting the resource and/or RACH waveform based on an index of the selected DL beam. In some cases, selecting the resource and/or RACH waveform includes: selecting the resource and/or RACH waveform based on a symbol of a subframe of the DL synchronization signal of the selected DL beam. In some cases, the resource is associated with one or more tones in a component carrier. In some cases, the resource is associated with a component carrier.

<FIG> shows a block diagram <NUM> of a UE synchronization manager <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The UE synchronization manager <NUM> may be an example of aspects of a UE synchronization manager <NUM>, a UE synchronization manager <NUM>, or a UE synchronization manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>. The UE synchronization manager <NUM> may include synchronization signal component <NUM>, beam selection component <NUM>, resource selection component <NUM>, preferred beam component <NUM>, RACH waveform component <NUM>, and correspondence management component <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

Synchronization signal component <NUM> may receive a DL synchronization signal from a base station on one or more DL synchronization beams. Beam selection component <NUM> may identify a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE. Resource selection component <NUM> may select a resource and/or RACH waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message to the base station, the resource and/or RACH waveform being selected based on the selected DL beam. In some cases, the resource selection component <NUM> may select a resource and/or RACH waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message to the base station based on an indication that correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station.

Preferred beam component <NUM> may identify a preferred beam from a number of beams transmitted by a base station. In some cases, identifying the selected DL beam includes: identifying a preferred DL beam based on a signal strength of the DL synchronization signal on the one or more DL synchronization beams, a signal quality of the DL synchronization signal on the one or more DL synchronization beams, or combinations thereof. RACH waveform component <NUM> may select a RACH waveform for transmission of the RACH message/scheduling request message/beam recovery or beam tracking message to the base station, the RACH waveform being selected based on the selected DL beam. In some cases, selecting the RACH waveform includes: selecting a RACH preamble, a cyclic shift, or combinations thereof based on an index of the selected DL beam.

Correspondence management component <NUM> may receive an indication that correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station. In some cases, correspondence management component <NUM> may transmit the RACH message/scheduling request message/beam recovery or beam tracking message to the base station during an entire duration of a RACH subframe based at least in part on the indication of the absent correspondence. In some cases, correspondence management component <NUM> may receive the indication in a MIB or a SIB. In some cases, correspondence management component <NUM> may transmit an indication that correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station. In some cases, correspondence management component <NUM> may transmit the RACH message/scheduling request message/beam recovery or beam tracking message to the base station during a first symbol of a first random access subframe and a second symbol of a second random access subframe. In some cases, correspondence management component <NUM> may transmit the indication of the absent correspondence of a UE in a RACH message <NUM>, PUCCH, or a PUSCH.

In some cases, correspondence management component <NUM> may receive an indication of a nature of correspondence between the one or more DL synchronization beams from the base station and one or more UL beams from the UE. In some cases, the nature of correspondence corresponds to one of: full correspondence, partial correspondence, or no correspondence. In some cases, correspondence management component <NUM> may determine that correspondence is present and select a transmission time for transmitting the RACH message/scheduling request message/beam recovery or beam tracking message to the base station based on the present correspondence. In some cases, the transmission time includes a symbol of a corresponding random access subframe. In some cases, correspondence management component <NUM> may determine that there is partial correspondence and select a transmission time for transmitting the RACH message/scheduling request message/beam recovery or beam tracking message to the base station based on the partial correspondence. In some cases, the transmission time includes multiple symbols of a corresponding random access subframe. In some cases, a UE may transmit multiple RACH messages if there is no beam correspondence at UE.

In some cases, correspondence management component <NUM> may select a transmission time, a frequency range, and a RACH preamble for transmitting the RACH message based on the nature of correspondence. In some cases, correspondence management component <NUM> may select the resource or RACH waveform based at least in part on a symbol associated with the DL synchronization signal and the indication of the nature of correspondence. In some cases, correspondence management component <NUM> may receive the indication of the nature of correspondence over a PBCH or an ePBCH. In some cases, correspondence management component <NUM> may receive the indication of the nature of correspondence in a MIB or a SIB.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Device <NUM> may be an example of or include the components of wireless device <NUM>, wireless device <NUM>, or a UE <NUM> as described above, for example, with reference to <FIG>, <FIG> and <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE synchronization manager <NUM>, processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, and I/O controller <NUM>. These components may be in electronic communication via one or more busses (e.g., bus <NUM>). Device <NUM> may communicate wirelessly with one or more base stations <NUM>.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a digital signal processor (DSP), a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), an field-programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting RACH conveyance of DL synchronization beam information for various DL-UL correspondence states).

Software <NUM> may include code to implement aspects of the present disclosure, including code to support RACH conveyance of DL synchronization beam information for various DL-UL correspondence states. Software <NUM> may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software <NUM> may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a base station <NUM> as described with reference to <FIG>. Wireless device <NUM> may include receiver <NUM>, base station synchronization manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

Base station synchronization manager <NUM> may be an example of aspects of the base station synchronization manager <NUM> described with reference to <FIG>. Base station synchronization manager <NUM> may transmit a DL synchronization signal on one or more DL synchronization beams, receive, on at least one of a resource or a RACH waveform, a RACH message/scheduling request message/beam recovery or beam tracking message from a UE, and identify, based on the resource and/or RACH waveform, a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE.

Transmitter <NUM> may also transmit one or more subsequent messages to the UE using the selected DL beam.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a wireless device <NUM> or a base station <NUM> as described with reference to <FIG> and <FIG>. Wireless device <NUM> may include receiver <NUM>, base station synchronization manager <NUM>, and transmitter <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

Base station synchronization manager <NUM> may be an example of aspects of the base station synchronization manager <NUM> described with reference to <FIG>. Base station synchronization manager <NUM> may also include synchronization signal component <NUM>, RACH component <NUM>, and selected beam component <NUM>.

Synchronization signal component <NUM> may transmit a DL synchronization signal on one or more DL synchronization beams. In some cases, a correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station.

RACH component <NUM> may receive, on a resource and/or RACH waveform, a RACH message/scheduling request message/beam recovery or beam tracking message from a UE. In some cases, receiving the RACH message/scheduling request message/beam recovery or beam tracking message includes: receiving the RACH message/scheduling request message/beam recovery or beam tracking message during an entire duration of a corresponding random access subframe. In some cases, receiving the RACH message/scheduling request message/beam recovery or beam tracking message includes: receiving the RACH message/scheduling request message/beam recovery or beam tracking message on a set of UL beams. In some cases, the resource is associated with one or more tones in a component carrier. In some cases, the resource is associated with a component carrier.

Selected beam component <NUM> may identify, based on the resource and/or RACH waveform, a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE. In some cases, identifying the selected DL beam includes: associating the resource and/or RACH waveform with an index of the selected DL beam. In some cases, identifying the selected DL beam includes: associating the resource and/or RACH waveform with a symbol of a subframe of the DL synchronization signal of the selected DL beam. In some cases, identifying the selected DL beam further includes: identifying the selected DL beam based on a RACH waveform of the RACH message/scheduling request message/beam recovery or beam tracking message. In some cases, identifying the selected DL beam includes: identifying the selected DL beam based on a RACH preamble of the RACH message, a cyclic shift of the RACH message, or combinations thereof. In some cases, the selected DL beam from the base station is different from a selected UL beam from the UE.

<FIG> shows a block diagram <NUM> of a base station synchronization manager <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The base station synchronization manager <NUM> may be an example of aspects of a base station synchronization manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>. The base station synchronization manager <NUM> may include synchronization signal component <NUM>, RACH component <NUM>, selected beam component <NUM>, quality measurement component <NUM>, UL beam component <NUM>, and correspondence management component <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

Synchronization signal component <NUM> may transmit a DL synchronization signal on one or more DL synchronization beams. RACH component <NUM> may receive, on at least one of a resource or a RACH waveform, a RACH message/scheduling request message/beam recovery or beam tracking message from a UE. Selected beam component <NUM> may identify, based on the resource and/or RACH waveform, a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE.

Quality measurement component <NUM> may measure a quality of the RACH message/scheduling request message/beam recovery or beam tracking message received on the set of UL beams. In some cases, measuring the quality of the RACH message/scheduling request message/beam recovery or beam tracking message includes: measuring one or more of a reference signal received power (RSRP), a received signal strength indicator (RSSI), a reference signal received quality (RSRQ), a signal to noise ratio (signal-to-noise ratio (SNR)), or a signal to interference plus noise ratio (SINR). UL beam component <NUM> may determine a selected UL beam for communications from the UE to the base station based on the quality.

Correspondence management component <NUM> may transmit an indication that correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station. In some cases, correspondence management component <NUM> may transmit the indication in a MIB or a SIB. In some cases, correspondence management component <NUM> may receive an indication that correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station and map DL beams used to transmit CSI-RSs to UL beams used to transmit SRSs or map UL beams used to transmit SRSs to DL beams used to transmit CSI-RSs. In some cases, correspondence management component <NUM> may receive an indication that correspondence is absent between the one or more DL synchronization beams from the base station and one or more UL receive beams at the base station and map DL beams used in DL beam training to UL beams used in UL beam training or map UL beams used in UL beam training to DL beams used in DL beam training.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Device <NUM> may be an example of or include the components of base station <NUM> as described above, for example, with reference to <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including base station synchronization manager <NUM>, processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, network communications manager <NUM>, and base station communications manager <NUM>. These components may be in electronic communication via one or more busses (e.g., bus <NUM>). Device <NUM> may communicate wirelessly with one or more UEs <NUM>.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting RACH conveyance of DL synchronization beam information for various DL-UL correspondence states).

Base station communications manager <NUM> may manage communications with other base station <NUM>, and may include a controller or scheduler for controlling communications with UEs <NUM> in cooperation with other base stations <NUM>. For example, the base station communications manager <NUM> may coordinate scheduling for transmissions to UEs <NUM> for various interference mitigation techniques such as beamforming or joint transmission. In some examples, base station communications manager <NUM> may provide an X2 interface within an Long Term Evolution (LTE)/LTE-A wireless communication network technology to provide communication between base stations <NUM>.

<FIG> shows a flowchart illustrating a method <NUM> for RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a UE synchronization manager as described with reference to <FIG>. In some examples, a UE <NUM> may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE <NUM> may perform aspects of the functions described below using special-purpose hardware.

At block <NUM> the UE <NUM> may receive a DL synchronization signal from a base station on one or more DL synchronization beams. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a synchronization signal component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may identify a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a beam selection component as described with reference to <FIG>.

At block <NUM> the UE <NUM> may transmit the RACH message/scheduling request message/beam recovery or beam tracking message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the selected DL beam. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a transmitter as described with reference to <FIG>.

At block <NUM> the UE <NUM> may transmit the RACH message/scheduling request message/beam recovery or beam tracking message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the selected DL beam, the resource or RACH waveform may also be selected based on an index of the selected DL beam. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a transmitter as described with reference to <FIG>.

<FIG> shows a flowchart illustrating a method <NUM> for RACH conveyance of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a base station <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a base station synchronization manager as described with reference to <FIG>. In some examples, a base station <NUM> may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station <NUM> may perform aspects of the functions described below using special-purpose hardware.

At block <NUM> the base station <NUM> may transmit a DL synchronization signal on one or more DL synchronization beams. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a synchronization signal component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may receive, on at least one of a resource or a RACH waveform, a RACH message/scheduling request message/beam recovery or beam tracking message from a UE. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a RACH component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may identify, based at least in part on the resource or the RACH waveform, a selected DL beam of the one or more DL synchronization beams for communications from the base station to the UE. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a selected beam component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may transmit one or more subsequent messages to the UE using the selected DL beam. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a transmitter as described with reference to <FIG>.

At block <NUM>, the base station <NUM> may receive, on at least one of a resource or a RACH waveform, a RACH message/scheduling request message/beam recovery or beam tracking message from a UE on a plurality of UL beams. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a RACH component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may measure a quality of the RACH message/scheduling request message/beam recovery or beam tracking message received on the plurality of UL beams. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a quality measurement component as described with reference to <FIG>.

At block <NUM> the base station <NUM> may determine or identify a selected UL beam, for example a preferred UL beam, for communications from the UE to the base station based at least in part on the measured quality of a RACH message. The base station may also transmit one or more subsequent messages to the UE conveying an indication of the preferred UL beam, for example in a RACH msg2. The one or more subsequent messages to the UE may include an identification or index of the preferred UL beam, for example an OCC index. The operations of block <NUM> may be performed according to the methods described with reference to <FIG>. In certain examples, aspects of the operations of block <NUM> may be performed by a UL beam component as described with reference to <FIG>.

In some cases, receiving the RACH message/scheduling request message/beam recovery or beam tracking message comprises: receiving the RACH message/scheduling request message/beam recovery or beam tracking message on a plurality of UL beams.

The terms "system" and "network" are often used interchangeably. A code division multiple access (CDMA) system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-<NUM>, IS-<NUM>, and IS-<NUM> standards. A time division multiple access (TDMA) system may implement a radio technology such as Global System for Mobile Communications (GSM).

An orthogonal frequency division multiple access (OFDMA) system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications system (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of Universal Mobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and Global System for Mobile communications (GSM) are described in documents from the organization named "3rd Generation Partnership Project" (3GPP). While aspects an LTE system may be described for purposes of example, and LTE terminology may be used in much of the description, the techniques described herein are applicable beyond LTE applications.

In LTE/LTE-A networks, including such networks described herein, the term evolved node B (eNB) may be generally used to describe the base stations. The wireless communications system or systems described herein may include a heterogeneous LTE/LTE-A network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB or base station may provide communication coverage for a macro cell, a small cell, or other types of cell. The term "cell" may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, eNodeB (eNB), Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area for a base station may be divided into sectors making up only a portion of the coverage area. The wireless communications system or systems described herein may include base stations of different types (e.g., macro or small cell base stations). The UEs described herein may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, relay base stations, and the like. There may be overlapping geographic coverage areas for different technologies.

A UE may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, relay base stations, and the like.

For example, an exemplary step that is described as "based on condition A" may be based on both a condition A and a condition B.

By way of example, and not limitation, non-transitory computer-readable media may comprise RAM, ROM, electrically erasable programmable read only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.

Claim 1:
A method for wireless communication at a user equipment (<NUM>), UE, comprising:
receiving (<NUM>; <NUM>; <NUM>) a downlink, DL, synchronization signal from a base station (<NUM>) on one or more DL beams (<NUM>), wherein each of the one or more DL beams are received in a respective symbol of a synchronisation subframe;
identifying (<NUM>; <NUM>; <NUM>) a selected DL beam of the one or more DL beams for communications from the base station to the UE based on at least a signal quality of the DL synchronisation signal received on the one or more DL beams;
receiving (<NUM>) an indication, from the base station, indicating whether beam correspondence between one or more DL beams (<NUM>) from the base station (<NUM>) and one or more uplink, UL, beams at the base station (<NUM>) is absent or present; and
transmitting (<NUM>; <NUM>; <NUM>), in response to the indication from the base station indicating that beam correspondence is absent, on a plurality of UL beams at the UE (<NUM>)a random access channel, RACH, message to the base station (<NUM>), using one of a resource or a RACH waveform, wherein the one of a resource or the RACH waveform is selected (<NUM>) based at least in part on the selected DL beam, and wherein the RACH message is transmitted in each symbol of the corresponding random access subframe.