Bandwidth agnostic tone mapping

Disclosed in this application are techniques to enabling and employing bandwidth agnostic tone mapping. Certain aspects of the present disclosure relate to methods and apparatus for mapping coded bits of a broadcast channel to tones of a symbol. Certain aspects of the present disclosure relate to methods and apparatus for mapping bits of a beamformed reference signal (BRS) signal to tones of a symbol. Other aspects, embodiments, and features are also claimed and described.

TECHNICAL FIELD

The technology discussed below generally relates to wireless communications and, more particularly, to techniques for mapping coded bits of a broadcast channel to tones in a subframe. Embodiments and aspects of the technology can enable and provide improved synchronization between components for wireless communication in a variety of network communication types, including mmWave systems.

INTRODUCTION

BRIEF SUMMARY OF SOME EXAMPLES

Cellular networks generally utilized synchronized efforts to enable communication. For example, in order for a terminal (or user equipment) to communicate with a base station in a cell (e.g., the coverage area of a base station), the terminal needs to be synchronized with the timing of the cell and also have certain system information. In some scenarios, networks use a broadcast channel to accomplish synchronized communication. Accordingly, embodiments and techniques described below enable generating synchronization signals to synchronize terminals with the cell timing and to generating and transmitting broadcast channels.

Certain aspects of the present disclosure provide a method for wireless communication by a base station. The method generally includes mapping coded bits of at least one of a physical broadcast channel (PBCH) or a beamformed reference signal (BRS) to tones of a symbol of a subframe. Some of the coded bits can be mapped to a same set of tones independent of system bandwidth and transmitting the at least one of the PBCH or BRS in the symbol according to the mapping.

Certain aspects of the present disclosure provide a method for wireless communication by a user equipment (UE). The method generally includes determining a mapping of coded bits of at least one of a physical broadcast channel (PBCH) or a beamformed reference signal (BRS) to tones of a symbol of a subframe. Some of the coded bits may be mapped to a same set of tones independent of system bandwidth and monitoring for the at least one of the PBCH or BRS in the symbol according to the mapping.

Aspects generally include methods, apparatus, systems, computer program products, computer-readable medium, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings. “LTE” refers generally to LTE, LTE-Advanced (LTE-A), LTE in an unlicensed spectrum (LTE-whitespace), etc.

DETAILED DESCRIPTION

According to aspects of the present disclosure, techniques are provided for mapping coded bits of a broadcast channel to tones in symbols of a subframe. In some cases, the mapping may be considered agnostic to system bandwidth. This advantageously can enable a receiving device to determine the tone locations regardless of the particular actual system bandwidth (which may not yet be known). In certain scenarios, wireless communication components (e.g., receiving devices, UEs, or terminals) can generate sequences for reference signals helping ability to decode certain channel measurements. This can aid to improve synchronization between communication components for follow-on wireless communication.

As will be described in greater detail below, a similar type of mapping may be applied to map a sequence of bits for a beam reference signal (BRS) to tones in a symbol. BRS may be transmitted in different directions, allowing a UE to provide feedback regarding a preferred direction. In some cases, BRS transmissions may be swept across different directions across symbols—or even within the same symbol.

FIG. 1is a diagram illustrating an example network architecture100in which aspects of the present disclosure may be practiced. While components of the network architecture may correspond to an LTE network architecture, aspects of the present disclosure may be utilized in other types of existing or future network architectures, such as mmWave network architectures used in 5G or so called new radio (NR) applications.

NR generally refers to a set of enhancements to the LTE mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation

Referring back to the example network architecture100ofFIG. 1, a base station (BS) (e.g., eNB106) selects an ESS sequence, applies a cyclic shift to the ESS sequence in the frequency domain based on the selected sequence and a symbol index in which the selected ESS sequence is to be transmitted. Further, the BS transmits the ESS sequence in a symbol corresponding to the symbol index to a UE (e.g., UE102).

A first core network (CN) (e.g., EPC110) associated with a first RAT (e.g., 4G or 5G), for example, receives first data from a first BS (e.g., eNB106) associated with the first RAT, the first data received at the first BS from a UE (e.g., UE102). The CN receives second data from a second CN (not shown) associated with a second RAT, the second RAT received at a second BS from the UE and communicated to the second CN by the second BS. The CN then aggregates the first and the second data.

The LTE network architecture100may be referred to as an Evolved Packet System (EPS)100. The EPS100may include one or more user equipment (UE)102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC)110, a Home Subscriber Server (HSS)120, and an Operator's IP Services122. The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. Exemplary other access networks may include an IP Multimedia Subsystem (IMS) PDN, Internet PDN, Administrative PDN (e.g., Provisioning PDN), carrier-specific PDN, operator-specific PDN, and/or GPS PDN. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB)106and other eNBs108. The eNB106provides user and control plane protocol terminations toward the UE102. The eNB106may be connected to the other eNBs108via an X2 interface (e.g., backhaul). The eNB106may also be referred to as a base station, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set, an access point, or some other suitable terminology. The eNB106may provide an access point to the EPC110for a UE102. Examples of UEs102include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a netbook, a smart book, an ultrabook, a drone, a robot, a sensor, a monitor, a meter, medical device, entertainment device, wearable, implantable device, or any other similar functioning device. The UE102may also be referred to by those skilled in the art 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.

The eNB106is connected by an S1 interface to the EPC110. The EPC110includes a Mobility Management Entity (MME)112, other MMEs114, a Serving Gateway116, and a Packet Data Network (PDN) Gateway118. The MME112is the control node that processes the signaling between the UE102and the EPC110. Generally, the MME112provides bearer and connection management. All user IP packets are transferred through the Serving Gateway116, which itself is connected to the PDN Gateway118. The PDN Gateway118provides UE IP address allocation as well as other functions. The PDN Gateway118is connected to the Operator's IP Services122. The Operator's IP Services122may include, for example, the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS (packet-switched) Streaming Service (PSS). In this manner, the UE102may be coupled to the PDN through the LTE network.

FIG. 2is a diagram illustrating an example of an access network200in an LTE network architecture in which aspects of the present disclosure may be practiced. For example, eNBs204and208may be configured to implement techniques for generating synchronization signals, in accordance with aspects of the present disclosure.

In this example, the access network200is divided into a number of cellular regions (cells)202. One or more lower power class eNBs208may have cellular regions210that overlap with one or more of the cells202. A lower power class eNB208may be referred to as a remote radio head (RRH). The lower power class eNB208may be a femto cell (e.g., home eNB (HeNB)), pico cell, or micro cell. The macro eNBs204are each assigned to a respective cell202and are configured to provide an access point to the EPC110for all the UEs206in the cells202. There is no centralized controller in this example of an access network200, but a centralized controller may be used in alternative configurations. The eNBs204are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway116. The network200may also include one or more relays (not shown). According to one application, a UE may serve as a relay.

In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR).FIG. 3is a diagram300illustrating an example of a DL frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames with indices of 0 through 9. Each sub-frame may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. Since each sub-frame is made up of 2 time slots, and thus 2 resource blocks, each sub-frame includes 14 OFDM symbols. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, as indicated as R302, R304, include DL reference signals (DL-RS). The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS)302and UE-specific RS (UE-RS)304. UE-RS304are transmitted only on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.

In LTE, in certain aspects, an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB. The primary and secondary synchronization signals may be sent in symbol periods 6 and 5, respectively, in each of subframes 0 and 5 of each radio frame with the normal cyclic prefix (CP). The synchronization signals may be used by UEs for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH may carry certain system information. In other wireless systems where this inventions are applied, an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB. The primary and secondary synchronization signals may be sent in plurality of symbol periods (e.g., in symbol periods), in each of synchronization subframe (e.g., subframes 0 and 25 of each radio frame with the normal cyclic prefix). The synchronization signals may be used by UEs for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in plurality of symbol periods of synchronization or other subframes. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe. The PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to 1, 2 or 3 and may change from subframe to subframe. M may also be equal to 4 for a small system bandwidth, e.g., with less than 10 resource blocks. The eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe. The PHICH may carry information to support hybrid automatic repeat request (HARQ). The PDCCH may carry information on resource allocation for UEs and control information for downlink channels. The eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data for UEs scheduled for data transmission on the downlink.

A number of resource elements may be available in each symbol period. Each resource element (RE) may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs). Each REG may include four resource elements in one symbol period. The PCFICH may occupy four REGs, which may be spaced approximately equally across frequency, in symbol period 0. The PHICH may occupy three REGs, which may be spread across frequency, in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong in symbol period 0 or may be spread in symbol periods 0, 1, and 2. The PDCCH may occupy 9, 18, 36, or 72 REGs, which may be selected from the available REGs, in the first M symbol periods, for example. Only certain combinations of REGs may be allowed for the PDCCH. In aspects of the present methods and apparatus, a subframe may include more than one PDCCH.

FIG. 4is a block diagram of an eNB410in communication with a UE450in an access network, in which aspects of the present disclosure may be practiced.

For example, a base station (BS) (e.g., eNB106) selects an ESS sequence, applies a cyclic shift to the ESS sequence in the frequency domain based on the selected sequence and a symbol index in which the selected ESS sequence is to be transmitted. Further, the BS transmits the ESS sequence in a symbol corresponding to the symbol index to a UE (e.g., UE102).

A UE (e.g., UE450), for example, receives the ESS sequence and based on the cyclical shift applied to the ESS sequence determines the symbol index of the symbol in which the ESS sequence was transmitted by the BS. Accordingly, the UE can determine the timing (symbol timing) of the BS to synchronize with the BS.

In the DL, upper layer packets from the core network are provided to a controller/processor475. The controller/processor475implements the functionality of the L2 layer, for example. In the DL, the controller/processor475provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE450based on various priority metrics. The controller/processor475is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE450.

At the UE450, each receiver454RX receives a signal through its respective antenna452. Each receiver454RX recovers information modulated onto an RF carrier and provides the information to the receiver (RX) processor456. The RX processor456implements various signal processing functions of the L1 layer, for example. The RX processor456performs spatial processing on the information to recover any spatial streams destined for the UE450. If multiple spatial streams are destined for the UE450, they may be combined by the RX processor456into a single OFDM symbol stream. The RX processor456then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB410. These soft decisions may be based on channel estimates computed by the channel estimator458. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB410on the physical channel. The data and control signals are then provided to the controller/processor459.

The controller/processor459implements the L2 layer, for example. The controller/processor459can be associated with a memory460that stores program codes and data. The memory460may be referred to as a computer-readable medium. In the UL, the controller/processor459provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink462, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink462for L3 processing. The controller/processor459is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.

In the UL, a data source467is used to provide upper layer packets to the controller/processor459, for example. The data source467represents all protocol layers above the L2 layer, for example. Similar to the functionality described in connection with the DL transmission by the eNB410, the controller/processor459implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB410, for example. The controller/processor459is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB410, for example.

Channel estimates derived by a channel estimator458from a reference signal or feedback transmitted by the eNB410may be used by the TX processor468to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor468are provided to different antenna452via separate transmitters454TX. Each transmitter454TX modulates an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB410in a manner similar to that described in connection with the receiver function at the UE450. Each receiver418RX receives a signal through its respective antenna420. Each receiver418RX recovers information modulated onto an RF carrier and provides the information to a RX processor470. The RX processor470may implement the L1 layer, for example.

The controller/processor475implements the L2 layer, for example. The controller/processor475can be associated with a memory476that stores program codes and data. The memory476may be referred to as a computer-readable medium. In the UL, the control/processor475provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE450. Upper layer packets from the controller/processor475may be provided to the core network. The controller/processor475is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. The controllers/processors475,459may direct the operations at the eNB410and the UE450, respectively.

In certain aspects, one or more of any of the components shown inFIG. 4may be employed to perform example operations700or800ofFIG. 7 or 8. The memory460and476may store data and program codes for the UE450and eNB410respectively, accessible and executable by one or more other components of the UE450and the eNB410.

As discussed above, a BS may generate and send a PSS and SSS for each cell assigned to the BS. A UE in the cell may receive these synchronization signals for cell detection and acquisition, meaning the UE may use these synchronization signals to synchronize with a timing of the BS. For example, as discussed with respect to LTE the PSS and SSS are always transmitted in particular symbol periods (e.g., 6 and 5, respectively) of particular subframes (e.g., 0 and 5) of each frame. The UE receiving such a PSS and SSS can synchronize to the symbol index level in such a system with the BS based on the received PSS and SSS. E.g., the UE can determine when the subframe starts.

Various components described above may be configured to perform operations described below. For example, TX processor416and controller/processor475may be configured to perform mapping operations described below with reference toFIG. 7, and to transmit signals according to the mapping via receiver transmitter(s)418. Similarly, RX processor456and/or controller/processor459may be configured to determine a mapping as described below with reference toFIG. 8, and to monitor for signals transmitted according to the mapping via receiver/transmitter(s)454.

Example Techniques for Bandwidth Agnostic Tone Mapping

According to aspects of the present disclosure, techniques are provided for mapping coded bits to tones in a bandwidth-agnostic manner. In other words, the mapping may result in coded bits being mapped to a same set of tones regardless of bandwidth. The same set of tones may be common to different available bandwidth configurations. The techniques may be used, for example, to map coded bits of a broadcast channel or a beamformed reference signal (BRS) to tones in symbols of a subframe. As noted above, the mapping may be considered agnostic to system bandwidth, meaning a receiving device may be able to determine the tone locations regardless of the particular actual system bandwidth. This may be advantageous, as a tone mapping that is agnostic to system bandwidth can allow a UE to know what tones to monitor for the broadcast channel before it knows the system bandwidth (which is typically provided in the broadcast channel).

For a UE to perform initial system access, it typically performs a procedure referred to as a cell search to identify a cell ID and/or symbol index of a potential target cell to access. The cell ID is typically identified by detecting primary synchronization signals (PSS) and secondary synchronization signals (SSS) transmitted by the cell base station.

As illustrated inFIG. 5, extended synchronization signals (ESS) may also be transmitted in each symbol, which may convey additional information. For example, a cyclic shift used in transmitting ESS may convey which symbol the ESS is transmitted in, which may help the UE know the boundaries of the synchronization subframe500.

As shown inFIG. 5, in some cases, PSS and SSS may be transmitted in each symbol of a synchronization subframe500. As part of this procedure, a UE decodes a broadcast channel, such as a physical broadcast channel (PBCH), to get additional system information. This additional information may include, for example, a system frame number (SFN), beam index, system bandwidth, and/or a random access channel (RACH) configuration. As noted above, at the cell search state, the UE may not know system bandwidth information (e.g., 80 or 100 MHz or higher tones) and other information (e.g., a number of antenna ports used for beamformed reference signal (BRS) transmission (e.g., 2, 4, or 8 antenna ports).

As illustrated inFIG. 5, PBCH and BRS may also be transmitted in each symbol of the synchronization subframe500. In some cases, the BRS may be transmitted in (“swept across”) different directions in different symbols.

For example, as illustrated inFIG. 6A, in a first symbol, BS sweeps four directions using four ports in a cell specific manner in the first symbol of the synchronization subframe. As illustrated inFIG. 6B, in a second symbol, the BS may sweep four different directions. These directions may be “coarse” beam directions and a UE may provide feedback regarding which of these directions is best (e.g., based on receive signal strength). Further, while beams inFIGS. 6A and 6Bare shown as adjacent for the purpose of illustration, in practice, beams transmitted during the same symbol may not actually be adjacent with each other.

BRS may help in determining and addressing issues related to path loss in millimeter wave (MMW) systems due to high carrier frequency and higher non-line-of-sight loss. Higher beamforming gain may be obtained in MMW because the wavelength of MMW band is small, making it possible to pack a higher number of antennas within a fixed array length. In other words, transmissions in MMW may be beamformed, i.e., directional, to mitigate higher path loss. To help select an optimal direction, the BS may transmit BRS by sweeping in all directions so that UE knows the beam ID (and may provide feedback of a corresponding beam ID based on results).

In some cases, it may be beneficial to operate with a smaller band (of overall system bandwidth) for cell search purposes. For example, a UE may search a smaller bandwidth to process its own cell's and neighboring PSS/SSS/ESS for power saving purpose. As another example, a UE may search for asynchronous base station (eNBs) deploying in indoor environment, which may have an impact on which Rx beam/subarray to use.

For certain existing systems, fixed resources may be used for transmitting certain signals. For example, for LTE systems, a center 6 resource blocks (RBs) may be used for PSS/SSS/CRS/PBCH, with additional cell specific reference signals (CRS) transmitted outside the center 6 RBs.

Again referring toFIG. 5, in some cases, PSS/SSS/ESS may be mapped to center RBs (e.g., 3×6 RBs), while BRS/PBCH may be mapped to other RBs. In one case, for example, this mapping may be at 13.5 MHz. In one or more examples, mapping additional BRS/PBCH can be provided in the rest of the RBs. For example, data tones that may be used for PBCH can be around 288 tones for a 100 MHz system. The remaining RBs may be used for BRS and DMRS for PBCH.

In certain cases, tone mapping of coded bits for PBCH may be from lower frequency to higher frequency (e.g., starting at the lowest tone index of system bandwidth to the highest tone index) and rate-matching around center 18 RBs and tones used for BRS and DMRS.

As noted above, however, this approach may present a challenge, as the actual tone locations depend on the actual system. Aspects of the present disclosure, however, provide tone mapping that is agnostic to system bandwidth.

FIG. 7illustrates example operations700for mapping coded bits of downlink transmissions in a manner that may be agnostic to system bandwidth. The operations700may be performed, for example, by a base station (BS).

The operations700begin, at702, by mapping a portion of coded bits of at least one of a physical broadcast channel (PBCH) or a beamformed reference signal (BRS) to tones of a symbol of a subframe in a bandwidth agnostic manner. In other words, at least a portion of the coded bits may be mapped to a same set of tones independent of system bandwidth. At704, the BS transmits the at least one of the PBCH or BRS in the symbol according to the mapping.

FIG. 8illustrates example operations800that may be considered complementary to operations700shown inFIG. 7. For example, operations800may be performed by a UE, for example, to process a downlink transmissions transmitted by a BS in accordance with operations700.

The operations800begin, at802, by determining a bandwidth agnostic mapping of coded bits of at least one of a PBCH or BRS to tones of a symbol of a subframe. At804, the UE monitors for (and decodes) the PBCH or BRS in the symbol according to the mapping.

While certain examples described below and shown in the Figures relate to bandwidth agnostic mapping of bits of a PBCH, those skilled in the art will recognize that the same or similar techniques may be used to map coded bits of other downlink transmissions, such as a BRS, in a bandwidth agnostic manner.

One or more additional aspects may be included in one or more cases. For example, in one or more cases, the coded bits of the PBCH may be mapped to at least one of: tones of the symbol from a first center tone to tones at a lower frequency, or tones of the symbol from a second center tone to tones at a higher frequency. In one or more cases, the mapping of coded bits of the PBCH to tones of the symbol from the first center tone to tones at the lower frequency may be different than the mapping of coded bits of the PBCH to tones of the symbol from the second center tone to tones at the higher frequency. The first and second center tones may define a boundary of a set of tones used for transmitting one or more synchronization signals.

For a first system bandwidth and a second system bandwidth greater than the first bandwidth, the coded bits may be mapped to a commons set of tones, and for the second system bandwidth, a repeated portion of the coded bits may mapped to a set of tones not included in the first bandwidth. In another case, for a first system bandwidth and a second system bandwidth greater than the first bandwidth, the coded bits may be mapped to a commons set of tones, and for the second system bandwidth, additional coded bits are mapped to a set of tones not included in the first bandwidth. The operations may further include transmitting beamformed reference signals (BRS) in tones of the symbol, each BRS transmitted in a different direction. PBCH may be transmitted in every symbol of the synchronization subframe. The base station transmits PBCH in different directions in different symbols of the synchronization subframe.

As illustrated inFIG. 9, in one possible PBCH tone mapping, coded bits of PBCH, d(0) to d(2M) may be mapped from lowest to highest frequency tones of the available system bandwidth. Unfortunately, in this tone mapping procedure, the UE needs to know the exact bandwidth to decode the PBCH signal. In contrast, the bandwidth agnostic tone mapping presented herein may start mapping from the boundaries of the center RBs outward, such that the starting tones (at least) are the same regardless of system bandwidth. In this manner, the tones for coded bit mapping for a first system bandwidth (BW X) may be contained in a second system bandwidth (BW Y, wherein X<Y). As will be described in greater detail below, in some cases, tone mapping for BRS sequences may also be bandwidth agonistic.

As shown inFIG. 9, the coded bits of the PBCH are mapped to tones of the symbol from a first center tone (e.g., a tone at the lower boundary of the center 18 RBs902) to tones at a lower frequency, to tones of the symbol from a second center tone (e.g., a tone at the upper boundary of the center 18 RBs902) to tones at a higher frequency, or both. In the example shown inFIG. 9, the same tones d(0)-d(M) are mapped in both directions. In some cases, however, the mapping of coded bits of the PBCH to tones of the symbol from the first center tone to tones at the lower frequency is different than the mapping of coded bits of the PBCH to tones of the symbol from the second center tone to tones at the higher frequency.

In some cases, for a wider bandwidth, a repeated portion of the coded bits are mapped to a set of tones not included in the narrower bandwidth. In this scenario, UEs are able to decode the PBCH signal as long as their bandwidth is greater than or equal to the narrower bandwidth. If UEs have higher bandwidth than the narrower bandwidth, the extra repetitions may provide a better coding rate to those UEs to decode the PBCH signal. As noted above, as an alternative, or in addition, beamformed reference signals (BRS) may also be transmitted using different tones of the symbol (e.g., with each BRS transmitted in a different direction).

In some cases, PBCH may be transmitted in every symbol of the synchronization subframe (e.g., with PBCH transmitted in different directions in different symbols of the synchronization subframe). As an alternative, or in addition, BRS may be transmitted in every symbol of the synchronization symbol (e.g., with BRS transmitted in different directions in different symbols of the synchronization subframe). In some cases, BRS sequences may be mapped per resource block (RB), for example, with each RB occupying a fixed number of tones (e.g., 12) and the sequence can be repeated throughout the entire component carrier, where each component carrier contains a fixed number of RBs (e.g. 100)

Using the mapping presented herein, even when system bandwidth for a carrier is unknown, the UE may know what tones to monitor for BRS sequences, and what tones to monitor for coded bits for PBCH and PBCH. As a result, the mapping proposed herein may help enable operation in a narrower bandwidth (relative to system bandwidth for a carrier) and data path to decode PBCH and BRS measurement.

One or more additional aspects may be included in one or more cases. For example, in one or more cases, the sequence of bits of the BRS may be mapped to at least one of: tones of the symbol from a first center tone to tones at a lower frequency, or tones of the symbol from a second center tone to tones at a higher frequency. In one or more cases, the mapping of the sequence of bits of the BRS to tones of the symbol from the first center tone to tones at the lower frequency may be different than the mapping of the sequence of bits of the BRS to tones of the symbol from the second center tone to tones at the higher frequency. The first and second center tones may define a boundary of a set of tones used for transmitting one or more synchronization signals.

For a first system bandwidth and a second system bandwidth greater than the first bandwidth, the sequence of bits of the BRS signal may be mapped to a common set of tones. For the second system bandwidth, a repeated portion of the sequence of bits of the BRS signal may be mapped to a set of tones not included in the first bandwidth. In one or more cases. The sequence of bits of BRS may be mapped per resource block (RB), each RB occupying a fixed number of tones. In one example, the fixed number of tones may be 12. In one or more cases, BRS may be transmitted in every symbol of the subframe. The base station may transmit BRS in different directions in different symbols of the subframe. In one or more examples, the operations may include decoding the BRS according to the determination.

Code Offset Across Multiple Sub-Frame

In some cases, coded bits of a broadcast channel, such as PBCH may be transmitted using resources across multiple sub-frames. For example, in some cases, PBCH payload may include 40 uncoded bits (e.g., 8 bit of system frame number, 16 bits of CRC, and 16 spare bits). In some cases, the spare bits may be used, for example, to transmit various information, such as a number of PCFICH symbols, system bandwidth, or the like. For a mm-wave system, such spare bits may be used to transmit system bandwidth, beam reference signal duration period, or system bandwidth.

Using resources across multiple subframes, a different (redundancy) version of the same coded bits may be sent. For example, every 10 ms the coded bits may be sent as a different redundancy version. Assuming a repetition value of 4, a new set of 40 uncoded bits may be transmitted after every 40 ms. As noted above, PBCH may include 8 bits of system frame number (SFN) and two additional bits may be used to convey a redundancy version. For example, these other 2 bits may come from transmitting different redundancy versions at different 10 ms duration. In this case, 8-bits of a 10-bit SFN field may be used to convey one of four different redundancy versions during 40 ms.

In this manner, an uncoded PBCH may be transformed into a set of coded bits, in the “bandwidth agnostic” manner described above. This set of coded bits may then get repeated a sufficient number of times for rate matching (e.g., repeated every 10 ms four times total). In this case, TBCC ⅓ coding could be used, such that 40 uncoded bits gets transformed to 120 coded bits. The rate matched and multiple repetitions of the coded bits may then get mapped to the region, for example, through QPSK modulation.

FIG. 10illustrates one example of transmitting redundant versions of PBCH using bandwidth agnostic mapping to resources across 4 different subframes. As illustrated, a different redundancy version (of the same PBCH payload) is sent every 10 ms. In the example, the four different redundancy versions are labeled d, d1, d2, and d3, with each having coded bits 0 to M−1.

FIGS. 11, 12, and 13illustrate how the redundancy versions may be related. For example,FIG. 11illustrates how bit mapping of redundancy version d1may relate to the bit mapping of d. As shown inFIG. 11, redundancy version d1is offset by a value K. Similarly,FIGS. 12 and 13illustrate how bit mappings of redundancy versions (RVs) d2and d3, respectively, relate to the bit mapping of d. InFIG. 12the redundancy version d2is shown offset by a value K′, while inFIG. 13redundancy version d3is shown being offset by a value K″.

One or more additional aspects may be included in one or more cases. For example, in one or more cases, coded bits of the PBCH may be mapped over a fixed number of resources across multiple subframes. The fixed number of resources may include a maximum allowed number of resources over one period of transmission. The maximum allowed number of resources may be determined by a maximum component carrier bandwidth. The maximum allowed number of resources can also, in part or in whole, be based on a predefined value. The mapping may include mapping coded bits of one period of PBCH transmission to a plurality of segments. In one or more examples, for each segment, coded bits of that segment may be mapped to a fixed starting offset regardless of available resource for the transmission. The fixed number of subframe resources may be dependent on at least one of system bandwidth or allowed bandwidth used for transmitting the PBCH.

According to one or more cases, first and second center tones may be adjacent to each other such that there may not be any gap between the first and second center tone that accommodate PSS, SSS, and ESS. Further, according to one or more aspects, synchronization signals and PBCH may be time division multiplexed.

For example,FIG. 14illustrates an example unified NR synchronization signal block design, in accordance with certain aspects of the present disclosure. As shown synchronization signals and the physical broadcast channel (PBCH) may be time-division multiplexed (TDM). In particular, the multiplexing ordering may be PBCH1402, PSS1404, SSS1406, and PBCH1408. Furthermore, the two PBCH symbols1402and1408within a SS block may be identical.

In one or more cases as shown inFIG. 14a synchronization signal block may consist of one OFDM symbol for PSS1404and one OFDM symbol for SSS1406. Furthermore, the synchronization signal block may contain two OFDM symbols for PBCH1402and1408which may be identical: one PBCH symbol1402in the beginning of SS block and the other1408in the end of SS block. Such two identical PBCH symbols1402and1408, which are separated by PSS1404and SSS1406, may allow a UE to refine the carrier frequency offset (CFO) estimation. More specifically, the UE may coarsely estimate the CFO based on synchronization signals and further refine the estimate by two looks of PBCH without decoding PBCH.

One benefit of the TDM design is that the SSS may be used as the reference for channel estimation of the PBCH symbols. In order to provide this benefit, the SSS is transmitted from the same antenna ports as PBCH. According to one or more cases, the specific TDM design may consists of 2 PBCH symbols transmitted at the beginning and the end of a SS block. Further the signal transmitted within these two sub-symbols may be the same (e.g. same redundancy version). This repeating structure may be used to provide a finer frequency offset estimation, without the UE having to decode PBCH first. Note that in some scenarios even better estimation can be achieved (especially at low SNR) after successful PBCH decoding, if the UE uses regenerated PBCH symbols.

Given this information, a UE may attempt to decode PBCH using different redundancy versions at different durations of 10 ms. The UE may then perform coherent combining after de-offsetting each different RVs. The UE may also know the 40 ms boundary (e.g., after at most observing for 70 ms duration) and after decoding PBCH transmitted during four subsequent 10 ms durations that contain the same 8 bit SFN. In other words, a change in SFN indicates a new set of coded bits for PBCH. It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase, for example, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, for example the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).