Patent Description:
As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP), a radio head, a transmit receive point (TRP), a <NUM> BS, a <NUM> Node B, and/or the like.

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless communication devices to communicate on a municipal, national, regional, and even global level. <NUM>, which may also be referred to as New radio (NR), is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). <NUM> 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 OFDM with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL), using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread ODFM (DFT-s-OFDM)) on the uplink (DL), as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and <NUM> technologies.

At times, a UE may need to perform an initial access (or initial acquisition) procedure to gain access to a wireless network. As part of the initial access procedure, the UE may need to search for a synchronization channel transmitted by a network access device, such as a base station, of the wireless network. In some cases, the UE may need to receive multiple repetitions of the synchronization channel (e.g., a PSS and/or an SSS) in order to perform the initial access procedure. For example, a CE and/or cost-reduced UE may need to receive multiple repetitions of the synchronization channel in order to perform the initial access procedure, while a legacy UE (e.g., a Long Term Evolution (LTE) UE, a MuLTEfire (MF) UE, and/or the like) may need to receive a single instance of the synchronization channel (e.g., as defined in a legacy PSS/SSS configuration) in order to perform the initial access procedure. However, in a case where the CE and/or cost-reduced UEs coexist with legacy UEs, the repetitions of the synchronization channel (needed by the CE and/or the cost-reduced UEs) should not interfere with operation of the legacy UEs. After performing the initial access procedure, a given UE (e.g., a CE and/or cost-reduced UE, a LTE UE, a MF UE, and/or the like) also may acquire various items of system information, such as information contained in a master information block (MIB) or one or more system information blocks (e.g., SIB1, SIB2, etc.) that may be transmitted in a physical broadcast channel (PBCH) transmission from a base station.

<CIT> discloses a measurement subframe structure that can be used to obtain measurements for a UE. The measurement subframe structure can be dedicatedly used for obtaining measurements (e.g. for coverage extension purposes), and the measurement subframe structure can be associated with a defined periodicity.

The described techniques relate to improved methods, systems, devices, or apparatuses that support a legacy compatible PSS/SSS design for CE and cost-reduced UEs. As described above, in some cases, a CE and/or cost-reduced UE may coexist with a legacy UE (e.g., the CE and/or cost-reduced UE may use a same frequency band as the legacy UE). However, since the CE and/or cost-reduced UE may need to receive multiple instances of a PSS and/or a SSS associated with performing an initial access procedure, repetitions of the PSS/SSS are needed, and these repetitions should not interfere with operation of the legacy UEs configured to search for a single instance of the PSS/SSS (e.g., in a first subframe of a frame).

One technique to address this issue is to introduce new (i.e., different) PSS/SSS sequences for use by the CE and/or cost-reduced UEs. In such a case, legacy UEs would not latch on to the new PSS/SSS repetitions and, thus, would be capable of performing initial access using the (legacy) PSS/SSS. However, introduction of new PSS/SSS sequences may cause a number of cross correlations, performed by the CE and/or cost-reduced UEs in association with receiving the PSS/SSS, to be increased (e.g., since a given CE and/or cost-reduced UE would need to perform cross correlation with the legacy PSS/SSS sequences for all timing hypotheses, as well as with the new PSS/SSS sequences for all timing hypotheses), thereby increasing (e.g., doubling) complexity at the CE and/or cost-reduced UE. Since CE and/or cost-reduced UEs are designed to be low cost (e.g., as compared to a legacy LTE UE or a MF UE), the number of cross correlations should be minimized, thereby rendering inclusion of new PSS/SSS sequences an undesirable solution.

Generally, aspects described herein provide techniques and apparatuses for a legacy compatible PSS/SSS design for CE and cost-reduced UEs according to the appended claims. The legacy compatible PSS/SS design for CE and cost-reduced UEs includes repetition of the PSS/SSS sequence in multiple subframes of a frame (e.g., within discovery reference signal (DRS) measurement timing configuration (DMTC) windows in each of the multiple subframes) where, in each repetition of the PSS/SSS sequence, the location of the PSS is swapped with the location of the SSS as compared to a legacy design.

For example, in the legacy design, PSS/SSS is included in a first subframe of a frame, and the SSS is one symbol before the PSS. According to the legacy compatible PSS/SSS design for CE and/or cost-reduced UEs, described herein, the PSS/SSS (i.e., the same sequences) may be included in multiple subframes of the frame (e.g., the first subframe, a second subframe of the frame, an Mth subframe of the frame), and the SSS is after the PSS (e.g., rather than before the PSS). This "swapping" of the PSS and SSS prevents operation of legacy UEs from being impacted (e.g., the swapped PSS/SSS would fail SSS detection at the legacy UEs and would be ignored), while allowing CE and/or cost-reduced UEs to coexist with the legacy UEs in the same frequency band.

According to the invention, a method, a user equipment, a base station, an apparatus, and a computer program product are provided according to the appended claims.

The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure, without departing from the scope of the appended claims.

It is noted that while aspects may be described herein using terminology commonly associated with <NUM> and/or <NUM> wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as <NUM> and later, including <NUM> technologies.

Wireless communications systems as described herein may be configured to configure and transmit synchronization signals (e.g., PSS, SSS, and/or the like) within subframes of a frame to aid a UE (e.g., a CE and/or cost-reduced UE, a legacy UE, a MF UE, and/or the like) in initial acquisition and communication with a base station. As described herein, In some examples, the UE may process the synchronization signals to obtain symbol timing and subframe timing of a base station for acquiring reference signal transmissions for decoding of a channel.

Detecting of PSS timing and initial frequency offset correction are bottlenecks that lengthen the amount of time for a UE to perform initial acquisition. In conventional solutions, a base station may transmit subframes transporting PSS and SSS within DMTC windows that occur periodically (e.g., every <NUM>, <NUM>, or <NUM> milliseconds). As described above, in a legacy solution, the PSS and SSS are transmitted only once within a DMTC periodicity, and the PSS/SSS is found only within the first <NUM> milliseconds (e.g., <NUM> bits of subframe information) of the DMTC window.

As described above, in some cases, a CE and/or cost-reduced UE may coexist with a legacy UE. However, since the CE and/or cost-reduced UE may need to receive multiple instances of a PSS and/or a SSS associated with performing an initial access procedure, repetitions of the PSS/SSS are needed, and these repetitions should not interfere with operation of the legacy UEs configured to search for a single instance of the PSS/SSS (e.g., in a first subframe of a frame).

Generally, aspects described herein provide techniques and apparatuses for a legacy compatible PSS/SSS design for CE and cost-reduced UEs. In some aspects, the legacy compatible PSS/SS design for CE and cost-reduced UEs includes repetition of the PSS/SSS sequence in multiple subframes of a frame (e.g., within DMTC windows in each of the multiple subframes) where, in each repetition of the PSS/SSS sequence, the location of the PSS is swapped with the location of the SSS as compared to a legacy design. This "swapping" of the PSS and SSS prevents operation of legacy UEs from being impacted (e.g., the swapped PSS/SSS would fail SS detection at the legacy UEs and would be ignored), while allowing CE and/or cost-reduced UEs to coexist with the legacy UEs in the same frequency band.

Aspects of the disclosure are initially described in the context of a wireless communications system. The wireless communications system may provide techniques and apparatuses for a legacy compatible PSS/SSS design for CE and cost-reduced UEs. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to synchronization for wideband coverage enhancement.

<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 a Long Term Evolution (LTE), LTE-Advanced (LTE-A) network, or a New Radio (NR) network (sometimes referred to as a <NUM> network). In some cases, wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (i.e., mission critical) communications, low latency communications, and communications with cost-reduced and low-complexity devices. In some aspects, the base station <NUM>-a may transmit a PSS and a SSS in a first set of symbols of a first subframe of a frame, wherein, within the first set of symbols of the first subframe, the SSS is transmitted in a symbol that is prior to a symbol of the first subframe in which the PSS is transmitted; and transmit the PSS and the SSS in a first set of symbols of a second subframe of the frame and in a second set of symbols of the second subframe, wherein, within the first set of symbols of the second subframe and within the second set of symbols of the second subframe, the SSS is transmitted in a symbol that is subsequent to a symbol in which the PSS is transmitted, as described herein.

Each base station <NUM> may provide communication coverage for a respective geographic coverage area <NUM>. Control information and data may be multiplexed on an uplink channel or downlink according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information transmitted during a transmission time interval (TTI) of a downlink channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region and one or more UE-specific control regions).

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, and/or the like.

Some UEs <NUM>, such as MTC or IoT devices, may be CE, cost-reduced, or low complexity devices, and may provide for automated communication between machines, i.e., Machine-to-Machine (M2M) communication.

In some cases, an MTC device may operate using half-duplex (one-way) communications at a reduced peak rate. MTC devices may also be configured to enter a power saving "deep sleep" mode when not engaging in active communications. In some cases, MTC or IoT devices may be designed to support mission critical functions and wireless communications system may be configured to provide ultra-reliable communications for these functions.

In some examples, base stations <NUM> may be macro cells, small cells, hot spots, and/or the like.

At least some of the network devices, such as base station <NUM> may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with a number of UEs <NUM> through a number of other access network transmission entities, each of which may be an example of a smart radio head, or a transmission/reception point (TRP).

Wireless communications system <NUM> may operate in an ultra-high frequency (UHF) frequency region using frequency bands from <NUM> to <NUM> (<NUM>), although some networks (e.g., a wireless local area network (WLAN)) 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 communications 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.

Thus, wireless communications system <NUM> may support millimeter wave (mmW) communications between UEs <NUM> and base stations <NUM>. Devices operating in mmW or EHF bands may have multiple antennas to allow beamforming. That is, a base station <NUM> may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE <NUM>. Beamforming (which may also be referred to as spatial filtering or directional transmission) is a signal processing technique that may be used at a transmitter (e.g., a base station <NUM>) to shape and/or steer an overall antenna beam in the direction of a target receiver (e.g., a UE <NUM>). This may be achieved by combining elements in an antenna array in such a way that transmitted signals at particular angles experience constructive interference while others experience destructive interference.

Multiple-input multiple-output (MIMO) wireless systems use a transmission scheme between a transmitter (e.g., a base station <NUM>) and a receiver (e.g., a UE <NUM>), where both transmitter and receiver are equipped with multiple antennas. Some portions of wireless communications system <NUM> may use beamforming. For example, base station <NUM> may have an antenna array with a number of rows and columns of antenna ports that the base station <NUM> may use for beamforming in its communication with UE <NUM>. Signals may be transmitted multiple times in different directions (e.g., each transmission may be beamformed differently). A mmW receiver (e.g., a UE <NUM>) may try multiple beams (e.g., antenna subarrays) while receiving the synchronization signals.

In some cases, the antennas of a base station <NUM> or UE <NUM> may be located within one or more antenna arrays, which may support beamforming or MIMO operation. 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>.

The MAC layer may also use Hybrid ARQ (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE <NUM> and a network device, base station <NUM>, or core network <NUM> supporting radio bearers for user plane data.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit (which may be a sampling period of Ts = <NUM>/<NUM>,<NUM>,<NUM> seconds). Time resources may be organized according to radio frames of length of <NUM> (Tf = 307200Ts), which may be identified by a system frame number (SFN) ranging from <NUM> to <NUM>. Each frame may include ten <NUM> subframes numbered from <NUM> to <NUM>. A subframe may be further divided into two. <NUM> slots, each of which contains <NUM> or <NUM> modulation symbol periods (depending on the length of the cyclic prefix prepended to each symbol). Excluding the cyclic prefix, each symbol contains <NUM> sample periods. In some cases the subframe may be the smallest scheduling unit, also known as a TTI. In other cases, a TTI may be shorter than a subframe or may be dynamically selected (e.g., in short TTI bursts or in selected component carriers using short TTIs).

A resource element may consist of one symbol period and one subcarrier (e.g., a <NUM> frequency range). A resource block may contain <NUM> consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, <NUM> consecutive OFDM symbols in the time domain (<NUM> slot), or <NUM> resource elements. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of symbols that may be selected during each symbol period). Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate may be.

Wireless communications system <NUM> may support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A carrier may also be referred to as a component carrier (CC), a layer, a channel, etc. The terms "carrier," "component carrier," "cell," and "channel" may be used interchangeably herein. A UE <NUM> may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation.

An eCC may be characterized by one or more features including: wider bandwidth, shorter symbol duration, shorter TTIs, and modified control channel configuration. An eCC may also be configured for use in unlicensed spectrum or shared spectrum (where more than one operator is allowed to use the spectrum). An eCC characterized by wide bandwidth may include one or more segments that may be utilized by UEs <NUM> that are not capable of monitoring the whole bandwidth or prefer to use a limited bandwidth (e.g., to conserve power).

A shorter symbol duration is associated with increased subcarrier spacing. A device, such as a UE <NUM> or base station <NUM>, utilizing eCCs may transmit wideband signals (e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc.) at reduced symbol durations (e.g., <NUM> microseconds). A TTI in eCC may consist of one or multiple symbols. In some cases, the TTI duration (that is, the number of symbols in a TTI) may be variable.

A shared radio frequency spectrum band may be utilized in an NR shared spectrum system. For example, an NR shared spectrum may utilize any combination of licensed, shared, and unlicensed spectrums, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across frequency) and horizontal (e.g., across time) sharing of resources.

For example, wireless communications system <NUM> may employ LTE License Assisted Access (LTE-LAA) or LTE Unlicensed (LTE U) radio access technology or NR technology in an unlicensed band such as the <NUM> Industrial, Scientific, and Medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations <NUM> and UEs <NUM> may employ listen-before-talk (LBT) procedures to ensure the channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a CA configuration in conjunction with CCs operating in a licensed band. Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, or both. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD), time division duplexing (TDD) or a combination of both.

<FIG> illustrates an example of a wireless communications system <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with various aspects of the present disclosure. Wireless communications system <NUM> includes base station <NUM>-a and UE <NUM>-a, which may be examples of aspects of the corresponding devices as described above with reference to <FIG>. In the example of <FIG>, the wireless communications system <NUM> may operate according to a radio access technology (RAT) such as a LTE, <NUM>, or new radio (NR) RAT, although techniques described herein may be applied to any RAT and to systems that may concurrently use two or more different RATs.

Base station <NUM>-a may communicate with UE <NUM>-a over a downlink carrier <NUM> and an uplink carrier <NUM>. In some cases, base station <NUM>-a may transmit frames <NUM> in allocated time and frequency resources using the downlink carrier <NUM>. The transmitted frames <NUM> may include synchronization signals that may be used by UE <NUM>-a for cell acquisition. In some cases, base station <NUM>-a may transmit using mmW frequencies.

<FIG> illustrates an example of a frame structure <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with various aspects of the present disclosure. The transmission timeline in the downlink may be partitioned into units of radio frames. Each radio frame may have a defined duration (e.g., <NUM> milliseconds (ms)) and may be partitioned into a defined number of subframes having corresponding indices (e.g., <NUM> subframes <NUM> with indices of <NUM> through <NUM>). Each subframe <NUM> may include two slots. Each radio frame <NUM> may include <NUM> slots with indices of <NUM> through <NUM>. Each slot may include L symbol periods <NUM>, e.g., L=<NUM> symbol periods <NUM> for a normal cyclic prefix (as shown in <FIG>) or L=<NUM> symbol periods <NUM> for an extended cyclic prefix. The <NUM> symbol periods <NUM> in each subframe may be assigned indices of <NUM> through <NUM>-<NUM>. The available time and frequency resources may be partitioned into resource blocks. Each resource block may cover N subcarriers (e.g., <NUM> subcarriers) in one slot. 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. In some cases, a DMTC window may be defined within a subframe that may be used to transport PSS, SSS, or both.

<FIG> illustrates an example of a process flowchart <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with various aspects of the present disclosure. In flowchart <NUM>, a base station <NUM>-a may transmit frames including synchronization signals which the UE <NUM>-a may use to obtain symbol and subframe timing for cell acquisition.

At <NUM>, the base station <NUM>-a may configure synchronization signals for transmission in a frame.

In an example, the synchronization signals may include a PSS sequence and a SSS (e.g., a SSS generated by the base station <NUM>-a). To enable robust PSS detection, the PSS may be a single sequence. In some examples, the base station <NUM>-a may transmit the PSS and SSS around a center frequency of a system bandwidth allocated for transmitting the frames <NUM>. Additional aspects of configuring PSS and SSS are described below in connection with <FIG>.

At <NUM>, the base station <NUM>-a may transmit frames <NUM> including the PSS and SSS. In some aspects, in order to implement a legacy compatible PSS/SSS design, the base station <NUM>-a may transmit the PSS and the SSS in a first set of symbols of a first subframe of a frame <NUM>, wherein, within the first set of symbols of the first subframe, the SSS is transmitted in a symbol that is before (e.g., prior to) a symbol of the first subframe in which the PSS is transmitted. Further, the base station <NUM>-a may transmit the PSS and the SSS in a first set of symbols of a second subframe of the frame <NUM> and in a second set of symbols of the second subframe, wherein, within the first set of symbols of the second subframe and within the second set of symbols of the second subframe, the SSS is transmitted in a symbol that is after (e.g., subsequent to) a symbol in which the PSS is transmitted. In some aspects, base station <NUM>-a may repeat this "swapped" transmission of the PSS/SSS in additional subframes of the frame <NUM>.

At <NUM>, the UE <NUM>-a may use frames <NUM> to initiate cell acquisition. In an example, the UE <NUM>-a may be powered on and begin searching for a cell with which to connect.

At <NUM>, the UE <NUM>-a may perform cross-correlation and auto-correlation to detect the PSS and to determine symbol timing of symbol periods of subframes transmitted by the base station <NUM>. The symbol timing may enable the UE <NUM>-a to detect the boundaries of each symbol within a frame <NUM>.

At <NUM>, the UE <NUM>-a may use the symbol timing to generate a SSS from a signal received from the base station, and determine subframe timing based on the SSS.

When the swapped PSS/SSS is repetitively transmitted, as described herein, a CE and/or cost-reduced UE <NUM>-a may be capable of detecting the PSS and determining the symbol timing and generating the SSS, while a legacy UE <NUM>-a may ignore these swapped repetitions, thereby allowing the CE and/or cost-reduced UE <NUM>-a and the legacy UE <NUM>-a to coexist in a same frequency band.

At <NUM>, the UE <NUM>-a may determine a subframe offset from the SSS, and determine a scrambling rule for a reference signal based on the subframe offset. In some examples, a reference signal may be a discovery reference signal (DRS), a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS), and/or the like.

At <NUM>, the UE <NUM>-a may descramble the reference signal using the scrambling rule, and decode a channel of the frame <NUM> using the descrambled reference signal. At <NUM>, the UE <NUM>-a may complete cell acquisition and exchange traffic with the base station <NUM>-a using the symbol and subframe timing.

<FIG> illustrates an example diagram <NUM> of subframes that support a legacy compatible PSS/SSS design for CE and cost-reduced UEs, in accordance with various aspects of the present disclosure. In example diagram <NUM>, time is depicted from left to right, and frequency is depicted from top to bottom. Base station <NUM>-a may allocate time and frequency resources for frame transmission.

In example diagram <NUM>, channel bandwidth <NUM> spans a portion of available frequencies, and OFDM symbols <NUM> to <NUM> of each subframe <NUM>-<NUM> to <NUM>-M within the bandwidth <NUM> are labeled across the top of the allocated resources. As discussed above, the PSS and the SSS may be transported on R sub-carriers <NUM> centered within the bandwidth <NUM>. Each of the R sub-carriers <NUM> may be offset by one another in frequency (e.g., <NUM> between each subcarrier). As shown in example diagram <NUM>, to provide a legacy compatible PSS/SSS design for CE and/or cost-reduced UEs, the base station <NUM>-a may transmit the PSS within a set of consecutive subframes (e.g., within symbol <NUM> and symbol <NUM> of subframe <NUM>-<NUM>, within symbol <NUM> and symbol <NUM> of each of subframes <NUM>-<NUM> through <NUM>-M). For example, if R = <NUM>, and the PSS sequence p may be a ZC sequence having a length of <NUM>, the <NUM> complex numbers of the ZC sequence may be mapped to <NUM> sub-carriers centered within the bandwidth <NUM>. As described above, the ZC sequence may be selected based at least in part on a cell identifier associated with the base station <NUM>-a (e.g., one of the three ZC sequences may be selected). The same R sub-carriers <NUM> may also be used to transport SSS (e.g., and PBCH or PBCH extension (PBCH Ex)) in subframes <NUM>-<NUM> through <NUM>-M. For example, to provide a legacy compatible PSS/SSS design for CE and/or cost-reduced UEs, the base station <NUM>-a may transmit the SSS within the set of consecutive subframes (e.g., within symbol <NUM> and symbol <NUM> of subframe <NUM>-<NUM>, within symbol <NUM> and symbol <NUM> of each of subframes <NUM>-<NUM> through <NUM>-M).

The unlabeled portions of the time and frequency resources of subframes <NUM>-<NUM> to <NUM>-M may be used to transport other information, such as, for example, legacy DRS, MF <NUM> ePSS, MF <NUM> eSSS, legacy Physical downlink Control Channel (PDCCH), SIB, MF SIB, PDCCH for SIB, and/or the like.

As shown in example diagram <NUM>, in subframe <NUM>-<NUM> (e.g., in a first DMTC window) the PSS sequence may be transmitted after the SSS sequence (e.g., in symbols <NUM> and <NUM>, respectively) according to a legacy design. As further shown, in some aspects, the PSS may also be repeated in subframe <NUM>-<NUM> and, in this repetition, the PSS sequence is transmitted before the SSS sequence (e.g., in symbols <NUM> and <NUM>, respectively). In other words, in some aspects the swapped PSS/SSS may be transmitted in subframe <NUM>-<NUM>. In some aspects, the swapped PSS/SSS may be repeated one or more additional times within subframe <NUM>-<NUM>. In some aspects, the swapped PSS/SSS can be transmitted before and/or after the legacy (i.e., non-swapped) PSS/SSS.

As further shown in example diagram <NUM>, in one or more other subframes of the frame, such as subframes <NUM>-<NUM> through <NUM>-M (e.g., in a second DMTC window through an Mth DMTC window), the swapped PSS and the SSS may be repeated one or more times in a given subframe. For example, as shown in subframe <NUM>-<NUM>, the swapped PSS/SSS (i.e., the PSS sequence followed by the SSS sequence) may be repeated (e.g., the PSS may be transmitted in symbol <NUM> and symbol <NUM>, while the SSS may be transmitted in symbol <NUM> and symbol <NUM>). In some aspects, the swapped PSS/SSS may be repeated one or more additional times within any of subframes <NUM>-<NUM> through <NUM>-M.

In example diagram <NUM>, the PSS is repetitively transmitted before (e.g., prior to) the SSS, as described above. In some aspects, repetitively transmitting the PSS before the SSS (e.g., rather than after the SSS as in a legacy design) prevents a legacy UE from attempting initial access based on the repetitions, thereby conserving battery power and/or processor resources of the legacy UE, while preventing an impact on an initial access procedure to be performed by the legacy UE. For example, since no SSS is present before the PSS in the swapped PSS/SSS transmission, the legacy UE will stop a synchronization procedure and/or not attempt to decode a PBCH associated with these transmission, which conserves battery power and/or processor resources of the legacy UE. Further, the repetitive transmission of the swapped PSS/SSS allows a CE and/or cost-reduced UE to receive repetitions of the PSS and the SSS that may be needed in order to perform initial access. In this way, the legacy UE and the CE and/or cost-reduced UE may coexist in a same frequency band.

A PSS detector of the UE <NUM>-a may detect a PSS within a subframe <NUM> for determining symbol timing of the symbol periods and for determining a cell identifier within a cell identifier group of base station <NUM>.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a user equipment (UE) <NUM> as described herein. Wireless device <NUM> may include receiver <NUM>, UE communications 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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs, etc.). For example, receiver <NUM> may receive a PSS and/or a SSS based at least in part on which wireless device <NUM> may synchronize with a base station, as described herein. Information may be communicated between other components of the device. For example, information <NUM> may be communicated between receiver <NUM> and UE communications manager <NUM>. Information <NUM> may include, for example, information associated with the PSS and/or the SSS and/or information or instructions associated with receiving the PSS and/or the SSS. The receiver <NUM> may be an example of aspects of the transceiver <NUM> described with reference to <FIG>. The receiver <NUM> may utilize a single antenna or a set of antennas.

UE communications manager <NUM> may be an example of aspects of the UE communications manager <NUM> described with reference to <FIG>.

UE communications manager <NUM> and/or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the UE communications manager <NUM> and/or at least some of its various sub-components may be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. The UE communications manager <NUM> and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, UE communications manager <NUM> and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, UE communications manager <NUM> and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

UE communications manager <NUM> may receive, by a UE, a signal from a base station, generate a set of symbols from the signal based on a timing hypothesis, cross-correlate the set of symbols with a sequence to generate a set of cross-correlation symbols, auto-correlate the cross-correlation symbols to generate a set of auto-correlation values, and synchronize the UE with the base station based on the auto-correlation values. The UE communications manager <NUM> may also generate, by a UE, a secondary synchronization signal (SSS) sequence based on a signal transmitted by a base station, determine, by the UE, a cell identifier group of a base station based on the SSS sequence, and synchronize the UE with the base station based on the SSS sequence and the cell identifier group. Information <NUM> may be communicated between UE communications manager <NUM> and transmitter <NUM>. Information <NUM> may include, for example, information associated with transmitting a signal associated with synchronizing with the base station based at least in part on a received PSS and/or SSS.

For example, transmitter <NUM> may transmit a signal, generated by UE communications manager <NUM>, associated with synchronizing with the base station based at least in part on a received PSS and/or SSS.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with 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>. Wireless device <NUM> may include receiver <NUM>, UE communications 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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs, 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>. The receiver <NUM> may utilize a single antenna or a set of antennas.

UE communications manager <NUM> may also include signal processor <NUM>, symbol generator <NUM>, cross-correlator <NUM>, auto-correlator <NUM>, symbol timing determiner <NUM>, cell identifier determiner <NUM>, and subframe timing determiner <NUM>.

Signal processor <NUM> may receive a signal from a base station.

Symbol generator <NUM> may generate a set of symbols from the signal based on a timing hypothesis, and generate a SSS sequence from the signal based on synchronizing the UE with the base station. In some cases, symbol generator <NUM> may generate a SSS sequence based on a signal transmitted by a base station, and receive a primary synchronization signal from a base station. In some cases, generating the set of symbols from the signal based on the timing hypothesis includes: partitioning, for each frequency bin of a set of frequency bins, a defined number of symbols from the signal into a defined number of column vectors. In some cases, the SSS sequence is generated by mapping a set of codewords generated by a shortened Reed Solomon encoder using a Galois Field alphabet and a generator polynomial to the first index. In some cases, the set of symbols from the signal are generated within a time interval corresponding to a duration of one or more subframes of a frame. In some cases, generating the SSS sequence includes: mapping a set of codewords generated by an encoder operating using a Galois Field alphabet to a root and cyclic shift. In some cases, each of the set of codewords is generated by the encoder using a generator polynomial.

Cross-correlator <NUM> may cross-correlate the set of symbols with a sequence to generate a set of cross-correlation symbols. In some cases, the sequence is based on a set of synchronization symbols and a cover code.

Auto-correlator <NUM> may auto-correlate the cross-correlation symbols to generate a set of auto-correlation values.

Symbol timing determiner <NUM> may synchronize the UE with the base station based on the auto-correlation values. In some cases, synchronizing the UE with the base station includes selecting one of the first timing hypothesis or the second timing hypothesis as a symbol timing of the base station. Symbol timing determiner <NUM> establish a symbol timing based on the primary synchronization signal, where generating the SSS sequence is based on the symbol timing.

Cell identifier determiner <NUM> may determine a physical cell identity of the base station based on the SSS sequence (e.g., based on a cell identifier group associated with the SSS) and the PSS sequence (e.g., based on a cell identifier associated with the PSS).

Subframe timing determiner <NUM> may determine subframe timing based on the SSS sequence, synchronize the UE with the base station based on the SSS sequence and the physical cell identity, and determine a subframe offset for a reference signal based on the SSS sequence. In some cases, synchronizing the UE with the base station includes determining a subframe timing of the base station based on the SSS sequence.

<FIG> shows a block diagram <NUM> of a UE communications manager <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with aspects of the present disclosure. The UE communications manager <NUM> may be an example of aspects of a UE communications manager <NUM>, a UE communications manager <NUM>, or a UE communications manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>. The UE communications manager <NUM> may include signal processor <NUM>, symbol generator <NUM>, cross-correlator <NUM>, auto-correlator <NUM>, symbol timing determiner <NUM>, cell identifier determiner <NUM>, subframe timing determiner <NUM>, cost determiner <NUM>, frequency estimator <NUM>, mapper <NUM>, offset determiner <NUM>, scrambling rule determiner <NUM>, decoder <NUM>, and descrambler <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

Symbol generator <NUM> may generate a set of symbols from the signal based on a timing hypothesis, and generate a SSS sequence from the signal based on synchronizing the UE with the base station. In some cases, symbol generator <NUM> may generate a SSS sequence based on a signal transmitted by a base station, and receive a primary synchronization signal from a base station. In some cases, generating the set of symbols from the signal based on the timing hypothesis includes partitioning, for each frequency bin of a set of frequency bins, a defined number of symbols from the signal into a defined number of column vectors. In some cases, the SSS sequence is generated by mapping a set of codewords generated by a shortened Reed Solomon encoder using a Galois Field alphabet and a generator polynomial to the first index. In some cases, the set of symbols from the signal are generated within a time interval corresponding to a duration of one or more subframes of a frame. In some cases, generating the SSS sequence includes mapping a set of codewords generated by an encoder operating using a Galois Field alphabet to a root and cyclic shift. In some cases, each of the set of codewords is generated by the encoder using a generator polynomial.

Cross-correlator <NUM> may cross-correlate the set of symbols with a sequence to generate a set of cross-correlation symbols. In some cases, the sequence is based on a set of synchronization symbols.

Symbol timing determiner <NUM> may synchronize the UE with the base station based on the auto-correlation values. In some cases, synchronizing the UE with the base station includes selecting one of the first timing hypothesis or the second timing hypothesis as a symbol timing of the base station. Symbol timing determiner <NUM> may establish a symbol timing based on the primary synchronization signal, where generating the SSS sequence is based on the symbol timing.

Cost determiner <NUM> may compute a cost for the timing hypothesis based on the auto-correlation values, where synchronizing the UE with the base station is based on a comparison of the computed cost to a threshold. Cost determiner <NUM> may compute a second cost for a second timing hypothesis based on a second set of auto-correlation values, where synchronizing the UE with the base station is further based on a comparison of the second computed cost to the threshold.

Frequency estimator <NUM> may determine a frequency estimate for the timing hypothesis based on the computed cost.

Mapper <NUM> may map the SSS sequence to a first index of a set of indices and map the SSS sequence to the first index includes mapping a root and cyclic shift of the SSS sequence to the first index.

Offset determiner <NUM> may determine a subframe offset for a reference signal based on the SSS sequence.

Scrambling rule determiner <NUM> may determine a scrambling rule for the reference signal based on the subframe offset and descramble the reference signal based on the scrambling rule.

Decoder <NUM> may decode a channel based on the reference signal.

Descrambler <NUM> may determine a scrambling rule for the reference signal based on the subframe offset and descramble the reference signal based on the scrambling rule.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with 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, e.g., with reference to <FIG> and <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including UE communications 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 buses (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 DSP, a central processing unit (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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs).

Software <NUM> may include code to implement aspects of the present disclosure, including code to support a legacy compatible PSS/SSS design for CE and cost-reduced UEs. 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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a base station <NUM> as described herein. Wireless device <NUM> may include receiver <NUM>, base station communications 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 communications manager <NUM> may be an example of aspects of the base station communications manager <NUM> described with reference to <FIG>.

Base station communications manager <NUM> and/or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the base station communications manager <NUM> and/or at least some of its various sub-components may be executed by a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. The base station communications manager <NUM> and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, base station communications manager <NUM> and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, base station communications manager <NUM> and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

Base station communications manager <NUM> may generate, by a shortened Reed Solomon (RS) encoder, a SSS sequence based on a cell identifier group of a base station and transmit the SSS sequence.

<FIG> shows a block diagram <NUM> of a wireless device <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with 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>. Wireless device <NUM> may include receiver <NUM>, base station communications 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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs, etc.). For example, receiver <NUM> may receive a signal associated generating a PSS and/or a SSS, a signal associated with synchronizing wireless device <NUM> with a UE (e.g., based at least in part on previously transmitted PSS and/or SSS), and/or the like, as described herein. Information may be communicated between other components of the device. For example, information <NUM> may be communicated between receiver <NUM> and base station communications manager <NUM>. Information <NUM> may include, for example, a signal, received from the UE, based at least in part on which wireless device <NUM> may synchronize with the UE, a signal associated with generating a PSS and/or a SSS to be transmitted by wireless device <NUM>, and/or the like. The receiver <NUM> may be an example of aspects of the transceiver <NUM> described with reference to <FIG>. The receiver <NUM> may utilize a single antenna or a set of antennas.

Base station communications manager <NUM> may also include sequence generator <NUM> and SSS processor <NUM>.

Sequence generator <NUM> may generate, by a shortened Reed Solomon (RS) encoder, a SSS sequence based on a cell identifier group of a base station and generate the SSS sequence is further based on a subframe offset of a reference signal within a frame. In some cases, the SSS sequence is a Zadoff-Chu sequence having a defined root and a defined cyclic shift.

SSS processor <NUM> may transmit the SSS sequence.

Information <NUM> may be communicated between base station communications manager <NUM> and transmitter <NUM>. Information <NUM> may include, for example, information associated with transmitting a SSS (e.g., a SSS generated by base station communications manager <NUM>) and/or a PSS, information associated with a received signal associated with synchronizing with a UE, and/or the like.

For example, transmitter <NUM> may transmit a PSS and/or a SSS generated by base station communications manager <NUM>, and/or another type of information.

<FIG> shows a block diagram <NUM> of a base station communications manager <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with aspects of the present disclosure. The base station communications manager <NUM> may be an example of aspects of a base station communications manager <NUM> described with reference to <FIG>, <FIG>, and <FIG>. The base station communications manager <NUM> may include sequence generator <NUM>, SSS processor <NUM>, primary synchronization signal (PSS) encoder <NUM>, PSS processor <NUM>, and mapper <NUM>. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

PSS encoder <NUM> may encode a PSS sequence to generate an encoded PSS sequence.

PSS processor <NUM> may transmit the encoded PSS sequence a defined number of times within a subframe of a frame.

Mapper <NUM> may store a table mapping a Galois Field alphabet to a set of Zadoff-Chu sequences each having a defined root and a defined cyclic shift.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with aspects of the present disclosure. Device <NUM> may be an example of or include the components of base station <NUM> as described above, e.g., 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 communications manager <NUM>, processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, network communications manager <NUM>, and inter-station communications manager <NUM>. These components may be in electronic communication via one or more buses (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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs).

Inter-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>. In some examples, inter-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 a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with 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 communications 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 <NUM>, the UE <NUM> may receive a PSS and a SSS in a first set of symbols of a first subframe of a frame. For example, the UE <NUM> may receive a PSS and a SSS in a first set of symbols of a first subframe of a frame, wherein, within the first set of symbols of the first subframe, the SSS is received in a symbol that is before (e.g., prior to) a symbol of the first subframe in which the PSS is received, as described above. The operations of block <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of block <NUM> may be performed by a signal processor as described with reference to <FIG>.

At <NUM>, the UE <NUM> may receive the PSS and the SSS in a first set of symbols of a second subframe of the frame and in a second set of symbols of the second subframe. For example, the UE <NUM> may receive the PSS and the SSS in a first set of symbols of a second subframe of the frame and in a second set of symbols of the second subframe, wherein, within the first set of symbols of the second subframe and within the second set of symbols of the second subframe, the SSS is received in a symbol that is after (e.g., subsequent to) a symbol in which the PSS is received, as described above. The operations of block <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of block <NUM> may be performed by a symbol generator as described with reference to <FIG>.

At <NUM>, the UE <NUM> may synchronize with the base station <NUM> based at least in part on the PSS and the SSS. The operations of block <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of block <NUM> may be performed by a symbol generator as described with reference to <FIG>.

In some aspects, the PSS and the SSS are received in a second set of symbols of the first subframe, wherein, within the second set of symbols of the first subframe, the SSS is received in a symbol that is subsequent to a symbol in which the PSS is received. In some aspects, within the first subframe, the first set of symbols is before the second set of symbols. In some aspects, within the first subframe, the first set of symbols is after the second set of symbols.

In some aspects, the PSS and the SSS are received in a first set of symbols of a third subframe of the frame and in a second set of symbols of the third subframe, wherein, within the first set of symbols of the third subframe and within the second set of symbols of the third subframe, the SSS is received in a symbol that is subsequent to a symbol in which the PSS is received.

In some aspects, the PSS and the SSS are received in at least a third set of symbols of the first subframe or at least a third set of symbols of the second subframe, wherein, within the at least third set of symbols of the first subframe or the at least third set of symbols of the second subframe, the SSS is received in a symbol that is subsequent to a symbol in which the PSS is received.

In some aspects, the first set of symbols of the second subframe includes a third symbol of the second subframe and a fourth symbol of the second subframe.

In some aspects, the second set of symbols of the second subframe includes a sixth symbol of the second subframe and a seventh symbol of the second subframe.

<FIG> shows a flowchart illustrating a method 1500for a legacy compatible PSS/SSS design for CE and cost-reduced UEs in accordance with 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 communications 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 <NUM>, the base station <NUM> may generate a SSS. The operations of block <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of block <NUM> may be performed by a sequence generator as described with reference to <FIG>.

At <NUM>, the base station <NUM> may transmit a PSS and the SSS in a first set of symbols of a first subframe of a frame. For example, the base station <NUM> may transmit the PSS and the SSS in a first set of symbols of a first subframe of a frame, wherein, within the first set of symbols of the first subframe, the SSS is transmitted in a symbol that is prior to a symbol of the first subframe in which the PSS is transmitted, as described above. The operations of block <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of block <NUM> may be performed by a SSS processor as described with reference to <FIG>.

At <NUM>, the base station <NUM> may transmit the PSS and the SSS in a first set of symbols of a second subframe of the frame and in a second set of symbols in the second subframe. For example, the base station <NUM> may transmit the PSS and the SSS in a first set of symbols of a second subframe of the frame and in a second set of symbols of the second subframe, wherein, within the first set of symbols of the second subframe and within the second set of symbols of the second subframe, the SSS is transmitted in a symbol that is subsequent to a symbol in which the PSS is transmitted, as described above. The operations of block <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of block <NUM> may be performed by a SSS processor as described with reference to <FIG>.

In some aspects, the PSS and the SSS are transmitted in a second set of symbols of the first subframe, wherein, within the second set of symbols of the first subframe, the SSS is transmitted in a symbol that is subsequent to a symbol in which the PSS is transmitted.

In some aspects, within the first subframe, the first set of symbols is before the second set of symbols. In some aspects, within the first subframe, the first set of symbols is after the second set of symbols.

In some aspects, the PSS and the SSS are transmitted in a first set of symbols of a third subframe of the frame and in a second set of symbols of the third subframe, wherein, within the first set of symbols of the third subframe and within the second set of symbols of the third subframe, the SSS is transmitted in a symbol that is subsequent to a symbol in which the PSS is transmitted.

In some aspects, the PSS and the SSS are transmitted in at least a third set of symbols of the first subframe or at a third set of symbols of the second subframe, wherein, within the at least third set of symbols of the first subframe or the at least third set of symbols of the second subframe, the SSS is transmitted in a symbol that is subsequent to a symbol in which the PSS is transmitted.

It is understood that the specific order or hierarchy of blocks in the processes / flow charts disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes / flow charts may be rearranged.

Claim 1:
A method (<NUM>) for wireless communication performed by a user equipment, UE, comprising:
receiving (<NUM>), from a base station, a first sequence of a primary synchronization signal, PSS, and a secondary synchronization signal, SSS, in a first set of symbols of a first subframe of a frame,
wherein, within the first sequence, the SSS is received in a symbol that is prior to a symbol of the first subframe in which the PSS is received, the first sequence of the SSS and the PSS enables synchronization signal, SS, detection at legacy UEs;
receiving (<NUM>), from the base station, repetitions of a second sequence of the PSS and the SSS in a first set of symbols of a second subframe of the frame and in a second set of symbols of the second subframe,
wherein, within the second sequence, the SSS is received in a symbol that is subsequent to a symbol in which the PSS is received, and wherein the second sequence of the PSS and the SSS received in the first and second sets of symbols of the second subframe is swapped with reference to the first sequence of the PSS and the SSS received in the first set of symbols of the first subframe; and
wherein the second sequence of the SSS and the PSS enables the SS detection at non-legacy UEs and causes the SS detection to fail at the legacy UEs; and
synchronizing (<NUM>) with the base station based at least in part on the PSS and the SSS.