Patent Description:
Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system). A wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). Some communication devices operating on wireless multiple-access communications systems may have limitations on operational frequency bandwidth. These devices may be known as narrow band (NB) devices. In some cases, a wireless communications system may use a combination of the above multiple-access systems to support multiple types of UEs.

NB devices, such as NB Internet of Things (NB-IOT) devices, face numerous challenges. For instance, NB communications may have a limited frequency dimension (e.g., a single resource block (RB)) that is shared by multiple users. Furthermore, timing offsets associated with large coverage areas envisioned for NB-IOT may extend beyond the range for which a cyclic prefix is capable of compensating. The <NPL>, expands on the description of the random access channel and provides performance evaluation of a narrow band OFDMA based solution as proposed in the draft GP-<NUM>. The GP-<NUM> draft provides a detailed description of the Physical Random Access channel and procedure. The PRACH channel configuration is flexible and can be tailored for each cell based on device distribution within the cell by allocating different set of tones for different coverage classes. Said draft inter alia proposes PRACH transmission based on a segmented ALOHA procedure which involves frequency hopping of g tones within the first <NUM> extended slots, <NUM>, <NUM>,. , <NUM> at the beginning of each odd-numbered slot, and random frequency hopping at the beginning of each even-numbered slot. There is still a need for more reliable PRACH procedures.

The present invention provides a solution according to the independent claims.

A physical random access channel (PRACH) may be used for initial system access by narrow band (NB) devices. Some PRACH transmissions may be single tone signals to provide flexibility in NB device support, which may impact determination of timing offsets. Described aspects are directed to frequency hopping patterns for PRACH transmissions by NB devices that include large and small frequency hops to facilitate the determination of timing offsets ("timing advances") from PRACH transmissions. For instance, a PRACH transmission may include frequency hops having a first frequency hopping distance (e.g., large frequency hops) and a second frequency hopping distance (e.g., small frequency hops). Frequency hopping patterns for a random access preamble may then be determined that perform a first number of frequency hops of the first distance and a second number of hops of the second distance. A distribution of large and small hops may be used to provide fine timing resolution and to resolve large propagation delays.

A method of wireless communication is described, as defined in claim <NUM>.

An apparatus for wireless communication is described, as defined in claim <NUM>.

A computer program for wireless communication is described, as defined in claim <NUM>.

Further scope of the applicability of the described systems, methods, apparatuses, or computer-readable media will become apparent from the following detailed description, claims, and drawings. The detailed description and specific examples are given by way of illustration only, since various changes and modifications within the scope of the description will become apparent to those skilled in the art.

According to the present disclosure, narrow band (NB) devices using frequency resources of a physical random access channel (PRACH) for system access may employ large and small frequency hops to facilitate the determination of timing offsets ("timing advances") for the NB devices. Aspects of the disclosure are described in the context of a wireless communication system. For example, a wireless communication system may support Long Term Evolution (LTE) or LTE-Advanced (LTE-A) communications in addition to NB communications concurrently (e.g., on the same or separate wireless channels). Devices may perform system access using resources configured as a NB PRACH. For example, an NB device may transmit an NB preamble sequence over NB PRACH resources without pre-scheduling from a base station. An NB preamble sequence may utilize a number of single-tone transmissions that frequency hop each transmission interval. A base station may use the received NB preamble sequence to determine a timing offset for subsequent (e.g., scheduled) transmissions from an NB device. In some cases, a distribution of large and small hops may be used to provide fine timing resolution and to resolve large propagation delays.

In one example, an NB PRACH may include a first portion of NB PRACH resources that are used for large frequency hops and a second portion of NB PRACH resources that are used for small frequency hops. Frequency hopping patterns may then be determined for this NB PRACH that include a number of large frequency hops, small frequency hops, random frequency hops, or a combination thereof. These frequency hopping patterns may be used to determine random access preambles for transmission over the NB PRACH. For instance, a user equipment (UE) may randomly select and transmit a random access preamble over the NB PRACH based on a frequency hopping pattern. The random access preamble may include a series of transmissions that each span a transmission interval and that may hop to a different frequency at the end of each transmission interval. A base station may detect a transmitted random access preamble based on the frequency hopping pattern used by the UE. After detecting the random access preamble, the base station may use information of the random access preamble (e.g., the different subcarrier frequencies transmitted across the preamble) to determine timing offsets for the UE that transmitted the random access preamble.

Different frequency hopping patterns may be used to generate non-overlapping random access preambles. For instance, a linear hash function, a cyclic shift, or both may be used to generate sequences used as random access preambles. In some cases, the frequency hopping patterns may transition between large and small frequency hops after N transmission intervals. Frequency hopping patterns for different devices may differ based on application of a pseudo-random function within the frequency hopping patterns, which may be determined based on a linear hash function, a cyclic shift, or a combination thereof. These and other aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts.

<FIG> illustrates an example of a wireless communications system <NUM> that supports NB frequency hopping patterns in accordance with various aspects of the present disclosure. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be an LTE/LTE-A network.

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

Some types of wireless devices may provide for automated communication. Automated wireless devices may include those implementing Machine-to-Machine (M2M) communication or MTC. M2M or MTC may refer to data communication technologies that allow devices (e.g., IoT devices, etc.) to communicate with one another or a base station without human intervention. Some UEs <NUM> may be MTC devices, such as those designed to collect information or enable automated behavior of machines. 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. MTC devices may be capable of single-tone communications, multi-tone communications, or both. A device that is capable only of single-tone communication may transmit using a single tone (subcarrier) per transmission time interval (TTI). A multi-tone device may use multiple tones per TTI.

LTE systems may utilize orthogonal frequency division multiple access (OFDMA) on the DL and single carrier frequency division multiple access (SC-FDMA) on the UL. OFDMA and SC-FDMA partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones or bins. Each subcarrier may be modulated with data. For example, K may be equal to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> with a subcarrier spacing of <NUM> kilohertz (KHz) for a corresponding system bandwidth (with guard band) of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> megahertz (MHz), respectively. The system bandwidth may also be partitioned into sub-bands. For example, a sub-band may cover <NUM>, and there may be <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> sub-bands. Some MTC UEs <NUM> may operate in a narrower bandwidth compared to the full system bandwidth.

The system resources may also be partitioned in time into different periods of times (e.g., frames, subframes, slots, symbol periods, etc.). In some examples, an LTE frame structure may define a frame to include <NUM> subframes, a subframe to include two slots, and a slot to include <NUM> to <NUM> symbol periods depending on a length of a cyclic prefix included in the symbol period. In some examples, a frame may span <NUM>, a subframe may span <NUM>, a slot may span <NUM>, and a symbol period may span ~<NUM> or <NUM>. In some cases, the subcarrier spacing may be based on the length of the symbol period (e.g., the inverse of the symbol period). The wireless communications system <NUM> may designate a resource block (RB) as the smallest number of resources that may be allocated to a UE <NUM>. The wireless communications system <NUM> may schedule communications to a UE using RBs, which may be defined to span <NUM> subcarriers and one slot, or <NUM> or <NUM> resources. In some cases, a UE <NUM> may perform transmissions that extend through a minimum duration, or TTI. In some cases, a TTI may span a single slot or subframe. In other cases, a TTI may span one or two symbol periods.

The wireless communications system <NUM> may use carriers, which may be referred to as component carriers (CCs), of different bandwidths (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>) that use the partitioned resources to transmit packets between a base station <NUM> and a UE <NUM>. The wireless communications system <NUM> may use the carriers along with frequency division duplex (FDD) (e.g., using paired spectrum resources) or time division duplex (TDD) operation (e.g., using unpaired spectrum resources) to perform bidirectional communications. Frame structures for FDD (e.g., frame structure type <NUM>) and TDD (e.g., frame structure type <NUM>) may be defined. For TDD frame structures, each subframe may carry UL or DL traffic, and special subframes may be used to switch between DL and UL communication. Allocation of UL and DL subframes within radio frames may be symmetric or asymmetric and may be statically determined or may be reconfigured semi-statically. Special subframes may carry DL or UL traffic and may include a Guard Period (GP) between DL and UL traffic. Switching from UL to DL traffic may be achieved by setting a timing offset at the UE <NUM> without the use of special subframes or a GP.

In some cases, multiple CCs may be aggregated or utilized concurrently to provide some UEs <NUM> with greater bandwidth and, e.g., higher data rates. Thus, individual CCs may be backwards compatible with legacy UEs <NUM> (e.g., UEs <NUM> implementing LTE release <NUM> or release <NUM>); while other UEs <NUM> (e.g., UEs <NUM> implementing post-release <NUM>/<NUM> LTE versions), may be configured with multiple component carriers in a multi-carrier mode. A CC used for DL may be referred to as a DL CC, and a CC used for UL may be referred to as an UL CC. A UE <NUM> may be configured with multiple DL CCs and one or more UL CCs for carrier aggregation. Each carrier may be used to transmit control information (e.g., reference signals, control channels, etc.), overhead information, data, etc. A UE <NUM> may communicate with a single base station <NUM> utilizing multiple CCs, and may also communicate with multiple base stations simultaneously on different CCs. In some examples, a UE <NUM> may receive information from CCs associated with different radio access technologies. For instance, a UE <NUM> may receive information on an LTE CCs and an unlicensed CC or an NB CC.

Wireless communications system <NUM> may use multiple channels, such as logical channels, transport channels, and physical layer channels, to communicate data. Channels may also be classified into Control Channels and Traffic Channels. Logical control channels may include paging control channel (PCCH) for paging information, broadcast control channel (BCCH) for broadcast system control information, multicast control channel (MCCH) for transmitting multimedia broadcast multicast service (MBMS) scheduling and control information, dedicated control channel (DCCH) for transmitting dedicated control information, common control channel (CCCH) for random access information, DTCH for dedicated UE data, and multicast traffic channel (MTCH), for multicast data. DL transport channels may include broadcast channel (BCH) for broadcast information, a DL shared channel (DL-SCH) for data transfer, paging channel (PCH) for paging information, and multicast channel (MCH) for multicast transmissions.

UL transport channels may include random access channel (RACH) for access and UL shared channel (UL-SCH) for data. DL physical channels may include a physical broadcast channel (PBCH) for broadcast information, physical control format indicator channel (PCFICH) for control format information, physical DL control channel (PDCCH) for control and scheduling information, physical HARQ indicator channel (PHICH) for hybrid automatic repeat request (HARQ) status messages, physical DL shared channel (PDSCH) for user data and physical multicast channel (PMCH) for multicast data. UL physical channels may include physical random access channel (PRACH) for access messages, physical UL control channel (PUCCH) for control data, and physical UL shared channel (PUSCH) for user data. In some cases, data associated with each channel may be mapped to the carrier structure for transmission across an air interface.

The PRACH may be allocated time and frequency resources during which UEs <NUM> may initiate communication with the wireless communications system <NUM> without prior scheduling. In some examples, the PRACH may have a bandwidth of six RBs and may span one to two subframes. The base station <NUM> may advertise the RBs reserved for the PRACH in a system information block (SIB), and a UE <NUM> may transmit a cyclic prefix, a preamble sequence, and a GP during the advertised PRACH resource. Since there is no prior scheduling or coordination, a UE <NUM> may select (e.g., randomly) the preamble sequence from a number of available preambles. The preamble may contain one or two PRACH symbols that span <NUM>, <NUM>, or <NUM> in length. The preamble sequence may be mapped to subcarriers and symbol periods and transmitted across a bandwidth of approximately <NUM> (e.g., <NUM> subcarriers at <NUM> subcarrier spacing or <NUM> subcarriers at <NUM> subcarrier spacing, etc.). Since there is no pre-coordination, a UE <NUM> may transmit the preamble without a timing offset (e.g., based on timing determined from synchronization signals transmitted by the base station <NUM>). The base station <NUM> may use the received preamble sequence to distinguish multiple UEs <NUM> that are each transmitting over the PRACH resources from one another and to determine respective timing offsets for each UE <NUM>.

Timing offsets may be used to adjust a time when UEs <NUM> scattered across a coverage area <NUM> begin UL transmissions so that the UL transmissions are aligned when they reach a corresponding base station <NUM>. For instance, a UE <NUM> that is a larger distance away from a base station <NUM> may begin transmitting earlier than another UE <NUM> that is a shorter distance away from the base station <NUM> to compensate for a longer propagation delay. In some cases, a cyclic prefix may be included in transmitted symbols to further resolve variations in the alignment of the transmissions received at the base station <NUM>.

In some cases, a wireless communications system <NUM> may utilize both LTE and NB radio access technologies. In some examples, NB communications may be used to serve MTC devices. NB communications may use limited frequency resources, and, in some cases, may be limited to a single RB of system bandwidth (e.g., <NUM>), a series of RBs, or portions of an RB. In some examples, the frequency resources set aside for NB communications may be located within an LTE carrier, in a guard band of an LTE carrier, or separate from an LTE carrier in a "standalone" deployment. In some cases, the NB resources may be simultaneously utilized by multiple UEs <NUM>. The NB resources may be used to provide deep coverage to support devices in environments that are associated with different coverage enhancement (CE) levels. For instance, certain stationary devices may be located in environments with poor coverage, such as a basement. Additionally, the NB resources may be associated with communications within a large coverage area <NUM> (e.g., greater than <NUM> kilometers (km)). Communications to a device at an edge of the coverage area <NUM> may have a large delay (e.g., <NUM>) in comparison to an LTE symbol time (e.g., <NUM>).

In some cases, wireless communications system <NUM> may utilize coverage enhancement (CE) techniques with either LTE or NB communications to improve the quality of a communication link <NUM> for UEs <NUM> located at a cell edge, operating with low power transceivers, or experiencing high interference or path loss. CE techniques may include repeated transmissions, TTI bundling, HARQ retransmission, PUSCH hopping, beamforming, power boosting, repetitive transmissions, or other techniques. The CE techniques used may depend on the specific needs of UEs <NUM> in different circumstances, and may be effective for reaching devices that are located in areas that routinely experience poor channel conditions. Different CE levels may be associated with different levels of coverage levels enhancements, and may be assigned to UEs <NUM> based on a signal strength detected at a UE <NUM>. For instance, a device that is near an edge of a coverage area <NUM> may be associated with a high CE level (e.g., an enhancement of <NUM> decibels (dBs)), while a device that is near a serving base station <NUM> may be associated with a low CE level (e.g., no enhancement).

Certain frequency resources may be allocated to an NB PRACH to enable access by NB devices (e.g., MTC devices, NB-UEs, NB-MTC devices, etc.). In some cases, the NB PRACH may be allocated one RB (e.g., a <NUM> bandwidth), a series of RBs, or a portion of an RB. An NB-UE <NUM> may transmit a preamble sequence as a series of tones across the PRACH resources to initiate communication with a base station <NUM> and allow the base station <NUM> to determine a timing offset. The NB PRACH may be designed to support both single tone and multi-tone devices, and may therefore be designed using a single tone transmission scheme. In some examples, a preamble sequence may hop across multiple tones at intervals that are greater than the duration associated with the round-trip delay at the edge of a coverage area <NUM>. That is, a preamble sequence may transmit an NB signal at the carrier frequency associated with a single subcarrier for a transmission interval and may then frequency hop to a second subcarrier to perform another transmission at the carrier frequency of the second subcarrier for another transmission interval. In some cases, the transmission intervals may be <NUM> in length and the NB signal may include un-modulated tones (e.g., no modulated preamble sequence). Furthermore, as the preamble sequence may use <NUM> transmission time intervals, the subcarrier spacing may be determined to be the inverse of the transmission time intervals, or <NUM>. Accordingly, for a resource block with a <NUM> bandwidth, there may be <NUM> PRACH tones, <NUM> of which may be designated as guard tones. The remaining <NUM> tones may be used to support <NUM> orthogonal PRACH resources. Alternatively, the PRACH may use different subcarrier spacing (e.g., <NUM>, <NUM>, <NUM>, etc.) and corresponding time intervals for each tone of the preamble.

As discussed above, an NB-UE <NUM> attempting to access the NB resources using the NB PRACH may not use a timing offset for a PRACH preamble transmission and, in some cases, it may be helpful for the base station <NUM> to use the received preamble sequence to determine the timing offset for subsequent transmissions. In some examples, the base station <NUM> may use the difference in the phase of two or more tones received at different frequencies to determine the timing offset. The timing accuracy for determining the timing offset based on two tones on different subcarriers may be dependent on the frequency difference between the tones. However, tones having large frequency separation may not be able to resolve ambiguity between delays having a multiple of the phase of the higher tone. Thus, large hops may not be effective for determining the timing offset for NB-UEs <NUM> that are distant from the base station <NUM>, because they experience a larger delay. Therefore, a combination of large and small frequency hops transmitted by a NB-UE <NUM> may be beneficial to determining the timing offset.

In some cases, dedicated frequency resources of the NB PRACH may be designated to large and small frequency hops. For instance, a first portion of an NB PRACH channel may be associated with a first frequency hopping distance (e.g., large frequency hops), and a second portion of the NB PRACH may be associated with a second frequency hopping distance (e.g., small frequency hops). Frequency hopping patterns for a random access preamble may then be determined that perform a first number of frequency hops of the first distance and a second number of hops of a second distance. The first number of frequency hops may be within the first portion of the NB PRACH and the second number of frequency hops may be within the second portion of the NB PRACH. In this way, preamble sequences that include a number of large or small frequency hops may be determined. In some cases, the NB PRACH may be further partitioned into portions associated with different (e.g., larger, medium, and smaller) frequency hop sizes.

<FIG> illustrates an example of a wireless communications subsystem <NUM> that supports NB frequency hopping patterns in accordance with various aspects of the present disclosure. Wireless communications subsystem <NUM> may include UE <NUM>-a, UE <NUM>-b, base station <NUM>-a, communication link <NUM>-a, and communication link <NUM>-b which may be examples of a UE <NUM>, a base station <NUM>, or a communication link <NUM> and may communicate with one another over a communication link <NUM> as described above with reference to <FIG>. In some examples, UE <NUM>-a and UE <NUM>-b may be NB-UEs as described above with reference to <FIG>.

In the example of <FIG>, communication between UEs <NUM>-a, UE <NUM>-b, and base station <NUM>-a may utilize an NB frequency hopping pattern for a random access preamble that includes small and large frequency hops across an NB PRACH. The NB PRACH may be allocated one or multiple contiguous RBs that span across multiple subframes or frames. In some examples, the NB PRACH may be allocated a single RB (e.g., <NUM>) in consecutive subframes. Furthermore, in some examples, a preamble tone interval for a preamble sequence using the NB PRACH may be <NUM> in length, and the NB PRACH may use <NUM> subcarrier spacing. A guard portion-e.g., <NUM> subcarriers at each end of the PRACH resources-of the NB PRACH may be left unused, a large frequency hop portion-e.g., <NUM> subcarriers at each end of the PRACH resources minus the guard portion-of the NB PRACH may be allocated for large frequency hops, and a small frequency hop portion-e.g., <NUM> subcarriers between subcarriers allocated to the large frequency hop portion-of the NB PRACH may be allocated for small frequency hops. Preamble sequences may then be generated according to frequency hopping patterns that include large frequency hops using the large frequency hop portion and small frequency hops using the small frequency hop portion, as will be discussed in more detail below and with reference to <FIG> and <FIG>.

Base station <NUM>-a may broadcast the time and frequency location of the NB PRACH resources over coverage area <NUM>-a. UE <NUM>-a and UE <NUM>-b may select a preamble sequence of the generated preamble sequences for transmission to base station <NUM>-a. When initiating a connection to base station <NUM>-a, UE <NUM>-a and UE <NUM>-b may transmit their selected preamble sequences over the PRACH resources. The preamble sequences may include an ordered set of indices that correspond to a frequency resource in either the large frequency hop portion or the small frequency hop portion. Transmitting the preamble sequences may include transmitting a first signal at a first subcarrier frequency for a first preamble tone interval, a second signal at a subcarrier frequency for a following preamble tone interval, and so on, as will be discussed in more detail below and with reference to <FIG> and <FIG>. However, as discussed above, neither UE <NUM>-a nor UE <NUM>-b may compensate for propagation delay of the received broadcast signal or the transmitted preamble sequence prior to transmitting the preamble sequence. Accordingly, the preamble sequence transmitted from UE <NUM>-a may reach base station <NUM>-a before the preamble sequence transmitted from UE <NUM>-b.

Base station <NUM>-a may perform preamble sequence detection by observing whether the preamble sequence transmitted from UE <NUM>-a or UE <NUM>-b has been received according to the corresponding frequency hopping pattern, as will be discussed in more detail below and with reference to <FIG> and <FIG>. After detecting that a preamble sequence for UE <NUM>-a or UE <NUM>-b has been received, base station <NUM>-a may use the frequencies of the received signals to determine a timing offset for subsequent transmissions from the corresponding UE <NUM>. Base station <NUM>-a may then transmit an indication of the timing offset to either UE <NUM>-a or UE <NUM>-b depending on which preamble sequences were successfully received.

<FIG> illustrates an example of an NB PRACH <NUM> that supports NB frequency hopping patterns in accordance with various aspects of the present disclosure. NB PRACH <NUM> may illustrate aspects of a transmission between a UE <NUM> and a base station <NUM>, as described above with reference to <FIG> and <FIG>. NB PRACH <NUM> may include a large hop region <NUM> which may be partitioned into a large hop sub-region <NUM>-a and a large hop sub-region <NUM>-b, a small hop region <NUM>, guard bands <NUM>, preamble tone intervals <NUM>, a first preamble <NUM>-a, a second preamble <NUM>-b, a third preamble <NUM>-c, and a fourth preamble <NUM>-d.

In the example of <FIG>, the NB PRACH <NUM> includes up to <NUM> subcarriers. The first large-hop sub-region <NUM>-a and the second large hop sub-region <NUM>-b may be associated with large frequency hopping distances and the small hop region <NUM> may be associated with small frequency hopping distances. The first and second large hop sub-regions <NUM>-a and <NUM>-b may each include <NUM> subcarriers, and the small hop region <NUM> may include <NUM> subcarriers. The small hop region <NUM> may further be partitioned into subcarrier groups <NUM>-a to <NUM>-n. Each subcarrier group may include a number of subcarriers that is an integer divisor of the total number of subcarrier included in the small hop region <NUM>, for instance, the small hop region <NUM> may be partitioned into <NUM> subcarrier groups of five subcarriers. The guard bands <NUM> may each include <NUM> subcarriers. In some cases, a preamble tone interval <NUM> may span an LTE subframe (e.g., <NUM>), and NB PRACH <NUM> may span multiple contiguous preamble tone intervals (e.g., <NUM> or three LTE frames). In other cases, NB PRACH <NUM> may span multiple dis-contiguous preamble tone intervals <NUM> (e.g., may span three dis-contiguous sets of ten preamble tone intervals). Furthermore, although NB PRACH <NUM> is depicted as a contiguous set of frequency resources, in some cases, NB PRACH <NUM> may include dis-contiguous resources. For instance, the small hop region <NUM> may be located above large hop sub-region <NUM>-a, while large hop sub-region <NUM>-b may still be located a second portion below from large hop sub-region <NUM>-a. In some examples, additional regions may be designated for frequency hops of different sizes (e.g., larger, medium, smaller, etc.). Additional hops may be used to determine intermediate time offset values.

With <NUM> subcarriers allocated to guard bands <NUM>, up to <NUM> non-colliding frequency hopping patterns may be determined to generate <NUM> preamble sequences. In the example of <FIG>, four preambles <NUM>-a to <NUM>-d are depicted. The first and second preambles <NUM>-a and <NUM>-b may hop in frequency each preamble tone interval <NUM> according to a frequency hopping pattern. In some examples, the frequency hopping pattern for the first and second preambles <NUM>-a and <NUM>-b may be realized as a sequence of numbers that correspond to the subcarriers in a subcarrier group <NUM> or in a large hop sub-region <NUM>. The first and second preamble sequences <NUM>-a and <NUM>-b may additionally alternate between performing N frequency hops at a first distance and then N frequency hops at a second distance. In some cases, the value of N is based on the number of subcarriers in a subcarrier group <NUM>. The first preamble <NUM>-a and the second preamble <NUM>-b may begin in the large hop sub-group <NUM>-a.

After each preamble tone interval <NUM>, the large frequency hopping pattern may include frequency hops between any subcarrier in the large hop sub-region <NUM>-a and any subcarrier in the large hop sub-region <NUM>-b. A preamble sequence may include random subcarriers selected within each of large hop sub-regions <NUM>-a and <NUM>-b. For instance, as depicted in <FIG>, the first preamble <NUM>-a may have the preamble sequence {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}, and the second preamble <NUM>-b may have the sequence {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}. In some examples, the subcarriers allocated to the large hop sub-regions may be further broken down in to groups G , where G may be in the range [<NUM>,. The preamble sequences <NUM>-a and <NUM>-b may be determined using a random linear hash function, a random linear cyclic shift, or both. The random linear hash function may be used to randomize NB PRACH resources in adjacent tones, and the random cyclic shift within a subcarrier group may be used to randomize interference with neighboring cells.

In some examples, the random linear hash function may be implemented by selecting a prime number p that is greater than the number of tones M in the large hop sub-regions <NUM>. The resources t in the large hop sub-regions <NUM> may be numbered as t = <NUM>, <NUM>,. , M - <NUM>, and a random number, r<NUM>, may be drawn from the range [<NUM>,<NUM>,. , p - <NUM>]. A hashed ordering H(k) may then be created for k = <NUM>, <NUM>,. , p - <NUM>, where: <MAT> Any number for which H(k) > M - <NUM> may be removed to create a shortened sequence H'(k). The resources t may then be mapped to H'(t). The number r<NUM> may be generated by taking L consecutive bits of the scrambling shift register sequence, forming an integer Z between <NUM> and <NUM>L - <NUM>, and then taking r<NUM> = Z mod(p - <NUM>). In some cases, the scrambling sequence can be initialized with a value that is a function of the physical cell identity (PCID). To generate a random cyclic shift, a random number r<NUM> may be generated similarly to r<NUM>, but may take a different L consecutive bits. And a shifted tone location may be determined by mapping t to (H'(t) + r<NUM> + <NUM>) mod M.

After N frequency hops in the large hop sub-regions <NUM>, the first and second preambles <NUM>-a and <NUM>-b may transition to the small hop region <NUM> and may further be located in subcarrier group <NUM>-b. The first and second preambles <NUM>-a and <NUM>-b may perform N frequency hops in the subcarrier group <NUM>-b. The small hop pattern may be determined by first selecting a resource index within the <NUM> tones from the range [<NUM>,<NUM>,. , <NUM>], and then determining a subgroup index by using the equation:
floor (resource index /G), where G may be in the range [<NUM>,. In one example, G = <NUM>, which yields the subgroup index [<NUM>, <NUM>,. The hopping pattern may then be determined within the subcarrier group <NUM> associated with the subgroup index. For instance, as depicted in <FIG>, the first preamble <NUM>-a may have the preamble sequence {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}, and the second preamble <NUM>-b may have the sequence {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}. In other examples, the preamble sequences <NUM>-a and <NUM>-b may be determined using a random linear hash function, a random linear cyclic shift within the number of subcarrier assigned to a subcarrier group <NUM>, or both.

In some examples, the linear hash may be accomplished by alternating within a frequency hopping cycle between two sequences-e.g., an even numbered sequence: {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>} and an odd number sequence: {<NUM>, <NUM>, <NUM>,<NUM>, <NUM>}. This may also be achieved by multiplying the index by <NUM> and taking modulo <NUM>. Additionally or alternatively, the linear hash may be accomplished by cycling through the following sequences: Sequence number <NUM> mod <NUM>: {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}; Sequence number <NUM> mod <NUM>: {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}; Sequence number <NUM> mod <NUM>: {<NUM>,<NUM>, <NUM>, <NUM>, <NUM>}; Sequence number <NUM> mod <NUM>: {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}. In some cases, the random cyclic shift may be accomplished by generating a random number rq, where q is the subgroup index (q = <NUM>, <NUM>,. , <NUM>) similar to how r<NUM> was generated but with a different L consecutive bits. The shifted tone location may be calculated by adding rq to the tone index within the subgroup and taking mod <NUM>. The third and fourth preambles <NUM>-c and <NUM>-d may use similar frequency hopping patterns but may begin in the small hop region <NUM> and then transition to the large hop sub-regions <NUM>.

A UE may transmit one of preambles <NUM>-a through <NUM>-d according to the determined frequency hopping pattern. A base station may detect the transmitted preambles <NUM> by observing the PRACH resources according to the corresponding frequency hopping patterns. For instance, for the first preamble <NUM>-a, at each subsequent preamble tone interval <NUM> the base station may sequentially observe each of the frequency locations {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>}. That is, the base station may observe the 35th subcarrier of large hop sub-region <NUM>-a at the first preamble tone interval <NUM>; the 0th subcarrier of large hop sub-region <NUM>-b of large hop sub-region <NUM>-b; etc. Based on observing these time and frequency resources, the base station may determine whether preamble <NUM>-a is present, a time offset value, and a frequency offset value. In one example, preamble <NUM>-a includes W tones in W preamble tone intervals <NUM>. The tone index in a kth subframe may be F(k), where k = <NUM>, <NUM>,. , W - <NUM>. and where F(k) is in the range [<NUM>,<NUM>,. , M - <NUM>] with M = <NUM>. For each preamble tone interval <NUM>, k, the observed signal in tone F(k) is Y(k). In some examples, Y(k) is an output of a fast Fourier transform (FFT) based on the signal received over the preamble tone interval <NUM> filtered to <NUM>.

A sequence s(j) may be formed where j = <NUM>, <NUM>,. , M - <NUM>. If j = F(k) for some k then s(j) = Y(k) * exp(-<NUM> * π * i * f * k * T), where T is the duration of preamble tone interval <NUM>, and where i is the imaginary component. And if j ≠ F(k) for any k then s(j) = <NUM>. If j = F(k) for more than one k then s(j) = mean (Y(k) * exp(-<NUM> * π * i * f * k * T)) for the k values for which j = F(k). The base station may take an FFT, inverse FFT (IFFT), discrete Fourier transform (DFT), or inverse DFT (IDFT) of s(j), where s(j) may be of M elements, or zero padded to more than M elements to perform time interpolation. Alternatively, the sequence s(j) can be formed in terms of differentials. For example, the sequence s(j) may be formed as follows: if j = F(k<NUM>) - F(k<NUM>) for a pair k<NUM> and k<NUM> then s(j) = Y(k<NUM>) * conj(Y(k<NUM>)) * exp(-<NUM> * π * i * f * (k<NUM> - k<NUM>) * T) and s(j) = <NUM> otherwise. In some examples, the choice of k<NUM> and k<NUM> may be limited to pairs that are close in time (e.g., abs(k<NUM> - k<NUM>) < e). If the limit e is chosen to be appropriately small then the term exp(-<NUM> * π * i * f (k<NUM> - k<NUM>) * T) may be small and may be ignored. A particular example is taking differentials of consecutive pairs-e.g., if j = F(k + <NUM>) - F(k) for some k then s(j) = Y(k + <NUM>) * conj(Y(k)). In another example, higher order differentials may also be formed, e.g., if j = (F(k<NUM>) - F(k<NUM>)) - (F(k<NUM>) - F(k<NUM>)) for a set of k<NUM>, k<NUM>, k<NUM> and k<NUM> then s(j) = (Y(k<NUM>) * conj(Y(k<NUM>))) * (conj(Y(k<NUM>) * conj(Y(k<NUM>)))), etc..

The base station may determine a maximum value and maximum location of the FFT output, and may compare the absolute value of the maximum value with a threshold to determine the presence of a preamble <NUM>. In some cases, the threshold may be a scaled version of the average of the FFT output value with or without the maximum value. The identified maximum location may be used to determine a time offset based on a received preamble <NUM>. The base station may further scale the determined time offset value based on subcarrier spacing, zero padding of the FFT, etc. In some cases, the time offset may be one-sided (e.g., include only positive or negative values) or may be two-sided (e.g., included positive and negative values).

In some examples, the NB PRACH <NUM> may be considered as one large portion and a fully randomized hopping pattern may be used. For instance, a frequency hopping pattern may be determined for a random access preamble that includes multiple frequency hops of pseudo-random distances. In the case of a single portion, the linear hash or cyclic shift hopping patterns used for the large hop pattern may similarly be used but with, for example, M = <NUM> and p = <NUM>. Alternatively, predefined hopping patterns may be used. For example, a hopping pattern may be defined that includes hops of several different distances, or a complete (or almost complete) set of hopping distances with fewer hops than orthogonal resources (e.g., having hops defined by a sparse ruler or Golomb ruler of order W and distance M, etc.). Information obtained from differentials may be weighted by the time between the differentials to reduce the effect of frequency error.

<FIG> illustrates an example of a process flow <NUM> for NB frequency hopping patterns in accordance with various aspects of the present disclosure. Process flow <NUM> may be performed by UE <NUM>-b , UE <NUM>-c, and base station <NUM>-b, which may be an example of a UE <NUM> and base station <NUM> described above with reference to <FIG> and <FIG>. In some examples, UE <NUM>-c and UE <NUM>-d may be NB devices and may transmit random access preambles to base station <NUM>-b based on received NB PRACH information. Base station <NUM>-b may detect the transmitted random access preamble sequences and may use the received random access preamble sequences to determine timing offsets for UE <NUM>-c and UE <NUM>-d for subsequent transmissions.

At <NUM>, base station <NUM>-b may identify the structure of a PRACH. For instance, base station <NUM>-b may identify that the PRACH includes a first portion of PRACH resources that are associated with a first frequency hopping distance (e.g., a large frequency hopping distance) and a second portion of PRACH resources that are associated with a second frequency hopping distance (e.g., a small frequency hopping distance). The first and second portions of the PRACH may be further partitioned into a number of subcarriers and preamble tone intervals. The subcarrier spacing may be an integer divisor of a data channel subcarrier spacing (e.g., <NUM>) and may be based on the length of the preamble tone intervals. In some cases, the length of a preamble tone interval is <NUM> and the subcarrier spacing is <NUM>. In some cases, the first portion includes a first sub-region and a second sub-region that each includes a number of subcarriers and may be separated by the bandwidth of the second portion, as described with reference to <FIG>. In some cases, the subcarriers of the second portion may be grouped into groups of N subcarriers, as described with reference to <FIG>. In some cases, base station <NUM>-b may designate which portions of the PRACH will be associated with which frequency hopping distances. In other cases, the wireless communication system may indicate to base station <NUM>-b how the PRACH is partitioned.

At <NUM>, base station <NUM>-b may determine frequency hopping patterns for one or more random access preamble sequences based on the identified PRACH structure. For instance, the base station may determine frequency hopping patterns that include a number of frequency hops that use the first portion of PRACH resources and the first frequency hopping distance, and a number of frequency hops that use the second portion of the PRACH resources and the second frequency hopping distance. In some cases, the number of hops may be based on environmental (e.g., location) or current channel conditions (e.g., received signal strength, signal-to-noise ratio, etc.). In one example, the number of frequency hops of the first distance and the second distance may be equal or substantially equal. For example, the number of frequency hops of the first distance may make up <NUM>-<NUM>% of the frequency hops and the number of frequency hops of the second distance may make up the remaining percentage. In some examples, the frequency hopping patterns are determined based on a pseudo-random linear hash function, a pseudo-random linear cyclic shift, or both, as described above with reference to <FIG>. For example, the frequency hopping patterns for one or both of the first portion and the second portion of PRACH resources may be based on a pseudo-random function.

At <NUM>, base station <NUM> may broadcast NB PRACH information over the cell's coverage area. The NB PRACH information may include information such as a cell ID, frequency hopping pattern types, the PRACH structure, seed index, etc. UE <NUM>-c and UE <NUM>-d may both received the transmitted NB PRACH information. In some cases, UE <NUM>-d may receive the information at a later point in time than UE <NUM>-c. For instance, UE <NUM>-d may be located further from base station <NUM>-b than UE <NUM>-c and may receive the signal later due to propagation delay. In some cases, UE <NUM>-c and UE <NUM>-d may determine the NB PRACH information independently of base station <NUM>-b-e.g., from a neighboring base station, hard-coding, etc..

At <NUM>, UE <NUM>-c and UE <NUM>-d may identify the location of NB PRACH resources based on the received NB PRACH information. In some cases, UE <NUM>-c and UE <NUM>-d may determine a duration from receiving the PRACH information to when the NB PRACH will be allocated resources. For instance, UE <NUM>-c and UE <NUM>-d may determine a wireless communications system timing based on a received synchronization signal, however, UE <NUM>-c and UE <NUM>-d may be unaware of the propagation delay from base station <NUM>-b. Therefore, the timing determined for the NB PRACH resources by UE <NUM>-c and UE <NUM>-d may also be offset by the propagation delay.

At <NUM>, UE <NUM>-c and UE <NUM>-d may determine frequency hopping patterns based on the NB PRACH information. UE <NUM>-c and UE <NUM>-d may use the determined frequency hopping patterns to generate a preamble sequence. In some cases, UE <NUM>-c and UE <NUM>-d may use the received NB PRACH information to determine the frequency hopping pattern (e.g., a linear hash function, a cyclic shift, or both) and may select a random number r, as described above with reference to <FIG>.

At <NUM>, UE <NUM>-c and UE <NUM>-d may select a preamble sequence based on the selected random number. UE <NUM>-c and UE <NUM>-d may generate and transmit preamble sequences <NUM>-a and <NUM>-b according to the determined frequency hopping pattern to base station105-b. As discussed above, UE <NUM>-c and UE <NUM>-d may determine a timing for the NB PRACH resource that is offset by a propagation delay and the preamble sequence <NUM> transmissions may begin after the starting boundary of NB PRACH <NUM>-a. The preamble sequence <NUM> transmissions may further experience propagation delays prior to reaching base station <NUM>-b. Furthermore, preamble sequence <NUM>-a may reach base station <NUM>-b before preamble sequence <NUM>-b based on environmental and channel conditions observed by UE <NUM>-c and UE <NUM>-d.

At <NUM>, base station <NUM>-b may detect the random access preambles based on the frequency hopping pattern advertised to and used by UE <NUM>-c and UE <NUM>-d. The base station <NUM>-b may observe sets of resources corresponding to different frequency hopping patterns to determine the presence of a random access preamble, a time offset value, and/or a frequency offset value, as discussed above with reference to <FIG>.

At <NUM>, base station <NUM>-b may use the detected random access preambles to determine timing offsets for subsequent transmissions by UE <NUM>-c and UE <NUM>-d, as discussed above with reference to <FIG>. At <NUM>, base station <NUM>-b may transmit the timing offsets to UE <NUM>-c and UE <NUM>-d, which may adjust the timing of subsequent transmissions using the timing offset values. In this way, the base station <NUM>-b may modify the timing of subsequent transmissions from UE <NUM>-c and UE <NUM>-d so that transmissions from UE <NUM>-c and UE <NUM>-d arrive at base station <NUM>-d at substantially the same time (e.g., within a normal cyclic prefix ~<NUM> of one another).

<FIG> shows a block diagram of a wireless device <NUM> configured for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. Wireless device <NUM> may be an example of aspects of a UE <NUM> or base station <NUM> as described with reference to <FIG>. Wireless device <NUM> may include a receiver <NUM>, a PRACH manager <NUM>, and a transmitter <NUM>. PRACH manager <NUM> may include a channel identifier <NUM> and a hopping pattern generator <NUM>. Wireless device <NUM> may also include a processor. Each of these components may be in communication with each other.

The 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 NB PRACH frequency hopping patterns and detection schemes, etc.) via communication link <NUM>. Information received at the receiver <NUM> may be passed on to the PRACH manager <NUM> via communication link <NUM>, and to other components of wireless device <NUM>.

The PRACH manager <NUM> may identify a first portion and a second portion of a PRACH, wherein the first portion is associated with a first frequency hopping distance and the second portion is associated with a second frequency hopping distance. The PRACH manager <NUM> may determine a frequency hopping pattern for a random access preamble that comprises a first number of frequency hops associated with the first frequency hopping distance and a second number of frequency hops associated with the second frequency hopping distance. For example, the frequency hopping pattern may have the first number of frequency hops within the first portion and the second number of frequency hops within the second portion.

The channel identifier <NUM> may identify a first portion and a second portion of a PRACH, wherein the first portion is associated with a first frequency hopping distance and the second portion is associated with a second frequency hopping distance as described with reference to <FIG>. In some examples, the first portion comprises a first set of subcarriers that span a first sub-region of the PRACH and a second set of subcarriers that span a second sub-region of the PRACH, and wherein the first sub-region and the second sub-region are separated in frequency by a bandwidth of the second portion. In some examples, the first frequency hopping distance may be greater than the second frequency hopping distance, and wherein the first frequency hopping distance may be greater than or equal to the bandwidth of the second portion. In some examples, the PRACH may be partitioned into a plurality of subcarriers and preamble tone intervals, and wherein a subcarrier spacing of the plurality of subcarriers may be an integer divisor of a data channel subcarrier spacing for a cell associated with the PRACH. In some examples, the second portion may be partitioned into a plurality of sub-regions, each sub-region of the plurality of sub-regions comprising a plurality of subcarriers.

The hopping pattern generator <NUM> may determine a frequency hopping pattern for a random access preamble that comprises a first number of frequency hops associated with the first frequency hopping distance and a second number of frequency hops associated with the second frequency hopping distance as described with reference to <FIG>. For example, the frequency hopping pattern may include the first number of frequency hops within the first portion and the second number of frequency hops within the second portion. In some examples, the first number of frequency hops is equal to the second number of frequency hops. In some examples, the frequency hops of the first number of frequency hops are determined based at least in part on at least one of a pseudo-random linear hash function or a pseudo-random linear cyclic shift. In some examples, the frequency hops of the second number of frequency hops are determined based at least in part on at least one of a pseudo-random linear hash function or a pseudo-random linear cyclic shift and the number of subcarriers included in the each sub-region. In some cases, PRACH manager <NUM> may generate and pass a random access preamble signal to transmitter <NUM> via communication link <NUM>. Alternatively, PRACH manager <NUM> may pass information indicative of how the random access preamble is to be constructed to transmitter <NUM>, and the transmitter may generate the random access preamble based on the received information.

The transmitter <NUM> may transmit signals received from other components of wireless device <NUM> via communication link <NUM>. In some examples, the transmitter <NUM> may be collocated with the receiver <NUM> in a transceiver module. The transmitter <NUM> may include a single antenna, or it may include a plurality of antennas. In some examples, a UE may use transmitter <NUM> to transmit a random access preamble according to the determined frequency hopping pattern via communication link <NUM>. In some examples, a base station may use receiver <NUM> to receive a random access preamble transmitted according to a determined frequency hopping pattern via communication link <NUM>.

<FIG> shows a block diagram <NUM> of a PRACH manager <NUM>-a which may be a component of a wireless device <NUM> for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. The PRACH manager <NUM>-a may be an example of aspects of a PRACH manager <NUM> described with reference to <FIG>. The PRACH manager <NUM>-a may include a channel identifier <NUM>-a, and a hopping pattern generator <NUM>-a. Each of these modules may perform the functions described with reference to <FIG>. The PRACH manager <NUM>-a may also include a preamble generator <NUM>.

In some cases, PRACH manager <NUM>-a may be implemented at a UE, such as a UE <NUM> as described with reference to <FIG>. Information received at a receiver, such as receiver <NUM> in <FIG>, may be passed to the PRACH manager <NUM>-a via communication link <NUM>-a. The channel identifier <NUM>-a may identify a PRACH for communication (e.g., between a UE <NUM> and a base station <NUM>). The channel identifier <NUM>-a may pass PRACH Information <NUM> to the hopping pattern generator <NUM>-a. The hopping pattern generator <NUM>-a may determine or generate a frequency hopping pattern within the identified PRACH. In some cases, the frequency hopping pattern may include a first number of hops associated with a first hop distance and a second number of hops associated with a second hop distance. The frequency hopping pattern may also include a pseudo-random frequency hop distance. The pseudo-random frequency hop distances at each of multiple preamble tone intervals may be different from one device to another and may correspond to a difference between preambles transmitted by different devices. The hopping pattern generator <NUM>-a may pass the frequency hopping pattern <NUM> to the preamble generator <NUM>.

The preamble generator <NUM> may generate the random access preamble based on the frequency hopping pattern <NUM> to include a plurality of single-tone transmissions, each of the plurality of single-tone transmissions spanning one of the plurality of preamble tone intervals as described with reference to <FIG>. In some examples, PRACH manager <NUM>-a may generate and pass a random access preamble signal to a transmitter, such as transmitter <NUM> in <FIG>, via communication link <NUM>-a.

<FIG> shows a block diagram <NUM> of a PRACH manager <NUM>-b which may be a component of a wireless device <NUM> for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. The PRACH manager <NUM>-b may be an example of aspects of a PRACH manager <NUM> described with reference to <FIG>. The PRACH manager <NUM>-b may include a channel identifier <NUM>-b, and a hopping pattern generator <NUM>-b. Each of these modules may perform the functions described with reference to <FIG>. The PRACH manager <NUM>-b may also include a preamble detector <NUM> and a timing offset calculator <NUM>.

In some cases, PRACH manager <NUM>-b may be implemented at a base station, such as a base station <NUM> as described with reference to <FIG>. Information received at a receiver, such as receiver <NUM> in <FIG>, may be passed to the PRACH manager <NUM>-b via communication link <NUM>-b. The channel identifier <NUM>-b may identify a PRACH for communication (e.g., between a UE <NUM> and a base station <NUM>). The channel identifier <NUM>-b may pass PRACH Information <NUM> to the hopping pattern generator <NUM>-b. The hopping pattern generator <NUM>-b may determine or generate frequency hopping patterns within the identified PRACH. In some cases, the frequency hopping patterns may include a first number of hops associated with a first hop distance and a second number of hops associated with a second hop distance. The frequency hopping patterns may also include a pseudo-random frequency hop distance. The pseudo-random frequency hop distance for each of multiple preamble tone intervals may be different for different frequency hopping patterns. The frequency hopping patterns <NUM> may be passed on to the preamble detector <NUM>.

The preamble detector <NUM> may detect random access preambles transmitted by NB-UEs <NUM> based at least in part on the frequency hopping patterns <NUM> as described with reference to <FIG>. For example, random access preambles transmitted by different devices may correlate to different frequency hopping patterns. In some examples, a preamble associated with a first device may include a first pattern of pseudo-random hopping distances and a preamble associated with a second device may include a second, different pattern of pseudo-random hopping distances. The detected preamble(s) <NUM> may be passed to the preamble detector <NUM>. The timing offset calculator <NUM> may determine timing offset(s) for uplink transmissions from NB-UE(s) <NUM> based on the detected preamble(s) <NUM>. The timing offset(s) may be based at least in part on comparisons of phase information in a plurality of tones of the detected random access preamble(s) as described with reference to <FIG>. In some examples, PRACH manager <NUM>-b may detect and pass information related to a random access preamble to a transmitter, such as transmitter <NUM> in <FIG>, via communication link <NUM>-b.

<FIG> shows a diagram of a system <NUM> including a UE <NUM>-e configured for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. System <NUM> may include UE <NUM>-e, which may be an example of a wireless device <NUM> or a UE <NUM> described with reference to <FIG>, <FIG>, <FIG>, and <FIG>. UE <NUM>-e may include a PRACH manager <NUM>, which may be an example of a PRACH manager <NUM> described with reference to <FIG>. UE <NUM>-e may also include components for bi-directional voice and data communications including components for transmitting communications and components for receiving communications. For example, UE <NUM>-e may communicate bi-directionally with UE <NUM>-f or base station <NUM>-c.

UE <NUM>-e may also include a processor <NUM>, and memory <NUM> (including software (SW) <NUM>), a transceiver <NUM>, and one or more antenna(s) <NUM>, each of which may communicate, directly or indirectly, with one another (e.g., via buses <NUM>). The transceiver <NUM> may communicate bi-directionally, via the antenna(s) <NUM> or wired or wireless links, with one or more networks, as described above. For example, the transceiver <NUM> may communicate bi-directionally with a base station <NUM> or another UE <NUM>. The transceiver <NUM> may include a modem to modulate the packets and provide the modulated packets to the antenna(s) <NUM> for transmission, and to demodulate packets received from the antenna(s) <NUM>. While UE <NUM>-e may include a single antenna <NUM>, UE <NUM>-e may also have multiple antennas <NUM> capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory <NUM> may include random access memory (RAM) and read only memory (ROM). The memory <NUM> may store computer-readable, computer-executable software/firmware code <NUM> including instructions that, when executed, cause the processor <NUM> to perform various functions described herein (e.g., NB PRACH frequency hopping patterns and detection schemes, etc.). Alternatively, the software/firmware code <NUM> may not be directly executable by the processor <NUM> but cause a computer (e.g., when compiled and executed) to perform functions described herein. The processor <NUM> may include an intelligent hardware device, (e.g., a central processing unit (CPU), a microcontroller, an application specific integrated circuit (ASIC), etc.).

<FIG> shows a diagram of a system <NUM> including a base station <NUM>-d configured for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. System <NUM> may include base station <NUM>-d, which may be an example of a wireless device <NUM> or a base station <NUM> described with reference to <FIG>, <FIG>, <FIG>, and <FIG>. Base station <NUM>-d may include a base station PRACH manager <NUM>, which may be an example of a base station PRACH manager <NUM> described with reference to <FIG>. Base station <NUM>-d may also include components for bi-directional voice and data communications including components for transmitting communications and components for receiving communications. For example, base station <NUM>-d may communicate bi-directionally with UE <NUM>-g or UE <NUM>-h.

In some cases, base station <NUM>-d may have one or more wired backhaul links. Base station <NUM>-d may have a wired backhaul link (e.g., S1 interface, etc.) to the core network <NUM>. Base station <NUM>-d may also communicate with other base stations <NUM>, such as base station <NUM>-e and base station <NUM>-f via inter-base station backhaul links (e.g., an X2 interface). Each of the base stations <NUM> may communicate with UEs <NUM> using the same or different wireless communications technologies. In some cases, base station <NUM>-d may communicate with other base stations such as <NUM>-e or <NUM>-f utilizing base station communications module <NUM>. In some examples, base station communications module <NUM> may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between some of the base stations <NUM>. In some examples, base station <NUM>-d may communicate with other base stations through core network <NUM>. In some cases, base station <NUM>-d may communicate with the core network <NUM> through network communications module <NUM>.

The base station <NUM>-d may include a processor <NUM>, memory <NUM> (including SW <NUM>), transceiver <NUM>, and antenna(s) <NUM>, which each may be in communication, directly or indirectly, with one another (e.g., over bus system <NUM>). The transceivers <NUM> may be configured to communicate bi-directionally, via the antenna(s) <NUM>, with the UEs <NUM>, which may be multi-mode devices. The transceiver <NUM> (or other components of the base station <NUM>-d) may also be configured to communicate bi-directionally, via the antennas <NUM>, with one or more other base stations (not shown). The transceiver <NUM> may include a modem configured to modulate the packets and provide the modulated packets to the antennas <NUM> for transmission, and to demodulate packets received from the antennas <NUM>. The base station <NUM>-d may include multiple transceivers <NUM>, each with one or more associated antennas <NUM>. The transceiver may be an example of a combined receiver <NUM> and transmitter <NUM> of <FIG>.

The memory <NUM> may include RAM and ROM. The memory <NUM> may also store computer-readable, computer-executable software code <NUM> containing instructions that are configured to, when executed, cause the processor <NUM> to perform various functions described herein (e.g., NB PRACH frequency hopping patterns and detection schemes, selecting coverage enhancement techniques, call processing, database management, message routing, etc.). Alternatively, the software <NUM> may not be directly executable by the processor <NUM> but be configured to cause the computer, e.g., when compiled and executed, to perform functions described herein. The processor <NUM> may include an intelligent hardware device, e.g., a CPU, a microcontroller, an ASIC, etc. The processor <NUM> may include various special purpose processors such as encoders, queue processing modules, base band processors, radio head controllers, digital signal processor (DSPs), and the like.

The base station communications module <NUM> may manage communications with other base stations <NUM>. In some cases, a communications management module may include a controller or scheduler for controlling communications with UEs <NUM> in cooperation with other base stations <NUM>. For example, the base station communications module <NUM> may coordinate scheduling for transmissions to UEs <NUM> for various interference mitigation techniques such as beamforming or joint transmission.

The components of wireless device <NUM> and PRACH manager <NUM> may, individually or collectively, be implemented with at least one ASIC adapted to perform some or all of the applicable functions in hardware. Alternatively, the functions may be performed by one or more other processing units (or cores), on at least one integrated circuit (IC). In other examples, other types of integrated circuits may be used (e.g., Structured/Platform ASICs, a field programmable gate array (FPGA), or another semi-custom IC), which may be programmed in any manner known in the art. The functions of each unit may also be implemented, in whole or in part, with instructions embodied in a memory, formatted to be executed by one or more general or application-specific processors.

<FIG> shows a flowchart illustrating a method <NUM> for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM> or its components as described with reference to <FIG>. For example, the operations of method <NUM> may be performed by the PRACH manager <NUM> 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 UE <NUM> to perform the functions described below. Additionally or alternatively, the UE <NUM> may perform aspects the functions described below using special-purpose hardware.

At block <NUM>, the UE <NUM> may identify a PRACH for communication between a base station <NUM> and the UE <NUM>, as described with reference to <FIG>. In some cases, the PRACH may be partitioned into a plurality of subcarriers and a plurality of preamble tone intervals. A subcarrier spacing of the plurality of subcarriers may an integer divisor of a data channel subcarrier spacing for a cell associated with the PRACH. The PRACH may include a first portion associated with a first frequency hopping distance and a second portion associated with a second frequency hopping distance. The first portion may include a first set of subcarriers that span a first sub-region of the PRACH and a second set of subcarriers that span a second sub-region of the PRACH. The first sub-region and the second sub-region may be separated in frequency by a bandwidth of the second portion. In certain examples, the operations of block <NUM> may be performed by the channel identifier <NUM> as described with reference to <FIG>.

At block <NUM>, the UE <NUM> may determine a frequency hopping pattern within the PRACH for a random access preamble comprising a plurality of single tone transmissions. The plurality of single tone transmissions may span one of a plurality of preamble tone intervals. In some examples, the frequency hopping pattern includes a first number of frequency hops associated with the first frequency hopping distance and a second number of frequency hops associated with the second frequency hopping distance, as described with reference to <FIG>. In some cases, the first number of frequency hops may be different from the second number of frequency hops. At least one frequency hop may be determined based at least in part on a pseudo-random function. The random access preamble may be one of a plurality of random access preambles and different frequency hopping patterns for each of the plurality of random access preambles may be generated using a pseudo-random function. In certain examples, the operations of block <NUM> may be performed by the hopping pattern generator <NUM> as described with reference to <FIG>.

At block <NUM>, the UE <NUM> may transmit the random access preamble according to the determined frequency hopping pattern, as described with reference to <FIG>. In certain examples, the operations of block <NUM> may be performed by the preamble generator <NUM> as described with reference to <FIG>.

<FIG> shows a flowchart illustrating a method <NUM> for NB PRACH frequency hopping patterns and detection schemes in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a base station <NUM> or its components as described with reference to <FIG>. For example, the operations of method <NUM> may be performed by the PRACH manager <NUM> 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 base station <NUM> to perform the functions described below. Additionally or alternatively, the base station <NUM> may perform aspects the functions described below using special-purpose hardware.

At block <NUM>, the base station <NUM> may identify a PRACH for communication between the base station <NUM> and a UE <NUM>, as described with reference to <FIG>. In some cases, the PRACH may be partitioned into a plurality of subcarriers and a plurality of preamble tone intervals. A subcarrier spacing of the plurality of subcarriers may an integer divisor of a data channel subcarrier spacing for a cell associated with the PRACH. The PRACH may include a first portion associated with a first frequency hopping distance and a second portion associated with a second frequency hopping distance. The first portion may include a first set of subcarriers that span a first sub-region of the PRACH and a second set of subcarriers that span a second sub-region of the PRACH. The first sub-region and the second sub-region may be separated in frequency by a bandwidth of the second portion. In certain examples, the operations of block <NUM> may be performed by the channel identifier <NUM> as described with reference to <FIG>.

At block <NUM>, the base station <NUM> may determine a frequency hopping pattern within the PRACH for a random access preamble comprising a plurality of single tone transmissions, the frequency hopping pattern comprising a first number of frequency hops associated with a first frequency hopping distance and a second number of frequency hops associated with a second frequency hopping distance, as described with reference to <FIG>. In some cases, the first number of frequency hops may be different from the second number of frequency hops. At least one frequency hop may be determined based at least in part on a pseudo-random function. The random access preamble may be one of a plurality of random access preambles and different frequency hopping patterns for each of the plurality of random access preambles may be generated using a pseudo-random function. In certain examples, the operations of block <NUM> may be performed by the hopping pattern generator <NUM> as described with reference to <FIG>.

At block <NUM>, the base station <NUM> may detect the random access preamble based at least in part on the determined frequency hopping pattern, as described with reference to <FIG>. In certain examples, the operations of block <NUM> may be performed by the preamble detector <NUM> as described with reference to <FIG>.

At block <NUM>, the UE <NUM> may identify a PRACH for communication between a base station <NUM> and the UE <NUM>, as described with reference to <FIG>. In some cases, the PRACH may be include a plurality of subcarriers. In certain examples, the operations of block <NUM> may be performed by the channel identifier <NUM> as described with reference to <FIG>.

At block <NUM>, the UE <NUM> may determine a frequency hopping pattern within the PRACH for a random access preamble comprising a plurality of single tone transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance, as described with reference to <FIG>. In some cases, the pseudo-random frequency hop distance may be determined based on at least one of a pseudo-random linear hash function, or a pseudo-random linear cyclic shift or may be determined based on a number of subcarriers of the PRACH. In certain examples, the operations of block <NUM> may be performed by the hopping pattern generator <NUM> as described with reference to <FIG>.

At block <NUM>, the UE <NUM> may identify a PRACH for communication between the base station <NUM> and a UE <NUM>, as described with reference to <FIG>. In some cases, the PRACH may be include a plurality of subcarriers. In certain examples, the operations of block <NUM> may be performed by the channel identifier <NUM> as described with reference to <FIG>.

At block <NUM>, the base station <NUM> may determine a frequency hopping pattern within the PRACH for a random access preamble comprising a plurality of single tone transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance, as described with reference to <FIG>. In some cases, the pseudo-random frequency hop distance may be determined based on at least one of a pseudo-random linear hash function, or a pseudo-random linear cyclic shift. According to the present invention, the pseudo-random frequency hop distance is determined based on a number of subcarriers of the PRACH. In certain examples, the operations of block <NUM> may be performed by the hopping pattern generator <NUM> as described with reference to <FIG>.

At block <NUM>, the base station <NUM> may detect the random access preamble based at least in part on the determined frequency hopping pattern, as described with reference to <FIG>. Detecting the random access preamble may include mapping the phase information for the plurality of tones to a sequence based at least in part on respective preamble tone intervals and respective subcarriers of the plurality of single tone transmissions, and performing a frequency transform on the mapped sequence. In some cases, detecting the random access preamble may include mapping differential phase information between two or more tones of the plurality of tones to a sequence based at least in part on the respective preamble tone intervals and respective subcarriers of the plurality of single tone transmissions, and performing a frequency transform on the mapped sequence. In certain examples, the operations of block <NUM> may be performed by the preamble detector <NUM> as described with reference to <FIG>.

In some examples, the base station <NUM> may determine a timing offset for uplink transmissions from the UE based at least in part on phase information in a plurality of tones of the random access preamble detected at <NUM>. In some examples, determining the timing offset may include identifying a location of a maximum value of an output of the frequency transform of the mapped sequence. Detecting the random access preamble may include comparing the maximum value with a threshold. In certain examples, determining the timing offset may be performed by the timing offset calculator <NUM> as described with reference to <FIG>.

Thus, methods <NUM>, <NUM>, <NUM>, and <NUM> may provide for NB PRACH frequency hopping patterns and detection schemes. It should be noted that methods <NUM>, <NUM>, <NUM>, and <NUM> describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified such that other implementations are possible. In some examples, aspects from two or more of the methods <NUM>, <NUM>, <NUM>, and <NUM> may be combined.

The description herein provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims.

Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), OFDMA, SC-FDMA, and other systems. The terms "system" and "network" are often used interchangeably. IS-<NUM> Releases <NUM> and A are commonly referred to as CDMA2000 1X, 1X, etc. IS-<NUM> (TIA-<NUM>) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications system (UMTS). UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). 3GPP LTE and LTE-A are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies. The description herein, however, describes an LTE system for purposes of example, and LTE terminology is used in much of the description above, although the techniques are applicable beyond LTE applications.

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

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

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

Each communication link described herein-including, for example, wireless communications systems <NUM> and <NUM> of <FIG> and <FIG>-may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies). Each modulated signal may be sent on a different sub-carrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, user data, etc. The communication links described herein (e.g., communication links <NUM> of <FIG>) may transmit bidirectional communications using FDD (e.g., using paired spectrum resources) or TDD operation (e.g., using unpaired spectrum resources). Frame structures may be defined for FDD (e.g., frame structure type <NUM>) and TDD (e.g., frame structure type <NUM>).

By way of example, and not limitation, non-transitory computer-readable media can comprise RAM, ROM, electrically erasable programmable read only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

Claim 1:
A method for wireless communication, comprising:
identifying (<NUM>) a physical random access channel, PRACH, for communication between a base station (<NUM>) and a user equipment (<NUM>), UE, the PRACH comprising a plurality of subcarriers; and
determining (<NUM>) a frequency hopping pattern within the PRACH for a random access preamble, the random access preamble comprising a plurality of single subcarrier transmissions, the frequency hopping pattern comprising a plurality of frequency hops across the plurality of subcarriers, at least one frequency hop of the plurality of frequency hops being associated with a pseudo-random frequency hop distance;
wherein the pseudo-random frequency hop distance is based on a number of subcarriers of the PRACH.