Patent Description:
In accordance with rapid developments and increasing needs of the Internet of Things (IoT), a new radio interface, a Narrowband Internet of Things (NB-IoT), has been proposed by the <NUM>rd Generation Partnership Project (3GPP). The NB-IoT is aimed to enhance existing Global System for Mobile Communications (GSM) and Long-Term Evolution (LTE) networks to better serve IoT uses or applications. Improved indoor coverage, support for massive number of low throughput end devices, low delay sensitivity, ultra-low device cost, coverage extension, battery lifetime extension, and backward compatibility are some exemplary objectives of the NB-IoT.

Generally, in a wireless communication system adopting the NB-IoT (hereinafter "NB-IoT system"), a user equipment device (UE) sends at least one preamble signal (hereinafter "Preamble'), typically via a Physical Random Access Channel (PRACH), to a base station (BS) to initiate a contention-based random access procedure. Such a Preamble is used as a temporary identity of the UE for the BS to estimate various information, e.g., timing advance command, scheduling of uplink resources for the UE to use in subsequent steps, such that the UE may use the above-mentioned information to finish the random access procedure.

An existing format of the Preamble includes a first set of four symbol groups (SGs) that are adjacent to one another in a time domain and subjected to only one frequency hopping over more than two subcarrier indexes in a frequency domain. The Preamble is sent using the first set of the four SGs, and when the Preamble is desired to be sent again or another Preamble is desired to be sent, a second set of four SGs, limited by the same criteria as described above, is used. Moreover, in the existing format of the Preamble, the first and second sets of SGs, for example, are randomly chosen from a pre-defined pattern, wherein the pattern is formed by a plurality of SGs that are confined within <NUM> subcarriers in the frequency domain.

However, it has been noted that the use of the exi sting format of the Preamble may encounter a variety of issues such as, for example, wrong estimation of the timing advance command when a respective coverage of the BS extends beyond <NUM> kilometers (typically known as a "cell"), strong interference among plural neighboring cells, etc. Accordingly, the existing format of the Preamble in the NB-IoT system is not entirely satisfactory.

<CIT> relates to a communications network being accessed by a wireless device associated with a coverage class selected from a set of coverage classes. <NPL> relates to support larger cell radius for NPRACH channel. <NPL> relates to a NB-PRACH design.

The exemplary embodiments disclosed herein are directed to solving the issues relating to one or more of the problems presented in the prior art, as well as providing additional features that will become readily apparent by reference to the following detailed description when taken in conjunction with the accompany drawings. In accordance with various embodiments, exemplary systems, methods, devices and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and not limitation, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of the appended claims.

Various exemplary embodiments of the invention are described below with reference to the accompanying figures to enable a person of ordinary skill in the art to make and use the invention. As would be apparent to those of ordinary skill in the art, after reading the present disclosure, various changes or modifications to the examples described herein can be made without departing from the scope of the invention. Thus, the present invention is not limited to the exemplary embodiments and applications described and illustrated herein. Additionally, the specific order or hierarchy of steps in the methods disclosed herein are merely exemplary approaches. Based upon design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be re-arranged while remaining within the scope of the present invention. Thus, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or acts in a sample order, and the invention is not limited to the specific order or hierarchy presented unless expressly stated otherwise.

<FIG> illustrates an exemplary wireless communication network <NUM> in which techniques disclosed herein may be implemented, in accordance with an embodiment of the present disclosure. In the following discussion, the wireless communication network <NUM> may be a NB-IoT network, which is herein referred to as "network <NUM>. " Such an exemplary network <NUM> includes a base station <NUM> (hereinafter "BS <NUM>") and a user equipment device <NUM> (hereinafter "UE <NUM>") that can communicate with each other via a communication link <NUM> (e.g., a wireless communication channel), and a cluster of notional cells <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> overlaying a geographical area <NUM>.

Such communication nodes may be capable of wireless and/or wired communications, in accordance with various embodiments of the invention.

<FIG> illustrates a block diagram of an exemplary wireless communication system <NUM> for transmitting and receiving wireless communication signals, e.g., OFDM/OFDMA signals, in accordance with some embodiments of the invention. The system <NUM> may include components and elements configured to support known or conventional operating features that need not be described in detail herein. In one exemplary embodiment, system <NUM> can be used to transmit and receive data symbols in a wireless communication environment such as the wireless communication environment <NUM> of <FIG>, as described above.

The BS <NUM> includes a BS (base station) transceiver module <NUM>, a BS antenna <NUM>, a BS processor module <NUM>, a BS memory module <NUM>, and a network communication module <NUM>, each module being coupled and interconnected with one another as necessary via a date communication bus <NUM>. The BS <NUM> communicates with the UE <NUM> via a communication channel <NUM>, which can be any wireless channel or other medium known in the art suitable for transmission of data as described herein.

In accordance with some embodiments, the UE transceiver <NUM> may be referred to herein as an "uplink" transceiver <NUM> that includes a RF transmitter and receiver circuitry that are each coupled to the antenna <NUM>. Similarly, in accordance with some embodiments, the BS transceiver <NUM> may be referred to herein as a "downlink" transceiver <NUM> that includes RF transmitter and receiver circuity that are each coupled to the antenna <NUM>. The operations of the two transceivers <NUM> and <NUM> are coordinated in time such that the uplink receiver is coupled to the uplink antenna <NUM> for reception of transmissions over the wireless transmission link <NUM> at the same time that the downlink transmitter is coupled to the downlink antenna <NUM>. Preferably there is close time synchronization with only a minimal guard time between changes in duplex direction.

In some exemplary embodiments, the UE transceiver <NUM> and the base station transceiver <NUM> are configured to support industry standards such as the Long Term Evolution (LTE) and emerging <NUM> standards, and the like. It is understood, however, that the invention is not necessarily limited in application to a particular standard and associated protocols.

Referring again to <FIG>, as discussed above, to initiate a random access procedure, the UE <NUM> sends a Preamble using a plurality of resource groups (e.g., SGs (symbol groups)) to the as <NUM>. The present disclosure provides various embodiments of a format of such a Preamble, hereinafter the "Preamble format," for the UE <NUM> to use. In some embodiments, the disclosed Preamble format includes a plurality of SG patterns, each of which is subjected to a respective frequency/time hopping rule. In some embodiments, such frequency/time hopping rule may be pre-defined in a protocol of the network <NUM> or transmitted in a higher-level signal (e.g., a radio resource control (RRC) signal) from the BS <NUM> to the UE <NUM>. Compared to the existing Preamble format, the respective frequency/time hopping rules advantageously allows the BS <NUM> to estimate the timing advanced command more accurately for the UE <NUM> (i.e., more accurate scheduling), for example, when the cell <NUM> is implanted as a cell that has a coverage greater than <NUM> kilometers (km), which will be discussed below. Moreover, when using the frequency/time hopping rules to send a Preamble, interference between the cell <NUM> and one or more other neighboring cells (e.g., <NUM>, <NUM>, <NUM>, etc.) may be substantially mitigated, which can in turn reduce a False Alarm Probability (FAP) happening to the Preamble.

<FIG> and <FIG> provide two exemplary frame structures of the SG <NUM> and <NUM>, respectively, that can be used by the disclosed Preamble format, in accordance with some embodiments of the present disclosure. Referring first to <FIG>, the SG <NUM> includes a cyclic prefix (CP) <NUM>-<NUM>, and three symbols (Ss) <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. More specifically, each of the symbols in the SG <NUM> extends across a time duration of about <NUM> microseconds (µs) and the CP <NUM>-<NUM> extends across <NUM> of such a time duration of the symbol (i.e., <NUM> × <NUM>) along the time domain, and is modulated on a <NUM> tone along the frequency domain, e.g., a <NUM> frequency spacing, which is typically known as a <NUM> subcarrier spacing. For purpose of consistency, the SG <NUM> is herein referred to as being defined on a <NUM> subcarrier spacing. As such, the SG <NUM> may extend across about <NUM> milliseconds (ms) in the time domain and spaced from another SG by <NUM> in the frequency domain.

Referring then to <FIG>, the SG <NUM> includes one CP <NUM>-<NUM>, and two symbols <NUM>-<NUM> and <NUM>-<NUM>. More specifically, each of the CP and symbols in the SG <NUM> extends across a time duration of about <NUM> along the time domain, and is modulated on a <NUM> tone along the frequency domain, e.g., a <NUM> subcarrier spacing, which is typically known as a <NUM> subcarrier spacing. For purpose of consistency, the SG <NUM> is herein referred to as being defined on a <NUM> subcarrier spacing. As such, the SG <NUM> may extend across about <NUM> milliseconds (ms) in the time domain and spaced from another SG by <NUM> in the frequency domain. It is noted that the frame structures of the SG <NUM> and <NUM>, of <FIG> and <FIG>, are merely provided for illustration purposes. Accordingly, any of a variety of other frame structures of the SG can be used in the following discussions of the disclosed Preamble format while remaining within the scope of the present disclosure. For example, the SG frame structure may have any desired length (e.g., time duration) of CP(s) and any desired number of symbol(s), respectively, and/or be modulated on any desired frequency of tone (i.e., having any desired frequency/subcarrier spacing).

In an embodiment, when an SG is defined based on the subcarrier spacing of <NUM> (e.g., the SG <NUM>), a disclosed Preamble format, which will be discussed with respect to <FIG> and <FIG>, is decided based on a pre-defined SG map <NUM> as illustrated in <FIG>. In the illustrated embodiment of <FIG>, the SG map <NUM> includes <NUM> SGs, each of which may be implemented by the SG <NUM>. More specifically, in some embodiments, the SG map <NUM> extends across <NUM> SGs with corresponding time durations (<NUM>) in the time domain, and across <NUM> SGs, i.e., <NUM> contiguous subcarrier spacings, in the frequency domain (<NUM>), respectively. In the time domain, each SG is associated with a respective SG index (e.g., SG index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>); and in the frequency domain, each SG is associated with a respective frequency index, for example, a respective subcarrier index (e.g., subcarrier index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>). In some embodiments, the first <NUM> SGs (i.e., the SGs with SG indexes <NUM>-<NUM>) and last <NUM> SGs (i.e., the SGs with SG indexes <NUM>-<NUM>) of the SG map <NUM> may be spaced from each other by a pre-defined time interval.

According to some embodiments, the SG map <NUM> are divided into two sub-groups <NUM> and <NUM>, which are filled with a dotted pattern and a diagonal stripes pattern, respectively, as shown in <FIG>. In some embodiments, in the SG map <NUM>, the SGs sharing a common SG index (i.e., along a same column of the SG map <NUM>) has a half that belongs to the sub-group <NUM> and the other half that belongs to the sub-group <NUM>. Further, along one of the columns of the SG map <NUM>, each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH (Physical Random Access Channel) index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; and each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In some embodiments, respective distributions of the PRACH indexes in terms of SG index/subcarrier index within each sub-group are pre-defined, as provided below.

For example, along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

The above-discussed distribution of PRACH indexes of the SG map <NUM> is pre-defined in accordance with a first frequency/time hopping rule that can be used by a UE (e.g., <NUM> of <FIG>) to send a Preamble to a BS (e.g., <NUM> of <FIG>) for initiating a random access procedure, in accordance with some embodiments. In accordance with some embodiments of the present disclosure, the first frequency/time hopping rule indicates that the Preamble is sent using at least <NUM> SGs (i.e., the Preamble includes at least <NUM> SGs), each of which is selected from a respective SG index. Further, the first frequency/time hopping rule indicates that either the sub-group <NUM> or <NUM> is selected, and subsequently, a first SG can be randomly chosen from the first column (i.e., the column with the SG index <NUM>) of the SG map <NUM> within the selected sub-group. Next, subsequent (e.g., remaining) SGs of the at least <NUM> SGs are each chosen from a respective column (i.e., the columns with SG indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) within the selected sub-group, wherein all <NUM> SGs share a same PRACH index, or alternatively, a first set of <NUM> SGs shares a first PRACH index and a second set of <NUM> SGs shares a second PRACH index.

In another embodiment, the first frequency/time hopping rule includes: randomly selecting an SG from the first column as the first SG of the at least <NUM> SGs; based on a respective sub-carrier index of the randomly selected SG in the first column, determining which of the sub-groups and which PRACH index to be used for the remaining <NUM> SGs of the at least <NUM> SGs.

In yet another embodiment, the first frequency/time hopping rule includes: randomly selecting an SG from the first column as the first SG of the at least <NUM> SGs; based on a respective sub-carrier index of the randomly selected SG in the first column, determining which of the sub-groups and which PRACH index to be used for the second, third, fourth SGs of the at least <NUM> SGs; randomly selecting an SG from the fifth column as the fifth SG of the at least <NUM> SGs within the sub-group that is selected by the first SG; based on a respective sub-carrier index of the randomly selected SG in the fifth column, determining which of the sub-groups and which PRACH index to be used for the sixth, seventh, eighth SGs of the at least <NUM> SGs. More specifically, a sub-carrier index of an (n+<NUM>)th SG within the at least <NUM> SGs can be determined by one of the following equations (<NUM>) and (<NUM>)<MAT><MAT> , wherein.

As such, the Preamble follows a corresponding Preamble format when the first frequency/time hopping rule is applied.

In an embodiment, when the first frequency/time hopping rule is applied and the Preamble is sent using more than <NUM> SGs, e.g., <NUM> SGs, respective subcarrier indexes of a first SG of a first set of <NUM> SGs and a first SG of a second set of <NUM> SGs may be randomly selected.

<FIG> and <FIG> provide two exemplary Preamble formats <NUM> and <NUM> that can be used by a Preamble including at least <NUM> SGs when the first frequency/time hopping rule is applied. As mentioned above, one of the sub-groups <NUM> and <NUM> is selected. In <FIG>, the sub-group <NUM> is selected. Next, within the sub-group <NUM>, a first SG with a corresponding subcarrier index is randomly chosen from the first column (the SG index = <NUM>) of the SG map <NUM>. In an example, the subcarrier index "<NUM>" is chosen as the first SG from the first column, which causes the first SG to be associated with the PRACH index <NUM> (within the sub-group <NUM>). Following the first frequency/time hopping rule, each of the remaining <NUM> SGs is chosen from a respective column within the sub-group <NUM> and having the same PRACH index as the first SG. As such, from the second column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as a second SG since it is associated with the PRACH index <NUM>; from the third column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as a third SG since it is associated with the PRACH index <NUM>; from the fourth column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as a fourth SG since it is associated with the PRACH index <NUM>; from the fifth column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as a fifth SG since it is associated with the PRACH index <NUM>; from the sixth column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as a sixth SG since it is associated with the PRACH index <NUM>; from the seventh column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as a seventh SG since it is associated with the PRACH index <NUM>; from the eighth column (the SG index = <NUM>), the SG with the subcarrier index "<NUM>" is chosen as an eighth SG since it is associated with the PRACH index <NUM>.

In some embodiments, when using the first frequency/time hopping rule to provide the Preamble format <NUM>, the first SG with a subcarrier index, e.g., subcarrier index "k," is chosen within the sub-group <NUM>, wherein k is randomly chosen and is <NUM> in the above example, and the remaining SGs (second, third, fourth, fifth, sixth, seventh, and eighth SGs) are chosen as follows. The second SG is chosen to hop "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG is chosen to hop "upwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the fourth SG is chosen to hop "downwardly" from the third SG by <NUM> subcarrier index, e.g., from "k+<NUM>" to "k+<NUM>. " The fifth SG with a subcarrier index, e.g., subcarrier index "n," is chosen, wherein n is not limited by the subcarrier index k and is <NUM> in the above example; the sixth SG is chosen to hop "upwardly" from the fifth SG by <NUM> subcarrier index, e.g., from "n" to "n+<NUM>;" the seventh SG is chosen to hop "downwardly" from the sixth SG by <NUM> subcarrier indexes, e.g., from "n+<NUM>" to "n-<NUM>;" the eighth SG is chosen to hop "downwardly" from the seventh SG by <NUM> subcarrier index, e.g., from "n-<NUM>" to "n-<NUM>.

The Preamble format <NUM> illustrated in <FIG> is substantially similar to the Preamble format <NUM> except that the sub-group <NUM> is selected. Thus, the Preamble format <NUM> is discussed briefly as follows. In the Preamble format <NUM>, the first SG is with a subcarrier index, e.g., subcarrier index "k," wherein k is randomly chosen; the second SG hops "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG hops "downwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k-<NUM>;" the fourth SG hops "downwardly" from the third SG by <NUM> subcarrier index, e.g., from "k-<NUM>" to "k-<NUM>. " The fifth SG is with a subcarrier index, e.g., subcarrier index "n," wherein n is not limited by the subcarrier index k; the sixth SG hops "upwardly" from the fifth SG by <NUM> subcarrier index, e.g., from "n" to "n+<NUM>;" the seventh SG hops "upwardly" from the sixth SG by <NUM> subcarrier indexes, e.g., from "n+<NUM>" to "n+<NUM>;" the eighth SG hops "downwardly" from the seventh SG by <NUM> subcarrier index, e.g., from "n+<NUM>" to "n+<NUM>.

It is noted that, in such an embodiment, at least two upward frequency hoppings and at least two downward frequency hoppings that each crosses over <NUM> subcarrier index and at least one upward frequency hopping and at least one downward frequency hopping that each crosses over <NUM> subcarrier indexes are present in each of the Preamble formats <NUM> and <NUM>. Accordingly, the Preamble, using either the Preamble format <NUM> or <NUM>, can follow a hopping pattern that includes a first hopping path associated with a first plurality of increasing subcarrier spacings, which correspond to a first plurality of increasing subcarrier indexes in the current example (e.g., from k+<NUM> to k+<NUM> in the format <NUM>, from n+<NUM> to n+<NUM> in format <NUM>, etc.), a second hopping path associated with a second plurality of decreasing subcarrier spacings, which correspond to a second plurality of decreasing subcarrier indexes in the current example (e.g., from n+<NUM> to n-<NUM> in the format <NUM>, from k+<NUM> to k-<NUM> in the format <NUM>), a third hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>, from k to k+<NUM> in the format <NUM>), a fourth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from k+<NUM> to k+<NUM> in the format <NUM>, from k-<NUM> to k-<NUM> in the format <NUM>), a fifth hopping path associated with <NUM> increasing subcarrier spacing (e.g., from n to n+<NUM> in the format <NUM>, from n to n+<NUM> in the format <NUM>), and a sixth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from n-<NUM> to n-<NUM> in the format <NUM>, from n+<NUM> to n+<NUM> in the format <NUM>). Further, in some embodiments, respective frequency intervals (or typically known as frequency hopping distances) of the first and second hopping paths may be equal to each other. In some alternative embodiments, such frequency intervals of the first and second hopping paths may be each of an integral times or a fractional times a respective subcarrier spacing (e.g., <NUM>). Alternatively stated, the first plurality of increasing subcarrier spacings and the second plurality of decreasing subcarrier spacings may be each an integral times or a fractional times the <NUM> subcarrier spacing in the current example.

In another embodiment, when an SG is defined based on the subcarrier spacing of <NUM> (e.g., the SG <NUM>), another disclosed Preamble format, which will be discussed with respect to <FIG> and <FIG>, is decided based on a respective pre-defined SG map <NUM> as illustrated in <FIG>. In the illustrated embodiment of <FIG>, the SG map <NUM> includes <NUM> SGs, each of which may be implemented by the SG <NUM>. More specifically, in some embodiments, the SG map <NUM> extends across <NUM> SGs with corresponding time durations (<NUM>) in the time domain, and across <NUM> SGs, i.e., <NUM> contiguous subcarrier spacings in the frequency domain (<NUM>), respectively. In the time domain, each SG is associated with a respective SG index (e.g., SG index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>); and in the frequency domain, each SG is associated with a respective subcarrier index (e.g., subcarrier index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>).

According to some embodiments, the SG map <NUM> are divided into two sub-groups <NUM> and <NUM>, which are filled with a dotted pattern and a diagonal stripes pattern, respectively, as shown in <FIG>. In some embodiments, in the SG map <NUM>, the SGs sharing a common SG index (i.e., along a same column of the SG map <NUM>) has a half that belongs to the sub-group <NUM> and the other half that belongs to the sub-group <NUM>. Further, along one of the columns of the SG map <NUM>, each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; and each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In some embodiments, respective distributions of the PRACH indexes in terms of SG index/subcarrier index within each sub-group are pre-defined, as provided below.

For example, along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; and the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

The above-discussed distribution of PRACH indexes of the SG map <NUM> is pre-defined in accordance with a second frequency/time hopping rule that can be used by a UE (e.g., <NUM> of <FIG>) to send a Preamble to a BS (e.g., <NUM> of <FIG>) for initiating a random access procedure. In accordance with some embodiments of the present disclosure, the second frequency/time hopping rule indicates that the Preamble is sent using at least <NUM> SGs (i.e., the Preamble includes at least <NUM> SGs), each of which is selected from a respective SG index. Further, the second frequency/time hopping rule indicates that either the sub-group <NUM> or <NUM> is selected, and subsequently, a first SG can be randomly chosen from the first column (i.e., the column with the SG index <NUM>) of the SG map <NUM> within the selected sub-group. Next, subsequent (e.g., remaining) SGs of the at least <NUM> SGs are each chosen from a respective column (i.e., the columns with SG indexes <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) within the selected sub-group, wherein all <NUM> SGs share a same PRACH index. In an alternative embodiment, the second frequency/time hopping rule includes: randomly selecting an SG from the first column as the first SG of the at least <NUM> SGs; based on a respective sub-carrier index of the randomly selected SG in the first column, determining which of the sub-groups and which PRACH index to be used for the remaining <NUM> SGs of the at least <NUM> SGs. As such, the Preamble follows a corresponding Preamble format when the second frequency/time hopping rule is applied.

In an embodiment, when the second frequency/time hopping rule is applied and the Preamble is sent using more than <NUM> SGs, e.g., <NUM> SGs, respective subcarrier indexes of a first SG of a first set of <NUM> SGs and a first SG of a second set of <NUM> SGs may be randomly selected.

<FIG> and <FIG> provide two exemplary Preamble formats <NUM> and <NUM> that can be used by a Preamble including at least <NUM> SGs when the second frequency/time hopping rule is applied. As mentioned above, one of the sub-groups <NUM> and <NUM> is first selected. In <FIG>, the sub-group <NUM> is selected. Next, a first SG within the sub-group <NUM> with a subcarrier index, e.g., subcarrier index "k," is chosen, wherein k is randomly chosen, and the remaining SGs (second, third, fourth, fifth, and sixth SGs) are chosen as follows. The second SG is chosen to hop "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG is chosen to hop "upwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the fourth SG is chosen to hop "downwardly" from the third SG by <NUM> subcarrier index, e.g., from "k+<NUM>" to "k+<NUM>;" the fifth SG is chosen to hop "downwardly" from the fourth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k;" and the sixth SG is chosen to hop "upwardly" from the fifth SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>.

The Preamble format <NUM> illustrated in <FIG> is substantially similar to the Preamble format <NUM> except that the sub-group <NUM> is chosen. Thus, the Preamble format <NUM> is discussed briefly as follows. In the Preamble format <NUM>, the first SG is with a subcarrier index, e.g., subcarrier index "k," wherein k is randomly chosen; the second SG hops "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG hops "downwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k-<NUM>;" the fourth SG hops "downwardly" from the third SG by <NUM> subcarrier index, e.g., from "k-<NUM>" to "k-<NUM>;" the fifth SG hops "upwardly" from the fourth SG by <NUM> subcarrier indexes, e.g., from "k-<NUM>" to "k;" the sixth SG hops "upwardly" from the fifth SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>.

It is noted that, in such an embodiment, at least two upward frequency hoppings, at least one downward frequency hopping that each crosses over <NUM> subcarrier index and at least one upward frequency hopping and at least one downward frequency hopping that each crosses over <NUM> subcarrier indexes are present in each of the Preamble formats <NUM> and <NUM>. Accordingly, the Preamble, using either the Preamble format <NUM> or <NUM>, can follow a hopping pattern that includes a first hopping path associated with a first plurality of increasing subcarrier spacings, which correspond to a first plurality of increasing subcarrier indexes in the current example (e.g., from k+<NUM> to k+<NUM> in the format <NUM>, from k-<NUM> to k in format <NUM>, etc.), a second hopping path associated with a second plurality of decreasing subcarrier spacings, which correspond to a second plurality of decreasing subcarrier indexes in the current example (e.g., from k+<NUM> to k in the format <NUM>, from k+<NUM> to k-<NUM> in the format <NUM>), a third hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>, from k to k+<NUM> in the format <NUM>), a fourth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from k+<NUM> to k+<NUM> in the format <NUM>, from k-<NUM> to k-<NUM> in the format <NUM>), and a fifth hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>, from k to k+<NUM> in the format <NUM>). Further, in some embodiments, respective frequency intervals (or typically known as frequency hopping distances) of the first and second hopping paths may be equal to each other. In some alternative embodiments, such frequency intervals of the first and second hopping paths may be each of an integral times or a fractional times a respective subcarrier spacing (e.g., <NUM>). Alternatively stated, the first plurality of increasing subcarrier spacings and the second plurality of decreasing subcarrier spacings may be each an integral times or a fractional times the <NUM> subcarrier spacing in the current example.

In yet another embodiment, when an SG is defined based on the subcarrier spacing of <NUM> (e.g., the SG <NUM>), a disclosed Preamble format, which will be discussed with respect to <FIG>, is decided based on a pre-defined SG map <NUM> as illustrated in <FIG>. In the illustrated embodiment of <FIG>, the SG map <NUM> includes <NUM> SGs, each of which may be implemented by the SG <NUM>. More specifically, in some embodiments, the SG map <NUM> includes two portions <NUM>-<NUM> and <NUM>-<NUM> spaced from each other by <NUM> contiguous subcarrier spacings in the frequency domain, and each of the portions <NUM>-<NUM> and <NUM>-<NUM> extends across <NUM> SGs with corresponding time durations (<NUM>) in the time domain and across <NUM> SGs, i.e., <NUM> subcarrier spacings, (<NUM>) in the frequency domain, respectively. In the time domain, each SG is associated with a respective SG index (e.g., SG index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>); and in the frequency domain, each SG is associated with a respective subcarrier index (e.g., subcarrier index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>). Because of the <NUM> contiguous subcarrier spacings between the portions <NUM>-<NUM> and <NUM>-<NUM>, it is noted that subcarrier indexes between <NUM> and <NUM> are not contiguous.

According to some embodiments, the SG map <NUM> are divided into four sub-groups <NUM>, <NUM>, <NUM>, and <NUM>, which are filled with a dotted pattern, a diagonal stripes pattern, a vertical stripes pattern, and a horizonal stripes pattern, respectively, as shown in <FIG>. In some embodiments, in the SG map <NUM>, the SGs sharing a common SG index (i.e., along a same column of the SG map <NUM>) has a first quarter that belongs to the sub-group <NUM>, a second quarter that belongs to the sub-group <NUM>, a third quarter that belongs to the sub-group <NUM>, and a fourth quarter that belongs to the sub-group <NUM>. Further, along one of the columns of the SG map <NUM>, each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH (Physical Random Access Channel) index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>; and each of the SGs, belonging to the sub-group <NUM>, is associated with a respective PRACH index that is selected from one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In some embodiments, respective distributions of the PRACH indexes in terms of SG index/subcarrier index within each sub-group are pre-defined, as provided below.

For example, along the column with the SG index <NUM>, the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively; the SGs within the sub-group <NUM> with the subcarrier indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are associated with respective PRACH indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Similarly, along each of other columns of the SG map <NUM>, the SGs belonging to each sub-group are each associated with a corresponding PRACH index in terms of the sub-carrier index, as illustrated in <FIG>. Thus, for purposes of brevity, discussions of the PRACH indexes for the SGs along columns with SG indexes <NUM>-<NUM> are not repeated here.

The above-discussed distribution of PRACH indexes of the SG map <NUM> is pre-defined in accordance with a third frequency/time hopping rule that can be used by a UE (e.g., <NUM> of <FIG>) to send a Preamble to a BS (e.g., <NUM> of <FIG>) for initiating a random access procedure. In accordance with some embodiments of the present disclosure, the third frequency/time hopping rule indicates that the Preamble is sent using at least <NUM> SGs (i.e., the Preamble includes at least <NUM> SGs), each of which is selected from a respective SG index. Further, the third frequency/time hopping rule indicates that one of the sub-groups <NUM>, <NUM>, <NUM>, and <NUM> is selected, and subsequently, a first SG can be randomly chosen from the first column (i.e., the column with the SG index <NUM>) of the SG map <NUM> within the selected sub-group. Next, subsequent (e.g., remaining) SGs of the at least <NUM> SGs are each chosen from a respective column (i.e., the columns with SG indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) within the selected sub-group, wherein all <NUM> SGs share a same PRACH index. In an alternative embodiment, the third frequency/time hopping rule includes: randomly selecting an SG from the first column as the first SG of the at least <NUM> SGs; based on a respective sub-carrier index of the randomly selected SG in the first column, determining which of the sub-groups and which PRACH index to be used for the remaining <NUM> SGs of the at least <NUM> SGs. As such, the Preamble follows a corresponding Preamble format when the third frequency/time hopping rule is applied.

In an embodiment, when the third frequency/time hopping rule is applied and the Preamble is sent using more than <NUM> SGs, e.g., <NUM> SGs, respective subcarrier indexes of a first SG of a first set of <NUM> SGs and a first SG of a second set of <NUM> SGs may be randomly selected.

<FIG> provides an exemplary Preamble format <NUM> that can be used by a Preamble including at least <NUM> SGs when the third frequency/time hopping rule is applied. As mentioned above, one of the sub-groups <NUM>, <NUM>, <NUM>, and <NUM> is selected. In <FIG>, the sub-group <NUM> is selected, for example. Next, a first SG within the sub-group <NUM> with a subcarrier index, e.g., subcarrier index "k," is chosen, wherein k is randomly chosen, and the remaining SGs (second, third, fourth, fifth, sixth, and seventh SGs) are chosen as follows. The second SG is chosen to hop "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG is chosen to hop "upwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the fourth SG is chosen to hop "downwardly" from the third SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the fifth SG is chosen to hop "upwardly" from the fourth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the sixth SG is chosen to hop "downwardly" from the fifth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" and the seventh SG is chosen to hop "downwardly" from the sixth SG by <NUM> subcarrier index, e.g., from "k+<NUM>" to "k.

It is noted that, in such an embodiment, at least one upward frequency hopping and at least one downward frequency hoppings that each crosses over <NUM> subcarrier index, at least two upward frequency hoppings that each crosses over <NUM> and <NUM> subcarrier indexes, respectively, and at least two downward frequency hoppings that each crosses over <NUM> and <NUM> subcarrier indexes, respectively, are present in the Preamble format <NUM>. According to the invention as claimed, the Preamble, using the Preamble format <NUM>, follows a hopping pattern that includes a first hopping path associated with a first plurality of increasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a second hopping path associated with a second plurality of decreasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), and may follow a third hopping path associated with a third plurality of increasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a fourth hopping path associated with a fourth plurality of decreasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a fifth hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>), and a sixth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from k+<NUM> to k in the format <NUM>).

Further, according to the invention as claimed, respective frequency intervals (or typically known as frequency hopping distances) of the first and second hopping paths are equal to each other, and respective frequency intervals of the third and fourth hopping paths may be equal to each other. In some alternative embodiments, such frequency intervals of the first, second, third, and fourth hopping paths may be each of an integral times or a fractional times a respective subcarrier spacing (e.g., <NUM>). Alternatively stated, the first plurality of increasing subcarrier spacings, the second plurality of decreasing subcarrier spacings, the third plurality of increasing subcarrier spacings, and the fourth plurality of decreasing subcarrier spacings may be each an integral times or a fractional times the <NUM> subcarrier spacing in the current example.

Still in yet another embodiment, when an SG is defined based on the subcarrier spacing of <NUM> (e.g., the SG <NUM>), another disclosed Preamble format, which will be discussed with respect to <FIG>, is decided based on a pre-defined SG map <NUM> as illustrated in <FIG>. In the illustrated embodiment of <FIG>, the SG map <NUM> includes <NUM> SGs, each of which may be implemented by the SG <NUM>. More specifically, in some embodiments, the SG map <NUM> includes two portions <NUM>-<NUM> and <NUM>-<NUM> spaced from each other by <NUM> contiguous subcarrier spacings in the frequency domain, and each of the portions <NUM>-<NUM> and <NUM>-<NUM> extends across <NUM> SGs with corresponding time durations (<NUM>) in the time domain and across <NUM> SGs, i.e., <NUM> subcarrier spacings, (<NUM>) in the frequency domain, respectively. In the time domain, each SG is associated with a respective SG index (e.g., SG index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>); and in the frequency domain, each SG is associated with a respective subcarrier index (e.g., subcarrier index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>). Because of the <NUM> contiguous subcarrier spacings between the portions <NUM>-<NUM> and <NUM>-<NUM>, it is noted that subcarrier indexes between <NUM> and <NUM> are not contiguous.

The above-discussed distribution of PRACH indexes of the SG map <NUM> is pre-defined in accordance with a fourth frequency/time hopping rule that can be used by a UE (e.g., <NUM> of <FIG>) to send a Preamble to a BS (e.g., <NUM> of <FIG>) for initiating a random access procedure. In accordance with some embodiments of the present disclosure, the fourth frequency/time hopping rule indicates that the Preamble is sent using at least <NUM> SGs (i.e., the Preamble includes at least <NUM> SGs), each of which is selected from a respective SG index. Further, the fourth frequency/time hopping rule indicates that one of the sub-groups <NUM>, <NUM>, <NUM>, and <NUM> is selected, and subsequently, a first SG can be randomly chosen from the first column (i.e., the column with the SG index <NUM>) of the SG map <NUM> within the selected sub-group. Next, subsequent (e.g., remaining) SGs of the at least <NUM> SGs are each chosen from a respective column (i.e., the columns with SG indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) within the selected sub-group, wherein all <NUM> SGs share a same PRACH index. In an alternative embodiment, the fourth frequency/time hopping rule includes: randomly selecting an SG from the first column as the first SG of the at least <NUM> SGs; based on a respective sub-carrier index of the randomly selected SG in the first column, determining which of the sub-groups and which PRACH index to be used for the remaining <NUM> SGs of the at least <NUM> SGs. As such, the Preamble follows a corresponding Preamble format when the fourth frequency/time hopping rule is applied.

In an embodiment, when the fourth frequency/time hopping rule is applied and the Preamble is sent using more than <NUM> SGs, e.g., <NUM> SGs, respective subcarrier indexes of a first SG of a first set of <NUM> SGs and a first SG of a second set of <NUM> SGs may be randomly selected.

<FIG> provides an exemplary Preamble format <NUM> that can be used by a Preamble including at least <NUM> SGs when the fourth frequency/time hopping rule is applied. As mentioned above, one of the sub-groups <NUM>, <NUM>, <NUM>, and <NUM> is selected. In <FIG>, the sub-group <NUM> is selected, for example. Next, a first SG within the sub-group <NUM> with a subcarrier index, e.g., subcarrier index "k," is chosen, wherein k is randomly chosen, and the remaining SGs (second, third, fourth, fifth, sixth, and seventh SGs) are chosen as follows. The second SG is chosen to hop "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG is chosen to hop "upwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the fourth SG is chosen to hop "downwardly" from the third SG by <NUM> subcarrier indexe, e.g., from "k+<NUM>" to "k+<NUM>;" the fifth SG is chosen to hop "downwardly" from the fourth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k;" the sixth SG is chosen to hop "upwardly" from the fifth SG by <NUM> subcarrier indexes, e.g., from "k" to "k+<NUM>;" and the seventh SG is chosen to hop "downwardly" from the sixth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k.

It is noted that, in such an embodiment, at least one upward frequency hopping and at least one downward frequency hoppings that each crosses over <NUM> subcarrier index, at least two upward frequency hoppings that each crosses over <NUM> and <NUM> subcarrier indexes, respectively, and at least two downward frequency hoppings that each crosses over <NUM> and <NUM> subcarrier indexes, respectively, are present in the Preamble format <NUM>. Accordingly, the Preamble, using the Preamble format <NUM>, can follow a hopping pattern that includes a first hopping path associated with a first plurality of increasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a second hopping path associated with a second plurality of decreasing subcarrier indexes (e.g., from k+<NUM> to k), a third hopping path associated with a third plurality of increasing subcarrier indexes (e.g., from k to k+<NUM>), a fourth hopping path associated with a fourth plurality of decreasing subcarrier indexes (e.g., from k+<NUM> to k), and a fifth hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>), and a sixth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from k+<NUM> to k+<NUM> in the format <NUM>).

Further, in some embodiments, respective frequency intervals (or typically known as frequency hopping distances) of the first and second hopping paths may be equal to each other, and respective frequency intervals of the third and fourth hopping paths may be equal to each other. In some alternative embodiments, such frequency intervals of the first, second, third, and fourth hopping paths may be each of an integral times or a fractional times a respective subcarrier spacing (e.g., <NUM>). Alternatively stated, the first plurality of increasing subcarrier spacings, the second plurality of decreasing subcarrier spacings, the third plurality of increasing subcarrier spacings, and the fourth plurality of decreasing subcarrier spacings may be each an integral times or a fractional times the <NUM> subcarrier spacing in the current example.

Still in yet another embodiment, when an SG is defined based on the subcarrier spacing of <NUM> (e.g., the SG <NUM>), yet another disclosed Preamble format, which will be discussed with respect to <FIG>, is decided based on a pre-defined SG map <NUM> as illustrated in <FIG>. In the illustrated embodiment of <FIG>, the SG map <NUM> includes <NUM> SGs, each of which may be implemented by the SG <NUM>. More specifically, in some embodiments, the SG map <NUM> includes two portions <NUM>-<NUM> and <NUM>-<NUM> spaced from each other by <NUM> contiguous subcarrier spacings in the frequency domain, and each of the portions <NUM>-<NUM> and <NUM>-<NUM> extends across <NUM> SGs with corresponding time durations (<NUM>) in the time domain and across <NUM> SGs, i.e., <NUM> subcarrier spacings, (<NUM>) in the frequency domain, respectively. In the time domain, each SG is associated with a respective SG index (e.g., SG index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>); and in the frequency domain, each SG is associated with a respective subcarrier index (e.g., subcarrier index <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>). Because of the <NUM> contiguous subcarrier spacings between the portions <NUM>-<NUM> and <NUM>-<NUM>, it is noted that subcarrier indexes between <NUM> and <NUM> are not contiguous.

The above-discussed distribution of PRACH indexes of the SG map <NUM> is pre-defined in accordance with a fifth frequency/time hopping rule that can be used by a UE (e.g., <NUM> of <FIG>) to send a Preamble to a BS (e.g., <NUM> of <FIG>) for initiating a random access procedure. In accordance with some embodiments of the present disclosure, the fifth frequency/time hopping rule indicates that the Preamble is sent using at least <NUM> SGs (i.e., the Preamble includes at least <NUM> SGs), each of which is selected from a respective SG index. Further, the fifth frequency/time hopping rule indicates that one of the sub-groups <NUM>, <NUM>, <NUM>, and <NUM> is selected, and subsequently, a first SG can be randomly chosen from the first column (i.e., the column with the SG index <NUM>) of the SG map <NUM> within the selected sub-group. Next, subsequent (e.g., remaining) SGs of the at least <NUM> SGs are each chosen from a respective column (i.e., the columns with SG indexes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) within the selected sub-group, wherein all <NUM> SGs share a same PRACH index. In an alternative embodiment, the fifth frequency/time hopping rule includes: randomly selecting an SG from the first column as the first SG of the at least <NUM> SGs; based on a respective sub-carrier index of the randomly selected SG in the first column, determining which of the sub-groups and which PRACH index to be used for the remaining <NUM> SGs of the at least <NUM> SGs. As such, the Preamble follows a corresponding Preamble format when the fifth frequency/time hopping rule is applied.

In an embodiment, when the fifth frequency/time hopping rule is applied and the Preamble is sent using more than <NUM> SGs, e.g., <NUM> SGs, respective subcarrier indexes of a first SG of a first set of <NUM> SGs and a first SG of a second set of <NUM> SGs may be randomly selected.

<FIG> provides an exemplary Preamble format <NUM> that can be used by a Preamble including at least <NUM> SGs when the fifth frequency/time hopping rule is applied. As mentioned above, one of the sub-groups <NUM>, <NUM>, <NUM>, and <NUM> is selected. In <FIG>, the sub-group <NUM> is selected, for example. Next, a first SG within the sub-group <NUM> with a subcarrier index, e.g., subcarrier index "k," is chosen, wherein k is randomly chosen, and the remaining SGs (second, third, fourth, fifth, sixth, seventh, ninth, and tenth SGs) are chosen as follows. The second SG is chosen to hop "upwardly" from the first SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>;" the third SG is chosen to hop "upwardly" from the second SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the fourth SG is chosen to hop "downwardly" from the third SG by <NUM> subcarrier index, e.g., from "k+<NUM>" to "k+<NUM>;" the fifth SG is chosen to hop "upwardly" from the fourth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the sixth SG is chosen to hop "upwardly" from the fifth SG by <NUM> subcarrier index, e.g., from "k+<NUM>" to "k+<NUM>;" the seventh SG is chosen to hop "downwardly" from the sixth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k+<NUM>;" the eighth SG is chosen to hop "downwardly" from the seventh SG by <NUM> subcarrier index, e.g., from "k+<NUM>" to "k+<NUM>;" the ninth SG is chosen to hop "downwardly" from the eighth SG by <NUM> subcarrier indexes, e.g., from "k+<NUM>" to "k;" and the tenth SG is chosen to hop "upwardly" from the ninth SG by <NUM> subcarrier index, e.g., from "k" to "k+<NUM>.

It is noted that, in such an embodiment, at least three upward frequency hoppings and at least two downward frequency hoppings that each crosses over <NUM> subcarrier index, at least two upward frequency hoppings that each crosses over <NUM> and <NUM> subcarrier indexes, respectively, and at least two downward frequency hoppings that each crosses over <NUM> and <NUM> subcarrier indexes, respectively, are present in the Preamble format <NUM>. Accordingly, the Preamble, using the Preamble format <NUM>, can follow a hopping pattern that includes a first hopping path associated with a first plurality of increasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a second hopping path associated with a second plurality of increasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a third hopping path associated with a third plurality of decreasing subcarrier indexes (e.g., from k+<NUM> to k+<NUM>), a fourth hopping path associated with a fourth plurality of decreasing subcarrier indexes (e.g., from k+<NUM> to k), a fifth hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>), a sixth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from k+<NUM> to k+<NUM> in the format <NUM>), a seventh hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k+<NUM> to k+<NUM> in the format <NUM>), an eighth hopping path associated with <NUM> decreasing subcarrier spacing (e.g., from k+<NUM> to k+<NUM> in the format <NUM>), and a ninth hopping path associated with <NUM> increasing subcarrier spacing (e.g., from k to k+<NUM> in the format <NUM>).

Further, in some embodiments, respective frequency intervals (or typically known as frequency hopping distances) of the first and third hopping paths may be equal to each other, and respective frequency intervals of the second and fourth hopping paths may be equal to each other. In some alternative embodiments, such frequency intervals of the first, second, third, and fourth hopping paths may be each of an integral times or a fractional times a respective subcarrier spacing (e.g., <NUM>). Alternatively stated, the first plurality of increasing subcarrier spacings, the second plurality of increasing subcarrier spacings, the third plurality of decreasing subcarrier spacings, and the fourth plurality of decreasing subcarrier spacings may be each an integral times or a fractional times the <NUM> subcarrier spacing in the current example.

Although, in the above discussions, the Preamble format (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) is directed to being used for transmitting a PRACH (Physical Random Access Channel) signal, it is noted that each of the above-discussed Preamble format can be used for transmitting an uplink signal (i.e., a signal transmitted from the UE <NUM> to the BS <NUM>) while remaining within the scope of the present disclosure. For example, each of the above-discussed Preamble format can be used for transmitting a Positioning Reference signal, a Scheduling Request Reference signal, or the like.

As mentioned above, each Preamble format includes a plurality of SGs (symbol groups), and each SG includes a plurality of CP and symbols. In some alternative embodiments, in order to further mitigate interference between neighboring cells (e.g., neighboring cells), the present disclosure provides various embodiments of a method <NUM> in <FIG> to allow each symbol to carry a number/value of a respective sequence, wherein such a sequence may be one of a plurality of pre-defined and/or pre-generated random sequences. Moreover, a length of such a sequence may be determined based on a length of a respective "symbol group set," which will be discussed in further detail below.

In accordance with some embodiments of the present disclosure, the method <NUM> starts with operation <NUM> in which a Preamble format is provided. Next, the method <NUM> proceeds to operation <NUM> in which respective SGs of the Preamble format is grouped into one or more SG sets. The method <NUM> proceeds to operation <NUM> in which a plurality of sequences are generated. In some embodiments, each of the plurality of sequences has a sequence length that may be determined based on a number of SGs included in the SG set provided in the operation <NUM>. The method <NUM> proceeds to operation <NUM> in which one of the plurality of sequences is selected to be used for one of the one or more SG sets. The method <NUM> proceeds to operation <NUM> in which symbol(s) within respective different SGs of the SG set are each assigned with a respective different value contained in the selected sequence. Various examples are provided below to illustrate how each symbol is assigned with a respective value when the method <NUM> is used.

In an example, the Preamble format <NUM> of <FIG> that includes at least <NUM> SGs is provided. Next, the at least <NUM> SGs are grouped into <NUM> SG sets. In an embodiment, two adjacent SGs are grouped into a respective SG set. For example, the first and second SGs are grouped into a first SG set (<NUM>st SG set); the third and fourth SGs are grouped into a second SG set (<NUM>nd SG set); the fifth and sixth SGs are grouped into a third SG set (<NUM>rd SG set); and the seventh and eighth SGs are grouped into a fourth SG set (<NUM>th SG set). Next, a plurality of sequences are generated, wherein each sequence has a sequence length that is consistent with a number of the SGs in each SG set, which is <NUM> in the above example. For example, the plurality of sequences may include: (<NUM>, <NUM>}, {<NUM>, -<NUM> }, {<NUM>, j}, and {<NUM>, -j}, wherein each of the sequence has a sequence length of <NUM>, and accordingly is composed of two respective sequence values. Next, one of the plurality of sequences is selected to be used by one of the SG sets. For example, the sequence {<NUM>, -<NUM>} is selected to be used by the first SG set. As such, the symbols of the first SG of the first SG set are each assigned with one of the sequence values, e.g., "<NUM>," and the symbols of the second SG of the first SG set are each assigned with the other of the sequence values, e.g., "-<NUM>. " Analogously, each of the remaining SG sets uses any of the four sequences, which can be identical to or different from the sequence used by the first SG set. For example, {<NUM>, -<NUM>}, which is identical to the one used by the first SG set, or one of {<NUM>, <NUM>}, {<NUM>, j}, and {<NUM>, -j}, which is different from the one used by the second SG set, may be used by the second, third, or fourth SG set.

In another example, the Preamble format <NUM> of <FIG> that includes at least <NUM> SGs is provided. Next, the at least <NUM> SGs are grouped into <NUM> SG sets, each of which has one SG. Next, a plurality of sequences are generated, wherein each sequence a sequence length that is consistent with a number of the SGs in each SG set, which is <NUM> in the above example. For example, the plurality of sequences may include: {<NUM>}, {-<NUM>}, {j}, and {-j}, wherein each of the sequence has a sequence length of <NUM>, and accordingly is composed of one respective sequence value. Next, one of the plurality of sequences is selected to be used by one of the SG sets. For example, the sequence {<NUM>} is selected to be used by a first SG set (i.e., a first SG in this example). As such, the symbols of the first SG set are each assigned with the sequence value of the sequence, "<NUM>. " Analogously, each of the remaining SG sets uses any of the four sequences, which can be identical to or different from the sequence used by the first SG set.

In yet another example, the Preamble format <NUM> of <FIG> that includes at least <NUM> SGs is provided. Next, the at least <NUM> SGs are grouped into <NUM> SG set. Next, a plurality of sequences are generated, wherein each sequence a sequence length that is consistent with a number of the SGs in each SG set, which is <NUM> in the above example. The present disclosure provides embodiments of a method to generate a plurality of sequences, each of which has a sequence length of <NUM>. In particular, the plurality of sequences may be generated by the following equation W, <MAT> wherein <MAT>, NSG = <NUM>, α ∈ [<NUM>, NSG - <NUM>], and n ∈ [<NUM>, NSG - <NUM>]. In the above equation, "n" represents an (n+<NUM>)th sequence value within a sequence, and "α" represents an αth sequence of the plurality of sequences. The present disclosure provides embodiments of another method to generate a plurality of sequences, each of which has a sequence length of <NUM>. In particular, the plurality of sequences may be generated by the following equation W, <MAT> wherein <MAT>, NSG = <NUM>, α ∈ [<NUM>, NSG - <NUM>], and n ∈ [<NUM>, NSG -<NUM>]. In the above equation, "n" represents an (n+<NUM>)th sequence value within a sequence, and "α" represents an αth sequence of the plurality of sequences. As such, for each sequence with the sequence length of <NUM>, <NUM> sequence values out of the <NUM> sequence values are selected to be respectively used by the <NUM> SG sets. In some embodiments, these <NUM> sequence values may be the first <NUM> sequence values of the <NUM> sequence values, the last <NUM> sequence values of the <NUM> sequence values, or randomly selected from the <NUM> sequence values.

In yet another example, the Preamble format <NUM> of <FIG> that includes at least <NUM> SGs is provided. The present disclosure provides embodiments of a method to generate a plurality of sequences, each of which has a sequence length of <NUM>. In particular, the plurality of sequences may be generated by the following equation W, <MAT> wherein <MAT>, NSG = <NUM>, α ∈ [<NUM>, NSG - <NUM>], and n ∈ [<NUM>, NSG -<NUM>]. In the above equation, "n" represents an (n+<NUM>)th sequence value within a sequence, and "α" represents an αth sequence of the plurality of sequences. For example, using the above equation, a plurality of sequences with the sequence length of <NUM> include: {<NUM>, <NUM>, <NUM>, <NUM>}, {<NUM>, j, -<NUM>, -j}, {<NUM>, -<NUM>, <NUM>, -<NUM>}, and {<NUM>, j, -<NUM>, j}. Similar to the method described above, the at least <NUM> SGs are grouped into a plurality of SG sets, each of which has <NUM> adjacent SGs. And each SG set, containing <NUM> SGs, uses one of the plurality of sequences with <NUM> respective different sequence values (because the sequence length is <NUM>), to assign the <NUM> SGs' respective symbols with the <NUM> respective different sequence values.

A person of ordinary skill in the art would further appreciate that any of the various illustrative logical blocks, modules, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e. g, a digital implementation, an analog implementation, or a combination of the two), firmware, various forms of program or design code incorporating instructions (which can be referred to herein, for convenience, as "software" or a "software module), or any combination of these techniques.

Claim 1:
A method, comprising:
receiving a resource allocation message indicative of a plurality of resource groups allocated for a physical layer random access preamble; and
transmitting the physical layer random access preamble using a portion of the plurality of resource groups,
wherein, in a frequency domain, the portion of the plurality of resource groups presents a predefined hopping pattern comprising at least a first predefined hopping path that is associated with increasing subcarrier frequency by a first amount of frequency spacings and a second predefined hopping path that is associated with decreasing subcarrier frequency by a second amount of frequency spacings,
wherein the first hopping path and the second hopping path are used by two different resource groups, respectively,
characterized in that:
the first amount of frequency spacings equals the second amount of frequency spacings, and
the second amount of frequency spacings immediately follows the first amount of frequency spacings.