GB2636827A - Index into list of random access occasions - Google Patents

Abstract

A method includes determining a list of random access (RACH) occasions distributed within one or more RACH periods; generating an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and, transmitting by a UE or receiving by a gNB a random access preamble via the identified RACH occasion. The list of RACH occasions is selected so that the RACH occasions are most equally spaced apart within the RACH period.

Description

INDEX INTO LIST OF RANDOM ACCESS OCCASIONS

TECHNICAL FIELD

[0001] This description relates to wireless communications.

BACKGROUND

[0002] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node AP (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments. Aspects of LTE are also continuing to improve.

[0004] 5G New Radio (NR) development is part of a continued mobile broadband evolution process to meet the requirements of 5G, similar to earlier evolution of 3G and 4G wireless networks. In addition, 5G is also targeted at the new emerging use cases in addition to mobile broadband. A goal of 5G is to provide significant improvement in wireless performance, which may include new levels of data rate, latency, reliability, and security. 5G NR may also scale to efficiently connect the massive Internet of Things (IoT) and may offer new types of mission-critical services. For example, ultra-reliable and low-latency communications (URLLC) devices may require high reliability and very low latency. 6G and other networks are also being developed.

SUMMARY

[0005] A method may include determining a list of random access (RACH) occasions 30 distributed within one or more RACH periods, wherein the list of RACH occasions includes a subset of available RACH occasions; generating an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and, transmitting or receiving a random access preamble via the identified RACH occasion.

[0006] An apparatus may include means for determining a list of random access (RACH) occasions distributed within one or more RACH periods, wherein the list of RACH occasions includes a subset of available RACH occasions; means for generating an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); means for identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and, means for transmitting or receiving a random access preamble via the identified RACH occasion. [0007] An apparatus may include at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: determine a list of random access (RACH) occasions distributed within one or more RACH periods, wherein the list of RACH occasions includes a subset of available RACH occasions; generate an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identify one of the RACH occasions of the list of RACH occasions based on the generated index; and transmit or receive a random access preamble via the identified RACH occasion.

[0008] A method may include selecting a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period; generating an index into the list of RACH occasions; identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and transmitting or receiving a random access preamble via the identified RACH occasion.

[0009] An apparatus may include at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: select a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period; generate an index into the list of RACH occasions; identify one of the RACH occasions of the list of RACH occasions based on the generated index; and transmit or receive a random access preamble via the identified RACH occasion.

[0010] An apparatus may include means for selecting a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period; means for generating an index into the list of RACH occasions; means for identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and means for transmitting or receiving a random access preamble via the identified RACH occasion.

[0011] Other example embodiments are provided or described for each of the example methods, including: means for performing any of the example methods; a non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform any of the example methods; and an apparatus including at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform any of the example methods.

[0012] The details of one or more examples of embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a block diagram of a wireless network.

[0014] FIG. 2A is a flow chart illustrating operation according to an example embodiment.

[0015] FIG. 2B is a flow chart illustrating operation according to an example embodiment.

[0016] FIG. 3 is a flow chart illustrating operation of a user device (or UE) and network node (or gNB) according to an example embodiment.

[0017] FIG. 4 is a diagram illustrating possible RACH occasions.

[0018] FIG. 5 is a diagram that illustrates remaining RACH occasions after some RACH occasions have been eliminated from the list of RACH occasions based on SSB period being greater than a threshold.

[0019] FIG. 6 is a diagram illustrating the list 610 of (e.g., ordered) RACH occasions that includes the first RACH occasion on the list 610.

[0020] FIG. 7 is a diagram illustrating a list 610 of RACH occasions that includes two RACH occasions, including a RACH occasion corresponding to index = 0 (RACH occasion 1.0.9) and RACH occasion corresponding to index = 1 (RACH occasion 3.0.9). [0021] FIG. 8 is a diagram illustrating a list 610 of RACH occasions that includes four RACH occasions (1.0.9, 3.0.9, 1.1.9, 3.1.9) according to an example embodiment.

[0022] FIG. 9 is a diagram of the list 610 of RACH occasions that includes all 8 selected RACH occasions for the list.

[0023] FIGs. 10A and 10B illustrate possible RACH occasions within a RACH period of 8 radio frames for cells with PCI 100, 101, 102 and 103 according to another example embodiment.

[0024] FIG. 11 is a diagram illustrating a list 1110 of RACH occasions that were selected based on the second example.

[0025] FIG. 12 is a block diagram of a wireless station or node (e.g., UE, user device, AP, BS, eNB, gNB, RAN node, network node, TRP, or other node) 1300 according to an example embodiment.

DETAILED DESCRIPTION

[0026] FIG. 1 is a block diagram of a wireless network 130. In the wireless network of FIG. 1, user devices 131, 132, 133 and 135, which may also be referred to as mobile stations (IVISs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB), a gNB or a network node. The terms user device and user equipment (UE) may be used interchangeably. A BS may also include or may be referred to as a RAN (radio access network) node, and may include a portion of a BS or a portion of a RAN node, such as (e.g., such as a centralized unit (CU) and/or a distributed unit (DU) in the case of a split BS or split gNB). At least part of the functionalities of a BS (e.g., access point (AP), base station (BS) or (e)Node B (eNB), gNB, RAN node) may also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices (or UEs) 131, 132, 133 and 135. Although only four user devices (or UEs) are shown as being connected or attached to BS 134, any number of user devices may be provided. BS 134 is also connected to a core network 150 via a SI interface 151. This is merely one simple example of a wireless network, and others may be used.

[0027] A base station (e.g., such as BS 134) is an example of a radio access network (RAN) node within a wireless network. A BS (or a RAN node) may be or may include (or may alternatively be referred to as), e.g., an access point (AP), a gNB, an eNB, or portion thereof (such as a central/centralized unit (CU) and/or a distributed unit (DU) in the case of a split BS or split gNB), or other network node.

[0028] Some functionalities of the communication network may be carried out, at least partly, in a central/centralized unit, CU, (e.g., server, host or node) operationally coupled to distributed unit, DU, (e.g., a radio head/node). Thus, 5G networks architecture may be based on a so-called CU-DU split. The gNB-CU (central node) may control a plurality of spatially separated gNB-DUs, acting at least as transmit/receive (Tx/Rx) nodes. In some examples, the gNB-DUs (also referred to as a DU) may comprise e.g., a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the gNB-CU (also referred to as a CU) may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too.

[0029] According to an illustrative example, a BS node (e.g., BS, eNB, gNB, CU/DU, ...) or a radio access network (RAN) may be part of a mobile telecommunication system. A RAN (radio access network) may include one or more BSs or RAN nodes that implement a radio access technology, e.g., to allow one or more UEs to have access to a network or core network. Thus, for example, the RAN (RAN nodes, such as BSs or gNBs) may reside between one or more user devices or UEs and a core network. According to an example embodiment, each RAN node (e.g., BS, eNB, gNB, CU/DU, ...) or BS may provide one or more wireless communication services for one or more UEs or user devices, e.g., to allow the UEs to have wireless access to a network, via the RAN node. Each RAN node or BS may perform or provide wireless communication services, e.g., such as allowing UEs or user devices to establish a wireless connection to the RAN node, and sending data to and/or receiving data from one or more of the UEs. For example, after establishing a connection to a UE, a RAN node or network node (e.g., BS, eNB, gNB, CU/DU, ...) may forward data to the UE that is received from a network or the core network, and/or forward data received from the UE to the network or core network. RAN nodes or network nodes (e.g., BS, eNB, gNB, CU/DU, ...) may perform a wide variety of other wireless functions or services, e.g., such as broadcasting control information (e.g., such as system information or on-demand system information) to UEs, paging UEs when there is data to be delivered to the UE, assisting in handover of a UE between cells, scheduling of resources for uplink data transmission from the UE(s) and downlink data transmission to UE(s), sending control information to configure one or more UEs, and the like. These are a few examples of one or more functions that a RAN node or BS may perform [0030] A user device or user node (user terminal, user equipment (UE), mobile terminal, handheld wireless device, etc.) may refer to a portable computing device that includes wireless mobile communication devices operating either with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and/or touch screen computer, a tablet, a phablet, a game console, a notebook, a vehicle, a sensor, and a multimedia device, as examples, or any other wireless device. It should be appreciated that a user device may also be (or may include) a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network.

[0031] Also, a user node may include a user equipment (UE), a user device, a user terminal, a mobile terminal, a mobile station, a mobile node, a subscriber device, a subscriber node, a subscriber terminal, or other user node. For example, a user node may be used for wireless communications with one or more network nodes (e.g., gNB, eNB, BS, AP, CU, DU, CU/DU) and/or with one or more other user nodes, regardless of the technology or radio access technology (RAT). In LTE (as an illustrative example), core network 150 may be referred to as Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility/handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks. Other types of wireless networks, such as 5G (which may be referred to as New Radio (NR)) may also include a core network.

[0032] In addition, the techniques described herein may be applied to various types of user devices or data service types, or may apply to user devices that may have multiple applications running thereon that may be of different data service types. New Radio (50) development may support a number of different applications or a number of different data service types, such as for example: machine type communications (MTC), enhanced machine type communication (eMTC), Internet of Things (IoT), and/or narrowband IoT user devices, enhanced mobile broadband (eMBB), and ultra-reliable and low-latency communications (URLLC). Many of these new 5G (NR) -related applications may require generally higher performance than previous wireless networks.

[0033] IoT may refer to an ever-growing group of objects that may have Internet or network connectivity, so that these objects may send information to and receive information from other network devices. For example, many sensor type applications or devices may monitor a physical condition or a status, and may send a report to a server or other network device, e.g., when an event occurs. Machine Type Communications (MTC, or Machine to Machine communications) may, for example, be characterized by fully automatic data generation, exchange, processing and actuation among intelligent machines, with or without intervention of humans. Enhanced mobile broadband (eMBB) may support much higher data rates than currently available in LTE.

[0034] Ultra-reliable and low-latency communications (URLLC) is a new data service type, or new usage scenario, which may be supported for New Radio (SG) systems. This enables emerging new applications and services, such as industrial automations, autonomous driving, vehicular safety, e-health services, and so on. 3GPP targets in providing connectivity with reliability corresponding to block error rate (BLER) of 10-5 and up to 1 ms U-Plane (user/data plane) latency, by way of illustrative example. Thus, for example, URLLC user devices/UEs may require a significantly lower block error rate than other types of user devices/UEs as well as low latency (with or without requirement for simultaneous high reliability). Thus, for example, a URLLC UE (or URLLC application on a UE) may require much shorter latency, as compared to an eMBB UE (or an eMBB application running on a UE).

[0035] The techniques described herein may be applied to a wide variety of wireless technologies or wireless networks, such as 5G (New Radio (NR)), cmWave, and/or mmWave band networks, loT, MTC, eMTC, eMBB, URLLC, 6G, etc., or any other wireless network or wireless technology. These example networks, technologies or data service types are provided only as illustrative examples.

[0036] A random access (RACH) procedure may be used by a UE to establish a connection with a cell or gNB. A UE may receive a RACH configuration index from a gNB via system information block (SIB) 1 that identifies a RACH configuration to be used for RACH preamble transmission. The RACH configuration may include information, e.g., such as an indication of time-frequency resources (or RACH occasions) in which transmission of a RACH preamble may take place, and information indicating a mapping between synchronization signal block (SSB) (or beam) indices and RACH occasions. Based on measured SSBs received from the gNB, the UE may select the best or strongest SSB, and then may transmit a RACH preamble via a RACH occasion that is associated with or mapped to the best or selected SSB. A set of RACH occasions for a cell may be determined via a RACH (or PRACH) configuration, e.g., which may indicate a RACH period or RACH periodicity and offset (in radio frames), the specific slots and time occasions within each slot for RACH occasions. As noted, the UE may select the RACH occasion corresponding to the best or strongest SSB beam measured by the UE, for uplink transmission of a RACH preamble to the gNB or cell.

[0037] Based on existing RACH configurations or RACH configuration index, many cells have their RACH occasions on the same slot(s). As a result, many UEs within a cell may transmit their RACH preambles to a gNB during the same slot or small subset of slots. This may result in possible RACH preamble transmission interference between UEs of neighbor cells. Furthermore, because the transmission of RACH preambles from UEs in a cell may be transmitted in a same slot or in very few slots to a gNB, this may require significant hardware or processing resources at the gNB to receive and process the received RACH preambles in a short period of time, since these RACH preambles are typically bunched or grouped together within a same slot or subset of slots.

[0038] Techniques are described herein that allow a list of RACH occasions to be determined by UE and gNB that are more distributed. One RACH occasion of the list of RACH occasions is identified based on an index, and used for transmitting (by a UE) and receiving (by a gNB or network node) a RACH preamble. In this manner, potential RACH preamble inter-cell interference may be reduced, and the RACH preamble processing load at a gNB may be more distributed in time.

[0039] FIG. 2A is a flow chart illustrating operation according to an example embodiment. Operation 210 includes determining a list of random access (RACH) occasions distributed within one or more RACH periods. The list of RACH occasions may include a subset of available RACH occasions. Operation 220 includes generating an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN). Operation 230 includes identifying one of the RACH occasions of the list of RACH occasions based on the generated index. And, operation 240 includes transmitting (e.g., by a UE or user device) or receiving (e.g., by a gNB or network node) a random access preamble via the identified RACH occasion. Thus, the operations of FIG. 2A may apply to, or may be performed by, either a UE or user device, or a gNB or network node.

[0040] With respect to the method of FIG. 2A, the generating may include generating the index into the list based on the physical cell identity (PCI), the global synchronization 5 channel number (GSCN) and a system frame number (SFN).

[0041] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include selecting a plurality of the RACH occasions to be on the list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period.

[0042] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include selecting the plurality of RACH occasions wherein at least some of the RACH occasions are selected to be on the list such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match.

[0043] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include selecting a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and selecting a second RACH occasion such that a first inter-RACH occasion distance between the first and second RACH occasions most closely matches a second inter-RACH occasion distance between the second RACH occasion and a slot position that is one RACH period after the first RACH occasion.

[0044] With respect to the method of FIG. 2A, the method may include repeating or iteratively performing, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match, or the RACH occasions are selected that are most equally spaced apart.

[0045] With respect to the method of FIG. 2A, the method may include if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeating one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0046] With respect to the method of FIG. 2A, the selecting may include in case of a tie between two RACH occasions that are equally spaced apart or have equal inter-RACH occasion distances, selecting a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0047] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include selecting a plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.

[0048] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include selecting a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and selecting a second RACH occasion such that a sum of: 1) a square of a first inter-RACH occasion distance in slots between the first and second RACH occasions, plus 2) a square of a second inter-RACH occasion distance in slots between the second RACH occasion and a slot that is one RACH period after the first RACH occasion, is minimized.

[0049] With respect to the method of FIG. 2A, the method may include repeating or iteratively performing, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.

[0050] With respect to the method of FIG. 2A, the method may include if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeating one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0051] With respect to the method of FIG. 2A, the selecting may include in case of a tie between two RACH occasions that cause a sum of squared distances in slots between adjacent selected RACH occasions to be equal, selecting a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0052] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include determining a set of RACH occasions in one or more radio frames up to a RACH period; and if a synchronization signal burst (SSB) period is greater than a threshold, eliminating RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0053] With respect to the method of FIG. 2A, the determining the list of random access (RACH) occasions distributed within one or more RACH periods may include receiving, by a user device from a network node, assistance information via system information block that provides configuration information for RACH occasions, including one or more parameters including one or more of: the RACH period or RACH periodicity, a starting symbol, a number of RACH preamble slots within a radio frame, a number of time durations within a slot, a RACH preamble duration and/or a subframe number for RACH occasions; and determining a set of RACH occasions in one or more radio frames up to a RACH period.

[0054] With respect to the method of FIG. 2A, the determining the set of RACH occasions may include if a synchronization signal burst (SSB) period is greater than a threshold, eliminating RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0055] With respect to the method of FIG. 2A, the method may further include determining the physical cell identity of a cell based on system information received from a network node; detecting a timing or position of a synchronization signal block from the network node; and determining the global synchronization channel number based on the timing or position of the synchronization signal block.

[0056] With respect to the method of FIG. 2A, the list of RACH occasions may be eight RACH occasions in length.

[0057] With respect to the method of FIG. 2A, the generating may include generating, by the user device, the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SFN)/128.

[0058] With respect to the method of FIG. 2A, the selecting the plurality of the RACH occasions to be on the list of RACH occasions may include selecting the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances(sqdist) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro_l, ro_2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro 1, ro 2, ro 3, ro n-1, ro n) is defined as sum= sqdist(ro 1, ro2) + sqdist(ro 2, ro 3) + + sqdist(ro n+1, ro n).

[0059] FIG. 2B is a flow chart illustrating operation according to another example embodiment. Operation 250 includes selecting a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period. Operation 260 includes generating, e.g., pseudo-randomly generating, an index into the list of RACH occasions. Operation 270 includes identifying one of the RACH occasions of the list of RACH occasions based on the generated index. And, operation 280 includes transmitting or receiving a random access preamble via the identified RACH occasion.

[0060] According to an example embodiment, instead of determining a single random access (RACH) occasion, multiple RACH occasions within a RACH periodicity (or RACH period) are determined. For example, a list (e.g., such as an ordered list) of potential RACH occasions may be determined. There may be an understanding or agreement by both the UE and gNB as to the order of RACH occasions on the list and/or as to a set of rules by which RACH occasions on the list and their order are to be determined. According to an example embodiment, a UE and gNB may be pre-configured (e.g., via specifications or a standard) with this understanding or agreement as to a set of rules or a policy for selecting and/or ordering RACH occasions for the list, and/or for generating an index into the list of RACH occasions. Thus, the list of RACH occasions (e.g., a list of 8 RACH occasions) may be an ordered list, such that the order of the RACH occasions on the list is known by or can be determined by both the UE and the gNB. There may be a number of different techniques or sets of rules by which a list of RACH occasions may be determined, and some example sets of rules or techniques are described herein. The RACH occasions on the list of RACH occasions may be distributed within one or more RACH periods (e.g., provided at different and/or various locations), wherein the list of RACH occasions includes a subset of available RACH occasions.

[0061] An index may be generated (by UE and/or gNB) into the list of RACH occasions based on a set of rules. For example, an index (e.g., index = 0 -7) may be generated into the list of RACH occasions (to identify one of the RACH occasions on the list) based on a physical cell identity (PCI) and a global synchronization channel number (GSCN). The PCI may be the PCI of a cell for which the UE would like to connect. The PCI may be broadcast by a gNB within primary synchronization signal (PSS) and secondary synchronization signal (SSS). The GSCN may identify (or may be associated with) a center frequency of a synchronization signal block (SSB) or set of SSBs within the carrier or channel. For example, a UE may determine a position of a SSB within a channel, e.g., by scanning one or more channels to detect the SSB transmitted by the gNB. The center frequency of the detected SSB is, or may be associated with, the GSCN. Thus, for example, a UE may determine a GSCN based on a center frequency of the detected SSB.

[0062] In an example embodiment, the index to the list of RACH occasions may be generated based on (or as a function of) the PCI and the GSCN. For example, index may be generated as, or as a function of: index = (PCI*pl + GSCN*p2) mod 8, where pl and p2 are numbers, e.g., prime numbers greater than 8 for example, and mod refers to the modulus operator. Alternatively, the UE and gNB may determine an index into the list of RACH occasions as a function of PCI, GSCN and system frame number (SFN). For example, the UE and gNB may determine the index as: index = (PCI*pl + GSCN*p2 + SFN/128) mod 8. These example functions may provide a pseudo-random determination of the index into the list of (e.g., 8) RACH occasions. In other words, such a function pseudo-randomizes the selection of the index into the list of PRACH occasions. For example, using the PCI and GSCN in the index calculation or determination may provide variety for cells on the same carrier or on different carriers. Also, according to an example embodiment, using the SFN as part of the index determination may allow a cell to use all indices over time. Other functions may be used to generate an index into the list of RACH occasions, for example using PCI and GSCN. As technology advances, similar information elements as PCI and GSCN may be used. However, such elements may have different names. Also, the use of PCI, GSCN and/or SFN are example parameters or values that may be used to generate or pseudo-randomly generate an index to or into the list of RACH occasions. Other parameters may be used to generate, e.g., pseudo-randomly generate, an index into the list of RACH occasions.

[0063] After generating the index to the list of RACH occasions, the UE and gNB may identify one of the RACH occasions from the list of RACH occasions based on the index (e.g., the RACH occasion identified by, or associated with, the index). The UE may transmit a RACH preamble via the identified RACH occasion (the indexed occasion), and the gNB or network node may receive (e.g., receive, detect and/or decode) the RACH preamble via the identified RACH occasion.

[0064] FIG. 3 is a flow chart illustrating operation of a user device (or UE) and network node (or gNB) according to an example embodiment. A UE would perform steps (0)-(70), whereas gNb would perform steps (10)-(70) of the method or flow chart of FIG. 3. At step 0, the UE may determine a need to perform a RACH procedure, e.g., to establish a connection with a gNB. A first example is illustrated in FIGs. 4-9. It is noted that steps at UE side and at gNB side do not necessarily need to be performed simultaneously. In some cases, some of the steps may be performed is a different order.

[0065] At step 10 of FIG. 3, the UE and gNB may determine RACH occasions in each radio frame up to one RACH period or RACH periodicity. FIG. 4 is a diagram illustrating possible RACH occasions. As an illustrative example, FIG. 4 is a diagram illustrating RACH occasions within a RACH period of four radio frames, for four cells with physical cell identities (PCIs of 100, 101, 102 and 103). Although not shown, a SSB (synchronization signal block) period may be 20ms or two radio frames, with only the even radio frames (0, 2, ...) having SSBs transmitted. There are no SSBs transmitted on the odd radio frames (1, 3, ...) in this example. As shown in FIG. 4, one RACH period includes four radio frames (radio frames 0-3), with each radio frame including two half-frames (half-frame 0 and 1). Each half-frame includes 10 slots (slots 0-9). Thus, in this example, one RACH period includes 80 slots across 4 radio frames. RACH occasion numbers are listed as: radioframe.half-frame.slot. For all four of the PCIs (PCI 100, 101, 102 and 103), there are 8 RACH occasions shown within this RACH period of four radio frames, including (410) RACH occasion 0.0.9 (corresponding to radio frame 0, half-frame 0 and slot 9), (412) RACH occasion 0.1.9 (corresponding to radio frame 0, half-frame 1 and slot 9), RACH occasion 1.0.9 (corresponding to radio frame 1, half-frame 0 and slot 9), RACH occasion 1.1.9 (corresponding to radio frame 1, half-frame 1 and slot 9), (414) RACH occasion 2.0.9 (corresponding to radio frame 2, half-frame 0 and slot 9), (416) RACH occasion 2.1.9 (corresponding to radio frame 2, half-frame 1 and slot 9), (418) RACH occasion 3.0.9 (corresponding to radio frame 3, half-frame 0 and slot 9), and (420) RACH occasion 3.1.9 (corresponding to radio frame 3, half-frame 1 and slot 9). These 8 RACH occasions are possible RACH occasions for our list of RACH occasions. Thus, this is an example of how a UE and gNB may determine RACH occasions in each radio frame up to one RACH period or RACH periodicity.

[0066] At step 20 of FIG. 3, if the SSB period or SSB burst period is greater than a threshold (e.g., greater than 10 ms), then the UE and gNB will (or may) eliminate or remove RACH occasions in radio frames with SSB from the list of RACH occasions. FIG. 5 is a diagram that illustrates remaining RACH occasions after some RACH occasions have been eliminated from the list of RACH occasions based on SSB period being greater than a threshold. In this example, although not shown, the SSB period may be 20ms or two radio frames, with only the even radio frames (0, 2, ...) having SSBs (SSBs are transmitted only within the even radio frames (0, 2, ...) in this example, due to the SSB period of 2 radio frames or 20 ms). There are no SSBs transmitted on the odd radio frames (1, 3, ...) in this example. Because the SSB period is greater than the threshold of 10 ms, or greater than period for one radio frame (which is 10 ms), this means that not all radio frames will have SSB transmissions. Rather, as noted, only every other radio frame (the even radio frames 0, 2) will have SSB transmissions. The UE may typically receive a SSB from a gNB, measure reference signal received power (RSRP) or reference signal received quality (RSRQ) for multiple SSBs and select the best or strongest SSB. The UE may then typically transmit a RACH preamble, e.g., via a RACH occasion corresponding to the best or strongest measured SSB (or SSB beam).

[0067] To decrease latency, it may be desirable for the UE to transmit the RACH preamble soon after measuring SSB(s) or soon after the radio frame that includes the SSBs (which may have been measured by the UE). There may not be sufficient time for the UE to both receive and measure SSBs and then transmit a RACH preamble within a RACH occasion within the same radio frame. After measuring SSBs (SSB beams) within radio frame 0, the UE may then transmit the RACH preamble via a RACH occasion during a RACH occasion of a next or subsequent radio frame. However, if the SSB period is greater than a threshold (e.g. the UE may determine that SSB period is greater than the threshold), e.g., where SSBs do not occur every radio frame, it may be preferable for the UE to only consider RACH occasions on radio frames that are immediately after SSB radio frames (radio frames that include SSB transmissions), or only consider RACH occasions within radio frames that are not on SSB radio frames (since the UE may want to transmit the RACH preamble during the radio frame between SSB frames). Thus, in this example, it may be preferable for the UE to receive and measure SSBs during the even radio frames, and then use RACH occasions for RACH preamble transmission during odd radio frames but not during even radio frames (e.g., only use RACH occasions for RACH preamble transmission during odd radio frames). This may allow the UE, e.g., to measure SSBs during radio frame 0 and/or 2, and then transmit a RACH preamble during RACH occasions during radio frames 1 and/or 3, respectively. Thus, in this example, the UE and gNB may eliminate RACH occasions from the SSB radio frames (the even radio frames 0 and 2), leaving remaining possible (or candidate) RACH occasions 1.0.9, 1.1.9, 3.0.9 and 3.2.9 in radio frames 1 and 9, which is shown in FIG. 5. If the SSB period/periodicity is not greater than a threshold (e.g., the UE may so determine), e.g., if SSBs occur every radio frame, then the UE and gNB does not or may not need to eliminate any RACH occasions from the RACH occasions of one RACH period.

[0068] FIG. 6 is a diagram illustrating the list 610 of (e.g., ordered) RACH occasions that includes the first RACH occasion on the list 610. In an example embodiment, at step 30 of FIG. 3, the UE and gNB may select the first or earliest (e.g., earliest in time, within the RACH period) RACH occasion to be on the list of RACH occasions. In this example (see FIGS. 5-6), the first possible RACH occasion or earliest RACH occasion is RACH occasion 1.0.9 (corresponding to radio frame 1, half-frame 0 and slot 9). This first or earliest RACH occasion of the possible RACH occasions (possible RACH occasions are shown in FIG. 5) is added or entered as the first entry on the list 610 of RACH occasions (see FIG. 6). Thus, in the list of RACH occasions shown in FIG. 6, index 0 corresponds to RACH occasion 1.0.9, which has been added or entered as the first or earliest entry of the list 610 of RACH occasions.

[0069] The UE and gNB may determine a list 610 of RACH occasions that are distributed within one or more RACH periods. According to an example embodiment, as shown in FIG. 6, the earliest or first possible RACH occasion 1.0.9 within the RACH period (see possible RACH occasions in FIG. 5) has been added or entered as the first RACH occasion (at or corresponding to index 0) of the list 610 of RACH occasions.

[0070] Additional RACH occasions will then be selected and added to this list 610 of RACH occasions, such that the RACH occasions are distributed within one or more RACH periods. There may be different or various techniques that may be used to select RACH occasions (e.g., distributed RACH occasions) to be on the list of RACH occasions. RACH occasions, e.g., distributed RACH occasions, may be selected to be on the list 610 of RACH occasions, including for example: selecting RACH occasions that are spaced apart from each other in some fashion, e.g., such as selecting RACH occasions that may be provided or occur in multiple radio frames or in different radio frames, selecting RACH occasions having a minimum space in slots between adjacent RACH occasions (e.g., a minimum of 5 slots inter-RACH occasion distance), selecting RACH occasions that may be most equally spaced apart, and/or selecting RACH occasions such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized (e.g., which may be an example way to determine or select RACH occasions that are most equally spaced apart). These are some examples, and other techniques may be used to select (e.g., distributed) RACH occasions to be on the list 610 of RACH occasions.

[0071] After selecting the first or earliest RACH occasion (step 30 of FIG. 3), steps 40-of FIG. 3 may be performed to add RACH occasions to list 610 of RACH occasions until the list 610 is full. At step 40 of FIG. 3, the UE and gNB may fill RACH occasion list 610 successively until the list 610 is full (e.g., 8 RACH occasions have been selected to be added to the list of RACH occasions), or no more RACH occasions are available in the RACH period. According to an example, embodiment, the UE and gNB may select for the next RACH occasion index on the list, the RACH occasion that is most equally spaced apart within the RACH period, or selecting RACH occasions for the list, where two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match. The distance of one full RACH period from the first RACH occasion on the list 610 may be considered when looking at spacing between RACH occasions.

[0072] FIG. 7 is a diagram illustrating a list 610 of RACH occasions that includes two RACH occasions, including a RACH occasion corresponding to index = 0 (RACH occasion 1.0.9) and RACH occasion corresponding to index = 1 (RACH occasion 3.0.9). An example process or procedure for selecting this second RACH occasion on list 610 will be briefly described. For example, to select a second RACH occasion to add to the list 610 of RACH occasions, a second RACH occasion may be selected such that a first inter-RACH occasion distance between the first RACH occasion (e.g., at 1.0.9, FIG. 5) and a second RACH occasion most closely matches a second inter-RACH occasion distance between the second RACH occasion (at 1.0.9, FIG. 5) and a slot position that is one RACH period after the first RACH occasion. The slot position that is one RACH period (4 radio frames) after the first RACH occasion (at 1.0.9) would be RACH occasion 5.0.9 (corresponding to radio frame 5, half-frame 0 and slot 9, not shown in FIG. 5).

[0073] As shown in FIG. 5, after the first or earliest RACH occasion 1.0.9, the next RACH occasions within the RACH period are RACH occasions 1.1.9, 3.0.9 and 3.1.9. In this example, the RACH occasion 3.0.9 is selected as the second RACH occasion to be added to list 610 of RACH occasions because a first inter-RACH occasion distance between the first RACH occasion at 1.0.9 and the second RACH occasion at 3.0.9 (which is 2 radio frames, or 40 slots) matches or most closely matches (compared to other possible next RACH occasions) a second inter-RACH occasion distance between the second RACH occasion at 3.0.9 and the slot that is 1 RACH period (4 radio frames) after the first RACH occasion of 1.0.9 (which is 5.0.9), which is also 2 radio frames or 40 slots. For example, the second RACH occasion may be selected such that these two inter-RACH distances most closely match (an exact match is not required, although those two distances just happen to exactly match in this example, if the RACH occasion 3.0.9 is selected as the second RACH occasion for the list 610). The other possible next/second RACH occasions (1.1.9 and 3.1.9) are not as equally spaced apart, are at slots or locations such that these two inter-RACH occasion distances do not match as closely as they do when selecting RACH occasion 3.0.9 as the second RACH occasion. The list 610 of RACH occasions in FIG. 7 shows RACH occasion 3.0.9 has been added to the list, corresponding to index 1 (the second entry of the list 610 of RACH occasions).

[0074] Next, a third RACH occasion may be selected to be added to the list 610 of RACH occasions that is most equally spaced between two RACH occasions, e.g., the RACH occasion that is most equally spaced between RACH occasions 1.0.9 (corresponding to index 0 or the first entry of the list 610) and 3.0.9 (corresponding to index 1 or the second entry of the list 610). The RACH occasion 1.1.9 is the only RACH occasion between these two RACH occasions (1.0.9 and 3.0.9), and appears 10 slots after RACH occasion 1.0.9). Thus, RACH occasion 1.1.9 is selected as the third RACH occasion for the list 610 of RACH occasions (and corresponds to index = 2). The RACH occasion 3.1.9 also appears or occurs between the second RACH occasion (at 3.0.9) and the slot that is 1 RACH period after the first RACH occasion (at RACH occasion 5.0.9). The RACH occasion 3.1.9 appears or occurs 10 slots after the second RACH occasion 3.0.9. Thus, in this example, there is a tie between the RACH occasions 1.1.9 and 3.1.9, as they both are equally spaced between adjacent selected RACH occasions (or one RACH period away from or after the first RACH occasion of the list 610). In this example, even though there was a tie between RACH occasions 1.1.9 and 3.1.9 in terms of being most equally spaced from adjacent selected RACH occasions or the end of the one RACH period after the first selected RACH occasion, the UE and gNB may select the earliest RACH occasion, e.g., RACH occasion 1.1.9 as the third RACH occasion for the list 610 of RACH occasions. These are example rules, and other rules may be used to select RACH occasions and fill the list 610 of RACH occasions.

[0075] FIG. 8 is a diagram illustrating a list 610 of RACH occasions that includes four RACH occasions (1.0.9, 3.0.9, 1.1.9, 3.1.9) according to an example embodiment. Thus, because of the tie between RACH occasion 1.1.9 and 3.1.9 (in terms of providing RACH occasions that are most equally spaced apart), RACH occasion 1.1.9 (corresponding to index = 2) is selected as the third RACH occasion for the list 610 of RACH occasions, and then RACH occasion 3.1.9 (corresponding to index = 3) is selected as the fourth RACH occasion for the list 610.

[0076] The slot 5.0.9, which is the slot that is 1 RACH period after or away from the first selected RACH occasions 1.0.9, is not a selected RACH occasion, but may be used as a place holder or reference point in the determination of whether a RACH occasion is most equally spaced apart from adjacent selected RACH occasions or end of 1 RACH period away from the first selected RACH occasion, e.g., since the goal may be to select a set of spaced apart RACH occasions within one RACH period, e.g., which may reduce inter-cell interference between UEs transmitting RACH preambles, and/or may reduce processing load of gNBs to receive and process RACH preambles, since the transmission of RACH preambles may be more distributed or spaced apart.

[0077] This process of selecting a next RACH occasion that is most equally spaced apart from adjacent selected RACH occasions (or with reference to end of 1 RACH period away from first selected RACH period) within the RACH period, may be repeated or iteratively performed to add additional RACH occasions to the list 610 of RACH occasions, until either the list is filled, or all available RACH occasions of the RACH period have been selected. In this example, all 4 of the RACH occasions (1.0.9, 3.0.9, 1.1.9, 3.1.9) within the RACH period have been selected.

[0078] At step 50 of FIG. 3, in case all available RACH occasions of the RACH period have been selected for the list, but the list 610 is not full (e.g., has not yet reached 8 entries or RACH occasions), the remaining entries of the list 610 should be filled by repeating the existing entries of the list, e.g., in the same order. Thus, in this case, since all available RACH occasions have been selected for the list, but the list is not full (only 4 entries are on the list 610), the first four entries (corresponding to indices 0-3) of the list 610 will be repeated as entries 5-8 (corresponding to indices 4-7). Thus, the RACH occasions 1.0.9, 3.0.9, 1.1.9 and 3.1.9 will be repeated on the list 610 as the last four RACH occasion entries. FIG. 9 is a diagram of the list 610 of RACH occasions that includes all 8 selected RACH occasions for the list. The list 610 of RACH occasions is now complete (the list 610 is full, as it has 8 RACH occasions).

[0079] At step 60 of FIG. 3, the UE and/or gNB may identify a RACH occasion based on an index. For example, an index to the list 610 of RACH occasions may be generated, e.g., based on a function of one or more of: PCI, GSCN and/or SFN. The UE and gNB may identify the RACH occasion based on the generated index, e.g., the RACH occasion on the list 610 corresponding to the generated index. For example, if an index = 2 is generated, then the UE and gNB may select RACH occasion 1.1.9 (which corresponds to index=2 on the list 610 of RACH occasions), to be used for the random access procedure.

[0080] At step 70 of FIG. 3, the UE and gNB may perform a RACH procedure based on or using the identified RACH occasion. For example, the UE may transmit the RACH preamble and the gNB may receive the RACH preamble via the identified RACH occasion. In this manner, by selecting a list of RACH occasions that may be spaced apart or distributed (and may even have one or more RACH occasions on the list that are most equally spaced apart), and then pseudo-randomly generating an index to identify one of these RACH occasions from the list, inter-cell interference between UEs transmitting RACH preambles may be reduced, and/or processing load of gNBs to receive and process RACH preambles may be more evenly distributed in time, thereby reducing peak RACH preamble receiving and/or processing load at the gNB.

[0081] A second example is described below and illustrated with reference to FIGs.

10A, 10B and 11, in which there are more than 8 possible RACH occasions within the RACH period. In this second illustrative example, the list of RACH occasions includes 8 RACH occasions, the RACH period is 8 radio frames (radio frames 0-7), and the SSB periodicity is 10 ms, which is not greater than the threshold of 10 ms. Thus, in this second example, each radio frame includes SSB transmissions.

[0082] FIGs. 10A-10B illustrate possible RACH occasions within a RACH period of 8 radio frames for cells with PCI 100, 101, 102 and 103 according to another example embodiment. The possible RACH occasions are marked with an X and appear at slot 9, within half-frames 0 and 1 within each of radio frames 0-7. Thus, the possible RACH occasions for this RACH period include RACH occasions 0.0.9, 0.1.9, 1.0.9, 1.1.9, 2.0.9, 2.1.9, 3.0.9, 3.1.9, 4.0.9, 4.1.9, 5.0.9, 5.1.9, 6.0.9, 6.1.9, 7.0.9 and 7.1.9. Because the RACH period is not greater than the threshold, there is no need to eliminate or remove some of the RACH occasions.

[0083] FIG. 11 is a diagram illustrating a list 1110 of RACH occasions that were selected based on the second example. The first possible RACH occasion 0.0.9 is selected for the list of RACH occasions, and corresponds to index = 0. Next, the RACH occasion is selected that is most equally spaced between the first RACH occasion (at 0.0.9) and a slot that is 1 RACH period (or 8 radio frames) away from the first RACH occasion (which would be slot at 8.0.9). The RACH occasion, of the possible RACH occasions shown in FIGs. 10A-10B, that is most equally spaced between the first RACH occasion (0.0.9) and the slot that is 8 radio frames or 1 RACH period away from the first RACH occasion is RACH occasion 4.0.9, which is exactly 4 radio frames away from the first RACH occasion 0.0.9, although the selected RACH occasion does not have to be exactly in the middle between those two, just the RACH occasion that is most equally spaced between those two points. Thus, the first two RACH occasions in the list 1110 are 0.0.9 (index=0) and 4.0.9 (index=1).

[0084] Next, the UE will select a third RACH occasion for the list 1110, which is most equally spaced between either the first and second RACH occasions (0.0.9 and 4.0.9) or most equally spaced between 4.0.9 and the slot at 8.0.9 that is 1 RACH period away from the first RACH period. Thus, in other words, for example, the LIE and gNB may search for the RO that can fill or be located in a gap and which is most equally spaced between two selected RACH occasions or between the last selected RACH occasion and the slot at 8.0.9. In this case, thus, RACH occasions 2.0.9 and 6.0.9 (a space of 2 radio frames for each of these, to the adjacent selected RACH occasion) are most equally spaced between selected RACH occasions and/or between a (e.g., last) selected RACH occasion and the slot at 8.0.9. Thus, according to a set of rules known by both the UE and gNB, in case of this tie (since both RACH occasions 2.0.9 and 6.0.9 are equally spaced apart from adjacent selected RACH occasions or 1 RACH period after the first selected RACH occasion, the UE and gNB may select the first of these RACH occasions (2.0.9) (index=2). After this selection of RACH occasion 2.0.9, there are now three selected RACH occasions (0.0.9, 4.0.9 and 2.0.9), and there are four gaps. The RACH occasion 6.0.9 is next selected as the fourth RACH occasion for the list (with index=3).

[0085] This process or procedure may be repeated or performed iteratively, until all entries of the list 1110 have been filled with RACH occasions or until all available RACH occasions of 1 RACH period have been selected. The selected RACH occasions for the list 1110 includes 0.0.9, 0.1.9, 1.0.9, 1.1.9, 2.0.9, 2.1.9, 3.0.9, 319, 4.0.9, 4.1.9, 5.0.9, 5.1.9, 6.0.9, 6.1.9, 7.0.9 and 7.1.9. In this second example, there are more than 8 available or possible RACH occasions, and the list 1110 of RACH occasions is filled with 8 RACH occasions from the available RACH occasions of the RACH period. Because the list 1110 of RACH occasions is now filled, there is no need to repeat any of the selected RACH occasions [0086] As noted, according to an example embodiment, RACH occasions for the list 610 of RACH occasions (first example) and/or list 1110 of RACH occasions (second example) may be selected that are distributed, and may even be or include RACH occasion(s) that are most equally spaced apart as possible within the RACH period. One example technique that may be used to select RACH occasions that are most equally spaced apart as possible within a RACH period may be to select RACH occasions such that a sum of squared distances (e.g., distance measured in slots) between adjacent selected RACH occasions is minimized. By minimizing these squared distances between selected RACH occasions, this may result in selecting RACH occasions for the list of RACH occasions that are most equally spaced apart, and/or create a most equally spaced apart list of RACH occasions within 1 period.

[0087] For example, mathematically, this can be expressed by defining a distance in slots between two selected RACH occasions and for a list of RACH occasions. ro refers to RACH occasion, rf refers to radio frame, hf refers to half-frame. For example, for TDD (time division duplex) with a subcarrier spacing of 30kHz, i.e., with 10 slots per half-frame: the position in slots pos(ro) of a RACH occasion: ro at radioframe rf half-frame hf, slot s, is defined as pos(ro) = rf*20 + hf'10 + s (in this case 1 slot is 0.5 ms, depends on subcarrier spacing, 30ICHZ). A squared distance in slots sqdist(ro 1, ro 2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and this provides a positive value associated with distance, although this is actually a square of the distance between two RACH occasions.

[0088] According to an example embodiment, the UE and gNB may select the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared di stances(sqdist) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro_l, ro_2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro 1, ro 2, ro 3, ro n-1, ro n) is defined as sum= sqdi st(ro_l, ro2) + sqdi st(ro2, ro_3) + + sqdist(ro_n+1, ro_n).

[0089] Each iteration, or to add an additional or a next RACH occasion to the list of RACH occasions, the UE and gNB may look for the RACH occasion that minimizes this sum of squared distances for the new/updated list of RACH occasions.

[0090] For example, to create the list of RACH occasions with equal spacing one starts with the RACH occasion ro 1 &his in step (10), FIG. 3. For the subsequent calculation one considers as well the RACH occasion in the next period of RACH occasions, e.g., if the RACH period is p radio frames, this is the RACH occasion at rf + p.hf.s. This gives a first list of RACH occasions 1rf hf. s, rf + p.hls1. The most equally spaced RACH occasion ro i at position rf i.hf i.s i is the one that minimizes the sum of squared distances of the RACH occasions, e.g., the RACH occasion with or associated with minimal value of sqdist({rf. hfs, rf i.hf rf + p.hf.s}). In case there are several RACH occasions with the same minimal distance after adding it to the list of RACH occasions, the earliest one, i.e. the one with smallest position, is selected to be added to the list of RACH occasions.

[0091] Also, for example, for FDD with a subcarrier spacing of 15kHz the notion of half-frames is not needed. In this case pos(ro) = rf*10 + s. For the first example with RACH occasions 1.0.9, 1.1.9, 3.0.9, 3.1.9, the first RACH occasion selected for the index list is 1.0.9. Due to the RACH period of 4 radio frames, this is repeated at 5.0.9. The initial distance list is { 1.0.9, 5.0.9} with a distance of 6400. To select the next RACH occasion the corresponding distances are calculated: Sum of squared distances for (11.0.9, 1.1.9, 5.0.9}) = 5000.

Sum of squared distances ({ 1.0.9, 3.0.9, 5.0.9}) = 3200 -this one, has smallest sum of squared distances between selected ROs, so these are most equally spaced set of selected ROs of the list.

Sum of sqdist(11.0.9, 3.1.9, 5.0.91) = 3400.

RACH occasion 3.0.9 gives the smallest value and is added to the index list and the distance list {1.0.9, 3.0.9, 5.0.9}).

In the next step, the UE and gNB may choose between RACH occasions 1.1.9 and 3.1.9: As the resulting sum of squared distance is the same for these two RACH occasions, the earlier RACH occasion 1.1.9 is selected to be added to the list next. In a last step, the remaining RACH occasion 3.1.9 is added to the list.

[0092] Some examples will now be described, based on the description and figures provided herein. A number of examples will now be described, based on the description and figures provided herein.

[0093] Example 1. An apparatus (e.g., 1300, FIG. 5; and/or UE 410 in FIG. 4) comprising: at least one processor (e.g., processor 1304, FIG. 5); and at least one memory Sum of sqdist(11.0.9, 1.1.9, 3.0.9, 5.0.9}) = 2600.

Sum of sqdist({1.0.9, 3.0.9, 3.1.9, 5.0.9}) = 2600.

(e.g., memory 1306, FIG. 5) storing instructions that, when executed by the at least one processor (1304), cause the apparatus at least to: determine a list of random access (RACH) occasions distributed within one or more RACH periods; generate an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identify one of the RACH occasions of the list of RACH occasions based on the generated index; and transmit or receive a random access preamble via the identified RACH occasion.

[0094] Example 2. The apparatus of example 1: wherein the apparatus comprises or is provided in a user device or user equipment; and wherein the apparatus is caused to transmit the random access preamble via the identified RACH occasion.

[0095] Example 3. The apparatus of example 1: wherein the apparatus comprises or is provided in a network node or gNB; and wherein the apparatus is caused to receive the random access preamble via the identified RACH occasion.

[0096] Example 4. The apparatus of any of examples 1-3, wherein the apparatus caused to generate comprises the apparatus caused to: generate the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SFN).

[0097] Example 5. The apparatus of any of examples 1-4, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a plurality of the RACH occasions to be on the list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period.

[0098] Example 6. The apparatus of any of examples 1-5, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select the plurality of RACH occasions wherein at least some of the RACE occasions are selected to be on the list such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match.

[0099] Example 7. The apparatus of any of examples 1-6, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; select a second RACH occasion such that a first inter-RACH occasion distance between the first and second RACH occasions most closely matches a second inter-RACH occasion distance between the second RACH occasion and a slot position that is one RACH period after the first RACH occasion.

[0100] Example 8. The apparatus of any of examples 6-7, wherein the apparatus is caused to repeat or iteratively perform, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match, or the RACH occasions are selected that are most equally spaced apart.

[0101] Example 9. The apparatus of example 8, wherein the apparatus is further caused to: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeat one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0102] Example 10. The apparatus of any of examples 5-9, wherein the apparatus caused to select comprises the apparatus caused to: in case of a tie between two RACH occasions that are equally spaced apart or have equal inter-RACH occasion distances, select a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0103] Example 11. The apparatus of any of claims 1-8, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.

[0104] Example 12. The apparatus of any of examples 1-11, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and, select a second RACH occasion such that a sum of: 1) a square of a first inter-RACH occasion distance in slots between the first and second RACH occasions, plus 2) a square of a second inter-RACH occasion distance in slots between the second RACH occasion and a slot that is one RACH period after the first RACH occasion, is minimized.

[0105] Example 13. The apparatus of any of examples 11-12, wherein the apparatus is caused to: repeat or iteratively perform, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized. [0106] Example 14. The apparatus of example 13, wherein the apparatus is further caused to: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeat one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0107] Example 15. The apparatus of any of examples 11-14, wherein the apparatus caused to select comprises the apparatus caused to: in case of a tie between two RACH occasions that cause a sum of squared distances in slots between adjacent selected RACH occasions to be equal, select a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0108] Example 16. The apparatus of any of examples 1-15, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: determine a set of RACH occasions in one or more radio frames up to a RACH period; and if a synchronization signal burst (SSB) period is greater than a threshold, eliminate RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0109] Example 17. The apparatus of any of examples 1-2 and 4-16, wherein the apparatus comprises a user device, and wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: receive, by the user device from a network node, assistance information via system information block that provides configuration information for RACH occasions, including one or more parameters including one or more of the RACH period or RACH periodicity, a starting symbol, a number of RACH preamble slots within a radio frame, a number of time durations within a slot, a RACH preamble duration and/or a subframe number for RACH occasions; and determine a set of RACH occasions in one or more radio frames up to a RACH period.

[0110] Example 18. The apparatus of example 17, wherein the apparatus caused to determine the set of RACH occasions comprises the apparatus caused to: if a synchronization signal burst (SSB) period is greater than a threshold, eliminate RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0111] Example 19. The apparatus of any of examples 1-2 and 4-18, wherein the apparatus comprises or is provided in a user device, the apparatus further caused to: determine the physical cell identity of a cell based on system information received from the network node; detect a timing or position of a synchronization signal block from the network node; and determine the global synchronization channel number based on the timing or position of the synchronization signal block.

[0112] Example 20. The apparatus of any of examples 1-19, wherein the list of RACH occasions is eight RACH occasions in length.

[0113] Example 21. The apparatus of example 4, wherein the apparatus caused to generate comprises the apparatus caused to: generate, by the user device, the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SEN)/128.

[0114] Example 22. The apparatus of example 11, wherein the apparatus caused to select the plurality of the RACH occasions to be on the list of RACH occasions comprises the apparatus caused to: select the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances(sqdist) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro_l, ro 2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro 1, ro 2, ro 3, ro n-1, ro n) is defined as sum= sqdist(ro 1, ro2) + sqdist(ro 2, ro 3) + . sqdi st(ro_n+1, ro_n).

[0115] Example 23. A method comprising: determining a list of random access (RACH) occasions distributed within one or more RACH periods; generating an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and transmitting or receiving a random access preamble via the identified RACH occasion.

[0116] Example 24. The method of example 23, comprising: transmitting, by a user device, the random access preamble via the identified RACH occasion.

[0117] Example 25. The method of example 23, comprising: receiving, by a network node or gNB, the random access preamble via the identified RACH occasion.

[0118] Example 26. The method of any of examples 23-25, wherein the generating comprises: generating the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SFN). [0119] Example 27. The method of any of examples 23-26, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a plurality of the RACH occasions to be on the list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period.

[0120] Example 28. The method of any of examples 23-27, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting the plurality of RACH occasions wherein at least some of the RACH occasions are selected to be on the list such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match.

[0121] Example 29. The method of any of examples 23-28, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and selecting a second RACH occasion such that a first inter-RACH occasion distance between the first and second RACH occasions most closely matches a second inter-RACH occasion distance between the second RACH occasion and a slot position that is one RACH period after the first RACH occasion.

[0122] Example 30. The method of any of examples 28-29, comprising: repeating or iteratively performing, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match, or the RACH occasions are selected that are most equally spaced apart.

[0123] Example 31. The method of example 30, further comprising: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeating one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0124] Example 32. The method of any of examples 27-31, wherein the selecting comprises: in case of a tie between two RACH occasions that are equally spaced apart or have equal inter-RACH occasion distances, selecting a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0125] Example 33. The method of any of examples 23-30, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.

[0126] Example 34. The method of any of examples 23-33, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and selecting a second RACH occasion such that a sum of: 1) a square of a first inter-RACH occasion distance in slots between the first and second RACH occasions, plus 2) a square of a second inter-RACH occasion distance in slots between the second RACH occasion and a slot that is one RACH period after the first RACH occasion, is minimized.

[0127] Example 35. The method of any of examples 33-34, comprising: repeating or iteratively performing, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized. [0128] Example 36. The method of example 35, further comprising: if all available 20 RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeating one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0129] Example 37. The method of any of examples 33-36, wherein the selecting comprises: in case of a tie between two RACH occasions that cause a sum of squared distances in slots between adjacent selected RACH occasions to be equal, selecting a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time. [0130] Example 38. The method of any of examples 23-37, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: determining a set of RACH occasions in one or more radio frames up to a RACH period; and if a synchronization signal burst (SSB) period is greater than a threshold, eliminating RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0131] Example 39. The method of any of examples 23-24 and 26-38, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: receiving, by a user device from a network node, assistance information via system information block that provides configuration information for RACH occasions, including one or more parameters including one or more of: the RACH period or RACH periodicity, a starting symbol, a number of RACH preamble slots within a radio frame, a number of time durations within a slot, a RACH preamble duration and/or a subframe number for RACH occasions; and determining a set of RACH occasions in one or more radio frames up to a RACH period.

[0132] Example 40. The method of example 39, wherein the determining the set of RACH occasions comprises: if a synchronization signal burst (SSB) period is greater than a threshold, eliminating RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0133] Example 41. The method of any of examples 23-24 and 26-40, further comprising: determining the physical cell identity of a cell based on system information received from a network node; detecting a timing or position of a synchronization signal block from the network node; and determining the global synchronization channel number based on the timing or position of the synchronization signal block.

[0134] Example 42. The method of any of examples 23-41, wherein the l st of RACH occasions is eight RACH occasions in length.

[0135] Example 43. The method of example 26, wherein the generating comprises: generating, by the user device, the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SFN)/128.

[0136] Example 44. The method of example 33, wherein the selecting the plurality of the RACH occasions to be on the list of RACH occasions comprises: selecting the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances(sqdist) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro 1, ro 2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro_l, ro_2, ro_3, ro_n-1, ro_n) is defined as sum= sqdist(ro 1, ro2) + sqdist(ro 2, ro 3) + + sqdist(ro n+1, ro n).

[0137] Example 45. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: select a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period; generate an index into the list of RACH occasions; identify one of the RACH occasions of the list of RACH occasions based on the generated index; and transmit or receive a random access preamble via the identified RACH occasion.

[0138] Example 46. The apparatus of example 45, wherein the apparatus caused to generate comprises the apparatus caused to: generate, by the user device or network node, the index into the list of RACH occasions based on one or more of: a physical cell identity (PCI); a global synchronization channel number (GSCN); and/or a system frame number (SFN).

[0139] Example 47. The apparatus of any of examples 45-46, wherein the apparatus caused to select the plurality of RACH occasions comprises the apparatus caused to: select the plurality of RACH occasions wherein at least some of the RACH occasions are selected to be on the list such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match.

[0140] Example 48. The apparatus of any of examples 45-47, wherein the apparatus caused to select the plurality of RACH occasions comprises the apparatus caused to: select a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; select a second RACH occasion such that a first inter-RACH occasion distance between the first and second RACH occasions most closely matches a second inter-RACH occasion distance between the second RACH occasion and a slot position that is one RACH period after the first RACH occasion.

[0141] Example 49. The apparatus of any of examples 45-48, wherein the apparatus is caused to: repeat or iteratively perform, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match, or the RACH occasions are selected that are most equally spaced apart.

[0142] Example 50. The apparatus of example 49, wherein the apparatus is further caused to: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeat one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0143] Example 51. The apparatus of any of examples 45-50 wherein the apparatus caused to select comprises the apparatus caused to: in case of a tie between two RACH occasions that are equally spaced apart or have equal inter-RACH occasion distances, select a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0144] Example 52. The apparatus of any of examples 45-51, wherein the apparatus caused to select the plurality of RACH occasions comprises the apparatus caused to: select the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.

[0145] Example 53. The apparatus of any of examples 45-52, wherein the apparatus caused to select the plurality of RACH occasions comprises the apparatus caused to: select a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; select a second RACH occasion such that a sum of 1) a square of a first inter-RACH occasion distance in slots between the first and second RACH occasions, plus 2) a square of a second inter-RACH occasion distance in slots between the second RACH occasion and a slot that is one RACH period after the first RACH occasion, is minimized.

[0146] Example 54. The apparatus of any of examples 52-53, wherein the apparatus is caused to: repeat or iteratively perform, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.

[0147] Example 55. The apparatus of example 54, wherein the apparatus is further caused to: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeat one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.

[0148] Example 56. The apparatus of any of examples 52-55, wherein the apparatus caused to select comprises the apparatus caused to: in case of a tie between two RACH occasions that cause a sum of squared distances in slots between adjacent selected RACH occasions to be equal, select a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.

[0149] Example 57. The apparatus of any of examples 45-56, wherein the apparatus caused to select the plurality of the RACH occasions to be on the list of RACH occasions comprises the apparatus caused to: select the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared di stances(sqdi st) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro 1, ro 2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro 1, ro 2, ro 3, ..., ro n-1, ro n) is defined as sum= sqdist(ro ro2) + sqdist(ro 2, ro 3) + + sqdi st(ro_n+1, ro_n).

[0150] Example 58. The apparatus of any of examples 45-57, wherein the apparatus caused to select comprises the apparatus caused to: determine a set of RACH occasions in one or more radio frames up to a RACH period; and if a synchronization signal burst (SSB) period is greater than a threshold, eliminate RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.

[0151] Example 59. A method comprising: selecting a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period; generating an index into the list of RACH occasions; identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and transmitting or receiving a random access preamble via the identified RACH occasion.

[0152] FIG. 12 is a block diagram of a wireless station or node (e.g., UE, user device, AP, BS, eNB, gNB, RAN node, network node, TRP, or other node) 1300 according to an example embodiment. The wireless station 1300 may include, for example, one or more (e.g., two as shown in FIG. 12) RF (radio frequency) or wireless transceivers 1302A, 1302B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit/entity (controller) 1304 to execute instructions or software and control transmission and receptions of signals, and a memory 1306 to store data and/or instructions.

[0153] Processor 1304 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 1304, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 1302 (1302A or 1302B). Processor 1304 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 1302, for example). Processor 1304 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1304 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and/or any combination of these. Using other terminology, processor 1304 and transceiver 1302 together may be considered as a wireless transmitter/receiver system, for example.

[0154] In addition, referring to FIG. 12, a controller (or processor) 1308 may execute software and instructions, and may provide overall control for the station 1300, and may provide control for other systems not shown in FIG. 12, such as controlling input/output devices (e.g., display, keypad), and/or may execute software for one or more applications that may be provided on wireless station 1300, such as, for example, an email program, audio/video applications, a word processor, a Voice over IP application, or other application or software.

[0155] In addition, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 1304, or other controller or processor, performing one or more of the functions or tasks described above.

[0156] According to another example embodiment, RF or wireless transceiver(s) 1302A/1302B may receive signals or data and/or transmit or send signals or data. Processor 1304 (and possibly transceivers 1302A/1302B) may control the RF or wireless transceiver 1302A or 1302B to receive, send, broadcast or transmit signals or data. [0157] Example embodiments are provided or described for each of the example methods, including: An apparatus (e.g., 1300, FIG. 12) including means (e.g., processor 1304, RF transceivers 1302A and/or 1302B, and/or memory 1306, in FIG. 12) for carrying out any of the methods; a non-transitory computer-readable storage medium (e.g., memory 1306, FIG. 12) comprising instructions stored thereon that, when executed by at least one processor (processor 1304, FIG. 12), are configured to cause a computing system (e.g., 1300, FIG. 12) to perform any of the example methods; and an apparatus (e.g., 1300, FIG. 12) including at least one processor (e.g., processor 1304, FIG. 12), and at least one memory (e.g., memory 1306, FIG. 12) including computer program code, the at least one memory (1306) and the computer program code configured to, with the at least one processor (1304), cause the apparatus (e.g., 1300) at least to perform any of the example methods.

[0158] Embodiments of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Embodiments may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Embodiments may also be provided on a computer readable medium or computer readable storage medium, which may be a non-transitory medium. Embodiments of the various techniques may also include embodiments provided via transitory signals or media, and/or programs and/or software embodiments that are downloadable via the Internet or other network(s), either wired networks and/or wireless networks. In addition, embodiments may be provided via machine type communications (MTC), and also via an Internet of Things (JOT).

[0159] As used in this application, the term circuitry' or "circuit" refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and soft-ware (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term 'circuitry' would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware. The term 'circuitry' would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device.

[0160] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer, or it may be distributed amongst a number of computers.

[0161] Furthermore, embodiments of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the embodiment and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers,...) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. The rise in popularity of smartphones has increased interest in the area of mobile cyber-physical systems.

Therefore, various embodiments of techniques described herein may be provided via one or more of these technologies.

[0162] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0163] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0164] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing, instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0165] To provide for interaction with a user, embodiments may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a user interface, such as a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0166] Embodiments may be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an embodiment, or any combination of such back-end, middleware, or front-end components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[0167] While certain features of the described embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the 30 various embodiments.

Claims (45)

1. WHAT IS CLAIMED IS: 1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine a list of random access (RACH) occasions distributed within one or more RACH periods; generate an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identify one of the RACH occasions of the list of RACH occasions based on the Generated index; and transmit or receive a random access preamble via the identified RACH occasion.
2. The apparatus of claim 1: wherein the apparatus comprises or is provided in a user device or user equipment; and wherein the apparatus is caused to transmit the random access preamble via the 20 identified RACH occasion.
3. 3. The apparatus of claim 1: wherein the apparatus comprises or is provided in a network node or g1\113, and wherein the apparatus is caused to receive the random access preamble via the identified RACH occasion.
4. 4. The apparatus of any of claims 1-3, wherein the apparatus caused to generate comprises the apparatus caused to: generate the index into the list based on the physical cell identity (PCI), the global 30 synchronization channel number (GSCN) and a system frame number (SFN).
5. 5. The apparatus of any of claims 1-4, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a plurality of the RACH occasions to be on the list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period.
6. 6. The apparatus of any of claims 1-5, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select the plurality of RACH occasions wherein at least some of the RACH occasions are selected to be on the list such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match.
7. 7. The apparatus of any of claims 1-6, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; select a second RACH occasion such that a first inter-RACH occasion distance between the first and second RACH occasions most closely matches a second inter-RACH occasion distance between the second RACH occasion and a slot position that is one RACH period after the first RACH occasion.
8. 8. The apparatus of any of claims 6-7, wherein the apparatus is caused to: repeat or iteratively perform, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match, or the RACH occasions are selected that are most equally spaced apart.
9. The apparatus of claim 8, wherein the apparatus is further caused to: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeat one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.
10. 10. The apparatus of any of claims 5-9, wherein the apparatus caused to select comprises the apparatus caused to: in case of a tie between two RACH occasions that are equally spaced apart or have equal inter-RACH occasion distances, select a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.
11. 11. The apparatus of any of claims 1-8, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.
12. 12. The apparatus of any of claims 1-11, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: select a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and select a second RACH occasion such that a sum of: 1) a square of a first inter-RACH occasion distance in slots between the first and second RACH occasions, plus 2) a square of a second inter-RACH occasion distance in slots between the second RACH occasion and a slot that is one RACH period after the first RACH occasion, is minimized.
13. 13. The apparatus of any of claims 11-12, wherein the apparatus is caused to: repeat or iteratively perform, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.
14. 14. The apparatus of claim 13, wherein the apparatus is further caused to: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeat one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.
15. 15. The apparatus of any of claims 11-14, wherein the apparatus caused to select comprises the apparatus caused to: in case of a tie between two RACH occasions that cause a sum of squared distances in slots between adjacent selected RACH occasions to be equal, select a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.
16. 16. The apparatus of any of claims 1-15, wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: determine a set of RACH occasions in one or more radio frames up to a RACH period; and if a synchronization signal burst (SSB) period is greater than a threshold, eliminate RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.
17. 17. The apparatus of any of claims 1-2 and 4-16, wherein the apparatus comprises a user device, and wherein the apparatus caused to determine the list of random access (RACH) occasions distributed within one or more RACH periods comprises the apparatus caused to: receive, by the user device from a network node, assistance information via system information block that provides configuration information for RACH occasions, including one or more parameters including one or more of the RACH period or RACH periodicity, a starting symbol, a number of RACH preamble slots within a radio frame, a number of time durations within a slot, a RACH preamble duration and/or a subframe number for RACH occasions; and determine a set of RACH occasions in one or more radio frames up to a RACH period.
18. 18. The apparatus of claim 17, wherein the apparatus caused to determine the set of RACH occasions comprises the apparatus caused to: if a synchronization signal burst (SSB) period is greater than a threshold, eliminate RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.
19. 19. The apparatus of any of claims 1-2 and 4-18, wherein the apparatus comprises or is provided in a user device, the apparatus further caused to: determine the physical cell identity of a cell based on system information received 10 from the network node; detect a timing or position of a synchronization signal block from the network node; and determine the global synchronization channel number based on the timing or position of the synchronization signal block.
20. 20. The apparatus of any of claims 1-19, wherein the list of RACH occasions is eight RACH occasions in length.
21. 21. The apparatus of claim 4, wherein the apparatus caused to generate comprises the apparatus caused to: generate, by the user device, the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SFN)/128.
22. 22. The apparatus of claim 11, wherein the apparatus caused to select the plurality of the RACH occasions to be on the list of RACH occasions comprises the apparatus caused to: select the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances(sqdist) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro 1, ro 2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro_l, ro_2, ro_3, ro_n-1, ro_n) is defined as sum= sqdist(ro 1, ro2) + sqdist(ro 2, ro 3) + + sqdist(ro n+1, ro n).
23. 23. A method comprising: determining a list of random access (RACH) occasions distributed within one or more RACH periods; generating an index into the list of RACH occasions based on a physical cell identity (PCI) and a global synchronization channel number (GSCN); identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and transmitting or receiving a random access preamble via the identified RACH 10 occasion.
24. 24. The method of claim 23, comprising: transmitting, by a user device, the random access preamble via the identified RACH occasion.
25. 25. The method of claim 23, comprising: receiving, by a network node or gNB, the random access preamble via the identified RACH occasion.
26. 26. The method of any of claims 23-25, wherein the generating comprises: generating the index into the list based on the physical cell identity (PC1), the global synchronization channel number (GSCN) and a system frame number (SFN).
27. 27. The method of any of claims 23-26, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a plurality of the RACH occasions to be on the list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period.
28. 28. The method of any of claims 23-27, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting the plurality of RACH occasions wherein at least some of the RACH occasions are selected to be on the list such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match.
29. 29. The method of any of claims 23-28, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and selecting a second RACH occasion such that a first inter-RACH occasion distance between the first and second RACH occasions most closely matches a second inter-RACH occasion distance between the second RACH occasion and a slot position that is one RACH period after the first RACH occasion.
30. 30. The method of any of claims 28-29, comprising: repeating or iteratively performing, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions such that two or more inter-RACH occasion distances between adjacent selected RACH occasions most closely match, or the RACH occasions are selected that are most equally spaced apart.
31. 31. The method of claim 30, further comprising: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeating one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.
32. 32. The method of any of claims 27-31, wherein the selecting comprises: in case of a tie between two RACH occasions that are equally spaced apart or have equal inter-RACH occasion distances, selecting a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.
33. 33. The method of any of claims 23-30, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.
34. 34. The method of any of claims 23-33, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: selecting a first RACH occasion that is an earliest RACH occasion in a RACH period to be on the list of RACH occasions; and selecting a second RACH occasion such that a sum of: 1) a square of a first inter-RACH occasion distance in slots between the first and second RACH occasions, plus 2) a square of a second inter-RACH occasion distance in slots between the second RACH occasion and a slot that is one RACH period after the first RACH occasion, is minimized.
35. 35. The method of any of claims 33-34, comprising: repeating or iteratively performing, until the list of RACH occasions has been filled or all available RACH occasions of the RACH period have been selected, the selecting of one or more additional RACH occasions to be on the list of RACH occasions, such that a sum of squared distances in slots between adjacent selected RACH occasions is minimized.
36. 36. The method of claim 35, further comprising: if all available RACH occasions of the RACH period have been selected but the list of RACH occasions has not been filled, then repeating one or more of the RACH occasions already on the list, until the list of RACH occasions has been filled.
37. 37. The method of any of claims 33-36, wherein the selecting comprises: in case of a tie between two RACH occasions that cause a sum of squared distances in slots between adjacent selected RACH occasions to be equal, selecting a RACH occasion of the two RACH occasions to be on the list that occurs earlier in time.
38. 38. The method of any of claims 23-37, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: determining a set of RACH occasions in one or more radio frames up to a RACH period; and if a synchronization signal burst (SSB) period is greater than a threshold, eliminating RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.
39. 39. The method of any of claims 23-24 and 26-38, wherein the determining the list of random access (RACH) occasions distributed within one or more RACH periods comprises: receiving, by a user device from a network node, assistance information via system information block that provides configuration information for RACH occasions, including one or more parameters including one or more of the RACH period or RACH periodicity, a starting symbol, a number of RACH preamble slots within a radio frame, a number of time durations within a slot, a RACH preamble duration and/or a subframe number for RACH occasions; and determining a set of RACH occasions in one or more radio frames up to a RACH period.
40. 40. The method of claim 39, wherein the determining the set of RACH occasions 20 comprises: if a synchronization signal burst (SSB) period is greater than a threshold, eliminating RACH occasions in the set of RACH occasions in any radio frames that have a synchronization signal burst transmission.
41. 41. The method of any of claims 23-24 and 26-40, further comprising: determining the physical cell identity of a cell based on system information received from a network node; detecting a timing or position of a synchronization signal block from the network node; and determining the global synchronization channel number based on the timing or position of the synchronization signal block.
42. 42. The method of any of claims 23-41, wherein the list of RACH occasions is eight RACH occasions in length.
43. 43. The method of claim 26, wherein the generating comprises: generating, by the user device, the index into the list based on the physical cell identity (PCI), the global synchronization channel number (GSCN) and a system frame number (SFN)/128.
44. 44. The method of claim 33, wherein the selecting the plurality of the RACH occasions to be on the list of RACH occasions comprises: selecting the plurality of the RACH occasions to be on the list of RACH occasions, such that a sum of squared distances(sqdist) in slots between adjacent selected RACH occasions is minimized, wherein a squared distance in slots sqdist(ro 1, ro 2) between two RACH occasions rol and ro2 is defined as square(pos(rol) -pos(ro2)), and wherein a sum of squared distances for a list of RACH occasions(ro_l, ro_2, ro_3, ro_n-1, ro_n) is defined as sum= sqdist(ro 1, ro2) + sqdist(ro 2, ro 3) + + sqdist(ro n+1, ro n).
45. 45. A method comprising: selecting a plurality of random access (RACH) occasions to be on a list of RACH occasions, wherein at least some of the RACH occasions are selected that are most equally spaced apart within a RACH period; generating an index into the list of RACH occasions; identifying one of the RACH occasions of the list of RACH occasions based on the generated index; and transmitting or receiving a random access preamble via the identified RACH occasion.