# US 10,771,987 B2 · User equipment and methods for operation in coverage enhancement mode with physical random access channel preamble > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,771,987 B2 - Document ID: US10771987B2 - Status: Granted - Kind: B2 - Application number: 15/935,402 - Filed: 2018-03-26 - Published: 2018-07-26 - Granted: 2020-09-08 - Earliest claimed: 2014-01-30 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Konstantinos D. Dimou; Gang Xiong; Seunghee Han; Hong He - Web page: https://patentgrep.com/patent/US10771987B2 ## CPC - H04W 24/02: Arrangements for optimising operational condition - H04W 24/08: Testing, {supervising or monitoring} using real traffic - H04W 48/12: using downlink control channel - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04W 36/08: Reselecting an access point - H04W 74/002: {Transmission of channel access control information} - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Embodiments of a User Equipment (UE) to operate in accordance with a physical random access channel (PRACH) are disclosed herein. The UE may comprise hardware processing circuitry to determine a coverage enhancement category for the UE based on downlink channel statistics related to reception of downlink signals at the UE from an Evolved Node-B (eNB) and an uplink-downlink imbalance parameter related to uplink reception at the eNB. The hardware processing circuitry may be further to select, for use in a coverage enhancement mode, a PRACH preamble from a set of candidate PRACH preambles based on the determined coverage enhancement category for the UE. In some embodiments, at least some of the candidate PRACH preambles may span a different number of sub-frames. ## Claims ### Claim 1 An apparatus of a user equipment (LE) comprising: a processor configured to: determine an enhanced coverage (EC) level to be used in communications with a an evolved Node-B (eNB); determine a physical random access channel (PRACH) preamble from a plurality of PRACH preambles based on the EC level; and encode, for transmission to the eNB, repetitions of the PRACH preamble based on the EC level; and a memory configured to store the PRACH preamble, wherein a number and timing of the repetitions is dependent on the EC level, and wherein a frequency hopping pattern of the repetitions is generated according to a system frame number. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the processor is further configured to: limit starting subframes for the repetitions to a subset of subframes allowed for preamble transmission. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the processor is further configured to: measure reference signals from the eNB; and determine the EC level based on reference signal received power (RSRP) measurements of the reference signals. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the processor is further configured to: use PRACH resources dependent on the RSRP measurements. ### Claim 5 (depends on 3) The apparatus of claim 3, wherein the processor is further configured to: decode a PRACH configuration from the eNB that maps the EC levelse PRACH resources. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein: the PRACH configuration maps the EC levels and the RSRP measurements. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the processor is further configured to: encode the repetitions of the PRACH preamble with the frequency hopping pattern that uses PRACH frequency resources reserved for UEs operating in coverage enhancement mode. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein: the frequency hopping pattern is generated according to a seed value that includes a subframe index of a subframe in which one of the repetitions of the PRACH preamble is transmitted. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein: available EC frequency resources comprise N physical resource blocks (PRBs) that are each indexed with a frequency index of between 0 and (N−1), each of which supports one of the repetitions of the PRACH preamble; a first frequency index is associated with a frequency location of PRACH frequency resources in a first subframe; a second frequency index is associated with a frequency location of PRACH frequency resources in a second subframe; and when the first and second subframe indices are adjacent in time, the second frequency index is determined by subtracting the first frequency index from a total number of frequency indices to form a mirror pattern. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein: the EC level is based on a static uplink-downlink imbalance parameter of the eNB, and the imbalance parameter is related to physical characteristics at the eNB. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein: the imbalance parameter is related to at least one of feeder losses, an antenna configuration or mounting characteristics at the eNB. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein the processor is further configured to: select the EC level based on a comparison between at least one of: a set of power level thresholds and a sum that includes a synchronization average power level at the UE and the uplink-downlink imbalance parameter, the synchronization average power level related to reception of a synchronization signal at the UE, a set of acquisition time thresholds and a synchronization acquisition time, the synchronization acquisition time related to reception of the synchronization signal, or the set of power level thresholds and a sum that includes an average power level of a set of values and the uplink-downlink imbalance parameter. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the set of values comprises at least one of: a broadcast channel average power level related to reception of a broadcast channel signal at the UE and a data traffic power level related to reception of a data traffic signal at the UE, or a system information block (SIB) average power level related to reception of an SIB at the UE and a master information block (MW) average power level related to reception of an MIB at the UE. ### Claim 14 An apparatus of an evolved Node-B (eNB) comprising: a processor configured to: encode for transmission to a user equipment (UE), a mapping between a physical random access channel (PRACH) preamble and an enhanced coverage (EC) level of the UE; and decode, from the UE, repetitions of the PRACH preamble based on the EC level; a memory configured to store the mapping, wherein a number of PRACH resources used by the repetitions are dependent on the EC level, and wherein a frequency hopping pattern of the repetitions is generated according to a system frame number. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein: starting subframes for the repetitions are limited to a subset of subframes allowed for preamble transmission. ### Claim 16 (depends on 14) The apparatus of claim 14, wherein: the processor is further configured to encode reference signals for transmission to the UE, and the EC level is based on reference signal received power (RSRP) measurements of the reference signals. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein: the PRACH resources used are dependent on the RSRP measurements. ### Claim 18 (depends on 16) The apparatus of claim 16, wherein: the processor is further configured to encode, for transmission to the UE, a PRACH configuration that maps the EC levels and the PRACH resources, and the PRACH configuration maps the EC levels and the RSRP measurements. ### Claim 19 (depends on 14) The apparatus of claim 14, wherein: the repetitions of the PRACH preamble with the frequency hopping pattern that uses PRACH frequency resources reserved for UEs operating in coverage enhancement mode. ### Claim 20 (depends on 19) The apparatus of claim 19, wherein: the frequency hopping pattern is generated according to a seed value that includes a subframe index of a subframe in which one of the repetitions of the PRACH preamble is transmitted. ### Claim 21 A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors to perform operations by a user equipment (UE), the operations to configure the UE to: determine an enhanced coverage (EC) level, from a plurality of enhanced coverage levels, to be used in communications with an evolved Node-B (eNB); select a physical random access channel (PRACH) preamble from a plurality of PRACH preambles based on the EC level; and repeatedly transmit the PRACH preamble a number of times, wherein a frequency hopping pattern of the repeated PRACH preamble transmissions is determined by a system frame number and dependent on the EC level. ### Claim 22 (depends on 21) The medium of claim 21, wherein the instructions further cause the UE to: limit starting subframes for the repetitions to a subset of subframes allowed for preamble transmission. ### Claim 23 (depends on 21) The medium of claim 21, wherein the instructions further cause the UE to: measure reference signals from the eNB; determine the EC level based on reference signal received power (RSRP) measurements of the reference signals; and use PRACH resources dependent on the RSRP measurements.