# US 2020/0404702 A1 · System and Method for Beam-Based Physical Random-Access > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0404702 A1 - Document ID: US20200404702A1 - Status: Published application - Kind: A1 - Application number: 17/009,912 - Filed: 2020-09-02 - Published: 2020-12-24 - Earliest claimed: 2014-03-25 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Mattias FRENNE; Håkan ANDERSSON; Johan FURUSKOG; Stefan PARKVALL; Henrik SAHLIN; Qiang ZHANG - Web page: https://patentgrep.com/patent/US20200404702A1 ## CPC - H04W 74/002: {Transmission of channel access control information} - H04B 7/0408: using two or more beams, i.e. beam diversity - H04B 7/0617: {for beam forming} - H04B 7/086: {using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming} - H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)} - H04W 16/28: using beam steering - H04W 72/046: {the resource being in the space domain, e.g. beams} - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal} - H04W 74/0838: using contention-free random access [CFRA] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method in a wireless device for performing random access to a network node. The method comprises receiving a set of downlink beam-specific reference signals, BRS, from the network node, and determining a preferred BRS based on the received signal power for each BRS. The method also comprises selecting, based on the preferred BRS, a random-access resource to be used for transmitting a random-access attempt to the network node, as well as using the selected random-access resource when transmitting a random-access attempt to the network node, whereby the selection of random-access resource indicates to the network node which downlink beam is preferred by the wireless device to be used for downlink transmissions. ## Claims ### Claim 1 A method in a wireless device for performing random access to a network node, the method comprising: receiving a set of downlink beam-specific reference signals, BRS, from the network node; determining a preferred BRS based on the received signal power for each BRS; and selecting, based on the preferred BRS, a random-access resource to be used for transmitting a random-access attempt to the network node; as well as using the selected random-access resource when transmitting a random-access attempt to the network node, whereby the selection of random-access resource indicates to the network node which downlink beam is preferred by the wireless device to be used for downlink transmissions. ### Claim 2 (depends on 1) The method according to claim 1, wherein the selecting comprises selecting a preamble from a set of preambles to be used for transmitting the random-access attempt. ### Claim 3 (depends on 2) The method according to claim 2, wherein the selecting comprises selecting a random-access preamble from a set of preambles using a function or look-up table, specified in a manual or standard, or given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device. ### Claim 4 (depends on 1) The method according to claim 1, wherein the selecting comprises selecting a time and/or frequency resource to be used for transmitting the random-access attempt. ### Claim 5 (depends on 1) The method according to claim 1, wherein the selecting comprises selecting the random-access resource based on one or more pre-defined association rules known to the wireless device. ### Claim 6 (canceled) ### Claim 7 A method in a network node for supporting random access from a wireless device the method comprising: transmitting a set of beam-specific reference signals, BRS; detecting a preamble in a signal received from the wireless device said preamble detection indicating a BRS preferred by said wireless device; and transmitting a random-access response in the same beam, and/or beam direction, and/or with the same beamforming weights, as the preferred BRS indicated by the preamble detection. ### Claim 8 (depends on 7) The method according to claim 7, further comprising selecting an uplink beam for the detecting of the preamble according to one or more pre-defined association rules between preambles and uplink beams known at the network node. ### Claim 9 (depends on 7) The method according to claim 7, further comprising: selecting a time and/or frequency resource for preamble detection according to one or more pre-defined association rules between preambles and time/frequency resources known at the network node. ### Claim 10 (depends on 7) The method according to claim 7, wherein the transmitting further comprises: transmitting the random-access response according to the one or more pre-defined association rules known at the network node. ### Claim 11 (depends on 7) The method according to claim 7, wherein the detecting further comprises searching a subset of preambles in each uplink beam for which subset an associated BRS is transmitted in downlink, each BRS pointing out a subset of preambles to be searched. ### Claim 12 (depends on 7) The method according to claim 7, wherein preamble sequences and resources are reused for BRSs associated with downlink beams having a pre-determined angular separation. ### Claim 13 (canceled) ### Claim 14 A wireless device configured to perform random access to a network node, the wireless device comprising a processor and a memory, the memory containing instructions executable by the processor to: receive a set of downlink beam-specific reference signals, BRS, from the network node; determine a preferred BRS based on the received signal power for each BRS; and select, based on the preferred BRS, a random-access resource to be used to transmit a random-access attempt to the network node; as well as to use the selected random-access resource when transmitting a random-access attempt to the network node, whereby the selection of random-access resource indicates to the network node which downlink beam is preferred by the wireless device to be used for downlink transmissions. ### Claim 15 (depends on 14) The wireless device according to claim 14, wherein the processing means is further configured to: select a preamble from a set of preambles to be used for transmitting the random-access attempt. ### Claim 16 (depends on 15) The wireless device according to claim 15, wherein the processing means is further configured to: select a random-access preamble from a set of preambles using a function or look-up table, specified in a manual or standard, or given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device. ### Claim 17 (depends on 14) The wireless device according to claim 14, wherein the processing means is further configured to: select a time and/or frequency resource to be used for transmitting the random-access attempt. ### Claim 18 (depends on 14) The wireless device according to claim 14, wherein the processing means is further configured to: select the random-access resource based on one or more pre-defined association rules known to the wireless device. ### Claim 19 (canceled) ### Claim 20 (canceled) ### Claim 21 (canceled) ### Claim 22 A network node configured to support random access from a wireless device the network node comprising a processor and a memory, the memory containing instructions executable by the processor: transmit a set of beam-specific reference signals, BRS; detect a preamble in a signal received from the wireless device said preamble detection indicating a BRS preferred by said wireless device; and transmit a random-access response in the same beam, and/or beam direction, and/or with the same beamforming weights, as the preferred BRS indicated by the preamble detection. ### Claim 23 (depends on 22) The network node according to claim 22, wherein the processing means is further configured to: select an uplink beam for detecting the preamble according to one or more pre-defined association rules between preambles and uplink beams known at the network node. ### Claim 24 (depends on 22) The network node according to claim 22, wherein the processing means is further configured to: select a time and/or frequency resource for preamble detection according to one or more pre-defined association rules between preambles and time/frequency resources known at the network node. ### Claim 25 (depends on 22) The network node according to claim 22, wherein the processing means is further configured to: transmit the random-access response according to the one or more pre-defined association rules known at the network node. ### Claim 26 (depends on 22) The network node according to claim 22, wherein the processing means is further configured to: search a subset of preambles in each uplink beam for which subset an associated BRS is transmitted in downlink, each BRS pointing out a subset of preambles to be searched. ### Claim 27 (depends on 22) The network node according to claim 22, wherein preamble sequences and resources are reused for BRSs associated with downlink beams having a pre-determined angular separation. ### Claim 28 (canceled) ### Claim 29 (canceled) ### Claim 30 (canceled) ### Claim 31 A wireless communication system comprising: a wireless device and a network node, the network node operable to transmit a set of downlink beam-specific reference signals, BRSs, and the wireless device operable to: receive the set of downlink beam-specific reference signals (BRSs) from the network node; determine a preferred BRS based on the received signal power for each BRS of the set of downlink beam-specific reference signals (BRSs); select, based on the preferred BRS, a random-access resource to be used to transmit a random-access attempt to the network node according to one or more pre-defined association rules defining an association between a random-access resource and a BRS; and use the selected random-access resource when transmitting a random-access attempt to the network node, whereby the selection of random-access resource indicates to the network node which downlink beam is preferred by the wireless device to be used for downlink transmissions; the network node further operable to: detect the preferred BRS of the wireless device based on the random-access resource that the wireless device uses when transmitting the random-access attempt; and transmit a random-access response in a same beam, and/or beam direction, and/or with same beamforming weights, as the preferred BRS.