System and method for beam-based physical random-access

Patent metadata

Field	Value
Publication number	US-12513737-B2
Application number	US-202318453399-A
Country	US
Kind code	B2
Filing date	Aug 22, 2023
Priority date	Mar 25, 2014
Publication date	Dec 30, 2025
Grant date	Dec 30, 2025

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.

First claim

The invention claimed is:

1 . A method in a user equipment for performing random access to a network node, the method comprising:
receiving a set of downlink beam-specific reference signals (BRSs) from the network node; determining a preferred BRS based on a received signal power for each BRS in the set; and selecting, based on the preferred BRS, a random-access preamble for transmitting a random-access attempt on a physical random-access channel (PRACH) to the network node according to one or more pre-defined association rules defining an association between a random-access preamble and a BRS, the selecting using a function that uses the preferred BRS as an input and provides the selected random-access preamble as an output, the function being configured by Radio Resource Control (RRC) signaling; and transmitting the selected random-access preamble on the PRACH to the network node, whereby the selection of the random-access preamble indicates to the network node which downlink beam is preferred by the user equipment to be used for downlink transmissions.

2 . The method according to claim 1 , wherein the function for selecting the random-access preamble is specified in a standard.

3 . The method according to claim 1 , wherein the selecting comprises selecting a time or frequency resource to be used for transmitting the random-access attempt.

4 . The method according to claim 1 , wherein the selecting comprises selecting the random-access preamble based on one or more pre-defined association rules known to the user equipment.

5 . The method according to claim 1 , wherein the preferred BRS corresponds to the strongest BRS received.

6 . A method in a network node for supporting random access from a user equipment, the method comprising:
transmitting a set of downlink beam-specific reference signals (BRS); detecting a random-access preamble in a signal received from the user equipment on a physical random-access channel (PRACH), said preamble detection indicating a preferred BRS of the set of downlink BRS, the preferred BRS being preferred by said user equipment according to one or more pre-defined association rules defining an association between a random access preamble and a BRS, wherein the random access preamble is based on a function that uses the preferred BRS as an input and provides the random-access preamble as an output, wherein the function is configured by Radio Resource Control (RRC) signaling; and transmitting a random-access response in a same beam, beam direction, or with same beamforming weights, as the preferred BRS indicated by the preamble detection.

7 . The method according to claim 6 , further comprising
selecting an uplink beam for the detecting of the random-access preamble according to one or more pre-defined association rules between random-access preambles and uplink beams known at the network node.

8 . The method according to claim 6 , further comprising:
selecting a time or frequency resource for random-access preamble detection according to one or more pre-defined association rules between random-access preambles and time/frequency resources known at the network node.

9 . The method according to claim 6 , 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.

10 . The method according to claim 6 , wherein the detecting further comprises searching a subset of random-access preambles in each uplink beam for which subset an associated BRS is transmitted in downlink, each BRS pointing out a subset of random-access preambles to be searched.

11 . The method according to claim 6 , wherein random-access preamble sequences and resources are reused for BRSs associated with downlink beams having a pre-determined angular separation.

12 . The method according to claim 6 , wherein the preferred BRS corresponds to the strongest BRS received by the user equipment.

13 . A user equipment configured to perform random access to a network node, the user equipment comprising a processor and a memory, the memory containing instructions executable by the processor to:
receive a set of downlink beam-specific reference signals (BRSs) from the network node; determine a preferred BRS based on a received signal power for each BRS in the set; and select, based on the preferred BRS, a random-access preamble for transmitting a random-access attempt to the network node according to one or more pre-defined association rules defining an association between a random-access preamble and a BRS, the selecting using a function that uses the preferred BRS as an input and provides the selected random-access preamble as an output, the function being configured by Radio Resource Control (RRC) signaling; and transmit the selected random-access preamble to the network node, whereby the selection of the random-access preamble indicates to the network node which downlink beam is preferred by the user equipment to be used for downlink transmissions.

14 . The user equipment according to claim 13 , wherein the function for selecting the random-access preamble is specified in a standard.

15 . The user equipment according to claim 13 , wherein the processor is further configured to:
select a time or frequency resource to be used for transmitting the random-access attempt.

16 . The user equipment according to claim 13 , wherein the processor is further configured to:
select the random-access preamble based on one or more pre-defined association rules known to the user equipment.

17 . The user equipment according to claim 13 , wherein the preferred BRS corresponds to the strongest BRS received.

18 . A network node configured to support random access from a user equipment, the network node comprising a processor and a memory, the memory containing instructions executable by the processor to:
transmit a set of downlink beam-specific reference signals (BRS); detect a random-access preamble in a signal received from the user equipment on a physical random-access channel (PRACH), said preamble detection indicating a preferred BRS of the set of downlink BRS, the preferred BRS being preferred by said user equipment according to one or more pre-defined association rules defining an association between a random access preamble and a BRS, wherein the random access preamble is based on a function that uses the preferred BRS as an input and provides the random-access preamble as an output, wherein the function is configured by Radio Resource Control (RRC) signaling; and transmit a random-access response in a same beam, beam direction, or with same beamforming weights, as the preferred BRS indicated by the preamble detection.

19 . The network node according to claim 18 , wherein the processor is further configured to:
select an uplink beam for detecting the random-access preamble according to one or more pre-defined association rules between random-access preambles and uplink beams known at the network node.

20 . The network node according to claim 18 , wherein the processor is further configured to:
select a time or frequency resource for random-access preamble detection according to one or more pre-defined association rules between random-access preambles and time/frequency resources known at the network node.

21 . The network node according to claim 18 , wherein the processor is further configured to:
transmit the random-access response according to the on

Assignees

• Ericsson Telefon Ab L M

Inventors

• Frenne Mattias
• Andersson Håkan
• Furuskog Johan
• Parkvall Stefan
• Sahlin Henrik
• Zhang Qiang

Classifications

• H04L5/0048

  Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091) · CPC title

• H04W16/28

  using beam steering · CPC title

• H04W74/0833

  Random access procedures, e.g. with 4-step access · CPC title

• H04W74/0838

  using contention-free random access [CFRA] · CPC title

• H04B7/0617

  for beam forming · CPC title