System and Method for Beam-Based Physical Random-Access

Patent metadata

Field	Value
Publication number	US-2016157267-A1
Application number	US-201414400579-A
Country	US
Kind code	A1
Filing date	Aug 27, 2014
Priority date	Mar 25, 2014
Publication date	Jun 2, 2016
Grant date	—

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

In the claims:

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.

2 . 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.

3 . 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.

4 . 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.

5 . 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.

6 . (canceled)

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.

8 . 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.

9 . 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.

10 . 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.

11 . 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.

12 . 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.

13 . (canceled)

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.

15 . 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.

16 . 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.

17 . 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.

18 . 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.

19 . (canceled)

20 . (canceled)

21 . (canceled)

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 to:
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.

23 . 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.

24 . 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.

25 . 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.

26 . 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.

27 . 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.

28 . (canceled)

29 . (canceled)

30 . (canceled)

31 . A wireless communication system comprising a wireless device according to claim 14 , and a network node according to claim 22 .

Assignees

• Ericsson Telefon Ab L M

Inventors

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

Classifications

• H04B7/086

  using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming · CPC title

• 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

• H04W72/046

  the resource being in the space domain, e.g. beams · CPC title

• H04B7/0617

  for beam forming · CPC title

• H04W16/28

  using beam steering · CPC title