System and method for beam-based physical random-access

Patent metadata

Field	Value
Publication number	US-9814068-B2
Application number	US-201414400579-A
Country	US
Kind code	B2
Filing date	Aug 27, 2014
Priority date	Mar 25, 2014
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

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 wireless device 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 the received signal power for each BRS of said set of downlink beam-specific reference signals (BRSs);
selecting, based on the preferred BRS, a random-access resource to be used 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 resource and a BRS; and
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;
wherein the random access resource comprises a random-access preamble, wherein the selecting comprises selecting from a set of preambles the random-access preamble to be used for transmitting the random-access attempt, the selecting using information that is in a look-up table, specified in a manual or standard, given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device, or 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 specified in a manual or standard, given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device.

2. The method according to claim 1 , wherein the selecting uses the information or the function that is given by the prior broadcast signaling.

3. 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.

4. The method according to claim 1 , wherein random-access resources are divided into groups, where each group is associated with a beam-specific reference signal, an association between BRS and preamble being given by standard specification.

5. A method in a network node for supporting random access from a wireless device, the method comprising:
transmitting a set of downlink beam-specific reference signals, BRSs;
detecting a random-access preamble in a signal received from the wireless device, said preamble detection indicating a preferred BRS of said set of downlink beam-specific reference signals (BRSs), the preferred BRS preferred by said wireless device according to one or more pre-defined association rules defining an association between a random access resource and a BRS, wherein the random-access preamble is based on information that is in a look-up table, specified in a manual or standard, given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device, or the selecting using a function that uses the preferred BRS as an input and provides the selected random-access preamble as an output, wherein the function is specified in a manual or standard, given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device; and
transmitting a random-access response in a same beam, and/or beam direction, and/or with same beamforming weights, as the preferred BRS.

6. The method according to claim 5 , further comprising
selecting an uplink beam for the detecting of the random-access preamble according to one or more pre-defined association rules between preambles and uplink beams known at the network node.

7. The method according to claim 5 , 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.

8. The method according to claim 5 , 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.

9. The method according to claim 5 , 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.

10. The method according to claim 5 , wherein preamble sequences and resources are reused for BRSs associated with downlink beams having a pre-determined angular separation.

11. 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, BRSs, from the network node;
determine a preferred BRS based on the received signal power for each BRS of said 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;

wherein the random access resource comprises a random-access preamble to be used for transmitting the random-access attempt and wherein, to select the random-access preamble from a set of preambles, the processor is configured to use information that is in a look-up table, specified in a manual or standard, given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device, or the selecting using a function that uses the preferred BRS as an input and provides the selected random-access preamble as an output, wherein the function is specified in a manual or standard, given by prior broadcast signaling, or configured by dedicated signaling on an assisting legacy network of the wireless device.

12. The wireless device according to claim 11 , wherein to select the random-access preamble from the set of preambles, the processor is further configured to use the information or the function that is given by the prior broadcast signaling.

13. The wireless device according to claim 11 , wherein the processor is further configured to:
select a time and/or frequency resource to be used for transmitting the random-access attempt.

14. The wireless device according to claim 11 , wherein the random-access resources are divided into groups, where each group is associated with a beam-specific reference signal, an association between BRS and preamble being given by standard specification.

15. 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 downlink beam-specific reference signals, BRSs;
detect a random-access preamble in a signal received from the wireless device, said preamble detection indicating a preferred BRS of said set of downlink beam-specific reference signals (BRSs), the preferred BRS preferred by said wireless device according to one or more pre-defined association rules defining an association between a random access resource

Assignees

• Ericsson Telefon Ab L M
• ERICSSON TELEFON AB L M (publ)

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

• H04B7/0408 Primary

  using two or more beams, i.e. beam diversity · CPC title

• H04W16/28

  using beam steering · CPC title

• H04B7/0617

  for beam forming · 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