System and method for beam-based physical random-access

• US 9,814,068 B2
• Filed: 08/27/2014
• Issued: 11/07/2017
• Est. Priority Date: 03/25/2014
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Frenne, Mattias, Andersson, Hkan, Furuskog, Johan, Parkvall, Stefan, Sahlin, Henrik, Zhang, Qiang
• Primary Examiner(s): Lai, Andrew
• Assistant Examiner(s): LEE, ANDREW CHUNG CHEUNG
• Application Number:
  US14/400,579
• Publication Number:
  US 20160157267A1
• Time in Patent Office: 1,168 Days
• Field of Search: 370329, 370442, 370252, 370280, 370347, 370462
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 72/046 the resource being in the space domain, e.g. beams
• CPC Class Codes: H04W 74/008 with additional processing of random access related information at receiving side
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access

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

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 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

transmit a random-access response in a same beam, and/or beam direction, and/or with same beamformning weights, as the preferred BRS.

16. The network node according to claim 15, 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 preambles and uplink beams known at the network node.

17. The network node according to claim 15, wherein the processor 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.

18. The network node according to claim 15, wherein the processor is further configured to:

transmit the random-access response according to the one or more pre-defined association rules known at the network node.

19. The network node according to claim 15, wherein the processor 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.

20. The network node according to claim 15, wherein preamble sequences and resources are reused for BRSs associated with downlink beams having a pre-determined angular separation.

21. 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

wherein the random access resource comprises a random-access preamble to be used by the wireless device for transmitting the random-access attempt and wherein, to select the random-access preamble from a set of preambles, the wireless device 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.