System and Method for Beam-Based Physical Random-Access

• US 20160157267A1
• Filed: 08/27/2014
• Published: 06/02/2016
• Est. Priority Date: 03/25/2014
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Frenne, Mattias, Andersson, H?kan, Furuskog, Johan, Parkvall, Stefan, Sahlin, Henrik, Zhang, Qiang
• Granted Patent: US 9,814,068 B2
• Time in Patent Office: Days
• 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, 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.

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

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)