# US 11,452,139 B2 · Random access procedure for latency reduction

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- Number: US 11,452,139 B2
- Document ID: US11452139B2
- Status: Granted
- Kind: B2
- Application number: 16/714,873
- Filed: 2019-12-16
- Published: 2020-04-16
- Granted: 2022-09-20
- Earliest claimed: 2015-09-18
- Assignees: Telefonaktiebolaget LM Ericsson (publ)
- Applicants: Telefonaktiebolaget Lm Ericsson (Publ)
- Inventors: Tuomas Tirronen; Osman Nuri Can Yilmaz; Helka-Liina Määttanen; Henrik Sahlin
- Web page: https://patentgrep.com/patent/US11452139B2

## CPC

- H04W 74/006: {in the downlink, i.e. towards the terminal}
- H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal
- H04W 74/0833: Random access procedures, e.g. with 4-step access
- H04W 72/20: Control channels or signalling for resource management
- H04W 74/0838: using contention-free random access [CFRA]
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Certain embodiments disclose a method in a wireless device. The wireless device receives a location of a time and/or frequency resource of a first Physical Random Access Channel (PRACH) from a network node. The wireless device receives a location of a time and/or frequency resource of a second PRACH. Furthermore, the wireless device transmits a first random access attempt via the first PRACH and transmits a second random access attempt via the second PRACH. The first PRACH and the second PRACH each have an associated preamble, and wherein the second PRACH preamble has a different length than the first PRACH preamble.

## Claims

### Claim 1

A method in a wireless device, the method comprising:
receiving a location of a time and/or frequency resource of a first Physical Random Access Channel (PRACH) from a network node;
receiving a location of a time and/or frequency resource of a second PRACH, the second PRACH being different from the first PRACH and the second PRACH using different subcarriers than the first PRACH;
transmitting a first random access attempt via the first PRACH; and
transmitting a second random access attempt via the second PRACH;
wherein the first PRACH and the second PRACH each have an associated preamble, and wherein the second PRACH preamble has a different length than the first PRACH preamble.

### Claim 2 (depends on 1)

The method of claim 1, wherein the second PRACH preamble is shorter than the first PRACH preamble.

### Claim 3 (depends on 1)

The method of claim 1, wherein the location of the time and/or frequency resource of the second PRACH is further restricted by a Physical Downlink Control Channel (PDCCH).

### Claim 4 (depends on 1)

The method of claim 1, wherein the first PRACH corresponds to contention-based access and wherein the second PRACH corresponds to contention-free access.

### Claim 5 (depends on 1)

The method of claim 1, further comprising receiving a Physical Downlink Control Channel (PDCCH) message triggering the transmitting a second random access attempt via the second PRACH.

### Claim 6 (depends on 1)

The method of claim 1, wherein downlink control information indicates the preamble to be used by the wireless device when sending random access attempts via the second PRACH.

### Claim 7 (depends on 1)

The method of claim 1, further comprising receiving downlink control information indicating the location of the second PRACH and indicating that the wireless device is to override the first PRACH.

### Claim 8

A method in a network node, the method comprising:
broadcasting a location of a time and/or frequency resource of a first Physical Random Access Channel (PRACH);
broadcasting a location of a time and/or frequency resource of a second PRACH, the second PRACH being different from the first PRACH and the second PRACH using different subcarriers than the first PRACH;
receiving a first random access attempt from a wireless device via the first PRACH; and
receiving a second random access attempt from the wireless device via the second PRACH;
wherein the first PRACH and the second PRACH each have an associated preamble, and wherein the second PRACH preamble has a different length than the first PRACH preamble.

### Claim 9 (depends on 8)

The method of claim 8, wherein the second PRACH preamble is shorter than the first PRACH preamble.

### Claim 10 (depends on 8)

The method of claim 8, wherein the location of the time and/or frequency resource of the second PRACH is further restricted by a Physical Downlink Control Channel (PDCCH).

### Claim 11 (depends on 8)

The method of claim 8, wherein the first PRACH corresponds to contention-based access and wherein the second PRACH corresponds to contention-free access.

### Claim 12 (depends on 8)

The method of claim 8, further comprising transmitting a Physical Downlink Control Channel (PDCCH) message triggering the receiving a second random access attempt via the second PRACH.

### Claim 13 (depends on 8)

The method of claim 8, wherein downlink control information indicates the preamble to be used by the wireless device when sending random access attempts via the second PRACH.

### Claim 14 (depends on 8)

The method of claim 8, further comprising transmitting downlink control information indicating the location of the second PRACH and indicating that the wireless device is to override the first PRACH.

### Claim 15

A wireless device comprising:
processing circuitry configured to:
receive a location of a time and/or frequency resource of a first Physical Random Access Channel (PRACH) from a network node;
receive a location of a time and/or frequency resource of a second PRACH, the second PRACH being different from the first PRACH and the second PRACH using different subcarriers than the first PRACH;
transmit a first random access attempt via the first PRACH; and
transmit a second random access attempt via the second PRACH;
wherein the first PRACH and the second PRACH each have an associated preamble, and wherein the second PRACH preamble has a different length than the first PRACH preamble.

### Claim 16 (depends on 15)

The wireless device of claim 15, wherein the second PRACH preamble is shorter than the first PRACH preamble.

### Claim 17 (depends on 15)

The wireless device of claim 15, wherein the location of the time and/or frequency resource of the second PRACH is further restricted by a Physical Downlink Control Channel (PDCCH).

### Claim 18 (depends on 15)

The wireless device of claim 15, wherein the first PRACH corresponds to contention-based access and wherein the second PRACH corresponds to contention-free access.

### Claim 19 (depends on 15)

The wireless device of claim 15, wherein the processing circuitry is further configured to receive a Physical Downlink Control Channel (PDCCH) message triggering the transmitting a second random access attempt via the second PRACH.

### Claim 20 (depends on 15)

The wireless device of claim 15, wherein downlink control information indicates the preamble to be used by the wireless device when sending random access attempts via the second PRACH.

### Claim 21 (depends on 15)

The wireless device of claim 15, wherein the processing circuitry is further configured to receive downlink control information indicating the location of the second PRACH and indicating that the wireless device is to override the first PRACH.

### Claim 22

A network node comprising:
processing circuitry configured to:
broadcast a location of a time and/or frequency resource of a first Physical Random Access Channel (PRACH);
broadcast a location of a time and/or frequency resource of a second PRACH, the second PRACH being different from the first PRACH and the second PRACH using different subcarriers than the first PRACH;
receive a first random access attempt from a wireless device via the first PRACH; and
receive a second random access attempt from the wireless device via the second PRACH;
wherein the first PRACH and the second PRACH each have an associated preamble, and wherein the second PRACH preamble has a different length than the first PRACH preamble.

### Claim 23 (depends on 22)

The network node of claim 22, wherein the second PRACH preamble is shorter than the first PRACH preamble.

### Claim 24 (depends on 22)

The network node of claim 22, wherein the location of the time and/or frequency resource of the second PRACH is further restricted by a Physical Downlink Control Channel (PDCCH).

### Claim 25 (depends on 22)

The network node of claim 22, wherein the first PRACH corresponds to contention-based access and wherein the second PRACH corresponds to contention-free access.

### Claim 26 (depends on 22)

The network node of claim 22, wherein the processing circuitry is further configured to transmit a Physical Downlink Control Channel (PDCCH) message triggering the receiving a second random access attempt via the second PRACH.

### Claim 27 (depends on 22)

The network node of claim 22, wherein downlink control information indicates the preamble to be used by the wireless device when sending random access attempts via the second PRACH.

### Claim 28 (depends on 22)

The network node of claim 22, wherein the processing circuitry is further configured to transmit downlink control information indicating the location of the second PRACH and indicating that the wireless device is to override the first PRACH.