# US 2021/0345277 A1 · Stable multi-point alignment

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- Number: US 2021/0345277 A1
- Document ID: US20210345277A1
- Status: Published application
- Kind: A1
- Application number: 17/271,593
- Filed: 2018-08-31
- Published: 2021-11-04
- Earliest claimed: 2018-08-31
- Assignees: Telefonaktiebolaget LM Ericsson (publ)
- Applicants: Telefonaktiebolaget LM Ericsson (publ)
- Inventors: Torbjörn WIGREN; Ramon DELGADO; Richard MIDDLETON; Katrina LAU
- Web page: https://patentgrep.com/patent/US20210345277A1

## CPC

- H04W 56/0045: {compensating for timing error by altering transmission time}
- H04L 5/0055: {Physical resource allocation for ACK/NACK (for physical mapping arrangements in ARQ protocols H04L1/1861)}
- H04L 43/0864: Round trip delays
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

According to a first aspect, there is provided a method for delay alignment in a multi-point communication system. The method comprises determining of a respective reference value of round trip time for n+1 signalling paths in the multi-point communication system, where n>0. The determination is performed using n reference values of round trip time skews between a respective signalling path and a single reference signalling path of the n+1 signalling paths, and a reference value of a sum of round trip times over all of the n+1 signalling paths as exclusive input values. The respective reference values of round trip times are limited within a predetermined allowed interval for round trip times. The method further comprises performing of a separate, preferably globally stable, control of data signalling in each single one of the n+1 signalling paths based on the respective reference values of round trip times.

## Claims

### Claim 1

A method for delay alignment in a multi-point communication system, wherein said method comprising:
determining a respective reference value of round trip time for n+1 signalling paths in said multi-point communication system, where n>0, using n reference values of round trip time skews between a respective signalling path and a single reference signalling path of said n+1 signalling paths, and a reference value of a sum of round trip times over all of said n+1 signalling paths as exclusive input values, said respective reference values of round trip times being limited within a predetermined allowed interval for round trip times;
performing a separate control of data signalling in each single one of said n+1 signalling paths based on said respective reference values of round trip times.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the performing the separate control of data signalling is performed by separate, globally stable, control of data signalling in each single one of said n+1 signalling paths based on said respective reference values of round trip times.

### Claim 3 (depends on 2)

The method according to claim 2, wherein said reference values of round trip time for said n+1 signalling paths are calculated as a linear combination of said n reference values of round trip time skews and said reference value of a sum of round trip times.

### Claim 4 (depends on 3)

The method according to claim 3, wherein said reference values of round trip time for said n+1 signalling paths ŤRTTref(t) are calculated as:
T
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where
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### Claim 5 (depends on 4)

The method according to claim 4 further comprising calculating, for each of said n+1 signalling paths, a value of an actual round trip time achieved by said separate, globally stable, control of data signalling.

### Claim 6 (depends on 5)

The method according to claim 5 further comprising deriving actual values of round trip time skews between said respective signalling paths and said single reference signalling path, as well as an actual value of a sum of round trip times over all of said n+1 paths, by linearly combining said values of an actual round trip time.

### Claim 7 (depends on 1)

The method according to that claim 1, wherein said reference values of round trip time skews between said respective signalling path and said single reference signalling path, as well as said reference value of said sum of round trip times over all of said n+1 signalling paths are varying with time.

### Claim 8 (depends on 2)

The method according to that claim 2 further comprising an acknowledgement signalling associated with said signalling in each single signalling path is performed in an acknowledgement signalling path, being selected according to a predetermined relationship with said each single signalling path.

### Claim 9 (depends on 8)

The method according to claim 8, wherein said separate, globally stable, control of data signalling in each single signalling path is performed by using a round trip time reference value ŤRTTref(t) as controller input, which is transformed into a data item in flight reference value yref(s) by division with a scheduled air interface rate {hacek over (w)}air(t−Tul,N) into a frequency domain, which data item in flight reference value yref(s) is compared with measured data item in flight y(s) and being control filtered C(s) into a control signal u(s).

### Claim 10 (depends on 9)

The method according to claim 9, wherein said control signal u(s) is saturated to ensure that it is non-negative.

### Claim 11 (depends on 9)

The method according to claim 9, wherein said measured data items in flight signal y(s) is based on a data item number v(s) of a last received data item and a latest sent data item number v(s).

### Claim 12 (depends on 2)

The method according to claim 2, wherein an acknowledgement signalling associated with said signalling in each single signalling path comprises an indication of a signalling path of said acknowledgement signalling.

### Claim 13 (depends on 12)

The method according to claim 12, wherein said separate, globally stable, control of data signalling in each single signalling path comprises:
collecting round trip time measurements for different combinations of uplink and downlink signalling paths during a time window; and
performing a linear regression based on said collected round trip time measurements, for achieving separate round trip time contributions for all used downlink and uplink signalling paths.

### Claim 14 (depends on 13)

The method according to claim 13, wherein said separate, globally stable, control of data signalling in each single signalling path further comprises:
computing a representative round trip time associated with each downlink signalling path in dependence of said contributions of uplink signalling paths used in connection with each separate downlink signalling path; and
using said representative round trip time as feedback in said separate, globally stable, control of data signalling in each single signalling path.

### Claim 15

A network node to perform globally stable delay alignment in a multi-point communication system, wherein said network node is comprising:
a processor; and
a memory comprising instructions which, when executed by the processor, cause the network node to:
determine a respective reference value of round trip time for n+1 signalling paths in said multi-point communication system, where n>0, using n reference values of round trip time skews between a respective signalling path and a single reference signalling path of said n+1 signalling paths, and a reference value of a sum of round trip times over all of said n+1 signalling paths as exclusive input values, said respective reference values of round trip times being limited within a predetermined allowed interval for round trip times; and
perform a separate control of data signalling in each single one of said n+1 signalling paths based on said respective reference values of round trip times.

### Claim 16 (depends on 15)

The network node according to claim 15, wherein the network node is to perform a separate, globally stable, control of data signalling in each single one of said n+1 signalling paths based on said respective reference values of round trip times.

### Claim 17

(canceled)

### Claim 18

A non-transitory computer readable storage medium comprising instructions which, when executed by at least one processor, cause the at least one the at least one processor to perform operations for delay alignment in a multi-point communication system comprising:
determining a respective reference value of round trip time for n+1 signalling paths (7, 7R) in said multi-point communication system, where n>0, using n reference values of round trip time skews between a respective signalling path (7) and a single reference signalling path (7R) of said n+1 signalling paths (7, 7R), and a reference value of a sum of round trip times over all of said n+1 signalling paths (7, 7R) as exclusive input values, said respective reference values of round trip times being limited within a predetermined allowed interval for round trip times; and
performing a separate control of data signalling in each single one of said n+1 signalling paths based on said respective reference values of round trip times.

### Claim 19

(canceled)