# US 11,445,527 B2 · User terminal and channel estimation method

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- Number: US 11,445,527 B2
- Document ID: US11445527B2
- Status: Granted
- Kind: B2
- Application number: 16/622,599
- Filed: 2017-06-15
- Published: 2020-07-09
- Granted: 2022-09-13
- Earliest claimed: 2017-06-15
- Assignees: Ntt Docomo, Inc.
- Applicants: Ntt Docomo, Inc.
- Inventors: Keisuke Saito; Kazuaki Takeda; Satoshi Nagata
- Web page: https://patentgrep.com/patent/US11445527B2

## CPC

- H04L 25/0226: {sounding signals per se}
- H04W 72/1263: Mapping of traffic onto schedule, e.g. scheduled allocation or multiplexing of flows
- H04B 7/0413: MIMO systems
- H04B 7/06: at the transmitting station
- H04B 7/08: at the receiving station
- H04L 5/005: {of common pilots, i.e. pilots destined for multiple users or terminals}
- H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal}
- H04L 5/10: with dynamo-electric generation of carriers; with mechanical filters or demodulators
- H04L 25/0204: {of multiple channels}
- H04L 27/26: Systems using multi-frequency codes (H04L27/32 takes precedence)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04B: TRANSMISSION

## Abstract

This user terminal is equipped with a receiving unit which receives, from a base station device, a downlink signal which includes a demodulation reference signal for a plurality of ports multiplexed in the time direction; a control unit which separates, from the downlink signal, the demodulation reference signal for the port assigned to the host device; and a channel estimation unit which calculates a channel estimation value using the separated demodulation reference signal. The control unit specifies the multiplexing method for the plurality of ports selected on the basis of at least one of carrier frequency, propagation environment, user terminal performance and base station performance, and separates the demodulation reference signal according to the specified multiplexing method.

## Claims

### Claim 1

A terminal, comprising:
a receiver that receives, from a base station apparatus, a downlink signal including demodulation reference signals of a plurality of ports multiplexed in a time direction; and
a processor that demaps a demodulation reference signal of a port allocated to the terminal from the downlink signal, and calculates a channel estimation value using the demapped demodulation reference signal,
wherein the processor identifies a multiplex method for the plurality of ports selected on the basis of at least one of a carrier frequency, propagation environment, performance of the terminal, and performance of the base station apparatus, and demaps the demodulation reference signal according to the identified multiplex method,
wherein the processor demaps the demodulation reference signal according to a method for multiplexing by applying an orthogonal sequence to the demodulation reference signals of the plurality of ports when the carrier frequency is less than a threshold value,
wherein the processor demaps the demodulation reference signal according to a method for time division multiplexing of the demodulation reference signals of the plurality of ports or a method for repetitively arranging the demodulation reference signals in the time direction, when the carrier frequency is equal to or more than the threshold value, and
wherein, when the terminal receives an instruction from the base station apparatus, the processor demaps the demodulation reference signal, regardless of the carrier frequency, according to the method for multiplexing by applying the orthogonal sequence, the method for time division multiplexing, or the method for repetitively arranging the demodulation reference signals in the time direction.

### Claim 2

A channel estimation method in a terminal communicating with a base station apparatus, the channel estimation method comprising:
receiving, from the base station apparatus, a downlink signal including demodulation reference signals of a plurality of ports multiplexed in a time direction;
identifying a multiplex method for the plurality of ports selected on the basis of at least one of a carrier frequency, propagation environment, performance of the terminal, and performance of the base station apparatus and demapping a demodulation reference signal according to the identified multiplex method;
calculating a channel estimation value using the demodulation reference signal; and
demapping the demodulation reference signal according to a method for multiplexing by applying an orthogonal sequence to the demodulation reference signals of the plurality of ports when the carrier frequency is less than a threshold value,
demapping the demodulation reference signal according to a method for time division multiplexing of the demodulation reference signals of the plurality of ports or a method for repetitively arranging the demodulation reference signals in the time direction, when the carrier frequency is equal to or more than the threshold value, and
demapping the demodulation reference signal, regardless of the carrier frequency, according to the method for multiplexing by applying the orthogonal sequence, the method for time division multiplexing, or the method for repetitively arranging the demodulation reference signals in the time direction, when the terminal receives an instruction from the base station apparatus.