US-12621190-B2 - Reference signal channel estimation

US12621190B2US 12621190 B2US12621190 B2US 12621190B2US-12621190-B2

Abstract

Aspects of this disclosure relate to reference signal channel estimation. A wireless communication channel between two nodes can be estimated based on a received reference signal, such as a Sounding Reference Signal. Techniques are disclosed to improve performance of reference signal channel estimation and make channel estimates more robust in the presence of one or more of a variety of impairments. Frequency domain processing and/or time domain processing can be performed to reduce distortion in channel estimates.

Inventors

Peter John Black
Jinghu Chen
Jing Jiang
Tamer Adel Kadous
Wanlun Zhao

Assignees

VIREWIRX, INC.

Dates

Publication Date: 20260505
Application Date: 20220623

Claims (20)

1 . A system for Sounding Reference Signal channel estimation, the system comprising: at least one antenna; a frequency domain processing circuit configured to generate a de-covered frequency domain signal from a Sounding Reference Signal received by the at least one antenna using a base sequence, and to perform pulse shaping on the de-covered frequency domain signal to cause a direct current offset in the de-covered frequency domain signal to be reduced; a time domain processing circuit having an input coupled to an output of the frequency domain processing circuit, the time domain processing circuit configured to suppress time domain channel impulse response leakage; a second time domain processing circuit configured to rotate the Sounding Reference Signal on an indicator of a frequency offset, the second time domain processing circuit having an output coupled to an input of the frequency domain processing circuit; and a channel estimation circuit configured to generate a channel estimate based on an output of the time domain processing circuit, wherein the channel estimate is associated with a wireless communication channel between a user equipment and a network node.
2 . The system of claim 1 , wherein the frequency domain processing circuit is configured to generate an estimated tone for an individual tone of the de-covered frequency domain signal based on at least two other tones of the de-covered frequency domain signal.
3 . The system of claim 2 , wherein the frequency domain processing circuit is configured to replace the individual tone with the estimated tone.
4 . The system of claim 2 , wherein the frequency domain processing circuit is configured to modify the individual tone based on the estimated tone.
5 . The system of claim 1 , wherein the frequency domain processing circuit is configured to perform pulse shaping using a raised cosine pulse.
6 . The system of claim 1 , wherein the network node is a base station.
7 . The system of claim 1 , wherein a base station comprises the channel estimation circuit.
8 . The system of claim 1 , wherein the frequency offset is associated with the user equipment.
9 . The system of claim 1 , further comprising a second frequency domain processing circuit configured to perform per-cyclic shift frequency domain processing, wherein the second frequency domain processing circuit is coupled between the time domain processing circuit and the channel estimation circuit.
10 . The system of claim 1 , wherein the time domain processing circuit comprises: a filter comprising taps; a noise power estimation circuit configured to estimate noise power for a sub-set of the taps of the filter corresponding to sub-carriers between channel impulse responses; and a filter tap scaling circuit configured to perform a per-tap scaling on at least a portion of the taps of the filter based on the estimated noise power.
11 . The system of claim 1 , wherein the time domain processing circuit is configured to move a spur outside of time domain windows for cyclic shifts of the Sounding Reference signal.
12 . A system for Sounding Reference Signal channel estimation, the system comprising: at least one antenna; a frequency domain processing circuit configured to generate a de-covered frequency domain signal from a Sounding Reference Signal received by the at least one antenna using a base sequence, and to perform pulse shaping on the de-covered frequency domain signal to cause a direct current offset in the de-covered frequency domain signal to be reduced; a time domain processing circuit having an input coupled to an output of the frequency domain processing circuit, the time domain processing circuit configured to suppress time domain channel impulse response leakage; a second time domain processing circuit configured to pulse shape the Sounding Reference Signal with a raised cosine pulse, the second time domain processing circuit having an output coupled to an input of the frequency domain processing circuit; and a channel estimation circuit configured to generate a channel estimate based on an output of the time domain processing circuit, wherein the channel estimate is associated with a wireless communication channel between a user equipment and a network node.
13 . The system of claim 12 , wherein the second time domain processing circuit is configured to rotate the Sounding Reference Signal on an indicator of a frequency offset.
14 . The system of claim 12 , wherein the frequency domain processing circuit is configured to generate an estimated tone for an individual tone of the de-covered frequency domain signal based on at least two other tones of the de-covered frequency domain signal.
15 . The system of claim 14 , wherein the frequency domain processing circuit is configured to replace the individual tone with the estimated tone.
16 . The system of claim 14 , wherein the frequency domain processing circuit is configured to modify the individual tone based on the estimated tone.
17 . The system of claim 12 , wherein the network node is a base station.
18 . The system of claim 12 , wherein a base station comprises the channel estimation circuit.
19 . The system of claim 12 , wherein the time domain processing circuit is configured to move a spur outside of time domain windows for cyclic shifts of the Sounding Reference signal.
20 . The system of claim 13 , wherein the frequency offset is associated with the user equipment.

Description

CROSS REFERENCE TO PRIORITY APPLICATION This application is a continuation of U.S. patent application Ser. No. 16/836,668, filed Mar. 31, 2020 and titled “REFERENCE SIGNAL CHANNEL ESTIMATION,” the disclosure of which is hereby incorporated by reference herein in its entirety and for all purposes. BACKGROUND Technical Field Embodiments of this disclosure relate to estimating a channel in a communications system using a reference signal. Description of Related Technology In a wireless communication system, it can be desirable to have an accurate estimation of a communication channel between a user equipment and a base station. Certain communication standards include reference signals that can be used to estimate a communication channel. Such a reference signal can be used to estimate an uplink channel from a user equipment to a base station. In certain applications, a downlink channel from the base station to the user equipment to the base station can be estimated based on the uplink channel. In real world wireless communication systems, a channel estimate can be degraded for a variety of reasons. SUMMARY OF CERTAIN INVENTIVE ASPECTS The innovations described in the claims each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of the claims, some prominent features of this disclosure will now be briefly described. One aspect of this disclosure is a method of reference signal channel estimation. The method comprises receiving a reference signal for channel estimation; de-covering the reference signal in a frequency domain to generate a de-covered reference signal; after the de-covering, frequency domain processing the de-covered reference signal to cause distortion of a direct current offset in the de-covered reference signal to be reduced; after the frequency domain processing, time domain processing to cause a noise floor associated with the de-covered reference signal to be reduced; and generating a channel estimate based on the frequency domain processing and the time domain processing, wherein the channel estimate is associated with a communication channel between a first node and a second node. The frequency domain processing can comprise generating an estimated tone for a tone of the de-covered frequency domain reference signal based on at least two other tones of the de-covered frequency domain reference signal. The frequency domain processing can comprise replacing the tone with the estimated tone to cause distortion associated with the direct current offset to be reduced. The frequency domain processing can comprise modifying the tone based on the estimated tone to cause distortion associated with the direct current offset to be reduced. The frequency domain processing can comprise pulse shaping the de-covered frequency domain reference signal to cause distortion associated with the direct current offset to be reduced. The time domain processing can comprise estimating noise power for a sub-set of time domain taps corresponding to sub-carriers between channel impulse responses, and performing a per-tap scaling on at least a portion of the time domain taps based on the estimating. The per-tap scaling can involve minimum mean squared error scaling. The per-tap scaling can involve thresholding. The method can further comprise pulse shaping the reference signal prior to the de-covering. The method can further comprise rotating the reference signal based on an indicator of a frequency offset prior to the de-covering. The time domain processing can comprise moving a spur outside of time domain windows for cyclic shifts of the reference signal. The method can further comprise pulse shaping the reference signal prior to the de-covering. The reference signal can be an uplink Sounding Reference Signal. The first node can be a user equipment and the second node can be a network node. The first node can be a user equipment and the second node can include a remote radio unit. The first node can be a user equipment and the second node can include a base station integrated with an antenna front-end. The first node can include a first remote radio unit and the second node can include a second remote radio unit. The first node can be a first user equipment and the second node can be a second user equipment. Another aspect of this disclosure is a system for channel estimation. The system comprises a frequency domain processing circuit, a time domain processing circuit, and a channel estimation circuit. The frequency domain processing circuit is configured to generate a de-covered frequency domain reference signal and to process the de-covered frequency domain reference signal so as to cause distortion associated with a direct current offset to be reduced. The time domain processing circuit has an input coupled to an output of the frequency domain processing circuit. The time domain processing circuit is configured to suppress time domain channel