# US 2019/0356441 A1 · Common reference signal design based on semi-uniform pilot spacing and orthogonal cover code > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0356441 A1 - Document ID: US20190356441A1 - Status: Published application - Kind: A1 - Application number: 16/526,478 - Filed: 2019-07-30 - Published: 2019-11-21 - Earliest claimed: 2014-12-19 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Jing Jiang; Joseph Binamira Soriaga; Krishna Kiran Mukkavilli; Tingfang Ji; Huilin Xu; Naga Bhushan; Raghuraman Krishnamoorthi; Peter Pui Lok Ang; John Edward Smee - Web page: https://patentgrep.com/patent/US20190356441A1 ## CPC - H04L 5/0026: {Division using four or more dimensions, e.g. beam steering or quasi-co-location [QCL]} - H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)} - H04L 5/005: {of common pilots, i.e. pilots destined for multiple users or terminals} - H04L 25/0202: {Channel estimation} - H04L 27/2613: {Structure of the reference signals} - H04W 72/0446: Resources in time domain, e.g. slots or frames - H04W 72/0453: Resources in frequency domain, e.g. a carrier in FDMA - H04W 72/0466: {the resource being a scrambling code} - 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) ## Abstract Systems and techniques are disclosed to reduce pilot overhead by providing common reference signals coded with cover codes that are orthogonal in time and frequency domains. Common reference signals that are coded by cover codes orthogonal in both domains can be de-spread in both the time and frequency domains for improved resolution and larger pull-in windows for both. Also disclosed is semi-uniform pilot spacing in both the frequency and time domains. In a time domain, a first pilot symbol pair is spaced by a first time interval from each other and a second pilot symbol pair is spaced by a second time interval from the first pair, the second interval being greater than the first. In a frequency domain, a first set of pilot symbols is densely placed in a selected frequency band and a second set of pilot symbols is sparsely placed surrounding and including the selected frequency band. ## Claims ### Claim 1 A method for wireless communication, comprising: receiving, at a wireless communications device, a first set of pilot symbols spread with a first cover code to a first plurality of subcarriers with a first frequency spacing at which a first subset of the first set of pilot symbols is placed and a second plurality of subcarriers with a second frequency spacing at which a second subset of the first set of pilot symbols is placed, the second frequency spacing being greater than the first frequency spacing; receiving, at the wireless communications device, a second set of pilot symbols spread with a second cover code to the first plurality of subcarriers at which a first subset of the second set of pilot symbols is placed and second plurality of subcarriers at which a second subset of the second set of pilot symbols is placed, the first and second sets of pilot symbols comprising a common reference signal; and de-spreading, by the wireless communications device, the first and second sets of pilot symbols in a frequency domain to recover at least two pilot observations in a time domain. ### Claim 2 (depends on 1) The method of claim 1, further comprising: computing, by the wireless communications device, a time domain window channel estimate using the first subset of the first set of pilot symbols and the first subset of the second set of pilot symbols with the first frequency spacing. ### Claim 3 (depends on 1) The method of claim 1, further comprising: computing, by the wireless communications device, a wideband channel state information estimate using the second subset of the first set of pilot symbols and the second subset of the second set of pilot symbols with the second frequency spacing. ### Claim 4 (depends on 3) The method of claim 3, further comprising: de-aliasing, by the wireless communications device, the wideband channel state information estimate based on de-spreading the received first subset of the first set of pilot symbols. ### Claim 5 (depends on 1) The method of claim 1, wherein the first plurality of subcarriers is located within a first frequency band, and the second plurality of subcarriers is located within a second frequency band that surrounds and includes the first frequency band. ### Claim 6 (depends on 5) The method of claim 5, further comprising: using, by the wireless communications device, the second subset of the first set of pilot symbols and the second subset of the second set of pilot symbols as a power reference signal for automatic gain control in the wireless communications device. ### Claim 7 (depends on 1) The method of claim 1, further comprising: updating, by the wireless communications device, a frequency tracking loop with the at least two pilot observations in the time domain. ### Claim 8 A wireless communications device, comprising: a transceiver configured to: receive a first set of pilot symbols spread with a first cover code to a first plurality of subcarriers with a first frequency spacing at which a first subset of the first set of pilot symbols is placed and a second plurality of subcarriers with a second frequency spacing at which a second subset of the first set of pilot symbols is placed, the second frequency spacing being greater than the first frequency spacing; and receive a second set of pilot symbols spread with a second cover code to the first plurality of subcarriers at which a first subset of the second set of pilot symbols is placed and second plurality of subcarriers at which a second subset of the second set of pilot symbols is placed, the first and second sets of pilot symbols comprising a common reference signal; and a processor configured to de-spread the first and second sets of pilot symbols in a frequency domain to recover at least two pilot observations in a time domain. ### Claim 9 (depends on 8) The wireless communications device of claim 8, wherein the processor is further configured to: compute a time domain window channel estimate using the first subset of the first set of pilot symbols and the first subset of the second set of pilot symbols with the first frequency spacing. ### Claim 10 (depends on 8) The wireless communications device of claim 8, wherein the processor is further configured to: compute a wideband channel state information estimate using the second subset of the first set of pilot symbols and the second subset of the second set of pilot symbols with the second frequency spacing. ### Claim 11 (depends on 10) The wireless communications device of claim 10, wherein the processor is further configured to: de-alias the wideband channel state information estimate based on de-spreading the received first subset of the first set of pilot symbols. ### Claim 12 (depends on 8) The wireless communications device of claim 8, wherein the first plurality of subcarriers is located within a first frequency band, and the second plurality of subcarriers is located within a second frequency band that surrounds and includes the first frequency band. ### Claim 13 (depends on 12) The wireless communications device of claim 12, wherein the processor is further configured to: use the second subset of the first set of pilot symbols and the second subset of the second set of pilot symbols as a power reference signal for automatic gain control in the wireless communications device. ### Claim 14 (depends on 8) The wireless communications device of claim 8, wherein the processor is further configured to: update a frequency tracking loop with the at least two pilot observations in the time domain. ### Claim 15 A non-transitory computer-readable medium having program code recorded thereon, the program code comprising: code for causing a wireless communications device to receive a first set of pilot symbols spread with a first cover code to a first plurality of subcarriers with a first frequency spacing at which a first subset of the first set of pilot symbols is placed and a second plurality of subcarriers with a second frequency spacing at which a second subset of the first set of pilot symbols is placed, the second frequency spacing being greater than the first frequency spacing; code for causing the wireless communications device to receive a second set of pilot symbols spread with a second cover code to the first plurality of subcarriers at which a first subset of the second set of pilot symbols is placed and second plurality of subcarriers at which a second subset of the second set of pilot symbols is placed, the first and second sets of pilot symbols comprising a common reference signal; and code for causing the wireless communications device to de-spread the first and second sets of pilot symbols in a frequency domain to recover at least two pilot observations in a time domain. ### Claim 16 (depends on 15) The non-transitory computer-readable medium of claim 15, wherein the program code further comprises: code for causing the wireless communications device to compute a time domain window channel estimate using the first subset of the first set of pilot symbols and the first subset of the second set of pilot symbols with the first frequency spacing. ### Claim 17 (depends on 15) The non-transitory computer-readable medium of claim 15, wherein the program code further comprises: code for causing the wireless communications device to compute a wideband channel state information estimate using the second subset of the first set of pilot symbols and the second subset of the second set of pilot symbols with the second frequency spacing. ### Claim 18 (depends on 17) The non-transitory computer-readable medium of claim 17, wherein the program code further comprises: code for causing the wireless communications device to de-alias the wideband channel state information estimate based on de-spreading the received first subset of the first set of pilot symbols. ### Claim 19 (depends on 15) The non-transitory computer-readable medium of claim 15, wherein the first plurality of subcarriers is located within a first frequency band, and the second plurality of subcarriers is located within a second frequency band that surrounds and includes the first frequency band. ### Claim 20 (depends on 19) The non-transitory computer-readable medium of claim 19, wherein the program code further comprises: code for causing the wireless communications device to use the second subset of the first set of pilot symbols and the second subset of the second set of pilot symbols as a power reference signal for automatic gain control in the first wireless communications device.