# US 10,693,693 B2 · Scattered pilot pattern and channel estimation method for MIMO-OFDM systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,693,693 B2 - Document ID: US10693693B2 - Status: Granted - Kind: B2 - Application number: 16/173,901 - Filed: 2018-10-29 - Published: 2019-04-25 - Granted: 2020-06-23 - Earliest claimed: 2001-10-17 - Assignees: BlackBerry Limited - Applicants: BlackBerry Limited - Inventors: Peiying Zhu; Wen Tong; Jianglei Ma; Ming Jia - Web page: https://patentgrep.com/patent/US10693693B2 ## CPC - 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)} - H04B 7/0413: MIMO systems - H04B 7/0684: {using different training sequences per antenna} - H04L 1/0618: {Space-time coding} - H04L 5/0023: {Time-frequency-space} - H04L 25/0204: {of multiple channels} - H04L 25/022: {of frequency response} - H04L 25/0234: {by non-linear interpolation} - H04L 25/0244: {with inversion} - H04L 27/2602: {Signal structure} - H04L 27/2613: {Structure of the reference signals} - H04L 27/26134: {Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain} - H04L 27/2627: {Modulators} - H04W 52/42: in systems with time, space, frequency or polarisation diversity - H04L 27/26035: {Maintenance of orthogonality, e.g. for signals exchanged between cells or users, or by using covering codes or sequences (using different training sequence per antenna H04B7/0684; code allocation H04J13/16)} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A method and apparatus are provided for reducing the number of pilot symbols within a MIMO-OFDM communication system, and for improving channel estimation within such a system. For each transmitting antenna in an OFDM transmitter, pilot symbols are encoded so as to be unique to the transmitting antenna. The encoded pilot symbols are then inserted into an OFDM frame to form a diamond lattice, the diamond lattices for the different transmitting antennae using the same frequencies but being offset from each other by a single symbol in the time domain. At the OFDM receiver, a channel response is estimated for a symbol central to each diamond of the diamond lattice using a two-dimensional interpolation. The estimated channel responses are smoothed in the frequency domain. The channel responses of remaining symbols are then estimated by interpolation in the frequency domain. ## Claims ### Claim 1 A method of receiving symbols using Orthogonal Frequency Division Multiplexing (OFDM) frames at an OFDM receiver having a plurality of processing paths to receive OFDM signals, the OFDM frames having a time domain and a frequency domain, each of the OFDM frames comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, the method comprising the steps of: for a first processing path of the OFDM receiver, receiving scattered pilot symbols in a scattered pattern in time-frequency by receiving a first set of pilot symbols in a first pattern in time-frequency and receiving a second set of pilot symbols in a second pattern in time-frequency at same frequencies as the first pattern, offset by one OFDM symbol in the time domain; and for a second processing path of the OFDM receiver, receiving scattered pilot symbols using the scattered pattern. ### Claim 2 (depends on 1) The method of claim 1, wherein at least one of the OFDM frames includes a preamble. ### Claim 3 (depends on 1) The method of claim 1, wherein receiving the scattered pilot symbols in the scattered pattern in time-frequency comprises: receiving the scattered pilot symbols at locations that form at least one diagonal arrangement in time-frequency. ### Claim 4 (depends on 1) The method of claim 1, further comprising: receiving the scattered pilot symbols with a power level greater than a power level of data symbols, depending upon a value reflective of channel conditions. ### Claim 5 (depends on 1) The method of claim 1, further comprising: receiving the scattered pilot symbols with a power level which is dynamically adjusted based on a function of a modulation type applied to sub-carriers carrying data. ### Claim 6 (depends on 1) The method of claim 1, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols having an equal spacing between pilot subcarriers in the frequency domain. ### Claim 7 A user equipment (UE) comprising: an Orthogonal Frequency Division Multiplexing (OFDM) receiver configured to receive symbols using OFDM frames, the OFDM frames have a time domain and a frequency domain, and each of the OFDM frames comprises a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, wherein the OFDM receiver comprises a plurality of processing paths to receive OFDM signals, and the OFDM receiver is configured to: for a first processing path of the OFDM receiver, receive scattered pilot symbols in a scattered pattern in time-frequency by receiving a first set of pilot symbols in a first pattern in time-frequency and receiving a second set of pilot symbols in a second pattern in time-frequency at same frequencies as the first pattern, offset by one OFDM symbol in the time domain; and for a second processing path of the OFDM receiver, receive scattered pilot symbols using the scattered pattern. ### Claim 8 (depends on 7) The UE of claim 7, wherein at least one of the OFDM frames includes a preamble. ### Claim 9 (depends on 7) The UE of claim 7, wherein receiving the scattered pilot symbols in the scattered pattern in time-frequency comprises: receiving the scattered pilot symbols at locations that form at least one diagonal arrangement in time-frequency. ### Claim 10 (depends on 7) The UE of claim 7, wherein the OFDM receiver is further configured to: receive the scattered pilot symbols with a power level greater than a power level of data symbols, depending upon a value reflective of channel conditions. ### Claim 11 (depends on 7) The UE of claim 7, wherein the OFDM receiver is further configured to: receive the scattered pilot symbols with a power level which is dynamically adjusted based on a function of a modulation type applied to sub-carriers carrying data. ### Claim 12 (depends on 7) The UE of claim 7, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols having an equal spacing between pilot subcarriers in the frequency domain. ### Claim 13 A non-transitory computer-readable medium storing instructions that are operable when executed by data processing apparatus to perform operations of receiving symbols using Orthogonal Frequency Division Multiplexing (OFDM) frames, the OFDM frames having a time domain and a frequency domain, each of the OFDM frames comprising a plurality of OFDM symbols in the time domain and a plurality of sub-carriers in the frequency domain, the operations comprising: for a first processing path, receiving scattered pilot symbols in a scattered pattern in time-frequency by receiving a first set of pilot symbols in a first pattern in time-frequency and receiving a second set of pilot symbols in a second pattern in time-frequency at same frequencies as the first pattern, offset by one OFDM symbol in the time domain; and for a second processing path, receiving scattered pilot symbols using the scattered pattern. ### Claim 14 (depends on 13) The non-transitory computer-readable medium of claim 13, wherein at least one of the OFDM frames includes a preamble. ### Claim 15 (depends on 13) The non-transitory computer-readable medium of claim 13, wherein receiving the scattered pilot symbols in the scattered pattern in time-frequency comprises: receiving the scattered pilot symbols at locations that form at least one diagonal arrangement in time-frequency. ### Claim 16 (depends on 13) The non-transitory computer-readable medium of claim 13, the operations further comprising: receiving the scattered pilot symbols with a power level greater than a power level of data symbols, depending upon a value reflective of channel conditions. ### Claim 17 (depends on 13) The non-transitory computer-readable medium of claim 13, the operations further comprising: receiving the scattered pilot symbols with a power level which is dynamically adjusted based on a function of a modulation type applied to sub-carriers carrying data. ### Claim 18 (depends on 13) The non-transitory computer-readable medium of claim 13, wherein the scattered pattern in time-frequency includes a first plurality of pilot symbols having an equal spacing between pilot subcarriers in the frequency domain.