# US 10,484,226 B2 · OFDM communication system with enhanced channel estimation and data detection techniques > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,226 B2 - Document ID: US10484226B2 - Status: Granted - Kind: B2 - Application number: 15/375,857 - Filed: 2016-12-12 - Published: 2018-06-14 - Granted: 2019-11-19 - Earliest claimed: 2016-12-12 - Assignees: Khalifa University of Science and Technology - Applicants: Khalifa University of Science, Technology & Research - Inventors: Arafat Jamil Al-Dweik; Youssef Iraqi - Web page: https://patentgrep.com/patent/US10484226B2 ## CPC - H04L 27/2647: {Arrangements specific to the receiver only (equalisation H04L27/01)} - H04L 25/02: Details {; arrangements for supplying electrical power along data transmission lines (systems for transmitting signals via power distribution lines H04B3/54)} - H04L 25/022: {of frequency response} - H04L 25/0232: {by interpolation between sounding signals} - H04L 27/0008: {arrangements for allowing a transmitter or receiver to use more than one type of modulation (negotiating modulation type for two-way transmission paths H04L5/1453)} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract There is provided an enhanced OFDM communication system using an enhanced channel estimation and data detection techniques. The system is based on replacing pilot symbols by real-valued information symbols, which enables realizing one-shot blind channel estimator (OSBCE) with low complexity. The channel estimator used is equivalent to pilot-based channel estimators for a wide range of signal to noise ratios (SNRs), yet, the OSBCE offers higher power and spectral efficiencies. ## Claims ### Claim 1 A channel estimation device in an Orthogonal Frequency Division Multiplexing (OFDM) system comprising an OFDM transmitter and an OFDM receiver adapted to communicate data symbols over a communication channel having channel conditions, the channel estimation device being adapted to: at the OFDM transmitter side, modulate the OFDM subcarriers by data symbols in a frequency domain using different modulation techniques for generating modulated data symbols having a diversified symbol type configuration, the different modulation techniques comprising a first modulation technique, a second modulation technique and a third modulation technique, the modulated data symbols having the diversified symbol type configuration being generated by modulating first OFDM subcarriers using the first modulation technique for generating first type symbols, modulating second OFDM subcarriers adjacent the first OFDM subcarriers in the frequency domain using the second modulation technique for generating second type symbols and modulating third OFDM subcarriers using the third modulation technique for generating third type symbols; and at the OFDM receiver side, consider the first type symbols as first channel responses and to process said first channel responses for detecting the second type symbols and to consider the second type symbols as second channel responses and to process said first and second channel responses for detecting the third type symbols, wherein the first, second and third type symbols used by the channel estimation device are data-bearing symbols only and are free of pilot symbols. ### Claim 2 (depends on 1) The channel estimation device as claimed in claim 1, wherein the different modulation techniques comprise MPSK, MASK and QAM. ### Claim 3 (depends on 2) The channel estimation device as claimed in claim 2, wherein the first modulation technique is MASK, the second modulation technique is MPSK and the third modulation technique is QAM. ### Claim 4 (depends on 1) The channel estimation device as claimed in claim 1, wherein the data symbols are modulated to form a plurality of symbol blocks and wherein each symbol block among said plurality of symbol blocks is generated according to the diversified symbol type configuration. ### Claim 5 (depends on 4) The channel estimation device as claimed in claim 4, wherein each symbol block comprises at least two pairs of adjacently formed first and second type symbols such that each pair of adjacently formed first and second type symbols is separated from another pair of adjacently formed first and second type symbols by a frequency spacing using third type symbols. ### Claim 6 (depends on 5) The channel estimation device as claimed in claim 5, wherein the channel estimation device is adapted to adjust the frequency spacing as a function of the channel conditions. ### Claim 7 (depends on 4) The channel estimation device as claimed in claim 4, wherein the symbol blocks are separated between each other by a time spacing using third type symbols. ### Claim 8 (depends on 7) The channel estimation device as claimed in claim 7, wherein the channel estimation device is adapted to adjust the time spacing as a function of the channel conditions. ### Claim 9 (depends on 1) The channel estimation device as claimed in claim 1, wherein the OFDM system is a Long Term Evolution LTE-Advanced (LTE-A) system. ### Claim 10 (depends on 1) The channel estimation device as claimed in claim 1, wherein the communication channel is a fading channel. ### Claim 11 (depends on 1) The channel estimation device as claimed in claim 1, wherein said device performs channel estimation in a Decision-Directed (DD) manner. ### Claim 12 An Orthogonal Frequency Division Multiplexing (OFDM) system for broadband communication of data symbols over a communication channel having channel conditions, the OFDM system comprising: an OFDM transmitter adapted to modulate the data symbols by OFDM subcarriers in a frequency domain using different modulation techniques for generating modulated data symbols having a diversified symbol type configuration, the different modulation techniques comprising a first modulation technique, a second modulation technique and a third modulation technique, the modulated data symbols having the diversified symbol type configuration being generated by modulating first OFDM subcarriers using the first modulation technique for generating first type symbols, modulating second OFDM subcarriers adjacent the first OFDM subcarriers in the frequency domain using the second modulation technique for generating second type symbols and modulating third OFDM subcarriers using the third modulation technique for generating third type symbols; and an OFDM receiver adapted to process the first type symbols as first channel responses and to process said first channel responses for detecting the second type symbols and to process the second type symbols as second channel responses and to process said first and second channel responses for detecting the third type symbols, wherein the first, second and third type symbols used by the channel estimation device are data-bearing symbols only and are free of pilot symbols. ### Claim 13 (depends on 12) The OFDM system as claimed in claim 12, wherein the different modulation techniques comprise MPSK, MASK and QAM, and wherein the first modulation technique is MASK, the second modulation technique is MPSK and the third modulation technique is QAM. ### Claim 14 (depends on 13) The OFDM system as claimed in claim 13, wherein the data symbols are modulated to form a plurality of symbol blocks and wherein each symbol block among said plurality of symbol blocks is generated according to the diversified symbol type configuration, and wherein each symbol block comprises at least two pairs of adjacently formed first and second type symbols such that each pair of adjacently formed first and second type symbols is separated from another pair of adjacently formed first and second type symbols by a frequency spacing using third type symbols and wherein the symbol blocks are separated between each other by a time spacing using third type symbols. ### Claim 15 (depends on 14) The OFDM system as claimed in claim 14 adapted to adjust the frequency spacing and the time spacing as a function of the channel conditions. ### Claim 16 (depends on 15) The OFDM system as claimed in claim 15, wherein the OFDM system uses a Long Term Evolution LTE-Advanced (LTE-A) system, the communication channel is a fading channel, and the OFDM receiver uses a Mean Squared Error (MSE) estimation in Decision-Directed (DD) manner. ### Claim 17 (depends on 16) The OFDM system as claimed in claim 16, wherein the OFDM system has equal complexity in comparison to an equivalent system using pilots for channel estimation, with a better bit error rate (BER) performance.