# US 2019/0173640 A1 · Transmitter and method for formatting transmit data into a frame structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0173640 A1 - Document ID: US20190173640A1 - Status: Published application - Kind: A1 - Application number: 16/260,975 - Filed: 2019-01-29 - Published: 2019-06-06 - Earliest claimed: 2016-07-29 - Assignees: Huawei Technologies Duesseldorf GmbH - Applicants: Huawei Technologies Duesseldorf GmbH - Inventors: Jian LUO; Anastasios KAKKAVAS - Web page: https://patentgrep.com/patent/US20190173640A1 ## CPC - H04L 27/2613: {Structure of the reference signals} - 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 25/0204: {of multiple channels} - H04L 25/03159: {operating in the frequency domain (H04L25/03165, H04L25/03178 take precedence)} - H04L 27/2607: {Cyclic extensions} - H04L 27/26134: {Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain} - H04L 27/26526: {with inverse FFT [IFFT] or inverse DFT [IDFT] demodulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] receiver or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A transmitter has a transmit chain that is configured to format transmit data into a frame structure that comprises signal blocks interspersed with training sequences for assisting a receive operation. The transmit chain is configured to insert two training sequences between a signal block and its following signal block in the frame structure. The transmitter also comprises a sequence generator configured to form the two training sequences, and in particular to form them such that a first of the training sequences is a negative of the second. Having one training sequence being the negative of the other helps to avoid the Direct Current (DC) subcarrier and provides good properties for channel estimation. ## Claims ### Claim 1 A transmitter comprising: a transmit chain configured to format transmit data into a frame structure that comprises signal blocks interspersed with training sequences for assisting a receive operation, and to insert two training sequences between a signal block and its following signal block in the frame structure; and a sequence generator configured to form the two training sequences such that a first of the two training sequences is a negative of the second of the two training sequences. ### Claim 2 (depends on 1) A transmitter as claimed in claim 1, the sequence generator being configured to form the two training sequences such that only odd subcarriers have non-zero values. ### Claim 3 (depends on 1) A transmitter as claimed in claim 1, the sequence generator being configured to form the first training sequence by: generating a Constant Amplitude Zero Autocorrelation (CAZAC) sequence; and allocating each odd subcarrier a corresponding value from the CAZAC sequence. ### Claim 4 (depends on 1) A transmitter as claimed in claim 1, the sequence generator being configured to set one or more odd subcarriers at an outer limit of the frequency spectrum represented by a training sequence to zero. ### Claim 5 (depends on 1) A transmitter as claimed in claim 1, the transmit chain being configured to vary a number of signal blocks that are inserted in the frame structure between pairs of signal blocks that have two training sequences between them, and to vary the number in dependence on a characteristic of a channel over which the data is to be transmitted. ### Claim 6 (depends on 1) A transmitter as claimed in claim 1, the transmit chain being configured to insert only one training sequence between some pairs of signal blocks and to insert two training sequences between other pairs of signal blocks. ### Claim 7 (depends on 1) A transmitter as claimed in claim 1, the transmit chain being configured to, for each signal block that is preceded by a first training sequence or a second training sequence, follow that signal block with another of the respective first training sequence or second training sequence. ### Claim 8 (depends on 1) A transmitter as claimed in claim 1, the transmit chain being configured to reverse an order of the first and second training sequences from one instance of two training blocks being inserted between a signal block and its following signal block in the frame structure to the next instance. ### Claim 9 (depends on 1) A transmitter as claimed in claim 1, the transmit chain being configured to transmit single carrier data in one of the signal blocks and multi-carrier data in another of the signal blocks. ### Claim 10 (depends on 1) A transmitter as claimed in claim 1, the sequence generator being configured to form each of the two training sequences to represent a unique word that is known by a receiver to which the data is being transmitted. ### Claim 11 A method implemented in a transmitter, the method comprising: formatting transmit data into a frame structure that comprises signal blocks interspersed with training sequences for assisting a receive operation; inserting two training sequences between a signal block and its following signal block in the frame structure; and forming the two training sequences such that a first of the two training sequences is a negative of the second of the two training sequences. ### Claim 12 A receiver comprising: a receive chain configured to receive data that is formatted into a frame structure that comprises signal blocks interspersed with training sequences for assisting a receive operation; a channel estimator configured to estimate what form a training sequence will take when it is received by the receiver; and a subtractor configured to: subtract any part of a training sequence that is predicted by the channel estimator to be included in a received signal block and its adjacent training sequence from that received signal block and its adjacent training sequence to form a subtracted signal block; and form a padded signal block by zero-padding the subtracted signal block to be twice the length of the transmitted signal block, and output the padded signal block for transforming into the frequency domain. ### Claim 13 (depends on 12) A receiver as claimed in claim 12, comprising a filter configured to equalise the padded signal block, discard one half of the equalised signal block and output the other half of the equalised signal block for further processing. ### Claim 14 A method implemented in a receiver, the method comprising: receiving data that is formatted into a frame structure that comprises signal blocks interspersed with training sequences for assisting a receive operation; estimating, by a channel estimator, what form a training sequence will take when it is received by the receiver; subtracting part of a training sequence that is predicted by the channel estimator to be included in a received signal block and its adjacent training sequence from that signal block and its adjacent training sequence to form a subtracted signal block; and forming a padded signal block by zero-padding the subtracted signal block to be twice the length of the received signal block, and output the padded signal block for transforming into the frequency domain.