CN-116527453-B - Waveform design and receiving method of orthogonal time-frequency code domain

CN116527453BCN 116527453 BCN116527453 BCN 116527453BCN-116527453-B

Abstract

The invention provides a waveform design and receiving method of an orthogonal time-frequency code domain. The method comprises the steps of utilizing an orthogonal spread spectrum sequence pool to distribute orthogonal spread spectrum combinations for each waveform in a waveform group, enabling each waveform to carry transmission data in an orthogonal time-frequency code domain according to the distributed orthogonal spread spectrum combinations, estimating multipath time delay, multipath fading and multipath Doppler experienced by a plurality of waveforms according to the orthogonal spread spectrum combinations of each waveform after receiving each waveform by a receiver, and utilizing the estimated multipath time delay, multipath fading and multipath Doppler of each waveform by the receiver and utilizing an MMSE criterion and an orthogonal spread spectrum combination structure to detect the transmission data carried by each waveform. The method designs unique orthogonal spread spectrum combination for different waveforms in the same waveform group, realizes multi-waveform orthogonal transmission under the same DD domain resource, and provides an alternative scheme for multi-user data transmission under the high-speed moving condition.

Inventors

AI BO
MA YIYAN
MA GUOYU
FENG BOTAO
XUE ZHEN
DAI JIMING

Assignees

北京交通大学

Dates

Publication Date: 20260512
Application Date: 20230411

Claims (5)

1. The waveform design and receiving method of orthogonal time-frequency code domain is characterized by comprising the following steps: allocating an orthogonal spread spectrum combination for each waveform in the waveform group by using the orthogonal spread spectrum sequence pool; each waveform carries transmission data in an orthogonal time-frequency code domain according to the allocated orthogonal spread spectrum combination; after each waveform is received by the receiver, estimating multipath time delay, multipath fading and multipath Doppler experienced by a plurality of waveforms according to the orthogonal spread spectrum combination of each waveform; the receiver detects the transmission data carried by each waveform by using the estimated multipath time delay, multipath fading and multipath Doppler of each waveform and using a Minimum Mean Square Error (MMSE) criterion and an orthogonal spread spectrum combined structure.
2. The method of claim 1, wherein assigning an orthogonal spreading combination to each waveform in the set of waveforms using the pool of orthogonal spreading sequences comprises: Setting the bandwidth occupied by the waveform group in transmitting data as The time is Wherein Representing subcarrier spacing Is a function of the number of (3), Representing time slots Is set to be common in waveform groups A waveform with each waveform having a serial number of , ; Taking each column of discrete Fourier transform DFT matrix to form orthogonal spread spectrum sequence pool Wherein Which represents the spreading factor of the spread spectrum, Expressed as: (1) (2) Wherein the vector is Representation matrix Is the first of (2) Column of (a) Orthogonal spreading sequences; in an orthogonal spread spectrum sequence pool Sequentially select The method comprises the steps of setting orthogonal spreading sequences to form orthogonal spreading combinations of different waveforms, wherein each waveform is allocated to two different orthogonal spreading combinations, and the orthogonal spreading combinations allocated to each waveform are orthogonal in a time-frequency code domain; First, the Orthogonal spread spectrum combining of individual waveforms Expressed as: (3)。
3. The method of claim 2, wherein each of the waveforms carries transmission data in an orthogonal time-frequency code domain according to the assigned orthogonal spread spectrum combination, comprising: each waveform utilizes an orthogonal spreading combination assigned thereto Carrying data in the orthogonal time-frequency code domain Using orthogonal spread spectrum combining The sequences used for pilot symbols in the carrier carry pilot symbols, and orthogonal spread spectrum combination is utilized The sequence for the data symbols carries the data symbols to obtain , Is the first of (2) The columns are shown as: (4) Wherein the method comprises the steps of Representation of Row of lines An identity matrix of the columns, Expressed in terms of As diagonal elements Row of lines A block diagonal array of columns; Each waveform is converted from a delay-doppler domain to a time-frequency domain for data transmission by operation of a two-dimensional DFT transform.
4. The method of claim 3, wherein the receiver, upon receipt of each waveform, estimates multipath delay, multipath fading, and multipath doppler experienced by the plurality of waveforms based on an orthogonal spread spectrum combination of each waveform, comprising: after the receiver receives signals from the plurality of waveforms, each waveform is converted from a time-frequency domain to a delay-Doppler domain through two-dimensional DFT conversion; Setting the waveform group received by the receiver in The length of time it takes for the air to flow, The signal carried on the bandwidth is ; The receiver separates the data carried by each waveform according to the orthogonal spread spectrum combination specified by the formula (3) and the inverse process of the formula (4) The calculation process is shown in formulas (5) and (6): (5) Wherein the method comprises the steps of Is the first of (2) The columns are obtained by: (6) according to the orthogonal spread spectrum combination specified in the formula (3), each waveform is used for completely orthogonal spread spectrum sequence carrying pilot frequency symbol, and the pilot frequency data carried by each waveform is stripped out and recorded as Based on the assumption of bi-orthogonality between transmit and receive waveforms And (3) with The relation of (2) is: (7) in the formula (7) of the present invention, Representing a complex Gaussian noise matrix with a noise compliance mean of 0 and a variance of 0 Is used for the complex gaussian distribution of (c), Representing an index matrix, the first of which Line 1 Column elements are The rest elements are all 0, , Representing a matrix of time-delay domain samples, Representing the channel fading matrix, Representing a matrix of doppler domain samples, Representing the number of receiver delay domain oversampling points, ; Wherein the method comprises the steps of And Representing the delay and doppler of a certain path, Multipath time delay and multipath fading, and the like, ; Representing a time-delay sampling matrix First, the Line (1) Elements of a column; representing Doppler domain sampling functions ; Finger channel fading matrix Line (1) Elements of a column; a sequence number representing a multipath delay, ; The sequence number of the finger multipath doppler, ; Sparsity pairs in the delay-doppler domain using multipath Estimating to obtain Wherein Representing the true multipath number, will Middle AND Extracting the corresponding row of the estimated multipath to obtain , Middle AND Dividing the estimated multipath corresponding row in the formula (7) And (3) with The other parts are marked as Estimation using MMSE criterion And then channel estimation is completed, and the formula is expressed as follows: (8) Wherein the method comprises the steps of Representing the ratio of the power of noise to pilot symbols in the data carried by each waveform, Representation of Row of lines A unit array of columns.
5. The method of claim 4 wherein the receiver using the estimated multipath delay, multipath fading and multipath doppler for each waveform and using a minimum mean square error MMSE criterion and orthogonal spreading combining structure to detect the transmission data carried by each waveform comprises: Number of system waveforms Is known, the sequence number of the waveform Based on the combination of orthogonal spreading designed for each user in equation (3), based on the content in equation (7) The cyclic structure of the matrix is rewritten as formula (7): (9) Representing And (3) with In the formula (7) Index matrix Time delay domain sampling matrix Channel fading matrix Doppler domain sampling matrix Joint channel fading; the estimated multipath time delay Joint influence of multipath Doppler and multipath fading Substitution into In the above, the input-output relationship between the received signal and the transmitted signal is obtained, Is a received signal Part of pilot symbol in the received signal The data symbols correspond to the shape as Is obtained by (7) shaping corresponding to the data symbols and pilot symbols Is arranged in a matrix The relationship between the received data symbols and the transmitted data symbols is obtained as follows: (10) the left side of equation (10) represents the signal to be received The shaping is performed in the form of a vector, Representing the channel fading between the received signal and the transmitted signal, the data item to the right of the equation representing the transmitted signal The shaping is performed in the form of a vector, Representing gaussian noise terms; The data recovery of the waveform group based on the orthogonal spread spectrum combination is realized by using an MMSE equalization mode, and the specific formula is expressed as follows: (11) Wherein the method comprises the steps of Representing the power ratio of noise to data symbols in the data carried by each waveform, Representation of Row of lines A unit array of columns and a plurality of rows, Representation of Is used to shift the conjugate of the (c) shift, Representing the received signal Shaping into a column vector; vector form of the transmission signal obtained in equation (11) Namely the first The same operation is carried out on the transmission data carried by the waveforms to other waveforms to finish all Detection of the transmission data carried by the waveforms.

Description

Waveform design and receiving method of orthogonal time-frequency code domain Technical Field The present invention relates to the field of wireless communication technologies, and in particular, to a method for designing and receiving waveforms in an orthogonal time-frequency code domain. Background In 2017, students proposed orthogonal time-frequency space (Orthogonal Time Frequency Space, OTFS) modulation techniques at Institute of Electrical and Electronics Engineers (IEEE) 2017 conference on wireless communication and networks (Wireless Communication and Network). From a communication principle, OTFS techniques can be regarded as precoded orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) modulation techniques. OTFS converts Time Frequency (TF) domain data to Delay Doppler (DD) domain by an operation of an octave fourier transform, and considers a system input-output relationship of the Delay Doppler domain. Note that in a high speed moving scenario, the channel of the delay-doppler domain has potential sparsity and stability compared to the time-frequency domain channel, so the likelihood of OTFS systems encountering deep fades is greatly reduced compared to OFDM modulation. For this reason, OTFS technology becomes an alternative to reliable transmission in high-speed mobile scenarios. Currently, one multi-waveform orthogonal transmission scheme of an OTFS system in the prior art includes considering the input-output relationship of the system in the DD domain. The two-dimensional cyclic shift exists between the transmission data and the receiving data obtained by the input-output relation of the OTFS system. Each waveform uses only part of DD domain resource to transmit data, and reduces the interference of multiple waveforms through other data processing means such as interleaving. The defects of the multi-waveform orthogonal transmission scheme of the OTFS system in the prior art include that the current OTFS multi-waveform scheme has strong sparsity assumption for channels, the performance of the current OTFS multi-waveform scheme under an actual channel needs to be verified, and in addition, each waveform in the scheme only utilizes part of DD domain resources, so that the DD domain resources are wasted under the condition of fewer concurrent transmissions. Disclosure of Invention The embodiment of the invention provides a waveform design and receiving method of an orthogonal time-frequency code domain, which is used for realizing multi-waveform orthogonal transmission under the condition of utilizing the same DD domain resource. In order to achieve the above purpose, the present invention adopts the following technical scheme. A waveform design and receiving method of orthogonal time-frequency code domain includes: allocating an orthogonal spread spectrum combination for each waveform in the waveform group by using the orthogonal spread spectrum sequence pool; each waveform carries transmission data in an orthogonal time-frequency code domain according to the allocated orthogonal spread spectrum combination; after each waveform is received by the receiver, estimating multipath time delay, multipath fading and multipath Doppler experienced by a plurality of waveforms according to the orthogonal spread spectrum combination of each waveform; the receiver detects the transmission data carried by each waveform by using the estimated multipath time delay, multipath fading and multipath Doppler of each waveform and using a Minimum Mean Square Error (MMSE) criterion and an orthogonal spread spectrum combined structure. Preferably, the allocating an orthogonal spreading combination to each waveform in the waveform group using the orthogonal spreading sequence pool includes: Setting the bandwidth occupied by the waveform group when transmitting data as M delta f and the time as NT, wherein M represents the number of subcarrier intervals delta f, N represents the number of time slots T, setting the total gamma waveforms in the waveform group, and setting the serial number of each waveform as gamma, gamma=1, 2, & gt, gamma; Taking each column of discrete Fourier transform DFT matrix to form orthogonal spread spectrum sequence pool Where q represents a spreading factor and E represents: E=[e1 … eq] (2) Wherein the vector is The ith column of the matrix E is represented as the ith orthogonal spread spectrum sequence; Sequentially selecting q orthogonal spreading sequences from an orthogonal spreading sequence pool E to form orthogonal spreading combinations of different waveforms, setting that each waveform is allocated to two different orthogonal spreading combinations, and the orthogonal spreading combinations allocated to each waveform are orthogonal in a time-frequency code domain; orthogonal spread spectrum combining of the gamma-th waveform Expressed as: preferably, each waveform carries transmission data in an orthogonal time-frequency code domain according to