Patent Description:
In general, wireless communication system components like a node supports in-band full-duplex communication mode. The in-band full-duplex communication mode includes the node transmitting and receiving signals from a plurality of user equipments (UEs) simultaneously. However, the challenge in achieving in-band full-duplex communication is to effectively decode a signal received by the node in the presence of a self-interference created by a signal transmitted by the node.

Existing self-interference suppression techniques in the in-band full-duplex communication mode provide self-interference suppression which limits the application of in-band full-duplex communication mode in wireless communication systems. Also, eliminating the self-interference requires accurate estimation of the self-interference channel and cancelling of the self-interference accordingly.

Patent application <CIT> discloses a MIMO wireless communication device includes, in part, a first transmit path adapted to transmit a first transmit signal from a first antenna, a second transmit path adapted to transmit a second transmit signal from a second antenna, a first receive path adapted to receive a first receive signal, an interference cancellation circuit and a controller. The cancellation circuit includes a cascaded filter structure each filter including a multitude of filter taps each including a variable element. The controller dynamically varies a value applied to each of the plurality of variable elements in accordance with frequency response characteristics of the variable element to remove a portion of a self-interference and/or cross-talk interference signal present in a signal received by the device. The device measures the frequency response characteristic of a multitude of communication channels, used in determining the values, via one or more preamble symbols that are jointly transmitted from the first transmit antenna and the second transmit antenna. A second portion of the interference signal is removed by a digital cancellation circuit using a multitude of samples of a transmitted signal.

The above information is presented as background information only to help the reader to understand the present invention.

The article by <NPL>, proposes a technique that exploits the structure of the received signal to train for SI channel in the presence of received signal. Specifically, this article proposes a time domain symmetric preamble packet in the received signal to create effective samples in which the received signal is absent. Further, this article bound the variance of the channel estimates thus obtained and observe that the performance is same as that of having a separate training period. The performance of the proposed technique is also evaluated by an experiment setup.

The principal object of the embodiments herein is to provide a method and system for decoding a received signal by a node in a wireless communication system.

Another object of the embodiments herein is to provide a received signal which includes a set of preambles where each preamble is identical to an at least one preamble in a preamble structure.

Another object of the embodiments herein is to utilize the identical preambles in the preamble structure to eliminate the received signal in a self-interference channel estimate.

Another object of the embodiments herein is to determine a self-interference channel estimate.

Another object of the embodiments herein is to decode the received signal by eliminating the self-interference signal from the received signal.

Another object of the embodiments herein is to use the self-interference channel estimate to eliminate the self-interference signal from the received signal.

Another object of the embodiments herein is to use a filter which is adaptive to determine the self-interference channel estimate.

Another object of the embodiments herein is to provide a method to estimate the self-interference channel in digital, analog and RF domain.

The invention is as defined in claim <NUM> provides a method for decoding received signal by node in wireless communication system. The method includes receiving a signal from a first User Equipment (UE), where the received signal comprises a set of preambles in which each preamble is identical to an at least one preamble in a preamble structure and obtaining a composite signal comprising a self-interference signal, where the self-interference signal is known at the node. Further, the method includes determining a difference between samples corresponding to locations of consecutive preambles in the composite signal using an adaptive filter, determining self-interference channel estimate using the composite signal and decoding the received signal by eliminating the self-interference signal from the received signal based on the self-interference channel estimate.

The invention is as defined in claim <NUM> provides a node for decoding a received signal in a wireless communication system. The node includes a processor, a memory coupled to the processor and a transceiver coupled to the processor and the memory. The transceiver is configured to receive a signal from a first User Equipment (UE), where the received signal comprises a set of preambles in which each preamble is identical to an at least one preamble in a preamble structure and obtain a composite signal comprising a self-interference signal, wherein the self-interference signal is known at the node. Further, the transceiver is configured to determining a difference between samples corresponding to locations of consecutive preambles in the composite signal using an adaptive filter, determine self-interference channel estimates using the composite signal and decode the received signal by eliminating the self-interference signal from the received signal, based on the self-interference channel estimate.

This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:.

Various embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

Herein, the term "or" as used herein, refers to a non-exclusive or, unless otherwise indicated.

The term "first" and "second" herein are used merely for labeling purpose and can be used interchangeably without departing from the scope of the embodiments.

The term "node" as used in the description includes any device or equipment that supports in-band full-duplex wireless communication such as for example a base station (BS), a user equipment (UE), a Wi-Fi access point, a transceiver or the like.

Accordingly, the embodiments herein provide a method for decoding received signal by node in wireless communication system. The method includes receiving a signal from a first User Equipment (UE), where the received signal comprises a set of preambles in which each preamble is identical to an at least one preamble in a preamble structure and obtaining a composite signal comprising a self-interference signal, where the self-interference signal is known at the node. Further, the method includes determining self-interference channel estimate using the composite signal and decoding the received signal by eliminating the self-interference signal from the received signal based on the self-interference channel estimate.

In an embodiment, the self-interference estimate is determined by finding the difference between identical preambles in the composite signal and using the resulting difference samples.

In an embodiment, the self-interference estimate is determined using an adaptive filter. Examples of adaptive filter include Least Mean Square filter, Recursive Least Squares filter etc..

In the conventional in-band full-duplex wireless communication methods and systems, in-band full-duplex two ways simultaneous communications does not work because of the self-interference experienced by the node due to simultaneous reception and transmission. Further, the self interference degrades the decoding of the received signal at the node.

In the conventional methods and systems, the transmitted signal is used in conjunction with the self-interference signal to generate a copy of the self-interference signal, which is subtracted at the receiver to suppress the self-interference. signal/noise.

Unlike to the conventional methods and systems, the proposed method includes using the set of symmetrically identical preambles in the received signal to eliminate the received signal component in the composite signal. Further, the composite signal is used to determine the self-interference channel estimates.

Unlike to the conventional methods and systems, the proposed method uses the self-interference channel estimates to eliminate the self-interference signal from the received signal while decoding the received signal.

Unlike to the conventional methods and systems, the proposed method eliminates the received signal component from the composite signal and determines the self-interference channel estimates, which ensures better channel estimation. Further, the self-interference channel estimates are used to eliminate the self-interference channel while decoding the received signal.

Unlike to the conventional methods and systems, in the proposed method the self-interference channel estimation is performed based on the composite signal, which either does not have the received signal component or has a significantly reduced component of the received signal.

<FIG> illustrates an in-band full-duplex wireless communication system <NUM> with node <NUM> and a plurality of UEs for self-interference cancellation at the node <NUM>, according to the embodiments as disclosed herein.

In the in-band full-duplex wireless communication system <NUM>, same frequency spectrum is used for both transmitting and receiving the signals simultaneously by the node <NUM> i.e., the node <NUM> can transmit the communication signals to the plurality of UEs (e.g., a first UE 102a and a second UE 102b) and receive the communication signals from the plurality of UEs (i.e., the first UE 102a and the second UE 102b) at the same time, in the same frequency spectrum. However, the possibility of using the same frequency spectrum for simultaneous transmission and reception requires that interference problems to be addressed accordingly. The primary type of interference that may be created when allowing the same frequency spectrum to be used for both transmitting and receiving the signals is the self interference where the node transmitter creates interference to its own receiver. Further, the suppression and generation of the self-interference signal may be performed partly in analog and partly in digital domain. Also, since the self-interference channel varies with the ambient environment, periodic estimation of the self-interference channel is crucial to suppressing the self-interference. Further, a desirable channel estimation method is the one which can estimate the self-interference channel efficiently in the presence of the received signal so as to avoid excess overhead.

Referring to the <FIG>, an exemplary in-band full-duplex wireless communication system <NUM> includes the node <NUM> and UEs i.e., the first UE 102a and the second UE 102b. The node <NUM> receives the signal from the first UE 102a and transmits a signal to the second UE 102b. However, when the node <NUM> receives an incoming signal from the first UE 102a, the node <NUM> also simultaneously indulges in the transmission of an outgoing signal to the second UE 102b. The transmitted signal to the second UE 102b creates self-interference to the processing of the received signal from the first UE 102a at the node <NUM>. For the node <NUM> to be able to effectively decode the incoming signal from the first UE 102a, the self-interference has to be suppressed.

The proposed method and system provides for a self interference cancellation technique. The signal transmitted by the first UE 102a is provided with a set of preambles. The set of preambles appear in pairs, wherein each preamble is identical to another preamble in the preamble pair and hence are symmetric. The symmetric preamble structure is used to eliminate the received signal components completely from the self-interference channel estimates, which are further used to decode the received signal. Further, the preamble may refer to any pair of identical IQ sample sequences where the IQ sample sequences might be separated in time. Further, the location and length of the sequences should be known at the node. For example, the sequences can include cyclic prefix in OFDM systems like LTE, <NUM> new radios, Wi-Fi (<NUM>. <NUM>), and the like.

At the node <NUM>, the composite signal obtained includes the received signal (i.e., the signal received from the first UE 102a) and the self-interference signal (i.e. the signal transmitted by the node <NUM> to the second UE 102b). Further, the composite signal is used to obtain the self-interference channel estimates. The self-interference channel estimates are used to eliminate the self interference in the received signal while decoding the received signal.

<FIG> is a block diagram illustrating various elements of the node200, according to the embodiments as disclosed herein.

Referring to the <FIG>, the node <NUM> may include a transceiver <NUM>, an encoder/decoder <NUM>, a processor <NUM> and a memory <NUM>.

In an embodiment, the transceiver <NUM> can be configured to receive the signal sent to the node <NUM> by the first UE 102a. The received signal includes the encoded data along with the symmetric preamble structure <NUM>. The symmetric preamble structure <NUM> includes a set of preambles (i.e., any pair of identical IQ sample sequences) which appear in preamble pairs. Further, each preamble in the preamble pair is symmetrically identical to successive preamble. Furthermore, the preamble structure is explained in <FIG> in the later parts of the description.

Further, the transceiver <NUM> can be configured to transmit the signal from the node <NUM> to the second UE 102b. The transceiver <NUM> of the node <NUM> simultaneously transmits to the UE and receives the signals from the UE.

In an embodiment, the encoder/decoder <NUM> can be configured to encode the data to be transmitted to the second UE 102b. The encoder/decoder <NUM> can also be configured to decode the signal received from the first UE 102a to extract the data from the received signal.

In an embodiment, the processor <NUM> can be configured to interact with the hardware elements such as the transceiver <NUM>, the encoder/decoder <NUM> and the memory <NUM> in the node <NUM> to execute one or more instructions for cancelling the self interference and to decode the received signal at the node <NUM>.

In an embodiment, the memory <NUM> can include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory <NUM> may, in some examples, be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term "non-transitory" should not be interpreted that the memory <NUM> is non-movable. In some examples, the memory <NUM> can be configured to store larger amounts of information than the memory. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache).

<FIG> is a block diagram illustrating various elements of a transceiver <NUM> of the node <NUM>, according to the embodiments as disclosed herein.

Referring to the <FIG>, the transceiver <NUM> can include a transmitter <NUM>, a receiver <NUM>, a self-interference estimator206 and a self-interference eliminator <NUM>.

In an embodiment, the transmitter <NUM> can be configured to transmit the signal to a plurality of UEs from the node <NUM>. The transmitter <NUM> may also include a digital-to-analog convertor (DAC) which converts the digital signal to an analog signal before transmission. Further, an up-converter may convert the analog signal to a high frequency band RF signal followed by a power amplifier which may amplify the high frequency band RF signal to be transmittable.

In an embodiment, the receiver <NUM> can be configured to receive the signals from a plurality of UEs. The receiver <NUM> may also include an analog-to-digital convertor (ADC) which converts the received analog signal to a digital signal before processing. A down-converter may convert the high frequency band RF signal to a baseband signal.

In an embodiment, the self-interference estimator206 can be configured to determine the self-interference channel estimate. The self-interference estimator206 obtains a composite signal. The composite signal is obtained when the received signal and the self-interference signal (i.e., the transmitted signal) are added up over the air. The self-interference signal is the signal transmitted by the node <NUM> to the second UE 102b and the self-interference signal is known at the node <NUM>. Further, the self-interference estimator <NUM> may include an adaptive filter which uses the known transmitted signal and determines the self-interference channel estimate by computing the difference between consecutive pairs of composite signal components. In an example, the adaptive filter can be one of least mean square filter, recursive least squares filter, etc. The adaptive filters continuously changing the estimated channel coefficient by tracking the channel coefficients estimated from SI1-SI2 and or SI3-SI4. The self-interference channel estimate obtained will either not have any component of the received signal or will have a significantly reduced component of the received signal. The absence of any component of the received signal in the self-interference channel estimate provides better channel estimation. Further, the number of components of the composite signal required for channel estimation is not dependent on the strength of the received signal.

In an embodiment, the self-interference eliminator <NUM> can be configured to use the self-interference channel estimate to cancel out the self-interference signal in the received signal.

<FIG> illustrates a time domain packet structure of the signal received by the node200 comprising a set of preambles, according to the embodiments as disclosed herein.

Referring to the <FIG>, the time domain packet structure includes a set of preambles. Each preamble is identical to another preamble (i.e., the one of the preambles) in a preamble pair of the time domain packet structure. Further, the preamble may refer to any pair of identical IQ sample sequences where the IQ sample sequences might be separated in time. Furthermore, the location and length of the sequences should be known at the node <NUM>. For example, the sequences can include cyclic prefix in OFDM systems like LTE, <NUM> new radios, Wi-Fi (<NUM>. <NUM>), and the like.

The preamble includes the preamble pairs for example, P1, P2, P3, P4, P5, P6, P7 and P8 where the a set of preamble pair are identical i.e., P1 is identical to P2, P3 is identical to P6, P5 is identical to P8 and P7 is identical to P4. In an embodiment, the set of preambles appear in preamble pairs and each preamble in the pair is identical to at least one other preamble in the preamble structure. The identical preambles of the preamble structure enable cancellation of the received signal while determining the self-interference channel estimates. Further, each preamble is a complex number with a specific value accorded to each preamble.

The time domain packet structure <NUM> of the signal received by the node <NUM> includes a preamble <NUM> and a data block <NUM>. The preamble <NUM> includes sequential preamble pairs within which individual preambles are identical to at least one other preamble in the preamble structure. The data block <NUM> includes the data to be transmitted by the first UE 102a to the node <NUM>. The preamble <NUM> is used by the node <NUM> to extract the data from the data block <NUM> of the time domain packet structure <NUM> of the signal received by the node <NUM>.

<FIG> illustrates a process of obtaining the composite signal using the received signal and the self-interference signal over air, according to the embodiments as disclosed herein.

Referring to the <FIG>, the composite signal is obtained by adding the received signal to the self-interference signal. The received signal includes the data along with the preamble <NUM>. In an example consider that the preamble includes the preamble pairs for example, P1, P2, P3, P4, P5, P6, P7 and P8 where the consecutive preamble pairs are identical i.e., P1 is identical to P2, P3 is identical to P4, P5 is identical to P6 and P7 is identical to P8. In another example consider that the a preamble in the preamble pair is identical to one another preamble in the preamble structure i.e., P1 is identical to P2, P3 is identical to P6, P5 is identical to P8 and P7 is identical to P4.

The self-interference signal is denoted as SI in the time domain packet structure. SI1, SI2, SI3 and SI4 correspond to the SI packet during P1, P2, P3 and P4 respectively.

CS1, CS2, CS3, CS4 denotes the composite signal that is obtained at the transceiver <NUM> of the node <NUM>. Therefore the value of CS1, CS2, CS3 and CS4 are computed as follows: <MAT> <MAT> <MAT> and <MAT>.

<FIG> is a flowchart <NUM> illustrating a method for decoding the received signal by the node <NUM> in the in-band full-duplex wireless communication system, according to the embodiments as disclosed herein.

Referring to the <FIG>, at step <NUM>, the method includes receiving the signal from the first UE 102a. The received signal includes a set of preambles in which each preamble is identical to the at least one preamble in the preamble structure.

At step <NUM>, the method includes obtaining the composite signal including the self-interference signal. The self-interference signal is known at the node as the self-interference is caused by the signal transmitted by the node <NUM> to the second UE 102b.

At step <NUM>, the method includes determining the self-interference channel estimates using the composite signal. The self interference channel estimates are obtained by determining the difference between consecutive pairs of composite signal components in the composite signal. Further, the received signal is eliminated from the composite signal.

At step <NUM>, the method includes decoding the received signal by eliminating the self-interference signal from the received signal. The elimination of the self-interference signal is based on the self-interference channel estimate. The self-interference channel estimates are used to eliminate the self-interference signal which interferes with the decoding of the received signal. Hence, a better quality of the received signal is obtained and the data decoded accordingly.

The various actions, acts, blocks, steps, or the like in the method may be performed in the order presented, in a different order or simultaneously.

<FIG> is a block diagram illustrating various elements of the UE <NUM>, according to the embodiments as disclosed herein.

Referring to the <FIG>, the UE <NUM> can include a transceiver <NUM>, an encoder/decoder <NUM>, a processor <NUM> and a memory <NUM>.

In an embodiment, the transceiver <NUM> may be configured to transmit the signal to the node <NUM>. The signal to be transmitted includes the encoded data along with a preamble structure <NUM>. The transceiver <NUM> can also be configured to receive the signal sent by the node <NUM>.

In an embodiment, the encoder <NUM> can be configured to provide the preamble structure <NUM> to the signal to be transmitted to the node <NUM>. The preamble structure <NUM> includes a set of preambles in which each preamble is identical to the at least one preamble in the preamble structure. Further, the preamble <NUM> is used for self-interference cancellation by the node <NUM>.

In an embodiment, the processor <NUM> can be configured to interact with the hardware elements such as the transceiver <NUM>, the encoder <NUM> and the memory <NUM> in the UE <NUM> to provide symmetric preamble structure <NUM> to the signal to be transmitted to the node <NUM>.

<FIG> is a flowchart <NUM> illustrating a method of transmitting the signal by the UE <NUM> in the in-band full-duplex wireless communication system, according to the embodiments as disclosed herein.

Referring to the <FIG>, at step <NUM>, the method includes providing the preamble structure to the signal to be transmitted and encode the data by the first UE 102a. The signal to be transmitted includes a set of preambles. Further, each preamble is identical to the at least one preamble in the preamble structure.

At step <NUM>, the method includes transmitting the encoded data by the first UE 102a to the node. The first UE 102a sends the signal to be transmitted to the node through the RF channel. The signal to be transmitted can be a RF analog signal or a baseband digital signal.

The various actions, acts, blocks, steps, or the like in the method may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention as defined by the appended claims.

<FIG> is an illustration of the self-interference channel estimate, according to the embodiments as disclosed herein.

Referring to the <FIG>, the self-interference channel estimates are obtained by determining the difference between consecutive pairs in the composite signal which eliminates the received signal. The adaptive filter is used to determine the self-interference channel estimates.

The adaptive filter employs active noise control (ANC), also known as noise cancellation or active noise reduction (ANR) to cancel the self interference signal for decoding the received signal. The ANC is a method for reducing a noise signal by the addition of a second signal specifically designed to cancel the noise signal. In the proposed method the noise signal is the self-interference signal and the second signal specifically designed to cancel the noise signal is the received signal which has the preamble <NUM> specifically to cancel the self-interference signal.

Further, the self-interference channel estimates is determined as follows: <MAT> Further, intermediate values are computed which are then used to determine the self-interference channel estimates. <MAT> <MAT> for two preambles being equal i.e., P1=P2 and P1- P2=<NUM> <MAT> <MAT> for P3=P8 and P3- P8=<NUM> in an exemplary preamble structure P1XXXXXXP8. Therefore, the intermediate values computed are used to determine the self-interference channel estimate which has only the self-interference channel components as the received signal components are cancelled out. The elimination of the received signal components from the composite signal provides better channel estimates. It should be noted that the number of samples required for channel estimation is not dependent on the received signal strength.

Claim 1:
A method for decoding a received signal by a node (<NUM>) in a wireless communication system, the method comprising:
receiving (<NUM>), by the node (<NUM>), a signal from a first User Equipment, UE, wherein the received signal includes encoded data and a set of preambles including consecutive preamble pairs consisting of two preambles that are symmetrically identical;
obtaining (<NUM>), by the node (<NUM>), a composite signal comprising a self-interference signal and the received signal, wherein the composite signal is obtained when the received signal is added to the self-interference signal over the air, wherein the self-interference signal is known at the node;
determining, by the node (<NUM>), a difference between the composite signal components that correspond to preambles of a preamble pair;
determining (<NUM>), by the node (<NUM>), self-interference channel estimate using said difference between the composite signal components and an adaptive filter; and
decoding (<NUM>), by the node (<NUM>), the received signal by eliminating the self-interference signal from the received signal based on the self- interference channel estimate.