Description:FIELD OF THE INVENTION
[0001] Embodiments of the present disclosure relates to index modulation based on pilot location for an Orthogonal time frequency space (OTFS)- based dual function radar and communication (DFRC) system to circumvent the complexity involved in conventional index modulation schemes.

BACKGROUND
[0002] Generally, Orthogonal Frequency Division Multiplexing (OFDM) is a widely used spectrum-efficient scheme and known to be a promising technology for fifth generation (5G) communication and beyond 5G due to its high data rate communication and its effectiveness in the mitigation of multi-path effects. Dual -function radar communication (DFRC) systems are in high demand for systems for applications, especially for connected autonomous vehicle networks (AVNs) to provide spectrum-efficient radar and information conveying capability utilizing common resources. To improve spectrum efficiency (SE) further, index modulation (IM) is a technique that may convey more information by indexing antennas for multiple-input multiple output (MIMO), subcarrier for orthogonal frequency division multiplexing (OFDM), and reflecting elements for intelligent reflecting surface (IRS) assisted communication system. However, estimating active antennas for the MIMO system, active subcarriers in OFDM, and an active reflecting element for the IRS system are challenging tasks especially for time-varying channels. Orthogonal time frequency space (OTFS) has emerged to provide spectacular performance for the time-varying channels, however, for rapid time-varying channels where the channel gets changed within the frame or after one or two frames and this become a challenge for estimation of indices in the spectrum.

SUMMARY
[0003] Embodiments of the present disclosure relate to a method and system for transmitting data over a communication network, and especially governed at the transmitter end. Embodiments of the present disclosure relate to receiving information bits sequence from an information source, wherein the information bits sequence is associated with data being transmitted over a communication network, from a transmitter to a receiver of the data. Embodiments of the present disclosure further relate to splitting the information bits received into two streams, the first stream including information symbols and the second stream including pilot symbols. Embodiments of the present disclosure further relate to selecting location of pilot symbols in an OTFS grid associated with the second stream, i.e. the pilot symbols. Embodiments of the present disclosure further relate to inserting pilot symbols at the selected location in the OTFS grid associated with the second stream. Embodiment of the present disclosure further relates to combining information symbols from the first stream and pilot symbols from the second stream forming the complete grid. Embodiment of the present disclosure further related to converting the symbols to a time domain and transmitting the signals to a destination over a communication network. Other embodiments with respect to the present disclosure are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description is described with reference to the accompanying figures. Features, aspects, and advantages of the subject matter of the present disclosure will be better understood with regard to the following description and the accompanying drawings. The figures are intended to be illustrative, not limiting, and are generally described in context of the embodiments, and it should be understood that it is not intended to limit the scope of the disclosure to these particular embodiments. In the figures, the same numbers may be used throughout the drawings to reference features and components. In order that the present disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages.
[0005] Figure 1 illustrates an exemplary block diagram of a Pilot Index Modulation Orthogonal time frequency space based dual function radar system in accordance with embodiments of the present disclosure.
[0006] Figure 2 illustrates an exemplary method for receiving and converting information into bits to be transmitted over a communication network in accordance with the embodiments of the present disclosure
[0007] Figure 3 illustrates an exemplary method of processing the information bit sequence in accordance with the embodiments of the present disclosure.
[0008] Figure 4 illustrates an exemplary graph of the spectral efficiency versus the number of pilot indices in accordance with the embodiments of the present disclosure.
[0009] Figure 5 illustrates an exemplary graph of the BER versus the SNR in accordance with the embodiments of the present disclosure.
[0010] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical elements. The figures as disclosed herein are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings are meant to only be provided as examples and/or implementations consistent with the description, and the description may not be limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTION
[0011] The following describes technical solutions in exemplary embodiments of the subject matter of the present disclosure with reference to the accompanying drawings. In this application as disclosed herein, “at least one” means one or more, and “a plurality of” means two or more. The term “and/or” describes an association relationship for describing associated objects and represents that three relationships may exist. For example, A and/or B may represent the following cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. The character “/” usually indicates an “or” relationship between the associated objects. “At least one item (piece) of the following” or a similar expression thereof means any combination of the items, including any combination of singular items (piece) or plural items (pieces). For example, at least one item (piece) of a, b, or c may represent a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c each may be singular or plural.
[0012] It should be noted that in this application articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”. Throughout this specification defined above, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably. In the structural formulae given herein and throughout the present disclosure, the following terms have been indicated meaning, unless specifically stated otherwise.
[0013] Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure. The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.
[0014] It should be noted that in this application, the term such as “example” or "for example" or “exemplary” is used to represent giving an example, an illustration, or descriptions. Any embodiment or design scheme described as an “example” or “for example” in this application should not be explained as being more preferable or having more advantages than another embodiment or design scheme. Exactly, use of the word such as “example” or “for example” is intended to present a related concept in only a specific manner.
[0015] In the embodiments of the present subject matter it should be understood that “B corresponding to A” indicates that B is associated with A, and B can be determined based on A. However, it should be further understood that determining B based on A does not mean that B is determined based on only A. B may alternatively be determined based on A and/or other information.
[0016] In the embodiments of this present disclosure, “a plurality of” means two or more than two. Descriptions such as ‘first”, “second” in the embodiments of this application are merely used for indicating and distinguishing between described objects, do not show a sequence, do not indicate a specific limitation on a quantity of devices in the embodiments of this application, and do not constitute any limitation on the embodiments of this application.
[0017] Exemplary embodiments of the present disclosure related to a method and a system for transmitting data over a communication network, between a transmitter and a receiver over a communication channel. An embodiment may include receiving information bits sequence from an information source. In an embodiment, the information bit sequence essentially includes content or data that has been converted into bits for transmission at a transmitter. In an embodiment, the information bits sequence may be being transmitted over a communication network, which may include a wired network, a wireless network, an optical network or a combination thereof. In an embodiment, essentially the communication relates to 4G, 5G, 6G and/or higher technologies..
[0018] A further embodiment may include splitting the information bits related to the content/data into two streams. In an exemplary embodiment, the information bits include at least two streams. It should be obvious to a person of ordinary skill in the art that as technology progresses and advances, there could be more than two streams in the representation, but the same methodology may be implemented, and all such variations fall within the scope of the present disclosure. In an embodiment, a first stream may include information symbols and a second stream may include pilot symbols. A further embodiment may include selecting a location of pilot symbols in an OTFS grid associated with the second stream. A further embodiment may include inserting the pilot symbols at selected location in the OTFS grid associated with the second stream. Yet a further embodiment may include combining the information symbols from the first stream and pilot symbols from the second stream. Yet a further embodiment may include converting the symbols (reference to symbols in this disclosure means both information symbols and pilot symbols) to a time domain and transmitting the signals from a source (the transmitter) to a destination (the receiver) over a communication network.
[0019] A further embodiment may include an input from the source, wherein the input is converted to an analog signal by a transducer. In a further embodiment e the analog signal may be preferably converted to a digital signal by an ADC. In a further embodiment, the digital signal is received as the information bit sequence at the transmitter. In a further embodiment the information bits are split into an information symbol stream (first stream) and a pilot symbol stream (second stream). In a further embodiment the first stream may include conventional mapping bits. In a further embodiment the second stream, wherein may include pilot sub-grid index selection bits. In a further embodiment, depending on the second stream bits, the pilot sub grid selector and pilot insertor may be configured to select location of the pilot symbols and insert them in the OTFS grid.
[0020] In a further embodiment may information symbols from the symbol mapper and pilot symbols inserted at the selected location in the OTFS grid may be combined to form a complete grid. In a further embodiment, symbols in the OTFS grid undergo an OTFS modulation, wherein the symbols may now be in a delay Doppler domain. In a further embodiment, the symbols in the delay Doppler domain undergo a ISFFT transformation and includes converting the delay Doppler domain symbols into time frequency domain symbols.
[0021] In a further embodiment the time frequency domain symbols being may be converted to a time domain signal by performing a Heisenberg transformation on the time frequency domain symbols. In a further embodiment an RF front end may be configured to amplify the signal and transmits the signal from the transmitter (source) to a receiver (destination) over a wireless network, preferably higher forms of wireless network beyond 4G. In a further embodiment a transmitter system may be configured to perform the method as disclosed above, in the claims and in the description of the present disclosure, and transmit the information sequence from the transmitter to a receiver (not shown in the Figure). At the receiver end, an inverse process is performed to recover the information bit sequence and the information (signal), which makes communication between the transmitter and the receiver efficient and cost effective.
[0022] Reference is now made to Figure 1, which illustrates an exemplary block diagram of a Pilot Index Modulation Orthogonal time frequency space based dual function radar system in accordance with embodiments of the present disclosure. Exemplary Figure 1 represents a transmitter that processed information and transmits the information (also referred to as content or data) to a receiver. The transmission receives information bit sequence as input at information bit sequence 110. The information bits originate from an information source, which can be an audio source or a video source, a voice source or any other source from where data can originate. A transducer converts information received into the analog signal, preferably an analog electrical signal. The analog electrical signal is then converted to an information bit sequence (digital signal) using an analog to digital converter.
[0023] Once the input signal is converted to an information bit sequence, the information bit sequence is input to a bit splitter 120. The bit splitter 120 splits the bit sequence b coming into the bit splitter 120 into two streams, namely data streams bits bd and indexing stream bits bI. The data stream bits bd are input to a symbol mapper 130 directly from the bit splitter 120. The data stream bits bd are inputted to conventional communication chain for symbol mapper like quadrature amplitude modulation (QAM). The indexing stream bits bI are provided as inputs to perform indexing mechanism. Depending on the bit stream bI the location of pilot pulses Pi , Pj …, etc., is selected in the N x M sized OTFS grid. Essentially the symbol mapper 120 maps the bits into symbols. Pilot sub grid selector 135 is configured to generate index of pilot location in the OTFS grid depending on the indexing stream bits bI.
[0024] OTFS grid formation 140 is where the pilot symbols are inserted at the selected location in the OTFS grid based on bI and it is surrounded by zero padding (ZP) which depends on the typical maximum value of delay and Doppler value of channel paths. The remaining grid locations are filled by the data symbols xd, which is an output from the output of symbol mapper 130. Therefore, OTFS grid is formed by multiplexing data symbols xd, pilot pulses Pi’s and the zero padding ZP. Post this the OTFS modulation 150 convers the delay Doppler domain symbols x[k,l] into time domain such that they symbols may be transmitted. Once the signal is converted to the time domain at the OTFS modulation 150, performing certain transformations as disclosed previously, the RF front end 160 at the transmitter is configured to amplify the signal, which can then be transmitted over the communication network from the transmitter to the receiver.
[0025] Reference is now made to Figure 2, which illustrates an exemplary method for receiving and converting information into bits to be transmitted over a communication network in accordance with the embodiments of the present disclosure. In step 210 signals are received at the transmitter, wherein the signal essentially may be a voice signal, data signal, audio signal, video signal etc., wherein the signal received is an antilog signal. In step 220 the analog signal is converted into a digital signal using for example an ADC or any other means for converting an antilog signal to a digital signal, essentially the digital signal including bits and the bits being provided as input in the form of information bits sequence.
[0026] Reference is now made to Figure 3, which illustrates an exemplary method of processing the information bit sequence in accordance with the embodiments of the present disclosure. In step 310 the information bit sequence is split into two streams. In step 320 the data bit stream which is provided to a symbol mapper and the indexing bit stream which are sent to a pilot sub-grid index selector and pilot impulse insertor. In step 330 OTFS grid formation is carried out where the pilot symbols are inserted at the selected location in the OTFS grid based on indexing bits bI and it is surrounded by zero padding (ZP) which depends on the typical maximum value of delay and Doppler value of channel paths. The remaining grid locations are filled by the data symbols xd, which is an output from the output of symbol mapper. Therefore, OTFS grid is formed by multiplexing data symbols xd, pilot pulses Pi’s and the zero padding ZP. In step 340 the OTFS modulation convers the delay Doppler domain symbols x[k,l] into time domain such that they symbols may be transmitted by performing appropriate transformations on the delay doppler domain symbols. In step 350, once the signal is converted to the time domain signal is amplified, which can then be transmitted over the communication network from the transmitter to the receiver.
[0027] Reference is now made to Figure 4, which illustrates an exemplary graph of the spectral efficiency versus the number of pilot indices in accordance with the embodiments of the present disclosure. The flat line indicates without any index modulation. The dotted line indicates index modulation for N=M=32, which shown a sharp rinse and then a sharp fall, and the solid line indicates index modulation for M=N=64, wherein there is a rise, the curve remains a relatively flat and then a fall is notices. The number of pilot indices in the case of the dotted line is less than 50, whereas the number of pilot indices in the case of the solid line varies from 0 to about 150. As illustrated in the Figure, for fixed values of M and N, the spectral efficiency (SE) increases with the number of pilot indices (r) to a certain point then again, it decreases. So, the best choice is r = Kt=2. However, for small and moderate OTFS grid size, inserting Kt=2 pilots surrounded by the ZP in high delay and Doppler shift scenarios becomes challenging due to high pilot overhead. The solution here is to choose n pilots somewhere in between 1 and Kt=2. From the figure, it maty be observed that the SE graph is highly steep till certain values of r, which allow to select r much lesser than Kt=2 without losing much SE. The figure also depicts that SE is more for higher values of M and N.
[0028] Reference is now made to Figure 5, which illustrates an exemplary graph of the BER versus the SNR in accordance with the embodiments of the present disclosure. The dotted line indicates index modulation at M=N=64 and r =6; and the solid line represent index modulation of N=M=16, and r =1. Both start off at almost the same BER and when the SNR is around 5 dB, the separation is notices which increases as the SNR increases. The BER plot show that for higher values of M, N, and corresponding high values of total pilot indices selected, the performance is better than the lower values of pilot indices. However, the number of pilot indices and BER performance has a trade-off since higher values of r increases the pilot overhead. It has also been shown that at a high SNR regime, small pilot indexing (r = 2) provides better BER performance compared to no pilot indexing (r = 1).
[0029] Although the present disclosure has been described with reference to several preferred embodiments, it should be understood that the present disclosure is not limited to the preferred embodiments disclosed here. Embodiments of the present disclosure are intended to cover various modifications and equivalent arrangements within the spirit and scope of the appended claims. Although the foregoing disclosure has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practised within the scope of the appended claims. Examples of the present disclosure have been described in language specific to structural features and/or methods. It should be noted that there are many alternative ways of implementing both the process and apparatus of the present invention. Accordingly, embodiments of the present disclosure are to be considered illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope and equivalents of the appended claims. It should be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained as examples of the present disclosure
, Claims:1. A method for transmitting data over a communication network, the method comprising:
- receiving information bits sequence from an information source, wherein the information bits sequence is associated with data being transmitted over a communication network;
- splitting the information bits into two streams, the first stream comprising information symbols and the second stream comprising pilot symbols;
- selecting location of pilot symbols in an OFTS grid associated with the second stream;
- inserting pilot symbols at the selected location in the OTFS grid associated with the second stream;
- combining information symbols from the first stream and pilot symbols from the second stream;
- converting the symbols to a time domain and transmitting the signals to a destination over a communication network.

2. The method as claimed in claim 1, wherein an input from the source is converted to an analog signal by a transducer.

3. The method as claimed in claim 1, wherein the analog signal is converted to a digital signal by an ADC, and the digital signal is received as the information bit sequence.

4. The method as claimed in claim 1, wherein the first stream comprises conventional mapping bits.

5. The method as claimed in claim 1, wherein the second stream comprises pilot sub-grid index selection bits, and depending on the second stream bits, the pilot sub grid selector and pilot insertor configured to select location of the pilot symbols and insert them in the OTFS grid.

6. The method as claimed in claim 1, wherein information symbols from the symbol mapper and pilot symbols inserted at the selected location in the OTFS grid are combined forming a complete grid.

7. The method as claimed in claim 6, wherein symbols in the OTFS grid undergo an OTFS modulation, wherein the symbols are in a delay Doppler domain.

8. The method as claimed in claim 7, wherein the symbols in the delay Doppler domain under a ISFFT transformation converting the delay Doppler domain symbols to time frequency domain symbols.

9. The method as claimed in claim 8, wherein the time frequency domain symbols are converted to a time domain signal by performing a Heisenberg transformation on the time frequency domain symbols.

10. The method as claimed in claim 9, wherein an RF front end amplifies the signal and transmits the signal to a destination over a wireless network.

11. A transmitter in a communication system configured to perform the method as claimed in any of the preceding claims 1 – 10.