TECHNICAL FIELD

[0001] The present disclosure relates to the field of modulation and demodulation in a communication system. More particularly, the present disclosure relates to a system and method for employing orthogonal frequency division multiplexing (OFDM) scheme in communication systems.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Orthogonal frequency-division multiplexing (OFDM) is a modulation scheme where data is encoded in multiple carrier frequencies by employing a large number of closely spaced orthogonal sub-carrier signals to carry data on several parallel data streams or channels. The OFDM scheme is advantageous over single-carrier scheme as it has ability to cope with severe channel conditions without using complex equalization filters. This is because OFDM uses numerous slowly modulated narrowband signals rather than one rapidly modulated wideband signal.

[0004] In a known OFDM based communication system as shown in FIG. 1A and FIG IB, a sequence of symbols (102), i.e. data to be transmitted to a receiver, can be converted from a serial form of data to parallel symbols by S/P block (104). These N parallel symbols (106) can be processed by N point IFFT (108) to a get an information sequence (1 10). The information sequence (1 10) can further be transformed by parallel to serial P/S block (1 12) to get a transformed information sequence (1 14), interchangeably called an OFDM codeword. If the transmitter generates OFDM codeword, the receiver performs the reverse operation.

[0005] FIG. IB illustrates sequence of operations performed by different components at receiver side. On receiving the symbols, symbols are converted to parallel form from serial form by an S/P block (154) to generate the OFDM sequencey = (Υο, Υχ, ... , y _N--1 )(156). The OFDM sequence (156) can be processed by N point FFT (158) to get the estimated information sequence. Further, a detection scheme (162) can be used to determine error present in the estimated information sequence (160). Error present in the estimated information sequence Y (160) can be corrected based on the error correction and corrected information sequence can be obtained (164). The symbols (164) can be passed through P/S block (166) to obtain serial symbols (168).

[0006] Thus, Fast Fourier Transform or other variants employed in OFDM scheme use N-by-N (i.e. NxN) FFT operations, where input symbols are N in number, and output samples are N in number, and these N samples are transmitted into a channel, which makes the process slow and uses more number of components.

[0007] Therefore, there is a need in the art to develop an OFDM scheme that requires transmission of fewer samples using less number of components and still be able to detect the transmitted sample of length N. Transmission of fewer samples is advantageous in a way that it makes the communication system much faster as compared with the conventional systems. Using less number of components enables the system to work on low power and makes the system cost effective.

[0008] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0009] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0010] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims. OBJECT OF THE INVENTION

[0011] An object of the present disclosure is to provide a system and method for employing orthogonal frequency division multiplexing (OFDM) scheme in communication systems.

[0012] An object of the present disclosure is to provide a system and method for employing OFDM scheme that requires transmission of less number of samples as compared to conventional OFDM techniques.

[0013] An object of the present disclosure is to provide a system and method for employing OFDM scheme that requires performing less number of operations using less number of components as compared to conventional OFDM techniques.

[0014] An object of the present disclosure is to provide a system and method for employing OFDM scheme that is faster as compared to conventional OFDM techniques.

[0015] An object of the present disclosure is to provide a system and method for employing OFDM scheme that consumes less power as compared to conventional OFDM techniques.

[0016] An object of the present disclosure is to provide a system and method for employing OFDM scheme that is cost effective.

SUMMARY

[0017] Embodiments of the present disclosure relate to systems and methods for employing orthogonal frequency division multiplexing (OFDM) scheme in communication systems. The proposed system requires transmission of only two complex samples, thus, making the system fast and cost-effective.

[0018] An embodiment of the present disclosure provides a system employing an OFDM scheme for transmission of a sequence of symbols, comprising: a transmitter and a receiver, wherein the transmitter and the receiver are coupled through a transmission channel, and wherein the transmitter comprises a Goertzel coefficient computing module enabled to use Goertzel' s algorithm to generate an OFDM codeword.

[0019] In an aspect of the proposed system, the OFDM codeword comprises two complex numbers.

[0020] In an aspect of the proposed system, the receiver comprises one or more threshold detectors for decoding, detecting and/or estimating the sequence of symbols. [0021] In an embodiment, the proposed system uses three threshold detectors, one for each dimension of a three-dimension plane for decoding, detecting and/or estimating the sequence of symbols.

[0022] An aspect of the present disclosure uses a transmitter that further comprises a source coding module enabled to remove redundancy in the OFDM codeword.

[0023] Another embodiment of the present disclosure provides a method for employing an OFDM scheme for transmission of a sequence of symbols, the method comprising the steps ofgenerating an OFDM codeword by using Goertzel coefficient computing module;transmitting the OFDM codeword through a transmission channel; and receiving the OFDM codeword using one or more threshold detectors, wherein the receiving includes decoding, detecting and/or estimating the sequence of symbols.

[0024] In an aspect, the proposed method further comprises a step of performing source coding to remove redundancy in the OFDM codeword. In an exemplary aspect, the source coding is performed after channel coding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the Figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0026] FIG. 1A illustrates exemplary functional blocks of a conventional transmitter configured to perform OFDM coded transmission.

[0027] FIG. IB illustrates an exemplary functional blocks of a conventional receiver configured to receive and generate information sequence.

[0028] FIG. 2 illustrates exemplary functional block of a transmitter configured to perform transmission using an OFDM scheme in accordance with an embodiment of the present disclosure.

[0029] FIG. 3 illustrates an exemplary flow diagram for employing an OFDM scheme for transmission in accordance with an embodiment of the present disclosure.

[0030] FIG. 4 illustrates exemplary functional block of a transmitter that uses source coding module to remove redundancy in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0031] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0032] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0033] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0034] Embodiments of the present disclosure relates to a systems and methods for employing orthogonal frequency division multiplexing (OFDM) scheme in communication systems. The proposed system requires the transmission of only two complex samples, thus, making the system fast and cost-effective.

[0035] An embodiment of the present disclosure provides, a system employing an OFDM scheme for transmission of a sequence of symbols, comprising: a transmitter and a receiver, wherein the transmitter and the receiver are coupled through a transmission channel, and wherein the transmitter comprises a Goertzel coefficient computing module enabled to use Goertzel' s algorithm to generate an OFDM codeword.

[0036] In an aspect of the proposed system, the OFDM codeword comprises two complex numbers.

[0037] In an aspect of the proposed system, the receiver comprises one or more threshold detectors for decoding, detecting and/or estimating the sequence of symbols.

[0038] In an embodiment, the proposed system uses three threshold detectors, one for each dimension of a three-dimension plane for decoding, detecting and/or estimating the sequence of symbols. [0039] An aspect of the present disclosure uses a transmitter, which further comprises a source coding module enabled to remove redundancy in the OFDM codeword.

[0040] Another embodiment of the present disclosure provides, a method for employing an OFDM scheme for transmission of a sequence of symbols, the method comprising the steps of: generating an OFDM codeword by using Goertzel coefficient computing module; transmitting the OFDM codeword through a transmission channel; and receiving the OFDM codeword using one or more threshold detectors, wherein the receiving includes decoding, detecting and/or estimating the sequence of symbols.

[0041] In an aspect, the proposed method further comprises a step of source coding, performed to remove redundancy in the OFDM codeword. In an exemplary aspect, the source coding is performed after channel coding.

[0042] FIG. 1A illustrates exemplary functional blocks of a conventional transmitter configured to perform OFDM coded transmission. FIG. IB illustrates an exemplary functional blocks of a conventional receiver configured to receive and generate information sequence.

[0043] Conventional OFDM based communication system can use components as shown in FIG. 1A and FIG IB. FIG. 1A shows sequence of operations performed by different components at transmitter side. Data to be transmitted to the receiver can be shown as sequence of symbols(102). The sequence of symbols (102) can be converted from serial form to parallel symbols C= (C ₀ , C _lt C _N--1 )(106)by Serial to Parallel (S/P) block (104). These N parallel symbols C= (C ₀ , _lt C _N _ ₁ )(106)can be processed by N point Inverse Fast Fourier Transform(IFFT)(108) to a get an information sequence V= (V _Q , ^, ... , V _n _ ₁ )(110) that can further be transformed by parallel to serial (P/S) block (112) to get a transformed information sequence (114), also referred interchangeably as OFDM code word for sending it over a suitable transmission channel to a receiver. The receiver performs a reverse operation. FIG. IB illustrates sequence of operations performed by different components at receiver side. On receiving the symbols, the OFDM codeword can be send to a serial to parallel (S/P) block (154) to generate the OFDM sequencey = (y ₀ , y _lt ... , y _N--1 )(156). The OFDM sequence(156) can be processed by N point Fast Fourier Transform (FFT)(158) to get the estimated information sequence Y = (Y ₀ , Y ₁₍ Y _N--1 )(160). Further, a detection scheme (162) can be used to determine error present in the estimated information sequence (160). Error present in the estimated information sequence Y (160) can be corrected based on the error correction and corrected information sequence can be obtained (164). The symbols (164) can be passed from parallel to serial (P/S) (166) to obtain serial symbols (168).

[0044] It is to be appreciated that in a conventional OFDM scheme, a band of baseband frequency can be divided into multiple channels, say N number of channels, such that the centre frequency of each channel is harmonic to the centre frequency of the first channel, i.e. the fundamental frequency. Each of the harmonics is called as sub-carrier. It can be verified that sinusoid of one sub-carrier frequency is orthogonal to sinusoid of another sub-carrier frequency. This orthogonality enables simple equalization at the receiver. Data can be converted into N parallel streams and symbol in each stream can modulate exactly one of the N sub-carriers. N such symbols will modulate N sub-carriers simultaneously, for exactly N symbol duration, and combined or added to get an analog or continuous wave signal that has exactly N sub-carriers as its frequency components. At the receiver, reverse operation can be performed. Further, in discrete time domain, such OFDM systems can be implemented using N-by-N DFT (or FFT) and N-by-N IDFT (or IFFT) operations.

[0045] It is further to be appreciated that the conventional techniques require the transmission of N number of samples, consequently, this makes the process slow and uses more number of components that require high cost and power. It is to be appreciated that the present disclosure, discloses an invention that requires only two complex samples to be transmitted thus, making the OFDM scheme fast and more cost-effective.

[0046] FIG. 2 illustrates exemplary functional block of a transmitter configured to perform transmission using an OFDM scheme in accordance with an embodiment of the present disclosure. As shown in FIG. 2, a sequence of symbols C= (C ₀ , _lt ... ^ _Ν--1 ) (204), corresponding to the data to be transmitted to a receiver can be processed using Goertzel coefficient computing module(202). The said module uses Goertzel' s algorithm to transform the symbols C= (C ₀ , _lt ^-i) into two complex numbers or two complex symbols V=(v(0), v(l)) (206) for sending it over a suitable transmission channel to a receiver. The two complex numbers or two complex symbols obtained are also referred interchangeably as OFDM codeword (206).

[0047] It is to be appreciated that FFT or conventional methods of employing OFDM scheme requires N-by-N (i.e. NxN) FFT operations where the input symbols are N in number and output samples are N in number. Hence, N output samples are to be transmitted into the channel. On the contrary, the present disclosure uses a technique, i.e. Goertzel' s algorithm which enables transmission of only two complex samples that can be represented as X= A+iB and Y= C+0*i =C. Thus, the two complex samples can more particularly be represented as three real samples i.e. A, B and C. The invention as discussed in the present disclosed is advantageous over conventional techniques as the transmission on only three real samples allows to retain the symbols without any loss of information over a Gaussian Noisy Channel.

[0048] In various embodiments of the present disclosure, the transmission channel can be a wired or a wireless channel that provides a connection between the transmitter and the receiver from which the data can be transmitted.

[0049] In an aspect, at the receiver, the received OFDM codeword or two complex symbols can be passed through a threshold detector. The threshold detector is enabled to decode, detect and estimate the sequence of symbols from the OFDM codeword.

[0050] In an aspect, the received OFDM codeword is passed through three threshold detectors, one for each dimension. The three threshold detectors can uniquely decode the sequence of symbols as each OFDM codeword corresponds to one point in a three-dimension space.

[0051] FIG. 3 illustrates an exemplary flow diagram for employing an OFDM scheme for transmission in accordance with an embodiment of the present disclosure. In a method for employing an OFDM scheme for transmission of a sequence of symbols as illustrated in FIG. 3, the method at step (302), generates an OFDM codeword by using Goertzel coefficient computing module. The Goertzel coefficient computing module uses Goertel's algorithm to compute two complex symbols or OFDM codeword as discussed in above mentioned aspect.

[0052] At step (304), the OFDM code word is transmitted through a transmission channel. The transmission channel can be a wired or a wireless communication channel to transmit data to a receiver.

[0053] Further, at step (306), the OFDM codeword is received using one or more threshold detectors. The receiving includes decoding, detecting and/or estimating the sequence of symbols. In an aspect, the receiving can be performed using three threshold detectors, one for each dimension. The three threshold detectors can uniquely decode the sequence of symbols as each OFDM codeword corresponds to one point in a three-dimension space.

[0054] To provide clarity, the above mentioned aspects of the present invention can be explained by way of the following example. If N=5, then FFT would have generated (2 ^A N=2 ^A 5=32) samples. First three samples and their corresponding complex output samples after Binary phase-shift keying (BPSK) modulation along with generated OFDM code word are shown below: Sample BPSK codeword OFDM codeword

(0 0 0 0 0) (- 5, 0, 0, 0, 0) (- 5, 0)

(0 0 0 0 1) (- 3,

0.6180340 + 1.902113i,

(- 3,

-1. 6180340 + 1.1755705i,

0.6180340 + 1.902113i) -1. 6180340 - 1.1755705i,

0.6180340 + 1.902113.)

(0 0 01 0) (-3,

-1. 6180340 + 1.1755705i,

(-3,

0.6180340 - 1.902113i,

-1. 6180340 + 1.1755705i) 0.6180340 + 1.902113i,

-1. 6180340 + 1.1755705i )

Table-1 Generation of OFDM codeword for N=5

[0055] It is to be appreciated that, for N= 5, for example, a sample (0 0 0 0 1), the conventional OFDM techniques would require to transmit 5 samples (- 3, 0.6180340 + 1.902113i, -1. 6180340 + 1.1755705i, -1. 6180340 - 1.1755705i, 0.6180340 + 1.902113i). However, the aspects of the present invention using Goertzel's algorithm would require only first two samples (- 3, 0.6180340 + 1.902113i) to be transmitted through the channel. These samples can further be represented as,

X= A+iB = 0.6180340 + 1.902113i and

Y= C+0*i =C= - 3

[0056] Thus, A= 0.6180340, B = 1.902113 and C = -3. Hence, 3 real samples can be obtained from each sample that is required to be transmitted. These two complex samples need not be consecutive as in this example or can be any two samples out of the 5 samples as long as set of all two complex (or three real) samples are unique, an obvious requirement of any encoding and decoding operation. And based on the description presented herewith, all such embodiments fall within the scope of the instant invention.

[0057] Further, at the receiver, the received samples can be passed through three threshold detectors, one for each dimension. As the three real samples are different and non- overlapping, all the three real values become uniquely decodable. Therefore, only three threshold detectors are required for correct estimation of the transmitted samples. [0058] FIG. 4 illustrates exemplary functional block of a transmitter that uses source coding module to remove redundancy in accordance with an embodiment of the present disclosure.

[0059] It is to be appreciated that source coding reduces redundancy in the source, and represents the source with fewer bits that carry more information. Thus as illustrated in FIG. 4, the OFDM codeword (v(0),v(l)) (408) is obtained by using Goertzel coefficient computing module (402)as discussed in above mentioned aspects. The obtained OFDM codeword (408) is passed through source coding module (404) to perform source coding in order to remove redundancy.

[0060] It is further to be appreciated that, channel coding is used to correct errors within transmitted message over the channel. Thus, channel coding adds redundancy to counter or reduce or correct errors due to channel noise. Generally, source coding is performed before channel coding. However, in an exemplary embodiment of the present disclosure, source coding can be performed after channel coding as there is lot of redundancy in OFDM output samples. Further in an exemplary aspect, encoding can be performed by using one set of source plus channel encoder before Goertzel coefficient computing module and another set of source plus channel encoder after Goertzel coefficient computing module. Similarly, reverse technique can be applied at the receiver.

[0061] The above mentioned embodiments, can be explained by way of an example, for example,N=2, then FFT would have generated (2 ^A N=2 ^A 2=4) samples. The samples and their corresponding codeword after Binary phase-shift keying (BPSK) modulation, OFDM codeword along with OFDM code word generated after source coding are shown below:

Table-2 Generation of OFDM codeword for N=2

[0062] Say for example, if it is required to transmit following sequence of Binary codeword:

(0, 0), (0, 1), (1, 0), (1, 1), (0, 1), (1, 0), (0, 0), (1, 1), (1, 1) [0063] The system incorporating OFDM scheme would transmit the following OFDM codeword:

(-2, 0), (0, -2), (0, 2), (2, 0), (0, -2), (0, 2), (-2, 0), (2, 0), (2, 0)

[0064] However, after performing source coding the following samples would be transmitted:

(-2), (0, -2), (0, 2), (2), (0, -2), (0, 2), (-2), (2), (2)

[0065] This above mentioned technique is advantageous in a way that it reduces number of samples required to be transferred and thus, considerably reduces time to transmit the information.

ADVANTAGE OF THE INVENTION

[0066] The present disclosure provides a system and method for employing orthogonal frequency division multiplexing (OFDM) scheme in communication systems.

[0067] The present disclosure provides a system and method for employing OFDM scheme that requires transmission of less number of samples as compared to conventional OFDM techniques.

[0068] The present disclosure provides a system and method for employing OFDM scheme that requires performing less number of operations using less number of components as compared to conventional OFDM techniques.

[0069] The present disclosure provides a system and method for employing OFDM scheme that is faster as compared to conventional OFDM techniques.

[0070] The present disclosure provides a system and method for employing OFDM scheme that is consumes less power as compared to conventional OFDM techniques.

[0071] The present disclosure provides a system and method for employing OFDM scheme that is cost effective.