Orthogonal frequency division multiplexing and its. Differential spacefrequency modulation and 2ddetection for mimo ofdm abstract. Orthogonal frequency division multiplexing ofdm is a special case of fdm, which is implemented in digital communication systems. Modulation in which the choice of the significant condition for any signal element is dependent on the significant condition for the previous signal element. Data detection and channel estimation of ofdm systems. Differential modulation is a noncoherent modulation technique which is used to solve the uncertainty channel problem. The orthogonal frequency division multiplexing ofdm technique has been proposed for terrestrial digital transmission systems due to its high spectral efficiency, its robustness in different. Performance of differentialphase ofdm systems over selective. Us7016425b1 quasidifferential modulationdemodulation.
In the zpofdm system, we can introduce a new optimization constraint that allows us to control easily 1 the tir quality and improve significantly the system performance as will be shown in section 6. Ofdm with differential index modulation for visible light. Index modulation techniques for nextgeneration wireless. Pdf differential subcarrier index modulation researchgate. A novel differential modulation scheme using fullrate. The zpofdm system uses less energy than cpofdm system. Singleblock differential transmit scheme for frequency selective mimo ofdm systems thanongsak himsoon, weifeng su, and k. Twodimensional differential demodulation for ofdm 581 fig. Most ofdm systems use a fixed modulation scheme over all carriers. Channel shortening techniques for differential encoded ofdm. Ofdm has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, dsl internet access, wireless networks, power line networks, and 4g mobile. What are the advantages of differential phase shift keying.
Differential pulse code modulation dpcm circuit working its. The signal phase follows the high or low state of the previous element. Intercarrier separation 1symbol duration no intercarrier guard bands controlled overlapping of bands. The modulation scheme needs to be cost efficient circuitry should be simple to implement and inexpensive e. Differential neighborhood demodulation of one ofdm subcarrier. Also proposed is a method to correct the amplitude distortion of the symbols on each subcarrier, either from the qam signal itself or from any psk signal, if available. Differential pulse code modulation is a technique of analog to digital signal conversion. Dynamic differential modulation of subcarriers in ofdm charles u. Compared with traditional ofdm with index modulation ofdm im, the proposed scheme decreases the average number of used subcarriers when transmits the same amount of information bits. To our knowledge, however, the performance of differential modulation in lte has not yet been evaluated.
Then rectangular differential coding is invoked during two adjacent subblocks, so that nocoherent detection can be employed for the proposed rd ofdm. In this system, the spreading operation is performed in time domain over the multicarrier frequencies. Design and performance analysis of a multiuser ofdm based. Request pdf differential modulation diversity for ofdm the application of differential modulation diversity dmd to orthogonal frequency division. Abstract in ofdm multiple carriers are used and it provides higher level of spectral efficiency as compared to frequency division multiplexing fdm. Differential modulation article about differential. Ofdm is a combination of modulation and multiplexing. Performance analysis for differential stbc and sfbc mimo. Performance analysis of coherent and noncoherent modulation. Represent each possible signal as a vector in a euclidean space spanned by an orthonormalbasis. Ray liu department of electrical and computer engineering, university of maryland, college park, md 20742. Blind channel shortening in mimoofdm systems using single. Differential spacefrequency modulation for mimoofdm systems via a smooth logical channel weifeng su and k. From basics to adaptive trelliscoded, turboequalised and spacetime coded ofdm, cdma and mccdma systems by l.
Performance analysis for ofdm system using fourier transform and wavelet transform with different modulation techniques qusay jalil, s nagakishore bhavanam. Jun 17, 2019 ofdm is a combination of modulation and multiplexing. Each parallel bit stream is modulated on one of n subcarriers. Ray liu department of electrical and computer engineering, and institute for systems research. Coherent demodulation means that the carrier sinusoid which is modulated by the messa. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. Postfft methods are performed in the frequency domain after ofdm demodulation. The combination of differential spacefrequency modulation dsfm with orthogonal frequencydivision multiplexing ofdm is attractive for transmission over timeand frequencyselective multiple. The input can be an analog signal or a digital signal. Comparison of time and frequency domain single and. An example of differential modulation is delta modulation. Dynamic differential modulation of subcarriers in ofdm. A novel differential modulation scheme using fullrate stbc.
As mentioned for bpsk and qpsk there is an ambiguity of phase if the constellation is rotated by some effect in the communications channel. In the proposed rd ofdm im scheme, n subcarriers are partitioned into g subblocks and index modulation is employed in each subblock first. The orthogonal frequency division multiplexing ofdm technique has been proposed for terrestrial digital transmission systems due to its high spectral eff. The most popular differential unitary modulation technique uses a spacetime block code stbc to improve the performance of differential modulation. One of the main challenges in orthogonal frequency division multiplexing ofdm subcarrier index modulation sim systems is the huge amount of resources required to obtain channel state. Differential coding in the frequency domain, for multicarrier transmission. Ofdm overview 23 ofdm orthogonal frequency division multiplexing the basic principle of ofdm is to split a highrate data stream into a number of lower rate streams that are transmitted simultaneously over a number of subcarriers.
Differential modulation diversity for ofdm request pdf. Multiplexing method of sharing a bandwidth with other independent data channels. It eliminates or alleviates the problem of multipath channel fading effect, low spectrum efficiency, and. Dpsk is a modulation scheme which facilitates non coherent demodulation.
Rectangular differential ofdm with index modulation. Jan 15, 2009 they discount differential modulation, but how does it compare with the simplest channel estimation techniques. Differential space time shift keying for dispersive multi. Organization and notations the remainder of the paper is organized as follows. Introduction to orthogonal frequency division multiplexing. Ndujiuba et al dynamic differential modulation of subcarriers in ofdm figure 1. Pdf ofdm with differential index modulation for visible light.
Novel timefrequency differential spacetime modulation for. Differential will lose due to noise doubling, and leastsquares depends on the quality of the estimate itself. Ofdm ls channel estimation or differential modulation. A guard interval using cyclic prefix is inserted in each ofdm symbol to avoid the intersymbol interference. Data can be encoded in the relative phase of consecutive ofdm symbols interframe modulation or in the relative phase of an ofdm symbol in adjacent subcarriers inframe modulation. In this paper, orthogonal frequency division multiplexing with differential index modulation ofdm dim is proposed for visible light communication. Lowcomplexity differential modulation for high mobility.
Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. Orthogonal frequency division multiplexing ofdm is a multicarrier modulation technique which is robust against multipath fading and very easy to implement in transmitters and receivers using the inverse fast fourier transform and the fast fourier. Section ii provides a brief overview of the considered modulation schemes. Normal modulation techniques like am, pm, fm, bpsk, qpsk, etc, are single carrier modulation techniques, in which the incoming information is modulated over a single carrier. In this paper we consider differential modulation with noncoherent detection for the lte downlink. Lowcomplexity differential modulation for high mobility mimo.
Performance of differentialphase ofdm systems over. The invention proposes the separate processing of the phase and amplitude of multiamplitude digital modulation techniques, such as a qam. Performance evaluation of differential modulation in lte. In this work, we also propose to exploit the first emitted symbol information. Dm ofdm dualmode ofdm df decodeandforward dsm differential spatial modulation dstsk differential spacetime shift keying dpsm dualpolarized spatial modulation eglim ofdm enhanced generalized led index modulation ofdm esm enhanced spatial modulation esmx enhanced spatial multiplexing eu ofdm enhanced unipolar ofdm fbmc filterbank multi. Orthogonal frequency division multiplexing ofdm modulation a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. Introduction to ofdm orthogonal frequency division multiplexing. Indus institute of engineering and technology abstract orthogonal frequency division multiplexing ofdm is a promising technique for high data rate wireless communications because it can combat intersymbol interference caused by. This system adopts the differential modulation in both time and frequency domains, and it is robust for timeand fre quencyselective rayleigh fading channels. Differential phase shift keying dpsk is a common form of phase modulation that conveys data by changing the phase of the carrier wave. Block differentially encoded ofdm with maximum multipath. For the ofdm transmission technique an absolute modulation scheme 64.
Interestingly, we detected a differential modulation of brain mir122 expression level after 4 weeks of highsalt dietary regimen, before stroke occurrence, in the shrsp as compared to the shrsr strain. Design and analysis of an ofdmbased differential chaos shift. Data detection and channel estimation of ofdm systems using. Pdf rectangular differential ofdm with index modulation. Differential spacefrequency modulation for mimo ofdm systems via a smooth logical channel weifeng su and k. Dhoni putra setiawan and huaan zhao graduate school of science and technology, kumamoto university, japan. Then rectangular differential coding is invoked during two adjacent subblocks, so that nocoherent detection can be employed for the proposed rd ofdm im scheme. Ofdm scheme ofdm is a digital multicarrier modulation scheme in which a single high rate data stream is divided into multiple low rate data streams. Performance analysis for ofdm system using fourier transform. Differential pulse code modulation dpcm circuit working. In this technique, the given resource bandwidth is shared among individual modulated data sources. Abstractmultiplemode orthogonal frequency division multiplexing with index modulation mm ofdm im, which transmits an ofdm signal with information bits embedded onto multiple distinguishable signal constellations of the same cardinality and their permutations, is a recently proposed im. Comparision of frequency and time domain differential modulation in.
Pdf adaptive permutation coded differential ofdm system. Differential space time shift keying for dispersive multiuser scenarios using ofdm s. Pdf differential pulse code modulation differential. We use differential modulation based incoherent detection in this thesis for the data detection of ofdm systems. In this paper, differential phase modulation has been chosen to study the performance of ofdm over frequencyselective multipath fading channels. Single highrate bit stream is converted to lowrate n parallel bit streams. They discount differential modulation, but how does it compare with the simplest channel estimation techniques. In this paper we present and study the performance of an ofdmmimo system with unitary. Differential pulsecode modulation dpcm is a signal encoder that uses the baseline of pulsecode modulation pcm but adds some functionalities based on the prediction of the samples of the signal. The phases are differentially modulated and the amplitudes coherently processed. Pdf design and analysis of an ofdmbased differential. Method and apparatus for performing differential modulation over frequency in an orthogonal frequency division multiplexing ofdm communication system ep00307616. Eigendecompositionbased partial fft demodulation for.
Design and analysis of an ofdm based differential chaos shift keying communication system article pdf available in journal of communications 103. In this paper, a multiuser ofdm based chaos shift keying mu ofdm dcsk modulation is presented. Abstract in ofdm multiple carriers are used and it provides higher level of spectral efficiency as compared to. As mentioned for bpsk and qpsk there is an ambiguity of phase if the constellation is rotated by some effect in the communications channel through which the signal passes. In this technology, multiplexing is applied to independent signals, which are subsets of one main signal, and applied to independent channels subcarriers of a bandwidth. This technique samples the analog signal and then quantizes the difference between the sampled value and its predicted value, then encodes the signal to form a digital value. In section iii, the sinr pdf, cdf and mgf is derived. In the interframe differential modulation scheme, only the first ofdm symbol is used for reference and no other symbols are used for pilot insertions. Siso differential communications supposing mpsk modulation scheme. Differential space time shift keying for dispersive multiuser scenarios using ofdm differential space time shift keying for. Differential modulation techniques for a 34 mbits radio channel. In differential phase shift keying dpsk the phase of the modulated signal is shifted relative to the previous signal element. The most popular differential unitary modulation technique uses a spacetime block code stbc to improve the performance of differential modulation technique in multiin multiout mimo system. Differential modulation techniques for a 34 mbits radio channel using orthogonal frequency division multiplexing.
Differential modulation in an ofdm system can be implemented either in the time domain or the frequency domain, depending on the channel and the presence of frequency offset. This dpsk technique doesnt need a reference oscillator. Twodimensional differential demodulation for ofdm erik haas, member, ieee, and stefan kaiser, senior member, ieee abstract in this paper, the possibility of combining differential demodulatorsintimedirection andfrequencydirection fororthogonal frequencydivision multiplexing ofdm frames is investigated. A reference ofdm symbol is then sent to serve as a. Pdf in this paper, orthogonal frequency division multiplexing with differential index modulation ofdmdim is proposed for visible light. Rectangular differential ofdm with index modulation surrey. Differential spacefrequency modulation for mimoofdm systems. Ofdm uses multiple carriers to modulate the data n carriers b modulation technique a user utilizes all carriers to transmit its data as coded quantity at each frequency carrier, which can be quadratureamplitude modulated qam. Ofdm systems with differential modulation schemes and turbo. Orthogonal frequency division multiplexing ofdm has some technical advantages compared with single carrier transmission in high data rate applications an. A novel differential modulation scheme using fullrate stbc for 4. Performance analysis for differential stbc and sfbc mimo ofdm systems under different modulation schemes in a rayleigh channel abstract. Generalized multiplemode ofdm with index modulation.
A cyclic prefix ofdm system with bpsk modulation by er. In this paper, a novel timefrequency differential spacetime tfdst modulation scheme is devel oped and applied to ofdm systems. Orthogonal frequencydivision multiplexing wikipedia. In telecommunications, orthogonal frequencydivision multiplexing ofdm is a type of digital modulation, a method of encoding digital data on multiple carrier frequencies. Orthogonal frequency division multiplexing ofdm is a multicarrier digital technology that. Pdf one of the main challenges in orthogonal frequency division multiplexing ofdm subcarrier index modulation sim systems is the huge amount of. Differential spacefrequency modulation and 2ddetection. In this paper we present and study the performance of an ofdm mimo system with unitary.
Orthogonal frequency division multiplexing ofdm has become a prevalent and widespread technique for the broadcast and transmission of signals over wireless channels and has been adopted in many wireless. Differential modulation in ltedownlink publikationsdatenbank tu. Rectangular differential ofdm with index modulation motivated by the concept of the rdsm system, in thissection,anovelrd ofdm imschemeisproposedto exploit the performance of ofdm im scheme dispensing with csi. Differential modulation is very appreciated where there are too much channels to be estimated however, a 3 db degradation is observed in the original version in comparison with a coherent scheme. Differential spacefrequency modulation for mimoofdm. Here a user utilizes all sub carriers to transmit its data. Design and analysis of an ofdm based differential chaos shift keying communication system.
This technique is very simple and achieves the channel shortening using only one symbol the first emitted symbol. Comparison of time and frequency domain single and double. In this article, we propose a nontrivial extension of this method to mimo ofdm systems. Singleblock differential transmit scheme for frequency. We use differential modulation based incoherent detection in this thesis for the data detection of. In this paper, a novel differential demodulator for ofdm combining traditional differential demodulation with neural computation has been introduced for differential detection. Psk typically does not support this, and therefore requires coherent demodulation only. School of electronics and information engineering, harbin institute of technology, harbin, china. In a pcm stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. With a view to improving the capacity of the differential ofdm modulation scheme, specified in the narrowband power line communications plc standards, in combating plc channel associated noise, we hereby propose a permutation coded modulation.
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