Data detection and channel estimation of ofdm systems using. 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. Single highrate bit stream is converted to lowrate n parallel bit streams. Multiplexing method of sharing a bandwidth with other independent data channels. The modulation scheme needs to be cost efficient circuitry should be simple to implement and inexpensive e.
Then rectangular differential coding is invoked during two adjacent subblocks, so that nocoherent detection can be employed for the proposed rd ofdm. In differential phase shift keying dpsk the phase of the modulated signal is shifted relative to the previous signal element. In section iii, the sinr pdf, cdf and mgf is derived. Introduction to ofdm orthogonal frequency division multiplexing. Dab uses differential qpsk modulation for the subcarriers. 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. From basics to adaptive trelliscoded, turboequalised and spacetime coded ofdm, cdma and mccdma systems by l. 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. Twodimensional differential demodulation for ofdm 581 fig. The most popular differential unitary modulation technique uses a spacetime block code stbc to improve the performance of differential modulation. In the interframe differential modulation scheme, only the first ofdm symbol is used for reference and no other symbols are used for pilot insertions. Ofdm systems with differential modulation schemes and turbo. Dhoni putra setiawan and huaan zhao graduate school of science and technology, kumamoto university, japan. Differential spacefrequency modulation for mimoofdm.
Rectangular differential ofdm with index modulation. Performance analysis for differential stbc and sfbc mimo ofdm systems under different modulation schemes in a rayleigh channel abstract. This dpsk technique doesnt need a reference oscillator. Us7016425b1 quasidifferential modulationdemodulation. Request pdf differential modulation diversity for ofdm the application of differential modulation diversity dmd to orthogonal frequency division.
As mentioned for bpsk and qpsk there is an ambiguity of phase if the constellation is rotated by some effect in the communications channel. Method and apparatus for performing differential modulation over frequency in an orthogonal frequency division multiplexing ofdm communication system ep00307616. In this paper, a multiuser ofdm based chaos shift keying mu ofdm dcsk modulation is presented. Jan 15, 2009 they discount differential modulation, but how does it compare with the simplest channel estimation techniques. 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 for mimoofdm systems. 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. Differential spacefrequency modulation for mimo ofdm systems via a smooth logical channel weifeng su and k. The signal phase follows the high or low state of the previous element. Organization and notations the remainder of the paper is organized as follows.
Differential modulation diversity for ofdm request pdf. What are the advantages of differential phase shift keying. Lowcomplexity differential modulation for high mobility mimo. Differential will lose due to noise doubling, and leastsquares depends on the quality of the estimate itself. Ray liu department of electrical and computer engineering, and institute for systems research. In this paper we present and study the performance of an ofdmmimo system with unitary. Siso differential communications supposing mpsk modulation scheme. Introduction to orthogonal frequency division multiplexing. Ofdm with differential index modulation for visible light. To our knowledge, however, the performance of differential modulation in lte has not yet been evaluated. In this paper we present and study the performance of an ofdm mimo system with unitary. A novel differential modulation scheme using fullrate stbc. Ndujiuba et al dynamic differential modulation of subcarriers in ofdm figure 1.
Novel timefrequency differential spacetime modulation for. 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. 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. Most ofdm systems use a fixed modulation scheme over all carriers. Channel shortening techniques for differential encoded ofdm. 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. Differential modulation techniques for a 34 mbits radio channel using orthogonal frequency division multiplexing. Coherent demodulation means that the carrier sinusoid which is modulated by the messa. Performance of differentialphase ofdm systems over selective. 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.
Pulsecode modulation pcm is a method used to digitally represent sampled analog signals. Performance evaluation of differential modulation in lte. In this paper, orthogonal frequency division multiplexing with differential index modulation ofdm dim is proposed for visible light communication. Differential space time shift keying for dispersive multiuser scenarios using ofdm s.
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. Pdf differential pulse code modulation differential. Modulation in which the choice of the significant condition for any signal element is dependent on the significant condition for the previous signal element. The combination of differential spacefrequency modulation dsfm with orthogonal frequencydivision multiplexing ofdm is attractive for transmission over timeand frequencyselective multiple. Represent each possible signal as a vector in a euclidean space spanned by an orthonormalbasis. 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. Differential spacefrequency modulation for mimoofdm systems via a smooth logical channel weifeng su and k. A novel differential modulation scheme using fullrate. Dynamic differential modulation of subcarriers in ofdm charles u. In this work, we also propose to exploit the first emitted symbol information. School of electronics and information engineering, harbin institute of technology, harbin, china. Generalized multiplemode ofdm with index modulation. Differential coding in the frequency domain, for multicarrier transmission.
Ray liu department of electrical and computer engineering, university of maryland, college park, md 20742. Ofdm ls channel estimation or differential modulation. Rectangular differential ofdm with index modulation surrey. Performance analysis for differential stbc and sfbc mimo. Comparison of time and frequency domain single and. This system adopts the differential modulation in both time and frequency domains, and it is robust for timeand fre quencyselective rayleigh fading channels. 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. Data detection and channel estimation of ofdm systems. In the proposed rd ofdm im scheme, n subcarriers are partitioned into g subblocks and index modulation is employed in each subblock first. We use differential modulation based incoherent detection in this thesis for the data detection of ofdm systems. 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. Psk typically does not support this, and therefore requires coherent demodulation only. Orthogonal frequency division multiplexing ofdm modulation a mapping of the information on changes in the carrier phase, frequency or amplitude or combination. To allow the multiple access scenario without using excessive bandwidth, each user has np predefined private frequencies from the n available frequencies to transmit its reference signal and share.
Pdf adaptive permutation coded differential ofdm system. Intercarrier separation 1symbol duration no intercarrier guard bands controlled overlapping of bands. Here a user utilizes all sub carriers to transmit its data. 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.
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. It eliminates or alleviates the problem of multipath channel fading effect, low spectrum efficiency, and. Pdf differential subcarrier index modulation researchgate. In this system, the spreading operation is performed in time domain over the multicarrier frequencies. We use differential modulation based incoherent detection in this thesis for the data detection of. Performance analysis for ofdm system using fourier transform.
Design and analysis of an ofdm based differential chaos shift keying communication system article pdf available in journal of communications 103. Orthogonal frequency division multiplexing ofdm is a special case of fdm, which is implemented in digital communication systems. Dpsk is a modulation scheme which facilitates non coherent demodulation. Jun 17, 2019 ofdm is a combination of modulation and multiplexing. Differential pulse code modulation dpcm circuit working. In this paper, a novel differential demodulator for ofdm combining traditional differential demodulation with neural computation has been introduced for differential detection. Design and analysis of an ofdm based differential chaos shift keying communication system. Simulations using a twopath channel model and mary differential phase shift keying mdpsk modulation have been run to investigate the performance characteristics of. Ofdm is a combination of modulation and multiplexing. The phases are differentially modulated and the amplitudes coherently processed. Eigendecompositionbased partial fft demodulation for.
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. Design and performance analysis of a multiuser ofdm based. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. 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. 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. Differential spacefrequency modulation and 2ddetection. 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 neighborhood demodulation of one ofdm subcarrier. 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. Orthogonal frequency division multiplexing ofdm is a multicarrier digital technology that.
Block differentially encoded ofdm with maximum multipath. The orthogonal frequency division multiplexing ofdm technique has been proposed for terrestrial digital transmission systems due to its high spectral eff. They discount differential modulation, but how does it compare with the simplest channel estimation techniques. The invention proposes the separate processing of the phase and amplitude of multiamplitude digital modulation techniques, such as a qam. Differential phase shift keying dpsk is a common form of phase modulation that conveys data by changing the phase of the carrier wave. Comparision of frequency and time domain differential modulation in. Blind channel shortening in mimoofdm systems using single. Abstract in ofdm multiple carriers are used and it provides higher level of spectral efficiency as compared to frequency division multiplexing fdm.
Differential pulse code modulation differential pulse code modulation. Orthogonal frequency division multiplexing and its. A guard interval using cyclic prefix is inserted in each ofdm symbol to avoid the intersymbol interference. Differential spacefrequency modulation and 2ddetection for mimo ofdm abstract. Differential space time shift keying for dispersive multiuser scenarios using ofdm differential space time shift keying for. In telecommunications, orthogonal frequencydivision multiplexing ofdm is a type of digital modulation, a method of encoding digital data on multiple carrier frequencies. Dynamic differential modulation of subcarriers in ofdm.
Pdf design and analysis of an ofdmbased differential. 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. Pdf rectangular differential ofdm with index modulation. Singleblock differential transmit scheme for frequency selective mimo ofdm systems thanongsak himsoon, weifeng su, and k. This technique is very simple and achieves the channel shortening using only one symbol the first emitted symbol. Design and analysis of an ofdmbased differential chaos shift. Singleblock differential transmit scheme for frequency.
Differential modulation techniques for a 34 mbits radio channel. Differential pulse code modulation dpcm circuit working its. A reference ofdm symbol is then sent to serve as a. Differential pulse code modulation is a technique of analog to digital signal conversion. 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. The input can be an analog signal or a digital signal. Section ii provides a brief overview of the considered modulation schemes. 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. Postfft methods are performed in the frequency domain after ofdm demodulation. A cyclic prefix ofdm system with bpsk modulation by er. Differential space time shift keying for dispersive multi. Each parallel bit stream is modulated on one of n subcarriers. Pdf ofdm with differential index modulation for visible light.
A novel differential modulation scheme using fullrate stbc for 4. Performance of differentialphase ofdm systems over. Orthogonal frequency division multiplexing ofdm has some technical advantages compared with single carrier transmission in high data rate applications an. Lowcomplexity differential modulation for high mobility. Differential modulation in ltedownlink publikationsdatenbank tu. For the ofdm transmission technique an absolute modulation scheme 64. Index modulation techniques for nextgeneration wireless. 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. Differential modulation is a noncoherent modulation technique which is used to solve the uncertainty channel problem. Comparison of time and frequency domain single and double. Performance analysis for ofdm system using fourier transform and wavelet transform with different modulation techniques qusay jalil, s nagakishore bhavanam. An example of differential modulation is delta modulation.
In this paper differential spacefrequency frequency division multiplexing mimo ofdm and multiplesymbol differential detection msdd without channel state information csi at the receiver is considered. Performance analysis for ofdm system using fourier. In this paper, a novel timefrequency differential spacetime tfdst modulation scheme is devel oped and applied to ofdm systems. 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. 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. Performance analysis of coherent and noncoherent modulation. Abstract in ofdm multiple carriers are used and it provides higher level of spectral efficiency as compared to. In this paper we consider differential modulation with noncoherent detection for the lte downlink. The zpofdm system uses less energy than cpofdm system.
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