PAPR Analysis of Class-III IN OFDM Signal Sequences

PAPR:

The transmit signals in an orthogonal frequency-division multiplexing (OFDM) system can have high peak values in the time domain since many subcarrier components are added via an inverse fast Fourier transformation (IFFT) operation. As a result, OFDM systems are known to have a high peak-to-average power ratio (PAPR) when compared to single-carrier systems. In fact, the high PAPR is one of the most detrimental aspects in an OFDM system as it decreases the signal-to-quantization noise ratio (SQNR) of the analog-digital convertor (ADC) and digital-analog convertor (DAC) while degrading the efficiency of the power amplifier in the transmitter.

 

Fig:OFDM

ORTHOGONAL frequency division multiplexing (OFDM) is a popular multicarrier modulation technique. Because of the orthogonality of its subcarriers, a receiver can recover the transmitted data without interference. Due to its robustness  against multipath fading, OFDM has been adopted as a standard technique for various wireless communication systems

When OFDM signals with high PAPR pass through nonlinear high power amplifier, they experience
in-band distortion and out-of-band radiation. Thus, in order to reduce PAPR, many schemes have been proposed such as selected mapping (SLM), partial transmit sequence  and tone reservation.Because of large computational complexity, the conventional SLM scheme in has been modified to many low complexity SLM schemes

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PAPR Analysis of Class-III IN OFDM Signal Sequences

GENERALIZATION OF ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING WITH INDEX MODULATION

OFDM:

orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) was proposed. By selecting a fixed number of sub carriers as active sub carriers to carry constellation symbols, the indices of these active sub carriers may carry additional bits of information 

Is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method. A large number of closely spaced orthogonal sub-carrier signals are used to carry data on several parallel data streams or channels.

 

 

 

 

                                         FIG: OFDM

 

 OFDM with generalized index modulation 1 (OFDMGIM1) and OFDM-GIM2, respectively. In OFDM-GIM1, the number of active sub carriers in an OFDM sub block is no longer fixed. Dependent on the input binary string, different number of active sub carriers are assigned to carry constellation symbols. In OFDM-GIM2, independent index modulation is performed on the in-phase and quadrature component per sub carrier.

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GENERALIZATION OF ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING WITH INDEX MODULATION

 

MUTUAL COUPLING ON THE CHANNEL CAPACITY OF MIMO SYSTEMS

Channal Capacity:

In modeling a MIMO channel, it is generally assumed that the coefficients of the channel transfer matrix are independent and identically distributed. When the antennas are placed close to one another or when there are fewer scatters in between the transmitting and the receiving arrays, the correlation coefficients will increase and hence the channel capacity will be reduced.

  Mutual coupling:

                           At smaller antenna spacings, the variation of mutual coupling among antennas will affect the channel capacity more significantly. It was reported that mutual coupling may increase the channel capacity by decreasing the spatial correlation coefficients under certain circumferences . In a network theory was used to derive the transfer matrix, which includes the coupling effects among antennas in both the transmitting and the receiving arrays, the multipath propagation channel, the receiver matching network, and the noise in the receiver amplifiers.

                               FIG:CHANNEL CAPACITY IN MIMO SYSTEMS

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EFFECT OF MUTUAL COUPLING ON THE CHANNEL CAPACITY OF MIMO SYSTEMS

HOW TO MAXIMIZATION SUM RATE USING TWO WAY RELAY SYSTEM?

Hi

we propose a novel joint beamforming scheme using mean-square error (MSE) duality to maximize the sum rate of a multiple-input multiple-output (MIMO) two-way relay system. It is difficult to solve the sum rate maximization  problem directly due to its non-convexity. To manage this difficulty, the optimization problem is reformulated as a problem that minimizes the product of the minimum mean-square errors

                                        
                                                                        FIG:  RELAY SECTION


 


 Then, we show that the per stream MSE duality holds in a two-way relay system under cross power constraints. Based on the per stream MSE duality, an alternate algorithm is proposed to jointly optimize the linear transceivers. The simulation results demonstrate that the proposed scheme outperforms the existing linear schemes in view of the sum rate maximization 


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SUM-RATE-MAXIMIZATION-OF-AN-MIMO-TWO-WAY-RELAY-SYSTEM-USING-MSE-DUALITY

WHAT IS MEANT BY CARRIER FREQUENCY OFFSET IN OFDM?

HI



Orthogonal frequency division multiplexing (OFDM) over wireless channels is sensitive to carrier frequency offset (CFO), which destroys orthogonality amongst subcarriers  giving rise to inter-carrier interference (ICI). Different techniques are available for estimating and compensating for the CFO at the receiver. However, in practice, a residual CFO remains at the receiver after CFO estimation, where the estimation accuracy depends primarily on the fractions of time and power used by the estimator. In this paper we propose to measure the efficiency of OFDM systems with CFO estimation errors in terms of the spectral efficiency, which accounts for both, the degradation in signal-to-interference plus noise ratio (SINR) due to the residual CFO, and the penalty of the extra power and spectral resources allocated to achieve the desired CFO estimation accuracy.

New accurate expressions are derived for the spectral efficiency of wireless OFDM systems in the presence of residual CFO and frequency-selective multipath fading channel. These are used to compare between two common CFO estimation methods in wireless OFDM systems  namely, the cyclic prefix based and the training symbols based CFO estimation techniques for fixed and variable pilot power. These results are further extended to include OFDM systems with transmit diversity techniques. In addition, the impact of imperfect channel estimation on the overall spectral efficiency is also included. Numerical results reveal that the cyclic prefix based CFO technique is more efficient than the training symbols based CFO technique when perfect channel state information (CSI) is known blindly at the receiver. Furthermore, fixed pilot power results in a spectral efficiency ceiling as SNR increases, whereas spectral efficiency increases with SNR without bound in the equal pilot and signal powers case



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SPECTRAL EFFICIENCY OF OFDM SYSTEMS WITH RANDOM RESIDUAL CFO

HOW TO INCREASE SUMRATE USING MIMO?

Hi

    The Gaussian MIMO Z channel and the Gaussian MIMO X channel. The MIMO X channel(XC) consists of two multiple antenna transmit-receive pairs, where each transmitter communicates with both receivers. An interesting model to study the effect of interference in communication systems is the single antenna two user interference channel, consisting of two point-to-point links which interfere with each other

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ON THE SUM-RATE OF THE GAUSSIAN MIMO Z CHANNEL AND THE GAUSSIAN MIMO X CHANNEL

HOW TO IMPROVING PHYSICAL LAYER SECURITY?

Hi,
              
Is  a new cognitive radio network (CRN), where cooperative beam-forming is designed to enhance the physical layer security for both primary users (PUs) and secondary users (SUs). Specially, the proposed design aims to minimize the transmit power of a secondary transmitter, while providing an eavesdropper, a primary receiver, and multiple secondary receivers with different signal-to-interference-and-noise ratio (SINR).

                                                          Fig:  Physical layer security





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IMPROVING PHYSICAL LAYER SECURITY FOR CRNS USING SINR-BASED COOPERATIVE BEAMFORMING