HOW TO WRITE MATLAB CODE FOR AMPLITUDE MODULATION?

AMPLITUDE MODULATION:

the modulation of a wave by varying its amplitude, used especially as a means of broadcasting an audio signal by combining it with a radio carrier wave.


CODING:

clc;
clear all;
close all;

Ac=2; %carrier amplitude
fc=0.5; %carrier frequency
Am=.5; %message signal amplitude
fm=.05; %message signal frequency
Fs=100; %sampling rate/frequency

ka=1; %modulation coefficient

t=[0:0.1:50]; %defining the time range & disseminating it into samples
ct=Ac*cos(2*pi*fc*t); %defining the carrier signal wave
mt=Am*cos(2*pi*fm*t); %defining the message signal
AM=ct.*(1+ka*mt); %Amplitude Modulated wave, according to the standard definition

subplot(3,1,1); %plotting the message signal wave
plot(mt);
ylabel('Message signal');

subplot(3,1,2); %plotting the carrier signal wave
plot(ct);
ylabel('carrier');

subplot(3,1,3); %plotting the amplitude modulated wave
plot(AM);
ylabel('AM signal');

             
                                                         Fig: Amplitude Modulation









FOR MORE DETAILS:    CLICK HERE

HOW TO DECREASE OUTAGE PROBABILITY OF RELAY ?

OUTAGE PROBABILITY:

In wireless slow fading channel scenario, outage probability is one of the most important parameters for system performance.Namely, when the instantaneous signal to noise ratio (SNR) is below the minimal acceptable threshold value, an outage event will occur. Some advanced techniques have been proposed to alleviate this problem in the literature. Among them, relay-aided cooperative transmission is an efficient way.However, the flexibility of relay node deployment is limited by existing power supply. Besides, maintenance costs, such as electric charge, also restrict the massive deployment.the performance analysis of energy harvesting relay-aided cooperative network with multiple available relay nodes in terms of outage behavior. Based on the Markov property of energy buffer status, an on off model is proposed to characterize the stochastic property of harvested energy flow. The explicit closed-form expression of outage probability in the proposed relay-aided cooperative protocol is obtained in the high SNR regime.

                                                     Fig : outage probability of relay
perspective of systematic level, an on-off Markov model was proposed to characterize the stochastic property of harvested energy flow. With the help of some approximations, the explicit closed form of outage probability of cooperative system has been derived in the high SNR regime. It can be observed that great improvement can be obtained by the proposed cooperative protocol in terms of minimizing outage probability



FOR MORE DETAILS:

OUTAGE PROBABILITY OF ENERGY HARVESTING RELAY-AIDED COOPERATIVE NETWORKS OVER RAYLEIGH FADING CHANNEL

AMPLIFY AND FORWARD RELAY

OUTAGE PERFORMANCE OF AMPLIFY AND FORWARD RELAY:
 
                      The amplify-and-forward relay protocol is a protocol defined for wireless Cooperative communication.An example of a wireless communication network in which cooperation improves the performance of the system is the relay Network In this case, the relay just amplies its received signal, maintaining a fixed average transmit power. selection amplify-and-forward (AF) relaying scheme which has the lower outage probability than that of a conventional AF relaying scheme in  cooperative relay networks. In real wireless environments, as the channel of source-to-destination (SD) link varies with an increase in time, we can also obtain a diversity gain through the SD link by re transmission in common with a conventional AF relaying scheme. Thus, we can expect a performance enhancement by adaptively determining the transmitting node between the relaying and source nodes

                                                                Fig :amplify and forward Relay


      In cooperative relay networks, relaying nodes can forward information from a single antenna terminal to form a virtual antenna array, and thereby achieving space diversity and improving the system performance, hence cooperative communications have attracted much attention. The relaying nodes essentially operate in either amplify and- forward (AF) and decode-and-forward relaying modes, which are basic for various evolved relaying schemes.the adaptive selective relaying scheme which determines the best among multiple AF relaying nodes having the maximum received SNR through the SR link was proposed, and its performances of outage  channel capacity , symbol error rate were analyzed



FOR MORE DETAILS

ON THE OUTAGE PERFORMANCE OF SELECTION AMPLIFY-AND-FORWARD RELAYING SCHEME

TO COOPERATE:AN OUTAGE ANALYSIS OF INTERFERENCE LIMITED WIRELESS NETWORKS

COOPERATIVE COMMUNICATION:

  An effective technique which provides diversity gains to combat the attenuation of radio signals caused by fading and path loss.Cooperative communication is an effective technique which provides diversity gains to combat the attenuation of radio signals caused by fading and path loss. By sharing each cooperative node’s antenna to form a virtual antenna array, the reliability of the wireless transmission can be significantly improved .In a wireless network of moderate or large size, however, the situation becomes more complicated because there may exist many concurrent transmissions. Since cooperative communication usually involves multiple-node transmissions, it may generate additional spatial interference to other concurrent data transmissions in the network

                                        Fig:Cooperative Communication

FOR MORE DETAILS

TO COOPERATE:AN OUTAGE ANALYSIS OF INTERFERENCE LIMITED WIRELESS NETWORKS

LDPC CODING AND REDUCED COMPLEXITY

LDPC CODING:

                    The constraint of minimizing the dependence between the  system’s receiving branches, thus reducing the relevant transmitter and receiver complexities.The concept of Multiple-Input Multiple-Output (MIMO) still represents a prevailing research direction in wireless communications due to its ever increasing capability to offer higher rate, more efficient communications, as measured by spectral utilization, and under low transmitting or receiving power.

                                                                             Fig:LDPC


globally optimal linear precoding techniques were presented for finite alphabet inputs, capable of achieving mutual information rates much higher than the previously presented MWF techniques, by introducing input symbol correlation through a unitary input transformation matrix in conjunction with channel weight adjustment (power allocation). These mutual information maximizing globally optimal pre coders are more appropriate for LDPC codes which are very popular currently, than e.g., Maximal Diversity Precoders (MDP).LDPC codes is addressed under the constraint of minimizing the dependence between the system’s receiving branches, thus reducing the relevant transmitter and receiver complexities.




 FOR MORE DETAILS:

Linear Precoding for MIMO With LDPC Coding and Reduced Complexity

LINE OF SIGHT COMMUNICATION IN MIMO?

LINE OF SIGHT: 
                Line of sight (LoS) is a type of propagation that can transmit and receive data only where transmit and receive stations are in view of each other without any sort of an obstacle between them. FM radio, microwave and satellite transmission are examples of line-of-sight communication.  We use space shift keying (SSK)  to present the idea of spatial modulation in line-of-sight (LOS) conditions and show under which conditions high performance can be achieved. The proposed framework is general and can be extended to generalized spatial modulation schemes .LOS transmission is typically seen in point-to-point communication (e.g., backhaul) and millimeter-wave (mmWave) communications.At mm Wave frequencies, the propagation is quasi-optical, sparsely scattered and with large reflection loss (typically 10 dB on average with 4 dB RMS deviation . To focus on our main target—to establish the operating conditions for LOS-SSK—and also for simplicity, only LOS components are considered

                              
                                                           Fig: Line of sight communication

We have shown that SSK can operate efficiently in LOS conditions. Two operating conditions, namely OSSK and BiSSK, are established. A system setup with dual TX arrays and single RX array is proposed to achieve BiSSK. The BEP for both schemes are derived and given in closed form.we analyses to Bit error performance.

FOR MORE DETAILS:

Space Shift Keying for LOS Communication at mmWave Frequencies

HOW TO DECREASE OUTAGE PROBABILITY OF RELAY AND RAYLEIGH FADING CHANNAL?

OUTAGE PROBABILITY:

In wireless slow fading channel scenario, outage probability is one of the most important parameters for system performance.Namely, when the instantaneous signal to noise ratio (SNR) is below the minimal acceptable threshold value, an outage event will occur. Some advanced techniques have been proposed to alleviate this problem in the literature. Among them, relay-aided cooperative transmission is an efficient way.However, the flexibility of relay node deployment is limited by existing power supply. Besides, maintenance costs, such as electric charge, also restrict the massive deployment.the performance analysis of energy harvesting relay-aided cooperative network with multiple available relay nodes in terms of outage behavior. Based on the Markov property of energy buffer status, an on off model is proposed to characterize the stochastic property of harvested energy flow. The explicit closed-form expression of outage probability in the proposed relay-aided cooperative protocol is obtained in the high SNR regime.

 

                                              Fig:outage probability 

perspective of systematic level, an on-off Markov model was proposed to characterize the stochastic property of harvested energy flow. With the help of some approximations, the explicit closed form of outage probability of cooperative system has been derived in the high SNR regime. It can be observed that great improvement can be obtained by the proposed cooperative protocol in terms of minimizing outage probability



FOR MORE DETAILS:

OUTAGE PROBABILITY OF ENERGY HARVESTING RELAY-AIDED COOPERATIVE NETWORKS OVER RAYLEIGH FADING CHANNEL

 

PAPR ANALYSIS OF CLASS-III SLM SCHEME BASED ON VARIANCE OF CORRELATION OF ALTERNATIVE OFDM SIGNAL SEQUENCES

PAPR:
                    Selected mapping (SLM) is a well-known peak-to average power ratio (PAPR) reduction technique for orthogonal frequency division multiplexing (OFDM) systems. Recently, a low-complexity SLM scheme, called Class-III SLM scheme, was proposed, which performs only one inverse fast Fourier transform (IFFT) to generate alternative OFDM signal sequences

                                                   
                                                            Fig:OFDM
      
                      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.Finally, three low-complexity SLM schemes using conversion vectors were proposed  Among them, it is known that the one using Class-III conversion vector (which we will refer to as Class-III SLM scheme) shows better PAPR reduction performance than Class-I and Class-II SLM schemes

FOR MORE DETAILS:

PAPR ANALYSIS OF CLASS-III SLM SCHEME BASED ON VARIANCE OF  CORRELATION OF ALTERNATIVE OFDM SIGNAL SEQUENCES

How to increase sumrate in MSE for two way Relay system?

SUM RATE MAXIMIZATION:

               TWO-WAY relay systems in wireless networks have received significant attention due to their high spectral efficiency.To enhance the data rate of non regenerative two-way relay systems, beam forming design schemes were studied based on the iterative method and channel parallelization. a new algorithm using the MSE duality is proposed that maximizes the sum rate for a non regenerative multiple-input multiple-output (MIMO) two-way relay system

                                                                Fig: Relay system

beam forming problem to maximize the sum rate is non-convex we present the per stream MSE duality for the MIMO two-way relay system and exploit the alternate algorithm using the MSE duality and convex optimization programming.The linear beam forming design was investigated to maximize
the sum rate of an MIMO two-way relay system. We derived the per stream MSE duality in the two-way relay system under cross power constraints. A novel iterative algorithm was developed using the per stream MSE duality and convex optimization programming to jointly optimize the linear transceivers.



FOR MORE DETAILS:

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

HOW TO INCREASE SPECTRAL EFFICIENCY OF OFDM SYSTEM?

SPECTRAL EFFICIENCY:

Spectrum efficiency is the optimized use of spectrum. so that the maximum amount of data can be transmitted with the fewest transmission errors. In a  Cellular telephone network, spectrum efficiency equates to the maximum number of users per cell that can be provided while maintaining an acceptable quality of service (OFDM) is the method of choice for combating frequency-selective multi path fading channels, and achieving high spectral efficiency in wireless communication systems. With the aid of sufficient cyclic prefix, inter-symbol interference (ISI) due to multi path fading is completely avoided without the need for complicated equalizers.

                                                          Fig: OFDM


However, despite the fact that CFO estimation and compensation is performed at the receiver, a random residual CFO still exists which increases at low number of training symbols and/or low to medium signal to noise ratio (SNR) region. Further, this residual CFO might degrade the OFDM system performance.
Even though CFO estimation is performed at the receiver, a residual frequency offset still exists and introduces ICI which degrades the OFDM system performance over multipath wireless channels.
In addition, low fixed pilot power results in a spectral efficiency ceiling as SNR increases, whereas in the equal pilot and signal powers case, spectral efficiency increases with SNR without bound


FOR MORE DETAILS:

SPECTRAL EFFICIENCY OF OFDM SYSTEMS WITH RANDOM RESIDUAL CFO

 

OFDM WITH INDEX MODULATION

OFDM:
    multi carrier transmission has become an  attractive technique in many wireless standards to meet the increasing demand for high data rate communication systems. One of the most popular multicarrier techniques, orthogonal frequency division multiplexing (OFDM), has developed into a widely-used scheme for wide band digital communication. The major advantage of OFDM over single-carrier schemes is its ability to cope with frequency-selective fading channel with only one-tap equalizer.

                                                    Fig: OFDM with index modulation


an OFDM with generalized index modulation (OFDM-GIM). The generalization is proposed in two aspects. First, a more flexible selection of active sub carriers is proposed to further improve the spectral efficiency.We also demonstrate that the two generalization schemes are compatible with each other and their combined scheme greatly outperforms existing works in spectral efficiency and BER performance, at the cost of a little higher complexity.


FOR MORE DETAILS:

GENERALIZATION OF ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING WITH INDEX

PERFORMANCE OF RECONFIGURABLE ANTENNAS IN A BELOW-DECKS ENVIRONMENT

RE CONFIGURABLE  ANTENNAS:

 Re configurable antennas have been proposed for mitigating multipath interference and increasing channel capacity in wireless networks. The majority of studies which have investigated these claims do so either in simulation or through the use of software defined radios in lab or office environments.
quantifies the performance gains provided by the use of electrically re configurable antennas in the place of omn idirectional antennas given varying environmental and system configurations. Wireless  measurements for various 802.11-like physical layers were performed in a set of multi deck,

                                                                       Fig: Reconfigurable antennas


we sought to quantify the performance of a selection of physical layers using only omni directional antennas over different wireless links and environment states (i.e., opening and closing bulkhead doors).  The current study focuses on evaluating performance gains when using re configurable antennas at the transmitter node in place of omni directional antennas. These performance gains are evaluated for a selection of physical layer configurations and across multiple transmitter/receiver links.


FOR MORE DETAILS;

PERFORMANCE OF RECONFIGURABLE ANTENNAS IN A BELOW-DECKS ENVIRONMENT

RELAY SELECTION IMPROVES THE SECURITY RELIABILITY TRADE OFF IN COGNITIVE RADIO SYSTEMS

RELAY:
A relay network is a broad class of network topology commonly used in wireless communication where the source and destination are interconnected. In such a network the source and destination cannot communicate to each other directly because the distance between the source and destination is greater than the transmission range of both of them, hence the need for intermediate node(s) to relay. A relay network is a type of network used to send information between two devices, for e.g. server and computer, that are too far away to send the information to each other directly. Thus the network must send or "relay" the information to different devices, referred to as nodes, that pass on the information to its destination. A well-known example of a relay network is the Internet. A user can view a web page from a server halfway around the world by sending and receiving the information through a series of connected nodes.


 

 

                                                              Fig: Relay Network


Hence, the CR users fail to accurately characterize their surrounding radio environment and may become misled or compromised, which leads to a malfunction. Alternatively, an illegitimate user may attempt to tap the communications of authorized CR users by eavesdropping, to intercept confidential information
Moreover, the SRT(Security-reliability trade-off) performance of MRS is better than that of SRS. Additionally, as the number of SRs increases, the SRTs of both the SRS and of the MRS schemes improve significantly, demonstrating their benefits in terms of enhancing both the security and reliability of secondary transmissions.


FOR MORE DETAILS;

RELAY SELECTION IMPROVES THE SECURITY RELIABILITY TRADE OFF IN COGNITIVE RADIO SYSTEMS

IMPROVING PHYSICAL LAYER SECURITY FOR CRN USING SINR BASED COOPERATIVE BEAMFORMING

 CRN:
Cognitive Radio (CR) is an adaptive, intelligent radio and network technology that can automatically detect available channels in a wireless spectrum and change  transmission parameters enabling more communications to run concurrently and also improve radio operating behavior. Cognitive radio uses a number of technologies including Adaptive Radio (where the communications system monitors and modifies its own performance) and Software Defined Radio (SDR) where traditional hardware components including mixers, modulators and amplifies  have been replaced with intelligent software.  wireless spectrum

                                                            Fig: cognitive radio Network



                            New CRN where both PU and SU transmit confidential information to intended receivers .Aiming to provide intended users with different SINR, we design joint information beamforming and AN beamforming at the secondary transmitter. Remarkably, it is proved that using semi-definite relaxation (SDR)  the initial non-convex optimization can be equivalently converted into a convex semidefinite programming (SDP), which can be efficiently solved




FOR MORE DETAILS

IMPROVING PHYSICAL LAYER SECURITY FOR CRN USING SINR BASED COOPERATIVE BEAMFORMING
 
 

ON THE SUM RATE OF THE GAUSSIAN MIMO Z CHANNAL AND THE GAUSSIAN MOIMO X CHANNEL

MIMO CHANNAL: 

           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.sum-rate capacity of the IC is characterized in the low-interference regime: a regime where using Gaussian inputs and treating interference as noise is optimal.By allowing messages on all the links of the IC, we obtain the X channel, i.e., both transmitters have an independent message for each receiver, for a total of four messages in the channel  In this sense, the X channel (XC) is a generalization of the IC.

     FIG: MIMO CHANNAL ESTIMATION


FOR MORE DETAILS  

ON THE SUM RATE OF THE GAUSSIAN MIMO Z CHANNAL AND THE GAUSSIAN MOIMO X CHANNEL

HOW TO ANALYSIS FOR THROUGHOUT IN WIRESLESS NETWORK?

 Throughput analysis:
                      
                        COGNITIVE radio technology has recently emerged as an aspirant solution for the problem of spectrum scarcity.Unlike the traditional static command-and-control approach, it provides a more dynamic means for spectrum management and utilization channel state information (CSI) is one of the main requisites for successful implementation of such dynamic cognitive radio protocols. However, its availability is often sidelined in most previous works  either assuming a centralized band manager or perfect instantaneous CSI feedback between primary and secondary networks

                                          
        
                                         Fig:Throughput analysis of Cognitive radio

                         the design of optimum distributed power control mechanisms for the cognitive uplink,allowing each SU to adjust its transmission power level  based only on local knowledge of its CSI. It also investigates multiuser diversity gains for the distributed cognitive uplink by deriving tight sum-rate capacity scaling laws under the optimum distributed power control mechanisms.

FOR MORE DETAILS

POWER CONTROL AND ASYMPTOTIC THROUGHPUT ANALYSIS FOR THE DISTRIBUTED COGNITIVE UPLINK

WHAT IS PAPR IN OFDM?

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

FOR MORE DETAILS:

PAPR Analysis of Class-III IN OFDM Signal Sequences

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

FOR MORE DETAILS

EFFECT OF MUTUAL COUPLING ON THE CHANNEL CAPACITY OF MIMO SYSTEMS

Noise over Fading Channels using CRN

CRN:

                        RADIO Frequency (RF) spectrum is an expensive and limited resource for wireless communications. The increasing demands for additional bandwidth have led to studies that indicate the spectrum assigned to primary license holders is under-utilized.Cognitive radio technology helps to use the RF spectrum more efficiently, by introducing secondary usage of the spectrum licensed to primary users (PU) but with a lower priority. A cognitive radio is able to change its transmitter parameters based on interaction with the environment. Secondary users (SU’s) equipped with cognitive radios can sense the spectrum and dynamically use spectrum holes in PU frequency bands for data transmission.

                                                    
                                                             Fig: Cognitive Network



It is often assumed that the additive noise samples are statistically independent. Although the AWGN assumption is valid in several situation, the work in this paper is mainly motivated by situations that we have encountered where the noise exhibits significant correlation.. In such applications, the noise as experimentally measured presents several characteristics, one of them being correlation in the time domain. The noise models needed in these cases  quickly become complicated and involve most often Markov transition models  Any realistic cognitive radio environment would require to at least take into account at some level the noise correlation

FOR MORE DETAILS

ANALYSIS OF THE POWER AMPLIFIER NONLINEARITY ON THE POWER ALLOCATION IN COGNITIVE RADIO NETWORKS 

COGNITIVE RADIO NETWORKS USED ANALYSIS OF THE POWER AMPLIFIER

COGNITIVE RADIO NETWORKS:


             The interference to the primary receiver (PR) is a critical issue in the resource allocation of cognitive radio (CR) networks. For instance, the non linearity of the power amplifier (PA) causes nonlinear interference to the PRs.A nonlinear PA with limited dynamic range and a lower limit on the transmit power is assumed for the secondary transmitter (ST). To control the resulting ACI from the ST to the PRs, the PA needs to be turned off in some fading blocks. To investigate the throughput,  an analytical expression for the probability of data transmission between the secondary users is derived as a function of the interference temperature limits of the PRs.

                                                    Fig:Cognitive radio network
     
 


RAPID growth of wireless communications and conventional fixed spectrum allocation policy have led to the problem of spectrum scarcity. However, according to a survey of spectrum utilization in the licensed spectrum is not used efficiently in both temporal and geographical dimensions. Cognitive radio (CR) which is one of the most promising technologies for the future radio spectrum management, improves spectrum utilization by using these underutilized parts of the spectrum. In CR networks, the secondary users are allowed to communicate, provided that the interferences caused to the primary receivers (PRs) are below a given threshold, called interference temperature limit 

FOR MORE DETAILS:

ANALYSIS OF THE POWER AMPLIFIER NONLINEARITY ON THE POWER ALLOCATION IN COGNITIVE RADIO NETWORKS 





 

OFDM Systems used for Eavesdropping Prevention

OFDM;

            ORTHOGONAL frequency-division multiplexing (OFDM) has been widely employed in modern wireless communications networks. Unfortunately, conventional OFDM signals are vulnerable to malicious eavesdropping due to their distinct time and frequency characteristics.Physical layer security, which targets communications security at the physical layer, is emerging as an effective complement to traditional security strategies in securing wireless OFDM transmission

 

                                       Fig: Eavesdropping prevention
 
these secrecy capacity based security techniques usually require the knowledge of the eavesdropping channel, which is conditioned on a successful detection of eavesdroppers. Also, additional resource may be needed like cooperative terminals and multiple antennas. Simple proactive eavesdropping prevention for OFDM at the physical layer, without significant modifications to off-the-shelf systems, has yet to be developed.




FOR MORE DETAILS:

DYNAMIC SUBCARRIER COORDINATE INTERLEAVING FOR EAVESDROPPING PREVENTION IN OFDM SYSTEMS

Outage Performance of Amplify-and-Forward Relaying

AMPLIFY AND FORWARD RELAY:
 
                      The amplify-and-forward relay protocol is a protocol defined for wireless Cooperative communication.An example of a wireless communication network in which cooperation improves the performance of the system is the relay Network In this case, the relay just amplies its received signal, maintaining a fixed average transmit power. selection amplify-and-forward (AF) relaying scheme which has the lower outage probability than that of a conventional AF relaying scheme in  cooperative relay networks. In real wireless environments, as the channel of source-to-destination (SD) link varies with an increase in time, we can also obtain a diversity gain through the SD link by re transmission in common with a conventional AF relaying scheme. Thus, we can expect a performance enhancement by adaptively determining the transmitting node between the relaying and source nodes

                                                                Fig :amplify and forward Relay


      In cooperative relay networks, relaying nodes can forward information from a single antenna terminal to form a virtual antenna array, and thereby achieving space diversity and improving the system performance, hence cooperative communications have attracted much attention. The relaying nodes essentially operate in either amplify and- forward (AF) and decode-and-forward relaying modes, which are basic for various evolved relaying schemes.the adaptive selective relaying scheme which determines the best among multiple AF relaying nodes having the maximum received SNR through the SR link was proposed, and its performances of outage  channel capacity , symbol error rate were analyzed



FOR MORE DETAILS

ON THE OUTAGE PERFORMANCE OF SELECTION AMPLIFY-AND-FORWARD RELAYING SCHEME

Channel Model for Satellite Communication Links Above 10GHz Based on Weibull Distribution

SATELLITE COMMUNICATION:


Modern satellite communication networks will employ frequencies above 10GHz. At these frequency bands, rain attenuation is the dominant fading mechanism.channel model, a synthesizer for generating rain attenuation time series for satellite links operating at 10GHz and above is presented. The proposed channel model modifies Maseng- Bakken (M-B) model since it generates rain attenuation time
series that follow the Weibull distribution

                                                   Fig : satellite communication

              THE increasing demand for high data rate services and the scarcity of the spectrum lead to the  employment of high frequency bands such as Ka and Q/V bands for the operation of satellite systems.
At operating frequencies above 10 GHz rainfall is the dominant fading mechanism since it causes the highest attenuation among the other atmospheric effects. Due to the high values of rain attenuation for small time percentage, though still critical for high availability systems, the adoption of a fixed power margin as a countermeasure of rain attenuation is not the optimal solution

          An extended comparative test took place considering experimental data from ITUs database of Study Group 3 (DBSG3)  in order to observe the suitability of Weibull distribution for modeling the rain attenuation exeedance probability. Considering 86 experiments from DBSG3 database it was found that the RMS value of the relative error was 13.47% for Weibull distribution and 13.8% for log normal distribution  This leads to the conclusion that Weibull distribution in many cases may describe better rain attenuation exceed probability than log normal distribution. This is a strong motivation in order to derive a rain attenuation synthesizer based on Weibull distribution

FOR MORE DETAILS


CHANNEL MODEL FOR SATELLITE COMMUNICATION LINKS ABOVE 10GHZ BASED ON WEIBULL DISTRIBUTION

Throughput Analysis for the Distributed Cognitive Uplink

 Throughput analysis:

COGNITIVE radio technology has recently emerged as an aspirant solution for the problem of spectrum scarcity.Unlike the traditional static command-and-control approach, it provides a more dynamic means for spectrum management and utilization channel state information (CSI) is one of the main requisites
for successful implementation of such dynamic cognitive radio protocols. However, its availability is often sidelined in most previous works  either assuming a centralized band manager or perfect instantaneous CSI feedback between primary and secondary networks

                                               Fig:Throughput analysis of Cognitive radio
the design of optimum distributed power control mechanisms for the cognitive uplink,allowing each SU to adjust its transmission power level  based only on local knowledge of its CSI. It also investigates multiuser diversity gains for the distributed cognitive uplink by deriving tight sum-rate capacity scaling laws under the optimum distributed power control mechanisms.



FOR MORE DETAILS

POWER CONTROL AND ASYMPTOTIC THROUGHPUT ANALYSIS FOR THE DISTRIBUTED COGNITIVE UPLINK

Outage Analysis of Wireless Networks

COOPERATIVE communication

Has attracted a great amount of interest in the past decade. Following certain coordination protocols, a set of nodes can essentially form a distributed multiple-antenna system and transmit signals to the destination in a cooperative manner. Significant performance gains can thereby be achieved by using the available signal processing techniques developed for conventional multiple antenna systems.

                                       
                                                                    Fig: Cooperative Netwok

                                     






In a wireless network of moderate or large size, however, the situation becomes more complicated because there may exist many concurrent transmissions. Since cooperative communication usually involves multiple-node transmissions, it may generate additional spatial interference to other concurrent data transmissions in the network. The aggregate interference power can easily be strong and cause negative impact on the performance of the network. In other words, although each cooperative transmission has the potential to improve the reception quality of its destination, the overall performance taking into account the increased interference level remains unclear






FOR MORE DETAILS
TO COOPERATE OR NOT TO COOPERATE: AN OUTAGE ANALYSIS OF INTERFERENCE-LIMITED WIRELESS NETWORKS

MIMO OFDM Systems in On-Ship Below-Deck Environments

MIMO:

Multiple-input multiple-output, or MIMO, is a radio communications technology or RF technology that is being mentioned and used in many new technologies these days.Wi-Fi, LTE; Long Term Evolution, and many other radio, wireless and RF technologies are using the new MIMO wireless technology to provide increased link capacity and spectral efficiency combined with improved link reliability using what were previously seen as interference paths.

Even now many there are many MIMO wireless routers on the market, and as this RF technology is becoming more widespread, more MIMO routers and other items of wireless MIMO equipment will be seen.

                                                                Fig: Below Deck Environments

 

 

BELOWDECK 

             There has been increased  interest in characterizing electromagnetic propagation in below-deck environments of naval vessels for the purpose of deploying wireless networks. Below-deck spaces are predominantly metal structures. These spaces constitute multipath-rich environments that introduce distinct challenges for deploying wireless networks. The RF spectrum on ships also introduces active radar and communication signals, emissions from working machinery, and interference by personnel on board  Still, deploying wireless networks in below-deck spaces is desirable as it offers significant potential in augmenting, and in some applications, replacing current wired network infrastructure.

The primary contribution of this letter is the quantification of the improvements in capacity, signal integrity, and throughput that can be observed through the use of OFDM and multi antenna techniques in below-deck environments.

FOR MORE DETAILS 

PERFORMANCE EVALUATION OF MIMO OFDM SYSTEMS IN ON-SHIP BELOW-DECK