The Page contains all published work in the form of conference proceedings and journal articles. The work presented here is from Antenna Design, OFDM, PAPR Reduction from OFDM, Channel Estimation for OFDM System, MIMO Channel Estimation, MIMO System Diversity and MIMO System Design on USRP.
MIMO is one of the techniques proposed to 3G and 4G LTE-A systems for its added benefits of higher data rates and low bit error rates. The gist of MIMO working is its ability to increase number of channels; thus increasing diversity gain. Correspondingly, more users are accommodated in one communication system. In this work, different MIMO schemes more specifically receive and transmit diversity are analyzed using MATLAB Simulations and the performance criteria are bit error rates (BER), Cumulative Distribution Function (CDF) and channel capacity. MIMO has perfect results but it increases system complexity and this particular constraint limits its implementation to 2 x 2. More advanced system now days are a bit advanced 4 x 4 system but this is the limit till now. It’s an open field and requires much attention for great explorations.
OFDM systems use efficiently the broad spectrum thus meeting the current requirements of new standards laid down by 3GPP. Along with the high data rates, it also competes with other mechanisms providing a good link quality. However, it suffers with Sample Time Offset (STO) and Carrier Frequency Offset (CFO) which must be taken care of at the receiver end. In the current work, effects of STO are studied and correspondingly different precautionary schemes are employed in the receiver to overcome it. These schemes are compared with the help of simulations done on MATLAB.
Optimization of the communication systems is one of the big challenges to the modern world. The problem is nicely dealt by the GNU Radio; a cheaper and powerful tool. GNU Radio companion (GRC) gives the simplicity to use as is the case with normal Python language used for programming. The Universal Software Radio Peripheral (USRP) gives the boost to GNU Radio capabilities. Software Defined Radio (SDR) is easily implemented by the combination of GNU Radio and USRP with its own ability of easier handling. Two techniques of Radio reception namely Amplitude Modulation (AM) and Single Side Band (Single Side Band) Modulation are compared and analyzed with the help of GRC in current work. The GNU Radio version 3.2.2 is used with USRP1.
Development in the wireless communication systems is the evolving field of research in today’s world. The demand of high data rate, low latency at the minimum cost by the user requires many changes in the hardware organization. The use of digital modulation techniques like OFDM assures the reliability of communication in addition to providing flexibility and robustness. Modifications in the hardware structure can be replaced by the change in software only which gives birth to Software Define Radio (SDR): a radio which is more flexible as compared to conventional radio and can perform signal processing at the minimum cost. GNU Radio with the help of Universal Software Peripheral Radio (USRP) provides flexible and the cost effective SDR platform for the purpose of real time video transmission. The results given in this paper are taken from the experiment performed on USRP-1 along with the GNU Radio version 3.2.2.
Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation and multiplexing technique proposed for 3G, 4G LTE-A systems to achieve higher data rates with better spectral efficiency at low latency. Time varying nature of the wireless channel can cause frequency selectivity and multipath fading which affects performance of the system badly. Channel estimation techniques are proposed to tackle the issue and results in improved performance. In this paper, training based channel estimation techniques like Least Square and Minimum Mean Square Error are discussed. Both techniques are compared for Bit Error Rate (BER) performance and computational complexity in MATLAB.
Orthogonal Frequency Division Multiplexing (OFDM) is an emerging field of research in the field of wireless communication and finds its application where high data rate is required at low latency and better spectral efficiency. Peak to Average Power Ratio (PAPR) is the limiting factor for an OFDM system as it degrades the system performance by reducing SQNR of ADC/DAC as well as affects transmitter amplifier. There are many techniques to overcome the problem of PAPR like Clipping and Filtering, Coding Technique, Scrambling Technique and many more. In this paper we discussed clipping and filtering technique which is easy to implement and reduces the amount of PAPR by clipping the peak of the maximum power signal. Moreover, analysis of PAPR is given by varying different parameters.
Wireless communication is the key area of research with increasing demand of high data rate applications at a low cost. Orthogonal Frequency Division Multiplexing (OFDM) is a promising solution for this problem. It is a multi carrier modulation and as well as a multiplexing technique proposed for 3G, 4G, LTE-A systems to support high data rate applications in a fading environment. Many problems linked with the multi carrier transmission like phase variations and Carrier Frequency Offset (CFO) are prominent. In this paper we analyze CFO and its effect in detail for OFDM symbol and then describe techniques to estimate CFO. The estimation techniques cover both domains; time and frequency for OFDM system. The simulations results are analyzed and presented in this paper are performed in MATLAB.