920 research outputs found
Bit Error Rate and Signal to Noise Ratio Performance Evaluation of OFDM System with QPSK and QAM M-array Modulation Scheme in Rayleigh, Rician and AWGN Channel Using MATLAB/Simulink
The Orthogonal Frequency Division Multiplexing (OFDM) is a practical application of both amplitude and phase modulation scheme and has taking its place in Multiplexing Techniques where a number of independent message signal are at the same time transmitted over a single channel. OFDM is beneficial in transmission with high data rate and better performance. High data rates are achieved by the use of multiple carriers and performance improvement. This paper is based on the QPSK and QAM of Different Modulation order. The performance Evaluation is done using the Bit Error Rate (BER) Against the Signal to Noise Ratio (SNR) parameters which shows a low BER to High SNR. At the end of the work, it was found out that the QPSK has more better performance in OFDM system than the QAM. QPSK has lower BER than the QAM in AWGN, Rayleigh and Rician channel. The performance of QPSK in OFDM is better than the QAM in the OFDM system. The simulation was done using MATLAB/SIMULINK. Keywords: Orthogonal Frequency Division Multiplexing, Quadrature Phase Shift Keying, Quadrature Amplitude Modulation, Bit Error Rate, Signal to Noise Ratio
Space-Time Coded Spatial Modulated Physical Layer Network Coding for Two-Way Relaying
Using the spatial modulation approach, where only one transmit antenna is
active at a time, we propose two transmission schemes for two-way relay channel
using physical layer network coding with space time coding using Coordinate
Interleaved Orthogonal Designs (CIOD's). It is shown that using two
uncorrelated transmit antennas at the nodes, but using only one RF transmit
chain and space-time coding across these antennas can give a better performance
without using any extra resources and without increasing the hardware
implementation cost and complexity. In the first transmission scheme, two
antennas are used only at the relay, Adaptive Network Coding (ANC) is employed
at the relay and the relay transmits a CIOD Space Time Block Code (STBC). This
gives a better performance compared to an existing ANC scheme for two-way relay
channel which uses one antenna each at all the three nodes. It is shown that
for this scheme at high SNR the average end-to-end symbol error probability
(SEP) is upper bounded by twice the SEP of a point-to-point fading channel. In
the second transmission scheme, two transmit antennas are used at all the three
nodes, CIOD STBC's are transmitted in multiple access and broadcast phases.
This scheme provides a diversity order of two for the average end-to-end SEP
with an increased decoding complexity of for an arbitrary
signal set and for square QAM signal set.Comment: 9 pages, 7 figure
LDPC concatenated space-time block coded system in multipath fading environment: Analysis and evaluation
Irregular low-density parity-check (LDPC) codes have been found to show exceptionally good performance for single antenna systems over a wide class of channels. In this paper, the performance of LDPC codes with multiple antenna systems is investigated in flat Rayleigh and Rician fading channels for different modulation schemes. The focus of attention is mainly on the concatenation of irregular LDPC codes with complex orthogonal space-time codes. Iterative decoding is carried out with a density evolution method that sets a threshold above which the code performs well. For the proposed concatenated system, the simulation results show that the QAM technique achieves a higher coding gain of 8.8 dB and 3.2 dB over the QPSK technique in Rician (LOS) and Rayleigh (NLOS) faded environments respectively
A Stochastic Geometric Analysis of Device-to-Device Communications Operating over Generalized Fading Channels
Device-to-device (D2D) communications are now considered as an integral part
of future 5G networks which will enable direct communication between user
equipment (UE) without unnecessary routing via the network infrastructure. This
architecture will result in higher throughputs than conventional cellular
networks, but with the increased potential for co-channel interference induced
by randomly located cellular and D2D UEs. The physical channels which
constitute D2D communications can be expected to be complex in nature,
experiencing both line-of-sight (LOS) and non-LOS (NLOS) conditions across
closely located D2D pairs. As well as this, given the diverse range of
operating environments, they may also be subject to clustering of the scattered
multipath contribution, i.e., propagation characteristics which are quite
dissimilar to conventional Rayeligh fading environments. To address these
challenges, we consider two recently proposed generalized fading models, namely
and , to characterize the fading behavior in D2D
communications. Together, these models encompass many of the most widely
encountered and utilized fading models in the literature such as Rayleigh, Rice
(Nakagami-), Nakagami-, Hoyt (Nakagami-) and One-Sided Gaussian. Using
stochastic geometry we evaluate the rate and bit error probability of D2D
networks under generalized fading conditions. Based on the analytical results,
we present new insights into the trade-offs between the reliability, rate, and
mode selection under realistic operating conditions. Our results suggest that
D2D mode achieves higher rates over cellular link at the expense of a higher
bit error probability. Through numerical evaluations, we also investigate the
performance gains of D2D networks and demonstrate their superiority over
traditional cellular networks.Comment: Submitted to IEEE Transactions on Wireless Communication
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