Performance of M-QAM, M-DPSK and M-PSK with MRC diversity in a Nakagami-m fading channel

The nature of a wireless communication channel is very unpredictable. To design a good communication link, it is required to know the statistical model of the channel accurately. The average symbol error probability(ASER) was analyzed for different modulation schemes. A unified analytical framework was presented to obtain closed-form solutions for calculating the ASER of M-ary differential phase-shift keying(M-DPSK), coherent M-ary phase-shift keying(M-PSK), and quadrature amplitude modulation(QAM) over single or multiple Nakagami-m fading channels. Moreover, the ASER was estimated and evaluated by using the maximal ratio-combining(MRC) diversity technique. Simulation results show that an error rate of the fading channel typically depends on Nakagami parameters(m), space diversity(N), and symbol rate(M). A comparison between M-PSK, M-DPSK, and M-QAM modulation schemes was shown, and the results prove that M-ary QAM(M-QAM) demonstrates better performance compared to M-DPSK and M-PSK under all fading and non-fading conditions.

Assessing the impacts of current and future changes of the planforms of river Brahmaputra on its land use-land cover

River bankline migration is a frequent phenomenon in the river of the floodplain region.Nowadays,channel dynamics-related changes in land use and land cover(LULC)are becoming a risk to the life and property of people living in the vicinity of rivers.A comprehensive evaluation of the causes and consequences of such changes is essential for better policy and decision-making for disaster risk reduction and management.The present study assesses the changes in the Brahmaputra River planform using the GIS-based Digital Shoreline Analysis System(DSAS)and relates it with the changing LULC of the floodplain evaluated using the CA-Markov model.In this study,the future channel of the Brahmaputra River and its flood plain’s future LULC were forecasted to pinpoint the erosion-vulnerable zone.Forty-eight years(1973–2021)of remotely sensed data were applied to estimate the rate of bankline migration.It was observed that the river’s erosion-accretion rate was higher in early times than in more recent ones.The left and right banks’average shifting rates between 1973 and 1988 were -55.44 m/y and -56.79 m/y,respectively,while they were-17.25 m/y and -48.49 m/y from 2011 to 2021.The left bank of the river Brahmaputra had more erosion than the right,which indicates that the river is shifting in the leftward direction(Southward).In this river course,zone A(Lower course)and zone B(Middle course)were more adversely affected than zone C(Upper course).According to the predicted result,the left bank is more susceptible to bank erosion than the right bank(where the average rate of erosion and deposition was -72.23 m/y and 79.50 m/y,respectively).The left bank’s average rate of erosion was -111.22 m/y.The research assesses the LULC study in conjunction with river channel dynamics in vulnerable areas where nearby infrastructure and settlements were at risk due to channel migration.The degree of accu-racy was verified using the actual bankline and predicted bankline,as well as the actual LULC map and anticipated LULC map.In more than 90% of cases,the bankline’s position and shape generally remain the same as the actual bankline.The overall,and kappa accuracy of all the LULC maps was more than 85%,which was suitable for the forecast.Moreover,chi-square(x^(2))result values for classified classes denoted the accuracy and acceptability of the CA-Markov model for predicting the LULC map.The results of this work aim to understand better the efficient hazard management strategy for the Brahmaputra River for hazard managers of the region using an automated prediction approach.

Pilot Contamination Reduction by Shifted Frame Structure in Massive MIMO TDD Wireless System

Pilot contamination limits the performance of massive multiple-input multiple-output（MIMO） system severely due to the degraded channel estimation. An efficient way to solve this problem in time division duplex（TDD） wireless system is shifting the location of pilots in time frames used in neighboring cells. However, the shifted frame structure has only been studied in MIMO system with the ideal independent and identically distributed（i.i.d.） channel coefficients. In this paper, the shifted frame structure is studied in a measured channel with a large number of antennas for a certain class of channel fading statistics. To deal with the high inter-cell interference caused by the shifted frame structure in such a measured channel condition, we propose a scenario with a covariance-aided channel estimator. This scenario shows that pilot contamination can be solved and the high inter-cell interference can be made to vanish asymptotically with the number of antennas. The key of the interference rejection is obtaining the precise condition on the second order statistics for the desired and interference signals. The most significant information of the second order statistics comes from two parts, one is the channel state information（CSI） among the base stations（BSs）, the other comes from the estimated information exchanged by the BSs, which depicts the channel between the BSs and the users. The simulations give powerful results of the interference rejection and the achievable rate promotion.