Department of Electrical and Electronics Engineering
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Item A dynamic resource allocation model along with adaptive power control in a multi-rate direct sequence CDMA with MIMO(IEEE, 2012) Chaubey, V.K.A throughput maximization algorithm for a CDMA system comprising of variable bit rate (VBR) groups has been proposed. The algorithm is aimed at efficiently utilizing the radio resources for maximal throughput while meeting the minimum data transmission rate and Quality of Service (QoS) requirements of each user group. The power of each group is also dynamically controlled so as to minimize the cell interference thereby maximizing the system capacity. The model also predicts the reduction in effective cell radius because of cell breathing under Gaussian noise and a Rayleigh faded channel. The simulation of multiple input multiple output (MIMO) antenna in such a system reports an improvement in the Bit Error Rate (BER) performance of the system by up to 80%. The allocation scheme efficiently utilizes as much as 99.9% of the available bandwidth in the system.Item Modeling and characterization of multi-rate direct sequence CDMA system using dynamic resource allocation scheme(IEEE, 2012) Chaubey, V.K.; Chamola, VinayIn this paper the resource allocation problem in multirate direct-sequence code division multiple access (DS-CDMA) has been discussed. A spectral efficiency maximization algorithm for a CDMA system comprising of variable bit rate (VBR) groups has been proposed here. The developed algorithm is capable to utilize the available radio resources efficiently to maximize the spectral efficiency of the system. The power of each group is dynamically controlled to minimize the cell interference thereby enhancing the system capacity. A mathematical model is also developed to estimate the effect of voice activity factor and antenna sectorization on dynamic resource allocation. The proposed model shows significant improvement in bandwidth utilization. The Bit Error Rate (BER) performance of the above model is also measured in presence of Gaussian Noise and Rayleigh fadingItem OVSF code generator for 3G wireless transceivers using Xilinx System Generator(IEEE, 2013) Chaubey, V.K.The Orthogonal variable spreading factor (OVSF) codes were first introduced for 3G standards. The OVSF are channelization codes are widely used for preserving the orthogonality between physical channels in a communication system. They become essential for increasing system capacity as well as to provide multiple data rates for supporting different bandwidth requirements. This scheme is known as OVSF-CDMA. This paper presents the hardware co-simulation realization of parameterized OVSF code with classical counter based approach using Xilinx System Generator software tools. The OVSF code is first modeled in MATLAB Simulink based system generator using Black box in VHDL for delay synthesis, timing analysis and validating for software testing as per required standard for WCDMA i.e. TCHIP is 260ns or FCHIP 3.84 MHz. The claimed result i.e. 2ns can meet the time specification of desired standards. The target FPGA device is Virtex-5 (XC5VLX50T-1ff1136).Item FPGA based implementation & power analysis of parameterized Walsh sequences(IEEE, 2014) Chaubey, V.K.This paper presents FPGA based implementation of the theory which replaces a general Sine and cosine function by set of orthogonal functions i.e. Walsh function. The paper further compares Parameterized `Serial In Serial Out' architectures based on classical counter approach. The investigation consider FPGA parameters like Area, Speed and Power and shows that using Gray-increment based architecture instead of Binary saves 6mW of power per symbol (64 Walsh chips per symbol) with 30% reduction in area. The design is implemented in VHDL code, simulated in MATLAB System Generator environment and validated with MATLAB Simulink Model. The design targeted Xilinx Virtex-5 “XC5VLX50T-1ff1136” FPGA device for the implementation and comparison. The design found their uses in many popular applications like Software Define Radio (SDR) including multiuser communications such as CDMA, WCDMA, VLSI testing, pattern recognition as well as image and signal processing.