Modified widely linear filter for simultaneous multi-impairment compensation
We present a modified w idely l inear s ingle-tap b lind e qualizer f or t he joint multi-impairment compensation of polarization mixing, IQ Imbalance and transceiver phase noise, analyze its performance through simulation and experiments for 32Gbaud PM-16QAM transmission.
Optimal MTM spectral estimation based detection for cognitive radio in HDTV
Cognitive radio based systems rely on spectrum sensing techniques to detect whitespaces to exploit. For the sake of ease of implementation, simple schemes such as energy detector have been proposed and studied widely. However, such simple schemes perform far from optimally, thereby affecting the performance of the underlying system. On the other hand sophisticated detectors are difficult to implement, giving rise to a trade-off. This paper explores the idea of using spectral estimates for detection. The case of HDTV based cognitive radio is explored and an optimal detection scheme following multi taper estimation is proposed and studied. © 2012 IEEE.
A new diagonally layered spatial multiplexing scheme with partial channel knowledge
Vertical layering with successive interference cancellation (SIC) at the receiver (e.g. V-BLAST) is a popular spatial multiplexing scheme that achieves high data rates over multi-antenna wireless channels. However, SIC suffers from low diversity gains and recently, with limited feedback, a diversity optimal SIC receiver has been proposed based on greedy QR decomposition (GQR-SIC). But the low diversity gain of the first decoded layer degrades the overall diversity gain. In this paper, we present a new diagonally layered spatial multiplexing scheme that employs GQR-SIC receiver but achieves significantly higher diversity gains. In the proposed scheme, the diversity gain of a weak layer is improved through interleaving the co-ordinates of the symbols transmitted over the weak layer and a strong layer. In this work, we focus on spatial multiplexing with only two layers and analyze the diversity multiplexing tradeoff to show that the proposed scheme achieves maximum diversity gain. When compared with other diagonally layered schemes, the proposed scheme has low decoding complexity. © 2008 IEEE.
Adaptive Referencing Multitap Filter for TX-IQ Imbalance and Residual ISI Tolerance
We present a multi-tap filter for residual intersymbol interference correction which is tolerant to the transmitter IQ imbalance by adapting the reference constellation simultaneously. We evaluate the algorithm's performance for various imbalance values for 32-GBd 16QAM signals through experiments.
Design of command and Data Management System for IITMSAT
In this paper we describe the design and development of the Command and Data Management System (CDMS) of the nano-satellite of IIT Madras, named IITMSAT. The CDMS module uses a 32-bit ARM microcontroller from Freescale - KL46Z256VLL4. This module is responsible for decoding the telecommands sent from the ground station, and transmits the time-stamped payload data back as telemetry packets. The SD card on the CDMS board stores the satellite's health and science data as and when it is acquired in the orbit. The data is transmitted to the ground station (GS) during the satellite's visibility period. The interface board (I/F) links the Flight Computer module and CDMS board along with other electronics onboard. Throughout the design phase, the cost was kept as low as possible, without compromising on performance of the system. Custom-designed protocol and data frame format for communication between the satellite and ground station was completely developed from scratch, based on CCSDS cubesat standards.
Set-partitioning based forward/backward soft decision algorithms for MIMO detection
A near maximum a posteriori (MAP)-optimal soft detector that outputs a posteriori probabilities (APP's) for multiple-input multiple-output (MIMO) systems in flat fading channels is proposed. This is referred to as 'reduced state maximum a posteriori (RSMAP)' algorithm. This detection algorithm is based on BCJR algorithm and also uses ideas from reduced state sequence estimation (RSSE) and set partitioning. This algorithm is shown to be near optimal and the computational complexity to implement it is estimated. Finally we also show that applying the well known max-log approximation on this algorithm results in nearly same performance at much lower complexity. © 2012 IEEE.
Faster-Than-Nyquist Signaling with Constraints on Pulse Shapes
Faster-Than-Nyquist (FTN) Signaling is a non-orthogonal transmission scheme which violates the Nyquist zero-ISI criterion providing higher throughput and better spectral efficiency than a Nyquist transmission scheme. This comes with a cost of higher transceiver complexity. In this paper, we focus on understanding pulse shapes and their inter-symbol-interference (ISI) and show that, under certain conditions on pulse shapes and τ (time acceleration factor), the ISI can be avoided completely with the help of precoding. This leads to a symbol-by-symbol detection. Further, we extend this idea to Orthogonal Frequency Division Multiplexing (OFDM) FTN systems and show that, under certain conditions, the average performance of OFDM system reaches that of a Nyquist system. Finally, simulation results of the performance of precoded and non-precoded single carrier and OFDM FTN systems are compared to a Nyquist system.
A low complexity EDGE demodulator based on FDE and impulse response shortening
In this paper, a new low-complexity frequency-domain based technique is proposed for channel equalization and symbol detection of an Enhanced Data Rate for Global Evolution (EDGE) cellular system, which uses 8-PSK modulation. The proposed method exploits the present of tail symbols in the EDGE slot structure and uses them as partial Cyclic Prefix in the frequency domain equalizer. For channels with longer memory than the tail length, the receiver computes a channel shortening filter such that, when the filter is cascaded with receive chain, results in a shorter effective impulse response. The parameters of the channel shortening are set such that the effective impulse response memory length is equal to the tail length. The performance of the proposed system is demonstrated by computer simulations. © 2007 IEEE.
Geometric Parameter Extraction-based Receiver IQ imbalance correction for MQAM systems
We present a modulation transparent geometric parameter extraction method to compensate for the receiver IQ imbalance. We evaluate the algorithm's performance for various imbalance values for 32-GBd 16/64QAM signals in both simulations and through experiments.
2-Inverted U-Slot Integrated Rectangular Patch Antenna Array for S band Applications
In this paper, a 2 inverted U-slot integrated rectangular patch antenna array is proposed that can be used for S band applications i.e., radar applications, communication and wireless networks. In the proposed antenna design 2 inverted U slots are introduced in the patch to improve bandwidth providing a bandwidth of 150 MHz and gain of 4.08 dBi resonating at 3.3 GHz. Furthermore, 4 X 4 antenna array is fabricated on 1.6 mm thick FR4 substrate with dielectric constant 4.4 providing a gain of 14.2 dBi. Ansys HFSS is used for antenna simulation and a prototype is fabricated and tested.