605 research outputs found
Shaping spectral leakage for IEEE 802.11 p vehicular communications
IEEE 802.11p is a recently defined standard for the physical (PHY) and medium access control (MAC) layers for Dedicated Short-Range Communications. Four Spectrum Emission Masks (SEMs) are specified in 802.11p that are much more stringent than those for current 802.11 systems. In addition, the guard interval in 802.11p has been lengthened by reducing the bandwidth to support vehicular communication (VC) channels, and this results in a narrowing of the frequency guard. This raises a significant challenge for filtering the spectrum of 802.11p signals to meet the specifications of the SEMs. We investigate state of the art pulse shaping and filtering techniques for 802.11p, before proposing a new method of shaping the 802.11p spectral leakage to meet the most stringent, class D, SEM specification. The proposed method, performed at baseband to relax the strict constraints of the radio frequency (RF) front-end, allows 802.11p systems to be implemented using commercial off-the- shelf (COTS) 802.11a RF hardware, resulting in reduced total system cost
Peak to Average Power Ratio Reduction in OFDM Using Pulse Shaping Technique
Orthogonal Frequency Division Multiplexing (OFDM) is a special type of multicarrier modulation in which a signal is split into several narrowband channels at different frequencies. Here data is divided into parallel data streams each transmitted on a separate band. One of the major drawbacks of multicarrier transmission is the high peak-to-average power ratio (PAPR) of the transmit signal. Nyquist filters provide ISI-free transmission. In this paper we are going to propose some new filters which can formulated in an effort to reduce the peak-to-average power ratio (PAPR) of the baseband signal. While maintaining the same excess bandwidth and the zero inter-symbol interference condition. The proposed filters contain various parameters which gives an additional degree of freedom to minimize PAPR for a given roll-off factor α
Weyl-Heisenberg Spaces for Robust Orthogonal Frequency Division Multiplexing
Design of Weyl-Heisenberg sets of waveforms for robust orthogonal frequency
division multiplex- ing (OFDM) has been the subject of a considerable volume of
work. In this paper, a complete parameterization of orthogonal Weyl-Heisenberg
sets and their corresponding biorthogonal sets is given. Several examples of
Weyl-Heisenberg sets designed using this parameterization are pre- sented,
which in simulations show a high potential for enabling OFDM robust to
frequency offset, timing mismatch, and narrow-band interference
ICI and PAPR enhancement in MIMO-OFDM system using RNS coding
The Inter-Carrier-Interference (ICI) is considered a bottleneck in the utilization of Multiple-Input-Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems, due to the sensitivity of the OFDM towards frequency offsets which lead to loss of orthogonality, interference and performance degradation. In this paper Residue Numbers as a coding scheme is impeded in MIMO-OFDM systems, where the ICI levels is measured and evaluated with respect to conventional ICI mitigation techniques implemented in MIMO-OFDM. The Carrier-to-Interference Ratio (CIR), the system Bit-Error-Rate (BER) and the Complementary Cumulative Distribution Function (CCDF) for MIMO-OFDM system with Residue Number System (RNS) coding are analyzed and evaluated. The results had demonstrated a performance of transmission model with and without RNS
Optical Time-Frequency Packing: Principles, Design, Implementation, and Experimental Demonstration
Time-frequency packing (TFP) transmission provides the highest achievable
spectral efficiency with a constrained symbol alphabet and detector complexity.
In this work, the application of the TFP technique to fiber-optic systems is
investigated and experimentally demonstrated. The main theoretical aspects,
design guidelines, and implementation issues are discussed, focusing on those
aspects which are peculiar to TFP systems. In particular, adaptive compensation
of propagation impairments, matched filtering, and maximum a posteriori
probability detection are obtained by a combination of a butterfly equalizer
and four 8-state parallel Bahl-Cocke-Jelinek-Raviv (BCJR) detectors. A novel
algorithm that ensures adaptive equalization, channel estimation, and a proper
distribution of tasks between the equalizer and BCJR detectors is proposed. A
set of irregular low-density parity-check codes with different rates is
designed to operate at low error rates and approach the spectral efficiency
limit achievable by TFP at different signal-to-noise ratios. An experimental
demonstration of the designed system is finally provided with five
dual-polarization QPSK-modulated optical carriers, densely packed in a 100 GHz
bandwidth, employing a recirculating loop to test the performance of the system
at different transmission distances.Comment: This paper has been accepted for publication in the IEEE/OSA Journal
of Lightwave Technolog
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