166 research outputs found
Simulation framework for multigigabit applications at 60 GHz
This dissertation describes the implementation of a OFDM-based simulation framework
for multigigabit applications at 60 GHz band over indoor multipath fading channels.
The main goal of the framework is to provide a modular simulation tool designed
for high data rate application in order to be easily adapted to a speci c standard or
technology, such as 5G. The performance of OFDM using mmWave signals is severely
a ected by non-linearities of the RF front-ends. This work analyses the impact of RF
impairments in an OFDM system over multipath fading channels at 60 GHz using the
proposed simulation framework. The impact of those impairments is evaluated through
the metrics of BER, CFR, operation range and PSNR for residential and kiosk scenarios,
suggested by the standard for LOS and NLOS. The presented framework allows
the employment of 16 QAM or 64 QAM modulation scheme, and the length of the
cyclic pre x extension is also con gurable. In order to simulate a realistic multipath
fading channel, the proposed framework allows the insertion of a channel impulse response
de ned by the user. The channel estimation can be performed either using
pilot subcarriers or Golay sequence as channel estimation sequences. Independently of
the channel estimation technique selected, frequency domain equalization is available
through ZF approach or MMSE. The simulation framework also allows channel coding
techniques in order to provide a more robustness transmission and to improve the link
budget
Efficient Implementation of Complementary Golay Sequences for PAR Reduction and Forward Error Correction in OFDM-based WLAN systems
In this paper the use of complementary Golay sequences (CGS) for peak-to-average power ratio (PAR) reduction and forward error correction (FEC) in an orthogonal frequency division multiplexing (OFDM)-based wireless local area network (WLAN) system is explored; performance is examined and complexity issues are analyzed. We study their PAR reduction performance depending on sequence lengths and we have found that, for the case that the number of sub-carriers differs from the sequence length, some interesting relationships can still be stated. Regarding their error correction capabilities, these sequences are investigated considering M-PSK constellations applied to the OFDM signal specified in IEEE 802.11a standard. Computational load for both Golay encoding and decoding processes is addressed and we provide an exhaustive analysis of their complexity. In order to overcome memory restrictions and speed up algorithmic operations, a novel algorithm for real-time generation of the Golay Base Sequences is proposed and evaluated giving as a conclusion that these sequences can be real-time generated with actual Digital Signal Processors (DSP). Our proposal lies on an efficient permutation algorithm that obtains the current permutation without the need for generating previous ones. Its complexity is calculated and turns out to be significantly low; the advantages are specially appreciated at the decoding stage. We also introduce a hybrid solution to get a trade-off between complexity and memory requirements. Moreover, the whole system is also implemented in a DSP to validate the proposal in a prototype, where its feasibility has been confirmed.This work has been partly funded by the Spanish government with projects MACAWI (TEC 2005-07477-c02-02) and MAMBO (UC3M-TEC-05-027)
Large Zero Autocorrelation Zone of Golay Sequences and -QAM Golay Complementary Sequences
Sequences with good correlation properties have been widely adopted in modern
communications, radar and sonar applications. In this paper, we present our new
findings on some constructions of single -ary Golay sequence and -QAM
Golay complementary sequence with a large zero autocorrelation zone, where
is an arbitrary even integer and is an arbitrary integer.
Those new results on Golay sequences and QAM Golay complementary sequences can
be explored during synchronization and detection at the receiver end and thus
improve the performance of the communication system
High power amplifier pre-distorter based on neural-fuzzy systems for OFDM signals
In this paper, a novel High Power Amplifier (HPA) pre-distorter based on Adaptive Networks - Fuzzy Inference Systems (ANFIS) for Orthogonal Frequency Division Multiplexing (OFDM) signals is proposed and analyzed. Models of Traveling Wave Tube Amplifiers (TWTA) and Solid State Power Amplifiers (SSPA), both memoryless and with memory, have been used for evaluation of the proposed technique. After training, the ANFIS linearizes the HPA response and thus, the obtained signal is extremely similar to the original. An average Error Vector Magnitude (EVM) of 10-6 can be easily obtained with our proposal. As a consequence, the Bit Error Rate (BER) degradation is negligible showing a better performance than what can be achieved with other methods available in the literature. Moreover, the complexity of the proposed scheme is reducedThis work was supported in part by projectsMULTIADAPTIVE
(TEC2008-06327-C03-02) and AECI Program of Research Cooperation
with MoroccoPublicad
Multicarrier-signal design with low peaks and low out-of-band power
Projecte fet en col.laboració amb el Department of Electrical and Information Technology. Lund UniversityThe high peak-to-average power ratio (PAPR) and the high out-of-band power
(OBP) are two major drawbacks of multicarrier communication systems. Many
PAPR reduction and OBP supression techniques have been proposed in the literature
whereas not much has been proposed regarding the jointly reduction performance.
This thesis focuses on joint reducing time-domain peaks and out-of-band
leakage of OFDM signals. The resulting algorithm combines the bene ts of both
methods and yields better results than each method does separately
Multicarrier-signal design with low peaks and low out-of-band power
Projecte fet en col.laboració amb el Department of Electrical and Information Technology. Lund UniversityThe high peak-to-average power ratio (PAPR) and the high out-of-band power
(OBP) are two major drawbacks of multicarrier communication systems. Many
PAPR reduction and OBP supression techniques have been proposed in the literature
whereas not much has been proposed regarding the jointly reduction performance.
This thesis focuses on joint reducing time-domain peaks and out-of-band
leakage of OFDM signals. The resulting algorithm combines the bene ts of both
methods and yields better results than each method does separately
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