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whitepaper This paper considers the performance degradation of a high QAM orthogonal frequency division multiplexing (OFDM) system over frequency selective time-varying fading channels. The statistics of the ICI for M-QAM systems are shown to be non-Gaussian...
[10 Apr 2008]
whitepaper Single carrier QAM and multicarrier OFDM are compared to demonstrate the strength of OFDM in multipath channels. A MATLAB program has been written to investigate Orthogonal Frequency Division Multiplexing (OFDM) communication systems.
[07 Jan 2008]
whitepaper Many upstream modulation profile variables can be changed, such as guard time of the burst, preamble, modulation (quadrature phase shift keying [QPSK] or 16-quadrature amplitude modulation [QAM]), and forward error correction (FEC) protection.
[27 Nov 2007]
whitepaper The IC transmits 9 dBm/8 dBm Error Vector Magnitude (EVM)-compliant output power for a 64-QAM OFDM signal. Recent years have seen the rapid deployment of Wireless Local Area Networks (WLANs) in offices, homes, and hot spots, and numerous...
[26 Apr 2007]
whitepaper This paper proposes the use of QAM modulations with the constellation size larger than the currently used modulations in HYPERLAN/2, in order to achieve higher spectrum efficiency and data rate. Transmitter diversity and coding techniques can be...
[18 Apr 2007]
whitepaper By making use of standard Gaussian approximation to the interference for the AWGN channel, the paper illustrates how to estimate the symbol error rate of a M-QAM system. The effects of performing channel estimation in AWGN and Rayleigh channels...
[18 Apr 2007]
whitepaper The channel capacity of some ISI channels is examined under the condition that OFDM in conjunction with QAM modulation for subcarriers and the BICM coding scheme is used. The combination of higher order modulation schemes and low rate codes yields...
[14 Apr 2007]
whitepaper This paper addresses the subject of reducing the impact of phase noise on a QAM-OFDM system transmitting over an AWGN channel. Phase noise is known to have two effects on OFDM systems, rotating each symbol by a different Common Phase Rotation (CPR...
[14 Apr 2007]
whitepaper The author presents the construction of non-square M-QAM symbols from a combination of QPSK and BPSK signals when M=2n and n is an odd number. By using QPSK and BPSK Golay (or Golay-like) sequences, M-QAM sequences with low PMEPR are generated.
[11 Apr 2007]
whitepaper The close relationship between the peak factor of a QPSK/OFDM system and the one from a 16-QAM/OFDM system is presented and analyzed. It is shown that a 16- QAM/OFDM system shows larger peaks and is more difficult to analyze unless use is made of...
[11 Apr 2007]
whitepaper The aim of this paper is the performance evaluation of different combinations of digital modulation (QPSK, 16-QAM, 64-QAM) and channel coding schemes under NLOS channel conditions. The challenge for new generation broadband fixed wireless access...
[11 Apr 2007]
whitepaper It is also demonstrated that, in this respect, OFDM/OQAM outperforms OFDM/QAM systems using rectangular pulses. The high sensitivity to carrier frequency offset of OFDM systems compared to single carrier systems is well known.
[11 Apr 2007]
whitepaper In OFDM the high speed data stream is divided into Nc narrowband data streams, Nc corresponding to the subcarriers or subchannels i.e.one OFDM symbol consists of N symbols modulated for example by QAM or PSK.
[11 Apr 2007]
whitepaper This paper suggests applying constellation shaping to reduce the peak and average power of Orthogonal Frequency Division Multiplexing (OFDM) signals using Quadrature Amplitude Modulation (QAM) in all subcarriers without clipping or reducing the...
[11 Apr 2007]
whitepaper Each standard operates using adaptive sub-band Quadrate Amplitude Modulation (QAM) and offers a maximum data rate of 54 Mbits/s over a 20 MHz channel. Coded Orthogonal Frequency Division Multiplexing (COFDM) is currently specified in all three of...
[11 Apr 2007]
whitepaper For conventional modulation methods such as Phase-Shift Keying (PSK) and Quadrature-Amplitude Modulation (QAM), the bivariate probability density function (pdf) of the ICI is shown to be a weighted Gaussian mixture.
[11 Apr 2007]
whitepaper In addition to enabling higher bandwidth through channel bonding, Cisco Wideband also makes use of low-cost, field-proven edge QAM modulators to dramatically lower costs and also to increase density. Subscribers are increasingly demanding "Many...
[06 Oct 2006]
whitepaper The digital modulation schemes considered are M-ary QAM, M-ary PSK, M-ary CPM, M-ary MHPM, and GMSK with varying bit-duration-bandwidth product. In this paper, various adaptive modulation based coded MC-CDMA systems have been studied in Rayleigh...
[16 Jun 2006]
whitepaper As QAM and GFSK signal can be demodulated by using the same type of algorithms, the outer receiver of HiperLAN/2 can be used as a Bluetooth demodulator. The Software Defined Radio SDR project aims at combining two different types of standards...
[17 Nov 2005]
whitepaper This paper talks about an adaptive transmission scheme using QAM and LDPC code proposed for an OFDM cellular system employing FDD. By approximating the LLR distribution to a Gaussian distribution, only two parameters, the mean and the normalized...
[26 Jul 2005]
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