Results 171 to 180 of about 8,421 (222)
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On the optimality of the OFDMA network
IEEE Communications Letters, 2005This letter studies the optimality of the OFDMA network. It is proved that in the multiuser multicarrier downlink system with independent decoding, OFDMA is the optimal multiple access scheme. It is also shown that the optimality of OFDMA holds for any adaptive modulation scheme whose rate-SNR/SINR function can be approximated as a convex function.
Guoqing Li, Hui Liu 0011
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An Analysis of Uplink OFDMA Optimality
IEEE Transactions on Wireless Communications, 2006Motivated by the increasing popularity of OFDMA, this paper studies the sum-rate optimality of OFDMA as an uplink multicarrier multiple-access scheme. We address the relationship between OFDMA and the optimal multicarrier multiple- access schemes.
Hongxiang Li 0001, Hui Liu 0011
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IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference, 2007
In current OFDMA systems, three major problems arise due to the large number of subcarriers, including high peak to average power ratio (PAPR), sensitivity to carrier frequency offset (CFO), and high complexity in user terminal. In this paper, based on an innovative concept of Layered FFT structure, we propose novel quadrature OFDMA system which can ...
Jian (Andrew) Zhang +2 more
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In current OFDMA systems, three major problems arise due to the large number of subcarriers, including high peak to average power ratio (PAPR), sensitivity to carrier frequency offset (CFO), and high complexity in user terminal. In this paper, based on an innovative concept of Layered FFT structure, we propose novel quadrature OFDMA system which can ...
Jian (Andrew) Zhang +2 more
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An Analysis of OFDMA, Precoded Ofdma and SC-FDMA for the Uplink in Cellular Systems
2007Orthogonal Frequency Division Multiple Access (OFDMA) appears today as a strong candidate in on-going standardization. Despite its attractive features, it has several drawbacks when employed in the uplink: The high peak-to-average power ratio (PAPR) inherited from Orthogonal Frequency Division Multiplexing (OFDM) and the inherent frequency diversity ...
Ciochina, Cristina +2 more
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2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, 2009
To alleviate the high peak-to-average power ratio (PAPR), high complexity in user terminal and sensitivity to carrier frequency offset (CFO) problems in current OFDMA systems, a Quadrature OFDM (Q-OFDMA) system has been recently proposed in the single-input single-output environment.
Lin Luo 0002 +2 more
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To alleviate the high peak-to-average power ratio (PAPR), high complexity in user terminal and sensitivity to carrier frequency offset (CFO) problems in current OFDMA systems, a Quadrature OFDM (Q-OFDMA) system has been recently proposed in the single-input single-output environment.
Lin Luo 0002 +2 more
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Opportunistic Feedback in OFDMA Downlink
IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference, 2007This paper presents an opportunistic feedback (OF) protocol that reduces the amount of channel-state-information (CSI) feedback for the OFDMA downlink system. The OF protocol associates a channel value instead of a user to each feedback slot. The users access the slots opportunistically based on their channel state measurement for each tone.
Rajiv Agarwal +3 more
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Approximability of OFDMA Scheduling
2009In this paper, we study the complexity and approximability of the orthogonal frequency-division multiple-access (OFDMA) scheduling problem with uniformly related communication channels.
Marcel Ochel, Berthold Vöcking
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Detection Opportunities for CDM-OFDMA
2006 IEEE 63rd Vehicular Technology Conference, 2006In this paper, we present a synchronous code division multiplexing (CDM) scheme that uses orthogonal frequency division multiple access (OFDMA) to separate different users. The CDM component multiplies each data symbol with a different phase shift. This results in unique chips, which represent a new alphabet.
Raulefs, Ronald +2 more
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Coded Cooperation in OFDMA Systems
2006 40th Annual Conference on Information Sciences and Systems, 2006A novel time-frequency cooperative communication strategy is proposed for coded OFDMA system over quasi-static frequency-selective Rayleigh fading. To take advantage of the frequency dispersion, each user transmits his partner's and his own data on different subcarriers spreading over the entire available bandwidth.
Jun Niu, I-Tai Lu
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OFDMA for underwater acoustic communications
2011 49th Annual Allerton Conference on Communication, Control, and Computing (Allerton), 2011We investigate the possibility of using orthogonal frequency division multiple access (OFDMA) for design of efficient underwater acoustic (UWA) networks. The major challenge for the OFDMA-based UWA communication systems is the Doppler-induced frequency scaling, which may cause severe intercarrier interference (ICI), and depending on the particular user
Kai Tu +3 more
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