Trade-Off Between Frequency Diversity Gain and Frequency-Selective Scheduling Gain in OFDMA Systems with Spatial Diversity

2007 ◽  
Vol 11 (6) ◽  
pp. 507-509 ◽  
Author(s):  
Seung Lee
Keyword(s):  
Spatial Diversity ◽  
Diversity Gain ◽  
Frequency Diversity ◽  
Trade Off ◽  
Frequency Selective

scholarly journals Single-RF Diversity Receiver for OFDM System Using ESPAR Antenna with Alternate Direction

1970 ◽  
Vol 6 (1) ◽  
pp. 89-93 ◽  
Author(s):  
Satoshi Tsukamoto ◽  
Minoru Okada
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Propagation ◽  
Maximal Ratio Combining ◽  
Diversity Gain ◽  
Efficient Technique ◽  
Selective Fading ◽  
Frequency Selective Fading ◽  
Frequency Selective ◽  
Diversity Scheme

This paper presents a single-RF diversity scheme for orthogonal frequency division multiplexing (OFDM) receiver using Electronically Steerable Passive Array Radiator (ESPAR) antenna whose direction changes alternately at the OFDM symbol rate. OFDM is widely used for mobile communication systems because of its broadband wireless transmission capability in a severe time dispersive multipath propagation channel. OFDM is, however, not efficient for mitigating the performance degradation due to fading. Diversity is an efficient technique for solving this problem. Although maximal ratio combining diversity is the most efficient technique, it requires the same number of RF front-end circuitry and analog-todigital converters (ADC) as antennas. Although ESPAR antenna-based diversity technique requires only a single-RF and ADC, the convergence is not fast enough to track fast variation of the channel state. Furthermore, it is not efficient in a frequency selective channel. In this paper, we propose a new OFDM diversity scheme using ESPAR antenna. The proposed scheme is capable of obtaining the diversity gain in a frequency selective fading environment and avoids the slow convergence rate problem in the conventional technique using ESPAR antenna. Computer simulation results show that the proposed scheme gives diversity gain in a frequency selective fading channel.

scholarly journals Frequency Diversity Gain of a Wideband Radar Signal

2021 ◽  
Vol 13 (23) ◽  
pp. 4885
Author(s):  
Mengmeng Shen ◽  
Feng He ◽  
Zhen Dong ◽  
Xing Chen ◽  
Lei Yu ◽  
...  
Keyword(s):  
Detection Probability ◽  
Signal To Noise Ratio ◽  
Optimal Number ◽  
Diversity Gain ◽  
Practical Significance ◽  
Radar Signal ◽  
Target Range ◽  
Frequency Diversity ◽  
Target Model ◽  
Wideband Radar

Wideband radar has high-range directional resolution, which can effectively reduce the fluctuation of echo and improve the detection probability of a target under the same detection probability requirement. In this paper, a unified wideband radar χ2 distribution target model with more practical significance is innovatively established, on which the probability density function and detection probability function of Swerling 0, Swerling II and Swerling IV targets are analyzed, respectively. A generalized “frequency diversity gain” of wideband radar is proposed and defined based on the contradiction between suppression of fluctuation and accumulation loss, which represents the ratio of Signal-to-Noise Ratio (SNR) gain between broadband signal and reference bandwidth signal under the same condition (when the reference bandwidth is used, the radar target has only one range unit), and the mathematical relation equation of the target detection performance and signal bandwidth (equivalent to the number of distinguishable range elements of the target) is given. A Monte Carlo simulation experiment is designed. Based on the target model established in this paper, the optimal number of target range units corresponding to different detection probability requirements is obtained, which verifies the correctness of the concept proposed in this paper.

scholarly journals Dual-Hop OSTBC Transmissions Over Fading Channels under Receiver Phase Noise for Regenerative Systems

2012 ◽  
pp. 22-26
Author(s):  
K. Sujatha ◽  
S. Varadarajan
Keyword(s):  
Fading Channels ◽  
Channel Model ◽  
Spatial Diversity ◽  
Space Time ◽  
Delay Spread ◽  
Frequency Diversity ◽  
Space Time Coding ◽  
Propagation Parameters ◽  
Space Frequency ◽  
Time Coding

Space-time coding for fading channels is a Communication technique that realizes the diversity benefits of multiple transmit antennas. Previous work in this area has focused on the narrowband flat fading case where spatial diversity only is available. In this paper, we investigate the use of space-time coding in OFDM based broadband systems where both spatial and frequency diversity are available. We consider a strategy which basically consists of coding across OFDM tones and will therefore be called space-frequency coding. For a spatial broadband channel model taking into account physical propagation parameters and antenna spacing, we derive the design criteria for space-frequency codes and we show that space-time codes designed to achieve full spatial diversity in the narrowband case will in general not achieve full space-frequency diversity. Specifically, we show that the Alamouti scheme across tones fails to exploit frequency diversity. For a given set of propagation parameters and given antenna spacing, we establish the maximum achievable diversity order. Finally, we provide simulation results studying the influence of delay spread, propagation parameters, and antenna spacing on the performance of Space-frequency codes.

scholarly journals A Low-Complexity Resource Allocation Algorithm for MIMO-OFDMA Multicast Systems with Spectrum-Guarantee Provisioning

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Ioannis G. Fraimis ◽  
Stavros A. Kotsopoulos
Keyword(s):  
Resource Allocation ◽  
Complexity Analysis ◽  
Multiple Input Multiple Output ◽  
Low Complexity ◽  
Spatial Diversity ◽  
Frequency Diversity ◽  
Resource Allocation Algorithm ◽  
Allocation Algorithm ◽  
Input Multiple Output ◽  
Efficient Resource

We study the important problem of resource allocation for the downlink of Multiple-Input Multiple output (MIMO) Multicast Wireless Systems operating over frequency-selective channels and we propose a low-complexity but efficient resource allocation algorithm for MIMO-enabled OFDMA systems. The proposed solution guarantees a minimum spectrum share for each user while also takes advantage of the multicast transmission mode. The presence of multiple antennas in both transmitter and receiver offers spatial diversity to the system along with the frequency diversity added by the OFDMA access scheme. The computational complexity is reduced from exponential to linear and validation of the proposed solution is achieved through various simulation scenarios in comparison with other multicast and unicast reference schemes used in MIMO-OFDMA systems. Numerical results and complexity analysis demonstrate the feasibility of the proposed algorithm.

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