A study of adaptive modulation technique in OFDM

IEICE Trans. Fundamentals

Handa

2012

SUMMARYOrthogonal frequency division multiplexing (OFDM) has great advantages such as high spectrum efficiency and robustness against multipath fading. In order to enhance the advantages, an Hermitesymmetric subcarrier coding for OFDM, which is used for transmission systems like the asymmetric digital subscriber line (ADSL) and multiband OFDM in ultra-wideband (UWB) communications, is very attractive. The subcarrier coding can force the imaginary part of the OFDM signal to be zero, then another data sequence can be simultaneously transmitted in the quadrature channel. In order to theoretically verify the effectiveness of the Hermite-symmetric subcarrier coding in wireless OFDM (HC-OFDM) systems, we derive closed-form equations for bit error rate (BER) and throughput over fading channels. Our analytical results can theoretically indicate that the HC-OFDM systems achieve the improvement of the performances owing to the effect of the subcarrier coding.

Section: Performance Analysismentioning

confidence: 99%

“…In order to enhance the advantages, many elemental wireless technologies have been combined with OFDM, for example, space-time (or space-frequency) coding for diversity [3]- [5], adaptive modulation [6], [7], forward error correction (FEC) [8]- [10] and multi-input multi-output (MIMO) [11], [12].…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Hermite-Symmetric Subcarrier Coding for OFDM Systems over Fading Channels

IEICE Trans. Fundamentals

Handa

2012

“…It is already known by [17] that the OFDM with diversity technique (the space-frequency coded OFDM) can outperform the RS coded OFDM, then we briefly show the advantage of both turbo coded and repetition coded OFDM systems in the case of R = 1. We use popular rate-1/2 punctured turbo code which consists of two recursive systematic convolutional encoders with constraint length of 3, generator polynomial (7,5), and interleaver size of 10000 concatenated in parallel. We also use the BCJR algorithm as a decoding method.…”

Section: Application Of Fec To Proposed Ofdm Systemsmentioning

confidence: 99%

Performance Analysis of Repetition Coded OFDM Systems with Diversity Combining and Higher-Level Modulation

Jia

Handa

et al. 2011

IEICE Trans. Commun.

SUMMARYOrthogonal frequency division multiplexing (OFDM) communication systems have great advantages, such as high spectrum efficiency and robustness against multipath fading. In order to enhance the advantages, this paper investigates an efficient utilization of both diversity combining and higher-level modulation (adaptive modulation) with a repetition code on the frequency domain in the OFDM systems. The repetition coded OFDM systems can achieve an improvement of performance with such a simple structure as one pair of transmit/receive antennas. In this paper, we derive simple closed-form equations for bit error probability (BEP) and throughput, and then improvements of those performances in the proposed OFDM systems are verified by both theoretical analysis and Monte Carlo simulation.

“…Many elemental wireless technologies can be combined with OFDM, for example, space-time (or space-frequency) coding for diversity [3]- [5] and error correcting coding (ECC) [6]- [8] to improve communication quality, adaptive modulation [9], [10] and multi-input multi-output (MIMO) [11], [12] to enhance system throughput.…”

Section: Introductionmentioning

confidence: 99%

Precise BER Analysis of Repetition Coded OFDM Systems over Time- and Frequency-Selective Rayleigh Fading Channels

Asada

Takyu

et al. 2015

IEICE Trans. Commun.

SUMMARYOrthogonal frequency division multiplexing (OFDM) has great advantages of high spectrum efficiency and robustness against multipath fading. When the received signal is deeply suppressed by deep fading, path loss and shadowing, the received carrier power must be increased in order to avoid degrading communication quality and provide high reliability at the cost of lower system throughput. A repetition coding is very attractive in providing the high reliability with simple configuration and the low decoding complexity of maximal ratio combining. In order to analytically confirm the effectiveness of repetition coded OFDM systems, we theoretically analyze the effect of increasing the number of repetitions (diversity branches) and acquiring both time and frequency diversity gain, and then derive a closed-form equation of average bit error rate (BER) to easily but precisely evaluate the performance.