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Composite media with reduced write temperature for heat assisted magnetic recording
(2019-09-15)
Natekar, N. A.
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Tipcharoen, W.
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Victora, R. H.
A major issue plaguing Heat Assisted Magnetic Recording (HAMR)is the high writing (T<inf>write</inf>)and peak heat spot temperatures (T<inf>peak</inf>). To counter this, a low temperature thermal exchange coupled composite (ECC)media with reduced write temperature relative to previous high temperature thermal ECC media is introduced. The FePt T<inf>c</inf> is reduced from 700 K to 500 K, and the write layer T<inf>c</inf> is reduced from 900 K to 600 K. Optimizations for M<inf>s</inf> and K<inf>u</inf> of the write layer generate values of M<inf>s</inf> = 700 emu/cm3 and K<inf>u</inf> = 1.0 × 107 erg/cm3 at 300 K. Switching Probability Distribution (SPD)calculations with lowered T<inf>peak</inf> = 650 K indicate T<inf>write</inf> = 487 K. This indicates a T<inf>write</inf> reduction by 34% as compared to the previous write temperature of 738 K for the high temperature thermal ECC media. Examining the FWHM of the SPD under 0% and 3% T<inf>c</inf> variation indicates a noise reduction of ∼20% relative to single layer high T<inf>c</inf> FePt media, and a much larger reduction relative to low T<inf>c</inf> FePt media. The jitter values at lowered T<inf>c</inf> approach the ideal value set by the grain size in the absence of any T<inf>c</inf> and K<inf>u</inf> variation. Simulations with uncorrelated and correlated T<inf>c</inf> and K<inf>u</inf> variations in the write and FePt layer generate similar results. Reduction of FePt T<inf>c</inf> may reduce the anisotropy relative to its undoped value: reduction of anisotropy by 33% is found to adversely affect the SPD by only 3–4%, but has a larger impact on jitter. These results help establish the usefulness of a low temperature thermal exchange coupled composite media for HAMR.
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Performance evaluation of concatenated coding with diversity reception for body area network
(2016-03-11)
Sansoda, Buncha
;
Choomchuay, Somsak
In wireless communication, it is of significance that the receiving information should be identical to the transmitted information. With this regards, an application of error correction coding (ECC) is one suitable method for maintaining the information precision between the transmission channels. With similar objectives, the diversity techniques are used to moderate the devaluation in the error performance due to the fading impairment by using multiple communication branches. This paper, we propose the application of concatenate codes combined with space diversity technique as maximal ratio combining. We focused on the bit error rate (BER) performance and the impact of Rician fading channel on wireless body area network (WBAN). The finding shows that the proposed scheme can provide considerable improvement on the BER performance compared with that of the traditional system. The concatenate code with MRC outperformed conventional ones, either RS or convolutional codes. At 10-4 of BER, the designed scheme is better than RS code by1.3 dB and convolutional code by2.2dB.
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An application of rate-adaptive RS-codes in wireless Body Area Network
(2015-08-17)
Khattiya, Wannarit
;
Choomchuay, Somsak
This paper proposes the preliminary investigation of rate adaptive error correction coding applied to MAC layer of Body Area Network (WBAN). Health monitoring is a crucial part of proactive patient treatment. As a nature to WBAN communication, there appears severe noise level surrounding the human body. The transmission quality is deterred according to the present of noise. The issue can be improved by appending Error Correction Code (ECC) to the communication message. However, such an effort can cause the packet overhead, latency, and more energy consumption. To mitigate these disadvantages, the rate adaptive of ECC is proposed. The Reed-Solomon (RS) code designed in GF256 has been employed in this study. It fits well the maximum MAC length which is 255 bytes. In our investigation, several MIT-BIH Arrhythmia databases are chosen as input data to represent the patient monitoring condition. The Rician fading channel model is involved as its quite nature to WBAN characteristic. The codes performances are measured in Bit Error Rate (BER) and energy consumption unit.
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Performance evaluation of LDPC codes on patterned WBAN data
(2015-01-26)
Sansoda, Buncha
;
Choomchuay, Somak
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Timakul, Sekson
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Khattiya, Wannarit
In this decade, WBAN plays vital role in health care monitoring environment. It has been used more intensively in wider applications. This paper proposes error control coding applied to WBAN. LDPC codes with the block size of 255 bytes are particularly of interest. Patterned information such as MIT-BIH's arrhythmia datasets extracted from Electrocardiography (ECG) of the patients who encountered heart disease. To measure the system performance, random data are also examined. The system was simulated on Rician channel where severe noise are quite nature to WBAN compared to AWGN channel. Rician channel with some K-factors was investigated. The obtained result shows that both patterned data and random data can be recovered well when Eb/N0 equals 3 dB and above. While the code rates were made varied from 0.50 to 0.75, we can obtain the gain of 3 dB, 5 dB, and 6 dB respectively.

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