Multi-track Detection Research Articles

Asymmetric Iterative Multi-Track Detection for 2-D Non-Binary LDPC-Coded Magnetic Recording

Inter-track interference (ITI) is a major source of signal impairment in the next-generation magnetic recording systems. The single-track read channel model, combined with anti-ITI signal detection schemes, is a popular way to recover single-track data from a readback signal corrupted by the ITI. On the other hand, the multi-track read channel model can be used to simultaneously recover multi-track data from a readback signal. However, the performance of multi-track detection is severely degraded by the weak signals from the sidetracks and the indistinguishable symbols. To improve this performance, in this paper we propose a two-dimensional coding in conjunction with an asymmetric iterative multi-track detection (A-IMD) scheme, which uses joint channel detection and decoding of two parallel six-symbol-based detectors concatenated with two parallel non-binary low-density parity-check (NB-LDPC) decoder over GF(4), to iteratively recover four-track data from two readback signals. Simulation results demonstrate that the performance of the multi-track detection can indeed be greatly improved by using the proposed A-IMD scheme.

Unequal error correction strategy for magnetic recording systems with multi-track processing

In multi-track detection, the simultaneous recovery of user data of all tracks is obtained from multi-head or single-head reader with buffer. Due to incomplete inter-track interference (ITI) information of the outer tracks, unequal error rates exist among tracks. For a system with three-track processing, the center track exhibits a better performance than the others. In this work, we propose the unequal error protection (UEP) schemes to improve the overall system performance of a 2-D interference bit-patterned recording system with multi-track detection. The performances of the proposed schemes are investigated for the BPM channels with and without the media noise. Based on the simulation results, the proposed schemes offer the gain of about 0.2–0.3 dB over the equal error protection (EEP) scheme at a bit error rate of 10−4.

Simplified multi-track detection schemes using a priori information for bit patterned media recording

Simplified multi-track detection schemes using a priori information for bit patterned magnetic recording (BPMR) are proposed in this paper. The proposed detection schemes adopt the simplified trellis diagram, use a priori information, and detect the main-track data in the along- and cross-track directions. The simplified trellis diagram, which has 4 states and 8 branches, can be obtained by setting the corner entries of the generalized partial response (GPR) target to zero and replacing the four parallel branches with a single branch. However, these simplified techniques seriously suffer from performance degradation in high density BPMR channels. To overcome the performance degradation, a priori information is used to give higher reliability to the branch metric. In addition, to fully use the characteristics of channel detection with a two-dimensional (2D) GPR target, the proposed schemes estimate a priori information and detect the main-track data in the along- and cross-track directions by using a 2D equalizer with a 2D GPR target. The bit error rate performances of the proposed schemes are compared with the previous detection schemes when areal density is 3 Tb/in2. Simulation results show that the proposed schemes with simpler structures have more than 2 dB gains compared with the other detection schemes.

Study on Multi-Track Wireless Communication and Laser Detection Device over the Line

This paper studied the transmission of the athletics starting signal and the end signal detection over the line in track and field competition. At the starting point, 433MHz wireless transmitter module coded and sent the start signal. In the race finish line, the laser device detected athletes signal over the line. The system used an embedded Microsoft Visual Basic 6.0 serial communication control to achieve a reasonable upper and lower computer hardware and software online. Experiments show that: The combination system of hardware and software control applies wireless communication technology and laser detection devices to avoid interference with normal visible light. It has many advantages of a timing accuracy, fast and accurate arrangement of athletes.

Iterative Multi-Track ITI Canceller for Nonbinary-LDPC-Coded Two-Dimensional Magnetic Recording

An iterative inter-track interference (ITI) cancelling scheme is described for multi-track signal detection in nonbinary (NB)-LDPC-coded two-dimensional magnetic recording. The multi-track iterative ITI canceller that we propose consists of multi-track soft interference cancellers (SICs), two-dimensional partial response (TDPR) filters, noise-predictive max-log-MAP detectors, and an NB-LDPC decoder. TDPR filters using an ITI-suppressing tap-weight vector mitigate ITI in the first iteration. Multi-track SICs and TDPR filters adjusted to the residual two-dimensional ISI signals efficiently detect multi-track signals in the latter iterations. The simulation results demonstrated that our proposed iterative multi-track ITI canceller achieves frame error rates close to those obtained in a non-ITI case in media-noise-dominant environments when the both-side off-track ratio is up to 50%.

Adaptive and Iterative ITI Canceller for Inter-Track Asynchronous Shingled Write Magnetic Recording

An adaptive and iterative intertrack-interference (ITI) cancelling scheme is described for multi-track signal detection in inter-track asynchronous shingled write magnetic recording. There is write-clock frequency drift in asynchronous recording systems. Read-back signals obtained with a wide read head scanning narrow tracks thus suffer from not only intersymbol interference (ISI) but also time-variant ITI. To efficiently cope with static ISI and time-variant ITI, multi-track soft interference cancellers and two-dimensional partial-response filters are incorporated based on per-survivor processing into each trellis state defined in a one-dimensional/two-dimensional trellis-switching max-log-MAP detector. In addition, the computational complexity can be reduced based on channel interpolation and intermittent TDPR-filter control by allowing small degradation in signal detection. Computer simulation results in media-noise-dominant environments demonstrate that the proposed adaptive and iterative ITI canceller achieves bit error rates close to those obtained in a non-ITI case when the read-head off-track ratio is up to 50% in write-clock frequency difference of 0.02%.

Intertrack Interference Mitigation on Staggered Bit-Patterned Media

One of the possible island distributions being considered for bit-patterned magnetic recording is a hexagonal array, leading to what is called staggered bit-patterned media. In this paper, we investigate the equalization techniques and bit error rate (BER) performance for two different recording methods on staggered media-namely, one array per track or single-track staggered media and two arrays per track or double-track staggered media. With single-track equalization, recording a track on two arrays may reduce intertrack interference (ITI) and outperform the single array per track recording. However, a new multitrack detection technique proposed recently can substantially mitigate ITI and dramatically change the BER performance of the two recording methods. Our investigation shows that by using this technique, the single-track staggered media can have better BER performance than double-track staggered media, even at very high areal densities.

Inter-Track Interference Mitigation for Bit-Patterned Magnetic Recording

In bit-patterned magnetic recording (BPMR), inter-track interference (ITI) becomes a major impairment due to the small track pitch. One way to mitigate the ITI is to equalize the read channel to a two dimensional (2D) partial-response (PR) target. However, we find that the channel detection on the center track cannot take advantage of the 2D target without good estimation of the data on the sidetracks. Therefore, we propose a multi-track detection technique, where the detection on the center track is aided by the information obtained from the detection of the sidetracks. This technique works with any equalizer capable of equalizing the channel to a 2D target. We apply this method to joint-track equalized and 2D equalized BPMR channels. Our simulation results show that the proposed technique provides a significant performance improvement.

Progress in low-pressure gaseous detectors

Abstract Some outstanding properties of low-pressure MWPCs open new prospects in the domain of heavy as well as light particle detection. In the present mode of operation, the mechanism of avalanche formation is divided into two steps: it combines an amplification process in a high, constant, electric field region with a second one, occurring in the vicinity of the proportional wires. Large gains associated with fast charge-collection times are reached at pressures as low as a fraction of a Torr, leading to excellent timing properties and to a high counting-rate capability. Transmission timing detectors, having a total thickness in the 100 μg/mm 2 range, have been designed for heavy-ion detection and offer time resolutions of the order of 100 ps (fwhm) at rates as high as 10 5 c/cm 2 s. The properties of this type of detectors are summarized and localization and multitrack detection capabilities are discussed. Present and future heavy-ion detection systems based on this simple, efficient and low cost technique are described. Possible applications in nuclear and particle physics are also discussed.