Magnetic tape provides a cost-effective way to retain the exponentially increasing volumes of data being created in recent years. The low cost per terabyte combined with tape’s low energy consumption make it an appealing option for storing infrequently accessed data and has resulted in a resurgence in use of the technology. Magnetic tape as a digital data storage technology was first commercialized in the early 1950’s and has evolved continuously since then. Despite its long history, tape has significant potential for continued capacity and data rate scaling. This article strives to provide an overview of linear magnetic tape technology, usage, history, and future outlook. After a short introduction, the article delves into the details of how modern tape drives and media operate, including the basic mechanism and physics of magnetic recording, current tape media technology, state-of-the-art tape head technology, tape layout and encoding, data retrieval, timing-based servo and mechatronics of a tape drive, and the capabilities of current drives. This is followed by a discussion of tape libraries, an overview of tape library performance modeling research, operating system-level and application-level tape support, tape use cases, and the future scaling potential and outlook of tape. The article concludes with a history of tape hardware, media, usage and software.

New optimum binary shortened cyclic codes with redundancy r = 32 and burst-error correction capability b are presented. The codes are found by performing an exhaustive computer search using the Kasami algorithm, and their performance is compared with analytical bounds by Reiger, Abramson and Campopiano. The true burst-error correction capability of the [2112, 2080] shortened Fire code selected for 10 Gb/s Ethernet is determined to be b = 11 and [2112, 2080] shortened cyclic codes with higher burst-error correction capability b = 13 are given. The double burst-error detection properties of three cyclic redundancy check codes used in standards are compared.

Multiple-antenna concepts for wireless communication systems promise high spectral efficiency and low error rates by proper exploitation of the randomness in multipath propagation. In this paper, we investigate the impact of channel uncertainty caused by channel estimation errors on the error rate performance. We consider a training-based multiple-antenna system that reserves a portion of time to sound the channel. Training symbols are used to estimate the channel by means of an arbitrary linear filter at the receiver. No channel state information (CSI) is assumed at the transmitter. We present a new framework to analyze training-based multiple-antenna systems by introducing an equivalent system model that specifies the channel by the estimated (and hence, known) channel coefficients and an uncorrelated, data-dependent, multiplicative noise. We derive the maximum-likelihood (ML) detector and highlight its behavior in the limiting cases of perfect CSI and no CSI, and its relation to several mismatched detectors. We deduce new exact expressions and Chernoff bounds of the pairwise error probability (PEP) used to assess word-error and bit-error rate bounds for ML and mismatched detection. Finally, we review the code design guidelines in terms of the deleterious effect of channel uncertainty for coherent and noncoherent signaling schemes, and present numerical results.

Multiple-antenna concepts for wireless communication systems promise high spectral efficiencies and improved error rate performance by proper exploitation of the randomness in multipath propagation. In this paper, we investigate the impact of channel uncertainty caused by channel estimation errors on the capacity of Rayleigh and Ricean block-fading channels. We consider a training-based multiple-antenna system that reserves a portion of time to sound the channel. The training symbols are used to estimate the channel state information (CSI) at the receiver by means of an arbitrary linear estimation filter. No CSI is assumed at the transmitter. Our analysis is based on an equivalent system model for training-based multiple-antenna systems which specifies the channel by the estimated (and hence, known) channel coefficients and an uncorrelated, data-dependent, multiplicative noise. This model includes the special cases of perfect CSI and no CSI. We present new upper and lower bounds on the maximum instantaneous mutual information to compute ergodic and outage capacities, and extend previous results to arbitrary (and possibly mismatched) linear channel estimators and to correlated Ricean fading. Several numerical results for single- and multiple-antenna systems with estimated CSI are included as illustration.

Multiple-antenna systems have been shown to achieve very high spectral efficiencies. In this paper, we derive simple single-integral expressions for the ergodic and outage capacity of a diversity system in correlated Ricean fading channels, where the channel coefficients are assumed to be known to the receiver only. For illustration purpose, we present numerical results showing the effect of channel correlation, Ricean components, angular spread and multipath components in an orthogonal frequency-division multiplexing (OFDM) system

This paper introduces an opportunistic medium-access control (MAC) scheme for controlling the uplink message transfer from sensor nodes to a central controller in wireless sensor networks (WSN). By equipping the controller with multiple antennas to communicate with single-antenna sensors, we propose a scheme that benefits from diversity reception at the controller and leads to a considerable reduction of battery energy consumption in sensor nodes. The performance of the scheme is illustrated using a Rayleigh fading channel model.

Multiple-antenna concepts for wireless communication systems promise high spectral efficiencies by proper exploitation of the randomness in multipath propagation. In this paper, we investigate the impact of channel uncertainty caused by channel estimation errors on the capacity of Rayleigh and Ricean block-fading channels. We consider a training-based multiple-antenna system that reserves a portion of time to sound the channel. The training symbols are used to estimate the channel state information (CSI) at the receiver by means of an arbitrary linear estimation filter. No CSI is assumed at the transmitter. We present an equivalent system model for training-based multiple-antenna systems, which specifies the channel by the estimated (and hence, known) channel coefficients and an uncorrelated, data-dependent noise. Based on this equivalent model, which includes the special cases of perfect CSI and no CSI, we derive upper and lower bounds on the maximum instantaneous mutual information and the ergodic capacity, and extend previous results to arbitrary (and possibly mismatched) linear channel estimators and to correlated Ricean fading

We investigate the use of adaptive bit loading in existing OFDM-based W-LAN standards. The performance gain is assessed through simulation and the use of higher-rate codes is considered to improve the performance. Some practical aspects, such as peak-to-average power ratio, channel estimation, signalling and spectral flatness are also addressed.