375 research outputs found
Constrained Codes for Joint Energy and Information Transfer
In various wireless systems, such as sensor RFID networks and body area
networks with implantable devices, the transmitted signals are simultaneously
used both for information transmission and for energy transfer. In order to
satisfy the conflicting requirements on information and energy transfer, this
paper proposes the use of constrained run-length limited (RLL) codes in lieu of
conventional unconstrained (i.e., random-like) capacity-achieving codes. The
receiver's energy utilization requirements are modeled stochastically, and
constraints are imposed on the probabilities of battery underflow and overflow
at the receiver. It is demonstrated that the codewords' structure afforded by
the use of constrained codes enables the transmission strategy to be better
adjusted to the receiver's energy utilization pattern, as compared to classical
unstructured codes. As a result, constrained codes allow a wider range of
trade-offs between the rate of information transmission and the performance of
energy transfer to be achieved.Comment: 27 pages, 14 figures, Submitted Submitted in IEEE Transactions on
Communication
An RLL code design that maximises channel utilisation
Comprehensive (d,k) sequences study is presented, complemented with the design of a new, efficient, Run-Length Limited (RLL) code. The new code belongs to group of constrained coding schemas with a coding rate of R = 2/5 and with the minimum run length between two successive transitions equal to 4. Presented RLL (4, oo) code uses channel capacity highly efficiently, with 98.7% and consequently it achieves a high-density rate of DR = 2.0. It is implying that two bits can be recorded, or transmitted with one transition. Coding techniques based on the presented constraints and the selected coding rate have better efficiency than many other currently used codes for high density optical recording and transmission
Energy Harvesting Wireless Communications: A Review of Recent Advances
This article summarizes recent contributions in the broad area of energy
harvesting wireless communications. In particular, we provide the current state
of the art for wireless networks composed of energy harvesting nodes, starting
from the information-theoretic performance limits to transmission scheduling
policies and resource allocation, medium access and networking issues. The
emerging related area of energy transfer for self-sustaining energy harvesting
wireless networks is considered in detail covering both energy cooperation
aspects and simultaneous energy and information transfer. Various potential
models with energy harvesting nodes at different network scales are reviewed as
well as models for energy consumption at the nodes.Comment: To appear in the IEEE Journal of Selected Areas in Communications
(Special Issue: Wireless Communications Powered by Energy Harvesting and
Wireless Energy Transfer
M-ary run length limited coding
This thesis consists of two parts: 1) a result of the rationality of channel capacity for the M -ary (d, k) constraint, and 2) a software package which has been designed to aid in the development of efficient, high density channel encoders for M -ary (d, k) constrained recording code. It has been written for the platforms of IBM PC or PC compatible and Sun Workstations. The designed software in this thesis involves three steps. The first step is to calculate the capacity of a RLL code after the user has chosen (M,d,k) . The channel capacity specifies the maximum ratio of information ( p ) bits/codeword ( q ) bits achievable in implementing these codes and gives options of code choice for any specific task. The second step is to find a code efficiency (eta) = R/C by choosing p and q , and display the state transition matrix of finite state transition diagram and finite state transition diagram of the code. The last step is to aid the user in the generation of a code, by using state splitting algorithm of R. Adler, D. Coppersmith and M. Hassner [10]
CHANNEL CODING TECHNIQUES FOR A MULTIPLE TRACK DIGITAL MAGNETIC RECORDING SYSTEM
In magnetic recording greater area) bit packing densities are achieved through increasing
track density by reducing space between and width of the recording tracks, and/or
reducing the wavelength of the recorded information. This leads to the requirement of
higher precision tape transport mechanisms and dedicated coding circuitry.
A TMS320 10 digital signal processor is applied to a standard low-cost, low precision,
multiple-track, compact cassette tape recording system. Advanced signal processing and
coding techniques are employed to maximise recording density and to compensate for
the mechanical deficiencies of this system. Parallel software encoding/decoding
algorithms have been developed for several Run-Length Limited modulation codes. The
results for a peak detection system show that Bi-Phase L code can be reliably employed
up to a data rate of 5kbits/second/track. Development of a second system employing a
TMS32025 and sampling detection permitted the utilisation of adaptive equalisation to
slim the readback pulse. Application of conventional read equalisation techniques, that
oppose inter-symbol interference, resulted in a 30% increase in performance.
Further investigation shows that greater linear recording densities can be achieved by
employing Partial Response signalling and Maximum Likelihood Detection. Partial
response signalling schemes use controlled inter-symbol interference to increase
recording density at the expense of a multi-level read back waveform which results in an
increased noise penalty. Maximum Likelihood Sequence detection employs soft
decisions on the readback waveform to recover this loss. The associated modulation
coding techniques required for optimised operation of such a system are discussed.
Two-dimensional run-length-limited (d, ky) modulation codes provide a further means of
increasing storage capacity in multi-track recording systems. For example the code rate
of a single track run length-limited code with constraints (1, 3), such as Miller code, can
be increased by over 25% when using a 4-track two-dimensional code with the same d
constraint and with the k constraint satisfied across a number of parallel channels. The k
constraint along an individual track, kx, can be increased without loss of clock
synchronisation since the clocking information derived by frequent signal transitions
can be sub-divided across a number of, y, parallel tracks in terms of a ky constraint. This
permits more code words to be generated for a given (d, k) constraint in two dimensions
than is possible in one dimension. This coding technique is furthered by development of
a reverse enumeration scheme based on the trellis description of the (d, ky) constraints.
The application of a two-dimensional code to a high linear density system employing
extended class IV partial response signalling and maximum likelihood detection is
proposed. Finally, additional coding constraints to improve spectral response and error
performance are discussed.Hewlett Packard, Computer Peripherals Division (Bristol
CROSSTALK-RESILIANT CODING FOR HIGH DENSITY DIGITAL RECORDING
Increasing the track density in magnetic systems is very difficult due to inter-track interference
(ITI) caused by the magnetic field of adjacent tracks. This work presents a
two-track partial response class 4 magnetic channel with linear and symmetrical ITI; and
explores modulation codes, signal processing methods and error correction codes in order
to mitigate the effects of ITI.
Recording codes were investigated, and a new class of two-dimensional run-length
limited recording codes is described. The new class of codes controls the type of ITI
and has been found to be about 10% more resilient to ITI compared to conventional
run-length limited codes. A new adaptive trellis has also been described that adaptively
solves for the effect of ITI. This has been found to give gains up to 5dB in signal to noise
ratio (SNR) at 40% ITI. It was also found that the new class of codes were about 10%
more resilient to ITI compared to conventional recording codes when decoded with the
new trellis.
Error correction coding methods were applied, and the use of Low Density Parity
Check (LDPC) codes was investigated. It was found that at high SNR, conventional
codes could perform as well as the new modulation codes in a combined modulation and
error correction coding scheme. Results suggest that high rate LDPC codes can mitigate
the effect of ITI, however the decoders have convergence problems beyond 30% ITI
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