14 research outputs found
Asymmetric Error Correction and Flash-Memory Rewriting using Polar Codes
We propose efficient coding schemes for two communication settings: 1.
asymmetric channels, and 2. channels with an informed encoder. These settings
are important in non-volatile memories, as well as optical and broadcast
communication. The schemes are based on non-linear polar codes, and they build
on and improve recent work on these settings. In asymmetric channels, we tackle
the exponential storage requirement of previously known schemes, that resulted
from the use of large Boolean functions. We propose an improved scheme, that
achieves the capacity of asymmetric channels with polynomial computational
complexity and storage requirement.
The proposed non-linear scheme is then generalized to the setting of channel
coding with an informed encoder, using a multicoding technique. We consider
specific instances of the scheme for flash memories, that incorporate
error-correction capabilities together with rewriting. Since the considered
codes are non-linear, they eliminate the requirement of previously known
schemes (called polar write-once-memory codes) for shared randomness between
the encoder and the decoder. Finally, we mention that the multicoding scheme is
also useful for broadcast communication in Marton's region, improving upon
previous schemes for this setting.Comment: Submitted to IEEE Transactions on Information Theory. Partially
presented at ISIT 201
Lossy Compression with Privacy Constraints: Optimality of Polar Codes
A lossy source coding problem with privacy constraint is studied in which two
correlated discrete sources and are compressed into a reconstruction
with some prescribed distortion . In addition, a privacy
constraint is specified as the equivocation between the lossy reconstruction
and . This models the situation where a certain amount of source
information from one user is provided as utility (given by the fidelity of its
reconstruction) to another user or the public, while some other correlated part
of the source information must be kept private. In this work, we show that
polar codes are able, possibly with the aid of time sharing, to achieve any
point in the optimal rate-distortion-equivocation region identified by
Yamamoto, thus providing a constructive scheme that obtains the optimal
tradeoff between utility and privacy in this framework.Comment: Submitted for publicatio
A New Coding Paradigm for the Primitive Relay Channel
We consider the primitive relay channel, where the source sends a message to
the relay and to the destination, and the relay helps the communication by
transmitting an additional message to the destination via a separate channel.
Two well-known coding techniques have been introduced for this setting:
decode-and-forward and compress-and-forward. In decode-and-forward, the relay
completely decodes the message and sends some information to the destination;
in compress-and-forward, the relay does not decode, and it sends a compressed
version of the received signal to the destination using Wyner-Ziv coding. In
this paper, we present a novel coding paradigm that provides an improved
achievable rate for the primitive relay channel. The idea is to combine
compress-and-forward and decode-and-forward via a chaining construction. We
transmit over pairs of blocks: in the first block, we use compress-and-forward;
and in the second block, we use decode-and-forward. More specifically, in the
first block, the relay does not decode, it compresses the received signal via
Wyner-Ziv, and it sends only part of the compression to the destination. In the
second block, the relay completely decodes the message, it sends some
information to the destination, and it also sends the remaining part of the
compression coming from the first block. By doing so, we are able to strictly
outperform both compress-and-forward and decode-and-forward. Note that the
proposed coding scheme can be implemented with polar codes. As such, it has the
typical attractive properties of polar coding schemes, namely, quasi-linear
encoding and decoding complexity, and error probability that decays at
super-polynomial speed. As a running example, we take into account the special
case of the erasure relay channel, and we provide a comparison between the
rates achievable by our proposed scheme and the existing upper and lower
bounds.Comment: 10 pages, 4 figures, in Proc. of ISIT'18 (short version) and in
Algorithms (full version
Polar Coding for the Cognitive Interference Channel with Confidential Messages
In this paper, we propose a low-complexity, secrecy capacity achieving polar
coding scheme for the cognitive interference channel with confidential messages
(CICC) under the strong secrecy criterion. Existing polar coding schemes for
interference channels rely on the use of polar codes for the multiple access
channel, the code construction problem of which can be complicated. We show
that the whole secrecy capacity region of the CICC can be achieved by simple
point-to-point polar codes due to the cognitivity, and our proposed scheme
requires the minimum rate of randomness at the encoder
Investigating the Impact of Unfocused Direct and indirect Written Corrective Feedback on Writing Accuracy of Iranian EFL Learners
Despite extensive studies concerning written error correction, it is imperative that more research be conducted to demonstrate the effectiveness of error correction on improving L2 writing. Driven by this gap, this study aimed to examine whether unfocused direct and indirect types of written corrective feedback had any impact on the writing accuracy of the Iranian English language learners’ new compositions. Through the random matching technique, ninety Iranian English language learners from seven foreign language centers in southwestern Iran were split into two groups for treatment and one group for control. As part of the evaluation, a writing test was utilized to determine whether the learners had improved their writing accuracy due to the treatment. The results showed that the participants in both treatment groups improved their writing accuracy, though the learning gains from both treatment were not significantly different. This study concludes with some implications for teachers regarding their use of appropriate types of written error correction
The Effects of E-Feedback (Electronic Feedback) on Developing EFL Students` Writing Competence: A Case Study on Tishk International University Students in Erbil, Iraq
Academic Writing course has been considered as indispensable in tertiary education for its numerous implications in real, social and professional life. Accordingly, several strategies have been postulated to master writing. Apart from writing strategies, the conduct of written corrective feedback matters which can be traditional, electronic or hybrid. In this respect, this study was conducted to measure the effects of electronic written corrective feedback at TISHK International University on Language Preparatory School students in Erbil, Iraq. 50 students were chosen by employing a purposive sampling method. The study lasted for 10 weeks in 2021-2022 Academic Year. Both groups received the feedback traditionally in the first submission. However, experimental group received e-feedback, whereas control group received paper-based feedback in the second submission. Based on the collected data via writing exams, interview and questionnaire, it was figured out that experimental group students who received a traditional and electronic feedback instruction equally outperformed in terms of writing scores, motivation and submission rates. The findings of this study can have some implications for the stakeholders who are responsible for running Academic Writing courses in different countries
Achieving Secrecy Capacity of the Gaussian Wiretap Channel with Polar Lattices
In this work, an explicit wiretap coding scheme based on polar lattices is
proposed to achieve the secrecy capacity of the additive white Gaussian noise
(AWGN) wiretap channel. Firstly, polar lattices are used to construct
secrecy-good lattices for the mod- Gaussian wiretap channel. Then we
propose an explicit shaping scheme to remove this mod- front end and
extend polar lattices to the genuine Gaussian wiretap channel. The shaping
technique is based on the lattice Gaussian distribution, which leads to a
binary asymmetric channel at each level for the multilevel lattice codes. By
employing the asymmetric polar coding technique, we construct an AWGN-good
lattice and a secrecy-good lattice with optimal shaping simultaneously. As a
result, the encoding complexity for the sender and the decoding complexity for
the legitimate receiver are both O(N logN log(logN)). The proposed scheme is
proven to be semantically secure.Comment: Submitted to IEEE Trans. Information Theory, revised. This is the
authors' own version of the pape