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index Codes for the Gaussian Broadcast Channel Using Quadrature Amplitude Modulation

IEEE COMMUNICATIONS LETTERS 2015年第8期19卷 1291-1294页

作者： Natarajan, Lakshmi Hong, Yi Viterbo, Emanuele Monash Univ Dept Elect & Comp Syst Engn Clayton Vic 3800 Australia

We propose index codes, based on multidimensional QAM constellations, for the Gaussian broadcast channel, where every receiver demands all the messages from the source. The efficiency with which an index code exploits receiver side information in this broadcast channel is characterised by a code design metric called side information gain. The known index codes for this broadcast channel enjoy large side information gains, but do not encode all the source messages at the same rate, and do not admit message sizes that are powers of two. The index codes proposed in this letter, which are based on linear codes over integer rings, overcome both these drawbacks and yet provide large values of side information gain. With the aid of a computer search, we obtain QAM index codes for encoding up to 5 messages with message sizes 2(m), m <= 6. We also present the simulated performance of a new 16-QAM index code, concatenated with an off-the-shelf LDPC code, which is observed to operate within 4.3 dB of the broadcast channel capacity.

关键词： Codes over rings Gaussian broadcast index coding quadrature amplitude modulation side information

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Coded Caching for Time-Varying Files Popularities and Asynchronous Delivery

IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY

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IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY 2021年 2卷 1458-1472页

作者： Amir, Mohamed Bedeer, Ebrahim Ahmed, Mohamed Hossam Khattab, Tamer Memorial Univ Elect & Comp Engn Dept St John NF A1B 1M6 Canada Univ Saskatchewan Elect & Comp Engn Dept Saskatoon SK S7N 5A2 Canada Univ Ottawa Elect Engn & Comp Sci Dept Ottawa ON K1N 6N5 Canada Qatar Univ Elect Engn Dept Doha Qatar

Data communication has seen exponential growth recently, and it currently dominates wireless communication. As a result, proactive caching was developed to minimize peak traffic rates by storing content, in advance, at different nodes in the network. We consider proactive caching for a broadcast wireless network with one central hub such as a satellite (ST) and K associated mobile units (MUs) such as mobile mini-ground stations or end users. The ST has a library of files, and the MUs demands are assumed to be limited to this library, while the popularity of the library files changes over time. We assume that the MUs demands arrive at different times, and hence, asynchronous file delivery is necessary. We propose a new scheme that minimizes the files delivery sum rate and show that we can use the file delivery messages to proactively and constantly update the MU finite caches. We show that this mechanism reduces the downloaded traffic of the network. The proposed scheme uses index coding to jointly encode the delivery of different demanded files with the cache updates to other MUs to follow the changes in the files popularities. An offline optimization of the delivery sum rate of the scheme is proposed, where it requires knowledge of the files popularities across the whole transmission period. In particular, the problem is formulated as a linear program and the optimal caching is obtained numerically. Moreover closed form solutions to two special cases are derived and a lowerbound to the achievable delivery sum rate is developed. Numerical results show the benefits of the proposed scheme over conventional caching schemes, in terms of reducing the delivery sum rate.

关键词： Coded caching data communications index coding proactive caching satellite broadcast

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Storage Codes on Coset Graphs with Asymptotically Unit Rate

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COMBINATORICA 2024年第6期44卷 1193-1209页

作者： Barg, Alexander Schwartz, Moshe Yohananov, Lev Univ Maryland Dept ECE Syst Res Inst College Pk MD 20742 USA Ben Gurion Univ Negev Sch Elect & Comp Engn IL-84105 Beer Sheva Israel McMaster Univ Dept Elect & Comp Engn Hamilton ON L8S 4K1 Canada Univ Maryland Inst Syst Res College Pk MD 20742 USA

A storage code on a graph G is a set of assignments of symbols to the vertices such that every vertex can recover its value by looking at its neighbors. We consider the question of constructing large-size storage codes on triangle-free graphs constructed as coset graphs of binary linear codes. Previously it was shown that there are infinite families of binary storage codes on coset graphs with rate converging to 3/4. Here we show that codes on such graphs can attain rate asymptotically approaching 1. Equivalently, this question can be phrased as a version of hat-guessing games on graphs (e.g., Cameron et al., in: Electron J Combin 23(1):48, 2016). In this language, we construct triangle-free graphs with success probability of the players approaching one as the number of vertices tends to infinity. Furthermore, finding linear index codes of rate approaching zero is also an equivalent problem.

关键词： Storage codes Coset graphs Triangle-free graphs index coding Hat games

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Decentralized Coded Caching for Shared Caches

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IEEE COMMUNICATIONS LETTERS 2021年第5期25卷 1458-1462页

作者： Dutta, Monolina Thomas, Anoop IIT Bhubaneswar Sch Elect Sci Khordha 752050 India

The demands of the clients in the client-server framework exhibit temporal variance leading to congestion in the network at random intervals. To alleviate this problem, popular data is loaded in cache memories scattered across the network. In the conventional cache framework, each user has an associated cache and cache loading is centrally coordinated. For large networks, a more practical approach is to make the loading of the caches decentralized. This letter considers the shared caching problem in which each cache can serve multiple clients. A new and optimal delivery scheme is proposed for the decentralized shared caching problem. The delivery scheme is shown to be optimal among all linear schemes, using techniques from index coding. It is shown that the rate achieved by the proposed scheme is comparable to the existing scheme which uses centralized prefetching.

关键词： Prefetching Servers indexes Encoding Cache memory Receivers Loading Coded caching decentralized caching shared caching index coding

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Single-Server Private Information Retrieval Schemes are Equivalent to Locally Recoverable coding Schemes

IEEE JOURNAL ON SELECTED AREAS IN INFORMATION THEORY

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IEEE JOURNAL ON SELECTED AREAS IN INFORMATION THEORY 2021年第1期2卷 391-402页

作者： Kadhe, Swanand Heidarzadeh, Anoosheh Sprintson, Alex Koyluoglu, O. Ozan Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA Texas A&M Univ Dept Elect & Comp Engn College Stn TX 77843 USA

The Private Information Retrieval (PIR) problem has recently attracted a significant interest in the information-theory community. In this problem, a client wants to download one or more messages belonging to a database while protecting the identity of the downloaded message(s). In this article, we focus on the scenarios in which (i) the entire database is stored on a single server and (ii) the client has prior side information, namely a subset of messages unknown to the server. Such prior side information is necessary to enable efficient private information retrieval in the single server scenario. In the last decade, there has also been a significant interest in Locally Recoverable Codes (LRCs), a class of storage codes in which each symbol can be recovered from a limited number of other symbols. More recently, there is an interest in cooperative locally recoverable codes, i.e., codes in which multiple symbols can be recovered from a small set of other code symbols. The central problem in this context is given a set of code parameters to design an LRC scheme that includes a locally recoverable code along with encoding, decoding, and repair functions. The paper establishes an equivalence between the single-server PIR schemes and LRC schemes. In particular, we present explicit algorithms that transform a given PIR scheme into an LRC scheme and vice versa. We show that (i) PIR schemes for retrieving a single message are equivalent to classical LRC schemes;and (ii) PIR schemes for retrieving multiple messages are equivalent to cooperative LRC schemes. These equivalence results allow us to recover upper bounds on the download rate for PIR schemes, and to obtain a novel rate upper bound on cooperative LRC schemes. Our results cover schemes based on both linear and non-linear codes.

关键词： Private information retrieval information-theoretic privacy locally recoverable codes index coding

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Improving Download Throughput by Saving the Transmission Bandwidth in Vehicular Networks

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ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2019年第4期44卷 3967-3976页

作者： Patil, Ashish Shet, N. Shekar V. Natl Inst Technol Karnataka Dept Elect & Commun Engn Wireless Sensor Networks Lab Surathkal India

Internet of vehicles focuses on globalization of vehicular networks by providing better communication means between vehicles and other infrastructures also between vehicles and human. The efficient data transfer between moving vehicles as well as between vehicles and roadside units is one of the current demands of vehicular network standards. index coding has proven its significance in reducing number of transmissions in wireless networks. In this paper, we focus on satisfying demands of multiple clients with reduced number of transmissions at server. The proposed contention-based protocol uses index coding to reduce transmissions. Multiple files can be transmitted in a single file using index coding, which eventually reduce transmissions and also save transmission bandwidth. The effect of vehicle speed and available number of clients on the system throughput is presented in this paper. Simulation results show that our proposed design achieves higher throughput than IEEE 1609.4 and VEMMAC, and it also saves the transmission bandwidth at server, since multiple files are transmitted in a single transmission.

关键词： Vehicular networks index coding Short duration links Download throughput Transmission bandwidth

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A New Design for Information Centric Networks

A New Design for Information Centric Networks

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48th Annual Conference on Information Sciences and Systems (CISS)

作者： Sadjadpour, Hamid R. UC Santa Cruz Suns Tech Corp Santa Cruz CA 95064 USA

ISBN: (纸本)9781479930012

Information Centric Network (ICN) is a content-based information dissemination approach that improves the content delivery and latency. We introduce a modified architecture for ICN which can reduce the traffic by combining multiple messages and facilitate the data distribution in the network. By observing the similarities between index coding and ICN architectures, we propose to combine these two techniques to arrive at a new architecture that enhances data delivery in networks beyond original ICN scheme. By taking advantage of some concepts such as linear network coding, caching and index coding, we demonstrate that we can reduce the traffic and increase the capacity of ICN architecture by combining (network encoding) multiple messages requested by different nodes and sending them in one transmission. We demonstrate that each node will be able to extract its desired message from the combined encoded messages. To achieve this goal, we first define a modified version of index coding in order to apply index coding for both wired and wireless networks. Further, we introduce a hybrid caching scheme that includes both central and distributed caching to support two different goals. Our hybrid caching approach is a combination of conventional caching in ICN that caches the content in various network locations in order to make the content readily available to nodes and a new distributed caching scheme across nodes in the network to improve the performance of the entire system. The purpose of the second caching scheme is to allow central cache system to combine multiple contents in order to serve several client nodes simultaneously with a single transmission of encoded messages. The focus of this paper is to describe the new ICN architecture and demonstrate the advantages of the new architecture.

关键词： Information Centric Network index coding Caching Network coding

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Multi-Version coding-An Information-Theoretic Perspective of Consistent Distributed Storage

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IEEE TRANSACTIONS ON INFORMATION THEORY 2018年第6期64卷 4540-4561页

作者： Wang, Zhiying Cadambe, Viveck R. Univ Calif Irvine Ctr Pervas Commun & Comp Irvine CA 92697 USA Penn State Univ Dept Elect Engn State Coll PA 16802 USA

In applications of distributed storage systems to distributed computing and implementation of key-value stores, the following property, usually referred to as consistency in distributed computing, is an important requirement: as the data stored changes, the latest version of the data must be accessible to a client that connects to the storage system. Motivated by technological trends where key-value stores are increasingly implemented in high-speed memory, an information theoretic formulation called multi-version coding is introduced in this paper in order to understand and minimize the memory overhead of consistent distributed storage. Multi-version coding is characterized by nu totally ordered versions of a message and a storage system with n servers. At each server, values corresponding to an arbitrary subset of the nu versions are received and encoded. For any subset of c servers in the storage system, the value corresponding to the latest common version or a later version, as per the total ordering, among the c servers is required to be decodable. An achievable multi-version code construction via linear coding and a converse result that shows that the construction is asymptotically tight when nu|(c-1) are provided. An implication of the converse is that there is an inevitable price, in terms of storage cost, to ensure consistency in distributed storage systems.

关键词： Consistency distributed storage distributed computing erasure coding index coding shared memory

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Finite-Length Analysis of Caching-Aided Coded Multicasting

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IEEE TRANSACTIONS ON INFORMATION THEORY 2016年第10期62卷 5524-5537页

作者： Shanmugam, Karthikeyan Ji, Mingyue Tulino, Antonia M. Llorca, Jaime Dimakis, Alexandros G. Nokia Bell Labs Murray Hill NJ 07974 USA Univ Texas Austin Dept Elect & Comp Engn Austin TX 78703 USA Univ Southern Calif Los Angeles CA 90089 USA Univ Utah Dept Elect & Comp Engn Salt Lake City UT 84112 USA Univ Naples Federico II DIETI Dept I-80138 Naples Italy

We study a noiseless broadcast link serving K users whose requests arise from a library of N files. Every user is equipped with a cache of size M files each. It has been shown that by splitting all the files into packets and placing individual packets in a random independent manner across all the caches prior to any transmission, at most N/M file transmissions are required for any set of demands from the library. The achievable delivery scheme involves linearly combining packets of different files following a greedy clique cover solution to the underlying index coding problem. This remarkable multiplicative gain of random placement and coded delivery has been established in the asymptotic regime when the number of packets per file F scales to infinity. The asymptotic coding gain obtained is roughly t = K M/N. In this paper, we initiate the finite-length analysis of random caching schemes when the number of packets F is a function of the system parameters M, N, and K. Specifically, we show that the existing random placement and clique cover delivery schemes that achieve optimality in the asymptotic regime can have at most a multiplicative gain of 2 even if the number of packets is exponential in the asymptotic gain t = K(M/N). Furthermore, for any clique cover-based coded delivery and a large class of random placement schemes that include the existing ones, we show that the number of packets required to get a multiplicative gain of (4/3)g is at least O((g/K)(N/M)(g-1)). We design a new random placement and an efficient clique cover-based delivery scheme that achieves this lower bound approximately. We also provide tight concentration results that show that the average (over the random placement involved) number of transmissions concentrates very well requiring only a polynomial number of packets in the rest of the system parameters.

关键词： Coded multicasting caching index coding clique-cover finite-length analysis

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Characterizing the Number of Optimal index Codes and Their Relation to Min-Max Probability of Error Performance

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2017年第12期66卷 11023-11038页

作者： Ambadi, Niranjana Radhakumar, Kavitha Rajan, B. Sundar Indian Inst Sci Dept Elect Commun Engn Bangalore 560012 Karnataka India

An index coding problem arises when there is a single source with a number of messages and multiple receivers each wanting a subset of messages knowing a different set of messages a priori. The noiseless index coding problem is to identify the minimum number of transmissions (optimal length) to be made by the source through a noiseless channel so that all receivers can decode their wanted messages using the transmitted symbols and their respective prior information. Recently (A. Thomas, R. Kavitha, A. Chandramouli, and B. Sundar Rajan, "Optimal index coding with min-max probability of error over fading channels," in Proc. IEEE 26th Annu. Int. Symp. Pers. Indoor Mobile Radio Commun., Hong Kong, 2015, pp. 889-894), it is shown that different optimal length codes perform differently in a noisy channel for single-uniprior index coding problems. Towards identifying the best optimal length index code, one needs to know the number of optimal length index codes. In this paper, we consider unicast index coding problems and present results on the number of optimal length index codes making use of the representation of an index coding problem by an equivalent network code. Our formulation results in matrices of smaller sizes compared to the approach of Koetter and Medard (R. Koetter and M. Medard, "An algebraic approach to network coding," IEEE/ACM Trans. Netw., vol. 11, no. 5, pp. 782-795, Oct. 2003.). Our formulation leads to a lower bound on the minimum number of optimal length codes possible for all unicast index coding problems (L. Ong and C. K. Ho, "Optimal index codes for a class of multicast networks with receiver side information," in Proc. IEEE Int. Conf. Commun., 2012, pp. 2213-2218), which is met with equality for several special cases of the unicast index coding problem. Furthermore, for noisy broadcast channels, a method to identify the best among the optimal length codes for unicast index coding problems in terms of minimum-maximum error probability is presented

关键词： index coding minrank min-max error probability unicast

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