對具回饋與緩存之抹除廣播通道的分析｜國立臺灣科技大學博碩士論文系統

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研究生：	賴怡均 Yi-Chun Lai
論文名稱：	對具回饋與緩存之抹除廣播通道的分析 Broadcast Erasure Channels with Cache and Feedback
指導教授：	林士駿 Shih-Chun Lin
口試委員:	許裕彬 Yu-Pin Hsu 黃琴雅 Chin-Ya Huang
學位類別：	碩士 Master
系所名稱：	電資學院 - 電子工程系 Department of Electronic and Computer Engineering
論文出版年：	2021
畢業學年度：	109
語文別：	英文
論文頁數：	85
中文關鍵詞：	抹除廣播通道、線性網路編碼、通道狀態資訊、緩存、有限長度
外文關鍵詞：	broadcast erasure channel, linear network coding, channel state information, cache, finite-length
相關次數：	點閱：227 下載：4
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此篇論文中，我們主要針對兩個接收端的廣播封包抹除通道 (broadcast packet erasure channels) 加上緩存 (cache) 與每個使用者的不同回饋狀態做分析。首先，利用既有的方法策略：其中一個使用者的延遲回饋分析與兩個使用者皆有延遲回饋加上緩存機制。我們將兩者合併，提出其中一個使用者的延遲回饋加上緩存的系統模型，得到最佳傳輸率範圍 (capacity region) 並用去中心化的緩存放置 (decentralized content placement) 做驗證。從結果得知，在加上緩存機制下，單一的延遲回饋可達到兩個使用者延遲回饋的傳輸率範圍。在這篇論文提到的緩存有別於一般認知的緩存，即使存取到非本身需要的訊息，也能視此訊息為旁側訊息 (side information) 進而減少總傳輸長度以達到增加總傳輸率的目的。藉由將兩個無延遲回饋的使用者視為兩個對稱使用者 (symmetric user)，延伸到三個接收端的廣播封包抹除通道加上隨機緩存及單個延遲回饋的模型。經由結果得知此總傳輸率可達到兩個接收端加上緩存與單個延遲回饋的總傳輸率，但沒辦法達到三個接收端皆具有延遲回饋的傳輸效率。另外，從第五代行動通訊的傳輸規範中得知低延遲為重要的特色之一，因此，我們提出有限長度 (finite-length) 對於線性網路編碼 (linear network coding) 的內界 (inner bound) 與任何線性網路編碼(linear network coding) 的外界 (upper bound) 傳輸分析。在此分析下，我們可得知在固定的延遲長度限制下能傳送多長的訊息且保證錯誤率小於某個特定的值。

The main problem we consider is the communications over two-user broadcast packet erasure channels with caching and each user has different types of channel state feedback (CSI).

Through utilizing the achievability strategy for single delayed CSI and combining it with the cached-enabled transmission scheme, we characterize the capacity region with single-user delayed CSI and distributed random cache, also, validate it by decentralized content placement. The result shows that the sum capacity is equal to that of global delayed CSI with cache. In contrast to the general knowledge of caching, even the user is caching some files which are requested by the other, the files can also be regarded as side-information to help reduce the transmission length, then, improve the total sum rate.

Moreover, motivated by the idea of assuming two symmetric no-state-feedback users (N-symmetric users) to extend to the three-user case, we derive the achievable rate region with single delayed CSI and random cache which can attain that of single-user delayed CSI for the two-user case, but, it can not reach the optimal rate region with global delayed CSI for three users.

Besides, under the feature of Ultra-Reliable Low Latency Communication (URLLC) in the Fifth Generation (5G) New Radio (NR) standard, a low-delay communication network is apparently important. As a result, we derive a new finite-length inner bound for opportunistic three-phase linear network coding (LNC) analysis and upper bound for any LNCs with global delayed CSI. Also, extend to LNC with cache for inner bound and upper bound. According to the result, we will learn the maximum message length can be sent under a finite-length constraint, meantime, ensure the error probability less than a specific value.

Contents

Introduction
1 Motivation
2 Organization of the Thesis

System Model
1 Caching
1.1 Two Users
1.2 Three Users
2 Encoding Function
2.1 Two Users
2.2 Three Users
3 Decoding Function
3.1 Global Delayed CSI (DD)
3.2 Single Delayed CSI (DN)
3.3 Global Delayed CSI (DDD)
3.4 Single Delayed CSI (DNN)

Broadcast Channels with Caching for Two Users
1 Global Delayed CSI (DD)
1.1 Rate Analysis
1.2 Simulation and Results
2 Single Delayed CSI (DN)
2.1 How to Decode in DN Scenario
2.2 Rate Analysis
2.3 Simulation and Results

Broadcast Channels with Caching for Three Users
1 Single Delayed CSI (DNN) without Caching
1.1 Rate Analysis
2 Single Delayed CSI (DNN) with Caching
2.1 Case 1: DNN with Single N-user Caching
2.2 Case 2: DNN with All Users Caching
3 Global Delayed CSI (DDD) with Caching
3.1 Rate Analysis
4 Simulation and Results
4.1 Complementary

Broadcast Channels with Delay Constraint
1 Linear Network Coding Inner-Bound
2 Routing
3 Linear Network Coding Capacity Upper-Bound
3.1 Optimal LNC through Dynamical Programming
4 Simulation and Results
4.1 Delay Constraint
4.2 Dynamical Programming
5 Linear Network Coding with Another Finite Field
6 Broadcast Channels with Delay Constraint and Caching
6.1 Inner-Bound
6.2 Upper-Bound

Conclusion

                                

References
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[9] Y. Polyanskiy, H. V. Poor, and S. Verdu, “Channel coding rate in the finite blocklength regime,” IEEE Transactions on Information Theory, vol. 56, no. 5, pp. 2307–2359, 2010.

[10] Y. Polyanskiy, H. V. Poor, and S. Verdu, “Feedback in the non-asymptotic regime,” IEEE Transactions on Information Theory, vol. 57, no. 8, pp. 4903–4925, 2011.

[11] T. K. Dikaliotis, A. G. Dimakis, T. Ho, and M. Effros, “On the delay advantage of coding in packet erasure networks,” IEEE Transactions on Information Theory, vol. 60, no. 5, pp. 2868–2883, 2014.

[12] C.-C. Wang and J. Han, “The capacity region of two-receiver multiple-input broadcast packet erasure channels with channel output feedback,” IEEE Transactions on Information Theory, vol. 60, no. 9, pp. 5597–5626, 2014.

[13] E. MolavianJazi and J. N. Laneman, “A second-order achievable rate region for gaussian multi-access channels via a central limit theorem for functions,” IEEE Transactions on Information Theory, vol. 61, no. 12, pp. 6719–6733, 2015.

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