Wireless Communications

Mobile users' data rate and quality of service are limited by the fact that, within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. In this two-part paper, we propose a new form of spatial diversity, in which diversity gains are achieved via the cooperation of mobile users. Part I describes the user cooperation strategy, while Part II (see ibid., p.1939-48) focuses on implementation issues and performance analysis. Results show that, even though the interuser channel is noisy, cooperation leads not only to an increase in capacity for both users but also to a more robust system, where users' achievable rates are less susceptible to channel variations.

http://dns2.asia.edu.tw/~ysho/YSHO-English/2000%20Engineering/PDF/IEE%20Tra%20Com51,%201927.pdf

User cooperation diversity. Part I. System description

Meyn & Tweedie is back! The bible on Markov chains in general state spaces has been brought up to date to reflect developments in the field since 1996 - many of them sparked by publication of the first edition. The pursuit of more efficient simulation algorithms for complex Markovian models, or algorithms for computation of optimal policies for controlled Markov models, has opened new directions for research on Markov chains. As a result, new applications have emerged across a wide range of topics including optimisation, statistics, and economics. New commentary and an epilogue by Sean Meyn summarise recent developments and references have been fully updated. This second edition reflects the same discipline and style that marked out the original and helped it to become a classic: proofs are rigorous and concise, the range of applications is broad and knowledgeable, and key ideas are accessible to practitioners with limited mathematical background.

Markov Chains and Stochastic Stability

In Distributed Algorithms, Nancy Lynch provides a blueprint for designing, implementing, and analyzing distributed algorithms. She directs her book at a wide audience, including students, programmers, system designers, and researchers.



Distributed Algorithms contains the most significant algorithms and impossibility results in the area, all in a simple automata-theoretic setting. The algorithms are proved correct, and their complexity is analyzed according to precisely defined complexity measures. The problems covered include resource allocation, communication, consensus among distributed processes, data consistency, deadlock detection, leader election, global snapshots, and many others.



The material is organized according to the system model-first by the timing model and then by the interprocess communication mechanism. The material on system models is isolated in separate chapters for easy reference.



The presentation is completely rigorous, yet is intuitive enough for immediate comprehension. This book familiarizes readers with important problems, algorithms, and impossibility results in the area: readers can then recognize the problems when they arise in practice, apply the algorithms to solve them, and use the impossibility results to determine whether problems are unsolvable. The book also provides readers with the basic mathematical tools for designing new algorithms and proving new impossibility results. In addition, it teaches readers how to reason carefully about distributed algorithms-to model them formally, devise precise specifications for their required behavior, prove their correctness, and evaluate their performance with realistic measures.


Table of Contents

1 Introduction 
2 Modelling I; Synchronous Network Model 
3 Leader Election in a Synchronous Ring 
4 Algorithms in General Synchronous Networks 
5 Distributed Consensus with Link Failures 
6 Distributed Consensus with Process Failures 
7 More Consensus Problems 
8 Modelling II: Asynchronous System Model 
9 Modelling III: Asynchronous Shared Memory Model 
10 Mutual Exclusion 
11 Resource Allocation 
12 Consensus 
13 Atomic Objects 
14 Modelling IV: Asynchronous Network Model 
15 Basic Asynchronous Network Algorithms 
16 Synchronizers 
17 Shared Memory versus Networks 
18 Logical Time 
19 Global Snapshots and Stable Properties 
20 Network Resource Allocation 
21 Asynchronous Networks with Process Failures 
22 Data Link Protocols 
23 Partially Synchronous System Models 
24 Mutual Exclusion with Partial Synchrony 
25 Consensus with Partial Synchrony

Distributed algorithms

Multiuser diversity is a form of diversity inherent in a wireless network, provided by independent time-varying channels across the different users. The diversity benefit is exploited by tracking the channel fluctuations of the users and scheduling transmissions to users when their instantaneous channel quality is near the peak. The diversity gain increases with the dynamic range of the fluctuations and is thus limited in environments with little scattering and/or slow fading. In such environments, we propose the use of multiple transmit antennas to induce large and fast channel fluctuations so that multiuser diversity can still be exploited. The scheme can be interpreted as opportunistic beamforming and we show that true beamforming gains can be achieved when there are sufficient users, even though very limited channel feedback is needed. Furthermore, in a cellular system, the scheme plays an additional role of opportunistic nulling of the interference created on users of adjacent cells. We discuss the design implications of implementing. this scheme in a complete wireless system.

https://web.stanford.edu/~dntse/papers/oppbf_it.pdf

Opportunistic beamforming using dumb antennas

This paper proposes a new media-access protocol for high-speed packet-switched multichannel networks based on a broadcast topology, for example, optical passive star networks using wavelength-division multiple access. The protocol supports connection-oriented traffic with or without bandwidth reservation as well as datagram traffic, in an attempt to integrate transport-layer functions with the media-access layer. It utilizes the bandwidth efficiently while keeping the processing requirements low by requiring stations to compute their transmission and reception schedules only at the start and end of each connection. A simple analysis shows that we can achieve low blocking probabilities for connections, as well as high network throughput.

https://dl.acm.org/doi/pdf/10.1145/144191.144195

An efficient communication protocol for high-speed, packet-switched multichannel networks

The problem of transporting constant-bit-rate (CBR) traffic through a packet network is analyzed. In the system considered, CBR traffic is packetized and packets from several similar sources are multiplexed on a transmission link. The bit streams are recreated at the receiving end by demultiplexing the packets and then playing out the packets of each CBR stream. Traffic fluctuations may cause gaps to appear in the playout process. Their frequency can be reduced by adding a smoothing delay to each stream. The queueing system analyzed has periodic arrivals and deterministic service times. A method of analysis, based on the ballot theorems of Takacs (1967), is presented to provide steady-state delay distributions as well as a transient analysis of the system to predict the statistics of the time for a gap to develop in the CBR stream as a function of the smoothing delay. >

Ballot theorems applied to the transient analysis of nD/D/1 queues

An optical system in which the available bandwidth is divided into F frequency bands is considered. The connectivity of an N*N wavelength routing device, or an all-optical network with passive wavelength routing, can be specified by an N*N matrix S, where the (i, j)th element, S(i, j), is the set of wavelengths connecting input i to output j. When the matrix S is a latin square, the device is called a latin router. A class of designs for very large latin routers using a relatively small number of components is presented. The designs use a minimal number of interconnections and can be implemented distributively. >

/pdf/latin-routers-design-and-implementation-3jivxp9hso.pdf

Latin routers, design and implementation

Let p(i) be a probability measure on the set of nonnegative integers. The Huffman optimum encoding technique is extended to a class of p(i) including those whose tail decreases

Optimal source coding for a class of integer alphabets (Corresp.)

This work considers the achievable diversity for coded systems appropriately characterized by a block-fading channel model. We are primarily interested in cases where the number of uncorrelated fading channel realizations (blocks) F, is small, so that ideal interleaving assumptions do not hold. This is usually the case in mobile radio systems which employ coded slow frequency-hopping such as the GSM system and its derivatives, We show that the diversity order is limited to a value less than or equal to F which depends on the code rate and the size of the signaling constellation. We report on the results of code searches for rate 1/n convolutional codes for simple AM constellations, which show the minimum complexity needed to achieve maximum diversity. We also present computer simulations of some codes in order to determine the effect of code complexity on the frame and bit error-rate performance.

Pierre A. Humblet

Papers

An efficient communication protocol for high-speed, packet-switched multichannel networks

Ballot theorems applied to the transient analysis of nD/D/1 queues

Latin routers, design and implementation

Optimal source coding for a class of integer alphabets (Corresp.)

Maximizing diversity on block-fading channels