Multiple Access Technology Towards Ubiquitous Networks Overview And Efficient Designs Neng Ye

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Multiple Access Technology Towards Ubiquitous
Networks

Neng Ye · Xiangming Li · Kai Yang · Jianping An
Multiple Access Technology
Towards Ubiquitous
Networks
Overview and Efficient Designs

Neng Ye
Beijing Institute of Technology
Beijing, China
Kai Yang
Beijing, China
Xiangming Li
Beijing, China
Jianping An
Beijing, China
ISBN 978-981-19-4024-8 ISBN 978-981-19-4025-5 (eBook)
https://doi.org/10.1007/978-981-19-4025-5
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023
This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether
the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse
of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and
transmission or information storage and retrieval, electronic adaptation, computer software, or by similar
or dissimilar methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication
does not imply, even in the absence of a specific statement, that such names are exempt from the relevant
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The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721,
Singapore

Preface
The future wireless communication networks are expected to provide ubiquitous
massive coverage to meet the requirements of diversified applications. With an expo-
nential increase of the number of users and devices, it is challenging to establish
fast and reliable connections in the ubiquitous network. As the core technology in
the evolution of wireless communication systems, multiple access technology can
enable effective massive connections and has become the prominent research trend
for ubiquitous networks. The goal of this book is to provide readers with a compre-
hensive overview of the state-of-the-art multiple access technologies for ubiquitous
network, with a focus on the novel ubiquitous multiple access technologies, the
signal construction techniques of multiple access and the enhanced multiple access
transceivers using Artificial Intelligence (AI). For each of these topics, this book
has tried to provide an advanced introduction, blending the basic multi-user infor-
mation principles with the advanced multiple access models and novel application
scenarios. In addition, this book has provided elaborate simulation results for each
topic to verify the feasibility of the corresponding schemes.
In particular, to have a comprehensive view for the application scenarios of the
multiple access technology, this book discusses the evolution and deployment of
multiple access in 5G and beyond, followed by the emerging multiple access tech-
nologies developed for the ubiquitous non-terrestrial networks. Facing the challenges
of massive connections in ubiquitous networks this book investigates the effective
signal construction techniques of multiple access, including constellation design and
rate splitting. Moreover, the enhancement of multiple access transceivers using AI is
presented. Specifically, this book resorts to AI for constructing unified optimization
framework and approaching the performance limit of multiple access system, and
enhances grant-free multiple access to match the features of Internet of Things (IoT)
with deep learning. This book systematically describes the theoretical framework and
physical layer technologies of ubiquitous access, which can reflect the application
prospect for future ubiquitous networks.
We believe that this book can provide useful insights for the theory and method of
ubiquitous multiple access, and display the wide application of ubiquitous networks
in the future 6G. This book can be used as a reference for graduate students,
v

vi Preface
researchers, and engineers in the field of wireless communications. We do hope
that the valuable time devoted to this book will bear fruit in stimulating interest in
the study of multiple access technologies.
Beijing, China Neng Ye
Xiangming Li
Kai Yang
Jianping An
Acknowledgements The works in this book have been supported by the National Natural Science
Foundation of China under Grants 62101048 and 62171030.

Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Evolution of Multiple Access Technology . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Signal Construction for Multiple Access Technology . . . . . . . . . . . . 3
1.4 AI-Enhanced Multiple Access Technology . . . . . . . . . . . . . . . . . . . . . 4
1.5 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Multiple Access Towards 5G and Beyond . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Typical Multiple Access Technologies . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 Bit-Level Non-orthogonal Multiple Access . . . . . . . . . . . . . . 10
2.2.2 Symbol-Level Non-orthogonal Multiple Access . . . . . . . . . . 15
2.2.3 Multi-user Detection Technologies . . . . . . . . . . . . . . . . . . . . . 23
2.3 Grant-Free Multiple Access for mMTC . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3.2 Grant-Free Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3.3 Typical Grant-Free Multiple Access Technologies . . . . . . . . 31
2.3.4 Detection Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.4 Implementation Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4.1 Scheduling-Based Multiple Access . . . . . . . . . . . . . . . . . . . . . 36
2.4.2 Grant-Free Multiple Access . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3 Multiple Access Towards Non-terrestrial Networks . . . . . . . . . . . . . . . . 47
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.2 Overview on Non-terrestrial IoT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.2.1 Satellite IoT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.2.2 UAV IoT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.3 Physical Layer Technologies of Satellite IoT . . . . . . . . . . . . . . . . . . . 51
3.3.1 Wireless Access Technologies . . . . . . . . . . . . . . . . . . . . . . . . . 52
vii

viii Contents
3.3.2 High-Efficacy Resource Allocation . . . . . . . . . . . . . . . . . . . . . 56
3.3.3 Large Dynamic Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3.4 MmWave Transmission System . . . . . . . . . . . . . . . . . . . . . . . . 58
3.3.5 Other Enabling Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.4 Non-physical Layer Technologies of Satellite IoT . . . . . . . . . . . . . . . 59
3.4.1 High-Efficacy Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.4.2 Ubiquitous Network Architecture . . . . . . . . . . . . . . . . . . . . . . 59
3.5 Multiple Access Technologies of UAV IoT . . . . . . . . . . . . . . . . . . . . . 60
3.5.1 Flexible Deployment and Route Planning . . . . . . . . . . . . . . . . 60
3.5.2 Low Power Consumption Design . . . . . . . . . . . . . . . . . . . . . . . 62
3.5.3 Collision Resolution Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.5.4 Large Dynamic Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4 Constellation Design Technique for Multiple Access . . . . . . . . . . . . . . . 77
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.2 System Model and Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . 78
4.3 Constellation Rotation Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.3.1 Problem Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.3.2 Variational Approximation Method . . . . . . . . . . . . . . . . . . . . . 80
4.4 Analysis and Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.4.1 Achievable Capacity with SIC Receiver . . . . . . . . . . . . . . . . . 82
4.4.2 Analysis on Infinite Number of Receiving Antenna . . . . . . . 83
4.5 Simulation Results and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
5 Rate-Adaptive Design for Multiple Access . . . . . . . . . . . . . . . . . . . . . . . . 87
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.1.1 Related Work and Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.1.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.2 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.3 Rate-Adaptive Multiple Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.3.1 Rate-Splitting Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.3.2 RAMA for Grant-Free Transmission . . . . . . . . . . . . . . . . . . . . 94
5.3.3 Implementation Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.4 Performance Analysis of Conv-GF and RAMA . . . . . . . . . . . . . . . . . 97
5.4.1 Outage Performance Analysis of Grant-Free Access . . . . . . . 97
5.4.2 Outage Performance Analysis of RAMA . . . . . . . . . . . . . . . . 102
5.4.3 Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.5 RAMA Amenable Constellations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.5.1 Overlapping Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5.5.2 Bundling Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
5.6 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Contents ix
5.6.1 Ideal Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
5.6.2 Realistic Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
6 Artificial Intelligence-Enhanced Multiple Access . . . . . . . . . . . . . . . . . . 119
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.1.1 Related Work and Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 120
6.1.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
6.2.1 Uplink NOMA System Model . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.2.2 Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6.3 DeepNOMA: An End-to-End DL Framework for NOMA
Based on Multi-task Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.3.1 Deep Multi-task Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.3.2 Network Structure of DeepNOMA . . . . . . . . . . . . . . . . . . . . . 126
6.3.3 Multi-task Balancing Technique . . . . . . . . . . . . . . . . . . . . . . . . 130
6.3.4 Training Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.4 DeepMAS: Model-Based MAS Mapping Network Design . . . . . . . . 132
6.4.1 Model-Based Transmitter Design . . . . . . . . . . . . . . . . . . . . . . . 133
6.4.2 Parameter Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.5 DeepMUD: Interference Cancellation-Based MUD Network
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
6.5.1 Interference Cancellation for Multiple Access Channel . . . . 135
6.5.2 ICNN: Interference Cancellation-Enabled DNN . . . . . . . . . . 136
6.5.3 DeepMUD Based on ICNN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
6.5.4 Training DeepMUD over Fading Channel . . . . . . . . . . . . . . . 140
6.6.1 Network Training Performance . . . . . . . . . . . . . . . . . . . . . . . . 142
6.6.2 Design Examples of DeepMAS . . . . . . . . . . . . . . . . . . . . . . . . 145
6.6.3 Performance Evaluation of DeepNOMA . . . . . . . . . . . . . . . . . 146
6.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
7 Deep Learning-Aided High-Throughput Multiple Access . . . . . . . . . . . 157
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
7.3 Deep Learning-Aided Grant-Free NOMA . . . . . . . . . . . . . . . . . . . . . . 161
7.3.1 Deep VAE for Grant-Free NOMA . . . . . . . . . . . . . . . . . . . . . . 161
7.3.2 Encoding Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
7.3.3 Decoding Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
7.4 Multi-loss Based Network Training Algorithm . . . . . . . . . . . . . . . . . . 165
7.4.1 Dataset Organization with Random User Activation . . . . . . . 165
7.4.2 Multi-loss Function Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
7.4.3 Overall Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

x Contents
7.5.1 Network Training Results and Design Examples . . . . . . . . . . 170
7.5.2 Detection Accuracy Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 172
7.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
8 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
8.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
8.2 Future Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

Acronyms
3GPP Third Generation Partnership Project
A2G Air-to-ground
ACRDA Asynchronous contention resolution diversity slotted ALOHA
ACS Asymmetric chirp signal
AI Artificial intelligence
ARM Adaptive random-selected multi-beamforming
AWGN Additive white Gaussian noise
BA Buffering-aided
BC Broadcast channel
BER Bit error rate
BS Base station
BTCs Block turbo codes
CCC Constellation-constrained capacity
CDG Compressive data gathering
CE Cross-entropy
CoAP Constrained limited application protocol
CP Cyclic-prefix
CRDSA Resolution diversity slotted ALOHA
CS Compressive sensing
CSA Coded slotted ALOHA
CSI Channel state information
CSS Chirp-spread spectrum
CTU Contention-based unit
D2D Device-to-device
DAE Deep auto-encoding
DAS Delay-aware selection
DAUS Delay sensing UAV selection
DC Difference of convex
DE Density evolution
DL Deep Learning
DL-PA Deep learning-based long-term power allocation
xi

xii Acronyms
DNN Deep neural network
DSA Diversity slotted ALOHA
E2E End-to-end
EAS Energy-aware selection
EAUS Energy sensing UAV selection
EE Energy efficiency
EM Expectation-maximization
eMBB Enhanced mobile broadband
EPA Estimation propagation algorithm
FEC Forward error-correction
FO Frequency offset
FTPA Fractional transmit power allocation
FTUS Fair weighing UAV selection
G2G Ground-to-ground
GEO Geostationary earth orbit
GOCA Group orthogonal coded access
HAP Hybrid access point
HARQ Hybrid automatic repeat request
IC Interference channel
ICI Inter-cell interference
ICNN IC-enabled DNN
IDMA Interleave-division multiple-access
IGMA Interleave-grid multiple access
IoT Internet of things
IRSA Irregular repetition slotted ALOHA
KKT Karush-Kuhn-Tucker
KL Kullback-Leibler
LAN Local area network
LCRS Low coding rate spreading
LEO Low Earth orbit
LLRA Low-latency routing algorithm
LPWAN Low power wide area network
LSSA Low code rate and signature based shared access
MABs Multiple access blocks
MAC Multiple access channel
MAP Maximum a posteriori
MASs Multiple access signatures
MBB Mobile broadband
MCSs Modulation and coding schemes
MER Message error rate
MF Match-filter
MI Mutual information
ML Maximum-likelihood
mMTC Massive machine-type communication
MPA Message passing algorithm

Acronyms xiii
MUD Multi-user detection
MUI Multi-user interference
MUSA Multi-user sharing access
MUST Multi-user sharing technology
NCC Non-orthogonal cover codes
NCMA Non-orthogonal coded multiple access
NFV Network function virtualization
NOCA Non-orthogonal coded access
NOMA Non-orthogonal multiple access
NOSA Non-orthogonal slotted ALOHA
OCCs Orthogonal cover codes
OFDM Orthogonal frequency division multiplexing
OFDMA Orthogonal frequency-division multiple access
OMA Orthogonal multiple access
PAPR Peak to average power ratio
PDF Probability density function
PDMA Pattern division multiple access
PF Proportional fairness
PIC Parallel interference cancellation
PMF Probability mass function
RA Random access
RAC Random access channel
RACH Random access channel
RAMA Rate-adaptive multiple access
RAR Random access response
RB Resource block
RDMA Repetition division multiple access
REs Resource elements
RHS Right-hand side
RLNC Random linear network coding
ROC Receiver operating characteristic
RS Rate splitting
RSMA Resource spread multiple access
SA Slotted ALOHA
SC Superposition coding
SC-FDMA Single-carrier frequency division multiple access
SCMA Sparse code multiple access
SCS Symmetric chip signal
SCSS Symmetry chirp spread spectrum
SDN Software defined network
SE Spectral efficiency
SGD Stochastic gradient decent
SIC Successive interference cancellation
SIN Space information network
SINR Signal to interference and noise ratio

xiv Acronyms
SJD Successive joint decoding
SM Spatial modulation
SR Scheduling request
SRRS Super-imposed radio resource sharing
SSA Spread slotted ALOHA
SSMA Short sequence spreading-based multiple access
TBSs Transmission block sizes
TDL Tapped-delay-line
TDMA Time division multiple access
TMs Transmission modes
TO Timing offset
TP True positive
TPA Transmission power allocation
UAV Unmanned aerial vehicle
UCI Uplink control information
UEP Unequal protection property
UNB Ultra narrow band
VA Variational approximation
VAE Variational auto-encoder
VA-M Variational approximation-maximization
VMF Von-mises-fisher
VPs Variational parameters
WBE Welch-bound-equality

Chapter 1
Introduction
Abstract This chapter first introduces the necessity of enhancing multiple access
technology for ubiquitous networks. Then, the evolution of multiple access is briefly
introduced and the aspects of enhancement methods of multiple access including
signal construction and AI-based transceiver design are discussed. Finally, the orga-
nization of this book is presented.
1.1 Background
How to establish stable and fast wireless connections of multiple mobile users is one
of the key issues in a wireless communication system. Multiple access technology,
which constructs multiple interference-limited single-user transmission channels by
dividing wireless resources in time, frequency, space, code and power domain, is the
core solution to address the key issues mentioned above. As a matter of fact, multiple
access technology has been the key enabler for the intergenerational evolution of
wireless communication system from 1G (1980s) to 5G (2020s) [1].
Wireless communication system towards 2030 is expected to break the limitations
of time/space and realize ubiquitous interconnections in multiple (air/space/ground)
domains [2]. While conventional cellular-based networks mainly focus on the ter-
restrial hotspot coverage, the spaceborne and airborne platforms in the ubiquitous
networks can directly serve widely distributed user equipments [3–5]. These plat-
forms can supply uninterrupted and undifferentiated communication for users, due
to their full coverage, all-time work, robustness to damage, flexibility and reliability.
Therefore, ubiquitous networks will provide seamless wireless connections and tend
to have a profound impact in the future 6G on coverage and connection density.
At present, radio access technology for ubiquitous networks has been a focus of
international standardization organizations such as 3GPP and ITU [6, 7].
Differentfromterrestrialnetworks,ubiquitousnetworkshavethecharacteristicsof
massive access users, large propagation distances, high channel dynamics, dynamic
topology, and limited power budget. Due to the above-mentioned differences, con-
ventional multiple access technologies for terrestrial networks are not suitable for
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023
N. Ye et al., Multiple Access Technology Towards Ubiquitous Networks,
https://doi.org/10.1007/978-981-19-4025-5_1
1

2 1 Introduction
ubiquitous access scenarios and requirements. To this end, it is necessary to study
advanced multiple access technology to improve the connectivity, spectral efficiency,
and reliability.
Inspired by the above stringent requirements, this book focuses on the state-
of-the-art multiple access technologies for ubiquitous networks. Specifically, this
book firstly investigates novel ubiquitous multiple access technologies for beyond
5G and space-air-ground integrated networks in 6G. Then, the signal construction
techniques of multiple access are studied, including constellation design and rate
splitting. Moreover, the enhancement of multiple access transceivers using artificial
intelligence (AI) is studied. In summary, this book systematically describes the the-
oretical framework and physical layer technology of ubiquitous access, which can
deepen the understanding of the theory and method of ubiquitous multiple access,
and promote the wide application of ubiquitous networks in the future 6G.
1.2 Evolution of Multiple Access Technology
Multiple access technology originates from multi-user information theory [8]. As
early as the 1970s, the research of multi-user information theory, i.e. network infor-
mation theory, theoretically pointed out that any point in the capacity domain of
multiple access channels and degraded broadcast channels can be achieved by super-
position coding (SC), rate splitting (RS) and successive interference cancellation
(SIC) reception [9, 10].
The orthogonal multiple access technology applied to the 1G-5G system considers
the orthogonal division of wireless resources and cannot reach the outer boundary of
multi-user capacity region, and suffers from limited access capability. Therefore, it
is necessary to study efficient multiple access technologies for ubiquitous networks.
Recently, the idea of non-orthogonal multiple access (NOMA) has been proposed to
achieve the entire capacity region of multiple access channel [11]. NOMA allows the
superposition transmissions of multiuser signals with controllable mutual interfer-
ence. By deploying advanced multiuser detector, NOMA significantly enhances the
connectivity, improves the spectral efficiency and simplifies the signaling interactions
compared with its orthogonal counterpart.
The earliest application of the non-orthogonal paradigm in multi-user informa-
tion theory to actual systems can be traced back to Gianluca Mazzini’s paper “Power
Division Multiple Access” in 1998 [12]. The key is to explicitly introduce the power
dimension and deploy cascaded detectors at the receiving end. In 2008, the research
group led by NTT docomo put forward a method to overlap and reuse the uplink
resources in the patent “Physical Resource Allocation Method, Device, Data Receiv-
ing Method and Receiver”. It is proposed that the natural near-far effect of CDMA
can be used to pair users with significantly different equivalent receiving powers and
realize uplink transmission with the same time-frequency physical resources, and
then distinguish users thruogh SIC receivers. This patent is the basic composition
patent of non-orthogonal multiple access in the industry.

1.3 Signal Construction for Multiple Access Technology 3
1.3 Signal Construction for Multiple Access Technology
Multiple access technology allows multiple users to perform superimposed transmis-
sion on wireless resources through specific transceiver design. This ensures a good
compromise between multiplexing gain and transmission reliability under control-
lable inter-user interference. In the general model of multiple access systems, each
user uses a specific transmitter and maps the source message into a coded signal
based on its specific access feature fingerprint. The coded signals of the multiple
users are then superposed in the wireless channel, and finally the receiver recovers
the source message using multi-user detection algorithm. Typically, multiple access
transmitters map the source messages (or bits) to complex modulation symbols (or
symbol sequences); and multi-user receivers then map the received signal to an esti-
mated source message. Therefore, design of transmission signal becomes a major
challenge in the research of multiple access technology [13].
In the design of transmitters, due to the difficulty of directly indicate the overall
system performance of multiple access, it is necessary to introduce some easy-to-
characterized indicators, such as Euclidean distance or channel capacity measure-
ment. For practical implementation, finite-alphabet signal should be transmitted. To
this end, signal design based on constellation-constrained capacity (CCC) needs to
be studied [14]. After fixing the single-user constellation diagram, it is a simple and
effective way to improve the system capacity by adjusting the rotation angle of the
constellation diagram. However, the existing literature mainly maximizes the CCC
by assuming the ideal maximum likelihood receiver, which leads to high receiving
complexity. Therefore, it is necessary to enhance the performance of multiple access
system with practical receiver via constellation rotation.
Another promising technique in multiple access signal design is rate splitting (RS)
[15]. RS is considered as a promising physical layer transmission mode for non-
orthogonal transmission, interference management and multiple access strategies in
6G. By splitting the user message into multiple independently coded signal layers
at the transmitter and partially decoding the interference and treating the remainder
of the interference as noise, the RS is able to gently bridge two extreme interfer-
ence management strategies, namely, interference is treated as noise (commonly
used in 4G/5G multi-user/mass/mmWave MIMO) and fully decode interference (in
non-orthogonal multiple access). RS can also effectively improve the robustness of
grant-free access systems by assigning different reliability to different data streams.
Therefore, it is promising to design a practical multiple access scheme to address
the unpredictable interference in grant-free access and to fully utilize the underlaid
physical channel.

4 1 Introduction
1.4 AI-Enhanced Multiple Access Technology
With the beginning of the 2020s, the existing multiple access technology system can
no longer meet the expectations of the future intelligent society for ubiquitous wire-
less access. For the wireless access of user equipment, one of the core requirements
of the future smart society is to use a unified technical framework to realize intel-
ligent ubiquitous connections—covering multiple meanings such as the number of
massive devices, extensive space-time characteristics, different business attributes,
and diversified performance indicators. This puts forward higher expectations for the
next-generation multiple access technology.
With the help of information theory and signal processing methods, we have been
able to approach the performance limit of the point-to-point communication system.
However, these methods face difficulties in modeling and optimizing the complicated
multi-user systems towards end-to-end transmission performance. Therefore, a new
research paradigm is required to further optimize multiple access technology.
Deep Learning (DL), which automatically extracts the distributed features
of the signals using deep models, provides unified signal processing architecture,
universal function approximation ability and data-driven end-to-end optimization
capability [16]. The recent breakthrough of DL and its positive applications to wire-
less communications have paved the way to tackle the above challenges of multiple
access technology. At present, AI technology represented by deep learning has been
closely coupled with mobile communication [17–20]. With the update iteration of
hardware semiconductor technology including cloud graphics processor and terminal
neural processing unit [21], it is expected to jointly enable a new intelligent wireless
air interface. However, the current DL approach for physical-layer enhancement is
still in its infancy. For example, many researches directly reuse the existing deep
learning models of AI, which lack the targeted design of communication systems.
And most of them only consider point-to-point communication scenarios, which lack
a unified end-to-end deep learning framework for multi-access systems. Moreover,
the potential superposition in multiple access technology further leads to exponen-
tially increased combinations of the feature, which requires the sophisticated design
of DL.
1.5 Organization
To have a comprehensive view of the multiple access technology, this book discusses
the the multiple access towards different scenarios in Chaps. 2 and 3, presents effec-
tive signal construction methods of multiple access in Chaps. 4 and 5, and multiple
access technologies enhanced by AI and DL in Chaps. 6 and 7. The rest of this book
is organized as follows.
Chapter 2 discusses the practical deployment of multiple access in 5G and beyond.
As a vital variant of multiple access, non-orthogonal multiple access (NOMA) plays

1.5 Organization 5
an important role in the standardization process of 5G, with regards to spectral effi-
ciency, reliability, low latency and peak data rate. This book presents a comprehensive
review on recent progress of multiple access technology in 5G and beyond, especially
NOMA technologies.
Chapter 3 discusses multiple access technology used in non-terrestrial wireless
communication systems for ubiquitous networks. Non-terrestrial networks here help
to break the location constraints that existing terrestrial IoT meets. This book pro-
vides a general look on the non-terrestrial network, including application scenarios,
technical proposals, key techniques and potential research directions.
Chapter 4 investigates the constellation rotation technique for enhancing the per-
formance of uplink multiple access network. A successive interference cancellation
(SIC) receiver is applied to achieve better capability, which is also the basic receiver
used in this proposed method. In this chapter, the best value of rotation angle is
obtained by maximizing the entropy of Gaussian mixture model and then used to
characterize the receiving signal. Lower bit error rate and larger capacity compared
to conventional multiple access can be found in the proposed structure.
Chapter5investigatesrate-adaptivemultipleaccessforuplinkgrant-freetransmis-
sion. Grant-free transmission helps simplify the signaling procedure through uplink
instant transmission, while in the other hand its collision problem causes smaller data
throughput and worse outage performance. In this chapter, a rate-adaptive multiple
access (RAMA) scheme is put forward to tackle the problem. The corresponding
receiver applied with successive interference cancellation algorithm is introduced to
detect multiple data streams. Compared to conventional grant-free scheme, RAMA
scheme can achieve higher average throughput and lower outage performance.
Chapter 6 investigates AI-aided multiple access for end-to-end optimization. Deep
learning is used to further approach the performance limit of NOMA. This chapter
regards the overlapped transmissions in NOMA as multiple distinctive but correlated
learning tasks, and then puts forward a unified multi-task deep neural network (DNN)
framework for NOMA, namely DeepNOMA. Compared to the conventional meth-
ods, DeepNOMA can achieve higher transmission accuracy and lower computational
complexity simultaneously under various channel models.
Chapter 7 investigates grant-free multiple access based on deep learning in a spe-
cific scenario, i.e., tactile Internet of Things (IoT). The benefit of grant-free access
and non-orthogonal transmissions are jointly exploited to achieve low latency mas-
sive access. However, reliability seems to be reduced due to the random interference.
This chapter formulates a variational optimization problem to improve the relia-
bility of grant-free NOMA. DNN is used to tackle the proposed problem and the
training process matches the highly automatic applications in tactile IoT. Significant
reliability gain can be found in the proposed scheme.
Chapter 8 summarizes this book and discusses the future directions of enhancing
multiple access technology for ubiquitous networks.

6 1 Introduction
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key technologies. IEEE Veh. Technol. Mag. 14(3), 28–41 (2019)
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One of our mules simply would not cross the bridge. No amount of
pushing and pulling, beating and shouting, would make him budge an inch.
Finally he was blindfolded and a rope tied to each front leg. His hind legs
were tied securely together, to prevent him from kicking, and by alternately
pulling the ropes attached to his front feet, he was forced in a most
ignominious manner to come onto the bridge and go a third of the way
across. Then the ropes were loosened and the blind taken off.
THE LARGE PLAZA OF AYACUCHO
THE BRIDGE OVER THE RIVER PAMPAS
We expected to see him turn and bolt for the nearest side but he was too
frightened to do anything of the sort, and became at once most docile, and
finished the trip in peace.
He was not the only one who did not like the bridge. The priest of
Chincheros, who had been delayed from accompanying us by the arrival of
a visiting cleric that morning, overtook us here. Although a sturdy native
Indian, he was rather portly and preferred not only to leave to some one else
the leading across of his mule, but even to have a poor Indian bearer give
him his shoulder to steady him on the swaying structure.
From the other end of the bridge we ascended the precipitous cliff by a
narrow winding path and found ourselves on a lofty terrace where the

enterprising Parodi Brothers have planted waving fields of sugarcane. Here
we were met by the Gobernador of Tambillo and the Parodis who escorted
us to their sugar factory at Pajonal, a most attractive hacienda nestled in a
valley at the foot of beetling crags. Our hosts had inherited from their father
an unusual stock of energy and skill. Owing to his efforts, a good irrigation
ditch had been constructed that furnished the canefields with an abundant
supply of water. The houses were in good repair and everything bore the
marks of prosperity. It was a pleasure to see such evidence of enterprise and
energy in this wild region. One brother, who ordinarily practices medicine
in Lima, was here on a visit. Another brother is being educated in the States.
We left Pajonal the next morning, accompanied by the Gobernador of
Tambillo, a very agreeable person of German-Peruvian descent. From
Pajonal the road ascends a little valley and then climbs a mountainside to
the village of Ocros, a most forlorn and wretched place, with an elevation of
nearly ten thousand feet.
The adobe church, like that at Chincheros, was set back from the plaza,
and had a new adobe wall around it. Earth for this seemed to have been
taken right out of the plaza. No attempt had been made to fill up the huge
holes that remained. The only building at Ocros that seemed to be in any
kind of repair was the local telegraph office where the officer from
Ayacucho who accompanied us, went to send a despatch to the Prefect.
On the way we had been struck by the extraordinary method of hanging
telegraph wires that prevails in this country. The linesmen had thought
nothing of planting three poles together on the top of one hill and the next
three not less than a quarter of a mile away on the top of another, stretching
their wire across the intervening distance in midair. This occurred not once
or twice but whenever they could save poles by so doing. The strain on the
wire must have been tremendous. We learned that the service was
“frequently interrupted.”
The road up from Ocros was the worst that we encountered anywhere. It
was really the bed of a mountain stream and our animals had the greatest
difficulty in picking their way among the rocks and boulders. It was hard to
imagine that this was really the highway between Cuzco and Lima. The
“road” grew worse and worse until it reached a bleak paramo at an
elevation of thirteen thousand feet, where snow, hail, and sleet, driven in
our faces by a high wind, added to our discomforts. A steep descent on the

other side of the range greatly tried the patience of our animals. The ground
seemed to be a hard clay that offered no support to their feet and they slid
and slipped, sometimes eight or ten feet at a time, without being able to
stop. Night was falling as we reached the little collection of wretched huts
called Matara. No one seemed to have any desire to receive us. In fact, the
Indian who had charge of the only dry hut in the place, locked the front
door and disappeared into the night. Unlike vigorous Caceres, who would
sooner have died than allow an inhospitable Indian to refuse admission to
the foreigner in his charge, the officer from Ayacucho was a timid soul who
had gone through the world bemoaning his ill fortune and doing nothing to
make it better. He could think of no solution of the problem except that we
make ourselves as comfortable as possible in the shelter of a kind of a porch
in front of this thatched hut. So we passed an exceedingly uncomfortable
night and experienced some of the hardships that the British soldiers, who
aided the patriot army in that last campaign against the Spanish viceroy,
must have suffered in this very locality.
The next morning our road led across half a dozen deep gulches whose
streams feed the river Colpahuayo. In one of these I was so fortunate as to
find in a gravel-bank at the side of the road, which had been heavily washed
by recent rains, a portion of an ancient Inca stone war-club shaped like a
huge doughnut.
The road continued to be extremely slippery and was not improved by
the almost continuous rain. At half past two we reached Tambillo. Here we
were welcomed by the pleasant wife of the Gobernador who had ridden
ahead to have a good breakfast prepared while we had waited in vain on a
hilltop hoping the rain would hold up sufficiently to let us photograph a
magnificent panorama that included the distant city of Ayacucho and the
heights of Condorkanqui and the famous battlefield.
After lunch we crossed another gulch whose treacherous sides more than
once caused our mules to fall heavily. In the village of Los Neques, we
were met by a very courteous emissary of the Prefect of Ayacucho who
turned out to be proprietor of the hotel. He had been sent out in the rain to
apologize for the fact that there was no committee to meet us and to explain
that the notables had mounted and ridden out to await us until driven back
by the inclemency of the weather, for all of which we were duly thankful, as
it meant that we had escaped the necessity of hurting anybody’s feelings by
declining to drink more copitas of brandy on an empty stomach.

Here at Los Neques the Indians were getting ready to celebrate the days
of Carnival which were soon to be upon us. A hundred men and women had
gathered in the courtyard of an old house. In one corner a red cloth shelter
had been erected
AYACUCHO
THE COURTYARD OF THE HOTEL
under which sat the old men around a table on which was scattered
popcorn, roast maize, and dishes of succotash. The other men and women
squatted on the ground with dishes of succotash and bowls of chicha in
front of them. As long as we looked on, all was orderly and quiet except
that two musicians with a violin and a primitive old harp were endeavoring
to cheer them up.
Soon after dark, in a pouring rain, we passed the high walls of the
Ayacucho cemetery, clattered over the cobble-stones of the narrow streets,
entered the plaza, and were ushered with a flourish through a stone arch
into the courtyard of the hotel. Acting on the orders of the Prefect, the
proprietor had reserved for our use an enormous parlor or reception room
where at least forty people could be comfortably seated, and a great
bedroom of nearly the same dimensions in which were four large bedsteads.
Notwithstanding the attractiveness of the hotel bedsteads, such is the

perversity of human nature that I decided to use my own little “Gold
Medal” folding cot that had served me faithfully for many weeks, and my
own blankets which, as they were folded up every morning as soon as I
arose and not unfolded until I was ready to sleep, could be relied upon to be
free from fleas, etc.
The plaza of Ayacucho is surrounded on three sides with private houses
that have arcades supported by stone pillars. The ground floors are taken up
with shops, while over the arcades are balconies that lead to the principal
rooms of the dwelling houses. Our hotel had been once occupied by one of
the principal families of the town and was a good specimen of the old
Spanish method of building. It had a large courtyard from which a flight of
stone steps led up to the galleries, and was ornamented by potted plants and
caged birds.
Hardly had we examined our rooms when we received a call from the
Prefect, Don Gaspar Mauro Cacho, a tall, finely proportioned Peruvian with
a remarkable sense of humor and an unfailing store of courtesy. On the
following day he took upon himself to show us the sights of the town,
including the fine old cathedral, the large public market, clean and well
kept, the picturesque old churches, and the Prefecture, a large double
quadrangle where were located the offices of the Department, the barracks
of the few troops stationed here, and the rooms allotted for the use of
himself and his family.
His wife and children had arrived from Lima not many months previous,
and the terrors of the overland journey were vividly in their minds. His
señora assured me that she had feared she would never reach Ayacucho
alive, notwithstanding the fact that the government had made every possible
provision for their comfort on the journey. One of the “guides” lost his way,
and they were quartered at an abandoned tambo where there was nothing to
eat or drink and no firewood. Having lived in Lima all their lives, they felt
the discomforts keenly. It was an interesting commentary on the state of the
roads that even a Prefect could not be sure that his family would travel with
a moderate degree of comfort.
I had sometimes felt that the life of an official in Peru was as easy as the
life of the poor Indians was hard, but I had to reverse that opinion before
leaving the country. While the Prefects are appointed directly by the
President and are responsible only to him, they are likely to be considered

troublesome by the local magistrates who, although elected by the citizens,
exercise very limited prerogatives. Were it not for the dozen or more
soldiers that take their orders directly from the Prefect, he would often be in
a precarious position. He must govern as well as he can, and yet if he does
not make himself popular with the people of the city in which he lives, his
lot is not at all an easy one. With such men as the Prefects whom we met in
Arequipa, Abancay, and Ayacucho, the central government is fortunate in
being able to be sure that the power which it delegates to them will be used
firmly and wisely and without causing friction.
This city, one of the largest in Peru, occupies an excellent central
situation and from it diverge roads in every direction. Yet so great is the
difficulty of bringing foreign merchandise over these mountain roads, that
we found few shops here of any importance, and almost all seemed to be
owned by natives of the country. The streets were all of the same pattern,
paved with rough stones, sloping, not away from the centre as with us, but
towards the centre, where in the middle there is invariably a ditch,
practically an open sewer. For those walking on the sidewalk, it is certainly
much pleasanter to have this ditch in the middle of the street.
In anticipation of the joys of eating and drinking connected with
Carnival, Indian women with huge cauldrons of chupe and immense jars of
chicha were preparing to take up all-night stands, sometimes in the centre
of the street or else on a busy corner where they would be sure to attract
trade. The effect of the women’s head-gear was most curious. It was exactly
as though the lady had found her shawl a bit too warm and had taken it off,
folded it into a square, and proceeded to carry it on her head for
convenience. We went through one old crumbling archway, attracted by
some beautiful clay jars, and found ourselves in a backyard that would have
delighted a painter. Not all painters, but the kind that loves a natural
combination of picturesque ruins, fine old jars tumbled about helter-skelter,
dirty little Indian children in dirtier hats and ponchos, very much too big for
them, a cat, and a long-legged pig who nosed about among the jars trying to
see which one contained chicha fit to gratify his thirst.
From the tower of one of the oldest churches we secured a splendid view
of the city and the surrounding country including nearly the entire region
occupied by the forces of Sucre and La Serna in the week preceding the
final battle of Ayacucho.

The old name of Ayacucho was Guamanga, which is said to have been a
Spanish adaptation of the Inca Huaman-ca (Take it, Falcon), a name that
was given to the district by an incident that followed a fierce battle in which
a warlike tribe of this vicinity was defeated and almost annihilated by the
armies
A PICTURESQUE CORNER IN AYACUCHO
CROSSING THE PONGORA RIVER ON THE SHAKY SUSPENSION BRIDGE
of the Inca Viracocha. It is said that when serving out rations of flesh to his
troops after the battle, the Inca threw a piece to a falcon that was soaring
over his head, saying “Huaman-ca.” However this may be, the town of
Guamanga was one of the earliest to be founded by Pizarro and was later
the site of a bloody encounter between Vaca de Castro, the legitimate
Viceroy, and young Almagro and his followers, who had assassinated
Pizarro.
The name Ayacucho was given to the town after the famous battle of
December 9, 1824, which was fought near the village of Quinua, thirteen
miles north. “Ayacucho” means “corner (or heap) of dead men” and refers
to the bloody character of this conflict and of those that had preceded it in
the Inca Conquest and in the Spanish Conquest of Peru.
On February 21, the three days of Carnival began. Although I had often
read of the impossibility of doing anything in Peru during that period of
jollification, I succeeded in persuading the kind-hearted Prefect to procure
us animals that we might ride to Quinua, thirteen miles away, and spend a

day or so investigating the battlefield. He tried to dissuade us, but as he
knew that it was for this purpose that we had come to Ayacucho, everything
was soon ready. The Gobernador of Quinua had been given orders to be on
hand, to act as our guide. Accompanied by him and the Secretary of the
Department and a small military escort, we left the hotel and took the road
to the northwest.
Our little cavalcade was strung out over a block or more by the time we
reached the suburbs as the streets were narrow and not in particularly good
repair. Suddenly the horses of our guides wheeled and bolted and were with
difficulty kept in the road. The cause was a characteristic piece of
carelessness on the part of somebody. A horse had recently died and his
thrifty owner had at once skinned him to save his hide, leaving the hideous
carcass in the very centre of the narrow road. It was necessary to make a
considerable detour through the neighboring fields, for none of our animals
would go within fifty feet of the disgusting spectacle.
For the first two leagues we followed the regular road to Lima and the
north, branching off when we reached the ford over the Pongora River, then
passing through several small plantations and near two vineyards, we
crossed the river Yucaes on a new suspension bridge and climbed the face
of a steep cliff by a zigzag trail. We had good animals and kept them going
at a comfortable trot so that we arrived at the little village of Quinua in
three and a half hours after leaving Ayacucho.
The plaza of Quinua is surrounded on three sides by houses and ruins,
the fourth side being taken up by the church. Like the other houses in the
vicinity, these were built of stone and earth and roofed with red tiles. Many
of the roofs had been allowed to fall into decay, and the house which was
pointed out as the place where the truce was signed after the battle, and
where the Spanish General surrendered to General Sucre, had entirely lost
its covering.
A hasty lunch was prepared for us at a little mud hut called a tavern, and
as soon after as possible we re-mounted and rode north for half a mile up
the face of a little hill and found ourselves on the plain where was fought
the last great battle of the South American Wars of Independence. A
monument, apparently made of some kind of plaster, and naturally in a very
bad state of repair, marked the centre of the plain. Near by was a kind of
shed or shelter for the horses, and a little to the westward the walls of a

memorial chapel that had not yet been completed. North of the plain the
heights of Condorkanqui rise abruptly. A new road had recently been
constructed over them to the warm valleys beyond, but it was still perfectly
possible to see the old trail down which the Spanish troops marched in their
attack on the patriots.
The altitude of the field is nearly eleven thousand feet, and romantically
inclined writers have sometimes spoken of this as the “battle above the
clouds.” As a matter of fact, we had considerable difficulty in taking
photographs owing to the low hanging clouds that continually swept down
from the summits of Condorkanqui. Fortunately it did not rain all the time.
Few battles have ever been fought on a height that offered such a
magnificent view. From all parts of the battlefield, a superb panorama is
spread out to the east, south, and west, embracing the entire valley of
Ayacucho.
After spending the afternoon on the field, we returned to the little tavern
where the evening passed very pleasantly and we were entertained by the
Indian villagers who were celebrating the Carnival. They came in throngs
bringing us parched corn, popcorn, and chicha, swearing eternal friendship,
and expressing their appreciation that we should come such a long distance
to see their famous battlefield. The village appeared to be divided into three
wards, and the alcalde of each ward was anxious that we should eat and
drink just as much of his offering as we had of the others.
They were easily satisfied, however, and appeared to be having a very
good time. I never saw Indians enjoy themselves more. As a conclusion to
the entertainment, two Indian women were instructed to sing for us. Their
performance consisted in a wailing duet, beginning loud and high,
ascending with a powerful crescendo to screeching falsetto notes and then
gradually descending and diminishing into a wheeze like a very old parlor
organ with leaky bellows.
We spent the next morning photographing different parts of the
battlefield and trying to get a better idea of the reasons for Sucre’s victory. I
was very forcibly impressed by the skill with which he had chosen his
position.
The little plain, really a plateau, is literally surrounded by ravines. It was
just large enough to allow Sucre to use his seven or eight thousand men to
the best advantage. An enemy attacking him must perforce come up hill on

every side, even though it would seem as though the Spanish troops
descending from Condorkanqui would have had some advantage. But they
were under fire all the time they were descending to the plain, and just
THE BATTLEFIELD OF AYACUCHO
THE BATTLEFIELD AS IT APPEARED TO THE SPANIARDS
before they reached it, they found themselves in a little gully up the sides of
which they had to scramble at a disadvantage before they could actually be
on a level with the defenders. La Serna was too good a general not to have
appreciated the strength of Sucre’s position. In fact, as General Miller
points out, the mistake of the Viceroy in attacking originated in allowing
himself to be over-persuaded by the eagerness of his troops. Their patience
had been exhausted by terrible marches which seemed to them to be
endless. Only a few days before the battle, the tents of the Viceroy and his
chief general had had lampoons pasted on them, accusing them of
cowardice. It may fairly be said that he was goaded into action contrary to
his own judgment.
The battle of Ayacucho, besides being the final combat, was one of the
most brilliant in the history of the Wars of Independence. The troops on
both sides were well-seasoned veterans. The generals in command were
among the ablest that the long wars had developed. Every man fought with
bravery. Although the Patriots were outnumbered, they made up for it by
enthusiasm and by a knowledge that there was no opportunity for them to
retreat. They were aided by the lay of the land, but the result was due to a

most determined valor and a heroic daring that must always gratify lovers
of Peruvian history.
We returned to the city in the middle of the afternoon in time to take a
little walk in the streets and be bombarded by little Carnival balloons filled
with scented water, egg-shells filled with colored powder, and the other
missiles that are commonly employed to bear witness to the fact that Lent is
approaching. The ladies and children, who occupied points of vantage in the
second-story windows, kept up a brisk fire on everyone who ventured along
the streets, and we had to do some very rapid dodging to avoid being
entirely soaked and colored with all the hues of the rainbow.
In the evening, notwithstanding a terrific downpour of rain, the “society
of Ayacucho,” including the Archbishop, the Prefect, and fifty or sixty of
their friends, “tendered us” an elaborate banquet which quite took the palm
for variety of food and drink. There were no less than fourteen courses
besides seven kinds of wine including champagne. The after-dinner
speeches were also quite remarkable. Hitherto, the chief interest in us had
been the fact that we had “visited the lost city of Choqquequirau,” but here
Choqquequirau meant little or nothing. The battlefield of Ayacucho meant
everything, and the fact that we were delegados from a country whose aid
Peru hoped to receive in case Chile became troublesome meant a great deal
more. Whether it was at this banquet or at one of those that preceded it in
the past three weeks, I do not remember, but the opinion was expressed
more than once that, rather than have another war with Chile, they would
surrender to the United States and become a protectorate. I mention this not
as an indication of national sentiment, but merely to show the state of
feeling that prevailed in the interior of Peru at the time, and the attitude with
which they regarded the possibility of another war with Chile.
A large part of the hatred that exists between Chilean and Peruvian is
due to their native ancestry. In the Chilean there is a large percentage of
Araucanian blood. In the Peruvian there is as much of the blood of the
Quichuas. The Araucanians are the hereditary foes of the Quichuas. For
centuries there was no peace between them. The Incas pushed their army of
Quichuas as far south as possible, but they never could conquer the lands
where the Araucanians roved. Even the all-conquering Spanish soldiers
were blocked in southern Chile. It is not necessary to repeat here the long
story of the Araucanian wars and the heroic deeds of Lautaro and his
kinsmen. Instead of being easily conquered by the handful of Spanish

adventurers as were the Incas and Quichuas, the Araucanians kept the
Spaniards at bay for centuries, and were in fact never subdued.
The Araucanians and the Quichuas had as different racial characteristics
as can be imagined. Although the Araucanians did not constitute a nation in
the proper sense of the word but were divided into a large number of clans,
each independent and recognizing no master, they never allowed any
outside people to interfere with their national life. They were intensely
independent. Even the chiefs lacked authority in time of peace. There were
no serfs or slaves. More important still, there were no laws; private wrongs
had to be settled privately. All of these elements must be taken into
consideration when contemplating the character of the Chilean of to-day.
His Spanish ancestors brooked no interference and recognized no central
government, but his Araucanian forebears were still more intensely fond of
individual liberty. His Spanish ancestors were brave and fearless. No better
soldiers existed in Europe in the sixteenth century. The Araucanians were
even more warlike, and after their first few defeats by the invaders, they
successfully assumed the offensive, storming Spanish towns and carrying
off cattle and horses. They organized troops of cavalry, learning to excel on
an animal that their fathers had never heard of, and which the Quichuas
even now rarely dare to mount. The entire Araucanian nation was less
numerous than the army of Quichuas that surrounded Atahualpa when he
was successfully attacked by Pizarro, yet they killed more Spanish soldiers
than fell in the conquest of the entire remainder of the continent. With such
an ancestry, it is not remarkable that the Chileans are notoriously the best
fighters on the continent to-day. Contrast their inheritance with that of the
Peruvians.
The Quichuas were and are a timid, peaceful folk lacking in dignity,
defending themselves rather with cunning and falsehood than by deeds of
arms. The servile sentiment is deeply rooted in the Quichua nature. He
maintains a sense of loyalty for his former masters, but he has absolutely no
idea of liberty or independence. The Quichuas had reached a higher state of
culture than the Araucanians but their manly characteristics were far less
developed. In fact, at the time of the Spanish conquest, they seem to have
been already in a decadent condition. With such blood in their veins, it is
not surprising that the Peruvians were easily defeated by the Chileans, their
country overrun and humiliated, their valuable nitrate fields seized, and the

seeds of intense national hatred planted that will take generations to
eradicate.

E
CHAPTER XXVI
AYACUCHO TO LIMA
very one had told us that it would be “absolutely impossible” to leave
Ayacucho until two or three days had elapsed after the end of the
Carnival. Possibly because we were a trifle homesick, and possibly
because we had been assured so positively that it could not be done, we
determined to try to leave Ayacucho on the last day of the three devoted to
Carnival. I must confess that it was rather cruel, not only to the two soldiers
who were ordered to accompany us, but also the arriero who was informed
that he must provide us with mules and go when we were ready to start. The
morning was spent in a great row over the mules and the question as to how
far they were to go with us, in which many tears were shed by drunken
Indian women who declared that they were sure they would never see their
husbands or animals back again. If it had not been for the Prefect’s
willingness to help us, we could never have persuaded any one to go, but he
did his part splendidly. We at length got off just at noon. The Prefect and his
friends, to the number of fourteen, escorted us for the first league out of the
city. Then we bade them an affectionate farewell and started off on the last
stage of our journey, determined, if possible, to travel henceforth as much
like private citizens as we could. To be sure, we had our little military
escort. Without them we should have found it almost impossible to proceed
at all for the next few days. Our first two leagues were over the same road
which we had used in going to Quinua, then, instead of fording the river, we
kept on its left bank until we reached a shaky suspension bridge. Its floor
was made of loose planks that were so easily misplaced by the mules that
Hay declared he had to set them all over again after I had passed in order to
avoid falling into the river.
We met on the road many Indians, celebrating Carnival, marching along
gayly, beating primitive little drums and blowing on bamboo-fifes. They
stopped at almost every house they passed, shouting and hullabalooing and
getting a few drinks of chicha.

As we were crossing the rocky bed of a little stream we met an itinerant
musician, a blind harpist, who was being helped across by a friend. His harp
was very curious, being a wooden box shaped like half a cone with two
wooden legs tacked into its base, and two eye-holes on the flat side which
made it look very much like some dwarfish animal. With great difficulty we
tried to persuade him to set up his harp in the dry bed of the stream and play
us a tune while we took his picture. Not having the slightest conception of
what we were trying to do, the poor blind musician was rather frightened,
and as he understood no Spanish whatever, we should not have succeeded
had it not been for the kind offices of a pleasant-faced mestizo family party
who were picnicking on the bank of the stream and who translated our poor
Spanish into Quichua. In the evening we reached Huanta, an historic little
town where savage Indian tribes from the Amazonian forests have
frequently come into collision with armed Peruvian forces. Although we
hoped to be able to slip into town unnoticed, we were met, a mile out, by
the usual dozen of hospitably inclined caballeros who, with the Gobernador
at their head, had been “celebrating” for the past two or three days. We were
by this time so fatigued by the labors of crossing Peru in the wet season,
that we found it very difficult to be as polite as we were expected to be to
the reception committees that had been our lot hitherto. However, in this
case, to put it bluntly, the Gobernador was very drunk, which made him
only the more friendly, and he insisted that we were two “princes of
America,” and that his house would be everlastingly famous in history as
having been the place where we stayed!
His wife and daughters behaved splendidly. They seemed to realize that
we knew it was customary for all the men to get drunk at this season of the
year. At the same time they did their best to make us comfortable and to see
that the male members of the family did not annoy us any more than they
could help.
Naturally, the “morning after” was a sad occasion, and had it not been
for our excellent soldiers, who had gone to bed sober, it would have been
very difficult to have persuaded our hosts to let us go. The Gobernador was
extremely cross. He had

THE BRIDGE OVER THE HUARPA
forgotten all about our princely lineage, and only remembered to charge us
treble for everything he could think of. Although we had gotten up at five
o’clock, no Indians sober enough to act as guides could be found for several
hours, and it was after ten before we finally left Huanta.
The son of the Gobernador was the only person who had energy enough,
or had sufficiently recovered from the debauch of the night before, to do us
the honor of escorting us out of town. This had come to be such a regular
feature of our travels since leaving Cuzco that we always looked forward
with curiosity to see what would happen. This young fellow was very polite
and went with us as far as the entrance of the local cemetery, a bizarre
white-washed adobe gate, protected from the weather by a little covering of
red tiles. There must have been something prophetic about his bidding us
good-by at the gates of a cemetery, for he was the last honorary escort that
we had in Peru.
Our road led us through a thickly populated region. Here and there on
the roadside, unfortunate individuals, both men and women, who had been
too far gone to reach home the night before, were sleeping off the effects of
the Carnival. Ordinarily one does not see much drunkenness in Peru, but
this certainly was an exception.
Small towns and villages followed in quick succession. Then we
descended into the valley of the Huarpa River and across a well-built toll-
bridge. The bridge was so long and so high above the stream that my mule
concluded he would stay on the east bank. He yielded to our combined
efforts, but only after much beating. We now passed through a semi-arid
region of cactus and mimosa trees like the basin of the Pampas River, until
we began to climb an extremely steep ravine. Several times we lost our
way, and in places the path had been completely washed out by the rains.
The crux came at a little waterfall only five feet high. So smooth was the

face of the rock over which the little stream of water trickled that our sure-
footed animals found it impossible to reach the upper level until we had
built a rude stone stairway which they cheerfully essayed to climb. Their
energetic scrambles were finally rewarded by success. For three hours the
trail wound upwards as steeply as it was possible to go, until we reached the
bleak paramo near Marcas.
A magnificent panorama lay spread out before us. In the foreground
were hillsides dotted with thatched huts and fields where sheep and cattle
grazed; in the middle distance, deep valleys whose rivers had cut their way
down into gorges out of our sight; and far beyond, a magnificent range of
mountains, some capped with snow and others with clouds. It was a little
after five o’clock when we entered the picturesque little village of Marcas
with its two dozen huts scattered about under the lee of the rocks or
clustered near the road. We recognized it as just the sort of village where we
would have been refused both food and shelter had we been alone. But as
we were accompanied by an energetic sergeant who did not propose to
allow any poor Indians to stand in the way of our progress, a hut no dirtier
or more comfortless than the rest was soon put at our disposal, and the
sergeant did his best to get us all a good supper out of our own provisions.
Our baggage animals had had a frightfully hard day of it and our soldiers
assured us that if we intended to catch the weekly train out of Huancayo, it
would be necessary to have at least one more beast of burden, for although
our luggage could be conveniently carried by two mules going at a walk, if
we expected to make forty miles a day, as we hoped to do, one animal must
be rested every other day. Accordingly the Indian alcalde of Marcas was
instructed to get us a mule. “But there are no mules here” he replied. A
horse then. “Very well, there is one old one which I will have ready for you
in the morning.” Soon after breakfast an old white horse appeared,
accompanied by a weeping Indian woman who had no desire to take our
money and who was thoroughly convinced that she would never see her
horse again. It was finally agreed that the horse should go only to the next
town where we could get another beast and send this one back by one of the
Indian alcaldes that now accompanied us from village to village, returning
as their task of acting as guides was taken up by the alcaldes of the next
place.
With the aid of the fresh horse, we made good time and skirted the
slopes of a high range of hills leaving the trim little town of Acobamba far

off on our left. It lies in the valley of the Lircay which is quite densely
populated and seemed to be very fertile. In the middle of the afternoon we
reached Urumyosi where there are curious great rocks shaped like sugar
loaves. They are of soft sandstone which is easily worked, and a number of
caves have been made by poor people at the base of the rocks. After a long
cold ride and ten hours in the saddle, we came in sight of a mud-colored
town called Paucara which has long had a very evil reputation. Whether this
is deserved or not we did not endeavor to discover. The sergeant persuaded
the owner of a rude little hut, half a mile from the town and on the direct
road, to let us spend the night there. One of our neighbors brought freshly
cut barley-straw for the mules, another brought a dozen eggs, and with the
aid of our own supplies and cooking utensils, we fared splendidly.
The night was excessively damp and as bitterly cold as it can be only in
a genuinely tropical country when the temperature drops forty degrees after
the sun goes down and an icy wind penetrates your very bones, even though
you have hurriedly put on two or three sweaters and a couple of ponchos as
it grew dark. There is no cold like the cold of the tropics. Furthermore the
carcass of a recently killed sheep hung dripping in the hut. The floor was
wet and muddy, there were no windows and only a small door. We wished
we had a tent.
There being no incentive to linger at this charming country-house, our
Indians were actually up and away before six o’clock. We had saved four
eggs the evening before to be cooked for our breakfast, and after loading
our pack animals and seeing them safely off with all our supplies, we
handed our
URUMYOSI

THE HUT NEAR PAUCARA
eggs and some tea to the housewife and asked her to prepare us a frugal
meal. Alas! it was quite impossible. The cooking activities of the evening
before had used up every stick of firewood within a radius of a mile, and
there was no way in which water could be boiled. The only provisions for
our breakfast were the raw eggs. We had before us a ride of forty miles over
an exceedingly rough country, part of which lay at an elevation of fourteen
thousand feet above the sea, so we hastily swallowed our eggs as best as we
could and started off with the prospect of twelve hours in the saddle.
At first the road wound slowly up the valley of Lircay, until finally it
climbed over the edge of the hills to a great bleak plateau where hundreds
of llamas were feeding. When you come to a llama range you may be fairly
certain that the altitude is not far from that of the top of Pike’s Peak. Add to
this a blinding snow-storm that keeps you from seeing more than six feet
ahead of you, a wearied mule, a very hungry rider, and the uncertainty as to
whether you are on the right road or not, and you will have a picture of our
predicament during part of that never-to-be-forgotten day. At length, to our
great delight, the trail began slowly to descend from cheerless paramos and
little mountain lakes into a great valley where, thousands of feet below, we
could see huts and cultivated fields.
Skirting the hills half-way up the valley and avoiding the attractive little
trails that led down to Indian villages, we kept turning more and more to the
westward until we rounded a spur and came on a magnificent view of the
great river Mantaro that on its way to join the Apurimac has cut a
wonderfully deep cañon through this part of Peru. A tortuous descent of two
thousand feet brought us to the new toll-bridge of Tablachaca and onto an
excellent road. Of course, this does not mean that it could be used for
wheeled vehicles, for of carts there are none in this part of the world. It
simply means that a trail four or five feet wide and reasonably free from

rocks and holes allowed the mules to jog along at a gait of nearly five miles
an hour. So slow had been our progress over the paramo that it was
considerably after dark before we reached the picturesque old stone bridge
of Yscuchaca, re-crossed the Mantaro, and clattered over the cobble-tones
of this well-built little town.
We had rather flattered ourselves that no one here knew we were coming
and so we had avoided an official reception and all possible attacks on our
digestive faculties. But we had to pay for it by finding that it took nearly
two hours longer than usual before we were able to secure any
accommodations whatsoever for the night. The Gobernador of Yscuchaca
lived a mile or more out of town on his country estate, and learning finally
that there were two “distinguished foreigners” in town, sent his head
servant to welcome us, gave us the use of a room in his town house,
provided our mules with pasturage, and the next morning charged us three
times the regular tariff. I regret to say that we took advantage of the absence
of the Gobernador to pay his major-domo what our sergeant told us was the
THE TOLL BRIDGE OF TABLACHACA
legitimate price and left him wondering why he had not been able to
overcharge us as he had certain American civil engineers who had been here
not long before, surveying for the extension of the central railway of Peru.
At present, that railway, begun many years ago, goes from Lima to
Oroya and thence south to Huancayo which is nearly fifty miles from
Yscuchaca. It is proposed now to continue it from Huancayo to Yscuchaca

and thence due south to Huancavelica where there are mines of quicksilver
and copper. Eventually it will form one of the links in the chain of the Pan-
American Railway.
Our mules were pretty tired and so were we, but when one is on the
home stretch it is easy to travel from early to late. We rose before five
o’clock. Our road first crossed the Mantaro, ascended the left bank of the
stream for several miles, passed several mineral springs, and then climbed
out of the narrowing cañon up toward the village of Acostambo. At one
place where the road had been cut through what looked like a fossil bed, I
was so fortunate as to find, in situ, a fossil bivalve. Professor Charles
Schuchert of Yale University has been so good as to identify it for me as
allorisma subcuneata. It has been found also in Brazil. Its geological
horizon, the upper carboniferous, is widely distributed in South America
and is well known about Lake Titicaca. The location of this fossil here may
indicate the presence in this vicinity of coal-beds. If any could be found, it
would be the greatest benefit, not only to the railway that hopes some day to
pass through this valley, but also to the copper-smelters in the vicinity. As a
matter of fact, Peru does not need the coal for power; these great and
rapidly flowing rivers like the Mantaro, the Pampas, and the Apurimac offer
an abundant water-power that, transformed into electricity, would run all the
railroads and factories that could possibly be crowded into Peru.
Personally, I do not believe in the construction of steam railroads in this
country. The difficulties of overcoming steep grades are serious, and the
cost of building is necessarily all out of proportion to the traffic that is
likely to be developed. I do believe, however, that the future of Peru
depends upon the development of her water-power and the building of light
electric railways that would be sufficient to handle economically the
product of the mines and to accommodate passengers. If the region were
one where extensive crops could be cultivated and a large amount of heavy
freight developed, this argument would not hold. Under the circumstances,
however, I believe that it is a much safer investment for capital and a much
more practical work for the government to develop electric traction.
At Acostambo, a town of perhaps two thousand inhabitants, we tried to
buy something to eat for lunch, but there was nothing to be had except some
dough cakes that had been “cooked” in cold ashes. After passing through
two or three small villages where most of the Indians seemed to be in a state
of intoxication, we crossed the Cordillera Marcavalle and found ourselves

on the well-travelled road to Pampas. Before us, spread out in a magnificent
panorama, the fertile, densely populated valley of Jauja. Watered by the
Upper Mantaro River and its affluents, there are over fifty villages, towns,
and cities, clustered together in this rich plain. Immediately ahead lay four
towns almost exactly in a straight line and less than ten miles apart: Pucará,
where we stopped long enough to buy some parched corn and freshly
roasted pork for supper, Sapallauga, Punta, and Huancayo. Instead of the
desolate region in which we had passed most of yesterday, we were now in
one of the most thickly populated parts of Peru, and felt as though we were
back again in civilization. This sensation was increased when we began to
clatter down the long street of Huancayo. It seemed like an age before we
finally reached the business centre of the city at 9 P.M. and surrendered
ourselves into the hands of a courteous Austrian hotel proprietor.
We had spent nearly fourteen hours in the saddle. This was quite
forgotten when we learned to our delight that there was to be a train for
Oroya the next day, for the first time in two weeks.
We had heard that the train from Huancayo left usually on Sundays, so
we had promised our soldiers a sovereign apiece if they would see to it that
we reached Huancayo by Saturday night. As they had to accompany the
slow-moving pack animals, they did not arrive themselves until the next
morning, somewhat in fear lest they had lost their promised reward. When
they were assured, however, that we had caught our train, and when they
had received their gold and what was left of our kitchen utensils and
supplies, their delight knew no bounds, and they were constrained to
embrace us in truly oriental fashion.
Sunday morning is a great event in Huancayo. Before sunrise, thousands
of Indians come in from the surrounding towns and villages for the weekly
Fair. Two large plazas are crowded with vendors of every conceivable kind
of merchandise: oxen and mules raised nearby, toys “made in Germany,”
pottery and ponchos made in Huancayo, and beer made in Milwaukee.
Overflowing from the crowded plazas the Fair extends for nearly a mile
through the main street of the city. The picturesque Indians in their
brilliantly colored ponchos, thronging the streets and alternately buying and
selling their wares, offer a field for diversion that no one should miss who
reaches Lima.

Like the Mexican Indians, so vividly depicted by Mr. Kirkham in his
artistic “Mexican Trails,” there are many among the throng who will “sell a
hen, later to bargain for a sombrero, presently to go upon their knees within
the church yonder, candle in hand; lastly to lie by the roadside, overfull of
pulque and oblivious of this world, or the next.”
The type is the same whether it be seen on a Sunday in the Andes of
Mexico, Peru, or Colombia. Only here it is chicha that is the favorite
beverage instead of pulque.
The long expected train was due to arrive at noon and “to leave soon
afterwards.” The platform and the newly constructed booths near the little
corrugated-iron station were crowded for hours by
SUNDAY MORNING IN HUANCAYO
intending passengers and friends of expected arrivals. But it was late in the
afternoon, almost dark in fact, before the belated little train pulled into the
station and the runners from the three Huancayo hotels had the satisfaction
of greeting their “friends.” We were informed that the train would not leave
before six o’clock the next morning so we tried to possess ourselves in
patience at our comfortable little hotel.
We were on hand, bright and early, just in time to see the train pull out of
the station. Happily it was only a false alarm, and the train soon backed
down to the platform again and waited for three quarters of an hour for
intending passengers to arrive. At length the conductor decided he could

wait no longer, and at 6:40 we pulled out, just before the sub-Prefect and his
friends arrived on the scene. A young politician on the train, who thought
that the sub-Prefect wanted to go to Lima, pulled violently at the bell-rope.
The engineer, accustomed to that form of stopping the train, had detached
the ropes from the locomotive so that all that the friends of the sub-Prefect
were able to do was to pull several yards of it into the rear coach. Rather
characteristically, the only four people who were on hand at six o’clock
ready for the train to start on time, were all Americans. The two besides
ourselves were artisans from the great copper mines of Cerro de Pasco who
were enjoying a week’s vacation.
At Jauja there is a spur track which runs from the main line a mile or
more back to the historic old city, celebrated in the annals of the Spanish
Conquest and the Wars of Independence. The good people of Jauja, not yet
accustomed to the necessary rules of a railroad train service, flocked on
board the train to say “good-by” to their departing friends and chat as long
as possible. Taking no heed of the screams of the engine and the cries of the
conductor, more than twenty ladies, who had no intention of leaving town,
were still on board when the train pulled out of the station. The conductor
took them a mile and a half down the track to the main line; then, fearing
that the mere fact that they would have to walk home would not sufficiently
impress them, he made each one pay for riding! Twenty more sheepish-
looking individuals than the garrulous ladies, whom the conductor lined up
in the field a short distance from the tracks and charged for their short ride,
would be hard to find.
At eleven o’clock we came to a wash-out and had to cross the Oroya
River on planks hastily thrown over the unfinished new railroad bridge. A
train was waiting for us on the other side, and with very little delay, all the
passengers and luggage were safely carried across and we reached Oroya
before four o’clock that evening.
Although there are rich mines in the vicinity and it is the terminus of the
new line, built by American capital, to the great Cerro de Pasco smelters,
Oroya is chiefly famous as the terminus of “the highest railroad in the
world,” and we looked forward with interest to our journey on the morrow.
The magnificent great viaduct which has frequently been pictured as
formerly one of the highest railroad bridges in existence, had come to grief
only a short time before, in a rather tragic manner. A car, loaded with

bridge-construction material and occupied by several American engineers,
was standing on the bridge to which repairs were being made. A run-away
engine came flying down the grade, struck the car, jumped into the air,
crashed back on the frail viaduct, which gave way and allowed a tangled
mass of men and metal to fall into the cañon two hundred and twenty feet
below.
This accident necessitated many delays, as all the passengers and freight
had to be transferred by mules or on foot down into the cañon and up the
other side to the train for Lima.
The ride from Oroya to Lima has been so frequently described by many
travellers and the excitement of coasting down from the summit tunnel
where the altitude is 15,666 feet to the Lima station, which is only a little
above sea level, is so well known, that I will not attempt to give my own
impressions here. Suffice it to say that the excitement was increased if
anything by the fact that besides the bridge accident another had occurred
only a few days previously in which a locomotive had left the tracks and
rolled down an embankment.
Owing to these accidents our train was provided with a very old engine
whose boilers were so leaky that we had a hard time climbing up from
Oroya to the divide. Several times we stopped; once for three quarters of an
hour to allow enough steam to accumulate to pull us around a curve. We did
not object, however, for the scenery was wonderful. The great craggy cliffs,
their slopes covered with snow and ice, made us realize that this was really
the roof tree of the continent. Just before entering the summit tunnel, the
train stopped again, and we had a chance to enjoy a magnificent panorama
of snow-capped mountains.
A hand-car with two workmen was sent down the road just ahead of our
train so as to give us some sense of assurance. It is well known that most
people coming up this road from Lima suffer greatly from soroche before
they reach the summit. On our way down, however, most of the passengers
were so well accustomed to high elevations that not more than three or four,
and they Peruvian ladies from Jauja and Oroya, seemed to be affected. So
far as I could judge, their trouble was due more to car-sickness and the lack
of ventilation than to the elevation.
We reached Lima about half past eight on the evening of March 2d. Who
can describe the comfort and luxury of those first few hours in the excellent

Hotel Maury?
My first duty the next day was to call on President Leguia, report on
what I had seen at Choqquequirau and tell him how very hospitably we had
been received in the interior towns and cities. After talking with him for a
few moments, we were no longer at a loss to understand why the Prefects
and sub-Prefects of Peru had been so courteous to us, for their chief is
himself the soul of courtesy. Well-travelled, well-educated, speaking
English fluently, a trained business man, not in the slightest degree the type
of South American President with which novel-readers and playgoers are
familiar, he impressed us as a man who would do his best to advance the
welfare of Peru without caring in the least how his own affairs might
prosper in the meantime.
The door-keeper was a fine, tall, gray-haired soldier who had the
manners of a general, was rather suspicious of us at first, but returned
almost immediately after taking in our cards and, with a magnificent bow
and a courtly gesture, ushered us at once into the inner reception room,
greatly to the disgust of several pompous, perspiring politicians who had
been warming their heels in the gilded salon for some time before we
arrived. We did not stay long, and on our way out were again given a
demonstration of interest by the courteous old brigadier. To our sorrow we
read a few months afterward that in the unsuccessful revolution already
referred to in the chapter on Arequipa, which began by seizing the
presidential offices and in securing the President himself and his Minister of
Foreign Affairs, the revolutionists had ruthlessly killed the old door-keeper.
Like every visitor to Lima, we too went into the cathedral to see the
mummified remains of Francisco Pizarro, the Conqueror of Peru, and then
we took a little victoria, drawn by a pair of speedy little trotters, and
explored the parks and boulevards. We saw the monuments and the new
public buildings, called on the American Minister, whom we found to be a
charming southern gentleman, exceedingly well suited to his diplomatic
profession; admired the many substantial foreign banks and business
houses, and regretted that so much of the flavor of the old colonial Lima
had been lost in the Chilean war and in the recent era of business prosperity.
With electric lights and electric cars and abundant foreign capital, it is not
easy to preserve those picturesque features which are so charming in the
interior cities.

At last my journey overland from Buenos Aires had been completed. I
cannot claim to know it as well or as intimately as the poor “foot-walker”
who, if he has been successful, must by this time have reached Buenos
Aires and walked on foot twice over this long dreary road. Nevertheless, I
can appreciate keenly some of the difficulties of travel in Spanish-America
during the colonial period when Lima was the gay capital and Buenos Aires
was merely a frontier post. It is small wonder that there was little sympathy
between Lima and Buenos Aires in those days.
Like my journey across Venezuela and Colombia, this taught me to feel
anew the stupendous difficulties that lie in the way of advancing South
American civilization. It made me admire tremendously the courage and
determination of those heroes of the Wars of Independence who marched up
and down this road for fourteen years until they had driven from it the last
vestige of a foreign army.

A
CHAPTER XXVII
CERTAIN SOUTH AMERICAN TRAITS
s one travels through the various South American republics, becomes
acquainted with their political and social conditions, reads their
literature, and talks with other American travellers, there are a number
of adverse criticisms that frequently arise. I shall attempt here to enumerate
some of them, to account for a few, and to compare others with criticisms
that were made of the people of the United States, half a century ago, by a
distinguished English visitor.
Although it is true that the historical and geographical background of the
South Americans is radically different from ours, it is also true that they
have many social and superficial characteristics very like those which
European travellers found in the United States fifty years ago. The period of
time is not accidental. The South American Republics secured their
independence nearly fifty years later than we did. Moreover, they have been
hampered in their advancement by natural difficulties and racial antipathies
much more than we have. Although the conditions of life in the United
States, as depicted by foreign critics seventy-five years after the battle of
Yorktown, were decidedly worse than the conditions of life in South
America seventy-five years after the battle of Ayacucho, the resemblances
between the faults that were found with us fifty years ago and those that are
noticeable among the South Americans of to-day, are too striking to be
merely coincidences. It is surely not for us to say that there is anything
inherently wrong with our Southern neighbors if their shortcomings are
such as we ourselves had not long ago, and possibly have to-day.
The first criticism that one hears, and the first one is likely to make after
getting beyond the pale of official good breeding in South America, is that
the manners of the ordinary South American are very bad. Lest the traveller
be inclined to take such a state of affairs too seriously, let him read what
Dickens wrote about us and our ways in 1855. It was a faithful picture of a
certain phase of American life. It should be confessed that it paints a
condition of affairs worse than anything I have seen in South America.

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