4G LTE-Advanced：移动宽带的高速转型与技术详解

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4G LTE-LTE-Advanced是3GPP（第三代合作伙伴项目）为移动宽带服务开发的新标准，它旨在提升网络速度，以满足消费者对高速移动多媒体应用的需求。这个标准在2010年12月被正式固定下来，作为LTE Release 10的一部分。本书《4GLTE/LTE-Advanced for Mobile Broadband》由埃里克森（Ericsson）的工程师们撰写，他们是该标准的主要开发者，因此提供了深入的技术洞察和标准背后的设计原理。书中涵盖了LTE的基础知识以及其进阶技术——LTE-Advanced，详细解释了为何需要向LTE演进以及如何实现这一转变。LTE的核心特点是其峰值下载速率的显著提升，从早期的几十兆比特每秒（Mbps）发展到LTE-Advanced的几百兆比特每秒，这使得移动设备能够流畅地处理高清视频流、大型游戏下载和云计算应用等数据密集型服务。 LTE-Advanced进一步引入了多个关键技术，如载波聚合（Carrier Aggregation）、多点MIMO（Multiple-Input Multiple-Output）和eNodeB之间的协同工作，这些都显著提高了频谱效率和网络容量。此外，它还支持更灵活的网络部署策略，包括室内分布系统和热点覆盖增强，以满足多样化的用户需求。本书对于通信工程技术人员来说是一本宝贵的参考资料，他们可以从中学习到如何设计、优化和维护一个高效、高带宽的4G LTE-LTE-Advanced网络，以及如何应对未来无线通信技术的挑战。通过阅读这本书，读者将理解网络架构的演变，以及如何通过技术创新来推动移动宽带服务的快速发展。本书不仅提供了技术背景，还强调了实际应用中的策略和案例，帮助工程师们掌握4G LTE-LTE-Advanced在移动宽带领域的最新进展，确保网络能够适应不断增长的用户需求和业务场景。无论是在技术研发、网络规划还是运营优化方面，本书都是不可或缺的参考资料。

xxiv Abbreviations and Acronyms

UCI Uplink Control Information

UE User Equipment, the 3GPP name for the mobile terminal

UL Uplink

UL-SCH Uplink Shared Channel

UM Unacknowledged Mode (RLC conﬁguration)

UMB Ultra Mobile Broadband

UMTS Universal Mobile Telecommunications System

UpPTS The uplink part of the special subframe (for TDD operation).

US-TDMA US Time-Division Multiple Access standard

UTRA Universal Terrestrial Radio Access

UTRAN Universal Terrestrial Radio Access Network

VAMOS Voice services over Adaptive Multi-user channels

VoIP Voice-over-IP

VRB Virtual Resource Block

WAN Wide Area Network

WARC World Administrative Radio Congress

WCDMA Wideband Code-Division Multiple Access

WG Working Group

WiMAX Worldwide Interoperability for Microwave Access

WLAN Wireless Local Area Network

WMAN Wireless Metropolitan Area Network

WP5D Working Party 5D

WRC World Radiocommunication Conference

X2 The interface between eNodeBs.

ZC Zadoff-Chu

ZF Zero Forcing

4G LTE/LTE-Advanced for Mobile Broadband.

Background of LTE

CHAPTER

1.1 INTRODUCTION

Mobile communications has become an everyday commodity. In the last decades, it has evolved from

being an expensive technology for a few selected individuals to today’s ubiquitous systems used

by a majority of the world’s population. From the ﬁrst experiments with radio communication by

Guglielmo Marconi in the 1890s, the road to truly mobile radio communication has been quite long.

To understand the complex mobile-communication systems of today, it is important to understand

where they came from and how cellular systems have evolved. The task of developing mobile tech-

nologies has also changed, from being a national or regional concern, to becoming an increasingly

complex task undertaken by global standards-developing organizations such as the Third Generation

Partnership Project (3GPP) and involving thousands of people.

Mobile communication technologies are often divided into generations, with 1G being the ana-

log mobile radio systems of the 1980s, 2G the ﬁrst digital mobile systems, and 3G the ﬁrst mobile

systems handling broadband data. The Long-Term Evolution (LTE) is often called “4G”, but many

also claim that LTE release 10, also referred to as LTE-Advanced, is the true 4G evolution step, with

the ﬁrst release of LTE (release 8) then being labeled as “3.9G”. This continuing race of increasing

sequence numbers of mobile system generations is in fact just a matter of labels. What is important is

the actual system capabilities and how they have evolved, which is the topic of this chapter.

In this context, it must ﬁrst be pointed out that LTE and LTE-Advanced is the same technology,

with the “Advanced” label primarily being added to highlight the relation between LTE release 10

(LTE-Advanced) and ITU/IMT-Advanced, as discussed later. This does not make LTE-Advanced

a different system than LTE and it is not in any way the ﬁnal evolution step to be taken for LTE.

Another important aspect is that the work on developing LTE and LTE-Advanced is performed as a

continuing task within 3GPP, the same forum that developed the ﬁrst 3G system (WCDMA/HSPA).

This chapter describes the background for the development of the LTE system, in terms of events,

activities, organizations and other factors that have played an important role. First, the technolo-

gies and mobile systems leading up to the starting point for 3G mobile systems will be discussed.

Next, international activities in the ITU that were part of shaping 3G and the 3G evolution and the

market and technology drivers behind LTE will be discussed. The ﬁnal part of the chapter describes

the standardization process that provided the detailed speciﬁcation work leading to the LTE systems

deployed and in operation today.

2 CHAPTER 1 Background of LTE

1.2 EVOLUTION OF MOBILE SYSTEMS BEFORE LTE

The US Federal Communications Commission (FCC) approved the ﬁrst commercial car-borne teleph-

ony service in 1946, operated by AT&T. In 1947 AT&T also introduced the cellular concept of reus-

ing radio frequencies, which became fundamental to all subsequent mobile-communication systems.

Similar systems were operated by several monopoly telephone administrations and wire-line opera-

tors during the 1950s and 1960s, using bulky and power-hungry equipment and providing car-borne

services for a very limited number of users.

The big uptake of subscribers and usage came when mobile communication became an interna-

tional concern involving several interested parties, in the beginning mainly the operators. The ﬁrst

international mobile communication systems were started in the early 1980s; the best-known ones are

NMT that was started up in the Nordic countries, AMPS in the USA, TACS in Europe, and J-TACS

in Japan. Equipment was still bulky, mainly car-borne, and voice quality was often inconsistent, with

“cross-talk” between users being a common problem. With NMT came the concept of “roaming”,

giving a service also for users traveling outside the area of their “home” operator. This also gave a

larger market for mobile phones, attracting more companies into the mobile-communication business.

The analog ﬁrst-generation cellular systems supported “plain old telephony services” (POTS) –

that is, voice with some related supplementary services. With the advent of digital communication

during the 1980s, the opportunity to develop a second generation of mobile-communication standards

and systems, based on digital technology, surfaced. With digital technology came an opportunity to

increase the capacity of the systems, to give a more consistent quality of the service, and to develop

much more attractive and truly mobile devices.

In Europe, the GSM (originally Groupe Spécial Mobile, later Global System for Mobile commu-

nications) project to develop a pan-European mobile-telephony system was initiated in the mid 1980s

by the telecommunication administrations in CEPT

and later continued within the new European

Telecommunication Standards Institute (ETSI). The GSM standard was based on Time-Division

Multiple Access (TDMA), as were the US-TDMA standard and the Japanese PDC standard that

were introduced in the same time frame. A somewhat later development of a Code-Division Multiple

Access (CDMA) standard called IS-95 was completed in the USA in 1993.

All these standards were “narrowband” in the sense that they targeted “low-bandwidth” services

such as voice. With the second-generation digital mobile communications came also the opportunity

to provide data services over the mobile-communication networks. The primary data services intro-

duced in 2G were text messaging (Short Message Services, SMS) and circuit-switched data services

enabling e-mail and other data applications, initially at a modest peak data rate of 9.6 kbit/s. Higher

data rates were introduced later in evolved 2G systems by assigning multiple time slots to a user and

through modiﬁed coding schemes.

Packet data over cellular systems became a reality during the second half of the 1990s, with

General Packet Radio Services (GPRS) introduced in GSM and packet data also added to other cellu-

lar technologies such as the Japanese PDC standard. These technologies are often referred to as 2.5G.

The success of the wireless data service iMode in Japan, which included a complete “ecosystem”

The European Conference of Postal and Telecommunications Administrations (CEPT) consists of the telecom administra-

tions from 48 countries.

31.2 Evolution of Mobile Systems Before LTE

for service delivery, charging etc., gave a very clear indication of the potential for applications over

packet data in mobile systems, in spite of the fairly low data rates supported at the time.

With the advent of 3G and the higher-bandwidth radio interface of UTRA (Universal Terrestrial

Radio Access) came possibilities for a range of new services that were only hinted at with 2G and

2.5G. The 3G radio access development is today handled in 3GPP. However, the initial steps for 3G

were taken in the early 1990s, long before 3GPP was formed.

What also set the stage for 3G was the internationalization of cellular standards. GSM was a pan-

European project, but it quickly attracted worldwide interest when the GSM standard was deployed in

a number of countries outside Europe. A global standard gains in economy of scale, since the market

for products becomes larger. This has driven a much tighter international cooperation around 3G cel-

lular technologies than for the earlier generations.

1.2.1 The First 3G Standardization

Work on a third-generation mobile communication started in ITU (International Telecommunication

Union) in the 1980s, ﬁrst under the label Future Public Land Mobile Telecommunications Systems

(FPLMTS), later changed to IMT-2000 [1]. The World Administrative Radio Congress WARC-92

identiﬁed 230 MHz of spectrum for IMT-2000 on a worldwide basis. Of these 230 MHz, 2  60 MHz

was identiﬁed as paired spectrum for FDD (Frequency-Division Duplex) and 35 MHz as unpaired

spectrum for TDD (Time-Division Duplex), both for terrestrial use. Some spectrum was also set aside

for satellite services. With that, the stage was set to specify IMT-2000.

In parallel with the widespread deployment and evolution of 2G mobile-communication systems

during the 1990s, substantial efforts were put into 3G research activities worldwide. In Europe, a

number of partially EU-funded projects resulted in a multiple access concept that included a Wideband

CDMA component that was input to ETSI in 1996. In Japan, the Association of Radio Industries and

Businesses (ARIB) was at the same time deﬁning a 3G wireless communication technology based

on Wideband CDMA and also in the USA a Wideband CDMA concept called WIMS was developed

within the T1.P1

committee. South Korea also started work on Wideband CDMA at this time.

When the standardization activities for 3G started in ETSI in 1996, there were WCDMA concepts

proposed both from a European research project (FRAMES) and from the ARIB standardization in

Japan. The Wideband CDMA proposals from Europe and Japan were merged and came out as part

of the winning concept in early 1998 in the European work on Universal Mobile Telecommunication

Services (UMTS), which was the European name for 3G. Standardization of WCDMA continued in

parallel in several standards groups until the end of 1998, when the Third Generation Partnership

Project (3GPP) was formed by standards-developing organizations from all regions of the world.

This solved the problem of trying to maintain parallel development of aligned speciﬁcations in mul-

tiple regions. The present organizational partners of 3GPP are ARIB (Japan), CCSA (China), ETSI

(Europe), ATIS (USA), TTA (South Korea), and TTC (Japan).

At this time, when the standardization bodies were ready to put the details into the 3GPP speci-

ﬁcations, work on 3G mobile systems had already been ongoing for some time in the international

arena within the ITU-R. That work was inﬂuenced by and also provided a broader international

framework for the standardization work in 3GPP.

The T1.P1 committee was part of T1, which presently has joined the ATIS standardization organization.

4 CHAPTER 1 Background of LTE

1.3 ITU ACTIVITIES

1.3.1 IMT-2000 and IMT-Advanced

ITU-R Working Party 5D (WP5D) has the responsibility for IMT systems, which is the umbrella

name for 3G (IMT-2000) and 4G (IMT-Advanced). WP5D does not write technical speciﬁcations for

IMT, but has kept the role of deﬁning IMT in cooperation with the regional standardization bodies

and to maintain a set of recommendations for IMT-2000 and IMT-Advanced.

The main IMT-2000 recommendation is ITU-R M.1457 [2], which identiﬁes the IMT-2000 radio

interface speciﬁcations (RSPC). The recommendation contains a “family” of radio interfaces, all

included on an equal basis. The family of six terrestrial radio interfaces is illustrated in Figure 1.1,

which also shows the Standards Developing Organizations (SDO) or Partnership Projects that pro-

duce the speciﬁcations. In addition, there are several IMT-2000 satellite radio interfaces deﬁned, not

illustrated in Figure 1.1.

For each radio interface, M.1457 contains an overview of the radio interface, followed by a list

of references to the detailed speciﬁcations. The actual speciﬁcations are maintained by the individual

SDOs and M.1457 provides references to the speciﬁcations maintained by each SDO.

With the continuing development of the IMT-2000 radio interfaces, including the evolution of

UTRA to Evolved UTRA, the ITU recommendations also need to be updated. ITU-R WP5D continu-

ously revises recommendation M.1457 and at the time of writing it is in its ninth version. Input to the

updates is provided by the SDOs and Partnership Projects writing the standards. In the latest revision

of ITU-R M.1457, LTE (or E-UTRA) is included in the family through the 3GPP family members for

UTRA FDD and TDD, as shown in the ﬁgure.

ITU-R Family of

IMT-2000 terrestrial Radio Interfaces

(ITU-R M.1457)

(UTRA TDD and

E-UTRA TDD)

IMT-2000

CDMA TDD

3GPP

IMT-2000

CDMA Multi-Carrier

(CDMA2000 and

UMB)

3GPP2

IMT-2000

CDMA Direct Spread

(UTRA FDD and

E-UTRA FDD)

3GPP

IMT-2000

OFDMA TDD WMAN

(WiMAX)

IEEE

IMT-2000

FDMA/TDMA

(DECT)

ETSI

IMT-2000

TDMA Single-Carrier

(UWC 136)

ATIS/TIA

FIGURE 1.1

The deﬁnition of IMT-2000 in ITU-R.

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