毕业设计外文翻译-基于MATLAB的TD-SCDMA通信系统的调制与解调仿真程序设计

附录 4 **** 大 学
本科录录录录（录文）外文 录 翻
录录名 ： 称 基于 MATLAB 的 TD-SCDMA 通信
系录的录制 解录 程序录录 与 仿真
院（系）： 学 信息科 工程 院 学与 学
年录录录：*** 录通信工程 3 班
生姓名： 学
指录 录： 教
完成日期： 20** 年 3 月 26 日
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Review of UMTS
1.1 UMTS Network Architecture
The European/Japanese 3G standard is referred to as UMTS. UMTS is one
of a number of standards ratified by the ITU-T under the umbrella of IMT-2000.
It is currently the dominant standard, with the US CDMA2000 standard gaining
ground, particularly with operators that have deployed cdmaOne as their 2G
technology. At time of writing,Japan is the most advanced in terms of 3G
network deployment. The three incumbent operators there have implemented
three different technologies: J-Phone is using UMTS,KDDI has a CDMA2000
network, and the largest operator NTT DoCoMo is using a system branded as
FOMA (Freedom of Multimedia Access). FOMA is based on the original UMTS
proposal, prior to its harmonization and standardization.
The UMTS standard is specified as a migration from the second generation
GSM standard to UMTS via the General Packet Radio System (GPRS) and
Enhanced Data for Global Evolution (EDGE), as shown in Figure. This is a
sound rationale since as of April 2003, there were over 847 Million GSM
subscribers worldwide1, accounting for
68% of the global cellular subscriber figures. The emphasis is on keeping as
much of the GSM network as possible to operate with the new system.
We are now well on the road towards Third Generation (3G), where the
network will support all traffic types: voice, video and data, and we should see
an eventual explosion in the services available on the mobile device. The driving
technology for this is the IP protocol. Many cellular operators are now at a
position referred to as 2.5G, with the deployment of GPRS, which introduces an
IP backbone into the mobile core network.The diagram below, Figure 2, shows
an overview of the key components in a GPRS network, and how it fits into the
existing GSM infrastructure.
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The interface between the SGSN and GGSN is known as the Gn interface
and uses the GPRS tunneling protocol (GTP, discussed later). The primary
reason for the introduction of this infrastructure is to offer connections to
external packet networks, such as the Internet or a corporate Intranet.
This brings the IP protocol into the network as a transport between the
SGSN and GGSN. This allows data services such as email or web browsing on
the mobile device,with users being charged based on volume of data rather than
time connected.
The dominant standard for delivery of 3G networks and services is the
Universal Mobile Telecommunications System, or UMTS. The first deployment
of UMTS is the Release ’99 architecture, shown below in Figure 3.
In this network, the major change is in the radio access network (RAN) with
the introduction of CDMA technology for the air interface, and ATM as a
transport in the transmission part. These changes have been introduced
principally to support the transport of voice, video and data services on the same
network. The core network remains relatively unchanged, with primarily
software upgrades. However, the IP protocol pushes further into the network
with the RNC now communicating with the 3G SGSN using IP.
The next evolution step is the Release 4 architecture, Figure 4. Here, the
GSM core is replaced with an IP network infrastructure based around Voice over
IP technology.
The MSC evolves into two separate components: a Media Gateway (MGW)
and an MSC Server (MSS). This essentially breaks apart the roles of connection
and connection control. An MSS can handle multiple MGWs, making the
network more scaleable.
Since there are now a number of IP clouds in the 3G network, it makes
sense to merge these together into one IP or IP/ATM backbone (it is likely both
options will be available to operators.) This extends IP right across the whole
network, all the way to the BTS.This is referred to as the All-IP network, or the
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Release 5 architecture, as shown in Figure 5. The HLR/VLR/EIR are generalised
and referred to as the HLR Subsystem(HSS).
Now the last remnants of traditional telecommunications switching are
removed, leaving a network operating completely on the IP protocol, and
generalised for the transport of many service types. Real-time services are
supported through the introduction of a new network domain, the IP Multimedia
Subsystem (IMS).
Currently the 3GPP are working on Release 6, which purports to cover all
aspects not addressed in frozen releases. Some call UMTS Release 6 4G and it
includes such issues as interworking of hot spot radio access technologies such
as wireless LAN1.2 UMTS FDD and TDD
Like any CDMA system, UMTS needs a wide frequency band in which to
operate to effectively spread signals. The defining characteristic of the system is
the chip rate, where a chip is the width of one symbol of the CDMA code.
UMTS uses a chip rate of 3.84Mchips/s and this converts to a required spectrum
carrier of 5MHz wide. Since this is wider than the 1.25MHz needed for the
existing cdmaOne system, the UMTS air interface is termed ‘wideband’ CDMA.
There are actually two radio technologies under the UMTS umbrella:
UMTS FDD and TDD. FDD stands for Frequency Division Duplex, and like
GSM, separates traffic in the uplink and downlink by placing them at different
frequency channels. Therefore an operator must have a pair of frequencies
allocated to allow them to run a network, hence the term ‘paired spectrum’. TDD
or Time Division Duplex requires only one frequency channel, and uplink and
downlink traffic are separated by sending them at different times. The ITU-T
spectrum usage, as shown in Figure 6, for FDD is 1920- 980MHz for uplink
traffic, and 2110-2170MHz for downlink. The minimum allocation an operator
needs is two paired 5MHz channels, one for uplink and one for downlink, at a
separation of 190MHz. However, to provide comprehensive coverage and
services, it is recommended that an operator be given three channels.
Considering the spectrum allocation, there are 12 paired channels available, and
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many countries have now completed the licencing process for this spectrum,
allocating between two and four channels per licence. This has tended to work
out a costly process for operators, since the regulatory authorities in some
countries, notably in Europe, have auctioned these licences to the highest bidder.
This has resulted in spectrum fees as high as tens of billions of dollars in some
countries.
The Time Division Duplex (TDD) system, which needs only one 5MHz
band in which to operate, often referred to as unpaired spectrum. The differences
between UMTS FDD and TDD are only evident at the lower layers, particularly
on the radio interface. At higher layers, the bulk of the operation of the two
systems is the same. As the name suggests, the TDD system separates uplink and
downlink traffic by placing them in different time slots. As will be seen later,
UMTS uses a 10ms frame structure which is divided into 15 equal timeslots.
TDD can allocate these to be either uplink or downlink,with one or more
breakpoints between the two in a frame defined. In this way, it is well suited to
packet traffic, since this allows great flexibility in dynamically dimensioning for
asymmetry in traffic flow.
The TDD system should not really be considered as an independent
network, but rather as a supplement for an FDD system to provide hotspot
coverage at higher data rates. It is rather unsuitable for large scale deployment
due to interference between sites, since a BTS may be trying to detect a weak
signal from a UE, which is blocked out by a relatively strong signal at the same
frequency from a nearby BTS. TDD is ideal for indoor coverage over small
areas.
Since FDD is the main access technology being developed currently, the
explanations presented here will focus purely on this system.
1.3 UMTS Bearer Model
The procedures of a mobile device connecting to a UMTS network can be
split into two areas: the access stratum (AS) and the non-access stratum (NAS).
The access stratum involves all the layers and subsystems that offer general
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services to the non-access stratum. In UMTS, the access stratum consists of all of
the elements in the radio access network, including the underlying ATM
transport network, and the various mechanisms such as those to provide reliable
information exchange. All of the non-access stratum functions are those between
the mobile device and the core network, for example, mobility management.
Figure 7 shows the architecture model. The AS interacts with the NAS through
the use of service access points (SAPs).
UMTS radio access network (UTRAN) provides this separation of NAS and
AS functions, and allows for AS functions to be fully controlled and
implemented within the UTRAN. The two major UTRAN interfaces are the Uu,
which is the interface between the mobile device, or User Equipment (UE) and
the UTRAN, and the Iu, which is the interface between the UTRAN and the core
network. Both of these interfaces can be divided into control and user planes
each with appropriate protocol functions.
A Bearer Service is a link between two points, which is defined by a certain
set of characteristics. In the case of UMTS, the bearer service is delivered using
radio access bearers.
A Radio access bearer (RAB) is defined as the service that the access
stratum (i.e.UTRAN) provides to the non-access stratum for transfer of user data
between the User Equipment and Core Network. A RAB can consist of a number
of subflows, which are data streams to the core network within the RAB that
have different QoS characteristics,such as different reliabilities. A common
example of this is different classes of bits with different bit error rates can be
realised as different RAB subflows. RAB subflows are established and released
at the time the RAB is established and released, and are delivered together over
the same transport bearer.
A Radio Link is defined as a logical association between a single User
Equipment (UE) and a single UTRAN access point, such as an RNC. It is
physically comprised of one or more radio bearers and should not be confused
with radio access bearer.
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Looking within the UTRAN, the general architecture model is as shown in
Figure 8 below. Now shown are the Node B or Base Station (BTS) and Radio
Network Controller (RNC) components, and their respective internal interfaces.
The UTRAN is subdivided into blocks referred to as Radio Network Subsystems
(RNS), where each RNS consists of one controlling RNC (CRNC) and all the
BTSs under its control. Unique to UMTS is the interface between RNSs, the Iur
interface, which plays a key role in handover procedures. The interface between
the BTS and RNC is the Iub interface.
All the ‘I’ interfaces: Iu, Iur and Iub, currently3 use ATM as a transport
layer. In the context of ATM, the BTS is seen as a host accessing an ATM
network, within which the RNC is an ATM switch. Therefore, the Iub is a UNI
interface, whereas the Iu and Iur interfaces are considered to be NNI, as
illustrated in Figure 9.
This distinction is because the BTS to RNC link is a point-to-point
connection in that a BTS or RNC will only communicate with the RNC or BTS
directly connected to it, and will not require communication beyond that element
to another network element.
For each user connection to the core network, there is only one RNC, which
maintains the link between the UE and core network domain, as highlighted in
Figure 10. This RNC is referred to as the serving RNC or SRNC. That SRNC
plus the BTSs under its control is then referred to as the SRNS. This is a logical
definition with reference to that UE only. In an RNS, the RNC that controls a
BTS is known as the controlling RNC or CRNC. This is with reference to the
BTS, cells under its control and all the common and shared channels within.
As the UE moves, it may perform a soft or hard handover to another cell. In
the case of a soft handover, the SRNC will activate the new connection to the
new BTS. Should the new BTS be under the control of another RNC, the SRNC
will also alert this new RNC to activate a connection along the Iur interface. The
UE now has two links, one directly to the SRNC, and the second, through the
new RNC along the Iur interface. In this case, this new RNC is logically referred
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to as a drift RNC or DRNC, see Figure 10. It is not involved in any processing of
the call and merely relays it to the SRNC for connection to the core. In summary,
SRNC and DRNC are usually associated with the UE and the CRNC is
associated with the BTS. Since these are logical functions it is normal practice
that a single RNC is capable of dealing with all these functions.
A situation may arise where a UE is connected to a BTS for which the
SRNC is not the CRNC for that BTS. In that situation, the network may invoke
the Serving RNC Relocation procedure to move the core network connection.
This process is described inSection 3.
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通用移录通信系录的回录
1.1 UMTS 录架 网 构
洲 欧 /日本的3G 录准，被 录 称UMTS。UMTS 是一 在 个 IMT-2000 保录录下
的ITU-T 批准的录多录准之一。 着美 的 随 国 CDMA2000 录准的录展， 是目前 它
占主录地位的录准，特录是 录商 运 将cdmaOne 部署录他录的2G 技录。在 录本录录 写 ，
日本是在3G 录部署方面最先录的。三名录任 录商已录录施了三 不同的技录 网 运 个 ：
J - PHONE 使用 UMTS，KDDI 录有 CDMA2000 录，最大的 录商 网 运 NTT
DoCoMo 正在使用品牌的FOMA（自由多媒 接入）系录。 体 FOMA 是基于
原 的 来 UMTS 录录，而且更加的录录和录准化。
UMTS 录准被定录录一 通录通用分录无录系录（ 个 GPRS）和全球演录的增强数
据技录（EDGE） 第二代 从 GSM录准到UNTS 的 移。录是一 泛录用的基 迁 个广
本原理，因录自2003 年4 月起，全球有超录 847
GSM用录，占全球的移录用录 字的 数 68％。重点是在保持 可能多的 尽
GSM 录录 新系录的操作。 网 与
我录录在在第三代(3G)的录展道路上，其中 录录 支持所有录型的流量：录 网 将
音，录录和 据，我录录录看到一 最录的爆炸在移录录录上的可用服录。此录录技录是 数 个
IP 录录。录在，录多移录 录商在录 录 运 称2.5G 的位置，伴随GPRS 的部署，即将IP
骨干 引入到移录核心 。 网 网
SGSN 和GGSN 之录的接口被 录 称Gn 接口和使用GPRS 隧道录录（GTP 的，
稍后录录）。引录录录基录录施的首要原因是提供录接到外部分录 录如， 网 Internet 或
企录 Intranet。录使IP 录录作录 SGSN和GGSN之录的 录工具录用到 录。录使得 运 网 数
据服录，如移录录录上的录子录件或录录 录，用录被起录基于 据流量，而不是录录录 网 数
接基录上的 据量。 数 3G 录和服录交付的主要录准是通用移录通信系录，或 网
UMTS。首次部署的UMTS 是录行'99 架 。 构
在录 录中，主要的录化是在无录接入 录（ 个网 网 RAN 的）CDMA 空中接口
技录的引录，和在录录部分 步录录模式作录一录录录方式。录些录化已录引入，主要是 异
录了支持在同一 录上的录音，录录和 据服录的 录。核心 录保持相录不录，主 网 数 运 网
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要是录件升录。然而， 着目前无录 录控制器使用 随 网 IP 与3G的GPRS 录录支持录
点录行通信，IP 录录录一步录用到 录。 网
未 的录化步录是第 来 4 版架 。在录里， 构 GSM的核心被以录音IP 技录录基录
的IP 录基录录施取代。 网
海安的录展分录 立部分：媒 录（ 两个独 体网 MGW）和 MSC 服录器
（MSS）的。录基本上是打破外录接的作用和录接控制。一个MSS 可以录理多
个MGW，使 录更具有录展性。 网
因录录在有一些在3G 录的 网 IP 云，合 录些到一 并 个IP 或IP/ ATM骨干网
是 有意录的（ 可能 提供 录录录录 录商）。录使 很 它很 会 两 运 IP 录利拓展到整 录 个网，
一直到BTS(基站收录信台)。录被 录全 称 IP 录，或推出五架 ，如录五所示。 网 构
在HLR/ VLR/VLR/EIR 被推 和 录 广 称HLR 的子系录（HSS）。
录在录录的录信交录的最后 余被录除，留下完全基于 残 IP 录录的 录 录，录 推 网 运并
了录多服录录型的 录。录录服录通录引入一 新的 录域名得到支持， 广 运 个 网 即IP 多
媒 子系录（ 体 IMS）。
目前3GPP 作用于第6 版，意在包含冷录版本 有涵盖所有方面。有些 没
人称UMTS 第6 版录 4G和 包括录点无录录接入技录，如无录局域 互录互通的 它 网
录录。
1.2 UMTS 的FDD和TDD
像任何CDMA系录，UMTS 需要一 录的录录，在录 录录上有效地录播信 个 个 号。
录系录的特点是芯片的速度，芯片是一 符 的 个 号 CDMA 代录的录度。 UMTS
使用的芯片速率录 3.84Mchips/秒，录录录到所需的录录录波录度录 5MHz。由于录比录