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bottlelewdMobile - Wireless

Dec 12, 2013 (4 years and 20 days ago)

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Chapter 1

Introduction

1.1 WCDMA in Third
-
Generation Systems

1.2 Spectrum Allocations for Third
-
Generation Systems

1.3 Requirements for Third
-
Generation Systems

1.4 WCDMA and its Evolution

1.5 System Evolution

1.1 WCDMA in Third Generation
Systems


1G systems


analog cellular systems


2G systems


digital cellular systems


voice communications, text messaging and internet
access


e.g., GSM (Global System for Mobile
Communications), PDC (Personal Digital Cellular),
cdmaOne (IS
-
95) and US
-
TDMA (IS
-
136)


3G systems


designed for
multimedia communication


applications


person
-
to
-
person

communication can be
enhanced with high
-
quality images and video


access to information and services on public and
private networks will be enhanced by
higher data
rates

and new
flexible communication
capabilities


WCDMA (Wideband Code Division Multiple Access)


emerged as the most widely adopted 3G
air
interface


specification has been created in 3GPP (the 3
rd

Generation Partnership Project), which is the joint
standardization project of the standardization bodies
from Europe, Japan, Korea, USA and China


Within 3GPP


WCDMA is called UTRA (Universal Terrestrial
Radio Access) FDD (Frequency Division Duplex)
and TDD (Time Division Duplex)


the term WCDMA being used to cover both FDD
and TDD operations


UTRA is the
radio access

part of the Universal
Mobile Telephone System (UMTS) network

1.2 Spectrum Allocations for Third
Generation Systems


Work to develop 3G mobile systems


1992, started with the World Administrative Radio
Conference (WARC) of the ITU (International
Telecommunications Union)


WARC
-
92 identified the frequencies around 2 GHz
that were available for use by future International
Mobile Telephony 2000 (IMT
-
2000) mobile
systems, both terrestrial and satellite


WRC
-
2000

World Radiocommunication Conference
2000 (Istanbul, Turkey 8 May
-
2 June 2000)


WARC
-
92 IMT
-
2000 Frequencies


WARC
-
92


1920
-
1980 and 2110
-
2170 MHz


Frequency Division Duplex

(FDD, W
-
CDMA) Paired uplink
and downlink, channel spacing is 5 MHz and raster is 200 kHz.
An Operator needs 3
-

4 channels (2x15 MHz or 2x20 MHz) to
be able to build a high
-
speed, high
-
capacity network.


1900
-
1920 and 2010
-
2025 MHz


Time Division Duplex

(TDD, TD/CDMA) Unpaired, channel
spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not
separated in frequency.


1980
-
2010 and 2170
-
2200 MHz


Satellite

uplink and downlink.


Channel spacing

is a term used in
radio frequency planning. It
describes the frequency difference
between adjacent allocations in a
frequency plan.


Channel raster

is 200 kHz, which
means that the carrier frequency
must be a multiple of 200 kHz.


WRC
-
2000 IMT
-
2000 Frequencies


WRC
-
2000


Identified the bands 1710
-

1885 and 2500
-

2690 MHz
for IMT
-
2000


Identified those parts of the band 806
-

960 MHz which
are allocated to the mobile service on a primary basis


Admitted that High Altitude Platform Stations (HAPS)
may use the WARC
-
92 frequency bands for terrestrial
IMT
-
2000 on restrictive conditions


Decided that the frequency bands 1525
-

1544, 1545
-

1559,
1610
-

1626.5, 1626.5
-

1645.5, 1646.5
-

1660.5 and 2483.5
-

2500 MHz may be used for the satellite component of IMT
-
2000, as well as the bands 2500
-

2520 MHz and 2670
-

2690
MHz, depending on market developments


Decided that "the bands, or portions of the bands, 1710
-

1885 MHz and 2500
-

2690 MHz, are identified for use by
administrations wishing to implement International Mobile
Telecommunications
-
2000 (IMT
-
2000). This identification
does not preclude the use of these bands by any application
of the services to which they are allocated and does not
establish priority in the Radio Regulations”


The WCDMA system is specified in 3GPP for all the
following frequency bands


IMT
-
2000 mobile spectrum around 2 GHz, 800

900 MHz and 2.6 GHz


further frequencies


700 MHz band in USA


2.3 GHz (Wireless Communication Services
(WCS) band in USA


part of the existing broadcast frequencies
between 400 and 700 MHz

Frequency Allocation around 2 GHz

Frequency Allocation around 800

900
MHz

Frequency Allocation around 2.6 GHz

1.3 Requirements for Third
-
Generation
Systems


2G air interfaces


GSM


IS
-
95 (the standard for cdmaOne)


PDC (Personal Digital Cellular)


US
-
TDMA


2G systems were built mainly to provide
speech

services in
macro

cells


New requirements of 3G systems


bit rates up to 2 Mbps


variable

bit rate to offer bandwidth on demand


multiplexing

of services with
different quality
requirements

on a single connection, e.g. speech,
video and packet data


delay requirements


from delay
-
sensitive
real time

traffic


to flexible
best
-
effort

packet data


quality requirements


from 10% frame error rate


to 10
-
6

bit error rate


co
-
existence of 2G and 3G systems and inter
-
system
handovers

for
coverage

enhancements and
load

balancing


support of
asymmetric

uplink and downlink traffic


e.g. web browsing causes more loading to
downlink than to uplink


high spectrum efficiency

Main differences between WCDMA
and GSM networks


Main differences between WCDMA/High Speed Packet
Access (HSPA) and GSM/Enhanced Data Rates for GSM
Evolution (EDGE) networks, e.g.


the larger bandwidth of 5MHz (vs. 200kHz) is needed to support
higher bit rates


HSPA Release 7


adds a Multiple Input Multiple Output (MIMO) multi
-
antenna
solution



higher order modulation 64QAM to support even higher data
rates


HSPA pushes more functionalities to the
base station

and
allows
flat

architecture, which improves the efficiency and the
Quality of Service (QoS) capabilities for packet services


Terms


carrier


a carrier wave, or carrier is a waveform (usually
sinusoidal) that is modulated (modified) to
represent the information to be transmitted


diversity


the property of being made up of two or more
different elements, media, or methods


note

in communications, diversity is usually
used to provide
robustness
,
reliability
, or
security


frequency diversity


the process of receiving a radio signal or
components of a radio signal on
multiple
channels

(different frequencies) or over a
wide
radio channel

(wide frequency band) to reduce
the effects of radio signal
distortions

(such as
signal fading) that occur on one frequency
component but do not occur (or not as severe) on
another frequency component

Graph of a Waveform and the Distorted
Versions of the Same Waveform

24


power control


WCDMA uses
fast closed loop

power control in
both
uplink

and
downlink


th
e
downlink

fast power control improves link
performance and enhances downlink capacity

Close
-
loop Power Control



WCDMA
中若沒有
uplink
power control
,一支手機發送
太大的功率,會使整個
cell

法動作
(block)


圖中
UE1

UE2
使用相同的頻
率,只利用不同的
spreading
code
來區別



UE1

cell
的邊緣正為
path loss
所苦惱,而
UE2
靠近
BS



UE1

UE2
未做
power
control
,而用相同的
power
來傳送,
UE1
的訊
號會被
UE2
的訊號蓋過,
稱為
near
-
far problem of
CDMA


解決方法:讓
BS
收到所有
手機訊號的
功率等級
相同


open
-
loop power control (
只單向
)


原理:利用手機計算
downlink beacon signal

平均值,來得到大概的
path loss
,然而若用此
值來決定手機的發送功率太不精確


原因:因
WCDMA uplink

downlink
使用的頻
道相離太遠,
uplink/downlink

fast fading
的形
態並不相關


結論:
open
-
loop power control
只用於當
UE

始與系統建立連結時做粗略的
power setting


fast
closed
-
loop power control


能解決上述
open
-
loop power control
的問題


uplink


BS
經常
(1.5kHz)
要估計接收到的
SIR
,並與
target SIR
比較



measured SIR > target SIR

BS
命令所

UE
降低
power



measured SIR < target SIR

BS
命令所

UE
提高
power


這樣的控制頻率比嚴重的
path loss

fast
Rayleigh fading
來得頻繁,才得以解決問題


downlink



cell
邊緣的
UE
受到周遭所有
BS
的干擾,
也因
Rayleigh fading
而希望
BS
能增強信


Outer Loop Power Control


outer
-
loop power control


用於設定
target SIR setpoint


對於各別的
radio link connection
,可設定其
uplink

frame error rate (FER)

bit error rate
(BER)
等服務品質


BS
藉由設定
target SIR setpoint
當做基準,要
求手機增加或減少
power

1.4 WCDMA and its Evolution


Evolution


European research work on WCDMA


initiated in the European Union research projects


CODIT (UMTS
C
ode
Di
vision
T
estbed)


FRAMES (
F
uture
R
adio wideb
A
nd
M
ultiple
acc
E
ss
S
ystems)


within large European wireless communications
companies, at the start of the 1990s


CODIT and FRAMES projects also


produced WCDMA
trial

systems to evaluate
link

performance


generated the basic understanding of WCDMA
necessary for standardization


in January 1998 the European standardization body
ETSI decided upon WCDMA as the 3G air interface


detailed standardization work has been carried out as
part of the 3GPP standardization process


the first full set of specifications was completed at the
end of 1999, called Release 99


3GPP specified important evolution steps on top of
WCDMA


Release 5: High Speed Downlink Packet Access
(HSDPA), commercially deployed in 2005


Release 6: High Speed Uplink Packet Access
(HSUPA), commercially deployed in 2007


Release 7: commercially deployed in 2009


HSPA evolution is also known as HSPA+


3GPP also specify a new radio system called Long
-
Term Evolution (LTE), where the target for finalizing
3GPP standardization is during 2007


Release
-
7 and
-
8 solutions for HSPA evolution will
be worked in parallel with LTE development, and
some aspects of LTE work are also expected to
reflect on HSPA evolution

Standardization and Commercial Operation
Schedule for WCDMA and its Evolution


Peak data rate evolution for WCDMA


WCDMA Release 99 in theory enabled 2 Mbps, but in
practice gave 384 kbps


HSPA in Release 5 and Release 6 pushes the peak rates
to 14 Mbps in downlink and 5.7 Mbps in uplink


HSPA evolution in Release 7 brings a maximum 28
Mbps in downlink and 11 Mbps in uplink


LTE will then further push the peak rates beyond 100
Mbps in downlink and 50 Mbps in uplink by using a 20
MHz bandwidth

Peak Data Rate Evolution for WCDMA


1.5 System Evolution


WCDMA is designed for coexistence with GSM,
including
seamless handovers

and
dual
-
mode

handsets


Most of WCDMA networks are deployed on top of the
existing GSM network


LTE is designed for
coexistence

with GSM and
WCDMA

System Evolution