Chapter 1 Introduction. 1.1 WCDMA in Third-Generation Systems 1.2 Spectrum Allocations for Third-Generation Systems 1.3 Requirements for Third-Generation.

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 3rd

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

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power control WCDMA uses fast closed loop power control in

both uplink and downlink the downlink fast power control improves link

performance and enhances downlink capacity

Close-loop Power Control

在 WCDMA中若沒有 uplink power control，一支手機發送太大的功率，會使整個 cell無法動作 (block)

圖中 UE1 與 UE2使用相同的頻率，只利用不同的spreading code來區別 若 UE1 在 cell的邊緣正為

path loss所苦惱，而 UE2靠近 BS

如 UE1 與 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的平均值，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 與 downlink使用的頻道相離太遠， uplink/downlink 之 fast fading的形態並不相關

結論： open-loop power control只用於當 UE 開始與系統建立連結時做粗略的 power setting

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

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 的 frame error rate (FER) 或 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 Code Division Testbed) FRAMES (Future Radio widebAnd Multiple

accEss Systems) 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