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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

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chapter 1

Chapter 1


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
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
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)

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.
  • 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.


    • 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
1 3 requirements for third generation systems
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/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
    • 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
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
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
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
        • 如measured SIR > target SIR,BS命令所有UE 降低power
        • 如measured SIR < target SIR,BS命令所有UE 提高power
      • 這樣的控制頻率比嚴重的path loss或fast Rayleigh fading來得頻繁,才得以解決問題
    • 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
    • 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
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

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
1 5 system evolution
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