lecture-slides4931(1)

Slide 1: 

Wireless Communications Engineering Lecture 12: 3G Systems Prof. Mingbo Xiao Dec. 23, 2004

Slide 2: 

Limits of 2G Cellular Systems 2G systems are highly successful, but … Capacity of the system saturated Transmit speed is too slow (9.6 Kbps or 14.4 Kbps) to support multimedia services Symmetric transmission so not suitable for Internet traffic Main service is voice, but voice service is becoming less profitable

Slide 3: 

Voice versus Data over Cellular

Slide 4: 

Internet Access from GSM

Enhanced Data for GSM Evolution (EDGE): 

Enhanced Data for GSM Evolution (EDGE) Common factor for GSM and IS-136; uses their existing spectrum bands Support both packet- and circuit-switched services Eight-phase-shift (8 PSK) modulation Every time slot can support up to 48 Kbps The highest speed is up to 384 Kbps 40 times of GSM and 3 times of GPRS

Packet-Switched Data in GPRS: 

Packet-Switched Data in GPRS

Packet and circuit-switch in GPRS: 

Packet and circuit-switch in GPRS

Protocol Architecture: 

Protocol Architecture

Protocol Architecture (cont.): 

Protocol Architecture (cont.) Physical layer: RFL (Physical RF Layer) – modulation, demodulation PLL (Physical Link Layer) – error control, congestion detect Data link layer: MAC (Medium Access Control) – slotted ALOHA RLC (Radio Link Control) – error correction LLC (Logical Link Control) – always connected

Protocol Architecture (cont.): 

Protocol Architecture (cont.) GPRS supports interworking of MSs with X.25-, IP-based networks by encapsulation and decapsulation Between SGSN and MS, further encapsulation is performed by SNDCP ( SubNetwork-Dependent Convergence Protocols) including: multiplexing, compression, segmentation The MAC is derived from a slotted reservation ALOHA protocol, and operate between MS and BTS

Goals of 3G Systems: 

More services Web browsing VoD Video phone call Mobile computation Improved quality Higher rates: 2.048 Mbps for low speed users, 384 Kbps for modest speed users and 144 Kbps for high speed users More reliable and larger capacity Compatible with 2G systems More flexible Support both circuit-switching and packet-switching Work in hierarchical mode with pico-/micro-/macro-cells Support asymmetric services … Goals of 3G Systems

Slide 19: 

Interest to 3G Applications Western Eastern USA Europe Europe Emails 4.5 4.7 4.3 City maps/directions 4.3 4.2 4.2 Latest news 4.0 4.4 4.0 Authorize/enable payment 3.4 3.8 3.0 Banking/trading online 3.5 3.4 3.2 Downloading music 3.1 3.4 3.2 Shopping/reservation 3.0 3.1 2.9 Animated images 2.4 2.7 2.6 Chat rooms, forums 2.3 2.9 2.2 Interactive games 2.0 2.2 2.4 Games for money 1.8 1.8 1.8 (Means based upon a six-point interest scale, where 6 indicates high interest and 1 indicates low interest.)

Slide 20: 

Upgrade Paths to 3G IS-136 PDC GSM IS-95 IS-95B HSCSD GPRS EDGE W-CDMA EDGE TD-SCDMA cdma200-1xRTT cdma2000-1xEV,DV,DO cdma200-3xRTT 2G 2.5G 3G

Slide 21: 

WCDMA Network

Network Elements: 

Network Elements BTS Base Transceiving Station BSC Base Station Controller MSC Mobile Switching Center GMSC Gateway MSC RNC Radio Network Controller MS Mobile Station HLR Home Location Register VLR Visitor Location Register EIR Equipment Identity Register AUC Authentication Center OMC Operation and Maintenance Center SGSN Serving GPRS Support Node GGSN Gateway GPRS Support Node GR GPRS register

Interface: 

Interface Iu : Interface between the RNC and the Core Network (MSC or SGSN). - Iucs: Iu circuit switched (voice from/to MSC) - Iups: Iu packet switched (data from/to SGSN) Iub: Interface between the RNC and the Node B. Iur: Interface between two RNCs. Gn: Interface between SGSN and GGSN Gi: Interface between GGSN and external packet data network

Slide 24: 

WCDMA Protocol Architecture Network Layer Data Link Layer Physical Layer Layer 3 RRC Medium Access Control Layer 2 Layer 1 Transport Channels Logical Channels MAC RLC Radio Link Control Physical Channels Radio Resource Control 3GPP

WCDMA Channels: 

WCDMA Channels

Logical Channel: 

Logical Channel Broadcast Control Channel (BCCH), Downlink (DL), carries system and cell specific information Paging Control Channel (PCCH), DL Dedicated Control Channel (DCCH), UL/DL Common Control Channel (CCCH), UL/DL Dedicated Traffic Channel (DTCH) for point-to-point data transmission in the uplink and downlink, UL/DL Common Traffic Channel (CTCH), Unidirectional (one to many)

Transport Channels: 

Transport Channels Dedicated Transport Channel (DCH), UL/DL, mapped to DCCH and DTCH Broadcast Channel (BCH), DL, mapped to BCCH Forward Access Channel (FACH) for massages from the base station to the mobile in one cell, DL, mapped to BCCH, CCCH, CTCH, DCCH and DTCH Paging Channel (PCH) for messages to the mobiles in the paging area, DL, mapped to PCCH Random Access Channel (RACH), UL, mapped to CCCH, DCCH and DTCH Uplink Common Packet Channel (CPCH), UL, mapped to DCCH and DTCH Downlink Shared Channel (DSCH), DL, mapped to DCCH and DTCH

Physical Channels: 

Physical Channels Dedicated Transport Channel (DCH), UL/DL, mapped to DCCH and DTCH Broadcast Channel (BCH), DL, mapped to BCCH Forward Access Channel (FACH) for massages from the base station to the mobile in one cell, DL, mapped to BCCH, CCCH, CTCH, DCCH and DTCH Paging Channel (PCH) for messages to the mobiles in the paging area, DL, mapped to PCCH Random Access Channel (RACH), UL, mapped to CCCH, DCCH and DTCH Uplink Common Packet Channel (CPCH), UL, mapped to DCCH and DTCH Downlink Shared Channel (DSCH), DL, mapped to DCCH and DTCH

Channel Multiplexing: 

Channel Multiplexing

IQ/code multiplexing with complex spreading circuit: 

IQ/code multiplexing with complex spreading circuit

Slide 31: 

WCDMA Parameters

cdma2000 Overview: 

cdma2000 Overview Introduction cdma2000 Architecture Physical Layer Forward Links Reverse Links Data Link Layer Link Access Control sublayer Media Access Control sublayer Data Service in cdma2000 Packet data service High-speed circuit data service Conclusions References

Introduction: 

Introduction Backward compatibility to TIA/EIA-95-B Supports TIA/EIA-95-B signaling and services Spreading bandwidths compatible with IS-95-B deployments Supports cdma2000 to IS-95/IS-95-B hard handoff Minimal changes to IS-41 and IS-634 Protects operator investment in existing cdmaOne networks Provides simple and cost-effective migration to 3G services Overlay upgrade to TIA/EIA-95-B Supports backward compatible common channels Forward Link orthogonality maintained between cdma2000 mobiles and IS-95-A/B mobiles

Introduction (cont.): 

Introduction (cont.) Support of IMT-2000 data rates Vehicular – 144 kbps (supported by 1X systems) Pedestrian – 384 kbps (supported by 3X systems) Indoor – 2 Mbps Advanced Medium Access Control (MAC) Support different quality of service for a wide range of advanced services concurrently Simultaneous voice/data support for multi-service QoS support for multimedia applications Significantly improved mobile stand-by time Spot beam and smart antenna coverage

cdma2000 Architecture: 

cdma2000 Architecture

Physical Layer: 

Physical Layer The Radio Configurations (RCs) specify the data rates, channel encoding, and modulation parameters supported on the traffic channel For Spreading Rates (SRs) 1 and 3, there are 6 RCs for the reverse link and 9 RCs for the forward link RCs 1 and 2 are specified to provide backward compatibility with TIA/EIA-95-B There are 6 reverse and 11 forward physical channels in cdma2000

Forward Links Features: 

Forward Links Features Supports chip rates of N x 1.2288 Mcps, N=1,3,6,9,12 N = 1 similar to IS-95B, but QPSK modulation and fast closed-loop power control are used N > 1 Multicarrier Direct spread

Multicarrier and Direct Spread: 

Multicarrier and Direct Spread

Key Characteristics of Forward Links: 

Key Characteristics of Forward Links Channels are orthogonal and use variable-length Walsh codes. QPSK modulation is used before spreading to increase the number of usable Walsh codes. Forward Error Correction (FEC) is used Convolutional codes (k=9) are used for voice and data. Turbo codes (k=4) are used for high data rate on SCHs Supports nonorthogonal forward link channelization These are used when running out of orthogonal space (insufficient number of Walsh codes) Quasiorthogonal functions are generated by masking existing Walsh functions

Key Characteristic of Forward Links (cont.): 

Key Characteristic of Forward Links (cont.) Synchronous forward links Forward link transmit diversity Fast-forward power control (closed loop) 800 times per second

Key Characteristics of Reverse Links: 

Key Characteristics of Reverse Links Continuous waveform Minimizes interference to biomedical devices Enables the interleaving to be performed over the entire frame Orthogonal channels with different-length Walsh sequences Higher data rate channels -> shorter Walsh sequences Rate matching Puncturing Symbol repetition Sequence repetition

Key Characteristics of Reverse Link (cont.): 

Key Characteristics of Reverse Link (cont.) Independent data channels Enables the system to be optimized for multiple simultaneous services The channels are separately coded and interleaved and may have different transmit power level and FER set points. Reverse power control Open loop Closed loop Outer loop

Key Characteristics of Reverse Link (cont.): 

Key Characteristics of Reverse Link (cont.) Separate dedicated control channels Allows for a flexible dedicated control channel structure that does not impact the other pilot and physical channel frame structures. Forward error correction Convolutional codes (k=9) are used for voice and data Parallel turbo codes (k=4) are used for high data rates on supplemental channels Fast-reverse power control 800 times per second

Data Link Layer: 

Data Link Layer Subdivided into two sublayers Link Access Control (LAC) sublayer Manages point-to-point communication channels between peer upper layer entities Provides framework to support a wide range of different end-to-end reliable link layer protocols Media Access Control (MAC) sublayer MAC control state Best-effort delivery Multiplexing and QoS control

Data Link Layer: MAC Control States: 

Data Link Layer: MAC Control States

Data Services in cdma2000: 

Data Services in cdma2000 (1) Packet data services Support a large number of mobile stations using packet data services Dedicated channels for packet service users are allocated on demand and released immediately after the end of the activity period Short data bursts can be transmitted over a common traffic channel Using Mobile IP to support wireless packet data networking capability

Data Services in cdma2000: 

Data Services in cdma2000

Data Services in cdma2000: 

Data Services in cdma2000 (2) High-speed circuit data service Dedicated traffic and control channels are typically assigned to the MS for extended periods of time during the circuit service sessions Some delay-sensitive services such as video applications require a dedicated channel for the duration of the call

Slide 49: 

什么是 TD － SCDMA Time Division-Synchronous Code Division Multiple Access （ 时分 双工 的同步码分多址技术） 是 ITU 正式发布的第三代移动通信空间接口技术规范之一，它得 到了 CWTS 及 3GPP 的全面支持 是中国电信百年来第一个完整的通信技术标准，是 UTRA － FDD 可替代的方案 是集 CDMA 、 TDMA 、 FDMA 技术优势于一体、系统容量大、频谱利用 率高、抗干扰能力强的移动通信技术 它采用了智能天线、联合检测、接力切换、同步 CDMA 、软件无线 电、低码片速率、多时隙、可变扩频系统、自适应功率调整等技术

Slide 50: 

TD-SCDMA 的关键技术 时分双工方式 智能天线： 降低多径、多址干扰 联合检测： 降低多址干扰 上行同步： 减少码间串扰 接力切换：提高切换可靠性 软件无线电 低码片速率 ...  (..) 5 4 2 1 3 6

智能天线 (Smart Antenna): 

智能天线 ( Smart Antenna ) Antenna array + BB digital data Processing Providing a beamformed pattern for each user Fast beamforming to follow the moving user 空分多址大大增加系统容量

智能天线 (Smart Antenna): 

智能天线 ( Smart Antenna ) 天线子系统 圆形天线阵 ：全向小区 扇形天线阵： 120 o 小区 射频前端集成在天线系统内以提高性能 实时校准技术 冗余设计，任何天线单元的失效都不会明显影响系统性能 低成本 天线阵 天线罩 射频前端 电缆出口

智能天线 (S.A.)的优势: 

使用智能天线 ... 定向发射、定向接收 正在通信的移动终端在整个小区内处于受跟踪状态 不使用智能天线 ... 全向发射、全向接收 所有小区内的移动终端均相互干扰，此干扰是 CDMA 容量限制的主要原因 智能天线的优势 减少 小区间 和 小区内干扰 降低 多径干扰 等效发射功率提高 提高接收灵敏度 改进了小区覆盖（合成波束） 增加了容量及小区覆盖半径 降低发射功率，基站成本降低 智能天线 (S.A.) 的优势

: 

联合检测 ( J.D.) 联合检测作用 避免多址干扰 检测动态范围急剧增大 小区内干扰最小化 联合检测原理 特定的空中接口（帧结构）允许收信机对无线信道进行信道估计 根据估计的无线信道，对所有信号同时进行检测 ＣＤＭＡ系统中多址干扰（ M.A.I. ）是主要干扰 ; 小区间的干扰在最恶劣 的情况下也不超过小区内部干扰的６０％。 传统的ＣＤＭＡ系统信号分离方法把ＭＡＩ看作热噪声。 J.D. 充分利用ＭＡＩ中的先验信息

智能天线和联合检测的结合: 

智能天线和联合检测的结合 智能天线的主要作用： 降低多址干扰，提高 CDMA 系统容量 提高接收灵敏度和发射 EIRP 智能天线所不能克服的问题 用户处于相同方向 多普勒效应 ( 高速移动 ) 联合检测：利用训练序列作信道估值，同时处理多码道的干扰抵消。但存在 多码道时处理复杂。 在 TD-SCDMA 移动通信系统中，结合使用智能天线和联合检测，获得了理 想的效果

Slide 56: 

动态信道分配 ( DCA) 在ＴＤＤ模式的ＣＤＭＡ系统中，信道的定义包括： 扩频码 – 码域 时隙 - 时域 载频 - 频域 波束 - 空域 动态信道分配是指： 在终端接入和链路持续期间，根据多小区之间的干扰情况和本小 区内的干扰情况，进行信道的分配和调整。 目的： 1) 增加系统容量 2) 减小干扰。

上行同步技术: 

定义 上行链路各终端信号在基站解 调器完全同步 优点 CDMA 码道正交， 降低码道间干扰， 提高 CDMA 容量 简化硬件，降低成本 t 基站解调器 码道 1 码道 2 码道 N 上行 同步技术

Slide 58: 

低码片速率 载波频带窄 ... 在1 .6MHz 带宽内可实现 2 Mbps 的数据业务 低码片速率的优势 频谱利用率高 频率使用灵活 系统设备成本低

接力切换: 

MS 和 BS0 通信 BS0 通知邻近基站信息 基站类型、工作载频、定时偏差、忙闲等等 MS 搜索基站, 建立同步 BS 或 MS 发起切换请求 系统决定切换执行 MS 同时接收来自两个基站的相同信号 完成切换 优点 节省系统资源，提高系统容量，降低设备成本 BS0 BS1 BS2 MS 接力切换

时分双工 (TDD): 

TD-SCDMA 的优势 易于使用非对称频段, 无需具有特定双工间隔的成对频段 适应用户业务需求，灵活配置时隙，优化频谱效率 上行和下行使用同个载频，故无线传播是对称的,有利于智能天线技术的实现 无需笨重的射频双工器，小巧的基站，降低成本 时分双工 ( TD-SCDMA): 上行频带和下行频带相同 D U D D D D D D 频分双工 ( FDD): 上行频带和下行频带分离 D D D D D D D U U 上行 D 下行 未使用 资源: 时分双工 ( TDD)

软件无线电: 

在通用芯片上 用软件实现专用芯片 的功能 软件无线电的优势 可克服微电子技术的不足 系统增加功能通过软件升级来实现 减少用户设备费用支出 快速适应新技术 软件无线电

TD-SCDMA物理层: 

TD-SCDMA 物理层 低码片速率 :1.28Mcps(WCDMA 的 1/3) ，带宽为 1.6MHz 适合智能天线和同步 CDMA 的帧结构 所有码道可以同时工作 采用和 3GPP 相同的调制、信道编码、交织和复接技术 提供不对称上下行业务 功率调整和同步控制 : 控制频率 :0-200 次 / 秒 功率控制步长 :1-3dB 同步控制精度 :1/8 码片宽度 开环和闭环控制

TD-SCDMA系统独特的帧结构: 

Radio frame 10ms System Frame Number Sub-frame 5ms TS5 TS4 TS0 TS2 TS1 GP TS3 TS6 DwPTS UpPTS Data Midamble Data 675us g L1 144chips TD-SCDMA 帧结构 每帧有两个上 / 下行转换点 TS0 为下行时隙 TS1 为上行时隙 三个特殊时隙 GP, DwPTS, UpPTS 其余时隙可根据根据用户需要进行灵活 UL/DL 配置 TD-SCDMA 系统独特的帧结构

时隙(TS)结构: 

每时隙由 704 Chips 组成，时长 675us ； 业务和信令数据由两块组成，每个数据块分别由 352 Chips 组成； 训练序列 ( Midamble) 由 144 Chips 组成； 16 Chips 为保护； 可以进行波束赋形； Data 352chips Midamble 144chips GP 16 Data 352chips 675  s 时隙 (TS) 结构

TD-SCDMA全向码道和赋形码道: 

TD-SCDMA 全向码道和赋形码道 两种赋形波束 得到小区覆盖的全向波束 针对用户终端的赋形波束 BCH/DwPTS 必须使用全向波束，覆盖整个小区，在帧结构 中使用专门时隙 业务码道通常使用赋形波束，只覆盖个别用户 G DwPTS UpPTS BCH TS5 TS4 TS0 TS2 TS1 TS3 TS6

TD-SCDMA系统应用特点: 

TD-SCDMA 系统应用特点 第三代移动通信的国际标准之一，中国自主知识产权 唯一事实上的 TDD 标准 具有最高的频谱利用率 最适合移动互联网的业务 能工作于各种环境，适应各种组网要求 成本低，对运营商和最终用户带来利益 TD-SCDMA 代表了未来技术的发展方向

TDD 双工方式的特点: 

TDD 双工方式的特点 频谱使用灵活性：不需要成对频谱 上下行链路使用相同载波频率，便于使用新技术 用时间来自适应上下行业务量，支持不对称数据业务， 适应无线互联网的需求，这是比 FDD 方式最突出的优点 低成本 TD-SCDMA 还有频谱利用率最高的优点

Slide 68: 

TD-SCDMA 系统具有最高的频谱利用率 定义： 话音通信：频谱利用率 == 同时工作信道数 /MHz/ 小区 数据： 频谱利用率 == 最大传输数据速率 /MHz/ 小区 GSM IS95 CDMA2000 WCDMA TD-SCDMA 频率复用系数 7 1 1 1 1 每载波频宽 (MHz) 0.4 2.5 2.5 10 1.6 每载波同时工作信道数 8 20 30 60 24 频谱利用率（话音） 2.8 8 12 6 15 最大数据传输速率 － － 2.5Mbps 4Mbps 2Mbps 频谱利用率（数据 , Mbps/MHz/cell ） 1.0 0.4 1.25

Slide 69: 

IMT-2000 技术发展方向 Main tech discussed in ITU WP8F (Ref. ITU Doc. 8F/TEMP/65-E, Oct. 2000, Geneva) Smart Antenna （智能天线） Not only for TDD(as TD-SCDMA), but also for FDD, it may lead to change physical layer design in FDD Software Defined Radio （软件定义无线电） Simplifying hardware Multi-mode UE for worldwide roaming High speed down-link package data transmission Using the concept in TDD: Higher modulation scheme (16QAM)----HDR in some time slots in FDD 结论： “ TD-SCDMA 代表 3G 技术发展方向 ”