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  1. 1X空口概述 • Section 1: IS-95 to CDMA2000 Evolution • Section 2: CDMA 基本原理 • Section 3: Physical Layer, Forward/Reverse Channels for CDMA2000-1X • Section 4: Power Control • Section 5: Handoff

  2. 第一部分 IS-95 到 CDMA2000 的进化

  3. IS-95 • IS-95 is the first CDMA protocol and is Protocol Revision 1*. • IS-95 was first published in July of 1993. * Protocol Revision Number could be checked in the Layer 3 specification, MOB_P_REV.

  4. IS-95A • IS-95A revision was published in May of 1995. • IS-95A is referred to as Protocol Revision 2. • Mobile Station—Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellar System. • Frequency band: 800Mhz • Compatible for both analog and CDMA • Limited Circuit data (Max. 9.6kbps)

  5. ANSI J-STD-008 • Personal Station—Base Station Compatibility Requirements for 1.8 to 2.0 Ghz CDMA Personal Communications Systems (PCS) • ANSI J-STD-008 was published in 1995 • Frequency band: 1900Mhz • Mostly same as IS-95A • Rate Set 1 (9.6kbps) and Rate Set 2 (14.4kbps) • Limited Circuit data (Max. 14.4kbps)

  6. TSB-74 • Telecommunications Systems Bulletin: • Describes interaction between IS-95A system and PCS system • Support for 14.4 kbps Data Rate and PCS Interaction for Wideband Spread Spectrum Cellular Systems • Rate Set 2 (14.4kbps) • PCS and Cellular Interaction (1900Mhz and 800Mhz) • IS-95A + TSB-74 are referred as Protocol Revision 3.

  7. IS-95B • IS-95B or TIA/EIA-95 combines: IS-95A + TSB-74 + ANSI J-STD-008 into a single document. • IS-95B or TIA/EIA-95 is Protocol Revision 4. • Frequency band: 800Mhz/1900Mhz • Deleted some analog information • Adds technical corrections • Adds new capabilities • Enhanced data Rate by use of Supplemental Code Channel 1~7, Max. Data Rate 115.2kpbs. (8 x 14.4kbps)

  8. cdmaOne • CDMA systems based on the IS-95 standards and related specifications are referred to as cdmaOnesystems.

  9. CDMA2000 • New Standards for 3G • An evolution of IS-95A/B • Compatible of IS-95A/B • New capabilities for both voice and data • More WALSH Code • Higher Data Rate 153.6kbps, 230.4kbps, 307.2kbpsand even higher.

  10. CDMA2000-1X • Both forward and reverse channels use a single direct-sequence spread carrier with a chip rate of 1.2288Mcps. • Also called Spreading Rate 1 1.25Mhz

  11. CDMA2000-3X • Forward channels use threedirect-sequence spread carriers each with a chip rate of 1.2288Mcps. • Reverse channels use a single direct-sequence spread carrier with a chip rate 3.6864Mcps. • Also called Spreading Rate 3

  12. CDMA2000-3X ForwardLink Reverse Link

  13. CDMA Technology Evolution CDMA2000 -1X DO IS-95A IS-95B CDMA2000 -1X CDMA2000 -1X DV

  14. IS-95 to CDMA2000 Evolution • IS-95 (P_rev 1) • IS-95A (P_rev 2 / P_rev 3) • IS-95B (P_rev 4 / P_rev 5) (IS-95A + TSB-74 + ANSI J-STD-008) • CDMA2000 Release 0 (P_rev 6) • CDMA2000 Release A (P_rev 7) • Now the newest release available is CDMA2000 Release C (May, 2002)

  15. Section 2: CDMA 基本原理

  16. 本章重点 • 介绍CDMA中使用的基本编码 • PN码的自相关特性(Auto-Correlation) • WALSH码的正交特性(Orthogonal) • CONVOLUTIONAL CODIND • TURBO CODING • INTERLEAVING • 理解CDMA的基本原理 • 如何利用编码实现信道和用户的区分

  17. Multiple Access Methods • FDMA 频分多址 • 用不同的频率划分来区分用户 • Analog system • TDMA 时分多址 • 在相同的频率上, 用不同的时隙来区分用户 • GSM system • CDMA 码分多址 • 在相同的时间和相同的频率上, 用不同的编码来区分用户 • IS-95 system

  18. Multiple Access Methods • FDMA 频分多址 每个用户占用不同的频道

  19. Multiple Access Methods • TDMA 频分多址 每个用户占用不同的时隙, 但频率是相同的.

  20. Multiple Access Methods • CDMA 码分多址 每个用户占用不同的编码, 但频率和时间是相同的.

  21. CDMA 码分多址的基本原理 • IS-95A/B和CDMA2000-1X的编码工作原理是相同的. • 采用的主要编码为: • 伪随机码 PN CODE (Pseudorandom Noise Code) • 沃尔什码 WALSH CODE • 卷积码 CONVOLUTIONAL CODE • 交织 INTERLEAVING • CDMA2000-1X新引入了TURBO CODE

  22. 伪随机码 PN CODE的自相关特性(Auto-Correlation) • Auto-Correlation: • 相同的PN SEQUENCE当时间对齐时, 其自相关的归一化值为1. • 相同的PN SEQUENCE当时间不对齐时, 其自相关的归一化值为-1/L. 当L趋于较大值时, 该值趋于0. • CDMA用此特性获取码同步和时间同步,以及反向信道的区分.

  23. 伪随机码 PN CODE的自相关特性(Auto-Correlation) 归一化值: +1 +7 +6 +5 +4 +3 +2 +1 00 - 1 归一化值: - 1/L 0 Time Shifts  0 1 2 3 4 5 6 7 

  24. 伪随机码PN CODE在CDMA2000中的应用 15 • 只有Two Short PN codes: 2 = 32768 (insert one ‘0’) • 分为I和Q支路,结构不同. • 用于正交扩谱. • 不同的offset用于识别不同的扇区. 64 chips, 512 offsets, for Spreading Rate 1 192 chips, 512 offsets, for Spreading Rate 3 • 重复周期26.67ms(1.2288Mcps), 2秒钟重复75次. PI(x) = x15 + x13 + x9 + x8 + x7 + x5 + 1 (for the in-phase (I) sequence) PQ(x) = x15 + x12 + x11+ x10 + x6 + x5 + x4 + x3 + 1 (for the quadrature-phase (Q) sequence).

  25. 伪随机码PN CODE在CDMA2000中的应用 42 • 只有One Long PN code: 2 (insert one ‘0’) • 在IS-95和CDMA2000-1X中用于扩谱Spread,扰码Scrambling, Data Burst Randomizer 算法, Position of Power Control Bits和反向信道区分. • Direct sequence spreading using the long code shall be applied to the Access Channel and the Reverse Traffic Channel with Radio Configurations 1 and 2.

  26. 长码的掩码LONG CODE MASK特性 • The mask used for the long code varies depending on the channel type on which the mobile station is transmitting. • 反向用于区分 Access Channel和Reverse Traffic Channel. • 不论MASK如何组成,只能产生相同的 LONG CODE SEQUENCE. 但重要的是产生了不同的时间位移Offset in Time.

  27. 沃尔什码 WALSH CODE的正交特性(Orthogonal Sequences) Conclusion: • 当两个二进制序列的模二加之和等于零,则称这两个二进制序列是正交的 (ORTHOGONAL) W(i)•W(j) = 0 i  j (互相关值为零, 与PN不同) • 两个相同的WALSH序列模二加之和等于1(归一化值) (自相关值为1, 与PN相同) • 任何一个WALSH序列由于误码变成另一个序列, 则必须产生至少L/2个错码. L 为该序列的长度 • 上述特性是在完全同步的条件下得出的. W(i)•W(j) = 1 (归一化值) i = j

  28. 沃尔什码 WALSH CODE的正交特性(Orthogonal Sequences) • WALSH CODE在CDMA2000-1X中用于前向FORWARD信道的区分, 在反向REVERSE信道做WALSH FUNCTION (Orthogonal Spreading). (IS-95 反向WALSH ORTHOGONAL MODULATION). • IS-95 can use WALSH up to length 64 • CDMA2000-1X can use WALSH up to length 128 • CDMA2000-3X can use WALSH up to length 256 (不包括CDMA2000的 Auxiliary Pilot and Auxiliary Transmit Diversity Pilot Channels, Max. length of WALSH is 512) • 由此可以看出CDMA2000能提供更多的WALSH序列, 即可以得到更多的用户信道分配.

  29. 沃尔什码 WALSH CODE的正交特性(Orthogonal Sequences) • Quasi-Orthogonal Functions (QOFs): 当WALSH序列都被占用时, 可用一组新的正交码叫做Quasi-Orthogonal Functions (QOFs) • Walsh Functions are used with RC1 and RC2. • Walsh Functions and QOFs are used with RC3through RC9. • These functions are generated by multiplying the Walsh codes by a vector of binary symbols, called the QOF mask, and then multiplying by a rotate enable function, Walshrot, it caused the phase of the signal to be rotated 90 degree. • The new orthogonal codes cannot be orthogonal to the original Walsh code. • Total code signal set size is (M+1)N. CDMA2000 uses M=3, code length N=128. Then code size could be 512. (RC: Radio Configuration, will be explained in Section 3)

  30. 沃尔什码 WALSH CODE的正交特性(Orthogonal Sequences) Quasi-Orthogonal Functions (QOFs): Masking Functions for Quasi-Orthogonal Functions with Length 256 for Spreading Rate 1 and Spreading Rate 3

  31. CONVOLUTIONAL CODING 卷积码 • 卷积码在IS-95和CDMA2000-1X中都得到了应用. 基本原理也相同. 主要用于VOICE和低速DATA的FEC前向纠错(Forward Error Correction). K = 9, Rate 1/2 Convolutional Encoder

  32. TURBO CODE • CDMA2000-1X新引入了TURBO CODE用于高速DATA的FEC前向纠错. • TURBO CODE又称为并行级联卷积码.在ICC 93 会议上提出.适用于高速数据,当BER10 , E/N0.7时,接近仙农定理bit/sym值. • TURBO CODE:A type of error-correcting code. A code symbol is based on the outputs of the two recursive convolutional codes (constituent codes) of the Turbo code. • 可提供优于卷积码约2dB的增益. -5

  33. CONVOLUTIONAL CODINGAND TURBO CODING • CONVOLUTIONAL CODING和TURBO CODING均为FEC前向纠错编码. 用于误码的检错和纠错. • CONVOLUTIONAL CODING可用于话音VOICE和数据DATA(低速率). • TURBO CODING适用于数据DATA(高速率). 用于RC3 ~ RC9.

  34. INTERLEAVING交织 • INTERLEAVING交织是一种将原始数据经一定的排列组合之后再输出的前向纠错编码方法. 可以将连续出现的误码分散为不连续的误码.与CONVOLUTIONAL CODING和TURBO CODING配合,用于误码的检错和纠错.

  35. Section 2: CDMA基本原理小结 • 伪随机码 PN CODE的自相关特性(Auto-Correlation) Only Two Shot PN Codes I/Q; One Long PN Code • 沃尔什码 WALSH CODE的正交特性(Orthogonal Sequences) WALSH 64 (IS-95), WALSH 128 (CDMA2000-1X), QUASI-ORTHOGONAL FUNCTIONS(QOFs) 上述二种编码主要用于扇区识别,信道区分等. • CONVOLUTIONAL CODING用于话音VOICE和数据DATA(低速率). • TURBO CODING适用于数据DATA(高速率). • INTERLEAVING交织,将误码离散化. 上述三种编码主要用于用于话音VOICE和数据DATA的前向纠错FEC.

  36. Section 3: Physical Layer, Forward/Reverse Channels for CDMA2000-1X

  37. CDMA2000-1X常用概念名词 • Spreading Rate (SR): • Spreading Rate 1 (SR1): 用于单载频(1X) Spreading Rate 1 is often referred to as .1X.. A Spreading Rate 1 Forward CDMA Channel uses a single direct-sequence spread carrier with a chip rate of 1.2288 Mcps. A Spreading Rate 1 Reverse CDMA Channel uses a single direct-sequence spread carrier with a chip rate of 1.2288 Mcps. • Spreading Rate 3 (SR3):用于多载频(3X) Spreading Rate 3 is often referred to as .3X.. A Spreading Rate 3 Forward CDMA Channel uses three direct-sequence spread carriers each with a chip rate of 1.2288 Mcps. A Spreading Rate 3 Reverse CDMA Channel uses a single direct-sequence spread carrier with a chip rate of 3.6864 Mcps. • 本课程重点介绍1X (SR1).

  38. CDMA2000-1X常用概念名词 • Rate Set (RS): • Rate Set 1: (RS1) 8kpbs; 9.6/4.8/2.4/1.2 • Rate Set 2: (RS2) 13kpbs; 14.4/7.2/3.6/1.8 不同的话音VOICE编码速率(信源编码)

  39. CDMA2000-1X常用概念名词 • Band Class: • CDMA2000 frequency bands, 分为 Band Class 0 ~ Band Class 10. • Band Class 0: (North American Cellular Band) (通常所说的800Mhz频段) • Band Class 1: (North American PCS Band) (通常所说的1.9Ghz频段) • Band 2 ~ Band 10 这里不过多介绍

  40. CDMA2000-1X常用概念名词 • Band Class 0: (North American CellularBand) (通常所说的800Mhz频段) Band Class 0 System Frequency Correspondence

  41. CDMA2000-1X常用概念名词 • Band Class 1: (North American PCSBand) (通常所说的1.9Ghz频段) Band Class 1 System Frequency Correspondence

  42. CDMA2000-1X常用概念名词 • Radio Configuration (RC): • A set of Forward Traffic Channel and Reverse Traffic Channel transmission formats that are characterized by physical layer parameters such as transmission rates, modulation characteristics, and spreading rate. • Reverse: RC1 ~ 6 • Forward: RC1 ~ 9 • RC1 and RC2are used for IS-95, will use Convolutional coding and BPSK • RC3 and above are used for 1X and 3X, will use Convolutional coding, Turbo coding and QPSK

  43. Radio Configuration Characteristics for the Reverse CDMA Channel IS-95 1X RS1 RS2 RS1 3X RS2

  44. Radio Configuration Characteristics for the Forward CDMA Channel IS-95 RS1 1X RS1 RS2 RS1 RS1 3X RS2 RS2

  45. CDMA2000-1X常用概念名词 • Radio Configuration Class: • A group of RCs. • IS-95 对应 Radio Configuration Class 1 • CDMA2000-1X 对应 Radio Configuration Class 2 • CDMA2000-3X 对应 Radio Configuration Class 3

  46. CDMA2000-1X常用概念名词 • Orthogonal Transmit Diversity (OTD): A forward link transmission method which distributes forward link channel symbols among multiple antennas and spreads the symbols with a unique Walsh or quasi-orthogonal function associated with each antenna. 数据分为两路发送,各50%数据,不同天线(10 wavelength apart),不同Walsh Code. 1101 Wi Data Stream Divider 10110011 0101 Wj

  47. CDMA2000-1X常用概念名词 • Space Time Spreading (STS): A forward link transmission method which transmits all forward link channel symbols on multiple antennas and spreads the symbols with complementary Walsh or quasi-orthogonal functions. 数据先分为两路,经处理后再重新交叉构成新的两路数据,两路发送数据相同,互补调制,去不同天线. (*better) C1 b1 b1C1 b1C1-b2c2 Even/Odd Separator + b _ C2 1/√2 b2 b2C2 b2C1 b2C1+b1c2 + + b1C2

  48. CDMA2000-1X常用概念名词 • BPSK(Binary Phase Shift Keying): • IS-95使用BPSK做前向/反向信号调制. • 相干解调性能比非相干解调性能约好3dB. 前向信道为相干(Coherent Demodulation)解调 反向信道为非相干(Non-Coherent Demodulation)解调. *注意,此处没有 串/并转换.因此 数据率不能提高.

  49. DEMUX X CDMA2000-1X常用概念名词 • QPSK(Quadrature Phase Shift Keying): CDMA2000-1X使用QPSK做前向信号调制. QPSK 的数据传输能力比BPSK高一倍.由于在反向信道引入了R-PICH导引信号,前向信道/反向信道均为相干解调(Coherent Demodulation). 串/并 转换,传输能力可提高一倍.

  50. CDMA2000-1X常用概念名词 • OQPSK(Offset Quadrature Phase Shift Keying): • IS-95和CDMA2000-1X均在反向信道的Q支路引入1/2 PN Chip延迟,原理上称为OQPSK*信号调制. (* 从数据率角度来看,仍为BPSK) • 这样做的目的是减少调制信号过零点,从而减少带外信号的杂散分量. 以降低对手机功放的要求.