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TDLTE的帧结构和协议相关知识


一、协议知识
1. LTE帧结构及物理资源基本概念RE/RB/CCE/REG/RBG 帧结构 Type1:FDD(全双工和半双工)(FDD 上下行数据在不同的频带里传输;使用成对频谱) 每一个无线帧长度为10ms,由20个时隙构成,每一个时隙长度为Tslot = 15630 x Ts = 0.5ms。 对于 FDD,在每一个 10ms 中,有 10 个子帧可以用于下行传

输,并且有 10 个子帧可以用于上行传输。上下行传输 在频域上进行分开。

#0 slot

#1 Sub-frame

#2

#18

#19

One radio frame = 10ms
帧结构Type2:TDD (TDD上下行数据可以在同一频带内传输;可使用非成对频谱) 一个无线帧10ms,每个无线帧由两个半帧构成,每个半帧长度为5ms。每一个半帧由8个常规时隙和DwPTS、GP和 UpPTS三个特殊时隙构成,DwPTS和UpPTS的长度可配置,要求DwPTS、GP以及UpPTS的总长度为1ms。
One radio frame =10 ms
One half frame =5 ms

1 ms #0 #2 #3 #4 #5 #7 #8 #9

DwPTS GP UpPTS

DwPTS GP UpPTS

DwPTS: Downlink Pilot Time Slot GP: Guard Period (GP越大说明小区覆盖半径越大) UpPTS: Uplink Pilot Slot Ts = 1 / (15000x2048) s Frame 帧的长度:Tf = 307200 x Ts = 10ms Subframe 子帧的长度:Tsubframe = 30720 x Ts = 1ms Slot 时隙的长度:Tslot = 15360 x Ts = 0.5ms 1 Sub-Carrier = 15 kHz; 1 TTI = 1 ms => 1 sub-frame => 2 slots (0.5 ms *2) # for one user, min 2 RB allocation. 1 RB = 12 sub-carriers during 1 slot (0.5 ms) =>12 * 15kHz = 180kHz (Bandwidth); => 12 * 7 symbols= 84 REs 1 RE = 1 sub-carrier x 1 symbol period (Each symbol is QPSK, 16QAM or 64QAM modulated.) LTE 支持可变带宽:1.4MHz, 3, 5, 10, 15 和 20MHz 一个小区最少使用 6 个 RB, 即最少包含 72 个 sub-carriers: 6 RB * 12 sub-carriers = 72 sub-carriers 一个小区最多支持 110 个 RB,相当于 1320 个 sub-carriers: 110 *12 =1320 sub-carriers Channel bandwidth 1.4 3 5 10 15 20 BWChannel [MHz] Transmission bandwidth 6 15 25 50 75 100 configuration NRB

Normal cyclic prefix in downlink DwPTS UpPTS Normal cyclic prefix in uplink
6592? Ts 19760? Ts

Extended cyclic prefix in downlink DwPTS UpPTS Normal cyclic prefix in uplink
7680? Ts

Special subframe configuration 0 1 2 3 4 5 6 7 8

Extended cyclic prefix in uplink

Extended cyclic prefix in uplink

20480? Ts
2192? Ts

21952? Ts 24144? Ts 26336? Ts
6592? Ts 19760? Ts

23040? Ts 25600? Ts
2560? Ts 7680? Ts 2192? Ts 2560? Ts

20480? Ts 23040? Ts
4384? Ts 5120? Ts 4384? Ts 5120? Ts

21952? Ts 24144? Ts

-

-

-

特殊帧格式5:DwPTS:GP:UpPTS => (6592Ts-16Ts) : (19744Ts-16Ts) : 4384Ts=> 3:9:2 特殊帧格式7:DwPTS:GP:UpPTS => (21952Ts-32Ts) : 4384Ts : 4384Ts=> 10:2:2 最小分配单位为: 2192? Ts Configure TDD: 上下行配置(下图) + 特殊帧格式(上图) (e.g.: 2:7 1:7) Uplink-downlink configuration 0 1 2:2 2 3:1 3 4 5 6 Downlink-to-Uplink Switch-point periodicity 5 ms 5 ms 5 ms 10 ms 10 ms 10 ms 5 ms 0 D D D D D D D 1 S S S S S S S Subframe number 2 U U U U U U U 3 U U D U U D U 4 U D D U D D U 5 D D D D D D D 6 S S S D D D S 7 U U U D D D U 8 U U D D D D U 9 U D D D D D D

TDD支持5ms和10ms的周期转换: => 5ms转换周期:一个帧的上下半帧的特殊帧格式配置相同, => 10ms转换周期:一个帧分成上下半帧,下半帧的特殊帧为DwPTS=1ms,用于DL传输(如上图3,4,5所示)

RE:Resource Element,称为资源粒子,是上下行传输使用的最小资源单位。 1 RE = 1 subcarrier x 1 symbol period RB:Resource Block,称为资源块,用于描述物理信道到资源粒子的映射。一个RB包含若干个RE。一个RB由12个 在频域上的子载波和时域上一个slot周期构成(1 RB = 12 subcarriers x 1 slot)。 1个RB在频域上对应180kHz:1 RB = 12 subcarriers x 15kHz = 180kHz 1个RB在时域上对应1个时隙,1 slot =0.5ms CCE:Control Channel Element,称为控制信道粒子,PDCCH在一个或多个CCE上传输,CCE对应于9个REG,每 个REG包含4个RE,CCE从0开始编号。(1 CCE = 9 REGs = 9 x 4 REs = 36 REs) PDCCH format与CCE之间的关系如下图所示: Number of PDCCH bits PDCCH format Number of CCEs Number of REGs (QPSK) 0 1 2 3 1 2 4 8 9 18 36 72 72 144 288 576

REG:Resource Element Group,用来定义控制信道到RE的映射.(1 REG = 4 REs) RBG:Resource Block Group,RBG是连续的PRB的集合,其大小根据系统带宽配置的不同而定,如下图所示: System Bandwidth RBG Size (P) (Number of DL RBs) 1 ≤10 11 – 26 2 27 – 6463 (e.g.: 10MHz - 50 RBs) 3 64 – 110 (e.g.: 20MHz - 100 RBs) 4

2. 下行物理信道及物理信号的功能和占用时频码域位置(DL:PDSCH/PDCCH/PHICH/PCFICH/PBCH/ PSS/SSS/RS)

Location of PBCH for FS2 (normal CP, exteded CP):
? Sanchar GmbH

TDD:
PCFICH

PHICH
Slot #0

Subframe #0 Slot #1

SSS
DwPTS

PSS

Special subframe GP UpPTS

Normal CP case

PDCCH

SSCH

PSCH

frequency frequency

PDSCH

PBCH

Central 6 RBs

Symbols
Slot #0 Subframe #0 Slot #1 DwPTS

Special subframe GP UpPTS

Extended CP case

PDCCH

SSCH

PSCH

PDSCH

PBCH

Central 6 RBs

Symbols
Page 72

2.1 PBCH:Physical Broadcast Channel (物理广播信道) - 主要用来传输MIB信息,MIB消息包含:DL带宽信息;PHICH组号;系统帧号SFN - MIB: DL-Bandwidth, PHICH-Config, SFN, # of antennas. - 占用中间的6个RB(72sc),在第2个slot的前4个symbol上传递(slot 1, symbol 0~3) - MIB消息的重复周期为40ms,起始位置为subfram#0 of SFN mod 4 = 0。每10ms传递一次MIB,传递内容一致, 40ms组成一个MIB消息。可实现时间分集,提高UE接收MIB消息时的增益,改善接收质量 2.2 PCFICH:Physical Control Format Indicator Channel (物理控制格式指示信道) - 用来指示在一个sub-frame中PDCCH传输的OFDM symbol数量(1, 2 or 3) - 在每个subframe(TTI)的第1个symbol上进行传递(symbol 0 within each TTI) - 承载CFI信息,每TTI占用16个RE资源,即4个REG 2.3 PDCCH:Physical Downlink Control Channel (物理下行控制信道) - 用于承载DCI信息,包括资源调度分配和其他控制信息,如与DL-SCH和PCH相关的HARQ信息等 - PDCCH在每个subframe的前3个symbol(symbol 0~2)中进行传递,占用个数由PCFICH承载的CFI消息来确定。 - PDCCH的大小对应于一个或者多个CCE,如下图所示:

PDCCH format 0 1 2 3

Number of CCEs 1 2 4 8

Number of REGs 9 18 36 72

Number of PDCCH bits 72 144 288 576

- DSS => Dedicated Search Space (for only one UE) & CSS => Common Search Space (for several UEs)

2.4 PDSCH:Physical Downlink Shared Channel (物理下行共享信道) - 用于承载DL-SCH信息,传递SIB信息(SIB消息传递方向:BCCH -> DL-SCH -> PDSCH) - SIB1消息的重复周期为80ms,初始位置为subframe#5 of SFN mod 8 = 0,在SFN mod 2 = 0的帧上重复. SIB – System Information Blocks - SIB1: Cell Access Info (PLMN, TAC, CID…); 小区选择相关信息; TDD相关配置信息; 余下SIB的时域调度信息 - SIB2: 公共信道的无线资源配置(PCCH, RACH); freqInfo (ul-carrierFreq, ul-bandwidth); defaultPagingCycle - SIB3: Cell re-selection information. (Intra/Inter frequency or/and Inter-RAT cell re-selection) - SIB4: Neighbor cell related info only for Intra-frequency cell re-selection information. - SIB5: E-UTRAN Inter-frequency cell re-selection information. - SIB6: UTRAN frequencies and neighboring cell re-selection. - SIB7: GERAN frequencies cell re-selection. - SIB8: CDMA2000 frequencies and neighbouring cell re-selection. - SIB9: Home eNB. - SIB10: ETWS primary notification. - SIB11: ETWS secondary notification.

- 如果UE专用参考信号不被传输,使用天线端口集合P = ?0? , ?0,1? , or ?0,1,2,3? - 如果UE专用参考信号被传输,则使用天线端口 P = 5 2.5 PHICH:Physical HARQ Indicator Channel (物理HARQ指示信道) - 用于承载HARQ的ACK/NACK - 在每个subframe的第1个symbol上进行传递(symbol 0 of each subframe) - 一个PHICH组对应于3个REG,12个RE资源 2.6 PMCH:Physical Multicast Channel (物理多播信道)- 目前不支持,无需掌握 ? 没有对传输分集方案进行标准化 ? 单天线端口传输,使用端口4 ? 在支持PDSCH和PMCH混合传输的载波上,PMCH不能再子帧0和5中传输

下行物理层信号:对应于一系列物理层使用的RE,这些RE不传递任何来自高层信息 注: 物理信号都由ZC序列生成,每一个子载波占用一个ZC序列的符号。 SSS和PSS同步信号内容固定,重复发送,不承载任何上层信息,是UE在进行小区搜索时第一个要找的信息。 UE进行盲检搜索同步信号,目前只支持Normal CP的格式。
2.7 PSS:Primary Synchronization Signal (主同步信号) - 频域上占系统带宽中间的6个RB,即72sc - 在第2个subframe的第3个symbol中进行传递(subframe 1 or 6, symbol 2) - 指示一个物理小区组内的id:Physical-layer id:0, 1, 2 (3个) 2.8 SSS:Secondary Synchronization Signal(辅同步信号) - 频域上占系统带宽中间的6个RB,即72sc - 在第1个subframe的最后1个symbol中进行传递(subframe 0 or 5, symbol 6)在subframe 0和5中的SSS结构相 同,但是在频域上错开,以区别前5ms或后5ms的半帧。 - 指示物理小区组号:Physical-layer cell-id group:0~167(168个) - Total cell IDs: 168 x 3 = 504 cell IDs. (0~503) 2.9 RS:Reference Signal (参考信号)(every slot, symbol 0&4) - 用于下行信道估计,信道质量测量以及相关解调,对UE来说是已知信号(RS信号与小区physical id有关,这个在 小区搜索过程中的同步信号中获得) - 频域上:每6个子载波分配一个RS - 时域上:每个slot的symbol 0&4 用来传递RS,symbol 0和4之间有3个SC的间差,用于时频域分集。

多天线传输情况下,天线端口集合与参考信号配置之间的关系:

- Cell-specific RS, non-MBSFN transmission => P = ?0? , ?0,1? , or ?0,1,2,3? - MBSFN RS, associated with MBSFN transmission => P = 4 - UE-specific RS. => P = 5 (用于BF技术) 3. 上行物理信道及物理信号的功能和占用时频码域位置(UL:PUSCH/PUCCH/PRACH/SRS/DMRS)

3.1 PUSCH:Physical Uplink Shared Channel (物理上行共享信道) - Carries the user data from UL-SCH. - Carries L1/L2 control information:ACK/NACK, CQI, PMI, RI (Rank Indicator) 3.2 PUCCH:Physical Uplink Control Channel (物理上行控制信道) - PUCCH承载上行控制信息(UCI),不与PUSCH同时传输,处于上行带宽的边缘,在TDD中不在UpPTS域上传输 - UCI信息包括以下4部分: o Scheduling Request (SR). CQI and Scheduling Requests are provided to Layer 2. o HARQ ACK/NACK for DL transmission; o CQI reports. o PMI reports. - PUCCH具有6种格式,1系列承载SR和ACK/NACK信息,2系列承载CQI/PMI信息,如下图所示:
PUCCH format 1 1a 1b 2 2a 2b Modulation scheme N/A BPSK QPSK QPSK QPSK+BPSK QPSK+QPSK Number of bits per subframe, M bit N/A 1 2 20 21 22 Type of information

Scheduling Request (SR) ACK/ NACK ACK/ NACK CQI/PMI/RI CQI/PMI + 1 bit ACK/ NACK CQI/PMI + 2 bits ACK/ NACK

3.3 PRACH:Physical Random Access Channel (物理随机接入信道) - Carries the random access preamble. PRACH Preamble: - 频域:6 RB x 180kHz = 1.08 MHz

- 时域:1ms / 2ms / 2 symbols(UpPTS) - 随机接入前导由具有零相关区的ZC(Zadoff-Chu)序列产生,有一个或多个根ZC序列产生。每个小区中包含64个 可用的前导。 - PRACH共有5种结构(0~4),目前支持Format 0, 1 & 4:

RACH: - FDD需要额外配置一个GP(Guard Period)以适应RTD(Round Trip Delay),在TDD的特殊帧中已包含这个GP - FDD在一个子帧中只能分配一个RACH资源,而TDD可以分配多于一个的随机接入资源 - TDD模式下,在UpPTS中,可以调度Short RACH(S-RACH),与GP结合使用,最多可配置6个RACH。

随机接入过程: - 基于竞争的随机接入过程:如UE初始接入

- 基于非竞争的随机接入过程:如小区切换

上行物理层信号:指物理层使用的但是不承载任何来自高层信息的信号,如参考信号。
3.4 DRS/DMRS:Demodulation Reference Signal (解调用参考信号)

- 与上行数据传输有关,both PUSCH and PUCCH。 - 用于信道评估,对PUSCH和PUCCH信道的连续检测和解调,上行功率控制,时间评估等??? - DRS在时域上的分配: o PUSCH: 每个slot的第4th个symbol(symbol 3 in every slot) o PUCCH: DRS由PUCCH的格式来决定(1/1a/1b 或者 2/2a/2b) - DRS在频域上的分配: o PUSCH: DRS与终端的上行传输具有同样的带宽。 o PUCCH: 如下图所示

3.5 SRS:Sounding Reference Signal (探测用参考信号)=> 与PUSCH和PUCCH无关 - 与上行数据传输无关,可用于评估上行信道质量,实现以下功能: - 初始化MCS(Modulation and Coding Scheme)选择 - 数据传输的功率控制 - TA(Timing Advance) - UL频率的独立调度(Frequency dependent scheduling for the UL) - SRS transmitted in the last SC-FDMA symbol in the configured subframes. - 在TDD模式中,UpPTS也可用作传递SRS。 4. 逻辑信道、传输信道与物理信道的映射关系: 4.1 逻辑信道(7) - BCCH:Broadcast Control Channel(广播控制信道:传输广播系统控制信息的下行信道) - PCCH:Paging Control Channel(寻呼控制信道:传输寻呼信息的下行信道) - CCCH:Common Control Channel(公共控制信道:UE与网络间传输控制信息的双向信道,无RRC连接时使用) - DCCH:Dedicated Control Channel(专用控制信道:传输专用控制信息的点到点双向信道,有RRC连接时使用) - DTCH:Dedicated Traffic Channel(专用业务信道:点到点双向信道,专用于一个UE,用于传输用户信息) - MCCH:Multicast Control Channel(多播控制信道:网络到UE的MBMS调度和控制信息,点到多点下行 信道) - MTCH:Multicast Traffic Channel(多播业务信道:点到多点下行信道) 4.2 传输信道(DL:UL => 4:2) - BCH:Broadcast Channel(广播信道 => PBCH) - PCH:Paging Channel(寻呼信道 => PDSCH) - MCH:Multicast Channel(多播信道 => PMCH) - DL-SCH:Downlink Shared Channel(下行共享信道 => PDSCH) - UL-SCH:Uplink Shared Channel(上行共享信道 => PUSCH) - RACH:Random Access Channel(随机接入信道 => PRACH) 4.3 物理信道(DL:UL => 6:3) - PBCH:Physical Broadcast Channel(物理广播信道)

-

PDSCH:Physical Downlink Shared Channel(物理下行共享信道) PDCCH:Physical Downlink Control Channel(物理下行控制信道) PCFICH:Physical Control Format Indicator Channel(物理控制格式指示信道) PHICH:Physical Hybrid-ARQ Indicator Channel(物理HARQ指示信道) PMCH:Physical Multicast Channel(物理多播信道) PUSCH:Physical Uplink Shared Channel(物理上行共享信道) PUCCH:Physical Uplink Control Channel(物理上行控制信道) PRACH:Physical Random Access Channel(物理随机接入信道)

5. MIMO technology - Two kinds of MIMO techniques for DL transmission: o Transmit diversity – use multiple channels to send the same information stream ? Improve coverage and robustness of data transmission o Spatial multiplexing – use multiple channels to send multiple information streams ? Increase throughput ? SU-MIMO/ MU-MIMO - MIMO techniques according to the number of Antennas: ? SISO ? MISO ? SIMO ? MIMO - MIMO techniques for UL transmission => MU-MIMO

Transmission Mode 与 DCI format之间的关系(传输模式信息在RRCConnectionReconfiguration 过程中指示): Transmission mode: DCI Format: TM1 Single-antenna port; port 0 1, 1A 单天线端口传输 TM2 Transmit diversity 1, 1A 传输分集 TM3 Open-loop spatial multiplexing 2A 开环 MIMO(Large delay CDD) TM4 Closed-loop spatial multiplexing 2 闭环 MIMO(PMI 反馈) TM5 Multi-user MIMO 1D TM6 Closed-loop Rank=1 precoding 1B TM7 Single-antenna port; port 5 1, 1A UE-specific RS,用于 beamforming Transmission Number of Antenna Rank Layer Codeword Mode ports TM1 (单天线) TM2 (传输分集) 1 1 1 2 TM3 & TM4 (空分复用) 2 3 4 1 2 4 2 2 3 4 1 1 1 2 2 2 2 1 2 4 2 4 4 4

6. PDSCH下行资源分配方式(Type0/1/2); Type 0: PDCCH DCI formats 1, 2 and 2A RBs are grouped to RBG. RBGs are selected. System Bandwidth RBG Size (P) (Number of DL RBs) 1 ≤10 11 -– 26 2 27 – 6463 (e.g.: 10MHz - 50 RBs) 3 64 – 110 (e.g.: 20MHz - 100 RBs) 4 Type 1: PDCCH DCI formats 1, 2 and 2A RBs are grouped to RBG subset. First select one RBG subset, then select the RBs in the RBG subset. RBG subset的值(P)与Type0中RBG的定义一致。 RBG subsets:Log2(P) RB assignment:

Type 2: PDCCH with DCI format 1A, 1B, 1C and 1D Start RB and width is assigned. 7. DCI Format DCI: Downlink Control Information (ref. 36.212) => Carriered by PDCCH 一个DCI传递上下行调度信息,或者针对一个RNTI的上行功率控制命令

DCI Format DCI 0 DCI 1 DCI 1A DCI 1C DCI 2

Use scope For the scheduling of PUSCH (For Uplink only) For the scheduling of one PDSCH codeword, TM1, 2 and 7 (Type0, 1) For the compact scheduling of one PDSCH codeword and random access procedure initiated by a PDCCH order, TM1~7 (Type 2) For very compact scheduling of one PDSCH codeword (Type 2) For MIMO (e.g.: CL MIMO), TM4 (Type0, 1) For the scheduling of one/two PDSCH codeword TPC command for PUCCH For MIMO (e.g.: OL MIMO), TM3 (Type0, 1) For the scheduling of one/two PDSCH codeword TPC command for PUCCH

DCI 2A

? ?

Format 0: 用于上行传输,PUSCH的调度 Flag for format0/format1A differentiation - 1 bit, 0=>format 0 and 1=>format 1A Resource block assignment and hoping resource allocation Modulation and coding scheme HARQ information and redundancy version TPC command for scheduled PUSCH – 2 bits CQI request – 1bit

Format 1:用于传输分集,单码字PDSCH的调度 (Used for the scheduling of single codeword PDSCH) (TM1, 2, and 7-not support) - Resource allocation type, e.g.: type 0 / type 1 – 1bit - Resource block assignment - Modulation and coding scheme – 5 bits - HARQ process number – 4 bits - TPC command for PUCCH – 2 bits Format 1A: 用于下行传输,单码字PDSCH调度,下行数据触发随机接入过程,适用所有TM传输模式。=> Compact scheduling of one PDSCH codeword and random access procedure initiated by a PDCCH order (为UE分配一个非竞争随机接入的特定preamble). - Flag for format0/format1A differentiation - 1 bit, 0=>format 0 and 1=>format 1A - Resource block assignment - Modulation and coding scheme – 5 bits - HARQ information – 4 bits - TPC command for PUCCH – 2 bits Format 1B: Compact scheduling of one PDSCH codeword with precoding information. Closed loop precoding with rank-1 transmission. (TM6, 目前不支持,不需要掌握) Format 1C: Very compact scheduling of single codeword PDSCH. (Paging, SIB, 系统广播信息 ? ) Resource block assignment Modulation and coding scheme Redundancy version Format 1D: Compact scheduling of one PDSCH codeword with precoding and power offset information. (using Multi-user MIMO, TM5,目前不支持) Format 2: For MIMO (Closed-Loop),两码字,下行PDSCH调度 (闭环模式,TM4,需要上报PMI信息) Format 2A: For MIMO (Open-Loop),两码字,下行PDSCH调度(开环模式,TM3)

?

? ? ? ? ?

?

Format 3/3A: Transmission of TPC commands for PUCCH and PUSCH with 2-bit or 1-bit power adjustments

8. LTE相关接口的控制面和用户面协议栈 Radio interface User Plane:

Control Plane:
UE NAS eNB MME NAS RRC PDCP RLC MAC PHY

UE PDCP RLC MAC PHY

eNB PDCP RLC MAC PHY

RRC PDCP RLC MAC PHY

PHY: L1 协议, ? Data Transfer via Transport Channels. ? Error Detection. Hybrid ARQ Combining. ? Channel Coding and Rate Matching. ? Modulation and Demodulation. ? Measurements. ? MIMO(多进多出), Transmit Diversity(发送分集), Beamforming(波速成型). ? RF Processing. MAC: L2 协议,主要实现与调度和 HARQ 相关的功能 ? Data Transfer via Logical Channels. ? 逻辑信道和传输信道之间的映射 ? UE 之间以及一个 UE 在不同逻辑信道之间的资源分配和调度 ? 传输格式选择 ? HARQ 纠错功能 RLC: L2 协议,主要实现与 ARQ 相关的功能,保证数据传输的可靠性 ? 上层 PDU 数据传输: TM(透明模式), UM(非确认模式), AM(确认模式)数据传输 ? ARQ 纠错功能(CRC 检验由物理层完成) ? 串联,分段及重分段功能 ? 顺序传送上层数据以及重复检测功能 PDCP: L2 协议,提供 ROHC 可靠头压缩功能,以及加密和完整性保护功能 RRC: L3 协议,提供广播、寻呼、RRC 连接管理、无线承载控制、移动性、UE 测量上报和控制功能等功能 NAS: 非接入层控制协议,主要实现以下功能: ? SAE 承载管理 ? 鉴权 ? LTE-IDLE 状态下的移动性管理

? ?

产生 LTE_IDLE 状态下的寻呼消息 安全控制

S1 interfaces User Plane (eNB-S-GW):

Control Plane (eNB-MME):

User plane PDUs
S1-AP

GTP-U UDP IP Data link layer Physical layer
X2 interfaces User Plane (eNB-eNB):

SCTP IP Data link layer Physical layer

Control Plane:

User plane PDUs
X2-AP

GTP-U UDP IP Data link layer Physical layer
9. 9.1 9.2 9.3

SCTP IP Data link layer Physical layer

LTE相关流程 Call Setup 呼叫流程 Cell Selection 小区搜索过程 Random Access 随机接入过程 - Initial access from RRC_IDLE; - RRC Connection Re-establishment procedure; - Handover; - DL data arrival during RRC_CONNECTED requiring random access procedure; - E.g. when UL synchronisation status is “non-synchronised”; - UL data arrival during RRC_CONNECTED requiring random access procedure; - E.g. when UL synchronisation status is "non-synchronised" or there are no PUCCH resources for SR available.

Contention based (applicable to all five events):
UE eNB

Non-contention based (Handover & DL data arrival):

1

Random Access Preamble

UE

eNB

Random Access Response

2

0

RA Preamble assignment

3

Scheduled Transmission

Random Access Preamble

1

Contention Resolution

4

2

Random Access Response

9.4 RRC connection establish procedure RRC连接建立过程 - SRB: Signalling Radio Bearer (Transmission of RRC&NAS messages.) o SRB0: for RRC msg, using CCCH o SRB1: for RRC & NAS (before SRB2 established) msg, using DCCH. o SRB2: for NAS msg, using DCCH. Configured after security activation together with DRB. - DRB: Data Radio Bearer (Transmission of user data)

RRC Connection Setup (SRB0,1) & reconfiguration (SRB2, DRB) UE eNB MME

UL-SCH RLC TM SRB0 RRC-ConnectionRequest DL-SCH RLC TM SRB0 RRC-ConnectionSetup

UL-SCH RLC AM SRB1 RRCConnectionSetupComplete NAS(EMM Attach Request (ESM PDN CONNECTIVITYREQUEST)) S1AP: INITIAL UE MESSAGE NAS (EMM Attach Request (ESM)) 1.0 Autentication and 2.0 Security Mode Procedures S1AP: INITIAL CONTEXT SETUP REQUEST NAS (EMM Attach Accept (ESM)) DL-SCH RLC AM SRB1 RRC-ConnectionReconfiguration NAS (EMM Attach Accept (ESM ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST)) UL-SCH RLC AM SRB1 RRC-ConnectionReconfigurationComplete S1AP: INITIAL CONTEXT SETUP RESPONSE UL-SCH RLC AM SRB2 RRC UplinkInformationTransfer NAS (EMM Attach Complete (ESM ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT)) S1AP: UPLINK NAS TRANSPORT NAS (EMM Attach Complete (ESM)) IP uplink and downlink traffic
Only for internal usage 8 ? Nokia Siemens Networks WBTS Architecture / 9/14/2010

9.5 ATTACH过程 9.6 Handover 切换过程 (6 types) - Handover types: o Intra-eNB handover (via X2 interface) o Inter-eNB handover (shall be via X2 interface, except some special conditions) o Inter-RAT handover (via S1 interface) o Inter-frequency handover (applicable to above 3 types) o Intra-frequency handover (applicable to above 3 types)

二、软件框架
1. 掌握BTS包含哪些模块及其功能: BTSOM/RROM/ENBC/CELLC/UEC/TUPC/TUPU/MAC/PHY/RFSW/TRSW;

Flexi BTS – SW Architecture
RAT specific Application CP and UP SW

Shown in next slide

WCDMA SW

LTE SW

GSM SW
I-HSPA ADA SW

BTS Common Application SW

Common Application SW

BTS Common SW

3rd party HW
SW

TRSW

DFT

BTSOM

UM

BTS Common Platform SW

BTS Site Mgr

GPS Receiver ALD

RFSW

Common Platform Services SW

SW

CC&S OS

HWAPI

DSP HWAPI

3rd party SW RF HW
FR/AAS Module HW

PC/ Workstation For internal use only
13 ? Nokia Siemens Networks
Primary colours: R 255 G 211 B8 R 255 G 175 B0 R 127 G 16 B 162

Flexi BTS System Module HW
LTE eNB SW Architecture / 2009.02.20
Supporting colours: R 255 G 255 B 255 R0 G0 B0 R 137 G 146 B 155 R 163 G 166 B 173 R 175 G0 B 51 R 52 G 195 B 51

1.1. BTS Common Software: ? BTS Site Manager: ? TRSW:传输模块 ? RFSW:射频模块 Platform Service SW: ? CC&S:Common Computer & Support SW ? HWAPI:Hardware Application Programming Interface (MCU environments) ? DSP HWAPI:(DSP environments) o SW download for Faraday-chip, startup of Faraday-chip, configures and synchronizes BB bus, maps local cells to antennas and provides monitor & test & debug services Common Application SW: ? BTSOM:BTS level Operation & Maintenance ? DFT:Design For Testability ? UM:Unit Management o UM is runtime SW entity that represents a HW resource (module or unit) o Unit specific O&M functions and agents o Unit level initialization and recovery o Unit level HW and SW management o Unit level fault management 1.2. LTE Specific SW: ? LTE RROM:LTE Radio Resource Operation and Maintenance o 为 Local Cell 分配基带资源(local cell 与 global cell 之间有映射关系); o 小区状态控制和配置处理,如:公共(common)和共享(shared)信道配置等; o 为 eNB 内部硬件分配逻辑资源 o BTS O&M 网络配置代理,如:通过 O&M 配置数据获得真实的 C/U 面配置参数 o 提供与其他 SC 之间的通信通道,只有 RROM 知道所有 SC 的内部地址 o Configure signalling associations on S1 and X2 interface, and link failure handling o 通过 PhyTest 和 MacTest 控制 3GPP Test Models. o RromMgmt & RromTest (BTSOM) ? LTE ENBC:LTE eNB Controller(Control function and RRM for BTS level) o X2 和 S1 通用信令的主要接入点,寻呼请求的分发 o S1 / X2 Reset 分布和协调,控制 S1/X2 建立过程 o X2 ICIC protocol handling o MME selection function o Load control & Congestion Control (BTS level, e.g. X2 / S1 interfaces) o 小区切换消息的转发(inter&intra eNB HO),源 eNB 到目标 eNB 或者源 UEC 到目标 UEC. => EnbcSgnl (LTE UEC) o Handling of Network and Cell Configuration, and link state changes => EnbcCrtl (LTE RROM) o C-plane control of data path failure/recovery cases, e.g.: TEID for failed user data path, UE ID for MMEs under of S1 reset. => EnbcIdMgmt (LTE UEC)

?

LTE CELLC:LTE Cell Controller (Control function and RRM for CELL level) o Cell 级别的寻呼调度 (requires AaLteTime service from CC&S on MCU) => CellcPaging (LTE ENBC) o 系统信息广播,寻呼以及系统信息的 RRC 协议处理 o CQI configuration parameter calculation => CellcCrtl (LTE RROM) o 小区测量控制,Configuration and evaluation of Cell Measurements o Admission Control(准入控制)and Congestion Control(拥塞控制) => CellcRrm (LTE UEC) LTE UEC:LTE User Equipment Controller (UE related control functions and RRM algorithms) o Dedicated procedures on S1/X2/RRC interfaces => UecSgnl (LTE ENBC) o UE State and Bearer management o 切换处理以及 UE 相关的 S1、X2 和小区重置过程 => UecHoSgnl (LTE UEC) o 执行约束控制(overload protection) o 完整性保护和加密配置 o Configuration of lower layers for all dedicated procedures (MAC, TUP, PDCP, etc.) => UecCtrl (LTE RROM) o Handling eNB internal dedicated UE measurements o UE failure handling (e.g. errors reported from lower layers) o Gap Assistance LTE TUPc o o LTE TUPu o o

?

? ?

Message routing for BTS external control plane interfaces => TupSgnlNw (LTE ENBC, LTE UEC) 主要处理 SCTP 传输控制 => TupLink (LTE RROM, LTE ENBC, LTE UEC) User plane protocols of X2 and S1(GTP-U) PDCP protocol

?

LTE MAC:L2 air interface protocols o Packet Scheduling (调度功能) o RLC and MAC protocols o Adaptive modulation and coding (自适应编码调制技术) o Provisioning of required PM and FM data via LOM LTE PHY:Baseband L1 (PHY) processing o DL transport channel processing: error protection (CRC), channel encoding, rate matching, channel interleaving. o DL physical channel processing: synchronization and pilot signal generation, scrambling, modulation, spatial processing (diversity, beamforming, MIMO), sub-frame mapping (multiplexing), OFDM symbol generation. o UL physical channel processing: channelization, channel estimation, noise variance, SNR, received signal power, frequency error and timing delay estimation, equalization, frequency error correction, demultiplexing, demodulation, descrambling. PRACH preamble detection and timing delay estimation. UL channel quality estimation for scheduling purposes. Advanced receiver functionality (IRC, iterative equalizer and MIMO equalizer) implementation (TBD). o UL transport channel processing : channel deinterleaving, rate dematching, HARQ combining, decoding, error detection (CRC). o Physical layer measurements. o OBSAI RP3 termination (UL) / generation (DL). o Support of PhyTest interface for control of proprietary testmodels by external test tool o Support of 3GPP compliant testmodels from INC 17 onwards (DL controled via direct interface, UL 3GPP testmodel handled by LTE MAC). o Provisioning of required PM and FM data via LOM

?

2. BTS硬件架构,掌握FCMD、FSPC的对应模块及功能部署;

System module: o FSME => 主流系统模块(Version: A101,M12,M14,A103), 可支持 3xFSPC ? FTXX: 传输板(Transmission), 类型有 FTLB, FTIB, etc. ? FCMD: 主控板(Configuration Management block), 包含 Crtl MCU&Clk gen, MUKSU, External IF Block, RF Mod. IF, etc. 2) FSPC: 基带板(Signal Process block), 一块 FSPC 包含 7 个 Faraday. (Faraday 法拉第:一块 FSPC 上有 7 个 法拉第,每个法拉第包含 3 个 CPU Core,所以 1 个 FSPC 包含 3x7=21 个 CPU Core,可以配置不同的 deployment,处理 DSP 以及其他 U 面的数据,承载 U 面相关的软件。FSPC 集成在 System Module(FSME) 上面,一个 system module 最多可配置 3 块 FSPC)
System Module FTXX ? Deployable Unit? TRSW ? Deployable Unit? SMA (BTSOM)

FCMD Control MCU ? Deployable Unit? LTE RROM ? Deployable Unit? LTE ENBC ? Deployable Unit? BTSOM ? Deployable Unit? UM(FCM) ? Deployable Unit? LTE TUPC ? Deployable Unit? LOM ? Deployable Unit? HWAPI ? Deployable Unit? DFT ? Deployable Unit? CC&S

FSPC BB MCU ? Deployable Unit? LTE UEC ? Deployable Unit? LTE CELLC ? Deployable Unit? LOM ? Deployable Unit? UM(FSP) ? Deployable Unit? HWAPI ? Deployable Unit? CC&S

Faraday #x CPUy ? Deployable Unit? LOM ? Deployable Unit? CC&S ? Deployable Unit? DSP HWAPI

Note: Each Faraday CPU have LOM, CC&S and DSP HWAPI, see separate pictures further down in this chapter (9.2.2/9.2.3/…) for user-plane application deployment

RF Module(s) ? Deployable Unit? RFSW

o o

FSMD => 支持 2xFSPC FSMC => 不支持

Transport (Sub) module: 集成在 FSME 上面 o FTIB => 2*GE + 4*E1/T1/JT1, 160 Mbit/s with IPSec o FTLB => 3*GE + 4*E1/T1/JT1, 2Gbit/s with IPSec. o FTJA => 2 x FE, 1 x GE, 4 x E1 coaxial o FTHA => 16 x E1/T1/JT1 RF module: RRH o FYRN => Version: X.26 o FYTB ? o FYMB ? o FRGH? 3. 了解BTSOM模式与OMStub模式软件启动过程。

三、操作维护
1. 掌握LTE系统环境搭建(UE--ENB--EPC) 2. 掌握基本工具使用:TM500/Peagsus/AHTI/BTSLog/BTSiteManager/FTP 3. 能够调试峰值速率

四、其他 LTE diary
1. LTE interfaces:
UTRAN SGSN GERAN S3 S1-MME S6a MME S11 LTE-Uu UE E-UTRAN S1-U S10 S12 S4 Serving Gateway S5 Gx PDN Gateway SGi PCRF Rx Operator's IP Services (e.g. IMS, PSS etc.) HSS

S1-MME: Reference point for the control plane protocol between E-UTRAN and MME. S1-U: Reference point between E-UTRAN and Serving GW for the per bearer user plane tunnelling and inter eNodeB path switching during handover. S3: It enables user and bearer information exchange for inter 3GPP access network mobility in idle and/or active state. S4: It provides related control and mobility support between GPRS Core and the 3GPP Anchor function of Serving GW. In addition, if Direct Tunnel is not established, it provides the user plane tunnelling. S5: It provides user plane tunnelling and tunnel management between Serving GW and PDN GW. It is used for Serving GW relocation due to UE mobility and if the Serving GW needs to connect to a non-collocated PDN GW for the required PDN connectivity. S6a: It enables transfer of subscription and authentication data for authenticating/authorizing user access to the evolved system (AAA interface) between MME and HSS. Gx: It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN GW. S8: Inter-PLMN reference point providing user and control plane between the Serving GW in the VPLMN and the PDN GW in the HPLMN. S8 is the inter PLMN variant of S5. S9: It provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function. S10: Reference point between MMEs for MME relocation and MME to MME information transfer.

S11: Reference point between MME and Serving GW. S12: Reference point between UTRAN and Serving GW for user plane tunnelling when Direct Tunnel is established. It is based on the Iu-u/Gn-u reference point using the GTP-U protocol as defined between SGSN and UTRAN or respectively between SGSN and GGSN. Usage of S12 is an operator configuration option. S13: It enables UE identity check procedure between MME and EIR. SGi: It is the reference point between the PDN GW and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses. Rx: The Rx reference point resides between the AF and the PCRF in the TS 23.203 [6]. SBc: Reference point between CBC and MME for warning message delivery and control functions. 2. The E-UTRAN architecture:

MME / S-GW

MME / S-GW

X2
eNB eNB

S1

eNB

3. Functional Split between E-UTRAN and EPC:

X2

S1
S1
X2

S1
E-UTRAN

eNB Inter Cell RRM RB Control Connection Mobility Cont. MME Radio Admission Control NAS Security eNB Measurement Configuration & Provision Dynamic Resource Allocation (Scheduler) RRC PDCP S-GW RLC MAC S1 PHY Packet Filtering internet E-UTRAN EPC Mobility Anchoring UE IP address allocation P-GW Idle State Mobility Handling EPS Bearer Control

4. Layer 2 structure:
Radio Bearers ROHC PDCP Security Security Security Security ROHC ROHC ROHC

RLC

Segm. ARQ etc

...

Segm. ARQ etc Logical Channels

Segm. ARQ etc

...

Segm. ARQ etc

CCCH BCCH

PCCH

Scheduling / Priority Handling

MAC

Multiplexing UE1

Multiplexing UEn

HARQ Transport Channels

HARQ

5. OBSAI 架构 OBSAI 是开放式基站架构联盟,旨在规定基站内部不同功能之间的接口,保证彼此互相连通。 一个基站系统一般包括以下四个模块: ? Radio Frequency(RF)射频模块;

? BaseBand 基带模块; ? Control 控制模块; ? Transport 传输模块。 OBSAI 旨在为自由市场上的这些 BTS 模块之间定义开放的标准接口,称之为 Reference Points (RP): ? RP1: 控制模块与其他 3 个模块之间通信的接口 ? RP2: 传输模块和基带模块之间的接口 ? RP3: 基带模块与射频模块之间的接口 ? RP3-01: RP3 的一个扩展接口,用于定义与远程 RF 模块(remote RF head)之间的通信

OBSAI Reference Architecture (Standard)
RP3 RP3-01
Local Converter Remote RF Block

Air Interface

RP2
External Network Interface
Transport Block Base Band Block RF Block

Air Interface

RP5
Integrated Network Module General Purpose Module

RP1
Power Control and Clock Block Control Traffic Clock Power Information

RP4

Confidential 10 ? Nokia Siemens Networks

TDLTE Kickoff / Christian Mahr / 21.10.2008

6. OFDMA / SC-FDMA 无线传输技术 => OFDMA - Orthogonal Frequency Division Multiple Access Benefits: - Good performance in frequency selective fading channels - Low complexity of base-band receivers - Good spectral properties and handling of multiple bandwidths - Link adaptation and frequency domain scheduling - Compatibility with advanced receiver and antenna technologies Challenges: - Tolerance to frequency offset - The high Peak-to-Average Power Ratio (PAPR) of the transmitter single. It requires transmitter with linear response in a large range. Those “high linear response” amplifiers have low power conversion efficiency and therefore they are not ideal for Mobile Stations. In LTE the problem was solved by adopting the SCFDMA for uplink, which has better power amplifier efficiency. => SC-FDMA – Single Carrier Frequency Division Multiple Access

-

Reduce the PAPR (Peak to Average Power Ratio) for low RF hardware requirements. (6..9 dB reduced compared to OFDMA) User Multiplexing in frequency domain (in OFDMA, is in sub-carriers domain) One user always continuous in frequency Uplink bandwidths: 180KHz (12 sub-carriers) ~ 20MHz

OFDMA 和 SCFDMA 的区别: - OFDMA transmits data in parallel across multiple carriers - SCFDMA transmits data in series employing multiple carriers 7. LTE Modulation Schemes: - Quadrature Phase Shift Keying, QPSK => control channel mainly use QPSK. - 16 Quadrature Amplitude Modulation, 16QAM - 64QAM (optional for UL in UE) 8. LTE DL/UL Peak Bit Rate: - DL: 172 Mbps => 20MHz, 2x2 MIMO, 64QAM - UL: 57 Mbps => 20MHz, 16QAM, 1*RB for PUCCH 9. UE Categories:

注:目前支持到 UE 类型 4,手机最大发射功率为 23dBm,手机上行发射只支持 1 路发射。 10. 下行物理信道处理过程: 11. RRC 状态 - RRC_CONNECTED: Network controlled mobility - RRC_IDLE: UE controlled mobility 12. 物理测量参数以及其他(RSSI/RSRP/RSRQ/SIR/SNR/BLER…) - RSSI: Received Signal Strength Indicator(接受的信号强度指示)

o 指接收信号总功率,单位dBm:包括有用信号,临区干扰,临频干扰,噪声功率等 - RSRP: Reference Signal Received Power(参考信号接收功率) o 参考信号接收功率,单位dBm。指同一时刻接收到参考信号的平均值,值越大越好 o -70dBm以内处于近点,信号好 o -70dBm ~ -100dB处于中点,信号一般 o -100dBm及以上,处于远点,接近小区边缘,信号差 - RSRQ: Reference Signal Received Quality(参考信号接收质量) o RSRQ = N*RSRP/RSSI,N指系统带宽对应的RB数目,单位为dB。 - SIR: Signal-to-Interference Ratio (信号干扰比) o 单位dB,值越大越好,说明信号越好 o 10dB及以内处于远点,离基站远,信号差 o 10dB~20dB,处于中点,在小区中间信号一般 o 30dB及以上,处于近点,离基站近,信号好,测试的理想值 - SINR: Signal-to-Interference plus Noise Ratio (信号与干扰加噪声比) o 指接收到的有用信号的强度与接收到的干扰信号(噪声与干扰)的强度 - SNR: Signal Noise Ratio (信噪比) o 单位为dB,信噪比越高表示信号越好 - BLER: Block Error Ratio(误块率) o 误块率(BLER)是传输块经过CRC校验后的错误概率,有差错的块与数字电路接收的总块数之比。 o BLER有上行和下行之分,可以从一些设备的计数器统计指标中通过公式计算得到。 o BLER是在信道解交错和解码后,由评价各传输块上的循环冗余检验(CRC)度量。BLER是在CRC之后测量,

每发生一个需要丢掉的误码块就记一个错误,因此BLER不但测量信道解码后的数据块的错误,而且还检查 CRC的错误。
13. dB 与 dBm 的区别

dB 表示一个相对值,表示两个量的比值大小,是功率增益的单位。计算公式为:dB = 10*lg(A/B)。 计算 A 的功率相比于 B 大或小多少个 dB 时,按公式 10 lg A/B 计算。 dB 和 dB 之间只有加减,用一个 dBm 减另外一个 dBm 时,得到的结果是 dB。如:30dBm - 0dBm = 30dB。 dBm 减 dBm 实际上是两个功率相除,信号功率和噪声功率相除就是信噪比(SNR)。 dBm 定义的是 毫瓦(miliwatt): 0 dBm=10lg1mw; dBm 是一个表示功率绝对值的单位,计算公式为:10lg(功率值/1mW)。例如:如果发射功率为 1mW,按 dBm 单位进行折算后的值应为:10 lg 1mW/1mW = 0dBm;对于 40W 的功率,则 10 lg(40W/1mW)=46dBm。 dBw 定义 瓦特(watt):0 dBw = 10lg1 W = 10lg1000 mw = 30 dBm。 30dBm=1w, 每减 3dB,等于功率减半(1/2),每增加 3dB,等于功率下大一倍(x2)。例如:A 功率比 B 功率大一 倍,那么 10 lg A/B = 10 lg 2 = 3dB。
14. MCS & TBS (ref. 36.213)

MCS: Modulation and Coding Scheme. TBS: Transport Block Size(s) => (TBS table dimension: 27 x 110)

PUSCH => Uplink
MCS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
For internal use only 2 ? Nokia Siemens Networks Presentation / Author / Date

PDSCH => Downlink
TBS 0 1 2 3 4 5 6 7 8 9 10 10 11 12 13 14 15 16 17 18 19 19 20 21 22 23 24 25 26 MCS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 reserved 30 31 Modulation 2 2 2 2 2 2 2 2 2 2 4 4 4 4 4 4 4 6 6 6 6 6 6 6 6 6 6 6 6 2 4 6 reserved TBS 0 1 2 3 4 5 6 7 8 9 9 10 11 12 13 14 15 15 16 17 18 19 20 21 22 23 24 25 26 2 2 2 2 2 2 2 2 2 2 2 4 4 4 4 4 4 4 4 4 4 6 6 6 6 6 6 6 6

Modulation

Primary colours: R 255 G 211 B8 R 255 G 175 B0 R 127 G 16 B 162

Supporting colours: R 255 G 255 B 255 R0 G0 B0 R 137 G 146 B 155 R 163 G 166 B 173 R 175 G0 B 51 R 52 G 195 B 51

15. ACK/NACK mode

ACK/NACK Bundling ACK/NACK Multiplexing
16. CP(Cyclic Prefix)


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