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WCDMA Design using Simulink

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1 WCDMA Design using Simulink
You should here music now. If you do not, check that your PC speakers are on and you can play sounds on your computer. © 2002 The MathWorks, Inc. Alex Rodriguez The MathWorks, Inc. May 30th, 2002

2 Agenda About WCDMA WCDMA Simulink Model Enhancements Radiolab 3G
About the models Physical Layer Mask parameters Coding and Multiplexing Modulation and Spreading RAKE Receiver Channel Models Visualizing the results Enhancements Radiolab 3G

3 About WCDMA … WCDMA stands for Wideband Code Division Multiple Access.
WCDMA is one of the five air-interfaces adopted by the ITU under the name "IMT-2000 Direct Spread”. WCDMA can support multiple and simultaneous communications such as voice, images, data, and video. Very high and variable bit rates: 144 kbps: vehicle speed, rural environ. 384 kbps: walking speed, urban outdoor. 2048 kbps: fixed, indoor. Different QoS for different connections. High spectrum efficient. Coexistence with current systems. WCDMA is being specified by the 3GPP (Third Generation Partnership Project). ITU-R (International Telecommunications Union Radio) Study Group 8

4 About WCDMA and the 3G Standardization Process
References: ITU (International Telecommunication Union) 3GPP (3 Generation Partnership Project) UWCC (Universal Wireless Communications Consortium) UMTS Forum: GSM World : CDMA Development Group ITU-R (International Telecommunications Union Radio) Study Group 8

5 About the models WCDMA has two basic modes of operation:
TDD (Time Division Duplex). Low Chip Rate TDD (TD-SCDMA) FDD (Frequency Division Duplex). Duplex communications: Downlink Channel From Node B (Base Station) to UE (User Equipment). Uplink Channel From UE to Node B Model simulates transmission of information data (DCH – Dedicated Channel) during a connection.

6 About the models R12.1 !! For NT, Linux and Unix w/o accelerator
WCDMA Library WCDMA Multiplexing and Coding WCDMA Spreading and Modulation WCDMA Physical Layer To open the models, type wcdmademos

7 Physical Layer Specifications
Physical layer provides data transport support to higher layers via Transport Channels. Functions of the Physical Layer: Error detection. FEC encoding/decoding. Rate Matching/Dematching. Multiplexing/Demultiplexing different Transport Channels into/from a Coded Composite Transport Channel (CCTrCH). Mapping/Demapping of CCTrCH into/from Physical Channels. Modulation and Spreading/Demodulation and Despreading. Power Weighting and combining of physical channels. RF Processing.

8 WCDMA Physical Layer Transmitter
DL Scrambling Code - Channelization Code - Transmit Diversity Slot Format - Power Settings - Transport Block Set Size - Transport Block Size - Transmission Time Interval - Size of CRC - Type of Error Correction - Coding Rate - Rate Matching Attribute Transport Format Transport Channels Channel Coding and Multiplexing Slot DPCH Physical Channel Mapping Spreading And Modulation DPCH CCTrCh Pilot Bits TPC TFCI Control Channels Interference (OCNS) Orthogonal Codes Layer 2 MAC Layer 1 Channel

9 WCDMA Physical Layer Model

10 Initial Settings Mask – Layer 2
Multiplexing and Coding Spreading and Modulation Variables are stored in the workspace. To view them, type who or whos

11 Coding and Multiplexing Specifications
Physical layer provides data transport support to higher layers via Transport Channels. There is a Transport Format associated to each Transport Channel that describes the processing (CRC size, encoding scheme, coding rate, …) to be applied by the Physical Layer. Every transport block is generated every 10, 20, 40 or 80 ms (Time Transmission Interval – TTI).

12 Coding and Multiplexing Overview
Layer 1 Radio Frame Segment Concat/ Segment Channel Encoder Rate Matching 1st Interleaver CRC CCTrCH Accommodates data rates to a fixed channel bit rate Attaches CRC Size={0,8,12,16,24} Limits Max Size of Codewords Interleaves bits within each Transport Channel Coding Schemes: No coding Convolutional Coding Turbocoding Multiplexes bits from different Transport Channels every 10 ms. Radio Frame Segment Channel Encoder Rate Matching 1st Interleaver Concat/ Segment CRC Transmission Time Interval {10,20,40 and 80ms} Radio Frame {10ms}

13 Coding and Multiplexing Model
Transport Channels Concatenation and Segmentation Channel Encoder Rate Matching First Interleaver CCTrCh CRC Transmission Time Interval {10,20,40 and 80ms} Radio Frame {10ms} Layer 2 Layer 1

14 Physical Channel Mapping Overview
Transport Format Combination Index contains information of how the different transport channel have been processed Interleaves bits within a Radio Frame coming from different Transport Channels Data is sent to the Modulation and Spreading block Slot Builder TFCI CCTrCh DPCH DPCH 2nd Interleaver DPCH Physical Channel Segmentation One CCTrCH can be mapped onto one or several PhCHs Power Control Bits Pilot Bits Structure of slot is defined by the Higher Layers via Slot Format Data 1 TPC TFCI Data 2 Pilot

15 Physical Channel Mapping Model
Slot Builder Physical channel segmentation 2nd Interleaver Radio Frame {10ms} Slot {10/15 ms}

16 References 3GPP TS 25.302 – “Services provided by the Physical Layer”.
3GPP TS – “Physical channels and mapping of transport channels onto Physical Channels (FDD)”. 3GPP TS – “Multiplexing and channel coding”. 3GPP TS – “Channel coding and multiplexing examples”.

17 Modulation and Spreading Specifications
QPSK. Same gain for I and Q components. Spreading or Channelization Operation: Transforms every bit into a given number of chips, hence increasing the bandwidth. Chip Rate = 3.84 Mcps. By using an orthogonal code for each physical channel, receiver can separate them. Orthogonal codes are real-valued OVSF codes (Orthogonal Variable Spreading Factor) of different length. Scrambling: Separates different Base Stations. Complex-valued Gold Code Sequences.

18 Modulation and Spreading Specifications
Power weighting: Different power is applied to each physical channel before being added together. Pulse shaping: Root-raised cosine filter with ß=0.22. Bandwidth is 5MHz.

19 Modulation and Spreading Specifications
Physical channels required during a connection: Dedicated Channel: DPCH  Dedicated Physical Channel Common Channels: P-CPICH  Primary Common Pilot Channel Could be used at the receiver end for channel estimation, tracking P-CCPCH  Primary Common Control Physical Channel SCH  Synchronization Channel Not multiplied by orthogonal code. Used mainly for cell search: slot and frame timing acquisition. PICH  Paging Indicator Channel OCNS  Orthogonal Channel Noise Simulator Simulates interference caused by other users or signals.

20 Modulation and Spreading Overview
Physical Channels are added before being sent to Pulse Shaping PN Sequence Gold Codes Channelization Orthogonal Codes OVSF Scrambling Power Settings QPSK Modulation Power Weighting Spreading Scrambling + DPCH I&Q Mapping To Channel Common Channels OCNS SCH Common Channels are introduced {3.84Mcps} Bit Rate Chip Rate

21 Modulation and Spreading Model
Pulse Shaping Introduce Common Channels Power Adjustment Introduce Interference Scrambling

22 References 3GPP TS 25.101 – “UE Radio Transmission and Reception”.
3GPP TS – “Physical channels and mapping of transport channels onto Physical Channels (FDD)”. 3GPP TS – “Spreading and Modulation (FDD)”.

23 RAKE Receiver Standard does not defined Receiver algorithms.
Although specifications has been defined in a such a way that a RAKE receiver will satisfy most of the cases. RAKE receiver consists of several branches (RAKE Fingers) each of them assigned to a different receive paths, due to: Diversity reception (“echoes”) : sum of attenuated and delayed versions of the transmitted signal. Handoff. The outputs of the different RAKE fingers are aligned in time and coherently combined. Convert destructive interference into constructive interference.

24 RAKE Receiver Rake finger consists of:
Downsampler Decorrelators for Data and Pilot Receiver requires knowledge of channelization codes used by Data (Dedicated Physical Channel) and Pilot. Channel Estimation By comparing receiving pilot signal with reference signal. Low Pass filter is introduced is smooth noise estimates. Data Derotation or Phase Correction Using channel estimates data is phase corrected. Current RAKE receiver assumes perfect carrier and timing synchronization.

25 + ↓ RAKE Finger Overview Pilot Reference Channel Estimation Phase
Paths are aligned and added coherently Pilot Sequence, Channelization and Scrambling Code are generated at the receiver Channel Estimation From Other Fingers Pilot Reference + Correlator From Channel Phase Correction To Decoder Orthogonal Codes Data / Pilot Derotates data using channel estimates Oversampled data From Other Fingers Tick Rate Chip Rate Bit Rate

26 RAKE Receiver Model Pilot and Data Correlators
Pilot Reference Generator Channel Estimator RAKE Combiner Sequence Generators Phase Correction

27 Channel Models 3GPP standard specifies minimum requirement tests under for different data rates under different propagation conditions: Static Channel (AWGN) Multipath Fading 6 different multipath profiles Moving Propagation Conditions Non fading channel with two taps (static – moving). Birth-Death Propagation Conditions Non fading channel with two taps that appear randomly. Channel models are implemented using a Configurable Subsystem.

28 Channel Models Use the mask of the demo, to select any predefined profile. To define any multipath profile, use the option User Defined.

29 References 3GPP TS – “UE Radio Transmission and Reception”.

30 Visualizing the results
Spreading and Modulation Demo Multiplexing and Coding Demo Physical Layer Demo BER (Bit Error Rate) Time Scopes Frequency Scopes BLER (Syndrome Detector) There is an intrinsic delay between transmission and reception of at least 2 TTI. Simulink libraries contain several other types of displays such as eye diagrams, scatter plots or histograms.

31 Visualizing the results
To open and close the scopes, double-click on the switch icon

32 Enhancements

33 Enhancements Current model and library can be used as a baseline to test different algorithms such as: Turbo coding Power Control AFC AGC Tracking Space Time Transmit Diversity Two transmit antennae and one receiver antenna. Open Loop Close Loop Mode I and II Cell Search Multi-user detection.

34 Radiolab 3G

35 Radiolab 3G: UMTS/W-CDMA Blockset
20 reference designs Uplink and downlink Transport channels and physical channels Viterbi and Turbo decoding Multi-user detection Vary data rates during simulation (Bursty) Fixed-point and floating-point “RadioLab3G”

36 Remember to fill out the survey !!

37 Thank you

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