WCDMA TDD vs. FDD Physical Layer Comparison
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This tutorial outlines the key differences between the WCDMA TDD (Time Division Duplex) and WCDMA FDD (Frequency Division Duplex) physical layers, as per UTRA (UMTS Terrestrial Radio Access) specifications.
WCDMA (UMTS) Basics
Before diving into the specifics, here are some fundamental concepts related to WCDMA (UMTS):
- UMTS Tutorial
- UMTS Channels Measurements
- PHY Layer TDD vs. FDD
- PHY RRC States
- Security
- Cell Search
- Bands
- UARFCN
- Frame Structure
Technical Specifications: WCDMA TDD vs. WCDMA FDD
The following table highlights the key differences in technical specifications between WCDMA TDD and WCDMA FDD:
Feature | WCDMA TDD Physical Layer | WCDMA FDD Physical Layer |
---|---|---|
Multiple Access Type | TDMA, CDMA (inherent FDMA) | CDMA (inherent FDMA) |
Duplex Scheme | TDD | FDD |
Channel Spacing | 5MHz and 1.66 MHz supported | 5 MHz |
Chip Rate | 3.84 Mcps and 1.28 Mcps | 3.84 Mcps |
Slot Structure | 15/14 slots per frame | 15 slots per frame |
Frame Length | 10ms | 10ms |
Multi-rate Capabilities | Multi-rate multi-code, multi-slot, and OVSF (Orthogonal Variable Spreading Factor) | Multi-code and OVSF |
FEC Codes | Convolutional coding R=1/2 or 1/3 constraint length K=9, turbo coding(8 state PCCC R=1/3), service based coding | |
Interleaving | Inter-frame interleaving (10/20/40/80ms) | |
Modulation | QPSK/8PSK | QPSK |
Detection | Coherent type and based on midamble | Coherent type and based on pilots |
Burst Types | Three types supported: traffic, random access, and synchronization | NA |
Dedicated Channel Power Control | Uplink: open loop, 100/200 Hz Downlink: closed loop, rate <= 800Hz | Fast closed loop, rate = 1500 Hz |
Intra-frequency Handover | Hard handover | Soft handover, softer handover |
Inter-frequency Handover | Hard handover | Hard handover |
Intra-cell Interference Cancellation | Joint detection | Advanced receivers at the base station |
Channel Allocation (UTRA R4) | DCA supported | No DCA needed |
Spreading Factors Supported (UTRA R4) | 1 to 16 | 4 to 512 |