Terminology » Mobile Communication » WCDMA TDD vs. FDD Physical Layer Comparison

WCDMA TDD vs. FDD Physical Layer Comparison

wcdma tdd fdd physical layer utra

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:

FeatureWCDMA TDD Physical LayerWCDMA FDD Physical Layer
Multiple Access TypeTDMA, CDMA (inherent FDMA)CDMA (inherent FDMA)
Duplex SchemeTDDFDD
Channel Spacing5MHz and 1.66 MHz supported5 MHz
Chip Rate3.84 Mcps and 1.28 Mcps3.84 Mcps
Slot Structure15/14 slots per frame15 slots per frame
Frame Length10ms10ms
Multi-rate CapabilitiesMulti-rate multi-code, multi-slot, and OVSF (Orthogonal Variable Spreading Factor)Multi-code and OVSF
FEC CodesConvolutional coding R=1/2 or 1/3 constraint length K=9, turbo coding(8 state PCCC R=1/3), service based coding
InterleavingInter-frame interleaving (10/20/40/80ms)
ModulationQPSK/8PSKQPSK
DetectionCoherent type and based on midambleCoherent type and based on pilots
Burst TypesThree types supported: traffic, random access, and synchronizationNA
Dedicated Channel Power ControlUplink: open loop, 100/200 Hz
Downlink: closed loop, rate <= 800Hz		Fast closed loop, rate = 1500 Hz
Intra-frequency HandoverHard handoverSoft handover, softer handover
Inter-frequency HandoverHard handoverHard handover
Intra-cell Interference CancellationJoint detectionAdvanced receivers at the base station
Channel Allocation (UTRA R4)DCA supportedNo DCA needed
Spreading Factors Supported (UTRA R4)1 to 164 to 512