Литература / UMTS-Report

Annex C:

Concept Group Gamma γ - Wideband TDMA (WB-TDMA)

This report contained in this annex was prepared during the evaluation work of SMG2 as a possible basis for the UTRA standard. It is published on the understanding that the full details of the contents have not necessarily been reviewed by, or agreed by, ETSI SMG or SMG2.

Concept Group Gamma -

WB-TDMA:

System Description Summary

Concept Group Gamma: System Description Summary

1 Introduction

The WB-TDMA concept described here constitutes a candidate Radio Transmission Technology (RTT) which includes the physical carrier structure, the radio dependent protocol layers from layer 1 to layer 3 as well as the related radio resource management algorithms. The flexibility and efficiency is provided by sophisticated multiple access means, which include adaptive mechanisms to optimise the performance of the physical layer. Further, it is not the efficient protocols or the physical layer techniques alone, which will provide an advanced radio transmission solution, rather the complete radio interface including effective radio resource management algorithms. These aspects have been fully considered as part of the work of the Gamma concept group.

The present document summarises the main system features. More detailed information can be found in the Gamma Group Evaluation Document (ETSI SMG2#24, Tdoc SMG2 365/97).

2 Key Technical Characteristics of the Basic System

3 Performance Enhancing Features

The features in the above table are not essential to the operation of WB-TDMA, but are generally considered highly desirable.

In addition, Link Adaptation in response to changes in channel conditions is considered essential for achieving high spectral efficiency.

4 System Description

The frame duration is chosen to be 4.615ms for compatibility with GSM. A similar multi-frame structure to GSM could also be adopted.

FDD frame structure of WB-TDMA.

The frame is divided into slots of relative size 1/16 and 1/64. The same frame duration is applied in both FDD and TDD modes, except that in TDD mode an adjustable switching point determines the fraction of capacity devoted to uplink and downlink.

A number of different transmission bursts are defined for WB-TDMA. As an example, the diagram below shows a data burst for a 1/16th slot.

Data burst structure. TB=tail symbols, TS=training sequence and GP= guard period.

The basic modulation scheme is Binary Offset Quadrature Amplitude Modulation (B-OQAM) with a symbol rate of 2.6Msymbols/s. For higher bit rates Quaternary-OQAM is used. The corresponding carrier spacing is 1.6MHz.

The WB-TDMA concept has been developed as a cost-effective flexible platform for implementation of the UTRA, which can easily adapt to a variety of operating environments and application requirements. It offers a high degree of backwards compatibility with GSM, while at the same time is “future proof” because it allows enhancement by application of technological developments. WB-TDMA could also be used in combination with other techniques, for example as a complement to CDMA for provision of high bit rates over short ranges.

Concept Group Gamma -

WB-TDMA:

Evaluation Summary

Concept Group Gamma: Evaluation Summary

1 Introduction

The performance of the WB-TDMA concept has been evaluated in detail within the Gamma group. Results of link level and system level spectrum efficiency simulations are given in the Gamma Group Evaluation Document (ETSI SMG2#24, Tdoc SMG2 365/97). This also contains in Annex the Technologies Description Template, answers to questions from operators, and analytical results for spectrum efficiency.

Specific aspects which have been considered in the development of the WB-TDMA concept are:

∙Support of high bit rates with a relatively simple terminal

∙Effective support of non-real-time traffic with fast variations in data rate and packet size

∙Support of TDD mode with data rates fulfilling the UMTS requirements

∙Possibility to implement simple low bit rate terminals

∙Narrow spectrum and low interference to adjacent carriers

∙Flexibility for introduction of enhancements

2 Fulfilment of the High Level Requirements

This section describes how the WB-TDMA concept meets the High Level Requirements for UTRA.

2.1Bearer capabilities

2.1.1Maximum user bit rate

∙Rural Outdoor: 144kbps will be available throughout the operator’s service area. The radio interface can tolerate the Doppler spread and rapidly changing channel characteristics associated with high speed vehicles (up to at least 1500km/h with 1/64 slot bursts). The maximum cell size depends on propagation conditions, but is comparable with GSM at 1800MHz (assuming similar requirements for bearer capabilities and quality of service).

∙Suburban Outdoor: 384kbps rate will be available with complete coverage of a suburban or urban area

∙Indoor/Low range outdoor: 2Mbps will be available indoors and over localised coverage outdoors

The maximum practical bit rate which can be provided depends on factors such as the operating environment, required quality of service, traffic loading and proximity of the mobile to the base station. However, the radio interface can support rates up to around 1Mbps for Rural and Suburban Outdoor, and 4Mbps over short ranges.