Isotropic air-interface technologies for fourth generation wireless communications
Journal
Wireless Communications & Mobile Computing
Journal Volume
3
Journal Issue
6
Pages
687-704
Date Issued
2003
Author(s)
Abstract
Abstract To implement 4G wireless that should deliver a much higher data‐rate than that possible in the current 3G systems, development of innovative air‐link technologies is the key. This article reviews our on‐going research activities in the design of ‘isotropic air‐interface technologies’ capable of substantially improving air‐link performance of a CDMA wireless system. To enable bidirectional high‐speed data transmission in the future 4G systems, the problem associated with incompatible up‐ and down‐link performance in 2–3G systems has to be addressed. The importance of the issue becomes even more evident due to the fact that the future wireless needs to support ‘mobile server’ applications, where a mobile terminal may act as a data source such that up‐link traffic can possibly exceed that in down‐link. In this article, two alternative methods enabling isotropic air‐interface will be discussed, either using ‘isotropic spreading techniques’ that ensure a homogeneous link‐performance regardless of its operation mode (synchronous or asynchronous), or relying on a precision up‐link synchronization control techniques to pave a way for successful application of orthogonal codes in up‐link channels, which otherwise are asynchronous and destroy the ‘orthogonality’ amongst the codes. The isotropic spreading techniques can minimize multiple access interference (MAI) and multipath‐interference (MI), the prevalent impairing effects in the current 2–3G systems. This article will introduce a promising complete complementary CC/DS‐CDMA scheme based on isotropic spreading techniques, which carries several extremely attractive properties such as MAI‐free, MI‐free, near–far effect resistance and low hardware complexity. The performance of the proposed CC/DS‐CDMA scheme is limited only by noise. To implement up‐link synchronization control, smart antenna and GPS‐based techniques play an important role and a working example based on TD‐SCDMA standard will be illustrated. Finally, we will also discuss the TDD techniques and its significance to implement isotropic air‐interface technologies for the future 4G systems. Copyright © 2003 John Wiley & Sons, Ltd.
SDGs
Type
journal article