An OFDM Based System Proposal for 4G Downlinks.

Arne Svensson, Chalmers U. of Technology,
Anders Ahlén, Uppsala University,
Anna Brunström, Karlstad University,
Tony Ottosson, Chalmers U. of Technology and
Mikael Sternad, Uppsala University

Multi-Carrier Spread Spectrum Workshop for Future Generation Wireless Systems Oberpfaffenhofen, Germany, Sept. 17-19 2003.

Outline:

The Swedish Wireless IP project studies problems that are crucial in the evolution of UMTS towards high data rates, as well as in future 4G technologies aimed at rapidly mobile terminals. The goal is to attain higher througputs for packet data in particular in downlinks, without unneccesary bandwidth expansion and while providing acceptable quality of service for various classes of traffic.

This paper outlines the adaptive OFDM downlink which is one focal point of our research. At IEEE VTC-Fall 2003, we presented our concept for an adaptive OFDM downlink in more detail, in four interrelated papers (see links below).

Abstract:

In this paper we describe an OFDM based 4G downlink for a wide area coverage and high mobility system. User data are multiplexed and OFDM modulated such that the user with the best predicted channel conditions are always using the channel. This user employs the linear modulation scheme that maximizes the spectral efficiency. We show that the system obtains a sector capacity that is significantly better than current 3G systems.

Various combinations of OFDM and CDMA are also discussed and it is concluded that it is difficult to motivate the significantly increased complexity of such schemes. Moreover, we also doubt that these combinations can increase spectral efficiency when predicted channel information is utilized at the transmitter.

Related publications:

Paper 1 at VTC2003, on adaptive modulation, multiuser diversity and channel variability within bins.

Paper 2 at VTC2003, on the OFDM downlink and cell planning for high SIR.

Paper 3 at VTC2003, on OFDM channel estimation and channel prediction.

Paper 4 at VTC2003, on the impact of prediction errors on the adaptive modulation.

The uplink of the system, presented at WWRF March 2002, and July 2002.

An overview of the Wireless IP Project (RVK02)

Proc. of the IEEE (Dec. 2007) invited paper on adaptive transmission in beyond-3G wireless systems.

Source:

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Postscript (151K)