Scheduling and Adaptive Transmission for the Downlink in 4G Systems.
Nilo Casimiro Ericsson, UU
Sorour Falahati, CTH,
Anders Ahlén, UU
Arne Svensson, CTH.
Future Telecommunication Conference
Beijing, China, November 2001.
Also presented at the
Wireless World Research Forum Workshop,
Paris, France, December 2001.
The Wireless IP project within the PCC program 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 bandwidth expansion and while providing acceptable
quality of service for various classes of traffic.
In this paper, we propose a system suitable for
efficient packet data transmission using the Internet
Protocols (IP) in wireless 4G systems. It
consists of a hybrid type-II Automatic Repeat
reQuest (ARQ) scheme combined with an Adaptive Modulation
(AMS) and a time-slot scheduler supplied by channel predictions.
This scheme is referred to as predictive HARQ-II/AMS.
The performance of the system
in a fast fading downlink channel is investigated through
simulations where in particular, BER and throughput
performance are studied.
The proposed system is compared to two
One has access to channel predictions and uses adaptive
modulation but does not employ error correction
and retransmission at the link layer
(referred to as predictive AMS).
The other has no access to the channel prediction
but uses HARQ-II/AMS in a blind way
(referred to as blind HARQ-II/AMS).
The results show that with
perfect channel prediction both predictive AMS and HARQ-II/AMS
satisfy the BER requirements, with some
advantages to the former in terms of efficient usage of channel
capacity. However, with imperfect channel prediction,
a retransmission protocol is required to meet the BER
requirement, making predictive HARQ-II/AMS the winner.
Earlier VTC00-fall paper
on the same topic.
Licenciate Thesis by Nilo C. Ericsson, June 2001.
Licenciate Thesis by Sorour Falahati, Feb. 2000.
- VTC01-spring paper
on channel prediction over 1-10 ms horizons.
Performance of 4G OFDM System based on these
principles (FTC 2001, Beijing)
An overview of the Wireless IP Project, NRS 01.