174 research outputs found
Resource Allocation for Power Minimization in the Downlink of THP-based Spatial Multiplexing MIMO-OFDMA Systems
In this work, we deal with resource allocation in the downlink of spatial
multiplexing MIMO-OFDMA systems. In particular, we concentrate on the problem
of jointly optimizing the transmit and receive processing matrices, the channel
assignment and the power allocation with the objective of minimizing the total
power consumption while satisfying different quality-of-service requirements. A
layered architecture is used in which users are first partitioned in different
groups on the basis of their channel quality and then channel assignment and
transceiver design are sequentially addressed starting from the group of users
with most adverse channel conditions. The multi-user interference among users
belonging to different groups is removed at the base station using a
Tomlinson-Harashima pre-coder operating at user level. Numerical results are
used to highlight the effectiveness of the proposed solution and to make
comparisons with existing alternatives.Comment: 12 pages, 6 figures, IEEE Trans. Veh. Techno
SNR maximization and modulo loss reduction for Tomlinson-Harashima precoding
Compared to linear precoding, Tomlinson-Harashima precoding (THP) requires less transmit power to eliminate the
spatial interference in a multi-user downlink scenario involving a multi-antenna transmitter and geographically
separated receivers. However, THP gives rise to certain performance losses, referred to as modulo loss and power loss.
Based on the observation that part of the users can omit the modulo operation at the receiver during an entire frame,
we present an alternative detector, which reduces the modulo loss compared to the conventional detector. In
addition, this contribution compares several existing and novel algorithms for selecting the user ordering and the
rotation of the constellations at the transmitter, to increase the SNR at the detector and decrease the modulo loss for
the alternative detector. Compared to the better of linear precoding and THP with conventional detector, the
optimized alternative detector achieves significant gains (up to about 4 dB) for terrestrial wireless communication,
whereas smaller gains (up to about 1 dB) are obtained for multi-beam satellite communication
Ordered Tomlinson-Harashima Precoding in G.fast Downstream
G.fast is an upcoming next generation DSL standard envisioned to use
bandwidth up to 212 MHz. Far-end crosstalk (FEXT) at these frequencies greatly
overcomes direct links. Its cancellation based on non-linear
Tomlinson-Harashima Precoding (THP) proved to show significant advantage over
standard linear precoding. This paper proposes a novel THP structure in which
ordering of successive interference pre-cancellation can be optimized for
downstream with non-cooperating receivers. The optimized scheme is compared to
existing THP structure denoted as equal-rate THP which is widely adopted in
wireless downlink. Structure and performance of both methods differ
significantly favoring the proposed scheme. The ordering that maximizes the
minimum rate (max-min fairness) for each tone of the discrete multi-tone
modulation is the familiar V-BLAST ordering. However, V-BLAST does not lead to
the global maximum when applied independently on each tone. The proposed novel
Dynamic Ordering (DO) strategy takes into account asymmetric channel statistics
to yield the highest minimum aggregated rate.Comment: 7 pages, 11 figures, Accepted at the 2015 IEEE Globecom 2015,
Selected Areas in Communications: Access Networks and Systems, 6-10 December,
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