12 research outputs found
Writing on Dirty Paper with Resizing and its Application to Quasi-Static Fading Broadcast Channels
This paper studies a variant of the classical problem of ``writing on dirty
paper'' in which the sum of the input and the interference, or dirt, is
multiplied by a random variable that models resizing, known to the decoder but
not to the encoder. The achievable rate of Costa's dirty paper coding (DPC)
scheme is calculated and compared to the case of the decoder's also knowing the
dirt. In the ergodic case, the corresponding rate loss vanishes asymptotically
in the limits of both high and low signal-to-noise ratio (SNR), and is small at
all finite SNR for typical distributions like Rayleigh, Rician, and Nakagami.
In the quasi-static case, the DPC scheme is lossless at all SNR in terms of
outage probability. Quasi-static fading broadcast channels (BC) without
transmit channel state information (CSI) are investigated as an application of
the robustness properties. It is shown that the DPC scheme leads to an outage
achievable rate region that strictly dominates that of time division.Comment: To appear in IEEE International Symposium on Information Theory 200
On Capacity of the Dirty Paper Channel with Fading Dirt in the Strong Fading Regime
The classical writing on dirty paper capacity result establishes that full
interference pre-cancellation can be attained in Gelfand-Pinsker problem with
additive state and additive white Gaussian noise. This result holds under the
idealized assumption that perfect channel knowledge is available at both
transmitter and receiver. While channel knowledge at the receiver can be
obtained through pilot tones, transmitter channel knowledge is harder to
acquire. For this reason, we are interested in characterizing the capacity
under the more realistic assumption that only partial channel knowledge is
available at the transmitter. We study, more specifically, the dirty paper
channel in which the interference sequence in multiplied by fading value
unknown to the transmitter but known at the receiver. For this model, we
establish an approximate characterization of capacity for the case in which
fading values vary greatly in between channel realizations. In this regime,
which we term the strong fading regime, the capacity pre-log factor is equal to
the inverse of the number of possible fading realizations
Filter and nested-lattice code design for fading MIMO channels with side-information
Linear-assignment Gel'fand-Pinsker coding (LA-GPC) is a coding technique for
channels with interference known only at the transmitter, where the known
interference is treated as side-information (SI). As a special case of LA-GPC,
dirty paper coding has been shown to be able to achieve the optimal
interference-free rate for interference channels with perfect channel state
information at the transmitter (CSIT). In the cases where only the channel
distribution information at the transmitter (CDIT) is available, LA-GPC also
has good (sometimes optimal) performance in a variety of fast and slow fading
SI channels. In this paper, we design the filters in nested-lattice based
coding to make it achieve the same rate performance as LA-GPC in multiple-input
multiple-output (MIMO) channels. Compared with the random Gaussian codebooks
used in previous works, our resultant coding schemes have an algebraic
structure and can be implemented in practical systems. A simulation in a
slow-fading channel is also provided, and near interference-free error
performance is obtained. The proposed coding schemes can serve as the
fundamental building blocks to achieve the promised rate performance of MIMO
Gaussian broadcast channels with CDIT or perfect CSITComment: submitted to IEEE Transactions on Communications, Feb, 200
On the Dirty Paper Channel with Fast Fading Dirt
Costa`s "writing on dirty paper" result establishes that full state
pre-cancellation can be attained in the Gel`fand-Pinsker problem with additive
state and additive white Gaussian noise. This result holds under the
assumptions that full channel knowledge is available at both the transmitter
and the receiver. In this work we consider the scenario in which the state is
multiplied by an ergodic fading process which is not known at the encoder. We
study both the case in which the receiver has knowledge of the fading and the
case in which it does not: for both models we derive inner and outer bounds to
capacity and determine the distance between the two bounds when possible. For
the channel without fading knowledge at either the transmitter or the receiver,
the gap between inner and outer bounds is finite for a class of fading
distributions which includes a number of canonical fading models. In the
capacity approaching strategy for this class, the transmitter performs Costa`s
pre-coding against the mean value of the fading times the state while the
receiver treats the remaining signal as noise. For the case in which only the
receiver has knowledge of the fading, we determine a finite gap between inner
and outer bounds for two classes of discrete fading distribution. The first
class of distributions is the one in which there exists a probability mass
larger than one half while the second class is the one in which the fading is
uniformly distributed over values that are exponentially spaced apart.
Unfortunately, the capacity in the case of a continuous fading distribution
remains very hard to characterize