46,225 research outputs found
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
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
State Amplification
We consider the problem of transmitting data at rate R over a state dependent
channel p(y|x,s) with the state information available at the sender and at the
same time conveying the information about the channel state itself to the
receiver. The amount of state information that can be learned at the receiver
is captured by the mutual information I(S^n; Y^n) between the state sequence
S^n and the channel output Y^n. The optimal tradeoff is characterized between
the information transmission rate R and the state uncertainty reduction rate
\Delta, when the state information is either causally or noncausally available
at the sender. This result is closely related and in a sense dual to a recent
study by Merhav and Shamai, which solves the problem of masking the state
information from the receiver rather than conveying it.Comment: 9 pages, 4 figures, submitted to IEEE Trans. Inform. Theory, revise
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