40 research outputs found
An Extended Fano's Inequality for the Finite Blocklength Coding
Fano's inequality reveals the relation between the conditional entropy and
the probability of error . It has been the key tool in proving the converse of
coding theorems in the past sixty years. In this paper, an extended Fano's
inequality is proposed, which is tighter and more applicable for codings in the
finite blocklength regime. Lower bounds on the mutual information and an upper
bound on the codebook size are also given, which are shown to be tighter than
the original Fano's inequality. Especially, the extended Fano's inequality is
tight for some symmetric channels such as the -ary symmetric channels (QSC).Comment: 5 pages, 4 figures, submitted to IEEE ISIT 201
A Queueing Characterization of Information Transmission over Block Fading Rayleigh Channels in the Low SNR
Unlike the AWGN (additive white gaussian noise) channel, fading channels
suffer from random channel gains besides the additive Gaussian noise. As a
result, the instantaneous channel capacity varies randomly along time, which
makes it insufficient to characterize the transmission capability of a fading
channel using data rate only. In this paper, the transmission capability of a
buffer-aided block Rayleigh fading channel is examined by a constant rate input
data stream, and reflected by several parameters such as the average queue
length, stationary queue length distribution, packet delay and overflow
probability. Both infinite-buffer model and finite-buffer model are considered.
Taking advantage of the memoryless property of the service provided by the
channel in each block in the the low SNR (signal-to-noise ratio) regime, the
information transmission over the channel is formulated as a \textit{discrete
time discrete state} queueing problem. The obtained results show that
block fading channels are unable to support a data rate close to their ergodic
capacity, no matter how long the buffer is, even seen from the application
layer. For the finite-buffer model, the overflow probability is derived with
explicit expression, and is shown to decrease exponentially when buffer size is
increased, even when the buffer size is very small.Comment: 29 pages, 11 figures. More details on the proof of Theorem 1 and
proposition 1 can be found in "Queueing analysis for block fading Rayleigh
channels in the low SNR regime ", IEEE WCSP 2013.It has been published by
IEEE Trans. on Veh. Technol. in Feb. 201
Uplink Age of Information of Unilaterally Powered Two-way Data Exchanging Systems
We consider a two-way data exchanging system where a master node transfers
energy and data packets to a slave node alternatively. The slave node harvests
the transferred energy and performs information transmission as long as it has
sufficient energy for current block, i.e., according to the best-effort policy.
We examine the freshness of the received packets at the master node in terms of
age of information (AoI), which is defined as the time elapsed after the
generation of the latest received packet. We derive average uplink AoI and
uplink data rate as functions of downlink data rate in closed form. The
obtained results illustrate the performance limit of the unilaterally powered
two-way data exchanging system in terms of timeliness and efficiency. The
results also specify the achievable tradeoff between the data rates of the
two-way data exchanging system.Comment: INFOCOM 2018 AOI Wkshp, 6 page
High Speed Railway Wireless Communications: Efficiency v.s. Fairness
High speed railways (HSRs) have been deployed widely all over the world in
recent years. Different from traditional cellular communication, its high
mobility makes it essential to implement power allocation along the time. In
the HSR case, the transmission rate depends greatly on the distance between the
base station (BS) and the train. As a result, the train receives a time varying
data rate service when passing by a BS. It is clear that the most efficient
power allocation will spend all the power when the train is nearest from the
BS, which will cause great unfairness along the time. On the other hand, the
channel inversion allocation achieves the best fairness in terms of constant
rate transmission. However, its power efficiency is much lower. Therefore, the
power efficiency and the fairness along time are two incompatible objects. For
the HSR cellular system considered in this paper, a trade-off between the two
is achieved by proposing a temporal proportional fair power allocation scheme.
Besides, near optimal closed form solution and one algorithm finding the
-optimal allocation are presented.Comment: 16 pages, 6 figure