4,644 research outputs found
HARQ Feedback in Spectrum Sharing Networks
This letter studies the throughput and the outage probability of spectrum
sharing networks utilizing hybrid automatic repeat request (HARQ) feedback. We
focus on the repetition time diversity and the incremental redundancy HARQ
protocols where the results are obtained for both continuous and bursting
communication models. The channel data transmission efficiency is investigated
in the presence of both secondary user peak transmission power and primary user
received interference power constraints. Finally, we evaluate the effect of
secondary-primary channel state information imperfection on the performance of
the secondary channel. Simulation results show that, while the throughput is
not necessarily increased by HARQ, substantial outage probability reduction is
achieved in all conditions.Comment: Published in IEEE Communications Letter
On the Outage Probability of the Full-Duplex Interference-Limited Relay Channel
In this paper, we study the performance, in terms of the asymptotic error
probability, of a user which communicates with a destination with the aid of a
full-duplex in-band relay. We consider that the network is
interference-limited, and interfering users are distributed as a Poisson point
process. In this case, the asymptotic error probability is upper bounded by the
outage probability (OP). We investigate the outage behavior for well-known
cooperative schemes, namely, decode-and-forward (DF) and compress-and-forward
(CF) considering fading and path loss. For DF we determine the exact OP and
develop upper bounds which are tight in typical operating conditions. Also, we
find the correlation coefficient between source and relay signals which
minimizes the OP when the density of interferers is small. For CF, the
achievable rates are determined by the spatial correlation of the
interferences, and a straightforward analysis isn't possible. To handle this
issue, we show the rate with correlated noises is at most one bit worse than
with uncorrelated noises, and thus find an upper bound on the performance of
CF. These results are useful to evaluate the performance and to optimize
relaying schemes in the context of full-duplex wireless networks.Comment: 30 pages, 4 figures. Final version. To appear in IEEE JSAC Special
Issue on Full-duplex Wireless Communications and Networks, 201
Wireless Information Transfer with Opportunistic Energy Harvesting
Energy harvesting is a promising solution to prolong the operation of
energy-constrained wireless networks. In particular, scavenging energy from
ambient radio signals, namely wireless energy harvesting (WEH), has recently
drawn significant attention. In this paper, we consider a point-to-point
wireless link over the narrowband flat-fading channel subject to time-varying
co-channel interference. It is assumed that the receiver has no fixed power
supplies and thus needs to replenish energy opportunistically via WEH from the
unintended interference and/or the intended signal sent by the transmitter. We
further assume a single-antenna receiver that can only decode information or
harvest energy at any time due to the practical circuit limitation. Therefore,
it is important to investigate when the receiver should switch between the two
modes of information decoding (ID) and energy harvesting (EH), based on the
instantaneous channel and interference condition. In this paper, we derive the
optimal mode switching rule at the receiver to achieve various trade-offs
between wireless information transfer and energy harvesting. Specifically, we
determine the minimum transmission outage probability for delay-limited
information transfer and the maximum ergodic capacity for no-delay-limited
information transfer versus the maximum average energy harvested at the
receiver, which are characterized by the boundary of so-called "outage-energy"
region and "rate-energy" region, respectively. Moreover, for the case when the
channel state information (CSI) is known at the transmitter, we investigate the
joint optimization of transmit power control, information and energy transfer
scheduling, and the receiver's mode switching. Our results provide useful
guidelines for the efficient design of emerging wireless communication systems
powered by opportunistic WEH.Comment: to appear in IEEE Transactions on Wireless Communicatio
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
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