16 research outputs found
Cooperative Retransmissions Through Collisions
Interference in wireless networks is one of the key capacity-limiting
factors. Recently developed interference-embracing techniques show promising
performance on turning collisions into useful transmissions. However, the
interference-embracing techniques are hard to apply in practical applications
due to their strict requirements. In this paper, we consider utilising the
interference-embracing techniques in a common scenario of two interfering
sender-receiver pairs. By employing opportunistic listening and analog network
coding (ANC), we show that compared to traditional ARQ retransmission, a higher
retransmission throughput can be achieved by allowing two interfering senders
to cooperatively retransmit selected lost packets at the same time. This
simultaneous retransmission is facilitated by a simple handshaking procedure
without introducing additional overhead. Simulation results demonstrate the
superior performance of the proposed cooperative retransmission.Comment: IEEE ICC 2011, Kyoto, Japan. 5 pages, 5 figures, 2 tables. Analog
Network Coding, Retransmission, Access Point, WLAN, interference, collision,
capacity, packet los
An Efficient Network Coding based Retransmission Algorithm for Wireless Multicasts
Retransmission based on packet acknowledgement (ACK/NAK) is a fundamental
error control technique employed in IEEE 802.11-2007 unicast network. However
the 802.11-2007 standard falls short of proposing a reliable MAC-level recovery
protocol for multicast frames. In this paper we propose a latency and bandwidth
efficient coding algorithm based on the principles of network coding for
retransmitting lost packets in a singlehop wireless multicast network and
demonstrate its effectiveness over previously proposed network coding based
retransmission algorithms.Comment: 5 pages, 5 figure
Collision Codes: Decoding Superimposed BPSK Modulated Wireless Transmissions
The introduction of physical layer network coding gives rise to the concept
of turning a collision of transmissions on a wireless channel useful. In the
idea of physical layer network coding, two synchronized simultaneous packet
transmissions are carefully encoded such that the superimposed transmission can
be decoded to produce a packet which is identical to the bitwise binary sum of
the two transmitted packets. This paper explores the decoding of superimposed
transmission resulted by multiple synchronized simultaneous transmissions. We
devise a coding scheme that achieves the identification of individual
transmission from the synchronized superimposed transmission. A mathematical
proof for the existence of such a coding scheme is given
Generation of Innovative and Sparse Encoding Vectors for Broadcast Systems with Feedback
In the application of linear network coding to wireless broadcasting with
feedback, we prove that the problem of determining the existence of an
innovative encoding vector is NP-complete when the finite field size is two.
When the finite field size is larger than or equal to the number of users, it
is shown that we can always find an encoding vector which is both innovative
and sparse. The sparsity can be utilized in speeding up the decoding process.
An efficient algorithm to generate innovative and sparse encoding vectors is
developed. Simulations show that the delay performance of our scheme with
binary finite field outperforms a number of existing schemes in terms of
average and worst-case delay.Comment: 5 pages, 4 figures, accepted for publication in the Proc. of IEEE
ISIT 201
Beyond the Min-Cut Bound: Deterministic Network Coding for Asynchronous Multirate Broadcast
In a single hop broadcast packet erasure network, we demonstrate that it is
possible to provide multirate packet delivery outside of what is given by the
network min-cut. This is achieved by using a deterministic non-block-based
network coding scheme, which allows us to sidestep some of the limitations put
in place by the block coding model used to determine the network capacity.
Under the network coding scheme we outline, the sender is able to transmit
network coded packets above the channel rate of some receivers, while ensuring
that they still experience nonzero delivery rates. Interestingly, in this
generalised form of asynchronous network coded broadcast, receivers are not
required to obtain knowledge of all packets transmitted so far. Instead, causal
feedback from the receivers about packet erasures is used by the sender to
determine a network coded transmission that will allow at least one, but often
multiple receivers, to deliver their next needed packet.
Although the analysis of deterministic coding schemes is generally a
difficult problem, by making some approximations we are able to obtain
tractable estimates of the receivers' delivery rates, which are shown to match
reasonably well with simulation. Using these estimates, we design a fairness
algorithm that allocates the sender's resources so all receivers will
experience fair delivery rate performance
Network coding-based reliable wireless multicast
Tohoku University亀山充