99,966 research outputs found
Reliable Physical Layer Network Coding
When two or more users in a wireless network transmit simultaneously, their
electromagnetic signals are linearly superimposed on the channel. As a result,
a receiver that is interested in one of these signals sees the others as
unwanted interference. This property of the wireless medium is typically viewed
as a hindrance to reliable communication over a network. However, using a
recently developed coding strategy, interference can in fact be harnessed for
network coding. In a wired network, (linear) network coding refers to each
intermediate node taking its received packets, computing a linear combination
over a finite field, and forwarding the outcome towards the destinations. Then,
given an appropriate set of linear combinations, a destination can solve for
its desired packets. For certain topologies, this strategy can attain
significantly higher throughputs over routing-based strategies. Reliable
physical layer network coding takes this idea one step further: using
judiciously chosen linear error-correcting codes, intermediate nodes in a
wireless network can directly recover linear combinations of the packets from
the observed noisy superpositions of transmitted signals. Starting with some
simple examples, this survey explores the core ideas behind this new technique
and the possibilities it offers for communication over interference-limited
wireless networks.Comment: 19 pages, 14 figures, survey paper to appear in Proceedings of the
IEE
Neighborhood gossip: Concurrent averaging through local interference
In this paper, we study a gossip algorithm for distributed averaging over a wireless sensor network. The usual assumption is that, through properly chosen codes, the physical layer is reduced to a set of reliable bit pipes for the distributed averaging algorithm. However, with a new channel coding technique, computation coding, we can exploit the interference property of the wireless medium for efficient averaging. This then provides a new abstraction for the physical layer: reliable linear equations instead of reliable bit pipes. The “neighborhood gossip” algorithm operates modularly on top of this abstraction. We will show that for certain regimes, such an approach can lead to energy savings that are exponential in the network size and time savings that are polynomial
Isn't Hybrid ARQ Sufficient?
In practical systems, reliable communication is often accomplished by coding
at different network layers. We question the necessity of this approach and
examine when it can be beneficial. Through conceptually simple probabilistic
models (based on coin tossing), we argue that multicast scenarios and protocol
restrictions may make concatenated multi-layer coding preferable to physical
layer coding alone, which is mostly not the case in point-to-point
communications.Comment: Paper presented at Allerton Conference 201
Transport capacity of wireless networks: benefits from multi-access computation coding
We consider the effect on the transport capacity of wireless networks of different physical layer coding mechanisms. We compare the performance of traditional channel coding techniques, turning the wireless network in reliable point-to-point channels, with multi-access computation coding, in which nodes receive functions of messages transmitted by different neighbours. In both cases, network coding is used on higher layers. For one-dimensional networks, the benefit in transport capacity of computation-coding over point-to-point channels is a factor of 2; for two-dimensional networks, we show it to be at least 2.5
Joint Compute and Forward for the Two Way Relay Channel with Spatially Coupled LDPC Codes
We consider the design and analysis of coding schemes for the binary input
two way relay channel with erasure noise. We are particularly interested in
reliable physical layer network coding in which the relay performs perfect
error correction prior to forwarding messages. The best known achievable rates
for this problem can be achieved through either decode and forward or compute
and forward relaying. We consider a decoding paradigm called joint compute and
forward which we numerically show can achieve the best of these rates with a
single encoder and decoder. This is accomplished by deriving the exact
performance of a message passing decoder based on joint compute and forward for
spatially coupled LDPC ensembles.Comment: This paper was submitted to IEEE Global Communications Conference
201
Relay selection for efficient HARQ-IR protocols in relay-assisted multisource multicast networks
This paper investigates relay selection for reliable data transmission in relay-assisted multisource multicast networks (RMMNs) where multiple source nodes distribute information to a set of destination nodes with the assistance of multiple relay nodes. Hybrid automatic repeat request with incremental redundancy (HARQ-IR) is used and supported by either a physical-layer network coding (PNC) or an analog network coding (ANC) technique employed at the relays. By deriving efficiency metrics of the HARQ-IR protocols, we propose relay selection schemes for RMMNs to minimize the transmission delay and energy consumption. Simulation results are provided to analyse each relay selection scheme
Relay selection for efficient HARQ-IR protocols in relay-assisted multisource multicast networks
This paper investigates relay selection for reliable data transmission in relay-assisted multisource multicast networks (RMMNs) where multiple source nodes distribute information to a set of destination nodes with the assistance of multiple relay nodes. Hybrid automatic repeat request with incremental redundancy (HARQ-IR) is used and supported by either a physical-layer network coding (PNC) or an analog network coding (ANC) technique employed at the relays. By deriving efficiency metrics of the HARQ-IR protocols, we propose relay selection schemes for RMMNs to minimize the transmission delay and energy consumption. Simulation results are provided to analyse each relay selection scheme
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