2 research outputs found
The Gaussian Two-way Diamond Channel
We consider two-way relaying in a Gaussian diamond channel, where two
terminal nodes wish to exchange information using two relays. A simple baseline
protocol is obtained by time-sharing between two one-way protocols. To improve
upon the baseline performance, we propose two compute-and-forward (CF)
protocols: Compute-and-forward Compound multiple access channel (CF-CMAC) and
Compute-and-forward-Broadcast (CF-BC). These protocols mix the two flows
through the two relays and achieve rates better than the simple time-sharing
protocol. We derive an outer bound to the capacity region that is satisfied by
any relaying protocol, and observe that the proposed protocols provide rates
close to the outer bound in certain channel conditions. Both the CF-CMAC and
CF-BC protocols use nested lattice codes in the compute phases. In the CF-CMAC
protocol, both relays simultaneously forward to the destinations over a
Compound Multiple Access Channel (CMAC). In the simpler CF-BC protocol's
forward phase, one relay is selected at a time for Broadcast Channel (BC)
transmission depending on the rate-pair to be achieved. We also consider the
diamond channel with direct source-destination link and the diamond channel
with interfering relays. Outer bounds and achievable rate regions are compared
for these two channels as well. Mixing of flows using the CF-CMAC protocol is
shown to be good for symmetric two-way rates.Comment: 8 pages, 7 figures Proceedings of 51st Annual Allerton Conference on
Communication, Control, and Computing, Monticello, IL, USA, Oct 201
Decode-Forward Transmission for the Two-Way Relay Channels
We propose composite decode-forward (DF) schemes for the two-way relay
channel in both the full- and half-duplex modes by combining coherent relaying,
independent relaying and partial relaying strategies. For the full-duplex mode,
the relay partially decodes each user's information in each block and forwards
this partial information coherently with the source user to the destination
user in the next block as in block Markov coding. In addition, the relay
independently broadcasts a binning index of both users' decoded information
parts in the next block as in independent network coding. Each technique has a
different impact on the relay power usage and the rate region. We further
analyze in detail the independent partial DF scheme and derive in closed-form
link regimes when this scheme achieves a strictly larger rate region than just
time-sharing between its constituent techniques, direct transmission and
independent DF relaying, and when it reduces to a simpler scheme. For the
half-duplex mode, we propose a 6-phase time-division scheme that incorporates
all considered relaying techniques and uses joint decoding simultaneously over
all receiving phases. Numerical results show significant rate gains over
existing DF schemes, obtained by performing link adaptation of the composite
scheme based on the identified link regimes.Comment: This work has been submitted to IEEE Transactions on Communications
for possible publicatio