Simple Relaying Strategies for Half-duplex Networks

We consider the diamond network where a source communicates with the destination through N non-interfering half-duplex relays. Using simple outer bounds on the capacity of the network, we show that simple relaying strategies having exactly two states and avoiding broadcast and multiple access communication can still achieve a significant constant fraction of the capacity of the 2 relay network, independent of the SNR values. The results are extended to the case of 3 relays for the special class of antisymmetric networks. We also study the structure of (approximately) optimal relaying strategies for such networks. Simulations show that optimal schedules have at most N + 1 states, which we conjecture to be true in general. We prove the conjecture for N = 2 and in special cases for N = 3.

Simple schedules for half-duplex networks

Siddhartha Brahma, Christina Fragouli

We consider the diamond network where a source communicates with the destination through N non-interfering half-duplex relays. Deriving a simple approximation to the capacity of the network, we show that simple schedules having exactly two states and avoiding broadcast and multiple access communication can still achieve a significant constant fraction of the capacity of the 2 relay network, independent of the channel SNRs. The results are extended to the case of 3 relays for the special class of antisymmetric networks. We also study the structure of (approximately) optimal relaying strategies for such networks. Simulations show that these schedules have at most N + 1 states, which we conjecture to be true in general. We prove the conjecture for N = 2 and for special cases for N = 3.(1)

Ieee2012

Switched Local Schedules for Diamond Networks

Siddhartha Brahma, Christina Fragouli, Ayan Sengupta

We consider a Gaussian diamond network where a source communicates with the destination through

n

non-interfering half-duplex relays. We focus on half-duplex schedules that utilize only local channel state information, i.e., each relay has access to its incoming and outgoing channel realizations. We demonstrate that random independent switching, resulting in multiple listen-transmit sub cycles at each relay, while still respecting the overall locally optimal listen-transmit fractions, enables to approximately achieve at least

3/4

of the capacity of the

2

-relay diamond network. With a single listen-transmit cycle, this fraction drops from

3/4

1/2

. We also provide simulation results that point to the same fractions of capacity being retained over networks with more than

2

relays.

2014

On the Complexity of Scheduling in Half-Duplex Diamond Networks

Siddhartha Brahma, Christina Fragouli, Ayfer Özgür Aydin

We consider an n-relay Gaussian diamond network where a source communicates to a destination with the help of n half-duplex relays. Achieving rates close to the capacity of this network requires to employ all the n relays under an optimal transmit/receive schedule. Even for the moderate values of n, this can have significant operational complexity as the optimal schedule may possibly have 2(n) different states for the network (since each of the relays can be in either transmitting or receiving mode). In this paper, we investigate whether a significant fraction of the network capacity can be achieved by using transmit/receive schedules that have only few active states and by using only few relays. First, we conjecture that the approximately optimal schedule has at most n+1 states instead of the 2(n) possible states. We prove this conjecture for networks of size n

Ieee-Inst Electrical Electronics Engineers Inc2016