  This paper considers the design of relay assisted F/TDMA ad hoc networks with
multiple relay nodes each of which assists the transmission of a predefined
subset of source nodes to their respective destinations. Considering the sum
capacity as the performance metric, we solve the problem of optimally
allocating the total power of each relay node between the transmissions it is
assisting. We consider four different relay transmission strategies, namely
regenerative decode-and-forward (RDF), nonregenerative decode-and-forward
(NDF), amplify-and-forward (AF) and compress-and-forward (CF). We first obtain
the optimum power allocation policies for the relay nodes that employ a uniform
relaying strategy for all nodes. We show that the optimum power allocation for
the RDF and NDF cases are modified water-filling solutions. We observe that for
a given relay transmit power, NDF always outperforms RDF whereas CF always
provides higher sum capacity than AF. When CF and NDF are compared, it is
observed that either of CF or NDF may outperform the other in different
scenarios. This observation suggests that the sum capacity can be further
improved by having each relay adopt its relaying strategy in helping different
source nodes. We investigate this problem next and determine the optimum power
allocation and relaying strategy for each source node that relay nodes assist.
We observe that optimum power allocation for relay nodes with hybrid relaying
strategies provides higher sum capacity than pure RDF, NDF, AF or CF relaying
strategies.
