Theoretical limitation of performance of decode-and-forward multinode cooperative communication systems with adaptive modulation scheme

The efficiency of multinode cooperative communication systems is an important issue to solve. One of the possible solutions is the adoption of the adaptive modulation (AM). In this work, we investigate the theoretical limitation of the performance of a multinode cooperative communication system with AM when decode-and-forward (DF) protocol is utilized at each relay. With DF protocol, the uncertainty of the decoding behavior of each relay complicates the support of AM in a multinode cooperative communication system. This uncertainty makes the performance analysis hard to access as well. We approach the performance of such a system under the assumption that the decoding results of relays are available at the destination. We further propose two models to mimic the chosen modulation level of the system and the decoding behavior of each relay. These two models help understand the behavior of a multinode cooperative communication system when AM and DF protocol are used. The extensive simulations are conducted to reveal the advantage of using AM in a multinode cooperative communication system and to verify the correctness of the proposed models.