System Spectral Efficiency Analysis of a 2-Link Ad Hoc Network

This paper analyzes the system spectral efficiency of a 2-link ad hoc network. The analysis shows that there are exactly three operating points that maximize system capacity: either both links transmit with maximum power simultaneously; or one single link transmits with maximum power while the other is silent. The impact of the scheduling policy on the system spectral efficiency is also studied: simultaneous transmission or sequential access where the two links share the medium by dedicated time/frequency slots without causing interference. An exhaustive numerical search over a wide range of pathloss parameters shows that sequential transmission is superior to simultaneous transmission in about two third of the cases. Even when simultaneous transmission outperforms sequential transmission, the gains are typically not substantial. Furthermore, we show that in case of simultaneous transmission power control causes only marginal degradation in terms of system spectral efficiency, while transmitting with maximum power pays off for sequential transmission. This highlights the importance of the joint optimization of power and rate adaptation together with scheduling for power constraint ad hoc networks.