Statistical analysis of dynamic coding and modulation theater level gains

High speed connectivity provides C4I and enables small unit rapid deployment at a unit of action (UA) level. This new operating paradigm will require a shift in the way the DoD plans, provisions and operates satellite links. Currently most satellite links are designed for worst case, or near worst case, operating conditions with the modulation and coding chosen to insure link closure between 97% and 99.5% of the time. This results in a substantial waste of link margin and a loss of spectral efficiency since that margin is seldom required. Dynamic coding and modulation (DCM) has been used in commercial networks to improve spectral efficiency and increase the number of users that can be supported with limited spectrum. DCM achieves this performance by adaptively changing modulation, coding and channel rate as environmental and link conditions changes. This allows RF links to operate with much smaller margins than is possible given static link operations. This paper evaluates the effectiveness of DCM for the MILSATCOM architecture. The authors describe a statistical link simulation model for estimating the advantage of DCM. The model was used to analyze the spectral requirements for a major theater of war containing over 1500 terminals. The paper analyzes a Korean theater scenario consisting of 7 FCS units of action (UA) and 6 BCT brigades as well as six UEx units and one UEy unit. The analysis was performed for a regenerative TSAT-like SATCOM architecture using advanced modulation. The paper compares static link operation to DCM operation and estimates gain in terms of spectral efficiency and transmit/receive burst rate. The results are presented as a function of link margin for a number of deployable army terminal classes, and as a theater aggregate. For the COTM terminal class, the results show that overall theater uplink spectral efficiency gains of 1.5x to 2x, and average burst rate increase of 2x to 4x are possible in high rain rate regions using DCM versus traditional planning and provisioning approaches.