Using retransmission information in a black side data link layer

In the current MIL-STD-188-184 [184], the data link layer is hosted on the RED side of the communications security (COMSEC). This constrains the set of solutions available to the link layer. This paper analyses the possible benefits of moving the link layer to the black side of COMSEC in increasing throughput for a given channel. The benefits of waveform switching, retransmission combining and ARQ protection of crypto synch are discussed in terms of throughput performance. Formulas for throughput are presented in terms of the signal to noise density ratio and the bit error probability function of the chosen modulation on coherent channels. Performance differences between BLACK side combining and the red side combining of 184 are discussed. Based on results given, the recommendation is made that MIL-STD-188-184A (184 A) allow for the eventual migration of the data link layer to the black side of the COMSEC engine. A proposal is made to use the new MIL-STD-188-181B (181B) preamble to allow this migration to begin now without sacrificing interoperability with older equipment.