5.2 Link-16 Waveform
Link-16 is one of the most sophisticated wireless tactical data systems in use by the US Joint and Coalition Services. It supports time-critical, robust radio communications and is integrated into many platforms, including fast movers. Link-16 supports voice, free text, and variable format messages. It is a complex waveform that deploys TDMA (time division multiple access), CDMA, and FDMA (frequency division multiple access) schemes.
As a legacy waveform, Link-16 was conceived before the standardization of the protocol stack layers discussed in Chapter 1. The core functionalities of this waveform are in the physical and data link layers. Link-16's equivalent of the MAC layer (where the apportionment of physical layer resources is handled) is done in the planning phase. In this phase, each Link-16 terminal is assigned a set of time blocks. Also, instead of MAC frames and IP packets, a block of 75 bits (known as a J-word) is used for transmitting and receiving data over the Link-16 net.
Let us delve further into the unique physical and data link features of the Link-16 waveform. Figure 5.1 details the slot structure of Link-16. Figure 5.1a illustrates the 127 different possible nets in Link-16 (horizontal rings numbered 0–126, with net 127 representing a stacked net); with the vertical axis representing the FDMA dimension of the waveform (each of these nets has its own FH pattern). Figure 5.1b demonstrates how a single ring (net) employs TDMA, creating 98 304 ...