Tactical Wireless Communications and Networks: Design Concepts and Challenges

5.6 IP Gateways

Link-16, EPLRS, and SINCGARS nets have IP gateways. These non-IP networks can be considered stub-networks¹⁵ to an IP core. The upside is the ability to make real time applications such as voice and situational awareness function on a variety of different non-IP protocols and IP networks. The downside includes issues such as low throughput efficiency and uncertain end-to-end QoS. Let us discuss some of these issues.

5.6.1 Throughput Efficiency

As you can see from Figure 5.2, the Link-16 data or information part can occupy about one half of the timeslot, leaving room for jitter, synchronization, time refine, and propagation. The single pulse structure in Figure 5.8 illustrates how off-time can be comparable to the time of pulse transmission with the single pulse (with the double pulse, the ratio of information to total duration of the double pulse is about 0.25). The need for the overhead of forward error correction (FEC) exists. The message validation requires reducing throughput efficiency by another factor of 2. The problem of throughput efficiency within a non-IP net pertains to this range (about 6–20% at best). As gateways allow non-IP payloads to traverse an IP core network, the end-to-end throughput is drastically affected. At the IP core network, throughput efficiency can be very low since the ratio of the IP-packet payload to headers can be small. These old non-IP waveforms were designed in the 1970s (before we even imagined streaming video) and are designed ...