The future success of high frequency (HF) communication systems rely on its ability to integrate and support IP diversity within a multiple intemet protocol (IP) based networks, such as satellite communication (SATCOM), local area network (LAN), wide area network (WAN) bearers. The introduction of new and proposed standards on HP-IP in recent years has increased the interest in the areas of performance analysis of HP -IP communication systems and networks. A wide range of modem services rely on IP and current HP-IP systems can support 2.4 to 19.2 kbps services such as e-mail and intemet. However, the reliability and the quality of service (QoS) still remains an issue of interest, particularly over longer distance skywave channels. These modem services require a higher data rate, much better bandwidth utilisation and a good QoS for its successful implementation. This work investigated HP-IP systems with the aim of improving the performance of legacy, current and proposed future systems without modifications to existing hardware systems. Initially the research conducted involved practical measurements and analysis on HF-IP systems complying with proposed NATO STANAG 5066 draft/edition 2 standards. Having investigated several NATO HF-IP standards (STANAG 5066 editionl, STANAG 5066 draft/edition 2, STANAG 4539/4285/4529, etc), a novel concept of error control coding (ECC) within the data link (DL) layer for HP-IP systems was proposed. Benefit of this proposed concept is that it does not require hardware modifications in legacy and current system for improving the performance. For application of this concept high performance low density parity check (LDPC) coding was considered. Two classes of short block length quasi-cyclic (QC) LDPC codes with switchable- rate single encoder/decoder structure; based on finite fields were designed and constructed. Several code rates were constructed within a single encoder/decoder structure resulting in reduced implementation complexity. Both classes of codes were simulated using HF channel model (ITU- R F.1487) covering latitudes and conditions for performance analysis. The simulation results show by using switchable-rate QC-LDPC coding scheme that there is coding gain of 2.4 dB compared to the existing STANAG 4539 convolutional coding scheme demonstrating the high performance of the proposed scheme in ITU-R F.l487 HF channel environment. In addition, the use of STANAG 5066 draft/edition 2 operating on a skywave multi-node HF-IP token ring (TR) WAN for a civilian disaster relief scenario was investigated. Here, a novel HF-IP network concept was proposed. The concept incorporates multi-node HF-IP TR WAN as an inner network, supported by an outer network made up of digital radio monodiale (DRM) service operating on a single frequency within the HF band. As STANAG 5066 draft/edition 2 was primarily designed to supporting multi-node HF-IP networks, it was vital to understand the network reliability and number of practical nodes that this network can support in different skywave HF channel conditions. A 3-node network based on skywave propagation covering a large geographical area was investigated. Using this scenario probability of reliability of a skywave multi-node HF-IP was analysed by simulations and practical measurements using STANAG 5066 draft/edition 2 IP protocol and STANAG 4539 modem setups. This analysis showed that the skywave multi-node HF-IP TR network can reliably operate between 3-5 nodes.