On packet size and error correction optimisations in low-power wireless networks

In wireless networks that operate in those bands where spectrum sharing occurs across a variety of wireless technologies, such as the license-free Industrial Scientific and Medical (ISM) bands, mitigating interference becomes challenging. Addressing interference is an important aspect for the design and development of solutions intended to satisfy the demands of applications requiring QoS guarantees. In this paper, we investigate dynamic radio resource adaptation techniques based on instantaneous spectrum usage. Using a novel metric to quantify the spectrum usage, we address packet size and error correction code overhead optimizations. On one hand, large payloads lead to energy and throughput gains due to the amortization of the transmission overheads, but on the other hand, larger payloads imply larger resource wastage in the event of packet collisions. Using real-world data, we found that payload size in the neighbourhood of 100 bytes leads to near-optimal performance in general in the IEEE 802.15.4 networks. Our data also shows that for very high interference scenarios, erasure codes capable of correcting 10% of the packet payload can provide an equivalent Signal to Interference plus Noise Ratio (SINR) gain of 25 dB with probability greater than 0.6. This is significant for interference management and for increasing spatial re-use by employing lower transmission power. We show that erasure codes drastically improve energy-efficiency and throughput of low-power wireless links. In the heavy interference regime, even though interference doubles the energy-per-usable-bit cost, erasure codes remain cost-effective for very large payload sizes, up-to 1500 bytes. Finally, we discuss interference-dependent dynamic adjustment of the correction capacity of erasure codes.