Inter-Multilevel Super-Orthogonal Space-Time Coding Scheme for Reliable ZigBee-Based IoMT Communications

Abstract

The Internet of Things (IoT) technology has revolutionized the healthcare industry by enabling a new paradigm for healthcare delivery. This paradigm is known as the Internet of Medical Things (IoMT). IoMT devices are typically connected via a wide range of wireless communication technologies, such as Bluetooth, radio-frequency identification (RFID), ZigBee, Wi-Fi, and cellular networks. The ZigBee protocol is considered to be an ideal protocol for IoMT communication due to its low cost, low power usage, easy implementation, and appropriate level of security. However, maintaining ZigBee's high reliability is a major challenge due to multi-path fading and interference from coexisting wireless networks. This has increased the demand for more efficient channel coding schemes that can achieve a more reliable transmission of vital patient data for ZigBee-based IoMT communications. To meet this demand, a novel coding scheme called inter-multilevel super-orthogonal space-time coding (IM-SOSTC) can be implemented by combining the multilevel coding and set partitioning of super-orthogonal space-time block codes based on the coding gain distance (CGD) criterion. The proposed IM-SOSTC utilizes a technique that provides inter-level dependency between adjacent multilevel coded blocks to facilitate high spectral efficiency, which has been compromised previously by the high coding gain due to the multilevel outer code. In this paper, the performance of IM-SOSTC is compared to other related schemes via a computer simulation that utilizes the quasi-static Rayleigh fading channel. The simulation results show that IM-SOSTC outperforms other related coding schemes and is capable of providing the optimal trade-off between coding gain and spectral efficiency whilst guaranteeing full diversity and low complexity.

Keywords: Internet of Medical Things (IoMT); ZigBee; channel coding; inter-level dependency codes; multilevel coding technique; super-orthogonal space–time codes.

Figure 1

Patient monitoring using a ZigBee wireless network.

Figure 2

(a) IEEE 802.15.4 channels and (b) IEEE 802.11b/g non-overlapping channels in North America.

Figure 3

The system flow chart.

Figure 4

The three-level partition chain in Example 1.

Figure 5

The two-state trellis in Example 1.

Figure 6

The encoding of IM-SOSTC-1.

Figure 7

The trellis of ${\overline{C}}^{(1,0)}$ in IM-SOSTC-1.

Figure 8

The coding configuration of IM-SOSTC.

Figure 9

The trellis of ${\overline{C}}^{(1,0)}$ in IM-SOSTC-4.

Figure 10

The simulation results of the two-state IM-SOSTC-4 vs. the other two-state coding schemes that use a QPSK constellation.

Figure 11

The generator matrix of ${\overline{C}}^{(3,2,1,0)}$.

Figure 12

The trellis of ${\overline{C}}^{(3,2,1,0)}$.

Figure 13

The trellis of $C^{\left(2\right)}$ and $C^{\left(3\right)}$, (4, 3, 2), in IM-SOSTC-4.

Figure 14

The trellis of $C^{\left(4\right)}$, (4, 4, 1), in IM-SOSTC-4.