## 3 Architecture and Design Methodology of the LHM-N Model
### Design Methodology of the LHM-N Model
#### 3.2.1 Overview of Technologies Adopted  
The technologies employed in this paper range from fundamental to emerging technologies, thus, leading to the novel proposed LHM-N model for IoT applications solution in smart cities scenario. As stated earlier, the model considers a 5G private network over a license-free band. The 5G new radio unlicensed (5G NR U) is part of the aspect that has been finalized in the recent 3 GPP release-17 [6]. It will enable industries and private networks to leverage sub-7 GHz as well as the millimeter wave (60 GHz) spectrum band for IoT and broadband solutions. Also, 1.9 GHz is a license-free band in the sub-7 GHz band. The 1.9 GHz band has been well advocated for supporting eMTC and industrial IoT (IIoT) technologies' devices by Multefire Alliance [40, 41]. Further, the 5G RedCap IoT device is well suited for medium to high IoT applications, including IIoT [42]. The 5G RedCap IoT device operates on both licensed and unlicensed spectrums. However, the 5G RedCap IoT will need to be well modified to have features nearer to an LPWAN. This modification or optimization may entail the employment of reliable technologies to be implemented at the physical (PHY) layer of the 5G RedCap IoT. The optimization will enable 5G RedCap IoT to support diverse LPWAN-IoT applications in smart city scenarios. One of the reliable technologies that can be implemented on RedCap is the Trellis code modulation (TCM). The TCM is a bandwidth-efficient scheme that is accomplished using convolutional code. It conserves bandwidth by doubling the constellation points of the signal, thus increasing the bit rate, but the symbol rate remains the same [43]. Hence, TCM is bandwidth and energy-efficient error correction coding (ECC) without a complexity cost, unlike the conventional ECC by Shannon's law, in which there is a trade-off between bandwidth and energy with complexity cost [44]. However, the author of TCM did not take into consideration a Rayleigh fading distribution; rather it was modeled under an additive white gaussian noise (AWGN) channel. For this scheme to work effectively over a Rayleigh fading channel distribution, there is a need to implement it alongside a technology that will produce a satisfactory result. A smart city is a typical terrain that requires Rayleigh fading channel distribution to model communication access technologies and application use cases in a smart city scenario. This is because several buildings in the city cause a non-line of sight (NLOS) and scattering of the wireless signal due to the multipath fading (Rayleigh fading). To overcome this shortfall, this work proposes a receiver diversity-based TCM technique, RX-TCM. Hence, the RX-TCM protocol alongside the LHM-N model is proposed to support medium to high data rate IoT applications. The RX-TCM protocol will be implemented on the LHM-N model for diverse IoT applications as a solution in smart cities scenarios. The LHM-N model consists of a multihomed LHM-N gateway and a multihomed LHM-N end device (ED). Both maintain the same technologies as well as the same radio module interfaces, except that the former has NB2-IoT and higher complexity in addition to supporting numerous LPWAN-IoT devices. Hence, the LHM-N model employs the following technologies. * 5G NR U: specifically, the 1.9 GHz band advocated by the Multifire Alliance
* Private 5G network
* 5G RedCap IoT
* RX-TCM  
These technologies are implemented specifically on the PHY layer of the RedCap radio module interface. Other radio module interfaces in the multihomed device are meant to offload dense IoT data to their respective use cases depending on the application's requirements. The RedCap interface is meant to support medium to high data rate IoT applications that cannot be supported by other low-data LPWANs (LoRaWAN, Sigfox, eMTC, and NB2-IoT) in smart city scenarios.