## 2 Literature Review  
Various approaches are found in the literature to boost the energy efficiency of NB-IoT communication; see [12; 13; 14; 15] and the references within. They include discontinuous reception, power-saving mode, coverage extension and others. While these mechanisms successfully enhance the energy efficiency of the network, unlike SCHC, they do not aim at providing IP interoperability. In fact, SCHC can work together with these mechanisms to achieve a more energy-efficient communication. Header compression has been studied in many works; see [16] and the references therein. By extensively surveying and comparing the major header compression standards, the authors of [16] concluded that SCHC will likely be widely adopted in resource-constrained IoT operations. In [17], the authors present SCHC as a proposed IPv6 adaptation layer for LPWANs. The efficiency of SCHC is presented by comparing the residue of compressing the IPv6 protocol in comparison with RoHC and 6 LoWPAN. Similarly, in [18], the authors show through ns3 simulations that SCHC is better than 6 LoWPAN in terms of header compression, with SCHC yielding smaller compressed headers. In [19], the authors study the benefits of using SCHC for multi-modal Low-Power Wide-Area Network (LPWAN) solutions. Comparing the performance of SCHC and 6 LoWPAN to compress and fragment CoAP block-wise transfers, the authors concluded that SCHC is the only protocol that is able to support end-to-end IPv6 connectivity for a multimodal device in LPWAN. Furthermore, the study also showed that SCHC has a small footprint and is suitable for an embedded device as it requires little memory. In [20], the authors develop a mathematical model to compute the most critical performance parameters for SCHC ACK-on-Error mode. The model is used to tune the main parameters used over LoRaWAN and Sigfox. Similarly, in [21], SCHC over Sigfox is evaluated with focus on the ACK-on-Error fragmentation mode. The authors perform a theoretical analysis and an experimental evaluation in real environments with different Sigfox radio settings. The results show that a small change in packet sizes may significantly affect the transfer times, especially when no duty cycle restrictions are considered. An energy consumption model of SCHC packet transfer over Sigfox is presented in [22]. The model, which is empirically derived, allows the energy performance of SCHC packet transfer over Sigfox to be determined considering several parameters and fragment transmission strategies. In addition, the model can be used to determine the lifetime of a battery-powered device. For example, the lifetime of a device powered by a 2000 mAh battery, transmitting packets every 5 days, is 1464 days for 77-byte packets. Ref. [23] evaluated the effectiveness of SCHC at compressing LWM2M traffic over LoRaWAN links. The results show that the compression can bring significant benefits, with a compression ratio of up to 75%. A model for determining the efficiency of the channel usage of SCHC on LoRaWAN is presented in [24]. The results showed that efficiency decreases when the probability of error increases and that there is a non-linear relationship between the spreading factor and efficiency. The end-to-end latency of IPv6 packets is evaluated for a real-world deployment of SCHC in [25], where the authors evaluated Acklio's implementation for a class C LoRaWAN device and Acklio SCHC gateway (IP Core). The results showed a latency of less than 1 s for small packets in the uplink. Similarly in [26], by using [PERSON]'s implementation of SCHC over LoRawAN, the experiments showed that the end-to-end latency for uplink and downlink directions is in the order of 0.5 s and 2.5 s, respectively, for both a local and remote end user transferring a 16-byte payload. The use of SCHC in the context of cellular IoT networks has already been considered in the literature. Ref. [27] proposes a multimodal approach, where multiple IoT technologies are used.