## 6 Design Considerations for LPWAN Networks
### Operations, Interrelationships, and Interworking  
Proprietary and standards-based LPWAN technologies have different strengths and weaknesses in terms of operations, co-existence, and interworking with each other. There are different challenges for the technologies operating in unlicensed and licensed bands [10]. For unlicensed bands, flexibility and faster time to market are major advantages. However, the transceivers become more complex, and interference needs to be managed. Proprietary technologies also need to adhere to regional regulations on the use of a shared spectrum. These may put limits on their operations, for example, transmitted radio frequency (RF) power. For technologies operating in licensed bands, standardized solutions, QoS management facilities, and more robust control of the network and devices are major advantages. However, the cost, complexities associated with acquiring and managing the allocated spectrum, and delays in time-to-market are the issues to be handled. In either case, the use of sub-GHz frequencies achieves wider coverage and better penetration into buildings and underground installations. The use of sub-GHz frequencies also leads to lower interference and increased sensitivity, making these technologies more energy-efficient.  
Traditionally, proprietary technologies optimize their costs by using customized implementations and lean and thin proprietary protocols. As competitiveness, portable services, availability of options to the users of multiple technologies, and utilization of common interfaces become more important, customized and simple protocols need to be replaced by standardized ones. Typically, communication based on Internet protocol (IP) between network server applications and the end devices becomes the interface of choice. This allows portable and more generic implementations based on IPv6 and constrained application protocol (CoAP) [14]. To incorporate simplicity, diverse radio technologies may need to exploit the compressed form of IPv6 and CoAP. LPWAN device implementation requires a small frame size owing to its very low data rates. Hence, traditional compression techniques that rely on octet or two available to signal both IP and CoAP may not be appropriate. The higher level IETF stack structure can also be used. This involves tradeoffs with cost and simplicity, as well.  
Cross-technology interference also influences the performance of LPWAN technologies. Therefore, service level agreements (SLAs) need to be put in place, especially for unlicensed band operations. Interoperability between heterogeneous technologies is crucial to the long term viability of LPWAN technologies. The issues mentioned in the previous paragraph also need to be addressed when it comes to interoperability. Again, standardized design structures and protocols become imperative. In addition, the emergence of new communication technologies introduces many integration challenges, including alignment of common practices, service descriptions, standards, and discovery mechanisms. This creates incompatibilities and does not allow interworking. Common application, identity, security, and service management models need to be utilized by any LPWAN technology desiring to work with others. For the technologies, this has an impact primarily on the physical and MAC layers in addition to work related to adherence to IP and IETF standards for higher layers.