# An Edge-Based LWM2M Proxy for Device Management to Efficiently Support QoS-Aware IoT Services
## 2 Related Work
### Related Work on IoT Proxies
It groups clients by their demands and computes an optimal observation period for each group such that the IoT device generates the minimum number of notifications; it finds an appropriate max-age value for each IoT device to cache notifications; and it combines notifications generated by IoT devices, so a proxy can forward fewer notifications to the client. However, in these solutions the proxies aim to reduce the traffic generated asynchronously by the IoT devices. Instead, we propose a solution that reduces the number of requests generated by the Servers and forwarded to the Clients. Moreover, we also propose that the Proxy implements a cache function, but the freshness of the cached items is measured by the Age of Information metrics [9] and the cached items are refreshed according to the IoT application freshness requirements. IoT gateways can also improve the management of IoT devices. To address the heterogeneity of IoT devices, there is the need of a common standard platform for managing them. OMA LWM2M can be particularly suitable for this scope because it is a light protocol and uses an efficient resource data model. For these reasons, it is becoming widely used by both the industrial and research worlds. For example, authors of [15] also consider the LWM2M protocol and they propose a LWM2M Proxy that implements a group management extension for LWM2M. In this case, the proxy is introduced to minimize the traffic towards the LWM2M Server: it reduces the number of bytes sent to the server and it avoids retransmissions collecting the messages coming from the LWM2M Clients and aggregating them in one response to be sent to the LWM2M Server. In our work we instead try to minimize the traffic towards the LWM2M Client to cope with the constraints of IoT devices and networks. Authors of [16] propose a cloud based virtual network operator for Low Power Wide Area Networks that homogenizes deployments using OMA LWM2M and that provides a unified way to communicate over different technologies using Static Context Header Compression, SCHC. However, they implemented the header compression mechanism for the CoAP/UDP/IPv6 stack, leaving the LWM2M payload uncompressed. Moreover in [17] authors show the benefits that the use of the SCHC mechanism provides to constrained IoT networks: they consider a LPWAN network and, by applying the header reduction to the CoAP/UDP/IPv6 stack, they enable the transmission of packets that could not be transmitted previously. Moreover, in this case, the compression is applied only to the headers of the packets. In this work, we propose an extension of the SCHC mechanism for LWM2M that allows to also compress the LWM2M payload. We propose the architecture of a Proxy that optimizes the LWM2M protocol and that also allows the implementation of one or more QoS-oriented customized functions that tackle the issues illustrated above. So, our proposed Proxy implements a freshness-aware cache, a shaper that buffers the requests to avoid network congestion, and a compressor that compresses the header and the payload of the packets to reduce their sizes. These functions can be applied singularly or together depending on the Server demands.