IEEE Consumer Electronics Magazine - November/December 2020 - 60

Consumer Electronics Communications

Figure 3. Network architecture and device on-boarding using HAS proxy. (a) Architecture using our HAS
proxy. (b) Device on-boarding onto HAS proxy. (c) HAS proxy on-boards the device onto the primary network
coordinator. (d) State of maintained data structures.

ZigBee networking protocol stack. Moreover, to
facilitate communication over the Internet, the
computing device should have Ethernet and/or
WiFi connection along with TCP/IP implementation. The relevant functionality of our HAS proxy
can be implemented using mentioned available
hardware and software components. As the HAS
proxy uses any existing protocol stack, its capacity is limited by an underlying protocol's design.
In this article, we use ZigBee protocol stack to
elaborate the HAS proxy functionality. In the
short addressing mode, ZigBee uses 2-byte for
assigning network layer addresses to nodes.
Hence, in this case, the maximum number of
nodes that the HAS proxy can handle is 212 . Our
HAS proxy is a software proxy implementation;
therefore, it does not eliminate the need for a
primary network coordinator.

Forming a Network and On-Boarding Devices
Onto the Primary Coordinator
As shown in Figure 3(a), our HAS proxy acts
as a man-in-the-middle between a smart home
device and the primary network coordinator.
Our HAS proxy implements some of a network
coordinator's functionalities; however, by its
nature, it is not a network coordinator. It has the
capabilities to form, manage, and supervise a
network based on a certain networking protocol
stack, for example, ZigBee. The HAS proxy periodically broadcasts a beacon frame with its personal area network (PAN) ID. Any new smart
device is initially manually on-boarded onto the
HAS proxy. During the on-boarding process,
the sequence of messages exchanged between

the smart device and the HAS proxy is shown in
Figure 3(b). The sequence of messages shown in
Figure 3 is standard ZigBee messages. At the end
of the on-boarding process with the HAS proxy,
the smart device has acquired the following
information: PAN ID, smart device network
address, and link security key. Similarly, the HAS
proxy has stored the smart device's MAC
address, network address, and link key in its
internal data structure.
As the HAS proxy acts as a man-in-the-middle,
the next step in the process is that the proxy onboards the smart device onto the primary coordinator, and this step is oblivious to the smart
device. The sequence of messages exchanged
between the proxy and the primary coordinator
to on-board the smart device onto the primary
coordinator is shown in Figure 3(c). As this process does not require any human interaction,
hence, this process is orders of magnitude faster
compared to manually on-boarding of a device
onto the proxy. Thus, the additional time
required by the proxy to on-board devices onto
the primary coordinator is negligible. At the end
of this step, the HAS proxy would have obtained
the following information. PAN ID, smart device
network address on the primary coordinator's
network, and the link security key for the smart
device. Now, the proxy keeps the mapping
between the smart device's network credentials
issued by the primary coordinator and the credentials issued by the proxy to the smart device
in its internal data structure. The proxy can also
maintain a copy of this data structure in the
cloud. As the proxy has to on-board multiple

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