Feature: RF design


As technologies advance, our homes become smarter and more interconnected, no longer requiring conventional switches but wirelessly-controlled setups


control home heating systems. Another common remote-control application for the smartphone can be the remote monitoring of a vehicle’s state, like its tyre pressure, door and windows, mileage, location, service history and more. Tere are many other applications for smartphones in home


automation. As technologies advance, our homes become smarter and more interconnected, no longer requiring conventional switches but wirelessly-controlled setups accessible through a smartphone. Tis type of remote control can be either via Wi-Fi or Bluetooth; see Table 1. In this article we will discuss Wi-Fi as the technology to


Customising smartphones for Wi-Fi-based remote control


applications By Dr Dogan Ibrahim, Electronics Design Consultant


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martphones are everywhere: people use them for business, work, social engagement and leisure, among many other functionalities. Tey already offer so many features besides communications – from e-mails, messages, calender and appointments to cameras, games, mobile


purchases, and a lot more. Tey’ve become so ubiquitous and treasured, people won’t part with them, not even for a moment. Now, in addition to their other functionalities, smartphones can also be used for remote control, one of the most common being to


18 February 2024 www.electronicsworld.co.uk


remotely control equipment with an Android smartphone. Communication is in the form of client and server nodes, with sockets being used to send and receive data packets. Te server side usually waits for connection from the client and, once established, a two-way communication can start. Tere are two main protocols used for sending and receiving


data packets over a Wi-Fi link: TCP (transmission control protocol) and UDP (user datagram protocol); see Table 2. TCP is a connection-based protocol which guarantees the delivery of packets. Packets are given sequence numbers and the receipt of each packet is acknowledged, to avoid them arriving in the wrong order. As a result of this confirmation, TCP is usually slow but reliable, since it guarantees the packets’ delivery. On the other hand, UDP is not connection-based: Packets don’t


have sequence numbers and, as a result, there’s no guarantee that they will arrive at their destinations or in the wrong sequence. Compared to TCP, UDP has lower overheads, making it faster.


UDP communication A typical UDP communication is carried out as follows:


Server side: 1. Create a UDP socket. 2. Bind the socket to server address. 3. Wait until datagram packet arrives from client. 4. Process the datagram packet. 5. Send a reply to the client or close the socket. 6. Go back to step 3 (if not closed).


Client side: 1. Create a UDP socket (and, optionally, bind). 2. Send message to the server.


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