Bluetooth has become a ubiquitous technology in today’s digital world. From smartphones to smart home gadgets, it’s the most common way electronics communicate wirelessly.
It works by sending short bursts of information over radio waves, at a frequency around 2.4 GHz. That’s the same frequency used by WiFi routers, but Bluetooth uses far less power than Wi-Fi.
Frequency Hopping
Frequency hopping is a wireless technology that spreads signals across a wide range of frequencies in short periods. This technique can help protect against jamming. It also improves communication performance by reducing interference.
It’s no secret that radio communications are susceptible to jamming. This can occur when too many competing signals are broadcast over the same wavelength. It’s a problem that can affect anything from mobile phones to military communications.
One way to combat this is to change the carrier frequency for each transmission. This can be done through a number of methods but frequency hopping is one of the most effective ones available.
Using frequency hopping spread spectrum (FHSS) technology, signal are broken into subfrequencies and shifted around in a pre-determined order. This helps to reduce interference from other devices operating on the same band, as well as prevents interference from fixed-frequency and random sources.
This approach has a number of advantages: It can use a much wider bandwidth than a single radio channel, and it reduces the degradation caused by narrowband interference. It also doesn’t require a separate antenna, so it can be implemented in a variety of applications.
Another advantage is that frequency hopping provides a high degree of immunity to interference. This makes it ideal for use in environments where WLAN and Bluetooth are present.
To implement adaptive frequency hopping, a number of changes need to be made to the baseband, Link Manager Protocol (LMP) and Host Controller Interface (HCI). Four key areas must be updated: the hopping kernel, definition of behavior during all modes of operation, link control messages, and a bad channel determination algorithm.
These updates are required to facilitate a device’s ability to adapt its hopping sequence to avoid channels that are already in use by other devices. In addition, the AFH algorithm must be backward compatible with Bluetooth Specification Version 1.1 and its hopping kernel.
The Bluetooth Special Interest Group (SIG) has approved a new Bluetooth specification for Adaptive Frequency Hopping (AFH). This is a modification to the existing Bluetooth specifications that allows a master and slave to adapt their hop channel sequence in order to reduce interference. It is a technique that is currently being used by a number of Bluetooth devices.
Spread Spectrum
Bluetooth is a wireless technology that allows devices to communicate without the need for a wired connection. It operates in the 2.4 GHz frequency band, which is used for a variety of applications such as wireless audio and video, security, and industrial control.
To avoid interference, Bluetooth uses a frequency-hopping spread spectrum technique that switches carriers between frequencies on the 2.4 GHz band at a rapid rate of 1600 hops per second. There are six defined hopping sequences that can be used for this purpose.
Another advantage of spread spectrum is its ability to expand the signal bandwidth several orders of magnitude in some cases. This can be helpful in overcoming strong jamming and in environments where communications quality is variable and unpredictable.
A third benefit of spread spectrum is that it is difficult to intercept. This is because the key or code that is used to spread the signal cannot be decoded by a nonauthorized listener. In addition, it can reduce the spectral density of the communication signal, which helps to make the message invisible to an eavesdropper.
Finally, spread spectrum can also help to increase the distance of a transmission. This is especially useful for enabling wireless connections between distant objects.
Bluetooth is a low power communication technology that has three different power levels, which are designated as Class 1, Class 2, and Class 3. The Class 1 is designed for long range communication up to 100m, while the other two are more for ordinary range devices with a range of 10cm or less.
The wireless connection between a Bluetooth device and another can be made via a USB port or through a radio antenna. The transmitter and receiver must be synchronized with each other. This is why so much research and money have gone into developing synchronization techniques.
This process requires advanced technologies and disciplines including RF antennas, powerful and efficient PAs, low-noise LNAs, compact transceivers, high-resolution ADCs and DACs, and rapid low-power digital signal processing (DSP). The synchronization of a spread-spectrum transmission can be challenging, but it is possible with sophisticated mathematical functions and application-specific integrated circuits (ASICs). These chips drive down the costs of the system by making generic building blocks available for a wide range of applications.
Inquiry Scanning
In the scanning phase of inquiry, teachers and leaders collect evidence from a range of sources about students’ learning. This can be about academic outcomes, using tools such as PAT (Progressive Achievement Tests) and NAPLAN (the National Assessment Program – Literacy and Numeracy), or diagnostic tests of mathematics or reading comprehension; it might also include behaviour, engagement, learning dispositions or teacher practice. The aim is to get a broad and thorough overview of the whole group, and to identify areas where improvement may be needed.
It is important to note that this is not a process of finding evidence that supports the status quo, but rather a gathering of new information and insights about students’ learning. In this phase, it is best to be open and curious about students’ experiences and what they are demonstrating or saying.
The results of this can be used to deepen understanding and to inform action to improve teaching practice or curriculum. As this is a cycle of inquiry, it will be necessary to repeat the process again and again as new insights come to light.
During this phase it is important to make the right choice of focus for the next stage of inquiry. Often, the information that is gathered will reveal many things that need attention, but it is crucial to keep focus on one area. This can be difficult at times, but it is essential to do so in order to maximise the impact of the work.
To carry out a page and inquiry scan, the Bluetooth transceiver uses a number of frequency scanners to perform a predetermined number of frequency sweeps over all Bluetooth frequencies. These sweeps are competed within a time period less than or equal to the duration of a page or inquiry scan message.
Once the scanning is completed, the energy detector measures the received energy at each of the frequencies that were scanned and compares it against a first threshold to generate a detection signal. This information is then used to determine if a page or inquiry scan message has been received.
Pairing
Pairing is a process in which a Bluetooth device equips itself with special security keys and causes other devices to trust it. This is done to protect the information on your phone or laptop and prevent others from accessing it.
When the two devices are within range of each other, an electronic conversation takes place to determine whether or not they can be trusted. This occurs automatically, so there is usually no user intervention required.
The pairing process may also involve a password or “Passkey” which is a shared code between the two devices that ensures they have both agreed to pair. This can be a number from four numbers to sixteen-character alphanumeric strings, and it can vary in length and complexity.
Depending on the device, pairing can take some time and the entire process may need to be completed manually by a user. This is especially true for devices that lack a graphical user interface (such as headsets).
Another factor to consider is the amount of power a device can use when it’s connected to a computer. Some Bluetooth devices have smart power management, which shuts off the technology if it’s not being used. This means that if the battery on your smartphone or other device runs low, it won’t be able to pair with other Bluetooth devices.
When pairing is complete, the device will store the information between it and other devices. This is similar to the way you would store a phone number on your mobile, so that other phones will be able to call it without needing to know your phone number.
In addition, some Bluetooth devices support multipoint pairing – this is a feature that allows you to connect multiple devices at once. This can be useful if you want to pair a phone with your headphones, or an audio device with your vehicle’s infotainment system.
The process of pairing differs from device to device and depends on how the devices are made. Some devices may require you to press a button, while others are designed to be easy to operate for even non-technical people. In any case, it’s important to follow the instructions on the product.