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Mobile phones and other devices typically require considerable processing power to control their computational and communications functions. The Central Processing Unit (CPU) of such a device allows for many functions, and often includes several software applications and drivers. Most mobile communications devices also include a Baseband Processor (BP), separate from the CPU. Generally, it manages the radio control functions, such as signal generation, modulation, encoding, as well as frequency shifting. It can also manage the transmission of signals.
The baseband processor is typically located on the same circuit board as the CPU, but consists of a separate radio electronics component. It can therefore have a different programming interface and control software. The hardware function is often independent of the operations of other phone components as well. A benefit to this is usually that changes to software applications and operating systems do not affect the operation of the BP. Software bugs can affect other capabilities, but the baseband processor will usually function without a problem in such a case.
An applications processor is often used to manage all of the software programs on a device. A separate baseband processor can also enable phone designers to create applications and user interfaces without having to worry about changes to the BP or the way radio signals are processed. Wireless communication capabilities have continued to increase through the early 21st century. Some baseband radio processor models can handle many channels at once, usually while processing all receive and transmit demands.
This type of device sometimes includes multiple processing components. One kind has four, so it can combine parameter estimation, signal searching, transmission, and receiving functions and other capabilities. The BP can also search for mobile signals and track them, as well as select antennas automatically. In many cases, a baseband processor is contained in a common integrated circuit package, such as a ball grid array. Low power models are often available as well.
As of 2011, baseband processor capabilities are often supportive of the fourth generation protocols for wireless communication. The processor is often part of the device’s modem, and can include other features such as Flash memory. A low power memory baseband processor often has connections to common interfaces, such as Universal Serial Bus (USB) found in most computers and mobile devices. The design of separate processors in a phone is not only efficient, but able to prevent malfunctions due to software bugs, which could cause widespread phone problems as well as network issues.
@Logicfest -- true, but there's also a disadvantage inherent in that design. Let's say you have a plan that limits your cellular data to 2 gigabytes -- once that threshold is reached, you will pay quite a bit to keep receiving cellular data.
If your Wi-Fi fails but you keep receiving data through the radio, then you might not know something is wrong with your Wi-Fi. In other words, you can burn through your cellular data limit in a hurry if you keep using your phone like it was connected to your "free" Wi-Fi network.
The baseband processor can, in a lot of ways, offer an unseen advantage. Quite often, the Wi-Fi and Bluetooth functions of a cell phone operate independently of the "radio" functions of a phone (the part of the cell that deals with cellular data and calls).
Why is that an advantage? It is not uncommon for the Wi-Fi or radio function in a phone to fail. By having those controlled by different bits of hardware, it is far more likely that one function will work if another fails.
For example, if your Wi-Fi stops working, you can usually still receive data through the radio. If the radio fails, you might not be able to make phone calls but at least you can still access Wi-Fi data. In other words, keeping those functions separate often means that you're not completely out of luck if one function fails as the other one will probably keep working.
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