Baseband processor

In smartphones and other radio network interface devices

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A baseband processor (also known as baseband radio processor, BP, or BBP) is a device (a chip or part of a chip) in a network interface controller that manages all the radio functions (all functions that require an antenna); however, this term is generally not used in reference to Wi-Fi and Bluetooth radios. A baseband processor typically uses its own RAM and firmware. Baseband processors are typically fabricated using CMOS (complementary metal&#;oxide&#;semiconductor) or RF CMOS technology,[1] and are widely used in radio-frequency (RF) and wireless communications.[2]

Overview

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Baseband processors typically run a real-time operating system (RTOS) as their firmware, such as ENEA's OSE, Nucleus RTOS (iPhone 3G/3GS/iPad), ThreadX (iPhone 4), and VRTX. There are more than a few significant manufacturers of baseband processors, including Broadcom, Icera, Intel Mobile Communications (former Infineon wireless division), MediaTek, Qualcomm, Spreadtrum, and ST-Ericsson.

The rationale of separating the baseband processor from the main processor (known as the AP or application processor) is threefold:

Radio performance

Radio control functions (signal modulation, encoding, radio frequency shifting, etc.) are highly timing-dependent, and require a real-time operating system.

Radio reliability

Separating the BP into a different component ensures proper radio operation while allowing application and OS changes.

Legal

Some authorities (e.g. the U.S. Federal Communications Commission (FCC)) require that the entire software stack running on a device which communicates with the mobile telephony network must be certified. Separating the BP into a different component allows reusing a stack without having to recertify the full AP.

Security concerns

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Since the software which runs on baseband processors is usually proprietary, it is impossible to perform an independent code audit. By reverse engineering some of the baseband chips, researchers have found security vulnerabilities that could be used to access and modify data on the remotely.[3][4] In March , makers of the free Android derivative Replicant announced they had found a backdoor in the baseband software of Samsung Galaxy phones that allows remote access to the user data stored on the .[5]

See also

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• OsmocomBB a free software for baseband processors

References

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Further reading

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Hello Sivam,

the two terms have different origins and cannot be compared directly.

If you want to learn more, please visit our website HUAXUN.

With broadband internet access we refer to all the current access technologies like ADSL, VDSL, cable modems, satellite based systems that provide much more bandwidth then the old dialup modems over PSTN ( up to 56 kbps downstream) that are not supported anymore in several countries.

Baseband refers to a signal that uses frequency from 0 Hz to an upper value.

In other terms a Baseband signal does not have a carrier ( a tone at a frequency).

A baseband signal can be used to modulate a carrier and this makes the carrier spectrum to be enlarged.

The simplest modulation tecnique is amplitude modulation (AM) where a carrier signal strenght changes over time using the modulating signal (think of radio AM stations).

For digital signals that need to send sequences of binary digits 01 we can use other forms of modulation based on frequency modulation  (FM) here the modulating signal is used to have an actual frequency of Fcarrier + Modulating_signal.

More complex modulations combining phase and amplitude modulations are possible and are called QAM.

Actually an ADSL or VDSL uses multiple carriers.

This is called Sub Carrier Multiplexing SCM or in ADSL terms DMT = Discrete Multitone modulation.

Classic ADSL uses 256 tones.

The first are unused to provide a protection for PSTN baseband signal.

Then there is range of tones used for upstream (from home to central office)

Then there is a blank range.

The remaining tones are used for downstream sent from CO modem to DTE modem.

Each tone senses the level of noise in its frequency interval and choices a suitable modulation scheme.

So actually an ADSL DMT modem is equivalent to 256 modems at different frequencies (tones).

VDSL uses more tones I think 512 tones the basic idea is the same.

In cable modem some TV carriers can be used for transporting data again two different carriers are needed for the upstream and the downstream direction.

Edit:

actually cable modems are a shared media like it is an ethernet hub so the MAC layer must manage competition for use of resources.

Also all mobile data access networks from GPRS to UMTS to LTE to next generation 5 are shared media: all phones and modems share the resources in the cell provided by a base station.

Hope to help

Giuseppe

For more information, please visit Baseband board.