What Is Baseband? | Definition from ...

What is baseband?

Baseband in the transmission of communications signals means only one path is available to send and receive digital signals between devices. Baseband communication systems have been in use for many years and is still used in technologies such as Ethernet and wireless communications.

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Baseband technology is used in several ways:

• Information is carried in digital form on a single signal channel that isn't multiplexed and uses a transmission medium, such as copper twisted-pair wires. Baseband network technology is used in various types of networks, including Ethernet and token ring local area networks.
• With multiplexing, a transmission channel derives additional paths over a baseband channel.
• A baseband signal transmits data streams as analog signals using modulation technology.
• With any frequency band on which information is superimposed, baseband can be used whether or not the band is multiplexed and information is sent on subbands. In this application, it's assumed that the carrier frequency band used isn't shifted to a different frequency band but remains at its original place in the electromagnetic spectrum.

Baseband vs. broadband

A broadband transmission and signal processing system supports multiple frequency bands, whereas baseband transmission uses only one transmission band. Both telecommunications technologies support multiple concurrent transmissions, but they use different equipment at each end to accommodate different signal transmission methods.

10BASE-T and its derivatives

Baseband technology is used in Ethernet networks. Ethernet is typically deployed in a star network configuration with the network hub and device connections radiating from the hub. The Institute of Electrical and Electronics Engineers (IEEE) defines current Ethernet transmission specifications as follows:

• 10BASE-T. The initial IEEE Ethernet standard, 10BASE-T provides 10 megabits per second (Mbps) of transmission bandwidth over a baseband channel using twisted-pair copper wiring.
• 100BASE-T. This standard supports transmission speeds up to 100 Mbps.
• BASE-T. The BASE-T standard supports transmission speeds up to 1,000 Mbps or 1 gigabit per second (Gbps). It is also referred to as Gigabit Ethernet.
• 10GBASE-T. The 10GBASE-T standard supports transmission speeds up to 10 Gbps.

In addition to twisted-pair copper cable, providers use coaxial cable and fiber optic cable as transmission media. The following are IEEE standards for each of these media:

• 10BASE-2. This standard is for thin-wire coaxial cable with a maximum transmission distance of 607 feet, or 185 meters.
• 10BASE-5. This is the thick-wire coaxial cable standard with a maximum transmission distance of 1,640 feet, or 500 meters.
• 10BASE-F. This is the standard for fiber optic transmission cables.
• 10BASE-36. The standard for broadband coaxial cable that supports transmission of multiple baseband channels over a maximum distance of 11,800 feet, or 3,600 meters.

Strengths and limitations of baseband

Baseband is a cost-effective technology that's easy to use and inexpensive to install using twisted pair cable. It's also simple to maintain, and its simple structure makes it easy to understand and work with.

However, baseband can only be used for voice and data communications. It isn't generally used for video, and it has a limited transmission range.

Learn more about the evolution of Ethernet as the standard has evolved over the last half century.

In smartphones and other radio network interface devices

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

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

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

• OsmocomBB a free software for baseband processors

References

Further reading

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