Overview of G.SHDSL Interfaces
G.SHDSL is a data communications technology that enables faster data transmission over copper twisted pairs. G.SHDSL employs frequencies that include those unused by traditional Plain Old Telephone Service (POTS) to provide symmetric transmit and receive data rates.
Asymmetric Digital Subscriber Line (ADSL) is the most commonly used broadband access technology. It provides asymmetric transmit and receive data rates over copper twisted pairs and is useful for transmitting asymmetric services such as Internet access and Video on Demand (VoD). However, ADSL cannot meet requirements of commercial broadband applications that require bidirectional and symmetric traffic and are sensitive to performance fluctuation. The G.SHDSL technology solves this problem.
G.SHDSL complies with ITU Recommendation G.991.2 and provides bidirectional data transmission with symmetric data rates over twisted pairs. It reduces the transmission spectrum, improves the anti-noise performance, and extends the maximum transmission distance to 6 km by using 16-trellis coded pulse amplitude modulation (TCPAM).
Advantages of G.SHDSL
G.SHDSL provides high-speed commercial broadband services and has the following advantages:
- Symmetric DSL technology: In contrast to ADSL, G.SHDSL provides symmetrical services with symmetric rates from 192 kbit/s to 15296 kbit/s on a single twisted pair. G.SHDSL can also achieve a higher bandwidth by using interface binding.
- Good compatibility: G.SHDSL is compatible with other access transmission technologies including Digital Subscriber Line (DSL). This extends the transmission distance.
- High-speed transmission: G.SHDSL supports high data transmission, meeting user requirements.
- Long transmission distance and high signal-to-noise ratio (SNR): Compared with other DSL technologies, G.SHDSL provides a longer transmission distance for the same transmission rate, a higher transmission rate for the same transmission distance, and a greater SNR for the same transmission distance and rate.
- Good performance and wide range of services: G.SHDSL provides comprehensive solutions for small- and medium-scale enterprises and branch networks of medium- and large-scale enterprises, meeting diverse requirements, such as security, Virtual Private Network (VPN), and service extension. It also provides voice, video, and video conference solutions for service providers.
G.SHDSL System
- A CO is an aggregation device that terminates G.SHDSL packets on the central office.
- A CPE is a user-side device that modules and demodulates user data, and transmits user data to a DSLAM.
The router can function as a CPE or CO.
In the G.SHDSL system, downstream transmission refers to data transmission from a CO to a CPE, and upstream transmission refers to data transmission from a CPE to a CO. G.SHDSL interfaces on the CPE are upstream interfaces.
Services Supported by the G.SHDSL Interface
This section provides only the physical attribute configuration of G.SHDSL interfaces. For details about the configuration of the G.SHDSL interface working in ATM mode including the PVC configuration, see ATM Configuration in the Configuration Guide - WAN. For details about the configuration of the G.SHDSL interface working in PTM mode including the PVC configuration, see PPPoE Configuration in the Configuration Guide - WAN.