Technology Overview
Broadband generally includes Internet access that is always on and faster than traditional dial-up access. The use of broadband has increased dramatically over recent years. In 2000, the percentage of US homes that had broadband Internet was 1%. By 2016, that number had grown to 82%. Several high-speed transmission technologies exist, such as Digital Subscriber Line (DSL), Cable Modem, Fiber, and Wireless. Much of the challenge resides in the “last mile” that includes the connection between the user’s location and the provider’s local switching office.
Digital Subscriber Line (DSL)
DSL is a wireline transmission technology that uses existing traditional copper telephone lines. The speed ranges from several Kbps to many Mbps. The availably and speed of DSL service usually depends on the customers distance to the closest telephone switching office. The basic flavor of DSL is Asymetrical Digital Subscriber Line (ADSL), which is mainly used by consumers, provides a faster speed in the downstream direction and is best suited for applications like web surfing, where users receive more data than they transmit. ADSL uses the same lines as a user’s voice customers and operates without disrupting regular telephone calls. Other forms of DSL include High data rate Digital Subscriber Line (HDSL) and Very High data rate Digital Subscriber Line (VDSL). Downstream rates for ADSL range from 1.5 to 8 Mbps and is specified by the ITU G.992.1 standard. VDSL uses additional bandwidth and more sophisticated processing to achieve rates of up 100 Mbit/s and is specified by the ITU G.993.1 standard.
Cable Modem
Cable modem service enables cable operators to provide broadband service using the same coaxial cable that delivers TV service. This service typically provides much higher data rates than DSL, but operates based on shared bandwidth and can vary depending on the number of users in an area. Cable modems are defined by DOCSIS (Data Over Cable Service Interface Specification) and the latest version, 3.1, provides speeds of 10Gbit/s using OFDM modulation and other sophisticated techniques. A CMTS (cable modem termination system) resides in the cable company’s headend and provides the connection between the user’s cable modem and the Internet.
Fiber (FTTH, xPON)
While fiber optic communication has long been the backbone of the Internet, more recently, operators have tried to solve the “last mile” problem to create all optical networks by providing a fiber connection directly to the end user, also known as FTTP (fiber-to-the premises), FTTH (fiber-to-the-home), or simply FTTx. FTTx is typically implemented with a PON (Passive Optical Network) that uses fiber and passive components, such as splitters and combiners. This can provide significant cost benefits overactive components like amplifiers, repeaters, or shaping circuits. The first fiber deployments several years ago used technologies called EPON and BPON and typically supplied 600 Mbit/s to be shared by as many as 64 customers. Today’s emerging technology, NG-PON2 (Next-generation Passive Optical Network 2, ITU standard G.989.1), offers up to 40Gbps.
Once the optical signals reach the customers location, they are converted into electrical signals through an ONT (optical network terminal) or ONU (optical network unit) and routed throughout the home.
Wireless Broadband
In addition to these wireline schemes, various wireless broadband schemes have also attempted to solve the “last mile” access problem. Wireless services, such as WiMAX, have had limited success in the past. The latest 5G wireless systems are reported to have initial deployment in 2018. This may be a game-changer for broadband access with potential data rates of more the 1 Gbps. It has yet to be determined, however, if 5G can overcome the many hurdles to accomplish these ambitious goals.