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Internet Access Technology

(Salem, Massachusetts - Harvard Taiwan ROC Student Club)

The connection between the LAN and the Internet (via the Internet Service Provider) is called the access network. A residential gateway (a type of router) or access router connects a home or office LAN to the Internet. A modem (modulator/demodulator) converts data between various analog formats as needed by the underlying media. Think of a modem as back-to-back NICs, each converting data to their type of media. Modems are generally built into access routers. Examples of access links are:


- Carrier Ethernet

Ethernet is the most commonly installed wired LAN technology and it provides services on the Physical and Data Link Layer of OSI reference model. Ethernet network speeds have evolved significantly over time and typically range from Ethernet (802.11) at 10 Mbps, Fast Ethernet (IEEE 802.3u) at 100 Mbps, Gigabit Ethernet (IEEE 802.3-2008) at 1000 Mbps and 10 Gigabit Ethernet (IEEE 802.3a) at 10 Gbps. In fact, history shows that Ethernet bit rates grow tenfold each time a new rate is defined. Gigabit Ethernet (GbE) interfaces are widely deployed in PCs and servers, and 10 Gb/s is quickly becoming the standard for LAN backbones. 

Please refer to "Carrier Ethernet and Local Area Network (LAN)" for more details.

- DSL (digital Subscriber Line)

DSL uses existing copper telephone wiring between your home and the phone company’s central office. Since voice uses only the 0 - 4 kHz range of frequencies, there is a lot of untapped bandwidth in a phone wire. DSL uses the 4 kHz through 50 kHz frequency band for upstream data (data you send) and the 50 kHz through 1 MHz band for downstream data (data you receive). A DSL modem serves as an access router and modem. At the phone company’s central office, the access link terminates at a DSLAM (digital subscriber line multiplexor). From there, the data signals are sent to the data network (Internet) and the voice signals are sent to the phone network.


- Cable Network

Internet service provided by a TV cable company uses the same coax cable that provides TV signals. With cable TV, hundreds of channels are transmitted at once, each occupying a different frequency band (high definition channels occupy a 6 MHz band and standard definition digital channels typically occupy a 1.5 GHz band). This type of transmission is called broadband. A certain number of channels are not used for TV services but instead are used for Internet access. The customer has an access router/modem that conforms to the DOCSIS (Data Over Cable Service Interface Specification) standard. Some number of channels are devoted to downstream communication (data you receive). Each channel provides 38 Mbps service. Another set of channels are devoted to upstream service, with each channel providing 27 Mbps service. The cable terminates at the cable company’s headend on a device called the CMTS, the cable modem termination system. Here, the Internet service frequencies are filtered to separate out the data and send it to the cable company’s Internet link. A key distinction between DSL and cable service is that the phone wire between the DSL modem and the phone company’s central office is a dedicated, non-shared line. The coax cable of cable TV service is shared among a neighborhood. However, even though the channel is shared, the capacity of coax media is greater than that of a phone line and its signal attenuation over distance is far lower.


Twin Towers_Kuala Lumpur_Malaysia_052316A
(Twin Towers, Kuala Lumpur, Malaysia - Hsi-Pin Ma)

- FTTH (Fiber to the Home) 

FTTN (fiber to the Neighborhood). Fiber offers even greater bandwidth than cable and can propagate signals longer distances without degradation. Fiber to the Home (FTTH) is an optical fiber link that connects a home to a central office and delivers a combination of TV, telephone, and Internet service. Verizon’s FiOS service is an example of a service that delivers fiber to the home. Access links in this architecture often use optical splitters to allow a single fiber from the central office to fan out to several homes (typically 16–128). FTTH requires an end-to-end fiber infrastructure, which is costly to deploy (Verizon spent $23 billion through 2010 deploying FiOS at a cost of over $800 per home). An alternative architecture that is designed to be more cost effective is Fiber to the Neighborhood (FTTN). AT&T’s U-verse service is an example of this. A fiber runs from the provider’s central office to the neighborhood (within a half mile of the customers’ homes). There, it goes to a mini headend that uses copper wiring to connect to each customer’s home via VDSL (very high bitrate DSL).  

- Cellular 4G LTE and 5G

It uses cellular telephony to send or receive packets through a nearby base station operated by the cellular network provider. 4G Long Term Evolution (LTE) and 5G offer high-speed wireless communication for mobile devices and increased network capacity. 5G technology has a theoretical peak speed of 20 Gbps, while the peak speed of 4G is only 1 Gbps. While earlier generations of cellular technology (such as 4G LTE) focused on ensuring connectivity, 5G takes connectivity to the next level by delivering connected experiences from the cloud to clients. 5G networks are virtualized and software-driven, and they exploit cloud technologies. As devices proliferate and become more intelligent, 5G technology will become increasingly essential.

5G is an ecosystem enabled by the three use cases. The march toward 5G continues what has been a natural progression of cellular technology innovation dating back to the early 1980s. But the economic impact stuffed into the promise of 5G is making this evolution the most significant. 5G is different from all “G” predecessors in a lot of ways. 5G is not simply a network, but rather an ecosystem that supports vertical applications and industries, enabled by the three use cases: eMBB (Enhanced Mobile Broadband), URLLC/uMTC (Ultra-reliable Low-latency Communication/ultra-reliable Machine-Type Communication), and mMTC (massive Machine-Type Communication" (mMTC). 

5G speed is data transmission in real time. The high-frequency bands, known as millimeter wave, don't travel very far - only a few city blocks from cell sites, in many cases - but they can carry a huge amount of data. Downloads in the bands available can approach 2 gigabits-per second, fast enough to download an entire movie almost instantaneously. The 5G era will bring unprecedented and transformative opportunities across industries. 

Please refer to "5G and Beyond Mobile Wireless Technology" for more details.

[More to come ...]



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