An overview of broad-band access technologies

Abstract

The provision of broad-band services based on either the Internet or the asynchronous transfer mode (ATM) technique requires a new generation of access networks. In the short term, solutions such as x-digital subscriber line (DSL) and hybrid fiber coaxial (HFC), allowing the reuse of existing infrastructures, look very promising. For the longer term, new infrastructures based either on radio or on optical access links seem preferable. Three x-DSL techniques aiming at high-bit-rate transmission over twisted pairs are presented: high-bit-rate DSL, asymmetrical DSL, and very-high-bit-rate DSL. An extension of existing cable television networks known as HFC is also described. Two other prospective approaches, wireless in the loop (WITL) and fiber in the loop (FITL), are then presented. Several techniques are considered for WITL: digital enhanced cordless telecommunication, local multipoint distribution service, wireless ATM, and low earth orbit satellite constellations. The various architectural alternatives for the FITL approach are discussed, a special interest being dedicated to the synchronous digital hierarchy self-healing loop and the ATM over passive optical network. In our presentation, we mention the main experiments and the standardization activities inherent to the domain.

Introduction to WLL: Digital Service Technologies

“…In practice that seems somewhat optimistic, and it might be expected that a cluster size of 2 would be more realistic. 22 …”

“…Otherwise, if the requested data rate is lower than 32 kbps, several FSUs can share a 32 kbps channel by skipping time slots. DECT offers toll quality digital speech and voiceband modem transparency either via a 32 kbps ADPCM codec (ITU-T G.726) or as a 64 kbps PCM (ITU-T G.711) bearer service [22]. DECT provides up to 504 Kbps full duplex data transfer and of course BRA ISDN [23].…”

ICT Diffusion in Developing Countries

“…The advantages of shifting from fixed narrowband to wireless broadband is easily identifiable in remote, isolated and rural regions, as they are better suited for rough physical conditions and cost-effective solutions for low-income people (Gagnaire 1997;. If no fixed infrastructure is available, to enhance growth in the Internet network coverage and usage, assuring the ubiquitous access to wireless broadband networks is considered an important target to be achieved .…”

Current and future services using wireless local loop (WLL) systems

“…To use DECT in WLL applications, one of the most important problems to be solved is to extend the maximum coverage of a "xed part (i.e. As of 1997, DECT provides 480 kbps full duplex data transfer and basic ISDN access [1]. A solution is to use directional antennas, by which the maximum diameter of a cell can be extended up to several kilometers.…”