Marilyn A. Bosito                                    07/22/08                                   OOA

SYANAL       

Mr. Pajo

Book: System Analysis and Design with Modern Methods

Author: Len Fertuck

Reference: LRC Extension (QA 402 F471995)

Book Review # 8

Chapter 5

“A computer terminal is not some clunky old television with a typewriter in front of it. It is an interface where the mind and body can connect with the universe and move bits of it about.”

 Douglas Adams quotes (British comic Writer, 1952-2001)

 This   Chapter introduces basic facts on the DSL family: ISDN, T1, E1, HDSL, ADSL, VDSL, HDSL2, and SDSL. Then it describes the history of multicarrier modulation and its major applications, it also describes ADSL network architecture, protocols, and equipment. This chapter analyzes ADSL deployment from the perspective of network architecture. It also describes the implementation aspects of ADSL systems, which use DMT transmission. This chapter is an excellent source for an ADSL modem design engineer to understand and look up all the important components of the transmitter and receiver. The author himself has extensive experience in designing ADSL modems; the materials covered here are most relevant to practical implementations. Chapter 9 discusses how to ensure that ADSL systems coexist with legacy services, such as voiceband services and ISDN.

DSL is a telephone loop technology that uses existing copper phones lines, and provides a dedicated, high speed Internet connection. One of the big advantages of some DSLs (notably ADSL), are that they can co-exist on the same line with a traditional voice service such as "POTS" (Plain Old Telephone Service), and even ISDN. This is accomplished by utilizing different frequency ranges above the voice range (voice is up to 4KHz). Essentially, this gives two lines in one: one for voice, and one for Internet connectivity. When all is working normally, there should be no interference between the two "lines". This gives DSL a potentially broad consumer base, and helps minimize costs for service providers.

Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over coppertelephone lines than a conventional voicebandmodem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter - or microfilter - allows a single telephone connection to be used for both ADSL service and voice calls at the same time.

VDSL or VHDSL (Very High Speed DSL) is a DSL technology providing faster data transmission over a single twisted pair of copper wires. These fast speeds mean that VDSL is capable of supporting new high bandwidth applications such as HDTV, as well as telephone services (Voice over IP) and general Internet access, over a single connection. VDSL is deployed over existing wiring used for POTS (Plain Old Telephone System) and lower-speed DSL connections.

Integrated Services Digital Network or Isolated Subscriber Digital Network (ISDN), originally "Integriertes Sprach- und Datennetz" (German for "Integrated Speech and Data Net"), is a conceptual view of the network to user interface of the telephone system. In the 1980's the phone system was viewed as a way to transport voice, with some special services available for data. The key features of this network are that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of ISDN defined: Basic Rate ISDN (BRI), Primary Rate ISDN (PRI) and Broadband-ISDN (B-ISDN).

ISDN is a circuit-switchedtelephonenetwork system, designed to allow digitaltransmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. It offers circuit-switched connections (for either voice or data) in increments of 64 kbit/s. Another major use case is Internet access, where ISDN typically provides a maximum of 128 kbit/s in both upstream and downstream directions(which can be considered to be broadband speed, since it exceeds the narrowband speeds of standard analog 56k telephone lines). ISDN channels may use BONDING to achieve a greater data rate, typically 3 or 4 BRIs (6 to 8 64Kbps channels) are BONDed.

      VDSL uses much wider bandwidth than ADSL to offer up to 26 Mb/s symmetric and/or asymmetric data rate. Chapter 10 describes the requirements and implementation of VDSL systems. The author compares various techniques and standard contributions proposed during the evolution of the VDSL standard, and expresses some interesting views on the VDSL standardization process.

      The last part describes many open issues and further improvements in DSL systems. This chapter is useful for modem designers to improve system performance.