From Voice over 802.11

As explained earlier in this book, a telephone network is comprised of three elements: access, switching, and transport. This chapter will introduce the reader to switching both for legacy TDM technologies and for VoIP. Vo802.11 replaces PSTN Class 4 and Class 5 switches with softswitch platforms. This potentially spares an enterprise high fees for Centrex services. In addition, a service provider utilizing softswitch technologies need not purchase multimillion-dollar Class 4 or Class 5 switches. In bypassing Class 4 and Class 5 switches, a Vo802.11 service provider can greatly lower the barriers to entry to the telecommunications market.

TDM Switching

To fully understand VoIP switching and subsequently Vo802.11, we must first understand the physics of voice switching. Much of this technology has evolved during the century of telephony. Many aspects of TDM voice technology have been incorporated by VoIP.


The earliest approach to enabling multiple conversations over one circuit was frequency-division multiplexing (FDM). FDM was made possible by the vacuum tube, in which the range of frequencies was divided into parcels that were distributed among subscribers. In the first FDM architectures, the overall system bandwidth was 96 kHz. This 96 kHz could be divided among a number of subscribers into, for example, 5 kHz per subscriber, meaning almost 20 subscribers could use this circuit.

FDM, however, is an analog technology and suffers from a number of shortcomings. It is susceptible to picking up noise along the transmission path. This FDM signal loses its power over the length of the...

Products & Services
Optical Line Terminals
Optical Line Terminals serve as service provider endpoints of a passive optical network by converting between electrical (voice, data, video, etc.) and fiber optic signals while also coordinating multiplexing between the two.
Packet Switching Chips
Packet switching chips are communication integrated circuits (ICs) used in packet-switched networks to rout packets between network nodes.
Time Division Multiplexers (TDM)
Time division multiplexers (TDM) share transmission time on the information channel among many data sources.
IC Analog Multiplexers
Analog multiplexers have sets of switches that connect several analog inputs to a common analog output, allowing a single analog-to-digital converter (ADC) to sample data from multiple inputs.
Q-switches are devices used in the optical resonator of a laser to prevent lasing action until a high level of inversion is achieved in the lasing medium.

Topics of Interest

To properly analyze the prospects for the use of Vo802.11 (given the variants of 802.11, this book will refer to 802.11 and not specify the many variants), it is necessary to categorize where...

Overview Imagine installing a Vo802.11 application in your corporate WLAN. How does the caller get voice mail, call forwarding, conferencing, three-way calling, last call returned, and other calling...

The purpose of this book is to overcome objections to using 802.11 as a means of transmitting voice over the Internet Protocol. First, this book sets forth the thesis that Vo802.11 can replace the...

A Previous Example of Disruptive Technology in the Long-Distance Industry The converging market demands greater flexibility in switching equipment. In order to take advantage of market opportunities,...

The greatest test 802.11 will have to face when being compared to the Public Switched Telephone Network (PSTN) is its capability to transmit voice with the clarity of the PSTN. The immediate...