Integrated Access Devices Expand Service Offerings over Existing TDM Infrastructure

Worldwide deregulation has significantly increased the competition among telecom service providers. Emerging alternative operators, as well as incumbent carriers, are looking for service strategies to increase their competitiveness, generate new revenue streams and reduce the cost of network ownership. The growing percentage of data traffic in public networks and the decreasing revenues from voice services add an additional incentive for traditional voice service providers to offer data services as well.

The Integrated Access Device (IAD) fulfills those needs in the Local Loop. By supporting voice and data services over a single E1/T1 access line, the IAD maximizes utilization of infrastructure investments. It opens the way for traditional voice carriers to add Internet access and data services, and for traditional data services and Internet access providers to add voice services, over existing access lines.

Integrated access can be provided using various technologies: ATM, Frame Relay, IP or TDM. Even though it is considered a legacy technology, TDM still proves to be the most cost-effective technology in the Local Loop, in terms of total ownership cost (equipment, installation and maintenance).

The TDM IAD provides voice and data connectivity over E1 or T1 facilities. PBX connectivity is provided through a digital E1/T1 link or through analog voice ports. Analog phones may also be connected directly to the IAD, either as ordinary POTS/Centrex phones or as remote extensions of a central site PBX. IADs may also provide ISDN connectivity for ISDN PBXs, phones, fax machines or video-conferencing systems. Data connectivity is provided either transparently through serial n x 56/64 kbps data ports or through a LAN port of an integrated router.

Standard E1/T1 frames divide the bandwidth into timeslots - 24 for T1 and 30 for E1. The IAD integrates several types of traffic by assigning each type to certain timeslots. The integrated E1/T1 link is routed through a digital cross connect (DACS) residing in the service provider's point-of-presence (POP). The DACS separates the different types of traffic and routes them to the appropriate backbone network - PSTN, Frame Relay or Internet - as shown in the illustration that follows.

Technology enthusiasts who know that TDM technology is mature and has been around for some time look at ATM or IP technologies as its successors. Though this may be true some time in the future, TDM is currently the most prevalent Local Loop technology, and the number of TDM-based installations is still growing (25% annual growth rate in the U.S., according to Dataquest).
There are several reasons for TDM to remain the technology of choice in the Local Loop:

- Bandwidth is becoming cheaper and more readily available, rendering various methods aimed at increasing bandwidth utilization (such as packetized voice or voice compression) less critical.

- Low cost of TDM equipment

- Ease of installation and maintenance

- Unsurpassed voice quality

- Maturity of technology and solutions

- Standards-based, with multi-vendor compatibility

- Low and constant delay

It is interesting to note that TDM integrated access is still attractive enough to draw several U.S. start-up companies to base their product portfolio on such technology.

Provisioning voice and data services on a single access line using an IAD offers service providers significant benefits:

- Higher return on infrastructure investments

- Shorter payback period

- Unified management and control of all services

- Added data services over existing access lines previously used for voice only, without any additional investment in infrastructure

- Managed router service earns additional returns on investment

- Increased customer loyalty through service bundling. A competitor has to offer a superior package to attract customers, and cannot win customers on the basis of cheaper voice or cheaper Internet access fees alone.

When data revenues are taken into account, E1/T1 links can be justified even for smaller businesses, which require a limited number of voice channels. Considering the large number of small business, the same service can cover a much larger target market.

RAD offers a wide range of TDM-based IAD products. The latest offering from RAD serving this market is the FCD-IP family, which provides a flexible and cost-effective solution to the specific requirements of this market:

- Copper or fiber E1/T1 network interface

- Integrated CSU/DSU or LTU

- Internal IP/IPX router with advanced Internet access support (NAT, Single IP and Solid Firewall(tm)) over Frame Relay or PPP

- One or two Ethernet ports

- A variety of voice interfaces - E1/T1 for digital PBX connectivity or up to 12 analog voice interfaces (FXS, FXO or E&M) for connecting an analog PBX or telephones

- Fail-safe bypass ensures uninterrupted voice service in the event of power failure

- Integrated ISDN backup

- Optional transparent data port (n x 56/64 kbps)

- Remote SNMP management, in-band and out-of-band

- HP OpenView- and PC-based central management system