Utility Networks in Transition from TDM to IP Not if but When

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Most commercial enterprises have standardized their networks on Internet Protocol, but utilities have more factors to consider when transitioning network technologies. The investments they have made in time-division multiplexing (TDM) infrastructure over decades rival the investments of all but the telcos themselves, and preserving these investments as long as possible makes good business sense.

This won't be the case much longer. The pressure to support energy initiatives such as smart grid and other new Internet Protocol-based applications that will streamline operations and boost profit is driving utilities to migrate their circuit-switched TDM infrastructures to Internet Protocol. How will these networks evolve, and what factors will ease the transition?

A New Network IQ

To improve operations and reduce costs, utilities will need highly intelligent networks that efficiently manage available bandwidth and optimize its use for applications such as supervisory control and data acquisition (SCADA), Internet Protocol-based mobile radio, video surveillance, Voice over Internet Protocol (VoIP) and collaboration tools.

Many utilities are investing in Internet Protocol networks in parallel with the continued operation and maintenance of their legacy TDM networks. The likely scenario is that during the next five years, utilities will make significant investments in Internet Protocol, but not at the expense of their existing circuit-switched networks. During this transitional phase, utilities must invest in technology that supports native TDM-based traffic and native Ethernet and Internet Protocol-based data from intelligent electronic devices, such as the type that will be used in smart grid implementations. This will allow utilities to better manage the real-time smart grid traffic load in addition to other critical data traveling over legacy systems, such as SCADA traffic.

Internet Protocol has evolved as the technology of choice for high-speed data networks, is well-understood and widely deployed in both local-area network (LAN) and wide-area network (WAN) environments and has shown it can adapt to new requirements. A packet-based network can efficiently and reliably handle massive amounts of two-way data communications between machines and automated systems, making it the logical choice for the smart grid, a system that promises to manage the electricity distribution better nationwide. Improved reliability, more predictable demands on power transmission, new products and services and environmentally friendly energy generation are the catalysts driving smart grid adoption. Electric utilities are dealing with integrating Internet Protocol network infrastructure to handle the transition.

More Capacity Back to the Core

With additional data loads, utility core networks will need more capacity. For every utility, this means a gradual build out of new core networks based on Internet Protocol's running in parallel with preserved TDM infrastructure. Eventually, these new core Internet Protocol rings will displace their TDM counterparts, but this hybrid architecture will ensure that increased Internet Protocol loads will not affect TDM but will deliver more predictable traffic loads and service-level agreements.

Complementing this transition in the core network will be a mix of wireless and fiber networking technologies deployed in the middle mile to support the access network for end points such as smart meters. Here, it all comes down to cost. In some instances, it makes sense for utilities to partner with mobile carriers or wireless broadband providers to aggregate smart meter traffic back to an Internet Protocol core. In other instances, utilities might deploy their own fiber-optic cables if time, money and rights of way issues allow. Finally, a promising new scenario that could defer the costs of deploying and managing middle mile networks is one in which utilities negotiate agreements with broadband cable and DSL providers for offloading smart meter traffic onto consumers' home Internet connections. Let smart meter traffic ride "over the top" of home broadband connections, right back to an Internet Protocol core.

Access, Capex and Opex in the middle mile then become the biggest challenge. In areas where terrestrial network access or network partnerships are not available, microwave offers a compelling solution. For years, microwave has been the preferred technology to transport data gathered from distributed utility monitoring and control points. Given the dramatic increase in smart grid traffic volume, existing backhaul infrastructures must change, and middle mile infrastructures, similar to the edge and the core of the network, should deliver significant Ethernet capacity while simultaneously supporting utilities' existing TDM infrastructures.

Future Topologies

The development of Internet Protocol networks provides an answer to how utilities initially will handle the type and volume of traffic smart grid will generate, but smart grid promises to change the development and capabilities of their networks for many years. Consider this: Many utilities are requesting microwave links with capacities in the 500 Mbps to 1 Gbps range to handle bandwidth-intensive traffic and to monitor additional substations throughout their coverage areas. They also are implementing point-to-multipoint installations to cost-effectively monitor more devices. Some utilities even have deployed LTE networks. These new network capabilities will allow utilities to offer advanced services and applications such as private access networks for mobile work forces, corporate LANs, and even wireless Internet service provider (ISP) services throughout their coverage areas.

Utilities can consider several network deployment alternatives to upgrade their networks:

  • Deploy an all Internet Protocol-based network and carry legacy TDM data using circuit emulation. This option results in initial complexity and additional time to transition TDM service and often is not seamless. Other issues include latency and loss of capacity (overhead).
  • Deploy a Multiprotocol Label Switching (MPLS)-based network. In most cases, MPLS is considered overkill for utilities' networks. It can solve many issues, but MPLS is highly complex, and additional Capex and Opex costs can be prohibitive. For example, to manage MPLS-converged services on an end-to-end basis, MPLS-capable devices are required at the access and edge of the network (in addition to metro and core), greatly increasing capital costs. In addition, planning, managing and monitoring an MPLS-based network requires an MPLS-trained technical staff using fairly sophisticated management tools, thereby increasing operating expenses.
  • Deploy a hybrid TDM/Internet Protocol network. The most likely solution for most utilities is to integrate Internet Protocol into existing TDM infrastructure to create hybrid TDM/Internet Protocol networks. Transitioning devices from TDM to Internet Protocol will be gradual—and also must be seamless—which makes the hybrid approach simple, cost-effective and future proof.

The challenge for utilities is to preserve the best of the TDM past while transitioning to an Internet Protocol future. Now, it's no longer a question of why move to Internet Protocol, but rather, how soon?

Jeremy Vincent is the field marketing director of Exalt Communications Inc.

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