Telecommunications Design & Analysis

September, 2001

On September 11th the World Trade Center, the most telecommunications intensive area in the entire world, was attacked. Four Verizon switches at West Street, a block from the World Trade Center, were severely damaged by dust blowing in through broken windows and steel beams from the collapsed towers next door. Flooding destroyed back-up power. In addition, ten Verizon Wireless cellular towers in the area were made inoperable because cable connecting cellular and landline networks had been routed through the World Trade Center. Of these ten antennas, two on-building ones were destroyed.

How is landline service being re-established?

Verizon hired 1600 contract workers to clean, rewire and repair the West Street systems. However, intermittent building evacuations slowed work until the first Sunday after the attack. Another 1500 workers were contracted to run new cabling to customers as much of the old outside cabling is buried under 30 to 40 feet of rubble. By seven days after the disaster, two million of the three million data circuits lost were restored.

How was New York Stock Exchange service restored in just six days?

Only 20% of the Verizon service was routed through West Street. It is now routed through other equipment in the Verizon network.

How was cellular service restored?

Verizon Wireless deployed COWs (cellular on wheels) portable antennas with associated electronics. The COWs were connected to cellular central offices and the landline network by a combination of microwave and new cabling. By Thursday, seven had been placed in northern New Jersey and lower Manhattan with nine more by a week after the disaster.

Why was restoration of cellular service faster than that of landline networks?

Two reasons, primarily because no cellular switching equipment was destroyed. The switches at the West Street facility serve huge areas of lower Manhattan, which still do not have fully restored lines.

Secondly, cellular service depends on far fewer physical connections. Each cellular tower and the electronics associated with it merely require a cable back to the mobile switch. With landline service, cabling is necessary to each customer.

Were networks able to keep up with the double the normal call volumes?

Verizon Wireless stated that 6% to 9% of calls were blocked nationwide with blockage higher in New York. Cellular service in NYC did not work from some carriers on September 11th.

What issues were demonstrated?

Countries depend on telecommunications in emergencies. All locations housing large amounts of cellular, Internet and landline facilities need to have back-up plans developed in case they are destroyed. The following are some questions about survivability.

• Do we have diverse routing on cabling connecting us to central offices and key facilities?
• Do we have the capability to re-route calls if service is disrupted?
• If cellular service is a key ingredient in a national emergency should issues such as capacity, back-up and diverse routing be looked at by the federal government?
• Are there sites (large directories or centers where many networks exchange traffic) in the Internet that if they were destroyed would cause the Internet to not function?

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