photo by Nate (n8foo : flickr)
Like many New Yorkers I can remember where I was on 9/11 and even during the first World Trade Center bombing. I can remember getting a call from my wife during that first bombing, she was in 5 world trade and felt the tremor. I often wonder how our communications network would bear up under a real crisis, such as a series of hurricanes or some other larger terrorist event.
During 9/11 many people couldn’t get through to their loved ones because of the strain being put on the network by everyone calling at the same time, the system simply couldn’t take it. In Louisiana during Katrina the transformers that powered the cell networks were under water and many of the networks were down. What I would like to do is look at two types of communication networks and how they might hold up under emergency situations.
The first is the SMS network through mobile handsets and the second is the amateur radio network through volunteer emergency workers. During a natural or “man-made” event communications networks either go down due to some damage to the infrastructure or are so completely overwhelmed by panic that they are rendered useless. The overarching need during these times is a channel for emergency communications, “health and welfare” traffic to affect rescues, dispatch medical help, or communicate evacuation orders.
The SMS network has the distinct advantage of being ubiquitous as a type of messaging, many people can communicate because of the relative small size of data that travels across the cellular network avoids the bottlenecks associated with voice communications. During 9/11 there were reports of people using blackberrys to send messages to loved ones, aside from their small size the way in which these messages were also able to negotiate for bandwidth affected their successful delivery. The term “Store and Forward” means that the messages can wait to be delivered when the network is ready, acting as a sort of buffer. The last technical reason that the SMS went through was the fact that it sends the data through something called the “control channel”, a separate channel from voice traffic. The main advantage when it works is also the ubiquity of handsets, effectively linking most everyone in the affected area which emergency personnel.
Amateur Radio Volunteers often go into action during disasters and provide communications when other networks are failing. The fact that these radio networks can get up and running so quickly is a testament to the state of readiness that some of these enthusiasts keep their equipment in. Where the cell SMS doesn’t have to compete with other kinds of traffic on the cell network, the amateur radio has readily available bandwidth because of the many frequencies and relative limited number of operators. During a typical disaster situation a group of volunteers can set up many radios in tandem, using a kind of mobile radio function called “repeaters” from a vehicle equipped with a mobile radio and a generator. The mobile radio with the repeater function can receive on one frequency and transmit that message out on a different frequency, allowing a message to pass through one operator to the next and extend the range of the message beyond the normal transmitting range of the hardware.
There are plans in the works for a portable SMS network that would work with the same flexibility as amateur radio networks by broadcasting from a helicopter during a disaster sending information and routing messages back to an unaffected area with a running network, in theory acting as its own portable cell on a cellular network.
This points out a major example of the strength of the amateur radio network. In the collection of radios that make up the network any one radio can shift from being a simple node to a control operator whenever it is needed. The network is not dependent on a central controller. Each radio mobile radio that can act as a repeater sets up its own network with its’ own power supply.
Routing calls in SMS networks is obviously automatic and during periods when there is some cellular capability preferable to amateur radio. Obviously you can’t call your aunt Betty in the next state on a radio directly, in amateur radio there is something called an “autopatch” that interfaces a radio into the phone network but this kind of setup is frankly more the exception than the norm.
The average mobile radio in a car can reach 50 miles, extend that with repeaters and the reach is without practical limit with the exception of oceans. Also, the amateur radio enthusiast is mobile and can extend the network wherever it is needed, changing the shape of the network to respond to the site and location of the emergency. Cellular towers are not mobile so the challenge for cell coverage would be where it is already down. The paradox is that in areas were it is hardest hit and communication most needed the towers would be down and repair long coming.
Communications protocol in Amateur radio is managed by agreement of the human operators to abide by FCC regulations and long standing practices. During times of emergency, regular radio traffic is suspended or curtailed and a “net control” operator is in charge of routing important messages from station to station. The term “station” is simply a licensed amateur operator with his equipment. This intelligent (albeit slow) method has the advantage of allowing the net-control operator to make judgments as to what messages are important. The order of priority is structured in 4 tiers; Emergency: messages having to due with life or death, Welfare: Messages of an official nature, Welfare and Routine. A cellular network, voice or SMS doesn’t have any way of weighing the importance of messages in this way.
The network of cellular providers are often a patchwork of different standards, but fortunately they all do SMS pretty much the same way. This offers some hope that in times of emergency we can look forward to limited cellular messages to get help to those who need it.
Amateur radio networks have the advantage of interfacing with many other channels of communication. Most mobile radio equipment and even hand held “talkies” can transmit on several different bands. Also they have wide receive capabilities to get news and official dispatches from the state police, national guard, air rescue and many other military and civilian organizations that monitor and use bands set aside by the FCC.
The key to the success of both these methods is due to their limited use in two areas. In cellular SMS the network that is affected still may carry emergency communications because of low bandwidth requirements.
In amateur radio communications the small population of licensed operators keeps the number of nodes small, but very motivated, mobile and flexible as to the methods to communicate in response to needs in an emergency. Virtually every technical way to transmit voice and data over the airwaves has been tried at some point and many enthusiasts have extensive communications knowledge.
On the 23rd of this month the FCC dropped the Morse code requirement in licensing for entry into much of the amateur radio spectrum. The lowering of this barrier might help to keep an otherwise marginalized hobby alive and along with it a flexible communications channel during emergencies.
One can also hope that the FCC might be forward looking to including a separate communications capability in mobile handsets to allow for communicating in some sort of mesh network in the VHF or UHF bands. Obviously more work can be done on this idea, what needs to be thought of are intelligent nodes that can operate independently from network and power infrastructures.