by Eric Kammerer | 2003-11-25 03:00:00-07
Solo. All by yourself. Middle of nowhere. 30 miles from the nearest road. Sounds great, doesn’t it? But, what if something goes wrong? What if you’re injured? What if a storm destroys your tent, or lightning starts a fire nearby? How will you get help?
Modern wireless communications might be the answer. But, what kind of coverage and service can you expect? What can you do to maximize your cell phone’s effectiveness in the wilderness? What are the weight/performance trade-offs? This article should give you a better feel for the answers to those questions, and help you decide if a cell phone is worth carrying.
The cellular system concept is simple. When you make or receive a call, your cellular phone communicates with a cell-site somewhere in the area. That cell-site connects to equipment at a central location that in turn connects to the regular telephone network. As you move around, the cellular system figures out which cell-site is best suited to handle your call. All of this is, or should be, transparent to you and the other party on the call. The system provides a service that works just like a regular telephone — only better.
Basic Radio Facts
Mobile phones operate on a specific range of radio frequencies. Why do frequencies matter? The answer requires a quick review of high school physics. First, all radio waves travel at the same speed — the speed of light. Frequency is measured in cycles per second — a measure of the number of complete waves transmitted in one second. Since the speed is constant, increasing frequency decreases the wavelength and decreasing frequency increases the wavelength.
Antenna length is a direct function of wavelength. Longer wavelengths require longer antennas. Shorter antennas mean shorter and hopefully lighter cell phones. That is not the whole story, however. Unfortunately, higher frequency signals attenuate more rapidly — a fancy way of saying they don’t travel as far. That requires either more cell-sites, or more power from the cell phone transmitter.
Analog and Digital
Frequency is also an indicator of the type of service available. The FCC grants licenses to carriers for specific services on specific frequencies. Cellular and PCS services are essentially the same, only in different frequency bands. A national carrier may actually have a cellular license in one area and a PCS license in another area. The older analog technology is only available from one of the two cellular carriers in any given area. Push-to-talk two-way radio service (no dialing required) is only available from an SMR (Specialized Mobile Radio) carrier. Digital services are available from all three types of carriers — but not all cellular carriers offer digital service.
There are four major types of digital service in the United States, and none are compatible. TDMA is the oldest system, used primarily by AT&T Wireless. AT&T Wireless has also created a GSM network. GSM is popular in Europe and used by several PCS carriers here. The SMR carrier Nextel uses iDEN®. Verizon Wireless, Sprint PCS, and other PCS carriers use CDMA. Due to industry consolidation (mergers), some carriers have portions of their digital network that are incompatible with other portions. All digital services require significantly less power than analog services and generally offer better overall voice quality, as well as longer battery life.
Analog service is the same everywhere. Although there are two frequency bands (“A” and “B”) for the two cellular carriers, the phones are capable of working on both bands. Some phones, sold primarily by carriers with both cellular and PCS licenses, are capable of working at both cellular and PCS frequencies. They will provide digital services in both bands, and may work with analog service. An FCC ruling will allow carriers to discontinue analog service in about four years.
If you’re a California resident planning a hike on the Appalachian Trail, you don’t have to call an East Coast company to get wireless service. Several carriers are truly nationwide and may have a license where you’re going. Even if your service provider doesn’t have a license, it may have a roaming agreement with a carrier that does have the license. Check with your service provider to see what’s available.
If your service provider doesn’t have a roaming agreement where you’re going, you may still be able to make a call. Most carriers offer “credit card roaming” for this situation (Editor’s Note: due to inherent insecurities in wireless cellular networks, there may be some risk in transmitting sensitive information such as credit card numbers). Dial a number, and you’ll be directed to a service that will ask for a credit card number before connecting your call. Check the rates before you decide to continue, or you may be very surprised at the bill. This only works if the technology used by your cell phone and the local service provider are identical. A GSM phone won’t work on a CDMA network.
A much bigger question is whether you’ll actually have coverage. In other words, are there any cell-sites handling the area where you want to backpack? The answer, of course, is — maybe.
Wireless carriers are in business to make money. They make more money where there are more people to make calls. Their natural preference is to cover populated areas first, and less populated areas later. Cell-sites are expensive, requiring hundreds of thousands of dollars to build, and still more dollars to operate and maintain.
A cell-site in a remote area may not generate enough revenue to pay operating costs. Most people making calls with that cell-site are just passing through on a nearby highway. Very few of them will go off the highway to any appreciable degree. The financial incentives for the carrier to build anything beyond decent highway coverage are weak at best.
Since radio transmission is a line of sight proposition, carriers build rural cell-sites where they can cover a large amount of territory. If you’re in a valley one ridge away from the only nearby cell-site, you may as well not have a phone. Climb the ridge and your service should be great. The more rugged the territory, the more this happens.
Even if the terrain permits line of sight transmission, nature may not. Trees do a very good job of absorbing radio waves. Heavily forested areas are very difficult to cover well. Reception may improve in the winter when the leaves have dropped. You may have to emulate GPS users and move to a meadow or clearing to get a good signal.
Combine market realities with geographic limitations, and you can see why the FCC rates rural coverage from both PCS and Cellular as “Poor.” The FCC doesn’t specifically discuss the quality of SMR coverage. However, SMR is primarily aimed at commercial dispatch users who have even less reason to go into the backcountry than most wireless users. The coverage maps for SMR carriers reflect that marketing emphasis.
The "Maintenance Window"
As you can probably imagine, most people use their cell phone during the day. Usage starts to ramp-up in the early morning, climbs as the morning progresses, levels off a bit at lunch, and then climbs to a late afternoon peak. It then tapers to a minimum level sometime in the very early morning. Naturally, service providers prefer to do any service-affecting work during the wee hours when few people are using the system. That time is called the “maintenance window.”
A midnight-to-five maintenance window isn’t likely to affect most backpackers. However, not all service-affecting work can get done during that time. Larger projects are usually completed during the other portion of the maintenance window — the weekend. If you’re an employed backpacker, a large portion of your hiking time is probably during a weekend.
On any given weekend, chances are good that somewhere in a wireless system, some site is off the air for an extended time. The odds of it being the site you need to use are small, but still present. Carriers don’t like this anymore than you do; they can’t generate revenue if people can’t call. A “planned service outage” is still an outage.
So, what can you do? Nothing, really. The carrier is unlikely to tell you to expect such an event. The service contract probably explicitly allows it, and the disclaimer on the coverage map will certainly cover the possibility. It will probably never affect you — just don’t count on it not happening.
You might consider some alternative technologies. The most likely options are Citizen’s Band (CB) Radio, Amateur (HAM) Radio, General Mobile Radio Service (GMRS) and Globalstar.
CB Radio is a short-range push-to-talk service. The portable handsets are heavy, and not very good without a 9-foot-long external antenna. People do monitor the emergency channel, but barring unusual atmospheric conditions you still need line-of-sight to get to them . It’s nowhere near as popular as it used to be, so there are fewer people listening who might help you. I don’t recommend it for lightweight backpacking. (Editor’s Note: Another push-to-talk technology that is gaining popularity to maintain communications within a two-mile line-of-sight distance among members of a party is FRS (Family Radio Service), made popular by the Motorola TalkAbout series radios. FRS technology is moving rapidly, with some FRS radios approaching the 4-oz per handset range, and coming with an ever-increasing number of features useful to outdoorsmen, including compasses, altimeters, and GPS).
Amateur Radio is much more interesting. It can reach for miles (in a straight line). A lot of people are very serious about monitoring it. You can get news from all over the world. You can get fairly light ham equipment. Although I’ve seen some portables weighing around six ounces, the more powerful ones weigh in the 8-15 ounce range. The biggest catch is that you need to get an FCC license to operate it. If you’re willing to study for the license, amateur radio may be a good solution for you.
GMRS is somewhat of a cross between Citizen’s Band and amateur radio. According to the FCC, the normal range for a GMRS mobile is five to twenty-five miles. However, that range is more typical of a fixed base station, not a portable unit. In urban areas, many of the same people that monitor the CB emergency channel also monitor GMRS. You do need to pay a fee to get a license, but you don’t need to take a test. GMRS portables cost several hundred dollars and weigh about the same as ham radio portables.
Globalstar is a system that uses satellites to provide comprehensive coverage. Globalstar does not cover the North or South Pole. It does cover just about everything else. It really does offer complete coverage in North America. You will pay dearly for that coverage though. Not only is it expensive to use, the handsets are expensive to buy, bulky and heavy (Editor’s Note: the average Globalstar handset still weighs about 12 oz). They resemble the cellular phones of ten years ago, but with a much bigger and fatter antenna. If you absolutely have to be able to call, no matter what, this is for you.
Editor’s Note: Technology will likely evolve in the direction of hybrid devices that support a variety of wireless communications technologies. Examples of this technology include location-reporting cellular phones, cellular/two-way handsets, and radio/GPS combination radios. SAR volunteers tell us that one ideal combination of wireless communication includes two devices – a five-watt two way radio to maintain communication among the entire party, and a cellular phone for use when the radios don’t work. I suspect that a four ounce device capable of cellular, satellite, and two-way communications, with a functional GPS display, weather station, and personal locator beacon, is not far away.
If you’re still interested in carrying a cell phone into the wilderness, you should consider some basic things. You need to choose the service provider and then the specific model of phone. You need to do some preparation before you travel, figure out the right way to pack the phone, and know how to use it in an emergency.
The first step in choosing a service provider is determining who has coverage where you’re going. Most service provider websites will have a coverage map that gives the approximate coverage for their system. They will probably also give you the address of the store nearest the area you’re interested in. Employees that live or work close to where you’re going will give you a much more reliable answer than those who live closer to your home. If there are no company stores, try to find an authorized agent. Even better, find several such sources.
If you’re not sure who has coverage, start with the cellular carriers. They have had more time to build out their networks. You can also check one or more of the comparison services on the Internet. They provide the ability to compare pricing from multiple carriers. Use more than one: I’ve found that any single service may not list all of your options — or even all of the service providers.
Once you’ve chosen a service provider, choose a phone. Since this is for emergency use, you don’t need fancy features. You do want lightweight. In general, smaller phones are lighter and more expensive. Some tips:
Before you go anywhere with the phone, learn to use it. If it’s a cellular phone, learn how to switch from the “A” system to the “B” system and back (or vice versa). Learn how to force a call into analog if it has that capability. Experiment with every feature in the manual. Like any other piece of gear, it’s only as good as you know how to make it.
When you pack the phone, keep a few things in mind. Water, extreme cold, and extreme shocks are all bad for cell phones. Pack it somewhere that is protected from all of the above. Turn it off before you pack it. Take advantage of any battery saving feature you can think of. Turn off vibrating ringers. Turn off service beeps or flashing lights. Minimize the keypad lighting interval. You’re packing this for emergencies, so you want it to work as long as possible.
If you do need to use it for an emergency, you’ll hopefully have service. If not, try forcing the call to analog. Still no luck — try to use another carrier’s system. If you still can’t call, start looking for high places. Climb the ridge, climb a tree, move into a meadow. Try all the things you tried initially. Make sure you have fully extended the antenna and try again. If you still can’t get through, self-reliance is the name of the game.
If you are able to make a call, you may still have a problem. You need to know where you are for people to help you. 911 operators are used to dealing with highway locations, not so used to dealing with clearings in a forest. Sounds obvious, but if your map skills aren’t that great, well… (Editor’s Note: The combination of a GPS unit and a cellular (or satellite) telephone can be a tremendous asset to SAR personnel. However, even without a GPS, your ability to read a map and communicate, for example, a quad name and your approximate UTM or lat/lon coordinates can expedite a rescue.)
Once you’ve made contact, consider scheduling times for future contacts and shutting the phone off in the meantime. This is especially important if you’re making an analog call on a small battery. In that situation, you only have a few hours of standby time, let alone talk time. The available time will shrink considerably if you’re in a limited coverage area requiring more power even in a standby mode.
In spite of the limitations, I’ve been able to call in a new forest-fire report with my cell phone faster than the ranger standing next to me could get through with his two-way radio. The system does work; you just have to work within its capabilities.
Wireless Service Providers:
Eric Kammerer has been an avid backpacker since 1974. He first used tarps in a 1978 Outward Bound course and started backpacking in tennis shoes somewhere in the early 1980's. He also remembers carrying an 80+ pound backpack - and won't do it again. Eric is a Senior Network Engineer for a major wireless carrier, where he is responsible for the design of switching elements and facilities for portions of two western states.
"Wireless in the Wilderness: An Overview of Communications Technologies for Backpackers," by Eric Kammerer. BackpackingLight.com (ISSN 1537-0364).
http://backpackinglight.com/cgi-bin/backpackinglight/00206.html, 2003-11-25 03:00:00-07.