How Mobile Broadband Services Work

Mobile broadband is powered by the same technology that makes cell phones work. It's all about radio waves and frequencies. Cell phones and cell-phone radio towers send packets of digital information back and forth to each other via radio waves. In the case of a phone call, the packets of information carry voice data. For mobile broadband, the packets of information would be other types of data like e-mails, Web pages, music files and streaming video.

There are two basic technologies used to operate cell-phone networks: Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA). GSM is more popular in Europe and Asia and CDMA is more common in the United States. The major technical differences between the two systems have to do with the way each technology shares space on the radio spectrum. Without getting into the details, both GSM and CDMA use different algorithms that allow multiple cell phone users to share the same radio frequency without interfering with each other.

Mobile broadband is also known as 3G, or third-generation cell-phone technology. Both GSM and CDMA have developed their own 3G technology solutions for delivering high-speed Internet access to mobile devices.

The CDMA-based mobile broadband technology is called EV-DO (Evolution-Data Optimized or Evolution-Data Only). The trick behind EV-DO is that it runs over a part of the cellular network devoted entirely to data. Voice calls require a lot of bandwidth to maintain sound quality. By separating the data channel from the voice channel, the network can maximize data transfers and provide higher-speed access to e-mail, the Internet and multimedia. The downside is that you can't access the Internet and other data tools when talking on your cell phone. EV-DO advertises average speeds of 300-400 Kbps (kilobytes per second), the equivalent of DSL.

To use an EV-DO network, you need to either have a device that's already loaded with EV-DO hardware (like a BlackBerry or other smartphone) or a special network card that plugs into your laptop. These network cards connect via USB ports or other standard PC card slots and act as antennas for mobile broadband signals. For the fastest download and upload speeds, you need to be within range of the EV-DO cellular signal. Otherwise, you'll be bumped down to the 1xRTT (Radio Transfer Technology) standard, which broadcasts at speeds between 60 and 100Kbps.

GSM's answer to EV-DO is something called HSDPA (High-Speed Downlink Packet Access). Unlike EV-DO, an HSDPA network can handle both voice and data transfers, so you can talk to mom and surf the Web at the same time. It maximizes data transfer speeds by focusing on downloading information, not uploading. HSDPA advertises average download speeds between 400 to 700 Kbps.

Like EV-DO, you'll need special network hardware to access HSDPA mobile broadband. You either need a device with a built-in HSDPA card or a special PC card that plugs into a laptop computer. You'll also need to be within range of an HSDPA signal, which is concentrated in metropolitan city centers and along major highways.

Now let's look at some of the features of mobile broadband service as offered by the large cell-phone providers in the United States.

In the United States, three large cellular-service providers offer mobile broadband services on their networks. Sprint and Verizon are both CDMA networks, so their services are based on EV-DO technology. AT&T, formerly Cingular, is a GSM network, so it's offering an HSDPA mobile broadband service.

All three of these companies have built nationwide cellular networks. But not every part of the network is created equal. If you're in a major metropolitan area, then you'll have the most data services available to you. But if you're out in a rural area, you may be limited to simply making phone calls or browsing the Web at dial-up speeds.

For example, AT&T's mobile broadband service is called BroadbandConnect. With BroadbandConnect, you can send e-mails, instant messages, browse the Web at speeds between 400 and 700Kbps, watch TV shows, and even record and share live video during a phone call.

But to access all of these BroadbandConnect services, you need to be within coverage range of AT&T's 3G network. Right now, that's confined to the nation's largest cities. If you're outside of that coverage area, you can still access some data services like e-mail, text messaging and Web browsing, but at speeds between 75 and 135Kbps.

Sprint and Verizon's services are the same. With Sprint's mobile broadband service, you can use your cell phone to send e-mails, listen to streaming radio stations, download songs and music videos, watch live TV, share photos, play games and browse the Web at speeds between 600Kbps and 1.4Mbps (megabytes per second).

But like AT&T, the most data services and the best connection speeds are only available in 3G coverage areas, which are usually found in the nation's biggest cities. On the fringes of these coverage areas are mobile broadband roaming areas, which offer limited multimedia and data services. Even further outside major cities is the regular Sprint nationwide cellular network, with basic data services and connection speeds between 50 and 70Kbps, similar to dial-up.

What you pay to access these mobile broadband networks depends on what device you're going to use. There are four basic options for connecting to a 3G network:

For each of these options, the cellular providers offer several different mobile broadband payment plans. There's usually an option for unlimited monthly access, which is the most expensive plan. Another option is to pick a plan that allows for a maximum amount of data transfer a month. Sprint, for example, has an option for laptop users to pay $39.99 a month for 40MB (megtabytes) of data transfer over the network. Verizon has a 5GB (gigabyte) plan for $59.99 a month. To give you an idea of what that means, Verizon says you could send 1,747,627 e-mails a month before reaching 5GB, or look up nearly 35,000 Web pages [source: Verizon].

Cellular providers generally package their mobile broadband services for cell phone users. Sprint's package is called Power Vision and AT&T's is called MEdia Net. You pay extra for these packages on top of your regular calling plan. Or you can sign up for an all-inclusive plan that gives you a certain amount of anytime minutes per month, plus unlimited mobile broadband usage. With a PDA or smartphone, you can choose from unlimited or maximum data usage plus a voice-calling plan.

If you don't want to sign up for a monthly plan, you can actually pay by the kilobyte of data transfer. Sprint, for example, charges three cents a kilobyte for mobile broadband access without a monthly plan.

Now let's break down the terms and fees of a mobile broadband plan.

Mobile broadband is a brand new technology, so expect to pay a premium to use it. Like all cellular services, mobile broadband requires a one- or two-year contract. If you cancel the contract early, the cellular provider can charge an early termination fee up to $200.

If you're going to use a cell phone for mobile broadband access, you might also need to buy a new phone. Cellular providers require that you use certain phones to access certain services. If you want to sign up for AT&T's BroadbandConnect service, for example, you'll choose from a dozen or so phones that have the right hardware and software to handle Web browsing and multimedia playback. And if you don't sign up for an all-inclusive voice and data plan, then you'll have to sign up for some kind of voice plan in addition to the mobile broadband contract.

The nice part is that the cellular providers often offer steep rebates and discounts when you buy a phone with a voice or data plan. Some phones and PC cards are even free after all of the instant discounts, online savings and mail-in rebates.

Make sure you read your mobile broadband contract closely and pay attention to all of the surcharges and taxes that apply. When you're quoted a monthly charge of $39.99 a month, that doesn't include any of the extra fees that will show up on your monthly bill. Let's talk about a few of them:

Some mobile broadband services have roaming areas that extend into parts of Mexico and Canada. Generally, if you use data or mobile broadband services within one of these extended roaming areas, you'll be charged an extra fee based on a set price per kilobyte or megabyte of data transfer.

We hope this has been a helpful introduction to the exciting possibilities of mobile broadband. For more information about mobile broadband services, wireless technology and related topics, check out the links on the next page.