Wireless 101

Wireless 101

Cellular telephones have revolutionized the communications arena, redefining how we perceive voice communications. Traditionally, cellular phones remained out of the hands of most consumers due to their high cost. As a result, cell phone carriers have invested time and resources into finding ways to give the systems higher capacity and thus lower cost. Cell systems are benefiting from this research and starting to develop into large-scale consumer products.

Today, cellular phones are truly consumer electronics devices with over 59 million subscribers. The Nokia Bowl and Qualcomm Stadium are further evidence of the idea that cell phones are consumer electronics devices. Since cell phones have ceased to be an exclusive status symbol of high-powered lawyers and are now in the hands of millions of consumers, they are now incredibly cost sensitive. Specifically, it is not the cost of the device that counts, but the cost of using the device. As a result, the cellular phone infrastructure is being optimized to allow calls to be placed as inexpensively and reliably as possible. Today, more than ever, cellular companies are looking for ways to bring down the call cost to attain even higher market penetration, especially in metropolitan areas.

In this report, we will begin by examining how cell phone systems work, paying close attention to details in system design that reduce cost and increase quality. After we have explained how cell phone systems work, we will examine the various cell phone systems in existence, examining the details of their operation and how that impacts the cost of using the system and the call quality on the system. Since the most important factor in cell phone airtime cost is the capacity, we will focus on issues related to capacity.

An Overview of how Cell Phones work

It is common knowledge that Cellular Phones (referred to as "cell" phones from here on) are wireless phones; however, many are confused about how a cell phone actually works. Essentially, cell phones use high-frequency radio signals to communicate with "cell towers" located throughout the calling area. Cell phones communicate in the frequency range of 806-890 MHz and 1850-1990 MHz for the newly allocated "PCS" frequency range.

When the user wants to make a call, the cell phone sends a message to the tower, asking to be connected to a given telephone number. If the tower has sufficient resources to grant the request, a device called a "switch" patches the cell phone’s signal throughout to a channel on the "public switched telephone network" (otherwise known as the PSTN). This call now takes up a wireless channel as well as a PSTN channel that will be held open until the call is completed. The following figure illustrates this process.