TDMA

TDMA (Time Division Multiple Access) was released in 1984. It uses the frequency bands available to the wireless network and divides them into time slots, with each phone user having access to one time slot at regular intervals. TDMA exists in North America at both the 800 MHz and 1900 MHz bands. Major U.S. carriers using TDMA are AT&T Wireless Services, BellSouth, and Southwestern Bell. A graphical depiction of TDMA is shown in Figure 4.2. As you can see, the TDMA architecture works in a “timeslot” format. In other words, one person speaks, and another is listening. For another person to speak, a timeslot (channel) must open up. Only one subscriber is assigned a channel at one time, and no other subscriber can access that same channel until the call is ended. As you can imagine, that makes for a great deal of channels. Advantages of TDMA include:

• Unlike spread-spectrum techniques, which can suffer from interference among the users all of whom are on the same frequency band and transmitting at the same time, TDMA’s technology, which separates users in time, ensures that they will not experience interference from other simultaneous transmissions.
• TDMA provides the user with extended battery life and talk time because the mobile is only transmitting a portion of the time (from 1/3 to 1/10) of the time during conversations.
• TDMA installations offer substantial savings in base-station equipment, space, and maintenance, an important factor as cell sizes grow ever smaller.
• TDMA is the most cost-effective technology for upgrading a current analog system to digital.
• TDMA is the only technology that offers an efficient utilization of hierarchical cell structures (HCSs) offering picocells, microcells, and macrocells. HCSs allow coverage for the system to be tailored to support specific traffic and service needs. By using this approach, system capacities of more than 40 times AMPS can be achieved in a cost-efficient way.
• Because of its inherent compatibility with analog systems, TDMA allows service compatibility with dual-mode handsets.

Taken From : Enterprise Guide to Gaining Business Value from Mobile Technologies

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