T-Mobile recently made a significant decision regarding its location tracking technology. In response to industry trends, T-Mobile, along with other major carriers like AT&T Wireless and Cingular Wireless, opted to transition from CPS’s Enhanced Observed Time Difference (EOTD) software to a different technology known as Time Difference of Arrival (TDOA).

The shift was primarily driven by the Federal Communications Commission’s mandate for all U.S. carriers to enhance emergency call centers’ ability to locate 95% of all handsets dialing 9-1-1 within 50 meters by 2005. While the carriers originally intended to leverage this technology for commercial services like “Friend Finder,” practical challenges and accuracy concerns led to the adoption of TDOA, which simplifies location tracking by measuring the time a call reaches location measuring units within a cell phone network base station.

According to industry insiders, EOTD faced limitations in meeting the required accuracy levels, with AT&T Wireless expressing reservations about its capability to achieve the 50-meter mandate promptly. In contrast, other carriers such as Verizon Wireless and Sprint PCS chose alternative methods involving satellite constellations for location tracking.

Despite the shift away from EOTD in the U.S. market, Cambridge Positioning Systems (CPS), the developer of EOTD, plans to focus on marketing its technology integrated into network gear to carriers in Europe and Asia. Recognizing the global potential of their product, CPS aims to capitalize on opportunities beyond the U.S. market, with ongoing trials by Singapore Telecommunications (Singtel) showcasing the technology’s versatility.

In summary, T-Mobile’s decision to transition to TDOA, along with other carriers’ strategic choices, reflects the dynamic landscape of location tracking technologies in the telecommunications industry. As technological advancements continue to shape the sector, companies like CPS are adapting their strategies to leverage opportunities in regional markets worldwide.


  1. Why did T-Mobile decide to switch from EOTD to TDOA?

    • T-Mobile, along with other carriers, transitioned to TDOA due to accuracy concerns and practical challenges associated with meeting the FCC’s location tracking mandate.
  2. What prompted the Federal Communications Commission to require enhanced location tracking capabilities for carriers?

    • The FCC mandated improved location tracking to enable emergency call centers to locate 95% of all handsets dialing 9-1-1 within 50 meters by 2005.
  3. How does TDOA differ from EOTD in terms of technology?

    • TDOA simplifies location tracking by measuring the time a call reaches location measuring units within a cell phone network base station, whereas EOTD requires software in both the network and handsets.
  4. What were the limitations of EOTD that led to carriers’ decisions to change technologies?

    • EOTD faced challenges in meeting the accuracy requirements, with concerns raised about its ability to locate targeted cell phones within the mandated 50-meter range.
  5. Which alternative methods did carriers like Verizon Wireless and Sprint PCS choose for location tracking?

    • These carriers opted for methods involving satellite constellations to enhance their location tracking capabilities.
  6. Where does CPS plan to focus its efforts following the transition away from EOTD in the U.S. market?

    • CPS aims to market its technology integrated into network gear to carriers in Europe and Asia, leveraging ongoing trials by companies like Singtel.
  7. How does the transition to TDOA impact the commercial services planned by carriers?

    • The shift to TDOA may influence the implementation of commercial services like “Friend Finder,” as carriers adapt to the new location tracking technology.
  8. What role did practical considerations play in T-Mobile’s decision-making process regarding location tracking technology?

    • Practical difficulties, such as vendor resources and attention allocation, influenced T-Mobile’s choice to transition to TDOA alongside other carriers.
  9. How does the global market potential of location tracking technologies impact developers like CPS?

    • Developers like CPS recognize the vast opportunities beyond the U.S. market, leading to strategic initiatives to market their technology in regions like Europe and Asia.
  10. What market insights did CPS gain from its experience in the U.S. market?

    • CPS leveraged its U.S. market experience to enhance the development of its technology, showcasing its adaptability and innovation in response to industry demands.
  11. How does the transition to TDOA align with industry trends in location tracking technologies?

    • The industry-wide shift towards more accurate and efficient location tracking methods, as seen with TDOA adoption, reflects ongoing advancements and innovations in the telecommunications sector.
  12. What considerations should carriers weigh when evaluating location tracking technologies for their networks?

    • Carriers need to assess factors like accuracy, practicality, and compatibility with regulatory mandates when selecting location tracking technologies to enhance their network capabilities.


The telecommunications industry witnessed a significant shift as T-Mobile, AT&T Wireless, and Cingular Wireless transitioned from EOTD to TDOA for location tracking. Driven by the FCC’s mandate to improve emergency call center capabilities, carriers adapted to meet stringent location accuracy requirements. Practical challenges and accuracy concerns influenced this decision, leading to the adoption of TDOA, a more streamlined technology for measuring location within cell phone networks.

As the industry embraces innovations in location tracking, companies like CPS are exploring global markets beyond the U.S. to market their technology. The transition underscores the dynamic nature of telecommunications technologies, emphasizing the importance of adapting to industry trends and regulatory demands. With a focus on enhancing network capabilities and commercial services, carriers are navigating the evolving landscape of location tracking technologies to meet customer needs effectively.

For more insights on technological advancements in the telecommunications sector and how companies are adapting to industry changes, visit our website for the latest updates and resources.