Which technology uses Time Division Multiple Access for slot allocation in mobile phones?

Time Division Multiple Access (TDMA) is a technology used in mobile communications to allocate time slots to multiple users on the same frequency channel, allowing for efficient utilization of the available spectrum. GSM (Global System for Mobile Communications) employs TDMA to manage how multiple mobile users share the same frequency band.

In GSM, each channel is divided into time slots, with each user assigned a specific time slot to transmit and receive data. This enables several conversations to occur simultaneously on the same frequency by assigning different time slots to different users, thus maximizing the use of the channel.

While other technologies like CDMA (Code Division Multiple Access) and WCDMA (Wideband Code Division Multiple Access) utilize spreading codes and different techniques to achieve multiplexing and maintain quality of service, they do not rely on time slots in the same way as TDMA does. LTE (Long Term Evolution) primarily uses a different method altogether called Orthogonal Frequency Division Multiple Access (OFDMA), which splits data into multiple subcarriers and assigns them dynamically. Therefore, the use of TDMA for slot allocation is a key characteristic of GSM, making it the correct answer.