Cellular phones as embedded systems

The trend in handheld devices is toward smaller multifunctional terminals with continuously-improving end-user satisfaction. In addition to being difficult to fulfill separately, the different requirements are often contradictory. This statement applies especially well in the case of cellular phones. The speed of their development has been unequalled, while delivery volumes have grown all the time, being now over 400 million per annum. The high level of integration and other technical challenges make the cellular phone an ideal example of an embedded communications system with tough requirements. In this paper, technologies needed to assemble a cellular phone are studied from different angles. Overall power consumption is one of the key performance indicators. This translates to concern, both for power-amplifier and DSP efficiency in the talk mode, and for various leakage currents in analog and digital receiver circuits in the standby mode. The emerging multimedia capabilities call for better displays and enhanced audio performance. The increasing amount of software needed sets wholly new requirements for the processing power and memory size of the device. Third-generation cellular standards support high data rates, and are based on the most recent advances in the telecommunications sphere. Packet-switched traffic and Internet protocols are growing in importance, whereas other more-traditional radio interfaces are integrated into cellular phones to form multi-radio devices. Evidently, the power consumption is affected simultaneously. In this review paper, the cellular phone is analyzed as an embedded system from the integration, performance, and power-consumption angles. We discuss the following key issues concerning cellular phones: terminal trends and their impact on power economy; radio technologies and multiradio concepts; technological implementations; integration challenges; related solid-state-circuit research-and-development expectations.