Christian Drewes

Closed loop transmission in EUTRA-LTE system

Closed-loop transmission combined with MIMO (multiple-input multiple-output) technologies have drawn most attentions during development of the LTE (Long Term Evolution) and LTE-Advanced systems. In LTE/LTE-A, the codebook based precoding scheme (termed as PMI-Precoding Matrix Index selection) is deployed for realizing the closed-loop transmission concept. In addition, dynamic transmission mode selection between the spatial multiplexing and transmit diversity, termed as RI (rank indicator) selection, and the adaptive MCS (modulation and coding schemes) selection, realized as CQI (channel quality indicator) selection are also deployed in LTE systems to provide more robust link connection. In this manuscript, the authors focused on the study of selection criteria on the feedback parameters in closed-loop transmission in LTE systems. With joint selection of the PMI, RI and CQI, the authors illustrate an impressive performance improvement given by closed-loop transmission in contrast to open loop transmission and furthermore conclude that the maximum mutual information is one of the optimal criteria for parameters selections.

Mobile Phones: The Driving Force Towards the Integration of Analog and Digital Blocks for Baseband and RF Circuitry

Next generation cellular systems are currently under standardization. Peak data rates will go well beyond 100 Mb/s; while the computational complexity has been constantly increasing, the complexity per transmitted bit has been reducing due to advances in algorithm design and semiconductor manufacturing. It is shown that an approach maximizing reuse will be an attractive way to implement future platforms for mobile phones, whereby an evolutionary approach would be preferred over a revolutionary software-centric approach. The main challenges that will be faced in developing future chip sets for cellular modems will be managing increasing complexity for systems verification, supporting higher levels of System on chip (SoC) integration, taming RF power consumption, and coping with exponentially growing development costs. On the other hand the Ultra Low Cost segment of the cellular phone market asks for inexpensive integrated solution that can provide the possibility to the large number of people in the unconnected part of the world to participate in the advantages of wireless connection to the world with voice and data services.