Fundamental Limits in MIMO Broadcast Channels

This paper studies the fundamental limits of MIMO broadcast channels from a high level, determining the sum-rate capacity of the system as a function of system paramaters, such as the number of transmit antennas, the number of users, the number of receive antennas, and the total transmit power. The crucial role of channel state information at the transmitter is emphasized, as well as the emergence of opportunistic transmission schemes. The effects of channel estimation errors, training, and spatial correlation are studied, as well as issues related to fairness, delay and differentiated rate scheduling

Wireless industrial monitoring and control networks: the journey so far and the road ahead

While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks

Medium access control for underwater acoustic sensor networks with MIMO links

The requirements of multimedia underwater monitoring applica-tions with heterogeneous traffic demands in terms of bandwidth and end-to-end reliability are considered in this article. To address these requirements, a new medium access control protocol named UMIMO-MAC is proposed. UMIMO-MAC is designed to i) adap-tively leverage the tradeoff between multiplexing and diversity gain according to channel conditions and application requirements, ii) select suitable transmit power to reduce energy consumption, and iii) efficiently exploit the UW channel, minimizing the impact of the long propagation delay on the channel utilization efficiency. To achieve the objectives above, UMIMO-MAC is based on a two-way handshake protocol. Multiple access by simultaneous and co-located transmissions is achieved by using different pseudo or-thogonal spreading codes. Extensive simulation results show that UMIMO-MAC increases network throughput, decreases channel access delay, and decrease energy consumption compared with ex-isting Aloha-like MAC protocols for UW-ASNs