What is old is new again!

The concern regarding the increase in data volume and stringent requirement for increasing the capacity of mobile broadband data is rising. Researchers from both academic and industry communities have started the activities around the fifth generation (5G) cellular networks. 5G networks should meet higher capacity demands, higher energy efficiency and low latency with many connected devices. However, there are different views on how to meet these challenges.

From Dr. Chih-Lin I’s perspective from China Mobile, who gave a keynote speech in ICC 2014, soft and green is the way to go towards 5G. By rethinking capacity metric designs and the notion of traditional cell-centric designs, she believes one can provide increase in the capacity and saving in the power. Feasibility of these ideas can already be seen in some research areas such as taking into account both spectral and energy efficiency in network design instead of prioritizing spectral efficiency, rethinking network architecture design, separating data and control signaling planes to different layers of cell (that is macro BS and small cell BS), and rethinking signaling for more load- and app-aware network design.

From another perspective in ICC by Prof. Theodore S. Rappaport, using higher frequency bands (millimeter wave) is the main key for meeting the demands of 5G networks. However, in order to evaluate resulting gains, an appropriate channel model is needed. His group has performed extensive channel measurements for millimeter wave on 28 and 73 Giga Hertz in Texas and New York City in order to quantify the gains. Due to the nature of millimeter wave, which is noise-limited, very narrow beams and macro-diversity are required in order to achieve high gains. Based on their measurements in highly non-line-of-sight environment like New York City, even up to 100-200 meters a strong signal can be observed. With these results, the order of magnitude capacity increase can be achieved compere to the state of the art that is 4G, and greater gains can be obtained by beam combining. However, these are initial results in this direction, and we are in early days for channel modeling and adaptive arrays for such high frequencies. In this new regime, links heavily rely on beamforming and cooperation and BS diversity offer potential improvements. So, we need to revisit the old concepts like relays, channels and narrows beams once again, and therefore, “what is old is new again”.

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