Millimeter wave (mmWave) is a new technology, that used for enabling 5G network. The idea comes after the big demand of having high data rate networks, so users can, for example, watch high quality videos, play online games, use what is called now metaverse from meta company, Facebook in previous days, and so on. Researchers in communication field find that to be able to provide this, other high bands, in our case mmWave, should be used.
MmWave works in 60 GHz band, far away from Wi-Fi bands, e.g., 2.4 GHz and 5 GHz. MmWave has wide bandwidth and low latency capabilities. As usual to make certain technology common and under use by people, it must be standardized so IEEE 802.11ad [1] considers as the standard for 60 GHz wireless local area networks (WLANs) that is defined to be used during working in mmWave technology. According to this standard, a maximum end-user data rate of 6.7 Gbps can be achieved by access points (APs) using orthogonal frequency division multiplexing (OFDM) modulations. Thus, when we say 6.7 Gbps data rate, imagine what speed will you have to do all your stuff, download a 4K movie in 1 second or watching your football team match without delay.
However, mmWave band suffers from harsh penetration and propagation losses due to its high operating frequency [2]. Propagation losses mean mmWave signal decreases while travelling in the space, and penetration losses mean signal cannot pass easily through obstacles like walls. Where according to Friis law, as the operating frequency of the wireless communication technology increases, the attenuation of the signal highly increases.
Moreover, mmWave communication link has a high probability to be blocked due to human shadowing. This means we as peoples make mmWave signal decreased or maybe destroyed. Thus, directional transmission using antenna beamforming becomes a necessity in this case. This beamforming is widely utilized based on large-scale mmWave antenna arrays to expand the coverage area of mmWave AP [3], thanks to the rapid progress in complementary metal-oxide-semiconductor (CMOS) radio frequency (RF) integrated circuits. Moreover, the interference in mmWave based networks can be cut down based on these highly directional beams, hence it becomes a noise-limited network. These beamforming concepts will come in the next blog.
[1] IEEE 802.11ad standard: “Enhancements for Very High Throughput in the 60 GHz Band," in IEEE Std 802.11ad-2012 (Amendment to IEEE Std 802.11-2012, as amended by IEEE Std 802.11ae-2012 and IEEE Std 802.11aa-2012) , vol., no., pp.1-628, 28 Dec. 2012 [Online] http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6392842&isnumber=6392841.
[2] T. S. Rappaport, F. Gutierrez, E. Ben-Dor, J. N. Murdock, Y. Qiao, and J. I. Tamir, "Broadband millimeter-wave propagation measurements and models using adaptive-beam antennas for outdoor urban cellular communications," IEEE transactions on antennas and propagation, vol. 61, pp. 1850-1859, 2013.
[3] J. Song, J. Choi and D. J. Love, "Codebook design for hybrid beamforming in millimeter wave systems," 2015 IEEE International Conference on Communications (ICC), London, 2015, pp. 1298-1303.
