The global bandwidth shortage in the wireless communication sector has motivated the study and exploration of wireless access technology known as massive Multiple-Input Multiple-Output (MIMO). Massive MIMO is one of the key enabling technology for next-generation networks, which groups together antennas at both transmitter and the receiver to provide high spectral and energy efficiency using relatively simple processing. Obtaining a better understating of the massive MIMO system to overcome the fundamental issues such as pilot contamination, channel estimation, precoding, user scheduling, energy efficiency, and signal detection is vital for the successful deployment of 5G and beyond networks. Some of the recent trends in massive MIMO are terahertz communication, ultra massive MIMO (UM-MIMO), visible light communication (VLC), machine learning, and deep learning.
With globalization, present-day networks are facing high traffic demands, and to fulfill these needs, cellular systems are deployed within a few hundred-meter distances, and wireless Local Area Networks (LAN) are placed almost everywhere. Along with increased mobile broadband service, the introduction of new concepts like the Internet of Things (IoT) and Machine-to-Machine Communication (M2M) are also contributing to the increased wireless traffic. The global deployment of cellular service cultivates the cell phone users to be used to the mobile data in their day to day life tremendously. The services like video calling, online gaming, social media applications like Facebook, Twitter, WhatsApp, have changed our life drastically with the capabilities of the third-generation (3G), fourth-generation (4G), and fifth-generation (5G) networks, like lower latency and high data rate . A full cell phone connected world is expected in the next few years, which will be mainly characterized by growth in users, connectivity, data traffic volume, and a wide range of applications. In the next few years, technology like augmented reality, virtual reality, ultra high definition video, 3D video, and features like a mobile cloud will become popular to enrich the ultimate user experience. From 2017–2022, smartphone traffic is expected to increase by ten times, and overall, mobile traffic will be increased by eight times . Figure 1 shows the growth in mobile data traffic and the number of connected devices from 2017–2022 . By the end of 2022, more than 90 percent of the traffic will come from cell phones. This colossal amount of mobile data traffic is challenging to manage with the capabilities of previous wireless generation systems.
Figure 1. Global mobile data traffic and growth in connected devices from 2017 to 2022.
The primary issue with the ongoing development of the wireless network is that it is dependent upon either increasing bandwidth (spectrum) or densifying the cells to achieve the required area throughput. These resources are rare and are reaching their saturation point within a few years. Also, increasing bandwidth or densifying the cells increases the cost of the hardware and increases latency. The third factor, which can improve area throughput, that is, spectral efficiency, has remained mostly untouched and unchanged during this rapid development and growth of the wireless network. An efficient wireless access technology that can increase the wireless area throughput without increasing the bandwidth or densifying the cell is essential to achieve the ongoing demands faced by the wireless carriers.
Massive Multiple-Input Multiple-Output (MIMO) is the most enthralling wireless access technology to deliver the needs of 5G and beyond networks. Massive MIMO is an extension of MIMO technology, which involves using hundreds and even thousands of antennas attached to a base station to improve spectral efficiency and throughput. This technology is about bringing together antennas, radios, and spectrum together to enable higher capacity and speed for the incoming 5G . The capacity of massive MIMO to increase throughput and spectral efficiency has made it a crucial technology for emerging wireless standards . The key here is the considerable array gain that massive MIMO achieves with a large number of antennas . Massive MIMO is a key enabling technology for 5G and beyond networks, and as intelligent sensing system primarily rely on 5G and beyond networks to function, massive MIMO and intelligent sensing system are inextricably linked. The data collection from the large number of smart sensors using traditional multi-access schemes is very impractical as it leads to excessive latency, low data rate, and reduced reliability. Massive MIMO with huge multiplexing gain and beamforming capabilities can sense data from concurrent sensor transmission with much lower latency and provide sensors with higher data rates and reliable connectivity. Massive MIMO systems will perform a crucial role to allow information gathered through smart sensors to be transmitted in real-time to central monitoring locations for smart sensor applications such as an autonomous vehicle, remote healthcare, smart grids, smart antennas, smart highways, smart building, and smart environmental monitoring.
Ukosefu wa bandwidth ya kimataifa katika sekta ya mawasiliano ya wireless imesababisha utafiti na utafutaji wa teknolojia ya upatikanaji wa wireless inayojulikana kama kubwa Multiple-Input Multiple-Output (MIMO). Massive MIMO ni moja ya teknolojia muhimu ya kuwezesha kwa ajili ya mitandao ya kizazi kijacho, ambayo makundi pamoja antennas katika wote transmitter na mpokeaji kutoa juu spectral na nishati ufanisi kutumia usindikaji rahisi. Kupata uelewa bora wa mfumo mkubwa wa MIMO ili kushinda masuala ya msingi kama vile uchafuzi wa majaribio, makadirio ya njia, pre-coding, ratiba ya watumiaji, ufanisi wa nishati, na utambuzi wa ishara ni muhimu kwa ajili ya kufanikiwa kupelekwa kwa 5G na zaidi ya mitandao. Mfano wa teknolojia ya MIMO ni mawasiliano ya terahertz, ultra-massive MIMO, mawasiliano ya mwanga inayoonekana (VLC), kujifunza mashine, na kujifunza kina. Kwa sababu ya utandawazi, mitandao ya leo inakabiliwa na mahitaji ya juu ya trafiki, na ili kukidhi mahitaji haya, mifumo ya seli hutumiwa ndani ya umbali wa mita mia chache, na Mitandao ya Eneo ya Wireless (LAN) huwekwa karibu kila mahali. Pamoja na kuongezeka kwa huduma ya mtandao wa simu, kuanzishwa kwa dhana mpya kama vile Mtandao wa Vitu (IoT) na Mawasiliano ya Mashine-kwa-Mashine (M2M) pia inachangia kuongezeka kwa trafiki ya wireless. Utangazaji wa huduma ya simu za mkononi ulimwenguni pote unazalisha watumiaji wa simu za mkononi kutumika kwa data ya simu za mkononi katika maisha yao ya kila siku sana. "Hizi ni huduma kama vile simu za video, michezo ya mtandaoni, programu za mitandao ya kijamii kama Facebook, Twitter, WhatsApp, na huduma nyingine ambazo zimebadilisha maisha yetu kwa nguvu na uwezo wa mitandao ya kizazi cha tatu (3G), kizazi cha nne (4G), na kizazi cha tano (5G) kama vile latency ya chini na kiwango cha juu cha data.""" Ulimwengu kamili wa simu za mkononi unatarajiwa katika miaka michache ijayo, ambayo itahusishwa hasa na ukuaji wa watumiaji, uunganisho, kiasi cha trafiki ya data, na anuwai ya matumizi. Katika miaka ijayo, teknolojia kama vile hali halisi iliyoongezwa, hali halisi ya virtual, video ya ufafanuzi wa juu, video ya 3D, na huduma kama wingu la rununu zitakuwa maarufu ili kutajirisha uzoefu wa mwisho wa mtumiaji. Kuanzia 2017 hadi 2022, trafiki ya simu mahiri inatarajiwa kuongezeka mara kumi, na kwa ujumla, trafiki ya rununu itaongezeka mara nane. Picha ya kwanza inaonyesha ukuaji wa trafiki ya data ya rununu na idadi ya vifaa vilivyounganishwa kutoka 2017 hadi 2022. Kufikia mwaka 2022, zaidi ya asilimia 90 ya trafiki itatoka kwa simu za mkononi. Kiasi hiki kikubwa cha trafiki ya data ya rununu ni changamoto ya kusimamia na uwezo wa mifumo ya kizazi cha wireless ya awali. Picha ya 1. Uendeshaji wa data ya rununu na ukuaji wa vifaa vilivyounganishwa kutoka 2017 hadi 2022 Tatizo kuu na maendeleo ya kuendelea ya mtandao wireless ni kwamba ni tegemezi juu ya ama kuongeza bandwidth (spectrum) au densifying seli kufikia required eneo throughput. Rasilimali hizo ni nadra na zinafikia kiwango chao cha kutosha ndani ya miaka michache. Pia, kuongeza bandwidth au densifying seli huongeza gharama ya vifaa na huongeza latency. Sababu ya tatu, ambayo inaweza kuboresha throughput eneo, yaani, spectral ufanisi, imebaki zaidi untouched na unchanged wakati huu wa maendeleo ya haraka na ukuaji wa mtandao wireless. Teknolojia ya ufikiaji wa wireless inayoweza kuongeza throughput ya eneo la wireless bila kuongeza bandwidth au densifying seli ni muhimu kufikia mahitaji ya kuendelea yanayokabiliwa na waendeshaji wa wireless. Massive Multiple Input Multiple Output (MIMO) ni teknolojia ya ufikiaji wa wireless ya kuvutia zaidi ya kutoa mahitaji ya 5G na zaidi ya mitandao. Massive MIMO ni upanuzi wa teknolojia ya MIMO, ambayo inahusisha kutumia mamia na hata maelfu ya antennas kushikamana na kituo cha msingi ili kuboresha spectral ufanisi na throughput. Teknolojia hii inahusisha kuunganisha antena, redio, na spectrum pamoja ili kuwezesha uwezo wa juu na kasi kwa ajili ya 5G inakuja. Uwezo wa MIMO kubwa ya kuongeza throughput na spectral ufanisi imefanya ni teknolojia muhimu kwa ajili ya viwango vya wireless zinazoibuka. Ufunguo hapa ni faida kubwa ya safu ambayo MIMO kubwa hupata na idadi kubwa ya antennas. Massive MIMO ni teknolojia muhimu ya kuwezesha kwa ajili ya 5G na zaidi ya mitandao, na kama mfumo wa utambuzi wa akili hasa hutegemea 5G na zaidi ya mitandao ya kufanya kazi, MIMO kubwa na mfumo wa utambuzi wa akili ni inextricably kushikamana. Kukusanya data kutoka kwa idadi kubwa ya sensorer smart kutumia jadi multi-upatikanaji mipango ni vigumu sana kama inaongoza kwa latency kupita kiasi, chini ya kiwango cha data, na kupunguzwa kuegemea. Massive MIMO na kubwa multiplexing faida na beamforming uwezo inaweza kuhisi data kutoka sensorer usafirishaji wakati huo huo na latency chini sana na kutoa sensorer na viwango vya juu data na kuaminika connectivity. Mifumo ya MIMO ya wingi itafanya jukumu muhimu kuruhusu habari zilizokusanywa kupitia sensorer za akili kusambazwa kwa wakati halisi kwa maeneo ya ufuatiliaji wa kati kwa matumizi ya sensorer za akili kama vile gari la kujitegemea, huduma za afya za mbali, gridi za akili, antena za akili, barabara kuu za akili, jengo la akili, na ufuatiliaji wa mazingira.