Abstract In the future, some of the main aims beyond4G that need to be addressed are reduced latency, energy efficiency and robustness.To achieve these requirements, severe improvements need to be accomplished incellular network architecture. This paper briefly introduces and reviews the fifthgeneration (5G) cellular network system and architecture. This paper will focuson one component of 5G technology, known as Massive MIMO, along with its advantagesand challenges. IntroductionMobile technology is going through fastchanges and wireless mobile communication system has become more popular. 5G technology is a term that has not beenofficially defined yet, but is still receiving heaps of attention in the media (Suttonand Tafazolli, 2017). It can be simply described as the fifth generation ofcellular networking (Gartenberg, 2017).
Theuprising of mobile communications is described in generations which go from 1G-first Generation to 5G -the fifth generation (Ravikumar and Sankar, 2017). Currently,a new fifth generation of mobile networks is expected to be installed by 2020 (Jungnickel,Manolakis and Zirwas, 2014). Great amount of research is being carried outtoday in order to provide the 5G vision of the future by advancing candidate technologies,in the UK and elsewhere (Sutton and Tafazolli, 2017). The fifth generation which is built on 4Gtechnologies is believed to be the future wireless communication system in deliveringwireless mobile multimedia internet networks which can be entirely wirelesscommunication without restriction (Ravikumar andSankar, 2017). The upcoming 5Gmobile technology advanced features will allow many everyday problems to bepotentially solved.
It is not apparentwhich technologies will benefit 5G the most in the long term, however a fewpreferences have emerged (Ravikumar and Sankar, 2017). Overviewof 5G systems Broader spectral bandwidth per frequency channel is to expectedto be delivered along with new and much varied frequency bands by 5G technologythan the previous generation (tutorialspoint, n.d.). Significant increase in peak bit rate have beenshown by the previous generations of mobile technologies (tutorialspoint, n.d.
).Larger number of supporting devices, higher reliability of communications,better connectivity regardless of which geographic locality one is in, highsystem spectral efficiency and many others are the advanced features of 5G ontop of the increase in bit rate (tutorialspoint, n.d.) . These advances make the upcoming revolutionof mobile technology different from the previous generation, especially 4G.
Thenetwork elements and several terminals are normally enhanced to afford a newsituation, so the architecture of 5G is highly developed. similarly, the developed technology can beexecuted to implement the value-added services without difficulty by theservice providers. Though, the ability to upgrade is established upon cognitiveradio technology that involves several significant features such as capabilityto identify their geographical location along with weather and temperature.Cognitive radio technology works as a transceiver, also referred to as a beam,that is able to sensitively gather and answer radio signals in its operatingenvironment as well as offer unbroken quality service (tutorialspoint, n.d.). Thesystem model of 5G is based completely on the IP model created for the wirelessand mobile networks (Tudzarov and Janevsk, 2011). The system includes severalnodes or terminals with one such node committed to the user-input.
The terminals carry out autonomous radioaccess technologies, in which each terminal has a unique Radio AccessTechnology (RAT) (Tudzarov and Janevsk, 2011). For the outside internet world, each of theradio access technologies is counted as the link. The IP technology is created to make sure necessarycontrol data for appropriate routing of IP packets associated to specificapplication connections is delivered. Furthermore,to make sure accessible routing of packets are managed in agreement with thegiven policies of the user (Tudzarov and Janevsk, 2011; Ravikumar and Sankar,2017). Thesuccess of 5G networks will depend on the implementation of a number of new technologies.These will allow the benefits of 5G to be fully noticeable, benefiting from itscapability to use a wide range of bandwidths and high data rates, amongst othersthings. The new main technology components are new spectrum, massive MIMO, networkslicing, multi-connectivity and in-build support for cloud implementation andedge computing (nokia, 2017).
Review: Massive MIMO and 5G Massive MIMO which (Multiple Input MultipleOutput) is an evolving area of 5G technology that has been advanced from thecurrent MIMO technology (Gupta and Jha, 2015). Itis the advancing technology of forthcoming networks, which is spectrumefficient, secure, robust, and efficient in energy (Gupta and Jha, 2015). This component can be in essence defined as awireless network that allows multiple data signals to be concurrentlytransferred and obtained over the same radio channel (Mundy,n.d.) . Massive MIMO involves the usage of larger antenna arrays at base stationsthan the number of mobile communication systems per signalling resource,whereas the standard MIMO networks use two or four antennas (Gupta and Jha,2015; National Instruments, 2017). Its purposeis to obtain all the advantages of the MIMO on a larger scale (Gupta and Jha,2015).
The largenumber of base station antennas allows the spectral efficiency andquasi-orthogonal channel response to improve significantly in comparative tothe number of mobile (National Instruments, 2017). Within a given cell contrastedto the current 4G systems, the settings would permit several more devices to beserved with the same frequency and time resources. (Mitsubishi Electric, n.
d.). Tests in large scale fields trials onmassive MIMO have yet to be done in order to demonstrate its discernibility forthe widespread commercial utilisation (NationalInstruments, 2017). However, recent discoveries show that it is possible toachieve huge improvements in spectral efficiency in real time over the airtrials (National Instruments, 2017). Despite these findings, there is stillseveral more problems to be resolved before commercial massive MIMO networksare exhibited.
Advantages ofMassive MIMO The radiatedenergy efficiency can be enhanced by massive MIMO by 100 times andsimultaneously can enhance the capacity of the order of 10 or more (Chauhan andParmar, 2017). These enhancementin capacity is attainable by using the spatial multiplexing technique inMassive MIMO systems. The large numberof antennas, allows the improvement in radiated energy efficiency to beachieved, as it can be focused in small areas in the space (Gupta and Jha, 2015; Larsson et al., 2014) . With the help of low power and less costlycomponents, massive MIMO systems can be put together (Gupta and Jha, 2015). MassiveMIMO systems uses hundreds of less expensive amplifiers in regards to expensiveultra-linear 50-Watt amplifiers since former has an output in the milliwattrange, which is much more beneficial than the latter which are normally being implementedin conventional systems (Gupta and Jha, 2015). Although,it uses only a little antenna’s that are being supplied from high power amplifiers,it has a significant effect, unlike the conventional array schemes.
Expensive,large number of items such as the large coaxial cable, are removed which is thegreatest progress (Larsson et al., 2014) . The noise, fading and hardwareshortages will be averaged, with the use of a large number of antennas inmassive MIMO technology since signals will be merged together in the free spacefrom a large number of antennas (Gupta and Jha, 2015; Nam et al., 2012).
Thestrength of massive MIMO will increase against the fading and failure of one ofthe antenna elements. In the forthcoming generation networks,latency is the main area of concern. Fading is considered as the main cause oflatency, in wireless communication.
This occurs when the base station transmitsthe signal, it goes through different multiple paths before it reaches theterminal because of the scattering, reflection and diffraction (Gupta and Jha,2015). A large number of antennas and with the idea of beam forming can preventfading dips, which causes the delay of data being received by the terminal asit has to wait for the transmission channel to alter when it is caught in afading dip. Then further latency reduction cannot take place (Larsson et al.,2014). Challenges with Massive MIMO There are many challenges when implementinga system with a very large number of antennas and terminals. Therefore itrequires more enhanced processing competence in the nodes (Tracy, 2016). Eachnode must be able to regulate the data transmitted from one antenna to thattransmitted from another in order to prevent limitations in the network performance(Tracy, 2016).
For this procedure towork, according to Marcham (n.d.), channel approximation and soundingtechniques are required. The challenges that need to be addressedare antenna mutual coupling and spatial correlation (Adnan,Rafiqul and Alam, 2016). As mentioned, in theory, the increase in number ofbase station antennas gives the potential to attain high spectral and energyefficiency along with system capacity. However, this notion might be misleadingwhen antenna coupling along with circuit power consumptions is studied (Adnan,Rafiqul and Alam, 2016). Antenna arraysare usually spaced out by a distance equal to wavelength of the transmittedfrequency or more (Hien Quoc Ngo, Larsson and Marzetta, 2013).
The restraintphysical area for arrangement of large number of antennas at the base stationis a challenge. Spatial correlation and antenna mutual coupling are caused correspondinglyby the closeness of the antenna elements as signal sources and electrical components(Masouros, Sellathurai and Ratnarajah, 2013). Research has been studied on suchantenna array to arrange the large number of antenna elements efficiently in arestricted space along with sustaining the needed performance, throughsimulations and testbed (Zeng, Zhang and Chen, 2014; ARAI et al., 2015; Adnan, Rafiqul and Alam, 2016).
AuthorsZeng, Zhang and Chen (2014) have systematically suggested a method ofintegrating an electromagnet (EM) with ULA (50 antenna elements) to decrease thespatial correlation along with improving the energy focusing. A linearstructure, however, is difficult to establish due to the space restriction ofbase station tower (Adnan, Rafiqul and Alam, 2016).Hardware impairments is a challenge toprepare massive MIMO base station with low cost hardware because It needs economyof scale in manufacturing as compared to mobile terminals (Larsson et al.
,2014). Also, with low cost components, the effect of hardware impairments onmassive MIMO systems increases, as they produce higher levels of quantisation noise(Adnan, Rafiqul and Alam, 2016). Although a high array gain is attained with alarge number of antennas used at the Base Station side, study by Bjornson etal., (2014) has demonstrated that hardware impairments can cause capacityceiling and channel estimation. Gravehardware impairments will be experienced by the user compared to the basestation side. Consequently, to prevent the phase noise problem, the transceiveralgorithm has to be created carefully (Adnan, Rafiqul and Alam, 2016). ConclusionThispaper briefly presented 5G systems along with the benefits and challenges of massiveMIMO technology. With 5G technologies, there is hope to build the wirelessnetwork that will come in great everyday use.
The technology massive MIMOprovides many advantages in terms of energy efficiency, spectral efficiency,reliability and robustness. There are high expectations from 5G systems to suchas reduced latency and improved data speeds for consumers. However, remainingchallenges will have to be resolved in order to achieve the full requirements andpotential of the technology. Therefore, this gives many challenges toresearchers in both academia and industry to deal with.