Cloud and Fog Computing in 5G Mobile Networks-IET(2017).pdf下载

In order to continue to ensure the sustainability of mobile communication services over the next decade and to meet the business and consumer demands, fifth genera- tion (5G) mobile communication services is expected to be rolled out by 2020. One of the major requirements for 5G networks is the significant spectral efficiency (SE) enhancement compared to fourth generation (4G) as the anticipated exponential increase in the volume of mobile data traffic is huge, for example, at least 1,000-fold in the 2020s compared to 2010. In particular, the peak data rate in 5G should be 10–20 Gbps that is 10–20 times the peak data rate in 4G, and the user experienced data rate should be 1 Gbps (100 times the user experienced data rate in 4G). In addition, the rapid development of Mobile Internet and the Internet of Things (IoT) exponentially accelerates the demands for high data rate applications, including high-quality video streaming, social networking, and machine-to-machine communications. In cellular network, the design of radio access technology, in general, and multiple access technique, in particular, are one of the most important aspects in improving the system capacity. Multiple access techniques are usually categorized into two orthogonal and nonorthogonal approaches [1]. In orthogonal approaches, 2 Cloud and fog computing in 5G mobile networks signals from different users are orthogonal to each other, that is, their cross correlation is zero (the available resources such as the system bandwidth (BW), and time is divided among users). Nonorthogonal schemes such as code division multiple access (CDMA) allow nonzero cross correlation among the signals from different users. Second and third generation cellular systems such as IS-95, CDMA2000, and wideband-CDMA (WCDMA) have adopted nonorthogonal multiple access (NOMA) techniques. CDMA is usually more robust against fading and cross-cell interference, but is susceptible to intracell interference. With careful cell planning, orthogonal multiple access (OMA) can avoid intracell interference. On that, most of the first and second generation cellular systems adopted orthogonal MA approaches. Even, orthogonal frequency division multiple access–based OMA has been adopted in 4G systems such as long-term evolution (LTE) and LTE-advanced. Despite a practical advantage of intracell interference avoidance capability, CDMA has limited data rate due to its spread-spectrum nature. OMA is a realistic choice for achieving good performance in terms of system-level throughput. However, due to the aforementioned upcoming wave, 5G networks require further enhancement in the system efficacy. Then again, to get the facilities of on-demand resource processing, delay-aware storage, and high network capacity, the cloud computing–based radio access infrastructure is a possible solution. And, advanced baseband computation and radio frequency communication are required to enable large-scale cooperative signal processing in the physical layer and adapted to new air interfaces in 5G systems. In this regard, researchers over the globe have started investigating NOMA as a promising multiple access scheme for future radio access. NOMA achieves superior spectral efficiencies by combining superposition coding (SC) at the transmitter with successive interference cancelation (SIC) at the recei- vers [2,3]. On the top of that, the evolution of wireless networks into 5G poses new challenges on energy efficiency (EE), as the entire network will be ultradense. With an extreme increase in number of infrastructure nodes, the total energy consump- tion may simply surpass an acceptable level. Although the substantial energy is basically consumed by the hardware, the NOMA has an inherent ability to adapt the transmission strategy according to the traffic and users channel state information (CSI). Thus, it can achieve a good operating point where both the spectrum efficiency and EE become optimum. In view of the fact that the IoT is expected to be widely used in our everyday life, the fog computing is growing in popularity. One of the primary objectives of fog networking is minimizing the use of BW. Although fog computing is implemented by handing some application services at edge devices and in a remote data center, some physical and medium access control layer issues can help to achieve its efficient spectrum utilization intention. In this regard, NOMA is important, as its target is also the efficient utilization of available spectrum. Over the past few years, NOMA has attracted huge attention of researchers to meet the 5G requirements. As a consequence, many research efforts on this field already exist. Research trends in NOMA include diverse topics, for example, performance analysis, cooperative communications, and fairness analysis. However, NOMA in 5G is still in its infancy. At this stage, a comprehensive knowledge on the up-to-date research status of NOMA in 5G systems is extremely useful to researchers to do more research in this area. In this chapter, we appraise the state of the art of NOMA schemes for 5G green mobile networks 3 NOMA research trends and disclose various issues that need to be addressed to transform radio access techniques through NOMA innovation.