Design of Sustainable Cloud Radio Access Networks

无线数据流量和移动设备数量的指数级增长预计将继续下去。例如，据思科预测，2021年人均移动设备数量将达到1.5台；将有116亿台移动连接设备，包括机器对机器模块。2016年至2021年间，全球移动数据流量将增长7倍。另一方面，全球蜂窝网络每年的能源消耗约为600亿千瓦时，预计在未来几年内将翻一番。具体来说，蜂窝网络使用的大部分（80%）电力被基站消耗，每年排放超过1亿吨的二氧化碳。对高无线数据速率的需求、电价的上涨以及环境问题的日益关注，使得蜂窝网络供应商面临着独特的挑战，导致资本和运营支出的大幅增加。因此，对无线网络以可持续的方式满足不断增长的无线数据需求的需求比以往任何时候都更加迫切。为了实现可持续能源和频谱效率的无线网络，一些有前途的技术，如大规模多输入多输出（MIMO）、毫米波通信、网络致密化和能量收集，正在研究中。云无线接入网（CRAN）被认为是实现网络致密化的一种潜在解决方案，因此将以成本和节能的方式满足无线网络流量的指数级增长。CRANs有助于增加网络容量和能源效率，同时降低网络资本支出和运营费用。然而，我们坚信CRANs的潜力仍然没有得到充分利用，通过结合大规模MIMO和能量收集等新技术，CRANs的性能可以得到显著提高。该项目的目的是设计可持续的高能量和频谱效率的CRANs。该项目的新颖之处在于，我们提出并优化了一种新的CRAN架构，该架构包含一个大规模MIMO中央单元和配备混合能源（即具有能量收集能力和与电网的连接）的远程无线电头（RRHs），以进一步提高无线网络的能量和频谱效率，同时保持可持续发展。为实现该项目的目标，我们将考虑建议的CRAN架构的长期和短期性能优化。在长期性能方面，由于使用无线前传提供了放置RRHs的灵活性，我们建议优化RRHs的放置。在短期性能方面，我们提出设计一种低复杂度的信道估计方法，并联合设计前传链路和接入链路。新的CRAN架构的优化设计将导致可持续和改进的能源和频谱效率无线网络。

The exponential growth in terms of wireless data traffic along with the number of mobile devices is expected to continue. For example, according to Cisco, it is predicted that the number of mobile devices will reach 1.5 per capita in 2021; there will be 11.6 billion mobile-connected devices including machine-to-machine modules. Global mobile data traffic will increase sevenfold between 2016 and 2021. On the other hand, the energy consumption of cellular networks world-wide per year is around 60 billion kWh and is expected to double within the next few years. Specifically, the large portion (80%) of electricity used in cellular networks is consumed by base stations, emitting over a hundred million tons of carbon dioxide annually. Combining the need for high wireless data rates, the increase in power prices and the raising environmental concerns, cellular network providers are facing unique challenges leading to huge increases in capital and operating expenditures. As a result, the need for wireless networks meeting the ever increasing demand in wireless data in a sustainable way is more pressing than ever.To achieve sustainable energy and spectrally efficient wireless networks, several promising technologies, such as massive multiple-input multiple-output (MIMO), millimetre wave communication, network densification and energy harvesting, are under investigation. Cloud radio access network (CRAN) is considered as a potential solution to achieve network densification, and hence will meet the exponential growth in wireless network traffic, in a cost and energy efficient manner. CRANs facilitate increase in network capacity and energy efficiency while reducing both network capital expenditure and operating expense. However, we strongly believe that the potential of CRANs is still not fully exploited and their performance can significantly be improved via incorporating new technologies such as massive MIMO and energy harvesting. The aim of this project is to design sustainable high energy and spectral efficiency CRANs. The novelty of this project is that we propose and optimise a new CRAN architecture incorporating a massive MIMO central unit and remote radio heads (RRHs) equipped with hybrid energy sources (i.e., with energy harvesting capability and connection to the power grid) to further improve the energy and spectral efficiencies of wireless networks while being sustainable. To achieve the goal of this project, we will consider both long-term and short-term performance optimisation of the proposed CRAN architecture. In terms of long-term performance, given the flexibility in placing the RRHs offered by using wireless fronthaul, we propose to optimise the placement of the RRHs. In terms of short-term performance, we propose to design a low complexity channel estimation method and to jointly design the fronthaul and access links. The optimised design of the new CRAN architecture will lead to sustainable and improved energy and spectral efficiency wireless networks.