Green & Soft RAN
The key design principle of 5G technology is the concept of “no more cells”. The concept of no more cells focus on user centric cells rather than cell centric networks. 5G technology requirements includes higher spectral efficiency , energy efficiency , low end to end latency and more number of connected nodes. With the increase in carbon emissions , global warming , air pollution and rise in sea levels , the most urgent issue worldwide is energy savings . 5G technology focus on energy and spectrum savings. To fulfill these requirements 5G majorly focus on two themes: green and soft.
In the 5G era, mobile data traffic is not only generated by mobile devices. With the increase in IOT applications , the mobile networks are used to transfer data between various machine devices. In order to achieve energy efficiency , various operators have been actively developing and deploying green technologies like green BS powered by renewable energy and infrastructure. Energy efficient infrastructure is cloud Radio access network.
Soft is also an important feature of 5G networks . as the infrastructure is growing with the advancement in generations and to meet the data demand of the users, so the network infrastructure is becoming more and more complex , so in order to solve this problem , the concept of soft has been introduced. It mainly focus on separating hardware and software , control plane and data plane has also separated from each other. Cost efficiency can be maintained with the concepts of SDN ( software defined networking ) and NFV ( network functions virtualization ).
CRAN is cloud radio access network
CRAN is cloud radio access network. It is also referred as centralized radio access network. It implements soft and virtualized BS (base station) with multiple baseband units which are integrated as virtual machines on the same servers. They are capable of supporting multiple radio access technologies. CRAN is centralized, cloud computing based architecture for future wireless communications. In CRAN architecture there are RRH ( Remote Radio Heads) which are connected to BBU ( baseband units ). Here is CRAN there is large scale deployment which means that hundreds or thousands of RRH units are connected to BBU pool. Any BBU pool can talk to other BBU pool with very high bandwidth. CRAN also has capability of real time virtualization. The architecture is based on distributed BSs where radio units are placed outdoors closer to the antenna and BBU units are placed indoors at cell sites. CRAN brings various BBU’s in a pool at a central location. Because of this centralisation , there is efficient cooling which leads to green networks. By virtualizing the baseband processing, new features can be added to the network.
EE and SE co-design :
It means that there is need to rethink shannon theorem , this is to overcome limited spectrum capacity problem and to meet the ever increasing demand of the capacity. Techniques like spatial modulation can utilize the antenna resource more efficiently. There is a need to optimize energy efficiency and spectrum efficiency together in order to meet capacity demand of the future.
No more cells :
Rethink: Ring & Young : the cell centric design in the cellular technologies is maintained from previous generations till 4G. This nature of cell centric design is that planning , optimisation , mobility management , resource management. Signalling and control is all done by single BS only.moving to the era of 5G , it focus on hetnets, distributed antenna systems, relays, coordinated multipoint etc, so there is a need of cell centric networks in future generations. So for this there is a concept of NMC (no more cells).
User centric cells :
The concept of no more cells is user centric in nature. Number of cells , decoupling signalling and data & decoupling of uplink and downlink signals are concepts which are there. In heterogeneous network, there are small cells and macro cells, the small cells are within the coverage of macro cell , with decoupling of control and data , the macro cell is responsible for signalling where as small cell is responsible for data only.in case when there is no data traffic in the small cell , it could be completely turned off to save energy and users can use the macro cell for operations when there is need of data transmission , the macro cell can coordinate with the small cell to turn it on. There is symmetric UL and DL transmission.
Rethink signalling & control :
Mobile networks are designed for many applications like conventional and streaming like voice and video. Traffic profiles have grown because of the rise of internet traffic. The massive connectivity involved in MTC may not be handled by wireless communication methods like 3G and 4G technologies. As per the statistics , there is a huge increase in data traffic because of the data generated from IOT devices. Therefore it is important to design new signalling mechanism to handle such huge amount of data. So it is important to redefine signalling and control in order to handle huge amount of data .
Aggregation of packet data from multiple MTC devices :
MTC devices are controlled by aggregator , which functions as wireless gateways to the cellular network. There are multiple services , services could be homogeneous or heterogeneous , they are sent to the aggregator in a scheduled manner. The aggregator will relay the various packets , they aggregate various packets together based on aggregation methods. Service aggregation of various MTC devices is the service aggregation of small sized packets from multiple applications together running on multiple mobile devices.
Multiple MTC devices are connected to the aggregator , the aggregators are connected to the servers which are further connected to various applications. Transmission between them are various transmission technologies like wifi , zigbee or 3GPP technologies. Relay modes for aggregator operates in two modes : the first mode is no RRC state : this state is always connected : in this, number of aggregators with the same MTC traffic behave on orthogonal resources on different frequency bands transmitting to the network in FDMA mode. The next mode is RRC connected mode : in this mode all frequency resources are shared in TDMA (time division multiple access).
Irregular antenna array :
Integrating multiple antenna elements into the environment , the BS’s can be made virtually invisible. Irregular antenna deployment in a practical deployment requires different system design and new signal signal processing. There is requirement of beamforming optimization , there are various challenges for irregular antenna arrays like synchronization , signalling and broadcast . spacing and relative position of each antenna should be required for signal transmission and processing of signals. This integration of massive number of antennas is massive MIMO technology. Massive MIMO technology is there for increase in data rates.
Full duplex radio :
Current cellular technologies like 3G, 4G technologies support TDD (time division duplex) and FDD ( frequency division duplex) modes . in order to have energy efficiency and spectrum efficiency full duplex operation is required for 5G systems. A full duplex BS can transmit and receives signals at the same time using the same frequency resources. Various self interference calculation schemes are used in the system . various techniques are required to build self interference management techniques. In duplex communication both transmission and reception of the signals can be performed at the same time. In future 5G technologies , advanced full duplex communication schemes will be required for high throughput applications and for simple spectrum management.
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