One of the reason 5G deployment is needed is the need for increase capacity. Exponential growth and availability of data in all forms is the main booster to the continuing evolution in the communication industry.
The immense amount of traffic generated by today's customers requires a paradigm shift in all aspects of mobile networks. Ultradense network (UDN) is one of the leading ideas in this racetrack.
What is UDN?
Ultra-Dense Networks (UDN) can be defined as those networks where there are more cells than active users. In other words the density of access points is greater than density of users.
Different quantitative definitions exist for Ultra dense networks exist such as when the measure of cell density is greater than 1000 cells / Km squared or when there are 600 active users / Km squared.
The network is densified by deploying small cells indoors in buildings
and stores, and outdoors on trees, lampposts, and building walls. Small
cell networks coexist with macrocells, either in the same spectrum or on a
dedicated carrier.
Types of Small Cells
Generally, the small cells in UDN can be classified into fully functioning base stations (BSs) which includes picocells and femto-cells. It also includes macro extension access points which includes relays and Remote Radio Heads (RRHs). Roughly divided into two categories
- Fully functioning base station
- Macro-extension access node
- Fully functioning base station is capable of performing all the functions of a macrocell with a lower power in a smaller coverage area.
- Macro-extension access node is an extension for the macrocells to effectively extend the signal coverage, and it performs all or some of the physical layer functions only.
In general small cells deployments in UDN feature different capabilities, transmission powers, coverage and deployment scenarios. A brief summary of the features of different small cell types is shown below.
Different Type of Small Cells
Challenges in UDN and Performance metrics
UDNs come with a unique set of challenging problems which require some unique solutions In addition, key performance indicators (KPIs) have been defined that are used in quantifying the performance of solutions for UDN challenges.
UDN Research Challenges and Performance Metrics
For more details, you can read at the source below
M. Kamel, W. Hamouda and A. Youssef, "Ultra-Dense Networks: A Survey," in IEEE Communications Surveys & Tutorials, vol. 18, no. 4, pp. 2522-2545, Fourth-quarter 2016.