Small Cells

Next generation 5G wireless networks will run applications requiring high demand for data rates. One of the solution to solve the data rate requirement is to allow densification of network by deploying small cells. Such densification results in higher spectral efficiency and can also reduce the power consumption of mobile due to its communication with nearby pico-cell. This solution significantly improves network coverage. However, this solution requires innovation in hardware miniaturization and cost reduction in the design of small cell base-station. Such small cell base-stations can be deployed as low powered femtocells typically used in enterprise/residential deployments or higher powered pico cells for improving outdoor coverage of macro cells. The concurrent operation of Macro-, micro-, pico- and femto-cells is termed as heterogeneous networks (HetNets). Interference management is one of the most critical challenges due to the uncoordinated nature of HetNet deployments. However, 3GPP has identified various scenarios and requirements in  for the enhancements of small cells.

Heterogeneous Networks

New Carrier Type

There has been recent push from both the academia and industry (3GPP) to enhance the operation of small cells by splitting control and data plane. The main idea here is that control plane provides connectivity and mobility, whereas user plane provides the data transport. This results in the fact that user equipment (UE) is connected to multiple base-stations, viz. macro and small cell. Such a definition of new carrier type in 3GPP (Rel 8-10), results in improved spectral efficiency  as data transport is handled by small cell. There is also significant gain in energy efficiency of network infrastructure as small cells can be switched off in case of lightly loaded scenarios.

LTE/WiFi Coexistence

5G wireless network design will see lot of convergence happening between LTE/WiFi networks. There has already been push from the industry to operate LTE in unlicensed bands. Such an approach will allow easier offloading of traffic from LTE to unlicensed bands. However, such offloading poses quality of service (QoS) issues for end users due to unmanaged and over-crowded nature of today’s WiFi deployments. IEEE 802.11 Working group has also initiated a study group on High Efficiency WLANs (HEW) to address the densification of access points and terminals.

Device to Device Communications

Device to Device (D2D) communications is an approach where terminals close by discover themselves automatically and interact with each other without the base-station. Such an approach is highly efficient from power control standpoint and can also reduce interference in unlicensed frequency bands.

Conventional cellular architecture does not allow for user equipments (UEs) to communicate directly. However, when the devices are close by, this can be very inefficient and D2D can be especially useful in machine-type-communication (MTC) scenarios where there are large number of devices operating closely with each other. D2D when combined with the fact that it can be coordinated with base-stations can bring significant advantages to the existing cellular architecture in terms of both energy efficiency and spectral efficiency. D2D is currently an active topic of discussion within 3GPP.