Table 4 Handover and network interaction

Resource management

Load balancing

Optimum resource reservation in conditional handover

Optimum resource reservation in multi-connectivity

[55,56,57,58,59,60, 84, 89, 103, 106]

CP/UP separation

Growth of handover rate

High signaling traffic

CP/UP Signaling synchronization

Growth of authentications

Optimum placement of CP/UP nodes

[61, 62, 64, 65, 75, 76, 107]

NF placement

Dynamic NF placement

Adaptive NF placement

Fully autonomous NF placement

Optimal signaling between separated NFs

[67,68,69, 108]

Signaling

Smooth transition from current to future cellular networks

Latency, transmission and processing costs.

Inter-RAT signaling

3GPP/non-3GPP signaling

[70,71,72, 86, 87, 109,110,111,112,113]

Multi-connectivity

Optimal selection of secondary BSs

Soft path switch (Minimize path switch delay)

Higher signaling load

Radio resource management

Energy management

[36, 62, 73,74,75,76,77,78, 100,101,102,103, 114,115,116,117]

D2D connections

Interference cancellation

Network discovery

Security

Beam forming at device side

Selection and establishment of relay stations

[80,81,82,83,84,85,86,87,88,89, 91, 94, 118]

mmWave

Severe channel intermittency

Highly susceptible to blockage

Beam forming needed due to high isotropic pathloss

High handover frequency

Imprecise signal quality measurement

[36, 45, 50, 51, 64, 65, 73, 75, 78, 81, 89, 91, 95, 98, 113, 114, 119,120,121,122,123,124,125,126,127]

TCP

Congestion control algorithm

Optimum TCP packet size

Buffer size in different protocol stack layers

[94,95,96, 98, 100,101,102,103]