Difference between Inband D2D vs Outband D2D communication

This page compares Inband D2D vs Outband D2D communication and mentions difference between Inband and Outband D2D communication with their advantages, disadvantages and other parameters.

D2D communication refers to Device to Device communication. Here device can be mobile phone, vehicle or UE (User Equipment). D2D communication co-exists with cellular communication.

D2D Communication

Using D2D concept, devices communicate directly with or without involvement of BS or eNB or eNodeB. D2D links offer ultra low latency and provides high data rate connection between devices which are in close proximity. The D2D links use either licensed or unlicensed spectrum as described in Inband and outband below.

Inband D2D communication

• In this type, both D2D and cellular communication links use licensed spectrum.
• Licensed spectrum if divided into non-overlapping parts for D2D and cellular allocations, than it is called "Overlay". This scheme is easy to implement.
• Licensed spectrum if not divided at all, than it is called "Underlay". This scheme is more efficient in spectrum utilization. This gives more profit to operators.
• In this type, the network operator can control interference between D2D devices and cellular phones.

Difference between Inband D2D vs Outband D2D

Outband D2D communication

• In this type, D2D communication uses unlicensed spectrum viz. 2.4 GHz ISM band, 38 GHz mmwave band. Cellular uses its own dedicated licensed spectrum.
• This technique eliminates interference between D2D users and cellular users.
• The interference is present from other electronic wireless devices such as bluetooth and wifi which operates in the same unlicensed band.
• In this type, it is not feasible to control the interference by the operator.
• Outband D2D is further categorized into "controlled" and "autonomous" types. In controlled category, D2D radio interface is controlled by cellular network. In Autonomous category, cellular network controls only cellular links where as D2D links are controlled by users themselves.

Difference between Inband D2D and Outband D2D communication

Figure depicts both InBand D2D (Underlay and Overlay) and Outband D2D communication types. Following table mentions difference between Inband D2D and Outband D2D.

Features Inband D2D Outband D2D
Spectrum Licensed spectrum is used by both D2D and Cellular users. Unlicensed spectrum is used by D2D where as licensed spectrum is used by cellular users.
Types • Underlay
• Overlay
• Controlled
• Autonomous
Advantages • QoS guaranteed as cellular spectrum can be fully controlled by the BS.
• Transmission distance of 1 Km and data rate of 1 Gbps
• No need of new interface
• Any cellular device can use inband D2D communication
• In Underlay D2D communication, spatial diversity techniques are used to enhance spectral efficiency.
• No interference issue between cellular and D2D
• No need of resource allocation
• Simultaneous D2D and cellular communication
Disadvantages • Challenge is to handle D2D and cellular interference
• Algorithm is complex for resource allocation
• Resource wastage can not be avoided in overlay D2D
• A user can not have simultaneous cellular and D2D transmissions.
• Unlicensed band interference uncontrollable
• Two interfaces are required i.e. cellular devices need two radio interfaces such as LTE and wifi to use out band D2D communication.
• Power management between two wireless interfaces is crucial to control power consumption of the device. Hence it is not power efficient which leads to low transmitter distance and data rate.

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