Category | Subcategory | Reference | Principle for energy saving | Drawback | Notes |
---|---|---|---|---|---|
Cooperative | Clustering and relay | [55] | Group devices into clusters; | High energy consumption | It is possible to combine |
design | Â | [56] | Cluster head relays the messages for | for cluster head; | cooperative relaying with |
 |  | [12] | other cluster member in the same | Scheduling and resource issues in | other emerging technologies |
 |  | [57] | group | order to manage the interference; | for the device-to-device |
 |  |  |  | Delay increase cause of relay | link |
 | Cooperation between MTC | [9] | Adjust MTC device setting | High complexity for MTC devices |  |
 | server and MTC devices |  | according to context |  |  |
 | M2M gateway | [23] | Similar to clustering and | Installation and deployment | Reduce implementation complexity |
 |  | [58] | relay, except that M2M gateway | cost of M2M gateway | for MTC device. |
 |  | [60] | is a special network node | for operators | Possible to use LoRa gateway |
 |  |  | instead of a MTC device |  | as M2M gateway. |
Design of | Modified DRX and | [62] | Make MTC devices stay in low | High delay | Simple method to |
energy efficient | Idle state | [63] | power mode as long as possible | Â | achieve energy saving |
signaling and | Â | Â | Â | Â | Â |
operation | Â | Â | Â | Â | Â |
 | Extending paging cycle | [1] | Make MTC devices stay in low | High delay |  |
 |  | [2] | power mode as long as possible |  |  |
 |  | [64] |  |  |  |
 | Reduction of RRC | [65] | Make MTC devices stay in low | Impact on H2H service |  |
 | Inactivity timer |  | power mode as long as possible |  |  |
 | Group-based and | [66] | Group paging for MTC devices | May reduce the paging capacity |  |
 | M2M- dedicated |  |  | of H2H; |  |
 | paging mechanism |  |  | Scalability and bacward- |  |
 |  |  |  | compatibility issues. |  |
 | Removal | [66] | Remove activities related to | Applicable uniquely for | Reduce the cost of MTC |
 | of unnecessary activities |  | mobility management (MM) | M2M application with no | device and energy |
 |  |  | for MTC Device | or low mobility | consumption |
 | Disconnect MTC-device | [67] | Instead of staying in low power mode, | High delay |  |
 | from network when inactive |  | turn devices radio off |  |  |
Radio resource | Formulation of | [71] | Convert radio resource allocation | High complexity; | Â |
allocation | optimization problem | [72] | into an optimization problem with | Scalability issues; | Â |
and packet | Â | Â | constraints | Possible impact for human | Â |
Category | Subcategory | Reference | Principle for energy saving | Drawback | Notes |
scheduling | Â | Â | Â | users. | Â |
 | Optimized with periodicity | [73] | Leverage the periodicity of MTC | Applicable uniquely to periodic |  |
 |  | [74] |  | M2M applications; |  |
 |  |  |  | Not easy applied in the presence |  |
 |  |  |  | of different period values. |  |
 | Packet scheduling | [76] | Propose packet scheduling | Compatibility with H2H; | Ensure QoS requirements |
 |  | [29] | adapted for cellular MTC context | May need modifications of the specification |  |
Energy efficient | New random access protocol | [15] | ALOHA-based random | It may be difficult to find a specified | Â |
random access | Â | Â | access protocol is not | random access protocol suitable | Â |
and MAC | Â | Â | the best option for MTC | for all cellular users | Â |
 | Fixed time alignment | [78] | Leverage the low mobility of MTC | Only applicable for M2M | Reduce the access collision |
 |  |  |  | with no mobility |  |
 | Transmit message in | [23] | Transmit message directly | Scalability issues | Reduce the signaling overhead |
 | MAC PDU or preamble |  | in access reservation stage |  |  |