|
| Reference | Problem | Proposed solution/Purpose | Description | Limitations |
|
| | High energy consumption of border nodes in SMAC | Schedule unifying algorithm (SUA) | SUA tracks the multiple schedules followed by the border nodes and immediately triggers a procedure to unify the schedules. | # High control overhead |
| # Network throughput not measured. |
| [191] | High energy consumption of border nodes | Low overhead WSN MAC (LO-MAC) | Introduced a unified schedule that lessens the synchronization time of the original SMAC by avoiding sending sync packets. | # No intercluster communication |
| # Not adaptable to an extensive network |
| # Higher average delay as sending interval increases |
| # Has shorter sleep time |
| [192] | High energy consumption of border nodes | An enhanced SMAC is proposed using selective intermediate nodes (SIN) | # SIN is utilized when border nodes send a unicast request to follow a schedule that is already following another schedule. | # Algorithm does not expatiate. |
| # An ACK is sent to nodes allowed to adapt to the schedule to reduce the number of schedules adopted by a border node. | # High control overhead |
| [193] | Forced wakeup problem in adaptive SMAC | CL-MAC protocol | The CL-MAC protocol utilizes routing layer information to determine nodes that need to be awake to communicate. Hence, nodes in sleep modes are excluded from the routing paths for data transmission. | # It does not ensure fairness in terms of the traffic loads |
| # Simulation tool not mentioned. |
| [189] | High energy consumption | Power controlled sensor MAC (PC-MAC) | # Modified the SMAC schedule table to include each node’s minimum power levels. | # The protocol is limited to reducing only the transmission power and energy consumption |
| # Uniform, exponential, and Gaussian distributions were used for the experiment. |
| [62] | High energy consumption of border nodes | A new unified scheduling algorithm is introduced to improve the lifetime of border nodes. | Constructs border nodes and broadcasts uni-scheduling packets from the border nodes to unify all schedules into a single schedule | # High control overhead |
| # Throughput not measured |
| [101] | High energy consumption of border nodes | Improved SMAC algorithm by merging virtual clusters | Virtual clustering in the original SMAC is modified to merge clusters to follow one cycle, thereby reducing the number of border nodes’ multiple schedules | Cross-layer optimizations |
| A dynamic duty cycle is utilized |
| 108 | # Inefficient use of energy | Energy-efficient sensor MAC (ES-MAC) | # Modified SMAC and T-MAC algorithms. | # Multihop scenarios |
| # Transmission of redundant data | # Selective data transmission is used to minimize the number of transmitted packets sleep interval improved by applying data cycle (DDC) | # Back-off mechanism |
| [194] | High energy consumption | ASS-MAC protocol dynamically alters the nodes’ sleeping time based on the last observed traffic. | The protocol “provides the schedule of the next period based on network behaviour during previous periods to adapt to network traffic” | # Network throughput |
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