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Energy-efficient GCSA medium access protocol for infrastructure-based cognitive radio networksThe major challenge encountered by battery-driven wireless local area networking devices is to conserve their energy for prolonged operation. This paper presents an energy-efficient medium access mechanism called group control slot allocation (GCSA) protocol for cognitive radio (CR) networks. GCSA utilizes the group priority allocation algorithm to allocate stations (STAs) into groups; subsequently STAs that have traffic buffered in an access point are assigned to a higher priority group. A management frame, namely group monitoring pointer, optimizes the sleep-awake cycle of the STAs by allocating transmission opportunities to groups based on their priority. GCSA employs publisher-subscriber and point-to-point messaging models for communication between the base station and STAs, respectively. Performance analysis of GCSA demonstrates that increasing the number of STAs which enter into sleep mode augments the percentage of energy saved. The overall system-level results show that energy saved is around 20% higher for GCSA than the IEEE 802.11e standard hybrid coordination function power-saving mode. Since GCSA benefits from history-assisted-led spectrum sensing, the paper also presents the relationship of the local storage of CRs with respect to history and suggests a hybrid approach as best option to keep a balance between the sensed data and its sharing with analytical engine database for history enrichment leading toward improved energy efficiency.
Euclidean geometry axioms assisted target cell boundary approximation for improved energy efficacy in LTE systemsLong Term Evolution (LTE) facilitates users with high data rate at the cost of increased energy consumption. The base station, also known as eNodeB, is the main energy hungry elements in LTE networks. Since power consumption directly affects the operational expenditure, thus the provision of cost-effective services with adequate quality of service has become a major challenge. This paper investigates reduced early handover (REHO) scheme aimed at increased energy efficiency in LTE systems. REHO, compared to standard LTE A3 event, initiates early handover, thereby resulting into reduced energy consumption. Axioms of Euclidean geometry are employed to estimate the target cell boundary towards calculation of the time difference ΔT between standard LTE and REHO. Performance analysis involved comparison of standard LTE with REHO in the presence of varying velocity and Hysteresis values. Early handover ΔT in REHO is calculated in terms of transmission time intervals and results into improved energy efficiency at the cost of slightly increased radio link failure (RLF). The key finding of the work is the nonsensitivity of users towards velocity in standard LTE, whereas REHO leads to considerably improved energy efficiency at low velocity thereby making it an advantageous scheme for urbanised densely deployed LTE networks. Outcomes provided also deliver a guideline for vendors to choose suitable value of hysteresis, while achieving appropriate results of energy saving and RLF.