## 1 Introduction
Multi-Factor Dynamic GTS Allocation Scheme (MFDGAS) in [17] proposed CFP slots allocation to nodes by considering their data traffic, communication delay and slot size requirement. This improves the GTS utilization of CFP at the cost of fairness. However, it does not address latency issues and QoS is compromised. In [18], Advanced GTS Scheduling (AGS) is proposed for industrial applications. Authors claim that AGS improves link utilization and also chances of collisions during GTS requests are avoided. [PERSON] et al. [19] proposed a priority-based algorithm for adaptive superframe adjustment and GTS allocation (PASAGA) for IoT applications. The algorithm prioritizes GTS to sensitive data as compared  
Figure 1: IEEE 802.15.4 Beacon enabled mode Superframe format. to other data traffic. The authors claim that PASAGA improves bandwidth utilization and improves delay for sensitive data in comparison to the standard. In [20], authors proposed an optimal relay selection technique for IEEE 802.15.4 based sensor to sink communications. The authors also propose an efficient channel access mechanism to improve the network throughput and reduce packet collisions resulting in lower energy consumption of the sensor nodes. In [21], a novel medium access protocol for the IEEE 802.15.4 Time-slotted Channel Hopping (TSCH) based wireless sensor networks is proposed. The proposed protocol uses Enhanced Beacons (EBs) based scheduling approach to minimize the collisions due to simultaneous transmissions of the sensor nodes. As compared to the centralized schemes, the proposed autonomous scheduling protocol improves the energy consumption and throughput. All research related to maximizing the throughput and reduce communication delay of the traffic in CFP consider the above-mentioned scenario mentioned in the 802.15.4. standard [22]. However, these constraints were properly addressed in [23] by proposing an Efficient Superframe Structure (ESS) where CFP precedes the CAP as shown in Figure 2. This superframe structure minimized the delay in a significant manner. The link utilization has also been improved by reducing the GTS duration to half of the normal slot length. A large number of applications offer adaptive data traffic with an adaptive duty cycle to meet QoS. One of the requirements of such applications is to avoid unnecessary delay, optimally scrutinize data requesting nodes in a superframe structure with improved link utilization. To meet these requirements, an adaptive duty cycle according to the data requests is required. Though \(ESS\) manages the delay and link utilization to some extent, however, \(ESS\) as well as standard does not meet the adaptive data requirements of GTS requesting nodes. In this work, an Efficient Superframe Structure with Adaptive Duty Cycle (\(ESS_{ADC}\)) is proposed to meet the adaptive data requirements. \(ESS_{ADC}\) follows the superframe structure of \(ESS\) by preceding CFP than CAP for reduced network delay and introduces an algorithm, that allows PAN coordinator to adjust its duty cycle according to the traffic requirements. Major contributions of \(ESS_{ADC}\) are:  
* \(ESS_{ADC}\) _adjusts active period of the superframe to improve the GTS utilization and offers better data transmission._
* _Similar to \(ESS\), GTSs have been doubled by reducing their slot size to half of the IEEE 802.15.4 standard. This helps in accommodating up to 14 GTS requesting nodes instead of 7._
* _PAN coordinator scrutinizes the GTS requesting nodes by applying Shortest Job First (SJF) algorithm instead of first come first serve. This helps in reducing the network delay._
* \(ESS_{ADC}\) _is backward compatible with the standard and adequate with existing parameter._  
Figure 2: Efficient Superframe Structure. The rest of the paper is organized in the following manner: Section 2 briefly describes the IEEE 802.15.4 standard by emphasizing on the GTS allocation procedure. Section 3 discusses the proposed superframe format along with the necessary modifications in the beacon frame fields.