Load Based Sleep Scheduling with Reduced State Transitions for IEEE 802.16e Networks

Load Based Sleep Scheduling with Reduced State Transitions for IEEE 802.16e Networks

Gopalan M. (Multimedia University, Cyberjaya, Malaysia), Marthandan G. (Multimedia University, Cyberjaya, Malaysia) and Eswaran C. (Multimedia University, Cyberjaya, Malaysia)
DOI: 10.4018/IJBDCN.2018070105
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IEEE 802.16e is extensively used these days for both data and voice communications as it makes available high-speed wireless access. However, in view of the fact that mobile subscriber stations are powered by a limited capacity battery, power saving mechanism is necessary to improve network performance. In this article, the authors introduce a load based sleep scheduling mechanism with reduced state transitions for IEEE 802.16e Networks. The mechanism encompasses two phases, load-based sleep scheduling and a reduced state transition (RST) algorithm. Considering network load information, the Base Station (BS) assigns a sleep window size for each mobile subscriber station (MS). The proposed RST algorithm reduces the number of state transitions between sleep and active mode by watchfully combining any two adjacent active bands. Further, the technique considers network load and delay as QoS metrics. Through simulation results, the authors prove the proficiency of their mechanism.
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1. Introduction

1.1. Worldwide Interoperability for Microwave Access (WiMAX)

IEEE 802.16 WiMAX is signified as a standard for accessing wireless broadband networks. It is thought up by Institute of Electrical and Electronics Engineers (IEEE) to satisfy various end users requirements (Arhaif, 2011). It exploits Orthogonal Frequency Division Multiple Access (OFDMA) with the spectrum ranges between 1.25 MHz and 28 MHz. It benefits both Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). Beam forming and Multiple Input Multiple Output (MIMO) are some of the sophisticated techniques used by WiMAX. Apart from this, it makes use of advanced coding techniques such as space-time coding and turbo coding (So-In, Jain, & Tamimi, 2009).

WiMAX is extensively used in data, telecommunications (VoIP) and IPTV services (triple play). The bandwidth range of WiMAX makes available broadband connectivity through variety of devices to overall the world (So-In et al., 2011).

1.2. Scheduling in WiMAX

Scheduling is the process of allocating available resources among users in the network. This technique achieves maximum throughput by guaranteeing fairness among all users (Wail Mardini & Alfoul, 2011). IEEE 802.16 describes five scheduling services namely unsolicited grant service (UGS), real-time polling service (rtPS), extended real-time polling service (ertPS), non-real-time polling service (nrtPS), and best effort service (BE) (Zhang, Chen, Fu, & Dai, 2008).

1.3. Power Control in IEEE 802.16e

Wireless systems turn out to be faster and intelligent these days. It supports not only voice communications but also data communication as e-mail, web-browsing, music downloading and payments. These flexibilities make wireless communication more suitable than wired network. On the other hand, this high-speed access leads to high power consumption of wireless systems. To accomplish high speed access for longer time, large capacity battery is essential. To alleviate this network degradation, lessening power consumption became an important factor of wireless broadband systems (Iseda, Tetsumei, and Kato, 2008).

Three types of power saving classes (PSCs) are initiated by IEEE 802.16e namely PSC of types 1, 2 and 3. In that classes Best Effort (BE) and non-real time variable rate (NRT-VR) traffics are supported by PSC I type and on the other hand unsolicited Grant service (UGS) and real time variable rate (RT-VR) traffics are assisted by PSC II type. The last PSC type III is recommended for management operation and multicast connections. Parameter, procedures of activation and deactivation and policies of one PSC differentiates another PSC. Implementing sleep mode operation is the central principle of power saving mechanism and it lessens mobile station (MS) power consumption significantly (Nguyen, Pham, & Moon, 2011).

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