**1. Introduction**

32 Mobile Networks

protocols were the most suitable to ensure QoS in all IPv6/MPLS network. A series of architectures for next generation hybrid networks were proposed, including several important applications for universities, industry and the government. In general, the coupling between the quality of service and mobility protocols mentioned before is an excellent option to provide QoS in mobile networks and, especially, in the ad-hoc mobile ones. An interesting topic that we are currently evaluating is the different security issues that are generated in coupling protocols, which can actually degrade the quality of service by the action of malware or malicious users. On the other hand, we can say that, in next generation networks (4G), an all IPv6/MPLS architecture will be critical in next generation wireless mobile networks, compatible with the standards proposed so far (WIMAX,

[1] "Mechanisms of quality of service and mobility in 4G".Jesús Hamilton Ortiz, Juan Carlos López and Carlos Lucero. Global Mobile Congress (GMC), Shanghai, China, 2009. [2] Integration of HMIPv6 mobility protocol and Diffserv quality of service protocols over

[3] "Integration of protocols FHMIPv6/MPLS in hybrids networks". Jesús Hamilton Ortiz, Jorge Perea, David Santibáñez, Alejandro Ortiz. Journal JSAT. 2011. [4] "FHMIPv6/MPLS to provide QoS in 4G". Jesús Hamilton Ortiz, Juan Carlos López.An

[5] "Metrics of QoS for HMIPv6/MPLS in a handover". Jesús Hamilton Ortiz, Jorge Perea, Juan Carlos López. An international Interdisciplinary Journal. 2011. [6] "AHRA: A routing agent supporting the IPv6 hierarchical mobile protocol with fast-

[8] "Services de mobile IP au dessus de MPLS". DEA, thesis, Lina E. Mekkaoui: Lebanese

[9] "Performance analysis on hierarchical mobile IPv6 with fast-handoff over end-to-end

[10] "A comparison of mechanisms for improving mobile IP handoff latency for end-to-end

Gonzales, Jorge Perea, Juan Carlos López. Journal, Editorial IJRRCS. [7] "Integration of protocols FHAMIPv6/AODV in Ad hoc networks" Jesús Hamilton Ortiz,

M-MPLS to provide QoS on IP mobile networks". Jesús Hamilton Ortiz. 10th IFIP International Wireless Communications Conference PWC´05 IEEE. Colmar, France,

handover over mobile ad-hoc network scenarios". Jesus Hamilton Ortiz, Santiago

Juan Carlos López, Jorge Perea. "Network Protocols and Algorithms" Macro think

advanced LTE/SAE, LTE/IMT, WiMAX/IMT).

August 25-27, 2005.

Institute.

University, 2005.

International Interdisciplinary Journal. 2012.

TCP". Robert Hsieh, GLOBECOM, 2002.

TCP". Robert Hsieh, Globes 2003.

**7. References** 

Recently, the IEEE 802.16 standard (IEEE Std 802.16-2004, 2004), a solution to broadband wireless access commonly known as Worldwide Interoperability for Microwave Access (WiMAX), has been considered as a promising standard for next generation broadband wireless access networks. IEEE 802.16e (IEEE Std 802.16e-2005, 2005), also called Mobile WiMAX (Li et al., 2007), provides enhancements to IEEE 802.16 to support the mobility of Mobile Subscriber Stations (MSSs) at vehicular speed. Like other wireless systems, conserving energy is one of the critical issues for MSSs in IEEE 802.16e. Therefore, it is required for the protocol to offer a well-designed energy-efficient algorithm for an MSS.

IEEE 802.16e is expected to support Quality of Service (QoS) for real-time applications such as Voice over IP (VoIP), video streaming, and video conferencing with different QoS requirements (Wongthavarawat & Ganz, 2003; Zhu & Cao, 2004). Such applications are delay and delay variation susceptible. For example, when data packets incur vast delays and delay variations, the quality of the application seriously degrades. In order to avoid such situation, QoS provides the guarantee of transmission. IEEE 802.16e defines five types of service classed: Unsolicited Grant Service (UGS), Real-Time Variable Rate (RT-VR), Non-Real-Time Variable Rate (NRT-VR), Best Effort (BE), and Extended Real-Time Variable Rate (ERT-VR). Among them, the UGS is designed to support Constant Bit Rate (CBR) services, such as T1/E1 emulation, and VoIP without silence suppression. These kinds of services generate fixed-size data packets on a periodic basis. They usually require stringent QoS delay constraints, so determining the length of sleeping duration of an MSS in IEEE 802.16e is not only bounded by the total amount of traffic generated by the connections in the MSS, but is also restricted by the connections' QoS delay constraints. IEEE 802.16e was developed for the targets on mobile devices which are generally powered by energy-limited batteries. Thus, the energy-efficiency is an important issue to extend the lifetime of MSSs (Jang et al., 2006; Mukherjee et al., 2005; Tian et al., 2007). When a connection is established, an MSS may shift the operation status into sleep mode in order to save the power consumption if there are no packets to send or to receive in certain frame durations. Under sleep mode, there are two intervals: sleeping interval and listening interval. During the sleeping interval, an MSS can be powered down by putting its wireless network interface into sleep mode. Aside from this, the MSS would be unable to send or to receive packets during sleeping intervals. After a sleeping interval finishes, the MSS switches to listening interval. The MSS wakes up during the listening interval to check

A QoS Guaranteed Energy-Efficient Scheduling for IEEE 802.16e 35

periods and a maximum interval of sleep periods without violating the QoS of all connections in an MSS. Additionally, the successive scheduling of time slots would reduce the number of status transitions between sleep periods and listen periods. This improvement greatly contributes to achieve the power-saving. The proposed approach can be adapted to the power-saving class of type III where the length of sleep and listen periods

In this chapter, the centrally controlled IEEE 802.16e wireless network with a central BS and an MSS with multiple real-time connections is considered. The uplink and downlink channel is divided into fixed-size frames, and the frames are subdivided into fixed-size time slots. Both the energy consumption and the bandwidth are calculated in time slots. Different QoS parameters have been defined for various type of services in IEEE 802.16e, and all of them can be mapped into the minimum data rate requirements of the MSSs (Andrews et al., 2005). Therefore, we only apply the minimum data rate as the bandwidth requirement of QoS for each type of connection. Additionally, other QoS requirements such as the maximum latency and tolerated jitter would be considered in this chapter. The notations in this chapter are as follows: *Taw* is the total number of time slots in which an MSS stays in the awake state; *Tst* denotes the total number of status transitions of an MSS from the sleep state to the awake state; *Paw* stands for the average energy consumption of each time slot by an MSS in the awake state; *Pt* represents the average energy consumption of each status transition from the sleep state to the awake state in an MSS; *n* denotes the index of time slot in an MSS; *rn* stands for the data rate in which an MSS has been allocated by time slot *n*; min *Rn* stands for the minimum data rate that an MSS should receive in order to guarantee its service quality in time slot *n*. We assume that there is no energy consumed during the sleep period of an MSS. Thus, the energy consumed of an MSS is determined by the number of the time slots it stays in the awake state and the number of status transitions it has from the sleep state to the awake state. The overall energy consumed by an MSS during period *T*,

The goal of the scheduling algorithm is to minimize the average energy consumed by an MSS during period *T*, while the QoS requirements such as minimum data rate, maximum delay constraint and tolerated jitter of an MSS must be guaranteed. Thus, we can minimize *P* by allocating the minimum time slots (*Taw*) to satisfy the minimum data rates ( min *Rn* ) and successively schedule the packets to reduce the status transitions (*Tst*). In order to acquire the optimal result, the power-saving scheduling algorithm should consider the properties of the QoS requirements. We discuss the solutions of previous studies and present our QoS guaranteed energy-efficient scheduling to acquire the optimal result in the next section.

First, we give the idea of our QoS guaranteed energy-efficient scheduling and perform the algorithm of our successive scheduling in an example. In the second part, we consider the

jitter constraint of packet scheduling to provide more precise QoS guarantees.

*PT P T P aw aw st t* (1)

are variable.

**2.2 System model** 

denoted as *P*, can be represented as follows:

**2.3 QoS guaranteed energy-efficient scheduling** 

whether there are packets destined to it. Message packets are checked to determine whether the MSS should be woken up or not. IEEE 802.16e defined three types of Power-Saving Classes (PSCs) for connections with different characteristics, and each PSC is defined for a set of connections with common properties. A PSC is composed of interleaved listening windows and sleep windows. In PSC Type I, the sleep window is exponentially increased from a minimum value to a maximum value. This is typically done when the MSS is doing best-effort and non-real-time traffic. PSC Type II has a fixed-length sleep window and is used for UGS service. PSC Type III allows for a one-time sleep window and is typically used for multicast traffic or management traffic when the MSS knows when the next traffic is expected.

There are many previous researches that have devoted their efforts to adapting the sleeping duration of IEEE 802.11 and IEEE 802.15 (Liao & Wang, 2008; Liu & Liu, 2003; Tseng et al., 2002; Ye et al., 2004; Zheng et al., 2005). However, due to lack of QoS requirements, the results of those searches cannot be applied to IEEE 802.16e directly. Several studies have been proposed to analyze the IEEE 802.16e's power while an MSS operates in the power-saving mode (Han & Choi, 2006; Lei & Tsang, 2006; Seo et al., 2004). Several studies (Fang et al., 2006; Huang et al., 2007; Jang et al., 2006; Tsao & Chen, 2008) investigated the power consumption issues of IEEE 802.16e and suggested algorithms to determine the sleep interval in order to improve energy efficiency. In (Jang et al., 2006), the length of sleeping period is adapted according to the traffic type. This scenario is valid only under one MSS, and the QoS delay constraint is not considered. In (Tsao & Chen, 2008), although the QoS delay constraints are considered, the scenario cannot consider the energy costs of status transition. In (Fang et al., 2006), a scheduling algorithm for multiple MSSs with QoS delay constraints is proposed. To save power, the algorithm grants a primary MSS the right to use the bandwidth in burst mode. Secondary MSSs are only given the necessary bandwidth to meet the requirements of QoS delay constraints. However, its benefit only exhibits when the total traffic loading of all MSSs is low. In (Huang et al., 2007), although the constant bit rate traffic with QoS delay constraint is considered, the scenario cannot consider the jitter constraint.

In this chapter, we propose a QoS guaranteed energy-efficient scheduling for IEEE 802.16e. We consider that delay and jitter types of QoS should be scheduled at the same time and integrate sleep duration in one MSS. The packets would be scheduled successively to reduce the number of status transitions under QoS requirements for delay and jitter. The proposed approaches not only minimize the power consumption of the MSS but also guarantee both delay and jitter QoS of real-time connections.
