Delay Tolerant Network (DTN) is emerging as a solution for supporting data transfer in intermittently connected networks. In DTN, to cope with long disconnections, messages are buffered for a long period of time. Thus, according to the queue management the performance can be affected significantly. Power is also a scarce resource in DTN. Energy can be saved by putting mobile nodes into sleep during long delayed connections. In this thesis, a Medium Access Control (MAC) protocol that supports adaptive sleep scheduling of a mobile node is proposed. Based on the MAC layer operation, an adaptive power management framework is developed. The framework considers power saving and buffer management together in order to minimize power consumption while minimizing the performance degradation of buffer management for the mobile node. Variations of the performance of a traffic source node which are affected by diverse network parameters are also investigated.

Delay Tolerant Network (DTN) is emerging as a solution for supporting data transfer in intermittently connected networks. In DTN, to cope with long disconnections, messages are buffered for a long period of time. Thus, according to the queue management the performance can be affected significantly. Power is also a scarce resource in DTN. Energy can be saved by putting mobile nodes into sleep during long delayed connections. In this thesis, a Medium Access Control (MAC) protocol that supports adaptive sleep scheduling of a mobile node is proposed. Based on the MAC layer operation, an adaptive power management framework is developed. The framework considers power saving and buffer management together in order to minimize power consumption while minimizing the performance degradation of buffer management for the mobile node. Variations of the performance of a traffic source node which are affected by diverse network parameters are also investigated.

<p>Internet access using IEEE 802.11 wireless local area networks has become very common. In home and office networks where voice, video and audio will be delivered, quality of service (QoS) support is essential so that customers can be offered video on demand, audio on demand, voice over IP and high-speed Internet access. In addition to the proliferation of WLAN hotspots, WLAN mesh networks are now being used as a cost-effective means for coverage extension and backhaul relaying between IEEE 802.11 access points (APs).</p> <p> In conventional IEEE 802.11, APs are always continuously powered using fixed wired connections. In future WLAN mesh networks however, wired power connections may not always be readily available, especially in Wi-Fi hotzone installations which cover expansive outdoor areas. In such cases, fixed power connections can often be replaced by a battery operated or solar powered design. For this reason, power saving on the AP is highly desirable for this type of application. Unfortunately, this is not possible since the existing IEEE 802.11 standard requires that APs remain active at all times.</p> <p> In this thesis, we propose and investigate a comprehensive framework for a power saving QoS-enabled access point (PSQAP), intended for use in solar and low power IEEE 802.11 infrastructure applications. An energy-efficient media access control protocol is proposed using the contention-based channel access mode for IEEE 802.11. When real-time flows are present, a PSQAP schedules its awakening/sleeping pattern in a manner that satisfies the delay and packet loss requirements for the admitted real-time flows. A dynamic connection-admission control algorithm is proposed for efficient management of wireless resources. We show that both background traffic and the synchronization of stations' transmissions due to AP's alternating between awake and sleep states can cause excess queuing and packet collision rate. These effects result in an increase in packet delay and power consumption at the mobile stations in contention-based channel access mode. We propose and investigate several scheduling methods for mitigating these effects. It is also shown that voice over IP over WLAN (VoWLAN) suffers a low capacity problem and high handset/AP power consumption. A novel adaptive voice packetization scheme is proposed which improves VoIP capacity and reduces power consumption. The work in this thesis is characterized by analytical models and evaluated through extensive network simulations to study and analyze the key performance aspects of the proposed framework and the associated protocols.</p> / Thesis / Doctor of Philosophy (PhD)

<p>Wireless sensor networks offer easy implementation, flexibility and mobility of hand held </p><p>devices. Sensors consist of an internal power source, which is the great limitation for </p><p>the life time and the usage of sensor networks. To increase the life time, sensors should </p><p>stay in energy saving sleep mode as long as possible, because in sleep mode the radio is </p><p>either shut down or working with less energy. Better energy handling is implemented in </p><p>different power saving mechanism of common Medium Access Control protocols, which are </p><p>evaluated and analyzed and further extensions and ideas to improve the energy efficiency </p><p>are presented. Slotted PSM is simulated with the NS2 and compared to the WLAN 802.11 </p><p>PSM technology and the results show that energy efficiency and power consumption are </p><p>much better implemented and life time increases with the use of Slotted PSM.</p>

Today, more and more embedded hardware devices are reaching the market and consumers with a demand for smaller and better devices than yesterday. Increasing the performance of a device decreases the operating time since more power is consumed, still, decreasing the size of the device also decreases operating time as the battery size decreases.To allow the performance to increase and the size of the device to decrease, the designer must nd techniques allowing the hardware to consume less power during normal usage of a device than during the peak usage.In this thesis an implementation of an ARM based microprocessor system is presented and used for measuring and evaluation of the power consumption possibilities of the system.

Wireless sensor networks offer easy implementation, flexibility and mobility of hand held devices. Sensors consist of an internal power source, which is the great limitation for the life time and the usage of sensor networks. To increase the life time, sensors should stay in energy saving sleep mode as long as possible, because in sleep mode the radio is either shut down or working with less energy. Better energy handling is implemented in different power saving mechanism of common Medium Access Control protocols, which are evaluated and analyzed and further extensions and ideas to improve the energy efficiency are presented. Slotted PSM is simulated with the NS2 and compared to the WLAN 802.11 PSM technology and the results show that energy efficiency and power consumption are much better implemented and life time increases with the use of Slotted PSM.

Energy is a critical resource in the design of wireless networks since wireless devices are usually powered by batteries. Battery capacity is finite and the progress of battery technology is very slow, with capacity expected to make little improvement in the near future. Under these conditions, many techniques for conserving power have been proposed to increase battery life. In this dissertation we consider two approaches to conserving the energy consumed by a wireless network interface. One technique is to use power saving mode, which allows a node to power off its wireless network interface (or enter a doze state) to reduce energy consumption. The other is to use a technique that suitably varies transmission power to reduce energy consumption. These two techniques are closely related to theMAC (Medium Access Control) layer. With respect to power saving mode, we study IEEE 802.11 PSM (Power Saving Mechanism) and propose a scheme that improves its energy efficiency. We also investigate the interaction between power saving mode and TCP (Transport Control Protocol). As a second approach to conserving energy, we investigate a simple power control protocol, called BASIC, which uses the maximum transmission power for RTS-CTS and the minimum necessary power for DATA-ACK. We identify the deficiency of BASIC, which increases collisions and degrades network throughput, and propose a power control protocol that addresses these problems and achieves energy savings. Since energy conservation is not an issue limited to one layer of the protocol stack, we study a cross layer design that combines power control at the MAC layer and power aware routing at the network layer. One poweraware routing metric is minimizing the aggregate transmission power on a path from source to destination. This metric has been used along with BASIC-like power control under the assumption that it can save energy, which we show to be false. Also, we show that the power aware routing metric leads to a lower throughput. We show that using the shortest number of hops in conjunction with BASIC-like power control conserves more energy than power aware routing with BASIC-like power control.

In this thesis, we proposed a simple yet novel multicast scheduling scheme for IEEE 802.16e wireless metropolitan area networks. Specifically, we want to solve the problem that how the base station schedules data messages in a multicast superframe such that mobile stations can receive their required multicast data and the total awake time of mobile stations is minimal. We first prove that this problem is NP-complete, and then propose a greedy k-approximation algorithm, named G-EEMS, whose running time is , where n is the total number of multicast data messages and k is the size of MBS (multicast and broadcast service) zone in a frame. Simulation results show that, in terms of energy throughput, G-EEMS significantly outperforms the existing scheme, called SMBC-D.

This work is related to wireless communication. In this Thesis three main issues are addressed for future cellular networks: power consumption, interference and mobility. These issues continue to be a burden on the system’s performance as long as technology keeps evolving. In the presented chapters, the focus was to introduce greater intelligence to the LTE system algorithms and bring to them a dynamic and self-organizing approach. The first approach concerns power consumption in wireless terminals. The currently applied solution to save energy is the DRX mechanism. It organizes the time when the terminal wakes up and starts receiving data, and when it goes into sleep mode in order to save its battery power. The current DRX is described as static or fixed which makes its parameters unsuitable for the nature of the bursty traffic. In this work an adaptive DRX mechanism is proposed and evaluated as the wireless terminal battery saving algorithm. The second approach is co-channel interference mitigation. To increase the system’s capacity and avoid spectrum scarcity, small cells such as Femtocells are deployed and operate on the same frequency bands as the Macrocell. Although these small nodes increase the system capacity, however, the challenges will be in the femtocells planning and management in addition to the interference issues. Here a dynamic interference cancellation approach is presented to enable the Femtocell to track the allocated resources to the Macro-users, and to avoid using them. The third approach concerns mobility management in heterogeneous networks. The wireless terminal may have different mobility levels during handover which increases the handover failures due to failure in handover commands and aging of the reported parameters. This issue is presented in detail with the aim to avoid performance degradation and improve the reporting mechanisms during fast mobility levels. For this regard the presented method proposes more cooperation between the serving cell and the end-user so that the large amount of overhead and measurement are reduced. Simulations with different configurations are conducted to present the results of the proposed models. Results show that the proposed models bring improvements to the LTE system. The enhanced self-organized architecture in the three presented approaches performs well in terms of power saving, dynamic spectrum utilization by Femtocells, and mitigation of sudden throughput degradation due to the serving cell’s downlink signal outage during mobility.

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