Channel Allocation in An Overlaid Mesh Network

In spite of recent advancement of Wireless Mesh Technology, a lot of research challenges remained to be solved to extract the full capacity of this modern technology. As 802.11a/b/g standards make available the use of multi radio multi channel in a wireless node, a lot of research activities are going on to efficiently allocate the channel of a Mesh Network to boost its overall performances. In this research, the prospect of dividing the total network area into two non-overlapping channels of a given Mesh Network is investigated and analyzed numerically. It is found that the throughput is doubled as well as the fairness improves considerably if we deploy two channels instead of single channel backbone. An extensive simulation study has been carried out to find the optimum coverage area between two channels. The study shows that at a particular point of allocation, the network gives the optimum response.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Traffic-Adaptive and Energy-Efficient Small Cell Networks-Energy, Delay and Throughput

The low power small cell network has emerged as a promising and feasible solution to address the massive wireless traffic resulting from the aggressive growth of wireless applications. It is also estimated that Internet of things (IoT) will consist of around 50 billion physical objects by 2020. As a result, besides capacity enhancement, other challenges, e.g., energy efficiency, dynamic addressing of UL/DL traffic asymmetry, low latency, multi-hop communications, reliability and coverage have become the crucial issues in wireless communication technology. Also, in LTE-A, the introduction of Local IP Address (LIPA), Selected IP Traffic Offload (SIPTO) and IP Flow Mobility (IFOM) have opened the opportunity to integrate WiFi or the non-3GPP devices with femto networks. In the above context, two dominant candidates for small cell technology, i.e., the WiFi (IEEE 802.11s) and LTE TDD femto networks, are studied in terms of energy, delay and throughput in this thesis. Basically, small cells are low power, short range and low cost small base stations (BSs) or access points (APs) that operate in either the licensed or unlicensed spectrum. In this thesis the performance of such small cells is studied both analytically and numerically. The experiments are carried out for both UDP and TCP traffic. For the IEEE 802.11s system, the peer-specific queue and the batch scheduling process for the energy saving MAC are introduced in this thesis. The study suggests that at the cost of delay-throughput, the IEEE 802.11s network can save up to 80% energy. In this multi-hop traffic adaptive system, the delay, throughput and fairness can be adjusted by changing the link specific power save modes as well as the beacon interval. For the licensed spectrum, the scope and feasibility of the dynamic LTE TDD network are examined in detail from the implementation perspective. A flexible frame selection scheme is introduced in this respect. At small load, a micro-sleep based operational framework at symbol level for LTE TDD is proposed in this thesis too. The study reveals that a BS can operate in micro-sleep mode while providing the necessary QoS and during off peak hours, the power amplifier (PA) can save up to 90% energy. Two centralized algorithms and one distributed algorithm, based on HNN, are introduced in the thesis to address the traffic asymmetry dynamically. It is found that the algorithms can add 13 to 20 percent additional capacity. Also the algorithms are portable to the 3GPP LTE TDD system. Regardless of the number of links the algorithms converge within the first few epochs

Hopfield Neural Network Based Uplink/Downlink Transmission Order Optimization for Dynamic Indoor TDD Femtocells

The Uplink/Downlink transmission mode or Transmission Order (TO) optimization has recently appeared as a new optimization domain in radio resource management. Such optimization is a combinatorics problem and requires good heuristic algorithm to be approximately solved within short time for the dynamic radio environment. This paper shows how the TO optimization problem in Time Division Duplex (TDD) indoor femtocells can be formulated and solved by the Hopfield Neural Network (HNN) based TO schedulers. Both centralized and distributed versions are analyzed in the context of indoor femtocells. We also examine proposed TO schedulers’ system performance in TDD indoor femtocells environment by extensive simulation campaigns. Our simulation results for a large 3-story building including 120 femtocells show that (i) the indoor femtocell system performance is improved up to 13 to 20 percent by the proposed HNN schedulers depending on the number of femtocells, (ii) the proposed TO schedulers converge within the first few epochs. (iii) The performance of the proposed schedulers are justified by a time-consuming but a thorough Genetic Algorithm Scheduler

Performance Analysis of the IEEE 802.11s PSM

With the introduction of IEEE 802.11 power save mode (PSM), a lot of work has been done to enhance the energy saving ability of the wireless nodes. The ultimate goal of the research is to make the networking equipment carbon neutral and prolong the lifetime of the energy limited device for various applications; in some cases it is a trade-off between energy efficiency and delay. However, few studies have been made until now in the area of IEEE 802.11s based link specific power mode. The essence of this method is the ability of a node to maintain different power modes with its different peer nodes at the same time. A new peer service period (PSP) mechanism is also proposed in IEEE 802.11s amendment for transmitting to a receiver operating in PSM. In this paper the performance of the link specific power mode is studied for a single- and a multilink network in terms of energy, delay throughput, and sleep duration. It is found that at small load the energy saving could be as high as eighty percent when compared with the active mode operation. A stochastic model, based on discrete time discrete state Markov chain, is developed for one peer link operation to study the system behavior closely during PSM operation

Performance Analysis of the IEEE 802.11s PSM

With the introduction of IEEE 802.11 power save mode (PSM), a lot of work has been done to enhance the energy saving ability of the wireless nodes. The ultimate goal of the research is to make the networking equipment carbon neutral and prolong the lifetime of the energy limited device for various applications; in some cases it is a trade-off between energy efficiency and delay. However, few studies have been made until now in the area of IEEE 802.11s based link specific power mode. The essence of this method is the ability of a node to maintain different power modes with its different peer nodes at the same time. A new peer service period (PSP) mechanism is also proposed in IEEE 802.11s amendment for transmitting to a receiver operating in PSM. In this paper the performance of the link specific power mode is studied for a single-and a multilink network in terms of energy, delay throughput, and sleep duration. It is found that at small load the energy saving could be as high as eighty percent when compared with the active mode operation. A stochastic model, based on discrete time discrete state Markov chain, is developed for one peer link operation to study the system behavior closely during PSM operation

Dynamic TDD in LTE small cells

Dynamic time-division duplexing (TDD) enables adjustments of uplink (UL) and downlink (DL) resources flexibly according to the instantaneous traffic load. Long-Term Evolution (LTE) systems can be implemented in TDD mode (TD-LTE). However, the dynamic change of a TDD configuration has not been well supported and investigated. In large macro cells, the high transmit power of base stations (BSs) easily blocks the weaker user equipment’s (UE) UL signal (called the UL-DL interference); and therefore, neighboring cells usually operate with the same TDD configuration. In small cells, such as femtocells, the BS and UE transmission powers are in the same order and the system can afford to have overlapping UL-DL subframes. In addition, when DL load is light, the BS transmits empty DL subframes with only a reference signal (RS). In this paper, we measured the interference caused by DL RS. This interference is not negligible; and therefore, it is beneficial to reduce the amount of DL subframes by switching lightly loadedBSs to UL-heavy subframe configuration. We illustrate with simulations that this can improve system efficiency. Changing the subframe configuration dynamically has a switching-related cost. Frequent switching between subframe configurations can actually decrease throughput. We describe conditions where configuration change is beneficial. We also propose an algorithm that decreases the switching overhead and improves the ability to adapt to varying loads.Peer reviewe