Lightweight mobile and wireless systems: technologies, architectures, and services

1Department of Information and Communication Systems Engineering (ICSE), University of the Aegean, 81100 Mytilene, Greece 2Department of Information Engineering and Computer Science (DISI), University of Trento, 38123 Trento, Italy 3Department of Informatics, Alexander Technological Educational Institute of Thessaloniki, Thessaloniki, 574 00 Macedonia, Greece 4Centre Tecnologic de Telecomunicacions de Catalunya (CTTC), 08860 Barcelona, Spain 5North Carolina State University (NCSU), Raleigh, NC 27695, US

Network capacity and quality of service management in F/TDMA cellular systems

As a consequence of rapidly increasing mobile communications, efficient utilization of the scarce radio resources becomes one of the most important issues in the system evolution. Increase of the system capacity has been investigated in two ways. The first way is to replace the fixed channel allocation (FCA), with the more efficient dynamic channel allocation (DCA). The second way is to utilize those traffic channels not being used by voice services to provide a packet data service, like general packet radio service (GPRS) and cellular digital packet data (CDPD). In this thesis, the author have proposed two DCA schemes and developed an analysis method to investigate the GPRS impact on the GSM voice services. In addition, the GPRS downlink performance is investigated and some guidelines or principles for GPRS network planning have been presented. In the proposed DCA algorithms, the effect of the channel allocation on existing calls is considered by the evaluation of the call outage rate or a cost function. In the first proposed algorithm, in order to evaluate the call outage caused by those candidate channels, a method of estimating the average signal to interference ratio (SIR) variation of on-going calls due to the assignment of a coming call has been developed. This algorithm improves the capacity or QoS performance compared with the first available and maximum SIR schemes. In the second proposed algorithm, a cost function has been introduced to estimate the cost of the assignment of a candidate channel. The performance evaluation shows that by using the cost-function for channel pre-selection the problem of high intracell handover rate for the first available based scheme can be decreased to an adequate level and the time of the call set-up can be shortened. An analysis method to calculate the outage probability of the GSM-GPRS network for both the non-frequency hopping and frequency hopping systems has been presented to investigate the GPRS impact on GSM voice services. It is found that: GPRS affects more on the QoS of voice services of the network with small reuse factor; GPRS will reduce the cell service area, but the reduction percentage of the cell service area for the system with small reuse factor is higher than that for the system with large reuse factor; those channels unused by voice services might not all be used for carrying GPRS traffic; the number of unused voice channels which can be allocated to GPRS depends on the difference between the outage level of the existing GSM network and the maximum acceptable level. From final part of this work, it is found that: GPRS capacity performance in downlink is quite different from that in uplink because of the difference in the transmission protocols; multiple-slot allocation does not show a gain of the mean throughput neither a decrease on the mean delay compared to single slot allocation. This result is different from the result of the uplink performance. In multi-rate services, the multi-slot services significantly increase the delay of the single-slot service, consequently, a control of the multi-slot services is needed.reviewe

A Cross-Layer Location-Based Approach for Mobile-Controlled Connectivity

We investigate into the potentiality of an enhanced Power and Location-based Vertical Handover (PLB-VHO) approach, based on a combination of physical parameters (i.e., location and power attenuation information), for mobile-controlled connectivity across UMTS and WLAN networks. We show that the location information in a multiparameter vertical handover can significantly enhance communication performance. In the presented approach a power attenuation map for the visited area is built and kept updated by exploiting the information sharing of power measurements with other cooperating mobile devices inside the visited networks. Such information is then used for connectivity switching in handover decisions. The analytical model for the proposed technique is first presented and then compared with a traditional Power-Based approach and a simplified Location-Based technique. Simulation results show the effectiveness of PLB-VHO approach, in terms of (i) network performance optimization and (ii) limitation of unnecessary handovers (i.e., mitigation ofping-pong effect)

Improving Frequency Reuse and Cochannel Interference Coordination in 4G HetNets

This report describes my M.A.Sc. thesis research work. The emerging 4th generation (4G) mobile systems and networks (so called 4G HetNets) are designed as multilayered cellular topology with a number of asymmetrically located, asymmetrically powered, self-organizing, and user-operated indoor small cell (e.g., pico/femto cells and WLANs) with a variety of cell architectures that are overlaid by a large cell (macro cell) with some or all interfering wireless links. These designs of 4G HetNets bring new challenges such as increased dynamics of user mobility and data traffic trespassing over the multi-layered cell boundaries. Traditional approaches of radio resource allocation and inter-cell (cochannel) interference management that are mostly centralized and static in the network core and are carried out pre-hand by the operator in 3G and lower cellular technologies, are liable to increased signaling overhead, latencies, complexities, and scalability issues and, thus, are not viable in case of 4G HetNets. In this thesis a comprehensive research study is carried out on improving the radio resource sharing and inter-cell interference management in 4G HetNets. The solution strategy exploits dynamic and adaptive channel allocation approaches such as dynamic and opportunistic spectrum access (DSA, OSA) techniques, through exploiting the spatiotemporal diversities among transmissions in orthogonal frequency division multiple access (OFDMA) based medium access in 4G HetNets. In this regards, a novel framework named as Hybrid Radio Resource Sharing (HRRS) is introduced. HRRS comprises of these two functional modules: Cognitive Radio Resource Sharing (CRRS) and Proactive Link Adaptation (PLA) scheme. A dynamic switching algorithm enables CRRS and PLA modules to adaptively invoke according to whether orthogonal channelization is to be carried out exploiting the interweave channel allocation (ICA) approach or non-orthogonal channelization is to be carried out exploiting the underlay channel allocation (UCA) approach respectively when relevant conditions regarding the traffic demand and radio resource availability are met. Benefits of CRRS scheme are identified through simulative analysis in comparison to the legacy cochannel and dedicated channel deployments of femto cells respectively. The case study and numerical analysis for PLA scheme is carried out to understand the dynamics of threshold interference ranges as function of transmit powers of MBS and FBS, relative ranges of radio entities, and QoS requirement of services with the value realization of PLA scheme.1 yea

Journal of Telecommunications and Information Technology, 2001, nr 2

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Energy Efficient Small Cell Planning For High Capacity Wireless Networks

This thesis presents a new strategy to densify Small Cells (i.e., add more low powered base stations within macro networks) and enhance the coverage and capacity of Heterogeneous Networks. This is accomplished by designing Micro Cell for outdoor applications, Pico and Femtocell for indoor applications. It is shown that, there exists a free space propagation medium in all propagation environments due to Fresnel zones, and the path loss slope within this zone is similar to free space propagation medium. This forms the basis of our development of the present work. The salient feature of the proposed work has two main considerations (a) The cell radius of Small Cells must be within the first Fresnel zone break point, and (b) The minimum inter-cell distance must be greater than twice of Small Cell radius. The proposed network is simulated in real a radio network simulator called ATOLL. The simulation results showed that densify Small Cells not only enhanced the capacity and coverage of Heterogeneous Networks but also improved the carrier to interference ratio significantly. Since the proposed work allows UE (user equipment) to have Line of Sight (LOS) communication with the serving cell, and UE can have higher uplink (UL) signal to interference plus noise ratio (SINR) that will further allow UE to reduce its transmission power, which will consequently lead to a longer battery life for the UE and reduce the interference in the system

OPTIMIZING RADIO RESOURCE MANAGEMENT IN VERY BAD CHANNEL CONDITIONS

Radio resource management is one of the most important parts of modern multi-user wireless communication systems. The main reason for this importance comes from the fact that the radio resources, such as bandwidth and power, are scarce. For instance, UMTS systems use 5MHz bandwidth for voice as well as data services. The optimum usage of the radio resource guarantees the highest efficient utilization of wireless networks. To optimize the radio resources, the transmitters need to estimate the channel conditions. This channel estimation is done by using pilot signal from the receiver. There are usually small delays between the measurements and the radio resource allocation. When the channel is highly correlated, this delay will not affect the performance, because the channel will not be significantly changed between the time of measurement and the time of transmission. However, if the mobile speed is high or the channel is very high dynamic, the correlation becomes very low. This is due to the timevarying nature of the channel. We call channels with very low correlation in time as bad condition channels. In this thesis we discuss this extremely important topic. The tools for analyzing bad condition channels are also proposed and discussed. Two power control algorithms to mitigate the low correlation of channels have been proposed. Our algorithms are validated through several simulations.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

A gradient-based optimum block adaptation ICA technique for interference suppression in highly dynamic communication channels

The fast fixed-point independent component analysis (ICA) algorithm has been widely used in various applications because of its fast convergence and superior performance. However, in a highly dynamic environment, real-time adaptation is necessary to track the variations of the mixing matrix. In this scenario, the gradient-based online learning algorithm performs better, but its convergence is slow, and depends on a proper choice of convergence factor. This paper develops a gradient-based optimum block adaptive ICA algorithm (OBA/ICA) that combines the advantages of the two algorithms. Simulation results for telecommunication applications indicate that the resulting performance is superior under time-varying conditions, which is particularly useful in mobile communications. Copyright (C) 2006 Hindawi Publishing Corporation. All rights reserved