• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 39
  • 10
  • 4
  • 3
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 64
  • 18
  • 16
  • 13
  • 11
  • 10
  • 10
  • 8
  • 8
  • 8
  • 8
  • 8
  • 7
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Quality of Heterogeneous Services with Distributed Resource Management for a WCDMA Uplink

Das, Pratik January 2006 (has links)
A radio resource management scheme for WCDMA uplinks is proposed that manages quality of service (QoS) for heterogeneous services whilst maintaining high channel utilisation efficiency. The proposed system is partitioned into the 3 modules, viz. a QoS-sensitive rate scheduler, an inter-service and intra-service user prioritisation schemes, and a frame admission controller for dynamic resource reallocation. Users are allocated the minimum resources required to manage their QoS requirements through just-in-time delivery of payload, leaving more room for best-effort service users. The transmission urgency of each user is estimated by the rate scheduler based on a target transmission delay - a unique parameter used in the proposed resource management strategy to enable just-in-time payload delivery, service differentiation, and uncomplicated mapping of application requirements to QoS parameters. Transmission rate change requests from the rate schedulers are collectively processed through inter-service and intra-service priority queuing in a manner that is shown to exhibit fairness in allocation of resources amongst users of a heavily loaded network. The performance of the proposed strategy is explored through discrete-event simulations for 3 classes of traffic - voice, video and data, over the WCDMA uplink in the presence of short-term Rayleigh fading, ARQ, FEC, target transmission delays and FER targets in a multi-cell environment. Two alternatives for distributed resource management have been studied, with the UE or Node-B in control of resource allocation. The UE controlled resource management system is shown to achieve higher channel utilisation efficiency at the cost of fairness. The Node-B controlled resource manager respects the priority of speech, video and data traffic in heavily loaded systems, as reflected in 95 percentile packet transmission delays. / PhD Doctorate
12

Voice-over-IP over Enhanced Uplink / Kapacitet för IP-telefoni i den förbättrade WCDMA-upplänken

Brännström, Nils January 2007 (has links)
<p>The traditional voice service in mobile networks is an important service that mobile users expect high quality from. With the convergence of mobile networks towards an all-IP network, an IP-based speech service becomes important which is referred to as Voice-over-IP (VoIP). The traditional voice service is highly optimized and a VoIP service must therefore fulfil strict quality requirements to provide the same speech service quality. The air interface technology, WCDMA, which is used in third generation communication systems in Europe is constantly developed. An improved concept for the mobile-to-network transmission, called the Enhanced Uplink (EUL) provides for higher uplink capacity for packet data services. It also includes features that may provide a sufficient VoIP service quality in mobile networks, when considering the uplink transmission. </p><p>The purpose of this thesis is to evaluate the VoIP capacity over EUL and identify crucial aspects of radio resource management in order to increase the capacity. This is done through dynamic system simulations, using a realistic VoIP traffic model. The VoIP capacity is also estimated by a derived theoretical framework.\newline </p><p>It is shown by simulation results and theoretical estimations, that power control is a vital mechanism in order to increase the capacity. Simulation results indicate that a VoIP over EUL capacity of 65\% of the traditional voice service capacity may be reached. The results also indicate that to improve the capacity for larger cells, the allowed VoIP packet delay must be increased.</p>
13

Comparing Geometric Models Against Empirical Data for Radiowave Landmobile Cellular Uplink AOA

Abdulla, Minaz January 2005 (has links)
There has been an increase in demand for efficient wireless systems. Smart antennas using position location are one possible way to improve the capacity of cellular systems. In order to deploy such systems successfully, the wireless network must properly exploit the processing of spatial information (ie. The uplink angle of arrival) through wireless channel models. Geometric modelling is a technique to model the wireless environment. When compared to other methods such as ray tracing simulations, geometric models allow one to classify a wide varity of environments within a single model. Secondly, there have been much research in the past to obtain empirical measurements in many different environment settings. These measurements have been recorded, however, there has been no research undertaken to systematically compare and validate the empirical findings with current geometric models. The goal of this research is to compare and constrast geometric models with empirical data in order to show which models are best suited for specific wireless environments. The uplink angle of arrival (AOA) probability distribution is the fading metric that will be used to compare and contrast these models.
14

LTE Uplink Modeling and Channel Estimation

Ahmed, Mohsin Niaz January 2011 (has links)
This master thesis investigates the uplink transmition from User Equipment (UE) to base station in LET (Long Term Evolution) and channel estimation using pilot symbols with parameter defined in 3GPP (3rd Generation Partnership Project) specifications. The purpose of the thesis was to implement a simulator which can generate uplink signal as it is generated by UE. The Third Generation (3G) mobile system was given the name LTE. This thesis focus on the uplink of LTE where single carrier frequency division multiple access (SC-FDMA) is utilized as a multiple access technique. The advantage over the orthogonal frequency division multiple access (OFDMA), which is used in downlink is to get better peak power characteristics. Because in uplink communication better peak power characteristic is necessary for better power efficiency in mobile terminals. To access the performance of uplink transmition realistic channel model for wireless communication system is essential. Channel models used are proposed by International Telecommunication Union (ITU) and the correct knowledge of these models is important for testing, optimization and performance improvements of signal processing algorithms. The channel estimation techniques used are Least Square (LS) and Least Minimum Mean Square Error (LMMSE) for different channel models. Performance of these algorithms has been measured in term of Bit Error Rate (BER) and Signal to Noise Ratio (SNR).
15

Voice-over-IP over Enhanced Uplink / Kapacitet för IP-telefoni i den förbättrade WCDMA-upplänken

Brännström, Nils January 2007 (has links)
The traditional voice service in mobile networks is an important service that mobile users expect high quality from. With the convergence of mobile networks towards an all-IP network, an IP-based speech service becomes important which is referred to as Voice-over-IP (VoIP). The traditional voice service is highly optimized and a VoIP service must therefore fulfil strict quality requirements to provide the same speech service quality. The air interface technology, WCDMA, which is used in third generation communication systems in Europe is constantly developed. An improved concept for the mobile-to-network transmission, called the Enhanced Uplink (EUL) provides for higher uplink capacity for packet data services. It also includes features that may provide a sufficient VoIP service quality in mobile networks, when considering the uplink transmission. The purpose of this thesis is to evaluate the VoIP capacity over EUL and identify crucial aspects of radio resource management in order to increase the capacity. This is done through dynamic system simulations, using a realistic VoIP traffic model. The VoIP capacity is also estimated by a derived theoretical framework.\newline It is shown by simulation results and theoretical estimations, that power control is a vital mechanism in order to increase the capacity. Simulation results indicate that a VoIP over EUL capacity of 65\% of the traditional voice service capacity may be reached. The results also indicate that to improve the capacity for larger cells, the allowed VoIP packet delay must be increased.
16

Comparing Geometric Models Against Empirical Data for Radiowave Landmobile Cellular Uplink AOA

Abdulla, Minaz January 2005 (has links)
There has been an increase in demand for efficient wireless systems. Smart antennas using position location are one possible way to improve the capacity of cellular systems. In order to deploy such systems successfully, the wireless network must properly exploit the processing of spatial information (ie. The uplink angle of arrival) through wireless channel models. Geometric modelling is a technique to model the wireless environment. When compared to other methods such as ray tracing simulations, geometric models allow one to classify a wide varity of environments within a single model. Secondly, there have been much research in the past to obtain empirical measurements in many different environment settings. These measurements have been recorded, however, there has been no research undertaken to systematically compare and validate the empirical findings with current geometric models. The goal of this research is to compare and constrast geometric models with empirical data in order to show which models are best suited for specific wireless environments. The uplink angle of arrival (AOA) probability distribution is the fading metric that will be used to compare and contrast these models.
17

Uplink TDMA Potential in WCDMA Systems

Persson, Markus January 2008 (has links)
<p>The evolvement of the uplink in the third generation mobile telecommunication system is an ongoing process. The Enhanced Uplink (EUL) concept is being developed to meet the expected need from more advanced services, like video streaming and mobile broadband. One idea for further improvement in the EUL concept is to introduce Time Division Multiple Access (TDMA), which is studied in this master thesis.</p><p>The master thesis assignment is to study the consequences of introducing TDMA in EUL. The goal has been to identify the gains and problems, and how they can be handled. A derived theoretical framework and system simulations, using a radio network simulator, are used.</p><p>The overall conclusion is that there is a potentially large gain with an introduction of TDMA in EUL. Simulations in favorable conditions have shown that the system throughput can increase by 100% when there are only User Equipment (UE) that are using EUL in the system and by 50% when there is a mix of speech and EUL UE’s. When using TDMA the uplink load also shows improvements, the mean is generally higher but the variance is generally smaller.</p><p>Due to major differences in experienced interference between passive and active UE’s, the signal quality will vary a lot. The big variation in signal quality is identified as the main problem with introducing TDMA in EUL. It is shown that this problem can generate extreme high uplink load, which have a negative impact both on the resource efficiency and the coverage.</p>
18

Uplink TDMA Potential in WCDMA Systems

Persson, Markus January 2008 (has links)
The evolvement of the uplink in the third generation mobile telecommunication system is an ongoing process. The Enhanced Uplink (EUL) concept is being developed to meet the expected need from more advanced services, like video streaming and mobile broadband. One idea for further improvement in the EUL concept is to introduce Time Division Multiple Access (TDMA), which is studied in this master thesis. The master thesis assignment is to study the consequences of introducing TDMA in EUL. The goal has been to identify the gains and problems, and how they can be handled. A derived theoretical framework and system simulations, using a radio network simulator, are used. The overall conclusion is that there is a potentially large gain with an introduction of TDMA in EUL. Simulations in favorable conditions have shown that the system throughput can increase by 100% when there are only User Equipment (UE) that are using EUL in the system and by 50% when there is a mix of speech and EUL UE’s. When using TDMA the uplink load also shows improvements, the mean is generally higher but the variance is generally smaller. Due to major differences in experienced interference between passive and active UE’s, the signal quality will vary a lot. The big variation in signal quality is identified as the main problem with introducing TDMA in EUL. It is shown that this problem can generate extreme high uplink load, which have a negative impact both on the resource efficiency and the coverage.
19

Comparative Performance Study of LTE Uplink Schedulers

SALAH, Mohamed 09 May 2011 (has links)
Long Term Evolution (LTE) constitutes a significant milestone in the evolution of 3G systems towards fourth generation (4G) technologies. The performance targets promised by LTE makes it an ideal solution to accommodate the ever increasing demand for wireless broadband. LTE's promised performance targets were made possible due to improvements such as a simplified system access architecture and a fully IP-based platform. LTE has also great enhancements in its enabling radio technologies by introducing Orthogonal Frequency Division Multiplexing (OFDM) and advanced antenna technologies. In addition, LTE capabilities are further improved with enhanced Quality of Service (QoS) support for multiple data services, such as voice and other multimedia applications. LTE packet scheduling plays an essential role as part of LTE's Radio Resource Management (RRM) to enhance the system's data rate and to support the diverse QoS requirements of mobile services. LTE packet scheduler should intelligently allocate radio resources to mobile User Equipments (UEs) such that the LTE network adheres to its performance requirements. In our work, we perform a performance evaluation of multiple LTE scheduling algorithms proposed for LTE uplink transmission. The evaluation takes place in single and mixed traffic scenarios to exploit the strengths and weaknesses of proposed algorithms. Simulation results illustrated the importance of a scheduler's awareness of uplink channel conditions and QoS requirements in the presence of single and multiple traffic scenarios. Accordingly, we provide recommendations for future scheduling algorithm proposals, and ways to enhance the existing schedulers. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-05-07 12:43:54.983
20

Blind signature waveform estimation and linear multiuser detection in direct sequence code division multiple access systems

Zarifi, Keyvan. Unknown Date (has links)
Techn. University, Diss., 2007--Darmstadt.

Page generated in 0.0336 seconds