[Show abstract][Hide abstract] ABSTRACT: This paper presents a performance evaluation of the Radio Frequency (RF) fingerprinting framework for positioning using Minimization of Drive Testing (MDT) measurements specified in LTE (Long Term Evolution) Release 10. Methods based on Mahalanobis distance and Kullback-Leibler divergence are used for estimating the geographical locations. Performance evaluation of the framework is verified with system simulator by generating MDT measurement data in intra- and inter-frequency LTE network deployments with rural and urban configurations. The focus of the research is to understand how RF fingerprint positioning accuracy changes when taking into account the prospects and constraints of the RF fingerprints constructed from the MDT measurement data. The results of the study indicate that the performances of Mahalanobis distance and Kullback-Leibler divergence based methods are quite similar in rural deployments. However, in denser network deployments, Kullback-Leibler divergence based method tends to be much better for both intra- and inter-frequency environments, resulting in better than 21 meters and 38 meters positioning accuracies for 68 percent of MDT samples in studied urban scenarios, being well below the E911 emergency positioning requirements.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a cooperative decentralized scheme for adjusting the Uplink (UL)-Downlink (DL) configuration of a Small Cell Network (SCN) with a TDD air interface. The goal of the cooperative decentralized scheme is to make a more efficient use of common wireless resources, selecting convenient TDD-frame configurations to maximize a sum utility function that takes into account both individual traffic demands and actual interference coupling situations. The cooperative decentralized scheme for UL/DL adaptation can be executed locally at each Base Station (BS), and relies solely on the exchange of low-rate signaling information among neighboring cells. Based on observed performance improvements, we conclude that cooperative decentralized schemes are a viable option for flexible-TDD implementation in SCN environments, particularly in presence of cells with strong interference coupling and low-rate signaling capabilities.
[Show abstract][Hide abstract] ABSTRACT: We discuss a distributed utility-based algori
thm for downlink carrier allocation in a multi-carrier system. The proposed dynamic frequency selection (DFS) algorithm aims to maximize the sum utility of the whole system. To achieve this goal, each base station (BS) selects the carrier allocatio
n strategy to maximize a surplus function comprising both own cell utility and utility prices received from the neighbors. Universal reuse is used as a baseline for comparison. Four different utility functions are considered: mean-rate, weighted fair-rate, proportional fair-rate and max-min. A dense femto deployment scenario is used to evaluate the performance of DFS. Simulation results show that the proposed algorithm is effective in predicting the capacity gain/loss in the system. DFS enhances not only the sum data rate of a system but also the degree of fairness in resource sharing among users.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a performance evaluation of Radio Frequency (RF) fingerprinting framework in heterogeneous Long Term Evolution (LTE) networks using Minimization of Drive Testing (MDT) measurements which allow automated construction of extensive RF fingerprint training databases. Fingerprint positioning was studied in heterogeneous small cell and regular macro networks using LTE cell detection performance requirements. Goal was to study how big effect the cell detection requirements have on positioning accuracy in interference limited inter-frequency small cell network deployment. The results show that RF fingerprint performance suffers degraded cell detection performance in fully loaded network deployments and results in lower dimensions of the RF signatures. However, in denser network deployments, the absolute positioning errors remain good being below the E911 emergency positioning requirements. This suggests that in dense small cell networks, MDT training databases can provide a good basis for location assisted Radio Resource Management (RRM) algorithms such as network based proximity detection.
[Show abstract][Hide abstract] ABSTRACT: In this paper we analyze the link-to-system interface for MIMO-OFDM system level simulations and propose a computationally efficient method for calculation of the effective SINR. The accuracy of the proposed fast approximation of the effective SINR is evaluated both analytically with error bound estimation and by simulated BLER performance comparison. The system level simulations in typical 3GPP LTE downlink scenario show that the proposed model is capable of accurate estimation of receiver performance for MIMO-OFDM transmission and brings up to 74% reduction in CPU simulation time.
[Show abstract][Hide abstract] ABSTRACT: We study a distributed approach for Primary Component Carrier (PCC) selection to manage interference and to improve cell edge performance in a heterogeneous network. To avoid cell outage caused by PCC selection based on path loss between neighboring base stations (BSs), we argue that carrier reselection based on handover measurements performed by the User Equipments (UEs) is necessary. We propose three strategies of PCC reselection; a Selfish, Altruistic and Symmetric approach. These are based on avoiding interference caused by neighboring cells, avoiding causing interference to neighbors, and avoiding both, respectively. The performance of the proposed strategies is compared to PCC selection based on path loss. We conclude that PCC reselection based on UE measurements completely removes outage and improves cell edge performance.
[Show abstract][Hide abstract] ABSTRACT: In this paper mobility performance is studied in heterogeneous networks with both macro and indoor base sta- tions. Due to abrupt changes in received signal and interference level as User Equipment (UE) enters and leaves a building with indoor Home eNodeB (HeNB) there may be additional challenges for handover compared to more homogeneous network layout. The purpose of this paper is, with dynamic system simulation tool, to evaluate the magnitude of the handover challenges and how would the system need to be configured to optimize the mobility performance. The results indicate that while general handover parameterization can be effectively utilized to avoid the most of mobility problems, cell-specific parameterization can further improve the mobility performance between eNB and HeNB. Additionally, attention should be paid to both inbound and outbound HeNB mobility due to possibly very different interference conditions in handover situations inside the building with HeNB and outdoor environment.
[Show abstract][Hide abstract] ABSTRACT: In this article we study and analyze the problems related to power limitation in Long Term Evolution (LTE) uplink (UL). Power control (PC) has been specified for LTE UL to account for pathloss and slow fading variations and minimize the interference. The maximum transmission power has been limited to 23 dBm. Especially in sparse networks, this can lead to so called power limitation, where the terminals at the cell edge are forced to use less power per Physical Resource Block (PRB) than needed. Power limitation could clearly increase the packet error probability and transmission delay due to increased number of retransmissions. This may be especially problematic for Radio Resource Control (RRC) messages, e.g. handover signaling, since their reliability affects evidently on user Quality of Service (QoS). In this article we have concentrated on power boosting to improve the RRC message reliability and the performance is evaluated by means of dynamic system level simulations. It may be concluded that power boosting notably reduces the power limitation probability and thus also improves the RRC signaling reliability.
[Show abstract][Hide abstract] ABSTRACT: In this paper we analyze the distribution of effective Signal-to-Interference-plus-Noise-Ratio (SINR) in multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with application to 3GPP Long Term Evolution (LTE) Downlink. The asymptotic distribution of effective SINR in case of correlated post-processed SINR is established analytically to obey normal distribution. The approximation for small number of correlated post-processed SINRs mapped to effective SINR is proposed to be the convolution of two Gamma distribution. The parameters for the Gamma distributions are analytically derived. Analytical results are verified by simulations.
No preview · Article · Nov 2010 · Circuits, Systems and Computers, 1977. Conference Record. 1977 11th Asilomar Conference on
[Show abstract][Hide abstract] ABSTRACT: In 3GPP Rel'8 access to a Home eNodeB may be restricted to only UEs belonging to a Closed Subscriber Group (CSG). These cells are called CSG cells and a UE with CSG subscription would have an Allowed CSG List containing CSG Identities associated with the CSG cells on which the UE is allowed access. This however, can be problematic for the users located near the CSG cells, but who are not allowed to access them. The interference caused by the CSG cell can be devastating if the UE is connected to a macro cell using the same frequency. Some solutions for these interference problems have been proposed in 3GPP standardization and in this study we have evaluated the performance of different options for handling the interference issues related to mixed carrier CSG deployments. The proposals utilize different details of the LTE re-selection algorithm and suggestion on the best solution is also given.
[Show abstract][Hide abstract] ABSTRACT: In this paper we study the performance of idle mode mobility state detection schemes targeted for 3rd Generation Partnership Project (3GPP) Evolved UTRAN. The purpose is to compare the mobility state detection scheme specified in 3GPP Release 8 and a dual trigger scheme for 3GPP Release 9 using different User Equipment (UE) velocity conditions and cell reselection triggering sensitivity levels. A single set of cell reselection parameters may not be optimal throughout the E-UTRAN velocity range, thus both schemes provide in a way a means of using UE velocity dependent cell reselection parameters. According to the results, both schemes provide gain over a single set of cell reselection parameters. Dual trigger provides gain over Release 8 mobility state detection scheme in terms of time spent in the best cell and downlink SINR. However, this comes with a small increase in power consumption due to increased amount of cell reselections per UE.
[Show abstract][Hide abstract] ABSTRACT: In this paper we study and benchmark the performance of 3rd Generation Partnership Project (3GPP) High Speed Downlink Packet Access (HSDPA) and 3GPP Long Term Evolution (LTE) Downlink with constant bit rate type traffic. In addition a non-regular simulation scenario is considered using realistic propagation data and base station positions related to Tokyo city downtown area. HSDPA was introduced in 3GPP Release 5 and in further releases the technology has been improved with e.g. receive and transmit diversity technologies and support for higher order modulation schemes. LTE was introduced in 3GPP Release 8 with completely new physical layer and improved Radio Resource Management (RRM) functionalities. The benchmarking is performed with fully dynamic system level simulators based on detailed and commonly accepted models for e.g. mobility, propagation, call generation and fading. The results show that LTE Release 8 outperforms HSDPA Release 8 in terms of spectral efficiency and user throughput. With 8 UEs per cell and LTE MIMO about 90% of UEs are fully satisfied, while about 45% of the UEs are fully satisfied with HSDPA MIMO. This results also about 30% gain in spectral efficiency even through with LTE the network is running half empty due to uneven UE distribution in non-regular network with variable cell sizes.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this paper is benchmark the performance of voice over IP in high speed downlink packet access and in long term evolution networks. Benchmarking is conducted in homogeneous and heterogeneous scenario layouts assuming realistic propagation data generated over Tokyo map. Tools used in this paper are two fully dynamic time driven system simulators which have been used to support 3GPP standardization work. This benchmarking study provides insights to what e.g. different radio access technologies, scheduling mechanisms and receivers do for the performance of voice over IP. This paper indicated in various scenarios that long term evolution can offer higher performance for voice over IP than high speed packet access.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present a fully dynamic simulative analysis of the Downlink (DL) Voice-over-IP (VoIP) performance in 3G Long Term Evolution (LTE) with both Uplink (UL) and DL control channel constraints. In UL the Physical Uplink Control Channel (PUCCH) capacity affects the Channel Quality Indicator (CQI) resolution and in DL the Physical Downlink Control Channel (PDCCH) capacity has an impact to the amount of multiplexed users per Transmission Time Interval (TTI). The results indicate that with realistic control channel assumptions, semi-persistent packet scheduling outperforms dynamic packet scheduling.
[Show abstract][Hide abstract] ABSTRACT: This paper proposes a potential enhancement for Discontinuous Reception (DRX) operation in Long Term Evolution (LTE) networks. In Third Generation Partnership Project's (3GPP's) Release 8 it is specified that User Equipment (UE) may be configured with DRX which controls the UE's Physical Downlink Control Channel (PDCCH) monitoring activity. By allowing discontinuous monitoring of PDCCH the UE can switch its receiver circuitry on and off for battery saving purposes. However, if UE turns its receiver circuitry off it is not capable to neither perform nor send any Channel Quality Indicator (CQI) measurements to the network prior to 'on-duration' (i.e., activity) period. This means that the Evolved Node B (e- Node B) might not have accurate CQI information and the scheduling and resource allocation could be based on outdated CQI information. To avoid reduced performance caused by the out-of-date information, this paper evaluates a scheme where a CQI preamble period is introduced prior to the actual 'on duration' time. During the preamble period UE measures the CQI and sends the measurement result to the e-Node B. The performance of the scheme is evaluated together with Voice over IP (VoIP) service. Used tool is a dynamic system level simulator which enables detailed simulation of users in multiple cells with realistic call generation, propagation, fading and mobility models. In addition to VoIP performance the UE power consumption is also evaluated with a simple model. This paper concludes that the preamble scheme can lead to improved performance in terms of VoIP capacity, and that the improvements can be achieved with acceptable trade-off in terms of battery saving opportunities
[Show abstract][Hide abstract] ABSTRACT: The purpose of this paper is to analyze the trade-off conditions between battery saving opportunities and long term evolution network performance. To achieve this goal voice over IP with discontinuous reception is studied. Analysis is conducted with vast amount of different settings, including on duration, inactivity and discontinuous reception cycle timers. The quality of service and battery saving opportunities with discontinuous reception are evaluated with a dynamic system simulator which enables detailed simulation of multiple users and cells with realistic assumptions. This paper indicates high battery saving, i.e., increased talk-time opportunities without compromising the performance when discontinuous reception is properly adapted.
[Show abstract][Hide abstract] ABSTRACT: In this paper we analyze cell hearability in UTRAN Long Term Evolution (LTE) Downlink for positioning purposes. The observed time difference of arrival technique has been specified in LTE for location estimation. Successful positioning estimate requires at least three geographically diverse base stations to be detected or heard. Reference signal hearability measurements, such as Reference Signal Received Power and signal-to-interference and noise ratio of the signal from a cell, are used for detection of the cell. By means of these measurements the cell hearability is evaluated by fully dynamic time-driven system simulator. In order to mitigate the interference and improve hearability, muting of the serving cell and fractional load technique are proposed. The simulation results show improved positioning capability with proposed techniques, since all user equipments can hear the required number of geographically diverse cells.
[Show abstract][Hide abstract] ABSTRACT: In this paper we present different idle mode mobility state detection mechanisms targeted for 3GPP Evolved UTRAN. The purpose is to study the reliability of the mobility state detection mechanism specified in 3GPP TS 36.304 for 3GPP Release 8 in varying conditions, such as different re-selection thresholds, UE velocities and inter-site distances. Three mobility states have been defined in TS 36.304 based on occurred cell re-selections in a certain time window. According to small inter-site distance simulations, pedestrian speeds (normal mobility state) can be detected with a quite satisfactory accuracy but distinguishing the medium and high mobility states is quite challenging, since UEs are experiencing quite large variance in number of re-selections with the same UE velocities. Simulations with large inter-site distances show similar results.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this paper is to evaluate the suitability of reference signal received quality (RSRQ) measurement for quality based inter-frequency handover in UTRAN long term evolution (LTE). Intra-frequency handovers in LTE are done based on reference signal received power (RSRP) measurements, which should ensure that users are always connected to the cell with the highest received power. However, in certain environments where interference causes service quality degradation for the user (which RSRP measurement is not able to detect) there might be situation where a quality-based measurement would enable better system performance. In this paper, we evaluate the success and correctness of RSRQ based inter-frequency handovers as means for preventing service degradation using dynamic system simulations. However, comparison of RSRQ and RSRP based triggering suggest that RSRQ is not able to provide robust detection of service quality degradation. Furthermore, RSRQ is found to be heavily dependent on current system loading and the measurement strategy.
[Show abstract][Hide abstract] ABSTRACT: In this paper we study the effect of reference signal received power (RSRP) measurement bandwidth on the accuracy of handovers and the UTRAN Long Term Evolution (LTE) system performance. In 3<sup>rd</sup> Generation Partnership Project (3GPP) it has been agreed that inter-frequency RSRP measurement requirements would be developed assuming 6 middle physical resource blocks measurement bandwidth, which has also been agreed to be used for developing intra-frequency RSRP measurement requirements. Wider handover measurement bandwidth could potentially provide better averaging against fading and thus, reduce the time required for performing inter-frequency handover measurements. These studies are conducted with fully dynamic time-driven system simulator and simulations are done with different RSRP measurement bandwidths and different filters. Based on these studies wider bandwidth provides only minor improvement in measurement accuracy and it does not clearly reduce the time required for performing measurements.