Cell Reselection Research Articles

Hierarchical and Hybrid Cell Load Balancing in 5G Heterogeneous Mobile Networks

SummaryIn Fifth Generation (5G) Heterogeneous Mobile Networks (HetNets), deploying dense small cell networks makes user association more challenging. The process of collecting cell load information from the User Equipments (UEs) and broadcasting the feedback message involves significant overhead and time complexity. Moreover, the UEs may not know the optimum cell to reselect, satisfying its data rate requirements. In order to overcome these drawbacks, in this paper, we propose to design an Hierarchical and Hybrid Cell Load Balancing (HHCLB) technique using Selective Handoff. In this technique, the UEs of each cell are grouped into clusters depending on their proximity distance. Each cluster contains a cluster controller (CC) which is in charge of determining the intra‐cell load and redirecting the cell‐reselection request of a UE. If the data rate of any UE in a cluster becomes less than its required rate, then the cell reselection process is performed. By simulation results, it is shown that load balancing can be done proactively (implicitly) by the CCs when the load is unbalanced or can be done on demand (explicitly) when a UE send a request for cell reselection. In the case of Macro cells, HHCLB attains 71% higher throughput for low load scenario and 59% higher throughput for high load scenario. Similarly, in the case of Femto cells, HHCLB attains 19% higher throughput for low load scenario and 27% higher throughput for high load scenario.

RSS-Based Localization and Mobility Evaluation Using a Single NB-IoT Cell.

Low Power Wide Area Networks (LPWAN) have the ability to localize a mobile transmitter using signals of opportunity, as a low power and low cost alternative to satellite-based solutions. In this paper, we evaluate the accuracy of three localization approaches based on the Received Signal Strength (RSS). More specifically, the performance of a proximity, range-based and optimized fingerprint-based algorithm is evaluated in a large-scale urban environment using a public Narrowband Internet of Things (NB-IoT) network. The results show a mean location estimation error of 340, 320 and 204 m, respectively. During the measurement campaign, we discovered a mobility issue in NB-IoT. In contrast to other LPWAN and cellular technologies which use multiple gateways or cells to locate a device, only a single cell antenna can be used for RSS-based localization in NB-IoT. Therefore, we address this limitation in the current NB-IoT hardware and software by studying the mobility of the cellular-based 3GPP standard in a localization context. Experimental results show that the lack of handover support leads to increased cell reselection time and poor cell sector reliability, which in turn results in reduced localization performance.

Inter Radio Access Technology [IRAT] Handover Algorithms for Heterogeneous Wireless Networks

Inter-system handover is important for 4G/5G networks as these heterogeneous wireless networks (HWNs) have integrated different radio access technologies with diverse levels of performance. One of the major challenges is to make cell reselection and handover between these technologies. In this paper, we considered convergence of HWNs such as an integrated 3rd generation partnership project long term evaluation with legacy networks like WCDMA, GSM and a wireless local area network. We propose inter-radio access technology hand off or inter-system handoff (ISHO) algorithms to evaluate the performance of integrated network model. Three different realistic handoff scenarios have been investigated in the proposed integrated HWN. The aim of this paper is to evaluate the inter-system handover performance for the network model proposed. The performance of our proposed network model has been carried out using proposed ISHO-algorithms in terms of the average number of handoffs and decision delay. To reduce the unnecessary handoffs, to stave off the ping-pong effect and to lessen the decision delay, additional parameters such as time to trigger and hysteresis values are considered.

IMPROVEMENT OF CALL SETUP TIME DURING CIRCUIT SWITCHED FALLBACK

In handover procedure, target cell would be prepared and UE will move on target cell based on the configuration sent by source eNodeB to User Equipment. Cell Reselection happens only when the user equipment (or Mobile Phone) is in Idle MODE, and the User Equipment needs to go a more appropriate cell. The main feature of CSFB Ps handover does not interrupt data transfer when switching from Long Term Evolution to UTRAN/GSM. After switching to 3G is already in connected mode it does not waste time to switch to connected mode. This feature let us improve call setup time when we make call in LTE.

UE‐Initiated Cell Reselection Game for Cell Load Balancing in a Wireless Network

A user changes its serving cell if the quality of experience (QoE) provided by the current serving cell is not satisfactory. Since users reselect cells to increase their QoEs selfishly, the system resource efficiency can be deteriorated and a system can be unstable if users are not driven to cooperate appropriately. In this paper, inspired by the minority game (MG) model, we design a UE‐initiated cell reselection policy. The MG has a salient characteristic that the number of players who win the game converges to a prespecified value even though players act selfishly without knowing the actions taken by the other players. Using the MG model, we devise a rule by which each UE plays a cell reselection game. We also design a criterion that a system controller uses to determine the result of a game and public information sent by a system controller to induce implicit cooperation among UEs. The simulation results show that compared with noncooperative method the proposed method increases not only the system performance, such as cell load balance index and system utility, but also the performance of UEs in terms of a downlink data rate and an outage probability received from a system.

Cellular Data Analytics for Detection and Discrimination of Body Movements

In this paper, we show the possibility of using the smartphone built-in cellular radio modem to track sudden changes in the environment around it, thus turning the cellphone into a radio–frequency (RF) virtual sensor. In particular, we demonstrate how to isolate anomalous RF patterns by applying time series modeling and analysis of downlink multi-cell radio signals. These RF anomalies may indicate a situation change, namely, a body or object(s), movement in the surrounding of the smart-phone. Unlike Wi-Fi and Bluetooth devices, that can be turned on and off according to the user demands, cellular radios are never really disconnected. Even in idle mode, they carry out continuous and autonomous measurements of the radio channel conditions, namely, the cellular signal quality (CSQ). This is performed in agreement with standardized cell reselection procedures. Body movements or scene changes in general in the surroundings of a cellular device are responsible for small CSQ fluctuations that can be isolated from normal network operations and classified accordingly. The validation of this unconventional RF sensing method is based on extensive measurement campaigns covering a period of one month, using up to four commercial off-the-shelf smartphones. As a practical application case study, we developed a real-time demonstrator that is able to detect body proximity events close to the device and discriminate other body-induced environmental changes in the surrounding of the smartphone. Usage of data analytics tools for passive sensing from cellular signals is a novel topic that shows great potential as paving the way to new applications and research opportunities.

Measurement threshold configuration scheme based on the traffic load

This study proposes a performance analysis of the measurements mechanism applicable to the terminal controlled cell reselection algorithm in a mobile cellular communication system. The cell reselection mechanism decides on which cell, a user equipment (UE) is camped on, when it is in the idle mode. The analysis demonstrates the impact of the neighbour cells measurement threshold setting during the reselection on the serving cell pilot channel quality and a measurement effort in the UE, in terms of the time spent measuring neighbour cells. The authors demonstrate that there is a trade-off between the cell reselection performance, in terms of the signal quality during the mobility and the battery life in the mobile terminal with different system configurations. Furthermore, a novel approach and enhanced load based measurement threshold configuration scheme is proposed, in order to improve this trade-off and also the overall system performance and the user experience. Performance analysis results are given in different scenarios to demonstrate the efficacy of the proposed scheme.

A distributed implementation of mobility load balancing with power control and cell reselection in 4G network

SUMMARYWe consider a self‐organizing network (SON) capability of mobility load balancing in a 4G network, which determines the transmission power level for individual base stations and cell reselection for individual mobile stations such that the network‐wide load is minimized while satisfying the minimum signal‐to‐noise and interference ratio (SINR) requirement of individual users. Both centralized and distributed schemes are proposed. The centralized scheme is based on the greedy algorithm, serving as a performance bound to the distributed scheme. The distributed scheme is to solve the system‐wide optimization problem in the flat network model, i.e. no central control node. Furthermore, it requires relatively low inter‐cell exchange information among neighboring cells over an inter‐cell channel, e.g. X2 interface in the LTE network. The proposed design objective is to minimize the number of mobile users that do not satisfy the specified average throughput, while distributing the user traffic load as uniformly as possible among the neighboring cells. Our simulation results for a uniform user distribution demonstrate that the proposed scheme can achieve up to almost 80% of a load balancing gain that has been achieved by a greedy algorithm in the centralized optimization. Copyright © 2014 John Wiley & Sons, Ltd.

The Development of RRM Conformance Test in TD-LTE Idle_State

In order for the RRM conformance of implementation in TD-LTE system idle_state, taking inter-frequency cell reselection procedure as the point of penetration, a new testing scheme is designed by developing testing and test control notation version 3(TTCN-3) test case to verify the RRM conformance. Furthermore, the test case is operated on the TTworkbench developed by German Testing tech. It also generates test execution flow chart to check the RRM conformance of idle_state functions.

LTE Radio Resource Management Conformance Testing: Exploration and Implementation

LTE is an evolution of 3G technology which possesses 100Mb/s data downloading capability. The technology of LTE is progressive and puts forward stricter requirements for terminals. All the LTE wireless terminals must pass the Radio resource Management (RRM) conformance testing before entering into the market. This paper first dissected TTCN-3 test system and RRM testing structure for the purpose of designing RRM testing model. The testing model proposed in this paper realized the equal data exchange between test system (TS) and system under test (SUT) in application layer, and thus solved a big problem in constructing test platform of RRM testcases. Then comes the most difficult tasks: develop RRM testcases, system adapter (SA) and codec (CD). Among the tasks, RRM testcases are developed based on the test suite released by European Telecommunication Standards Institute (ETSI). Important runtime testing processes including Authentication and Key Agreement (AKA) process, preamble transfer process and cell reselection process are dissected in detail for the purpose of programming. SA is developed according to TRI specification using socket programming. CD is developed according to TCI specification.. On the basis of massive practical work, the implementation of RRM conformance testing is shown. Index Terms—Radio resource management, LTE, TTCN-3, AKA, Conformance testing

A semi-Markov decision process-based joint call admission control for inter-RAT cell re-selection in next generation wireless networks

In the next generation wireless networks (NGWNs), where different radio access technologies (RAT) will coexist and work in collaboration to provide ubiquitous access, a mechanism called Joint Call Admission Control (JCAC) will play an important role by deciding whether or not an incoming service request will be accepted according to an admission constraint as well as determining in which RAT (among the available) it will be connected. In this paper, we propose an optimal JCAC for inter-RAT cell re-selection problem also referred to as initial RAT selection in co-located wireless networks, which supports both real-time services and non-real-time services. To properly meet the JCAC goals, we propose a cost function that weigh two criteria: the blocking cost function, which takes into account the priority of each service class in each RAT, and the alternative acceptance cost, which reflects the multiplicity of RATs working in a collaborative fashion, mandatory in NGWN. We use the framework of Semi-Markov Decision Process (SMDP) to formulate the optimization problem and the value iteration algorithm to compute the optimal policy. Our model still takes into consideration the ratio between the radius of the co-located RATs and shows how it may impact on optimal initial RAT selection. Numerical results, supported by an analysis of the structure of the optimal policy, show that the proposed optimal JCAC selects for real-time service class the biggest RAT and for non-real-time service class the smallest one. This optimal JCAC policy is ratified by the current trend in the design of NGWN and also follows the 3rd Generation Partnership Project (3GPP) expectations.

Adjustment of mobility parameters for traffic steering in multi-RAT multi-layer wireless networks

Mobile broadband traffic has been increasing in the last years. To cope with such traffic demand, heterogeneous networks are an effective solution characterized by deploying networks with different cell sizes, radio access technologies (RATs) and carrier frequencies. Since the coverage area of these networks (or layers) is partially overlapped, users can be steered to a specific layer in order to improve network performance. In this work, two mechanisms of traffic steering are analyzed in a realistic high-speed packet access/long-term evolution deployment scenario, where the objective is to offload traffic from the macro-layer to pico-cells. In idle mode, i.e., the state in which no dedicated resources have been established for the user, a static adjustment of the layer priorities in the cell reselection algorithm is performed. In connected mode, where dedicated resources have been established, the parameters of the inter-RAT handover triggering condition are statically adjusted to offload the macro-layer. Simulation results show that further offloading can be achieved by modifying these algorithms so that user satisfaction is improved.

Analysis of the Impact of Site Planning on the Performance of Relay Deployments

Network planning tools are routinely used by operators to improve the system performance and to provide a satisfactory service with minimal deployment expenditure. In this context, the deployment flexibility of relay nodes, which mainly stems from the wireless backhaul link, compact physical characteristics, and low power consumption, can be exploited to enhance the system performance. In this paper, we model and analyze two simple approaches that can be used for the planning of two-hop cellular relay networks. The aim of the so-called relay location selection and serving cell selection approaches is to enhance system performance by improving the quality of the wireless relay backhaul link. Location selection takes into account the shadowing properties at the different possible relay node deployment locations, considering only the link quality toward the serving base station. On the other hand, cell selection considers the case where a relay node performs cell reselection from a severely shadowed serving base station to a neighboring cell that is less shadowed. A simple model for evaluating and analyzing the impact of both network planning techniques on the system performance of relay deployments is given. In addition, we present the analytical framework through closed-form derivations of the signal-to-interference ratio (SIR) and end-to-end rate distributions. Performance evaluations that investigate the impact of site planning on the quality of the relay backhaul link, end-to-end rate, resource allocation on the two hops, upper bounds on planning gains, access-link limitations, and the deployment of multiple relay nodes are carried out. Results show significant improvements, which justify the need for relay site planning in relay enhanced networks.

Analysis of Heuristic Graph Partitioning Methods for the Assignment of Packet Control Units in GERAN

Over the last few years, graph partitioning has been recognized as a suitable technique for optimizing cellular network structure. For example, in a recent paper, the authors proposed a classical graph partitioning algorithm to optimize the assignment of cells to Packet Control Units (PCUs) in GSM-EDGE Radio Access Network. Based on this approach, the quality of packet data services in a live environment was increased by reducing the number of cell re-selections between different PCUs. To learn more about the potential of graph partitioning in cellular networks, in this paper, a more sophisticated, yet computationally efficient, partitioning algorithm is proposed for the same problem. The new method combines multi-level refinement and adaptive multi-start techniques with algorithms to ensure the connectivity between cells under the same PCU. Performance assessment is based on an extensive set of graphs constructed with data taken from a live network. During the tests, the new method is compared with classical graph partitioning approaches. Results show that the proposed method outperforms classical approaches in terms of solution quality at the expense of a slight increase in computing time, while providing solutions that are easier to check by the network operator.

Access Probability Aware Cell Reselection for 3G Evolution

In LTE, AC barring check is performed before RRC connection. In some cells with a low access probability, the UEs keep retrying access which results in higher connection failure and longer access delay. We therefore propose balancing the UEs by adjusting the cell reselection criteria based on the access probability, so that the UEs shall be more encouraged to reselect a cell with a higher access probability.

A Method for Soft-Decision UMTS Cell Reselection Based on a Database Solution

A novel idea of cell reselection in a UMTS system is presented in this article. The proposed method offers performance enhancements when compared to the algorithm that complies with the 3GPP specifications. This reselection algorithm specifics new criteria that are iteratively computed in every measurement cycle. And to continuously perform the iterative nature of the algorithm, a database solution also is proposed. The database must follow certain rules to maintain the required efficiency.

Optimal 3GPP packet-switched streaming service (PSS) over GPRS networks

3GPP packet-switched streaming service (PSS) is a standardized packet-based mobile streaming service, which is based on IETF RTSP/SDP standards. PSS can be implemented over GPRS networks; however these cannot usually guarantee any data rates or delay bounds, but allow sufficient bandwidth for mobile streaming. GPRS cell reselections pose additional challenges for streaming, since several seconds of data transmission breaks may occur, and data may even be lost. The level of error protection of GPRS is good enough for mobile streaming, if the correct quality of service (QoS) profile is configured. In this paper, we study the effect of different QoS parameters configurations to find optimal values for PSS over GPRS. The paper shows also a method for optimizing cell reselection management at the application layer, in order to provide seamless mobility. Results show that despite all the limitations of a GPRS environment, PSS is feasible with a decent quality of service.

Optimization of the assignment of cells to packet control units in GERAN

In GSM EDGE radio access network (GERAN), the assignment of cells to packet control units within a base station-controller is of key importance to optimize the quality of service experienced by end users. In this paper, a novel methodology is presented to optimize this assignment by means of graph partitioning theory. The proposed algorithm aims at minimising the number of cell re-selections between cells on different packet control units based on handover information. Results from the application of the method in a live network show its capability to improve end-user performance in terms of service delay and application throughput.

Preferential expression of a mutant allele of the amplified MDR1 (ABCB1) gene in drug-resistant variants of a human sarcoma.

Activation of the MDR1 (ABCB1) gene is a common event conferring multidrug resistance (MDR) in human cancers. We investigated MDR1 activation in MDR variants of a human sarcoma line, some of which express a mutant MDR1, which facilitated the study of allelic gene expression. Structural alterations of MDR1, gene copy numbers, and allelic expression were analyzed by cytogenetic karyotyping, oligonucleotide hybridization, Southern blotting, polymerase chain reaction, and DNA heteroduplex assays. Both chromosome 7 alterations and several cytogenetic changes involving the 7q21 locus are associated with the development of MDR in these sarcoma cells. Multistep-selected cells and their revertants contain three- to six-fold MDR1 gene amplification compared with that of the drug-sensitive parental cell line MES-SA and single-step doxorubicin-selected mutants. MDR1 gene amplification precedes the emergence of a mutant allele in cells that were coselected with doxorubicin and a cyclosporin inhibitor of P-glycoprotein (P-gp). Allele-specific oligonucleotide hybridization showed that the endogenous mutant allele was present as a single copy, with multiple copies of the normal allele. Reselection of revertant cells with doxorubicin in either the presence or the absence of the P-gp inhibitor resulted in exclusive reexpression of the mutant MDR1 allele, regardless of the presence of multiple wild-type MDR1 alleles. These data provide new insights into how multiple alleles are regulated in the amplicon of drug-resistant cancer cells and indicate that increased expression of an amplified gene can result from selective transcription of a single mutant allele of the gene.

Functional areas for advanced mobile satellite systems

In the third generation of mobile systems several satellite systems, each tailored to specific user requirements are expected to be integrated with the terrestrial cellular network. This article deals with the extension to satellite systems of the advanced networking concepts which are emerging in the third-generation framework. In particular, it focuses on the basic functional areas for mobile satellite systems, namely, the cell and the location area. It is worth stressing that proper definitions of the satellite cell and satellite location area concepts, as well as an appropriate design of the satellite cell and satellite location area layouts, are essential, since the mobility procedures (cell reselection, paging, localization, handover) make systematic reference to these concepts. The topics exposed in this article are applicable to any satellite system regardless of orbit type, from geostationary (GEO) to low Earth orbits (LEO): the satellite spot-beam arrangement, access technique, and on-board switching capabilities (ranging from transparent payloads with reduced switching capabilities to satellite systems provided with on-board processing capabilities and intersatellite link).