GSM/EDGE Radio Access Network Research Articles

Radio Resource Management in Heterogeneous Networks, Functional Models and Implementation Requirements

The scope of this paper is to provide a detailed description of the selected architecture and the functionalities considered for the AROMA project. This project focuses on a heterogeneous radio access network which includes several Radio Access Technologies (RAT) , namely; UMTS Terrestrial Radio Access Network (UTRAN), GSM/EDGE Radio Access Network (GERAN), and Wireless Local Area Network (WLAN). The corresponding Common Core Network (CN) is considered to provide and satisfy different kind of services, thus, different identified services have different QoS, then, so the goal is to study and analyze some algorithms, that best fit in the network in order to enable quality of service (QoS) based on the service demand in the network. Radio Resource Management (RRM) refers to a group of algorithms that are collectively responsible for efficiently utilizing the radio resources within a RAT to provide services with an acceptable level of QoS. Mainly, at present, Radio Resource Management (RRM) algorithms are implemented independently in each RAT. In the meanwhile, The Common RRM (CRRM) strategy, has been proposed in the literature to coordinate radio resources utilization among a number of RATs in an optimized way. This paper analyze CRRM solutions with particular attention on implementations. Starting from an analysis of the state of the art, the most interesting solutions have been critically analyzed and then some in depth investigations on some of the identified solutions have been performed.

Improved joint radio resource management usage grey fuzzy control in heterogeneous wireless networks

This paper presents an innovative approach to joint radio resource management (JRRM) over a complex heterogeneous network by using several realistic radio access technologies (RATs). This work applies a novel grey fuzzy control process to joint radio resource management (JRRM). In this architecture, the JRRM techniques are divided between grey fuzzy control (GFC) and grey fuzzy multi-attribute decision making (GFMADM). These enhancements lead to a new JRRM architecture which seeks to minimize the multi-user interference, decrease blocking, lower dropping probabilities and improve load balancing. The policy uses the signal strength, path loss, and load algorithms for admission control (AC), horizontal handoff (HHO) and vertical handover (VHO) in a heterogeneous wireless scenario which includes GSM/ EDGE radio access network (GERAN), high-speed packet access (HSPA) and long term evolution (LTE) RATs. Our simulation results show that the proposed GFC/GFMADM algorithm can decreases multi-user interference which results in the increasing system radio capacity, decreasing blocking and dropping probabilities and enhancing load balancing.

Joint OSC Receiver for Evolved GSM/EDGE Systems

This paper is focused on evolved GSM/EDGE systems complying to the new feature Voice services over Adaptive Multi-user channels on One Slot (VAMOS), recently introduced in the 3GPP GSM/EDGE radio access network (GERAN) standard. VAMOS enables the transmission of two GSM voice streams on the same radio resource through the so called Orthogonal Sub Channel (OSC) multiple access technique which aims at doubling the number of users served by a cell. When adopting this feature, the GSM network experiences a mixture of in-cell and out-of-cell interference which has to be handled by advanced receivers with interference rejection capabilities. In this paper, a novel two-stage receiver is proposed and tested for the uplink of GSM VAMOS systems. The new scheme combines a pre-filtering stage for out-of-cell interference mitigation with a multi-user detector (MUD) for joint equalization of the two multiplexed OSC streams. The approach is suited for either single-antenna or multi-antenna base stations and can accommodate multiple filters for each user to cope with complex multipath propagation scenarios. The new solution is compared with other existing interference cancellation techniques here applied to the specific OSC scenario. Numerical results show significant performance gains in realistic multi-cell simulated scenarios.

An efficient integer programming formulation for the assignment of base stations to controllers in cellular networks

In mobile networks, the assignment of base stations to controllers when planning the network has a strong impact on network performance. In a previous paper, the authors formulated the assignment of base stations to packet controllers in GSM-EDGE Radio Access Network (GERAN) as a graph partitioning problem, which was solved by a heuristic method. In this paper, an exact method is presented to find optimal solutions that can be used as a benchmark. The proposed method is based on an effective re-formulation of the classical integer linear programming model of the graph partitioning problem, which is solved by the branch-and-cut algorithm in a commercial optimization package. Performance assessment is based on an extensive set of problem instances built from data of a live network. Preliminary analysis shows some properties of the graphs in this problem justifying the limitations of heuristic approaches and the need for more sophisticated methods. Results show that the proposed method outperforms classical heuristic algorithms used for benchmarking, even under runtime constraints. Likewise, it improves the efficiency of exact methods previously applied to similar problems in the cellular field.

Network performance model for location area re-planning in GERAN

In mobile networks, location area (LA) planning has a strong influence on network performance. This paper addresses the problem of optimising an existing LA plan in a live GSM-EDGE radio access network (GERAN) based on statistical measurements. Unlike prior work, where the quality of an LA plan was assessed based on the number of location update and paging requests, the main focus in this paper is on estimating the impact of changing the LA plan on the air-interface signalling load. For this purpose, a performance model is proposed to estimate changes in the traffic load in dedicated signalling channels. With such a model, it is possible to estimate the change that a new LA plan will cause in terms of the required number of signalling channels in the whole network, providing an indication of the capacity benefit obtainable, which is a more significant figure of merit for operators. Model assessment is carried out based on measurements taken before and after changing the LA plan of a limited geographical area in a live network. Then, a comparison of several LA re-planning algorithms is performed over measurements in a larger area by using the proposed performance model. Results show that the signalling traffic (and, hence, the required signalling resources) can be significantly reduced by improving the existing LA plan in a live GERAN system.

Joint radio resource management in heterogeneous wireless networks by using combined fuzzy logic and MADM

This paper addresses a novel mechanism to solve the scalable problem in JRRM. Due to the flexibility and simplification, the fuzzy logic control (FLC) is chosen to make effective utilisation of resources. The combined fuzzy logic and multi-attribute decision making (MADM)-based algorithm can make proper initial RAT selection, horizontal handoff, vertical handoff, admission control and load balancing. The MADM-based RAT selection also has better efficiency than the traditional RRM mechanisms. By considering three kinds of traffic, voice, video and data respectively, the proposed scheme provides lower new call blocking probability and handoff call dropping probability in the heterogeneous wireless network that includes GSM/EDGE radio access network (GERAN), high-speed packet access (HSPA) and mobile worldwide interoperability for microwave access (WiMAX) RATs.

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.

Performance Analysis of Dedicated Signalling Channels in GERAN by Retrial Queues

GERAN (GSM-EDGE Radio Access Network) operators have traditionally used the Erlang B formula to estimate the number of signalling channels on a per-cell basis. Thus, it is assumed that the network behaves as a loss system with Poisson arrivals. However, the presence of automatic retrial mechanisms and correlated arrivals in these channels suggests that these assumptions might not be valid. This paper presents a performance analysis of the Stand-alone Dedicated Control CHannel in GERAN. Preliminary analysis shows that the Erlang B formula underestimates congestion and blocking on this channel. To address this issue, a queueing model with retrials and correlated arrivals is proposed, where correlation between arrivals is modelled by a simple Markov-Modulated Poisson Process. The proposed model can be tuned on a per-cell basis by statistics in the Network Management System. Model assessment is based on performance statistics from a live GERAN system. Results show that a simple retrial queueing model fails to explain blocking in cells with a large number of channels. These limitations are overcome by adding correlated arrivals in the retrial model.

Optimal Traffic Sharing in GERAN

In a mobile communications network, the uneven spatial distribution of traffic demand can be dealt with by redefining cell service areas. When resizing cells, network operators often aim at equalizing call blocking rates throughout the network in the hope that this will maximize the total carried traffic in the network. In this paper, an analytical teletraffic model for the traffic sharing problem in GSM-EDGE radio access network (GERAN) is presented. From this model, a closed-form expression is derived for the optimal traffic sharing criterion between cells. Using this expression, it can be shown that balancing call blocking rate between adjacent cells is not the optimal strategy. Results show that using the optimal traffic sharing criterion instead of balancing blocking rates across the network can increase network capacity, even under restrictions in the cell resizing process.

A Markovian Approach to Radio Access Technology Selection in Heterogeneous Multiaccess/Multiservice Wireless Networks

This paper addresses the problem of radio access technology (RAT) selection in heterogeneous multi-access/multi-service scenarios. For such purpose, a Markov model is proposed to compare the performance of various RAT selection policies within these scenarios. The novelty of the approach resides in the embedded definition of the aforementioned RAT selection policies within the Markov chain. In addition, the model also considers the constraints imposed by those users with terminals that only support a subset of all the available RATs (i.e. multi-mode terminal capabilities). Furthermore, several performance metrics may be measured to evaluate the behaviour of the proposed RAT selection policies under varying offered traffic conditions. In order to illustrate the validation and suitability of the proposed model, some examples of operative radio access networks are provided, including the GSM/EDGE Radio Access Network (GERAN) and the UMTS Radio Access Network (UTRAN), as well as several service-based, load-balancing and terminal-driven RAT selection strategies. The flexibility exhibited by the presented model enables to extend these RAT selection policies to others responding to diverse criteria. The model is successfully validated by means of comparing the Markov model results with those of system-level simulations.

Optimization of the Assignment of Base Stations to Base Station Controllers in GERAN

In GSM-EDGE radio access network (GERAN), the assignment of base stations to base station controllers has a strong impact on network performance. In this paper, an exact method is proposed to improve an existing assignment of base stations to base station controllers. The aim is to minimize the number of handovers between base station controllers given a maximum number of base stations re-allocations. Results from a real case study show that the proposed method outperforms classical re-partitioning approaches in terms of solution quality.

Optimization of Handover Parameters for Traffic Sharing in GERAN

Cellular network traffic is unevenly distributed both in time and space, which greatly complicates network dimensioning. As a result, some cells in the network are permanently congested, while others are underutilized. In a previous paper, the authors showed that this problem can be effectively solved in GSM/EDGE Radio Access Networks (GERAN) by modifying handover boundaries. However, several drawbacks prevent operators from fully exploiting the potential of this technique. This paper investigates the limitations of current traffic-sharing approaches with tight frequency reuses in GERAN. To deal with such limitations, an algorithm is proposed to jointly optimize handover margins and signal-level constraints based on network statistics for traffic sharing in GERAN. A complementary algorithm is proposed to adjust cell (re)selection offsets to minimize the number of handovers. Simulation results show that the proposed method achieves a significant reduction in call blocking without excessive call quality impairment or increase of network signaling load when compared to the current approaches. More traffic can thus be handled without the need for any hardware upgrades, providing a cost-effective means to increase network capacity.

Identification of missing neighbor cells in GERAN

In GSM/EDGE Radio Access Networks (GERAN), the number of neighbor cells defined per cell for handover purposes is limited. Due to the large number of cells and, consequently, neighbor cells in the system, neighbor cell management proves a complex and time-consuming process during network operation. Hence, it is very likely that, on some cells, important neighbor cells are missing. This paper outlines a new approach for determining these missing neighbors, based only on information from the network management system. Thus, the need for propagation data from network planning tools is circumvented, which makes the method especially suitable for the operational stage of an existing network. Results from the application of the method in a live network show its capability to spot such missing neighbors. Although performance benefits from the method are rather limited for the entire network, significant benefits can be obtained on individual cells.

Trial Results of Intelligent Paging in GERAN

In cellular networks, location managements has a strong impact on signaling load. To minimise mobility-based signaling traffic. Location Areas (LAs) have to be defined correctly. Large LAs increase paging traffic, while small LAs increase location updates. Thus, operators have to trade-off these two constraints to maximize network performance. Several authors have proposed selective paging to reduce paging load. This paper describes an intelligent paging algorithm based on most-recent interaction data. Trial results in a live GSM-EDGE Radio Access Network (GERAN) show that the algorithm can reduce paging traffic significantly, while keeping paging success rates almost unaltered.

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.

Performance of data services in GERAN networks

The performance of data based services such as Internet browsing and e-mailing in GSM EDGE Radio Access Networks (GERAN) is described. Results from networks around the world show that quite significant performance differences exist, despite the fact that all systems are based on the same technical standard.

Impact of antenna downtilting on network performance in GERAN systems

Antenna downtilting is often mentioned in the literature as a powerful method for improving network performance in cellular systems. The antenna elevation angle on a number of GSM EDGE radio access network (GERAN) cells has been modified to quantify the impact of this method in a real network. In addition, a novel approach to prioritizing the cells to be tilted, which uses network statistics only, has been tested. Trial results indicate that downtilting can improve certain performance aspects, especially those related to signal quality, but not all of them on every cell.

Trial results from adaptive hand-over boundary modification in GERAN

Modification of hand-over boundaries allows resizing of the effective cell service area. This method has been used in GSM/EDGE radio access network (GERAN) to deal with tele-traffic congestion that is caused by operator tariffs. Results from the application of this method in an actual network show that significant performance benefits can be obtained.