Johan Moe

Neighbor Cell Relation List and Physical Cell Identity Self-Organization in LTE

Automation of radio network management is a key determinant to work reduction for wireless operators. By replacing time consuming and costly tasks with automatic mechanisms, operational expenditure can be reduced. In this paper we present a method for automatic configuration of locally-unique physical cell identities and neighbor cell relation lists in 3G long term evolution (LTE). This method makes use of mobile measurements to update the neighbor cell relation lists in the cells and to detect local cell identity conflicts, report the conflicts to the operation support systems (OSS) and resolve them. The performance of the approach is determined using simulations of realistically deployed macro networks. Conducted simulations illustrate the ability of the method to resolve local cell identity conflicts. In particular, the method is capable of both accommodating new cells and handling a worst case scenario where all cells are initiated with the same local cell identities and where neighbor cell relation lists are empty.

On self-optimization of the random access procedure in 3G Long Term Evolution

Operationally efficient radio networks typically feature a high degree of self-organization. This means less planning efforts and manual intervention, and a potential for better radio resource utilization when network elements adapts its operation to the observed local conditions. The focus in this paper is self-optimization of the random access channel (RACH) in the 3G Long Term Evolution (LTE). A comprehensive tutorial about the RACH procedure is provided to span the complexity of the self-optimization. Moreover, the paper addresses RACH key performance metrics and appropriate modeling of the various steps and components of the procedure. Finally, some coupling between parameters and key performance metrics as well as self-optimization examples are presented together with a feasibility discussion. The main ambition with this workshop paper is to present and define a relevant set of self-optimization problems, rather than to provide a complete solution.

Neighbor cell relation list and measured cell identity management in LTE

Radio network management simplification concerns to some extent the removal, not the simplification, of tasks. In this paper we present an approach for automatic network management in 3G long term evolution (LTE), namely, methods for automatic configuration of locally-unique physical cell identities and neighbor cell relation lists. We show that these issues can be removed from the list of planning tasks and completely replaced by autonomous algorithms. These algorithms make use of mobile measurements to detect local cell identity conflicts, resolve them, and to update the neighbor cell relation lists in the cells. The performance of the approach is determined using simulations of realistically deployed macro networks. The simulations illustrate the ability of the algorithms to resolve local cell identity conflicts. In particular, the algorithms are capable of both accommodating new cells and handling a worst case scenario where all cells are initiated with the same local cell identities and where neighbor cell relation lists are empty. The contributions in this paper are meant to aid operators by allowing them to replace time consuming and costly tasks with automatic mechanisms, thus, reducing operational expenditure.

Using execution trace data to improve distribute systems

One of the most challenging problems facing todays software engineer is to understand and modify distributed systems. One reason is that in actual use systems frequently behave differently than the developer intended. In order to cope with this challenge, we have developed a three‐step method to study the run‐time behavior of a distributed system. First, remote procedure calls are traced using CORBA interceptors. Next, the trace data is parsed to construct RPC call‐return sequences, and summary statistics are generated. Finally, a visualization tool is used to study the statistics and look for anomalous behavior. We have been using this method on a large distributed system (more than 500000 lines of code) with data collected during both system testing and operation at a customers site. Despite the fact that the distributed system had been in operation for over three years, the method has uncovered system configuration and efficiency problems. Using these discoveries, the system support group has been able to improve product performance and their own product maintenance procedures. Copyright

Exploiting Tracking Area List for Improving Signaling Overhead in LTE

Reducing the overhead required for tracing mobile devices is one of the major aspects in the study of mobility management of a cellular network. The Long Term Evolution (LTE) systems give a more flexible configuration of Tracking Area (TA) design by means of Tracking Area List (TAL). Being a novel concept, TAL goes beyond the capability of the conventional TA approach. Although TAL is expected to be able to reduce the overall signaling overhead by overcoming a couple of major limitations of the conventional TA concept, how to apply TAL in large scale networks, remains unexplored. In this paper, we present a novel approach for allocating and assigning TA lists. The approach does not require any data other than what is needed for conventional TA design. We present numerical results to illustrate the approach for a realistic network of Lisbon city. The experiments demonstrate the ability of TAL in reducing the signaling overhead compared to the conventional TA concept.

Dynamic Tracking Area List configuration and performance evaluation in LTE

Reducing the signaling overhead for tracing user equipment (UE), while maintaining the improved performance over time despite the changes in UE location and mobility patterns, is a challenging issue in the area of mobility management. Flexibility and automatic reconfiguration are two significant features in Long Term Evolution (LTE) systems. The Tracking Area List (TAL) is a novel concept in LTE systems, which allows a more flexible configurations, expecting to reduce the overall signaling overhead. In this paper, we first present a ”rule of thumb” method to allocate and assign TALs for a network. The easily applied approach does not require any data other than what is available for conventional TA design. Second we compare the performance of an optimum conventional TA design with the suggested TAL design for a large scale network in Lisbon, Portugal. A thorough computation is done to make a justified evaluation. We follow the comparison during specific time intervals for one complete day, and we illustrate the performance of reconfiguration for each approach. The results clearly demonstrate the ability of dynamic TAL in reducing the signaling overhead and maintaining a good performance due to reconfiguration compared to the conventional TA design.

Evaluations of LTE Automatic Neighbor Relations

In recent years, there has been a strong focus on network management simplicity under the device self-organizing networks (SON). A number of SON use cases and features have been and are discussed for 3G Long Term Evolution (LTE). The main SON feature in the first LTE release is methods for automatic configuration of neighbor cell relations - Automatic Neighbor Relations (ANR). In this paper, we describe the neighbor relations management and ANR, and evaluate ANR in a pre-launch, commercially deployed network cluster. The results indicate that ANR configures discovered and needed neighbor relations such that handover can be performed in combination with the neighbor relation establishment without dropping the connection.

Towards Random Access Channel Self-Tuning in LTE

Future radio access networks are expected to show a high degree of self-organization. This paper addresses self- tuning of the random access channel (RACH) in the 3G Long Term Evolution (LTE). The feasibility of self-tuning is investigated by means of simulation, where the coupling between several parameters and the performance of RACH is provided. The conclusion of the simulations is that RACH self-tuning is indeed possible given that UE assisted measurements are available for the self-tuning mechanism.

Optimizing the Tradeoff between Signaling and Reconfiguration: A Novel Bi-Criteria Solution Approach for Revising Tracking Area Design

Improving the tracking areas (TA) configuration over time to reduce signaling overhead is vital for location management of Long Term Evolution networks. The user location and mobility patterns have ...

Self-optimizing antenna muting - energy consumption and user thoughput analysis

Energy consumption in mobile networks, e.g. 3G networks, may be a substantial part of an operators expenses. A large part of the total energy of the network is consumed by the radio access network. Today operators are saving energy by turning off carriers or cells during periods with low traffic by manually configuring on-off periods. At the same time, operators are seeking to increase cost efficiency through simplifying network management processes by means of automation. In this paper we address energy saving by introducing an approach that automatically and without operator involvement deactivates radio units during periods with low load. We demonstrate the benefits of antenna deactivation using a dynamic simulator and a realistic deployment based on a major Western European city. The results presented suggest that there is potential for significantly enhancing the energy efficiency in mobile networks by adaptive activation of radio units.