System for indoor cellula networks automatic frequency planning

SYSTEM FOR INDOOR CELLULA NETWORKS AUTOMATIC FREQUENCY PLANNING

DESCRIPTION

0003It is known that PLMN frequency planning of indoor systems is considerably problematic due to lack of available frequency bands and to high frequency re-use especially in areas with base stations high density.

0004Frequency planning conventional modes are based at employment of tools for coverage prediction where mutual interference matrix between cells, is defined . Such matrix makes up the automatic frequency planning algorithm input. The inconvenience of this application in the indoor scenario is that the simulation coverage tools often lack detailed topographic database and urban clutter able to predict indoor area coverage, thus assigning frequencies in a non-optimum way. Another method used by GSM mobile operators involves a series of measurements in indoor area before WOS installation, and assignment of frequencies. This method is highly reliable because based on measured and not simulated power levels but it requires repeated measurements on site, at each data change in the PLMN. It is also known that the majority of WOS systems implements (ref. Fig. 1), at OMC (3) and BSS (4) levels, a Radio Interference Recording function, which results, processed together with some statistical counters, advice the operator on the adequate change of frequencies in WOS to better radio connection quality.

0005Independently of the chosen method, process for frequency assignment and cells data management has to be made by the mobile operator, who should also produce configuration files, command files and their loading on the network OMC. Main purpose of the present invention is to provide a system for automatic frequenc planning and GSM WOS parameters self-configuration in a completely automatic way, without any action from the GSM mobile operator.

0006Another advantage of such invention is that it guarantees a low interference level and a better quality of radio connection thanks to the real time detection of frequencies present in indoor area and related power levels. The Self planner may be combined to all GSM WOS: it always provides the frequency automatic planning feature and the definition of cell parameters data base compliant with the WOS OMC syntax , containing the informations for network data reconfiguring. It is obvious that, to make automatic the network re-configuring, the WOS OMC has to be able to import a cell parameters database in any format. Should this performance not be available, the possibility of manually loading the cell parameters database in the OMC by the system administrator remains. The mobile operator may define, case by case, and according to his needs, if to keep a totally automatic procedure or operate during process phases for a greater control. To this purpose the Self Planners offers various choices, in both procedure and elaboration levels.

0007In particular, in WOS which implement performances of Radio Interference Recording, the Self Planner provides the possibility to elaborate the frequency planning process by simply processing results of Radio Interference Recording and using them as input for planning algorithm, and also by integrating such results with collected measurements.

0008To better clarify the explanation concerning application of present invention innovating principles, and its advantages against the already known technique, a description (with the aid of attached diagrams) of a possible, but not exclusively, GSM

0009900-1800/1900 MHz system realization will follow.

0010According to the invention principles, the Self Planner is a system able to accomplish the following operations: a) Monitoring of affiliated operator's network (PLMN) b) Measurement of Received Level Average per Cell (RLA_C) values for each GSM channel reserved to that PLMN c) De-coding and recording of Information Elements transmitted on broadcast control channels: Absolute Radio Frequency Channel Number (ARFCN), Location Area Code (LAC), Cell Identity (CI), Base Station Identity Code (BSIC). Reduced

0011Frame Number (RFN) d) Data collection and processing e) Monitoring of PLMN frequency plan from comparison between cycles of subsequent measurements f) Processing of frequency planning algorithm for indoor network micro cells g) BSIC and frequency automatic loading in OMC for each micro cell h) WOS automatic reconfiguration

0012A set of monitors receivers is installed in the indoor area, where WOS is present Monitors (1) are able to perform (a) (b) (c) operations. In particular, to have a reliable measurement procedure in each possible interference situation, it is possible to set the monitor with the following parameters: list of down-link channels on which the monitor has to operate;

0013- detectable maximum and minimum values of Received Level Average per Cell (RLA_C)

0014- measurement period on each radio channel

0015For each WOS, it is possible to install one or more monitors in proximity of each microcell coverage area. Each monitor collects data for frequency planning of one or more microcells, according to its position. Data processing and collection takes place through a computer, the "manager" (2). To transmit collected data, monitors may be connected to the "manager" through dedicated cabling as shown in fig. 2 (wired solution) and/or through radio by equipping monitor and manager with antennas (fig.

00166) as shown in fig. 3 (wireless solution).

0017The manager (2) is a service computer or an OMC CLIENT which manages conditions and time of data collecting procedures of all monitors; afterwards it elaborates frequency planning algorithms.

0018The manager compares measurement sessions received by the monitors and, if needed, detects PLMN frequency plan changes.

0019In case of data change, according to registered measurements, the manager chooses a group of frequencies which measured power level is below a threshold, considered not interfering and which total number is greater than WOS channels to be planned.

0020Afterwards, two or more groups of frequencies, with higher safe threshold, are chosen; this to obtain in each group more and more available frequencies.

0021At this point, the manager is able to elaborate the frequency assignment algorithm.

0022Algorithm Description

0023Inputs listed below show how the frequency planning algorithm is elaborated:

0024- Group 1, 2 ...m of available frequencies

0025- Correspondence between monitor and micro cells

0026- List of micro cells ordered according to their building position compared to the outside area (maximum priority to micro cells next to windows and doors in upper floors of the building)

0027- Channel dimensioning for WOS microcells

0028- Neighbours list between microcells

0029- Specific frequency re-use restrictions for WOS equipment 1. The algorithm starts by considering frequencies of Group 1 corresponding to lower interference threshold, thus potentially less interfering and, according to the dimensioning of each cell, assigns first all broadcast channels, afterwards all traffic channels of each micro cell respecting priority order and verifying the re-use restrictions at each assignment. After assignment occurs the frequency is marked as assigned, thus not reusable for adjacent cells.

0030The procedure is sequential up to when a block occurs due to violation of re-use restrictions or to neighbours list. In this case, the next available frequency (not assigned) in the considered group is assigned . 2. Once all available frequencies are used, and a block occurs again, the algorithm deletes the already planned frequencies going backwards, starting from the last frequency before the blocking one, and repeats the procedure with a new frequency, going on as already described in point 1.

00313. Once all frequencies inside the minimum interference threshold group run out, the entire procedure of point 1 is repeated considering the second group of frequencies with a higher interfering level, obviously a larger group.

00324. At elaboration ending, the algorithm provides a frequency plan which respects all above said restrictions and that, according to interference restrictions, limits and optimizes the interference level, since it uses channels with lower measured power levels. The frequency plan fills cell parameter data base containing new frequencies and BSIC of WOS microcells.

0033When the indoor network frequency plan is defined, the manager fills out the command files in the syntax of the WOS OMC. Command files are transferred to OMC, which automatically reconfigures the indoor network and re-starts service. , In case the manager is an OMC CLIENT, it has to simply have a software able to fill out command files directly, starting from the cell parameters database. Automatic submission to BSC is made directly from the CLIENT. On the contrary case, the manager has to have a dedicated program to translate cell parameters data' base in command files and afterwards to transfer them into OMC. Once they are in¹-, OMC, automatic submission to BSC has to be possible for cells reconfiguration.

0034The Self Planner may be modified in some of its parts for automatic configuration of 3^rd generation indoor systems.