AU785032B2

AU785032B2 - Apparatus for estimating a traffic in a multi-sector antenna system of a mobile communication system

Info

Publication number: AU785032B2
Application number: AU21155/02A
Authority: AU
Inventors: Young Lae Choi; Jong Heon Lee; Sang Jun Lee; Sang Yeon Lee; Uh Seung Lee; Jong Cheol Yun
Original assignee: SK Telecom Co Ltd
Current assignee: SK Telecom Co Ltd
Priority date: 2000-11-27
Filing date: 2001-11-26
Publication date: 2006-08-31
Anticipated expiration: 2021-11-26
Also published as: EP1338100A4; CN1397110A; EP1338100A1; JP2004515110A; WO2002043276A1; CN1220340C; KR100360010B1; KR20020041124A; AU2115502A

Description

WO 02/43276 PCT/KR01/02036

DESCRIPTION

APPARATUS FOR ESTIMATING A TRAFFIC IN A MULTI-SECTOR ANTENNA SYSTEM OF A MOBILE COMMUNICATION SYSTEM 1. Technical Field The present invention relates to a method of estimating each traffic on multi beams or multi sectors using received signal power of a reverse link in a multi-sector antenna system of a mobile communication network.

2. Background Art .0 In a mobile communication system, a BTS (Base Station) is classified into two types, 'Omni' and 'Sector'. However, most base stations are 'sector' type. In a sector-typed BTS, its service area is divided into three or six sectors. A sector-typed BTS in the CDMA system has three sectors in general.

The sector-typed BTS uses antennas with fixed beamwidth for each sector, thus, the geographic area of coverage of a sector is fixed. However, because traffic is usually unbalanced among sectors of a BTS, the frequency resource is :0 allotted enough for a sector processing the heaviest traffic.

As a result, the efficiency of frequency resource is low in a sector of light traffic and, in a sector of heavy traffic, the efficiency of wireless channels may be decreased and the coverage may be shrunken. Therefore, there arise problems such as low service efficiency and high frequency resource management/maintenance cost in a BTS having trafficunbalanced sectors.

Furthermore, if the distribution of traffic load is changed among three sectors in a BTS of which sectors have 1 respective fixed coverage, such situation is manually dealt with, namely, an operator turns antenna mounted on a steel tower properly to adapt to the change of traffic load distribution. However, such manual works are very dangerous and tedious, and the antenna adjusting time is too long as well. In conclusion, manual maintenance is inefficient.

To resolve such problems, a multi-sector antenna system changing each coverage of sectors based on traffic load on each sector was proposed. Implementing such a multi-sector antenna system requires traffic monitoring or estimating techniques rightfully. However, traffic monitoring or estimating techniques proposed until now have several drawbacks to apply them to physical systems.

Because the conventional traffic estimating techniques estimate traffic indirectly based on signal power of a forward link and must be coupled with hardware of a BTS in operations, they require complicated hardware structure and are inefficient from a cost point of view, moreover, their estimating performance is not good.

Specially, these problems become great prominent figures in a multi-sector antenna system using array antennas each of which radiates several, four or eight beams.

Accordingly, a multi-beam traffic estimating technique capable of estimating traffic of each antenna element is 25 urgently demanded.

3. Disclosure of Invention S. It would be desirable for the present invention to provide a multi-beam or multi-sector traffic estimating apparatus, which can be implemented separately from a BTS, of receiving individual signal power inputted from multi beams and estimating traffic of each beam or sector based on each received signal power in a multi-sector antenna system radiating multi beams.

The present invention provides a traffic estimating apparatus of a multi-sector antenna system having a plurality of array antennas radiating N beams, comprising: a power sampling module for sampling the respective signal power of the N beams received from the array antennas; a N:1 switching module for sequentially selecting N signal power samples from the power sampling module at a given interval; a filtering/amplifying module for converting sequential power outputs from the N:l switching module to respective signals of a desired frequency band and amplifying the signals; a power detecting module for converting the power of each signal outputted sequentially from the filtering/amplifying module to respective voltage; and a system controlling module providing a timing clock for the sequential input selection of the N:l switching module, calculating each average of the respective voltage values, and estimating traffic on each beam or each sector using the calculated average values.

A traffic estimating apparatus of a multi-sector antenna 20 system in accordance with an embodiment of the present invention is characterized in that, where the multi-sector antenna system equips with a plurality of array antennas radiating N( 2) beams, it comprises a power sampling module sampling respective signal power of N beams received from the array antennas; a N:1 switching 25 module selecting sequentially N signal power samples from the power sampling module circularly at a given interval; a filtering/amplifying module converting sequential power outputs from the N:1 switching module to respective signals of desired frequency band and amplifying the signals properly; a power detecting module converting power of each signal outputted sequentially from the filtering/amplifying module to respective voltage; and a system controlling module providing a timing clock required for circulating input selection of the N:l switching module, calculating each average of the respective voltage values, and estimating traffic on each beam or each sector using the calculated average values.

In accordance with a multi-beam or multi-sector traffic estimating apparatus of which structure is very simple, the installation and maintenance cost is remarkable reduced and the performance of traffic estimation is also improved, furthermore, traffic balance among all sectors can be achieved through the improved traffic estimation of each beam or sector, which would result in effective use of frequency resources.

4. Brief Description of Drawings The accompanying drawing, which is included to provide a further understanding of the present invention, illustrates the preferred embodiments of the invention, and together with the description, serves to explain the principles of the present invention, and wherein: 99 o good oo *ooo **o e**ge WO 02/43276 PCT/KR01/02036 Fig. 1 is a block diagram of an apparatus of estimating traffic in a multi-sector antenna system of a mobile communication network in accordance with the present invention.

5. Modes for Carrying out the Invention In order that the invention may be fully understood, a preferred embodiment thereof will now be described with reference to the accompanying drawing.

An embodiment of a traffic estimating apparatus of a multi-sector antenna system of a mobile communication network in accordance with the present invention will be described on the assumption that whole service coverage of a BTS is divided into three sectors and an array antenna radiating four or eight beams is used for each sector. Accordingly, the embodiment of the present invention estimates traffic on each beam or each sector based on individually-received signal power of total KxM, namely, twelve (or twenty four) beams.

Fig. 1 is a block diagram of an apparatus of estimating traffic in a multi-sector antenna system radiating KxM beams in accordance with the present invention. The apparatus of Fig. 1 comprises K array antennas 100; a power sampling module 102; a N:l switching module 104 where N=KxM; a filtering/amplifying module 106; a power detecting module 108; and a system controlling module 110.

As shown in Fig. 1, the power sampling module 102 samples every Nbeams received from K array antennas 100 each of which radiates M beams. The power sampling module 102 may be implemented with 20dB directional couplers. The N: 1 switching module 104 selects sequentially the N sampled outputs from the power sampling module 102 at a given interval and outputs one by one according to the selection order. A timing clock required for the periodic circulating selection of the N:l 4 WO 02/43276 PCTKROI/02036 switching module 104 is provided from the system controlling module 110.

The filtering/amplifying module 106 conducts the functions of converting sequential power outputs from the N: I switching module 104 to respective signals of desired frequency band and amplifying the signals properly.

The power detecting module 108 converts the power of each signal outputted sequentially from the filtering/amplifying module 106 to respective voltage values and sends the converted values to next system controlling module 110 sequentially. The power detecting module 108 can change its original cut-off frequency to proper one between 1KHz and 10KHz suitable to eliminate noise of relatively high frequency which might be inserted in the above signal treatment and forwarding processes. The power detecting module 108 contains a capacitor filter (not shown) of which function is to eliminate noise as aforementioned. The detailed explanation for this capacitor filter is omitted since it is apparent to those skilled in the art.

The system controlling module 110 classifies the voltage values received from the power detecting module 108 according to beam or sector and then calculates each average of the voltage values stored until then for each beam or sector.

From each calculated average of the voltage values, the average traffic of each beam or sector is estimated. After estimation of each traffic, the system controlling module 110 also measures how unbalanced the traffic is among beams or sectors.

In addition, the system controlling module 110 also generates a multi-channel control signal synchronized with the timing clock supplied to the N:1 switching module 104.

The multi-channel control signal is used for synchronization between internal or coupled operations in the processes of WO 02/43276 PCT/KR01/02036 received power detection, transmission, classification, and store for each beam.

The system controlling module 110 further conducts beam switching control of a multi-beam based on the estimated average traffic of each beam or sector (or the estimated traffic difference among beams or sectors). Namely, it generates a beam dividing/combining control signal to make traffic be distributed uniformly among K sectors. The uniform distribution of traffic among sectors will be achieved through changing or re-allocating a beam or beams to other sectors whose traffic is relatively heavy according to the beam dividing/combining control signal.

The above-explained traffic estimating apparatus, which is implemented as a sub-system of a BTS having sector-changeable multi beams, can be also applicable to other system such as a switching smart antenna system.

It will be apparent to those skilled in the art that various modifications and variations can be made in the explained embodiments without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

2. The traffic estimating apparatus of claim 1, wherein the power sampling module is implemented with directional couplers.
3. The traffic estimating apparatus of claim i, wherein the power detecting module has a cut-off frequency to eliminate noise which might be inserted in the received signal power.
4. The traffic estimating apparatus of claim 3, wherein the cut- off frequency is in the range of 1KHz to The traffic estimating apparatus of claim 1, wherein the system controlling module further outputs a signal to control individual sector allocation of the N beams based on the estimated traffic on each beam or each sector.
6. A traffic estimating apparatus substantially as hereinbefore described with reference to the accompanying drawing. Dated 3 July 2006 Freehills Patent Trade Mark Attorneys Patent Attorneys for the Applicant/s: SK Telecom Co., Ltd. *8