WO2009038507A1

WO2009038507A1 - A tdd testing device

Info

Publication number: WO2009038507A1
Application number: PCT/SE2007/050664
Authority: WO
Inventors: Jiuhui Du; Lei Xiao; Bin Xu
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2007-09-18
Filing date: 2007-09-18
Publication date: 2009-03-26
Anticipated expiration: 2010-03-18
Also published as: CN101803249B; TW200929910A; CN101803249A; TWI456922B

Abstract

In a TDD radio system, the interfering signal power is determined by shifting the uplink and downlink transmission time intervals of a time division duplex radio base station. The signal power in the shifted uplink transmission time slot is then measured so that the interfering signal power from surrounding radio base stations can be measured. Based on the measurements, the surrounding base stations as well as a new base station can be configured and tuned so that interference within the system is kept within an acceptable range.

Description

A TDD TESTING DEVICE

TECHNICAL FIELD The present invention relates to a method and a device for testing and tuning a radio system network. In particular, the present invention relate to a method and a device for testing and tuning a Time Division Duplex radio base station.

BACKGROUND In cellular radio communications a number of different transmission schemes and communication modes exist. TDD (Time Division Duplex), is a communication mode, whose uplink and downlink transmission between a radio base station and a mobile station connected to the cellular radio system are located in the same frequency band but separated by the time slot such that data traffic only exist in one direction at the time. In other communication modes the uplink and downlink transmissions between the radio base station and the mobile station may be divided in frequency as FDD (Frequency Division Duplex).

In TDD mobile systems, if the time spacing of uplink and downlink is short enough there is channel reciprocity between uplink and downlink because the bi-directional radio links have almost the same propagation condition. In other words if the switching time between two successive uplink and downlink transmissions is short enough there is not propagation characteristics change between the two transmissions.

Furthermore Time Division-Synchronous Code Division Multiple Access TD-SCDMA, which is a TDD Code Division Multiple Access, CDMA, system, is a global 3 G RAT

(Radio Access Technology) specified in 3GPP. TD-SCDMA and its evolved systems such as Time Division High Speed Downlink Packet Access, TD-HSDPA and TD-SCDMA compatible Long-Term Evolution LTE TDD is dominantly developed in China with a high speed.

Mobile communication has become one of the key global driven technologies. As a result, more and more RATs are standardized and developed, and more and more mobile Radio Access Networks RANs are established and running. In number of countries and areas, in particular modern countries and areas, various networks are co-existing, for example, GSM, WCDMA/HSDPA, CDMA2000/EvDo, WiFi/WiMax systems and so on. Also today many operators build overlapping mobile networks by using the same or different RATs. However, due to the frequency band signal energy leak, there exists the co -existence interference between networks on adjacent frequency bands. In particular, the co-existence interference is a severe problem in CDMA system, with character of self- interference.

TDD system transmits both uplink and downlink signal in the same frequency band so that it is possible to generate a Base Station to Base Station interference if the physical frame synchronization between adjacent Radio Base Stations can not be guaranteed strictly. Since the propagation between Radio Base Stations (RBS) is similar to that in free space and also the transmitted signal power and receiver sensitivity is relatively high, the Base Station to Base Station interference will impact the network robustness severely. In particular, in TDD CDMA, a strong Base Station to Base Station interference could potentially block one or more cells.

Hence, there exist a need for a method and a device that is able to identify potentially troublesome configurations of Base Stations so that Base Station to Base Station Interference can be avoided.

SUMMARY It is an object of the present invention to overcome or at least reduce some of the problems associated with configuring new and existing Radio Base Stations.

It is another object of the present invention to provide a tool that enables detection of potentially interfering configurations of Radio Base Stations, in particular for a specific site- fixed or site-searching RBS.

It is yet another object of the present invention to provide a tool that facilitates configuration of TDD Radio Base Stations operating in an environment with many co-existing radio system networks.

These objects and others are obtained by the method and system as set out in the appended claims. Thus, by providing a TDD testing device enabled to measure the received signal power at a TDD radio base station during time slots when data traffic normally is transmitted by the radio base station, the device can measure the power from existing adjacent TDD radio base stations within the transmission range of the radio base station. By using the information collected by measuring uplink data interference during downlink transmission intervals enables a system administrator to configure the radio base station and also tune surrounding base stations belonging to the same or other radio system network so that the interference level at the new radio base station site is within an acceptable range.

In addition, when deploying a TDD system a proposed base station set up need to be tested so that the Base station to Base Station interference is guaranteed to be within an acceptable range using the same measured signal power.

Thus, by configuring a device such that it is enabled to receive a TDD RBS downlink time slot as uplink time slot, a TDD radio base station can be used as a tester to measure both intra-radio access technology interference and inter-radio access technology interference as a reference of intra-RAT networking and systems co-existence handling.

The testing device in accordance with the invention can advantageously by used to deal with or improve some network planning issues in both intra-RAT and inter-RAT systems.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which:

- Fig. Ia is a view illustrating an area covered by cellular radio system networks,

- Fig. Ib is a schematic view of a device for testing a cellular radio system, - Fig. 2 is a flow chart illustration steps performed when using a test device in accordance with a first aspect, and

- Fig. 3 is a flow chart illustration steps performed when using a test device in accordance with a second aspect

DETAILED DESCRIPTION

In Fig.l a view illustrating a cellular radio system 100 is shown. The cellular radio system comprises a number of cells 101. Each cell 101 is associated with a radio base station (RBS) 103. The area covered by the cellular radio system 100 may also be covered by other cellular radio systems belonging to the same or other radio access technologies. However, to simplify figure Ia, only one cellular radio system is shown in Figure Ia. In order to test the interference at some location in the area of the cellular radio system a testing device 105 comprising a configured as a TDD radio base station with the downlink time slot essentially set as the uplink time slot is provided.

In Fig. Ib a schematic view of the testing device 105 is shown. Thus, the device 105 comprises a unit 111 for measuring and determining the signal power. The device 105 further comprises a unit 113 for manipulating the uplink and downlink transmission time slots and also a control unit 115 for controlling the units 111 and 113 and for receiving input commands from a user as well as providing an output from the device. The device can further be adapted to be configured using a computer program product loaded into a memory 117 of the device. In figs 2 and 3 different steps performed in some different scenarios when testing a new TDD radio base station site are described in more detail.

In Fig. 2 a flow chart illustrating different steps performed when using the test device to find a suitable location for a new radio base station of the radio system 100 and to tune the cellular radio system 100 is shown.

First in a step 201 a testing device comprising a TDD radio base station is located at a test site. Next, in a step 203 the TDD radio base station downlink time slot is set to essentially correspond to the uplink time slot in order to enable the TDD radio base station as test device to measure the signal power from the existing TDD radio base stations 103 of the cellular radio system 100 in which a new radio base station is to be deployed. The step 203 may for example be executed by shifting the time slot switching point of a TD-SCDMA radio base station or a radio base station of any evolved TD-SCDMA system so that the downlink time slot is shifted to the uplink time slot in order to receive the signal from surrounding active TDD radio base stations.

Next in a step 205, configurable parameters of the surrounding active TDD radio base stations are tuned. The tuning in step 205 may for example involve tuning the down tilt of surrounding radio base stations. Thereupon in step 207 the signal power from the surrounding cells of the new site is measured. If the signal power from the surrounding radio base stations is within an acceptable range the tuning of the cellular radio system is completed and the procedure stops in a Step 209. However, if the signal power received from surrounding radio bas stations is not within an acceptable range the tuning process continues and the procedure returns to the step 205.

In another exemplary embodiment described in conjunction with Fig. 3, the testing device can be used to provide test data that can be used to find an acceptable configuration that enables co -existence between different radio access networks. The other radio access networks may belong to the same radio access technology or other radio access technologies.

First in a step 301 , a TDD radio base station 105 is located at a test site. Next, in a step 303 the TDD radio base station downlink time slot is set to essentially correspond to the uplink time slot in order to enable the TDD radio base station as test device to measure the signal power from the existing adjacent radio networks of the cellular radio system 100. The step 303 may for example be executed by shifting the time slot switching point of a TD-SCDMA radio base station or a radio base station of any evolved TD-SCDMA system so that the downlink time slot is shifted to the uplink time slot in order to receive the signal from surrounding active TDD radio base stations.

Next, in a step 305, configurable parameters of the new radio base station 105, and or surrounding radio base stations are tuned. The tuning in step 305 may for example involve tuning the down tilt of the new radio base station. Thereupon in step 307 the signal power from the surrounding radio access networks of the new site is measured. If the signal power from the surrounding radio base stations is within an acceptable range the tuning of the new radio base station 105 is completed and the procedure stops in a step 309. However, if the signal power received from surrounding radio access networks is not within an acceptable range the tuning process continues and the procedure returns to the step 305.

The present invention may be software implemented and stored on a computer program product which can be loaded into the memory of a computer configured to execute the software.

Using the method and device as described herein will provide a radio system network operator operating a cellular TDD radio system network with an efficient tool to efficiently configure and tune an over all radio system network that may comprise many different radio system technologies.

Claims

1. A method of determining interfering signal power in a time division duplex cellular radio system, characterized by the steps of:

- shifting (203, 303) the uplink and downlink transmission time intervals of a time division duplex radio base station,

- measuring (207, 307) the signal power in the shifted uplink transmission time slot,

- determining (207, 307) the interfering signal power based on the measured signal power in the shifted uplink transmission time slot.

2. The method according to claim 1, characterized by the additional step of:

- tuning parameters of at least one surrounding radio base station belonging to the same radio system as the time division duplex radio base station in response to the determined interfering signal power.

3. The method according to claim 2, characterized in that the tilt angle of the at least one surrounding base station is adjusted.

4. The method according to any of claims 1 - 3, characterized by the additional step of:

- tuning parameters of at least one surrounding radio base station belonging to another radio system as the time division duplex radio base station in response to the determined interfering signal power.

5. The method according to claim 4, characterized in that the least one surrounding radio base station belonging to another radio system employs another radio access technology than the time division duplex radio base station.

6. The method according to any of claims 1 - 5, characterized by the additional step of:

- configuring parameters of the time division duplex radio base station in response to the determined interfering signal power.

7. The method according to any of claims 1 - 6, when the TDD radio system is a Time Division Synchronous Code Division Multiple Access (TD-SCDMA) radio system, characterized in that the shifting of the uplink and downlink transmission time intervals of the time division duplex radio base station is executed by shifting the time slot switching point of a TD-SCDMA radio base station

8. A device (105) for determining the interfering signal power in a time division duplex cellular radio system, characterized by:

- means (113) for shifting the uplink and downlink transmission time intervals of a time division duplex radio base station,

- means (111) for measuring the signal power in the shifted uplink transmission time slot, and

- means (111, 115) for determining the interfering signal power based on the measured signal power in the shifted uplink transmission time slot.

9. The device according to claim 8, characterized by:

- means for tuning parameters of at least one surrounding radio base station belonging to the same radio system as the time division duplex radio base station in response to the determined interfering signal power.

10. The device according to claim 9, characterized by means for adjusting the tilt angle of the at least one surrounding base station.

11. The device according to any of claims 8 - 10, characterized by: - means for tuning parameters of at least one surrounding radio base station belonging to another radio system as the time division duplex radio base station in response to the determined interfering signal power.

12. The device according to claim 11, characterized by means for tuning parameters of at least one surrounding radio base station employing another radio access technology than the time division duplex radio base station.

13. The device according to any of claims 8 - 12, characterized by:

- means for configuring parameters of the time division duplex radio base station in response to the determined interfering signal power.

14. The device according to any of claims 8 - 13, where the TDD radio system is a Time Division Synchronous Code Division Multiple Access (TD-SCDMA) radio system, characterized in that the means for shifting of the uplink and downlink transmission time intervals of the time division duplex radio base station is configured to shift the time slot switching point of a TD-SCDMA radio base station

15. A computer program product (117) characterized in that the computer program product comprises program segments that when executed on a computer causes the computer to perform method according to any of claims 1 - 7.