CN100369515C

CN100369515C - Coverage test method for fixed beam intelligent antenna base station system

Info

Publication number: CN100369515C
Application number: CNB2005100022891A
Authority: CN
Inventors: 李晟
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2005-01-20
Filing date: 2005-01-20
Publication date: 2008-02-13
Anticipated expiration: 2025-01-20
Also published as: CN1809198A

Abstract

The present invention relates to the technical field of wireless cellular communication and proposes a coverage test method for a smart antenna base station system with fixed wave beams. In the method, on the basis of the existing test method, a test link for the influence of the load distribution of different systems on coverage is added; under the conditions of zero load coverage, homogeneous distribution half load coverage and non-uniform distribution half load coverage testing, forward and reverse service channel coverage conditions are tested, and the test result is output in the form of figures. If the method of the present invention is adopted, the defect of the existing method is remedied, and the coverage conditions of a smart antenna system with fixed wave beams can be determined under various conditions sufficiently, accurately and comprehensively, which provides a guarantee for the overall awareness of system performance.

Description

Coverage test method for fixed beam intelligent antenna base station system

Technical Field

The present invention relates to the field of wireless cellular communications, and in particular, to a coverage test method for a CDMA (Code Division Multiple Access) base station system using a fixed beam smart antenna.

Background

In the coverage test process for CDMA system, the current method is to test in units of sectors. For the coverage of a sector, a test device is usually used to measure the total received power value in a predetermined coverage area of a target sector, and a coverage boundary is determined by whether the total received power value is lower than a minimum received threshold value. For the current CDMA system, the coverage area of each sector is less affected by the distribution of the system load in the sector, so the existing test method does not care about the distribution of the load when testing the system coverage.

With the development of mobile communication, although CDMA systems have advantages in capacity and service quality compared to TDMA (Time Division Multiple Access) systems and FDMA (Frequency Division Multiple Access) systems, since CDMA system users share one wideband channel, the capacity of CDMA systems is limited by co-channel interference between users, and thus any degree of interference reduction will directly bring about capacity improvement. Generally, a method of dividing a cell into a plurality of sectors by using a directional antenna on a base station side can improve capacity by a large amount, and the narrower the sector, the more the capacity is improved, but the too many sectors cause problems such as too many soft handover areas, reduction of air resource utilization, and increase of pilot pollution. Therefore, new technologies are introduced to overcome these effects, such as smart antenna technology, which is a new technology in the field of mobile communications and includes two broad categories, namely fixed beam smart antenna and adaptive smart antenna, wherein the fixed beam smart antenna is easy to implement and has low development cost and is used in the first place. The cell is divided into a plurality of beams by adopting the fixed beam intelligent antenna, so that the co-channel interference of users in the same cell and adjacent cells is reduced, and the capacity is increased.

The theoretical basis for smart antenna coverage is briefly described below.

Assuming s (t) is the signal from the user arriving at the base station antenna array, the data vector after passing through the antenna array is equal to

U (t) = s (t) × α (θ, Φ) + N (t) (formula 1)

Where α (θ, φ) is called a steering vector, and represents the phase difference between each array element and the reference array element (array element 0) signal when a plane wave is incident from the direction of (θ, φ):

α(θ，φ)＝[1α ₁ (θ，φ)...α _M-1 (θ，φ)](formula 2)

In the formula (2), M is the number of arrays.

In formula (1), the vector N (t) contains the noise contribution to each array element, and each element of N (t) has a variance of σ _n ² Complex gaussian random variables.

For the U (t) signal, we select the appropriate vector

W＝[w ₀ w ₁ ...w _M-1 ](formula 3)

The signal z (t) of a certain beam can be obtained, for simplicity, let us say

W = a (θ, φ) (equation 4)

The beam signals after passing through the combining network are:

z(t)＝U(t)*W ^H ＝s(t)*α(θ，φ)*α ^H (θ，φ)+N(t)*α ^H (θ，φ)

＝M*s(t)+N(t)*α ^H (theta, phi) (equation 5)

Further determining a signal-to-noise ratio of the beam signals passing through the array as

(equation 6)

Wherein

Is the signal-to-noise ratio of the signal on a single array element.

It can be seen that the multi-beam antenna element improves the signal-to-noise ratio of the signal, thereby improving coverage. The above calculation is a conclusion obtained under a very ideal situation, the gain in an actual system is smaller than that calculated, and it can be seen from the derivation process that different beams can be obtained by setting different W, and the value of W is related to (θ, φ), that is, the geographic location of the user, and the intelligent antenna system spatially distinguishes the users, thereby increasing the coverage, so the coverage test of the intelligent antenna base station system is based on the distribution of the user space in addition to the method of considering the common cell test. In the base station system using the fixed beam smart antenna, the coverage area of each sector is divided into the coverage areas of several beams, and a mobile station cannot feel which beam is in the coverage area, but through a signal processing system of the base station, the mutual interference of users between the beams in the same sector can be greatly reduced, and the capacity of the system is improved. Because the coverage area of each sector is less affected by the distribution of the system load in the sector for the current CDMA system, the distribution of the load is not concerned when testing the system coverage, but different distributions of the system load affect the coverage area of the beam and the sector, and cannot provide guarantee for the overall understanding of the system performance.

Disclosure of Invention

The invention aims to provide a coverage test method of a fixed beam intelligent antenna base station system, which is characterized in that on the basis of the existing coverage test method, a test link for the influence of different system load distributions on coverage is added, and the defects of the existing test method are overcome.

In order to achieve the above object, the present invention provides a coverage testing method for an intelligent antenna base station system, which includes the following processing steps:

step 1, no-load coverage test, wherein under the condition that a cell is approximately no-load and a mobile station is tested, the coverage distance of a forward service channel and a pilot frequency and the coverage distance of a reverse service channel are tested, and a test result is output in a graphic mode to verify a directional diagram of a forward wave beam;

step 2, evenly distributing half-load coverage test, wherein the lambda is generally 50% under the condition that the load is lambda, or other proportions can be adopted, the coverage condition of the forward and reverse traffic channels when the mobile station is evenly distributed in each beam is output by a test result in a pattern mode;

and 3, testing the non-uniformly distributed half-load coverage, wherein the lambda is generally 50% under the condition that the load is lambda, or other proportions can be adopted, the coverage condition of the forward and reverse traffic channels when the mobile station is non-uniformly distributed in each beam is tested, and the test result is output in a graphic mode.

On the basis of the existing coverage test method, the invention fully considers the characteristic that the coverage of a base station system applying the new technology of the fixed beam intelligent antenna is influenced by the load distribution of the system, adds the forward and reverse coverage test links corresponding to different load distributions in the test step, makes up the defects of the existing method, can fully, accurately and comprehensively determine the coverage condition of the fixed beam intelligent antenna system under various conditions, provides a test method of the corresponding relation between the coverage and the space, and provides guarantee for comprehensively knowing the performance of the system.

Drawings

Fig. 1 is a flow chart of a forward reverse coverage test.

Detailed Description

The coverage test method of the fixed beam intelligent antenna system can be specifically realized according to the following steps, and a flow chart is shown in figure 1:

(1) The preparation process comprises the following steps:

preparing various testing devices and software, unifying a road tester, a testing mobile station and a base station clock into GPS (Global positioning System) time, connecting the testing devices, starting the related testing software, and simultaneously determining a testing route, wherein the route needs to traverse the expected coverage range of each beam as much as possible, and three beams are taken as an example.

The forward traffic channel coverage and the reverse traffic channel coverage tests comprise three items, namely a no-load coverage test, an evenly distributed half-load coverage test and an unevenly distributed half-load coverage test, the three items all require that a base station is set to be in a full-rate Markov call mode, a test mobile station starts to dial an 8k Markov call, and the following differences exist in the preparation process:

in the coverage test of the forward and reverse traffic channels, the evenly distributed half-load test needs to evenly distribute half of the load of the traditional cell in the coverage areas of three beams in the preparation process stage, the unevenly distributed half-load coverage test needs to simulate the half-load level of the traditional cell by using a test mobile station in the main lobe direction of a first beam, and the other two beams are in no-load configuration, so that the influence on the coverage of the other two beams when the relief load is concentrated on a single beam is achieved.

(2) Moving along a predetermined route at a predetermined speed, and collecting related data information:

for the test of the forward traffic channel coverage and the reverse traffic channel coverage, the difference of the collected data information is as follows:

the forward service channel coverage test needs to record the full-rate forward frame error rate, the strongest pilot signal-to-noise ratio, the forward effective transmitting power, the forward receiving total power and the like of the mobile station, and synchronously acquire beam switching state indication provided by the background;

the reverse service channel coverage test needs to record the full-rate reverse frame error rate of the mobile station, the transmitting power of the mobile station and the like;

(3) When the mobile station is disconnected in the test, the test and the data acquisition are finished;

(4) Returning the test vehicle on the original path until the mobile station can establish a call with the base station again, continuing to operate away from the base station, starting a road tester to record, operating the test vehicle until the mobile station drops, stopping the test vehicle again, and ending the data acquisition;

(5) Repeating the call drop for several times to obtain test data for several times, averaging the distance between the base station and the measured distance, and recording the signal-to-noise ratio of the pilot channel at the edge as the coverage edge of the beam service channel in the direction;

(6) And traversing all identified paths of all beams one by one, and finally determining the coverage boundaries of all beams.

Claims

1. A coverage test method of a fixed beam intelligent antenna base station system is characterized by comprising the following steps:

step 1, no-load coverage test, wherein under the condition that a cell is approximately no-load, the coverage distance of a forward service channel and a pilot frequency and the coverage distance of a reverse service channel are tested, the test result is output in a graphic mode, and a directional diagram of a forward wave beam is verified;

step 2, evenly distributing half-load coverage test, testing the coverage condition of the forward and reverse traffic channels when the mobile station is evenly distributed in 3 wave beams under the condition that the load is lambda, and outputting the test result in a pattern mode;

step 3, non-uniform distribution half-load coverage test, testing the coverage condition of the forward and reverse traffic channels when the load is lambda and the mobile station is distributed in the main lobe direction of the first beam of the 3 beams, and outputting the test result in a pattern mode.

2. The method of claim 1, wherein the base station is configured in a full rate markov call mode and the test mobile station begins to place an 8K markov call.

3. The method according to claim 1, wherein the load λ is 50%.

4. The method of claim 1, 2 or 3, wherein in the forward and reverse coverage test, the forward coverage test records the full-rate forward frame error rate, the strongest pilot signal-to-noise ratio, the forward effective transmission power and the forward reception power of the mobile station, and synchronously acquires the beam switching status indication provided by the background; and the reverse coverage test records the full-rate reverse frame error rate of the mobile station and the transmitting power of the mobile station.