CN100369516C

CN100369516C - Capacity test method for fixed beam intelligent antenna base station system

Info

Publication number: CN100369516C
Application number: CNB2005100329700A
Authority: CN
Inventors: 李晟
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2005-01-21
Filing date: 2005-01-21
Publication date: 2008-02-13
Anticipated expiration: 2025-01-21
Also published as: CN1809201A

Abstract

The present invention proposes a volume testing method for an intelligent aerial base station system with fixed wave beams, which comprises a single beam front reverse volume test in which the front reverse volume condition in a single wave beam when traveling platforms are respectively distributed in the main lobe direction of each wave beam is tested, a multi-beam ideal condition front reverse volume test in which the front reverse volume condition when the traveling platforms are simultaneously distributed in the main lobe direction of each wave beam is tested, and a multi-beam non-ideal condition front reverse volume test in which the front reverse volume condition when the traveling platforms are simultaneously distributed in the switching areas of every two wave beams of all the wave beams; the test results are recorded in groups, and each group of test data recorded under various conditions is imported in the existing front reverse volume calculation formula to work out the front reverse limit volume of a system. If the method of the present invention is adopted, the volume conditions of the intelligent aerial system with fixed wave beams under various conditions are determined, which provides a guarantee for the overall comprehension of system performance.

Description

Capacity test method for fixed beam intelligent antenna base station system

Technical Field

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

Background

In a capacity test process for a CDMA system, a current method is to test in units of sectors, for a test of Reverse capacity of a sector, a test method based on RSSI (received Signal Strength Indicator) is generally adopted, a limit capacity of the system is calculated by measuring elevation of bottom noise at a receiving end of the sector, and for a test of forward capacity of the sector, a method based on collection of effective transmission power of each channel is generally adopted to calculate the limit capacity of the system. For the current CDMA system, the capacity size 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 capacity.

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 communication 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 first. 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 the capacity of the smart antenna 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 the signals of each array element and a reference array element (array element 0) 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, let us say for simplicity

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

(formula 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 capacity and coverage. The above calculation is the conclusion that under the ideal condition, the gain in the actual system is smaller than that calculated, and it can be seen from the derivation process that we can obtain different beams by setting different W, and the value of W is related to (θ, Φ), that is, the geographical location of the user, and the smart antenna system spatially distinguishes the user, thereby increasing the coverage and capacity, so the capacity test of the smart antenna base station system is based on the distribution of the user space in addition to the method of considering the common cell test. The coverage area of each sector of the base station system using the fixed beam intelligent antenna is divided into the coverage areas of a plurality of beams, and for a mobile station, the coverage area of which beam is positioned cannot be felt, but through a signal processing system of the base station, the mutual interference of users among the beams in the same sector can be greatly reduced, and the capacity of the system is improved. Because the capacity 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 and capacity, but the different distribution of the system load affects the capacity level of the beam and the sector, which cannot provide guarantee for the overall understanding of the system performance.

Disclosure of Invention

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

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

step 1, single-beam forward and reverse capacity testing, namely testing the forward and reverse capacity conditions of a mobile station in a single beam when the mobile station is respectively distributed in the main lobe direction of each beam, and grouping and recording the test results by beam splitting;

step 2, testing the forward and reverse capacity when the multi-beam is uniformly distributed, testing the forward and reverse capacity when the mobile station is uniformly distributed in the main lobe direction of each beam, and recording the test result in groups;

step 3, testing the forward and reverse capacity when the multi-beam is non-uniformly distributed, testing the forward and reverse capacity when the mobile station is simultaneously uniformly distributed in the switching area of every two beams of each beam, and grouping and recording the test result;

and 4, importing each group of test data recorded under the conditions into the existing forward and reverse capacity calculation formula, and calculating the forward and reverse limit capacity of the system.

On the basis of the existing capacity test method, the invention fully considers the characteristic that the capacity 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 test links of the forward and reverse capacity corresponding to different load distributions in the test step, makes up the defects of the existing method, can fully, accurately and comprehensively determine the capacity condition of the fixed beam intelligent antenna system under various conditions, provides the test method of the corresponding relation between the capacity and the space, and provides guarantee for comprehensively knowing the system performance.

Drawings

Fig. 1 is a front reverse capacity test flow chart.

Detailed Description

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

(1) The preparation process comprises the following steps:

based on the coverage test method, the actual coverage ranges and switching areas of the three beams are obtained, and the system background noise of the cell to be tested is known.

In the capacity testing method, the capacity testing method comprises a forward capacity testing and a reverse capacity testing, and the two types of tests also comprise a single-beam capacity testing, a three-beam load uniform distribution capacity testing and a three-beam load non-uniform distribution capacity testing, wherein the three testing items are different in a preparation stage:

the single beam capacity test requires that the mobile stations participating in the test be distributed in the coverage area of the main lobe direction of each beam in turn. 3. The beam load uniform distribution capacity test requires that the mobile stations participating in the test are equally divided into three groups, and are simultaneously and uniformly distributed in the coverage area of the three beam main lobe directions. The three-beam load non-uniform distribution capacity test requires that the mobile stations participating in the test are equally divided into two groups and are simultaneously and uniformly distributed in two beam switching areas among three beams.

(2) All mobile stations are activated simultaneously, a Markov full rate call is placed with an average voice activation factor of 1, and the call is continued for 30 minutes.

All mobile stations are required to maintain the call state, and if a call drop occurs, the test is stopped and all mobile stations reestablish the call.

(3) Collecting related data:

the data collected for the forward and reverse capacity tests are different: the forward capacity test requires recording the traffic channel gain of each test mobile station, and recording the full Rate forward FER (Frame Error Rate) of some of the test mobile stations. The reverse capacity test requires recording the reverse FER of each mobile station, recording the full rate reverse FER, forward ERP (Effective forward Radiated Power) or digital gain of one of the test mobile stations, and RSSI of each beam.

(4) After 30 minutes of continuous calling, the test is finished. To eliminate the limitation due to the distribution of the mobile stations, the original distribution of the mobile stations is changed in the predetermined coverage area, and the test is performed again, as mentioned above, to collect the relevant data.

(5) And the mobile station traverses all the designated areas and tests are carried out according to the steps.

According to the algorithm of forward and reverse capacity calculation, on the basis of the test method, 3-4 groups of values are required to be tested according to the difference of the number of the mobile stations, and the results are averaged to obtain the final system forward and reverse limit capacity.

Claims

1. A method for testing system capacity of an intelligent antenna base station is characterized by comprising the following steps:

step 3, testing the forward and reverse capacity when the multi-beam is non-uniformly distributed, testing the forward and reverse capacity when the mobile station is simultaneously uniformly distributed in each two beam switching areas of each beam, and grouping and recording the test result;

and 4, importing the test data recorded under the three conditions into the existing forward and reverse capacity calculation formula to calculate the forward and reverse limit capacity of the system.

2. The method of claim 1, wherein the forward capacity test records the forward traffic channel gain of each test mobile station and records the full rate forward frame error rate of one of the test mobile stations in the data collected by the forward and reverse capacity test; the reverse capacity test records the reverse frame error rate of each mobile station, and records the full-rate reverse frame error rate, the forward effective radiation power, the digital gain and the received signal strength index of each beam of one of the mobile stations.

3. The method of claim 1, wherein after the testing of all steps is completed, the original mobile station distribution is changed and the testing is resumed within the predetermined coverage area.

4. A method according to claim 1, characterized in that 3-4 sets of values are tested depending on the number of mobile stations, and the results are averaged to obtain the final forward reverse limit capacity of the system.