Smart antennas are key technologies in TD-LTE and TD-SCDMA, and their application level directly affects the quality of network quality. This paper discusses the application and technological innovation of smart beam antennas in large-scale networking, which makes the network quality greatly improved. The application of multi-polarized antennas in TD-LTE indoor distribution, multi-polarized room sub-antennas Space diversity increases system capacity and expands coverage, and its size is small and construction is convenient. Finally, the analysis and research results in the future development direction of mobile antennas, and it is necessary to use the narrow beam characteristics of small base stations and smart antennas.
1. Research results and applications of smart antennas1.1, TD duplex + TD-SCDMA system frame structure + smart antenna features
TD duplex is allocated to the uplink and downlink work at different times in the same frequency band to realize the information transmission and reception of the communication system. The TD-SCDMA system adopts the frame structure working mode of FIG. 1, that is, the TS0 time slot provides the downlink common channel to face each terminal user in the coverage cell, whether in the uplink and downlink communication or in the standby state, the TS1-TS6 time slot is mainly used. The service channel is provided to face the end user in the ongoing uplink and downlink communication in the cell. A common channel and some traffic channels may be referred to as a broadcast channel when they need to face each end user at the same time. The smart antenna is a multi-antenna system. The most widely used smart antenna is the array element array array antenna + weight control system. The beam of the smart antenna is formed by superposition of electromagnetic field vectors under the action of the antenna structure and the array element electrical signal (amplitude + phase), and is called an shaped beam. One of the characteristics of the array element array array antenna is that the antenna beam gain is in the maximum direction and the line array is directly in front of the line, and the beam is the narrowest. In a wireless network, the antenna structure, ie the relative position of each of the array elements, is fixed, so that the electrical signal changes on each array element will change the gain and shape of the antenna shaped beam, as shown in Figure 1 below.
Figure 1-1 Relationship between the working principle of smart antenna and TD-SCDMA frame structure
TD duplex + TD-SCDMA system frame structure + smart antenna features, we realized that in order to meet the normal operation of TD-SCDMA system, the shaped beam of smart antenna is different in different time slots, and the broadcast channel needs to cover the entire cell or cell. The coverage is determined by the beam corresponding to the broadcast time slot, or the broadcast beam.
1.2. Technical innovation and application of smart antennas
The weight adjustment of the smart antenna beamforming can be used in network planning and optimization. The following are the research results:
1) Broadcast beamforming technology applied to network optimization and network planning
2) Application of broadcast beam weight adjustment in the relocation adjustment of base stations along the railway
3) Technology of intelligent antenna broadcast beam adjustment instead of ESC antenna
4) Research on new antennas for covering high-rise buildings with smart antenna beams
5) Research on high-dimensional optimization algorithm for determining the weight of broadcast beamforming in reverse
Make full use of the characteristics of smart antennas, creatively propose the principle of TD-SCDMA smart antenna broadcast beam adjustment, and adjust the technical framework. The specific implementation method of the TD-SCDMA smart antenna broadcast beam adjustment technology framework is proposed: the correspondence between the normalization parameter weight table and the antenna horizontal field map, and the correspondence between the antenna horizontal field map and the coverage scene, and then indicate the future application method. The TD-SCDMA smart antenna broadcast beam adjustment technology is applied to wireless network optimization and planning, and the results are summarized and analyzed. Multi-polarized antenna research
1.3. Relationship between TD-LTE system and smart antenna
Figure 3 TD-LTE and TD-SCDMA frame formats
As can be seen from Figure 3, the working principle of TD-LTE has many similarities with the "TD duplex + TD-SCDMA system frame structure + smart antenna characteristics" mentioned above. The difference is that TD-SCDMA does not use MIMO technology, the antenna works in a single-flow state, and the TD-LTE antenna operates in a multi-stream state. This multi-stream requires each stream to be similar to the TD-SCDMA single-stream signal strength, which is completely uncorrelated with the stream. Therefore, when the transceivers are multi-streamed, the bandwidth of the stream can be increased by several times. When the number of the transceivers is different, the bandwidth of the stream with the number of streams is increased by several times, and the capacity increase and anti-interference performance by spatial diversity can be obtained. And the expansion of the coverage area.
1.4, three polarization chamber sub-antenna
In order to better solve the problems of large construction difficulty and difficult transformation in indoor distribution system and make full use of indoor multipath characteristics, we propose a three-polarized antenna applied to indoor distribution system and give its basic structure diagram. , see Figure 4;
Figure 4 Basic structure of a triple-polarized antenna
The structural feature is: a three-polarized ceiling antenna structure comprising three identical antenna elements, and the vertical distance between the radiation center of each antenna element fixed on the support member and the mirror reflection ground plate is adjustable, any two antennas The vibrators are orthogonal to each other, and the polarization direction of each antenna element is the same as the angle formed by the ground plane; each antenna element is connected to the feed network board through a coaxial cable, and the feed network board can independently adjust each antenna. The amplitude and phase of the signal transmitted and received on the vibrator. Another form of the antenna structure is that the X-axis, the Y-axis, and the Z-axis respectively use a λ/4 monopole or a λ/2 monopole as the vibrator.
Aiming at the problem of LTE indoor distribution system transformation, the new idea of ​​implementing MIMO transmission in single-channel distributed system by using frequency conversion technology is jointly launched, and the LTE indoor “one-line†solution is jointly launched.
Figure 2.2-1 Schematic diagram of the installation and deployment system of the three-polarized indoor antenna
Advantages: After three channels of data flow, if the terminal is three channels, the transmission rate can be increased. Otherwise, space diversity can be obtained to increase system capacity, expand coverage, improve user experience, and have small size and convenient construction.
2. What the future mobile antenna needs to study2.1. Future mobile antenna development direction
Current problems in the sky:
1) Coexistence of multiple operators, multiple standards, and multiple business forms;
2) The current allocation of spurious frequency bands, but operators are too eager to re-site;
3) causing many types of antennas in the sky;
4) The flow demand in the coverage area is extremely unbalanced.
It can be seen from the foregoing that the main content or development direction of future mobile antenna research is:
1) Multi-band antennas, not only for studying wide-band oscillators, but also for wide-band oscillator combinations or wide-band array elements, wide-band arrays;
2) Multi-polarized antennas;
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