CN102196477A - Method for optimizing wireless network fit for high-speed vehicle-mounted environment - Google Patents

Abstract

The invention discloses a wireless network optimization method suitable for a high-speed vehicle environment, which includes the following steps: (1) When a system is about to communicate and needs to access the frequency spectrum, detect the frequency spectrum usage status in the area where it is located, and according to the preset method and the size of its own business volume, select an appropriate frequency band for access, and at the same time, sufficient protection bandwidth must be reserved between each frequency band to avoid harmful interference; (2) After accessing the frequency spectrum, each system will (3) Due to the increase of system traffic, the bandwidth occupied by the system expands, resulting in the reduction of the protection bandwidth, and each system can automatically adjust the spectrum to move towards the direction of the free spectrum, To meet the bandwidth and protection bandwidth of their respective needs.

Description

Wireless network optimization method suitable for high-speed vehicle environment

technical field

The invention relates to cell reselection and handover in the case of UE moving at high speed in the field of wireless communication.

Background technique

The current communication cell switching technology is only applicable to the situation that the cell users are static or moving at a low speed. However, in a high-speed mobile scenario, due to the small distance between stations and the high speed of vehicles, the time to pass through the cell will be greatly shortened, resulting in frequent handover of the cell, and the user does not have enough time to complete the handover process. disconnected. To solve this problem, it is necessary to prolong the time for cell switching. On the base station antenna tower along the driving route, or set up a base station antenna, or set up a direct antenna adjacent to the base station on one side, or erect a direct antenna adjacent to the base station on both sides. It is used to increase the coverage radius of the handover area, thereby prolonging the time for executing the handover process.

Contents of the invention

The purpose of the present invention is to provide a wireless network optimization method suitable for high-speed vehicle environments, which can effectively solve the problem of unlicensed frequency bands. According to the method set by the present invention, access to suitable frequency bands can increase The sum of the transmission power of itself and the power of the potential interfering signal must be less than the threshold specified in the predetermined method. When the system traffic increases, the occupied spectrum bandwidth can be appropriately increased, but the guard bandwidth GBW between adjacent spectrums cannot be smaller than the minimum guard bandwidth specified in the preset method. If the business volume continues to increase, the required bandwidth continues to increase, and the protection bandwidth is now smaller than the forced protection bandwidth MoveGBW specified in the preset method. At this time, each system dynamically adjusts the frequency band it occupies according to the preset method. position, while satisfying the required frequency band, make the protection bandwidth GBW as large as possible larger than the forcing protection bandwidth MoveGBW. If the protection bandwidth GBW of the system is still smaller than the mandatory protection bandwidth MoveGBW after each system is adjusted, but the system still needs to expand the bandwidth, the system can be allowed to continue to expand the bandwidth, but the protection bandwidth GBW must be greater than or equal to the minimum protection bandwidth MinGBW. When the system bandwidth is expanded to make the guard bandwidth GBW equal to the minimum guard bandwidth MinGBW, the system stops expanding the bandwidth, and then adjusts the spectrum status of each system again, so that the guard bandwidth of the system increases, and then the system can move and expand the spectrum.

In order to achieve the above object, the present invention provides a wireless network optimization method suitable for high-speed vehicle environment, comprising the following steps:

(1) When a system is about to communicate and needs to access the spectrum, detect the spectrum usage status in the area where it is located, and select an appropriate frequency band for access according to the preset method and the size of its own traffic. Reserving sufficient guard bandwidth to avoid harmful interference;

(2) After accessing the frequency spectrum, each system adjusts its transmission power and occupied bandwidth according to the channel conditions and the size of its own traffic;

(3) Due to the increase of system traffic and the expansion of bandwidth occupied by the system, the protection bandwidth is reduced. Each system can automatically adjust the spectrum to move towards the direction of the free spectrum to meet the bandwidth and protection bandwidth required by each system.

It has been verified that the method for dynamically sharing the frequency spectrum provided by the present invention can enable multiple systems to share the wireless frequency spectrum well (see the specific implementation process for the detailed process).

In one embodiment of the present invention, the step (1) is specifically:

(21) According to a preset method, each system that has access to the spectrum periodically broadcasts its own spectrum usage information;

(22) According to the preset method, the system that will access the spectrum sends a spectrum request, and collects the spectrum usage information of each system that has accessed the spectrum;

(23) According to the preset method, the system that does not need to access the spectrum remains silent;

(24) According to the preset method, the system that applies for access to the spectrum obtains a spectrum usage map based on the collected information, and selects an appropriate frequency band for access according to the system in the map and its own required bandwidth.

(25) According to the preset method, the guard bandwidth (GBW) between the frequency band selected for access by the system and the frequency band occupied by the adjacent system should be greater than the forced guard bandwidth (MoveGBW).

In one embodiment of the present invention, the step (24) is specifically:

(31) According to the preset method, whether to transmit signals in a certain frequency band, it is necessary to compare the collected transmission power information of other systems (other systems can be regarded as potential interference signals) with a certain threshold specified in the preset method. Compare;

(32) The threshold value is a function in the preset method;

(33) According to a preset method, if the power level of the potential interfering signal is lower than the threshold level, the system transmits a signal on the wireless channel;

(34) According to a preset method, if the power level of the potential interfering signal is higher than the threshold level, the system needs to switch channels to transmit signals;

In one embodiment of the present invention, the step (2) is specifically:

(41) After the system successfully accesses the frequency spectrum, in order to increase the signal-to-noise ratio (SNR), the system will increase the transmission power. At this time, it is necessary to compare the sum of the power of the interference signal and the transmission power with the threshold described in step (41), Increase the transmit power until it approaches the threshold level;

(42) After the system successfully accesses the spectrum, when the number of services increases, the bandwidth of the spectrum occupied by the system needs to increase accordingly, which may cause a decrease in the protection bandwidth until the minimum protection bandwidth MinGBW specified by the preset method;

In one embodiment of the present invention, the step (3) is specifically:

(51) Due to the increase in system business demand, the occupied bandwidth continues to increase, and the protection bandwidth between the adjacent frequency spectrum will be reduced to the minimum protection bandwidth stipulated in the agreement;

(52) If the protection bandwidth is too small, the harmful interference to the system will be very large, and it is necessary to adjust the spectrum usage of each system;

(53) Since each system is a decentralized topological network, each system needs to dynamically adjust the spectrum usage status according to a preset method, so that sufficient protection bandwidth is left between each system.

Description of drawings

Fig. 1 is a flow chart of a wireless network deployment and optimization method suitable for a high-speed vehicle environment;

Figure 2 is a preliminary plan for the wireless network coverage map of the high-speed vehicle environment in the handover area;

Figure 3 is a wireless network coverage diagram of a high-speed vehicle environment that introduces a handover macro area;

Figure 4 configures the wireless network coverage diagram of the high-speed vehicle environment with base station and repeater antenna transmission power.

Reference numerals: 1-Iron Tower A; 2-Iron Tower B; 3-Iron Tower C; 4-Iron Tower D; 5-Iron Tower E; 6-Iron Tower I; 7-Iron Tower G; ;za-direct antenna A; zb-direct antenna B; zy-direct antenna Y; zz-direct antenna Z; area-switch macro area; L-two-way vehicle road; sector1-sector 1; sector2- sector 2

Detailed ways

In order to make it easier for those skilled in the art to understand and implement the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

(1) The base station antenna + direct station antenna is used for networking, which can effectively perform linear coverage, increase the switching distance, prolong the switching time, and reduce the number of switching times, thereby improving the network coverage quality on the vehicle line.

(2) On this basis, introduce the handover macro area area, make the position of handover fixed in the handover macro area (as shown in Figure 3), and meet two-way handover, improve the success rate of handover, reduce the drop rate of cell edge.

(3) Specific description of the handover macro area: as shown in Figure 3, the handover area mainly refers to the handover road section, and the handover area can be larger than the cell coverage radius. When the handover area is larger than the cell coverage radius, it is called a handover macro area.

(4) In the coverage scheme of the high-speed vehicle-mounted wireless communication network, using the base station antenna + repeater antenna for networking is more advantageous than the traditional base station coverage method, because a handover macro area is generated, which makes the high-speed vehicles have long enough to complete the handover process. As shown in accompanying drawing 4, there are iron tower A 1, iron tower B 2, iron tower C 3, iron tower D 4, iron tower E 5, iron tower E 6 and iron tower G 7 iron towers. We use iron tower B 2 and iron tower E 5 as the intermediate vehicle driving route L as an example, base station antenna A a is set up on iron tower B 2, and base station antenna Bb is set up on iron tower E 5. Considering the bi-directionality of vehicle driving, the direct antenna A za and the direct antenna B zb are installed on the iron tower C 3 and the iron tower D 4 . The transmit power of the repeater antenna A za on Tower C 3 is the same as that of the base station antenna A a , but it must be considered that the subcarrier signals of the same frequency on the base station antenna A a and the repeater antenna A za cannot be allocated to the same user , to prevent co-channel interference, and the transmission power of the direct antenna A za on Tower 4 can be artificially reduced by xdB compared with the base station antenna A a . Putting the antenna A za makes the coverage of the base station antenna A a expand to one side, thereby expanding the coverage of the base station antenna A a; the transmission power of the direct antenna B zb on the iron tower 4 and the transmission power of the base station antenna B b The same, also considering that the subcarrier signals of the same frequency on the base station antenna B and the repeater antenna B cannot be allocated to the same user to prevent co-channel interference, and the transmit power of the repeater antenna B on the tower C is the same as that of the base station antenna B The ratio can be artificially decreased by xdB. The purpose of this is to expand the coverage of the base station antenna B b to one side through the two direct antennas B zb erected beside the base station antenna B b, thus expanding the coverage of the base station antenna B b coverage. The handover macro area is formed where the base station antenna A a and the base station antenna B b cover overlap. For switching the radius of the macro area area, it depends on the actual situation. You can adjust the transmit power of the direct antenna B zb on the tower C 4 (direct broadcast B@-xdB) and the direct antenna A za on the tower D 4. Transmitting power (direct amplifier A@-xdB) to form a suitable handover macro area. Suppose a high-speed vehicle travels from Tower B2 to Tower E5, the mobile station on the vehicle receives the power transmitted by the base station antenna A a gradually weakens, and receives the power transmitted by the base station antenna Bb gradually increases, when the vehicle enters the handover macro After the area area, the mobile station on the vehicle will cut off the connection with the base station antenna A a after it is completely connected with the base station antenna B b. During this process, due to the switching of the macro area area, the vehicle has a long enough The switching time completes the switching process and realizes seamless switching. When the vehicle running at high speed travels from iron tower E 5 to iron tower B 2, the switching process is as described above. The coverage of the handover macro area can also be covered by two directional sector sector 1 sector1 and sector 2 sector2 of a dedicated base station antenna, and the handover process of the mobile station on the vehicle is also as described above.

The above description is only used to illustrate the specific implementation cases of the present invention, and is not intended to limit the scope of the present invention. For example, all those skilled in the art have accomplished everything without departing from the spirit and principles indicated by the present invention. Equivalent changes or modifications should still be covered by the scope of the claims of the present invention.

Claims (3)

1. A wireless network optimization method suitable for high-speed vehicle environment, characterized in that it may further comprise the steps: Step 1. According to the coverage environment and coverage requirements of the high-speed vehicle wireless network, estimate the radius of the cell, and initially plan the handover area. Among them, the radius of the cell is mainly determined according to the coverage requirements and actual construction conditions; The area is larger than the cell coverage radius. When the handover area is larger than the cell coverage radius, it is called a handover macro area; Step 2. On the base station antenna tower along the driving route, set up the base station antenna, the direct release antenna adjacent to the base station on one side or the direct release antenna adjacent to the base station on both sides. Step 3: Set the power of the antenna port of each base station and the antenna port of each repeater, so as to ensure that the vehicle has enough time to complete the switching process without dropping the call or dropping the line when the vehicle passes the switching area within the design speed per hour. 2. the wireless network optimization method that is suitable for high-speed vehicle-mounted environment as claimed in claim 1, is characterized in that: described step 2 can also use two sectors of an independent base station to specially cover the handover macro area, 3. The wireless network optimization method suitable for high-speed vehicle environment as claimed in claim 1, characterized in that: the execution of the switching process in the step 3 means that the process of the air interface and the process of the network side have been executed.

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