CN102769872B - Broadband wireless access method and system, central control system - Google Patents

Abstract

The invention discloses a broadband wireless access method and system, and a central control system. The method includes the following steps: the central control system CCS periodically sends a signaling signal to a relay node set on a high-speed moving object through the current RRU, and Receive the confirmation message of the signaling signal from the relay node; CCS determines the status information of the high-speed moving object according to the received confirmation message, and turns on the target RRU corresponding to the status information through the optical switch, and turns off the target RRU corresponding to the status information. The source RRU corresponding to the information, where the state information includes the current location and driving direction. The invention simplifies the control, operation and maintenance process of the system, reduces the waste of frequency spectrum resources and energy, and improves user experience.

Description

Broadband wireless access method and system, and central control system

technical field

The invention relates to the field of mobile communication, in particular to a broadband wireless access method and system, and a central control system.

Background technique

With the rapid development of my country's high-speed railways, providing reliable, real-time, and efficient broadband wireless network access services for high-speed train passengers has become a hot spot in mobile broadband communication research at home and abroad. At present, there are three main schemes for wireless network coverage of high-speed railways: satellite communication scheme, leaky cable scheme and cellular technology scheme.

The satellite communication solution refers to the direct connection between the high-speed train and the ground through a satellite network. In areas where satellite signals cannot be covered, such as tunnels and stations, it is switched to the ground cellular network, and the interior of the train is covered by a Wi-Fi network. This solution has been applied to European Thalys high-speed trains to provide passengers with wireless Internet access services. However, this solution uses expensive satellite links for vehicle-to-ground wireless communication, and the inherent large transmission delay and low data rate of satellite communication are disadvantages that cannot be ignored. When a high-speed train enters an area that cannot be covered by satellite signals and needs to switch to the ground cellular network, the large switching delay caused by satellite communication will also greatly affect the communication effect between trains and ground.

The leaky cable scheme refers to opening a series of slots on the coaxial cable, so that part of the energy of the electromagnetic wave in the cable leaks from the slots to the space along the line. A small number of frequency points are reused without interfering with each other, so the utilization rate of the frequency band is high. However, the slotting of leaky cables has strict requirements on the process size, and the radio wave attenuation is relatively large. A large number of repeaters need to be installed along the line to compensate for the transmission loss. The transmission index of leaky cable is quite strict, and the transceiver and relay equipment are relatively complicated. The initial investment cost of using it to form the access network is very high, and it is not suitable for the laying of the whole railway line.

The cellular technology solution is based on the existing cellular network architecture, through a baseband processing unit (BuildingBaseband Unit, referred to as BBU) to control multiple remote radio units (Remote Radio Unit, referred to as RRU) networking to increase the radius of the cell and Reduce the number of cell switching. RRUs belonging to different physical locations of the same BBU can be configured as the same cell wireless resources, including the frequency and number of carriers, so that there is no need to switch when the train passes through multiple RRUs of the same BBU. However, this solution still needs to lay a large number of expensive base station equipment along the railway line, and because the high-speed trains run far apart, the spectrum resources and processing capabilities of these equipment are idle when no train is located within their coverage area, resulting in resource and energy waste.

3GPP Long-Term Evolution (LTE for short), as an evolution version of Universal Mobile Telecommunications System (UMTS for short), is a mainstream wireless communication technology in the future. The LTE access network is only composed of an evolved NodeB (eNB for short), and provides an evolved UMTS Terrestrial Radio Access Network (Evolved UMTST Terrestrial RadioAccess Network, E- UTRAN) is the protocol termination point for the control plane and user plane. The eNB is connected to the core network through the S1 interface, and supports many-to-many connection mode. Therefore, the LTE network structure can effectively reduce call establishment delay and data transmission delay.

However, if the LTE-based BBU+RRU is directly deployed on the high-speed railway, there will be problems of waste of spectrum resources and high construction costs.

Contents of the invention

The main purpose of the present invention is to provide a broadband wireless access solution to at least solve the problems in the above-mentioned related technologies that use cellular technology to cover high-speed railways with wireless networks, resulting in waste of spectrum resources, energy and high construction costs.

In order to achieve the above object, according to one aspect of the present invention, a broadband wireless access method is provided.

The broadband wireless access method according to the present invention includes the following steps: the central control system CCS periodically sends a signaling signal to a relay node set on a high-speed moving object through the current RRU, and receives the signaling signal from the relay node The confirmation message; CCS determines the state information of the high-speed moving object according to the received confirmation message, and turns on the target RRU corresponding to the state information through the optical switch, and turns off the source RRU corresponding to the state information, wherein the state Information includes current location and driving direction.

Preferably, before the CCS periodically sends signaling signals to the relay node through the current RRU, the method further includes: the CCS assigns corresponding baseband processing resources and spectrum resources to each high-speed moving object in the controlled area, where different High-speed moving objects correspond to different frequency resources.

Preferably, the CCS periodically sending signaling signals to the relay node through the current RRU includes: the CCS uses optical signals of different wavelengths to perform wavelength division multiplexing on different frequency resources, and sends the wavelength division multiplexed signals through optical fibers To the current RRU; the current RRU performs WDM photoelectric conversion on the wavelength division multiplexed signal, and sends the converted signal to the relay node.

Preferably, the CCS determining the state information of the high-speed moving object according to the received confirmation message includes: the CCS determining the state information of the high-speed moving object according to the identification information of the RRU sending the confirmation message.

Preferably, when the working cell is the source RRU and the current RRU, the CCS periodically sends signaling signals to the relay node through the current RRU.

Preferably, the CCS turns on the target RRU corresponding to the state information through the optical switch, and turns off the source RRU corresponding to the state information includes: the CCS switches the working cell from the source RRU and the current RRU to the current RRU and the target RRU through the optical switch.

Preferably, the method is applicable to CDMA system and OFDM system.

Preferably, the above-mentioned high-speed moving object is a high-speed train or a high-speed car.

In order to achieve the above purpose, according to another aspect of the present invention, a CCS is also provided.

According to the CCS of the present invention, it includes: a sending module, which is used to periodically send a signaling signal to a relay node set on a high-speed moving object through the current RRU; a receiving module, which is used to receive the signaling signal from the relay node A confirmation message; a determination module, configured to determine the state information of the high-speed moving object according to the received confirmation message, wherein the state information includes the current position and driving direction; and a control module, configured to conduct and communicate with the The target RRU corresponding to the status information, and the source RRU corresponding to the status information are shut down.

In order to achieve the above purpose, according to still another aspect of the present invention, a broadband wireless access system is also provided.

The broadband wireless access system according to the present invention includes the above-mentioned CCS, a plurality of RRUs connected to the CCS, and a relay node set on a high-speed moving object.

Through the present invention, the mode of switching the currently turned on RRU by using the optical switch solves the problem of spectrum resources, energy waste and high construction cost caused by the use of cellular technology in the wireless network coverage of the high-speed railway in the related art, and simplifies the system Control, operation and maintenance processes reduce network deployment costs and improve user experience.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

FIG. 1 is a flow chart of a broadband wireless access method according to an embodiment of the present invention;

Fig. 2 is a structural block diagram of a CCS according to an embodiment of the present invention;

Fig. 3 is a structural block diagram of a broadband wireless access system according to an embodiment of the present invention;

4 is a schematic diagram of a broadband wireless access network architecture of a RoF-based high-speed railway according to Embodiment 1 of the present invention;

5 is a schematic diagram of the internal structure of the CCS and the RRU according to Embodiment 2 of the present invention;

FIG. 6 is a flow chart of RRU handover according to Embodiment 3 of the present invention.

detailed description

Hereinafter, the present invention will be described in detail with reference to the drawings and examples. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

According to an embodiment of the present invention, a broadband wireless access method is provided. Fig. 1 is a flowchart of a broadband wireless access method according to an embodiment of the present invention. As shown in Fig. 1, the method includes the following steps:

Step S102, the central control system (Center Control System, referred to as CCS) periodically sends signaling signals to the relay node set on the high-speed moving object through the current RRU, and receives the confirmation of the signaling signal from the relay node information;

Step S104, the CCS determines the state information of the high-speed moving object according to the received confirmation message, and turns on the target RRU corresponding to the state information through the optical switch, and turns off the source RRU corresponding to the state information, wherein the state information includes Current location and direction of travel.

Through the above steps, the optical switch is used to switch the currently turned on RRU, which solves the problems of spectrum resources, energy waste and high construction cost caused by the use of cellular technology to cover high-speed railways with wireless networks in related technologies, and simplifies the system. Control, operation and maintenance processes reduce network deployment costs and improve user experience.

Preferably, before step S102, the CCS may allocate corresponding baseband processing resources and spectrum resources to each high-speed moving object in the controlled area, wherein different high-speed moving objects correspond to different frequency resources. This method can improve the effectiveness and accuracy of the system.

Preferably, in step S102, the CCS uses optical signals of different wavelengths to perform wavelength division multiplexing on different frequency resources, and sends the wavelength division multiplexed signals to the current RRU through an optical fiber; The WDM photoelectric conversion is performed on the signal, and the converted signal is sent to the relay node. The method enables the CSS to send signaling signals to relay nodes set on high-speed moving objects based on the RoF technology, thereby improving the compatibility of the system.

Preferably, in step S104, the CCS may determine that it is the status information of the high-speed moving object according to the identification information of the RRU in the confirmation message. For example, according to which RRU the confirmation message comes from, the CCS can determine the current location of the high-speed moving object from the geographical area under the jurisdiction of this RRU. The method is simple to implement and highly operable.

Preferably, when the working cell is the source RRU and the current RRU, the CCS periodically sends signaling signals to the relay node through the current RRU. For example, in the implementation process, the mode of dual-cell work is adopted, that is, two RRUs are turned on at the same time as the working cells, while other cells (that is, other RRUs connected to the CCS are in a sleep or off state) are conducive to improving the performance of the system. Stability and resource utilization.

Preferably, in step S104, the CCS may switch the working cell from the source RRU and the current RRU to the current RRU and the target RRU through an optical switch. The method provides a mechanism for cell switching, which can effectively utilize system resources.

Preferably, the above broadband wireless access method is applicable to CDMA system and OFDM system.

Preferably, the high-speed moving object can be a high-speed train or a high-speed car. The method is simple to implement and highly operable.

According to an embodiment of the present invention, a CCS is also provided. FIG. 2 is a structural block diagram of a CCS according to an embodiment of the present invention. As shown in FIG. 2 , the CCS 20 includes: a sending module 22 for periodically sending signaling signals to the relay node through the current RRU; a receiving module 24 , for receiving the confirmation message of the signaling signal from the relay node; the determining module 36, connected to the receiving module 24, is used for determining the state information of the high-speed moving object according to the received confirmation message, wherein the state information includes The current location and driving direction; and the control module 28, connected to the determination module 26, for turning on the target RRU corresponding to the state information through an optical switch, and turning off the source RRU corresponding to the state information.

Corresponding to the above method, an embodiment of the present invention also provides a broadband wireless access system. Fig. 3 is a structural block diagram of a broadband wireless access system according to an embodiment of the present invention. As shown in Fig. 3, the system 30 includes the above-mentioned CCS 20, a plurality of RRUs 32 connected to the CCS 20, and relays arranged on high-speed moving objects A node 34, wherein the relay node 34 can be connected to its nearest RRU 32.

It should be noted that the embodiment of the present invention adopts an optical switch as the switching mode, and only performs optical path switching at the physical layer, which can avoid signaling exchange above the MAC layer. Therefore, the time required for the switching mode in the embodiment of the present invention is Much smaller than traditional switching methods.

The implementation process of the above-mentioned embodiments will be described in detail below in conjunction with preferred embodiments and accompanying drawings.

Embodiment one

This embodiment provides an improved LTE network architecture based on RoF technology, which can provide wireless access for high-speed moving objects (for example, high-speed trains), and also provides a cell handover mechanism under this architecture, so as to Improve system throughput and reduce handover call drop rate.

FIG. 4 is a schematic diagram of a broadband wireless access network architecture of a RoF-based high-speed railway according to Embodiment 1 of the present invention. As shown in FIG. 4 , the relay node (Relay Node, RN for short) in the existing LTE system architecture is placed On a high-speed train, the wireless transmission between the ground and the train is realized by using the eNodeB to Relay Node (eNB-RN) air interface. Among them, the RN has two functions: one is that the RN acts as a relay between the eNB and the user, and establishes a wireless link between the LTE user in the carriage and the eNB beside the track; the other is that the RN supports multiple communication systems by connecting the inside of the carriage (For example, GSM/WCDMA/HSDPA/WLAN, etc.) wireless access point (Access Point, referred to as AP) provides access to various wireless terminal equipment of passengers, restores the information of different standards to bit stream, and packages it through The eNB-RN link performs vehicle-to-ground transparent transmission.

On the basis of this access method, the terrestrial LTE cell uses a CCS to connect and control multiple RRUs through RoF. According to the running time and direction of the high-speed train, different RRUs are turned on or off through the optical switch in the CCS, and the RRU cells that cover the high-speed train with radio waves are switched. In the downlink transmission, the data of the core network is processed by the CCS baseband, modulated into a radio frequency signal, and transmitted to the RRU where the high-speed train is located through a specific wavelength in the optical fiber. The RRU performs WDM photoelectric conversion and amplification, and transmits the radio frequency signal to the RN of the high-speed train; in the uplink transmission, the RRU converts the received user radio frequency signal into an optical signal through WDM, and transmits it to the CCS through the optical fiber, and the CCS transmits it from a specific wavelength The optical signal is extracted from the optical signal for photoelectric conversion and then demodulated and delivered to the core network.

As the train moves, the CCS always only turns on the few RRUs closest to the train (for example, the two closest RRUs to the train) through the optical switch, while the other RRUs are all in a dormant state, so that the cell (that is, The cell covered by the RRU) all available spectrum resources move with the movement of the train, that is, it can be realized that the vehicle-mounted RN (that is, the relay node set on the train or car) or the LTE user within the control range of an eNB does not need to Logical handover (Hand-over), which reduces call drops caused by frequent handovers and improves user experience.

Specifically, different from the eNB function in the existing cellular network, the CCS in this embodiment is not only responsible for baseband signal modulation and demodulation, media access control and radio resource management, but also selects different RRUs to communicate with trains by controlling WDM equipment.

In the implementation process, first, CCS can allocate a logical eNB for each high-speed train in the controlled area, and allocate corresponding baseband processing, transmission resources and spectrum resources; then, CCS will use radio frequency signals from different logical eNBs to Different wavelength bearers are transmitted to different RRUs for photoelectric conversion.

Embodiment two

Since the trajectory of the high-speed trains running on the high-speed railway is usually fixed, its running time and direction are also predictable, and the distance between the trains is large, so this embodiment provides an improved LTE network architecture based on the RoF technology. A method for accessing a communication network of a wireless AP in a high-speed train.

As shown in Figure 4, in the process of the embodiment, the relay node (Relay Node, RN for short) in the LTE system architecture can be placed on the high-speed train, and the wireless transmission between the ground and the train can be realized by using the eNB-RN air interface. For example, the RN can establish a wireless link between the LTE users in the car (that is, wireless APs in multiple modes) and the eNB beside the track through various communication modes supported in the car. On the basis of this access method, the LTE cell next to the track uses a CCS to connect and control a large number of RRUs through RoF. The distance between the RRUs depends on the LTE frequency band and the directional antenna gain used, and the distance is usually greater than the total number of trains. length.

Figure 5 is a schematic diagram of the internal structure of the CCS and RRU according to Embodiment 2 of the present invention. As shown in Figure 5, the CCS can turn on or off different RRUs through optical switches according to the running time and direction of the high-speed train to switch to the high-speed train The RRU cell for radio coverage (that is, the current working cell). In the downlink transmission, the core network data is processed by the CCS baseband, modulated into radio frequency signals (for example, RF ₁ , RF ₂ and RF ₃ ), and passed through specific wavelengths in the optical fiber (for example, λ ₁ , λ ₂ and λ ₃ ) Transmission to the RRU where the high-speed train is located, the RRU performs WDM photoelectric conversion and amplification, and transmits the radio frequency signal to the RN of the high-speed train; in the uplink transmission, the RRU will receive the user terminal (that is, wireless AP) from the vehicle-mounted RN ) radio frequency signals are converted into optical signals by WDM, and then transmitted to CCS through optical fiber. CCS extracts optical signals from specific wavelengths for photoelectric conversion, and then demodulates them and delivers them to the core network.

The CCS in this embodiment can select different RRUs to communicate with the train by controlling its own WDM equipment, which is equivalent to realizing the function of a base station pool (eNB pool). For example, CCS allocates a logical eNB for each high-speed train in the controlled area, and allocates corresponding baseband processing, transmission resources and spectrum resources. Since the high-speed trains are far apart (assuming a speed of 350 km/h and a departure interval of 15 minutes, the interval between two adjacent trains is more than 80 km), the radio wave interference between them can be ignored (this is also because most of the RRUs are in the "sleep" state). Therefore, all spectrum resources can be allocated to each train. Specifically, the CCS can carry radio frequency signals from different logical eNBs with different wavelengths, and transmit them to different RRUs for photoelectric conversion.

It can be seen that in this embodiment, the CCS is responsible for centralized control, baseband processing, photoelectric conversion, etc.; the RRUs distributed along the railway have simple functions such as radio frequency transmission and reception, amplification, and photoelectric conversion, which makes the network deployment cost of operators It is greatly reduced, and the system operation, control and maintenance are also more convenient.

Embodiment Three

In actual situations, the speed of high-speed trains is changing at any time, and it is impossible to accurately judge the time when the train enters the next RRU. Therefore, the simultaneous operation mode of two cells can be adopted, that is, RRU1 and RRU2 are turned on at the same time, and jointly form an RRU that moves together with the train. light chasing area. CCS can confirm the location and direction of the train by periodically sending beacon signals and receiving ACK signals from on-board RNs forwarded by different RRUs. That is, as the train moves, the CCS can only turn on the RRU closest to the train through the optical switch, and put the other RRUs in a sleep state, so that all the available spectrum resources of the cell can move with the train movement, without spectrum The waste of resources also reduces the consumption of electric energy and realizes green communication.

As shown in Figure 5, the train runs from RRU1 to RRU2, RRU1 is the source RRU, RRU2 is the current RRU, and RRU3 is the target RRU. When the train enters RRU2, the CCS starts to switch, turns on RRU3, and turns off RRU1 at the same time, that is, set RRU2 and RRU3 as the same frequency cell, and classify it as a light-following cell.

FIG. 6 is a flow chart of RRU switching according to Embodiment 3 of the present invention. As shown in FIG. 6 , in the implementation process, the flow of this switching mechanism may include the following steps:

Step S602, the CCS periodically sends a beacon signal to the train through the current RRU;

Step S604, the on-board RN sends an ACK signal to the CCS after receiving the beacon signal, and the CCS judges the location of the train according to which RRU the latest received ACK signal comes from (that is, judges whether it has entered the current RRU coverage area);

Step S606, when it is judged that the train enters the coverage area of the current RRU, the CCS turns on the target RRU, communicates with the on-board RN through RRU2 and RRU3 at the same time, and then turns off the source RRU to complete the handover.

It can be seen that the CCS can accurately control the opening and closing time of the RRU according to the running direction and location information of the high-speed train, and realize smooth switching, thus avoiding the communication interruption caused by the sharp drop of the receiving level at the overlapping area of the switching method in the related technology . Because the optical switching method in this embodiment can still maintain a high receiving level of the receiver at overlapping cells, it can reduce the interruption probability and improve user satisfaction.

It should be noted that the embodiments of the present invention are applicable to CDMA and OFDM systems.

To sum up, the embodiment of the present invention provides a method for broadband wireless access and cell handover under high-speed mobile conditions. By this method, broadband wireless network coverage can be effectively performed on high-speed mobile objects (for example, high-speed trains). It simplifies the control, operation and maintenance process of the system, reduces the waste of spectrum resources and energy, and improves the user experience.

Obviously, those skilled in the art should understand that each module or each step of the above-mentioned present invention can be realized by a general-purpose computing device, and they can be concentrated on a single computing device, or distributed in a network formed by multiple computing devices Optionally, they can be implemented with program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, or they can be made into individual integrated circuit modules, or their Multiple modules or steps are implemented as a single integrated circuit module. As such, the present invention is not limited to any specific combination of hardware and software.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A broadband wireless access method, characterized in that, comprising the following steps: The central control system CCS allocates corresponding baseband processing resources and spectrum resources for each high-speed moving object in the controlled area, where different high-speed moving objects correspond to all spectrum resources; The CCS periodically sends a signaling signal to a relay node set on a high-speed moving object through the current remote radio frequency unit RRU, and receives an acknowledgment message of the signaling signal from the relay node; The CCS determines the state information of the high-speed moving object according to the received confirmation message, and turns on the target RRU corresponding to the state information through an optical switch, and turns off the source RRU corresponding to the state information, wherein , the state information includes the current location and driving direction. 2. The method according to claim 1, wherein the CCS periodically sending the signaling signal to the relay node through the current RRU comprises: The CCS uses optical signals of different wavelengths to perform wavelength division multiplexing on different frequency resources, and sends the wavelength division multiplexed signals to the current RRU through optical fibers; The current RRU performs WDM photoelectric conversion on the wavelength division multiplexed signal, and sends the converted signal to the relay node. 3. The method according to claim 1, wherein the CCS determining the state information of the high-speed moving object according to the received confirmation message comprises: The CCS determines that it is the status information of the high-speed moving object according to the identification information of the RRU that sent the confirmation message. 4. The method according to claim 1, wherein when the working cell is the source RRU and the current RRU, the CCS periodically sends to the relay node through the current RRU The signaling signal. 5. The method according to claim 4, wherein the CCS turns on the target RRU corresponding to the status information through the optical switch, and turning off the source RRU corresponding to the status information comprises: The CCS switches the working cell from the source RRU and the current RRU to the current RRU and the target RRU through the optical switch. 6. The method according to any one of claims 1 to 5, characterized in that the method is applicable to CDMA systems and OFDM systems. 7. The method according to claim 1, wherein the high-speed moving object is a high-speed train or a high-speed automobile. 8. A central control system CCS, characterized in that it comprises: The sending module is used to periodically send signaling signals to the relay node set on the high-speed moving object through the current remote radio frequency unit RRU; a receiving module, configured to receive an acknowledgment message of the signaling signal from the relay node; A determining module, configured to determine state information of the high-speed moving object according to the received confirmation message, wherein the state information includes the current position and driving direction; and A control module, configured to turn on the target RRU corresponding to the state information through an optical switch, and turn off the source RRU corresponding to the state information; Wherein, the CCS is also used to allocate corresponding baseband processing resources and spectrum resources to each high-speed moving object in the controlled area, wherein different high-speed moving objects correspond to all spectrum resources. 9. A broadband wireless access system, characterized by comprising the CCS according to claim 8, a plurality of RRUs connected to the CCS, and a relay node set on a high-speed moving object.