WO2008019542A1

WO2008019542A1 - A method for laying out sfn based on ofdm technology

Info

Publication number: WO2008019542A1
Application number: PCT/CN2006/003782
Authority: WO
Inventors: Xiaoguang Zhu
Original assignee: Zte Corporation
Priority date: 2006-08-08
Filing date: 2006-12-30
Publication date: 2008-02-21
Also published as: CN100551111C; CN101123781A

Abstract

A method for laying out SFN (Single Frequency Networks) based on OFDM technology solves the channel interference problem between sub-networks at the area crossover in SFN, the channel interference affects the network quality at the area crossover. The method comprises steps: laying out resource of the SFN uniformly; addressing the area of serving SFN uniformly so that the adjacent areas have different network address; synchronizing the air signal of SFN; classing the transmitter and cellular in the SFN; determining the optimal distance between transmitters in the SFN; processing the control channel of the SFN that correlates the area; processing the service channel of the SFN that correlates the area. The SFN needs logical layout the area service in different area crossover, and reduces the channel interference between different area systems and increases the service quality of the SFN.

Description

TECHNICAL FIELD The present invention relates to wireless communication: t or, in particular, to a single frequency network based on Orthogonal Frequency Division Multiplexing (OFDM) technology. Planning method. Background technique

OFDM technology is a multi-carrier digital modulation technology and a multiplexing technology that enables high-speed wireless digital communication. Due to its high transmission rate, strong anti-multipath interference capability and high spectral efficiency, OFDM technology has received more and more attention in the field of communication. Currently, it is in DAB (Digital Audio Broadcasting), DVB (Digital Video Broadcasting: Digital Video Broadcasting) and WLAN (Wireless Local Area Networks) based on the IEEE802.il standard have been put into practical use. In the subsequent evolution of the third generation mobile communication, OFDM modulation technology is also mainly used. In recent years, OFDM-based digital multimedia single frequency network (SFN: Single Frequency Networks) technology has been rapidly developed, such as DVB network. The main features of this network are: wireless transmitters in a synchronized state from multiple different locations (transmitting The base station or the transmitting station transmits the same signal at the same time and at the same frequency to achieve reliable coverage of a certain service area, which is beneficial to frequency planning, saves frequency resources, and improves spectrum utilization, so the mobile receiving system is different at the same time. The RF electromagnetic signals received by the transmitter are the same. However, if the single-frequency network system sends a part of the geographically differentiated service in addition to the service of the entire network, that is, the multi-frequency network (MFN: Multiple Frequency Networks) in the single-frequency network, then the 交 will lead to the geographical boundary. Channel interference occurs between the sub-networks, which affects the network quality of the respective borders. Therefore, it is necessary to provide a single-frequency network planning method based on OFDM technology to prevent channel interference at different geographical boundaries and thus to transmit different channels in different regions. Digital multimedia broadcasting service. SUMMARY OF THE INVENTION In view of the deficiencies and deficiencies of the prior art, the present invention provides a OFDM-based OFDM-based technology that can prevent channel interference at different geographic boundaries to achieve different digital multimedia broadcast services in different regions. Frequency network planning method. To achieve the above objective, the present invention adopts the following technical solutions: A single frequency network planning method based on orthogonal frequency division multiplexing technology includes the following steps: Step A: Perform unified resource planning on a single frequency network; Step B, The area where the frequency network provides services is uniformly addressed, so that adjacent areas have different network addresses; Step C, synchronizing the air signals of the single frequency network; Step D, classifying the transmitters and cells in the single frequency network; E. determining an optimal distance between the transmitters in the single frequency network; Step F: processing the single frequency network control channel related to the area; Step G, processing the single frequency network service channel related to the area. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the step A includes the following steps: Step A1: dividing the control channel of the single frequency network into the control channel affected by the area and the unaffected area The affected control channel; Step A2, dividing the traffic channel of the single frequency network into a geographically affected traffic channel and a geographically unaffected traffic channel. Step A3: All transmitters in the single-frequency network send the same control information on the control channel that is not affected by the area; Step A4, all the transmitters in the single-frequency network send different control information on the control channel affected by the area; Step A5: All the transmitters in the single-frequency network send the same service information on the service channel that is not affected by the area; step A6, all the transmitters in the single-frequency network are sent differently on the affected or affected traffic channels. Business information. Preferably, in the single frequency network planning method based on the Orthogonal Frequency Division Multiplexing (OFDM) technology, the area in step B is divided by the service provided by the single frequency network, and the same air channel resources in the single frequency network in the two regions are divided. The geographically related services transmitted are different. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, step C is specifically: Step C1, obtaining a maximum internal delay of the single frequency network system; Step C2, maximizing the delay in the single frequency network When the time is the reference, the other transmitter temporarily saves the data to be transmitted locally by adding a buffer method; Step C3, taking the time input by the global positioning system as the standard, when the time of transmitting the frame data to the single frequency network, the slave cache Take out the data. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, step C1 is specifically: Step C11, the network center control node sends a loop test message to the transmitter at the initial timing. The message includes a face code; step C12, when the transmitter 1 receives the message, immediately returns the message to the network center control node; Step C13, the network center control node stops timing after receiving the returned message Whether the comparison risk code is consistent, the start and stop time difference is the double delay of the transmitter 1. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the transmitter and the cell in the single frequency network in step D are divided into a transmitter and a regional border transmitter in the area, and a cellular and Regional boundary honeycomb. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the optimal distance between the transmitters in step E is smaller than the guard interval time in the orthogonal frequency division multiplexing parameter multiplied by Air signal propagation rate. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the step F is specifically: In the step F1, at the geographic boundary of the single-frequency network, for the control message affected by the area, the frequency of transmission of the regional border cell by the geographical boundary is reduced; Step F2, the regional border cell sends the control message by using the time-division interval; Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the step F2 is specifically: the regional border cell sends a regional control message in the previous frame, and the next frame sends another region control. In the message, the address identifier of the area is added in the message to provide the receiving terminal system identification. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the step G is specifically: using a sacrificial boundary cell method or an isolation band method to implement a single frequency network for transmitting different services in different regions. Preferably, in the single frequency network planning method based on the Orthogonal Frequency Division Multiplexing (OFDM) technology, the step G is specifically: implementing a single frequency network for transmitting different monthly services in different regions by using a sacrificing resource method. Preferably, in the single frequency network planning method based on the orthogonal frequency division multiplexing technology, the sacrificial boundary cellular method or the isolation band method is: not transmitting the ground in the regional boundary cell at least one side of the geographical boundary i or the difference of the task. Preferably, in the single frequency network planning method based on the Orthogonal Frequency Division Multiplexing (OFDM) technology, the method for sacrificing resources is to transmit regional difference services alternately on both sides of the region, that is, to transmit a regional monthly I of the previous frame. The next frame transmits the regional service of the adjacent area. In the Buxian A, ^"single-frequency network into ^" unified resource planning, regardless of the single-frequency network system using frequency division method or time division method, strictly distinguish between services that are not affected by the geographical area and services that are affected by the area, The control channel and the service (data) channel of the single-frequency network are uniformly allocated, and the air resources of the single-frequency network system are uniformly allocated. If the single-frequency network system divides the frequency according to the frequency division method; if the single-frequency network system is in the time division manner, Unified allocation of time, that is, in the OFDM system, the OFDM symbols are uniformly allocated, and the same OFDM symbols are uniformly occupied in each frame for the air resources occupied by the services not affected by the geographical area, and the geographically-affected services are uniformly allocated. OFDM symbols, such resources are shared between different regions. In the step B, the area is uniformly addressed, so that the adjacent areas have different network addresses to distinguish the areas, and the geographical concept can be divided by the services provided by the single frequency network, two areas. The geographically related services transmitted by the same air channel resources in a single frequency network are different. In the step C, the single-frequency network air signal is synchronized. Since the single-frequency network is characterized in that different transmitters transmit the same signal at the same time and at the same frequency, it is necessary to consider the air signal synchronization problem between the transmitters. Generally, a network system is controlled by a network center control node to transmit service data to various transmitters in the network. There are various physical transmission media between the network center control node and the transmitter, such as wired and wireless (satellite, jingbo, etc.). However, in either case, the data has different delays from the network center control node to the transmitter. The larger the coverage area of the single-frequency network, the greater the internal delay of the network system. If the internal delay of the network system is not considered, Then, the single-frequency network system will generate inter-channel interference and inter-OFDM interference, so the internal delay of the network system has an impact on the air signal synchronization. To solve the single-frequency network air signal synchronization, two aspects need to be considered: First, the maximum internal delay of the network system can be obtained through the internal test method or evaluation method of the network system; secondly, the transmitter cache size is determined according to the delay of the network system, Ensure that the data is not lost or is covered by the back frame data before being transmitted from the transmitter; finally, in order to ensure that each frame of data is transmitted simultaneously in all the single-frequency networks, according to the maximum delay in the network system, the control node in the network center passes The data transmission timestamp method is added to each frame of data to unify the transmission time to ensure air synchronization. In the step D, the transmitter and the cell are classified into a transmitter and a regional boundary transmitter in the area, and a cell at the geographical boundary is defined as a boundary cell. In the step E, the inter-transmitter distance in the single frequency network based on the OFDM technology is calculated. In the single-frequency network signal cross-coverage area, since the receiving system can receive the same signal from different transmitters, there is a propagation difference in the time when the signals from different transmitters arrive at the receiving terminal, if the propagation difference is smaller than the guard interval (cyclic prefix) in the OFDM parameters. There will be no inter-channel interference and inter-OFDM interference, and the optimal distance between the transmitting stations is less than the guard interval time in the OFDM parameters multiplied by the airborne signal propagation rate (the speed of light in air). In the step F, the single frequency network control channel is processed. At the geographical boundary of the single-frequency network, for the geographically-affected control message, the frequency of transmission of the border cell at the geographical junction is reduced, and the time-division interval is used to transmit, that is, a regional control message is sent in the previous frame, and the latter The frame sends another (adjacent) area control message, and the address identifier of the area is added in the message to provide the receiving terminal system identification, such as affecting the terminal roaming, and the interval to send the area-related control channel message is only for the border cell. The cells in the area are not affected by the network plan, and the control channel messages that are not related to the area are not required to be sent at time intervals. In the step G, the single frequency network service (data) channel is processed. At the location or boundary of the single-frequency network, for a geographically differentiated service (data) channel, that is, the OFDM channel transmits a zone t or a sexual service, there are two ways to implement a single-frequency network that transmits different services in different regions. : Sacrifice the boundary cell method or the isolation band method, that is, the service that does not transmit the geographical difference is only transmitted in the boundary cell at the geographical junction.

3⁄4 are not transmitted on both sides, or transmitted on one side and not on the other side, thus forming a natural isolation, so that the single-frequency network channels in different regions are not disturbed. This method sacrifices all or part of the geographical boundary. Regional service; Sacrifice resource method, that is, the geographical difference service on both sides of the geographical area alternately transmits, that is, the previous frame transmits a regional service of the same domain, and the next frame transmits the regional service of the adjacent region. The disadvantage of this method is that Waste of resources, for example, the two regional areas alternately transmit their respective regional services, which requires twice the air resources, and leads to the intra-area network is also the transmission method, so this method leads to a decrease in the utilization rate of the single-frequency network system. If the single-frequency network is a natural isolation zone at the ground or the junction, that is, there is no single-frequency network coverage at the ground or junction, or there is no cross-over coverage between the two, so there is no impact on the entire single-frequency network system. This special network plan. For single-frequency network planning, a geographical isolation band or two networks can be used to send single-frequency network services in different frequency bands, so that interference does not occur between single-frequency networks. The geographical isolation zone means that there is no geographical overlap between the signal coverage of the single-frequency network, and there is no mutual interference; in different frequency bands, the occupied spectrum resources are quite different, such as one is 700MHz, and one is 750MHz. The single-frequency network needs reasonable planning for regional services at different geographical boundaries, reduces channel interference between different regional systems, and improves the service quality of single-frequency networks. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a single frequency network system; FIG. 2 is a time division based frame planning; FIG. 3 is a network system internal loop test flow chart; FIG. 4 is a basic block diagram of a transmitter delay processing; FIG. 5 is a single frequency network coverage planning classification; FIG. 6 is a time domain diagram of an OFDM symbol; FIG. 7 is a time division mode planning diagram of a single frequency network ^ ί air channel; FIG. 8 is a (data) channel time division mode planning of a sacrificial boundary cellular method; Figure 9 is a (data) channel time division mode planning diagram of the victim network resource method. DETAILED DESCRIPTION Referring to FIG. 1 , a network side of a single frequency network system is mainly composed of a network center control node and a transmitter. The network center control node uniformly transmits media stream data to each transmitter, but between the network center control node and the transmitter. There are many types of data transmission media, such as cable, microwave, satellite, and the like. 2 is a time division mode frame planning, that is, a unified planning resource based on a time division single frequency network, in which each channel includes one or more OFDM symbols, wherein control channels 1 and 2 are not affected by geographical influence. Channel, all transmitters in a single frequency network send the same control information on these two channels, control channels 3 to n are geographically affected control channels; traffic channels 1 and 2 are geographically unaffected traffic channels, within a single frequency network All transmitters transmit the same service content on traffic channel 1, while traffic channels 3 through n are geographically distinct traffic channels, and services transmitted in different regions are also different. The single-frequency network system requires different transmitters to transmit the same signal at the same time and at the same frequency, and the delay of transmitting data to the different transmitters by the network center control node is different. For the air signal synchronization, the internal delay of the network system must be obtained. Time. FIG. 3 shows a test method for a network center control node to inter-transmit delay, and; H is as follows: The network center control node sends a loop test message to the transmitter at the initial timing, and the message includes 3⁄4^ positive code; when the transmitter 1 receives the message, it will return the message to the network center control node; after receiving the returned message, the network center control node stops timing, compares the verification code, and starts and The cutoff time difference is the double delay of the transmitter 1. The same method tests all transmitter delays in a single-frequency network, compares the length of the delay time, to single The longest delay in the frequency network is the reference. The other transmitters temporarily save the data to be transmitted locally by adding the buffer method, which is based on the time of the GPS input. When the time of the frame data is transmitted by the single frequency network, The data is fetched from the cache, thus ensuring the time consistency of the single-frequency network data transmission. Figure 4 shows the main modules included for the delay processing transmitter, including the cache portion. Figure 5 shows the transmitter classification of a single-frequency network, where the transmitter A of the area 1 and the transmitter B of the area 2 are on the two sides of the geographical boundary, respectively, the regional boundary transmitter, and the transmitter C in the area 2 The border transmitter B is in the same area and adjacent, so the transmitter C is the intra-area transmitter, the boundary cell of the border transmitter A is the omnidirectional cell, and the border cell of the border transmitter B is the 60-degree angle cell, and the mobile reception The terminal crosses the coverage of the border transmitters A and B to receive the service. Figure 6 shows the time composition of adjacent symbols in OFDM in the time domain, including guard interval and effective time. The main role of guard interval is anti-multipath expansion. The distance of OFDM single-frequency network transmitter is related to guard interval. Single-frequency network transmission The optimal distance between the machines is less than the guard interval and the air signal propagation speed, otherwise inter-channel interference and inter-symbol interference are generated in the cross-coverage area, or the signal coverage is discontinuous. 7 is a timing division scheme of a control channel in the case of the transmitter distribution of FIG. 4, wherein the control channel 1 is region-independent in a single frequency network, that is, the information transmitted in the same area is the same; and the control channel 2 is in a single frequency network. Geographically related, that is, the content transmitted by the control channel 2 is different in the areas 1 and 2, and the control channel 2 in the border cellular network is alternately transmitted in the network frame, and the control channel 1 is not geographically restricted, regardless of the geographical boundary or Within the territory; the cells within the area also normally transmit control channels in every frame, as in transmitter C. FIG. 8 and FIG. 9 respectively illustrate two geographically-related service (data) channel time division mode planning methods, wherein the service (data) channel 1 is independent of a region in a single frequency network, whether in a border cell or a regional cell. The transmission content is the same, and the service (data) channel 2 is geographically related in the single frequency network, that is, the content transmitted in the areas 1 and 2 is different. Figure 8 uses the Sacrificial Boundary Cellular Method to isolate the traffic (data) channel 2 in Region 1 and Region 2, where the traffic (data) channel 2 is not transmitted at the border cell in Transmitter B, but the internal transmission in Region 2 Machine C normally transmits the service (data) channel 2; in Figure 9, the victim resource method is used to make the area 1 and the area 2 alternately transmit the service (data) channel 2, and the internal transmitter C in the area 2 and the border transmitter B use the same transmission. method. The invention may, of course, be embodied in various other embodiments and various modifications and changes can be made in accordance with the present invention without departing from the spirit and scope of the invention. Modifications are intended to fall within the scope of the appended claims.

Claims

Claim

A single frequency network planning method based on orthogonal frequency division multiplexing technology, comprising the following steps: Step A: performing unified resource planning on a single frequency network;

Step B: Perform unified addressing on the area where the single-frequency network provides the monthly service, so that the adjacent areas have different network addresses;

Step C, synchronizing the air signals of the single frequency network;

Step D: classifying the transmitter and the cell in the single frequency network;

Step E: determining an optimal distance between transmitters in the single frequency network;

Step F: processing the single-frequency network control channel related to the region; Step G, processing the single-frequency network traffic channel related to the region.

2. The single frequency network planning method based on Orthogonal Frequency Division Multiplexing (OFDM) technology according to claim 1, wherein the step At comprises the following steps:

Step A1, dividing the control channel of the single frequency network into a control channel affected by the area and a control channel not affected by the area;

Step A2, dividing the service channel of the single frequency network into a service channel affected by the area and a service channel not affected by the area;

Step A3: All transmitters in the single frequency network send the same control information on the control channel that is not affected by the area;

Step A4: All transmitters in the single frequency network send different control information on the control channel affected by the area;

Step A5: All transmitters in the single-frequency network send the same service information on the service channel that is not affected by the area;

Step A6: All transmitters in the single-frequency network send different service information on the geographically affected service channel. '

The OFDM-based single-frequency network planning method according to claim 1, wherein the area in step B is divided by a monthly service provided by a single-frequency network, where two locations are used. The domain is different from the geographically related service transmitted by the same air channel resource in a single frequency network.

4. The single frequency network planning method based on Orthogonal Frequency Division Multiplexing (OFDM) technology according to claim 1, wherein the step C is specifically:

Step C1, obtaining a maximum internal delay of the single frequency network system;

Step C2: Taking the maximum delay in the single-frequency network as a reference, the other transmitters temporarily save the data to be transmitted locally by adding a buffer method;

Step C3, based on the time input by the global positioning system, when the time of transmitting the frame data by the single frequency network, the data is taken out from the cache.

The method for planning a single frequency network based on the Orthogonal Frequency Division Multiplexing (OFDM) technology according to claim 4, wherein the step C1 is specifically:

Step C11: The network center control node sends a loop test message to the transmitter at the initial timing, where the message includes a face code;

Step C12, when the transmitter 1 receives the message, immediately returns the message to the network center control node;

Step C 13. After receiving the returned message, the network center control node stops timing and compares whether the verification code is consistent. The difference between the start and the end time is the double delay of the transmitter 1.

The OFDM-based single-frequency network planning method according to claim 1, wherein the transmitter and the cell in the single-frequency network in step D are divided into intra-area transmitters and regional boundary transmissions. Machine, cellular and geographical boundary cells in the area.

The unidirectional frequency division multiplexing (OFDM)-based single frequency network planning method according to claim 1, wherein the optimal distance between the transmitters in step E is smaller than the orthogonal frequency division multiplexing parameter. The medium guard interval is multiplied by the air signal propagation rate.

The method for planning a single frequency network based on the Orthogonal Frequency Division Multiplexing (OFDM) technology according to claim 1, wherein the step F is specifically:

Step Fl, at a geographical boundary of the single-frequency network, for the control message affected by the area, reducing the frequency of transmission of the regional boundary cell of the geographical boundary;

Step F2, the regional border cell sends control messages at time-sharing intervals.

9. The single frequency network planning method based on orthogonal frequency division multiplexing (OFDM) according to claim 8, wherein the if dispute is that step i F2 is specifically:

The regional border cell sends a control message of a region in the previous frame, and the control message of another region is sent in the latter frame, and the address identifier of the region is added in the message to provide the receiving terminal system identification.

The method for planning a single frequency network based on the Orthogonal Frequency Division Multiplexing (OFDM) technology according to claim 1, wherein the step G is specifically: using a sacrificial boundary cell method or a separation band method to implement a single service for transmitting different services in different regions. A frequency network, or a sacrificial resource method to implement a single-frequency network that transmits different services in different regions.

11. The single frequency network planning method based on Orthogonal Frequency Division Multiplexing (OFDM) according to claim 10, wherein the sacrificial boundary cell method or the isolation band method is at least one side of a geographical boundary. The geographically bordered cell does not transmit the geographically differentiated service; the method of sacrificing resources is to alternately transmit the geographical difference service on both sides of the geographical area, that is, the regional service of transmitting one region in the previous frame, and the regional monthly transmission of the adjacent region in the next frame. Business.