WO2009033366A1 - Service multiplexing method and apparatus of broadcast multicast system - Google Patents

Abstract

A service multiplexing method of MBMS system includes: in the MBMS system of OFDM and in the region area which is overlapped by at least two MBMS services, processing the two MBMS services with TDM; based on service coverage area being in direct proportion to the inserted CP length in each OFDM symbol in TDM time slots which bear MBMS service, and according to size relation of coverage area between at least two MBMS services, inserting respectively different length values CP in each OFDM symbol of TDM time slots which bears corresponding MBMS service. The service multiplexing method of the MBMS system can make use of CP more effectively and improve band utilization rate.

Description

 Service multiplexing method and device in broadcast multicast system

 The present invention relates to broadcast multicast technology, and more particularly to a service multiplexing method and related apparatus in a broadcast multicast system. Background technique

 Multimedia Broadcast and Multicast Service (MBMS) technology broadcasts or multicasts multimedia data to mobile terminals by sharing a transmission link. The purpose is to provide multiple users from one point to the point in an efficient, economical and shared way. Multi-point single-directional downlink multimedia data. Current user requirements are demanding high data transmission rates, while high-speed data transmissions require large transmission bandwidths to satisfy. As bandwidth increases, channel frequency selectivity is more pronounced. Orthogonal Frequency Division Multiplex (OFDM) technology introduces cyclic prefix (CP, Cyclic Prefix) technology, which can effectively overcome the effects of frequency selective fading, and OFDM technology can easily support bandwidth expansion and guarantee The technical compatibility of systems with different bandwidths provides strong support for business diversity. Currently, the Long Time Evolution (LTE) technology and the MBMS in the 3G (B3G, Beyond 3G) system are based on Orthogonal Frequency Division Multiplexing (OFDM).

Combined with the strong unidirectional nature of MBMS, the current MBMS systems are mostly designed based on individual carriers. In an MBMS service area, users can receive related MBMS services. Meanwhile, in order to obtain macro diversity gain, a single carrier MBMS system It often covers large areas. For example, one MBMS service area includes multiple nodes (Node Bs), or multiple base stations, or multiple cells, using the same frequency resources in each service area to transmit the same data under strict time synchronization conditions. Since an MBMS service area is relatively large, the user equipment (UE, User Equipment) needs to diversity the MBMS signals from different Node Bs, different base stations, and different cells, and therefore, the signals required to reach the UE fall on the CP of the OFDM symbol. Within the scope, To ensure correct demodulation of the OFDM signal. Summary of the invention

 The technical problem to be solved by the present invention is to provide a method and apparatus for service multiplexing in an MBMS system, so that the CP can be utilized more effectively and the frequency band utilization of the MBMS system can be improved.

 An embodiment of the present invention provides a service multiplexing method in a broadcast multicast system, including the following steps: In a broadcast multicast system based on orthogonal frequency division multiplexing, in an area covered by at least two broadcast multicast services a time division multiplexing process on the at least two broadcast multicast services; and orthogonal frequency division multiplexing in a time division multiplexing time slot for carrying the broadcast multicast service based on the coverage of the broadcast multicast service The cyclic prefix length inserted in the symbol is proportional to each other, and according to the size relationship of the coverage of the at least two broadcast multicast services, respectively, each orthogonal frequency division in the time division multiplexing time slot carrying each corresponding broadcast multicast service A cyclic prefix with different length values inserted in the multiplex symbol.

 The embodiment of the present invention further provides a service multiplexing device in a broadcast multicast system, including: a time division multiplexing unit, configured to be broadcast by at least two in a broadcast multicast system based on orthogonal frequency division multiplexing The at least two broadcast multicast services are time-division multiplexed in the area covered by the overlap of the multicast services; the cyclic prefix insertion unit is configured to be used for carrying the broadcast multicast service based on the broadcast multicast service coverage The relationship between the cyclic prefix lengths inserted in the orthogonal frequency division multiplexing symbols in the time division multiplexing time slot is proportional, according to the size relationship of the coverage of the at least two broadcast multicast services, respectively carrying the corresponding broadcast multicast A cyclic prefix of a different length value is inserted into each orthogonal frequency division multiplexing symbol in the time division multiplexed time slot of the service.

The MBMS system in the MBMS system according to the embodiment of the present invention overlaps the service multiplexing scheme, and uses the TDM method to perform MBMS service multiplexing, the large coverage area uses a long CP, and the small coverage area uses a short CP. , thereby reducing the waste of the CP and improving the frequency band utilization of the MBMS system. DRAWINGS FIG. 1 is a schematic structural diagram of service multiplexing in which coverage coverage overlaps in an MBMS system, in which a single MBMS service representing a cell A, a separate MBMS service on behalf of a cell, a separate MBMS service on behalf of a cell C, and a public MBMS service on behalf of a community A, B, and C. ;

 2 is a schematic structural diagram of two service multiplexing in which coverage coverage overlaps in an MBMS system, where represents a small coverage service (cell A separate MBMS service), and a country representative large coverage service (cell A, B, C public MBMS service);

 FIG. 3a is a schematic diagram showing different numbers of time slots occupied by different coverage areas in an MBMS system multiplexed by TDM;

 FIG. 3b is a schematic diagram of time slot allocation allocated by different coverage areas in an MBMS system multiplexed by TDM;

 4 is a schematic diagram of a method for overlapping service coverage in an MBMS system according to an embodiment of the present invention;

 FIG. 5 is a schematic structural diagram of an apparatus for overlapping service coverage in an MBMS system according to an embodiment of the present invention. detailed description

 In order to improve the frequency band utilization of the MBMS system, MBMS services with overlapping coverage areas can be multiplexed in the same MBMS system. In the MBMS system, MBMS services with overlapping coverage can be reused by Time Division Multiplexing (TDM). In the MBMS service time division multiplexing system in which the coverage area overlaps, it is also necessary to consider the CP length design inserted in each OFDM symbol in the TDM time slot carrying the MBMS service.

The service multiplexing technical solution with overlapping coverage in the MBMS system according to the embodiment of the present invention is: In the OFDM-based MBMS system, the at least two MBMS services are performed in an area covered by overlapping of at least two MBMS services. Performing TDM processing; based on the MBMS service coverage, in a relationship proportional to the CP length value inserted in each OFDM symbol in the TDM time slot for carrying the MBMS service, according to the size relationship of the at least two service coverage areas, respectively A CP of a different length value is inserted in each OFDM symbol in a TDM slot carrying each corresponding service. Specific embodiments of the present invention are described below in conjunction with the drawings.

 FIG. 1 is a schematic structural diagram showing service overlap of overlapping coverage in an MBMS system. The MBMS system includes four MBMS services with different coverage ranges, as follows:

 The coverage of service 1 is cell A, the coverage of service 2 is cell B, the coverage of service 3 is cell C, and the coverage of public service 4 of cells A, B, and C is cell A, B, and C. Among them, service 1, service 2, and service 3 can be time-multiplexed with service 4 through the same communication system.

 For the sake of simplicity, the following is a method for multiplexing the coverage of two different coverage MBMS services to illustrate the method of overlapping service coverage in the MBMS system, as shown in FIG. 2, a city based on OFDM technology. The single carrier MBMS system includes a small coverage service covering only cell A, and a large coverage service covering cells A, B, and C. In the figure, UE1 is a user equipment that uses only small coverage services, and UE2 is a user equipment that uses services shared by cells A, B, and C. The UE1 that uses the cell-specific service receives the MBMS signal of the small coverage service from the cell A, uses the corresponding MBMS service of the own cell, and the UE2 that uses the shared service of the cells A, B, and C pairs the cells from the cells A, B, and C. The MBMS signals of the large coverage service are grouped and used, and the MBMS services shared by the three cells are used. For the MBMS system in cell A, there is a problem of overlapping service coverage, and the services of the two different coverage areas belong to the same MBMS communication system of the city.

In the embodiment of the present invention, the MBMS communication system of the city adopts the TDM mode to perform multiplexing of the large coverage service and the small coverage service. It is assumed that there are N time slots in the single carrier MBMS system of the city, wherein the large coverage service covering the cells A, B, and C uses N _L time slots, and the small coverage service covering only the cell A uses N _S time slots, and N _L + N _S = N. The values of N _l and N _s are from 0 to N. The specific values can be dynamically adjusted according to the requirements of the service. For details, see Figure 3a. At the same time, time slots corresponding to services of different coverage areas can be allocated continuously (as shown in FIG. 3a), and can also be allocated at intervals. For details, as shown in FIG. 3b, whether continuous allocation is performed according to specific service requirements is configured. The system uses the TDM method to implement the multiplexing of MBMS services. The design method of the specific CP is shown in Figure 4. The services of different coverages use their respective CPs, and the long CPs are used in large coverage services to satisfy the UE. Divide and combine; use short CPs in small coverage services to improve the efficiency of MBMS systems.

 For unicast, the length of the CP is the time delay for the user equipment to receive the multipath signal in the unicast cell, which is generally 5us. In this embodiment, the coverage of the small coverage service is only the cell A, which can be small. The value of the length of the coverage service CP is set to 5us. For the MBMS service with large coverage, the CP length is set longer because of the need to consider the combination of multiple cell base station signals, which can be covered by the MBMS service. It is determined by the distance between the two farthest base stations that the length of the CP is generally the distance of the two base stations farthest from the large coverage MBMS service divided by the speed of light.

 In a specific design, in order to improve the frequency band utilization of the system, ensure the complete unification of the frame structure, and reduce the complexity of the terminal processing, a preferred method is to use the number of OFDM symbols in the time slots occupied by the services of different coverage areas. The length of the OFDM symbol is adjusted to be the same as the length of the OFDM symbol of the M short CPs, that is, the time slot occupied by the large coverage service and the time slot occupied by the small coverage service are the same.

 Of course, the length of the data in the OFDM symbol can be adjusted according to the number of OFDM symbols in the time slot occupied by the services of different coverages, so that the OFDM symbol length of the K long CPs is the same as the OFDM symbol length of the M short CPs.

In this embodiment, it is assumed that the distance between two base stations having the longest distance in the large coverage service is 10 km, and the length of the CP corresponding to the large coverage service is: 10 km/(3×10 ⁸ m/s) = 33.33x 1 C ⁶ s = 33.33us.

 In order to ensure the complete unification of the frame structure, it is assumed that there are K OFDM symbols in one slot of the large coverage service and M OFDM symbols in one slot of the small coverage service, and the following relationship needs to be satisfied between them:

KX (length of long CP + data length of OFDM symbol) = MX (length of short CP + data length of OFDM symbol) = length of one slot (Equation 1) Assuming a slot length in the MBMS system in this embodiment 1 ms, the number of OFDM symbols According to the length of 57.5US, substituted into Equation 1:

 K ( 33.33US + 57.5us ) = M ( 5us + 57.5us ) = 1 ms (Equation 2) Through the specific calculation of Equation 2, M=16, K=11.0095, that is, the OFDM symbol in one slot corresponding to the large coverage service is obtained. The number of OFDM symbols is 16 in one slot corresponding to the small coverage service. If the K value or the M value obtained by such calculation is not an integer or a number that is very close to an integer, then a small range adjustment of the length of the CP or a small range adjustment of the data length of the OFDM symbol can be performed. , so that the calculated K value and M value are integers.

 By designing the CP length for multiplexing services with overlapping coverage in the MBMS system, the CP length is longer for services with large coverage, and all cells A, B, and C in the coverage range can be guaranteed. The UEs that use the services shared by the cells A, B, and C perform effective diversity and obtain macro diversity gain to improve the quality and reception efficiency of the MBMS service. For the small coverage service, the CP length is shorter, corresponding to the small coverage. The cell, here is only the cell A, there is no problem that the UE performs diversity combining; even if the small coverage service covers several cells, the UE can perform effective diversity combining to improve the frequency band utilization of the MBMS system.

 The CP length design idea in the service overlap overlapping coverage in the MBMS system proposed here can also be applied to the MBMS system of Time Division Duplex (TDD) and the Frequency Division Duplex (FDD). In the MBMS system.

The present invention proposes a method for overlapping service coverage in an MBMS system, which proposes that services with overlapping coverage in the same OFDM-based MBMS system use different time slots for transmission, that is, TDM mode. Reuse. The length of the time slot is the same, and the number of OFDM symbols in each time slot is different, and the specific number of OFDM symbols is determined by the length of the CP. The time slots of different coverage services can be allocated continuously or intermittently, that is, flexible multiplexing can be performed between time slots of different services. In addition, in order to meet the requirements of diversity combining UEs using large coverage services, and to improve the receiving efficiency of small coverage services, different lengths of CPs are used for services of different coverage areas, thereby improving the frequency band utilization of the MBMS system. The method of the invention can ensure the reliable transmission of the different service coverage, reduce the waste of the CP, and improve the frequency band utilization of the system. According to an embodiment of the technical solution of the present invention, the present invention provides a service multiplexing device with overlapping coverage in an MBMS system implementing the technical solution. As shown in FIG. 5, the device includes: a time division multiplexing unit 51, In the OFDM-based broadcast multicast system, the at least two broadcast multicast services are time-division multiplexed in an area covered by at least two broadcast multicast services.

 a cyclic prefix insertion unit 52, configured to be proportional to a cyclic multicast service coverage range, and a cyclic prefix length inserted in each orthogonal frequency division multiplexing symbol in a time division multiplexing time slot for carrying a broadcast multicast service, And according to the size relationship of the at least two service coverages, cyclic prefixes of different length values are respectively inserted into each orthogonal frequency division multiplexing symbol in the time division multiplexing time slot carrying each corresponding service.

 If the coverage of the broadcast multicast service is one cell, the cyclic prefix insertion unit 52 determines to insert into the time division multiplexing time slot carrying the broadcast multicast service according to the time extension degree of the multipath signal received by the user equipment of the cell. The cyclic prefix length value in each orthogonal frequency division multiplexing symbol.

 If the coverage of the broadcast multicast service is at least two cells, the cyclic prefix insertion unit 52 determines the time of insertion into the broadcast multicast service according to the distance between the two farthest base stations in the coverage range. The cyclic prefix length value in each orthogonal frequency division multiplexing symbol in the multiplexed slot.

 Also included is a cyclic prefix adjustment unit 53 for determining each of the broadcast multicast systems based on the data length value inserted in each orthogonal frequency division multiplexing symbol and the cyclic prefix length value inserted by the cyclic prefix insertion unit 52. When a fixed length of time division multiplexing time slot cannot carry an integer number of orthogonal frequency division multiplexing symbols, each time division multiplexing time is ensured by adjusting a cyclic prefix length value inserted into each orthogonal frequency division multiplexing symbol. An integer number of orthogonal frequency division multiplexing symbols can be carried in the slot.

 Also included is a data length adjusting unit 54 for determining each of the broadcast multicast systems based on the data length value inserted in each orthogonal frequency division multiplexing symbol and the cyclic prefix length value inserted by the cyclic prefix insertion unit 52. When a fixed length of time division multiplexing time slot cannot carry an integer number of orthogonal frequency division multiplexing symbols, each time division multiplexing time slot is ensured by adjusting a data length value inserted into each orthogonal frequency division multiplexing symbol. It can carry an integer number of orthogonal frequency division multiplexing symbols.

It should be noted that each functional unit mentioned in the above device can be based on software programming. Implementation can also be implemented based on retrofitting existing hardware devices. The present invention will be described in detail with reference to the preferred embodiments, and those skilled in the art should understand that the technical solutions in the embodiments of the present invention may be modified or substituted without departing from the technical solutions of the embodiments of the present invention. Spirit and scope.

Claims

Rights request  A service multiplexing method in a broadcast multicast system, comprising the steps of: overlaying an area covered by at least two broadcast multicast services in a broadcast multicast system based on orthogonal frequency division multiplexing; a time division multiplexing process on the at least two broadcast multicast services; and orthogonal frequency division multiplexing in a time division multiplexing time slot for carrying the broadcast multicast service based on the coverage of the broadcast multicast service The cyclic prefix length inserted in the symbol is proportional to each other, and according to the size relationship of the coverage of the at least two broadcast multicast services, respectively, each orthogonal frequency division in the time division multiplexing time slot carrying each corresponding broadcast multicast service A cyclic prefix with different length values inserted in the multiplex symbol.  The method according to claim 1, wherein, if the coverage of the broadcast multicast service is one cell, determining, according to the time extension of the multi-path signal received by the user equipment of the cell, determining to insert and bear the broadcast The cyclic prefix length value in each orthogonal frequency division multiplexing symbol in the time division multiplexing time slot of the multicast service.  3. The method of claim 2, wherein the inserted cyclic prefix length value is equal to the time extension value of the multipath signal.  The method according to claim 1, wherein if the coverage of the broadcast multicast service is at least two cells, determining according to a distance between two farthest base stations in the coverage range A cyclic prefix length value inserted into each orthogonal frequency division multiplexing symbol in a time division multiplexed slot carrying the broadcast multicast service.  5. The method according to claim 4, wherein the inserted cyclic prefix length value is a value obtained by dividing a distance between two base stations farthest in the coverage by a speed of light.  The method according to any one of claims 1 to 5, further comprising the steps of: According to the data length value and the cyclic prefix length value inserted in each orthogonal frequency division multiplexing symbol, it is determined that an integer number of orthogonal frequency divisions cannot be carried in each fixed length time division multiplexing time slot in the broadcast multicast system. When multiplexing symbols, it is ensured that an integer number of orthogonal frequency division multiplexing symbols can be carried in each time division multiplexing time slot by adjusting the cyclic prefix length value inserted into each orthogonal frequency division multiplexing symbol. The method according to any one of claims 1 to 5, further comprising the steps of:  According to the data length value and the cyclic prefix length value inserted in each orthogonal frequency division multiplexing symbol, it is determined that an integer number of orthogonal frequency divisions cannot be carried in each fixed length time division multiplexing time slot in the broadcast multicast system. When multiplexing symbols, it is ensured that an integer number of orthogonal frequency division multiplexing symbols can be carried in each time division multiplexing time slot by adjusting the data length value inserted into each orthogonal frequency division multiplexing symbol.  8. A service multiplexing device in a broadcast multicast system, comprising:  a time division multiplexing unit, configured to time divide the at least two broadcast multicast services in an area covered by at least two broadcast multicast services in a broadcast multicast system based on orthogonal frequency division multiplexing Multiplexing processing;  a cyclic prefix insertion unit, configured to be based on a broadcast multicast service coverage, and proportional to a cyclic prefix length inserted in each orthogonal frequency division multiplexing symbol in a time division multiplexing time slot for carrying a broadcast multicast service, According to the size relationship of the coverage of the at least two broadcast multicast services, cyclic prefixes of different length values are inserted into each orthogonal frequency division multiplexing symbol in the time division multiplexing time slot of each corresponding broadcast multicast service.  The apparatus according to claim 8, wherein if the coverage of the broadcast multicast service is one cell, the cyclic prefix insertion unit is configured according to the time extension of the multi-path signal received by the user equipment of the cell. A cyclic prefix length value inserted into each orthogonal frequency division multiplexing symbol in a time division multiplex slot carrying the broadcast multicast service is determined.  The device according to claim 8, wherein if the coverage of the broadcast multicast service is at least two cells, the cyclic prefix insertion unit is configured according to two farthest base stations in the coverage range. The distance between them determines the cyclic prefix length value inserted into each orthogonal frequency division multiplexing symbol in the time division multiplexing slot carrying the broadcast multicast service. 11. The apparatus according to claim 8, 9 or 10, further comprising a cyclic prefix adjustment unit for converting a data length value and a cyclic prefix length value inserted in each orthogonal frequency division multiplexing symbol Determining that when each fixed-length time division multiplexing time slot in the broadcast multicast system cannot carry an integer number of orthogonal frequency division multiplexing symbols, the adjustment is inserted into each orthogonal frequency division multiplexing symbol. The cyclic prefix length value is used to ensure that an integer number of orthogonal frequency division multiplexing symbols can be carried in each time division multiplexed time slot.  12. The apparatus according to claim 8, 9 or 10, further comprising a data length adjusting unit for converting a data length value and a cyclic prefix length value inserted in each orthogonal frequency division multiplexing symbol Determining, by adjusting the length of data inserted into each orthogonal frequency division multiplexing symbol, when each of the fixed length time division multiplexing time slots in the broadcast multicast system cannot carry an integer number of orthogonal frequency division multiplexing symbols The value is to ensure that an integer number of orthogonal frequency division multiplexing symbols can be carried in each time division multiplexed time slot.