CN103108213B - A kind of method by digital ground multimedia broadcast system bidirectional - Google Patents
A kind of method by digital ground multimedia broadcast system bidirectional Download PDFInfo
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Abstract
The present invention proposes a kind of method and system by digital ground multimedia broadcast system bidirectional, and the method is by descending for DTB Digital Terrestrial Broadcasting and GPRS compatibility up combining.In channel physical layer, descending received terrestrial digital broadcasting transmission means of continuing to use, increases wireless uplink, one or more 200KHz bandwidth channel of up utilization free time ground wireless transmission band, using compatible GPRS uplink transmission mode, up-downgoing belongs to asymmetric frequency division duplex mode.On physical layer, the medium education of broadcasting multiplex and two-way broadband carries out Combined design, descending broadcast, broadband services and signaling data time division multiplex downlink transfer passage.The method uses 200KHz channel that unidirectional digit broadcasting system can upgrade to interaction broadcast and broadband access emerging system, support the asymmetric two-way services that the descending and medium and small bandwidth of big bandwidth is up, be suitable for providing interaction broadcast and WiMAX converged services towards suburb, rural area and small and medium-sized cities low cost.
Description
Technical field
The present invention relates to received terrestrial digital broadcasting (TV or multimedia broadcasting) and terrestrial wireless broadband technology field, particular for terrestrial television/multimedia broadcasting net Two-way and wireless broadband Internet access integration technology, namely the present invention provides a kind of method by digital ground multimedia broadcast system bidirectional.
Background technology
Digital multimedia/television broadcasting realizes mainly through three kinds of transmission means such as satellite, wire cable and terrestrial wireless.Terrestrial wireless broadcast is with its unique ability receiving convenient and mobile reception, it is possible to meet Modern Information based Society people whenever and wherever possible for the demand of information.
DTB Digital Terrestrial Broadcasting system of the present invention comprises ground TV broadcast system and the multimedia broadcasting of fixed reception and portable mobile reception.In China, mainly include China Mobile multimedia broadcasting system CMMB, the DMB T-DMB and the numeral terrestrial TV system DTTB that realize in terrestrial wireless mode.
At present, abroad defining three big ground digital television broadcast transmission standards, i.e. the ISDB-T standard of the ATSC standard of the U.S., the DVB-T standard in Europe, Japan, the U.S. adopts single carrier mode, and Europe and Japan are orthogonal frequency pair OFDM multi-carrier transmission pattern.
The research of terrestrial DTV is formally carried out from China in 1996 in inland of China, and formulated national digital ground TV broadcast standard DTTB in August, 2006, this standard fusion multicarrier and two kinds of transmission modes of single carrier.
The CMMB standard CMMB that the domestic portable hand-held TV for broadcast system mainly has General Bureau of Radio, Film and Television to release.China Mobile multimedia broadcasting standard CMMB is based on the terrestrial transmission solution of OFDM technology; DVB-T and DAB/T-DMB is with reference in transport layer; defining working channel bandwidth is 8MHz and 2MHz both of which; it is respectively adopted 4K subcarrier and 1K subcarrier OFDM+BPSK/QPSK/16QAM modulation system; recycling-guard prefix is unified long for 1/8OFDM symbol; chnnel coding adopts RS and LDPC scheme for combining, can provide the transmission capacity being up to 16Mbps under 8MHz pattern.
Along with integrated services constantly deeply, traditional unidirectional television broadcasting is difficult to meet the demand of user, and broadcasting user is desirable for interactive service, further, it is desirable to obtain interactive multimedia broadcast and broadband connections converged services.Interactive television service is provided to spread out along with the enforcement of the integration of three networks by cable digital TV broadcast mode, thering is provided interactive television service still rare in terrestrial wireless broadcast mode, only two-way interactive terrestrial digital TV standard DVB-RCT has been formulated in Europe at present.Mostly adopting the mode by mobile communications network to provide return path in industry, this mode crosses over different network systems and different operators, it is necessary to the very long Connection Time, runs and maintenance cost is high.
Universal Information technology standardization technical committee in JIUYUE, 2006 is formally set up the project and is formulated broadband radio multi-media (BroadbandWirelessMultimedia, the BWM) standard based on " broadcast ", " communication " and " wireless broadband Internet access " integration of three networks.BWM network is a Wideband mobile radio network merging mobile tv network and BRAN technical characteristic.In Radio Access Network framework, BWM considers the networking feature of mobile tv network and BRAN, both the great Qu pattern having supported the big base station+little base station of traditional broadcast television network to cover, supports again the cell pattern covered with the complete little base station that beehive net is feature.
Relative analog TV, terrestrial DTV has the higher availability of frequency spectrum.Along with analog television broadcast is changed to DTV, if originally radio and television frequency range is all for providing visual broadcast service, number of programs will be made to be multiplied, or less than half of original shared frequency range only need to be used can to provide the television program of as much, then some resources of frequency range will be gone out the free time.And meanwhile, various wireless broadband communication technical developments make available frequency band be increasingly difficult to arrange, continue to be not appropriate for terrestrial transmission toward high frequency such as 3GHz/5GHz development to cover, and the frequency range such as VHF/UHF frequency range that applicable overland propagation covers is mostly used in broadcast television service and communicates with 2G.WiMAX is seeking to share the TDD resource of frequency range of 3G.First wireless communication system standards IEEE802.22 utilizing cognitive radio in the world, utilizes idle radio and television frequency range in 54MHz～862MHzVHF/UHF frequency range to realize fixing wireless area network by aware dynamic.For the high-quality free time frequency range of surface TV traditionally, urgent the intentionally getting and using of wireless broadband communication industry, but TV industry analog/digital conversion various countries progress is uneven, and analog-and digital-radio and television also will continue and deposit for many years.Television system is substantially all with 6/7/8MHz for bandwidth partition channel, and the working frequency range width even higher up to 20MHz for broadband connections industry then needs to use the serial frequency range of multiple free time, reduces opportunity available.It addition, traditional tv frequency band is reclassified as the way used by broadband wireless communications frequency range, it is helpless to low cost and meets the demand to interaction broadcast Yu broadband connections converged services.Mutual broadband services is the same with digital broadcasting service gradually, it is desirable to provide popularization public service, eliminates " digital divide ", ensures the information right to know of the public, right to choose and expression power with low cost, is the necessity of the lasting balanced development of informationized society.For responding this type of demand cry, in the 4G concept of WiMAX industry, as LTE/IMT-ADVANCED plans to merge in Wireless Broadband Communication Systems to support broadcast capability, but not cost effective.
GPRS (general packet radio service) and strengthen version (GPRS/EDGE) and develop based on the digital cellular communication system GSM of Global prevalence, by changing the global system for mobile communications (GSM) circuit exchange mode used by continuous voice or data communication into block exchange mode, on-demand dynamically take wireless channel, only just use radio channel resource when actual transmission and reception, one user can take multiple wireless channel, and multiple users also can share a wireless channel.In conventional gsm system, every 200kHz bandwidth channel is divided into 8 time slots by time division multiple acess TDMA, and 8 time slots form tdma frames, every slot transmission one road speech or data service, it is provided that 8 speeches or 9.6kbps～14.4kbps data channel.GPRS can be combined and uses multiple time slots, and message transmission rate may be up to 160kb/s.The enhanced edition EDGE of GPRS is supporting that GPRS continues to use on the GMSK modulation basis of GSM, increase and support 8PSK modulation mode, speed brings up to the follow-up evolution version of 500kbps, GPRS/EDGE will support higher order modulation such as 16QAM, 32QAM and multi-antenna technology, and flank speed brings up to about 1Mbps.
Digital broadcasting and the developing direction that the fusion of wide-band communication system is following broadcast and wireless broadband system.There are respective pluses and minuses in the broadcast system of one-way transmission and the wide-band communication system of transmitted in both directions.The unidirectional transmission property of broadcast system makes broadcast system can only support the one way traffic of point-to-multipoint.Although the communication system based on honeycomb is provided that two-way services, but its micro-honeycomb structure and clean culture send mode and there is the inefficient shortcoming of distribution.
User wishes to obtain multimedia broadcasting, interaction broadcast and the broadband inserting service merged.But all cannot effectively provide multimedia broadcasting, interaction broadcast and broadband access converged services individually with existing digital broadcast technologies or wireless broadband communication technology, existing digital broadcasting it is used in combination and wireless broadband communication relates to different technologies system and the operation system interface coordination of two big industries, inefficiency, cost is high.
Summary of the invention
It is an object of the invention to, for overcoming existing terrestrial broadcast system and Wireless Broadband Communication Systems cannot effectively provide the shortcoming of interactive multimedia broadcast and broadband connections converged services, thus providing a kind of method by DTB Digital Terrestrial Broadcasting system bidirectional.
The present invention provides a kind of method by DTB Digital Terrestrial Broadcasting system bidirectional for achieving the above object, the method realizes broadcast and merges on the level of the transport layer with wireless broadband communication, described Two-way method is: DTB Digital Terrestrial Broadcasting downlink transfer and GPRS/EDGE uplink are combined, continue to use received terrestrial digital broadcasting transmission means channel physical layer is descending, and increase wireless backhaul up channel, described wireless uplink return path is available 200KHz bandwidth idle channels, and described uplink and downlink adopt asymmetric frequency division duplex FDD mode.
The up media access control MAC of two-way services and signaling adopts GPRS compatibility mode, the descending MAC layer package of two-way services adopts corresponding DTB Digital Terrestrial Broadcasting system data broadcasting service packaging multiplexing processing mode, the descending MAC of Signalling exchange processes the package mode adopting GPRS compatible, it is packaged into the data traffic information bag of corresponding digital multimedia broadcasting system again, the information bag that these comprise downlink signaling message is sent in time by broadcasting service time slot and two-way services descending time slot, to improve the real-time of Signalling exchange.
In technique scheme, time division multiplexing mode is adopted when described down going channel transmits broadcast downstream business, two-way services downlink data and Signalling exchange downlink data, the downlink data of broadcasting service and two-way services takies different descending time slot, and Signalling exchange downlink data sends with time slot and two-way services time slot.
Optionally, one or more 200KHz bandwidth channels that described wireless uplink return path utilizes in digital broadcast base stations coverage in the radio band of idle ground carry out, by increasing wireless backhaul sending module in digital broadcast receiving terminal side and increasing the realization of wireless backhaul receiver module in digital broadcast base stations side.The up passback mode up for passback mode compatibility GRPS/EDGE of described 200KHz wireless backhaul channel.
Optionally, described wireless backhaul channel adopts demand assigned time division multiple acess TDMA to realize wireless uplink passback access, wireless backhaul physical layer and GPRS/EDGE uplink protocol-compliant in conjunction with frequency division multiple access FDMA.
The downlink data of described broadcasting service and two-way services carries out time-division slot based on time division multiplex and merges transmission process, merges the media access control layer/multiplex layer after transmission and has data framing, network insertion and bandwidth distribution function.
In addition, the present invention also provides for a kind of method by CMMB system Two-way, described CMMB system is the DTB Digital Terrestrial Broadcasting system described in claim 1, and this Two-way method is based on the DTB Digital Terrestrial Broadcasting system bidirectional strategy of claim 1, the described method by CMMB system Two-way comprises: by increasing the wireless backhaul of the up compatibility of GPRS/EDGE in the head-end system of CMMB system and terminal unit and supporting the subsystem of two-way broadband interactive service；The physical layer of descending compatible mobile multimedia broadcast system, merges the descending MAC layer of two-way wireless communication and CMMB broadcasting multiplex layer simultaneously, to support broadcast and two-way services；Described broadcast and data service are provided by same base, broadcast consistent with the power grade of data service downlink data, support that largest cell radius is 60KM.
A kind of CMMB Two-way system is provided based on the above-mentioned Two-way method present invention, system CMMB is expanded to Two-way system based on the Two-way method of claim 7 by this system, and described system comprises: base station, gateway server, broad access network gate, media server, scheduling of resource center and customer data base；Described base station comprises digital broadcasting and wireless backhaul air interface physical layer, MAC layer function, completes broadcast data and issues and the transmitting-receiving of mutual bi-directional data, business mapping, convergence, power control, network insertion and initialization；Described gateway server is responsible for authentication and network address configuration；Described broad access network gate is responsible for broadband access, resource control and management；Described media server be responsible for providing broadcast, program request or push away broadcast/transmission service content is localized storage and broadcasts；Scheduling of resource and the content distribution of broadcast and data service is responsible at described scheduling of resource center；Described customer data base comprises user-network access data and service customizing information, is used for managing customer service；Wherein, described CMMB Two-way system also comprises physical layer and MAC layer.
The physical layer of described CMMB Two-way system continues to use CMMB terrestrial broadcast transmission mode in the downstream direction, and up direction adopts GPRS/EDGE physical layer compatibility mode.
The MAC layer of described CMMB Two-way system processes as follows: the up direction MAC of two-way services and Signalling exchange adopts GPRS/EDGE compatible processing mode, two-way services down direction MAC layer adopts CMMB data broadcast processing mode, and two-way services upper layer protocol data is packaged into CMMB data broadcasting protocols bag and issues；The descending MAC of Signalling exchange adopts GPRS compatibility package mode, then is packaged into CMMB data broadcast compatible information bag, and these information bags are sent in time by time slot and mutual time slot, to improve the real-time of signaling.
In technique scheme, time division multiplexing mode is adopted when described down going channel transmits broadcasting service, two-way services and Signalling exchange downlink data, broadcasting service and two-way services downlink data take different descending time slot, and Signalling exchange downlink data sends with broadcasting service and two-way services descending time slot.
One or more 200KHz bandwidth channels that described wireless uplink return path utilizes in digital broadcast base stations coverage in the radio band of idle ground carry out, by increasing wireless backhaul sending module in digital broadcast receiving terminal side and increasing the realization of wireless backhaul receiver module in digital broadcast base stations side.
One of optional passback mode is as follows, the passback mode up for passback mode compatibility GRPS/EDGE of described 200KHz wireless backhaul channel.Described wireless backhaul channel adopts demand assigned time division multiple acess TDMA to realize wireless uplink passback access, wireless backhaul physical layer and GPRS/EDGE uplink protocol-compliant in conjunction with frequency division multiple access FDMA.
The downlink data of described broadcasting service and two-way services carries out time-division slot physical layer based on time division multiplex and merges transmission, and media access control layer and broadcasting multiplex layer merge, and complete data framing, network insertion and bandwidth distribution function.
MAC and the fusion of broadcasting multiplex layer include: the up MAC of two-way services and signaling adopts GPRS compatibility mode；The descending MAC package of two-way services adopts the data broadcast packaging multiplexing mode of respective digital terrestrial broadcast system；The descending MAC of Signalling exchange processes the package mode adopting GPRS compatible, it is packaged into the data traffic information bag of corresponding digital multimedia broadcasting system again, these information bags are sent in time by broadcasting service time slot and two-way services descending time slot, to improve the real-time of Signalling exchange.
nullThe invention have the advantages that protection existing digital broadcast terminal investment while existing DTV (or multimedia) broadcast system Two-way can being upgraded，Existing terminal need not be upgraded and still can be received digital broadcast television business，Up passback aspect，Utilize GSM/GRPS/EDGE mature technology basis，Adopt compatible GPRS/EDGE wireless uplink passback technology，Carry out suitability amendment to simplify，Two-way through low cost is upgraded and can be supported interaction broadcast and wireless broadband business，Simultaneously bi-directionally change system and can realize One-to-All Broadcast、The fusion transmission of interaction broadcast and two-way broadband business，Broadcast base station great Ta great district is utilized efficiently to cover advantage and small and medium-sized cities、Rural area, suburb and area, island stop the better feature of transmission condition without high building interference，By building Unicasting broadband emerging system，Towards small and medium-sized cities、Rural area, suburb and island provide low cost interaction broadcast and wireless broadband services.
In a word, the present invention utilizes and broadcasts the Industrial Resources ripe with the two big industries that communicate and technology, realize broadcast to merge on the level of the transport layer with wireless broadband communication, modern digital broadcast system spectrum aboundresources and the high feature of information transfer efficiency can be played, the up passback technical advantage of maturation of present wide-band communication system can be combined with again, the Interaction return path of flexibility and reliability is provided for broadcast system, wireless broadband Internet access function is provided at lower cost, supports asymmetric broadband connections and interaction broadcast mixed service that upstream and downstream bandwidth demand difference is bigger.In a word, unidirectional terrestrial broadcast system upgrading can be the broadcast broadband emerging system supporting One-to-All Broadcast, interaction broadcast and broadband access by the present invention, wireless backhaul channel can not only be provided to realize wide-band bidirectional business, and also can strengthen terrestrial broadcasting frequency range utilizes motility and efficiency simultaneously.
Accompanying drawing explanation
Fig. 1 is the mobile multimedia/television broadcasting WiMAX UNE architectural framework of the present invention；The descending superframe structure (for CMMB) of the Two-way system of Fig. 2 present invention；
The Two-way system uplink/downlink frames structure (frame is extended for 4.808ms for descending compatible CMMB, up compatible GRPS) of Fig. 3 present invention；
The mutual descending time slot frame structure of Two-way system broad (for compatible CMMB broadcast downstream) of Fig. 4 present invention；
The CMMB Two-way system multiplexing of Fig. 5 present invention and MAC fusion protocol trestle structure (CMMB broadcast downstream, GPRS is up).
Detailed description of the invention
Below in conjunction with accompanying drawing, present disclosure is described in further detail.
Wireless broadband communication technology is merged by the present invention with terrestrial television/multimedia broadcasting techniques, both broadcast system spectrum aboundresources and the high feature of multimedia data contents descending distribution efficiency had been played, utilize again the advantage of the support transmitted in both directions of ripe broadband communications technologies, the return path of flexibility and reliability is provided for broadcast system, so that low cost supports the broadband wireless access of non-symmetrical service, and making existing broadcast terminal can need not upgrade and can use original broadcasting service in Two-way system, the upgrading of simple low cost can support interaction broadcast and WiMAX fused business.
For above-mentioned purpose, the present invention devises terrestrial television/multimedia broadcasting Two-way system architecture, base station side adopts software and radio technique to complete wireless backhaul reception and processes, devise wireless backhaul mode up for compatible GPRS/EDGE and physical channel structure, including corresponding with Two-way system descending physical transfer frame slot to adaptation method, compatibility GRPS/EDGE up passback physical layer and wireless link RLC/ medium access MAC layered protocol structure thereof with 200KHz bandwidth partition wireless backhaul channel, compatible time division multiple acess multiplexing tdma frame up for GPRS/EDGE.Devise the descending MAC/MUX layer fusion structure that broadcast is merged with broadband.
Main contents of the present invention include: system architecture designs, and physical layer merges transmission design and MAC/MUX Combined design.Detailed design thought and method combination are embodied as example and are illustrated.
For achieving the above object, the present invention provides a kind of method by DTB Digital Terrestrial Broadcasting system bidirectional, the method realizes broadcast and merges on the level of the transport layer with wireless broadband communication, described Two-way method is: DTB Digital Terrestrial Broadcasting downlink transfer and GPRS uplink are combined, continue to use received terrestrial digital broadcasting transmission means channel physical layer is descending, and increase wireless backhaul up channel, described wireless uplink return path is available 200KHz bandwidth idle channels, and described uplink and downlink adopt asymmetric frequency division duplex FDD mode.
Two-way with existing CMMB system turns to a kind of detailed description of the invention that embodiment is Two-way method of the present invention; the inventive concept adopting the present invention can also be used for other digital terrestrial television or the Two-way of digital multimedia broadcasting system and wireless broadband communication fusion, and such equivalent replacement also belongs to scope of patent protection of the present invention.Two-way system architecture
China Mobile multimedia broadcasting CMMB WiMAX emerging system (or Two-way system) is on the basis of existing CMMB one-way system CMMB, by increasing the wireless backhaul of the up compatibility of GPRS/EDGE in head-end system and terminal unit and supporting the subsystem of two-way broadband interactive service and build.
The principle of the physical layer of descending compatible mobile multimedia broadcast system is followed in the design of Two-way emerging system, simultaneously because the multiplex layer MUX of CMMB one-way system (being equivalent to the descending MAC layer of two-way communication) only has simple multi-service broadcasting multiplex function, therefore the MAC layer with reference to two-way broadband wireless communication system is extended, realize descending MAC and broadcasting multiplex MUX to merge, to support broadcast and two-way services.
The CMMB Two-way network architecture of the present invention, as it is shown in figure 1, wherein broadcast and provided by same base with data service, is broadcasted consistent with the power grade of business downlink data, is supported that largest cell radius is 60KM.
Two-way network architecture is mainly made up of base station, gateway server, broad access network gate, media server, scheduling of resource center and customer data base.
(1) base station comprises digital broadcasting and wireless backhaul air interface physical layer, MAC layer function, completes broadcast data and issues and the function such as interaction data transmitting-receiving, business mapping, convergence, power control, network insertion and initialization.
(2) gateway server is responsible for authentication and network address configuration.
(3) broad access network gate is responsible for broadband access, resource control and management etc..
(4) media server is responsible for providing broadcast, program request, is pushed away and broadcast/the localization storage of the media content such as transmission service and broadcasting.
(5) broadcast and the scheduling of resource of data service, content distribution are responsible in scheduling of resource center.
(6) customer data base comprises user-network access data and service customizing information, is used for managing customer service.
Physical layer design
Broadcast and the mutual time-multiplexed mode of descending employing in broadband in CMMB Two-way system, this multiplexing structure is conducive to broadcasting service and the independent operation of broadband wireless access business, it is also possible to compatible existing mobile multimedia broadcast system to the full extent.
In order to flexible configuration broadcast and the mutual time division multiplex relation in broadband, with the two-way example that turns to of CMMB system, the superframe structure of design Two-way system is as shown in Figure 2.Superframe duration is 1s, is divided into 40 time slots, each time slot 25ms.Broadcast and broadband divide alternately in units of 25ms time slot, in order to ensure that wide-band bidirectional business has good real-time, limit the time slot of configuration continuously less than 3.
First 25ms time slot of each descending superframe is defined to time slot, the configuration information of this time slot broadcast transmission Two-way broadcast broadband emerging system, comprises time slot configuration information and the up-link configuration information of broadcasting service and wide-band bidirectional business in current super frame.After a certain broadcast program is arranged into the assigned timeslot position of superframe, it will keep identical position in each superframe until broadcast next time and the scheduling of wide-band bidirectional service resources are repartitioned.Owing to only issuing broadcast and wide-band bidirectional business time-slot division information in superframe at first time slot of superframe, for traditional mobile multimedia broadcast receiving terminal, need to wait until first time slot of next superframe, can start receive system configuration information and select to receive multimedia broadcasting according to configuration information.
For Two-way system terminal, Network access delay is caused in order to avoid waiting next frame superframe to arrive, the present invention designs each wide-band bidirectional business time-slot and comprises the instruction information of next wide-band bidirectional business time-slot, Two-way system terminal is when search superframe goes on the air time slot failure, the mutual time slot in broadband is searched in trial, after it is successfully searched a mutual time slot in broadband, the mutual gap information in next broadband can be passed through and progressively know the mutual time slot in broadband subsequently, make terminal need not wait for next superframe to arrive, just can carry out broadband to access alternately, thus accelerating network insertion process, avoid operating long lasting for web search, reduce power consumption of terminal.
This superframe structure has two advantages: (1) broadcast and data business time-slot can flexible configuration, and dynamic change, the time granularity of change is 1s；(2) this superframe design makes existing mobile multimedia broadcast receiving terminal can continue to the broadcast in Two-way system, has backwards capability.
At broadcast and mutual broadband downstream time slot, the downlink channel transmission physical layer of existing ground digital television broadcast (such as CMMB) is continued to use in physical layer descending direction.In time slot, base station sends broadcast service data, but increases broadcast and broadband interactive data service time slot division information in the system configuration information of superframe header 25ms time slot per second and need to notify the system-level up return path configuration information (such as upstream channel frequency, uplink random access slot and delay) of all terminals.
The mutual descending time slot in broadband, except the mutual downlink data in transmission broadband, the configuration control information of relevant to particular terminal and business broadband interactive channel configuration control information also gap transmission, this category information and the up passback of GPRS/EDGE at this moment has cooperated up-downgoing channel resource allocation manager between different terminals and business.
The up upstream direction of physical layer adopts software and radio technique in base station side, in order to system can extend the multiple passback mode of support.Channel dividing mode for compatible existing multiple radio and television and communication system, adopting 200KHz bandwidth is that unit divides return path, up passback adopts the uplink mode of compatible GPRS/EDGE, from wireless link RLC/MAC to channel coding modulation PHY, adopt and GPRS/EDGE compatible protocol.
200KHz divides the channel being easy to compatible FM and secondary communication system GSM and divides, and utilizes the disposal ability of PC and existing intelligent terminal CPU can realize return path signal simultaneously and sends Base-Band Processing.Under 200KHz bandwidth passback mode, area, available vast Small Urban idle frequency modulation broadcasting FM frequency range and unlicensed band in a large number, constituted Two-way system with FDD duplex mode and existing terrestrial broadcast system.200KHz returns mode and adopts the up technology of compatible GPRS/EDGE base band, and time division multiple acess TDMA is in conjunction with frequency division multiple access FDMA access way in distribution according to need, it is simple to utilize industry mature technology.
nullTerminal set up GPRS/EDGE compatibility up channel needed for signaling and business transmission configuration control information (such as available return path frequency、Distribute with the ascending time slot for business datum for controlling management、Stochastic accessing and access allow to confirm、Paging information etc.) it is sent by descending GPRS channel in the GPRS/EDGE system of original standard，In this emerging system，Only with the ascender that GPRS/EDGE is compatible，The system configuration information that terminal is set up in the head 25ms frame of the system-level up channel configuration control essential information 1s superframe by CMMB needed for initial uplink channel continues to use the descending transmission of digital broadcast television transmission channel，Control information is configured according to system-level up channel，After setting up the compatible data feedback channel of GPRS/EDGE by random access request/receiving process，System base-station and terminal utilize mutual broadband downstream passage and GPRS data feedback channel exchange service data information and carry out the service channel that the Signalling exchange of necessity is set up with maintenance management.
As follows about downstream transmission time synchronizing.Two-way for CMMB system is upgraded, and down physical layer transmission is divided into and sends by 25ms/ frame, has transmission frame synchronizing information in each 25ms frame header.First the synchronizing information of the first 25ms frame of CMMB every superframe second is obtained when terminal starts to access, receive and resolve configuration information in first 25ms frame, obtain broadcast downstream time slot, the mutual descending time slot in broadband, upstream channel parameter, the system common configuration information such as uplink random access slot, set up Tong Bu with downlink transfer 25ms frame head, with first descending 25ms frame head synchronizing information per second for benchmark, offset a preset time backward (such as 30ms, the system configuration information notice issued in transmission frame by first 25ms broadcast is sent), as 52 TDMA multiframe start times of up GPRS/EDGE basic transfer unit, corresponding 1 second of 52 up TDMA multiframes of 4 groups of continuous print.nullUplink frame structure is as follows with compatible GPRS/EDGE compatibility method: every 52 TDMA multiframes constitute the up logic channel of GPRS/EDGE and map distribution elementary cell to physical channel，Duration is extended for 250ms by 52 TMDA frame * 4.615ms/ frame=240ms of original standard GPRS/EDGE，This duration is corresponding with 10 25ms downlink frame，Be equivalent to each up tdma frame duration and increased to 4.808ms by original 4.615ms，Increase part distributes to time slot 0 (the i.e. Time-slot0 of tdma frame，TS0)，When TS0 is arranged to transmission uplink random access sequence，The duration that TS0 increases is for expanding the protection of Stochastic accessing time delay，When TS0 is for transport service or mutual signaling，Then postpone (4.808-4.615) ms=193us to send，Be equivalent to the idle protective time slot added at TS0 time slot head.
Owing to all uplink random access burst sequences of emerging system are sent by time slot TS0, originally standard GPRS/EDGE system single base station maximal cover radius is 35KM, this radius is determined by random access time slot TS0 and the Stochastic accessing burst sequences protection duration of gprs system, after expanding TS0 time slot, the delay protection increased allows bigger Stochastic accessing (being used for finding range) round-trip transmission to postpone, base station covering radius correspondingly expands 35km+ (4.808-4.615) ms*300M/ms (i.e. the light velocity)/2=64km to, consider to hold the Stochastic accessing process delay that distinct device realizes, taking maximal cover radius is 60km, it is suitable for efficiently covering small and medium-sized cities and suburb, rural area on a large scale.
Above-mentioned GPRS/EDGE compatibility uplink mode is for building the method for synchronizing time of the return path of CMMB, being applied equally to build the return path of terrestrial television GB DTTB/DAB and DVB-TH/T2 system, simply GPRS/EDGE is up does a small amount of adjustment with descending time slot corresponding relation.Such as, with DAB broadcast in conjunction with time, DAB broadcast downstream divides transmission frame time slot with 24ms, 48ms or 96ms, 52 TDMA multiframe time span 240ms and DAB broadcast downstream frame slots of GPRS uplink ultimate unit can be completely corresponding, do not adjust up tdma frame duration, correspondingly, the up covering radius in conjunction with the broadcast broadband emerging system support of DAB broadcast downstream realization of GPRS is identical with GSM/GPRS system, i.e. 35KM.With GB DTTB in conjunction with time, owing to DTTB transport layer has 125ms superframe structure, two superframes be 250ms, GPRS/EDGE compatible up in connection time downstream transmission time slot correspondence to adjust mode identical with the above-mentioned embodiment in conjunction with CMMB.
Up passback in conjunction with existing ground digital television broadcast and compatible GPRS/EDGE, it may be achieved Digital Terrestrial Television Broadcast and the fusion of the up mature technology of GPRS/EDGE, is suitable for the asymmetric wide-band bidirectional business that big bandwidth is descending and smaller strip width is up alternately.
Ground digital multimedia/television broadcasting system adopts above-mentioned asymmetric frequency division duplex FDD mode to upgrade to bilateral system, only need to increase corresponding passback holding equipment and existing terrestrial television/multi-media broadcasting system multi-business multiplexing device protocol software carries out upgrading is support that the fusion protocol that broadcasting service multiplexing MUX and broadband interaction data medium access control MAC can support two-way services at existing DTV/multi-media broadcasting system head end.Head-end digital multimedia/equipment such as television broadcasting manipulator and transmitter remains unchanged, existing digit TV/multi-media broadcast terminal continues to broadcasting service not to be affected by Two-way upgrading, and novel two-way interactive terminal increases supports compatible wireless backhaul mode up for GPRS/EDGE.
In FDD duplex mode, one descending 8MH channel only configuration can use a 200KHz bandwidth channel can set up the data feedback channel of broadband interactive broadcast systems for wireless backhaul, when downlink channel is positioned at time slot, user still can carry out upstream data transmission at uplink band, as shown in Figure 3.
When this method is for CMMB system Two-way, mutual broadband downstream physical layer compatibility CMMB downlink broadcast physical layer, adopt 25ms time slot framing.Mutual time slot frame is used for transmitting mutual frame control head (FCH), uplink-downlink configuration information (DL-MAP, UL-MAP), and other MAC layer controls information and mutual broadband services downlink data, the configuration information of the mutual descending time slot in broadband issues the bandwidth allocation information of several uplink interaction time slots thereafter.The downlink information of mutual time slot is broadcasted packaging multiplexing with CMMB data and is issued.As shown in Figure 4.
In order to reduce wide-band bidirectional business and signaling delay, except limit the time slot of continuously configuration less than 3 except, the downlink broadcast time slot of mutual broadband broadcast emerging system and the transmission of mutual broadband downstream time slot select low time delay interleaving mode.
When downlink broadcast services band is roomy, time slot need to be taken more than 3 or when above-mentioned mutual time slot configuration cannot meet mutual requirement of real time, for requiring demand service interactive command and the mutual signaling of system administration that time delay is little, it is possible to be inserted in broadcasting service time slot as real-time interaction order and signaling data and issue as additional mutual downlink data.
The upgrading of above FDD duplex mode Two-way is little to the amendment of existing broadcast system, is conducive to Two-way system deployment.The broadcast system Two-way starting stage, a descending pairing one 200KHz upstream channel of distribution that has only to of 8MHz channel can build two-way broadband interactive system.Increase with two-way interactive broadband services, adopt and configure multiple 8MHz combinations of channels and be downlink channel group and multiple 200KHz combinations of channels is up return channel group, to increase Two-way system upstream and downstream bandwidth capacity.
The design of MUX/MAC layer is merged in broadcast and mutual broadband
The multiplexing MUX layer of the mobile multimedia broadcast system of one-way transmission has simple efficient multiplexing structure to control data framing, simple in construction, overhead is little, and in order to provide the whole network broadcasting service and broadband wireless access business, the media access control layer (MAC) of CMMB Two-way system needs have the functions such as complete data framing, network insertion and bandwidth distribution.It is illustrated in figure 5 CMMB Two-way system MUX and MAC fusion protocol trestle structure.MAC_B is base station side, and MAC_T is end side.MUX system configuration information and broadcasting service map directly to time slot 0 and the broadcasting service time slot of physical layer transmission frame.The downlink data of two-way services such as IP data and Signalling exchange is mapped to physical layer alternating transmission time slot through MAC package, CMMB multiplexing and encoding.The upstream data of two-way services and Signalling exchange adopts the MAC package mode of the up compatibility of GPRS/EDGE to process.The MAC package of downlink service data processes and adopts the data broadcasting packages mode of CMMB CMMB and broadcasting service multiplexing to issue, and the descending MAC layer of Signalling exchange adopts MAC layer package compatible for GPRS to be issued by CMMB data broadcasting packages multiplexing after processing.Application layer includes two large divisions, and Part I is broadcasting service, including audio-video-frequency broadcast, data broadcast and electron service instruction；Part II includes the business such as internet data and interaction broadcast.IP-based business datum is sent to mobile terminal by physical layer and radio circuit by MAC/MUX fused layer in the channel time slot of distribution.For compatible existing mobile multi-media broadcast terminal, in base station end for broadcasting service, broadcasting service bag is assembled into broadcasting multiplex code stream with traditional broadcast multiplexing MUX frame structure, then according to the modulation specified of broadcast configuration information and coded system are transmitted at corresponding time slot；When user side receives broadcasting service, its broadcast codes stream received at respective broadcast time slot demultiplexes, and the audio frequency and video of acquisition and data content is directly submitted to application layer and presents to user.
It should be noted that the embodiment of present invention described above and and unrestricted.It will be understood by those of skill in the art that any amendment to technical solution of the present invention or the equivalent replacement spirit and scope without departure from technical solution of the present invention, it all should be encompassed in scope of the presently claimed invention.
Claims (8)
1. the method by DTB Digital Terrestrial Broadcasting system bidirectional, the method realizes broadcast and merges on the level of the transport layer with wireless broadband communication, described Two-way method is: DTB Digital Terrestrial Broadcasting downlink transfer and GPRS/EDGE uplink are combined, continue to use received terrestrial digital broadcasting transmission means channel physical layer is descending, and increase wireless backhaul up channel, described wireless backhaul up channel is available 200KHz bandwidth idle channels, and described uplink and downlink adopt asymmetric frequency division duplex FDD mode；
When described DTB Digital Terrestrial Broadcasting system is CMMB system, up-downgoing carries out time synchronized in the following manner；
Two-way for CMMB system is upgraded, and down physical layer transmission is divided into and sends by 25ms/ frame, has transmission frame synchronizing information in each 25ms frame header；First the synchronizing information of the first 25ms frame of CMMB every superframe second is obtained when terminal starts to access, receive and resolve configuration information in first 25ms frame, obtaining system common configuration information, described system common configuration information comprises broadcast downstream time slot, the mutual descending time slot in broadband, upstream channel parameter and uplink random access slot；Set up the time synchronized with downlink transfer 25ms frame head, namely with first descending 25ms frame head synchronizing information per second for benchmark, offset a preset time backward, transmit the time started of elementary cell that is 52 tdma frame as up GPRS/EDGE, corresponding 1 second of 52 up tdma frames of 4 groups of continuous print；Uplink frame structure is as follows with GPRS/EDGE compatibility method: every 52 tdma frames constitute the up logic channel of GPRS/EDGE and map distribution elementary cell to physical channel, duration is extended for 250ms by 52 tdma frame * 4.615ms/ frame=240ms of original standard GPRS/EDGE, this duration is corresponding with 10 25ms downlink frame, be equivalent to each up tdma frame duration and increased to 4.808ms by original 4.615ms, increase part distributes to the time slot 0 i.e. TS0 of tdma frame, and described tdma frame comprises 8 time slots；
The compatible up passback of above-mentioned structure GPRS/EDGE and the method for synchronizing time of CMMB system, be equally applicable to the time synchronized setting up the up return path of GPRS/EDGE with DTTB, digital audio/multimedia terrestrial broadcasting and DVB-TH/T2 system bidirectional base station；When with national standard digital television terrestrial broadcasting in conjunction with time, owing to the transport layer of national standard digital television terrestrial broadcasting has 125ms superframe structure, two superframes are 250ms, thus downstream transmission time synchronizing method up with above-mentioned GPRS/EDGE in conjunction with CMMB system time adjustment mode identical；nullWhen with digital audio/multimedia terrestrial broadcasting broadcast in conjunction with time，Broadcast downstream is with 24ms、48ms or 96ms transmission frame divides time slot，The integral multiple of 52 tdma frame duration 240ms of GPRS uplink ultimate unit and digital audio/multimedia terrestrial broadcasting downlink frame time slot can be completely corresponding，Do not adjust up tdma frame duration，Every 480ms or 960ms of broadcast base station sends broadcast and the two-way channel configuration information of system，First the configuration information obtaining this transmission frame is searched when terminal accesses，Obtain system common configuration information，Described system common configuration information comprises broadcast downstream time slot、The mutual descending time slot in broadband、Upstream channel parameter and uplink random access slot，Set up and base station down transmission synchronized relation，With system configuration information transmission frame broadcast moments for benchmark，Offset a preset time backward，Starting point as up 52 tdma frames of GPRS/EDGE basic transfer unit，Thus setting up and maintain the time synchronized corresponding relation of downstream transmission frame.
2. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, it is characterised in that described method also comprises the steps of:
The up media access control MAC of two-way services and signaling adopts GPRS compatibility mode, the descending MAC layer package of two-way services adopts corresponding DTB Digital Terrestrial Broadcasting system data broadcasting service package multiplexing process mode, the descending MAC of Signalling exchange processes the package mode adopting GPRS compatible, it is packaged into the data traffic information bag of corresponding digital multimedia broadcasting system again, the information bag comprising downlink signaling message is sent in time by broadcasting service time slot and two-way services descending time slot, to improve the real-time of Signalling exchange.
3. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, it is characterized in that, time division multiplexing mode is adopted when down going channel transmits broadcast downstream business, two-way services downlink data and Signalling exchange downlink data, the downlink data of broadcasting service and two-way services takies different descending time slot, and Signalling exchange downlink data sends with time slot and two-way services time slot.
4. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, it is characterized in that, one or more 200KHz bandwidth channels that described wireless backhaul up channel utilizes in digital broadcast base stations coverage in the radio band of idle ground are transmitted, by increasing wireless backhaul sending module in digital broadcast receiving terminal side and increasing the realization of wireless backhaul receiver module in digital broadcast base stations side.
5. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 4, it is characterised in that described passback mode up for wireless backhaul up channel compatibility GPRS/EDGE.
6. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 5, it is characterized in that, described wireless backhaul up channel adopts demand assigned time division multiple acess TDMA to realize wireless uplink passback access, wireless backhaul physical layer and GPRS/EDGE uplink protocol-compliant in conjunction with frequency division multiple access FDMA.
7. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 3, it is characterized in that, the downlink data of described broadcasting service and two-way services carries out time-division slot based on time division multiplex and merges transmission process, merges the media access control layer/multiplex layer after transmission and has data framing, network insertion and bandwidth distribution function.
8. the method by DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, it is characterised in that the method for CMMB system Two-way is specifically comprised:
Physical layer continues to use CMMB terrestrial broadcast transmission mode in the downstream direction, and up direction adopts GPRS/EDGE physical layer compatibility mode；
MAC layer processes as follows: the up direction MAC of two-way services and Signalling exchange adopts GPRS/EDGE compatible processing mode, two-way services down direction MAC layer adopts CMMB data broadcast processing mode, and two-way services upper layer protocol data is packaged into CMMB data broadcasting protocols bag and issues；
The descending MAC of Signalling exchange adopts GPRS compatibility package mode, then is packaged into CMMB data broadcast compatible information bag, and the information bag comprising downlink signaling message is sent in time by time slot and mutual time slot, to improve the real-time of signaling.
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