CN103108213A - Method for enabling digital ground multimedia broadcasting system to be bi-directional - Google Patents
Method for enabling digital ground multimedia broadcasting system to be bi-directional Download PDFInfo
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Abstract
The invention provides a method and a system for enabling a digital ground multimedia broadcasting system to be bi-directional. The method combines a digital ground broadcasting downlink with a general packet radio service (GPRS) compatible uplink. In a channel physical layer, the downlink continues to use a digital ground broadcast transmission mode to increase a wireless uplink, and the uplink utilizes one or a plurality of 200KHz bandwidth frequency channels of an idle ground wireless transmission frequency range and uses a GPRS uplink transmission mode. The uplink and the downlink belong to asymmetric frequency division duplex modes. Above the physical layer, media access control of broadcast multiplex and bi-directional bandwidth carries out integration design, and broadcasting services, broadband services and signaling data of the downlink carry out time division multiplexing to a downlink transmission channel. Through utilization of the 200KHz frequency channel, the method upgrades a one-way digital broadcasting system to an interactive broadcast and broadband access integration system, supports asymmetric bi-directional services of a broadband downlink and a medium-small bandwidth uplink, and is suitable for providing interactive broadcast and wireless broadband integration services to suburbs, villages and middle-sized and small cities in low cost.
Description
Technical field
The present invention relates to received terrestrial digital broadcasting (TV or multimedia broadcasting) and terrestrial wireless broadband technology field, for terrestrial television/multimedia broadcasting net Two-way and WiMAX access integration technology, namely the invention provides a kind of method with the digital ground multimedia broadcast system bidirectional especially.
Background technology
Digital multimedia/television broadcasting mainly via satellite, three kinds of transmission meanss such as wire cable and terrestrial wireless realize.The ability of terrestrial wireless broadcast and mobile reception convenient with its unique reception can satisfy the Modern Information based Society people whenever and wherever possible for the demand of information.
DTB Digital Terrestrial Broadcasting of the present invention system comprises ground TV broadcast system and the multimedia broadcasting that fixed reception and portable mobile receive.In China, mainly comprise the China Mobile multimedia broadcasting CMMB of system, the DMB T-DMB and the digital terrestrial television DTTB of system that realize in the terrestrial wireless mode.
At present, formed three large ground digital television broadcast transmission standards abroad, i.e. the ISDB-T standard of the DVB-T standard in the ATSC standard of the U.S., Europe, Japan, the U.S. adopts single carrier mode, and Europe and Japan be orthogonal frequency pair OFDM multi-carrier transmission pattern.
The research of terrestrial DTV is formally carried out from China in 1996 in the inland of China, and has formulated national digital ground TV broadcast standard DTTB in August, 2006, and this standard has merged multicarrier and two kinds of transmission modes of single carrier.
Domestic portable hand-held TV for broadcast system mainly contains the Mobile Multimedia Broadcasting standard C MMB that General Bureau of Radio, Film and Television releases.China Mobile multimedia broadcasting standard C MMB is based on the terrestrial transmission solution of OFDM technology; in transport layer with reference to DVB-T and DAB/T-DMB; stipulated that the working channel bandwidth is 8MHz and two kinds of patterns of 2MHz; adopt respectively 4K subcarrier and 1K subcarrier OFDM+BPSK/QPSK/16QAM modulation system; the unification of recycling-guard prefix is long for the 1/8OFDM symbol; chnnel coding adopts RS and LDPC scheme for combining, and the transmission capacity that is up to 16Mbps can be provided under the 8MHz pattern.
Along with integrated services are constantly goed deep into, traditional unidirectional television broadcasting has been difficult to satisfy user's demand, and broadcasting user wishes to use interactive service, further, wishes to obtain mutual multimedia broadcasting and broadband connections converged services.Provide the interactive TV business along with the enforcement of the integration of three networks spreads out by the cable digital TV broadcast mode, provide the interactive TV business still rare in the terrestrial wireless broadcast mode, only have at present Europe to formulate two-way interactive terrestrial DTV standard DVB-RCT.Mostly adopt the mode by mobile communications network that return path is provided in industry, this mode is crossed over different network systems and different operators, needs the very long connect hours, and the operation and maintenance cost is high.
Broadband radio multi-media (Broadband Wireless Multimedia, the BWM) standard based on " broadcasting ", " communication " and " WiMAX access " integration of three networks is formulated in the formal project verification of in September, 2006 of whole nation Language Information Technology Standardization technical committee.The BWM network is a Wideband mobile radio network that merges mobile tv network and BRAN technical characterictic.Aspect the Radio Access Network framework, BWM has considered the networking feature of mobile tv network and BRAN, both support the Da Qu pattern that large base station+little base station covers of traditional broadcast television network, supported again the cell pattern that the complete little base station take beehive net as feature covers.
Relative simulated television, terrestrial DTV has the higher availability of frequency spectrum.Along with analog television broadcast is changed to Digital Television, if originally the radio and television frequency range all is used to provide visual broadcast service, number of programs will be multiplied, or only need use the television program that as much can be provided below half of original shared frequency range, will go out some resources of frequency range the free time so.And meanwhile, various wireless broadband communication technical developments make available frequency band more and more be difficult to arrange, the past high frequency of continuation such as 3GHz/5GHz development and face transmission covering inappositely, and the frequency range that suitable overland propagation the covers broadcast television service that is used for as most of in the VHF/UHF frequency range is communicated by letter with 2G.WiMAX seeks to share the TDD resource of frequency range of 3G always.First utilizes the wireless communication system standards IEEE 802.22 of cognitive radio in the world, utilizes by aware dynamic that in 54MHz～862MHz VHF/UHF frequency range, idle radio and television frequency range realizes fixing wireless area network.For the idle frequency range of the high-quality of surface TV traditionally, the urgent hope of wireless broadband communication industry obtains and uses, 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 divided channel take 6/7/8MHz as bandwidth, for the broadband connections industry need to use the serial frequency range of a plurality of free time up to the even higher working frequency range width of 20MHz, reduced opportunity available.In addition, the traditional tv frequency band is reclassified as broadband wireless communications frequency range way used, is helpless to the low-cost demand that satisfies mutual broadcasting and broadband connections converged services.Mutual broadband services is the same with digital broadcasting service gradually, and the popularization public service need to be provided, eliminate " digital divide ", and with information right to know, right to choose and the expression power of low-cost ensure public, be the inevitable demand that informationized society continues balanced development.For responding this type of demand cry, in the 4G concept of WiMAX industry, plan to merge in Wireless Broadband Communication Systems as LTE/IMT-ADVANCED and support broadcast capability, but cost efficiency is low.
GPRS and enhancing version (GPRS/EDGE) thereof develop based on the digital cellular communication system GSM of Global prevalence, by changing global system for mobile communications (GSM) into block exchange mode for lasting speech or data communication circuit exchange mode used, dynamically take as required wireless channel, only just use radio channel resource when reality transmits and receive, a user can take a plurality of wireless channels, and a plurality of 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 access TDMA, and 8 time slots form a tdma frame, and every slot transmission one road speech or data service provide 8 speeches or 9.6kbps～14.4kbps data channel.A plurality of time slots of GPRS use capable of being combined, message transmission rate can be up to 160kb/s.The enhanced edition EDGE of GPRS modulates on the basis at the GMSK that supports GPRS to continue to use GSM, increase and support 8PSK modulation mode, speed is brought up to 500kbps, and the follow-up evolution version of GPRS/EDGE will be supported more high order modulation such as 16QAM, 32QAM and multi-antenna technology, and flank speed is brought up to approximately 1Mbps.
The fusion of digital broadcasting and wide-band communication system is the developing direction of following broadcasting and wireless broadband system.There are pluses and minuses separately 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 can provide two-way services, there are the inefficient shortcoming of distribution in its micro-honeycomb structure and clean culture send mode.
The multimedia broadcasting that the user wishes to obtain to merge, broadcasting and broadband inserting service alternately.But utilize separately existing digital broadcasting technology or wireless broadband communication technology all can't effectively provide multimedia broadcasting, alternately broadcasting and the broadband access converged services, uniting the different technologies system and the operation system interface that use existing digital broadcasting and wireless broadband communication to relate to two large industries coordinates, inefficiency, cost is high.
Summary of the invention
The object of the invention is to, can't effectively provide the shortcoming of mutual multimedia broadcasting and broadband connections converged services for overcoming existing terrestrial broadcast system and Wireless Broadband Communication Systems, thereby a kind of method with the DTB Digital Terrestrial Broadcasting system bidirectional is provided.
The invention provides for achieving the above object a kind of method with the DTB Digital Terrestrial Broadcasting system bidirectional, the method realizes that broadcasting and wireless broadband communication merge on transport layer, described Two-way method is: DTB Digital Terrestrial Broadcasting downlink transfer and GPRS/EDGE uplink are combined, in the descending received terrestrial digital broadcasting transmission means of continuing to use of channel physical layer, 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 the 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 that adopts the GPRS compatibility, be packaged into again the data traffic information bag of corresponding digital multimedia broadcasting system, these packets of information that comprise downlink signaling message in time send by broadcasting service time slot and two-way services descending time slot, to improve the real-time of Signalling exchange.
In technique scheme, adopt time division multiplexing mode when described down going channel transmission 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 slots, and the Signalling exchange downlink data sends with time slot and two-way services time slot.
Optionally, described wireless uplink return path utilizes that the one or more 200KHz bandwidth channels in the radio band of idle ground carry out in the digital broadcasting base station range, realizes by increasing the wireless backhaul sending module in the digital broadcast receiving terminal side and increasing the wireless backhaul receiver module in the digital broadcasting base station side.The up passback mode of the compatible GRPS/EDGE of up passback mode of described 200KHz wireless backhaul channel.
Optionally, described wireless backhaul channel adopts demand assigned time division multiple access 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 multiplexing and merges transmission process, and the media access control layer/multiplex layer that merges after transmitting has data framing, network insertion and allocated bandwidth function.
In addition, the present invention also provides a kind of method with the CMMB system bidirectional, 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, and described method with the CMMB system bidirectional comprises: by head-end system and the terminal equipment wireless backhaul that increases the up compatibility of GPRS/EDGE and the subsystem of supporting the two-way broadband interactive service in the CMMB system; The physical layer of descending compatible mobile multimedia broadcast system, descending MAC layer and the CMMB broadcasting multiplex layer with two-way wireless communication merges simultaneously, to support broadcasting and two-way services; Described broadcasting and data service are provided by same base, broadcast unanimously with the power grade of data service downlink data, support that the largest cell radius is 60KM.
The invention provides a kind of CMMB Two-way system based on above-mentioned Two-way method, this system expands to the Two-way system based on the Two-way method of claim 7 with the CMMB of 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 that broadcast data issues and mutual bi-directional data transmitting-receiving, 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 broadcasting, program request or push away broadcast/the transmission service content carries out localization storage and broadcasts; Scheduling of resource and the contents distribution with data service is responsible for broadcasting in described scheduling of resource center; Described customer data base comprises user-network access data and service customizing information, is used for the leading subscriber business; Wherein, described CMMB Two-way system also comprises physical layer and MAC layer.
The physical layer of described CMMB Two-way system is continued to use CMMB terrestrial broadcasting transmission means on down direction, up direction adopts GPRS/EDGE physical layer compatibility mode.
The MAC layer of described CMMB Two-way system is processed 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 packet becomes CMMB data broadcast protocol package to issue; The descending MAC of Signalling exchange adopts the compatible package mode of GPRS, then is packaged into CMMB data broadcast compatible information bag, and these packets of information in time send by time slot and mutual time slot, to improve the real-time of signaling.
In technique scheme, adopt time division multiplexing mode when described down going channel transmission broadcasting service, two-way services and Signalling exchange downlink data, broadcasting service and two-way services downlink data take different descending time slots, and the Signalling exchange downlink data sends with broadcasting service and two-way services descending time slot.
Described wireless uplink return path utilizes that the one or more 200KHz bandwidth channels in the radio band of idle ground carry out in the digital broadcasting base station range, realizes by increasing the wireless backhaul sending module in the digital broadcast receiving terminal side and increasing the wireless backhaul receiver module in the digital broadcasting base station side.
One of optional passback mode is as follows, the up passback mode of the compatible GRPS/EDGE of the passback mode of described 200KHz wireless backhaul channel.Described wireless backhaul channel adopts demand assigned time division multiple access 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 the time-division slot physical layer based on time division multiplexing and merges transmission, and media access control layer and broadcasting multiplex layer merge, and complete data framing, network insertion and allocated bandwidth function.
MAC and the fusion of broadcasting multiplex layer comprise: the up MAC of two-way services and signaling adopts the 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 that adopts the GPRS compatibility, be packaged into again the data traffic information bag of corresponding digital multimedia broadcasting system, these packets of information in time send by broadcasting service time slot and two-way services descending time slot, to improve the real-time of Signalling exchange.
advantage of the present invention: protection existing digital broadcast terminal investment when can upgrade to existing Digital Television (or multimedia) broadcast system Two-way, existing terminal need not be upgraded still can the receiving digital broadcast television services, up passback aspect, utilize the GSM/GRPS/EDGE mature technology basic, adopt compatible GPRS/EDGE wireless uplink passback technology, carry out suitability and revise simplification, can support mutual broadcasting and wireless broadband business through Two-way upgrading cheaply, while, the Two-way system can realize One-to-All Broadcast, the fusion transmission of mutual broadcasting and two-way broadband business, utilize efficient advantage and the small and medium-sized cities of covering, broadcast base station Da Tada district, the better characteristics of transmission condition that stop are disturbed without high building in rural area, suburb and area, island, by building Unicasting broadband emerging system, towards small and medium-sized cities, rural area, suburb and island provide low-cost mutual broadcasting and wireless broadband services.
In a word, the present invention utilizes Industrial Resources and the technology of broadcasting and the two large industry maturations of communicating by letter, realize that broadcasting and wireless broadband communication merge on transport layer, can bring into play the high characteristics of modern digital broadcast system spectrum aboundresources and information transfer efficiency, again can be in conjunction with the ripe up passback technical advantage of utilizing present wide-band communication system, the mutual passback path of flexibility and reliability is provided for broadcast system, the WiMAX access function is provided at lower cost, supports asymmetric broadband connections and mutual broadcasting mixed service that upstream and downstream bandwidth demand difference is larger.In a word, the present invention can be with unidirectional terrestrial broadcast system upgrading for supporting One-to-All Broadcast, the broadcasting broadband emerging system of broadcasting and broadband access alternately, not only can provide the wireless backhaul channel to realize the wide-band bidirectional business, also can strengthen the terrestrial broadcasting frequency range simultaneously and utilize flexibility and efficient.
Description of drawings
Fig. 1 is mobile multimedia of the present invention/television broadcasting WiMAX UNE architectural framework; The descending superframe structure (take CMMB as example) of Fig. 2 Two-way of the present invention system;
Fig. 3 Two-way of the present invention system uplink/downlink frames structure (frame is extended for 4.808ms for descending compatible CMMB, up compatible GRPS);
The mutual descending time slot frame structure of Fig. 4 Two-way system broad of the present invention (take compatible CMMB broadcast downstream as example);
Fig. 5 Mobile Multimedia Broadcasting Two-way of the present invention system multiplexing and MAC fusion protocol trestle structure (CMMB broadcast downstream, GPRS is up).
Embodiment
Below in conjunction with accompanying drawing, content of the present invention is described in further detail.
The present invention is with wireless broadband communication technology and terrestrial television/multimedia broadcasting technological incorporation, the high characteristics of the descending distribution efficient of broadcast system spectrum aboundresources and multimedia data contents had both been brought into play, utilize again the advantage of the support transmitted in both directions of ripe broadband connections technology, the passback path of flexibility and reliability is provided for broadcast system, so that the low-cost broadband wireless access of supporting non-symmetrical service, and existing broadcast terminal can need not be upgraded can use original broadcasting service in the Two-way system, simple low-cost upgrading can be supported mutual broadcasting and WiMAX fused business.
For above-mentioned purpose, the present invention has designed terrestrial television/multimedia broadcasting Two-way system architecture, base station side adopts software and radio technique to complete the wireless backhaul reception ﹠ disposal, designed compatible GPRS/EDGE up wireless backhaul mode and physical channel structure, comprised with the 200KHz bandwidth and divide the up multiplexing tdma frame of time division multiple access of wireless backhaul channel, compatible GPRS/EDGE corresponding with Two-way system descending physical transfer frame slot to adaptation method, compatible GRPS/EDGE up passback physical layer and Radio Link RLC/ medium access MAC layered protocol structure thereof.Designed the descending MAC/MUX layer fusion structure that merge in broadcasting and broadband.
Main contents of the present invention comprise: Transmission Design is merged in system architecture design, physical layer and MAC/MUX merges design.The detailed design thought and method is illustrated in conjunction with concrete exemplifying embodiment.
For achieving the above object, the invention provides a kind of method with the DTB Digital Terrestrial Broadcasting system bidirectional, the method realizes that broadcasting and wireless broadband communication merge on transport layer, described Two-way method is: DTB Digital Terrestrial Broadcasting downlink transfer and GPRS uplink are combined, in the descending received terrestrial digital broadcasting transmission means of continuing to use of channel physical layer, 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 two-way embodiment of turning to existing CMMB system is a kind of embodiment of Two-way method of the present invention; adopt inventive concept of the present invention also to can be used for other digital terrestrial television or the Two-way of digital multimedia broadcasting system and wireless broadband communication fusion, such replacement that is equal to belongs to scope of patent protection of the present invention equally.The Two-way system architecture
China Mobile multimedia broadcasting CMMB WiMAX emerging system (or Two-way system) is on the basis of existing Mobile Multimedia Broadcasting one-way system CMMB, by increasing the wireless backhaul of the up compatibility of GPRS/EDGE and support the subsystem of two-way broadband interactive service to build in head-end system and terminal equipment.
The principle of the physical layer of descending compatible mobile multimedia broadcast system is followed in the design of Two-way emerging system, multiplex layer MUX (the descending MAC layer that is equivalent to two-way communication) due to the Mobile Multimedia Broadcasting one-way system only has simple multi-service broadcasting multiplex function simultaneously, therefore expand with reference to the MAC layer of two-way broadband wireless communication system, realize that descending MAC and broadcasting multiplex MUX merge, to support broadcasting and two-way services.
Mobile Multimedia Broadcasting Two-way network system framework of the present invention as shown in Figure 1, wherein broadcasting and data service are provided by same base, broadcast unanimously with the power grade of business downlink data, support largest cell radius is 60KM.
Two-way network system framework mainly is comprised 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 functions 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 broadcasting, program request, is pushed away and broadcast/media contents such as transmission service localization storage and broadcasting.
(5) scheduling of resource, the contents distribution with data service is responsible for broadcasting in the scheduling of resource center.
(6) customer data base comprises user-network access data and service customizing information, is used for the leading subscriber business.
Physical layer design
Broadcasting and the time-multiplexed mode of the mutual descending employing in broadband in Mobile Multimedia Broadcasting Two-way system, this multiplexing structure is conducive to the independent operation of broadcasting service and broadband wireless access business, also compatible existing mobile multimedia broadcast system to the full extent.
For can flexible configuration broadcasting and the mutual time division multiplexing relation in broadband, turn to example with the CMMB system bidirectional, design the superframe structure of Two-way system as shown in Figure 2.The superframe duration is 1s, is divided into 40 time slots, each time slot 25ms.Broadcasting and broadband are divided alternately take the 25ms time slot as unit, have real-time preferably in order to guarantee the wide-band bidirectional business, and the time slot that limits configuration continuously is no more than 3.
First 25ms time slot of each descending superframe is defined as time slot, this time slot broadcast transmission Two-way is broadcasted the configuration information of broadband emerging system, comprises time slot configuration information and the up-link configuration information of the interior broadcasting service of current superframe and wide-band bidirectional business.After a certain broadcast program was arranged into the assigned timeslot position of superframe, it will keep identical position in each superframe until broadcasting next time and wide-band bidirectional service resources are dispatched repartitions.Because first time slot at superframe issues broadcasting and wide-band bidirectional business time-slot division information in superframe, for traditional mobile multimedia broadcast receiving terminal, first time slot of next superframe need to be waited until, the receiving system configuration information can be begun and according to configuration information selective reception multimedia broadcasting.
for the Two-way system terminal, cause Network access delay for fear of waiting for the next frame superframe to arrive, the present invention designs the indication information that each wide-band bidirectional business time-slot comprises next wide-band bidirectional business time-slot, when the Two-way system terminal is gone on the air the time slot failure at the search superframe, to attempt the mutual time slot in search broadband, after it successfully searches a mutual time slot in broadband, can progressively know subsequently the mutual time slot in broadband by the mutual gap information in next broadband, next superframe arrives to make terminal not need by the time, just can carry out the broadband accesses alternately, thereby accelerating network access procedure, avoid continuing for a long time the web search operation, reduced power consumption of terminal.
This superframe structure has two advantages: (1) broadcasting and data service time slot can flexible configuration, and capable of dynamic changes, and the time granularity of change is 1s; (2) this superframe design makes existing mobile multimedia broadcast receiving terminal can continue to receive broadcasting in the Two-way system, has the backward compatibility ability.
At broadcasting and mutual broadband downstream time slot, the physical layer descending direction is continued to use the downlink channel transmission physical layer of existing ground digital television broadcast (as CMMB).In time slot, the base station sends broadcast service data, but increases broadcasting and broadband interactive data service time slot division information and need to notify the system-level up return path configuration information (as upstream channel frequency, uplink random access slot and delay) of all terminals in the system configuration information of per second superframe head 25ms time slot.
The mutual descending time slot in the broadband, except the mutual downlink data of transmission broadband, with the also gap transmission at this moment of broadband interactive channel configuration control information of particular terminal and traffic aided, the configuration control information of this category information and the up passback of GPRS/EDGE cooperatively interacts and completes the allocation manager of up-downgoing channel resource between different terminals and business.
The up upstream direction of physical layer adopts software and radio technique in base station side, so that system can expand the multiple passback mode of supporting.Channel division mode for the existing multiple radio and television of compatibility and communication system, adopting the 200KHz bandwidth is that unit divides return path, the uplink mode of compatible GPRS/EDGE is adopted in up passback, RLC/MAC modulates physical layer protocol to chnnel coding from Radio Link, adopts and the GPRS/EDGE compatible protocol.
200KHz divides the channel division of being convenient to compatible FM and two generation communication system GSM, utilizes simultaneously the disposal ability of PC and existing intelligent terminal CPU can realize that return path signal sends Base-Band Processing.Under 200KHz bandwidth passback mode, can utilize the vast Small Urban a large amount of idle FM broadcasting FM frequency ranges in area and exempt to authorize frequency range, with FDD duplex mode and existing terrestrial broadcast system formation Two-way system.200KHz passback mode adopts the up technology of compatible GPRS/EDGE base band, and TDMA is in conjunction with frequency division multiple access FDMA access way for the distribution according to need time division multiple access, is convenient to utilize the industry mature technology.
terminal is set up the required signaling of the compatible up channel of GPRS/EDGE and the control information of business transmission configuration (as available return path frequency, being used for control and management distributes with the ascending time slot that is used for business datum, random access and access allow to confirm, paging information etc.) be to send by descending GPRS channel in the GPRS/EDGE of original standard system, in this emerging system, only adopt the ascender of GPRS/EDGE compatibility, terminal is set up the required system-level up channel configuration control essential information of initial uplink channel and is continued to use the descending transmission of digital broadcast television transmission channel by the system configuration information in a 25ms frame of the 1s superframe of CMMB, according to system-level up channel configuration control information, after setting up the data feedback channel of GPRS/EDGE compatibility by random access request/admittance process, the mutual broadband downstream passage of system base-station and terminal utilization and GPRS data feedback channel reciprocal exchange of business data message and carry out the service channel that necessary Signalling exchange is set up with maintenance management.
As follows about the synchronous processing of up-downgoing transmission time.For the Two-way upgrading of CMMB system, the down physical layer transmission is divided into by the 25ms/ frame and sends, and in each 25ms frame header, the transmission frame synchronizing information is arranged.when beginning to access, terminal at first obtains the synchronizing information of the first 25ms frame of the every superframe of CMMB second, receive and resolve configuration information in first 25ms frame, obtain the broadcast downstream time slot, the mutual descending time slot in broadband, the upstream channel parameter, system's common configuration information such as uplink random access slot, set up and synchronize with downlink transfer 25ms frame head, take the first descending 25ms frame head synchronizing information of per second as benchmark, be offset backward a preset time (as 30ms, the system configuration information notice that issues in transmission frame by first 25ms broadcasting sends), as 52 TDMA multiframe start times of up GPRS/EDGE basic transfer unit, corresponding 1 second of 4 groups of continuous 52 up TDMA multiframes.uplink frame structure and compatible GPRS/EDGE compatibility method are as follows: every 52 TDMA multiframes consist of the up logic channel of GPRS/EDGE and distribute elementary cell to the physical channel mapping, 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 be increased to 4.808ms by original 4.615ms, increasing the time slot 0 of partly distributing to tdma frame (is Time-slot 0, TS0), when TS0 is arranged to transmission uplink random access sequence, the duration that TS0 increases is used for enlarging random access delay protection, when TS0 is used for transport service or mutual signaling, postponing (4.808-4.615) ms=193us sends, be equivalent to the idle protective time slot that increased at TS0 time slot head.
because all uplink random access burst sequences of emerging system send by time slot TS0, originally standard GPRS/maximum covering radius of EDGE system's single base station is 35KM, this radius is determined by random access time slot TS0 and the random access burst sequence protection duration of gprs system, after enlarging the TS0 time slot, the delay protection that increases allows larger random access (being used for range finding) round-trip transmission to postpone, the base station covering radius correspondingly expands 35km+ (4.808-4.615) ms*300M/ms (being the light velocity)/2=64km to, consider to hold the random access processing delay that distinct device is realized, getting maximum covering radius is 60km, be fit to efficiently cover small and medium-sized cities and rural suburb on a large scale.
The compatible uplink mode of above-mentioned GPRS/EDGE is used for the method for synchronizing time of the return path of structure CMMB, be applicable to too to build the return path of terrestrial television GB DTTB/DAB and DVB-TH/T2 system, just GPRS/EDGE is up does a small amount of adjustment with the descending time slot corresponding relation.For example, with DAB broadcasting in conjunction with the time, the DAB broadcast downstream is divided the transmission frame time slot with 24ms, 48ms or 96ms, 52 TDMA multiframe time span 240ms of GPRS uplink base unit can be fully corresponding with DAB broadcast downstream frame slot, do not adjust up tdma frame duration, correspondingly, the covering radius that GPRS is up to be realized in conjunction with the DAB broadcast downstream broadcasting broadband emerging system is supported is identical with the GSM/GPRS system, i.e. 35KM.When GB DTTB was combined, because the DTTB transport layer has the 125ms superframe structure, two superframes were 250ms, GPRS/EDGE compatible up with its in conjunction with the time the corresponding adjustment mode of up-downgoing transmission time slot identical with above-mentioned execution mode in conjunction with CMMB.
Up passback in conjunction with existing ground digital television broadcast and compatible GPRS/EDGE can realize the fusion of Digital Terrestrial Television Broadcast and the up mature technology of GPRS/EDGE, is fit to the descending and mutual up asymmetric wide-band bidirectional business of less bandwidth of large bandwidth.
Ground digital multimedia/television broadcasting system adopts above-mentioned asymmetric frequency division duplex FDD mode to upgrade to bilateral system, and only needing increases corresponding passback support equipment and existing terrestrial television/multi-media broadcasting system multi-business multiplexing device protocol software carried out upgrading can support two-way services for the fusion protocol of supporting the multiplexing MUX of broadcasting service and broadband interaction data medium access to control MAC at existing Digital Television/multi-media broadcasting system head end.The equipment such as head end digital multimedia/television broadcasting modulator and transmitter remain unchanged, existing digit TV/multi-media broadcast terminal continues receiving broadcast service and not affected by the Two-way upgrading, and novel two-way interactive terminal increases the up wireless backhaul mode of compatible GPRS/EDGE of supporting.
In the FDD duplex mode, a descending 8MH channel can only configure and use a 200KHz bandwidth channel to be used for the data feedback channel that wireless backhaul can be set up the broadband interactive broadcast systems, when downlink channel was positioned at time slot, the user still can carry out upstream data at uplink band and send, as shown in Figure 3.
When this method was used for the CMMB system bidirectional, the compatible CMMB downlink broadcast of mutual broadband downstream physical layer physical layer adopted the 25ms time slot to divide frame.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 control information and mutual broadband services downlink data, issue the bandwidth allocation information of several uplink interaction time slots thereafter in the configuration information of the mutual descending time slot in broadband.The downlink information of mutual time slot issues with CMMB data broadcast packaging multiplexing.As shown in Figure 4.
In order to reduce wide-band bidirectional business and signaling delay, except the time slot that limits continuous configuration is no more than 3, the downlink broadcast time slot of mutual broadband broadcasting emerging system and the transmission of mutual broadband downstream time slot are selected low time delay interleaving mode.
When descending broadcasting service band roomy, in the time of need taking time slot and surpass 3 or above-mentioned mutual time slot configuration and can't satisfy mutual requirement of real time, for requiring the little demand service interactive command of time delay and the mutual signaling of system management, can be used as real-time interaction order and signaling data and be inserted in the broadcasting service time slot as additional mutual downlink data and issue.
The upgrading of above FDD duplex mode Two-way is revised little to existing broadcast system, be conducive to the Two-way system and dispose.The broadcast system Two-way starting stage, descending needs pairing of a 8MHz channel distributes a 200KHz upstream channel can build the two-way broadband interactive system.Increase with the two-way interactive broadband services, adopting a plurality of 8MHz combinations of channels of configuration is that downlink channel group and a plurality of 200KHz combinations of channels are up passback channel group, to increase Two-way system upstream and downstream bandwidth capacity.
Broadcasting is merged the design of MUX/MAC layer with mutual broadband
The multiplexing MUX layer of the mobile multimedia broadcast system of one-way transmission has simple multiplexing structure efficiently and controls data framing, simple in structure, overhead is little, and for the whole network broadcasting service and broadband wireless access business are provided, the media access control layer (MAC) of Mobile Multimedia Broadcasting Two-way system need to have the functions such as complete data framing, network insertion and allocated bandwidth.Be illustrated in figure 5 as the Mobile Multimedia Broadcasting Two-way MUX of system 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 the mutual transmission time slot of physical layer 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 is processed the data broadcast package mode that adopts Mobile Multimedia Broadcasting CMMB and is issued with broadcasting service is multiplexing, and it is rear by multiplexing the issuing of CMMB data broadcast package that the descending MAC layer of Signalling exchange adopts the MAC layer package of GPRS compatibility to process.Application layer comprises the two large divisions, and first is broadcasting service, comprises audio-video-frequency broadcast, data broadcast and electron service instruction; Second portion comprises the business such as internet data and mutual broadcasting.The MAC/MUX fused layer is sent to mobile terminal by physical layer and radio circuit with IP-based business datum on the channel time slot of distributing.For the existing mobile multi-media broadcast terminal of compatibility, at the base station end for broadcasting service, the broadcasting service bag is assembled into the broadcasting multiplex code stream with the multiplexing MUX frame structure of traditional broadcast, and then modulation and the coded system according to the appointment of broadcast configuration information sends at the time slot of correspondence; When the user side receiving broadcast service, it carries out demultiplexing at the broadcast codes stream that the respective broadcast time slot receives, and the audio frequency and video that obtain and data content directly is submitted to application layer presents to the user.
Need to prove, embodiment of the present invention of above introduction and and unrestricted.It will be understood by those of skill in the art that any modification to technical solution of the present invention or be equal to substitute not break away from the spirit and scope of technical solution of the present invention, it all should be encompassed in claim scope of the present invention.
Claims (9)
1. method with the DTB Digital Terrestrial Broadcasting system bidirectional, the method realizes that broadcasting and wireless broadband communication merge on transport layer, described Two-way method is: DTB Digital Terrestrial Broadcasting downlink transfer and GPRS/EDGE uplink are combined, in the descending received terrestrial digital broadcasting transmission means of continuing to use of channel physical layer, 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.
2. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, is characterized in that, described method also comprises following steps:
The up media access control MAC of two-way services and signaling adopts the 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 that adopts the GPRS compatibility, be packaged into again the data traffic information bag of corresponding digital multimedia broadcasting system, the packets of information that comprises downlink signaling message in time sends by broadcasting service time slot and two-way services descending time slot, to improve the real-time of Signalling exchange.
3. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, it is characterized in that, adopt time division multiplexing mode when described down going channel transmission 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 slots, and the Signalling exchange downlink data sends with time slot and two-way services time slot.
4. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, it is characterized in that, described wireless uplink return path utilizes that the one or more 200KHz bandwidth channels in the radio band of idle ground carry out in the digital broadcasting base station range, realizes by increasing the wireless backhaul sending module in the digital broadcast receiving terminal side and increasing the wireless backhaul receiver module in the digital broadcasting base station side.
5. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, is characterized in that, the up passback mode of the compatible GRPS/EDGE of up passback mode of described 200KHz wireless backhaul channel.
6. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 5, it is characterized in that, described wireless backhaul channel adopts demand assigned time division multiple access 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 with the 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 multiplexing and merges transmission process, and the media access control layer/multiplex layer that merges after transmitting has data framing, network insertion and allocated bandwidth function.
8. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 1, is characterized in that, described DTB Digital Terrestrial Broadcasting system is the CMMB system.
9. the method with the DTB Digital Terrestrial Broadcasting system bidirectional according to claim 8, is characterized in that, described method with the CMMB system bidirectional specifically comprises:
Physical layer is continued to use CMMB terrestrial broadcasting transmission means on down direction, up direction adopts GPRS/EDGE physical layer compatibility mode;
The MAC layer is processed 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 packet becomes CMMB data broadcast protocol package to issue;
The descending MAC of Signalling exchange adopts the compatible package mode of GPRS, then is packaged into CMMB data broadcast compatible information bag, and the packets of information that comprises downlink signaling message in time sends by time slot and mutual time slot, to improve the real-time of signaling.
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