A kind of wireless multi-hop relay networking method that supports multi-media broadcasting service
Technical field
The present invention provides a kind of networking plan based on relaying specially at multi-media broadcasting service.This scheme promptly can be applicable to traditional cell mobile communication systems and emerging wireless broadband access system, as WLAN (wireless local area network), wireless MAN etc., also is applicable to wireless television system, also can be applicable to heterogeneous wireless communication system.
Background technology
Traditional cell mobile communication systems adopts honeycomb, but the 4th generation (4G) wireless communication system with superelevation data rate still adopts traditional honeycomb can have a lot of problems, main cause is: the first, and the transmission rate of 4G system is wanted high two ranks than the third generation (3G) system.Under the situation of specified transmission power level, symbol (bit) energy can be linear along with the raising of transmission rate and descend, and therefore, this demand will produce serious power problems.The second, for the frequency spectrum of 4G system granting will be positioned at more than the employed 2GHz frequency range of 3G system undoubtedly.And but the radio propagation of these frequency ranges is under non-sighting distance condition usually, and effect is on duty mutually, but but not the typical mode of operation of the current just city cellular communication of sighting distance condition.
Overcome the above problems, must significantly increase the density of base station, this can cause the quite high cost of arranging net, and if number of users does not increase with same speed, this cover solution cost is too high, the economic benefit shortcoming.In addition, cover in order to realize the whole network, necessary a large amount of layout base station, this network design to real system also is a challenge.In addition, consider that 4G will for the channeling that makes the next generation wireless communication system reaches 1 as far as possible, improve the spectrum efficiency of system based on the OFDM technology, adopt traditional honeycomb will face a lot of challenges.
How to reduce the interference of minizone, improve systematic function, be the focus of industry research always.Professional for multimedia broadcasting and multicast (MBMS), how guaranteeing can provide quality the business identical with speed in the zone of a base station services, is very important.
Present wireless communication system generally adopts the repeater to come extended coverage range, and along with the development of wireless self-organization network theory, for the ease of convenient and swift networking, and the survivability of enhancing Radio Link etc., the centralized Control Network architecture with multi-hop characteristic has also put forward.Relaying technique will occupy important function in the next generation wireless communication system.
The coverage that adopts relay station to come extended network is to come from the repeater development of legacy cellular mobile communication system.But the relay station of being mentioned among the present invention no longer is traditional repeater notion, but can regard the receiver of an enhancing as, it not only has the function of the data of relaying being carried out power amplifier, can also improve the terminal received signal quality by adopting multi-antenna technology and coding etc.
Specifically, relay station is the enhancing to the repeater, and traditional repeater generally just has the function of amplifying and transmitting to signal, and the function that relay station also has decoding and transmits.The amplification of repeater and forwarding (AF) function is meant that to the signal that receives operation such as do not decode directly carry out power amplification at radio-frequency head, in general, this operation is very simple, and equipment is very cheap.And the decoding of the advanced line number word of the decoding of relay station and forwarding (DF), the signal of recompile relaying before transmitting then, this process is sometimes referred to as " regenerative repeating " or " digital junction ".
By DF, relay station can with the base station together, carry out RRM and traffic control, and can adopt advanced technology, for example coordinate conflict management and joint transmission.
From present relaying technique,, relay station can be divided into three kinds of main types: fixed relay station, temporary fixed relay station and mobile-relay station according to mobility or deployment concept.Fixed relay station can not move, be installed on a fixed position, main purpose be in obtaining the access point sub-district that fully covers, do not expand the coverage area, increase capacity or each user throughput, perhaps with the zone of coverage extension to the access point coverage.Removable relay station can be defined as, can move to the relay station of another location from a position according to the needs of coverage, be that relay station can be positioned at different positions, and change in time with various relayings and base station and communicate, but do not carry out handoff procedure.And the mobility of mobile-relay station and the user terminal population/target area " relevant " that will cover need to support complicated flow process (as switching), can be regarded as a kind of portable terminal of increased functionality.
From top introduction as can be known, relaying technique has the incomparable benefit of a lot of traditional group net modes, is one of key mechanism of future broadband wireless communication systems.At present, the research of relevant relaying technique is less, also mainly is rest on the repeater conceptive, and purpose is to adopt the repeater to enlarge the coverage of sub-district.Development along with the multi-hop wireless ad hoc technology, adopt the relay station of multi-hop to come extended coverage range to become the focus of current focus, but all technology relevant with relaying also concentrate on the amplification of relay data and transmit at present, relaying technique is not expanded, more do not make full use of the feature of relaying technique, to network configuration and wish that framework strengthens.
Summary of the invention
The objective of the invention is to propose a kind of wireless multi-hop relay networking method that supports multi-media broadcasting service, come relaying technique is expanded, make it can not only realize replenishing the function that covers, and can provide diversity gain, reduce presence of intercell interference, improve spectrum efficiency, make that the frequency duplex factor as one based on the NGBW communication system of OFDM can reach 1; Use relaying technique from system group network and network architecture design aspect, improve the overall performance of network, simplify the planning and the design of wireless network, do not require that the base station realizes seamless covering; Provided the wireless signal treatment mechanism of terminal, to support novel layering overlay network framework.This method is mainly used in bearing multimedia broadcast multicast packet business, but also can be used to carry various Packet data services.
When technical scheme of the present invention is described, at first be described below basic principle:
1. adopt the advantage of relay station: terminal is generally without multi-antenna technology, in order to obtain MIMO or diversity gain, so relay station adopts MIMO technique (MIMO) or diversity technique; By adopting relaying technique, the transmitting power of base station can be less, thereby can reduce the interference to adjacent sub-district; Relay station is encoded to the received signal, and the signal quality of terminal can significantly improve; Can obtain from one or more relay stations and from the multilink diversity gain of base station for the terminal that is in base station and relay station coverage; Can obtain service by relay station for the terminal that is not in base station range, and can obtain to come from the multilink diversity gain of a plurality of relay stations, expand professional coverage, guarantee quality of service by the relaying of a plurality of relay stations.
2. the setting of relay station and layering cover: according to the Service coverage of the receiving ability of service in base station covering power, relay station, relay station and reach the enough little requirement of interference signal in the base station range, base station and the common Service coverage of its corresponding relay station are divided into three parts: be the center with the base station, receiving ability according to terminal is a standard, and the border circular areas that the terminal around the base station can normally receive the business of base station transmission is the basic cover layer of service in base station; Because the height and the signal reception of relay station will be much larger than terminals, therefore the receiving ability with relay station is a standard, also exist outside with respect to the Service coverage of terminal one to be that the annular section at center is that relay station sends professional range of receiving with respect to the base station with the base station in the base station, this annular section has constituted the professional receiving area of ring-type of relay station in conjunction with relay station jointly with respect to the Service coverage of terminal, is the merging cover layer of network; Owing to adopt a free-revving engine of relay station to be the coverage of activating business, while is in conjunction with the professional covering power of relay station, outside the professional range of receiving of relay station, exist one to be that the circumferential strip at center is the 3rd cover layer of network with the base station, be called the expansion cover layer.Be the seamless covering that guarantees in the overlay area of whole base station and corresponding relay station, to reach good, therefore need satisfy during being provided with of the underway station of continuing: relay station must be within its professional range of receiving, to guarantee that relay station can correctly receive and demodulation BTS service signal; The inboard of relay station covers annular section must certain overlapping with the overlay area of base station, make terminal in this second layer overlay area, can obtain the merging receiving gain of base station and relay station, to guarantee the professional continuity that receives in whole base station and the relay station overlay area.Therefore the ring-type between relay station and the base station overlay area merges cover layer and should be determined jointly by the receiving ability and the covering power of relay station, should choose a less choice of location standard of arranging net as relay station in the distance of relay station that both do not decide and base station.
It act as to be in the interior relay station of zones of different: be positioned over the relay station within the basic cover layer in hot zones and base station, be mainly used in the raising signal quality, this moment, terminal can be received the multilink signal from base station and relay station, thereby obtained diversity gain; Be placed on the relay station that merges between cover layer and the expansion cover layer and be mainly used in the coverage of extended base station, reduce interference from adjacent minizone.Thereby can simplify the network planning and design, make their frequency duplex factor as one reach 1 based on the NGBW communication network of OFDM.
3. message transmission between base station and the relay station and synchronized transmission:
By relay station the coverage of network is expanded, the business information that relay station sends to the terminal in its coverage in terms of content should with the base station synchronously, and consider the networking cost, between base station and the relay station by wireless mode service data transmission, consider that base station information processing time delay is received in relay station butt joint and from the propagation delay of signal of base station, therefore, the downlink transfer of base station and relay station takes the mode of time-division to carry out, promptly send service data information by base station down earlier, relay station receives and handles simultaneously, is carried out the forwarding of business datum then in its down sending time by relay station.By both descending being sent on the time domain are separated, disturb to reach to eliminate, the effect of diversity is provided for terminal.Be relay station when carrying out downlink data transmission in the base station, can adopt the base station in advance for the time that relay station carries out downlink business shifts to an earlier date transmission means, also can take base station down is the time delay send mode that terminal and relay station send downlink business simultaneously.
The synchronized transmission of synchronized transmission between the relay station and relay station and base station is the basis that obtains diversity gain for terminal, when carrying out the downlink data transmission in the base station, for relay station can be received synchronously, before downlink data frame, send and be used for the forward pilot signal of use synchronously, terminal also can receive this pilot signal and base station synchronization simultaneously, receives the base station down data.When if system's employing time shifts to an earlier date send mode, the base station is after having transmitted downlink data in advance for relay station, must leave certain time interval to be used for the processing that relay station carries out data, the time interval that keeps later the base station once more pilot signal transmitted carry out synchronously to be used for relay station and base station, relay station receive the pilot signal that sends for the second time of base station and form with the base station synchronously, treat that down sending time arrives, relay station sends downlink data according to indication information in the base station pilot signals and base station synchronization, and the downlink data of transmission is relay station received and finished processing in the base station shifts to an earlier date sending time slots base station down data.If system adopts the time delay send mode, then the base station is after sending the forward pilot signal that is used for using synchronously, carry out terminal and relay station are sent descending business datum simultaneously, relay station receives downlink data that the base station sends go forward side by side row cache and processing synchronously, after the base station sends downlink data, leave certain time interval and be used for the data processing of relay station and adjustment synchronously, this time interval must enough be used for relay station and carry out data processing and synchronous the adjustment.When adjusting synchronously, the time tag information that each relay station is used to adjust synchronously use in can the business control information according to the transmission of base station is determined separately the time adjustment amount with respect to the down-going synchronous delivery time of relay station, carry out the adjustment of down sending time then separately, carry out synchronized transmission at relay station down-going synchronous delivery time.During the descending transmission of relay station; at first send and be used for terminal and carry out synchronous synchronizing information; send downstream data traffic then; data that descending data service can send for last base station down or the data that send of certain base station down more forward, data that relay station is sending and the data of just reception having been finished in the base station add that at the transmission time interval of base station end the protection that system leaves must and adjust the time synchronously more than or equal to the processing delay of relay station maximum at interval.
4. terminal is to the reception of business:
In real network, following scene can appear:
(1) is in to merge cover layer or expand tectal terminal and can not directly receives useful signal from the base station, can only receive the signal of single relay station, the signal that receive this moment is owing to there is the relaying effect of relay station, so well very many under the situation at the more non-relay station of quality, coverage that can extended base station;
(2) if the base station shifts to an earlier date transmission mode in the employing time, and terminal can be received simultaneously from a relay station and service signal of base station, owing to these two signals can guarantee synchronously, so terminal can obtain diversity gain; Or relay station adopts time delay emission transmission mode, be in basic cover layer and merge tectal terminal and can receive signal respectively at different time from the same information of a relay station and serving BS, terminal can the MAC layer or more the upper strata finish and select to merge, and be in two tectal terminals and can select whether needs continue to receive the same information that relay station sends according to the check results of the information that receives from the base station.
(3) if be in and merge cover layer and the tectal terminal of expansion and can receive signal from a plurality of relay stations, because relay station reaches the synchronized transmission identical content, therefore, the signal of different relay stations can directly merge, and obtains diversity gain.
(4) if the base station shifts to an earlier date transmission mode in the employing time, be in basic cover layer and merge tectal terminal and can receive information from serving BS, also receive simultaneously a plurality of signals from relay station, because the relay station signal can be synchronous, so terminal can directly adopt physical layer to merge, and obtains diversity gain; Or relay station adopts time delay emission transmission mode, be in basic cover layer and merge tectal terminal and can receive signal respectively at different time from the same information of serving BS and a plurality of relay stations, because signal Synchronization between the relay station, therefore terminal can be finished the merging of a plurality of relay station signals in physical layer, to the same information that receives respectively from base station and a plurality of relaying, terminal can the MAC layer or more the upper strata finish and select to merge, and terminal can select whether needs continue to receive the same information that a plurality of relay stations send according to the check results of the information that receives from the base station.
5. the using and distribute of relay station and base station resource: adopt the mode of unified control in base station and scheduling, the details that each accesses terminal are known in the base station, know that also it connects the information of relay station, and purpose is to realize synchronously and carries out the unified of resource and dispatch.
Concrete technical scheme of the present invention:
The network design embodiment:
The first step according to traffic carrying capacity and actual environment etc., is arranged some large-scale base stations, constitutes the basic cover layer of network.Multi-antenna mode is adopted in big base station, and the basic principle that base station location is selected is to guarantee that the presence of intercell interference that the terminal in the base station range receives is enough little, this moment wireless network be cover limited, but not interference-limited;
Second step, by being set, suitable relay station comes the extended wireless coverage, in order to guarantee the quality of relay station received signal, want the reasonable Arrangement relay station, avoid a relay station can receive the signal that send other base station, promptly reduce the coverage of adjacent base station as far as possible, the setting of determining relay station according to the receiving ability and the covering power of relay station, the coverage of guaranteeing the coverage of relay station and base station simultaneously has suitable overlapping, to constitute the merging cover layer of network, the outside of relay station constitutes the expansion cover layer simultaneously;
The 3rd step, scheduling resource is unified in the base station, adopts suitable transmission means, guarantees can to transmit in the network configuration of three layers of covering and not disturbed from the service in base station data, coordinate the downlink transfer of relay station, guarantee that same information can reach each intratectal terminal;
The 4th step, relay station carries out encoding process to relayed information, coordinate between base station and the relay station, simultaneously relay station is also adjusted synchronously, guarantee to be in merge that cover layer and the intratectal terminal of expansion receive can time synchronized from the signal of relay station or base station and relay station;
In the 5th step, terminal adopts technology raising received signal qualities such as diversity, can receive from a plurality of relay stations or signal of base station, guarantees that the information that receives can be synchronously, the acquisition diversity gain;
In the above step, the scheduling of resource, access control, power control, switching controls, Timing Advance control etc. all come unified management by the base station.
For MBMS transmission business under with the layering overlay network framework of deploy,, designed and supported the basic frame structure that the MBMS business is transmitted in wireless multi-hop relay network according to above-mentioned basic principle and network actual scene demand:
(1) understands the information of the specifying information and the relay station that terminal connects of each terminal for satisfying system's needs, the unified scheduling of the resource of implementation system, therefore, the frame structure of system is divided into downlink frame and uplink frame on time domain, downlink frame is mainly used in the descending transmission of base station end business datum and the descending forwarding of relay station, uplink frame is used for terminal and relay station uplink information, and they constitute a complete system-frame jointly.
(2), eliminate because base station that the processing delay of relay station causes and the interference between the relay station are divided into base station down transmission subframe and relay station downlink transfer subframe in the downlink frame of system in order to reach the synchronized transmission of relay station.The downlink transfer subframe of base station is made of Forward Pilot Channel, base station down transmission frame, comprises the control information and the service data information of system in the base station down transmission frame.Be divided into two kinds of patterns according to information transferring methods different between base station and the relay station in the downlink frame of relay station, when base station and relay station employing time shift to an earlier date transmission mode, the descending sub frame of relay station transmission system control information and business datum, and descending forward pilot information from base station sends, and when relay station carried out the transmission of downlink data, the base station is the downlink service data of synchronized transmission identical content also; When adopting the time delay send mode between base station and the relay station, relay station sends downlink data in its descending sub frame transmitting time inter-sync, comprise forward pilot information, system control information and service data information, descending transmission is not carried out in the base station when relay station sends downlink service data.
(3) transmit the frame head control information that includes the downlink transfer subframe in subframe and the relay station downlink transfer subframe at base station down, comprise down channel description, the distribution of indication upstream and downstream bandwidth, control information etc., also comprise service data information in the downlink transfer time slot.
(4) uplink frame is made up of up access subframe of terminal and the up access subframe of relay station, terminal inserts in the subframe time by different terminals and sends upstream data to separately access base station or relay station, sends to the base station in the up access subframe of relay station by the terminal upstream data that relay station will receive in the terminal uplink frame time.
(5) each complete system wireless frame all leaves certain time interval between the radio frames when transmitting; Keep certain time interval between the uplink/downlink frames in each system wireless frame as the up-downgoing transmission switch protecting time interval; Keeping certain time interval between the downlink transfer subframe of base station and relay station is used for relay station and carries out data processing and adjust synchronously.
(6) corresponding frame structure will be selected to use according to the information transferring method that adopts between base station and the relay station by system.
Basic frame structure schematic diagram is seen accompanying drawing 2.
Beneficial effect of the present invention is, adopts the wireless multi-hop trunk network of relay station technical support multi-media broadcasting service can mainly obtain following benefit:
1. simplified the design of Radio Access Network of future generation, arranged large-scale base station, reduced the cost of arranging the base station, alleviated loaded down with trivial details work such as the siting of station, base station planning optimization by reducing.The mast of placement relay station does not need the same with the base station high yet, so just can reduce operation expenses (renting pylon and maintenance cost as the service provider).
2. relay station does not carry out wired connection with backbone network, the data that their storages receive from base station radio, handle, forward it to user terminal then, vice versa, need not like this between base station and wired backbone, to be the relay station mounting interface, thereby saved the expense of base plate (using) as interface.
3. for Cell Edge User, the base station is more much bigger than the path loss through relay station relays to the direct propagation loss between the terminal, employing relay station technology can improve each the link of terminal data rate away from the base station, thereby solved the covering problem of high data rate in the relatively large sub-district potentially, improved the signal quality of cell edge.
4. pass through between base station and relay station to adopt multi-antenna technology, improved the transmission performance of link; The transmission of radio links of control and supervisory relay and terminal, improve the transmission signals quality by receiving advanced technologies such as carrying out the diversity processing after repeating signal and the signal of base station, relay station adopts advanced signal processing technologies such as coding, has improved the signal quality that terminal receives.
5. provided the wireless treatment mechanism between base station and the relay station, so that diversity gain to be provided, eliminated because the interference that the processing delay of relay station causes and cause the possibility of system's closed loop vibration.
6. a kind of effective basic transmission frame-form at the MBMS business under the wireless multi-hop relay network has been proposed, base station and relay station have been realized, base station and terminal, the up-downgoing transmission between relay station and the terminal, and the synchronized transmission of relay station and Network Layering expansion covering.Simultaneously basic frame structure also possesses extensibility, the professional and support multi-hop transmission mode of other under the network configuration that can support effectively to be proposed.
7. present networks framework and wireless treatment mechanism also can be expanded and support the multi-hop wireless relay transmission, thus extended coverage range flexibly, and flexible networking etc.
In addition, the most suitable ofdm system of this method is because this system has solved the problem of adjacent sub-district identical networking.
In sum, relaying technique has the incomparable benefit of a lot of traditional group net modes, is one of key mechanism of future broadband wireless communication systems.
Description of drawings
Fig. 1 supports the wireless multi-hop relay network topology diagram of multi-media broadcasting service
Fig. 2 supports the frame structure of the wireless multi-hop relay network of multi-media broadcasting service
Fig. 3 supports the network design key step of the wireless multi-hop relay network of multi-media broadcasting service
Fig. 4 base station time shifts to an earlier date the transmission mode schematic diagram
Fig. 5 relay station time delay sends the transmission mode schematic diagram
Fig. 6 single-hop relay transmission pattern diagram
Embodiment
Fig. 1 has provided the wireless multi-hop relay network topological structure of the support multi-media broadcasting service that obtains according to method of the present invention, and wherein the base station just covers less zone, constitutes the basic cover layer of network, shown in Fig. 1 Smalt zone.Grey annular section among Fig. 1 is according to the receiving ability of relay station and the definite jointly inboard area of coverage of relay station of coverage, in this zone owing to can receive the signal of base station and relay station, therefore constitute the merging cover layer of network, the annular section of white is the outside expansion cover layer of relay station.The service range of single relay station is far smaller than the coverage of base station, is mainly used in to replenish to cover (shown in dotted line among Fig. 1 and chain-dotted line wire loop shape zone), and the interference that reduces the minizone, just provide diversity gain in addition.
In actual mechanical process, be also noted that following some:
First, the service range of relay station extended base station (being the coverage), the resource allocation of terminal and relay station and scheduling are all by base station united and coordinating and control, in order to simplify the complexity of network, the single-hop relay station is supported in suggestion earlier, and the multi-hop relay station is supported in expansion more later on;
The second, for the terminal that is in the overlay area, can receive from signal of base station.If wish to improve signal quality, relay station can be set in the overlay area, thereby obtain extra diversity gain from relay station;
The 3rd, the terminal in the coverage can receive the signal of one or more relay station, because a plurality of repeating signals all come centralized control by same base station, can realize between the relay station synchronously, so terminal can obtain diversity gain;
The coverage of the four, two base station can be overlapping, for overlapping areas, because the information of two base station transmits is the same, can merge the relay station of two base station service areas, thereby improve the MBMS performance.
Fig. 2 has provided the frame structure of the wireless multi-hop relay network that supports multi-media broadcasting service, frame assumption diagram (a) at be the employing time shift to an earlier date transmission technology, figure (b) at be to adopt the time delay send mode.
Among Fig. 2 (a), the leading channel of BS is used for the base station and sends forward pilot information, and the DL-BS base station down sends subframe, and DL-BS, RS are relay station and base station synchronization downlink transfer subframe, and UL-SS is a terminal uplink subframe, and UL-RS is a relay station uplink subframe; TI is system retention time interval; DL-BS and DL-BS; TI between the RS is that relay station is used for signal processing and adjusts guard time synchronously at interval; DL-BS; the RS and the UL-SS up-downgoing transmission switch protecting time interval; last system's retention time of whole system radio frames is used for the separation between each system wireless frame at interval, and the data in the downlink frame of base station and relay station comprise the business control information and the service data information of system, and their separations are encapsulated in each sending time slots of physical layer.
Among Fig. 2 (b), the leading channel of BS is used for the base station and sends forward pilot information, and the DL-BS base station down sends subframe, and DL-RS is relay station DL synchronization transmission subframe, and UL-SS is a terminal uplink subframe, and UL-RS is a relay station uplink subframe; TI is system retention time interval; TI between DL-BS and the DL-RS is that relay station is used for signal processing and adjusts guard time synchronously at interval; the DL-RS and the UL-SS up-downgoing transmission switch protecting time interval, last system's retention time of whole system radio frames is used for the separation between each system wireless frame at interval.Data in the downlink frame of base station and relay station comprise the business control information and the service data information of system, and their separations are encapsulated in each sending time slots of physical layer.
Fig. 3 has provided the network design key step that supports the wireless multi-hop relay network of multi-media broadcasting service, specifically comprises as follows:
The first step, according to traffic carrying capacity and actual environment etc., arrange several large-scale base stations, multi-antenna mode is adopted in big base station, the basic principle that base station location is selected is to guarantee that the presence of intercell interference that the terminal in the base station range receives is enough little, determine the basic cover layer of network, this moment, wireless network was that covering is limited, but not interference-limited.
In second step,, suitable relay station comes the extended wireless coverage by being set.In order to guarantee the quality of relay station received signal, want the reasonable Arrangement relay station, take all factors into consideration the covering power and the receiving ability of relay station, avoid a relay station can receive the signal that send other base station, promptly reduce the coverage of adjacent base station as far as possible, for relay station is selected suitable position, with merging cover layer and the expansion cover layer that constitutes network.Can adopt various advanced technologies this moment, as directive antenna, MIMO technology etc.In order to save cost, and simplify networking, use wireless communication technology to communicate between relay station and base station.The coverage of base station range and the relay station relevant with this base station is synthesized together the coverage of whole base station.
In the 3rd step, scheduling resource is unified in the base station, guarantees relay station can receive the downlink information of base station transmission and the synchronized transmission of relay station, need select the transmission means between base station and the relay station.In the time of can being chosen in downlink transfer, the base station can shift to an earlier date a period of time information is sent to relay station, Timing Advance more than or equal to relay station from receiving the processing time that sends again.From this angle, the two-layer scheduling of resource of carrying out is generally divided in the base station, and ground floor is that relay station is carried out scheduling of resource, and the second layer is directly the terminal that is in the base station range to be dispatched, and have correlation between the two.Perhaps can take to send information by the base station earlier, this information sends to the terminal in the base station overlay area and can receive the relay station of this information, relay station is handled and buffer memory the information that receives, relay station the information that receives is handled with buffer memory in be sent in once or preceding receive several times by base station information that send and that finished processing, the information that relay station is sending and just finished the information of reception must be at the transmission time interval of base station end more than or equal to the processing delay of relay station.So, the information of base station sends and is primarily aimed at intratectal substantially terminal and attached relay station, the information of relay station sends mainly to serve and merges cover layer and the intratectal terminal of expansion, the information of base station and relay station sent from the time to be separated, thereby can not cause interference, and sending identical information simultaneously, a plurality of relay station can provide diversity for terminal.The information that base station and relay station send respectively has certain correlation.
The 4th step, relay station carries out encoding process to relayed information, coordinate between base station and the relay station, relay station is adjusted synchronously according to the transmission mode between employed base station of system and the relay station, and guaranteeing that terminal is received can time synchronized from the signal of the model of relay station or base station and relay station.If the time that system uses shifts to an earlier date transmission means, when downlink transfer, the base station can shift to an earlier date a period of time information is sent to relay station, relay station is handled after receiving base station signal, and adjusting synchronously in the adjustment time interval synchronously, receive the forward pilot signal that the base station sends then, finish with the base station synchronously and the transmission of downlink business.If system's delayed delivery service time mode, then relay station is receiving laggard row cache of downlink data and the processing that the base station sends, adjust synchronously in the synchronous adjustment time interval subsequently, then relay station carries out synchronized transmission forward pilot information and business datum.If terminal can be received the signal from a plurality of relay stations of same base station service areas, then the base station wants to distribute for this targeted customer carries out same asset between these several relay stations simultaneously, and the time shifts to an earlier date and scheduling of resource.In order to simplify the design of terminal, adopt identical wireless standard from the base station with signal, and can realize the merging of physical layer from relay station.During the terminal access of radio network, the signal that judgement can be discerned if there are multiple signals can discern (from the base station or from relay station), then adopt the high specific gain to merge diversity and handles.From signal of base station with from the signal of relay station coding gain is arranged, promptly relay station can carry out Space Time Coding to the received signal and handles, and then forwards.
In the 5th step, terminal adopts technology raising received signal qualities such as diversity, can receive from a plurality of relay stations or signal of base station, guarantees that the information that terminal receives can be synchronous, obtains diversity gain.
In the above step, the scheduling of resource, access control, power control, switching controls, Timing Advance control etc. all come unified management by the base station.
Fig. 4 has provided the base station time and has shifted to an earlier date the signal of downlink transfer subframe once complete in the transmission mode.Same informational needs shifts to an earlier date a period of time and sends to relay station, can receive the signal from base station and relay station synchronously to guarantee terminal, and this scheduling feature to the base station has proposed very high specification requirement.A kind of method of accommodation then is separately from signal of base station or from the signal of relay station on time domain, the time of both incoming terminals is different, be that both adopt different time slots to send, for example a frame is divided into two subframes and sends, first subframe is used for the base station and sends, and relay station receives and handles simultaneously, and second subframe is used for relay station and the base station sends simultaneously, signal from base station and relay station just can not disturb like this, and can obtain the diversity gain of MAC layer.
Fig. 5 has provided the signal of downlink transfer subframe once complete in the relay station time delay transmission transmission mode.For guaranteeing that the information synchronization between the relay station sends, the present invention still adopts the sending time slots that carries out base station and relay station on time domain to separate, once complete sending time slots is made of twice sending time slots, and last time slot sends information by the base station, and back one time slot sends information by relay station.Sending time slots between base station and the relay station leaves certain protection blanking time, uses with the synchronous adjustment of doing relay station.When the base station sent information in its sending time slots after, the relay station in the overlay area was handled information after receiving information, and relay station sends by the base station in once preceding or preceding base station several times in the relay station sending time slots that arrives simultaneously
The 4th step, relay station carries out encoding process to relayed information, coordinate between base station and the relay station, simultaneously relay station is also adjusted synchronously, guarantee to be in merge that cover layer and the intratectal terminal of expansion receive can time synchronized from the signal of relay station or base station and relay station;
In the 5th step, terminal adopts technology raising received signal qualities such as diversity, can receive from a plurality of relay stations or signal of base station, guarantees that the information that receives can be synchronously, the acquisition diversity gain;
In the above step, the scheduling of resource, access control, power control, switching controls, Timing Advance control etc. all come unified management by the base station.
For MBMS transmission business under with the layering overlay network framework of deploy,, designed and supported the basic frame structure that the MBMS business is transmitted in wireless multi-hop relay network according to above-mentioned basic principle and network actual scene demand:
(1) understands the information of the specifying information and the relay station that terminal connects of each terminal for satisfying system's needs, the unified scheduling of the resource of implementation system, therefore, the frame structure of system is divided into downlink frame and uplink frame on time domain, downlink frame is mainly used in the descending transmission of base station end business datum and the descending forwarding of relay station, uplink frame is used for terminal and relay station uplink information, and they constitute a complete system-frame jointly.
(2), eliminate because base station that the processing delay of relay station causes and the interference between the relay station are divided into base station down transmission subframe and relay station downlink transfer subframe in the downlink frame of system in order to reach the synchronized transmission of relay station.The downlink transfer subframe of base station is made of Forward Pilot Channel, base station down transmission frame, comprises the control information and the service data information of system in the base station down transmission frame.Be divided into two kinds of patterns according to information transferring methods different between base station and the relay station in the downlink frame of relay station, when base station and relay station employing time shift to an earlier date transmission mode, the descending sub frame of relay station transmission system control information and business datum, and descending forward pilot information from base station sends, and when relay station carried out the transmission of downlink data, the base station is the downlink service data of synchronized transmission identical content also; When adopting the time delay send mode between base station and the relay station, relay station sends downlink data in its descending sub frame transmitting time inter-sync, comprise forward pilot information, system control information and service data information, descending transmission is not carried out in the base station when relay station sends downlink service data.
(3) transmit the frame head control information that includes downlink frame in subframe and the relay station downlink transfer subframe at base station down, comprise down channel description, the distribution of indication upstream and downstream bandwidth, control information etc., also comprise service data information in the downlink transfer time slot.
(4) uplink frame is made up of up access subframe of terminal and the up access subframe of relay station, terminal inserts in the subframe time by different terminals and sends upstream data to separately access base station or relay station, sends to the base station in the up access subframe of relay station by the terminal upstream data that relay station will receive in the terminal uplink frame time.
(5) each complete system wireless frame all leaves certain time interval between the radio frames when transmitting; Keep certain time interval between the uplink/downlink frames in each system wireless frame as the up-downgoing transmission switch protecting time interval; Keep certain time interval between the downlink transfer subframe of base station and relay station and be used for that relay station carries out data processing and the method for synchronization is: relay station carries out conjugation to the received signal to be handled and then forwards.Because the processing delay of relay station, the signal of relaying and direct signal with identical content from the base station, bigger delay was arranged on both times, this moment is to cushioning in physical layer earlier from signal of base station of receiving, the signal for the treatment of relay station merges together, and it is just enough that the window size of merging is arranged on 8 TTI.
Above scheme requires terminal to increase a bigger buffer, need carry out bigger change to physical layer, a kind of alternative method is to adopt multi-antenna technology in terminal, and terminal can identify arrogant signal of base station, still from the signal of relay station, merge at the MAC layer then.
Although the present invention is described and illustrates with reference to embodiment, and do not mean that the present invention is limited to the execution mode of these descriptions.Be noted that simultaneously technical scheme among the present invention is not specially at any specific wireless communication system.