CN104660315A - Novel method for controlling coordinated transmission downlink signals in CoMP transmission system - Google Patents

Abstract

The invention discloses a novel method for controlling coordinated transmission downlink signals in a coordinated multipoint (CoMP) transmission system, and belongs to the field of electronic information. In the evolution of an LTE standard, the CoMP transmission is an important technology, the core idea is to form a virtual multiple-input multiple-output (VMIMO) by multi-point coordination so as to improve the cell-edge performance. The CoMP transmission contains various ways of the coordination between different remote radio frequency units (RRU) in a base station, the coordination between the base station and a base station-owned relay, the coordination between the base stations and the like.

Description

The novel method controlling cooperative transmission of downlink signal in cooperative multipoint transmission system

The novel method controlling cooperative transmission of downlink signal in cooperative multipoint transmission system of the present invention belongs to electronic information field.

In the evolution of LTE standard, collaborative multicast communication (CoMP) is a kind of important technology,

Its core concept is by multipoint cooperative, forms virtual multiple-input and multiple-output (VMIMO), to promote cell-edge performance.

Collaborative multicast communication has different long-distance radio frequency unit (RRU) cooperation, base station and the various ways such as relay cooperative and cooperation between base stations belonging to it in base station.

The realization of various different collaborative multipoint transmission mode is all based on following two conditions:

1. the information sharing (be included in the part or all of channel condition information of subscriber equipment, also require the data message sharing to subscriber equipment under some cooperation mode) between cooperation point.

2. federated resource distributes/scheduling.

In 3GPP RAN1 the 57th meeting, each manufacturer has adopted unanimously and may adopt following 3 kinds of feedback strategies in collaborative multicast communication (CoMP) technology: explicit channel status/statistical information feedback; Implicit information channel state/statistical information feedback, as: channel quality instruction (CQI), pre-coding matrix instruction (PMI), order instruction (RI);

In tdd mode, utilize channel heterogeneite to obtain descending channel condition information based on up detection reference signal (SRS) Signal estimation.For various different feedback method, there is different precoding modes accordingly.

Different by the degree of the information of sharing, CoMP can be divided into Combined Treatment (JP) and cooperative beam shaping (CBF) two kinds of modes.

Wherein CBF requires the channel condition information of sharing users equipment (UE) between cooperative node; JP requires channel condition information and the data message of sharing UE between cooperative node.

Because multi-user Cooperation multicast communication (CoMP-MU) mode based on JP can obtain larger performance boost, the CoMP-MU method for precoding herein in main research indoor baseband processing unit (BBU)+multiple RRU scene under JP mode.

In CoMP system, associating precoding can having come in the mode of centralization by RRU multiple in same BBU.

The RRU of these cooperations is called " CoMP-RRU ", is a UE group service using identical time/frequency source block.

The precoding of CoMP-RRU allied signal reduces presence of intercell interference, to improve system spectral efficiency, and the particularly throughput of edge customer.

Suppose that each RRU has a n t transmitting antenna, each UE has a n r reception antenna.

Because transmitting terminal can obtain the equivalent channel after precoding, thus UE after obtaining precoding

Capacity, match so user can be chosen based on the principle of maximum capacity.

Direct channels matrix feedback can provide abundant channel information, but is impossible for fdd mode perfect channel matrix information feedback, and the channel relevancy of time domain or frequency domain must be utilized to compress feedback quantity and adopt suitable quantification technique.

Average on time domain, frequency domain or quantize the serious distortion that all may cause H to H is capable, analyzes method that is average and that quantize two kinds of compressed feedback amounts under different scenes to the impact of performance.

In tdd mode CoMP, if adopt SRS design can bring the problem of the SRS serial correlation poor-performing of cooperation cell SRS received power deficiency and different districts, in order to support CoMP-JP, may need that existing SRS signal is carried out certain and strengthening.

Based on the method for precoding of spatial correlation matrix

Under some condition, the average or compression of channel matrix on time domain, frequency domain will reduce its validity greatly, and this also makes the feedback of channel matrix compress and becomes comparatively difficulty.

But average on frequency domain or time domain of the spatial correlation matrix of channel but can not cause very large distortion, so carry out precoding based on channel covariance matrices may become one

More efficiently method for precoding.

Based on the method for precoding of code book

Its principle of method for precoding based on code book prestores a code book (i.e. the set of pre-coding matrix), receiving terminal selects best pre-coding matrix according to current channel status with certain criterion, and pre-coding matrix numbering (PMI) is fed back to transmitting terminal.

Because its feedback quantity is little, simultaneously good with Rel.8 compatibility, in standardized process, obtain the support of a lot of company.

Rel.8 code mainly designs for the carrying out of SU-MIMO, and concerning MU-MIMO or CoMP-MU, its performance is not fine.

From CoMP, due to multicast communication, the antenna number that code book needs are supported can to 8, and the performance boost that 4 bit feedback 8 antenna codebooks bring compared with 4 bit feedback 4 antenna codebooks is very limited, so need more number of bits of feedback to support CoMP-MU.

Scheme is a fixed codebook design, and the number of bits of feedback of increase is for supporting larger code book.

The novel feature controlling the method for cooperative transmission of downlink signal in cooperative multipoint transmission system of the present invention is that realization is simple, feedback overhead is little.

But this scheme code book is to the adaptive capacity of scene, and be limited to the lifting of systematic function.

Research shows, along with the increase of code book, the performance boost of acquisition can be tending towards saturated very soon, simultaneously, for different codebook design (such as: based on the codebook design of DFT, the codebook design etc. of Householder conversion), when zone of saturation, its performance is closely.

Another scheme is a kind of adaptive codebook of design, and when utilizing channel correlation matrix long, value of feedback is to adjust the code book of current employing.

Because in slow fading channel, the change of channel correlation matrix R is slow, so the feedback interval of R (i.e. the code book adaptive time interval) can arrange longer, the feedback quantity of increase is very little compared with fixed codebook method like this.

Uplink SRS signal can be used for estimating R in some cases.

First adaptive code the design will determine a base code book, for the code book based on multiple Hadamard conversion (CHT) of 8 × 16.

When not utilizing channel space correlation matrix R, code book is WDS; When adopting R, code book will be adopted: wherein, two norms of each row are normalized to 1 to W=normalize (RWCHT) by function normalize (g) expression.

In addition the R Rk that also can be made up of a front k characteristic vector

Replace: compared with fixed codebook method, adaptive code this method can obtain larger performance boost, but compared with first two method, its performance that can reach is still very limited.

In addition based in the method for precoding of code book, user's pairing is a more scabrous problem, which also limits the ability of the method for precoding improving performance based on code book.

For the method for precoding of fixed codebook, wave beam distance minimum criteria (MBD) of the pre-coding matrix can only chosen based on each user carries out user's pairing; For adaptive codebook method for precoding, first do based on R the thinking that user's pairing is a kind of solution, but due to the feedback interval of R comparatively large, the validity of this method needs further checking.

Long Term Evolution (LTE) technology designs good advanced techniques.

In wireless access mesh portions, first, utilize descending and up OFDM/discrete Fourier transform (DFT)-spread-spectrum orthogonal frequency division multiplexing (OFDM/DFT-SOFDM) technology to achieve completely orthogonal channel in community, greatly eliminate same area interference; Secondly, the flexible conversion of the occupation mode such as transmit-receive diversity, space division multiplexing, wave beam forming of multi-antenna technology, the flexible utilization characteristic of space channel, augmented flow, overcomes interference; In addition, multiple cell interference coordination (ICIC) mechanism, first time breaches the thinking that single subdistrict independently controls, and multiple cell is regarded as an Iarge-scale system, introduces the thought of joint coordination interference.Therefore, the link flow of LTE system is close to shannon limit, in the follow-up evolution of LTE system, for higher spectral efficiency requirements, the work that link level technological improvement can be done is limited, and in order to reach the object of improve link level performance (SINR), must then seek system-level solution.

Cooperative communication technology is exactly be introduced under this background in LTE system.

Collaboration communication refers to that multiple base station (eNodeB) in system or multiple base station and antenna station long-distance radio frequency unit (RRU) carry out the technology of multiple spot sending/receiving simultaneously, and user terminal (UE) will link and communicates with setting up between multiple base station and antenna station up-downgoing.

Can carry out netted interconnected between base station and multiple antenna station, multiple base station with optical fiber.

Specifically, in network, insert antenna station, or formed distributed based on existing website

Antenna system, carries out and MIMO between UE, is called collaborative multicast communication technology; When directly utilizing existing network, with fiber interconnect between each base station, multiple base station directly communicates with UE, is called coordination technique between base station.These two kinds of forms are all collaboration communication application in practice.

In this case, one of them base station is the dominant base communicated with UE, and other base stations then deteriorate to RRU antenna station.

Collaboration communication mainly make use of the gain of system process, the gain cooperated to bring multistation, needs in concrete technology, consider multistation cooperation problem.

At present also topmost several key technologies under study for action have:

(1) intelligent association.UE can the minimum transmitting station of automatic searching path loss access.

(2) stand between load balancing technology.Multiple website shares the traffic load in overlay area jointly, needs interior communication to coordinate business and shares and resource service condition.

(3) multi-antenna cooperative MIMO technology.

Multiple covering website is each can adopt different multiple-input and multiple-output (MIMO) types of service, the region that such as multi-site covers, different user can take identical running time-frequency resource, but respectively wave beam forming is carried out to different user by multiple website, distinguish user, improve spectrum efficiency.

(4) collaboration site selecting technology.

Select appropriate website number, distributing position carries out multistation cooperation, to reaching optimum cooperation effect.

(5) dynamic I CIC technology.In multistation collaboration communication, adopt multiple base stations energy of Fiber connection

Enough carry out data communication fast, therefore, it is possible to realize real dynamic I CIC technology, coordinate the interference of minizone.

Macro station, microcellulor composition layering hybrid network are commonly used in the macrocellular networking of the e-learning quality classics after application collaboration communication network technology, macro station covers continuously, microcellulor is used for focus covering, blind area covers, the traffic hotspots of macrocellular is absorbed, supplements covering leak and blind area that macrocellular covers generation continuously simultaneously.

The form covered, employing soft-frequency reuse (SFR) mode carries out the frequency planning between multiple community, between grand microcellulor, so network construction form.

Existing system is in order to solve the problem of co-channel interference between the co-channel interference of community handover region, grand Microcell, and the mode adopting SFR, ensures that different school district adopts different frequency ranges at the fringe region that overlap covers more, adopts frequency division multiplexing to come Cochannel interference.

But this problem caused is the: Chan availability of frequency spectrum to be reduced.

The mode of frequency division multiplexing reduces interference by the mode of the sacrifice availability of frequency spectrum.

Chan reduces communication quality.

In the moving process of UE to cell edge, will carry out the passive change of working frequency range frequently, this change can destroy the performance of the link adaptation in frequency selection scheduling process, thus reduces communication quality.

Chan too relies on the scheme that Internal and external cycle divides.

Different splitting schemes will have an impact to systematic function, if will obtain the coordinating district interference scheme that is suitable for high speed, low speed, underloading, heavily loaded various scene, system ICIC algorithm complex is high, which increases the burden of each eNodeB.

When after introducing multistation cooperative communication technology, be connected with optical fiber between base station, one of them base station is as dominant base, and for service communication, other base stations deteriorate to RRU, and multiple spot sends simultaneously and receives.

In this case, increase the coverage of dominant base, reduce Zone switched, become traditional grand Microcell Hierarchical Network and be covered as many NodeB node and divide

Undertake He great district to cover.During frequency planning Zhong great district between this multiple community, between grand microcellulor covers, multiple spot transmitting-receiving not only makes up-downgoing coverage distance increase, and, because UE can select the website minimum with path loss to access, multiple spot transmitting-receiving simultaneously brings the macro diversity of soft handover in similar 3G system, thus also stronger in covering power, covering quality is better, and mulching measures is higher.

In addition, utilize the design to dispatching algorithm and multistation tuning algorithm in collaboration communication, traffic load multistation in great Qu is dynamically shared, support business all in great Qu simultaneously, the base station that different UEs can choose at random signal quality best is accessed, and when UE moves in the scope that master station and follow station covers, is equivalent in the area of coverage of same dominant base, can steadily switch fast, QoS (QoS) impression is better.

Thus, spectrum efficiency, service feature are promoted to some extent, and ICICl algorithm complex also can corresponding reduction some.

Interference analysis

In multistation cooperation communication system, in multiple websites of cooperation, a base station is as dominant base, and other base stations deteriorate to RRU, like this, master station controls the coupled UE communication in coverage, coordinates resource service condition with other base stations deteriorating to RRU simultaneously.

Like this, in coverage, originally the up-downgoing co-channel interference of multiple minizone is greatly reduced, and even can reach the situation of nearly orthogonal, so, and the interference that the group of base stations of other the collaborative work being far-end produces by the interference source of system.

The network model of simple for use one LTE system model and cooperation communication system is carried out the research of interference analysis below.

The network of R8 LTE system, each community can be subject to the co-channel interference from other neighbor cells; For multistation cooperative communication network, one group, 3 base stations, carry out multipoint cooperative communication in group, each group of co-channel interference that can be subject to other groups, the up-downgoing interference variations situation that this section will compare in the coverage of NodeB in two kinds of situations.

When not adopting any added technique (such as smart antenna Anti-Jamming Technique, interference coordination technique etc.).

It is the analysis of the interference lifting in downlink coverage, it is the interference lifting analysis in uplink coverage, can see, the interference brought by multi-site collaboration communication separately decreases, from down link, the reduction of interference rank entirety is about about 2 dB, and the interference reduction of up link is about 2 ~ 4 dB.

The novel method controlling cooperative transmission of downlink signal in cooperative multipoint transmission system of the present invention have employed the reduction of simple scene to the interference that cooperation communication system brings and analyzes, in reality, due to macrocellular, microcellulor layering networking structure, appropriate choosing is grand, microcellulor node cooperates, the effect that the interference brought reduces will be better, consider antenna downtilt, ICIC, the use of multi-antenna technology, cooperative communication network will become in a community, the system of presence of intercell interference all nearly orthogonal, interference is reduced greatly on the impact of throughput of system, spectrum efficiency gets a promotion.

Although cooperative communication technology brings obvious system gain, the technical advantage of this technology is all brought into play, also have many problems to need research, such as:

(1) covering problem of signaling channel, multiple site collaboration sends the coverage expanding single station,

But first need control channel to reach good covering performance in whole coverage, this is a problem needing to be studied in great detail.

(2) how all system loadings in large coverage, share between multiple NodeB, and this part work can increase the signaling traffic between NodeB.

(3) dynamic I CIC.Dynamic I CIC real between base station needs a large amount of interior communications, and the increase along with cooperative base station scale constantly increases by this, follow-uply will study.

These problems are the key issues run in cooperative communication technology application above, resolve these problems, systematic function will be made to have higher lifting.

CoMP (Coordinated multiple point, collaborative multiple spot) is that LTE-Advanced system dilates network edge covers, one of the important technology ensureing edge customer QoS, is the exclusive technology of LTE-Advanced system.

In LTE-Advanced system, CoMP comprises two kinds of scenes: cooperation between base stations and distributing antenna system.From data flow always, CoMP can be divided into again descending transmission CoMP and uplink receiving CoMP.WLAN (wireless local area network) refers to the computer network adopting wireless transmission medium, combines up-to-date computer networking technology and wireless communication technology.First, WLAN (wireless local area network) is the extension of cable LAN.Use wireless technology to transmit and receive data, decrease the line demand of user.

In wired world, Ethernet has become the lan technology of main flow, and its development not only walks abreast with the development of Wireless LAN standard, and really predictive of the developing direction of the latter.By the definition of Electrical and Electronic research institute (IEEE) 802.3 standard, Ethernet provides a development, at a high speed, is widely used and possesses the network standard of interoperability characteristic.This standard also develops in continuation, to catch up with modern LAN requirement in message transmission rate and throughput.Ethernet standard only can provide the message transmission rate of 10 megabit per seconds (Mbps) at first, has developed into the message transmission rate that can provide network backbone and 100 megabit per seconds required by bandwidth intensive application.IEEE 802.3 standard is open, decreases the obstacle of market access, and result in can select for ethernet user in a large number supplier, product and value point generation.The most important thing is, as long as meet ethernet standard just can be implemented to operability, thus a kind of product enabling user select multiple supplier to provide, guarantee that these products can use jointly simultaneously.

First generation wireless lan technology is that low speed (1-2 megabit per second) proprietary product provides.Although there are these shortcomings, wireless brought freedom and flexibility are for these early productions occupy one seat in vertical market, and as retail business and warehousing industry, the mobile workman of these industries uses handheld device to carry out inventory management and data acquisition.Subsequently, hospital uses wireless technology that the information of patient is directly sent to beside sickbed.Along with computer enters classroom, school and university start installing wireless network network, to avoid wiring cost and collineation axis access.The wireless provider of fighing in the van shortly is recognized, for making this technology obtain accepting extensively of market, needs the standard setting up a kind of similar Ethernet.Suppliers were joined to together in 1991, and first time suggestion also establishes a standard based on respective technology subsequently.In June, 1997, IEEE has issued 802.11 standards for WLAN (wireless local area network).

Allow data to carry out transmission by twisted-pair feeder and coaxial cable just as 802.3 standards the same, 802.11WLAN standard allows to carry out transfer of data by different media.Operable medium comprises infrared ray and two kinds of wireless radio transmission on 2.4 gigahertz bands without the need to securing permission: frequency-hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS).Spread spectrum is a kind of modulation technique of the exploitation forties, can in a very wide level radio frequency band transmitting signal.This technology is the ideal chose of data communication, because it is not very sensitive to radio interference, and produces interference hardly.FHSS is limited to the message transmission rate of 2 megabit per seconds, is only recommended in very special application as used in the water carrier of some type.For the application of other all WLAN, DSSS is better selection.The IEEE evolution version 802.11b issued can provide the message transmission rate of 11 megabit per seconds suitable with Ethernet by DSSS.FHSS does not support the message transmission rate of more than 2 megabit per seconds.

The multilevel security secrecy provision of Aironet/IEEE, greatly strengthen the security reliability of wireless network, and user also can increase some auxiliary functions to reach higher confidentiality, wireless network has then had same the wired local area network even confidential nature of higher level.

Compared with cable LAN, WLAN (wireless local area network) has that exploitation operation cost is low, the time is short, and investment repayment is fast, easily expands, affects little by natural environment, landform and disaster, the advantages such as networking flexibility is quick." anyone at any time, any place communicates with anyone by any way " can be realized, compensate for the deficiency of conventional wired LAN.Along with formulation and the implementation of IEEE802.11 standard, the product of WLAN (wireless local area network) will be abundanter, and the compatibility of different product will be strengthened.The transfer rate of wireless network has reached and has exceeded 10Mbps, and is constantly accelerating.Outside WLAN (wireless local area network) decapacitation transmitting voice information, can also successfully carry out novelly in cooperative multipoint transmission system, controlling the method shape of cooperative transmission of downlink signal, the novel transmission controlling the media such as method picture and digitized video of cooperative transmission of downlink signal in cooperative multipoint transmission system.

Well-known cable network is connected together by each network equipment by netting twine, no matter is router, switch or computer, and network communication all needs netting twine and network interface card; Wireless network is then different greatly, we carry out communication by 2.4GHz wireless signal at 802.11 standard wireless network of extensive use, owing to adopting wireless signal communication, just more flexible in network insertion, as long as there is signal just can be completed the object of network insertion by wireless network card; Simultaneously network manager also need not be worried switch or router port lazy weight again and cannot complete dilatation work.The feature that generally speaking medium-sized and small enterprises wireless network compares conventional wired networks is mainly reflected in following two aspects.

(1) wireless network networking is more flexible:

Wireless network uses wireless signal communication, and network insertion is more flexible, as long as there is the place of signal the network equipment can be linked into corporate intranet whenever and wherever possible.Therefore when corporate intranet application needs mobile office or instant demonstration, wireless network advantage is more obvious.

(2) upgrading of wireless network scale is convenient:

Wireless network terminal equipment access restricted number is less, compare the corresponding equipment of cable network interface, wireless router allows that multiple wireless terminal device is linked into wireless network simultaneously, and therefore when enterprise network scale is upgraded, wireless network advantage is more obvious.

Vision of the future is after technology of new generation has just released market, and higher technology application is is researched and developed in laboratory.The NTT DoCoMo company of Japan represents, the experimental network of 4G communication has been deployed in the research and development garden, Yokosuka of company, this network has assembled test base station and mobile terminal, NTT DoCoMo company also represents simultaneously, 4G communication service will be released in 2010, the speed of download of network can reach 100Mbps, and upload speed is 20Mbps.The test of the 4G communication network that AT & T company of the U.S. releases, allegedly can coordinate EDGE to carry out wireless uploading, and reach quick-downloading object by OFDM technology.AT & T company of the U.S. claims approximately also needs 5 years, and this technology could be issued; Have in a decade or so again, 4G really could put into commercial stage.Europe four mobile device manufacturers---Alcatel, Ericsson, Nokia and Siemens constitute wireless research forum of the world (WWRF), to study the later developing direction of 3G.WWRF estimates that 4G technology will start in 2010 to drop into application.This generation communication technology can by different WLAN and communication standard, mobile phone signal, and radio communication and television broadcasting and satellite communication combine, and such cellphone subscriber just can arbitraryly roam.At European Region, radio area loop and digital audio broadcasting are applied for its indoor (Indoor) and carry out relevant research and development, test event comprises the application of 10Mbps and MPEG image transmission, forth generation mobile communication technology will be then the extension of existing two research and development technologies, first technology starts indoor, then expands to outdoor mobile communication network gradually.A high-ranking official of Ericsson represents, the said firm can not reduce the budget of research and development forth generation wireless communication technique when economic depression, the director of the said firm represents simultaneously, the R&D work of the said firm has the perspective of 3-10, and temporary transient weak demand can not make the said firm slow down the speed of research.

International Telecommunication Union's Radiocommunications is also reached common understanding, and mobile communication system will be combined with other system, is that data transmission rate reaches 100Mbps before 2010.For more senior 3G system, ITU determines two standards simultaneously developing IMT-2000---improving the transmission rate of packet and audio files---by the WCDMA of Japanese NTT DoCoMo and J-Phone two company employing by the maximum downloading rate reaching 8Mbps of energy, and CDMA2000 system also will reach the speed of 2.4Mbps.Simultaneously externally the issue a statement frequency range of forth generation mobile communication of ITU not yet comes into question and formulation, but will be based on high band frequency spectrum in principle, also will use the relevant technology of microwave and frequency range in addition.

Forth generation mobile communication system should possess following several fundamental characteristics:

(1) service in complete set: every business such as personal communication, information system, broadcast and amusement will be combined into an entirety, and being supplied to user serves widely than ever and apply; The use of system will be more safe, convenient and more look after the individual character of user.

(2) immanent mobile access: in a 4 g system, the main access way that mobile access will be to provide the business such as speech, high speed information business, broadcast and amusement, people can be linked in system at any time, everywhere.

(3) subscriber equipment miscellaneous: mobile device miscellaneous for use is linked into 4G system by user.Exchanging between equipment with people is no longer only simply listen, say, see, can also be exchanged by other approach with user.This will be large easy for people to use, the particularly use of some disabled user.

(4) autonomous network configuration: the network of 4G system will be a Complete autonomy, adaptive network, and it can manage automatically, dynamically change the structure of oneself to meet the requirement of system change and development.

Access way is according to different applied environments, and the topological structure that WLAN (wireless local area network) adopts mainly contains four kinds, bridge connecting-type, access node connecting-type, HUB access type and non-stop layer type.

1, bridge connecting-type.This structure is mainly used in the interconnection between wireless or cable LAN.When two local area network (LAN)s cannot realize wired connection or use wired connection to have difficulties, bridge connecting-type can be used to realize point-to-point connection.Communication in such an embodiment between local area network (LAN) is realized by respective wireless bridge, and wireless bridge serves the effect of network path selection and protocol conversion.

2, access node connecting-type.This structure adopts mobile cellular communication net access way, communication between each mobile site is first got off by receives information by wireless receiving station (access node: AP) nearby, then the information received is passed to " mobile switching centre " by wired network, then is sent on all wireless receiving stations by mobile switching centre.At this moment in network coverage, this signal can be received Anywhere, and can roaming communication be realized.

3, HUB access type.In cable LAN, utilize HUB can set up Star Network structure.Wireless aps equally also can be utilized to set up the WLAN (wireless local area network) of hub-and-spoke configuration, and its working method is very similar with wired hub-and-spoke configuration.But General Requirements wireless aps should have function of exchange in simple net in a wireless local area network.

4, non-stop layer type structure.The operation principle of this structure is similar to the working method of wired peer-to-peer network.It requires all directly to carry out information exchange between any two websites in net.Namely each website is work station, is also server.

Networking products radio network product.

Wireless

1, versatility--the single platform of multiple Presence Protocol and application can be supported simultaneously;

The system of 2, simplification--easy to understand, operation and maintenance;

3, validity--save the extendible network of frequency spectrum and power.

Above key characteristic brings following advantage:

Total ownership cost can drop to minimum by the single wireless facility 1, being applied to whole factory;

2, connect multinomial mounted industrial protocol (as HART, OPC, Modbus etc.) simultaneously;

3, with existing industrial safety Realization of Product Seamless integration-;

4, the most reliable network--the longest uptime can be provided through on-site verification;

5, current the most scalable factory wireless system.

WLAN

WLAN communication system is selected generally to be used in same seat building as the another kind beyond wired lan.WLAN uses ISM (Industrial, Scientific, Medical) radio broadcasting band communication.The 802.11a standard of WLAN uses 5 GHz frequency ranges, and the maximal rate of support is 54 Mbps, and 802.11b and 802.11g standard uses 2.4 GHz frequency ranges, supports the speed of maximum 11 Mbps and 54 Mbps respectively.

WLAN is similar to wired ethernet, and they are all distribute MAC (Media Access Control) address from same address pool, and are all the network equipment layers appearing at operating system as ethernet device.Such as, ARP (Address Resolution Protocol) table is filled with WLAN MAC address and ethernet mac address.But WLAN and wired ethernet make a big difference at link layer.Such as, 802.11 standards use conflict avoidance (CSMA/CA) to replace the collision detection (CSMA/CD) of wired ethernet.And, with ethernet frame unlike, WLAN frame is identified.

Due to the smeared out boundary between WLAN work station, WLAN link layer has the agreement removing a region before transmission.For security consideration, Wired Equivalent Privacy (WEP) encryption mechanism of WLAN provides the level of security identical with cable network.40 bits or 104 bit keys and 24 random bit initial vectors combine in order to encryption and decryption data by WEP.WLAN supports two kinds of communication patterns: Ad Hoc pattern is used for need not using between small group work station the interior communication of the short time of accessing points, and all communications of Infrastructure pattern must pass through accessing points.Accessing points periodically broadcasts a service set identifier (SSID), and SSID is used for a wlan network and other networks to distinguish to come.

Most of available WLAN card is based on Intersil Prism or Lucent Hermes chipset.Compaq, Nokia, Linksys and D-Link card uses Prism chipset.

Descending transmission CoMP comprises two class technology: cooperative scheduling and beam forming, Combined Treatment and transmission.

And for uplink receiving CoMP, then only have and combine reception and a kind of technology of process.

In LTE-A, the complexity of various CoMP-JP method for precoding, signaling and resource requirement and the performance that can obtain are had nothing in common with each other.

Look up from technical side, still mainly concentrate on compressed feedback amount at present and optimize codebook design.Because the viewpoint of each manufacturer on the realization means of CoMP precoding is different, and difference is comparatively large, and the standardized process that in fact result in CoMP is relatively slower, still awaits further further investigation.

The upgrading of network, has simultaneously carried out simple comparative analysis for the disturbed condition of a cooperative communication network and existing system.

Can see, collaboration communication concept promotes for the systematicness of single station communication technology, no matter covers, disturbs, flow can obtain higher performance.

The summit that its introducing will really make this technology of LTE become the communication technology, meets the demand of business development in current and following one period, and can guide the continuous rise of new business, opens the New Times of mobile data communication.

Claims (9)

1. the novel method controlling cooperative transmission of downlink signal in cooperative multipoint transmission system of the present invention belongs to electronic information field;

In the evolution of LTE standard, collaborative multicast communication (CoMP) is a kind of important technology,

Its core concept is by multipoint cooperative, forms virtual multiple-input and multiple-output (VMIMO), to promote cell-edge performance.

2. collaborative multicast communication has different long-distance radio frequency unit (RRU) cooperation, base station and the various ways such as relay cooperative and cooperation between base stations belonging to it in base station;

The realization of various different collaborative multipoint transmission mode is all based on following two conditions:

Information sharing (be included in the part or all of channel condition information of subscriber equipment, also require the data message sharing to subscriber equipment under some cooperation mode) between cooperation point;

Federated resource distributes/scheduling;

In 3GPP RAN1 the 57th meeting, each manufacturer has adopted unanimously and may adopt following 3 kinds of feedback strategies in collaborative multicast communication (CoMP) technology: explicit channel status/statistical information feedback; Implicit information channel state/statistical information feedback, as: channel quality instruction (CQI), pre-coding matrix instruction (PMI), order instruction (RI);

In tdd mode, utilize channel heterogeneite to obtain descending channel condition information based on up detection reference signal (SRS) Signal estimation; For various different feedback method, there is different precoding modes accordingly;

Different by the degree of the information of sharing, CoMP can be divided into Combined Treatment (JP) and cooperative beam shaping (CBF) two kinds of modes;

Wherein CBF requires the channel condition information of sharing users equipment (UE) between cooperative node; JP requires channel condition information and the data message of sharing UE between cooperative node;

Because multi-user Cooperation multicast communication (CoMP-MU) mode based on JP can obtain larger performance boost, the CoMP-MU method for precoding herein in main research indoor baseband processing unit (BBU)+multiple RRU scene under JP mode;

In CoMP system, associating precoding can having come in the mode of centralization by RRU multiple in same BBU;

The RRU of these cooperations is called " CoMP-RRU ", is a UE group service using identical time/frequency source block;

The precoding of CoMP-RRU allied signal reduces presence of intercell interference, to improve system spectral efficiency, and the particularly throughput of edge customer;

Suppose that each RRU has a n t transmitting antenna, each UE has a n r reception antenna;

Because transmitting terminal can obtain the equivalent channel after precoding, thus UE after obtaining precoding

Capacity, match so user can be chosen based on the principle of maximum capacity;

Direct channels matrix feedback can provide abundant channel information, but is impossible for fdd mode perfect channel matrix information feedback, and the channel relevancy of time domain or frequency domain must be utilized to compress feedback quantity and adopt suitable quantification technique;

Average on time domain, frequency domain or quantize the serious distortion that all may cause H to H is capable, analyzes method that is average and that quantize two kinds of compressed feedback amounts under different scenes to the impact of performance.

3., in tdd mode CoMP, if adopt SRS design can bring the problem of the SRS serial correlation poor-performing of cooperation cell SRS received power deficiency and different districts, in order to support CoMP-JP, may need that existing SRS signal is carried out certain and strengthening;

Based on the method for precoding of spatial correlation matrix

Under some condition, the average or compression of channel matrix on time domain, frequency domain will reduce its validity greatly, and this also makes the feedback of channel matrix compress and becomes comparatively difficulty;

But average on frequency domain or time domain of the spatial correlation matrix of channel but can not cause very large distortion, so carry out precoding based on channel covariance matrices may become one

More efficiently method for precoding;

Based on the method for precoding of code book

Its principle of method for precoding based on code book prestores a code book (i.e. the set of pre-coding matrix), receiving terminal selects best pre-coding matrix according to current channel status with certain criterion, and pre-coding matrix numbering (PMI) is fed back to transmitting terminal;

Because its feedback quantity is little, simultaneously good with Rel.8 compatibility, in standardized process, obtain the support of a lot of company;

Rel.8 code mainly designs for the carrying out of SU-MIMO, and concerning MU-MIMO or CoMP-MU, its performance is not fine;

From CoMP, due to multicast communication, the antenna number that code book needs are supported can to 8, and the performance boost that 4 bit feedback 8 antenna codebooks bring compared with 4 bit feedback 4 antenna codebooks is very limited, so need more number of bits of feedback to support CoMP-MU;

Scheme is a fixed codebook design, and the number of bits of feedback of increase is for supporting larger code book;

The novel feature controlling the method for cooperative transmission of downlink signal in cooperative multipoint transmission system of the present invention is that realization is simple, feedback overhead is little;

But this scheme code book is to the adaptive capacity of scene, and be limited to the lifting of systematic function;

Research shows, along with the increase of code book, the performance boost of acquisition can be tending towards saturated very soon, simultaneously, for different codebook design (such as: based on the codebook design of DFT, the codebook design etc. of Householder conversion), when zone of saturation, its performance is closely;

Another scheme is a kind of adaptive codebook of design, and when utilizing channel correlation matrix long, value of feedback is to adjust the code book of current employing;

Because in slow fading channel, the change of channel correlation matrix R is slow, so the feedback interval of R (i.e. the code book adaptive time interval) can arrange longer, the feedback quantity of increase is very little compared with fixed codebook method like this;

Uplink SRS signal can be used for estimating R in some cases;

First adaptive code the design will determine a base code book, for the code book based on multiple Hadamard conversion (CHT) of 8 × 16;

When not utilizing channel space correlation matrix R, code book is WDS; When adopting R, code book will be adopted: wherein, two norms of each row are normalized to 1 to W=normalize (RWCHT) by function normalize (g) expression.

4. the R Rk that also can be made up of a front k characteristic vector in addition

Replace: compared with fixed codebook method, adaptive code this method can obtain larger performance boost, but compared with first two method, its performance that can reach is still very limited;

In addition based in the method for precoding of code book, user's pairing is a more scabrous problem, which also limits the ability of the method for precoding improving performance based on code book;

For the method for precoding of fixed codebook, wave beam distance minimum criteria (MBD) of the pre-coding matrix can only chosen based on each user carries out user's pairing; For adaptive codebook method for precoding, first do based on R the thinking that user's pairing is a kind of solution, but due to the feedback interval of R comparatively large, the validity of this method needs further checking;

Long Term Evolution (LTE) technology designs good advanced techniques;

In wireless access mesh portions, first, utilize descending and up OFDM/discrete Fourier transform (DFT)-spread-spectrum orthogonal frequency division multiplexing (OFDM/DFT-SOFDM) technology to achieve completely orthogonal channel in community, greatly eliminate same area interference; Secondly, the flexible conversion of the occupation mode such as transmit-receive diversity, space division multiplexing, wave beam forming of multi-antenna technology, the flexible utilization characteristic of space channel, augmented flow, overcomes interference; In addition, multiple cell interference coordination (ICIC) mechanism, first time breaches the thinking that single subdistrict independently controls, and multiple cell is regarded as an Iarge-scale system, introduces the thought of joint coordination interference; Therefore, the link flow of LTE system is close to shannon limit, in the follow-up evolution of LTE system, for higher spectral efficiency requirements, the work that link level technological improvement can be done is limited, and in order to reach the object of improve link level performance (SINR), must then seek system-level solution.

5. cooperative communication technology is exactly be introduced in LTE system under this background;

Collaboration communication refers to that multiple base station (eNodeB) in system or multiple base station and antenna station long-distance radio frequency unit (RRU) carry out the technology of multiple spot sending/receiving simultaneously, and user terminal (UE) will link and communicates with setting up between multiple base station and antenna station up-downgoing;

Can carry out netted interconnected between base station and multiple antenna station, multiple base station with optical fiber;

Specifically, in network, insert antenna station, or formed distributed based on existing website

Antenna system, carries out and MIMO between UE, is called collaborative multicast communication technology; When directly utilizing existing network, with fiber interconnect between each base station, multiple base station directly communicates with UE, is called coordination technique between base station; These two kinds of forms are all collaboration communication application in practice;

In this case, one of them base station is the dominant base communicated with UE, and other base stations then deteriorate to RRU antenna station.

6. collaboration communication mainly make use of the gain of system process, the gain cooperated to bring multistation, needs in concrete technology, consider multistation cooperation problem;

At present also topmost several key technologies under study for action have:

Intelligent association; UE can the minimum transmitting station of automatic searching path loss access;

Load balancing technology between standing; Multiple website shares the traffic load in overlay area jointly, needs interior communication to coordinate business and shares and resource service condition;

Multi-antenna cooperative MIMO technology;

Multiple covering website is each can adopt different multiple-input and multiple-output (MIMO) types of service, the region that such as multi-site covers, different user can take identical running time-frequency resource, but respectively wave beam forming is carried out to different user by multiple website, distinguish user, improve spectrum efficiency;

Collaboration site selecting technology;

Select appropriate website number, distributing position carries out multistation cooperation, to reaching optimum cooperation effect;

Dynamic I CIC technology; In multistation collaboration communication, adopt multiple base stations energy of Fiber connection

Enough carry out data communication fast, therefore, it is possible to realize real dynamic I CIC technology, coordinate the interference of minizone;

Macro station, microcellulor composition layering hybrid network are commonly used in the macrocellular networking of the e-learning quality classics after application collaboration communication network technology, macro station covers continuously, microcellulor is used for focus covering, blind area covers, the traffic hotspots of macrocellular is absorbed, supplements covering leak and blind area that macrocellular covers generation continuously simultaneously;

The form covered, employing soft-frequency reuse (SFR) mode carries out the frequency planning between multiple community, between grand microcellulor, so network construction form;

Existing system is in order to solve the problem of co-channel interference between the co-channel interference of community handover region, grand Microcell, and the mode adopting SFR, ensures that different school district adopts different frequency ranges at the fringe region that overlap covers more, adopts frequency division multiplexing to come Cochannel interference;

But this problem caused is the: Chan availability of frequency spectrum to be reduced;

The mode of frequency division multiplexing reduces interference by the mode of the sacrifice availability of frequency spectrum;

Chan reduces communication quality;

In the moving process of UE to cell edge, will carry out the passive change of working frequency range frequently, this change can destroy the performance of the link adaptation in frequency selection scheduling process, thus reduces communication quality;

Chan too relies on the scheme that Internal and external cycle divides;

Different splitting schemes will have an impact to systematic function, if will obtain the coordinating district interference scheme that is suitable for high speed, low speed, underloading, heavily loaded various scene, system ICIC algorithm complex is high, which increases the burden of each eNodeB;

When after introducing multistation cooperative communication technology, be connected with optical fiber between base station, one of them base station is as dominant base, and for service communication, other base stations deteriorate to RRU, and multiple spot sends simultaneously and receives.

7. in this case, increase the coverage of dominant base, reduce Zone switched, become traditional grand Microcell Hierarchical Network and be covered as many NodeB node and divide

Undertake He great district to cover; During frequency planning Zhong great district between this multiple community, between grand microcellulor covers, multiple spot transmitting-receiving not only makes up-downgoing coverage distance increase, and, because UE can select the website minimum with path loss to access, multiple spot transmitting-receiving simultaneously brings the macro diversity of soft handover in similar 3G system, thus also stronger in covering power, covering quality is better, and mulching measures is higher;

In addition, utilize the design to dispatching algorithm and multistation tuning algorithm in collaboration communication, traffic load multistation in great Qu is dynamically shared, support business all in great Qu simultaneously, the base station that different UEs can choose at random signal quality best is accessed, and when UE moves in the scope that master station and follow station covers, is equivalent in the area of coverage of same dominant base, can steadily switch fast, QoS (QoS) impression is better;

Thus, spectrum efficiency, service feature are promoted to some extent, and ICICl algorithm complex also can corresponding reduction some;

Interference analysis

In multistation cooperation communication system, in multiple websites of cooperation, a base station is as dominant base, and other base stations deteriorate to RRU, like this, master station controls the coupled UE communication in coverage, coordinates resource service condition with other base stations deteriorating to RRU simultaneously;

Like this, in coverage, originally the up-downgoing co-channel interference of multiple minizone is greatly reduced, and even can reach the situation of nearly orthogonal, so, and the interference that the group of base stations of other the collaborative work being far-end produces by the interference source of system;

The network model of simple for use one LTE system model and cooperation communication system is carried out the research of interference analysis below;

The network of R8 LTE system, each community can be subject to the co-channel interference from other neighbor cells; For multistation cooperative communication network, one group, 3 base stations, carry out multipoint cooperative communication in group, each group of co-channel interference that can be subject to other groups, the up-downgoing interference variations situation that this section will compare in the coverage of NodeB in two kinds of situations;

When not adopting any added technique (such as smart antenna Anti-Jamming Technique, interference coordination technique etc.);

It is the analysis of the interference lifting in downlink coverage, it is the interference lifting analysis in uplink coverage, can see, the interference brought by multi-site collaboration communication separately decreases, from down link, the reduction of interference rank entirety is about about 2 dB, and the interference reduction of up link is about 2 ~ 4 dB.

8. the novel method controlling cooperative transmission of downlink signal in cooperative multipoint transmission system of the present invention have employed the reduction of simple scene to the interference that cooperation communication system brings and analyzes, in reality, due to macrocellular, microcellulor layering networking structure, appropriate choosing is grand, microcellulor node cooperates, the effect that the interference brought reduces will be better, consider antenna downtilt, ICIC, the use of multi-antenna technology, cooperative communication network will become in a community, the system of presence of intercell interference all nearly orthogonal, interference is reduced greatly on the impact of throughput of system, spectrum efficiency gets a promotion,

Although cooperative communication technology brings obvious system gain, the technical advantage of this technology is all brought into play, also have many problems to need research, such as:

The covering problem of signaling channel, multiple site collaboration sends the coverage expanding single station,

But first need control channel to reach good covering performance in whole coverage, this is a problem needing to be studied in great detail;

How all system loadings in large coverage, share between multiple NodeB, and this part work can increase the signaling traffic between NodeB;

Dynamic I CIC; Dynamic I CIC real between base station needs a large amount of interior communications, and the increase along with cooperative base station scale constantly increases by this, follow-uply will study;

These problems are the key issues run in cooperative communication technology application above, resolve these problems, systematic function will be made to have higher lifting;

CoMP (Coordinated multiple point, collaborative multiple spot) is that LTE-Advanced system dilates network edge covers, one of the important technology ensureing edge customer QoS, is the exclusive technology of LTE-Advanced system;

In LTE-Advanced system, CoMP comprises two kinds of scenes: cooperation between base stations and distributing antenna system; From data flow always, CoMP can be divided into again descending transmission CoMP and uplink receiving CoMP.

9. descending transmission CoMP comprises two class technology: cooperative scheduling and beam forming, Combined Treatment and transmission;

And for uplink receiving CoMP, then only have reception and a kind of technology of process of combining;

In LTE-A, the complexity of various CoMP-JP method for precoding, signaling and resource requirement and the performance that can obtain are had nothing in common with each other;

Look up from technical side, still mainly concentrate on compressed feedback amount at present and optimize codebook design; Because the viewpoint of each manufacturer on the realization means of CoMP precoding is different, and difference is comparatively large, and the standardized process that in fact result in CoMP is relatively slower, still awaits further further investigation;

The upgrading of network, has simultaneously carried out simple comparative analysis for the disturbed condition of a cooperative communication network and existing system;

Can see, collaboration communication concept promotes for the systematicness of single station communication technology, no matter covers, disturbs, flow can obtain higher performance;

The summit that its introducing will really make this technology of LTE become the communication technology, meets the demand of business development in current and following one period, and can guide the continuous rise of new business, opens the New Times of mobile data communication.