CN101018362B - A media access control method based on the OFDMA technology - Google Patents
A media access control method based on the OFDMA technology Download PDFInfo
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- CN101018362B CN101018362B CN2007100636021A CN200710063602A CN101018362B CN 101018362 B CN101018362 B CN 101018362B CN 2007100636021 A CN2007100636021 A CN 2007100636021A CN 200710063602 A CN200710063602 A CN 200710063602A CN 101018362 B CN101018362 B CN 101018362B
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Abstract
The disclosed media access control method based on FDMA comprises: with resource pre-served mechanism, setting flag bit in user data package to show whether pre-serve same resource in next frame, and adjusting transmission resource from BS to mobile platform according to data quantity in buffer. This invention improves system efficiency.
Description
Technical field
The present invention relates to OFDM (OFDMA) system, relate in particular to a kind of medium access control (MAC) method based on the OFDMA technology.
Background technology
The quick growth with user's request of developing rapidly along with mobile communication technology, multimedia services such as audio frequency, video, image and the Internet will become the dominant traffic of future mobile communications, and these business obviously improve for the requirement of transmission of radio links ability, in the case, OFDM (OFDM) technology is shown up prominently gradually.The OFDM technology will not only have the ability of anti-multipath time delay, and eliminate the intersymbol interference (ISI) that causes by multidiameter delay fully, the OFDM technology is adopted by several communication standards at present, and is acknowledged as one of basic fundamental of next generation mobile communication system physical layer substantially.OFDM (OFDMA) technology is exactly by the subcarrier of quadrature is distributed to different users neatly, make in communication system, realized inserting in the multi-user, the dynamic change resource allocation methods, can satisfy the multiple services service quality of multi-user (QoS) demand in the future mobile communication system, so OFDMA is one of multi-address method of very likely adopting of next generation mobile communication system.
Based on the growth requirement of future mobile communications and the key technology of physical layer, the MAC layer need carry out adaptive to the key technology of physical layer, can satisfy the high rate data transmission of data and the dynamic change of data rate, can carry out flexible allocation, improve systematic function Radio Resource.MAC method for present classics, for example PRMA agreement and MPRMA agreement, wherein the PRMA agreement combines the access way of slotted-ALOHA, MT uses the available time slot access base station of the access way competition up channel of slotted-ALOHA, have only speech business just can preengage, data service can't continue the reservation of resource; And the MPRMA agreement is the improvement to the PRMA agreement, at access contention time slot end, BS informs the access situation of each travelling carriage by ACK message, after MT is allowed to access, the nearest available time slot of chosen distance access contention time slot sends data, and by flag bit show whether need the reservation, though this agreement allows voice user and data user to preengage, but this cut-in method still adopts time division multiplexing (TDMA) technology, can not be applied to advanced OFDMA/TDD system carries out dynamically, distributing system resource neatly, thereby can not satisfy future mobile communications increase power system capacity, and reduce access delay, reduce the requirement of system cost.
Summary of the invention
Task of the present invention provides a kind of medium access control (MAC) method based on OFDM (OFDMA) technology.
Substantially conceive according to the present invention, mac frame structure based on OFDMA technology tdd mode has been proposed, the Radio Resource that system is provided is divided into the elementary cell of little time-frequency piece (MTFB) as message transmission from time domain and frequency domain, is that the center is dynamically controlled the Radio Resource of system with the base station; Simultaneously, method has adopted the method for dynamic change system access probability threshold value, parameters such as minimum available time-frequency block threshold value when system allows the data user to insert according to the number of current system available resources, system and service priority are dynamically admitted control to the non real-time user, have improved systematic function effectively; This method has adopted resource reservation mechanism, flag bit is set in user data package, in order to whether to show application to the next frame resource, and MT informs quantity of data packets to be sent in the MT buffer of base station (BS) by the form of bearing (pigyback) in packet, BS judges thus to MT to be increased transfer resource or reduces the transfer resource that distributes, can reduce the Signalling exchange of system by volume like this, and can be adapted to the transmission demand of variable Rate business, improve system effectiveness.
According to the present invention, a kind of media access control method based on OFDM is provided, described method comprises step:
Use resource reservation mechanism,, whether the same resource of next frame is reserved application in user data package in order to show by flag bit is set, and
According to quantity of data packets to be sent in the travelling carriage buffer, the base station increases transfer resource or reduces the transfer resource that distributes to travelling carriage.
Preferably, this method also comprises step:
If flag bit is not set, then the base station discharges resource, and the state of resources that base station described in the status register discharges is revised as available so that the resource that other users use described base station to discharge;
If flag bit is set, then the base station continues as described user and reserves former resource to carry out transfer of data.
Preferably, this method also comprises step:
The base station sends the number of bag according to user's needs and to the judgement of type of service, described user is reduced former Resources allocation or appends new Resources allocation, to satisfy the transmission demand of variable Rate real time business and non-real-time service.
Preferably, this method also comprises step:
The Radio Resource that is used for the up-downgoing transfer of data that orthogonal frequency division multiple access system is provided is divided into the elementary cell of little time-frequency piece as message transmission from time domain and frequency domain, and is that the center is dynamically controlled the Radio Resource of system with the base station.
Preferably, wherein each little time-frequency piece is made up of mini-slot on the time domain and the subband on the frequency domain.
Preferably, one of them mini-slot comprises 3 OFDM symbols, and a subband on the frequency domain comprises 12 adjacent sub-carriers.
Preferably, wherein the up stage of the mac frame of orthogonal frequency division multiple access system is made up of access slot and uplink time slot;
The user initiates to insert request at access slot, subcarrier to active user picked at random different frequency on frequency domain sends the request of access, and the non real-time user controlled its access probability before the request initiating, to reduce the probability that the user bumps and the processing complexity of mobile station side;
The descending stage is made up of time slot and downlink transfer time slot, and the base station sends at time slot the user is inserted the answer of request and resource reservation request and to the allocation result of resource.In addition, between the uplink and downlink frame, has protection at interval.
Preferably, the non real-time user is specifically comprised in the step of initiating before the request its access probability to be controlled:
The non real-time user is adopted dynamic change system access probability threshold value,
Wherein the access probability threshold value of system is determined according to the number of current system loading conditions, current system available resources, the prediction of follow-up access customer number purpose and professional priority, according to the situation that last subsystem inserts system's access probability threshold value is dynamically adjusted, and system's access probability threshold value of upgrading is sent to the user with the form of broadcasting, the system that makes can dynamically admit control to the data user, reduces the collision probability the when user inserts next time.
Preferably, travelling carriage is informed quantity of data packets to be sent in the travelling carriage buffer by the form of bearing to the base station in packet, and the base station is judged thus to travelling carriage to be increased transfer resource or reduce the transfer resource that distributes.
Preferably, this method also comprises step:
The non real-time user is one of generation access probability value Pa at random before send inserting request, and compares with the access threshold value Pc of orthogonal frequency division multiple access system,
When Pa could send the request of access during greater than Pc, thereby when the orthogonal frequency division multiple access system load is busy, reduce too high and other the professional time delays that cause of data user's collision rate;
After the base station receives the request of inserting, admit control, if orthogonal frequency division multiple access system still has available resources, and to judge this type of service be real time business, then allows described travelling carriage connecting system, allows its transmission information.
Description of drawings
Fig. 1 shows the mac frame structural representation of tdd mode of the present invention.
Fig. 2 shows the running time-frequency resource cell schematics in this invention.
Embodiment
For making purpose of the present invention, technical method and advantage clearer, to the present invention, especially the access procedure of inventive method, adaptively changing system access probability threshold value, Dynamic Resource Allocation for Multimedia mechanism are described further below in conjunction with accompanying drawing and concrete preferred embodiment.
As shown in Figure 1, in the mac frame structure of this inventive method tdd mode, the up stage is made up of access slot and uplink time slot, user (MT) initiates to insert request at access slot, this cut-in method has adopted the subcarrier to active user picked at random different frequency on frequency domain to send the request of access, and the mechanism that the non real-time user was controlled its access probability before initiating request, to reduce the probability that the user bumps and the processing complexity of MT side.Detailed access control process can describe below in conjunction with the preferred embodiments.MT utilizes transmission time slot to send customer service, for Resources allocation effectively dynamically, agreement is further divided into mini-slot with conventional transmission time slot, with its least unit as transmission resource division on the time domain, supposes that each conventional transmission time slot is divided into Lm mini-slot.The descending stage is made up of time slot and downlink transfer time slot, and BS sends at time slot the user is inserted the answer of request and to the allocation result of resource.In addition, between the uplink and downlink frame, has protection at interval.
As shown in Figure 2, consider the characteristics of OFDMA system resource, the least unit that we define running time-frequency resource in this invention is little time-frequency piece (MTFB), with its base unit as the business transmission.For example, a MTFB in the supposing the system can be made up of the subband (comprising 12 adjacent sub-carriers) on a mini-slot on the time domain (comprising 3 OFDM symbols) and the frequency domain, can reduce the Signalling exchange and the implementation complexity of system like this.
The inventive method has been utilized the main feature of OFMDA/TDD technology, and is feasible more flexible to the distribution of resource, and can reduce signaling consumption, improves the performance of system.
Introduce the operation of medium access control (MAC) method in detail according to the present invention below in conjunction with preferred embodiment.
Voice user and data user are arranged in the supposing the system.When travelling carriage has service needed to send, at first access slot at random the chooser carrier wave send the request of access, wherein insert and comprised the type of service that MT will send in the solicited message.But the data user also will produce an access probability value Pa at random before sending the request of access, and compare with the access threshold value Pc of system, have only as Pa to send the request of access during greater than Pc, when system load is busy, can effectively reduce too high and other the professional time delays that cause of data user's collision rate like this.After BS receives the request of inserting, admit control, if system still has available resources, and to judge this type of service be speech business, then allows this MT connecting system, allows its transmission information.Insert threshold value Pc for system, the present invention proposes the method for dynamic change access probability threshold value Pc, this value can be according to the number of system load, system's available resources, dynamic change is carried out in follow-up access customer number purpose prediction and service priority, suppose that Pt is the access probability value of default, Rf is that current system can be with the number of time-frequency piece, and N is the minimum time-frequency block threshold value of system when allowing the data user to insert.Ω represents service priority, from 0 to n value, is worth more for a short time according to the height of service priority, and priority is high more.N
D(t+M) be the estimated value of the number of users of (t+M) frame request access, then:
Wherein, suppose that it is the Poisson distribution of λ that Mobile Origination inserts request obedience parameter, then:
Wherein, N
D(i) be the number that sends the data user of the request of access in the i frame, Ns (i) inserts successful data user's number in the i frame.Simultaneously, BS informs Pc value after each travelling carriage upgrades by the mode of periodic broadcasting.If system does not have available resources, then refuse this user and insert.Handle all users' access request as BS after, respectively the voice-and-data business is carried out resource allocation, and the label that will distribute to user's time-frequency piece resource is broadcast to MT in the descending stage of same frame.
After MT correctly receives ACK information, if be allowed to access, then from ACK information, read the time-frequency piece resource label of distributing to oneself, and utilize this resource to send packet, and territory (piggyback), i.e. flag bit are born in setting in this packet.If this flag bit is " 0 ", represent that then the data transmission of travelling carriage oneself finishes, there have not been data to send in the buffer.If this flag bit is " 1 ", then MT informs number of data packets to be sent in the own buffer of BS simultaneously, so that carry out resource reservation.BS reads the flag bit of user data package like this, if flag bit is not set, then this state of resources is available in the base station modification status register, so that other users use this resource; If flag bit is set, then the judged result of this type of service is carried out resource allocation to this user according to the number and the front of the bag of travelling carriage needs transmission at present.If this user is the voice user, just thinks then etc. that bag number to be sent increase resource can for this user greater than the threshold value V1 of default and system's available resources during greater than threshold value V2, otherwise continue to give this user to distribute running time-frequency resource identical in the next frame; If this user is the data user, to have only when number of data packets to be sent and when threshold value V3 is above, could apply for more running time-frequency resource, distribution mechanism is identical with the voice user.In system, set like this and carry out that resource is appended or the threshold mechanism that reduces goes for the transmission of variable Rate business, take into account the fairness that guarantees between the user simultaneously; And be that mode that the center is controlled resource status can reduce by each travelling carriage and controls the computation complexity that causes separately with the base station.
This invention has demonstrated fully the advantage of being carried out center control access and Dynamic Resource Allocation for Multimedia by the base station, compare with PRMA, MPRMA method and can increase power system capacity, reduce user's access delay, can be under the condition that guarantees speech business QoS, more effectively support the transmission of data service, can satisfy the requirement of future mobile communications network support multi-service type, many transmission rate services.
Claims (9)
1. the media access control method based on OFDM is characterized in that, described method comprises step:
Use resource reservation mechanism,, whether the same resource of next frame is reserved application in user data package in order to show by flag bit is set, and
According to quantity of data packets to be sent in the travelling carriage buffer, the base station increases transfer resource or reduces the transfer resource that distributes to travelling carriage.
2. method according to claim 1 is characterized in that, described method also comprises step:
If flag bit is not set, then the base station discharges resource, and the state of resources that base station described in the status register discharges is revised as available so that the resource that other users use described base station to discharge;
If flag bit is set, then the base station continues as described user and reserves former resource to carry out transfer of data.
3. method according to claim 1 is characterized in that, described method also comprises step:
The base station sends the number of bag according to user's needs and to the judgement of type of service, described user is reduced former Resources allocation or appends new Resources allocation, to satisfy the transmission demand of variable Rate real time business and non-real-time service.
4. method according to claim 1 is characterized in that, described method also comprises step:
The Radio Resource that is used for the up-downgoing transfer of data that orthogonal frequency division multiple access system is provided is divided into the elementary cell of little time-frequency piece as message transmission from time domain and frequency domain, and is that the center is dynamically controlled the Radio Resource of system with the base station.
5. method according to claim 4 is characterized in that, each little time-frequency piece is made up of mini-slot on the time domain and the subband on the frequency domain.
6. method according to claim 1 is characterized in that, the up stage of the mac frame of orthogonal frequency division multiple access system is made up of access slot and uplink time slot;
The user initiates to insert request at access slot, subcarrier to active user picked at random different frequency on frequency domain sends the request of access, and the non real-time user controlled its access probability before the request initiating, to reduce the probability that the user bumps and the processing complexity of mobile station side;
The descending stage is made up of time slot and downlink transfer time slot, and the base station sends at time slot the user is inserted the answer of request and resource reservation request and to the allocation result of resource.
7. method according to claim 6 is characterized in that, the non real-time user is specifically comprised in the step of initiating before the request its access probability to be controlled:
The non real-time user is adopted dynamic change system access probability threshold value,
Wherein the access probability threshold value of system is determined according to the number of current system loading conditions, current system available resources, the prediction of follow-up access customer number purpose and professional priority, according to the situation that last subsystem inserts system's access probability threshold value is dynamically adjusted, and system's access probability threshold value of upgrading is sent to the user with the form of broadcasting, the system that makes can dynamically admit control to the non real-time user, reduces the collision probability the when user inserts next time.
8. method according to claim 1, it is characterized in that, travelling carriage is informed quantity of data packets to be sent in the travelling carriage buffer by the form of bearing to the base station in packet, the base station is judged thus to travelling carriage to be increased transfer resource or reduce the transfer resource that distributes.
9. method according to claim 6 is characterized in that, described method also comprises step:
The data user is one of generation access probability value Pa at random before send inserting request, and compares with the access threshold value Pc of orthogonal frequency division multiple access system,
When Pa could send the request of access during greater than Pc, thereby when the orthogonal frequency division multiple access system load is busy, reduce too high and other the professional time delays that cause of data user's collision rate;
After the base station receives the request of inserting, admit control, if orthogonal frequency division multiple access system still has available resources, and to judge this type of service be real time business, then allows described travelling carriage connecting system, allows its transmission information.
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| CN101374264B (en) * | 2007-08-22 | 2012-06-06 | 中兴通讯股份有限公司 | Method for distributing real time business bandwidth resource |
| CN101414960B (en) * | 2007-10-15 | 2011-05-11 | 中兴通讯股份有限公司 | Method for configuring transmission resource |
| CN101499848B (en) * | 2008-01-31 | 2012-12-19 | 电信科学技术研究院 | Uplink scheduling method and apparatus |
| CN101242662B (en) * | 2008-03-14 | 2012-02-29 | 中兴通讯股份有限公司 | A broadband resource configuration method |
| CN101925192B (en) * | 2010-07-27 | 2013-07-24 | 新邮通信设备有限公司 | Signal channel access method |
| CN103379636B (en) * | 2012-04-26 | 2016-08-17 | 中国移动通信集团上海有限公司 | The distribution method of a kind of wireless carrier resource and equipment |
| CN106465357B (en) * | 2014-06-17 | 2019-12-06 | 华为技术有限公司 | Method for transmitting information, access point and station |
| EP3171652B1 (en) | 2014-08-19 | 2019-08-14 | Huawei Technologies Co., Ltd. | Data transmission method and apparatus |
| CN104244257B (en) * | 2014-09-03 | 2017-11-24 | 北京航空航天大学 | Adaptive reservation and dynamic time slot allocating method and device |
| CN104993902A (en) * | 2015-02-03 | 2015-10-21 | 协同通信技术有限公司 | Satellite communication system channel reuse method |
| WO2016183782A1 (en) | 2015-05-18 | 2016-11-24 | 华为技术有限公司 | A terminal device, network device and data transmission method |
| CN105429964B (en) * | 2015-11-05 | 2019-03-22 | 河北远东通信系统工程有限公司 | A kind of media server resources control distribution method |
| CN115884269A (en) * | 2021-09-27 | 2023-03-31 | 中兴通讯股份有限公司 | Resource unit allocation method and device, storage medium and electronic device |
| CN114726726B (en) * | 2022-05-24 | 2022-08-23 | 深圳市德兰明海科技有限公司 | Method for improving CAN bus communication efficiency |
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| CN1222271A (en) * | 1996-06-19 | 1999-07-07 | 北方电讯有限公司 | Medium access control scheme for data transmission on code division multiple access (CDMA) wireless systems |
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