WO2006035027A1 - Multiple access method for isonchronic or quasi-isochronic data traffic - Google Patents

Abstract

The invention relates to a method for transmitting data signals in a communication system with decentrally organized multiple access to a transfer medium, wherein a useful data packet (data) is transmitted from a transmitting station (S2) to a receiving station (S1) and a confirmation signal (ACK) confirming receipt of the useful data packet (data) is sent back by the receiving station (S1). The useful data packet (data) and/or the confirmation signal (ACK) are provided with additional network access vector information (FNI) for reserving a future transmision right (FNAV(ACK), FNAV(DATA)) of the transmitter station (S2). As a result, it is possible to improve efficiency, particularly in the case of isochronic or quasi-isochronic data traffic, and quality of service support.

Description

description

Multiple access methods for isochronous or quasi-isochronous data traffic

The present invention relates to a multiple access method for isochronous or quasi-isochronous Daten¬ traffic and in particular to a method for realizing a data traffic in a CSMA / CA communication system with decentralized multiple access with Kollisionsvermei¬ tion according to the modified standard IEEE 802.11, where a predictive reservation of resources is performed to reduce signaling overhead and to improve QoS.

Although the decentralized multiple access method with collision avoidance (CSMA / CA, Carrier Sense Multiple Access with Collision Avoidance), which is widely used for example in conventional communication systems according to the IEEE 802.11 standard, is simple to implement, it involves a relatively high signaling overhead and indefinite delay times for each individual subscriber ("best effort Service "), whereby the efficiency of such conventional methods is limited.

The IEEE 802.11 standard specifies in particular the multiple access control (MAC) method and the physical characteristics for so-called WLAN (Wireless Local Area Network) communication systems. In this case, a so-called medium access control unit supports the components of a physical layer depending on availability of the spectrum with regard to its access authorization to the transmission medium.

In principle there are two coordination possibilities for the

Access available, namely the central and the decentralized organized access functionality. At the centrally organized The coordination function logic is active only in one station of a communication system, as long as the network is in operation. In contrast, in the case of a decentralized organized access functionality (DCF, distributed coordination function), the same coordination function logic is active in each station of the communication system as long as the network is in operation.

To illustrate a decentralized multiple access functionality to a transmission medium, an exemplary configuration according to the IEEE 802.11 standard will first be described with reference to FIGS. 1 and 2.

FIG. 1 shows a simplified representation for illustrating a spatial distribution or a topology of a plurality of stations S 1 to S 5 within such a communication system. In this case, the station S2 represents a transmitting station or a transmitter and S1 a receiving station or a receiver, which lies in the radio range of the transmitting station S2. Furthermore, a station S3 in a radio range from the transmitting station S2 and a station S4 within a radio range of the receiving station S1 are located. The station S5 is in the topology of Figure 1 outside a radio range of the transmitting station S2 and the receiving station Sl.

FIG. 2 shows a simplified data frame structure for the data exchange of a decentrally organized multiple access system (DCF) according to the IEEE 802.11 standard. For this reason, reference should explicitly be made to this standard, in which all the terms and abbreviations essential to the invention are to be found again with regard to their meaning and functionality.

According to FIG. 2, after a first waiting time DIFS (DCF interframe space) is transmitted from the transmitting station S2 to the network remaining stations of the communication system a Sendbereit¬ RKS signal (Ready To Send) sent. With regard to the structure of this ready-to-send signal RTS, reference is again made to the standard. Essential for the invention is only a network access vector information NI, which is within the send ready signal RTS in a so-called "Duration" block and allows a reservation ei¬ nes current broadcasting rights with a predetermined period of time. After a short second waiting time SIFS (Short Interframe Space), the receiving station S1 selected by the transmitting station S2 transmits a ready-to-receive signal CTS (Clear To Send) for indicating a readiness for reception, within which a "Duration" block is again provided Network access vector information NI may be included. After a further short second waiting time SIFS, the transmitting station S2 sends a user data packet Data from the transmitting station S2 to the receiving station S1, in which the network access vector information NI can again be contained within a "Duration" block. After the transmission of the data in the data packet Data, after a further short waiting time SIFS, the receipt of the user data packet Data is confirmed by the receiving station S1 by means of an acknowledgment signal ACK (Acknowledge).

The network access vector information NI, which is contained in particular in the transmit and receive ready signals RTS and CTS, sets a so-called network access vector NAV in the other stations S3 and S4 of the communication network located in the reach of the transmitting or receiving station S2 and Sl (Network Allocation Vector), which specifies how long a transmission to the radio medium or the transmission medium can not be performed by the respective station. More precisely, the further stations S3 and S4 lying within the hearing range are assigned a broadcasting ban for the period of time defined by the network access vector information NI. The access to the communication system or the transmission medium is only again possible after expiration of this period. In the subsequent contention window, in order to avoid a collision, a further delay takes place around a due backoff time. The backoff time here is usually a random variable, which is different for each user and, after a successful access to the medium, is repeatedly "rescored" or randomly determined by the respective user.

As has already been explained in the introduction, the low signaling data overhead of the transmission and reception readiness signals RTS and CTS and the repeated waiting times SIFS and DIFS result in only a low efficiency of this conventional method, in particular in the case of short data packets. A further disadvantage, in particular of the represented distributed access system (Distributed Coordinated Function) as a special CSMA / CA realization form, lies in the lacking support of a so-called "Quality of Service" (QoS).

While the competition for resources or transmission channels on the air interface, which is anchored in the CSMA / CA method, is constantly recurring, for bursty traffic such as e.g. However, FTP (File Transfer Protocol) is still appropriate, but in particular for isochronous data traffic, such. Speech or video streaming, disadvantages in terms of its efficiency. Under isochronous data traffic, one usually associates specific applications which deliver data at regular intervals. In fact, one can also convert "bursty traffic" into quasi-isochronous data traffic for a certain time interval using corresponding "queues" and corresponding scheduling and then also use the same mechanisms.

In conventional methods, for example, to increase the efficiency of the CSMA / CA method, for example, the RTS / CTS mechanism is either completely omitted or several Confirmation signals ACK summarized. On the other hand, to improve support for the "Quality of Service", so-called prioritization of different "traffic" classes via dedicated Arbitrary Interframe Spaces (AIFS) as well as dedicated backoff settings can be enabled

(see IEEE 802.1Ie). Also, a so-called polling of the various stations of a central unit is possible.

In contrast, the invention has for its object to provide a method for transmitting data signals in a kommunikati¬ onssystem with decentralized organized multiple access to a transmission medium, which allows for improved Ef¬ efficiency and improved support for a "Quality of Service" (QoS) ,

According to the invention this object is achieved by the measures of claim 1.

In particular, by sending additional network access vector information (Future NAV Information) for serving a future transmission right of the transmitting station at a reserved time for a reserved period of time, in particular in the case of isochronous or quasi-isochronous data traffic, a significant increase in efficiency and extended support a "Quality of Service" can be achieved.

Preferably, the network access vector information is repeated by the receiving station in its ready-to-receive signal, whereby a spatial range of the pre-serve is increased and so-called "hidden nodes" are avoided.

Furthermore, in an initialization phase, the transmitting station can transmit transmission parameters for the desired isochronous data traffic to the receiving station, the receiving station depending on an analysis of this transmission path. parameter and / or its resource situation releases isochronous traffic. In this way, already made reservations in the vicinity of the receiving station, which are not yet known to the transmitting station (because they originate from stations that are in the "hearing range" of the receiver but not of the transmitter), can be taken into account.

Preferably, the additional network access vector information transmitted in the ready-to-send and / or ready-to-receive signal can be retrieved again in the user data packet, whereby a complete reservation of the transmission rights can be realized.

Furthermore, to reserve a further future transmission right, a further additional network access vector information can be sent in the acknowledgment signal of the receiving station, whereby a flexible adaptation of the system is made possible taking into account the analysis of the transmission parameters and / or the resource situation in the receiving station , The confirmation signal can also be used for channel identification.

The time intervals of the user data packets in the steady state defined by the additional network access vector information are preferably determined as integral multiples of a common time constant of the communication system, whereby the multiplexing of several independent data streams on the basis of the described reservation mechanism can be made substantially more efficient.

In the further subclaims further advantageous embodiments of the invention are characterized.

The invention will be described below with reference to a Ausführungsbei- game with reference to the drawings.

Show it: FIG. 1 shows a simplified representation of a spatial topology of stations in a communication system;

2 shows a signaling structure for illustrating a conventional method for transmitting data signals in a communication system with centrally organized multiple access to a transmission medium on the basis of a CSMA / CA; and

FIG. 3 shows a signaling structure for illustrating a method according to the invention for transmitting data signals in a communication system with decentralized multiple access to a transmission medium.

FIG. 3 shows a simplified representation of a signaling structure for illustrating a multiple access method according to the invention with collision avoidance for isochronous data traffic, the same reference symbols designating the same or corresponding elements or phases as in FIG. 2 and a repeated description being omitted below.

To define isochronous data traffic, it should first be established that a connection is isochronous if the slots or time slots available in a TDMA system (Time Division Multiple Access) are not allocated to a particular channel in fixed periodic times, such as for example a synchronous connection, but the times between the slots or time slots unterschied¬ Lich are long. Although it is understood that isochronous Daten¬ traffic usually specific applications that provide data at regular intervals, you can also burst-like traffic "bursty traffic" using ent speaking "queues" and appropriate "scheduling" for convert a certain time interval into a quasi-isochronous Daten¬ traffic, whereby the Mechanis¬ men invention men can be applied to such quasi-isochronous data traffic ange¬.

According to a preferred embodiment, therefore, a modification of the conventional CSMA / CA method for isochronous data traffic shown in FIG. 2 is proposed such that the necessary resources (in this case time resources) for a respective subsequent user data packet are already present when transmitting a current user data packet is pre-reserved. This essentially corresponds to an implicit prioritization of the isochronous data traffic compared to a so-called burst-like data traffic. This possibility of pre-reserving user data packets thus allows, in addition to improved support for a so-called quality of service (QoS), in particular with regard to compliance with additional delay times, also a reduction in particular of the CSMA / CA signaling overhead What is described in detail below: "Quality of Service" (QoS) is understood to mean all factors which, in the broadest sense, influence the quality of a service or service. QoS is often referred to as quality of service or quality of service.

According to FIG. 3, the signaling structure according to the invention has an initialization phase for initializing the data connection for the isochronous or quasi-isochronous data traffic and a steady state in which a data connection for isochronous or quasi-isochronous data traffic is installed. With regard to the spatial topology or the spatial distribution of the individual stations within the communication network, reference is again made by way of example to a distribution, as shown in FIG. In an initialization phase, according to FIG. 3, the transmitting station S2, which wishes to issue isochronous data traffic for a certain period of time, firstly transmits the transmission parameters ÜP for this isochronous traffic, such as an average data rate, permissible delay times, etc., to the possible receiving station Sl forwarded. In addition, information about an already existing occupancy of the channel with isochronous or quasi-isochronous data traffic from the point of view of the transmitting station S2 and / or an FNI proposal for an additional network access vector information FNI could be transmitted. These transmission parameters U P of the isochronous data traffic can be appended to a transmission readiness signal RTS of the transmitting station S2, for example. However, they can also be exchanged, for example, in anticipation by means of a conventional CSMA / CA-based communication (Carrier Sense Multiple Access with Collision Avoidance) or in any other way and manner with the receiving station S1.

On the basis of this information, ie the requested transmission parameter ÜP for the isochronous or quasi-isochronous connection, as well as the known (by evaluation of the data packets on the air interface) and / or over a time window measured channel assignment, the receiving station Sl can first decide whether the requested service, ie i-sochronic or quasi-isochronous data traffic with the requested parameters ÜP, can be supported at all. If a service for the isochronous data connection can be supported by the receiving station, free resources are determined by the receiving station S1, in particular already active isochronous data connections in its immediate environment (for example between the stations S4 and S5) being taken into account , More precisely, the receiving station S1 can release the isochronous or quasi-isochronous data traffic depending on an analysis of the transmission parameters transmitted by the transmitting station S2 and / or its local resource situation, or else postpone a shift in the reservation proposed by the transmitter. initiate window for the transmission of the first packet.

To simplify this procedure, the time intervals between two reservations, i. E. between two Nutzdatenpake¬ th data or two acknowledgment signals ACK (if present) preferably as integer multiples of a common time constant of the communication system set. In this way, a plurality of isochronous or quasi-isochronous data traffic streams can be interleaved between adjacent station pairs, without causing collisions or the need for a reorganization, at least if certain maximum specifications for the packet length are adhered to.

According to FIG. 3, a transmission ready signal RTS for indicating a readiness to send having a current network access vector information NI for the purpose of serving a current transmission right with a predetermined time duration is therefore first transmitted from a transmitting station S2 to the network. Consequently, the current network access vector information NI of the ready-to-send signal RTS issues a transmission prohibition for all stations which can hear the transmitting station S2 or are within its range, for example a station S3.

The additional network access vector information FNI effects a reservation of a transmission right for the transmitting station S2 at all stations with respect to a time ti for a time duration Δti, which in turn can hear the station S2.

According to FIG. 3, as a result of the request by means of the transmission parameters UP from the transmitting station S2, the receiving station S1 can provide additional network access vector information FNI corresponding to the FNI proposal or modified to the ready-to-receive signal CTS to be sent for the future payload packet of the transmitting station Attach S2. The additional network access vector information FNI causes a reservation of a transmission right for the transmitting station S2 at all stations, which in turn can hear the station S2 (eg station S4), for a period of time Δti after a delay time period ti after the reception ready signal has been sent CTS begins. Similarly, the conventional current network access vector information NI (NAV information) in the receive ready signal CTS can also be repeated unchanged or changed, as a result of which, in particular, a range for the reservation of the

Broadcasting rights increased. More precisely, this also informs the station S4 with regard to the reservation of the transmission right for the station S1, with all stations of the communication network which can hear the receiving station S1 or within its range receive a broadcasting ban. Because the

Station S5 is outside the range of the transmitting station S2 and the receiving station Sl, this station would remain unaffected according to Figure 1 thereby.

As already indicated, the receiving station S1 can carry out an overhaul or analysis of the channel assignment to determine whether the proposed occupation is compatible with the in particular isochronous or quasi-isochronous traffic streams at its local location. If this is not the case, the receiving station S1 could forward such information about the seizure of the channel from its local point of view to the transmitting station S2, so that the transmitting station S2, for example, occupies new resources which are more suitable for both stations or defines new transmission parameters ÜP.

If, however, as shown in FIG. 3, the assignment proposed by the transmitting station S2 is compatible with the traffic streams of the receiving station S1, the receiving station S1 would repeat the additional network access vector information FNI unchanged, so that all stations, such as the Station S4, within reach of this receiving station Sl, but out of range of the transmitting station S2, this Mark resources as occupied. More specifically, a future transmission right FNAV (CTS) reservation is made for the station Sl after a delay period ti and for a reserved additional time period Δti. For this future reservation, all further stations which can hear the receiving station S1 receive in turn a broadcasting ban.

Thereupon, the transmission of a user data packet data from the transmitting station S2 to the receiving station S1 takes place, in which case either the readiness ready signal CTS or in the

Ready to send signal RTS transmitted Netzwerkzugriffsvek¬ tor information NI and / or FNI in Nutzdatenpaket data wie¬ can be repeated. This optional additional repetition of the network access vector information NI and / or FNI therefore essentially serves a spatial extension for reserving the transmission rights.

In the repetition of the additional network access vector information FNI in the useful data packet data shown in FIG. 3, a modification of this information carried out in the receiving station S1 can be forwarded to all stations within range of the transmitting station S2, such as station S3 ,

Consequently, the additional network access vector information FNI can be adapted by the receiving station S1 as a function of a performed analysis with respect to the transmission parameters and / or its resource situation, wherein such modified or adapted network access vector information can also be repeated in the user data packet da¬ ta , More precisely, a reservation of a future transmission right FNAV (DATA) for the station S3 occurs after a delay time period ti 'after the user data packet data and for a reserved additional time period Δti. For this future reservation, all other stations that can hear the transmitting station S2, again a broadcast ban. In the subsequent steady state, the receiving station S1 can respond according to FIG. 3, for example, with a positive or negative acknowledgment signal ACK for confirming the preservation of the user data packet Data. In turn, to reserve a further future transmission right, a further additional network access vector information FNI can be sent in the actuation signal ACK, wherein either the original additional network access vector information FNI is repeated or an additional network access vector information modified on the basis of an analysis is determined. Again, a reservation of a future transmission right FNAV (ACK) for the station S4 takes place after a delay time t ₂ after the acknowledgment signal ACK and for a reserved additional time period At ₂ . More precisely, immediately after the transmission of the acknowledgment signal ACK, a time assignment in the form of the additional network access vector information FNI for the next-but-one payload data packet can be transmitted. Again, a reservation of a future transmission right FNAV (DATA) for the station S3 takes place after a delay period t ₂ 'after the user data packet data and for a reserved additional time period At ₂ .

The positioning of such an ACK signaling immediately before a new user data packet data has the advantage that a channel identification in the transmitting station S2 can also be carried out on the basis of which a timely adaptation of the parameters of the physical layer (PHY parameters) is possible , The transmitting station S2 can repeat this additional network access vector information FNI and, depending on the state of the acknowledgment signal ACK, either append the (obviously incorrectly transmitted) old data sequence or send a new data sequence as the useful data packet data.

This process is repeated until the isochronous traffic stream has dried up or an ACK signaling packet from transmitter S2 is no longer received correctly. In the latter case, the isochronous data connection must be rebuilt again (new initialization).

Since isochronous or quasi-isochronous data traffic may also have some dynamics, it is possible to set the reservation parameters of the additional network access vector information FNI, ie the reserved time periods Δti and Δt ₂ and the delay periods ti, ti 'and t ₂ , t ₂ * adapt to occupancy. Such an adaptation between the stations could, for example, be handled via the higher layers of an ISO layer model. For a simpler management of the resources, it makes sense that the acknowledgment signals ACK always follow at the identical distance t1 = t2 = ... = tx and are always the same length (which can generally be assumed in IEEE 802.11). The length of the time intervals Δti, At2, ... may well vary, but what tion a Varia¬ of the time intervals t _± ', t _2', ... implied.

It should be noted that the representations according to FIGS. 2 and 3 are not true to scale, since in reality the transmit and receive ready signals RTS and CTS as well as the acknowledgment signal ACK are usually much shorter than the payload data packets. In addition, the arrangement of signaling within a respective package is almost arbitrarily chosen.

It should also be pointed out that the position of the additional network access vector information FNI within the useful data packet data or the acknowledgment signal ACK in principle does not matter in the closed state, but preferably can also be placed at the beginning so that the other stations do not first The entire data packet must be evaluated, but the analysis of the packet can be interrupted at an early stage if it has collected all relevant information. It should also be pointed out that each acknowledgment signal ACK and user data packet data can in addition to the additional network access vector information FNI itself also contain the current network access vector information NI.

The invention has been described above with reference to a multiple access method with collision avoidance for isochronous data traffic according to standard IEEE 802.11. However, it is not limited to this and equally includes alternative distributed access methods.

Further, the network access vector information has been arranged at predetermined locations within the respective data packets. However, this arrangement is only an example and can be done in the same way in other places.

Claims

claims A method of transmitting data signals in a communication system with decentralized multiple access to a transmission medium comprising the steps of: a) transmitting a user data packet (data) from a transmitting station (S2) to a receiving station (S1); and b) transmitting an acknowledgment signal (ACK) to confirm receipt of the payload data packet from the receiving station (S1), since the payload packet (data) and / or the acknowledgment signal (ACK) contain additional network access vector information (FNI ) for reserving a future broadcasting right (FNAV (ACK), FNAV (DATA)) of the transmitting station (S2). 2. Method according to claim 1, characterized in that, in an initialization phase, a ready-to-send signal (RTS) for indicating a transmission readiness is transmitted, which has a transmission parameter (ÜP) for requesting isochronous or quasi-isochronous data traffic; and a ready-to-receive signal (CTS) for indicating a reception readiness of the selected receiving station (S1) is transmitted, which contains additional network access vector information (FNI) for reserving a future transmission right (FNAV (CTS)) of the transmitting station (S2). , wherein the additional network access vector information (FNI) is determined on the basis of the transmission parameters (ÜP). 3. The method according to claim 1 or 2, characterized in that a current network access vector information (NI) for serving a current transmission right (NAV (CTS), NAV (RTS)) with a predetermined period of time in the user data packet (data), Confirmation signal (ACK), ready to receive signal (RTS) and / or ready to receive signal (CTS) is included. 4. Method according to one of the claims 1 to 3, characterized in that the additional network access vector information (FNI) is repeated unchanged by the receiving station (S1) in the readiness-ready signal (CTS) or as a function of a conducted analysis is adjusted. 5. The method according to claim 1, characterized in that at least one reserved additional time duration (At ₂ ) is used as the transmission right in the transmission medium, which after a delay time period (ti ', t ₂ , t ₂ ') after the Nutzdaten¬ packet (data) and / or acknowledgment signal (ACK) begins, with further in the range of the transmitting and / or Empfangs¬ station (Sl, S2) lying stations (S3, S4) for the at least one reserved additional period (At ₂ ) receive a broadcast ban. 6. The method according to any one of claims 2 to 4, since ¬ characterized in that as the transmission right (NAV (CTS)) at least one reserved additional loan period (.DELTA.ti) is used in the transmission medium, after a delay period (ti) after the Empfangs¬ Ready signal (CTS) begins, with further in the range of the receiving station (Sl) lie¬ ing stations (S4) for the reserved additional Zeitdau- er (.DELTA.ti) receive a broadcasting ban 7. Method according to one of the claims 1 to 6, characterized in that at least one space or frequency is used in the transmission medium as the transmission right, further stations being within the range of the transmitting and / or receiving station (S1, S1). S2) lying stations (S3, S4) for the at at least one room or the at least one frequency receive a broadcast ban. 8. Method according to one of the claims 1 to 7, characterized in that the further additional network access vector information (FNI) transmitted in the acknowledgment signal (ACK) and / or payload data packet (DTA) is repeated unchanged or as a function of one adjusted analysis. 9. Method according to one of the claims 2 to 8, characterized in that the receiving station (S1) releases the isochronous or quasi-isochronous data traffic as a function of an analysis of the transmission parameters (ÜP) and / or a local resource situation , 10. The method as claimed in one of claims 2 to 9, wherein the transmission parameters (ÜP) are appended to the ready-to-transmit signal (RTS) or exchanged by means of a CSMA / CA-based communication. 11. The method according to claim 1, characterized in that the sums comprising the delay time duration (t ₂ ) of the acknowledgment signals (ACK) and the duration of the acknowledgment signals (ACK) are in the form of integer multiples of a common time constant of the communication system and are the same length. 12. The method according to any one of claims 1 to 11, da¬ characterized in that the confirmation signal (ACK) is used for channel identification. 13. The method according to any one of the claims 1 to 12, da¬ characterized in that it meets the requirements of Stan¬ dard IEEE 802.11.