Random access burst transmission scheme and apparatus

The This invention relates to an apparatus for transmitting and receiving of signals in a wireless telecommunication system and a A method for transmitting of random access bursts in such an apparatus. In particular relates to the present invention provides a feedback or time delay scheme (Backoff scheme) for transmission of random access bursts in a mobile station of a wireless Telecommunications system.

at wireless telecommunication systems such as the GSM system uses the portable or mobile station (mobile station, mobile station, eg mobile phone) to the random access channel (random access channel (RACH)) to random access burst for obtaining services from the sending network. For example, if a mobile station of a Mobile system or Mobilzellularsystems a data channel for transmitting User data needed sends it via the random access channel, a random access action or a random access burst for selected Base station. The a random access burst receiving base station sends an acknowledgment or confirmation message to the mobile Station to indicate that the transmission of the random access burst has been successful by the mobile station to the base station. The confirmation information can sent from a base station access grant information to indicate that the requested service is granted, be. After a successfully transmitted random access burst shares the base station to each requested service, for example, a user data channel, the mobile station.

The transfer a random access burst from a mobile station to a base station is competition-based, and it can Collisions occur. For example, when multiple mobile stations within a single cell of the telecommunication system simultaneously send random access bursts, may Collisions, and the random access burst can of the base station are not received and acknowledged correctly. Having sent a random access burst to a base station, checks the mobile station determines whether an acknowledgment from the base station or received confirmation information has been. If after a predetermined time an acknowledgment information is not has been received, the mobile station determines that the transmission attempt the random access burst has not been successful. After such a failed random access burst determines a feedback or time delay mechanism (Backoff mechanism) if a new transmission of the random access burst to be held. The same goes for a retransmission of a Random access burst and not only for the first delivery attempt.

in the State of the art are different types of feedback and time delay mechanisms known. For example, in a so-called Bayes-time delay scheme (Bayesian backoff scheme) estimates the network side, that is the Base station, on whether the random access channel has been occupied or whether collisions occurred or if a random access burst successfully transferred has been. To the mobile stations information about the assessment Result of this assessment sent so that the mobile stations of their time delay mechanisms of the assessment information dependent may choose. A Another known possibility is a detection of collisions of competing random access bursts on the user device side. require the known system much downlink resource (downlink resources), since the base station transmit regular assessment information to the mobile stations or she must be very complicated since a collision detection necessary is.

Out US patent no. 5544 196 is an apparatus and a method for reducing a message collision between mobile stations in a wireless telecommunication system simultaneously to the base station access apparent. Here is a mobile station, a random delay between successive random access burst transmissions one if it receives no acknowledgment after a predetermined period of time. The random delay is random Choose a time point from a predetermined time interval set. Consequently, the time interval from which a new time for transfer a random access burst is selected, a fixed setting. This relatively simple coupling mechanism is also in the GSM system used. Particularly in cases in which the random access channel is very busy and a lot collisions occur, this known system is very ineffective, as many random access burst transmission attempts with a very low probability of a successful transmission accomplished will.

The Object of the present invention is therefore to provide an apparatus for transmission and for receiving signals in a wireless telecommunication system and a method for the transmission of Random access bursts in an apparatus for transmitting and receiving provide signals in a wireless telecommunication system, the more effective feedback scheme for the transmission provide the random access burst.

These Object is achieved by a device to <?page 3?>transmission and for receiving signals in a wireless telecommunication system according to claim 1, comprising: a transfer means to transfer of random access bursts, receiving means for receiving a confirmation information, the successful transmission a random access burst confirmed a decision means for deciding whether confirmation information has been received, and control means for randomly choosing a Time point for an attempt to random access burst back or re send, by an interval if no acknowledgment information has been received after a random access burst transmitted has been, characterized in that the control device the length the interval depends of the number of unsuccessful attempts, a random access burst transferred to, adjusts dissolved.

The above object is also by a method for transmitting of random access bursts in an apparatus for transmitting and receiving of Signals in a wireless telecommunication system according to claim 9, comprising the steps of: transmitting a random access burst, deciding whether a confirmation information a successful transfer confirmed the random access burst, received has been, and coincidentally Choose a date for an attempt to return or retransmission the random access burst from an interval if no acknowledgment information received has been characterized by adjusting the length of interval depends of the number of unsuccessful attempts to transmit a random access burst, dissolved The present invention thus provides a feedback or time delay scheme re-transmission a random access burst ready, the very effective and flexible is not the high complexity requires. Specifically, the present invention does not require a A system for detecting or estimating collisions of random access burst on the network side, but simultaneously allows a flexible Adjustment of feedback or Zeitvezögerungsschemata to the current random access channel situation. By setting the length the interval from the time for the re-transmission dependent is selected from the number of previous unsuccessful attempts at random, the number can no successful attempts to a successful transfer a random access burst can be reduced. Thereby, the Performance or performance and system stability improved. simultaneously , a high and effective throughput of random access burst be achieved on a random access random access channel. When the present Invention in mobile stations of a wireless telecommunications system can advantageously be used, so it can also on terminal or Other systems can be advantageous.

Advantageously, is the interval length longer set, when the number of unsuccessful attempts increases. This is in situations of heavy traffic on the random access random access channel and a large Number of collisions, the time for retransmission moved or re-transmission, and the probability of a successful retransmission is significantly increased. in this connection hanging the interval length advantageously exponentially by the number of unsuccessful Attempts off.

Advantageously, selects Control means the time for a return or retransmission attempt randomly, after a predetermined offset time has elapsed. After a transfer or retransmission a random access burst is only after a predetermined offset time passed is determined whether an acknowledgment information, for example, from a selected Base station has been received.

In addition, the controller a date for a re-transmission test just choose if it is determined that the number unsuccessful attempts lower than a predetermined maximum number of unsuccessful Experiments is. , by setting the maximum number of experiments be avoided that an infinite number of tests is performed. Since, according to the present invention, the length of the interval of the Number does not depend of successful attempts, the probability that the maximum number of re-transmission is achieved, reduced.

The Concept of the present invention is also advantageous in that allows the transmitted with the random access burst service requests different priorities allot. In this way, the interval length of different priority classes the random access burst depends be adjusted. Advantageously, the interval length for higher priority classes shorter set. This allows a very small mean time to a successful transmission a random access burst for provide service high priority requests, said random access burst lower priority classes consequently, a higher have mean time until a successful transmission.

In addition, the interval as advantageous by a series of numbers that represent time slots in the wireless communication system is illustrated.

In the following description, the present invention has the Basis of a preferred embodiment reference to the accompanying Drawings in greater detail, in which

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<figref idrefs="S18">1</figref> on Flow chart for explaining the Feedback process of the present invention, and

<figref idrefs="S19">2</figref> on Block diagram of a terminal of a wireless communication system, the feedback time delay mechanism or a structure according to the present having invention shows.

<figref idrefs="S18">1</figref> shows a flowchart of a method for transmitting random access bursts in a terminal a wireless communication system according to the present invention. At step S1, a first transmission of the terminal Random access burst generated sent. For example, if a mobile station of the wireless communication system a channel to transfer needed user data, is a service request in the form of a random access burst for selected transmitted base station. successfully in the case that the base station, the random access burst receives, generates and transmits a confirmation information to the mobile station back. The confirmation information may be. For example, an access grant information or the like. successfully in the case that the mobile station the acknowledgment information receives, it decides in step S2 that the first transmission of the random access burst has been successful. Consequently, there are no re-transmission attempts necessary, and the procedure is terminated at step S3. A base station can together with or integrated into the confirmation information further information regarding transferred the allocation of the requested service, for example, the for transfer used by user data channel.

After the transfer a first random access burst at step S1 decides the Device, for example, the mobile station determines whether a confirmation information has been received or not. In the event that after elapse of a predetermined offset time period do not receive a confirmation information has been, the decision is negative, and it is not a successful transfer accepted. In the case where a displacement within the predetermined time period confirmation information is received, the decision is positive, and it is a successful transfer adopted.

In the case where the decision in step S2 is negative going, the procedure advances to step S4, in which the number of unsuccessful Attempts is accumulated. At the next step S5, it is determined whether the number of unsuccessful attempts, a predetermined number has reached of attempts. If this is the case, the procedure is completed at step S6. In the case that the accumulated number unsuccessful attempts not the predetermined maximum has reached number of attempts, the procedure goes to step S7. In step S7, a new time interval is set, from the at step S8, a new time for the next transmission of the random access burst chosen is. This is the set at step S7 new time interval on the basis of the accumulated number of previous unsuccessful attempts calculated. The time interval is thereby by calculating one of the accumulated number of unsuccessful attempts dependent Number set of time slots. The time interval is thus by a series of numbers {1, 2, ..., MW + S × B^{PO + NF}} shown, where each number is a number of time slots than the represents base unit. The time slots are the time slots based of the respective wireless telecommunication system. The influencing factor MW is the minimum length the time interval, the influencing variable S is a scale factor, the influencing factor B is a basic factor that influence quantity is PO an energy or power offset influencing factor, and the influencing factor NF the number of failures. The number of failures is in this case calculated in step S4 accumulated number of unsuccessful attempts. All factors are nonnegative Numbers, where the influencing factor NF of Experiment of trial varies. The other factors can be either or slower preset on the basis of other system parameters be varied.

At the Step S8 is the time interval set in step S7 a new date for the next transmission or the re-transmission of Random access burst at random selected. Here, the new date on the basis of the uniform probability distribution is accidentally drawn. As the above formula can be seen, the time between transmissions increases with an increasing number of unsuccessful attempts or failures. especially due to the exponential dependence is the time interval from which the new time is randomly chosen, greatly expanded, not so that the probability of random successful attempts, for example, due to collisions, is significantly reduced. Consequently, the entire system stability is greatly improved.

The Influencing factor MW which determines the minimum width of the time interval, for example, be set to ten time slots, so that a certain minimum Time interval is ensured. The factors S, B and PO can to Support different priority classes for the Random access bursts are used. Here these factors are preset, that the time interval for higher priority classes shorter is. If at&lt;?page 5?&gt;for example, four different priority classes for four different Classes of service requirements and consequently random access bursts are believed to the influencing variables for different priority classes have different values. Here, it is sufficient, for example only the scaling factor S for the different priority classes to vary. For the highest priority class could be set the factors as follows: S = 1, B = 2, PO = 0. For the second priority class could the following values ​​are used: S = 4, B = 2, PO = 0. For the third Priority class could Factors such follows be set: S = 8, B = 2, PO = 0. For the fourth and lowest priority class could the factors such follows be set: S = 12, have B = 2 and PO = 0. simulations shown that it is sufficient and consequently advisable only the influence of size S to vary, so that the calculation scheme is simplified.

After Step S8 is the random selected Time retransmission the random access bursts performed. Having determined the set at step S7 time interval, starting from the end of the predetermined offset time, the number of time slots, which is determined in step S2 whether a confirmation information has been received or not. The absolute time for a retransmission a random access burst is thus defined by the predetermined offset time plus the selected at step S8 given time. As shown in the above example, is advantageously only the scaling factor for different priority classes varies. The base parameter B and the power offset parameter PO remain unchanged, these parameters also changed can be, to the securing mechanism (backup mechanism) to slowly varying adjust system conditions.

In <figref idrefs="S19">2</figref> is a block diagram of an apparatus for transmitting and for receiving signals in a wireless telecommunication system according to the invention shown. The apparatus shown<figref>1</figref> can For example, a mobile station of a cellular mobile system be and is formed so that it in relation to the <figref idrefs="S18">1</figref> shown and explained steps performs. This shows the block diagram of <figref idrefs="S19">2</figref> only the Items that are important in relation to the present invention. Other elements to operate the equipment shown <figref>1</figref> in have a corresponding telecommunication system necessary such as modulators, demodulators, interleavers, microphone, Speaker, etc., are not shown in order to ensure clarity.

The device <figref>1</figref> has an antenna <figref>2</figref> for receiving and transmitting signals in the wireless telecommunications system. The antenna<figref>2</figref> is with a transmission device <figref>3</figref> and a receiving device <figref>4</figref> connected. The transfer means<figref>3</figref> serves to transfer signals and, for example, a corresponding high-frequency section exhibit. The receiving device<figref>4</figref> used to receive signals and has a corresponding high-frequency section for downconversion the received radio frequency signals to baseband. The receiving device<figref>4</figref> is a decision means <figref>5</figref> connected. The transfer means<figref>3</figref> is a random access channel generating means <figref>7</figref> connected, are generated in the random access burst. Both the random access generation means<figref>7</figref> as also the. decision means<figref>5</figref> are connected to a control means in the form of a central processing unit <figref>6</figref> connected.

In the case that the device <figref>1</figref> a Service request or the like. To another device of the telecommunication system is to make the central unit <figref>6</figref> a corresponding Signal to the random access generation means <figref>7</figref>. to generate the necessary random access burst. The random access burst is then transferred from the transfer means <figref>3</figref> transfer. The decision means <figref>5</figref> checks if within a predetermined Offset time a corresponding acknowledgment information from the receiver <figref>4</figref> has been received. The central processing unit<figref>6</figref> informed therefore, the decision means <figref>5</figref> on the date of transfer a random access burst by the transfer means <figref>3</figref>. so that the decision means <figref>5</figref> capable of a timing or timing generator given actual time with the time of transmission the random access burst incipient predetermined offset time to compare. In the event that by said receiving means<figref>4</figref> within the predetermined offset time period receive a confirmation information will not transfer a random access burst necessary. In the event that after elapse of the predetermined offset time received no acknowledgment information has been selected the control means <figref>6</figref> happen to have a date for a Attempt to re-transmission of a Random access burst from a time interval. The time interval is in this case by the control device <figref>6</figref> of the number previous unsuccessful attempts to transmit the random access burst dependent set. The control means<figref>6</figref> this represents the time for the next attempt as described in relation to steps S7 and S8, the <figref idrefs="S18">1</figref> described on.

That's why the present invention provides a feedback or delay scheme to transfer of random access bursts in a telecommunication device with the Compared to known systems a very good performance and with egg&lt;?page 6?&gt;ner very high stability ready. In particular, even at high loads, for example, high in areas busy periods, the throughput still considerably high. also No feedback- or time delay specific Resources with respect to the Downlink channel required and the detection of collisions on the network side is not necessary.