CN100539753C - The method of transmission data in the radio communications system - Google Patents

Abstract

In order between a code conversion unit of a base station and wireless communication system, to transmit data, distribute a transmission capacity for a user, select in the group's amount that has two amounts at least of its size by prior regulation.Transmission capacity can provide with the time frame form of different frame lengths.Time frame is realized as the chain of each subframe that constant length is arranged, and different long time frames have different many subframes.In addition, the access right to the public resource can be by priority control relevant with load and that provided by radio condition.

Description

Method for transmitting data in a radio communication system

technical field

The invention relates to a method of transmitting data in a radio communication system.

Background technique

Radio communication systems use electromagnetic waves to transmit information, voice or data between radio sending and receiving stations via a radio interface, also called an air interface. The example of a radiocommunication system is exactly the known GSM-mobile radio network, its structural form in B.Walke, <mobile radio network and its protocol> (Mobilfunknetze und ihre Protokolle), volume 1, Teubner publishing house Stuttgart, 1998 edition 139 Instructions on pages 151 to 151 and 295 to 311. For this purpose, a channel formed by a narrowband frequency band and a time slot is provided in each case for the transmission of a subscriber signal. Since a user signal differs in frequency and time from other user signals in a channel, the receiving radio station is able to detect the user signal data. In newer radio communication systems, such as UMTS systems, the individual users are also distinguished by different spreading codes.

A radio communication system, for example a GSM mobile radio network, comprises a large number of mobile switching centers (MSCs), which are meshed with each other and establish paths to the fixed network. Furthermore, the mobile switching stations are connected to at least one base station controller (BSC). At this time, a transcoding unit (transcoding and rate adaptation unit, Transcoding and Rate Adaptation Unit TRAU) is always provided between the mobile switching station and the base station controller. Base station control makes it possible to connect at least one base station (Base Transceiver Station, BTS) and manages the radio technical resources of the connected base station. Such a base station is a radio station which can establish a message connection to a mobile station via a radio interface.

During a message connection between a mobile station and a base station, the mobile station's digital, source-coded speech signal is error-protected coded and encrypted for transmission over the air interface. At this time, a time slot of one time frame is allocated to the message connection. Different message connections are transmitted in a time-division multiplexing system, and eight time slots constitute a time frame at this time.

During transmission from a mobile station to a base station, the signal is decoded in the base station and the error protection is removed. A message connection, ie the digital signal transmission of a subscriber, takes place between the base station and the transcoding unit in a time frame, which is called a TRAU frame or TRAU time frame. A TRAU frame is fixedly allocated to each user. A TRAU frame is a time frame with a predetermined length, and the transmission capacity is 16kbit/s or 8kbit/s. The length of a TRAU-time frame is 20 ms.

In the transcoding unit, the voice signal is converted from the connection to the fixed network to the format of the fixed network, for example the standard ISDN format. In this case, convert the 8kbit/s or 16kbit/s TRAU-time frame to the 64kbit/s ISDN-time frame. For a connection between two mobile stations, such switching, which is always associated with a loss of data quality, cannot take place. This is called Tandem free operation.

For the transmission of data between the base station and the transcoding unit, a fixed size transmission capacity is allocated to each connection. The size of the transmission capacity must then be selected such that the effective data rate transmitted via the air interface within a time slot is such that the required signaling information can be transmitted. Therefore, the size of the transmission capacity allocated to a user is chosen according to the maximum data rate that can be transmitted on the air interface in one time slot for the user. Due to the fixed assignment of the transmission rate to the transmission capacity of a TRAU time frame on the air interface, the possible effective data rate is limited on the air interface to a maximum of 16 kbit/s. A further reduction of the maximum data rate to be transmitted takes place by means of additional signaling.

A method is known from WO 99/59358 A2 in which transmission frames, for example TRAU-time frames, are transmitted via N transmission channels between a base station and a transcoding unit. Each transmission time frame includes a frame number and/or a number of the transmission channel used, which serve the base station or the transcoding unit in order to guide the transmission frames in the correct time sequence. In this way, an N-fold data rate of a single transmission frame is achieved between the base station and the transcoding unit.

Contents of the invention

It is therefore the object of the present invention to provide a method for transmitting data in a radio communication system in which the transmission capacity between the base station and the transcoding unit can be adjusted and used economically.

This task is solved according to the method of the following technical solution according to the present invention. Further developments of the invention emerge from the remaining claims.

A method for transmitting data in a radio communication system according to the invention, in which method, for transmitting data between a base station and a transcoding unit, a user is assigned a transmission capacity whose size is determined in advance by at least two selected from the group quantity of a quantity; in this method, the transmission capacity is provided in the form of time frames of different frame lengths; in this method, the time frame includes at least one subframe of constant length, and the time frames of different lengths have different multiple subframes; in this method, the first subframe of a time frame includes signaling information for data transmission; and, in this method, if the time frame has other subframes, these other subframes A frame includes a signature of a subframe and a signature of a time frame, and logically links the first subframe with other subframes.

In a method for transmitting data in a radio communication system, in order to transmit data between a base station of the radio communication system and a transcoding unit, a user is allocated a transmission capacity whose size is defined by a group of at least two quantities specified in advance selected from the quantity. By providing transmission capacities of different sizes, the transmission capacity allocated to the user can be adapted to the actual existing data rate. Thus, the transmission route between the base station and the transcoding unit is better utilized.

Within the scope of the invention, a user is provided with the allocated transmission capacity in time frames of different frame lengths.

Preferably, the time frame includes at least one subframe (Teilrahmen) of constant length, and time frames of different lengths have different multiple subframes with the same length. When using the method in a GSM-like mobile radio network, the use of this method has the advantage that known TRAU-time frames can be used as subframes and a complete conversion to the ISDN-format can be achieved in this way .

According to an embodiment of the invention, the respective first subframes of a time frame contain signaling information for the additional data transmission of the user data. If the time frame has further subframes, these additional subframes include a signature of the subframe and a signature of the time frame in addition to the useful data. In this way, the first subframe is logically linked with other subframes. This has the advantage that the subframes which together form a time frame do not have to be transmitted one after the other. For example, after the first subframe of the first time frame, the first subframe of the second time frame can be transmitted, and then the other subframes of the first time frame can be transmitted. In this way, the real-time requirements of different users can be better taken care of. At the same time, redundant management fees are avoided, that is, only signaling information is included in the first subframe, and other subframes only include a signature of the subframe and a signature of the time frame, which are the time frames composed of the subframes. required.

Preferably, the subframes include information controlling the time position on an interface between the base station and the transcoding unit, with which information the arrival times of the subframes are controlled in the base station. For the transmission of speech data, high demands are placed on the delay times for psycho-acoustic reasons. These requirements can be met according to this embodiment of the invention by using a mechanism for temporal synchronization of the subframes of a time frame. In this case, a temporal relationship is established between subframes and additional delay time is avoided.

The method can also be used for data transmission in a GERAN system (GSM EDGE Radio Access Network) with Enhanced Circuit Switched Data (ECSD). ECSD is a connection-switched data transmission method in which data is modulated over the air interface for eight PSK transmissions. In order to be able to transmit the high data rates per time slot given by ECSD on the air interface also efficiently on the ground connection, time frames of different lengths are dynamically assigned according to the invention, the length of which is controlled by a priority .

Furthermore, the method is also suitable for transmitting data between the base station and the transcoding unit according to the Internet Protocol (IP) method or the ATM method. In this case, the data transmission between the base station and the transcoding unit takes place in the form of data packets. At this time, different sizes of transmission capacity are allocated to each user.

The utilization of the transmission path between the base station and the transcoding unit can be further improved by dynamically allocating the transmission capacity. In this case, with the prioritization assigned to the user concerned and with the radio conditions specified for the user concerned, a greater or lesser transmission capacity is allocated to the user concerned when the load on the transmission path changes. In this way, it is ensured that on the one hand, all possible users are served, and on the other hand, as many users as possible get the best quality.

In addition, within the scope of the invention, a speech coding or modulation method or cell switching is performed for a subscriber assigned a larger or smaller transmission capacity.

The use of the method according to the invention is particularly advantageous in an adaptive multi-rate (AMR) method. In an AMR method, different encoding methods are available which are assigned to a subscriber connection depending on the transmission conditions. Because the coding method used in the AMR-method is different from the GSM full-rate, GSM half-rate and GSM-enhanced full-rate methods, in these methods a constant division of the total-bit rate is based on a fixed channel coding fraction Performed with a fixed speech coding part, the coding method applied in the AMR-method has a variable switching between coding methods with different channel coding parts or speech coding parts, so the AMR-method has the ability to make the applied The coding method is adaptively adapted to the transmission conditions of the air interface. In this way, the coding method which is best adapted to the instantaneous transmission conditions can be selected and adapted further to changed transmission conditions, thereby significantly improving the speech quality in mobile radio networks.

For the so-called AMR broadband method, the coding method is standardized with a source bit rate (quell bitrate) between 6.60 kbit/s and 23.85 kbit/s. This effective bit rate is transmitted by a subscriber via the air interface via the time slot assigned to him. These bit rates must be transmitted in a time frame between the base station and the transcoding unit. By applying the method of the invention, the size of the applied time frame is determined according to the existing bit rate. If a bottleneck occurs on the transmission path between the base station and the transcoding unit, only a lower bit rate coding method is assigned to a lower priority user, and a smaller time frame is allocated to the user. If the radio condition of a user obviously deteriorates, then it is also arranged for him to change from a group on possible coding methods to a group of coding methods with a smaller bit rate, thereby arranging a greater robustness on the air interface, giving him Allocate a smaller time frame. If, on the contrary, the load in the network decreases, a group change to a coding method with a higher bit rate is arranged for a higher priority user, who is assigned a larger transmission capacity, i.e. a larger time frame. If the radio conditions of a user improve and allow the loading of the system, a group change to a higher effective-bit rate coding method is arranged for the user, a larger time frame is assigned to the user.

Description of drawings

The invention is explained in more detail below using the exemplary embodiments shown in the figures.

Figure 1 shows a fragment of a radio communication system in which the method of the invention can be used.

Figure 2 shows some time frames.

Figure 3 shows a flowchart for allocating time frames.

Figure 4 shows a flowchart for determining radio conditions.

Figure 5 shows the formulation of a distribution list.

Detailed ways

A radio communication system comprises a plurality of base stations BTS1, BTS2, BTS3 via which a radio connection to a mobile station MS can be established (see FIG. 1). Each base station BTS is assigned a base station controller BSC. The interface between the base station BTS and the base station controller BSC is called the _Abis -interface.

The base station controller BSC is connected via a transcoding unit TRAU to a mobile switching center MSC, which represents the interface to other networks. The interface between the base station controller BSC and the transcoding unit TRAU is called the A _sub interface. The interface between the transcoding unit TRAU and the mobile switching center MSC is called the A interface.

On the transmission path between a base station of a radio communication system and a transcoding unit, each user is assigned a time frame ZR1, ZR2, ZR3 (see FIG. 2). Time frames ZR1, ZR2, ZR3 have different lengths. Each time frame ZR1, ZR2, ZR3 comprises at least one first subframe TR11, TR21, TR31. Furthermore, the longer time frame ZR1, ZR3 has another subframe TR12, TR32. The first group of subframes TR11, TR21, TR31 and the further subframes TR12, TR32 have the same constant length. The first group of subframes TR11, TR21, TR31 and the further subframes TR12, TR32 have such a length that they have a transmission capacity of 16 kbit/s on the given transmission line. Thus, they have a length of 40 octets = 320 bits.

In addition to valid data, the first group of subframes TR11, TR21, TR31 also includes signaling information for data transmission, e.g. information for power control, information about base station uplink measurements (e.g. RXLEV, RXQUAL), relevant Downlink signaling information from the base station to the mobile station, and redundant information such as CRC (Cyclic Redundancy Check).

In addition to valid data, the additional subframes TR12, TR32 contain additional information, which are used to logically link with the respective first subframes TR11, TR31, for example indicating which subframe of the time frame to be transmitted is an existing and the signature of the time frame to which each subframe belongs. The signature can be implemented as a shortened time frame number.

For the sake of backward compatibility, it is advantageous to additionally provide an identifier for the type of time frame used in the first subframe TR11 , TR21 , TR31 .

Preferably, all subframes include information controlling the temporal position on the _Abis -interface. Thus, each subframe can be shifted in time independently of all other subframes belonging to a time frame. In this way, when a 16kbit/s channel is connected, different paths can be selected for the subframe. The passage of time can ensure that all subframes belonging to a certain frame arrive at the base station at the same time. This is important because the subframes must be reassembled at the base station before they can be sent over the air interface. Subframes are temporally elapsed by adding and removing extra bits at the end of each subframe. The number of bits removed or added determines the transition time (4bit = 250μs). In this way, the influence of _Abis transmission in the 16kbit/s channel can be balanced.

In the direction of transmission from the mobile station to the base station, ie the uplink direction, the base station has to break down the time frame received over the air interface into the required subframes.

In the direction of transmission from the base station to the mobile station, ie in the downlink direction, the base station selects data and signaling information. In the downlink direction, the BTS removes and checks the redundant information CRC for each subframe. The useful data are then combined from all associated subframes into a total time frame.

In order for all subframes to arrive at a certain time, the base station calculates and controls the required arrival times for each subframe individually by means of a transcoding unit. For the calculation, the moment at which a single subframe arrives in the downlink direction and the moment at which the combined frame has to be sent on the air interface is used. The transcoding unit is informed of possible deviations with the signaling information of the associated subframe in the uplink direction. Then, the transcoding unit supplements or removes a certain number of bits in the downlink direction. As a result, all subframes belonging to a frame arrive at the same time and can be sent without intermediate storage. This is especially important due to the real-time requirements on voice communication connections.

Data transmission then takes place via the air interface. For this purpose, the total time frame is coded according to the selected coding method and transmitted with the corresponding modulation method.

When applying the method according to the invention in an AMR wideband method, in order to allocate time frames with an adapted length, it can be traced back to the division of the coding methods available in the AMR method into four coding methods at most for a user. group. The possible coding methods are divided into, for example, four groups called active codec sets (Active Codec Sets, ACS), each with a maximum of four coding methods. A time frame length is predetermined for each group ACS1, ACS2, ACS3, ACS4.

For example, a time frame with only one subframe is allocated to the AMR narrowband group ACS1, and the group ACS1 includes encoding methods with transmission rates of 12.2 kbit/s, 7.95 kbit/s, 5.9 kbit/s and 4.75 kbit/s. The same applies to the group ACS2 for AMR wideband, which has, for example, encoding methods with transmission rates of 6.60, 8.85 and 12.65 kbit/s. The group ACS3 for AMR broadband, this group ACS3 includes the coding method that transmission rate is 23.85, 15.85, 12.65 and 6.60kbit/s; And the group ACS4 of AMR broadband, this group ACS4 includes transmission rate is 15.85kbit/s, 12.65kbit/s s, 8.85kbit/s and 6.60kbit/s encoding methods, allocate a time frame with the first subframe and other subframes. Which time frame is assigned to a connection is determined with the selected coding method group ACSi, i=1 to 4, and then the corresponding time frame length is selected. The selection of the group assigned to a connection is evaluated on the one hand according to the traffic load-dependent specification and on the other hand according to the radio conditions, for example the level determined by the RXLEV value of the SDCCH when a call is established.

The assigned ACS-group can be changed by a handover, for example intra-cell handover and assignment of a new ACS-group or by exchanging the encoding method contained in an ACS during the connection.

In order to achieve an optimal load on the transmission route between the base station and the transcoding unit, the transmission capacity assigned to each connection must be dynamically matched (see FIG. 3 ). In one embodiment, three threshold values are specified for this. If the instantaneous load exceeds the first threshold, new connections will only be allocated a time frame with only one subframe. If the momentary load exceeds a second threshold value, a time frame with only one subframe is assigned to the selected connection which previously had a time frame with a plurality of subframes available. For this, a change in the ACS group is generally required. A possible change of the coding method can be performed by allocating a new ACS group which occupies only one time frame with only one subframe.

If the instantaneous load is below a third threshold calculated as the difference between the second threshold and a hysteresis value, then for the connection selected so far able to utilize a time frame of only one subframe, A time frame with multiple subframes is allocated.

If the momentary load falls below a first threshold value, the new connection can also be assigned a time frame corresponding to the given requirement.

The instantaneous load of the system is determined, for example, by taking into account all relevant influencing variables. This includes the interface A _bis between the base station and the base station controller, and the interface A _sub between the base station controller and the transcoding unit as well as the base station controller and the transcoding unit.

The allocation of a further time frame to those connections is selected on the basis of the momentary load, on the one hand in accordance with a priority list and on the other hand in accordance with the given radio conditions. The C/I-value, which reflects the desired signal-to-interference relationship, is a suitable parameter for evaluating radio conditions for this purpose. For example, two thresholds are specified. If the C/I value exceeds a first threshold C/I threshold 1, an ACS group with a high-rate coding method with good radio conditions is assigned to the connection. If the C/I-value is below the second threshold C/I-Threshold 2, which is smaller than the first threshold C/I-Threshold 1, a more durable and sometimes lower-rate codec with poor radio conditions The ACS-group of the method is assigned to this connection (see Figure 4). Combinations of different ACS-group coding methods can optionally require time frames of different sizes for data transmission on the ground.

For allocating a larger time frame or a smaller time frame for a given connection, due to the actual load on the system (see Fig. 3), a list Z ₁ or Z ₂ is drawn up which in turn includes the users in which they are to be assigned Assign a different time frame (see Figure 5). The list Z ₁ for allocating a smaller time frame and the list Z ₂ for allocating a larger time frame are generated on the basis of a priority list P and a radio condition list F. The priority list P contains a priority for each subscriber, which is assigned to the subscriber on the basis of eg agreement conditions or similar information from the operator. The radio condition list F contains the distances of each subscriber's actual C/I-value to a first threshold C/I-Threshold1 and to a second threshold C/I-Threshold2. Lists Z ₁ , Z ₂ are generated on the basis of Lists P and F. The user list Z ₁ for assigning a smaller time frame to the user only includes users who have actually been assigned a larger time frame. The user list Z ₂ that is to be assigned a larger time frame to the user only includes the users who are actually assigned a smaller time frame. The user in the top position of the list Z ₁ , Z ₂ is the user whose assigned time frame is changed the next time the corresponding threshold value (see FIG. 3 ) is exceeded or dropped below.

When determining the actual load, all services that occupy the corresponding resources must be observed. The _Abis -interface between the base station and the base station controller is used not only for voice users, but also for packet-switched data traffic, for example. In order to determine the loading of the individual components, for example, a counter can be implemented which counts the loading of all components.

In the case of a connection between two mobile stations in which there is no conversion to ISDN-format in the transcoding unit at the two mobile stations, i.e. in tandem-free operation, it is advantageous to observe both when evaluating the system load. A mobile station and the assigned base station, base station controller and transcoding unit as well as the associated A _bis - and A _sub -interfaces. The allocation of such time frames for a connection only makes sense if a time frame with several subframes is used for a connection by two base station systems.

To set up a new call for user 1 with user priority 1, the RXLEV-level of the SDCCH is first measured. This level is used, for example, to determine that the radio conditions are good enough to use an ACS group with a high-rate source bit rate coding method. For this, a time frame with several subframes is required.

In a next step it is checked whether the instantaneous traffic load is less than a first threshold value (see FIG. 3 ). This is for example the case. Thus, the connection is assigned a time frame with a first subframe and another subframe. The network thus provides the best possible quality for the connection.

Now, the load on the _Abis -interface rises above the first threshold. At this time there is a request from another user 2 who also wants to set up a call. User2 has a UserPriority2 which is greater than UserPriority1. The RXLEV-level measurements of SDCCH show that the radio conditions are suitable for assigning an ACS-group with a high-rate coding method. However, since the momentary load is higher than the first threshold value, the connection is assigned a group ACS, which is only the content of the low-rate coding method, for which a time frame with only one first subframe is sufficient.

The instantaneous load is now above the third threshold, so that no larger time frames can be allocated to existing connections.

If the load falls below the third threshold, it is possible to allocate larger time frames. On the basis of good radio conditions, user 2 is filled in list Z ₂ (see FIG. 5 ) in order to allocate a larger time frame. Since additional resources are available on the basis that the instantaneous load is lower than the third threshold, and users with higher priority are not included in the list Z ₂ , the ACS-group is replaced with and thus replaced by This connection provides the coding method used to assign a time frame with a first subframe and another subframe to user 2. With the possibility of assigning another ACS-group and utilizing higher rate coding methods, the speech quality of the user 2 connection is improved.

If the instantaneous load rises again and exceeds the second threshold, a smaller time frame with only one first subframe is assigned to user 1 in the first position in list _Z1 , who has a relationship with user 2 Same radio conditions, but less user priority. Simultaneously, subscriber 1 is deleted from list Z ₁ and is accepted into list Z ₂ due to good radio conditions.

Claims (6)

1. A method of transmitting data in a radio communication system, - in the method, for the transmission of data between a base station and a transcoding unit, a user is allocated a transmission capacity whose size is selected from a predetermined group of at least two quantities; - In this method, the transmission capacity is provided in time frames of different frame lengths; - In the method, the time frame includes at least one subframe of constant length, and time frames of different lengths have different numbers of subframes; - in the method, the first subframe of a time frame includes signaling information for data transmission; and - In this method, if the time frame has other subframes, these other subframes include a signature of the subframe and a signature of the time frame, and the first subframe and other subframes are logically Link. 2. The method of claim 1, In this method, the subframe includes information for controlling the time position on an interface between the base station and the code conversion unit, and the information is used to control the timely arrival of the subframe in the base station. 3. The method of claim 1 or 2, In this method, the assignment of the transmission capacity is carried out dynamically, in which case the user concerned is allocated a larger or larger transmission capacity with respect to its currently assigned transmission capacity by means of the prioritization given to the user concerned and the radio conditions specified for the user concerned. Smaller transmission capacity. 4. The method of claim 3, In this method, the speech coding or modulation method or the cell is switched for a user assigned a larger or smaller transmission capacity. 5. The method as claimed in claim 1 or 2, wherein an adaptive multi-rate speech codec is used and the radio communication system is a GERAN mobile radio transmission system. 6. The method as claimed in claim 1 or 2, wherein the radio communication system is a GERAN system and uses enhanced circuit switching methods for data transmission.

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