Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation
  • H04W72/044—Wireless resource allocation based on the type of the allocated resource
  • H04W72/0446—Resources in time domain, e.g. slots or frames
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/50—Allocation or scheduling criteria for wireless resources
  • H04W72/52—Allocation or scheduling criteria for wireless resources based on load

Definitions

• Radio communication systems are used to transmit information, voice or data using electromagnetic waves via a radio interface, also known as an air interface, between a transmitting and a receiving radio station.
• a radio communication system is the known GSM mobile radio network, the architecture of which is described, for example, in B. Walke, Mobile Radio Networks and Their Protocols, Volume 1, Teubner-Verlag Stuttgart, 1998, pages 139 to 151 and pages 295 to 311.
• a channel formed by a narrowband frequency range and a time slot is provided for the transmission of a subscriber signal. Since a subscriber signal in a channel differs in frequency and time from the other subscriber signals, the receiving radio station can carry out a detection of the data of the subscriber signal.
• the individual subscribers are also distinguished by different spreading codes.
• a radio communication system for example a GSM mobile radio network, comprises a multiplicity of mobile switching centers (MSC) which are networked with one another and which provide access to a fixed network. Furthermore, these mobile switching centers are connected to at least one base station controller (base station controller BSC). It is between the MSC and BSC.
• the base station controller enables a connection to at least one base station (base transceiver station, BTS) and manages the radio resources of the connected base stations.
• BTS base transceiver station
• Such a base station is a radio station that uses a radio interface can establish a communication connection to mobile stations.
• Voice signals from the mobile station are coded in error protection and encrypted via the air interface.
• a time slot of a time frame is assigned to the message connection.
• Different communication links are transmitted in time division multiplex, with eight time slots forming a time frame.
• the signals When transmitting from a mobile station to a base station, the signals are decrypted in the base station and the error protection is removed.
• a TRAU frame is permanently assigned to each participant.
• a TRAU frame is a time frame of a predetermined length, so that the transmission capacity is 16 kbit / s or 8 kbit / s.
• the length of a TRAU time frame is 20 ms.
• voice signals from connections to the fixed network are converted to the format of the fixed network, for example standard ISDN format.
• the 8 kbit / s or 16 kbit / s TRAU time frames are converted to 64 kbit / s ISDN time frames.
• This implementation which is always associated with a loss of data quality, can be omitted for connections between two mobile stations. One then speaks of tandem free operation.
• each connection is therefore assigned a transmission capacity of a fixed size.
• the size of the transmission capacity must be such that the useful Data rate that is transmitted via the air interface in a time slot plus the necessary signaling information can be transmitted.
• the measurement of the size of the transmission capacity assigned to a subscriber is therefore based on the maximum data rate that can be transmitted for the subscriber in a time slot on the air interface. Due to the fixed assignment of the transmission rate on the air interface to the transmission capacity of a TRAU time frame, the possible useful data rate on the air interface is limited to a maximum of 16 kbit / s. The maximum data rate to be transmitted is further reduced by additional signaling.
• the invention is therefore based on the problem of specifying 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 adapted and used economically.
• a subscriber is assigned a transmission capacity for the transmission of the data between a base station and a transcoding unit of the radio communication system, the size of which is selected from a predetermined quantity with at least two sizes.
• the transmission capacity assigned to the subscriber can be adapted to the actually available data rate. This makes better use of the transmission path between the base station and transcoding unit. It is within the scope of the invention to provide the transmission capacity assigned to a subscriber in the form of time frames of different frame lengths.
• the time frames preferably comprise at least one subframe of constant length, with differently long time frames having different numbers of subframes, each of the same length.
• the first subframe of a time frame contains signaling information for data transmission in addition to useful data. If the time frame has further subframes, the further subframes contain, in addition to useful data, an identifier of the subframe and an identifier of the time frame. The first subframe and the further subframes are thereby logically linked. This has the advantage that the subframes that together form a time frame do not necessarily have to be transmitted one after the other. For example, after the first subframe of a first time frame, a first subframe of a second time frame can be transmitted and then further subframes of the first time frame. This enables the real-time requirements of different participants to be better taken into account.
• the signaling information is only contained in the first subframe and the further subframes only contain an identifier of the subframe and an identifier of the time frame, which are required for assembling the subframes into the time frame.
• the subframes preferably contain information for controlling the temporal position on an interface between the base station and the transcoding unit, with which the the arrival of the subframes in the base station is controlled. For psycho-acoustic reasons, very high demands are placed on the delay times for the transmission of voice data. According to this embodiment of the invention, these requirements can be met by using a mechanism for time synchronization of the subframes of a time frame. The temporal relationship between the subframes is established and additional delay times are avoided.
• ECSD circuit switched data
• GSM EDGE Radio Access Network GSM EDGE Radio Access Network
• time frames of different lengths are dynamically allocated according to this invention and their length is controlled by priorities.
• the method is also suitable for the transmission of data between the base station and the transcoding unit according to an Internet Protocol (IP) method or an ATM method.
• IP Internet Protocol
• ATM ATM
• the data transmission between the base station and the transcoding unit takes place in the form of data packets.
• the individual participants are assigned differently sized transmission capacities.
• the utilization of the transmission path between the base station and the transcoding unit can be further improved by assigning the transmission capacity dynamically.
• a larger or smaller transmission capacity is allocated to the respective subscriber on the basis of a prioritization assigned to the respective subscriber and on the basis of the radio conditions determined for the respective subscriber when the load on the transmission link changes. grasslands. This ensures that, on the one hand, as many participants as possible are served and, on the other hand, as many participants as possible receive optimal quality.
• AMR adaptive multi rate
• various coding processes are available that are assigned to a subscriber connection depending on the transmission conditions. Since the coding methods used in AMR methods are in contrast to the GSM full rate, GSM half rate and GSM enhanced fill rate methods, in which a rigid division of the total bit rate into a fixed channel coding component and a fixed speech coding component If a variable change is made between coding methods with different channel coding components or voice coding components, AMR methods are able to adapt the coding method used adaptively to the transmission conditions of the air interface. As a result, the coding method that is best suited for the current transmission condition can be selected and continuously adapted when the transmission conditions change, and the voice quality in the mobile radio network can thus be significantly improved.
• Coding methods with a source bit rate between 6.60 kbit / s and 23.85 kbit / s have been standardized for the so-called AMR wide band method.
• This useful bit rate is transmitted for a subscriber via the time slot assigned to him via the air interface.
• These bit rates must be transmitted in a time frame between the base station and the transcoding unit.
• the size of the time frame used after the measured present bit rate If bottlenecks occur on the transmission link between the base station and the transcoding unit, subscribers of lower priority are only initiated coding processes with a low bit rate, and the subscriber is assigned a smaller time frame.
• the radio conditions deteriorate significantly for a subscriber, a change in the group of possible coding methods to a group with coding methods with low bit rates and thus greater robustness on the air interface is likewise initiated for him and a smaller time frame is assigned to him. If, on the other hand, the load in the network drops, a switch to a group of coding methods with a higher bit rate is initiated for a subscriber of higher priority and a larger transmission capacity, ie a larger time frame, is allocated to it. If the radio conditions for a subscriber improve and the utilization of the system permits, a change in the group of coding methods to higher useful bit rates is initiated for this subscriber and the subscriber is assigned a larger time frame.
• FIG. 1 shows a section of a radio communication system in which the method according to the invention can be used
• Figure 2 shows some time frames.
• FIG. 3 shows a flow chart for assigning time frames.
• FIG. 4 shows a flow chart for determining the radio conditions.
• FIG. 5 shows the creation of assignment lists.
• 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 of the base stations BTS is assigned to a base station controller BSC.
• the interface between the base station BTS and base station controller BSC is referred to as the A to 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.
• Each subscriber is assigned a time frame ZR1, ZR2, ZR3 on the transmission link between a base station and a transcoding unit of a radio communication system (see FIG. 2).
• the time frames ZR1, ZR2, ZR3 have different lengths.
• Each time frame ZR1, ZR2, ZR3 contains at least a first subframe TR11, TR21, TR31.
• the longer time frames ZR1, ZR3 also have a further subframe TR12, TR32.
• the first subframes TR11, TR21, TR31 and the further subframes TR12, TR32 have the same, constant length.
• the first subframes TR11, TR21, TR31 also contain signaling information for data transmission, such as information on power control, via U link measurements of the base station (for example RXLEV, RXQUAL), down link signaling from the base station to the mobile station, and redundancy information such as CRC (Cyclic Redundancy Check).
• signaling information for data transmission such as information on power control, via U link measurements of the base station (for example RXLEV, RXQUAL), down link signaling from the base station to the mobile station, and redundancy information such as CRC (Cyclic Redundancy Check).
• the further subframes TR12, TR32 contain, in addition to user data, additional information which is used for logical chaining with the respective first subframe TR11, TR31, such as, for example, the specification of how many subframes of the time frame to be transmitted is the present and an identifier of the time frame, to which the respective subframe belongs. This identifier can be implemented as a shortened time frame number.
• All subframes preferably contain information for controlling the temporal position on the Abis interface.
• Each subframe can thus be shifted in time independently of all other subframes that belong to a time frame.
• the subframes can take different paths when switching the 16 kbit / s channels.
• the time shift can ensure that all subframes belonging to a specific frame arrive at the base station at the same time. This is important because the subframes have to be reassembled in the base station before they can be sent on the air interface.
• the base station In the transmission direction from the base station to the mobile station, that is to say in the downlink direction, the base station extracts the data and the signaling information. In the downlink direction, the BTS removes and checks the redundancy information CRC for each subframe. The user data is then composed of all associated subframes for the entire time frame.
• the base station calculates and controls the required time of arrival separately for each subframe with the aid of the transcoding unit.
• the time at which a single subframe arrives in the downlink direction and the time at which the composite frame has to be sent on the air interface are used for the calculation. Any deviations are communicated to the transcoding unit in the signaling information of the associated subframe in the up link direction.
• the transcoding unit then supplements or omits 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 buffering. This is particularly important because of the real-time requirements for voice connections.
• the data is then transmitted via the air interface.
• the entire time frame is encoded according to the selected coding method and transmitted using the corresponding modulation method.
• the time frame can be assigned with of the adjusted length for a subscriber, it can be used that in AMR procedures the available coding procedures are divided into groups with a maximum of four coding procedures.
• the possible coding methods are divided into four groups, for example, which are referred to as Active Codec Set (ACS), each with a maximum of four coding methods.
• ACS Active Codec Set
• a time frame length is specified for each of the groups ACS1, ACS2, ACS3, ACS4.
• the group ACS1 for AMR narrow band which contains coding methods with transmission rates of 12.2 kbit / s, 7.95 kbit / s, 5.9 kbit / s, and 4.75 kbit / s, is provided with a time frame assigned to only one subframe.
• the groups ACS3 for AMR wide band which contain coding methods with transmission rates of 23.85, 15.85, 12.65 and 6.60 kbit / s
• the groups ACS4 for AMR wide band the coding methods with transmission rates of 15 , 85 kbit / s, 12.65 kbit / s, 8.85 kbit / s and 6.60 kbit / s
• a time frame with a first subframe and a further subframe is assigned.
• a group that is assigned to a connection takes place on the one hand according to traffic load-related criteria and on the other hand according to radio conditions, whereby for example the level during call setup, which is determined by the RXLEV value of the SDCCH, is evaluated.
• a third limit value which is calculated as the difference between the second limit values and a hysteresis value
• new connections can also be assigned a time frame according to the given requirements.
• the current load of the system is determined, for example, by considering all the relevant factors. 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, and the base station controller and the transcoding unit.
• the selection of the connections to which a different time frame is assigned due to the current load takes place on the one hand according to a list of priorities and on the other hand according to the given radio conditions.
• the C / I value which represents the ratio of useful signal to interference, is a suitable parameter for assessing the radio conditions. For example, two thresholds are defined. If the C / I value exceeds a first threshold C / I threshold, the connection can be assigned an ACS group with high-rate coding methods for good radio conditions. If the C / I value falls below a second threshold C / I threshold 2, which is smaller than the first threshold C / I threshold, the connection is assigned an ACS group with more robust and possibly lower-rate coding methods for poor radio conditions (see Figure 4).
• the composition of the coding method for the different ACS groups can be selected in such a way that time frames of different sizes are required for the terrestrial data transmission.
• lists Z ⁇ and Z 2 are created which contain the participants in the order in which they are used by another Time frame should be assigned (see Figure 5).
• the list Z x for the allocation of a smaller time frame and the list Z 2 for the allocation of a larger time frame are generated on the basis of a priority list P and a radio conditions list F.
• the priority list P contains a priority for each participant, which is assigned to him on the basis of the information available to the operator, for example contract terms or the like.
• the list of radio conditions F contains the distance of the current C / I value to the first threshold C / I threshold and to the second threshold C / I threshold 2 for each subscriber.
• the A to interface between the base station and base station controller is used, for example, not only by voice subscribers, but also by packet-switched data services.
• counters can be implemented, for example, which count the utilization of all components.
• both mobile stations and the assigned base stations, base station controls and transcoding units, and the associated A bis and A sub interfaces Only if a time frame with several subframes is available for the connection for both base station systems, does it make sense to assign such time frames for the connection.
• the next step is to check whether the current traffic load is less than the first limit (see figure 3). This is the case, for example.
• a time frame with a first subframe and a further subframe is thus assigned to the connection.
• the network thus offers the connection optimal quality.
• the load on the A to interface increases and the first limit value is exceeded.
• a request from another subscriber 2 who also wants to set up a conversation is received.
• the subscriber 2 has a subscriber priority 2 that is greater than the subscriber priority 1.
• the measurement of the RXLEV level of the SDCCH shows that the radio conditions are suitable for assigning an ACS group with a high-rate coding method.
• the connection is assigned a group ACS, which only contains low-rate coding methods, for which a time frame with only a first subframe is sufficient.
• the current load is now higher than the third limit, so that larger connections cannot be assigned to existing connections.
• subscriber 1 who is in first place in list Z, but which has the same radio conditions as subscriber 2 but a lower subscriber priority, is assigned a smaller time frame with only a first subframe. At the same time, subscriber 1 is deleted from list Z x and, due to the good radio conditions, added to list Z 2 .

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• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 2003
  • 2003-03-12 WO PCT/EP2003/050058 patent/WO2003079590A2/de active Application Filing
  • 2003-03-12 CN CNB03806152XA patent/CN100539753C/zh not_active Expired - Fee Related

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