MXPA00007219A - Method for variable block scheduling indication by an uplink state flag in a packet data communication system - Google Patents

Abstract

A packet data communications system uses a USF (Uplink State Flag) transmitted on the downlink and interleaved with downlink data, to schedule traffic on the uplink for one or several mobile users utilizing the same physical channel. The USF indication is made variable and defined in the control signaling at setup of a packet transmission. A USF indicates to a mobile that one or several consecutive radio blocks is reserved for uplink transmission from a specific mobile. The mobile does not have to receive the USF during the remaining period defined by the number of radio blocks scheduled. The solution is especially advantageous in combination with adaptive antennas when all radio blocks on the downlink transmissions do not have to be broadcast to all users on a certain channel.

Description

METHOD FOR INDICATING THE PROGRAMMING OF VARIABLE BLOCKS THROUGH A LINKED STATUS FLAG ASCENDING IN A SYSTEM OF DATA COMMUNICATION IN PAQUE ES BACKGROUND The present invention relates, in general, to packet data communications systems and, more specifically, to a method and apparatus for dynamic allocation of transmission resources. The growth of commercial communication systems and, in particular, the explosive growth of cellular radiotelephone systems have prompted system designers to look for ways to increase system capacity without reducing the quality of communication beyond the limits of consumer tolerance. At the same time, the use of mobile communication equipment for data transmission instead of voice has become increasingly popular among consumers. The possibility of sending and receiving email and using a network explorer to gain access to the world-wide-web is often discussed as services that will be increasingly used in wireless communication systems. In response to this, the designers of communication systems seek ways to efficiently transfer data information to and from mobile users. There are fundamental differences between the requirements for data communication and, for example, voice communication. For example, the delay requirements are greater for voice, which is a real-time service, and the error requirements are greater for data communication, while the challenge restrictions are lower. The use of packet data protocols, which are more suitable for data transmission than circuit-switched protocols, begins to be carried out in cellular communications systems. The integration of services in packets in GSM cellular systems as well as cellular systems DAMPS is currently being standardized. Currently, GSM systems provide a data switching service, which can be used to interconnect with external data networks. The data switching service is used for switched circuits as well as for packet switched data communication. To make switched data communication into more efficient packets, a new packet data switching service called GPRS (General Packet Radio Services) is introduced as a part of GSM. GPRS will allow packet-switched communication, for example, IP or circuit-switched virtual communication. The GPRS will support both protocols for wireless connections (for example IP) as well as a protocol oriented for connection (X.25). One of the advantages with a packet data switching communication protocol is that a single transmission resource can be shared between different users. Thus, in the case of, for example, a GSM cellular system, a time slot in a radiofrequency carrier can be used by various mobile users for the reception and transmission of data. The shared transmission resource is managed by the network side of the cellular system for downlink and uplink transmissions. The GPRS is a GSM service and parts of the GSM infrastructure will be used. These parts of the GSM communication system are described in document ETS 300 574 of the European Telecommunications Standard Institute (ETSI) which is incorporated herein by reference. An advantage of introducing a packet data protocol in cellular systems is the possibility of supporting transmissions with a high data rate and at the same time obtaining flexibility and efficient use of radio frequency bandwidth over the radio interface. The concept of GPRS is designed for the so-called "multi-slot operations" where a single user is allowed to occupy more than one transmission resource simultaneously. Figure 1 shows an overview of the architecture of the GPRS network. The information packets of external networks 122, 124 will enter the GPRS network in a GGSN (Gateway GPRS Service Node, Gateway GPRS Service Node) 120. The packet is then routed from the GGSN through a main network, 118, to an SGSN (Serving GPRS Support Node, GPRS Support Node Server) 116, which is serving the area in which it receives the addressed GPRS mobile. From the SGSN the packets are routed to the correct BSS (Base Station System, Base Station System), in a dedicated GPRS transmission. The GPRS registry, 115, will keep all the data of the GPRS subscription. The GPRS registry may or may not be integrated with the HLR (Home Location Register) of the GSM system. The subscriber data can be exchanged between the SGSN and the MSC to guarantee service interaction, such as restricted roaming. Figure 2 illustrates the packet transformation flow for a GPRS system. This is also briefly described in D. Turina et al., "A Proposal for Multi-Slot MAC Layer Operation for Packet Data Channel in GSM", ICUPC, 1996, vol. 2, pp. 572-576, which is incorporated herein by reference. The packets that are received from the network 210 are mapped onto one or more logical link control (LLC) frames 212, containing an information field, a frame header (FR) and a frame check sequence ( FCS). An LLC frame is mapped onto a plurality of radio link data blocks (RLC data blocks) 214, each of which includes a block header (BH), the information field and the block check sequence (BCS) ), which can be used in the receiver to verify errors in the information field. A block, as well recognized by those skilled in the art, is the smallest part of the package that is retransmitted over the air interface. The RLC blocks are also mapped onto the radio blocks in the physical layer. In a GPRS system, a radio block is mapped over four normal bursts sent consecutively on a GSM physical channel. The header of the block includes a Uplink State Flag (USF) field to support the method of dynamic access to the medium over the uplink. The USF is used in a packet data channel to allow multiplex e of the radio blocks from different mobile users, i.e. the dynamic allocation of the shared transmission resources in the uplink. The USF contains three bits of information that allow the encoding of eight different USF states which are used to ultiplex the uplink traffic. The USF is included in the beginning of each radio block transmitted in the downlink, i.e., interleaved with the downlink traffic for a specific mobile user. Since the USF is transmitted in each radio block in the downlink, all mobiles that use the dynamic allocation method and share a certain transmission resource must therefore always listen to the downlink channel to determine if the USF indicates Free uplink transmission for any of the mobiles. If a mobile user is indicated a USF, the transmission in the uplink is allowed in the next uplink radio block. This technique is illustrated in Figure 3, where USF = Rl indicates that mobile 1 (MSI) can use the next four bursts to transmit on the uplink. In the case of multi-slot allocation, when a mobile is assigned with more than one time slot in each TDMA frame, more than one RLC block can be transmitted for four TDMA frames, however, each individual RLC block is always interleaved on four bursts in a physical channel, that is, the time slot.

Then, according to Figure 3, if the USF = R2, this indicates that the mobile 2 (MS2) can use the next four bursts to transmit on the uplink. The "F" value defines a Packet Rando Access Channel (PRACH) which is used by mobile users to initiate uplink transmissions. A drawback with the protocol described above is evident when considering the use of adaptive antenna arrays that increase the capacity of the cellular system and the efficient use of scarce radio resources. The establishment of the antenna arrays can allow more efficient transmission and reception of the radio signals, since the transmitted energy can be directed towards a certain receiver in the lobes of the antenna. This significantly limits the level of general interference in cellular systems and the transmitted output power can be decreased and limited to certain directions from, for example, a base station transmitter. It is of great importance that the increases in the capacity of future cellular systems for these adaptable antennas be used efficiently. However, there are limitations to the gain in performance achieved by implementing adaptive antennas and, for example, the downlink traffic directed to a specific mobile user is interleaved in some bursts as downlink control signaling proposed to other users. An example is the aforementioned USF flag being included in the downlink transmissions for a specific user. Different mobiles may be geographically distant and it is then impossible to concentrate the energy of the transmitted signal to only one or some directions. In the same way it is difficult to obtain an efficient energy control algorithm for transmissions addressed to more than one mobile user. Another drawback with the described protocol is the (no) possibility of introducing new modulation for certain radio blocks in the downlink. Namely, the newest development in GSM suggests the use of a new higher level modulation for users with good radio conditions that can then increase the user's data rate and system performance in general. It would be advantageous to be able to freely multiplex the radio blocks using the existing and new modulation on the downlink thus obtaining the link gain. In the current protocol, it is not possible in situations where a GPRS mobile station is monitoring the USF that has to arrive in the radio block that uses the existing modulation. One possibility to overcome this disadvantage is to use a method of accessing the fixed allocation means, where the initial set-up signaling would specify when users are allowed to transmit on the uplink. However, there are advantages with dynamic multiplexing in the uplink due to, for example, increased flexibility in the allocation of transmission resources.

COMPENDIUM It is an object of the present invention to increase efficiency in a packet data communications system by employing a dynamic resource allocation method by introducing additional flexibility in the multiplexing of uplink transmission resources. By using a USF in the downlink to indicate that a mobile is programmed to transmit an arbitrary number of consecutive radio blocks on a physical channel, the mobile does not have to listen to the USF during several subsequent downlink blocks, a number based on the indication provided in the channel assignment message to this specific mobile station. The determination of what indicates a reception of a USF for the mobile station using an uplink assignment is specified in the initial signaling when a transmission resource is allocated, that is, a physical channel. In a TDMA system a physical channel can be a time slot. In multi-slot systems, various time slots can be assigned, but there will be different assigned USF values for each assigned time slot, which may or may not indicate the same number of consecutive radio block transmissions in the uplink. In addition, a USF occurrence may indicate a different number of uplink radio block transmissions for different users depending on the individual channel assignments. By programming the transmission of an arbitrary number of consecutive radio blocks for uplink transmission on a physical channel, there is no need for a mobile user to listen to the USFs during this transmission, before the last scheduled uplink radio block . As a result, transmission in the downlink can, for example, by means of adaptive antennas and power control algorithms, be performed with greater efficiency and a decrease in overall interference can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS The above objectives and features of the present invention will become more apparent from the following description of the preferred embodiments with reference to the accompanying drawings in which: Figure 1 illustrates a GPRS network architecture; Figure 2 illustrates a packet transmission stream and information mapping in an exemplary packet data communication system; Figure 3 illustrates a USF flag indicating uplink transmission multiplexing; Figure 4 illustrates uplink transmission multiplexing performed by a USF indicating transmission of an uplink radio block; Figure 5 illustrates multiplexing of the uplink transmission performed by a USF indicating transmission of more than one uplink radio block; and Figure 6 illustrates an exemplary traffic situation in a packet data communications system in accordance with the present invention.

DETAILED DESCRIPTION The invention will now be described with respect to a GPRS system where a method of dynamic resource allocation is provided for the multiplexing of mobile users by means of a USF transmission in the downlink. Mobile users sharing a broadcast resource listen to a USF transmission on the downlink to determine when uplink transmissions are allowed. The dynamic uplink allocation method, according to traditional systems, is based on a USF granulation of a radio block, that is, the appearance of a single USF in a downlink radio block determines the preservation of the link ascending during only one block. This is illustrated in Figure 4, where each downlink radio block includes a USF allocating the next uplink block for a mobile user. The present invention recognizes that the USF granulation can be modified by assigning individual channels from one to several consecutive blocks, which means that a single occurrence of the assigned USF is interpreted by a mobile station as an assignment of several radio blocks in sequence for the uplink transfer. This technique slightly decreases the flexibility of the dynamic allocation method, but provides advantages for other applications. Because the reservation of a plurality of blocks in the uplink can start anywhere, it is advantageous to transmit the appropriate USF only in the first block in the sequence, while in the rest of the radio blocks a non-zero value is transmitted. used for the USF in order to prevent other users from transmitting on the uplink. A mobile that has first received an allocation indication for a number of consecutive radio blocks, on receipt of such unused USF, will ignore this during the period defined by the uplink assignment. An unused USF value should be available in a packet data channel also for other purposes, for example, to have a way to prevent MSs from transmitting over the uplink in certain cases, such as during certain transmissions of data. control information. By assigning, for example, four consecutive radio blocks in an uplink time slot by a USF appearance, it is possible to use the other three radio blocks more freely in the downlink. This would greatly simplify the use of adaptive antenna arrays, where at least three of four radio blocks in the downlink can be sent within the lobes directed to the mobile station (MS) currently receiving radio blocks in the downlink . This assignment example is illustrated in Figure 5. In Figure 5, a USF is illustrated indicating that four consecutive radio blocks are assigned to mobile 1. The assignment is indicated only in the first radio block and provides that the next and The following three radio blocks are available for uplink transmission. The three consecutive downlink blocks, after the radio block indicating the assignment to the mobile 1, include an unused USF (Un) indicating that the receiving MSs should not transmit in the uplink. During this time, the downlink transmission does not have to reach the mobile 1 for multiplexing purposes of the uplink transmission, and may instead be directed, by means of a transmission lobe of the antenna array towards the mobile receives in the downlink. Of course, this can sometimes be the same mobile programmed to transmit on the uplink. One skilled in the art will know that the number of consecutive radio blogs that are illustrated in Figure 5 was provided simply as an example. In fact, it is possible to program any number of consecutive radio blocks in the uplink. The meaning of a USF is defined in the initial signaling and assignment of a physical channel for a mobile user. In an alternative embodiment of the present invention, where the meaning of a USF is the same for all mobiles in, for example, a certain cell, it may also be possible to transmit the number of blocks that a mobile user can transmit. It is also possible that the USF itself can be used to specify the number of consecutive radio blocks that can be transmitted. In such a situation, the USF may require additional information symbols to transport the appropriate number of blocks to the mobile user. Figure 6 illustrates an exemplary traffic situation according to the present invention, where a physical channel is shared by three mobiles. It should be noted that the control signaling has been left out of the figure since it is not necessary for the proper understanding of the invention. As indicated in the scheme of the TDMA frame of Figure 6, a mobile 1 receives a USF (Rl) on an assigned physical carrier, for example, a time slot, indicating that the transmission in the uplink is allowed for the following four periods of consecutive radio blocks. In GPRS, this corresponds to the following 16 TDMA frames. The USF indicating the mobile 1 is included in the downlink transmissions for the mobile 3. This downlink radio block is transmitted to all the mobile that share the same physical channel. The mobile 2 can also receive the downlink transmission and the USF which would indicate to the mobile 2 that no resource is allocated for the uplink transmission. In the next radio block, the TDMA frames 8-11, an uplink transmission occurs from the mobile 1, while the downlink transmission continues to the mobile 3. In this downlink radio block it is only possible to transmit to the mobile 3, since mobile 1 already knows that four consecutive blocks are assigned in the uplink. An unused USF (Un) is then interspersed in the downlink to prevent other mobiles from transmitting in the uplink. During the last scheduled uplink radio block, the TDMA frames 19-22, the downlink transmission must again be transmitted to all users to ensure that mobile 2, which is indicated in the USF, (R2), as well as Like other users, they receive the uplink assignment of yet another number of consecutive blocks. Then the course of events described above occurs again. It should be noted that a mobile user may have additional physical channels, for example, time slots assigned on the same or different frequencies, where similar, but not necessarily the same, indications of the USF apply. Any number of consecutive radio blocks can be indicated by a USF and the number is defined by mobile user based on the initial signaling. Figure 6 shows two antenna directions, or lobes 610 and 612. These lobes illustrate that downlink transmission that includes an unused USF can be directed to the mobile that receives data only in the downlink, that is, mobile 3 in the example described above. This is possible in a system where adaptive antenna arrays are implemented. By limiting the transmission of the energy of the signal to certain angle ranges, and perhaps also to the power control with respect to only one (or some) of the mobiles, it is possible to obtain a significant decrease in the level of interference. Although the invention has been described with respect to a GPRS system, those skilled in the art will understand that modifications similar to the multiplexing of the uplink transmission can be made in other packet data systems as well, and similar advantages as those mentioned can be achieved. Therefore, the invention should not be considered as limited to the described modalities, but defined only by the following clauses that are proposed to include all the equivalents thereof.

Claims (25)

REI INDICATIONS

1. A method for transmitting information in a packet-switched communication system where the uplink and downlink transmissions are segmented into radio blocks and several mobile stations share a single transmission resource, the method comprising the steps of: informing a mobile station of an arbitrary number of radio blocks that can be transmitted consecutively upon receipt of a Uplink State Flag (USF); transmitting a USF in a downlink transmission to the mobile station to initiate an uplink transmission of the arbitrary number of radio blocks; and transmitting consecutively, by the mobile station, the number of blocks in the uplink transmission.

2. The method according to claim 1 further comprises the step of: transmitting, during consecutive transmission of the arbitrary number of radio blocks when the arbitrary number is greater than 1, at least one USF not used to indicate that other mobile stations are it prevents them from transmitting in the uplink of the transmission resource.

3. The method according to claim 1, wherein the step of further reporting comprises: transmitting a value of the arbitrary number of blocks to the mobile stations. The method according to claim 1, wherein the step of further reporting comprises: specifying a value of the arbitrary number of blocks when the transmission resources are allocated between a mobile station and the system. 5. A method for programming uplink transmissions in a communication system where the uplink and downlink transmissions are segmented into radio blocks and a number of mobile stations share a single transmission resource, the method comprises the steps of : transmitting an indicator in a downlink transmission to a mobile station during the establishment of a radio connection between the mobile station and a base station; wherein the indicator indicates a number of radio blocks that the mobile station can transmit consecutively over the transmission resource upon receipt of a flag addressed to the mobile station. 6. The method according to claim 5, wherein the communication system is a radio packet communications system. The method according to claim 5, wherein the communication system is a Time-Division Multiple Access (TDMA) system. 8. A system for transmitting information in a packet-switched communication system where the uplink and downlink transmissions are segmented into radio blocks and a number of mobile stations share a single transmission resource, the system comprising: means for informing a mobile station of an arbitrary number of radio blocks that can be transmitted consecutively upon receipt of an Uplink State Flag (USF) Ascendant); means for transmitting a USF in a downlink transmission to the mobile station to initiate an uplink transmission of the arbitrary number of radio blocks; and the means for transmitting consecutively, through the mobile station, the number of blocks in the uplink transmission. The system according to claim 8 further comprises means for transmitting, during consecutive transmission of the arbitrary number of radio blocks when the arbitrary number is greater than 1, at least one USF not used to indicate that to other mobile stations they are prevented from transmitting in the uplink of the transmission resource. The system according to claim 8, wherein the means for further reporting comprises: means for transmitting an arbitrary number of blocks value to the mobile stations. 11. The system according to claim 8, wherein the means for further reporting comprises: means for specifying a value of the arbitrary number of blocks when the resources of the transmission are allocated between a mobile station and the system. 12. A base station for transmitting data packets comprises: an array of antennas for transmitting packet data in at least one of a plurality of antenna lobes; and the means to transmit packets including a Uplink State Flag (USF) in a first series of the plurality of lobes and to transmit packets in a second series of the plurality of lobes directed towards a specific mobile station. The base station of claim 12, wherein the USF identifies the mobile station that can transmit, in the uplink, a predetermined, consecutive number of blocks. 1

4. A method for programming uplink transmissions in a communication system, where the uplink and downlink transmissions are segmented into radio blocks and a number of mobile stations share a single transmission resource, the method comprises the steps of : transmitting an Uplink State Flag (USF) in a downlink transmission to a mobile station during the establishment of a radio connection between the mobile station and a base station; wherein the USF indicates a number of radio blocks that the mobile station can transmit consecutively over the transmission resource. 1

5. The method according to claim 14 further comprises the step of: transmitting, during a transmission of the number of radio blocks when the number of blocks is greater than 1, at least one USF not used to indicate that the transmission in the Uplink of the transmission resource is not allowed. 1

6. The method according to claim 14, wherein the communication system is a radio packet communications system. 1

7. The method according to claim 14, wherein the communication system is a Time-Division Multiple Access (TDMA) system. 1

8. The method according to claim 14, wherein the base station comprises an array of adaptive antennas. 1

9. A system for programming uplink transmissions in a communications system where the uplink and downlink transmissions are segmented into radio blocks, the system comprising: a single transmission resource that is shared by a number of mobile stations; and the means to transmit an Uplink State Flag (USF) in a downlink transmission to a mobile station during an establishment of a connection between the mobile station and a base station; wherein the USF indicates a number of radio blocks that the mobile station can transmit consecutively over the transmission resource. The system according to claim 19, further comprises means for transmitting, during a transmission of the number of radio blocks when the number of radio blocks is greater than 1, at least one USF not used to indicate that other Mobile stations are prevented from transmitting on an uplink of the transmission resource. 21. The system according to claim 19, wherein the communication system is a radio packet communications system. 22. The system according to claim 19, wherein the communication system is a Time-Division Multiple Access (TDMA) system. 23. The system according to claim 19, wherein the base station comprises an array of adaptive antennas. 24. A method for transmitting data packets comprises the steps of: transmitting data packets including a Uplink State Flag (USF) in a first series of a plurality of antenna lobes; and transmitting data in packets in a second series of the plurality of antenna lobes directed to a particular mobile station. 25. The method of claim 24, wherein the USF identifies the mobile station that can transmit, in the uplink, a predetermined, consecutive number of blocks.