BANDWIDTH RESERVATION IN A TELECOMMUNICATIONS SYSTEM

Abstract: Device at a telecommunications system including a communications system which includes two modes, one of which is specified, at which the specified mode (mode 1) is intended for asynchronous communication and big packets, and the other mode (mode 2) is adapted to synchronous communication such as speech, video and short regularly recurrent packets at which the system spectrum can efficiently carry ATM-packets of service class type A and B, owing to that the nodes of the second mode (mode 2) are regularly the only nodes which are allowed to use the highest priority; reserves bandwidth for such packets that shall be transmitted with regularly recurrent intervals. This in order to be guaranteed necessary transmission capacity; shall reserve bandwidth by transmitting information in a time slot, BRP (Bandwidth Reservation Phase), according to Figure 2 about how much bandwidth it reserves after the node has got access to the medium, at which the BRP time slot shall be transmitted immediately after the node has got permission to use the medium. I.e. in HIPERLAN BRP shall be transmitted after PAP and CP.

Description: TITLE OF THE INVENTION Bandwidth reservation in a telecommunications system TECHNICAL FiSfcP The invention relates to a procedure and a device according to the introduction to the patent claims PRXQR ART The standard which exists for cordless LAN has got the name HIPERLAN and is a decentralized and cordless system for short distance communication and includes asynchronous as well as synchronous communication. This, however, makes special demands on the MAC (Medium Access Control) protocol which is used for access to the communication media. Asynchronous communication requires short response times on an average but can tolerate comparatively big variations round the average. For synchronous communication the case is the opposite. Synchronous communication can accept comparatively long delays but instead makes great demands on that the variations round the average is small. In addition synchronous communication requires a guaranteed access of necessary transmission capacity during comparatively long periods. HIPERLAN can by utilization of suggested invention efficiently transmit ATM-traffic. DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM The aim with the invention is to make one in relation to the prior art improved and simplified access method for HIPERLAN which satisfies given demands. HIPERLAN consists of two modes, one of which is specified. The specified mode (mode 1) is intended for asynchronous communication and big packets. The other mode (mode 2) shall be adapted to synchronous communication such as speech, video, to, in a spectrum-efficient way be able to carry ATM-packets of service class type A, B, C and D. ATM service class A corresponds to connection oriented traffic with constant bit rate and where it exists a synchronization dependency between the end points. Examples of such traffic are 64 kbit/s speech channels and circuit switched 2 Mbit/s signals acccording to G.702. ATM service class B represents connection oriented traffic with a synchronization dependency and which supports variable bit rate. Speech and video encoders for variable bit rates are examples of service class B. ATM service class C relates to connection oriented traffic with variable bit rate where there is no need for synchronization between the terminal points. (Frame relay, X.25) . ATM service class D is characterized by connectionless transmission without need for synchronization which supports variable bit rate. ATM-packets are small compared with normal LAN-packets. Mode 1 uses an access method called EY-NPMA (Elimination Yield Non-Pre-emptive Priority Multiple Access) . This access method includes three phases; PAP (Priority Access Phase) , CP (Contention Phase) and TP (Transmission Phase), see Figure 1. In the PAP the node transmits the priority (out of five different PAP priority levels) of the packet it wants to transmit. The priority is set by the MAC-layer with information from overlaying OSI-layers. The information from overlaying OSI-layer consists of two parameters; user priority and NRML (Normalized Residual HMSDU (HIPERLAN MAC Service Data Unit) Lifetime) . NRML simply expressed corresponds to remaining lifetime for packet divided by the number of nodes the packet must pass before it reaches the destination node. User priority can take the value one or zero. In order to separate nodes which transmits packets with the same PAP priority there is CP, in which the nodes compete for the medium. After CP there shall only remain one node which is allowed to transmit a packet in TP. (A packet consists of one or more smaller blocks) . The access method EY-NPMA does not guarantee the access to the communication media for more than one following packet, which is required for synchronous services such as speech, video etc. Further the EY-NPMA is a very spectrum inefficient access method for small packets. The demands in service class A and B can not be fulfilled in the systems of today. Efficiency lower than 0,20 for packets type ATM (53 bytes) can be expected with EY-NPMA. Simulations have been performed where 90% of the packets are small (64 bytes) and 10% are big (1500 bytes), then the net bit rate in HIPERLAN will be about 5 Mbit/s out of a "raw" bit rate of 23,5 Kbit/s. The efficiency in this case is barely 0,25. In figure 22 is illustrated the problem with electromagnetically hidden nodes. The illustration shows, how unwanted interference between two nodes can arise. Radio waves transmitted from C and λ interfere in node B. Unfilled circles illustrate coverage. Mode λ and C are electromagnetically hidden for each other which means that they cannot physcically communicate with each other. If we imagine a situation where both node λ and C try to transmit a TP at about the same point of time, TP will collide with each other in node B and both the transmissions will fail. In spite of that both node λ and node C have followed the access rules which are valid, i.e. passed as "victories* from PAP and CP, and informed neighbouring nodes within the coverage with BRP about which bandwidth reservation it has made, collision occurs in node B. THE SOLUTION The above mentioned aims are achieved by the invention showing the in the enclosed patent claims indicated characteristics. ADVANTAGES The invention gives a lot of advantages, among other things is obtained a raise of the capacity for HIPERLAN- transmission of short messages/data packets and a raised transmission probability for information given priority to. By suggested access method synchronous services will have possibility to be guaranteed access to the communication medium after connection. Further it will be possible to heavily raise the spectrum efficiency, the capacity and the efficiency for small packets of the type ATM. At last the invention solves the problem with electromagnetically hidden nodes for synchronous traffic. DESCRIPTIONS OF FIGURES The invention shall now be described by means ' of not restricted examples of embodiment and with reference to enclosed, schematically performed drawings. In the drawings are shown in: Figure 1: Simplified drawing of the access method EY- NPMA. Figure 2: Suggested access method including suggested BRP-field. Figure 3: Example of how the BRP-fields can be arranged. Figure 4: Description of flow of packets in HIPERLAN. Figure 5: Description over flow of packets in ATM at which the figure only shows a part of the AAl-layer, and that is AAL! (which is adapted to ATM service class A). Figure 6: Example of interworking between the ATM- interface and HIPERLAN MAC. Figure 7: Example of interworking between AAL (ATM adaption layer) and HIPERLAN MAC. Figure 8: Alternative embodiment of the invention. Figure 9: Alternative embodiment of the invention. Figure 10: Alternative embodiment of the invention. Figure 11: Alternative embodiment of the invention. Figure 12: Alternative example of parameters which can be included in the BRP-field. Figure 13: Alternative example of how the BRP-field can be arranged. Figure 14: Alternative example of how the BRP-field can be arranged. Figure 15: Example of how the BDP-field can be arranged and parameter which can be included in BDP. Figure 16: Example of how the BDP-field can be arranged and parameter which can be included in BDP. Figure 17: Example parameters which can be included in the BUP-field. Figure M: The invention shown in one more embodiment. Figure 19: One more variant of implementation of BRP. Figure 20: Alternative example of parameters which can be included in BRP-field. Figure 21: Alternative example of parameters which can be included in BRP-field. Figure 22: The illustration shows how unwanted interference between two nodes can arise. DETAILED DESCRIPTION The nodes of the second mode (which is shown i Figure 2) , mode 2 : are the only nodes which are allowed to regularly use the highest priority. reserves bandwidth for such packets that shall be transmitted with regularly recurrent interval. This in order to guarantee necessary transmission capacity. shall reserve bandwidth by transmitting information in a time slot, BRP (Bandwidth Reservation Phase) according to Figure 2, about how much bandwidth it reserves after the node has got access to the medium. The BRP time slot shall be transmitted immediately after the node has got permission to use the media. I. e. in HIPERLAN BRP shall be transmitted after PAP and CP. The invention further consist of that all HIPERLAN nodes shall be able to detect information in the BRP-field. The TPs which in BRP are reserved by a node may in principle not be used by other nodes which are within radio coverage. The invention can however in an alternative embodiment allow exceptions from the above mentioned principle according to the following: The reserved blocks in TP which follow after an empty detectable reserved block may be used by other nodes. I. e. those after an empty not used block following blocks are temporarily lost to the node which originally reserved these blocks. Use of these blocks should however be restricted to mode 1 nodes. Node which performs "BRP-reservation" need only use PAP, CP and BRP before TP 1. I.e. TP 2, 3.. ATPmax can be transmitted without PAP, CP and BRP. But BRP must always be transmitted at a time within the time interval Tmax. If the application lasts longer than Tmax, a new BRP must consequently be transmitted within each Tmax interval. The node, however, need not compete for the medium by means of PAP and CP at these extra BRP-transmissions. Tmax consequently determines ATPmax: ATPmax = INT (Tmax/TInt) (INT = is rounded off to integer downwards) . Tmax shall be dimensioned in such a way that other nodes can get information of HIPERLAN-status and what remains of the BRF-reservation without need to listen during unnecessary long time. Tmax shall however be sufficiently big not to restrict the transmission capacity by unnecessary frequent signalling. Node which wants access to the transmission medium must before then have listened to the carrier in question during a period of time at least as long as Tmax. Bearing in mind the small need for bandwidth of mode 2 nodes in relation to the bandwidth of the HIPERLAN- spectrum, it is not likely that reserving nodes risk to outrival not reserving nodes. But it can still be of value to introduce ABmax. This conception signifies maximal number of blocks which totally is allowed to be reserved by a node based on only one competition by means of PAP and CP. It should be noticed that ABmax can include a number of Tmax-intervals. ABmax can either be a system constant or be subject to variations to achieve optimal system behaviours in time. If one allows just any values of Tint, this can, if a large number of different reservations have been performed, possibly result in difficulties to calculate which times that are vacant. This possible difficulty is solved by allowing only one or a few basic values of Tint. Application which segments information in packets (for instance ATM) and after that saves the packets in a buffer while waiting for the packets to be transmitted, has information about how many packets that are queuing in the buffer. The invention implies that HIPERLAN-node can read such queue information. This information can be utilized by both mode 1- and mode 2 nodes. The length of the queue can be used to determine ATP and/or AB. It should be noticed that the AB-determination based on queue information also can be performed without BRP- reservation but then for only one TP. Further queue should be created for packing in bigger AB for such information the lifetime of which is not threatened. The Figures 4 and 5 show in a simplified way packet flows between OSI-layers in ATM respective HIPERLAN. The intention with the figures is to show different ways of mapping HIPERLAN and ATM/AAL-packets on each other. The invention suggests IWF-maps CS-SDU directly on HMSDU. Another solution is that IWF transfers I ATM-SDU or buffers and combines a number of ATM-SDUs and creates an HMSDU. One solution is that HIPERLAN MAC buffers ATM-SDU and combines a number of ATMSDU or HMSDU when necessary to one HMPDU. Figure 5. Description of packet flow in ATM. The figure shows only a part of the AAL-layer, and that is AALl (which is adapted for ATM service class A) . The above described solutions also relate to interworking between HIPERLAN and other similar systems which carry corresponding type of traffic and which have similar packet structures . The Figures 6 and 7 below show two different ways, at OSI-level, to implement interworking between HIPERLAN and ATM. The figures do not intend to be a description of the invention, but more to show the possibility to connect these two systems. Time interval between TPs which are multiples of blocks is most favorable to use. This to prevent that different reservations slide into each other and by that interfere with each other. BRP need not indicate how many TP that are reserved. The reservation is valid until the node no longer uses the reservation or transmits a dereservation. The invention also includes a function in HIPERLAN-CAC which unites short HCSDUs which have the same priorites, this in order to improve the spectrum-efficiency. Below follows a number of alternative embodiments. The method which at first hand is recommended is illustrated by Figure 11 in combination with the Figures 20 and 21. I.e. BRP shall be transmitted immediately before, alternatively after, the first block in respective reserved TP. BRP can be arranged in a way that it becomes considerably shorter than a block, making the increased capacity load very restricted, compared with methods which transmits BRP or BUP less frequent. In Figure 8 is shown a first alternative embodiment of the invention where BDP can be located directly after or directly before last TP of in last TP. BDP indicates that node does not intend to use prereserved time slots. In Figure 9 is shown a second alternative embodiment of the invention where BUP can be located directly after or directly before TP or in TP. BUP is transmitted at regular intervals making it possible for neighbouring nodes to update reservation status. In Figure 10 is shown a third alternative embodiment of the invention which is a combination of the first and the second embodiment where BRP and BUP can be of the same type of packet and contain the same information. Figures 11-16 illustrate alternative embodiments of the invention as well as parameters which can be included in BRP-field and arrangement of BDP-field and parameters. In Figure 17 is shown example of embodiment of BUP. The internal succession can be different from that which is shown. The aim with BUP is to update previous reservation for nodes which are within radio coverage. In Figure 18 the invention is shown in one more embodiment where the bandwidth reservation field, BRP, shall be added after CP (contention phase) in EY-NPMA. A mode 2 node which has won PAP and CP is the only node which has right to transmit corresponding BRP-shower. Mode 1- and mode 2 nodes listen och detect the BRP-field and follows according to predetermined rules the information in the field. Mode 2 nodes have possibility to reserve bandwidth for packets which usually act in way that it can guarantee bandwidth after contact for more than one TP. The mode 2 nodes are mainly the only nodes which have right to utilize the highest priority in CAC. For instance mode 2 can be the only nodes which are allowed to use HIPERLAN User Priority 1 (In ATM connectionless services only Cell Loss Priority 0 is allowed to be used) . Mode 2 nodes are allowed to use Priority 1 if, and only if, packets are used by a service defined in ATM service class A or B, or if the packets from ATM have CELL Loss Priority 1. The TP which in BRP are reserved by a node may in principle not be used by other nodes which are within radio coverage. The invention can however in an alternative embodiment allow exceptions from the above mentioned principle according to the following: The reserved blocks in TP which follow after an empty detectable reserved block may be used by other nodes. I.e. the after an empty not used block following blocks are temporarily lost for the node which originally reserved these blocks. Use of these blocks should however be restricted to mode 1 nodes. Figure 19 shows one further variant of implementation of BRP. A node (mode 1 or 2) which intends to transmit, must listen to the medium during at least a predetermined time TCTPmax, which is the longest time between two TCTPs, before it has right to try to get access to the medium. Mode 2 nodes which have made BRP- reservations need only transmit PAP, CP and BRP before TPs . With this is meant that TP 2, 3 can be transmitted without PAP and CP. Figure 20 shows one more variant of BRP intended to be used together with in Figure 21 shown BRP. Figure 21 shows yet one more variant of BRP intended to solve the problem with electromagnetically hidden nodes. The invention is not restricted to the shown examples of embodiment but can be varied in just any way within the frame of the idea of invention, such it is defined in the following patent claims. Text to Figures Fiqure 1: PAP Priority Access Phase (502-1280 bits) CP Contention Phase (502-3072 bits) TP Transmission Phase (450-23762 bits) Figure 2: PAP Priority Access Phase CP Contention Phase BRP Banwidth Reservation Phase Fiqure 3: ATP Number of TP. Indicates total remaining number of TPs which the node reserves for the application in question. Tint: Time interval between TP. Indicates the time between start of two for the reservation consecutive TP. Consequently it gives the period for the reservation. AB: Number of blocks in TP. Indicates how many blocks that maximally shall be included in each TP which is included in the reservation. Figure 6: IWU Interworking Unit IWF Interworking Function AAL ATM Adaption Layer CAC Channel Access Control Figure 8: PAP Priority Access Phase CP Contention Phase BRP Bandwidth Reservation Phase BDP Bandwidth Dereservation Phase Figure 9: PAP Priority Access Phase CP Contention Phase BRP Bandwidth Reservation Phase BUP Bandwidth Update Phase Figure 10: PAP Priority Access Phase CP Contention Phase BRP Bandwidth Reservation Phase BDP Bandwidth Dereservation Phase BUP Bandwidth Update Phase Figure 11 PAP Priority Access Phase CP Contention Phase BRP Bandwidth Reservation Phase Figure 12: Tint: Time interval between TP. Indicates the time between start of two for the reservation consecutive TP. Consequently it gives the period for the reservation. The reservation is valid until packet containing dereservation has been transmitted, or a time, t^, has elapsed during which no BRP has been transmitted. Only predefined Tint which are mul¬ tiples of block should be allowed. Figure 12: AB: Number of blocks in TP. (cont) Indicates how many blocks that maximally shall be included in each TP which is included in the reservation. RS: One or a number of bits which indicates whether it is a reservation or a dereservation. Figure 13: IFA: Indicates the type of predefined access rule. Access rules can differ for instance regarding: allowed time interval between TP, number of blocks in TP, number of reserved TP etc. Fiqure 14: IB: Indicates that this is a BRP-field. The access rule is predetermined which means that allowed time interval between TP, number of blocks in TP etc has predefined values which are known by all nodes, Fiqure 15: IBDP: Indicates that node dereserves previously reservations and/or that this is a BDP-packet. Figure 16: IBDPi Indicates that this is a BDP- field. IX: Indicates which reservations are dereserved. Figure 17: Tints Time interval between TP. Indicates the time between start of two for the reserfvation consecutive TP. Figure 17 Consequently gives the period for (cont) the reservation. The reservation can be valid until BDP (Bandwidth Dereservation Phase) has been transmitted. AB: Number of blocks in TP. Indicates how many blocks that maximally shall be included in each TP which is included in the reservation. TR: Indicates time reference making it possible for receiving node to decide starting time for reserved TP. Compare Figure 4 where TR need not be indicated because BRP is transmitted in immediate connection to the TP in question. Figure 18: PAP Priority Access Phase CP Contention Phase BRP Bandwidth Reservation Phase TP Transmission Phase Figure 19: BRP: One bit that indicates if this is a BRP or BDP. BDP indicates that a mode 2 node dereserves earlier made reservation. ITCTP: Indicator Time between Consecutive TP. TCTP is the time between the start of two consecutive TP. The reservation will be valid until a BDP has been sent or a time t mi.l. (cont) has elapsed within no BRP has been sent. Only predetermined Figure 19: TCTP that are multiples of (cont) blocks should be allowed. NTP: Number of blocks in TP. Indicates how many blocks that maximum can be a part of the reserved TP. Figure 20: IS(1) : Indicator Symmetric connection. Indicates if this is a short or a long BRP. ITCTP(8): Indicator Time between Consecutive TP. TCTP is the time between the start of two consecutive TP. The reservation will be valid until a BDP has been sent, ' or a time tHUJ .1 has elapsed within no BRP has been sent. Only predetermined TCTP that are multiplies of blocks should be allowed. NTP(6): Number of blocks in TP. Indicates how many blocks that maximum can be a part of the reserved TP. BRP(1) : One bit that indicates if this is a BRP or BDP (Bandwidth De- reservation Phase). BDP indi¬ cates that a mode 2 node dere¬ serves earlier made reservation. Figure 21 IS(1) : Indicator Symmetric connection. Indicates if this is a short or a long BRP. ITCTP(8): Indicator Time between Consecutive TP. TCTP is the time between the start of two consecutive TP. The reservation will be valid until a BDP has been sent, * or a time t m mx l n n has elapsed within no BRP has been sent. Only predetermined TCTP that are multiples of blocks should be allowed. NUTP(6): Number of blocks in TP. Indicates how many blocks that maximum can be a part of the reserved TP. BRP(l): One bit that indicates if this is a BRP or BDP (Bandwidth De¬ reservation Phase). BDP indi¬ cates that a mode 2 node dere¬ serves earlier made reservation. TBBRP(15): Time Between uplink BRP and downlink BRP. With this information a node A can let nodes in his radiorange know that the node B has made this reservation. The accuracy need for TBBRP is first of all dependent of expected number of nodes in the area. Figure 21: NDTP(6): Number of reserved blocks in (cont) Downlink TP. Notice! Node A doesn't reserve bandwidth for node B. Node A only let other nodes know the reservation that node B has made. If a node notices that his reserved channel is interfered (e.g. a hidden node), the node can make a handover, which means that the node makes a new channel reservation and dereserves his old channel.

Claims: PATENT CLAIMS 1. Procedure at telecommunications system including a communications system for both asynchronous and synchronous communication for transmission of services, c h a r a c t e r i z e d in that synchronous services are guaranteed highest access to the used communication media after connection, and that a rise of the capacity for the transmission is made by reservation of bandwidth being executed for such packets which shall be transmitted at regular recurrent intervals. 2. Procedure according to patent claim 1, c h a r a c t e r i z e d in that the reservation of bandwidth is made by transmission of a time slot BRP (Bandwidth Reservation Phase). 3. Procedure according to patent claim 2, c h a r a c t e r i z e d in that the BRP time slot is transmitted immediately after intended node has got permission to use the media. 4. Procedure according to patent claim 1, c h a r a c t e r i z e d in that the communications system is a decentralized and cordless system for short distance communication. 5. Procedure according to patent claim 3, c h a r a c t e r i z e d in that all nodes in the system can detect the information in the BRP-field. 6. Use of an access method at a communications system preferably a communications system which is a decentralized and cordless system for short distance communication which guarantees synchronous services by bandwidth reservation and raises the transmission capacity. 7. Device at a telecommunications system including a communications system which includes two modes, one of which (mode 1) is intended for asynchronous communication and big packets, and the other mode (mode 2) is adapted to synchronous communication such as speech, video, c h a r a c t e r i z e d in that the system spectrum efficiently can carry ATM-packets of service class type A and B, owing to that the nodes of the second mode, mode 2: are the only nodes which regularly are allowed to use the highest priority. reserve bandwidth for such packets that shall be transmitted with regularly recurring intervals. This in order to be guaranteed necessary transmission capacity. shall reserve bandwidth by transmitting information in a time slot, BRP (Bandwidth Reservation Phase) according to Figure 2, about how much bandwidth it reserves after the node has got access to the media, at which the BRP time slot shall be transmitted immediately after the node has got permission to use the media. I.e. in HIPERLAN, BPR shall be transmitted after PAP and CP. 8. Device according to patent claim 7, c h a r a c t e r i z e d in that ATM service class A corresponds to connection oriented traffic with constant bit rate and where a synchronization dependency between the end points exists. 9. Device according to patent claim 7, c h a r a c t e r i z e d in that ATM service class B represents connection oriented traffic with a synchronization dependency and which supports variable bit rate. 10. Device according to any of the patent claims above c h a r a c t e r i z e d in that the communications system is a decentralized and cordless system for short distance communication. 11. Device according to any of the patent claims above c h a r a c t e r i z e d in that nodes which communicate with each other repeat the bandwidth reservations of nodes. 12. Device according to any of the patent claims above c h a r a c t e r i z e d in that packing of ATM-packets in big multiblocks (big TP HIPERLAN) is based on access to queue information in ATM-buffer.

Inventors: ALEXIUS STAFFAN, WICKMAN JOHAN, ALEXIUS, STAFFAN, WICKMAN, JOHAN
Applicants: ALEXIUS STAFFAN, TELIA AB, WICKMAN JOHAN, ALEXIUS, STAFFAN, WICKMAN, JOHAN
Application year: 1996
Main classification: H04L12
IPC codes: H04J3, H04L12, H04Q11