SE514987C2 - Procedure and apparatus for a telecommunications system for HIPERLAN transmission - Google Patents

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

30 35 514 987 ATM service class B represents connection-oriented traffic with a synchronization dependency and supporting variable bit rate. Variable bit rate speech and video codecs are examples of service class B.

ATM service class C refers to connection-oriented traffic with variable bit rate where there is no need for synchronization between the terminal points (Frame relay, X25).

ATM service class D is characterized by connectionless transmission without the need for synchronization that supports variable bit rate.

ATM packets are small compared to normal LAN packets.

Mod l uses an access method called EY-NPMA (Elimination Yield Non-Preemptive Priority Multiple Access). This access method contains three phases: PAP (Priority Access Phase), CP (Contetion Phase) and TP (Transmission Phase), see Fig. 1.

In the PAP, the node broadcasts the priority (of five different PAP priority levels) of the packet it wants to send. The priority is set by the MAC layer with information from the upper OSI layer. The information from the upper OSI layer consists of two parameters; user priority and NRML (N ormalized Residual HMSDU (HIPERLAN MAC Service Data Unit) Lifetime. NRML simply corresponds to the remaining lifetime of the packet divided by the number of nodes the packet must pass before reaching the destination node. User priority can take the value one or zero.

To distinguish nodes that send packets with the same PAP priority, there is a CP, in which the nodes compete for the medium. After the CP, only one node remains that is allowed to send a packet in the TP (A packet consists of one or more smaller blocks).

The EY-NPMA access method does not guarantee access to the communication medium for more than one subsequent packet, which is required for synchronous services such as voice, video, etc. Furthermore, EY-NPMA is a very spectrum-inefficient access method for small packets.

The requirements of service classes A and B cannot be met in today's system. Efficiency ratios of less than 0.20 for ATM type packets (53 bytes) are to be expected with EY-NPMA.

Simulations have been performed where 90% of the packets are small (64 bytes) and 10% are large (1500 bytes) then the net data rate in HIPERLAN is approximately 5 Mbps out of a raw data rate of 23.5 Mbps. The efficiency in this case is just under 0.25.

Fig. 22 illustrates the problem of electromagnetically hidden nodes. Fig. 22 shows how unwanted interference between two nodes can occur. Radio waves transmitted from C and A interfere in node B. Unfilled circles illustrate coverage areas.

Nodes A and C are electromagnetically hidden from each other, which means that they cannot physically communicate with each other. If we imagine a situation where both nodes A and C try to send a TP at approximately the same time, the TPs will collide with each other in node B and both transmissions will fail. Despite both nodes A and node C having followed the applicable access rules, i.e. having passed through the PAP and CP as victors and having notified surrounding nodes within the coverage area with the BRP of the bandwidth reservation it has made, a collision occurs in node B.

The solution The above-mentioned objects are achieved by the invention having the features set forth in the attached patent claims.

Advantages The invention provides a number of advantages, including an increase in the capacity for HIPERLAN transmission of short messages/data packets and an increased transmission uniformity for prioritized information. With the proposed access method, synchronous services will be able to be guaranteed access to the communication medium after connection. Furthermore, the spectrum efficiency, capacity and efficiency will be able to be greatly increased for small packets of the ATM type. Finally, the invention solves the problem of electromagnetic hidden nodes for synchronous traffic.

DESCRIPTION OF THE FIGURES The invention will now be described with the aid of non-limiting exemplary embodiments with reference to the attached, schematically illustrated drawings. The drawings show: Fig. 1 simplified view of the access method EY-NPMA; Fig. 2 proposed access method containing proposed BRP field; Fig. 3 example of how the BRP fields can be designed; Fig. 4 description of packet flow in HIPERLAN; Fig. 5 description of packet flow in ATM, whereby the figure only shows a part of the AAl layer, namely AALI (which is adapted for ATM service class A); Fig. 6 example of interworking between the ATM interface and HIPERLAN MAC; Fig. 7 example of interworking between AAL (ATM adaptation layer) and HIPERLAN MAC; Fig. 8 alternative embodiment of the invention; Fig. 9 alternative embodiment of the invention; Fig. 10 alternative embodiment of the invention; Fig. 11 alternative embodiment of the invention; Fig. 12 alternative example of parameters that can be included in the BRP field; Fig. 13 alternative example of how the BRP field can be designed; Fig. 14 alternative example of how the BRP field can be designed; Fig. 15 example of how the EDP field can be designed and parameters that can be included in the BDP; Fig. 16 example of how the BDP field can be designed and parameters that can be included in the BDP; Fig. 17 example of parameters that can be included in the BUP field; Fig. 18 shows the invention in a further embodiment; Fig. 19 shows a further variant of implementation of BRP; Fig. 20 alternative example of parameters that can be included in the BRP field; Fig. Fig. 21 alternative example of parameters that can be included in BRP fields; and Fig. 22 the problem with electromagnetically hidden nodes.

DETAILED DESCRIPTION The second mode (as shown in Fig. 2) mode 2 nodes: - are the only nodes that are regularly allowed to use the highest priority. - reserves bandwidth for such packets that are to be transmitted at regularly recurring intervals. This is to guarantee the necessary transmission capacity. - shall reserve bandwidth by sending out information in a time slot, BRP (Bandwidth Reservation Phase) according to Fig. 2, about how much bandwidth he reserves after the node has gained access to the medium. The BRP time slot shall be sent immediately after the node has gained permission to use the medium. 1 HIPERLAN shall therefore BRP be sent after PAP and CP.

The invention further consists in all HIPERLAN nodes being able to detect the information in the BRP field. The TPs that are reserved in the BRP by a node may in principle not be used by other nodes that are within radio coverage. However, the invention can in an alternative embodiment allow exceptions to the above principle as follows: the 10 15 20 25 30 35 514 987 5 reserved blocks in the TP that follow an empty detectable reserved block may be used by other nodes. That is, the blocks that follow an empty unused block are temporarily lost for the node that originally reserved these blocks. However, the use of these blocks should be limited to mode 1 nodes.

Nodes performing "BRP reservation" only need to use PAP, CP and BRP before TP1, i.e. TP2, 3... ATPmax can be transmitted without PRP, CP and BRP.

However, the BRP must always be sent at some point within the time interval Tmax. If the application lasts longer than Tmax, a new BRP must therefore be sent within each Tmax interval. However, the node does not have to compete for the medium using PAP and CP during these extra BRP transmissions. Tmax thus determines ATPmax: ATPmax = INT (Tmax / Tint) (INT = rounded down to an integer) Tmax must be dimensioned so that other nodes can obtain information about the HIPERLAN status and what remains of the BRF reservation without having to listen for an unnecessarily long time. However, Tmax must be large enough not to limit the transmission capacity through unnecessarily frequent signaling.

A node that wishes to access the transmission medium must have previously listened to the current carrier for a time that is at least as long as Tmax.

Given the low bandwidth requirements of mode 2 nodes relative to the bandwidth of the HIPERLAN spectrum, it is unlikely that reserving nodes will compete out non-reserving nodes. However, it may still be of value to introduce Abmax. This term denotes the maximum number of blocks that may be reserved in total by a node based on only one contention using PAP and CP. Note that Abmax can encompass several Tmax intervals. Abmax can either be a system constant or can be varied to achieve optimal system behavior over time.

Allowing arbitrary values for TInt can, if a large number of different reservations have been made, lead to difficulties in calculating which times are free. This potential difficulty is solved by only allowing one or a few basic values for TInt.

An application that segments information into packets (e.g. ATM), and therefore saves the packets in a buffer while waiting to be sent, has information about how many packets are queuing in the buffer. The invention means that a HIPERLAN node can resolve such queuing information. This information can be used by both mode 1 and mode 2 nodes. 10 15 20 25 30 35 514 987 6 The queue length can be used to determine ATP and/or AB. Note that the AB determination based on the queue information can also be done without BRP reservation, but then for only one TP. Furthermore, a queue should be created for packaging in larger AB for such information whose lifetime is not threatened here.

Figures 4 and 5 show simplified packet flows between OSI layers in ATM and HIPERLAN, respectively. The purpose of the figures is to show different ways of mapping HIPERLAN and ATM/AAL packets to each other. The invention proposes that the IWF maps the CS-SDU directly onto the HMSDU. Another solution is that the IWF transmits the ATM-SDU or buffers and merges several ATM-SDUs and forms an HMSDU. One solution is that the HIPERLAN MAC buffers the ATM-SDU and merges several ATM-SDUs or HMSDUs if necessary into an HMPDU.

Fig. 5 describes a packet flow in ATM. The figure shows only a part of the AAL layer, namely ΛΕA (which is adapted for ATM service class A).

The above solutions also refer to interworking between HIPERLAN and other similar systems that carry the same type of traffic and have similar packet structures.

Figures 6 and 7 show two different ways at OSI level to implement interworking between HIPERLAN and ATM. The figures are not intended to be a description of the invention, but rather to demonstrate the possibility of interconnecting these two systems.

Time intervals between TPs that are multiples of blocks are most advantageous to use.

This is to prevent separate reservations from sliding into each other and thereby interfering with each other.

The BRP does not need to specify how many TPs are reserved. The reservation is valid until the node no longer uses the reservation or sends a dereservation.

The invention also includes a function in HIPERLAN-CAC that merges short HC SDUs that have the same priorities, to improve spectrum efficiency.

Below are a number of alternative embodiments. The method that is primarily recommended is illustrated by Fig. 11 in combination with Fig. 20 and 21. That is, the BRP should be sent immediately before or after the first block in the 10 15 20 25 30 35 514 987 7 reserved TP, respectively. The BRP can be designed to be considerably shorter than a block, so that the increased capacity load is very limited compared to methods that send the BRP or BUP less frequently.

In Fig. 8 a first alternative embodiment of the invention is shown where the BDP can be located directly after or directly before the last TP or in the last TP. The BDP indicates that the node does not intend to use pre-reserved time slots.

In Fig. 9 a second alternative embodiment of the invention is shown where the BUP can be located directly after or directly before the TP or in the TP. The BUP is sent out at regular time intervals so that surrounding nodes can update the reservation status.

In Fig. 10 a third alternative embodiment of the invention is shown, which is a combination of the first and second embodiments where BRP and BUP can be the same type of packet and contain the same information.

Fig. 11 - 16 illustrate alternative embodiments of the invention and parameters that may be included in BRP fields and the design of BDP fields and parameters.

Fig. 17 shows an example of an embodiment of BUP. The order of the nodes may differ from that illustrated. The purpose of BUP is to update previous reservations for nodes that are within radio coverage.

In Fig. 18 the invention is shown in a further embodiment where the bandwidth reservation field, BRP, is to be added after the CP (contention phase) in EY-NPMA. A mode 2 node that has won the PAP and CP is the only node that has the right to transmit the corresponding BRP burst. Mode 1 and Mode 2 nodes listen and detect the BRP field and follow the information in the field according to predefined rules.

Mode 2 nodes have the ability to reserve bandwidth for packets that typically occur so that it can guarantee bandwidth after contact for more than one TP. Mode 2 nodes are predominantly the only nodes that are allowed to utilize the highest priority in CAC. For example, mode 2 may be the only nodes that are allowed to use HIPERLAN User Priority 1 (In ATM, connectionless services may only use Cell Loss Priority 0). 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 TPs that are reserved by a node in BRP may in principle not be used by other nodes that are within radio coverage. However, the invention may in an alternative embodiment allow exceptions to the above principle as follows: 10 15 20 514 987 8 the reserved blocks in the TP that follow an empty detectable reserved block may be used by other nodes. That is, the blocks following an empty unused block are temporarily lost to the node that originally reserved these blocks. However, use of these blocks should be limited to mod l nodes.

Fig. 19 shows a further variant of the implementation of BRP. A node (mode l or 2) that intends to transmit must listen to the medium for at least a predetermined time TCTP-max, which is the longest time between two TCTPs, before it is entitled to attempt to access the medium. Nodes of mode 2 that have made the BRP reservation only need to transmit PAP, CP and BRP before TP1. This means that TP2,3 can be transmitted without PAP and CP.

Fig. 20 shows another variant of BRP intended to be used together with the BRP shown in Fig. 21.

Fig. 21 shows another variant of BRP intended to solve the problem of electromagnetically hidden nodes.

The invention is not limited to the illustrated embodiments, but can be varied in any manner within the scope of the inventive concept, as defined by the following patent claims.

Claims (9)

10 15 20 25 30 35 40 514 987 ß: PATENTKRAV Procedure for a HIPERLAN system, characterized in that synchronous services are guaranteed maximum access to the used communication medium after connection and that an increase in the transmission capacity takes place by effecting reservation of bandwidth for such packets to be transmitted at regular intervals, said reservation of bandwidth taking place by transmitting a time slot BRP all nodes in the system can detect the information in the BRP field, whereby BRP must always be transmitted at one time (Bandwith Reservation Phase) and that within the time interval Tmax, which time interval Tmax so that other nodes can receive information about HIPERLAN status and what remains of the BRP reservation without having to listen unnecessarily long. Method according to claim 1, characterized in that the BRP time slot is transmitted immediately after the intended node has obtained permission to use the medium. Method according to claim 1, characterized in that the communication system is a decentralized and wireless system for short-range communication. ' Device in a HIPERLAN system, characterized in that the system can carry ATM packets of service class types A and B spectrum efficiently, in that the second mode mod 2 nodes: - are the only nodes that may regularly use the highest priority, ~ reserves bandwidth for packets to be transmitted at regular intervals to ensure the necessary transmission capacity, - to reserve bandwidth by transmitting information in a time slot, BPR (Bandwith Reservation Phase) on how much bandwidth is reserved after the node has access to the medium, whereby the BRP time slot must be transmitted immediately after the node has gained permission to use the medium, whereby in HIPERLAN BRP is transmitted after PAP and CP, all nodes in the system can detect information in the BRP field, whereby BRP must always be transmitted at one time within the time interval Tmax, which time- And aW that 10 15 20 514 987 IO intervals are dimensioned so that nodes in the system can get information about HIPERLAN status and what remains of the BRP reservation without having to listen for an unnecessarily long time. Device according to claim 4, characterized in that ATM service class A corresponds to connection-oriented traffic with a constant bit rate and where there is a synchronization dependence between the endpoints. Device according to claim 5, characterized in that ATM service class B represents connection-oriented traffic with a synchronization dependency and which supports variable bit rate. Device according to one of Claims 4 to 6, characterized in that the communication system is a decentralized and wireless system for short-range communication. Device according to one of Claims 4 to 7, characterized in that nodes which communicate with one another repeat the bandwidth reservations of nodes. Device according to one of Claims 4 to 8, characterized in that ATM packets are packaged in large multiblocks (large TP HIPERLAN) by having access to queue information in ATM buffer.