WO2000054463A1

WO2000054463A1 - Method for bandwidth adapted utilization

Info

Publication number: WO2000054463A1
Application number: PCT/SE2000/000247
Authority: WO
Inventors: Rolf Anders BERGSTRÖM; Kenth Vilhelm Andersson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1999-03-05
Filing date: 2000-02-08
Publication date: 2000-09-14
Also published as: SE521606C2; SE9900798D0; SE9900798L; AU3848600A

Abstract

The present invention relates to methods for bandwidth adapted utilisation of a bandwidth restricted communication link between a first and a second node (11, 12) in a communication system, wherein a communication link (CL) has a total bandwidth Btot which cannot be exceeded. The invented method comprises inserting a determined bandwidth indicator for a specific sublink (SLk). All sublinks which are connected to the communication link (CL) have their specific bandwidth indicator. The sublinks are combined (41) within said total bandwidth Btot into a data stream, and the data stream including the sublink bandwidth indicator (BIk) in a certain fixed position in each sublink is transmitted (42) over said communication link (CL) to the second node (12). The bandwidth indicators (BIk) are received (43) and read (44) at said second node and the data stream is split (45) into the different sublinks according to the respective sublink data and the bandwidth indicator (BIk). The invention is also a circuit switched, frame based communication system (10) for bandwidth adapted utilisation of a bandwidth restricted communication link (CL) between a first and a second node (11, 12) in the system in accordance with the methods.

Description

METHOD FOR BANDWIDTH ADAPTED UTILIZATION.

Field of the Invention

The present invention relates to methods and means for bandwidth reduction in a communication system. More in detail, the invention refers to methods for bandwidth adaption of the information transmitted over a bandwidth restricted communication link between a first and a second node in a communication system.

State of the Art

Communication systems usually include at least two nodes and a communication link between them. In this specification a location in a network is denoted a node. A node can have a complete specified system that is communicating with a different system located in another node of the network system. It is also possible that a system is divided into subsystems and one node only has a subsystem. Each node is connected to at least one other node of the network and each connection is a communication link. Thus a unit in one node can be connected by a communication link to a unit in another node .

The capacity or bandwidth of a communication link is restricted. This means that the amount of bits per time unit, which can be transmitted over that link, is limited in order to avoid deterioration of the information transmitted by the bits.

In prior art systems a communication link carries a number of sublinks. Every sublink has a predetermined bandwidth and each sublink carries data related to a number of users. A group of users shares a sublink and their data is put together by a sublink generator. A number of sublink generators are connected to one of said two nodes. A first node includes a multiplexing unit that multiplexes the data of the sublinks according to a multiplexing algorithm to be sequentially transmitted to the second node over a communication link to which the sublinks are connected. Each sublink is addressed to one of a group of sublink receivers connected to say second node. This node includes a demultiplexing unit that receives the data flow of sublinks, splits them and distributes each sublink to the correct sublink receiver in the order they were multiplexed. A protocol for the transmission of data over the communication link has therefore to be designed for this distribution.

However, different users and user groups have different need of data transmission capacity. Users can choose among different data services. A data service often generates data with a specified data rate. Different data rates are used by different services. The ratio between two data rates may be two or three times or even more. In some user groups the amount of high data rate services is high and in some user groups there are no such users . Some user groups would therefore need sublinks having high capacity and some user groups need only low capacity sublinks. However, as stated above, the protocol is only designed for one condition: the same bandwidth for all sublinks and user groups. This condition results in two main alternatives, either low data rate implying a risk for congestion or a high data rate for all sublinks which implies high costs.

Thus, there is a problem in a communication system where the sublinks are dimensioned for the highest data rate services. Sublinks carrying data generated by user groups having low data rate services only will therefore also carry a lot of dummy information to fill out the unused space. In a commercial network, customers rent communication links on a transmission link and a customer has to pay for unused transmission capacity. The alternative with low capacity sublinks has the effect that user groups can be locked out.

It is previously known, see W096/21999, in a mobile radio system which transfer messages in a single interface, to provide a discrimination parameter which can be used to discriminate between the frames belonging to different radio interfaces and signalling protocols, however, not for discriminating between different bandwidth demands.

Summary of the Invention

The present invention is concerned of solving the above- described cost and capacity problems.

An object of the invention is to provide flexible and easy methods to adapt the bandwidth of a user group to the needed bandwidth if the individual users in said user group needs more or less sublink bandwidth over a longer time period.

The above-mentioned problems are solved by supplying each of the sublinks with a bandwidth indicator and the communication system is applied with means for utilising the information of the respective bandwidth indicator.

According to one aspect, the invention is a method for bandwidth adapted utilisation of a bandwidth restricted communication link between a first and a second node in a communication system. Said system comprises means for transmitting and receiving digital information on sublinks wherein said communication link has a total bandwidth B_toc which cannot be exceeded. The invented method comprises one step for allocating and combining said sublinks within said total bandwidth B_tot into a data stream, a following step for transmitting said data stream including a sublink bandwidth indicator in a certain fixed position in each sublink over said communication link to said second node and a step for reading said sublink bandwidth indicators at said second node and splitting said data stream into the different sublinks according to said indicators.

According to another aspect, the invention is a circuit switched, frame based communication system which includes means for bandwidth adapted utilisation of a bandwidth restricted communication link between a first and a second node in the system. The communication system comprises means for allocating and combining sublinks within said total bandwidth B_tot into a data stream, means for transmitting said data stream including a sublink bandwidth indicator in a certain fixed position in each sublink frame over said communication link to said second node and at this node means for reading said sublink bandwidth indicators and splitting said data stream into the different sublinks according to said indicators.

Advantages afforded with this invention are that the above- described capacity problem can be solved. The sublink bandwidth is adaptable to the need of the user group it belongs to. Furthermore, one advantage afforded is that the invention provides a flexible and easy method to adapt the needed bandwidth of a user group if said user group needs more or less sublink bandwidth over a longer time period.

Another advantage is that the invention provides a more cost and transmission effective communication system.

Brief Description of the Drawings

For a more complete understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings wherein: Figure 1 is a block diagram of two nodes and connected terminals in a communication system that illustrates the invented method;

Figure 2 illustrates a flow chart of one embodiment of the invented method;

Figure 3 illustrates two different frame structures for transmission in the system according to Fig 1 and in which the inventive method is used.

Figure 4 is a diagram which illustrates the bandwidth demand of three different sublinks in the system according to Fig 1 and in which the inventive method is used.

Description of Preferred Embodiments

The invention will now be described in more detail referring to both Figure 1 and Figure 2.

This invention relates to a method and apparatus for traffic adapted utilisation of a bandwidth restricted communication link between a first and a second node in a communication system which comprises means for transmitting and receiving digital information on sublinks, wherein said communication link has the total bandwidth B_tot . Each sublink carries data associated to a number of users .

Figure 1 is a block diagram of a communication system 10 showing two nodes - a first node 11 and a second node 12 - and a communication link CL between them. The first node 11 is regarded as a master node comprising a control unit 13 for controlling the means and functions of the node 11. Besides said control unit 13 , the first node 11 comprises input ports 16 to a corresponding number of sublinks, a source communication unit 14, supervising means 21, packing means 23, transmitting means 24 and an allocating means 22. To node 11 a number of generator units 15 and to the node 12 a number of destination units 31 are connected. One generator unit 15 communicates data information on a frame basis over the communication link CL to a destination unit 31. The nodes and the units are separated by the dotted lines 18 and 32 and by the communication link CL .

The first node 11, also called the master node, has at least two but usually several input ports 16. Each input port 16 is connected to one sublink generator 15. Each sublink generator 15 generates digital information and transmits the information on a sublink according to a sublink protocol.

The first node 11 includes a source communication unit 14 having means for transmitting and receiving digital signals over an interface, indicated by the dotted line 18 between the sublink generators 15 and the first node 11. Said means is chosen depending on different parameters like medium (e.g. air, wire etc.), coding, modulation etc. The source communication unit 14 makes it possible to receive sublinks defined by different protocols.

According to the present invention, a bandwidth indicator BI1,BI2, ..., Blk is allocated to the respective sublink in order to indicate the required bandwidth for the digital information transferred over that sublink. The BI : s can be allocated by the allocating means 22. In the present embodiment according to Fig 1, however, the BI : s are incorporated in the frame structure for the respective sublink already from the start of the communication and in the respective sublink generator 15 as will be described more in detail according to fig 3. Several such sublink generators 15 of the system 10 generate digital information transmitted on several sublinks SL which are transmitted to the different input ports 16 of the first node 11. The inserted bandwidth indicator Blk for a certain sublink thus gives information about the required bandwidth for receiving in the receiving node 12. This required bandwidth is then less than if the bandwidth indicator had not been used, whereby a bandwidth reduction on the communication link CL can be obtained.

From the source communication unit 14, the sublinks are forwarded to means 21 for supervising the bandwidth of each sublink. Said supervising means 21 reads the bandwidth indicator of every sublink. Preferably, all forwarded sublinks must include a correct bandwidth indicator.

The different input ports 16 are connected to the source communication unit 14. Data information of a sublink SLk is forwarded from the source communication unit 14 to the supervising means 21 and the subsequent packing means 23. Said means 23 is a means for packing the data of the sublinks into a continuous data stream. The means 21 for supervising and the means 24 for packing is connected to and controlled by the allocating means 22. The packing means multiplexes the sublinks into the data stream, which is forwarded by the transmitting means 24 over the communication link CL to the second node 12.

Means for inserting the appropriate bandwidth indicator Blk into the respective sublink SLk can be provided for by a protocol converter 19 which is connected to the supervising means 21. The protocol converter 19 has a memory unit 20, where protocol data about the different input ports 16 are stored. The protocol data indicates if an input port 16 receives a sublink carrying an indicator or an indicatorless sublink. The protocol converter 19 is inserting automatically the bandwidth indicator bits into an indicatorless sublink, e.g. in the header of the sublink. If the bandwidth of a sublink is changed, the value of the indicator is changed by means of the protocol converter 19. The protocol converter 19 compares the stored indicator value of a sublink with the corresponding received indicator value. When the stored indicator value differs from the received value the protocol converter will amend the incorrect value to the stored value. The protocol converter 19 provides the system 10 with the feature to change bandwidth indicator without changing the protocol. The protocol converter 19 and the associated memory 20 can, however, be omitted if the appropriate bandwidth indicator is inserted into the data stream already in the sublink generators 15.

The bandwidth information is read by the allocating means 22 in the first node 11 which will use this information for controlling the means for packing each sublink into a serial (or parallel) data stream. The allocating means 22 is programmed to combine the received sublinks into a data stream within a total bandwidth B_to .

The second node 12 of the system 10 is regarded as a slave node, includes a control unit 17 which can receive control data and control signals from the control unit 13 in the first node 11.

The second node 12 also comprises means 25 for receiving the transmitted data stream from the first node 11, means 26 for reading data from the data stream, means 28 for splitting the data stream into different sublinks and means 27 for controlling the splitting means 28. Finally the node 12 also includes means 29 distributing the data information of the respective one of said sublinks to the different output ports 30.

The communication link CL is connected to the receiving means 25, which receives the data stream and forwards the data stream to the reading means 26. This reading means 26 is connected both to the splitting control means 27 and the splitting means 28. The digital information and the bandwidth indicators which were provided in the sublink generator 15 or are inserted into the digital information on the first node 11 by the protocol converter 19, as it has been described above, now appears on the second node 12 as a data stream preferably separated by the bandwidth indicators BI:s .

The bandwidth indicators Blk in the serial data stream are detected and read by the reading means 26 and this information is forwarded to the splitting control means 27. The splitting control means 27 sends control signals to the splitting means 28 which, based on the bandwidth indicator values BI : s read, splits the received data stream from the connected reading means 26 into data information of each of its sublinks according to the value of the respective one of the indicators and distributes them via the following distributing unit 29 to the correct outputs 30. Thus, for a certain bandwidth indicator Blk read by the reading means 26 an information signal is sent to the splitting control means 27 which gives a control signal to the splitting means 28 indicating that the information subsequent to the bandwidth indicator Blk read is to be directed to the correct sublink SLk. The splitting means 28 can be an ordinary switch controllable by the splitting control means 27.

The outputs 30 are connected to the destination units 31. Each of said units 31 includes a sublink receiver (not shown) that reads the bandwidth indicator Blk of the received information over sublink SLk. The indicator is used as information for controlling and adjusting the destination unit 31 to the correct sublink bandwidth given by the bandwidth indicator for that sublink. As mentioned above this bandwidth given by the inserted bandwidth indicator for that sublink gives information about the required bandwidth for correct receiving in destination unit 31.

As an example, the system can use three sublinks SLl,SL2 and SL3 each having a maximum bitrate of 64 kbit/s. In order to transfer the information having these bitrates, respectively a transmission medium would require 3x64 = 192 kbit/s equal to the maximum bitrate of the three transmissions. If for a certain transmission the sublinks SL1-SL3 would require only, for instance, bl = 32; b2 = 32 and b3 =64 kbit/s still a transmission medium of 3x64 kbit is used. By the present method, the bandwidth indicators would indicate that the transmission medium will only call for 32+32+64=128 kbit/s. Since it is seldom that all the sublinks are using the availble transmission medium at maxium and at the same time each with its maximum rate, there would be a waste if the communication link CL was dimensioned for this case.

The data stream is transmitted by the transmitting means 24 over the communication link CL to the receiving means 25 of the second node 12. The receiving means 25 is only an interface unit between the communication link CL and the function modules of the second node 12. The receiving means 25 forwards said data stream to the reading means 26 which is reading the bandwidth indicators of the sublinks. Said information is used by the splitting control means 27 for controlling the splitting means 28 which is splitting said data stream into the different sublinks according to said read indicators . The bandwidth indicator brings information to the split control means 27 where to find the following sublink and the associated indicator Blk. After the splitting of the data stream the sublinks are forwarded to a distributing unit 29 having several output ports 30. Each output port is connected to the destination unit 31. The distributing unit 29 is an interface unit between the output ports and the function modules of the second node 12. Each of said units 31 includes a sublink receiver 32 that detects the bandwidth indicator of the received sublink. The indicator is used as information for controlling and adjusting the destination unit 31 to the correct sublink bandwidth.

Figure 2 is a flow chart illustrating the steps of the invented method in the case the bandwidth indicator is supplied by a sublink generator. The value of the bandwidth indicator Blk is determined based on the demanded bandwidth for a sublink SLk and supplied by e.g. a sublink generator 15 in Figure 1 together with the data to be transmitted over that sublink. In a first step, step 40, the sublink data including the thus predetermined bandwidth indicator Blk are received together with data and bandwidth indicators from other sublinks in the system.

The following step, step 41, is to packing said sublink adjacent to one of the closest preceding or following sublink to build up a continuous data stream within said total bandwidth B_tot.

The last step, step 42, in the first node is to transmitting the sublink via said data stream over said communication link CL to said second node.

The first step of the second node, step 43, is to receiving said data stream over a communication link, e.g. the communication link CL of Figure 1. The following step, step 44, is to reading each sublink bandwidth indicator Blk when they arrive and passing it to the allocating means for controlling the following step, step 45, a splitting of the data stream into the original sublinks . The preceding and last step, step 46, is to distributing each sublink to the correct sublink receiver.

In another case the demanded bandwidth for a sublink is supervised by checking a sublink in the first node the bandwidth indicator value Blk is determined in the first node (in the protocol converter 19), indicating the required bandwidth of that sublink.

Figure 3 illustrates a frame structure for a transmission between the nodes 11,12 in the communication system according to Fig 1. The frame structure includes a number of fields Fl,F2,..., Fn each of which can contain control and data information to be transmitted over the communication link CL for each sublink. Thus, a sublink SLk has its own frame structure dependent on the required bandwidth and indicated by the bandwidth indicator Blk in accordance with the present invention. However, two (or more) sublinks can have the same frame structure if they have the same bandwidth demand .

Field FI usually carries a frame header indicating the start of the frame (not shown) . An unused space in this field can be used for the bandwidth indicator BI for the respective link. In Figure 3, two bandwidth indicators BI1, BI2 , each occupying two bits are indicated. Indicator BI1 belongs to data information transmitted over sublink SLl, while indicator BI2 belongs to data information transmitted over sublink SL2. In this example, sublink SLl requires higher bandwidth than the sublink SL2 and therefore BI1>BI2.

The second field F2 contains frame sync pattern (not shown) for synchronization of the receiver when the frame is to be received, e.g. in a destination unit 31.

The remaining fields F3,...,Fn are used and can contain the data information to be transmitted, spare bits and guard bits. Since these parts of the frame structure has nothing to do with the inventive idea they have not been treated in detail here.

According to the invention, the bandwidth indicator Blk for a the sublink SLk is inserted in the unused space of field FI, marked by the respective bandwidth indicators in Figure 3. As mentioned above the bandwidth indicator value can be inserted already in the transmitting sublink generators 15 on the first node 11 or added by the allocating means 22 on the transmitter side.

The frames of other sublinks SLk have been organized in the same manner either with the same protocol or with different protocols but with a bandwidth indicator Blk. This can be in the beginning of a frame as illustrated in Figure 3 or in the middle of the frame.

Figure 4 illustrates three arbitrary sublink frames FRx, FRx+1, FRx+2 which for each sublink SL1,SL2 and SL3 arrives at the packing means 23 in order to be multiplexed to form a serial bit stream transmitted over the medium CL. Each frame FRx, FRx+1 , FRx+2 transmits data and bandwidth indicator BIl, BI2 and BI3 for the three sublinks SLl, SL2 , SL3. Each frame has a number of bits and all the bits in a frame forms a block as previously shown in Figure 3. It is assumed that SLl needs more bandwidth than the sublink SL2 and the sublink SL3 needs more bandwidth than each of the other sublink SL1,SL2.

The lowest blocks in Figure 4 represent the bandwidth demand of sublink SLl indicated by its bandwidth indicator BIl. The next lowest blocks in Figure 4 represent sublink SL2 which This sublink is transmitted within a certain bandwidth B2 which is less than the bandwidth Bl of sublink SLl. The bandwidth indicators BIl, BI2 and the consecutive frames FRx and FRx+1, FRx+2 are shown.

The highest situated blocks in Figure 4 represent sublink SL3 which is assumed to have the bandwidth demand. This sublink is transmitted within a certain bandwidth B3 which is considerably greater than each of Bl and B2. The bandwidth indicator BI3 and the consecutive frames FRx and FRx+1. FRx+2 are shown.

The hatched area is the spare bandwidth up to the total available bandwidth B_tot for the transmission link CL in Figure 2 and is intended to represent the bandwidth which should have been required without applying the metod according to the present invention.

The invention is not limited to the embodiments shown in Figures 1 and 2. It can also be used when transmitting from the node 12 to node 11, i.e. in the reverse direction in the case the destination units 31 can be sublink generators and the sublink generators 15 are destination units, and also be used for full duplex communication.

Claims

CLAIMS :

1. Method for bandwidth adapted utilization of a bandwidth restricted communication link (CL) between a first and a second node (11,12) in a circuit switched, frame based communication system in which digital information from a number of generator units (15) communicating with the first node (11) via a number of sublinks is transmitted to respective destination terminals (31) communicating with the second node (12) via a corresponding number of sublinks (SLk) , wherein said communication link (CL) has a determined total bandwidth (B_tot) , comprising the following steps:

determining a bandwidth indicator (BI1,BI2, ...) for at least one of said sublinks (SLk) , said indicator indicating the minimum required bandwidth for transmitting said digital information over the respective sublink;

providing (40) said bandwidth indicator (Blk) in a certain generator unit (15) communicating with the first node (11) ,

combining (41) said sublinks (SLk) within said total bandwidth (B_ot) into a data stream;

transmitting (42) said data stream including said bandwidth indicator over said communication link (CL) to said second node.

2. Method according to claim 1, comprising the following further steps:

receiving (43) the transmitted data stream in said second node (12) , reading (44) said bandwidth indicator in a number of sublinks ( SLk, SLk+1 , ...) ,

splitting (45) said sublinks in accordance with the bandwidth indicators read, and

distributing (46) the thus read sublinks individually to the respective destination unit (31) .

3. Method according to claim 1, wherein said bandwidth indicator (Blk) is transmitted in a certain fixed position in each sublink according to a certain protocol associated with that transmission.

4. Method for bandwidth adapted utilization of a bandwidth restricted communication link (CL) between a first node and a second node (11, 12 , resp . ) in a circuit switched, frame based communication system when transmitting and receiving digital information via a number of sublinks (SLk), wherein said communication link (CL) has a determined total bandwidth (B_tot) , comprising the following steps

supervising (21) the demanded bandwidth for every sublink;

inserting (19) a bandwidth indicator (BI1,BI2, ...) into at least one of said sublinks (SLl , SL2 , ...) , said indicator indicating the minimum required bandwidth for the respective sublink (SLk) ;

allocating (22) and combining (23) said sublinks within said total bandwidth (B_tot) into a data stream;

transmitting (24) said data stream including said bandwidth indicator in a certain fixed position in each sublink according to a certain protocol over said communication link (CL) to said second node.

5. Method according to claim 4,

comprising the further following steps:

receiving (25) said data stream at said second node;

reading (26) each of said bandwidth indicators; and

splitting (28) said data stream into the different sublinks according to said indicators (BIl, BI2 , ...) , and

distributing (29) the data information of each sublink to the respective destination unit (31) .

6. A circuit switched, frame based communication system which includes means for bandwidth adapted utilisation of a bandwidth restricted communication link (CL) between a first node and a second node in the system and including a number of generator units (15) communicating with the first node (11) via a number of sublinks, where digital information is transmitted to respective destination terminals (31) communicating with the second node (12) via a corresponding number of sublinks (SLk) , comprising:

means for providing a bandwidth indicator (Blk) in a certain generator unit (15) of the first node (11), said indicator having a value which indicates the minimum required bandwidth (Bk) for transmitting data associated with that generator to a destination unit (31) of the second node (12) over a certain sublink (SLk) ,

means (22,23) for allocating and combining sublinks within said total bandwidth B_tot into a data stream, means (24) for transmitting said data stream including said sublink bandwidth indicator (Blk) in a certain fixed position in each sublink (SLk) over said communication link (CL) to said second node.

7. System according to claim 6, comprising the further

means (25) for receiving the transmitted data stream in said second node (12),

means (26) for reading said bandwidth indicator in a number of sublinks (SLk, SLk+1, ...) ,

means (28) for splitting said sublinks in accordance with the bandwidth indicators read, and

means (29) for distributing the thus read sublinks individually to the respective destination unit (31) .

8. A circuit switched, frame based communication system which includes means for bandwidth adapted utilisation of a bandwidth restricted communication link between a first and a second node in the system and including a number of generator units (15) communicating with the first node (11) via a number of sublinks, where digital information is transmitted to respective destination terminals (31) communicating with the second node (12) via a corresponding number of sublinks (SLk) ,

a certain sublink requiring a certain minimum bandwidth (Bk) , comprising

means (22,23) for allocating and combining sublinks within said total bandwidth B_tot into a data stream, means (24) for transmitting said data stream including a sublink bandwidth indicator (Blk) in a certain fixed position in each sublink over said communication link to said second node, and

means (25,26,28) at this node for reading said sublink bandwidth indicators and splitting said data stream into the different sublinks according to said indicators.

9. System according to claim 8, comprising the following further

means (21) in the first node for supervising the demanded bandwidth (Bk) for every sublink (SLk) , and

means (19,20) associated with said supervising means (21) for inserting said bandwidth indicator (Blk) into the respecitive sublink (SLk) corresponding to said demanded bandwidth (Bk) .

10. System according to claim 8, wherein

said means (19,20) for inserting is a protocol conversion means (19) and memory means (20), said memory means storing a number of possible values of the bandwidth indicators (Blk) .