WO2008115108A1

WO2008115108A1 - A method and a device for improved state switching

Info

Publication number: WO2008115108A1
Application number: PCT/SE2007/050176
Authority: WO
Inventors: Martin Skarve
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-03-20
Filing date: 2007-03-20
Publication date: 2008-09-25
Also published as: WO2008115108A9

Abstract

The invention discloses a method (400) for use in a wireless access network (100) with a number of cells (110), each cell being able to accommodate a number of user terminals (114), UE, the traffic to and from the UEs in a cell 5 being controlled by a node (112) in the system. Data packets can be exchanged between the UEs in a cell and the controlling node of the cell. The UEs can assume different states (210, 220, 230, 240) which have different capabilities such as data transfer speed, and according to the method of the invention, data packets which are sent to or from a UE (114) are analyzed 0 (410) in order to see if the UE should be transferred from one state to another, and in the UE may be instructed to change state as a result of the analysis.

Description

TITLE

A method and a device for improved state switching.

TECHNICAL FIELD The present invention discloses a method and a device for improved state switching in a User Equipment in a wireless access system.

BACKGROUND

In wireless access systems such as, for example, the 3G system, a user can utilize different kinds of equipments, such as, for example, telephones, portable computers etc, in order to communicate via the system. The user equipment, from now on referred to as UE, can assume a number of different states, which have inter alia, different data transfer rates. The different states also have different transfer times, i.e. the time necessary in order to switch from that state to one of the other states.

The time it takes for a UE to switch between different states may have a high impact on the system on the system performance with regard to that UE.

SUMMARY

As explained above, an improved and more rapid way of letting a UE in a wireless access system switch between different states could have a significantly positive impact on the application performance.

Accordingly, this is one problem that is addressed by the present invention in that it discloses a method for use in a wireless access network in which there is a number of cells, and in which each cell is able to accommodate a number of user terminals.

In the network for which the invention is intended, the traffic to and from the user terminals in a cell is controlled by a node in the system, and data packets can be exchanged between the user terminals in a cell and the controlling node of the cell. The controlling node sends data packets from the user terminals further into the system, and data packets which are received from the system are sent to the user terminals by the controlling node.

The terminals are able to assume a number of different states which have different capabilities such as data transfer speed, and according to the method of the invention, data packets which are sent to or from a user terminal are analyzed in order to see if the terminal should be transferred from one state to another. As a result of the analysis, the UE may be instructed to change state.

Thus, by means of the invention, it is made possible to initiate a change of state in a user terminal at a more optimal point in time than previously, which will improve system performance.

The invention also discloses a node with functions corresponding to those of the method of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail in the following, with the aid of the appended drawings, in which

Fig 1 shows a schematic view of a system in which the invention may be applied, and Fig 2 shows different states for a UE, and

Fig 3 shows a block diagram of a node of the invention, and Fig 4 shows a flow chart of a method of the invention.

DETAILED DESCRIPTION Fig 1 shows a schematic view of a wireless access system 100 in which the invention may be applied. It can be pointed out that the invention may be applied in a variety of different systems, as will be realized by those skilled in the art upon reading this description. Thus, although the system and the invention may be described with terminology from one particular wireless access system, it should be pointed out that this is merely to facilitate the reader's understanding of the invention, and is not intended to restrict the scope of protection sought for the present invention.

For example, the term "Radio Base Station" will be used as the term for a node in the network which controls traffic to and from users in a cell of the system. However, in other systems in which the invention may be applied, a similar function is performed by nodes referred to as, for example, Radio Transceiver Station, Node B, or eNodeB. It should thus be understood that terms used in the following in order to describe the system 100 and the invention as such are used as generic terms for a particular function.

Returning now to the system 100 of fig 1 , the system 100 is a wireless access network in which there is a number of cells, one of which is shown as 110. Each cell 110 is able to accommodate a number of user terminals, UE, one of which is shown as 114 in fig 1.

The traffic to and from the UEs 114 in a cell 110 are controlled by a node 112 in the system, such as an RBS, and data packets can be exchanged between the UEs 114 in a cell and the RBS 112 of the cell. The UEs 114 in a cell 110 are able to assume a number of different states which, inter alia, have different capabilities such as, for example, data transfer speeds.

Fig 2 shows some of the states which a UE in the system 100 can assume. It should again be pointed out that the states which are shown in fig 2 are taken from one particular system, in this case the UTRAN system, and are merely intended to exemplify the invention, the invention can also be applied to UEs which can assume other states than those shown in fig 2. A state change in a UE is usually caused by an instruction from the system 100, usually as a result of a time limit having been reached, or as a result of the analysis of the traffic throughput or data buffer size.

The states which are shown in fig 2 are:

210: IDLE, no data transfer, switch time to CELL_DCH = 2 sec,

220:URA_PCH, no data transfer, switch time = 0.4s,

230: CELL_FACH, low transfer rate, switch time = 0.4s,

240: CELL_DCH, high transfer rate.

A problem which the present invention is intended to address is the point in time when a UE switches state, the invention being intended to make it possible to initiate such a change at more optimal point in time than previously possible.

The problem can be exemplified using the CELL_FACH state: CELL_FACH is a common state as it may be used as both a "go through" state from URA_PCH to CELL_DCH and a possible state in itself. The time it takes for a UE to switch from CELL_FACH to DCH will therefore have a large impact on the total application performance, for example for web browsing, as there could be a certain inactivity time between each page download.

If, for example, the time needed for channel switching from CELL_FACH to CELL_DCH could be reduced, it would be possible to have a more aggressive (i.e. shorter) DCH inactivity timer, which would increase the capacity of RAN, Radio Access Network,, based on codes, power, channel elements, etc. Briefly, one way of achieving a more rapid state switching according to the invention is to analyze data packets which are sent to or from a UE in order to see if the UE should be transferred from one state to another, and if so, the UE may be instructed to change state as a result of the analysis.

The analysis as such will be described first, following which there will be a discussion of where in the system the analysis may be carried out.

Thus, a basic concept of the invention is to use the information available (for example IP and TCP flags) in the user data packet sent to and/or from a UE, and to use that information to decide if more data is expected within a certain time frame. If that is the case, cell state switching, for example CELL_FACH to CELLJDCH state switching is initiated at point in time which is more optimal than today, making it possible to improve/reduce the end-user effecting state switching time, which in turn will improve end user performance.

It should be noted that the time to carry out a state switch is not affected; instead the switch is carried out at a more optimal point in time than at present. This also introduces the possibility for system operators to reduce the inactivity timers, thereby saving capacity with less impact on end user performance than previously.

By means of analyzing the traffic sent to or from a UE, it is possible to predict with a rather good reliability if an increase or decrease in traffic to or from the UE can be expected, as a result of which a switch in UE.

As an example, information in the IP and TCP packets can be used to the desired effect: In an IP packet, one byte is used as a flag to define if the packet is a TCP packet, and in a TCP packet one part of a byte is used to define if the so called SYN flag is set. Either, or suitably both, of these flags may be used as an indication that an increase in traffic may be expected, as a result of which the UE should be switched to a more active state, suitably CELLJDCH.

Thus, depending on the embodiment, if one or both of the flags are "set", the conclusion is that the UE should be switched to a more active state, such as CELL_DCH.

Other bytes or flags may be used to the same effect, either on their own or in combination. Examples of other such flags are SYN or ACK.which may be used either on their own or in combination.

The invention may also be used "in the other direction", i.e. an analysis of data packets to or from the UE may indicate that the UE should be instructed to assume a state in which less data is transferred, for example the IDLE state. An example of one such flag in an IP packet is the FIN flag, and another example is the RST flag.

Turning now to where in the system that the function of the invention may be implemented, a number of possibilities may be envisioned: • The invention may be implemented by a function in the RNC₁ Radio

Network Controller. Thus, such a function in the RNC will suitably check the present state of the UE from or to which traffic is sent/received, and will also check the proper flags/bytes in the traffic to see if the state of the UE is the proper one, or if it needs to be changed. If a change of state is needed, the RNC will send a corresponding message to the UE.

• The invention may also be implemented in the RBS of the system. A function in the RBS will function in the same way as the function in the

RNC as described above. If the RBS does not have access to information about the present state of the UE, it may retrieve that information either from the UE or the RNC. • The invention may also be implemented by a function in the UE as such.

Fig 3 shows functionalities which will be used in all three of the examples above, i.e. RNC, RBS, UE. Fig 3 thus shows a "generic node" 300, which may be any of the three examples given above.

The node 300 comprises means 310 for sending messages, and means 320 for receiving messages. Suitably, these means are the normal send/receive functions of the RNC/RBS/UE.

Additionally, the node 300 comprises means 330 for retrieving information about the present state of the UE from or to which traffic is received/sent. In the case of the RNC and UE, this information is available naturally, while it, in the case of an RBS as the node 300, may need to be retrieved using the send/receive functions. The retrieval means 330 may in the case of the RNC or the UE be a memory which is accessible by a microcomputer.

Also, the node 300 needs to have means 340 for comparing the present state of the UE with the state which it desirable to have the UE in, using the information available in the traffic to/from the UE. These comparing means are suitably a computing means of some kind, such as a microprocessor.

The microprocessor preferably also serves as decision means 350, for deciding if the state of the UE should be changed. If a change is decided upon, a message can be sent to the UE via the transmit means 310.

Finally, fig 4 shows some steps in a method 400 of the invention. Steps which are options or alternatives are shown with dashed lines.

Step 410 shows that data packets which are sent to or from a UE are analyzed in order to see if the UE should be transferred from one state to another, and step 420 shows that the UE may be instructed to change state as a result of the analysis.

Step 430 shows that the analysis may be carried out on at least a first flag in an analyzed data packet, or, as shown in step 440, the analysis can be carried out on at least a first and a second flag in an analyzed data packet, as a result of which a UE is transferred from one state to another if both flags are in the same state.

As indicated in step 450, the data packets can be IP packets, or, as shown in step 460, TCP packets in combination with IP packets.

The invention is not restricted to the examples of embodiments described above and shown in the drawings, but may be freely varied within the scope of the appended claims.

For example, instead of TCP packets, the invention may be applied to UDP packets in combination with IP packets.

Also, an example of a system other than UTRAN to which the invention can be applied is the LTE system, in which case the analysis is carried out by the eNodeB, which also sends the instructions for state switch to the UE. The analysis can also be carried out by a UE in such a system.

If the invention is applied to a 3G system such as UTRAN, the node of the invention may be an RNC, Radio Node Controller, an RBS, Radio Base Station, or in fact also a UE.

Claims

1. A method (400) for use in a wireless access network (100) in which there is a number of cells (110), each cell being able to accommodate a number of user terminals (114), UEs, the traffic to and from the UEs in a cell being controlled by a node (112) in the system, in which network data packets can be exchanged between the UEs in a cell and the controlling node of the cell, the UEs being able to assume a number of different states (210, 220, 230, 240) which have different capabilities such as data transfer speed, the method (400) being characterized in that data packets which are sent to or from a UE (114) are analyzed (410) in order to see if the UE should be transferred from one state to another, and in that (420) the UE may be instructed to change state as a result of the analysis.

2. The method (400, 430) of claim 1 , according to which the analysis is carried out on at least a first flag in an analyzed data packet.

3. The method (400) of claim 2, according to which the analysis (410, 440) is carried out on at least a first and a second flag in an analyzed data packet, and according to which a UE is transferred from one state to another if both flags indicate that a change of state should be made.

4. The method (400, 450) of any of the previous claims, according to which the data packets are IP packets.

5. The method (400, 460) of claim 4, according to which the data packets are TCP or UDP packets in combination with the IP packets.

6. The method (400) of claim 4 or 5, according to which one of the analyzed flags is a flag which defines the data packet as a TCP or UDP packet.

7. The method (400) of any of claims 4-6, according to which one of the analyzed packets is the SYN flag in a TCP packet.

8. The method (400) of claim 1 , according to which the analysis is carried out on at least a first data bit in an analyzed data packet.

9. The method (400) of claim 8, according to which the analysis is carried out on at least a first and a second data bit in an analyzed data packet, and according to which a UE is transferred from one state to another if both bits indicate that a change of state should be made.

10. The method (400) of any of the previous claims, applied to the 3G system, and according to which the analysis is carried out by the RNC, which also sends the instructions for state switch to the UE.

11. The method (400) of any of the previous claims, applied to the 3G system, and according to which the analysis is carried out by the RBS, which also sends the instructions for state switch to the UE.

12. The method (400) of any of the previous claims, applied to the LTE system, and according to which the analysis is carried out by the eNodeB, which also sends the instructions for state switch to the UE.

13. The method (400) of any of claims 1-9, according to which the analysis is carried out by the UE, which also instructs itself regarding the state switch.

14. A node (300) for use in a wireless access network (100) in which there is a number of cells (110), each cell being able to accommodate a number of user terminals (114), UE, the traffic to and from the UEs in a cell being controlled by a node (112) in the system, in which network data packets can be exchanged between the UEs (114) in a cell and the controlling node (112) of the cell, the UEs (114) being able to assume a number of different states

14. A node (300) for use in a wireless access network (100) in which there is a number of cells (110), each cell being able to accommodate a number of user terminals (114), UE, the traffic to and from the UEs in a cell being controlled by a node (112) in the system, in which network data packets can be exchanged between the UEs (114) in a cell and the controlling node (112) of the cell, the UEs (114) being able to assume a number of different states (210, 220, 230, 240) which have different capabilities such as data transfer speed, the node (300) being characterized in that it comprises means (340, 350) for analyzing data packets which are sent to or from a UE in order to see if the UE should be transferred from one state to another, the node also comprising means (310) for instructing the UE to change state as a result of the analysis.

15. The node (300) of claim 14, in which the analysis is carried out on at least a first flag in an analyzed data packet.

16. The node (300) of claim 15, in which the analysis is carried out on at least a first and a second flag in an analyzed data packet, and in which the instructing means (310) cause a UE to be transferred from one state to another if both flags indicate that a change of state should be made..

17. The node (300) of any of claims 14-16, in which the analysis is carried out on at least a first data bit in an analyzed data packet.

18. The node (300) of claim 17, in which the analysis is carried out on at least a first and a second data bit in an analyzed data packet, and which instructs

(320) a UE to transfer from one state to another if both bits indicate that a change of state should be made.

19. The node (300) of any of claims 14-18, said node being an RNC in a 3G system.

20. The node (300) of any of claims 14-18, said node being an RBS in a 3G system.

21. The node (300) of any of claims 14-18, said node being a UE in a 3G system.

22. The node (300) of any of claims 14-18, said node being a UE in the network.