WO2011086070A1

WO2011086070A1 - Control of mid-call announcements during local call local switch by in-band tones

Info

Publication number: WO2011086070A1
Application number: PCT/EP2011/050287
Authority: WO
Inventors: Jarkko Reijo Tapani Pyykkonen
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-01-12
Filing date: 2011-01-12
Publication date: 2011-07-21

Abstract

The application relates to Local Call Local Switch as defined, by GPP TR 23.889. While a call is established the core network might send announcements or tones on the user plane to UE. Such mid-call announcements and tones need to be delivered also to locally switched calls. The mid-call announcements and tones are currently generated by the core network and need to be delivered to the user via the BSS also for locally switched calls. Five alternative solutions have been identified how to ensure the delivery comprising 1. Signalling to indicate start and stop of mid-call announcement/tone. However, the drawbacks of this solution are that a new signalling message needs to be specified and that there is a timing problem in that the BSS receives the out of band "announcement start/stop" indicator either too late or too early. The application proposes to solve this problem by the use of "start announcement" and "stop announcement" in-band tones

Description

DESCRIPTION

Title

CONTROL OF MID-CALL ANNOUNCEMENTS DURING LOCAL CALL LOCAL SWITCH BY IN-BAND TONES

FIELD OF THE INVENTION The invention generally relates to a method of allowing an announcement message to pass from a first part to a second part of a communications network. More particu^¬ larly, the invention relates to the handling of mid-call tones and announcements in local switched calls (local call local switching (LCLS) ) .

BACKGROUND OF THE INVENTION

The transmission of a Cellular Radio Access network (i.e. in Abis and A interfaces) is an important component for mobile communication networks. In some parts of the world, especially in wide rural areas or far remote areas, operators face the difficulties of developing services and/or deploying networks due to the lack of or cost of fast and reliable backhaul transport resources. However, according to statistical data, many calls in a mobile com^¬ munication network, especially in the above-mentioned ar^¬ eas, are local calls. That is, these calls are generated and terminated by users served by the same base station (BTS) or the same BTS cluster or the same base station controller (BSC) .

Mainly because of these reasons the 3GPP has started (Rel9) a feasibility study (i.e. standardization activi- ties) to analyse how the local calls could be locally switched. The main goal of this study is to define a Local Call Local Switching (LCLS) solution for 2G calls which would enable savings in transmission resources of the Abis and A interfaces. (Potential savings in these interfaces are particularly significant especially in cases where the connection uses Satellite or microwave links) .

Figure 1 schematically shows a reference architecture of LCLS in 2G calls. It highlights only the main nodes and interfaces in the core and radio networks and differenti^¬ ates between "originating" nodes and interfaces (oBTS, oMSS/oMGW, oAbis, oA) and "terminating" nodes and interfaces (tBTS, tMSS/tMGW, tAbis, tA) . It also includes an Intermediate MSS and MGW (iMSS, iMGW) , which may be a (G)MSC or other intermediate core network (CN) control node and its MGW.

The main intention of the LCLS is to loop the user plane in a BTS or BSC between the BTSs in order that user plane data (speech) is not required to be routed to the core network .

When a call is established, the core network may send announcements or tones on the user plane to the mobile subscriber station or user equipment (UE) , for example a warning message about a pre-paid account running low.

Such mid-call announcements and tones need to be delivered also to locally switched calls. The mid-call announce^¬ ments and tones are currently generated by the core net^¬ work and need to be delivered to the user via the base station subsystem (BSS) in the radio access network. Various solutions have been proposed for handling mid- call tone and announcements in LCLS . However, none of the existing LCLS solutions introduced in the 3GPP Technical Report are able to handle mid-call announcements satisfac- torily.

One solution involves Out-of-band (OoB) signalling to indicate the start and stop of the announcement. The MSC Server (MSS) informs the BSS, possible via another MSS, that there will be an announcement arriving and therefore the BSS should let the announcement go through on the specified call leg and mute the unrelated call leg. The MSS controlling the MGW shall inform the BSS that the an- nouncement is over and that the BSS shall resume dropping user plane data coming from the A interface.

A drawback of this solution is that specific OoB interface signalling has to be defined to inform the BSC about the announcement. New BSSAP messages need to be defined and a new ISUP/BICC/SIP-I message also has to be defined to inform the BSS about mid-call announcements and tones. In this solution there exists also a problem with timing, whereby either the BSC receives an OoB "announcement start" indication too late so that part of the announce^¬ ment is lost or the BSC receives the OoB "announcement start" indication too early when some downlink user plane data is delivered to end user.

Furthermore, this solution is especially problematic when Lawful Interception is activated in local switched call. In order to allow support for the Lawful Intercep^¬ tion (LI) feature in the Core Network, user plane data for CS voice calls to be intercepted needs to be conveyed to the Core Network, even if the calls are local. In 3GPP the goal of LI solution has been to maintain the same end user perception in terms of end-to-end speech delay in LCLS calls also when LI is activated. This can be achieved if the user plane data are both locally switched and in addi^¬ tion copied and forwarded to the Core Network as well ( "bi-casting" ) , while user plane data coming from the Core Network via the A-interface in downlink are both dropped at the BSS side. When LI is not activated the "bi-casting" is not done but only some "silence codeword" is sent to the Core Network.

If a mid-call tone or announcement is required to be generated in a call where LI is activated it is possible that end user can detect that the call is intercepted (LI) because of above described timing problem (OoB "announce^¬ ment start" indication received too early) . The timing problem (conversely) is valid also concerning the OoB "an^¬ nouncement stop" indication.

Therefore this solution is complex and not workable in call cases where LI is used. In addition it requires re^¬ configuration of core network components. Another solution is provided by announcement detection in the BSS. The BSS uses voice detection to distinguish announcements and tones on the downlink. The BSC then stops through-connecting the downlink user plane data to the user and resume LCLS user plane data after it has de- tected that the announcement/tone has finished. However, announcements cannot be detected from the downlink user plane traffic, since they are in exactly the same format as the other user plane data; i.e., speech. Special voice detection functionality would be required to detect the announcement from speech in the BSS, which in practice is not possible to implement.

Therefore a need exists in 3GPP LCLS TR for a method which enables a workable solution for the handling of mid- call tones and announcements in local switched calls.

SUMMARY OF THE INVENTION

Accordingly, the invention provides a method of allowing an announcement message to pass from a first part to a second part of a communications network. Generation of a tone is requested in the first part of the network, where the tone indicates a start of the announcement. Genera^¬ tion of the announcement in the first part of the network is then requested. A start of the tone generated by the first part of the network is detected at a node of the second part of the network. Transmission of the announce- ment from the first part of the network to the node through the second part of the network is started when the said tone indicating the start of the announcement (a "start announcement" tone) is detected by the node of the second part of the network.

When it is required to play an announcement, a request for generation of a "start announcement" tone is made be^¬ fore the generation of the announcement is requested. The network node can then detect the "start announcement" tone. In this way, the network node can know exactly when downlink user plane data is allowed to pass through. This means that, when a call is taking place in the second part of the network, for example a LCLS call, a mid-call an^¬ nouncement can be received at the correct time and none of the announcement is lost due to receiving the indication about "start announcement" too early.

Furthermore, this solution requires no specific addi- tional OoB signalling in the first part of the network to inform the second part of the network that an announcement is starting or ending) and is thus a simple and workable solution . Preferably, the method further comprises requesting gen^¬ eration of a tone in the first part of the network indi^¬ cating an end of the announcement and requesting to stop the generation of said announcement in the first part of the network. Transmission of the announcement from the first part of the network to the node through the second part of the network can then be stopped when the said tone indicating an end of the announcement is detected (a "stop announcement" tone) by the node of the second part of the network. In this way, none of user plane data which is not allowed to pass through is sent in the downlink direction because the indication about an end of the announcement is never received too late.

Advantageously, requesting generation of the announce- ment takes place immediately after requesting generation of the tone, which further improves the timing of the an^¬ nouncement start and finish.

In one embodiment of the invention, requesting genera- tion of the announcement automatically generates the tone.

In another embodiment of the invention, the tone is generated as part of the announcement. This means that sepa^¬ rate requests are not required for generating an announce^¬ ment and a tone, which provides a simplified procedure. Only one request for generating an announcement is re^¬ quired. The tone is then generated automatically by the announcement generation request or is generated as part of the announcement itself.

Preferably, the method further comprises terminating a through-connection of user plane data between users when the start of the tone (a "start announcement" tone) is de^¬ tected and resuming the through-connection of user plane data between the users when the tone indicating the end of announcement (a "stop announcement" tone) is detected. For example, if a user is making a call, the user plane data between users will be terminated only for exactly the amount of time that the announcement is taking place.

Upon detection of the tone, transmission of the announcement may be triggered to start from the first part of the network to the node through the second part of the network. When this network node detects the tone, this may automatically trigger the announcement message to be allowed to be transmitted in the downlink from the second part of the network. Further, the method may comprise sending a request to generate a tone in the first part of the network for triggering the announcement to start or finish.

Advantageously, the tone can be suppressed immediately when it is detected and when transmission of the announce^¬ ment from the first part of the network to the node through the second part of the network is started. In this way, none of the announcement message is obscured by the tone. In an exemplary embodiment, the first part of the net^¬ work is a core network and the second part of the network is a radio access network. The node beyond the second part of the network is mobile subscriber station or user equip- ment (UE) .

In this case, the MSS requests the MGW to generate the tone and the announcement. The step of requesting can then take place over a H.248 interface. The invention also provides a communications network.

The communications network includes a first part and a second part. The first part includes a server node and a gateway node. The server node is adapted to request the gateway node to generate an announcement and a tone indi- eating a start and stop of the announcement. The second part includes a network node, with the network node having a detector adapted to detect the tone. The network node also includes a receiver for receiving the announcement from the first part of the network when the start of the generation of the tone is detected at the detector. In ad^¬ dition, the network node includes a sender for sending the received announcement in downlink direction to the node (e.g. mobile subscriber station) when it is allowed. Since the second part of the network can detect a tone indicat- ing that an announcement is about to start or stop, this provides the advantage that no specific signalling is re^¬ quired by the first part of the network to inform the sec^¬ ond part of the network about the announcement. In addi^¬ tion, no timing problem in the start / stop announcement indication exists with the communications system according to the invention. The invention will now be described, by way of example only, with reference to specific embodiments, and to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a simplified schematic diagram of a conven^¬ tional wireless communications network using LCLS; and

Figure 2 is a simplified schematic diagram of a communi^¬ cations network according to an embodiment of the inven^¬ tion .

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Figure 1 schematically shows a wireless communications network according to an embodiment of the invention. The network has two parts: a core network CN and a radio ac^¬ cess network RAN. Only the network nodes relevant to the invention are shown here for simplicity.

The core network CN includes server nodes MSS1, MSS2 and gateway nodes MGW1, MGW2 in communication with the respective server nodes MSS1, MSS2 over an interface H.248. The server nodes MSS1, MSS2 are in communication over an ISUP, BICC or SIP-I interface. The server node MSS1, MSS2 is in communication with the radio network RAN over a BSSAP interface. Specifically, the server node MSS1, MSS2 and the gateway node MGW1, MGW2 communicate with the radio network RAN via a base station controller BSC in the radio network RAN. The radio network RAN also includes two base sta- tions BTSl and BTS2 controlled by the base station con^¬ troller BSC so that the base stations BTSl and BTS2 and base station controller BSC form a base station subsystem. Two users A-subscriber and B-subscriber can access the network via the base stations BTSl and BTS2, respectively.

The base station controller BSC includes a receiver R for receiving downlink user plane data from the core network CN and a tone detector D for detecting tones gener- ated in the core network CN that are received at the re^¬ ceiver R with the downlink user plane data.

During a call between the users A-subscriber and B- subscriber when the call is being locally switched (in a local call local switching (LCLS) situation) , the estab^¬ lished user plane A is looped in the base station subsys^¬ tem BSS between the base stations BTSl and BTS2 in a loop LL . In this case, the core network CN is aware that the call is being locally switched.

If it is required by the core network CN to make an an^¬ nouncement to either of the users A-subscriber or B- subscriber during a locally switched call, the server MSS sends a request to the gateway node MGW1, MGW2 via the in- terface H.248, which requests the gateway node MGW1, MGW2 to generate a tone indicating a start of the announcement: a "start announcement" tone. The server MSS1, MSS2 then sends a request to the respective gateway node MGW1, MGW2 to generate the actual announcement immediately after the "start announcement" tone generation request.

The receiver R in the base station controller BSC receives the "start announcement" tone followed by the an nouncement itself in the downlink user plane data from core network CN. The detector D in the base station controller BSC detects the "start announcement" tone indicat^¬ ing the start of the announcement and, when the "start an^¬ nouncement" tone has been detected, the base station con^¬ troller BSC allows the announcement to be passed through to the end user (A-subscriber or B-subscriber depending on the use case) via the respective base station BTS1 or BTS2. At the same time, the local switched (loop LL) user plane is stopped towards a subscriber who receives the an^¬ nouncement .

In other words, detection of the "start announcement" tone at the detector D can be used as a trigger for the base station controller BSC to pass through the announce^¬ ment from the core network CN to end user.

Respectively, when the announcement is finished, the server MSS1, MSS2 requests the respective gateway node MGW1, MGW2 via the interface H.248 to generate a tone in^¬ dicating an end of the announcement: "a stop announcement" tone. The "stop announcement" tone is detected by the de^¬ tector D in the downlink user plane data received at the receiver R. When the detector D detects the "stop announcement" tone, through connection of the announcement from the core network CN to the end user A-subscriber or B-subscriber is stopped. In other words, the "stop an^¬ nouncement" tone is used as a trigger by the base station controller BSC or base station subsystem BSS to stop through-connection of the announcement from the core net^¬ work CN in the downlink user plane to the user A- subscriber or B-subscriber, re-establish the loop LL and resume the LCLS call between the users A-subscriber and B- subscriber . These requests for generating the "start announcement" and "stop announcement" tones are sent from the server MSS1, MSS2 to the respective gateway node MGWl, MGW2 over the interface H.248, which contains a tone generator pack- age ({tonegen (0x0003)}; play tone signal {pt (0x0001) } ; and specific tone ids for "start announcement" / "stop an^¬ nouncement" tone ) . In this way the server node MSS uses the tone generator package {tonegen (0x0003)} to request the gateway node MGW to play the "start announcement" and "stop announcement" tones.

In a preferred embodiment, the base station controller BSC suppresses the "start announcement" tone immediately after it has been detected at the detector D. In other words, the "start announcement" tone is not sent to the user A-subscriber or B-subscriber .

In an alternative embodiment, instead of being generated separately from the announcement, the tone may be gener- ated automatically before the actual announcement is gen^¬ erated or generated as part of the announcement. In these cases, the server node MSS1, MSS2 does not have to make separate requests to the gateway node MGWl, MGW2 to gener^¬ ate the start and stop announcement tones followed by the announcement. Rather, the server node MSS1, MSS2 sends a request to the respective gateway node MGWl, MGW2 to gen^¬ erate an announcement including a tone. The tone is then detected at the detector D in the base station controller BSC as described above, which triggers the announcement to be allowed to pass through to the user A-subscriber or B- subscriber .

Although the invention has been described hereinabove th reference to specific embodiments, it is not limited to these embodiments and no doubt further alternatives will occur to the skilled person that lie within the scope of the invention as claimed.

Claims

1. A method of allowing an announcement message to pass from a first part to a second part of a communica- tions network, the method comprising:

requesting generation of a tone in the first part of the network indicating a start of said announcement;

requesting generation of said announcement in the first part of the network;

detecting a start of said tone at a node of the second part of the network; and

starting a transmission of the announcement from the first part of the network to said node through the second part of the network when said tone is detected by the node of the second part of the network.

2. The method according to claim 1, further comprising requesting generation of a tone in the first part of the network indicating an end of said announcement and re^¬ questing to stop the generation of said announcement in the first part of the network; and stopping the transmis^¬ sion of the announcement from the first part of the net^¬ work to said node through the second part of the network when said tone indicating an end of said announcement is detected in the second part of the network.

3. The method according to claim 1 or claim 2, further comprising requesting playing of said announcement immediately after requesting generation of said tone.

4. The method according to claim 1 or claim 2, wherein requesting generation of said announcement automatically generates said tone.

5. The method according to claim 4, wherein said tone is generated as part of said announcement.

6. The method according to any of claims 2 to 5, wherein the method further comprises terminating a

through-connection of user plane data between users when the start of the tone indicating a start of said announce^¬ ment is detected and resuming the through-connection of user plane data between the users when the tone indicating the end of announcement is detected.

7. The method according to any of claims 1 to 6, wherein upon detection of the transmission of the announcement is triggered to start from the first part of the network to said node in the second part of the net^¬ work .

8. The method according to any of claims 1 to 7, fur^¬ ther comprising suppressing the tone when transmission of the announcement from the first part of the network to said node is started.

9. The method according to any of claims 1 to 8, fur^¬ ther comprising sending a request to generate a tone in the first part of the network for triggering the announce^¬ ment to start or finish.

10. The method according to any of claims 1 to 6,

wherein the first part of the network is a core network and the second part of the network is a radio access network .

11. The method according to claim 10, wherein the MSS requests the MGW to generate said tone and said an^¬ nouncement .

12. The method according to claim 11, wherein the step of requesting takes place over a H.248 interface.

13. A communications network comprising a first part and a second part, the first part including a server node and a gateway node,

the server node being adapted to request the gateway node to generate an announcement and a tone indicating a start and stop of said announcement in the gateway node; and the second part having a network node including a detector adapted to detect said tone; and

a receiver for receiving the announcement from the first part of the network when the start of the generation of said tone is detected at the detector.