Patent Application
20080317009
The invention relates to arranging voice transmission and particularly to implementing voice transmission in a network part connected to subscriber lines of a public switched telephone network.
During the past few years, IP voice transmission (VoIP; Voice over Internet Protocol) has become increasingly popular along with broadband Internet access, in particular. An IP call refers to voice data transmission over an IP-based network between two or more terminals. An IP call is based on transmission of packets containing voice information over an IP network. An IP network is any fixed or wireless network employing an IP protocol, such as the Internet, intranet or a local area network.
VoIP systems comprise a signalling protocol and a voice transmission protocol. The most common signalling protocols are H.323 defined by the ITU-T and SIP (Session Initiation Protocol) defined by the IETF. The end point of a VoIP protocol layer may be a VoIP gateway or an IP phone, and a gatekeeper in H.323 networks and a proxy in SIP networks may function as the control device.
IP calls are classified according to their source and destination: from a (public switched telephone network) phone to a phone; from a personal computer PC to a PC, i.e. a point-to-point VoIP call; from a PC to a phone; and from a phone to a PC. The phone-to-phone connection functions such that subscriber A makes a call by an ordinary phone to a gateway, from which the call is transmitted to an IP network and then the call is switched from the IP network to the public switched telephone network where subscriber B is. This is used in international calls, for example. The PC-to-PC connection is a totally IP-based connection, and calls are transmitted over an IP network from one computer to another, for example in a dedicated computer network of a company.
To enable simultaneous use of a subscriber line for analog voice transmission and DSL data transmission, the band has to be divided by a splitter 102. In respect of calls terminating to or originating from a phone 100 in a public switched telephone network, the phone 100 is connected through a band division filter 110 of a distribution frame rack 108 located in the cross-connection site to a local phone concentrator 112. The local phone concentrator 112 connects a voice signal to a switching centre of a PSTN network 114 (not shown). From the switching centre, the call may be arranged as a VoIP call instead of an ordinary PSTN network call. In that case, the switching centre is connected to an IP gateway, which connects the PSTN network and the IP network, functions as the edge node of the IP network and performs voice conversion between the PSTN network and the IP network. VoIP call information is transmitted in both directions over the IP network, i.e. from the IP gateway to an IP server or VoIP repeater and vice versa. The VoIP server may further transmit VoIP information in both directions, for example, to another IP gateway or a VoIP terminal, which may also be called an IP phone. The IP gateway functionality is typically implemented in connection with the switching centre of a PSTN network. For example, the TIPHON project (Telecommunications and Internet Protocol Harmonization Over Networks) under the ETSI (European Telecommunications Standards Institute) has defined gateway implementations for use between a PSTN network and an IP network.
EP 1357730 describes an interface device located in the subscriber's premises for transmitting voice and data from a DSL data stream received in an ATM format from a DSL concentrator DSLAM to subscriber interface gates. If the DSL data stream includes voice, the voice data are converted into a digital voice signal and transmitted to a gate defined for an analog voice signal. The interface device functions in a corresponding manner in the case of an uplink voice signal. This arrangement, however, requires installation of a specific device in the subscriber's premises, which causes extra costs to the subscriber.
US 2004/0042510 describes implementation of DSL service in a conversion apparatus, which performs a conversion between the DSL service offered to a subscriber and the DSL service of the data network. The conversion apparatus may also digitize a POTS service into a PCM format, and the digitized information may be multiplexed with DSL data.
A new and improved arrangement has now been devised for voice transmission. The object of the invention is achieved by an arrangement, a method, a network element and a computer program product which are characterized by what is stated in the independent claims. Preferred embodiments of the invention are described in the dependent claims.
The invention is based on a new concentrator network part that supports the transmission of both data and voice information and is capable of transmitting voice information between an analog subscriber line and a network supporting a packet format voice transmission protocol, such as a network supporting the VoIP protocol. Concentrator network part of this kind comprises voice traffic processing means arranged to perform a conversion between analog voice signals of subscriber lines and IP voice packets (VoIP, Voice over IP), transceiver and multiplexing means for transmitting and receiving data transferred over analog subscriber lines, and packet traffic switching means, which are connected to the voice traffic processing means and transceiver and multiplexing means. The packet traffic switching means are arranged to receive and transmit IP packets, and the voice traffic processing means further comprise means for arranging IP call signalling in an IP network. In this context, the concentrator network part generally refers to any device or combination of devices capable of connecting a plurality of subscriber lines to another telecommunications network. The concentrator network part may be applied in a local cross-connection site, for example.
According to an embodiment of the invention, the transceiver and multiplexing means are represented by a DSL multiplexing device.
An advantage of the arrangement according to the invention is that local cross-connection sites or other premises with concentrators no longer require an interface to the operator's switching centre, but also the low-band voice signal of an analog subscriber line can be converted into a packet format already in a local concentrator and transmitted to a packet-switched network as VoIP packets. Furthermore, as the solutions according to the invention become more common, the amount of transmission resources required for circuit-switched calls in a network decreases. These advantages enable offering of ordinary calls at lower prices. From the subscriber's point of view, it is advantageous that the benefits of packet-switched voice transmission are applicable to a larger portion of the transmission path while the subscriber may utilize ordinary calls and needs no computer, application suitable for IP voice transmission, DSL modem, etc. In that case, at least some of the cost savings provided by VoIP transmission are available to users who do not want to acquire these devices. The number of voice service providers and the amount of competition may increase as different service providers may, thanks to lower initial costs, start offering analog voice services. The configuration of VoIP applications, which is often difficult for users, can also be avoided. If the subscriber only needs voice transmission, local DSL modems are no longer necessary. A further advantage compared to earlier VoIP services offered to subscribers is that voice transmission does not decrease the capacity of the DSL band.
Preferred embodiments of the invention will be described in greater detail in the accompanying drawings, in which
a to 4c illustrate frequency components of signals transferred over different interfaces of
For the sake of clarity, the figures illustrate the present embodiments in a simplified manner.
In the following, an embodiment according to the invention will be described with reference to additional functions to be implemented in a DSL concentrator. The invention is not, however, in any way limited to DSL technology but any present and future techniques usable in an analogue subscriber line may be applied. The DSL concentrator DSLAM described in the following can be replaced by a DLC device (Digital Loop Carrier), for example, or by another device connectable to an analog subscriber line. It should also be noted that, in the following, all the functions the DSL concentrator network element comprises are not necessarily performed by one device but they may be decentralized to several devices, even outside the local concentrator.
Any DSL protocol suitable for transmitting data over an analog subscriber line may be employed between the DSL modem 104 and the DSL concentrator 200. Examples include ADSL (asymmetric digital subscriber line), HDSL (high bit rate digital subscriber line), RDSL, SDSL (symmetric digital subscriber line) and VDSL (very high bit rate digital subscriber line). It should be noted that there may also be other elements between the subscriber equipment and the DSL concentrator 200, such as a house cross-connection site. In addition to data transmission, the DSL concentrator 200 according to the present embodiment takes care of voice transmission from a packet-switched network (core network 118 in the example of
The DSL concentrator 200 is connected to the operator's packet-switched core network 118 via interface G, possibly by means of a separate switch. Telecommunications protocols known per se may be applied at interface G. Examples include ATM and an Ethernet/IP-based network, but the invention is not limited to any specific core network 118 type. According to an embodiment, the DSL concentrator 200 is connected over interface G to an edge router of an Internet service provider (ISP), through which traffic is transmitted to the Internet.
The voice traffic processing means 302 are responsible, in particular, for performing a conversion between analog voice signals and voice data in a packet format. The voice traffic processing means 302 thus function as an end point of an analog subscriber connection and, on the other hand, as an end point of a packet-switched voice transmission context or a logical connection towards the core network 118 and another end point. In addition to conversion of voice information, the main tasks of the voice traffic processing means 302 include arranging signalling, such as responding to incoming signalling messages received from interface G. It also transmits the voice information packets it has generated to the packet traffic switching means 306 as well as receives packets therefrom, such as VoIP packets. In respect of a downlink incoming call, the voice traffic processing means 302 also perform signalling required by the analog subscriber line, such as call alert and call waiting signalling.
Referring to
Referring to
At interface I, data traffic is transmitted in a digital format between the packet traffic switching means 306 and the data traffic processing means 304. The packet traffic switching means 306 receive traffic from interface G and terminate the necessary protocol levels (e.g. ATM). They also separate voice traffic packets from the packets to the voice traffic processing means 302 and data traffic packets from interface G to interface I, i.e. to the data traffic processing means 304. In uplink, the packet traffic switching means 306 receive voice packets from interface H and data packets from interface I, add the necessary header fields and transmit the packets further to interface G. The packet traffic switching means 306 also take care of traffic multiplexing. The division of information in the speech traffic processing means 302 and in the data traffic processing part 304 may be arranged in various ways.
According to an embodiment, the means 302 and 304 have different IP addresses, in which case the packet traffic switching means 306 transmit the packets to the correct part on the basis of the IP destination addresses of the received packets. The packet traffic switching means 306 may also comprise a routing table which associates IP destination addresses with identifiers of means 302, 304 or other kind of association information for transmitting data and voice packets to the correct means on the basis of the IP destination address of the received IP packet. In the uplink, data and voice packets (possibly received from the same subscriber) have different IP source addresses, which the means 302 and 304 add to the packets. It should be noted that in an embodiment, these addresses are subscriber-specific, i.e. when voice transmission to a subscriber is being arranged, the (subscriber-specific) IP source address of an IP call is associated with the voice traffic processing means 302. The device 302 may include a domain of IP addresses, from which an IP address is allocated dynamically to the subscriber's connection for an IP connection terminating to the data traffic processing means 304 or voice traffic processing means 302.
According to another embodiment, TCP gate numbers (Transmission Control Protocol) are employed, in which case the packet traffic switching means analyze the gate numbers of TCP header fields and transmit the packet to the means 302, 304 associated with the gate number defined in the header field. According to another embodiment, UDP (User Datagram Protocol) gate identifiers are used. A combination of a TCP (or UDP) identifier and an IP address is also feasible.
According to a further embodiment, packets are transmitted to the correct means 302, 304 in the packet traffic switching means 306 utilizing a VPI/VCI (Virtual Path Identifier/Virtual Channel Identifier) identifier pair when the traffic of interface G is ATM-based. At least some of the functions of the device 200 described above can be executed in the processor of the device 200, which executes a computer program code to implement these functions. On the other hand, some of the functions may be implemented by hardware, and also a combination of hardware and software solutions can be used to implement the inventive features. Functions that require a lot of processing capacity, in particular, can be implemented by hardware. According to an embodiment, the voice traffic processing means 302, packet traffic switching means 306 and data traffic processing means 304 are controlled by executing a computer program. It should be noted that the means 302, 304 and 306 are not necessarily physically and/or functionally separate, but at least some of the functions of the blocks can be implemented in a single process. Thus, the term “means” should be understood broadly to refer to any means for implementing the defined functions. For example, the computer program code portion that controls switching of packets to the voice processing means and data processing means may form packet traffic switching means. It should also be noted that the device 200 may comprise several other functions, such as other interfaces, whose description is not necessary for understanding the invention. According to an embodiment, the device 200 supports transmission or updating of a computer program code over a data transmission network 118.
Block 508 represents an entity that controls all the functions of the voice traffic processing means 302. One of its tasks may be to control block 510 to start IP set-up in response to call set-up information received from block 502. Block 510 represents means that take care of signalling related to IP-based voice transmission and block 506 represents a block that terminates the IP connection. In other words, block 506 is responsible for establishing and unpacking IP packets, i.e. for functions of the IP protocol layer, and, according to an embodiment, also for functions of the TCP and UDP protocol layers, which are well known per se.
In the following, call set-up and termination are illustrated with reference to the example of
One supplementary feature the DSL concentrator 200 may be provided with is remote management, where the owner of the DSL concentrator 200 or service provider may manage the functions of the voice traffic processing means 302 and/or other functions of the DSL concentrator 200, for example configure IP addresses, over the IP connection using a specific configuration application. Block 512 illustrates a remote management part which may be used in controlling the IP termination block 506, signalling termination block 510 and call monitoring and controlling block 508. It should be noted that all the elements shown in
According to an embodiment, the voice traffic processing means 302 comprise a VoIP client application. This VoIP application may be, for example, a client application in accordance with the H.323 protocol, an SIP user agent or an application in accordance with the MGCP protocol. Some further VoIP signalling protocols applicable in the present concentrator 200 include SCCP (Skinny Client Protocol), MINET and IAX (Inter-Asterisk Exchange). A further example of VoIP technology is Skype, which is based on peer-to-peer networks.
For example, in an embodiment utilizing the SIP protocol, SIP user agent software may take care of the functions of blocks 504, 508 and 510 and the IP termination 506 may be performed by the IP protocol entity. In respect of a more detailed description of the SIP protocol, reference is made to IETF specification RFC 2543, “SIP: Session Initiation Protocol”, M. Handley et al, March 1999.
In the embodiment applying the H.323 protocol, VoIP functions are taken care of by H.323 client end point functionality in the DSL concentrator 200. The details of this functionality are known from H.323 specifications of the ITU and prior art H.323 client end point solutions. In that case, management and signalling may be implemented in blocks 508 and 510 utilizing the H.245 protocol, Q.931 protocol and/or the RAS protocol (Registration Admission and Status).
The VoIP system also comprises other elements. In the H.323 system, for example, these include a gateway, a gatekeeper providing call management services or an MCU unit (Multipoint Control Unit) for controlling conference calls, but there is no need to describe these elements more closely here.
It should be noted that the features described above represent only some embodiments of the invention. Referring to
Data transmission is illustrated by a dotted line 800. Data are transmitted in an ATM format to the multiplexing device 200, which forwards the data to an ADSL layer in the example of
Voice transmission (and signalling related to voice transmission) is illustrated by a dot-and-dash line 802. Downlink ATM header fields are removed from the data packets, i.e. the ATM protocol is terminated, in the multiplexing device 200. In the example of
As appears from the example of
According to an embodiment, the system may prioritize calls. A prioritized call can be transmitted along a guaranteed band, which is free from interference by other traffic. In the direction of the packet-switched network 118, it is possible to utilize quality of service reservation and checking functions which are known per se and have been applied in connection with the SIP protocol, for example. On detecting that a call initiated by a subscriber is a call to be prioritized, the voice traffic processing means 302 are arranged to reserve the resources required by a high priority call for the voice packets to be transmitted. It should be noted that the quality of service reservation and checking functions may be performed on all calls. An example of quality of service reservation protocols is an RSVP (Resource Reservation Protocol) defined in RFC specification 2205 by the IETF, but the application of the present embodiment is not limited to any specific protocol.
A call directed to an emergency call number may be defined in the voice traffic processing means 302 as a call to be prioritized over data traffic and possibly over other calls. The emergency call number may be connected directly to the nearest local emergency call centre, to which a packet-switched prioritized connection can be established from the DSL concentrator 200.
According to an embodiment, the voice traffic processing means 302 are arranged to route calls, at least calls directed to the emergency call number, directly to the PSTN network. This embodiment may be applied when the DSL concentrator 200 and the voice traffic processing means 302, in particular, are connected directly or indirectly to the PSTN network 114 or to its phone concentrator 112. Routing of emergency calls from the local concentrator 200 is one advantage over VoIP calls originating from the subscriber, which may be difficult to route to the caller's nearest emergency call centre. It is obvious to a person skilled in the art that as technology advances, the inventive concept may be implemented in various ways. The invention and its embodiments are thus not restricted to the examples described above but they may vary within the scope of the claims. In some cases, the features described in this application may be used as such, regardless of the other features. On the other hand, if necessary, the features presented in this application may be combined to obtain various combinations. The drawings and the related description are only intended to illustrate the inventive concept.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20055379 | Jul 2005 | FI | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FI2006/050303 | 6/30/2006 | WO | 00 | 6/12/2008 |
