Patent Application
20070160034
This invention relates to IP telephony.
Notwithstanding the proliferation of IP Telephony, it still requires less effort to effect telephone communication using PSTN or cellular telephones than using IP telephones. IP networks frequently employ Network Address Translation (NAT) to allow a single device, such as a router, to act as an agent between the Internet (or “public network”) and a local (or “private”) network. The NAT may map an unregistered IP address to a registered IP address on a one-to-one basis or from a group of registered IP addresses, or it may map multiple unregistered IP addresses to a single registered IP address by using different ports. This is known also as PAT (Port Address Translation), single address NAT or port-level multiplexed NAT. By such means, only a single, unique IP address is required to represent an entire group of computers.
IP addresses allocated locally in local area networks (LANs) may overlap with registered IP addresses used on another network. To avoid conflict, the router must maintain a lookup table of these addresses so that it can intercept them and replace them with registered unique IP addresses. This must be done both for incoming and outgoing traffic, thus requiring the NAT router to translate the “internal” addresses to registered unique addresses as well as translate the “external” registered addresses to addresses that are unique to the private network.
If the IP telephone is placed behind the NAT or NAPT (Network Address and Port Translation) device, as is typical in concurrent IP networks, calling the IP telephone becomes even more difficult to manage because the calling party does not directly know its own IP address.
It would therefore be desirable to provide a dual-mode telephone that operates as a PSTN or cellular telephone when used to call another PSTN or cellular telephone and operates automatically as an IP telephone when the called party has an IP address.
U.S. Pat. No. 6,876,648 published Apr. 5, 2005 to Unidata Communication Systems et al. discloses an Internet based telephone apparatus for embodying a telephone-to-telephone type of Internet based telephone, the apparatus having a gateway function where communication is possible between a general telephone connected via PSTN with another Internet based telephone connected through Internet network without separate Internet telephone gateway installed between the Internet network and PSTN, and a dual channel communication function where a communication is possible by being connected to a third Internet based telephone when there is a communication connection between a general telephone connected via PSTN and a second Internet based telephone connected through Internet network.
U.S. 2005/053051 published Mar. 10, 2005 in the name of Siemens Communications Inc. discloses a dual mode packet phone comprising a first connector to connect the phone with a data network, and a second connector to connect the phone with a backup network. The phone automatically switches between the data and backup networks in the event that the data network fails to process the call in a timely manner.
WO 99/12365 (Hyllander et al.) published Mar. 11, 1999 discloses a communication system including a cellular radio communication network, such as a Global System for Mobile Communication (GSM) network, that is adapted to enable a GSM subscriber to make an Internet telephone call to an Internet user. In particular, a ‘short message service’ (SMS) is used to transfer address information for the Internet user to an Internet server. The system also relates to a method for enabling a GSM subscriber to make an Internet telephone call to an Internet user using SMS to transfer address information for the Internet user. But this is done by means of a dedicated telephony/Internet server that intercepts GSM calls and redirects them via the Internet. The server provides a special service that requires a calling party to access the server in order to reach another GSM subscriber using VoIP. To this end, a ‘short message service’ (SMS) is used to transfer address information for the Internet user to an Internet server, which is then able to map an incoming GSM number of a target telephone to a corresponding IP address. There is no provision for the calling party to dial the GSM number of the target telephone directly in order to establish IP communication.
U.S. Pat. No. 6,424,648 (Ng et al.) published Jul. 23, 2002 discloses a method and system for automatically establishing a phone call over an Internet connection, wherein a caller party automatically dials a telephone number of a recipient party to establish a telephone phone call connection. The caller party automatically initiates a dialing routine to notify the recipient party of an intended phone call connection across an Internet connection. The caller and recipient parties automatically end the telephone call connection in response to the recipient party detecting the dialing routine by the caller party. The caller and recipient parties each automatically undertake to make a separate connection with an Internet service provider and then make a connection to a directory service on the Internet. Each of the caller and recipient parties automatically provide their respective Internet protocol address and telephone number, and the caller party submits the recipient party's telephone number. Each of the caller and recipient party automatically complete the Internet connection for the intended phone call connection.
US 2004/017910 (Joksang et al.) published Jan. 29, 2004 discloses a dual phone that recognizes one of ISDN mode, IP mode, and external connection mode from a user input, and connects or releases a voice path between an ISDN phone and the IP phone based on the recognized mode, thereby enabling calling between an external ISDN phone and an IP phone. In the case of an origination call, the ISDN phone circuit unit and the IP phone circuit unit operate in the same manner as the existing ISDN phone and IP phone. That is, if a dial tone is heard when the handset is picked up, a calling party may dial the called party's phone number. At this time, in order to operate the ISDN phone circuit unit, the calling party should press the ISDN/IP button, while in order to operate the IP phone circuit unit, the calling party should press the ISDN/IP button once again. In other words, the ISDN/IP button is toggled. There is no suggestion to allow seamless VoIP redirection to a target telephone by dialing the PSTN address of the target telephone.
US 2004/017901 (Lim) published Jan. 29, 2004 discloses a communications terminal that operates in multiple modes including a wired phone mode, an Internet phone mode, and a combined mode. The terminal includes a wired phone unit and an IP phone unit which separately processes calls to/from PSTN- and Internet-communications networks. The terminal also includes a processor which processes a call through a voice path which connects the wired phone unit and the IP phone unit in a third mode of operation which is referred to as an external connection mode.
None of the above references allows seamless routing of a telephone call via VoIP over an Internet connection between two subscribers to a non-IP telephone network (such as PSTN or Cellular) using dual mode telephones that are compatible with VoIP and an appropriate non-IP protocol, whereby a source subscriber can call a target subscriber by dialing the target subscriber's number of the non-IP network.
It is an object of the invention to provide a method, system and enhanced telephone having two communication ports having respective first and second addresses for connecting to a non-IP network and an IP network, respectively for allowing seamless routing of a VoIP telephone call via an IP network between a source telephone and a target telephone by dialing the first address of the target telephone.
This object is realized in accordance with a first aspect of the invention by a method of effecting seamless routing of a VoIP telephone call via an IP network between a source telephone and a target telephone both having two communication ports having respective first and second addresses for connecting to a non-IP network and an IP network, respectively, by dialing the first address of the target telephone, the method comprising:
In one embodiment of the invention, the source and target telephones are dual mode IP/PSTN telephones that are both connected to both the PSTN and an IP network, such as the Internet. But the invention is also applicable for use with any dual mode telephone having a VoIP compatible port as well a non-IP port that is connectable to a different communications network for effecting non-IP communication with another telephone connected to the same network. So, for example, the invention is applicable also to dual mode cellular/IP that effect IP communication using Packet Data wireless services such as Wi-Fi or GPRS.
According to a second aspect of the invention there is provided a dual mode, dual protocol telephone, comprising:
a first communication port having a first address for connecting to a non-IP network,
a second communication port having a second address for connecting to an IP network,
a user interface for allowing entry or selection of the first address of a remote similar dual mode, dual protocol telephone with which VoIP communication is required between the respective second communication ports of both telephones, and
a processing unit adapted to retrieve the respective second addresses of both telephones and to seamlessly establish a VoIP communication therebetween.
In the case where the dual mode, dual protocol telephone is coupled to the Public IP network via a NAT, the address will minimally include Public IP and Port number so as to provide sufficient information necessary for NAT traversal for establishing peer-to-peer communication over IP. This ensures that a message conveyed from the source telephone includes the respective Private IP addresses of the source and target telephones as well as their respective Public IP addresses and the port numbers of the port in their corresponding domestic routers or NAT servers. In this connection, it is to be noted that port numbers of the target phone are known to its domestic NAT, via the rendezvous server, which provides them to the target phone, but not to the source phone, which must know them to initiate direct, peer-to-peer call with the target. In other words, the source phone should send its packets to the target phone's public IP plus port, in order to reach target phone. The target phone's domestic NAT will translate Public IP address plus Port number to Private IP address of the target phone, and therefore be able to resolve the address, otherwise it may not be able to do this, given that there may be more than one target phone connected to the target domestic NAT and having the same logical port number. It is to be noted that this is only one possible implementation of a NAT. Other implementations are also known and all possible implementations are embraced by the invention. A further discussion of NAT Traversal may be found in the following publications:
All of these publications are accessible over the Internet and are included in the File Wrapper of the present US application by way of an IDS.
The source NAT maps the source telephone Private IP address to a logical port number of the source NAT to which the source telephone is connected with the. A message sent from the source telephone to the target telephone is first received by the target NAT having the public IP address of the target telephone. The target NAT relays the incoming data to the port number in the target NAT embedded in the message so as to convey the message to the target telephone. When a reply message is relayed by the target telephone to the source telephone, a symmetrical procedure is carried out.
In contrast to a dual mode, dual protocol telephone that is coupled to the Public IP network via a NAT, in the case of a dual mode, dual protocol telephone coupled to the Public IP network directly, the address need include only the Public IP of the respective telephone.
Therefore in the context of the invention and the appended claims, it is to be understood that the term “address” envisages any information that enables data to be conveyed unambiguously to an identified target telephone from an identified source telephone. As noted, the address minimally includes the Public IP address of a telephone when connected directly to the Public IP network; and may further include the port number of a NAT via which the telephone is coupled to the IP network address. Alternatively or additionally, the address may also include the Private IP address: all depending on the NAT's ability to map a Private IP address to the corresponding port to which the telephone is connected, and vice versa.
A PSTN/VoIP telephone according to the invention may further include a Customer Premises Equipment Call Waiting Caller ID protocol emulator coupled to the processing unit for conveying a retrieved IP address and NAT traversal information of the dual mode PSTN/VoIP telephone to a remote PSTN/VoIP telephone. Likewise, a Cellular/IP (e.g. over WiFi or GPRS) telephone according to the invention may fuirther support an SMS protocol conveying a retrieved IP address and NAT traversal information of the dual mode Cellular/VoIP telephone to a remote Cellular/VoIP telephone.
In order to understand the invention and to see how it may be carried out in practice, an embodiment will now be described, by way of non-limiting example only, with regard to seamlessly routing a VoIP telephone call via an 1P network between a pair of dual mode PSTN/IP telephones and with reference to the accompanying drawings, in which:
a and 3b are block diagrams showing respective functionalities of dual mode PSTN/VoIP and cellular/VoIP telephones for use in the system shown in
For the sake of completeness, the system 10 includes a PSTN/IP gateway 17 a PSTN/Cellular gateway 18 and a Cellular/IP Gateway 19 for conveying signaling and media from one network to the other with regard to single mode telephones or other telephones that are not enhanced dual mode telephones according to the invention. For such telephones, the respective gateways operate in a manner well known in the art to convert the signals between PSTN and IP or PSTN and Cellular or Cellular and IP protocols and vice versa. The PSTN/IP gateway 17, the PSTN/Cellular gateway 18 and the Cellular/IP Gateway 19 are all adapted to emulate the Call Waiting Caller ID protocol in respect of the source telephones in the respective networks.
However, the need for protocol conversion that is the raison d'êitre of these gateways is eliminated for enhanced dual mode telephones according to the invention, which communicate either over PSTN or cellular only (during an initial session wherein they exchange their IP addresses) or (subsequently) via IP only. Therefore, no further discussion of the gateways or their operation, which in any case are known per se, will be given, since they are not required for communication between enhanced dual mode telephones according to the invention.
a is a block diagram showing the functionality of a dual mode, dual protocol PSTN/VoIP telephone 11a for use in the system shown in
The PSTN interface 31a is connected to an RJ-11 telephone socket 33 (constituting a first communication port) for coupling to the PSTN. Likewise, the LAN/WAN interface 32a is connected to an RJ-45 socket 34 (constituting a second communication port) for coupling to the Internet. The processing unit 30 includes a voice processing unit 35 for processing the voice to/from the PSTN, and a data processing unit 36 for processing the data to/from the IP network. The processing unit 30 also includes a voice and data gateway 37 that converts the voice to IP packets, and an address linking module 38 that is coupled to the memory 25 and is responsive to a first address for extracting the corresponding second address from the memory. The address linking module 38 includes or is coupled to a user interface (such as an alpha-numeric keypad and scrolling keys as shown in
Although the above description is directed specifically to PSTN/VoIP telephones, it is to be understood that the principles apply to other dual mode, dual protocol telephones such as Cellular/IP. Thus,
In similar manner, dual mode, dual protocol Cellular/IP telephones may exchange their IP address using SMS, for example according to the mechanism described in above-mentioned WO 99/12365.
When a PSTN call is initiated for the first time between the source and target telephones, there are two options. According to one option, the PSTN call continues in normal manner until terminated by the source subscriber who may, of course, immediately redial the PSTN address of the target telephone in order to establish VoIP communication since the corresponding IP address of the target telephone is now known to the source telephone. According to an alternative scenario, the PSTN call is automatically terminated and VoIP communication established seamlessly.
It is to be noted that the flow diagrams are intended to show the principal operations carried out by the source and target telephones and so not necessarily dictate an order in which they are carried out. So, for example, in
It will be appreciated that modifications will be apparent to those of average skill in the art without departing from the spirit of the invention. In particular, while the preferred embodiment has been described with particular regard to a dual mode PSTN/IP telephone it is equally applicable to cellular/IP telephones. Likewise, while it has been described to relay IP addresses during a PSTN connection using Call Waiting Caller ID protocol and during a Cellular connection using SMS, any other suitable means may be employed. Thus, as noted, the IP addresses can be exchanged manually in an initialization process and then stored. Subsequent updating of IP addresses will continue to be effected automatically via the IP network thus ensuring that the initialization process, even if performed manually, need ever be performed only once. It should also be noted that since there is only a need to obtain for a source telephone the target telephone's IP address over the PSTN, or other non-IP network, only once during first use, all subsequent uses will rely on the fact that the target telephone's IP address is already stored and mapped to its PSTN number. The invention as claimed is intended to cover such subsequent communication, as well as a telephone that has dual ports for effecting IP and non-IP communication and is able to map a non-IP address to a corresponding IP address of a target telephone in order to establish seamless IP communication by dialing the non-IP address thereof.
