Communication system, gateway device and adapter device

A gateway device which mutually converts communication protocols among a subscriber network including a base station wirelessly housing a mobile terminal and an Internet Protocol processor to bring an interface from the base station into an Internet Protocol process, a public switched telephone network and a packet communication network, includes a synchronized network terminating unit which terminates the public switched telephone network to generate the in-device signal, a packet network terminating unit which terminates the packet communication network to generate the in-device signal, a subscriber network terminating unit which houses the base station via the interface to which the Internet Protocol process is applied and terminates the subscriber network to generate the in-device signal, and an exchange unit which exchanges in-device signals each generated from the synchronized network terminating unit, the packet network terminating unit and the subscriber network terminating unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-033859, filed Feb. 14, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gateway device which mutually connects, for example, between a public switched telephone network and an Internet Protocol (IP) network, and a communication system provided with this kind of device.

2. Description of the Related Art

As needs for information communication become high and liberalization of communication advances, information communication services including voice and data communication have diversified. In accordance with such a background, the number of carriers who newly enter a communication service field has increased, and service competition among the carriers has become serious. The new carriers are called new common carriers (NCCs), and provide a variety of services by using techniques such as voice over Internet Protocol (VoIP), etc. VoIP is a technique which integrates a voice system network and a data system network by packetizing to transmit digital voice data.

The NCCs often lease facilities such as exchanges from a specific carrier which owns subscriber lines at predetermined charges. For the most part of the NCCs construct their own networks such as IP networks by their own funds. In addition to these networks, by adding a public switched telephone network (PSTN) of a specific carrier, a communication system is formed. To provide services to subscribers (users), these facilities are utilized in an interdisciplinary manner.

For mutually connecting different communication networks like the PSTN and the IP network, a gateway device is utilized. This kind of device includes an IP conversion unit to convert voice data and binary data into IP packets, and a packet switching unit which switches the IP packets. All of these units act as network interfaces for the IP network.

Some of this kind of gateway devices work with base stations of a mobile phone system. The mobile phone system includes a so-called a cellular phone system and, in Japan, a so-called personal handy-phone system (PHS). Hereinafter, this kind of a radio communication system is generically called a mobile communication system.

BRIEF SUMMARY OF THE INVENTION

At the present moment, there is a problem such that a bandwidth of a transmission line or network between a gateway device and the base station is not enough. If we leave the problem as it is, since this problem becomes a bottle neck to respond a communication demand which will further expand in future, any countermeasure is required. A method of resolving the problem is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-290480; however the method described in this patent document does not assume communication among mobile terminals and the PSTN.

An object of the present invention is to provide a communication system, a gateway device, and an adapter device which intends to expand the band width enough communication capacity between base stations and the gateway.

According to an aspect of the present invention, there is provided a communication system, comprising: a subscriber network consists of the base stations which wirelessly communicate with the mobile terminal therein; a public switched telephone network; a packet communication network; a gateway device which mutually converts communication protocols among the subscriber network, the public switched telephone network and the packet communication network to mutually connect these networks; and an Internet Protocol processing means which is installed on the subscriber network and brings an interface between the gateway device and the base station into an Internet Protocol process, wherein the gateway device comprises: a synchronized network terminating unit which terminates the public switched telephone network to generate in-device signals; a synchronized network terminating unit which terminates the packet communication network to generate the in-device signals; a subscriber network terminating unit which communicates with the base station via an interface which has been processed into the Internet Protocol and terminates the subscriber network to generate the in-device signals; and an exchange unit which exchanges in-device signals each generated from the synchronized network terminating unit, the packet network terminating unit, and the subscriber network terminating unit.

By taking such measures, the base stations and the gateway device are processed into an IP. Thereby, in comparison to house the base stations via the existing digital synchronized network (in a PHS, via an I′ interface), the band may be expanded dramatically. Accordingly, communication speed and the number of channels may be increased spectacularly.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a system diagram depicting an embodiment of a communication system regarding the present invention. The system ofFIG. 1includes a public switched telephone network100; an IP network200as a packet communication network; and a subscriber network300. These networks are connected to a gateway10. The network100is connected with the gateway10, for example, via an I′ interface. The IP network200is connected with the gateway10via an IP interface.

The gateway10mutually converts communication protocols among the subscriber network300, the public switched telephone network100and the IP network200to connect these networks with one another. Inside of the gateway10, data on each network is exchanged each other in accordance with synchronized exchange connections by using a time-division switch.

The subscriber network300includes a plurality of base stations21-2n. Each base station21-2ncommunicates with a mobile terminal PS such as a PHS via a wireless channel. Among the base stations, the base station21has a channel to be directly connected to the gateway10via the I′ interface, and has a channel to be connected to the gateway10via an adapter30A. The base station22is connected with the gateway10via an adapter30B. The base station2nincludes a built-in adapter50and is connected with the gateway10by means of the adapter50via the IP interface.

Between the adapters30A and30B and the gateway10, and between the base station2nand the gateway10are each connected to the gateway10via the existing optical fiber network400. Optical fibers F which are extended from the respective base station21-2nare line-concentrated by a line concentration unit500and are connected to the gateway10.

The optical fiber network400is an IP network which utilizes, for example, a passive optical network (PON) technique. A network-node interface among each base station21-2nand the optical fiber network400is processed in an IP by means of functions of the bases stations themselves or the adapter30. The base station21has two output interfaces. One of the two interfaces is the I′ interface to be connected to the gateway10.

The gateway10includes a public network interface11for the public switched telephone network100, and an IP interface12for the IP network200. The public network interface11terminates the public switched telephone network100to generate pulse code modulation (PCM) data that is time division data. The IP interface12terminates the IP network200to generate the PCM data.

Further, the gateway10is provided with an optical interfacing unit13, a packet conversion unit14and a main control unit15. The optical interfacing unit13houses the base stations21-2nvia the optical fibers Fs which are line-concentrated by the line concentration unit500. That is, the optical interfacing unit13optically and electrically converts optical signals come from the optical fiber network400and also terminates the IP packets to generate the PCM data.

The main control unit15includes a time switch15ain addition to a function of integrally controlling the gateway10. The time switch15aexchanges and connects the public switched telephone network100, the IP network200and the subscriber network300by switching the PCM data. At this moment, the signal toward the IP network200is packetized into IP packets through the packet conversion unit14. The data toward the optical fiber network400is packetized as IP packets by the optical interfacing unit13.

In the inside of the gateway10, the PCM data is transmitted via a PCM highway (PCM-HWY). The IP packets are transmitted via a local area network (LAN) or a data LAN.

The optical interfacing unit13includes an optical switch13a, an optical interface13b, a layer 2 switch for data (L2SW)13cand a packet conversion unit13d. The optical switch13aswitches a route of the optical fiber F from the optical fiber network400. Thereby, the communication system may switch to operate the base stations21-2n, and may prompt to improve fault-tolerant performance.

The optical signal introduced inside the device via an optical switch13ais converted into an electrical signal through an opto-electric conversion element (not depicted) which is provided for the optical interface13b. The optical interface13breproduces IP packets from the electrical signal. The IP packets are routed by the L2SW13cto be transmitted to the IP interface12or the packet conversion unit13d. The packet conversion unit13dmutually converts the packets flowing through a control LAN, packets flowing through a data LAN and time division data flowing through the PCM-HWY.

FIG. 2shows the detail of the optical interfacing unit13and the flow of data. The optical interfacing unit13has a clock processing unit20. The clock processing unit20adds timing information to the PCM data to be packetized. Thereby, the system may transmit the PCM data and the synchronizing timing data in the same channel, and may respond to the base stations having only the digital synchronizing interfaces.

In the optical housing unit13ofFIG. 2, the transmission data including voice or binary codes traces the route of the optical interface13b, the L2SW13c, the packet conversion unit14, the main control unit15, in that order to be transmitted. The transmitted data is exchanged by the time switch15aof the main control unit15, packetized again by the packet conversion unit14and transmitted to the IP interface via the IP interface12.

Since the base station21has both the IP interface and the digital synchronizing interface, the base station21may transmit synchronized information through the digital synchronized network. In this case, the system may transmits the transmitted data as it is in the packets to the IP network from the IP interface of the base station via the IP interface12passing through the optical interface13band the L2SW13cfor data, in that order. As an example of the digital synchronized network, the Integrated Services Digital Network (ISDN) widely used in Japan is a possible approach.

FIGS. 3A and 3Bshow functional block diagrams depicting an embodiment of the adapters30A and30B inFIG. 1. In the adapter30A, the IP packets transmitted from the base station21are optimized as they are in packet forms by the electro-optic conversion unit35via the LAN interface32and transmitted to the optical fibers F. In the adapter30B, the time division data from the base station22is packetized by time division multiplexing (TDM) interface33. The packets are optimized by the electro-optic conversion unit36through the clock processing unit34to be transmitted to the optical fiber F. The packets from the optical fiber F are applied clock transmission processing in an upper layer to be transmitted to the I′ interface. Such processing is integrally performed by a central processing unit (CPU)31or a CPU32.

FIG. 4shows a functional block diagram depicting an embodiment of the built-in adapter50inFIG. 1. Including this built-in adapter50enables the base station2nto handle both the packets and TDM signals. The packets among them are optimized by an electro-optic conversion unit55via a signal processing unit54from a LAN switch52to be transmitted to the optical fibers F. After being added clock information from the clock processing unit53, the TDM signals are optimized by an electro-optic conversion unit55through the signal processing unit54to be transmitted to the optical fibers Fs. Such processing is integrally controlled by the CPU51.

According to the foregoing configuration, either interface of the base station and of the gateway10is processed into an IP. In other words, the adapter30packetizes the TDM signal from the base station into IP packets. Also in the gateway10, the PCM data applied line exchange is packetized into IP packets at the optical interfacing unit13. Thereby, since the subscriber network300is processed into an IP network, the system may expand the transmission band which is larger than the conventional subscriber network that has been a time division network. Further, in this embodiment, the subscriber network300is optimized, and an optical transmission network in which PON techniques are combined with the optical fiber network400is formed. Thereby, channel speed of the subscriber network300may ensure up to upper limit speed of the PON (100 Mbps or 1.25 Gbps).

Moreover, installing the built-in adapter50in the base station enables simplifying the configuration of the adapter itself and also enables directly connecting the optical fibers Fs to the base stations21-2n, and enables obtaining merit such as a reduction in lightning damage.

In short, in this embodiment, the system installs the adapters30,50on the subscriber network300and converts the I′ interface from the base stations21-2ninto the IP interface, and optimizes a physical layer interface. The system also installs the optical interfacing unit13in the gateway10to house the optical fibers Fs from the adapters30and50, and converts the IP packets into the PCM data to process the IP packets in the device. Accordingly, the system may also convert and connect the transmitted data from the subscriber network300inside the gateway10. Therefore, the public switched telephone network100, the IP network200and the subscriber network300may be connected to one another. Thus, the communication system, the gateway device and the adapter device, which intend to improve the communication speed by expanding the band capable of being housed, may be provided.