Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-02-28
2003-08-05
Le, Thanh Cong (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S464000, C320S118000
Reexamination Certificate
active
06603975
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication network control system and, more particularly, to a flow control in a packet exchange for switching an IP (Internet Protocol) packet in the downward direction transmitted from the Internet to a mobile terminal.
2. Description of Related Art
Current communication networks include not only a conventional wire communication network using metallic line or optical fiber but also a communication network such as a mobile communication network using radio as media of signal transmission. The mobile communication network includes:
(1) a PDC (Personal Digital Cellular) for transmitting a signal in a time slot in a manner similar to an existing STM (Synchronous Transfer Mode) communication network (a time division communication network for transmitting a signal in time slots which are time-divided in synchronized frames as described in p. 29-30 of “Easy-to-understand digital exchange” issued by The Telecommunications Association) as described in p. 217-251 and 301-326 in “Mobile Communication Handbook” issued by Ohm-sha;
(2) a PHS (Personal Handyphone System) communication network; and
(3) a CDMA (Code Division Multiple Access) communication network for modulating a signal by using a code different according to each signal and transmitting the modulated signal as described in p. 32-36 in “Easy-to-understand Digital Mobile Communication” issued by The Telecommunications Association.
Among them, a wide band CDMA (W-CDMA) described from page 85 in “Nikkei Electronics”, No. 680 issued by Nikkei BP Co. is a communication network which is expected to be a communication system capable of transmitting and receiving signals of various kinds and speeds such as voice, image, and high-speed data with quality similar to that of the existing wire communication network even if the user terminal moves at high speed. The communication network is expected to be rapidly introduced in future.
On the other hand, current communication networks include various communication networks such as: the STM communication network; a packet communication network for transmitting a signal on a variable length packet, described in p. 128-133 in “Basic knowledge of data transfer” issued by The Telecommunications Association; an ATM (Asynchronous Transfer Mode) communication network for transmitting a signal on a fixed length packet called a cell, described in p. 64-79 in “B-ISDN textbook with pictures” issued by Ohm-sha; and the IP network (Internet) for transmitting an IP packet in accordance with the procedure called the Internet protocol (IP) by sending a signal on a variable length packet called an IP packet described in p. 98-103 10 in “Mastering TCP/IP, Introduction” issued by Ohm-sha. In each of the communication networks, media of voice, image and data are transmitted/received.
In recent years, a mobile packet network such as the Internet and a PDC-P (PDC-Packet) has been greatly introduced. In the Internet protocol (refer to RFC791, as per Internet Engineering Task Force) used on the Internet as a de facto standard communication protocol in the packet communication, controlling of a communication bandwidth of data or the like has not been examined in consideration of a data flow. That is, the most primitive method of transmitting data as much as possible unless a transmission path is congested in accordance with the order of arrival of data and transmitting no data when the transmission path is congested is used.
The method has a problem that a data flow of data such as a moving picture which should not be delayed but may be dropped a little and a data flow of data such as an electronic mail which may be delayed but should be complete cannot be dealt separately. In other words, the characteristic of the data flow is ignored. Especially, at the time of congestion, the problem is fatal. When data is not dealt according to the characteristic of the data flow, data to be preferentially sent when the transmission path is congested cannot be determined. An unpreferable situation such that an electronic mail which may be delayed is transmitted before a moving picture which should not be delayed can occur.
It is therefore considered that improvement on this point will be necessary in future by, for example, allocating a bandwidth to transmission of moving pictures wider than that of electronic mail so as to transmit the moving picture first. In the communication network in the next generation, it is presumed that a QoS (Quality of Service) control such as a control on a data transmission bandwidth is an important technique.
The Internet, however, originally lacks a function of supporting a mobile terminal on the network side. In the case of transmitting the IP packet from a fixed terminal on the Internet side to a mobile terminal on a mobile communication network side, especially, the fixed terminal performs a packet transmission without considering whether the data flow is for a mobile terminal or not.
A wireless access network peculiar to the mobile communication network positioning between a mobile terminal and a subscriber exchange on the mobile communication network side accommodates a number of mobile terminals and the bandwidth in the radio zone is narrow. Consequently, an upper limit is set so that the bandwidth in the wire zone allocated to each IP data flow does not exceed the channel bandwidth in the radio zone.
In order to prevent occurrence of an overflow of data in a wireless base station or the like for performing interwork between the wire zone and the radio zone, in the subscriber exchange on the mobile communication network side, it is necessary to perform a flow control (an example of the QoS control) on the flow of data entering from the Internet in the downward direction, of which bandwidth is not limited.
A specification required for the packet exchange service in the mobile communication network is being formed by including the flow control for each data flow in the downward direction. As an example, various service requirements are defined in documents in the IMT-2000 system based on the GPRS method (ETSI: GSM 03.60 Stage 2 Service Description of the General Packet Radio Service (GPRS)). The QoS control includes a bandwidth control, a delay control, a priority control, and a reliability control. It is presumed that the importance of the QoS control system for each data flow of a packet transmitted from a fixed terminal on the Internet side to the mobile terminal on the IMT-2000 system will be increased with the spread of the mobile packet communication in future.
As mentioned above, the flow control for the conventional IP data flow is performed by adjusting the traffic amount. Specifically, traffic of the IP data flow is actually measured by an intermediate exchange. When the traffic amount tends to increase, a radio channel is switched to a channel of a wider bandwidth and, simultaneously, an increase in the flow in the wire zone is permitted within the radio resources allowable range. The traffic which can be measured by the intermediate exchange is classified into effective traffic to be actually flowed and retransmission traffic occurring in association with degradation in the communication quality in the radio zone or the like.
Since the packet is encrypted and compressed in the mobile communication network, when the retransmission traffic increases, it is very difficult to distinguish between the retransmission traffic and the effective traffic in the intermediate exchange. Consequently, the exchange regards that the traffic of the IP data flow sent from the Internet increases.
As described above, when an ordinary flow control is executed on the basis of only the measured traffic amount, in the conventional flow control system for permitting the increase in traffic entering from the Internet side, a data loss frequently occurs in an apparatus such as a wireless base station having a small buffer capacity. As a result, the retransmission traffic further increases and the data loss more freq
Inouchi Hidenori
Ohishi Takumi
Antonelli Terry Stout & Kraus LLP
Cong Le Thanh
Hitachi, ltd.
Lei Tsuleun R
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