Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-12-04
2004-12-14
Phunkulh, Bob A. (Department: 2661)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S389000, C370S349000, C370S455000, C370S503000
Reexamination Certificate
active
06831908
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a data communication system that sends and receives data to or from an application server via a transmission line comprising one type of a wire communication network, a wireless communication network, and both a wire communication network and a wireless communication network. More particularly, the present invention relates to a data communication system and a data communication method not affected by transmission line characteristics.
BACKGROUND OF THE INVENTION
Recently, as the Internet technology has become widely used, the user accesses the Internet from a data communication terminal in a variety of ways.
Conventionally, the user accesses the Internet, in most cases, via a wire communication network such as a LAN (Local Area Network) in which terminals are connected by Ethernet or via a wire communication network in which telephone lines and modems are used. Today, in addition to access via those networks, more and more users access the Internet via both a wireless communication network, such as PHS (Personal Handy Phone System) and PDC (Personal Digital Cellular), and a wire communication network.
The only requirement for accessing the Internet is that the IP (Internet Protocol) must be used for the communication protocol hierarchy (layer) that provides data communication terminals with the terminal-to-terminal data transfer function. It is requested to transmit data as effectively as possible on a transmission protocol hierarchy layer in the communication protocol hierarchy. For increased efficiency, many transmission protocols are proposed.
A transmission protocol for accessing the Internet in a wire communication network is optimized for the characteristics of the configuration of a wire network in which a plurality of LANs are connected via routers. The protocol is designed for providing best performance in such a wire network.
On the other hand, a transmission protocol for accessing the Internet in a wireless communication network is optimized for the characteristics of a wireless network that has a large data transmission delay and a narrow transmission bandwidth, so that the protocol is designed for providing best performance in such a network.
SUMMARY OF THE DISCLOSURE
Under the conditions described above, a data communication terminal efficiently accesses the Internet using the same protocol via one of a wire communication network, a wireless communication network, and both a wire communication network and a wireless communication network in one of the following methods:
(1) Install both transmission protocols on a data communication terminal, which are switched depending upon the transmission line to be used.
(2) Install the transmission protocol optimized for one type of communication networks, wire or wireless. The effect of the characteristics of the other communication network is suppressed.
First, the former (1) has a problem that increases the amount of memory resources of the data communication terminal, increases the terminal size, and therefore makes the terminal impractical. The latter (2) has a second problem that significantly decreases the throughput of the other, non-optimized communication network and therefore requires positive unit for suppressing the effect of the characteristics of the other communication network.
SUMMARY OF THE DISCLOSURE
According to the investigations toward the present invention, the following analyses are given to the conventional art.
In solving the above problems, there are two factors that are affected by the characteristics of a wire communication network and a wireless communication network. One is the server processing time (RTT: Round Trip Time) that determines the time that is set in the retransmission timer. The other is the amount of free space in the receiving buffer at the destination that determines the sending buffer size.
FIG. 8
is a diagram showing the amount of the free space in the receiving buffer at the destination. As shown in the figure, when a data communication terminal sends or receives data to or from an application server (AP server) using the same protocol via a transmission line over one of a wire communication network, a wireless communication network, and both a wire communication network and a wireless communication network, the amount of free space in the receiving buffer at the destination affects the transmission speed of the communication network and the processing speed of the destination terminal.
That is, in case where the sending data communication terminal determines the sending buffer size based on the amount of free space of the receiving buffer of the destination AP server, the above-described first problem of allocating unnecessary memory resources arises if the communication network speed is lower than the processing speed of the destination terminal.
FIG. 9
is a diagram showing the relation between the application server processing time and the retransmission time. As shown in this figure, when the data communication terminal sends or receives data to or from the application server using the same protocol via a transmission line in one of a wire communication network, a wireless communication network, and both a wire communication network and a wireless communication network, the AP server processing time (RTT) is closely associated with a transmission delay (or none) caused by data errors on the communication network and with the retransmission time (timer). Therefore, an improper retransmission timer value, if set, would result in an incorrect data-loss detection and an unnecessary retransmission of a packet or in an unnecessary suppression of packet retransmission, thus generating the second problem which decreases throughput significantly. In other words, when a value that is set in the retransmission timer is too small, a data loss is detected mistakenly and an unnecessary packet or packets is retransmitted. Conversely, when a value that is set in the retransmission timer is too large, a data loss cannot be detected even if generated and so the retransmission of a packet or packets is delayed.
Thus there is much to be desired in the art.
In view of the foregoing, it is an object of the present invention to provide a data communication system and a data communication method not affected by the transmission line characteristics when data is transferred between a data communication terminal and an AP server using the same protocol via a transmission line comprising one of a wire communication network, a wireless communication network, and both a wire communication network and a wireless communication network.
To solve the above problems, a data communication system which sends or receives data to or from an application server using the same protocol via a transmission line comprising one type of a wire communication network, a wireless communication network, and both a wire communication network and a wireless communication network is provided. The data communication system comprises a first table containing therein a relation among a service identifier of the application server, a destination address, a communication network type, and a processing time of the application server; and a retransmission timer setting unit which references the first table to find the processing time of the application server based on the service identifier, destination address, and communication network type during transmission or reception of data to or from the application server and sets the time as a retransmission time.
This formulation sets the retransmission timer properly and therefore reduces the possibility of unnecessary retransmission of packets due to an incorrect data-loss detection or the possibility of unnecessary suppression of transmission at retransmission time, significantly increasing throughput.
Preferably, the data communication system further comprises a radio status acquisition unit which acquires a radio wave strength of the wireless communication network and an error rate of data sent to or received from the w
Dickstein Shapiro Morin & Oshinsky LLP.
Phunkulh Bob A.
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