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Radio communication method, radio mobile device and radio base station accommodation apparatus

Radio communication method, radio mobile device and radio base station accommodation apparatus description/claims

The present application claims priority from Japanese application JP2007-078138 filed on Mar. 26, 2007, the content of which is hereby incorporated by reference into this application.

The present invention relates to a radio communication method, a radio mobile device and a radio base station accommodation apparatus and particularly to a radio communication method, a radio mobile device and a radio base station accommodation apparatus which can restore data certainly irrespective of network conditions upon hand-off.

The 3rd Generation Partnership Project 2 (3GPP2) which is the International Organization for Standardization standardizes the CDMA (Code Division Multiple Access) 2000 1xEV-DO (1x Evolution-Data Only) system which is the mobile radio communication system specialized exclusively to the data communication. This system improves the frequency utilization efficiency by being specialized to the data communication. In the CDMA 2000 1xEV-DO system, when data communication requiring high real-time efficiency such as VoIP (Voice over Internet Protocol) is performed, there is a problem that a data transmission stop period occurs upon hand-off and jitter occurs due to it. As measures for solving this problem, the hand-off method using the protocol named the Route Selection Protocol (RSP) is standardized in C. S0063-0 v2.0 which is 3GPP2 standard. Furthermore, A. S0008-C and A. S0009-C stipulating the protocol between base stations to which RSP is applied is being stipulated currently.

In the hand-off method using RSP, the Radio Link Protocol (RLP) of the data transmission protocol having the independent sequence number management system is provided in each of hand-off source base station and hand-off destination base station. The RLP is the protocol for performing retransmission control and order control for compensating for lack of packet and change of packet order occurring in radio transmission and manages the sequence numbers in order to realize it. By using the RLP, any base station can perform receiving processing properly when the base station receives data from a mobile device.

In the hand-off method using RLP, there are two RLPs for hand-off source and hand-off destination. Each of the RLPs is named route and, for example, the route for the hand-off source is named route A, the route for the hand-off destination being named route B. Conversely, the route for the hand-off source may be named route B and the route for the hand-off destination may be named route A. In this specification, the route A is applied to the hand-off source and the route B is applied to the hand-off destination.

The RLP stipulates the protocol for changing route for making communication. A mobile device makes communication using route A upon communication in hand-off source and makes communication using route B upon communication after hand-off. This change of routes can be performed instantaneously, so that the data communication stop time upon hand-off is minimized.

IP packets transmitted from a mobile device through a base station to an application server are subjected to HDLC (High-level Data Link Control) like framing according to RFC (Request for Comments) 1662 in the mobile device. Then, RLP packets which are radio packets are produced by C. S0063-0 v2.0 and are transmitted to the base station by CDMA 2000 1xEV-DO radio according to C. S0024-A. The base station restores the RLP packets from the data received by the 1xEV-DO radio and subjects the RLP packets to deframing by HDLC like framing to restores the IP packets. The IP packets are sent to the application server to make data communication possible.

When the mobile device transmits IP packet to the application server through the base station, the IP packet is subjected to HDLC like framing to be fragmented into a plurality of packets in the form suitable for radio transmission, so that RLP packets are produced. When RLP packets produced from one IP packet are transmitted to the application server through the base station, the following case sometimes occurs. The case is that when the transmission delay between a hand-off destination base station and Packet Data Serving Node (PDSN) which is an apparatus for accommodating the base station is shorter than that between a hand-off source base station and PDSN by a fixed time or more in case where the hand-off using RSP is applied, route change by RSP occurs on the way of transmitting RLP packets. In such a case, when the route change by RSP is made to perform hand-off, the order of packets received in PDSN cannot be maintained and the packets cannot be restored in PDSN, so that the packets are annulled.

It is an object of the present invention to provide a radio communication method, a radio mobile device and a radio base station accommodation apparatus which can restore packets certainly irrespective of network conditions such as transmission delay between a base station and PDSN.

According to the present invention, when a mobile device which performs hand-off using RSP changes a route, transmission control is made so that RLP packets produced from one IP packet do not spread over routes.

More particularly, in a radio communication system including at least one radio mobile device, a plurality of radio base stations and a radio base station accommodation apparatus to accommodate them and in which when hand-off of the radio mobile device is performed from a first radio base station to a second radio base station, sequence numbers of radio packets transmitted to the first radio base station and sequence numbers of radio packets transmitted to the second radio base station are managed independently,

the radio mobile device controls to apply, when the hand-off is performed while transmission data is subjected to fragmentation to be divided into a plurality of radio packets and the plurality of radio packets are transmitted, sequence numbers of radio packets managed by the first radio base station to the plurality of fragmented radio packets even after the hand-off is performed and to apply sequence numbers of radio packets managed by the second radio base station to data transmitted subsequently after completion of transmission of the plurality of fragmented radio packets, and

the radio base station accommodation apparatus identifies a radio base station managing radio packets on the basis of the sequence numbers managed in each radio base station and restores data for each radio base station.

According to the present invention, packets can be restored in PDSN irrespective of network conditions such as transmission delay between a base station and PDSN.

Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram illustrating the whole configuration of 1xEV-DO system to which the present invention is applied;

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