The present invention relates to a base station controller and a wireless packet processing device. The invention more particularly relates to a base station controller and a wireless packet processing device, which, when messages from a different subnet are received, perform relevant call connection processing and process such a message.
CDMA 2000 1xEvolution-Data Only (1xEV-DO) is a mobile wireless communication scheme specializing in data communications and is standardized in Non-Patent Document 1 (“cdma2000 High Rate Packet Data Air Interface Specification”, 3GPP2 C.S0024-A Version 3.0 Sep. 2006) by 3rd Generation Partnership Project 2 (3GPP2) that is an international organization for standardization. CDMA 2000 1xEV-DO specializes in data communications to improve the frequency usage efficiency.
When an access terminal (AT) (that is a mobile terminal) performs communications with a radio access network (RAN), the RAN assigns unicast access terminal identifiers (UATI32 and UATI128) to the AT. The UATI32 and the UATI128 serve as identifiers that uniquely identify the AT. The following describes the configurations of the UATI32 and the UATI128 that are defined in Non-Patent Document 1 with reference to FIGS. 1 and 2.
As shown in FIG. 1, the UATI32 200 is constituted by 32 bits. Upper 8 bits of the UATI32 200 indicate ColorCode 201 that identifies the RAN. Lower 24 bits of the UATI32 200 can be freely assigned by the RAN as UATI24 202.
As shown in FIG. 2, the UATI128 210 is constituted by 128 bits. Upper 104 bits of the UATI128 210 indicate Subnet information 211 that identifies the RAN. Lower 24 bits of the UATI128 210 can be freely assigned by the RAN as UATI24 212. The UATI32 200 and the UATI128 210 are collectively called a UATI.
When the UATI is assigned to the AT, the AT and the RAN configure a wireless session therebetween. The wireless session indicates a group of a protocol and a parameter that are determined on the basis of functions that can be supported by the AT and the RAN and are confirmed by the AT and the RAN.
In order to perform data communications between the AT and the RAN, a wireless link is established between the AT and the RAN and a point-to-point protocol (PPP) is established between the AT and a packet data service node (PDSN). The state of the AT in this case is called an active state.
When a certain non-communication state occurs, the AT and the RAN release the wireless link. In this case, the wireless session is maintained in the RAN and the PPP is maintained between the AT and the PDSN. The state of the AT in this case is called a dormant state.
The AT regularly receives broadcast information such as a SectorParameters message (shown in FIG. 3A) from a base station transceiver subsystem that is included in the RAN. As shown in FIG. 3A, the SectorParameters message 400 is constituted by fields (such as MessageID, CountryCode, SectorID 401, SubnetMask, SectorSignature, SecondaryColorCodeIncluded, SecondaryColorCodeCount, SecondaryColorCode 402, and Reserved) and lengths (bits) of the fields. As shown in FIG. 3B, SectorID 401 of 128 bits is constituted by Subnet information 4011 of 104 bits and a sector identifier 4012 of 24 bits.
When the AT moves and passes through a boundary between RANs, the AT detects that the Subnet information 4011 of the SectorID 401 included in the SectorParameters message 400 transmitted from the destination RAN (to which the AT moves) is different from the Subnet information 211 included in the UATI128 210 of the AT. The AT that detects the movement transmits a UATIRequest message to the destination RAN in order to request assignment of a new UATI. The RAN receives the UATIRequest message and then acquires a wireless session of the AT from the RAN from which the AT moves. The RAN then assigns the new UATI to the AT. This handoff is called inter-RAN dormant handoff.
On the other hand, handoff that is performed when the AT that is in the active state moves and passes through a boundary between RANs is called inter-RAN active handoff. In the inter-RAN active handoff, a wireless session is taken over by the RAN from the other RAN and a UATI is reassigned to the AT under the condition that a wireless link is established.
When the AT is located at the boundary between the RANs, the AT alternately receives SectorParameters messages 400 that include the Subnet information 4011 of the RANs. Assignment of an UATI to the AT and transfer (takeover) of the wireless session are frequently performed between the RANs by using the messages as triggers when the AT is located at the boundary between the RANs. This results in waste of CPU utilization of network devices included in the RANs and waste of network resources and wireless resources. This effect is generally called a ping-pong effect.
To avoid this problem, Non-Patent Document 1 proposes use of SecondaryColorCode. ColorCode of a first RAN is registered, as SecondaryColorCode 402, into the SectorParameters message 400 that is transmitted by a base station transceiver subsystem that is included in a second RAN (that is adjacent to the first RAN) and located at the boundary between the first and second RANs, while ColorCode of the second RAN is registered, as SecondaryColorCode 402, into the SectorParameters message 400 that is transmitted by a base station transceiver subsystem that is included in the first RAN and located at the boundary between the first and second RANs. The AT does not transmit the UATIRequest message as long as the ColorCode 201 included in the UATI32 200 of the AT matches the SecondaryColorCode 402 included in the SectorParameters message 400. Thus, CDMA 1xEV-DO suppresses occurrence of the ping-pong effect between the RANs.
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